Abstract:

In both academic and corporate research arenas, 3D printing is still developing quickly. Fused deposition modeling (FDM) is a manufacturing method used in additive manufacturing that takes filaments as input material. The filaments are laid down next to and above one another. The mechanical characteristics of items made with FDM are determined by the bonding strength of the contact between these filaments.  Among all 3D printing processes, these parts have the lowest dimensional accuracy and resolution. Furthermore, the pieces of an FDM model have visible layer lines that need postprocessing to obtain a smooth, flat surface and less uniform behavior. Despite the fact that FDM has a wide variety of applications, it is ineffective for producing structural elements due to low mechanical characteristics. This limitation limits their use in many applications. Contrary to any traditional polymer processing techniques, pressure is not used during the consolidation of layers in additive manufacturing procedures.

This research investigates how a high-pressure autoclave chamber with air or nitrogen atmosphere affects layer consolidation throughout the FDM process, as well as the mechanical properties of the printed products. A setup that comprises of a 3D printer integrated inside a customized autoclave (Fig. 1) has been built to attain high strength qualities similar to injection molded specimens. A maximum temperature of 185°C and 135 bar of pressure may both be maintained in the autoclave.

PLA 3D printing was done in the previously mentioned autoclave at different pressures: compressed air (0, 5, 10, 15, and 20 bar) and nitrogen (5, 10 and 15 bar) in longitudinal and transverse direction.  Furthermore, the same PLA material was used for injection molding. Tensile, flexural, and Charpy tests  were performed on 3D printed and injection molded materials. The nitrogen gas environment in the chamber prevents layer oxidation and 

hence promotes better layer adhesion. Autoclave preheating prior to printing, as well as autoclave pressure during printing, significantly improve layer consolidation, imprinting mechanical strength in 3D printed things that are almost as strong as injection-molded components. The pressure is built up inside the Autoclave by sending compressed air into it via a compressor. Nitrogen gas pressure was created inside the chamber by sending it through pipes that were readily available in cylinders. The temperature inside the chamber is maintained by heating coils around it and is fully insulated.

All of the tests reveal that the samples printed in nitrogen have raised mechanical properties to the level of injection-molded samples and above. The Young´s modulus was enhanced by 30% in longitudinal and by 70% in transverse direction (Fig.2). Further results on improved values (tensile strength, flexural strength, impact strength) will be provided during the presentation.

Dr. Jens Schuster is a Professor and Head of the Institute for Polymer Technology in West-Palatinate (IKW) at the University of Applied Sciences Kaiserslautern, Germany.

Professor Schuster received his Engineering Diploma at the RWTH in Aachen, Germany and his PhD at the Institute for Composite Materials (IVW) at the University of Kaiserslautern.

Throughout his career Dr. Schuster actively pursued international research collaborations, including close partnerships with the Center for Composite Materials at the University of Delaware, the Centre for Advanced Composite Materials (CACM) in Auckland, New Zealand, and an honorary professorship at Moscow State University for Design and Technology.

Dr. Schuster’s research has been focused on ultrasonic nondestructive testing of polymeric materials, rotational molding, thermal conductivity of composites, biodegradable polymers, and most recently on 3-D printing and fused deposition modeling (FDM).

Abstract:

In both academic and corporate research arenas, 3D printing is still developing quickly. Fused deposition modeling (FDM) is a manufacturing method used in additive manufacturing that takes filaments as input material. The filaments are laid down next to and above one another. The mechanical characteristics of items made with FDM are determined by the bonding strength of the contact between these filaments.  Among all 3D printing processes, these parts have the lowest dimensional accuracy and resolution. Furthermore, the pieces of an FDM model have visible layer lines that need postprocessing to obtain a smooth, flat surface and less uniform behavior. Despite the fact that FDM has a wide variety of applications, it is ineffective for producing structural elements due to low mechanical characteristics. This limitation limits their use in many applications. Contrary to any traditional polymer processing techniques, pressure is not used during the consolidation of layers in additive manufacturing procedures.

This research investigates how a high-pressure autoclave chamber with air or nitrogen atmosphere affects layer consolidation throughout the FDM process, as well as the mechanical properties of the printed products. A setup that comprises of a 3D printer integrated inside a customized autoclave (Fig. 1) has been built to attain high strength qualities similar to injection molded specimens. A maximum temperature of 185°C and 135 bar of pressure may both be maintained in the autoclave.

PLA 3D printing was done in the previously mentioned autoclave at different pressures: compressed air (0, 5, 10, 15, and 20 bar) and nitrogen (5, 10 and 15 bar) in longitudinal and transverse direction.  Furthermore, the same PLA material was used for injection molding. Tensile, flexural, and Charpy tests  were performed on 3D printed and injection molded materials. The nitrogen gas environment in the chamber prevents layer oxidation and 

hence promotes better layer adhesion. Autoclave preheating prior to printing, as well as autoclave pressure during printing, significantly improve layer consolidation, imprinting mechanical strength in 3D printed things that are almost as strong as injection-molded components. The pressure is built up inside the Autoclave by sending compressed air into it via a compressor. Nitrogen gas pressure was created inside the chamber by sending it through pipes that were readily available in cylinders. The temperature inside the chamber is maintained by heating coils around it and is fully insulated.

All of the tests reveal that the samples printed in nitrogen have raised mechanical properties to the level of injection-molded samples and above. The Young´s modulus was enhanced by 30% in longitudinal and by 70% in transverse direction (Fig.2). Further results on improved values (tensile strength, flexural strength, impact strength) will be provided during the presentation.

Dr. Jens Schuster is a Professor and Head of the Institute for Polymer Technology in West-Palatinate (IKW) at the University of Applied Sciences Kaiserslautern, Germany.

Professor Schuster received his Engineering Diploma at the RWTH in Aachen, Germany and his PhD at the Institute for Composite Materials (IVW) at the University of Kaiserslautern.

Throughout his career Dr. Schuster actively pursued international research collaborations, including close partnerships with the Center for Composite Materials at the University of Delaware, the Centre for Advanced Composite Materials (CACM) in Auckland, New Zealand, and an honorary professorship at Moscow State University for Design and Technology.

Dr. Schuster’s research has been focused on ultrasonic nondestructive testing of polymeric materials, rotational molding, thermal conductivity of composites, biodegradable polymers, and most recently on 3-D printing and fused deposition modeling (FDM).