A Model Of Parallel Kinematics For Machine Calibration

Abstract

Parallel kinematics have been adopted by more than 25 manufacturers of high-end desktop 3D printers [Wohlers Report (2015), p.118] as well as by research projects such as the WASP project[WASP (2015)], a 12 meter tall linear delta robot for Additive Manufacture of large scale components for construction engineering applications. The parallel kinematics of a linear delta robot has the potential to out-complete Cartesian point-based deposition systems with respect of acceleration- and thus repositioning speeds since the primary movable mass in these types of systems can be kept to a minimum. The aim of this research is to address one of the primary disadvantages to parallel kinematics systems. Calibration and Geometric validation. Calibration of a delta robot can be a source of frustration. This research aim to provide the operator with a strong tool for easing this task. The kinematics and calibration of delta robots, in particular, are less researched than that of traditional Cartesian robots, for which tried-and-true methods for calibrating are well known. A forwards and reverse virtual model of a delta robot has been developed in order to decompose the different types of geometrical errors into 6 elementary cases. Deliberate introduction of errors to the virtual machine has subsequently allowed for the generation of deviation plots that can be used as a strong tool for the identification and correction of geometrical errors on a physical machine tool.