El St VIER (‘mpurer zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQP Inregmred Manufaflm,q .S,wrms Vol. I I. No. l-2, 1’. 43-S I, 1998 0 1998 Elsevier Science I.td. All right\ resewed Printed in Great Britain o4cI-i24~l/Yx $-WC front matter zyxwvuts PII: SO951-5240(98)00008-l Intelligent planning of CAD-directed inspection for coordinate measuring machines Kuang-Chao Fan* and Ming C. Leut zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJ *Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan, ROC tDepartment of Mechanical and Industrial Engineering, New Jersey Institute of Technology, Newark, New Jersey, USA A method of CAD-directed inspection path planning for coordinate measuring machines is developed in this study. With the general three-dimensional objects designed in a surface model by the use of Autocad, the measuring points on each specified surface are generated automatically with even distribution. The probe inspection path is planned to touch each measuring point from a normal direction. With the swept-volume analysis of the probe path, any possible collisions can be detected and a new detoured path generated. This system is developed on the personal computer to make it more applicable to small- and medium-sized companies. 0 1998 Elsevier Science Ltd. All rights reserved Keywords: coordinate measuring machine, CAD-directed inspection, path planning Introduction Design, manufacture, and inspection are three main procedures which are the instigators of any new product in industry. Modern technology has employed CAD/CAM systems to transform the design procedure from tedious manual drafting into computerized drawing, and to transform the manufacturing procedure directly from laborious manual machine shop operation into NC machining. These breakthroughs have significantly improved production efficiency and established a closer connec- tion between design and manufacturing. Neverthe- less, while many inspection machines developed in recent years have enhanced their capabilities by adding computer hardware and software, nowadays the inspection procedure is still often being carried out independently of CAD/CAM. An effective system which incorporates a computer-aided inspection (CAI) subsystem into a CAD/CAM system for indus- trial use is urgently needed. Since coordinate measuring machines (CMM) have been widely accepted as the key inspection device, the integration of CMM and CAD at the design stage to improve automation efficiency has been a central interest of research since the concept of CAD-directed inspec- tion was introduced in the early 1980~‘.~. CAD-directed inspection aims to generate inspec- tion points on a CAD-defined object according to surface definition and then to automatically command the CMM for executing the inspection task”“. Many relevant issues in this regard have been studied, such as linkage between CMM and CAD/CAM’ and inspection path planning on toler- ance-based features, wireframe objects, CSG (constructive solid geometry) objects, and B-rep sculptured surface?I’. Some researchers have also considered collision avoidance between the probe and the measured object”“‘. In this paper, an integrated solution for intelligent inspection path planning of CMM probes for feature- based objects is proposed. For implementation on a personal computer, it links directly from Autocad modelling of the surface model of an object. Measuring points on any selected surface can be automatically generated. The inspection path is analysed by the swept-volume method for probe colli- sion detection, and any detected collision can be avoided by tilting the probe or introducing an inter- mediate point for the probe path. A simulation 43