Performance verification of co-ordinate measuring machines using lasers and artefacts

In order to meet the ever increasing demands on product quality it is essential that the accuracy of Coordinate Measuring Machines (CMMs) are regularly monitored and their stated performance levels verified against accepted standards. Performance verification testing is currently carried out according to a number of international standards, of which the most widely used in Europe is ISO 10360, Part 2. This Standard specifies a complex and wide range of mechanical artefacts for CMM performance verification and this wide range can cause some confusion amongst CMM users. Also it is difficult to verify the performance of CMMs with working volumes in excess of one cubic metre using existing artefacts. As the size of a large CMM may be as much as 100 cubic metres or more, performance verification using existing artefacts is very difficult to achieve. In the machine tool industry performance verification testing using a laser interferometer is widely accepted and included in the appropriate standard (ISO 230-2). Also all CMM manufacturers now use the laser interferometer for performance verification, mainly during the build and on-site calibration of their machines. However, the laser interferometer has yet to be fully accepted for CMM performance verification and is not included in ISO 10360-2. Hence the laser is not yet widely used by CMM users. The aim of this work is to define simplified test procedures for performance verification of CMMs of all sizes, types and configurations, using a laser interferometer and a new universal artefact. In addition to the many sizes and different configurations of conventional CMMs, the work also includes the latest articulated arm machines and mobile optical systems, which are popular in the automotive industry.