Development of a Method of Additive Manufacturing by Material Extrusion Along Three-Dimensional Curves

Abstract

A method of additive manufacturing (AM) for the extrusion of material along three-dimensional curves is proposed as an alternative to conventional methods of layer-based AM for the manufacture of components designed using topology optimisation. The objectives of the study are to formulate a toolpath-generation algorithm for the extrusion process, to design the testing apparatus and methods for the validation of the proposed extrusion process, and to generate feedback based on the results obtained during testing and validation for possible implementation in topology optimisation software. The outcome of the study is a process by which toolpaths can be generated for simple geometries, and implemented using a mounted extruder serving on to a serial robotmounted build platform. OPSOMMING Die ekstrusie van materiaal langs driedimensionele krommes deur middel van toevoegingsvervaardiging word voorgehou as ʼn alternatief vir konvensionele, topologie-optimeerde, laaggebaseerde toevoegingsvervaardiging. Die doelstellings van hierdie navorsing is om ʼn gereedskapstuk trajek algoritme vir die ekstrusie proses te formuleer, om die toetsapparaat en validasie-metodes vir die voorgestelde proses te ontwerp en om terugvoer te gee aan die hand van die resultate. Die einddoel is om die benadering in te sluit in topologie-optimering sagteware. Die resultaat van hierdie studie is ʼn proses waarvolgens gereedskapstuk trajekte genereer kan word vir eenvoudige geometrieë en geïmplementeer kan word deur die gebruik van ʼn matrys op ʼn serie, robot-gemonteerde bouplatform.

System Development for the Five-Axis Extrusion of a Photopolymer

“…The extrusion of each segment was divided into three phases: initiation, extrusion, and termination. As discussed previously by Kirkman et al [10], initiation consisted of priming and 'lights-off' extrusion. Parameters for determining the priming distance and the height above which the lasers would be activated were retained.…”

“…An overview of the system first presented by Kirkman et al [10] is required before discussing further developments.…”

“…The system that was developed by Kirkman et al [10] consisted of a stationary extruder mounted in the vertical orientation. An extrusion bed was mounted on a Motoman SDA-10D six-axis robotic arm for the execution of five-axis toolpaths.…”

“…These angles defined the intrinsic rotations of the bed coordinate system required to line up with the tool coordinate system, and were used by the robot controller in determining tool posture. These angles were initially used to implement the passive inclination control by reducing their values to relax the tangency constraints of the extrusion with the nozzle, as discussed in Kirkman et al [10] and illustrated in Figure 8 below. However, the intrinsic nature of these angles made it difficult to develop an intuitive approach to directly manipulate the angle of the nozzle relative to the extrusion.…”

“…These drawbacks, among others, limit the application of polymer AM for the production of end-use parts in a manufacturing environment [8], [9]. This paper presents developments in previous research [10]. By examining the extrusion of material in 3D space without the need for support structures, the study aims to prove that the freeform extrusion of a photopolymer could be developed as an alternative to layer-based AM processes for the manufacture of load-bearing components.…”