Development of surface reversal algorithm for datum error identification in surface topography characterization

Proper measurement is essential to ensure a good performance of a machine to produce a high-quality product. To have a good measurement, the first thing to consider is the datum since it is used primarily for manufacturing and inspection setups. However, the common datum as defined by ASME and ISO somehow is not practical to be used for a rotating machine tool. Thus, this paper focuses to define an appropriate datum for a 3D simulated surface by including a possible source of variation or error that may exist. To achieve the objective of this paper, surface reversal measurement is used as the main approach along with aid of the correlation function in the image-processing tool. Development of the surface reversal algorithm begins as two simulated surfaces are created and undergo surface correlation to achieve the best match point between both surfaces. Then, after one of the surfaces is translated to the desired position, surface subtraction is conducted to determine the inclined plane (real datum) of the simulated surface. The algorithm ends with the validation process through surface characterization by comparing the Sz value. As a result, both surfaces show different Sz values although both have the same surface topography and result for A minus with the real datum (LSPAB) providing less error on the surface topography data compared to A-minus with AB. This evaluation proves that an appropriate datum is necessary for every measurement so that the result obtained is accurate. Moreover, the objective to improvise the datum definition is successfully achieved since the error found along with the datum has been removed.