An adaptive computer-aided path planning to eliminate errors of contact probes on free-form surfaces using a 4-DOF parallel robot CMM and a turn-table

Abstract

Nowadays, digitizing precise parts consisting of free-form surfaces is essential in geometrical inspections and reverse engineering. Despite the ease of use and high speed of non-contact techniques, contact methods have higher precision. However, using touch probes confront a few difficulties. Various compensation approaches that are often post-processing techniques have been introduced for contact probe errors consisting of ball-tip-radius error, stylus tilt, pre-travel, and probe lobbing. Moreover, in precise applications, achieving satisfying results is difficult and time-consuming.The current paper proposes a computer-aided planning method by implementing a new 4-DOF parallel robot and a cost-effective linear contact probe. This parallel structure exploits three translational DOF and one rotational DOF. Furthermore, the robot is equipped with a precise turn-table. A measuring algorithm for free-form surfaces by normal-to-surface contact has been developed. Evaluating the simulation and the practical measuring results shows excellent feasibly of the method on elimination or great reduction of errors.