Additive Manufactoring - Contributi utente [it]

Manufacturing and characterization of similar to foam steel components processed through selective laser melting

2020-02-03T12:03:34Z

BaldassareVitaggio:

'''Authors''': Fabrizia Caiazzo, Sabina Luisa Campanelli, Francesco Cardaropoli, Nicola Contuzzi, Vincenzo Sergi, Antonio Domenico Ludovico

'''Keywords''': Selective laser melting; Additive manufacturing; Stainless steel; Lightweight structures; Steel foam

'''Purpose''': The purpose is to produce periodic cellular lattice structures that can be used to develop of structures with advanced or multifunctional performance for high value engineering products. These periodic lattice structures, however, currently face a higher manufacturing complexity and costs than the stochastic structures.

'''Methodology''': The first choise, very important, was made on the powder to be used.The periodic porous structures were made from a 17–4 PH alloy powder, which was purchased from Electro Optical System (EOS) GmbH, Germany. A powder with a mean particle size of 20 μm has been used in this investigation, and alloy chemical composition is listed. The powder quality is important to reduce the content of impurities (oxygen, hydrogen and nitrogen), which might negatively affect mechanical properties of laser-sintered parts with phenomena like embrittlement. Figure 1 depicts the SEM images of the 17–4 PH alloy powder at different scales. The powder has a nearly spherical shape and smooth surfaces, which lead to a good flowability. Table 2 highlights 17–4 PH stainless steel mechanical properties. The method tried to design of similar to foam structures.To characterize the porous structures there are Several superimposed pore layers of two different types (type A and type B, Fig. 2).

'''Findings''': This paper has studied the possibility of manufacturing lightweight steel structures with spherical porosity adopting SLM technology. A stainless steel powder has employed, using an EOSINT M270 titanium version laser sintering system considering optimized parameters to have minimal content of porosity in laser-sintered parts. Different samples, having an effective average porosity ranging from 70.1 to 72.5% were successfully fabricated.

'''Limitations/benefits''': SLM has the capability of producing structures of complex freeform geometry. It has been demonstrated to manufacture cellular lattice structures with fine features, showing a great potential to make advanced lightweight structures and products that are highly desired by engineering sectors such as aerospace, automotive and medical industries. However, SLM requires support structure to build an overhang section if its angle from the horizontal is less than a certain degree. This introduces design and manufacturing complications for the SLM of lightweight cellular structures and engineering components. The cellular lattice structures with a large unit cell size or low strut angles from the horizontal (usually lower than 30°) could not be built using the SLM process because overhanging struts led to the occurrence of serious deformation.

'''Link''': https://link.springer.com/article/10.1007/s00170-017-0311-4

[[Utente:BaldassareVitaggio|BaldassareVitaggio]]

'''Full Reference''': Caiazzo, F., Campanelli, S. L., Cardaropoli, F., Contuzzi, N., Sergi, V., & Ludovico, A. D. (2017). Manufacturing and characterization of similar to foam steel components processed through selective laser melting. The International Journal of Advanced Manufacturing Technology, 92(5-8), 2121-2130.

'''Graphical abstract'''

[[File:Images of the 17-4 PH alloy powder .png|miniatura|sinistra|Two images of the 17-4 PH alloy powder at different scales]]

[[File:Layes type A and Layer type B.png|miniatura|destra|Example of two different type of Layes: A and B]]

Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique

2020-02-03T12:01:10Z

BaldassareVitaggio:

'''Authors''': Massimiliano Annoni, Hermes Giberti, Matteo Strano

'''Keywords''': Direct metal deposition, Fused deposition modeling, Metal injection molding, Parallel kinematics

'''Purpose''': This paper describes the feasibility study of a new additive manufacturing (AM) technique based on extrusion of a feedstock made of metallic (or ceramic) particles and a polymeric binder.

'''Design, benefits and limitations''': The main innovations introduced with the extrusion-based AM system presented in this paper are:

-Parallel kinematics work table:

An extrusion-based system equipped with a parallel kinematics 5-axis work table is proposed in this paper, which is unprecedented, at least to the authors’ knowledge. The motivations for this innovative design are: x The extrusion head is stationary, which is an advantage in terms of positioning accuracy since the head is heavy (about 25 kg) and powerful (power = 3 kW; maximum injection pressure = 134 MPa); x Parallel kinematics allows high positioning accuracy of the TCP (tool center point); x The 5-axis work table orientation allows a better surface quality and limits the need for workpiece supports during the deposition process.

-Extrusion Head:

In this Extrusion Head a plasticizing screw, positioned at 45° with respect to the vertical direction, continuously rotates and loads the injection cylinder with heated feedstock. A vertical piston moves and pressurizes the heated feedstock through the injection nozzle. The diameter of the piston is 14 mm. This configuration allows for continuity and stability of the extrusion process and large extrusion force, i.e. the possibility of extruding highly viscous fluids through small nozzle exit diameters. The injection pressure on the heated material upstream the nozzle can be set at a very high value, up to 140 MPa. The maximum amount of material that can be deposited during one single piston stroke is 9000 mm3 . If a 0.6 mm diameter wire is extruded, an approximate wire length of 32000 mm can be deposited before recharging the injection cylinder.

-Extrusion nozzles:

The nozzle design is even more important in the proposed system than in conventional FDM due to the high pressure required by the extrusion (from 10 to 140 MPa). Three different nozzle designs have been prepared and tested (Figure 5): x Nozzle A: convergent-divergent profile, used in injection molding, suited for relatively large wire diameters and aimed at minimizing the pressure drops inside the nozzle; x Nozzle B: convergent-parallel profile, suited for medium wire diameters, aimed at stabilizing the direction of the outgoing viscous flow. The calibrated part of the nozzle makes it suitable for controlling the wire diameter; x Nozzle C: convergent-stepped profile, suited for small wire diameters, aimed at reducing the wire diameter while maintaining low pressure drops. Since the calibrated part of the nozzle is shorter that the nozzle B one, swelling is more likely to occur.

-Extruded materials:

Two types of commercial MIM feedstock based on AISI 630 stainless steel powders (nominal median particle size = 13 Pm) and zirconia (nominal median particle size = 0.6 Pm) were preliminary tested.

-Hybrid manufacturing :

The configuration of the presented AM machine is suitable for hosting also a milling head on board of the top plate.

'''Findings''': The test described in this paper allowed to screen out some preliminary designs for extrusion nozzles and to verify the role of the binder percentage on the process capability. The possibility to bond the deposited wires after sintering was demonstrated on AISI 630, while zirconia seems to need a higher binder percentage to adhere during the deposition. Obtained material density is good, even if porosity exists, mainly for AISI 630 when sintered in argon instead of hydrogen. Future studies will be devoted to fully develop the proposed process/system.

'''Link''': https://www.sciencedirect.com/science/article/pii/S2351978916300919

'''Full Reference''': ANNONI, Massimiliano; GIBERTI, Hermes; STRANO, Matteo. Feasibility study of an extrusion-based direct metal additive manufacturing technique. Procedia Manufacturing, 2016, 5: 916-927.

[[Utente:BaldassareVitaggio|BaldassareVitaggio]]

'''Graphical abstract'''

[[File:3D printer conceptual design.png|miniatura|centro|3D printer conceptual design where it's possible to see: extrusion head,nozzle and work table]]

Additive manufacturing by means of laser-aided directed metal deposition of 2024 aluminium powder

2020-02-03T12:00:00Z

BaldassareVitaggio:

'''Authors''': Fabrizia Caiazzo, Vittorio Alfieri, Paolo Argenio and Vincenzo Sergi

'''Keywords''': Directed metal deposition, aluminium alloy, additive manufacturing, optimization, microstructures

'''Purpose''': The process is receiving increasingly interest in the frame of additive manufacturing to the purpose of maintenance, repair and overhaul of condemned products when severe conditions hindering the working order have been experienced.

'''Methodology''': A laser beam is used as focused heat source to scan the surface, thus creating a melting pool over an existing substrate. Since metal impinging the pool is fed concurrently (i.e. in singlestage processing) in the form of wire or loose powder,5 a deposited metal trace results, with metallurgical bonding to the substrate thanks to fusion and diffusion.

'''Findings''': The aspect and the corresponding macrographs in the transverse cross-section have been discussed for each processing condition (Table 3). Successful cladding resulted, based on visual inspections; shielding is deemed to be effective, no cracks neither macropores resulted on the surface. Nevertheless, a number of micropores, ranging in size from 10 to 75mm on average, have been found (Figure 5). One may assume this would not result in rejection of parts at quality checks. Usual international or customer standards for quality in laser welding30 are borrowed, since no specific regulations are available at present for DMD.

'''Benefits''': Minimal distortion of the workpiece, reduced heataffected zones (HAZs) and better surface quality are benefited in laser-aided DMD in comparison with conventional coating and repairing techniques such as arc welding and plasma spraying.

'''Limitations''': According to the trend of microhardness in the cross-section, softening is experienced in both the HAZ and the fusion zone, due to overaging with coalescence of dispersoids in the former and precipitation to grain boundaries in the latter, with respect to parent metal in T3 state.

'''Practical implications''': A condition with 2.5 kW laser power, 420 mm min21 processing speed is suggested for given feeding rate of 3 g min21 and 3 mm beam diameter, which is deemed to be robust, given the shape of the response surface of the overall desirability.

'''Link''':https://journals.sagepub.com/doi/full/10.1177/1687814017714982

'''Full Reference''' : CAIAZZO, Fabrizia, et al. Produzione additiva mediante deposizione metallica diretta al laser di polvere di alluminio 2024: studio e ottimizzazione. Progressi nell'ingegneria meccanica , 2017, 9.8: 1687814017714982.

[[Utente:BaldassareVitaggio|BaldassareVitaggio]]

'''Graphical abstract'''

[[File:Transverse cross-section.png|miniatura|sinistra|Trace aspects and corresponding samples of transverse cross-section for each processing condition]]

[[File:Micropores in the fusion zone.png|miniatura|destra|Micropores in the fusion zone;central condition of the plan(2.5kW laser power,400mm/min speed)]]

Manufacturing and characterization of similar to foam steel components processed through selective laser melting

2020-02-03T11:59:25Z

BaldassareVitaggio:

'''Authors''': Fabrizia Caiazzo, Sabina Luisa Campanelli, Francesco Cardaropoli, Nicola Contuzzi, Vincenzo Sergi, Antonio Domenico Ludovico

'''Keywords''': Selective laser melting; Additive manufacturing; Stainless steel; Lightweight structures; Steel foam

'''Purpose''': The purpose is to produce periodic cellular lattice structures that can be used to develop of structures with advanced or multifunctional performance for high value engineering products. These periodic lattice structures, however, currently face a higher manufacturing complexity and costs than the stochastic structures.

'''Methodology''': The first choise, very important, was made on the powder to be used.The periodic porous structures were made from a 17–4 PH alloy powder, which was purchased from Electro Optical System (EOS) GmbH, Germany. A powder with a mean particle size of 20 μm has been used in this investigation, and alloy chemical composition is listed in Table 1. The powder quality is important to reduce the content of impurities (oxygen, hydrogen and nitrogen), which might negatively affect mechanical properties of laser-sintered parts with phenomena like embrittlement. Figure 1 depicts the SEM images of the 17–4 PH alloy powder at different scales. The powder has a nearly spherical shape and smooth surfaces, which lead to a good flowability. Table 2 highlights 17–4 PH stainless steel mechanical properties. The method tried to design of similar to foam structures.To characterize the porous structures there are Several superimposed pore layers of two different types (type A and type B, Fig. 2).

'''Findings''': This paper has studied the possibility of manufacturing lightweight steel structures with spherical porosity adopting SLM technology. A stainless steel powder has employed, using an EOSINT M270 titanium version laser sintering system considering optimized parameters to have minimal content of porosity in laser-sintered parts. Different samples, having an effective average porosity ranging from 70.1 to 72.5% were successfully fabricated.

