Influence of coordinate measurement parameters on a free-form surface inspection results

Coordinate measurements are the source of digital data in the form of coordinates of the measurement points of a discrete distribution on the measured surface. The local geometric deviations of free-form surfaces are determined (at each point) as normal deviations of these points from the nominal surface (the CAD model). Obtaining discrete data is inseparably connected with losing information on the surface properties. In contact measurements, the ball tip functions as a mechanical-geometric filter. The results of coordinate measurements of geometric deviations depend not only on the grid size but also on the ball tip diameter. This article presents foundations of the influence of the ball tip diameter and the grid size on coordinate measurement results along with the experimental results of measurement of a free-form milled surface in order to determine its local geometric deviations.