1. Copyright @ CSIR 2005 www.csir.co.za CMM AUDIT PROGRAMME - RESULTS AND LESSONS LEARNT Speaker : F. J. van der Walt E-mail: fvdwalt@csir.co.zafvdwalt@csir.co.za Tel.: (012) 841- 4799 07 September 2005

2. Copyright @ CSIR 2005 www.csir.co.za 3D Coordinate Measuring Machine (CMM) DEA Global Image CMM

3. Copyright @ CSIR 2005 www.csir.co.za Why a CMM audit programme ? 1.To identify/analyse CMM capabilities. 2.To establish measurement traceability for CMM measurements. 3.Assess the influence of environmental conditions on CMM measurements. Scientific Research Council Act (Act No 46 of 1988, as amended by Act 71/1990)

4. Copyright @ CSIR 2005 www.csir.co.za Audit Part Material = 7075-T6 CTE = 23,6 x 10 -6 K -1

5. Copyright @ CSIR 2005 www.csir.co.za Top view X+ Y+

6. Copyright @ CSIR 2005 www.csir.co.za Section A - A Z+ X+

7. Copyright @ CSIR 2005 www.csir.co.za Evaluation of Measurements All the measurements from the participating laboratories were recorded and evaluated. It was found that: a. Length measurements and Diameter measurements are acceptable. b. Roundness, angle, and concentricity measurements are cause for concern.

8. Copyright @ CSIR 2005 www.csir.co.za Length Measurement 0,031131,381

9. Copyright @ CSIR 2005 www.csir.co.za Roundness Measurement

10. Copyright @ CSIR 2005 www.csir.co.za Error Sources 1.Spatial errors are errors in the measured position of a point on the surface of the workpiece, and are caused by: a. guideways, scales, probing system, etc. b. environmental conditions. c. probing strategy. d. workpiece characteristics.

11. Copyright @ CSIR 2005 www.csir.co.za CMM Errors Lxx Lyy Positional errors (3) Lzz Lxy, Lxz Lyx, Lyz Linearity errors (6) Lzx, Lzy

12. Copyright @ CSIR 2005 www.csir.co.za CMM Errors (continued) Rxx, Rxy, Rxz Ryx, Ryy, Ryz Rzx, Rzy, Rzz 9 Rotation Errors

13. Copyright @ CSIR 2005 www.csir.co.za CMM Errors (continued) Qxy Qyz Qzx Squareness errors (3)

14. Copyright @ CSIR 2005 www.csir.co.za Error Sources (continued) 2. Computation errors are errors in the estimated dimensions and form deviations for the measured points on the surface of the workpiece, caused by: a. software used to estimate the geometry. b. the precision of the computer used. c. the number and position of the measured points. d. the extent to which the geometry departs from the ideal geometrical form.

15. Copyright @ CSIR 2005 www.csir.co.za CMMComputer Transformation Correctio n Computation Evaluation Controlling Tasks performed by the computer of the CMM

16. Copyright @ CSIR 2005 www.csir.co.za Causes of Measurement Errors Probe system used. Parameter settings. Environmental conditions. CMM errors. Metrologist/operator skills.

17. Copyright @ CSIR 2005 www.csir.co.za The measured value for a distance of 5,0 mm was reported as 12,207 mm The measured value for the overall length of 250 mm was reported as 131,381 mm The measured value for the overall length of 250 mm was reported as 0,031 mm. Operator Skills NEGLIGENCE, CARELESSNESS, ………..???

18. Copyright @ CSIR 2005 www.csir.co.za Uncertainty of CMM Measurements Machine Specification: ± (1,9 + 3L ) µm Very few participants reported the uncertainty of measurement or even their machine spec! Can not perform conformance testing without machine spec or estimated uncertainty. MAJOR CONCERN !!

19. Copyright @ CSIR 2005 www.csir.co.za Conclusion Length and diameter measurements are acceptable. Inconsistency of roundness, angle and concentricity measurements. CMM operators must know/estimate the uncertainty of measurement. Need for CMM metrologist/operator training. Participants with poor results should implement corrective actions. Participate again.

20. Copyright @ CSIR 2005 www.csir.co.za Upcoming CMM Course Presenter: Mr. Kostadin Doytchinov NRC Canada Venue: Pretoria and Port Elizabeth Date: November 2005

21. Copyright @ CSIR 2005 www.csir.co.za Thank you for attending this presentation. Have a nice day.