'''Limitations/benefits''': SLM has the capability of producing structures of complex freeform geometry. It has been demonstrated to manufacture cellular lattice structures with fine features, showing a great potential to make advanced lightweight structures and products that are highly desired by engineering sectors such as aerospace, automotive and medical industries. However, SLM requires support structure to build an overhang section if its angle from the horizontal is less than a certain degree. This introduces design and manufacturing complications for the SLM of lightweight cellular structures and engineering components. The cellular lattice structures with a large unit cell size or low strut angles from the horizontal (usually lower than 30°) could not be built using the SLM process because overhanging struts led to the occurrence of serious deformation.

'''Link''': https://link.springer.com/article/10.1007/s00170-017-0311-4

[[Utente:BaldassareVitaggio|BaldassareVitaggio]]

'''Full Reference''': Caiazzo, F., Campanelli, S. L., Cardaropoli, F., Contuzzi, N., Sergi, V., & Ludovico, A. D. (2017). Manufacturing and characterization of similar to foam steel components processed through selective laser melting. The International Journal of Advanced Manufacturing Technology, 92(5-8), 2121-2130.

'''Graphical abstract'''

[[File:Images of the 17-4 PH alloy powder .png|miniatura|sinistra|Two images of the 17-4 PH alloy powder at different scales]]

[[File:Layes type A and Layer type B.png|miniatura|destra|Example of two different type of Layes: A and B]]

Manufacturing and characterization of similar to foam steel components processed through selective laser melting

2020-02-03T11:50:16Z

BaldassareVitaggio:

'''Authors''': Fabrizia Caiazzo, Sabina Luisa Campanelli, Francesco Cardaropoli, Nicola Contuzzi, Vincenzo Sergi, Antonio Domenico Ludovico

'''Keywords''': Selective laser melting; Additive manufacturing; Stainless steel; Lightweight structures; Steel foam

'''Abstract''': The growing interest from the industry for lightweight metal components has driven the development of processes that would allow creating lightweight high melting point metals as steels, able to guarantee mechanical characteristics superior to existing foam (typically aluminium), without penalizing one of the characteristics that cell structures have: lightness.
Conventional manufacturing methods, such as casting, however, face difficulty in making complex periodic steel structures with designed shape and size and volume fraction. This study evaluates the manufacturability and performance of lightweight 17–4 PH steel components with spherical porosity fabricated via selective laser melting (SLM). Samples were designed and fabricated with the purpose to produce a structure similar to foam. Built samples were characterized in terms of dimensional accuracy, mechanical strength under compression and energy absorbed per unit mass. The designed structures have a designed relative density or volume
fraction ranging between 31.1 and 32.8%.

'''Purpose''': The purpose is to produce periodic cellular lattice structures that can be used to develop of structures with advanced or multifunctional performance for high value engineering products. These periodic lattice structures, however, currently face a higher manufacturing complexity and costs than the stochastic structures.

'''Methodology''': The first choise, very important, was made on the powder to be used.The periodic porous structures were made from a 17–4 PH alloy powder, which was purchased from Electro Optical System (EOS) GmbH, Germany. A powder with a mean particle size of 20 μm has been used in this investigation, and alloy chemical composition is listed in Table 1. The powder quality is important to reduce the content of impurities (oxygen, hydrogen and nitrogen), which might negatively affect mechanical properties of laser-sintered parts with phenomena like embrittlement. Figure 1 depicts the SEM images of the 17–4 PH alloy powder at different scales. The powder has a nearly spherical shape and smooth surfaces, which lead to a good flowability. Table 2 highlights 17–4 PH stainless steel mechanical properties. The method tried to design of similar to foam structures.To characterize the porous structures there are Several superimposed pore layers of two different types (type A and type B, Fig. 2).

'''Findings''': This paper has studied the possibility of manufacturing lightweight steel structures with spherical porosity adopting SLM technology. A stainless steel powder has employed, using an EOSINT M270 titanium version laser sintering system considering optimized parameters to have minimal content of porosity in laser-sintered parts. Different samples, having an effective average porosity ranging from 70.1 to 72.5% were successfully fabricated.

'''Limitations/benefits''': SLM has the capability of producing structures of complex freeform geometry. It has been demonstrated to manufacture cellular lattice structures with fine features, showing a great potential to make advanced lightweight structures and products that are highly desired by engineering sectors such as aerospace, automotive and medical industries. However, SLM requires support structure to build an overhang section if its angle from the horizontal is less than a certain degree. This introduces design and manufacturing complications for the SLM of lightweight cellular structures and engineering components. The cellular lattice structures with a large unit cell size or low strut angles from the horizontal (usually lower than 30°) could not be built using the SLM process because overhanging struts led to the occurrence of serious deformation.

'''Link''': https://link.springer.com/article/10.1007/s00170-017-0311-4

[[Utente:BaldassareVitaggio|BaldassareVitaggio]]

'''Full Reference''': CAIAZZO, Fabrizia, et al. Manufacturing and characterization of similar to foam steel components processed through selective laser melting. The International Journal of Advanced Manufacturing Technology, 2017, 92.5-8: 2121-2130.

'''Graphical abstract'''

[[File:Images of the 17-4 PH alloy powder .png|miniatura|sinistra|Two images of the 17-4 PH alloy powder at different scales]]

[[File:Layes type A and Layer type B.png|miniatura|destra|Example of two different type of Layes: A and B]]

Manufacturing and characterization of similar to foam steel components processed through selective laser melting

2020-02-03T11:49:24Z

BaldassareVitaggio:

'''Authors''': Fabrizia Caiazzo, Sabina Luisa Campanelli, Francesco Cardaropoli, Nicola Contuzzi, Vincenzo Sergi, Antonio Domenico Ludovico

'''Keywords''': Selective laser melting; Additive manufacturing; Stainless steel; Lightweight structures; Steel foam

'''Abstract''': The growing interest from the industry for lightweight metal components has driven the development of processes that would allow creating lightweight high melting point metals as steels, able to guarantee mechanical characteristics superior to existing foam (typically aluminium), without penalizing one of the characteristics that cell structures have: lightness.
Conventional manufacturing methods, such as casting, however, face difficulty in making complex periodic steel structures with designed shape and size and volume fraction. This study evaluates the manufacturability and performance of lightweight 17–4 PH steel components with spherical porosity fabricated via selective laser melting (SLM). Samples were designed and fabricated with the purpose to produce a structure similar to foam. Built samples were characterized in terms of dimensional accuracy, mechanical strength under compression and energy absorbed per unit mass. The designed structures have a designed relative density or volume
fraction ranging between 31.1 and 32.8%.

'''Purpose''': The purpose is to produce periodic cellular lattice structures that can be used to develop of structures with advanced or multifunctional performance for high value engineering products. These periodic lattice structures, however, currently face a higher manufacturing complexity and costs than the stochastic structures.

'''Methodology''': The first choise, very important, was made on the powder to be used.The periodic porous structures were made from a 17–4 PH alloy powder, which was purchased from Electro Optical System (EOS) GmbH, Germany. A powder with a mean particle size of 20 μm has been used in this investigation, and alloy chemical composition is listed in Table 1. The powder quality is important to reduce the content of impurities (oxygen, hydrogen and nitrogen), which might negatively affect mechanical properties of laser-sintered parts with phenomena like embrittlement. Figure 1 depicts the SEM images of the 17–4 PH alloy powder at different scales. The powder has a nearly spherical shape and smooth surfaces, which lead to a good flowability. Table 2 highlights 17–4 PH stainless steel mechanical properties. The method tried to design of similar to foam structures.To characterize the porous structures there are Several superimposed pore layers of two different types (type A and type B, Fig. 2).

'''Findings''': This paper has studied the possibility of manufacturing lightweight steel structures with spherical porosity adopting SLM technology. A stainless steel powder has employed, using an EOSINT M270 titanium version laser sintering system considering optimized parameters to have minimal content of porosity in laser-sintered parts. Different samples, having an effective average porosity ranging from 70.1 to 72.5% were successfully fabricated.

'''Limitations/benefits''': SLM has the capability of producing structures of complex freeform geometry. It has been demonstrated to manufacture cellular lattice structures with fine features, showing a great potential to make advanced lightweight structures and products that are highly desired by engineering sectors such as aerospace, automotive and medical industries. However, SLM requires support structure to build an overhang section if its angle from the horizontal is less than a certain degree. This introduces design and manufacturing complications for the SLM of lightweight cellular structures and engineering components. The cellular lattice structures with a large unit cell size or low strut angles from the horizontal (usually lower than 30°) could not be built using the SLM process because overhanging struts led to the occurrence of serious deformation.

'''Link''': https://link.springer.com/article/10.1007/s00170-017-0311-4

[[Utente:BaldassareVitaggio|BaldassareVitaggio]]

'''Graphical abstract'''

[[File:Images of the 17-4 PH alloy powder .png|miniatura|sinistra|Two images of the 17-4 PH alloy powder at different scales]]

[[File:Layes type A and Layer type B.png|miniatura|destra|Example of two different type of Layes: A and B]]

Selective Laser Melting

2020-02-03T11:44:32Z

BaldassareVitaggio:

[[Process Optimization]]

[[Manufacturing and characterization of similar to foam steel components processed through selective laser melting]]

[[Additive manufacturing by means of laser-aided directed metal deposition of 2024 aluminium powder]]

Additive manufacturing by means of laser-aided directed metal deposition of 2024 aluminium powder

2020-02-03T11:43:25Z

BaldassareVitaggio:

'''Authors''': Fabrizia Caiazzo, Vittorio Alfieri, Paolo Argenio and Vincenzo Sergi

'''Keywords''': Directed metal deposition, aluminium alloy, additive manufacturing, optimization, microstructures

'''Abstract''': Directed metal deposition by means of laser beam is investigated in this article. The process is receiving increasingly interest in the frame of additive manufacturing to the purpose of maintenance, repair and overhaul of condemned products when severe conditions hindering the working order have been experienced. Minimal distortion, reduced heataffected zones and better surface quality are benefited in comparison with conventional techniques. Namely, metal feeding of 2024 aluminium powder is considered to produce clad traces on 2024 aluminium plates, aiming to give grounds for repairing damaged real components using materials with same or similar features with respect to the parent metal. A fibre-delivered disc laser and a three-way feeding nozzle are used. The responses are discussed in terms of geometry, microstructure and microhardness both in the fusion zone and in the heat-affected zone; the optimization is conducted via desirability functions, based on proper technical constraints upon numerical modelling. Reparation of real parts, where cracks are machined to produce V-grooves to be filled, is aimed.

'''Purpose''': The process is receiving increasingly interest in the frame of additive manufacturing to the purpose of maintenance, repair and overhaul of condemned products when severe conditions hindering the working order have been experienced.

'''Methodology''': A laser beam is used as focused heat source to scan the surface, thus creating a melting pool over an existing substrate. Since metal impinging the pool is fed concurrently (i.e. in singlestage processing) in the form of wire or loose powder,5 a deposited metal trace results, with metallurgical bonding to the substrate thanks to fusion and diffusion.

'''Findings''': The aspect and the corresponding macrographs in the transverse cross-section have been discussed for each processing condition (Table 3). Successful cladding resulted, based on visual inspections; shielding is deemed to be effective, no cracks neither macropores resulted on the surface. Nevertheless, a number of micropores, ranging in size from 10 to 75mm on average, have been found (Figure 5). One may assume this would not result in rejection of parts at quality checks. Usual international or customer standards for quality in laser welding30 are borrowed, since no specific regulations are available at present for DMD.

'''Benefits''': Minimal distortion of the workpiece, reduced heataffected zones (HAZs) and better surface quality are benefited in laser-aided DMD in comparison with conventional coating and repairing techniques such as arc welding and plasma spraying.

'''Limitations''': According to the trend of microhardness in the cross-section, softening is experienced in both the HAZ and the fusion zone, due to overaging with coalescence of dispersoids in the former and precipitation to grain boundaries in the latter, with respect to parent metal in T3 state.

'''Practical implications''': A condition with 2.5 kW laser power, 420 mm min21 processing speed is suggested for given feeding rate of 3 g min21 and 3 mm beam diameter, which is deemed to be robust, given the shape of the response surface of the overall desirability.

