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Abstract and Manuscript Management System - Abstract Detail |
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Co-ordinate Measuring Machines, (CMM’s), are widely used in the South African industry for purposes ranging from quality control on manufactured components to the design of tooling jigs. Their measurement volumes range from less than one cubic metre, to more than twelve cubic metres. Traditionally there has been a lack of standardised verification methods for CMM’s as well as no or limited formal training programs for CMM users/operators. This can potentially lead to CMM’s being incapable of performing measurements to within their specified and ultimately to measurement inaccuracies. Since the extent of the potential problem is unknown, it was decided at a meeting of the CMM Specialist Technical Committee (CMM-STC), that an audit programme would be an objective way of assessing the depth and nature of possible CMM measurement problems in industry. The CMM-STC forms part of the South African National Accreditation System (SANAS), SANAS is recognised by the South African Government as the National Accreditation Body. During the CMM-STC meeting the decision was made that the audit programme should simulate a “typical” measurement in industry and not simply the auditing of the machine accuracies. The CMM audit program, controlled and coordinated by the National Metrology Institute of South Africa (NMISA), was initiated and involves the measurement of certain features and geometries of a locally manufactured part. From results obtained through this audit programme, the need for an extended audit programme that includes the ability of CMM’s to measure within their specified accuracies has been identified. To ensure a simple, quick and cost effective method to independently validate the performance of a CMM, an investigation was conducted to find a suitable, thermally and geometrically stable, light weight, 3D artifact (tetrahedron), which could be used to benchmark the capability of CMM’s, determine the most accurate volume location of a CMM, and reduce the downtime of the CMM during the performance evaluation. The Spatial Reference System (SRS) system is under investigation for this purpose. This paper present some results obtained to date and discusses the lessons learnt and follow up actions required to address problems identified. |
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