Selection of sampling points for accurate evaluation of flatness error using coordinate measuring machine

Dimensional inspection, in integrated manufacturing environments, requires accurate inspection while minimizing the cost and time of inspection. The selection of sampling plan—sample size and sample point locations, the method of evaluating the form error and the nature of the manufactured surfaces will play an important role in deciding the best inspection strategy to be adopted. This paper deals with the strategy for evaluation of flatness error which is one of the most commonly used form tolerances for control of manufactured surfaces. Investigations have been carried out to ascertain the influence of surface quality (surface roughness) in determining the sampling strategy for accurate determination of flatness error while inspecting on a coordinate measuring machine (CMM). The sampling plan utilizes the Hammersley sequence for point location and the flatness error is evaluated using the minimum zone method (MZM) based on computational geometry techniques. Results indicate that the surface roughness influences the accuracy of inspection and can be used as a parameter for determining an initial sample size for the determination of flatness error.