'''Link''':https://journals.sagepub.com/doi/full/10.1177/1687814017714982

'''Full Reference''' : CAIAZZO, Fabrizia, et al. Produzione additiva mediante deposizione metallica diretta al laser di polvere di alluminio 2024: studio e ottimizzazione. Progressi nell'ingegneria meccanica , 2017, 9.8: 1687814017714982.

[[Utente:BaldassareVitaggio|BaldassareVitaggio]]

'''Graphical abstract'''

[[File:Transverse cross-section.png|miniatura|sinistra|Trace aspects and corresponding samples of transverse cross-section for each processing condition]]

[[File:Micropores in the fusion zone.png|miniatura|destra|Micropores in the fusion zone;central condition of the plan(2.5kW laser power,400mm/min speed)]]

Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique

2020-02-03T11:42:05Z

BaldassareVitaggio:

'''Authors''': Massimiliano Annoni, Hermes Giberti, Matteo Strano

'''Keywords''': Direct metal deposition, Fused deposition modeling, Metal injection molding, Parallel kinematics

'''Abstract''': A new extrusion-based additive manufacturing technique is described in this paper together with the main components of the machine capable of carrying out the process. Innovative characteristics of the machine are the fixed extrusion head and the workpiece moving thanks to a 5-axis parallel kinematics handling system, allowing the capability of inclining the part during the material deposition and consequently avoiding support structures. The extrusion head and nozzle have been designed in order to be able to extrude high viscosity mixtures with low polymeric content. Preliminary tests prove that a good final density can be obtained after de-binding and sintering and that it is possible to achieve a good bonding of extruded and deposited wires in case of AISI 630 stainless steel.

'''Purpose''': This paper describes the feasibility study of a new additive manufacturing (AM) technique based on extrusion of a feedstock made of metallic (or ceramic) particles and a polymeric binder.

'''Design, benefits and limitations''': The main innovations introduced with the extrusion-based AM system presented in this paper are:

-Parallel kinematics work table:

An extrusion-based system equipped with a parallel kinematics 5-axis work table is proposed in this paper, which is unprecedented, at least to the authors’ knowledge. The motivations for this innovative design are: x The extrusion head is stationary, which is an advantage in terms of positioning accuracy since the head is heavy (about 25 kg) and powerful (power = 3 kW; maximum injection pressure = 134 MPa); x Parallel kinematics allows high positioning accuracy of the TCP (tool center point); x The 5-axis work table orientation allows a better surface quality and limits the need for workpiece supports during the deposition process.

-Extrusion Head:

In this Extrusion Head a plasticizing screw, positioned at 45° with respect to the vertical direction, continuously rotates and loads the injection cylinder with heated feedstock. A vertical piston moves and pressurizes the heated feedstock through the injection nozzle. The diameter of the piston is 14 mm. This configuration allows for continuity and stability of the extrusion process and large extrusion force, i.e. the possibility of extruding highly viscous fluids through small nozzle exit diameters. The injection pressure on the heated material upstream the nozzle can be set at a very high value, up to 140 MPa. The maximum amount of material that can be deposited during one single piston stroke is 9000 mm3 . If a 0.6 mm diameter wire is extruded, an approximate wire length of 32000 mm can be deposited before recharging the injection cylinder.

-Extrusion nozzles:

The nozzle design is even more important in the proposed system than in conventional FDM due to the high pressure required by the extrusion (from 10 to 140 MPa). Three different nozzle designs have been prepared and tested (Figure 5): x Nozzle A: convergent-divergent profile, used in injection molding, suited for relatively large wire diameters and aimed at minimizing the pressure drops inside the nozzle; x Nozzle B: convergent-parallel profile, suited for medium wire diameters, aimed at stabilizing the direction of the outgoing viscous flow. The calibrated part of the nozzle makes it suitable for controlling the wire diameter; x Nozzle C: convergent-stepped profile, suited for small wire diameters, aimed at reducing the wire diameter while maintaining low pressure drops. Since the calibrated part of the nozzle is shorter that the nozzle B one, swelling is more likely to occur.

-Extruded materials:

Two types of commercial MIM feedstock based on AISI 630 stainless steel powders (nominal median particle size = 13 Pm) and zirconia (nominal median particle size = 0.6 Pm) were preliminary tested.

-Hybrid manufacturing :

The configuration of the presented AM machine is suitable for hosting also a milling head on board of the top plate.

'''Findings''': The test described in this paper allowed to screen out some preliminary designs for extrusion nozzles and to verify the role of the binder percentage on the process capability. The possibility to bond the deposited wires after sintering was demonstrated on AISI 630, while zirconia seems to need a higher binder percentage to adhere during the deposition. Obtained material density is good, even if porosity exists, mainly for AISI 630 when sintered in argon instead of hydrogen. Future studies will be devoted to fully develop the proposed process/system.

'''Link''': https://www.sciencedirect.com/science/article/pii/S2351978916300919

'''Full Reference''': ANNONI, Massimiliano; GIBERTI, Hermes; STRANO, Matteo. Feasibility study of an extrusion-based direct metal additive manufacturing technique. Procedia Manufacturing, 2016, 5: 916-927.

[[Utente:BaldassareVitaggio|BaldassareVitaggio]]

'''Graphical abstract'''

[[File:3D printer conceptual design.png|miniatura|centro|3D printer conceptual design where it's possible to see: extrusion head,nozzle and work table]]

Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique

2020-02-03T11:41:11Z

BaldassareVitaggio:

'''Authors''': Massimiliano Annoni, Hermes Giberti, Matteo Strano

'''Keywords''': Direct metal deposition, Fused deposition modeling, Metal injection molding, Parallel kinematics

'''Abstract''': A new extrusion-based additive manufacturing technique is described in this paper together with the main components of the machine capable of carrying out the process. Innovative characteristics of the machine are the fixed extrusion head and the workpiece moving thanks to a 5-axis parallel kinematics handling system, allowing the capability of inclining the part during the material deposition and consequently avoiding support structures. The extrusion head and nozzle have been designed in order to be able to extrude high viscosity mixtures with low polymeric content. Preliminary tests prove that a good final density can be obtained after de-binding and sintering and that it is possible to achieve a good bonding of extruded and deposited wires in case of AISI 630 stainless steel.

'''Purpose''': This paper describes the feasibility study of a new additive manufacturing (AM) technique based on extrusion of a feedstock made of metallic (or ceramic) particles and a polymeric binder.

'''Design, benefits and limitations''': The main innovations introduced with the extrusion-based AM system presented in this paper are:

-Parallel kinematics work table:

An extrusion-based system equipped with a parallel kinematics 5-axis work table is proposed in this paper, which is unprecedented, at least to the authors’ knowledge. The motivations for this innovative design are: x The extrusion head is stationary, which is an advantage in terms of positioning accuracy since the head is heavy (about 25 kg) and powerful (power = 3 kW; maximum injection pressure = 134 MPa); x Parallel kinematics allows high positioning accuracy of the TCP (tool center point); x The 5-axis work table orientation allows a better surface quality and limits the need for workpiece supports during the deposition process.

-Extrusion Head:

In this Extrusion Head a plasticizing screw, positioned at 45° with respect to the vertical direction, continuously rotates and loads the injection cylinder with heated feedstock. A vertical piston moves and pressurizes the heated feedstock through the injection nozzle. The diameter of the piston is 14 mm. This configuration allows for continuity and stability of the extrusion process and large extrusion force, i.e. the possibility of extruding highly viscous fluids through small nozzle exit diameters. The injection pressure on the heated material upstream the nozzle can be set at a very high value, up to 140 MPa. The maximum amount of material that can be deposited during one single piston stroke is 9000 mm3 . If a 0.6 mm diameter wire is extruded, an approximate wire length of 32000 mm can be deposited before recharging the injection cylinder.

-Extrusion nozzles:

The nozzle design is even more important in the proposed system than in conventional FDM due to the high pressure required by the extrusion (from 10 to 140 MPa). Three different nozzle designs have been prepared and tested (Figure 5): x Nozzle A: convergent-divergent profile, used in injection molding, suited for relatively large wire diameters and aimed at minimizing the pressure drops inside the nozzle; x Nozzle B: convergent-parallel profile, suited for medium wire diameters, aimed at stabilizing the direction of the outgoing viscous flow. The calibrated part of the nozzle makes it suitable for controlling the wire diameter; x Nozzle C: convergent-stepped profile, suited for small wire diameters, aimed at reducing the wire diameter while maintaining low pressure drops. Since the calibrated part of the nozzle is shorter that the nozzle B one, swelling is more likely to occur.

-Extruded materials:

Two types of commercial MIM feedstock based on AISI 630 stainless steel powders (nominal median particle size = 13 Pm) and zirconia (nominal median particle size = 0.6 Pm) were preliminary tested.

-Hybrid manufacturing :

The configuration of the presented AM machine is suitable for hosting also a milling head on board of the top plate.

'''Findings''': The test described in this paper allowed to screen out some preliminary designs for extrusion nozzles and to verify the role of the binder percentage on the process capability. The possibility to bond the deposited wires after sintering was demonstrated on AISI 630, while zirconia seems to need a higher binder percentage to adhere during the deposition. Obtained material density is good, even if porosity exists, mainly for AISI 630 when sintered in argon instead of hydrogen. Future studies will be devoted to fully develop the proposed process/system.

'''Link''': https://www.sciencedirect.com/science/article/pii/S2351978916300919

'''Full Reference''': ANNONI, Massimiliano; GIBERTI, Hermes; STRANO, Matteo. Feasibility study of an extrusion-based direct metal additive manufacturing technique. Procedia Manufacturing, 2016, 5: 916-927.

[[BaldassareVitaggio|Utente:BaldassareVitaggio]]

'''Graphical abstract'''

[[File:3D printer conceptual design.png|miniatura|centro|3D printer conceptual design where it's possible to see: extrusion head,nozzle and work table]]

Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique

2020-02-03T11:38:38Z

BaldassareVitaggio:

'''Authors''': Massimiliano Annoni, Hermes Giberti, Matteo Strano

'''Keywords''': Direct metal deposition, Fused deposition modeling, Metal injection molding, Parallel kinematics

'''Abstract''': A new extrusion-based additive manufacturing technique is described in this paper together with the main components of the machine capable of carrying out the process. Innovative characteristics of the machine are the fixed extrusion head and the workpiece moving thanks to a 5-axis parallel kinematics handling system, allowing the capability of inclining the part during the material deposition and consequently avoiding support structures. The extrusion head and nozzle have been designed in order to be able to extrude high viscosity mixtures with low polymeric content. Preliminary tests prove that a good final density can be obtained after de-binding and sintering and that it is possible to achieve a good bonding of extruded and deposited wires in case of AISI 630 stainless steel.

'''Purpose''': This paper describes the feasibility study of a new additive manufacturing (AM) technique based on extrusion of a feedstock made of metallic (or ceramic) particles and a polymeric binder.

'''Design, benefits and limitations''': The main innovations introduced with the extrusion-based AM system presented in this paper are:

-Parallel kinematics work table:

An extrusion-based system equipped with a parallel kinematics 5-axis work table is proposed in this paper, which is unprecedented, at least to the authors’ knowledge. The motivations for this innovative design are: x The extrusion head is stationary, which is an advantage in terms of positioning accuracy since the head is heavy (about 25 kg) and powerful (power = 3 kW; maximum injection pressure = 134 MPa); x Parallel kinematics allows high positioning accuracy of the TCP (tool center point); x The 5-axis work table orientation allows a better surface quality and limits the need for workpiece supports during the deposition process.

-Extrusion Head:

In this Extrusion Head a plasticizing screw, positioned at 45° with respect to the vertical direction, continuously rotates and loads the injection cylinder with heated feedstock. A vertical piston moves and pressurizes the heated feedstock through the injection nozzle. The diameter of the piston is 14 mm. This configuration allows for continuity and stability of the extrusion process and large extrusion force, i.e. the possibility of extruding highly viscous fluids through small nozzle exit diameters. The injection pressure on the heated material upstream the nozzle can be set at a very high value, up to 140 MPa. The maximum amount of material that can be deposited during one single piston stroke is 9000 mm3 . If a 0.6 mm diameter wire is extruded, an approximate wire length of 32000 mm can be deposited before recharging the injection cylinder.

