Automotive Test & Measurement Case Studies SAAMF Roadshow Durban CSIR NML Eddie Tarnow Metrologist: Torque & Automotive 14 June 2006

Slide 2 © CSIR Case Study 1 – Seat safety testing A testing laboratory was required to perform a yield test on a seat frame to be used in motor vehicles The technical specification required that the seat yield at an applied force of >20 kN, with a tolerance of ± 1 %. The lab standard loadcell used had been calibrated by a SANAS accredited calibration laboratory Since inadequate contract review took place between the testing lab and the calibration lab the calibration was not fit-for- purpose

Slide 3 © CSIR Case Study 1 – Seat safety testing (2)

Slide 4 © CSIR Case Study 1 – Seat safety testing (3) Test limits – 20 kN +/- 1 % = 19,8 kN to 20,2 kN Range due to uncertainty of measurement quoted on the calibration certificate for the standard loadcell 20,1 kN +/- (0,5 % + 2 kN) = 17,9995 kN to 22,2005 kN Clearly the uncertainty of measurement on the calibration of the loadcell is larger than the test specification requirement Conclusion: The loadcell, with its calibration CANNOT be used for the test. Solution: To conduct a proper contract review with the calibration service provider and insist on a smaller uncertainty. Alternatively purchase a better quality loadcell if the loadcell itself contributed to the large calibration uncertainty.

Slide 5 © CSIR Case Study 2 – Dimensional measurement of a boot-lid-hinge A 1 st tier supplier of boot-lid-hinges to the OEMs was required to test their products for dimensional conformance to a technical specification They used a coordinate measuring machine to perform the measurements The dimensional technical specifications were indicated on a drawing from the OEM The component, as supplied, did not fit. This in spite of the performance of conformance testing. In an effort to solve the problem, a sample hinge was measured at CSIR NML with the following results:-

Slide 6 © CSIR Case Study 2 – Dimensional measurement of a boot-lid-hinge (2)

Slide 7 © CSIR Case Study 2 – Dimensional measurement of a boot-lid-hinge (3) On further investigation the following problems were discovered relating to the CMM:- The calibration spheres being used for the compensation for probe error were un-calibrated The accuracy of CMM was unknown due to inadequate verification by an external calibration service provider, even though it is used for conformance testing Other general metrology related problems found were:- The balance used for the twice daily checks on the dipping oil was un- calibrated and there was no check-weight for use as a confidence check The hardness block being used as a standard was invalid as it had been indented too many times and the indentations were too close to each other

Slide 8 © CSIR Case Study 2 – Dimensional measurement of a boot-lid-hinge (4) Conclusions: the company has a serious lack of awareness about measurement and testing requirements The risk in this case is that of potentially losing the contract to supply these components Solutions: The SAAMF has consulted with them and a number of wide ranging corrective actions have been identified.

Slide 9 © CSIR Case Study 3 – Feedback on CMM audit programme The CSIR NML initiated a CMM audit programme for the purposes of:- Identifying and analysing national CMM capabilities. Assessing the validity of measurement traceability for CMM measurements. Assessing the influence of environmental conditions on CMM measurements. The audit part was manufactured from aluminium to purposely simulate the many aluminium components being measured on CMMs The audit part was manufactured to simulate a typical automotive component to evaluate the capabilites of CMMs in measuring related parameters

Slide 10 © CSIR Case Study 3 – Feedback on CMM audit programme (2)

Slide 11 © CSIR Case Study 3 – CMM audit Results (3) [PCD 66 mm]

Slide 12 © CSIR Case Study 3 – CMM audit Results (4) [Bore Diameter 90 mm]

Slide 13 © CSIR Case Study 3 – CMM audit Results (5) [Distance 5 mm]

Slide 14 © CSIR Case Study 3 – CMM audit Results (6) [Distance 250 mm]

Slide 15 © CSIR Case Study 3 – CMM audit Results (7) [Outside Diameter 14 mm]

Slide 16 © CSIR Case Study 3 – CMM audit Results (8) [Outside Diameter 28 mm]

Slide 17 © CSIR Case Study 3 – CMM audit Results (9) [Concentricity]

Slide 18 © CSIR Case Study 3 – CMM audit Results (10) [Roundness of Bore]

Slide 19 © CSIR Case Study 3 – CMM audit Results (11) [Included Angle]

Slide 20 © CSIR Case Study 3 – CMM audit Results (12) Problems experienced: Labs do not stick to timings or follow the protocol (audit instructions) Very few labs can estimate uncertainty or even know the accuracy of their CMM Differences may be due to software packages used e.g. Roundness, Concentricity (Form Measurements) Audit sample not suitable for large CMMs Lack of enthusiasm to participate (perhaps ignorance of value to be gained) CMM agents reluctant to participate or distribute amongst their customers

Slide 21 © CSIR Case Study 3 – CMM audit Results (13) Conclusions: Length measurements and diameter measurements were in general acceptable Roundness, angle and concentricity measurements are cause for concern Operator/metrologist competence maybe questionable……… 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.

Slide 22 © CSIR Case Study 3 – CMM audit Results (14) Solutions CMM training courses through the NLA CMeTSA More audit parts so as to speed up the programme Create an improved awareness of measurement & testing principles Implement an audit programme for large volume CMMs typically used for vehicle bodies in the automotive industry

Slide 23 © CSIR Case Study 4 – Local calibration of a ball bar There was a requirement in industry to have a ball-bar calibrated to a specific uncertainty (same as the overseas calibration service provider) Initially the CSIR NML turned away the calibration as it could not perform the calibration at such small uncertainties Further investigation revealed that the calibration uncertainty provided by the overseas cal service provider was significantly better than the ball-bar specification The manufacturer revealed that the repeatability of the ball-bar (Breaking it down for transport to cal, building it up during cal, breaking it down for transport back to factory and building up for use to calibrate the CMM) was significantly worse than the calibration uncertainty quoted.

Slide 24 © CSIR Case Study 4 – Local calibration of a ball bar (2) There was therefore no point in having it calibrated at a low uncertainty which could not be repeated during use!! The CSIR NML undertook, as part of the calibration, to perform an experiment and include the repeatability performance of the ball-bar into their calibration uncertainty The resultant uncertainty would still be more then small enough to support the accuracy required for the calibration of the large volume CMMs This would mean the calibration could be performed locally thereby reducing the costs significantly and reducing the risk of damage due to international transporting.

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