Abstract
The Screw Extrusion Additive Manufacturing (SEAM) technology provides output rates up to 10 kg/h, a melt pressure up to 350 bar and temperatures up to 400 °C as well as strands with an adjustable bead width between 1-8 mm. Due to a bypass nozzle, position jumps without material extrusion, local wall thickness reduction, and the control of the volume flow (0-100 %) are made possible. Further, the extruder is able to process fiber-reinforced as well as highly filled plastics and integrates a regranulation system to return bypassed material into the process. The hexapod parallel kinematic meets the process requirements, as it generates a rapid movement of the workpiece (up to 1 m/s) in 6 degrees of freedom within a large printing workspace (1100 × 800 x 600 mm3), where an additional Z-axis carries the extruder and realizes the part height. Eccentric joints provide high accuracy and stiffness while being cost-efficient at the same time. The commercial Beckhoff TwinCAT control allows G-code processing and provides an HTML based GUI for machine and extruder control. Consequently, high accuracy is achieved, which is verified by the use of a double-ball-bar measuring device and by producing a test workpiece.
Highlights
Introduction and Approach of theScrew Extrusion Additive Manufacturing (SEAM) technologyThe field of 3D printing of thermoplastic components is currently partitioned in a large number of processes, such as powder bed fusion (PBF), material extrusion (MEX), material jetting (MJT) or vatphotopolymerization (VPP) [1-3]
In 1989 Scott Crump [1] submitted the patent for the 3D printing process via Fused Deposition Modelling (FDM) [4] and is considered to be co-founder of today's FDM 3D printing
This paper presents the automated, fully integrated additive manufacturing technology demonstrator SEAMHex that brings the SEAM technology into application, Figure 1
Summary
The field of 3D printing of thermoplastic components is currently partitioned in a large number of processes, such as powder bed fusion (PBF), material extrusion (MEX), material jetting (MJT) or vatphotopolymerization (VPP) [1-3]. Due to the thick crosssection strands, these processes allow limited dimensional accuracy, especially in corners when there is no volume flow reduction, and a very rough component structure that is often smoothed by a subsequent milling process This compromise between accuracy and speed is the field where the Screw Extrusion Additive Manufacturing (SEAM) technology operates. SEAM stands for Screw Extrusion Additive Manufacturing and its technology, with an output rate of up to 10 kg/h, is characterized by the fact that relatively thin strands, e.g. to process with a cross section of 3 x 0.8 mm, in combination with a very fast movement system with speeds of up to 1 m/s can be realized This enables optimum productivity and attention to detail as well as surface quality to be achieved through rapid solidification of the melt strands. Direct and indirect accuracy assessments using a double-ball-bar measuring system and a test workpiece, respectively, are presented (Section 5)
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