-Extrusion nozzles:

The nozzle design is even more important in the proposed system than in conventional FDM due to the high pressure required by the extrusion (from 10 to 140 MPa). Three different nozzle designs have been prepared and tested (Figure 5): x Nozzle A: convergent-divergent profile, used in injection molding, suited for relatively large wire diameters and aimed at minimizing the pressure drops inside the nozzle; x Nozzle B: convergent-parallel profile, suited for medium wire diameters, aimed at stabilizing the direction of the outgoing viscous flow. The calibrated part of the nozzle makes it suitable for controlling the wire diameter; x Nozzle C: convergent-stepped profile, suited for small wire diameters, aimed at reducing the wire diameter while maintaining low pressure drops. Since the calibrated part of the nozzle is shorter that the nozzle B one, swelling is more likely to occur.

-Extruded materials:

Two types of commercial MIM feedstock based on AISI 630 stainless steel powders (nominal median particle size = 13 Pm) and zirconia (nominal median particle size = 0.6 Pm) were preliminary tested.

-Hybrid manufacturing :

The configuration of the presented AM machine is suitable for hosting also a milling head on board of the top plate.

'''Findings''': The test described in this paper allowed to screen out some preliminary designs for extrusion nozzles and to verify the role of the binder percentage on the process capability. The possibility to bond the deposited wires after sintering was demonstrated on AISI 630, while zirconia seems to need a higher binder percentage to adhere during the deposition. Obtained material density is good, even if porosity exists, mainly for AISI 630 when sintered in argon instead of hydrogen. Future studies will be devoted to fully develop the proposed process/system.

'''Link''': https://www.sciencedirect.com/science/article/pii/S2351978916300919

'''Full Reference''': ANNONI, Massimiliano; GIBERTI, Hermes; STRANO, Matteo. Feasibility study of an extrusion-based direct metal additive manufacturing technique. Procedia Manufacturing, 2016, 5: 916-927.

[[Utente:BaldassareVitaggio]]

'''Graphical abstract'''

[[File:3D printer conceptual design.png|miniatura|centro|3D printer conceptual design where it's possible to see: extrusion head,nozzle and work table]]

Additive manufacturing by means of laser-aided directed metal deposition of 2024 aluminium powder

2020-02-03T11:35:21Z

BaldassareVitaggio:

'''Authors''': Fabrizia Caiazzo, Vittorio Alfieri, Paolo Argenio and Vincenzo Sergi

'''Keywords''': Directed metal deposition, aluminium alloy, additive manufacturing, optimization, microstructures

'''Abstract''': Directed metal deposition by means of laser beam is investigated in this article. The process is receiving increasingly interest in the frame of additive manufacturing to the purpose of maintenance, repair and overhaul of condemned products when severe conditions hindering the working order have been experienced. Minimal distortion, reduced heataffected zones and better surface quality are benefited in comparison with conventional techniques. Namely, metal feeding of 2024 aluminium powder is considered to produce clad traces on 2024 aluminium plates, aiming to give grounds for repairing damaged real components using materials with same or similar features with respect to the parent metal. A fibre-delivered disc laser and a three-way feeding nozzle are used. The responses are discussed in terms of geometry, microstructure and microhardness both in the fusion zone and in the heat-affected zone; the optimization is conducted via desirability functions, based on proper technical constraints upon numerical modelling. Reparation of real parts, where cracks are machined to produce V-grooves to be filled, is aimed.

'''Purpose''': The process is receiving increasingly interest in the frame of additive manufacturing to the purpose of maintenance, repair and overhaul of condemned products when severe conditions hindering the working order have been experienced.

'''Methodology''': A laser beam is used as focused heat source to scan the surface, thus creating a melting pool over an existing substrate. Since metal impinging the pool is fed concurrently (i.e. in singlestage processing) in the form of wire or loose powder,5 a deposited metal trace results, with metallurgical bonding to the substrate thanks to fusion and diffusion.

'''Findings''': The aspect and the corresponding macrographs in the transverse cross-section have been discussed for each processing condition (Table 3). Successful cladding resulted, based on visual inspections; shielding is deemed to be effective, no cracks neither macropores resulted on the surface. Nevertheless, a number of micropores, ranging in size from 10 to 75mm on average, have been found (Figure 5). One may assume this would not result in rejection of parts at quality checks. Usual international or customer standards for quality in laser welding30 are borrowed, since no specific regulations are available at present for DMD.

'''Benefits''': Minimal distortion of the workpiece, reduced heataffected zones (HAZs) and better surface quality are benefited in laser-aided DMD in comparison with conventional coating and repairing techniques such as arc welding and plasma spraying.

'''Limitations''': According to the trend of microhardness in the cross-section, softening is experienced in both the HAZ and the fusion zone, due to overaging with coalescence of dispersoids in the former and precipitation to grain boundaries in the latter, with respect to parent metal in T3 state.

'''Practical implications''': A condition with 2.5 kW laser power, 420 mm min21 processing speed is suggested for given feeding rate of 3 g min21 and 3 mm beam diameter, which is deemed to be robust, given the shape of the response surface of the overall desirability.

'''Link''':https://journals.sagepub.com/doi/full/10.1177/1687814017714982

'''Full Reference''' : CAIAZZO, Fabrizia, et al. Produzione additiva mediante deposizione metallica diretta al laser di polvere di alluminio 2024: studio e ottimizzazione. Progressi nell'ingegneria meccanica , 2017, 9.8: 1687814017714982.

'''Graphical abstract'''

[[File:Transverse cross-section.png|miniatura|sinistra|Trace aspects and corresponding samples of transverse cross-section for each processing condition]]

[[File:Micropores in the fusion zone.png|miniatura|destra|Micropores in the fusion zone;central condition of the plan(2.5kW laser power,400mm/min speed)]]

Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique

2020-02-03T11:32:07Z

BaldassareVitaggio:

'''Authors''': Massimiliano Annoni, Hermes Giberti, Matteo Strano

'''Keywords''': Direct metal deposition, Fused deposition modeling, Metal injection molding, Parallel kinematics

'''Abstract''': A new extrusion-based additive manufacturing technique is described in this paper together with the main components of the machine capable of carrying out the process. Innovative characteristics of the machine are the fixed extrusion head and the workpiece moving thanks to a 5-axis parallel kinematics handling system, allowing the capability of inclining the part during the material deposition and consequently avoiding support structures. The extrusion head and nozzle have been designed in order to be able to extrude high viscosity mixtures with low polymeric content. Preliminary tests prove that a good final density can be obtained after de-binding and sintering and that it is possible to achieve a good bonding of extruded and deposited wires in case of AISI 630 stainless steel.

'''Purpose''': This paper describes the feasibility study of a new additive manufacturing (AM) technique based on extrusion of a feedstock made of metallic (or ceramic) particles and a polymeric binder.

'''Design, benefits and limitations''': The main innovations introduced with the extrusion-based AM system presented in this paper are:

-Parallel kinematics work table:

An extrusion-based system equipped with a parallel kinematics 5-axis work table is proposed in this paper, which is unprecedented, at least to the authors’ knowledge. The motivations for this innovative design are: x The extrusion head is stationary, which is an advantage in terms of positioning accuracy since the head is heavy (about 25 kg) and powerful (power = 3 kW; maximum injection pressure = 134 MPa); x Parallel kinematics allows high positioning accuracy of the TCP (tool center point); x The 5-axis work table orientation allows a better surface quality and limits the need for workpiece supports during the deposition process.

-Extrusion Head:

In this Extrusion Head a plasticizing screw, positioned at 45° with respect to the vertical direction, continuously rotates and loads the injection cylinder with heated feedstock. A vertical piston moves and pressurizes the heated feedstock through the injection nozzle. The diameter of the piston is 14 mm. This configuration allows for continuity and stability of the extrusion process and large extrusion force, i.e. the possibility of extruding highly viscous fluids through small nozzle exit diameters. The injection pressure on the heated material upstream the nozzle can be set at a very high value, up to 140 MPa. The maximum amount of material that can be deposited during one single piston stroke is 9000 mm3 . If a 0.6 mm diameter wire is extruded, an approximate wire length of 32000 mm can be deposited before recharging the injection cylinder.

-Extrusion nozzles:

The nozzle design is even more important in the proposed system than in conventional FDM due to the high pressure required by the extrusion (from 10 to 140 MPa). Three different nozzle designs have been prepared and tested (Figure 5): x Nozzle A: convergent-divergent profile, used in injection molding, suited for relatively large wire diameters and aimed at minimizing the pressure drops inside the nozzle; x Nozzle B: convergent-parallel profile, suited for medium wire diameters, aimed at stabilizing the direction of the outgoing viscous flow. The calibrated part of the nozzle makes it suitable for controlling the wire diameter; x Nozzle C: convergent-stepped profile, suited for small wire diameters, aimed at reducing the wire diameter while maintaining low pressure drops. Since the calibrated part of the nozzle is shorter that the nozzle B one, swelling is more likely to occur.

-Extruded materials:

Two types of commercial MIM feedstock based on AISI 630 stainless steel powders (nominal median particle size = 13 Pm) and zirconia (nominal median particle size = 0.6 Pm) were preliminary tested.

-Hybrid manufacturing :

The configuration of the presented AM machine is suitable for hosting also a milling head on board of the top plate.

'''Findings''': The test described in this paper allowed to screen out some preliminary designs for extrusion nozzles and to verify the role of the binder percentage on the process capability. The possibility to bond the deposited wires after sintering was demonstrated on AISI 630, while zirconia seems to need a higher binder percentage to adhere during the deposition. Obtained material density is good, even if porosity exists, mainly for AISI 630 when sintered in argon instead of hydrogen. Future studies will be devoted to fully develop the proposed process/system.

'''Link''': https://www.sciencedirect.com/science/article/pii/S2351978916300919

'''Full Reference''': ANNONI, Massimiliano; GIBERTI, Hermes; STRANO, Matteo. Feasibility study of an extrusion-based direct metal additive manufacturing technique. Procedia Manufacturing, 2016, 5: 916-927.

'''User:BaldassareVitaggio'''

'''Graphical abstract'''

[[File:3D printer conceptual design.png|miniatura|centro|3D printer conceptual design where it's possible to see: extrusion head,nozzle and work table]]

Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique

2020-02-03T11:30:02Z

BaldassareVitaggio:

'''Authors''': Massimiliano Annoni, Hermes Giberti, Matteo Strano

'''Keywords''': Direct metal deposition, Fused deposition modeling, Metal injection molding, Parallel kinematics

'''Abstract''': A new extrusion-based additive manufacturing technique is described in this paper together with the main components of the machine capable of carrying out the process. Innovative characteristics of the machine are the fixed extrusion head and the workpiece moving thanks to a 5-axis parallel kinematics handling system, allowing the capability of inclining the part during the material deposition and consequently avoiding support structures. The extrusion head and nozzle have been designed in order to be able to extrude high viscosity mixtures with low polymeric content. Preliminary tests prove that a good final density can be obtained after de-binding and sintering and that it is possible to achieve a good bonding of extruded and deposited wires in case of AISI 630 stainless steel.

'''Purpose''': This paper describes the feasibility study of a new additive manufacturing (AM) technique based on extrusion of a feedstock made of metallic (or ceramic) particles and a polymeric binder.

'''Design, benefits and limitations''': The main innovations introduced with the extrusion-based AM system presented in this paper are:

-Parallel kinematics work table:

An extrusion-based system equipped with a parallel kinematics 5-axis work table is proposed in this paper, which is unprecedented, at least to the authors’ knowledge. The motivations for this innovative design are: x The extrusion head is stationary, which is an advantage in terms of positioning accuracy since the head is heavy (about 25 kg) and powerful (power = 3 kW; maximum injection pressure = 134 MPa); x Parallel kinematics allows high positioning accuracy of the TCP (tool center point); x The 5-axis work table orientation allows a better surface quality and limits the need for workpiece supports during the deposition process.

