CAD-based CMM dimensional inspection path planning - a generic algorithm

This paper describes a newly developed algorithm for CAD-based dimensional inspection path planning utilizing coordinate measuring machines (CMMs). Th e algorithm guarantees to provide optimum collision-free inspection probe p aths by using the topological structure of the boundary representation (B-r ep) solid CAD models of the inspected parts. A concept of automatic generat ion of optimum and collision free path in three dimensional space using ava ilable CAD database is proposed. The algorithm is generic for generating pr obe path over prismatic polyhedral parts. It serves as a principal part of the inspection path planning system. It is based on the modified ray tracin g technique which uses a B-Rep data from any geometric modeling systems. Be tween start point and target point, an imaginary ray is established and if an intersection with part is encountered, an optimal detour path is created avoiding interference of the probe with the part. The generated path consi sts of linear segments joining start point and target point by various inte rmediate points. To locate these intermediate points in the consideration s pace, topological and geometrical structures of the part models are used at the time of decision making. To examine and implement the algorithm, a use r-friendly application is developed employing AutoCAD Runtime Extension (AR X) development environment with object oriented programming (OOP) technique s, running on a Windows NT workstation. The effectiveness of the proposed a lgorithm is verified by the results of the implementation demonstrating opt imum collision-free dimensional inspection path generation for four represe ntative prismatic part models. All in all, this work contributes to the kno wledge-base formation of automated dimensional inspection research area and paves a way for the integration of CMMs into a CAD/CAM environment, thus a utomate the process of design, manufacturing and quality assurance.