Kistler Torque Sensors Test New Jaguar Steering Column

Kistler: Located on the Rassau Industrial Estate at Ebbw Vale, Gwent, ZF Steering Systems Nacam Ltd (Nacam) manufactures steering columns for most European passenger car companies, which means that QA is of critical importance. The thrust of the QA regime has always been to use the best technology to minimize the possibility of human error compromising product quality. Naturally, with safety critical components, the primary objective is to ensure that a component does not fail in service but there is the secondary consideration of protecting the company’s well-established reputation for quality and reliability. For a number of years, Nacam has used Kistler (www.kistler.com) sensors and monitoring systems in QA applications and the latest is a test rig to ensure that the screw threads in the universal joints for the new Jaguar XF are within specification.

The test rig, designed by Nacam with technical assistance from Kistler, uses two Kistler Type 4502 miniature torque sensors to check that both threads have been formed correctly and are neither too loose or to tight. This latter parameter is important as during installation on the car, the clamping screws are inserted after the steering column is in situ and space is tight. If the threads are not within spec, the whole column has to be removed: an expensive operation for which Nacam has to pay. More importantly, if only one U/J fails customer inspection, the whole batch will be rejected.

The operation of the test rig, built by AC Solutions of Neath, is fully automatic once a U/J has been manually placed in the holder, which accurately locates the joint and checks the correct position of the clamps. Two test screws are driven into the threaded clamping bolt holes via Kistler Type 4502 torque sensors that measure the torque needed to rotate the test screws. A linear position sensor measures the distance the test screws travel to confirm that the spot faces have been correctly machined. The outputs from the torque and position sensors are sent to two Kistler CoMo View control monitoring systems that evaluate the signals and send a final pass/fail indication to the operator and the machine PLC. If a U/J fails in any one of the three parameters, the PLC locks out the test rig until the faulty unit is de-tected passing through the reject chute. A joint that is in specification generates a pass signal that initiates the automatic engraving of a date code on the joint to provide end-to-end traceability.

The CoMo View control monitor can be set-up with a range of parameters but at Nacam they are used to check that output of the two torque sensors matches a pre-programmed profile throughout the travel of the test screw. Any deviation outside the specified profile results in a fail signal. All data generated by the CoMo View system are transmitted via Ethernet to the central production control computer system for production tracking and archiving for future production analysis and product tracing. Before selecting the Kistler solution, Paul Richards investigated a number of alternatives, all of which would have cost significantly more. The flexibility of the Kistler sensor/control monitor combination coupled with the build expertise of AC Solutions allowed costs to be saved without compromising performance or reliability. Typically, the motors used to drive the screws are manufactured by Nacam for another steering column contract. This not only saves money, it also means that spares are easily available on site.

"Kistler sensors are a premium product", says Paul Richards, Nacam's Manufacturing Engineering Manager "but that does not mean they are expensive. Over the years, we have used sensors from a number of sources and, given the budget, I would replace them all with Kistler tomorrow."

Kistler Group

Kistler’s core competence is the development, production and use of sensors for measuring pressure, force, torque and acceleration. Kistler’s know-how and electronic systems can be used to prepare measuring signals for use in analyzing physical processes, controlling and optimizing industrial processes, improving product quality in manufacturing and improving performance in sports and rehabilitation.

Kistler offers a comprehensive range of sensors and systems for engine development, automotive engineering, plastics and metal processing, installation technology and biomechanics.

A worldwide sales presence in the form of 23 group companies and 30 distributors ensures customer proximity, application support on an individual level and short lead times.

With a staff of 850, the Kistler Group is one of the world’s leading providers of dynamic measuring instrumentation. The Kistler Group achieved turnover of 195 million Swiss Francs in the 2007 financial year.