-Extrusion Head:

In this Extrusion Head a plasticizing screw, positioned at 45° with respect to the vertical direction, continuously rotates and loads the injection cylinder with heated feedstock. A vertical piston moves and pressurizes the heated feedstock through the injection nozzle. The diameter of the piston is 14 mm. This configuration allows for continuity and stability of the extrusion process and large extrusion force, i.e. the possibility of extruding highly viscous fluids through small nozzle exit diameters. The injection pressure on the heated material upstream the nozzle can be set at a very high value, up to 140 MPa. The maximum amount of material that can be deposited during one single piston stroke is 9000 mm3 . If a 0.6 mm diameter wire is extruded, an approximate wire length of 32000 mm can be deposited before recharging the injection cylinder.

-Extrusion nozzles:

The nozzle design is even more important in the proposed system than in conventional FDM due to the high pressure required by the extrusion (from 10 to 140 MPa). Three different nozzle designs have been prepared and tested (Figure 5): x Nozzle A: convergent-divergent profile, used in injection molding, suited for relatively large wire diameters and aimed at minimizing the pressure drops inside the nozzle; x Nozzle B: convergent-parallel profile, suited for medium wire diameters, aimed at stabilizing the direction of the outgoing viscous flow. The calibrated part of the nozzle makes it suitable for controlling the wire diameter; x Nozzle C: convergent-stepped profile, suited for small wire diameters, aimed at reducing the wire diameter while maintaining low pressure drops. Since the calibrated part of the nozzle is shorter that the nozzle B one, swelling is more likely to occur.

-Extruded materials:

Two types of commercial MIM feedstock based on AISI 630 stainless steel powders (nominal median particle size = 13 Pm) and zirconia (nominal median particle size = 0.6 Pm) were preliminary tested.

-Hybrid manufacturing :

The configuration of the presented AM machine is suitable for hosting also a milling head on board of the top plate.

'''Findings''': The test described in this paper allowed to screen out some preliminary designs for extrusion nozzles and to verify the role of the binder percentage on the process capability. The possibility to bond the deposited wires after sintering was demonstrated on AISI 630, while zirconia seems to need a higher binder percentage to adhere during the deposition. Obtained material density is good, even if porosity exists, mainly for AISI 630 when sintered in argon instead of hydrogen. Future studies will be devoted to fully develop the proposed process/system.

'''Link''': https://www.sciencedirect.com/science/article/pii/S2351978916300919

'''Full Reference''': ANNONI, Massimiliano; GIBERTI, Hermes; STRANO, Matteo. Feasibility study of an extrusion-based direct metal additive manufacturing technique. Procedia Manufacturing, 2016, 5: 916-927.

''' BaldassareVitaggio'''

'''Graphical abstract'''

[[File:3D printer conceptual design.png|miniatura|centro|3D printer conceptual design where it's possible to see: extrusion head,nozzle and work table]]

Hybrid Additive Manufacturing

2020-02-03T11:24:20Z

BaldassareVitaggio:

*[[Hybrid Additive Manufacturing SLM-CS]]

[[Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique]]

Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique

2020-02-03T11:13:51Z

BaldassareVitaggio:

'''Authors''': Massimiliano Annoni, Hermes Giberti, Matteo Strano

'''Keywords''': Direct metal deposition, Fused deposition modeling, Metal injection molding, Parallel kinematics

'''Abstract''': A new extrusion-based additive manufacturing technique is described in this paper together with the main components of the machine capable of carrying out the process. Innovative characteristics of the machine are the fixed extrusion head and the workpiece moving thanks to a 5-axis parallel kinematics handling system, allowing the capability of inclining the part during the material deposition and consequently avoiding support structures. The extrusion head and nozzle have been designed in order to be able to extrude high viscosity mixtures with low polymeric content. Preliminary tests prove that a good final density can be obtained after de-binding and sintering and that it is possible to achieve a good bonding of extruded and deposited wires in case of AISI 630 stainless steel.

'''Purpose''': This paper describes the feasibility study of a new additive manufacturing (AM) technique based on extrusion of a feedstock made of metallic (or ceramic) particles and a polymeric binder.

'''Design, benefits and limitations''': The main innovations introduced with the extrusion-based AM system presented in this paper are:

-Parallel kinematics work table:

An extrusion-based system equipped with a parallel kinematics 5-axis work table is proposed in this paper, which is unprecedented, at least to the authors’ knowledge. The motivations for this innovative design are: x The extrusion head is stationary, which is an advantage in terms of positioning accuracy since the head is heavy (about 25 kg) and powerful (power = 3 kW; maximum injection pressure = 134 MPa); x Parallel kinematics allows high positioning accuracy of the TCP (tool center point); x The 5-axis work table orientation allows a better surface quality and limits the need for workpiece supports during the deposition process.

-Extrusion Head:

In this Extrusion Head a plasticizing screw, positioned at 45° with respect to the vertical direction, continuously rotates and loads the injection cylinder with heated feedstock. A vertical piston moves and pressurizes the heated feedstock through the injection nozzle. The diameter of the piston is 14 mm. This configuration allows for continuity and stability of the extrusion process and large extrusion force, i.e. the possibility of extruding highly viscous fluids through small nozzle exit diameters. The injection pressure on the heated material upstream the nozzle can be set at a very high value, up to 140 MPa. The maximum amount of material that can be deposited during one single piston stroke is 9000 mm3 . If a 0.6 mm diameter wire is extruded, an approximate wire length of 32000 mm can be deposited before recharging the injection cylinder.

-Extrusion nozzles:

The nozzle design is even more important in the proposed system than in conventional FDM due to the high pressure required by the extrusion (from 10 to 140 MPa). Three different nozzle designs have been prepared and tested (Figure 5): x Nozzle A: convergent-divergent profile, used in injection molding, suited for relatively large wire diameters and aimed at minimizing the pressure drops inside the nozzle; x Nozzle B: convergent-parallel profile, suited for medium wire diameters, aimed at stabilizing the direction of the outgoing viscous flow. The calibrated part of the nozzle makes it suitable for controlling the wire diameter; x Nozzle C: convergent-stepped profile, suited for small wire diameters, aimed at reducing the wire diameter while maintaining low pressure drops. Since the calibrated part of the nozzle is shorter that the nozzle B one, swelling is more likely to occur.

-Extruded materials:

Two types of commercial MIM feedstock based on AISI 630 stainless steel powders (nominal median particle size = 13 Pm) and zirconia (nominal median particle size = 0.6 Pm) were preliminary tested.

-Hybrid manufacturing :

The configuration of the presented AM machine is suitable for hosting also a milling head on board of the top plate.

'''Findings''': The test described in this paper allowed to screen out some preliminary designs for extrusion nozzles and to verify the role of the binder percentage on the process capability. The possibility to bond the deposited wires after sintering was demonstrated on AISI 630, while zirconia seems to need a higher binder percentage to adhere during the deposition. Obtained material density is good, even if porosity exists, mainly for AISI 630 when sintered in argon instead of hydrogen. Future studies will be devoted to fully develop the proposed process/system.

'''Link''': https://www.sciencedirect.com/science/article/pii/S2351978916300919

'''Graphical abstract'''

[[File:3D printer conceptual design.png|miniatura|centro|3D printer conceptual design where it's possible to see: extrusion head,nozzle and work table]]

Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique

2020-02-03T10:19:47Z

BaldassareVitaggio:

'''Authors''': Massimiliano Annoni, Hermes Giberti, Matteo Strano

'''Keywords''': Direct metal deposition, Fused deposition modeling, Metal injection molding, Parallel kinematics

'''Abstract''': A new extrusion-based additive manufacturing technique is described in this paper together with the main components of the machine capable of carrying out the process. Innovative characteristics of the machine are the fixed extrusion head and the workpiece moving thanks to a 5-axis parallel kinematics handling system, allowing the capability of inclining the part during the material deposition and consequently avoiding support structures. The extrusion head and nozzle have been designed in order to be able to extrude high viscosity mixtures with low polymeric content. Preliminary tests prove that a good final density can be obtained after de-binding and sintering and that it is possible to achieve a good bonding of extruded and deposited wires in case of AISI 630 stainless steel.

'''Purpose''': This paper describes the feasibility study of a new additive manufacturing (AM) technique based on extrusion of a feedstock made of metallic (or ceramic) particles and a polymeric binder.

'''Design, benefits and limitations''': The main innovations introduced with the extrusion-based AM system presented in this paper are:

-Parallel kinematics work table:

An extrusion-based system equipped with a parallel kinematics 5-axis work table is proposed in this paper, which is unprecedented, at least to the authors’ knowledge. The motivations for this innovative design are: x The extrusion head is stationary, which is an advantage in terms of positioning accuracy since the head is heavy (about 25 kg) and powerful (power = 3 kW; maximum injection pressure = 134 MPa); x Parallel kinematics allows high positioning accuracy of the TCP (tool center point); x The 5-axis work table orientation allows a better surface quality and limits the need for workpiece supports during the deposition process.

-Extrusion Head:

In this Extrusion Head a plasticizing screw, positioned at 45° with respect to the vertical direction, continuously rotates and loads the injection cylinder with heated feedstock. A vertical piston moves and pressurizes the heated feedstock through the injection nozzle. The diameter of the piston is 14 mm. This configuration allows for continuity and stability of the extrusion process and large extrusion force, i.e. the possibility of extruding highly viscous fluids through small nozzle exit diameters. The injection pressure on the heated material upstream the nozzle can be set at a very high value, up to 140 MPa. The maximum amount of material that can be deposited during one single piston stroke is 9000 mm3 . If a 0.6 mm diameter wire is extruded, an approximate wire length of 32000 mm can be deposited before recharging the injection cylinder.

-Extrusion nozzles:

The nozzle design is even more important in the proposed system than in conventional FDM due to the high pressure required by the extrusion (from 10 to 140 MPa). Three different nozzle designs have been prepared and tested (Figure 5): x Nozzle A: convergent-divergent profile, used in injection molding, suited for relatively large wire diameters and aimed at minimizing the pressure drops inside the nozzle; x Nozzle B: convergent-parallel profile, suited for medium wire diameters, aimed at stabilizing the direction of the outgoing viscous flow. The calibrated part of the nozzle makes it suitable for controlling the wire diameter; x Nozzle C: convergent-stepped profile, suited for small wire diameters, aimed at reducing the wire diameter while maintaining low pressure drops. Since the calibrated part of the nozzle is shorter that the nozzle B one, swelling is more likely to occur.

-Extruded materials:

Two types of commercial MIM feedstock based on AISI 630 stainless steel powders (nominal median particle size = 13 Pm) and zirconia (nominal median particle size = 0.6 Pm) were preliminary tested.

-Hybrid manufacturing :

The configuration of the presented AM machine is suitable for hosting also a milling head on board of the top plate.

'''Findings''': The test described in this paper allowed to screen out some preliminary designs for extrusion nozzles and to verify the role of the binder percentage on the process capability. The possibility to bond the deposited wires after sintering was demonstrated on AISI 630, while zirconia seems to need a higher binder percentage to adhere during the deposition. Obtained material density is good, even if porosity exists, mainly for AISI 630 when sintered in argon instead of hydrogen. Future studies will be devoted to fully develop the proposed process/system.

'''Graphical abstract'''

[[File:3D printer conceptual design.png|miniatura|centro|3D printer conceptual design where it's possible to see: extrusion head,nozzle and work table]]

Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique

2020-02-03T10:19:06Z

BaldassareVitaggio:

'''Authors''': Massimiliano Annoni, Hermes Giberti, Matteo Strano

'''Keywords''': Direct metal deposition, Fused deposition modeling, Metal injection molding, Parallel kinematics

'''Abstract''': A new extrusion-based additive manufacturing technique is described in this paper together with the main components of the machine capable of carrying out the process. Innovative characteristics of the machine are the fixed extrusion head and the workpiece moving thanks to a 5-axis parallel kinematics handling system, allowing the capability of inclining the part during the material deposition and consequently avoiding support structures. The extrusion head and nozzle have been designed in order to be able to extrude high viscosity mixtures with low polymeric content. Preliminary tests prove that a good final density can be obtained after de-binding and sintering and that it is possible to achieve a good bonding of extruded and deposited wires in case of AISI 630 stainless steel.

