Dynamic face offset compensation for CNC machine tools

Nowadays, the demand of tighter tolerance components requires more accurate machine tools with volumetric compensation. In mass production, post-machining inspection of the workpiece on a Coordinate Measuring Machine (CMM) provides statistical quality control information on the variability of the manufacturing process. The dynamic face offset (DFO) is proposed to compensate the machine tool errors. The method is utilizing the part quality CMM data to determine the specific compensation parameters that are used in the machine tool controller to minimize the machine tool errors for specific part faces. The DFO does not considers the table offset parameters as when using the global offset compensation method. The table errors are incorporated within the local offsets. This paper presents the development of a DFO compensation method utilizing the measurements of the machined part(s). The DFO for 4-axis and 5-axis machine tools is estimated through a model while utilizing the computed deviations between the measured and nominal dimensions of the part. The measuring results before and after compensation are compared and demonstrate that the errors are reduced and compensated successfully.