Singularities in five-axis machining: Cause, effect and avoidance

Singular configurations of five-axis machines have long been observed. Machining near to such singularities drastically affects the behaviour of machine axes movements. Singularities have been linked to the kinematic chain of the machine configuration but not necessarily machine axes movement. The first contribution of this paper is a link between cutter motion in work-piece and machine coordinate systems. This leads to a description for the machine axes movements for a given tool path. Unstable machine axes movements are discovered near singular configurations of the rotary axes. By relating these configurations to orientations in the workpiece coordinate system, a simple approach that avoids singularities by reorienting the workpiece is proposed. Machining tests verify the effectiveness of this approach. •Machining near to singularities results in unpredictable machine axes movements.•The novel approach is to consider machine axes movement.•Unstable movements are predicted in near-singular configurations of the rotary axes.•A simple approach that avoids singularities by reorienting the workpiece is proposed.•Experimental evidence of theoretical results is given.