A study of the accuracy of industrial robots and laser-tracking for timber machining across the workspace

The aim of the present study was to investigate the accuracy of an industrial robot when milling glued-laminated timber along a vertical work plane while maximising the advantageous size of the workspace. The authors discovered a research gap in the machining accuracy within the workspace of an industrial robot. Hence, the examination comprises 50 distinct positions allocated in a grid, each with 3 machined specimens resulting in a total of 150 samples. The workpiece positions were referenced using laser-tracking technology to adjust the robot machining code to the actual workpiece position, while simultaneously assessing the machining accuracy using laser scans of the samples. As a result, accuracy maps are presented indicating the nominal-actual deviation including referencing errors and workpiece dimensional deviations (absolute accuracy) and the robot-only nominal-actual deviation (relative accuracy), subsequently proving that both comply with the EN 14080 standard. Furthermore, a calculation of the centre of accuracy defines the point of highest relative accuracy. The objective was achieved and advocated for a more pronounced utilisation of the workspace when machining timber with industrial robots. Applying these insights to the machining of large complex parts, multi-workpiece stacks and mobile robot platforms can enhance the possibilities and efficiency within timber construction.