Characterization of a granulate-based strand deposition process in the FLM-method for definition of material-dependent process strategies

Abstract

Purpose This study aims to characterize the suitability of a direct extrusion process in the fused layer manufacturing (FLM)-method under processing of granulated plastics. Design/methodology/approach In this paper, a granulate-based direct extrusion system in the FLM method is presented. This system is characterized with respect to the strand deposition mechanism and resulting component properties (geometrically and mechanically). Findings The extruder output could be identified as a linear relation between the applied extruder speed and the resulting mass flow. A developed model for the material and temperature-dependent strand deposition process was validated under experimental investigations. Further, it was possible to define process windows to realize desired strand widths and strand heights. In addition, analyses were conducted to determine the tensile strength transversely to the orientation of the layer plane. Research limitations/implications The extrusion system was characterized under the processing of materials ABS Magnum 8434 and PLA Ingeo 4043D. Due to the restricted choice of materials, further investigations are planned under an extension of the test materials. Furthermore, the degree of the geometric complexity of the test components should be increased to finally characterize the process. Originality/value By means of the characterization of the direct extrusion system, it is possible for users to classify the process and to use the process in specific application areas. In comparison to filament-based extrusion systems, significant advantages can be achieved by means of direct extrusion. These include, for example, the use of less expensive work materials (by factor >10), the use of existing test certificates and the advantage of higher mechanical properties. This makes it possible to meet modern product requirements and to produce competitive components.

Screw-assisted 3D printing with granulated materials: a systematic review

“…Most experimental screw-assisted printheads that were specifically developed (or could be applied) for large-scale 3D printing share the same general configuration of the vertical extruders presented in the previous subsection. Some systems appropriated from commercially available extruders [ 56 , 57 , 60 ], while others presented custom-made deposition heads with auger screw [ 58 ], or typical extrusion screw with a compression profile [ 59 , 62 ]. The use of robotic arms in experimental systems [ 58 – 60 , 62 ] was more frequent than Cartesian platforms [ 56 , 59 ].…”

“…The focus of their paper was on the algorithm developed to generate the printing trajectory of 2D geometries projected to the deposition surface. Similarly, the AM system described by Schmidt et al [ 62 ] had a fixed printhead, with the deposition surface attached to a robotic arm that could move on six axes. The custom-made printhead included a screw with a compression profile.…”

“…The extrusion screw from the system developed by Schmidt et al [ 62 ] followed the conventional design guidelines from polymer extrusion theory to achieve a certain mass output, avoid material agglomeration at the feeding zone, and thermal degradation of the melt. Pellets of ABS and PLA were processed.…”

“…Stepper motors were often used [ 15 , 18 , 19 , 24 , 33 – 35 , 37 , 38 , 41 , 70 , 71 ], probably due the good relation between the torque provided and dimensions, low cost, and for its easiness of control. Although it can be seen as the core of the printhead, screw design was strictly considered by few authors [ 13 , 15 , 39 , 59 , 62 ] mostly to meet specific performance requirements. Peripherals such as independent feeding systems [ 13 , 35 , 72 ], pre-melting chamber [ 19 , 45 ], additional cooling elements [ 36 , 58 , 71 ], additional heaters [ 34 ], and other mechanisms to improve the state of the deposited layer [ 34 , 56 , 57 , 63 ] have also been proved important to achieve consistent results.…”

“…The printhead should be integrated into an adequate positioning system to comply with its planned application, which goes through defining the number of degrees-of-freedom, and structure type. Some authors used robotic arms [ 56 – 58 , 60 , 62 ] with multiple degrees of freedom or CNC systems [ 25 , 59 ]. When the design of the printhead limited its movements, the positioning system enabled 3D printing through a moveable deposition surface [ 13 , 17 , 34 , 51 , 58 , 62 ].…”