'''Purpose''': This paper describes the feasibility study of a new additive manufacturing (AM) technique based on extrusion of a feedstock made of metallic (or ceramic) particles and a polymeric binder.

'''Design, benefits and limitations''': The main innovations introduced with the extrusion-based AM system presented in this paper are:

-Parallel kinematics work table:

An extrusion-based system equipped with a parallel kinematics 5-axis work table is proposed in this paper, which is unprecedented, at least to the authors’ knowledge. The motivations for this innovative design are: x The extrusion head is stationary, which is an advantage in terms of positioning accuracy since the head is heavy (about 25 kg) and powerful (power = 3 kW; maximum injection pressure = 134 MPa); x Parallel kinematics allows high positioning accuracy of the TCP (tool center point); x The 5-axis work table orientation allows a better surface quality and limits the need for workpiece supports during the deposition process.

-Extrusion Head:

In this Extrusion Head a plasticizing screw, positioned at 45° with respect to the vertical direction, continuously rotates and loads the injection cylinder with heated feedstock. A vertical piston moves and pressurizes the heated feedstock through the injection nozzle. The diameter of the piston is 14 mm. This configuration allows for continuity and stability of the extrusion process and large extrusion force, i.e. the possibility of extruding highly viscous fluids through small nozzle exit diameters. The injection pressure on the heated material upstream the nozzle can be set at a very high value, up to 140 MPa. The maximum amount of material that can be deposited during one single piston stroke is 9000 mm3 . If a 0.6 mm diameter wire is extruded, an approximate wire length of 32000 mm can be deposited before recharging the injection cylinder.

-Extrusion nozzles:

The nozzle design is even more important in the proposed system than in conventional FDM due to the high pressure required by the extrusion (from 10 to 140 MPa). Three different nozzle designs have been prepared and tested (Figure 5): x Nozzle A: convergent-divergent profile, used in injection molding, suited for relatively large wire diameters and aimed at minimizing the pressure drops inside the nozzle; x Nozzle B: convergent-parallel profile, suited for medium wire diameters, aimed at stabilizing the direction of the outgoing viscous flow. The calibrated part of the nozzle makes it suitable for controlling the wire diameter; x Nozzle C: convergent-stepped profile, suited for small wire diameters, aimed at reducing the wire diameter while maintaining low pressure drops. Since the calibrated part of the nozzle is shorter that the nozzle B one, swelling is more likely to occur.

-Extruded materials:

Two types of commercial MIM feedstock based on AISI 630 stainless steel powders (nominal median particle size = 13 Pm) and zirconia (nominal median particle size = 0.6 Pm) were preliminary tested.

-Hybrid manufacturing :

The configuration of the presented AM machine is suitable for hosting also a milling head on board of the top plate.

'''Findings''': The test described in this paper allowed to screen out some preliminary designs for extrusion nozzles and to verify the role of the binder percentage on the process capability. The possibility to bond the deposited wires after sintering was demonstrated on AISI 630, while zirconia seems to need a higher binder percentage to adhere during the deposition. Obtained material density is good, even if porosity exists, mainly for AISI 630 when sintered in argon instead of hydrogen. Future studies will be devoted to fully develop the proposed process/system.

'''Graphical abstract'''

[[File:3D printer conceptual design.png|miniatura|centro|3D printer conceptual design where it's possible to see: extrusion head,nozzle and work table]]

Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique

2020-02-03T10:17:37Z

BaldassareVitaggio: Creata pagina con "'''Authors''': Massimiliano Annoni, Hermes Giberti, Matteo Strano '''Keywords''': Direct metal deposition, Fused deposition modeling, Metal injection molding, Parallel kinema..."

'''Authors''': Massimiliano Annoni, Hermes Giberti, Matteo Strano

'''Keywords''': Direct metal deposition, Fused deposition modeling, Metal injection molding, Parallel kinematics

'''Abstract''': A new extrusion-based additive manufacturing technique is described in this paper together with the main components of the machine capable of carrying out the process. Innovative characteristics of the machine are the fixed extrusion head and the workpiece moving thanks to a 5-axis parallel kinematics handling system, allowing the capability of inclining the part during the material deposition and consequently avoiding support structures. The extrusion head and nozzle have been designed in order to be able to extrude high viscosity mixtures with low polymeric content. Preliminary tests prove that a good final density can be obtained after de-binding and sintering and that it is possible to achieve a good bonding of extruded and deposited wires in case of AISI 630 stainless steel.

'''Purpose''': This paper describes the feasibility study of a new additive manufacturing (AM) technique based on extrusion of a feedstock made of metallic (or ceramic) particles and a polymeric binder.

'''Design, benefits and limitations''': The main innovations introduced with the extrusion-based AM system presented in this paper are:
-Parallel kinematics work table:
An extrusion-based system equipped with a parallel kinematics 5-axis work table is proposed in this paper, which is unprecedented, at least to the authors’ knowledge. The motivations for this innovative design are: x The extrusion head is stationary, which is an advantage in terms of positioning accuracy since the head is heavy (about 25 kg) and powerful (power = 3 kW; maximum injection pressure = 134 MPa); x Parallel kinematics allows high positioning accuracy of the TCP (tool center point); x The 5-axis work table orientation allows a better surface quality and limits the need for workpiece supports during the deposition process.
-Extrusion Head
In this Extrusion Head a plasticizing screw, positioned at 45° with respect to the vertical direction, continuously rotates and loads the injection cylinder with heated feedstock. A vertical piston moves and pressurizes the heated feedstock through the injection nozzle. The diameter of the piston is 14 mm. This configuration allows for continuity and stability of the extrusion process and large extrusion force, i.e. the possibility of extruding highly viscous fluids through small nozzle exit diameters. The injection pressure on the heated material upstream the nozzle can be set at a very high value, up to 140 MPa. The maximum amount of material that can be deposited during one single piston stroke is 9000 mm3 . If a 0.6 mm diameter wire is extruded, an approximate wire length of 32000 mm can be deposited before recharging the injection cylinder.
-Extrusion nozzles
The nozzle design is even more important in the proposed system than in conventional FDM due to the high pressure required by the extrusion (from 10 to 140 MPa). Three different nozzle designs have been prepared and tested (Figure 5): x Nozzle A: convergent-divergent profile, used in injection molding, suited for relatively large wire diameters and aimed at minimizing the pressure drops inside the nozzle; x Nozzle B: convergent-parallel profile, suited for medium wire diameters, aimed at stabilizing the direction of the outgoing viscous flow. The calibrated part of the nozzle makes it suitable for controlling the wire diameter; x Nozzle C: convergent-stepped profile, suited for small wire diameters, aimed at reducing the wire diameter while maintaining low pressure drops. Since the calibrated part of the nozzle is shorter that the nozzle B one, swelling is more likely to occur.
-Extruded materials
Two types of commercial MIM feedstock based on AISI 630 stainless steel powders (nominal median particle size = 13 Pm) and zirconia (nominal median particle size = 0.6 Pm) were preliminary tested.
-Hybrid manufacturing
The configuration of the presented AM machine is suitable for hosting also a milling head on board of the top plate.

'''Findings''': The test described in this paper allowed to screen out some preliminary designs for extrusion nozzles and to verify the role of the binder percentage on the process capability. The possibility to bond the deposited wires after sintering was demonstrated on AISI 630, while zirconia seems to need a higher binder percentage to adhere during the deposition. Obtained material density is good, even if porosity exists, mainly for AISI 630 when sintered in argon instead of hydrogen. Future studies will be devoted to fully develop the proposed process/system.

'''Graphical abstract'''

[[File:3D printer conceptual design.png|miniatura|centro|3D printer conceptual design where it's possible to see: extrusion head,nozzle and work table]]

File:3D printer conceptual design.png

2020-02-03T10:16:24Z

BaldassareVitaggio:

3D printer conceptual design where it's possible to see:extrusion head,nozzle, work table

Direct Metal Deposition

2020-02-03T10:12:58Z

BaldassareVitaggio: Creata pagina con "Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique"

[[Feasibility Study of an Extrusion-based Direct Metal Additive Manufacturing Technique]]

Fused Deposition Modeling

2020-02-03T10:12:29Z

BaldassareVitaggio:

[[Education]]

[[Design for manufactoring]]

[[Validation study of an analytical model of FDM accuracy]]

[[Direct Metal Deposition]]

Manufacturing and characterization of similar to foam steel components processed through selective laser melting

2020-02-03T10:09:46Z

BaldassareVitaggio:

'''Authors''': Fabrizia Caiazzo, Sabina Luisa Campanelli, Francesco Cardaropoli, Nicola Contuzzi, Vincenzo Sergi, Antonio Domenico Ludovico

'''Keywords''': Selective laser melting; Additive manufacturing; Stainless steel; Lightweight structures; Steel foam

'''Abstract''': The growing interest from the industry for lightweight metal components has driven the development of processes that would allow creating lightweight high melting point metals as steels, able to guarantee mechanical characteristics superior to existing foam (typically aluminium), without penalizing one of the characteristics that cell structures have: lightness.
Conventional manufacturing methods, such as casting, however, face difficulty in making complex periodic steel structures with designed shape and size and volume fraction. This study evaluates the manufacturability and performance of lightweight 17–4 PH steel components with spherical porosity fabricated via selective laser melting (SLM). Samples were designed and fabricated with the purpose to produce a structure similar to foam. Built samples were characterized in terms of dimensional accuracy, mechanical strength under compression and energy absorbed per unit mass. The designed structures have a designed relative density or volume
fraction ranging between 31.1 and 32.8%.

'''Purpose''': The purpose is to produce periodic cellular lattice structures that can be used to develop of structures with advanced or multifunctional performance for high value engineering products. These periodic lattice structures, however, currently face a higher manufacturing complexity and costs than the stochastic structures.

'''Methodology''': The first choise, very important, was made on the powder to be used.The periodic porous structures were made from a 17–4 PH alloy powder, which was purchased from Electro Optical System (EOS) GmbH, Germany. A powder with a mean particle size of 20 μm has been used in this investigation, and alloy chemical composition is listed in Table 1. The powder quality is important to reduce the content of impurities (oxygen, hydrogen and nitrogen), which might negatively affect mechanical properties of laser-sintered parts with phenomena like embrittlement. Figure 1 depicts the SEM images of the 17–4 PH alloy powder at different scales. The powder has a nearly spherical shape and smooth surfaces, which lead to a good flowability. Table 2 highlights 17–4 PH stainless steel mechanical properties. The method tried to design of similar to foam structures.To characterize the porous structures there are Several superimposed pore layers of two different types (type A and type B, Fig. 2).

'''Findings''': This paper has studied the possibility of manufacturing lightweight steel structures with spherical porosity adopting SLM technology. A stainless steel powder has employed, using an EOSINT M270 titanium version laser sintering system considering optimized parameters to have minimal content of porosity in laser-sintered parts. Different samples, having an effective average porosity ranging from 70.1 to 72.5% were successfully fabricated.

'''Limitations/benefits''': SLM has the capability of producing structures of complex freeform geometry. It has been demonstrated to manufacture cellular lattice structures with fine features, showing a great potential to make advanced lightweight structures and products that are highly desired by engineering sectors such as aerospace, automotive and medical industries. However, SLM requires support structure to build an overhang section if its angle from the horizontal is less than a certain degree. This introduces design and manufacturing complications for the SLM of lightweight cellular structures and engineering components. The cellular lattice structures with a large unit cell size or low strut angles from the horizontal (usually lower than 30°) could not be built using the SLM process because overhanging struts led to the occurrence of serious deformation.

