Kinematic nonlinearity analysis in hexapod machine tools: Symmetry and regional accuracy of workspace

•We developed the theory of kinematic error in hexapod machine tools.•The symmetry of hexapod mechanism was studied.•Accuracy of toolpath in different parts of workspace was studied.•The results can be used in industry for optimal workpiece setup planning.

The kinematic nonlinearity of hexapod machine tools is the source of an error which requires special consideration during toolpath planning and command generation. Analytical formulation for such an error is presented in this paper. The presented formulation can also be employed in optimal toolpath planning and workpiece setup. The effects of toolpath parameters such as the length, orientation, and the location of the toolpath together with the upper platform travel speed are considered in this investigation. Toolpaths are categorized based on their orientation into vertical toolpaths, horizontal–horizontal toolpaths, horizontal–vertical toolpaths, horizontal-inclined toolpaths, and inclined toolpaths. Variation of the kinematic nonlinearity error and the regional accuracy of the machine's workspace are presented in this paper. Workspace symmetry is studied and it is shown that one-sixth of the machine's workspace can represent the whole workspace. Eventually, the presented formulation and the effect of parameters are experimentally verified.