On-machine profile measurement of machined surface using the combined three-point method

The combined 3-point method, which combines the generalized 3-point method with the sequential 3-point method, is described in the present paper. The combined 3-point method can not only measure profiles that include high-frequency components whose spatial wavelengths are shorter than the probe distance, but also cancel the influence of the z-directional error and the pitching error in the scanning motion. In the combined 3-point method, some data points from a profile evaluated by the generalized 3-point method are chosen as reference points of the standard area and are used to determine the relative heights among the data groups of the sequential 3-point method. An automatic selection method was used to select the standard area correctly and quickly. Theoretical analyses and computer simulations were performed to confirm the effectiveness of the combined 3-point method. Experimental profile measurements were also carried out using three capacitance-type displacement probes.