'''Link''': https://link.springer.com/article/10.1007/s00170-017-0311-4

'''Graphical abstract'''

[[File:Images of the 17-4 PH alloy powder .png|miniatura|sinistra|Two images of the 17-4 PH alloy powder at different scales]]

[[File:Layes type A and Layer type B.png|miniatura|destra|Example of two different type of Layes: A and B]]

File:Layes type A and Layer type B.png

2020-02-03T10:09:30Z

BaldassareVitaggio:

Example of two different type of Layes: A and B

File:Images of the 17-4 PH alloy powder .png

2020-02-03T10:07:20Z

BaldassareVitaggio:

Two images of the 17-4 PH alloy powder at different scales

Additive manufacturing by means of laser-aided directed metal deposition of 2024 aluminium powder

2020-02-03T10:01:51Z

BaldassareVitaggio:

'''Authors''': Fabrizia Caiazzo, Vittorio Alfieri, Paolo Argenio and Vincenzo Sergi

'''Keywords''': Directed metal deposition, aluminium alloy, additive manufacturing, optimization, microstructures

'''Abstract''': Directed metal deposition by means of laser beam is investigated in this article. The process is receiving increasingly interest in the frame of additive manufacturing to the purpose of maintenance, repair and overhaul of condemned products when severe conditions hindering the working order have been experienced. Minimal distortion, reduced heataffected zones and better surface quality are benefited in comparison with conventional techniques. Namely, metal feeding of 2024 aluminium powder is considered to produce clad traces on 2024 aluminium plates, aiming to give grounds for repairing damaged real components using materials with same or similar features with respect to the parent metal. A fibre-delivered disc laser and a three-way feeding nozzle are used. The responses are discussed in terms of geometry, microstructure and microhardness both in the fusion zone and in the heat-affected zone; the optimization is conducted via desirability functions, based on proper technical constraints upon numerical modelling. Reparation of real parts, where cracks are machined to produce V-grooves to be filled, is aimed.

'''Purpose''': The process is receiving increasingly interest in the frame of additive manufacturing to the purpose of maintenance, repair and overhaul of condemned products when severe conditions hindering the working order have been experienced.

'''Methodology''': A laser beam is used as focused heat source to scan the surface, thus creating a melting pool over an existing substrate. Since metal impinging the pool is fed concurrently (i.e. in singlestage processing) in the form of wire or loose powder,5 a deposited metal trace results, with metallurgical bonding to the substrate thanks to fusion and diffusion.

'''Findings''': The aspect and the corresponding macrographs in the transverse cross-section have been discussed for each processing condition (Table 3). Successful cladding resulted, based on visual inspections; shielding is deemed to be effective, no cracks neither macropores resulted on the surface. Nevertheless, a number of micropores, ranging in size from 10 to 75mm on average, have been found (Figure 5). One may assume this would not result in rejection of parts at quality checks. Usual international or customer standards for quality in laser welding30 are borrowed, since no specific regulations are available at present for DMD.

'''Benefits''': Minimal distortion of the workpiece, reduced heataffected zones (HAZs) and better surface quality are benefited in laser-aided DMD in comparison with conventional coating and repairing techniques such as arc welding and plasma spraying.

'''Limitations''': According to the trend of microhardness in the cross-section, softening is experienced in both the HAZ and the fusion zone, due to overaging with coalescence of dispersoids in the former and precipitation to grain boundaries in the latter, with respect to parent metal in T3 state.

'''Practical implications''': A condition with 2.5 kW laser power, 420 mm min21 processing speed is suggested for given feeding rate of 3 g min21 and 3 mm beam diameter, which is deemed to be robust, given the shape of the response surface of the overall desirability.

'''Link''':https://journals.sagepub.com/doi/full/10.1177/1687814017714982

'''Graphical abstract'''

[[File:Transverse cross-section.png|miniatura|sinistra|Trace aspects and corresponding samples of transverse cross-section for each processing condition]]

[[File:Micropores in the fusion zone.png|miniatura|destra|Micropores in the fusion zone;central condition of the plan(2.5kW laser power,400mm/min speed)]]

Additive manufacturing by means of laser-aided directed metal deposition of 2024 aluminium powder

2020-02-03T10:00:50Z

BaldassareVitaggio:

'''Authors''': Fabrizia Caiazzo, Vittorio Alfieri, Paolo Argenio and Vincenzo Sergi

'''Keywords''': Directed metal deposition, aluminium alloy, additive manufacturing, optimization, microstructures

'''Abstract''': Directed metal deposition by means of laser beam is investigated in this article. The process is receiving increasingly interest in the frame of additive manufacturing to the purpose of maintenance, repair and overhaul of condemned products when severe conditions hindering the working order have been experienced. Minimal distortion, reduced heataffected zones and better surface quality are benefited in comparison with conventional techniques. Namely, metal feeding of 2024 aluminium powder is considered to produce clad traces on 2024 aluminium plates, aiming to give grounds for repairing damaged real components using materials with same or similar features with respect to the parent metal. A fibre-delivered disc laser and a three-way feeding nozzle are used. The responses are discussed in terms of geometry, microstructure and microhardness both in the fusion zone and in the heat-affected zone; the optimization is conducted via desirability functions, based on proper technical constraints upon numerical modelling. Reparation of real parts, where cracks are machined to produce V-grooves to be filled, is aimed.

'''Purpose''': The process is receiving increasingly interest in the frame of additive manufacturing to the purpose of maintenance, repair and overhaul of condemned products when severe conditions hindering the working order have been experienced.

'''Methodology''': A laser beam is used as focused heat source to scan the surface, thus creating a melting pool over an existing substrate. Since metal impinging the pool is fed concurrently (i.e. in singlestage processing) in the form of wire or loose powder,5 a deposited metal trace results, with metallurgical bonding to the substrate thanks to fusion and diffusion.

'''Findings''': The aspect and the corresponding macrographs in the transverse cross-section have been discussed for each processing condition (Table 3). Successful cladding resulted, based on visual inspections; shielding is deemed to be effective, no cracks neither macropores resulted on the surface. Nevertheless, a number of micropores, ranging in size from 10 to 75mm on average, have been found (Figure 5). One may assume this would not result in rejection of parts at quality checks. Usual international or customer standards for quality in laser welding30 are borrowed, since no specific regulations are available at present for DMD.

'''Benefits''': Minimal distortion of the workpiece, reduced heataffected zones (HAZs) and better surface quality are benefited in laser-aided DMD in comparison with conventional coating and repairing techniques such as arc welding and plasma spraying.

'''Limitations''': According to the trend of microhardness in the cross-section, softening is experienced in both the HAZ and the fusion zone, due to overaging with coalescence of dispersoids in the former and precipitation to grain boundaries in the latter, with respect to parent metal in T3 state.

'''Practical implications''': A condition with 2.5 kW laser power, 420 mm min21 processing speed is suggested for given feeding rate of 3 g min21 and 3 mm beam diameter, which is deemed to be robust, given the shape of the response surface of the overall desirability.
'''Graphical abstract'''
[[File:Transverse cross-section.png|miniatura|sinistra|Trace aspects and corresponding samples of transverse cross-section for each processing condition]]
[[File:Micropores in the fusion zone.png|miniatura|destra|Micropores in the fusion zone;central condition of the plan(2.5kW laser power,400mm/min speed)]]

'''Link''':https://journals.sagepub.com/doi/full/10.1177/1687814017714982

File:Micropores in the fusion zone.png

2020-02-03T09:59:57Z

BaldassareVitaggio:

Micropores in the fusion zone;central condition of the plan(2.5kW laser power,400mm/min speed)

File:Transverse cross-section.png

2020-02-03T09:55:45Z

BaldassareVitaggio:

Trace aspects and corresponding samples of transverse cross-section for each processing condition

Finite element(FEM) modelling of Wire-Arc-Additive-Manufacturing process

2020-01-26T16:44:04Z

BaldassareVitaggio:

'''Authors''': Filippo Montevecchia, Giuseppe Venturinia, Antonio Scippaa , Gianni Campatellia

'''Keywords''': Welding; Finite element method (FEM); Additive manufacturing;

'''Abstract''': Wire-Arc-Additive-Manufacturing (WAAM) is an Additive-Manufacturing (AM) process, allowing to produce metal components layer by layer by means of Gas-Metal-Arc-Welding (GMAW) technology. The advantages of this technology are the capability to create large parts with a higher deposition rate with respect to other AM technologies. Despite these great benefits, WAAM components are affected by severe distortions and residual stresses issues. Finite element process simulation provides an efficient way to study mitigation strategies for such issues. In this paper, a WAAM modelling strategy is proposed based on a novel heat source model that takes into account the actual power distribution between filler and base materials. In order to prove the effectiveness of proposed modelling, an experimental validation is provided by comparing the measured distortions of a WAAM tests-case with the simulated ones, highlighting the accuracy of proposed model.

'''Purpose''': Simulate the WAAM process to test the effect of different deposition patterns on residual stresses field, optimizing the process

'''Methodology''': The heat transfer from the arc to the molten pool is simulated using a heat source model, which prescribes a heat generation per unit volume in the molten pool region. Material deposition is taken into account by means of specific elements activation algorithms. In this model the heat input is delivered over a moving double ellipsoid region according to a Gaussian distribution

'''Findings''': Proposed process modelling allows to accurately simulate the WAAM process, without the need to perform time-consuming tuning operations to identify heat source parameters.

'''Limitations''': There are some inaccuracies infact, percentage errors on the maximum displacements points are 2% and 26%. Despite the latter result may seem inaccurate, it should be considered that material data have been derived from literature, hence actual material behavior could be different from the model one.

'''Benefits''': Proposed modelling results are in general agreement with the experimental ones, allowing to achieve an higher accuracy with respect to the traditional technique

'''Link''': https://www.sciencedirect.com/science/article/pii/S2212827116309131

Finite element(FEM) modelling of Wire-Arc-Additive-Manufacturing process

2020-01-26T16:43:22Z

BaldassareVitaggio:

'''Authors''': Filippo Montevecchia, Giuseppe Venturinia, Antonio Scippaa , Gianni Campatellia

'''Keywords''': Welding; Finite element method (FEM); Additive manufacturing;

'''Abstract''': Wire-Arc-Additive-Manufacturing (WAAM) is an Additive-Manufacturing (AM) process, allowing to produce metal components layer by layer by means of Gas-Metal-Arc-Welding (GMAW) technology. The advantages of this technology are the capability to create large parts with a higher deposition rate with respect to other AM technologies. Despite these great benefits, WAAM components are affected by severe distortions and residual stresses issues. Finite element process simulation provides an efficient way to study mitigation strategies for such issues. In this paper, a WAAM modelling strategy is proposed based on a novel heat source model that takes into account the actual power distribution between filler and base materials. In order to prove the effectiveness of proposed modelling, an experimental validation is provided by comparing the measured distortions of a WAAM tests-case with the simulated ones, highlighting the accuracy of proposed model.

'''Purpose''': Simulate the WAAM process to test the effect of different deposition patterns on residual stresses field, optimizing the process

'''Methodology''': The heat transfer from the arc to the molten pool is simulated using a heat source model, which prescribes a heat generation per unit volume in the molten pool region. Material deposition is taken into account by means of specific elements activation algorithms. In this model the heat input is delivered over a moving double ellipsoid region according to a Gaussian distribution

'''Findings''': Proposed process modelling allows to accurately simulate the WAAM process, without the need to perform time-consuming tuning operations to identify heat source parameters.

'''Link''': https://www.sciencedirect.com/science/article/pii/S2212827116309131

'''Limitations''': There are some inaccuracies infact, percentage errors on the maximum displacements points are 2% and 26%. Despite the latter result may seem inaccurate, it should be considered that material data have been derived from literature, hence actual material behavior could be different from the model one.

'''Benefits''': Proposed modelling results are in general agreement with the experimental ones, allowing to achieve an higher accuracy with respect to the traditional technique

Finite element(FEM) modelling of Wire-Arc-Additive-Manufacturing process

2020-01-25T14:25:13Z

BaldassareVitaggio: Creata pagina con "'''Authors''': Filippo Montevecchia, Giuseppe Venturinia, Antonio Scippaa , Gianni Campatellia '''Keywords''': Welding; Finite element method (FEM); Additive manufacturing;..."

