Form error compensation in soft wheel polishing by contact force optimization

An efficient sub-aperture soft wheel polishing was realized on a four-axis precision CNC machine tool. The stable and controllable contact force was supplied by a voice coil motor during the polishing process. Considering the machining efficiency and CNC tool technical restrictions, a time-variant tool influence function (tv-TIF) regime was introduced to improve form accuracy for rotational symmetric workpiece polishing with a spiral tool path in which it is easy to produce a center dent caused by velocity truncation. A constrained polishing force optimization was employed in the tv-TIF regime, and it was expressed as a piecewise function. As the variant polishing force, the size and the material removal rate of TIF changed simultaneously. Applying the tv-TIF regime, a simulation was conducted to obtain the optimized polishing force and the crossfeed velocity for restraining the center dent during the polishing process. In addition, the pitch-variant tool path combined with the variant contact patch was taken into consideration in generating the removal track. Using the tv-TIF regime and the main spindle speed compensation, the polishing experiments were conducted and the form error compensation was realized by alleviating the center dent successfully.