New Methodology for Inspecting Ruled and Free-Form Surface in Metrology

Abstract

A new method is proposed to find the cutter contact (CC) points for both 3- and 5-axis CNC machining, and use this to determine measurement points using CMM. The first part of this research focuses on deriving a mathematical formulation to determine the CC points while using ball nose end mills and standard end mills to machine a given ruled surface, with a focus on surface finish operation. Then, the freeform surface is measured, using the Gaussian curvature and mean curvature at each grid point. These measurements at each grid point on the free-form surface are classified then into concave, convex, or saddle point surface. This way boundary surfaces are allowed to vary. This allows for a more accurate way to measure free form surfaces by distributing sample points within each boundary patch (rather than rectangular or square patches as is conventional). This will help the determination of upper and lower boundary for each patch, so that the free form surface is accurately measured. Simple experimental verification was done to demonstrate the validity of methods developed.