Wire Arc Additive Manifacturing

2020-01-25T14:23:54Z

BaldassareVitaggio:

*[[Finite element modelling of Wire-Arc-Additive-Manufacturing process]]
*[[Selection of optimal process parameters for wire arc additive manufacturing]]
*[[Cutting forces analysis in additive manufactured AISI H13 alloy]]
*[[Environmental and economic comparison between WAAM and machining]]
*[[Additive manufacturing by means of laser-aided directed metal deposition of 2024 aluminium powder]]
*[[Finite element(FEM) modelling of Wire-Arc-Additive-Manufacturing process]]

Manufacturing and characterization of similar to foam steel components processed through selective laser melting

2020-01-25T14:21:55Z

BaldassareVitaggio:

'''Authors''': Fabrizia Caiazzo, Sabina Luisa Campanelli, Francesco Cardaropoli, Nicola Contuzzi, Vincenzo Sergi, Antonio Domenico Ludovico

'''Keywords''': Selective laser melting; Additive manufacturing; Stainless steel; Lightweight structures; Steel foam

'''Abstract''': The growing interest from the industry for lightweight metal components has driven the development of processes that would allow creating lightweight high melting point metals as steels, able to guarantee mechanical characteristics superior to existing foam (typically aluminium), without penalizing one of the characteristics that cell structures have: lightness.
Conventional manufacturing methods, such as casting, however, face difficulty in making complex periodic steel structures with designed shape and size and volume fraction. This study evaluates the manufacturability and performance of lightweight 17–4 PH steel components with spherical porosity fabricated via selective laser melting (SLM). Samples were designed and fabricated with the purpose to produce a structure similar to foam. Built samples were characterized in terms of dimensional accuracy, mechanical strength under compression and energy absorbed per unit mass. The designed structures have a designed relative density or volume
fraction ranging between 31.1 and 32.8%.

'''Purpose''': The purpose is to produce periodic cellular lattice structures that can be used to develop of structures with advanced or multifunctional performance for high value engineering products. These periodic lattice structures, however, currently face a higher manufacturing complexity and costs than the stochastic structures.

'''Methodology''': The first choise, very important, was made on the powder to be used.The periodic porous structures were made from a 17–4 PH alloy powder, which was purchased from Electro Optical System (EOS) GmbH, Germany. A powder with a mean particle size of 20 μm has been used in this investigation, and alloy chemical composition is listed in Table 1. The powder quality is important to reduce the content of impurities (oxygen, hydrogen and nitrogen), which might negatively affect mechanical properties of laser-sintered parts with phenomena like embrittlement. Figure 1 depicts the SEM images of the 17–4 PH alloy powder at different scales. The powder has a nearly spherical shape and smooth surfaces, which lead to a good flowability. Table 2 highlights 17–4 PH stainless steel mechanical properties. The method tried to design of similar to foam structures.To characterize the porous structures there are Several superimposed pore layers of two different types (type A and type B, Fig. 2).

'''Findings''': This paper has studied the possibility of manufacturing lightweight steel structures with spherical porosity adopting SLM technology. A stainless steel powder has employed, using an EOSINT M270 titanium version laser sintering system considering optimized parameters to have minimal content of porosity in laser-sintered parts. Different samples, having an effective average porosity ranging from 70.1 to 72.5% were successfully fabricated.

'''Limitations/benefits''': SLM has the capability of producing structures of complex freeform geometry. It has been demonstrated to manufacture cellular lattice structures with fine features, showing a great potential to make advanced lightweight structures and products that are highly desired by engineering sectors such as aerospace, automotive and medical industries. However, SLM requires support structure to build an overhang section if its angle from the horizontal is less than a certain degree. This introduces design and manufacturing complications for the SLM of lightweight cellular structures and engineering components. The cellular lattice structures with a large unit cell size or low strut angles from the horizontal (usually lower than 30°) could not be built using the SLM process because overhanging struts led to the occurrence of serious deformation.

'''Link''': https://link.springer.com/article/10.1007/s00170-017-0311-4

Wire Arc Additive Manifacturing

2020-01-25T14:21:23Z

BaldassareVitaggio:

*[[Finite element modelling of Wire-Arc-Additive-Manufacturing process]]
*[[Selection of optimal process parameters for wire arc additive manufacturing]]
*[[Cutting forces analysis in additive manufactured AISI H13 alloy]]
*[[Environmental and economic comparison between WAAM and machining]]
*[[Additive manufacturing by means of laser-aided directed metal deposition of 2024 aluminium powder]]
*[[Finite element modelling of Wire-Arc-Additive-Manufacturing process]]

Manufacturing and characterization of similar to foam steel components processed through selective laser melting

2020-01-25T14:15:09Z

BaldassareVitaggio:

'''Title''': Manufacturing and characterization of similar to foam steel components processed through selective laser melting

'''Authors''': Fabrizia Caiazzo, Sabina Luisa Campanelli, Francesco Cardaropoli, Nicola Contuzzi, Vincenzo Sergi, Antonio Domenico Ludovico

'''Keywords''': Selective laser melting; Additive manufacturing; Stainless steel; Lightweight structures; Steel foam

'''Abstract''': The growing interest from the industry for lightweight metal components has driven the development of processes that would allow creating lightweight high melting point metals as steels, able to guarantee mechanical characteristics superior to existing foam (typically aluminium), without penalizing one of the characteristics that cell structures have: lightness.
Conventional manufacturing methods, such as casting, however, face difficulty in making complex periodic steel structures with designed shape and size and volume fraction. This study evaluates the manufacturability and performance of lightweight 17–4 PH steel components with spherical porosity fabricated via selective laser melting (SLM). Samples were designed and fabricated with the purpose to produce a structure similar to foam. Built samples were characterized in terms of dimensional accuracy, mechanical strength under compression and energy absorbed per unit mass. The designed structures have a designed relative density or volume
fraction ranging between 31.1 and 32.8%.

'''Purpose''': The purpose is to produce periodic cellular lattice structures that can be used to develop of structures with advanced or multifunctional performance for high value engineering products. These periodic lattice structures, however, currently face a higher manufacturing complexity and costs than the stochastic structures.

'''Methodology''': The first choise, very important, was made on the powder to be used.The periodic porous structures were made from a 17–4 PH alloy powder, which was purchased from Electro Optical System (EOS) GmbH, Germany. A powder with a mean particle size of 20 μm has been used in this investigation, and alloy chemical composition is listed in Table 1. The powder quality is important to reduce the content of impurities (oxygen, hydrogen and nitrogen), which might negatively affect mechanical properties of laser-sintered parts with phenomena like embrittlement. Figure 1 depicts the SEM images of the 17–4 PH alloy powder at different scales. The powder has a nearly spherical shape and smooth surfaces, which lead to a good flowability. Table 2 highlights 17–4 PH stainless steel mechanical properties. The method tried to design of similar to foam structures.To characterize the porous structures there are Several superimposed pore layers of two different types (type A and type B, Fig. 2).

'''Findings''': This paper has studied the possibility of manufacturing lightweight steel structures with spherical porosity adopting SLM technology. A stainless steel powder has employed, using an EOSINT M270 titanium version laser sintering system considering optimized parameters to have minimal content of porosity in laser-sintered parts. Different samples, having an effective average porosity ranging from 70.1 to 72.5% were successfully fabricated.

'''Limitations/benefits''': SLM has the capability of producing structures of complex freeform geometry. It has been demonstrated to manufacture cellular lattice structures with fine features, showing a great potential to make advanced lightweight structures and products that are highly desired by engineering sectors such as aerospace, automotive and medical industries. However, SLM requires support structure to build an overhang section if its angle from the horizontal is less than a certain degree. This introduces design and manufacturing complications for the SLM of lightweight cellular structures and engineering components. The cellular lattice structures with a large unit cell size or low strut angles from the horizontal (usually lower than 30°) could not be built using the SLM process because overhanging struts led to the occurrence of serious deformation.

'''Link''': https://link.springer.com/article/10.1007/s00170-017-0311-4

Manufacturing and characterization of similar to foam steel components processed through selective laser melting

2020-01-25T14:13:43Z

BaldassareVitaggio:

Manufacturing and characterization of similar to foam steel components processed through selective laser melting

2020-01-25T14:12:04Z

BaldassareVitaggio:

Manufacturing and characterization of similar to foam steel components processed through selective laser melting

2020-01-25T14:06:25Z

BaldassareVitaggio: Creata pagina con "'''Title''': Manufacturing and characterization of similar to foam steel components processed through selective laser melting '''Authors''': Fabrizia Caiazzo, Sabina Luisa Ca..."

Selective Laser Melting

2020-01-25T14:03:30Z

BaldassareVitaggio:

[[Process Optimization]]

[[Manufacturing and characterization of similar to foam steel components processed through selective laser melting]]

Selective Laser Melting

2020-01-25T14:02:49Z

BaldassareVitaggio:

[[Process Optimization]]
[[Manufacturing and characterization of similar to foam steel components processed through selective laser melting]]

Additive manufacturing by means of laser-aided directed metal deposition of 2024 aluminium powder

2020-01-25T10:59:59Z

BaldassareVitaggio: Creata pagina con "'''Authors''': Fabrizia Caiazzo, Vittorio Alfieri, Paolo Argenio and Vincenzo Sergi '''Keywords''': Directed metal deposition, aluminium alloy, additive manufacturing, optimi..."

'''Authors''': Fabrizia Caiazzo, Vittorio Alfieri, Paolo Argenio and Vincenzo Sergi

'''Keywords''': Directed metal deposition, aluminium alloy, additive manufacturing, optimization, microstructures

'''Abstract''': Directed metal deposition by means of laser beam is investigated in this article. The process is receiving increasingly interest in the frame of additive manufacturing to the purpose of maintenance, repair and overhaul of condemned products when severe conditions hindering the working order have been experienced. Minimal distortion, reduced heataffected zones and better surface quality are benefited in comparison with conventional techniques. Namely, metal feeding of 2024 aluminium powder is considered to produce clad traces on 2024 aluminium plates, aiming to give grounds for repairing damaged real components using materials with same or similar features with respect to the parent metal. A fibre-delivered disc laser and a three-way feeding nozzle are used. The responses are discussed in terms of geometry, microstructure and microhardness both in the fusion zone and in the heat-affected zone; the optimization is conducted via desirability functions, based on proper technical constraints upon numerical modelling. Reparation of real parts, where cracks are machined to produce V-grooves to be filled, is aimed.

'''Purpose''': The process is receiving increasingly interest in the frame of additive manufacturing to the purpose of maintenance, repair and overhaul of condemned products when severe conditions hindering the working order have been experienced.

'''Methodology''': A laser beam is used as focused heat source to scan the surface, thus creating a melting pool over an existing substrate. Since metal impinging the pool is fed concurrently (i.e. in singlestage processing) in the form of wire or loose powder,5 a deposited metal trace results, with metallurgical bonding to the substrate thanks to fusion and diffusion.

'''Findings''': The aspect and the corresponding macrographs in the transverse cross-section have been discussed for each processing condition (Table 3). Successful cladding resulted, based on visual inspections; shielding is deemed to be effective, no cracks neither macropores resulted on the surface. Nevertheless, a number of micropores, ranging in size from 10 to 75mm on average, have been found (Figure 5). One may assume this would not result in rejection of parts at quality checks. Usual international or customer standards for quality in laser welding30 are borrowed, since no specific regulations are available at present for DMD.

'''Benefits''': Minimal distortion of the workpiece, reduced heataffected zones (HAZs) and better surface quality are benefited in laser-aided DMD in comparison with conventional coating and repairing techniques such as arc welding and plasma spraying.

'''Limitations''': According to the trend of microhardness in the cross-section, softening is experienced in both the HAZ and the fusion zone, due to overaging with coalescence of dispersoids in the former and precipitation to grain boundaries in the latter, with respect to parent metal in T3 state.

'''Practical implications''': A condition with 2.5 kW laser power, 420 mm min21 processing speed is suggested for given feeding rate of 3 g min21 and 3 mm beam diameter, which is deemed to be robust, given the shape of the response surface of the overall desirability.

'''Link''':https://journals.sagepub.com/doi/full/10.1177/1687814017714982

Wire Arc Additive Manifacturing

2020-01-25T10:45:28Z

BaldassareVitaggio: