An investigation into theperformance of probes on coordinate measuring machines

Coordinate measuring machines (CMMs) have become very widely used in recent years because of their ability to measure most or all of the individual geometrical features on complex engineering components. Compared with traditional methods, which normally employ a variety of separate instruments, CMMs are fast in operation and are adequately accurate for many applications. However, accuracy limitations often inhibit their use for high precision metrology. Accuracy is limited by such factors as straightness and orthogonality of the CMM movements; established techniques exist for determining these factors. In many cases, the errors introduced by the probes are very significant and often exceed the errors from other sources. This paper describes an investigation into the nature of probe errors, the factors that influence their performance and proposes a method of verifying the probe performance. Results from a number of probes used in different modes are presented. The application of the work to linking CAD systems to CMMs is briefly described.