Local toolpath smoothing for five-axis machine tools

• A C3 continuous tool tip position smoothing algorithm is proposed.
• A C3 continuous tool tip orientation smoothing algorithm is proposed.
• Synchronization of position and orientation splines are carried out.
• Smooth toolpath is generated while satisfying user-defined corner error tolerance limits.

When five axis CNC machine tools follow series linear toolpath segments, the drives experience velocity, acceleration and jerk discontinuities at the block transition points. The discontinuities result in fluctuations on machine tool motions which lead to poor surface quality. This paper proposes to insert quintic and septic micro-splines for the tool tip and tool-orientation, respectively, at the adjacent linear toolpath segments. Optimal control points are calculated for position and orientation splines to achieve C3 continuity at the junctions while respecting user-defined tolerance limits. The geometrically smoothed corners are traveled at a smoothly varying feed with cubic acceleration trajectory profile. The proposed method is experimentally demonstrated to show improvements in motion smoothness and tracking accuracy in five-axis machining of free-form surfaces found in dies, molds and aerospace parts.