QMT Features: December 2009
Indentec pokes its nose into GKN's steering systems
Hardeness testers have allowed GKN Driveline in India to test components imediately they leave the heat treatment furnace


GKN Driveline has 2 plants in India, one in Delhi and the other in Chennai. As specialists in component tooling and fixturing design and manufacture, Indentec are already a proven supplier of this type of equipment to the Driveline Group.  The most recent purchase was as a result of a technical visit to the Zwick Roell Group’s production plant in Germany to discuss a specification for hardness testing of constant velocity (CV) joints used in automotive steering systems.

Prior to the new purchase GKN had been experiencing difficulty in checking the hardness of CV joints due to their awkward shape which offers only restricted access to the points to be tested. Without accurate and reliable hardness measurements the longevity of the part could be compromised. 

Indentec’s unique nose mounted indenter enables hardness tests to be performed inside hollow enclosures, bores and tubes. Combined with an easy to use component clamping fixture, operators are guaranteed to test in exactly the right position. The inside of the CV joint has a complex geometry requiring accurate positioning of the specimen in relation to the indenter, combined with ridged support is critical for a successful test.

Prior to buying the two Indentec 4150 SK Rockwell hardness testers, GKN Driveline were cutting the CV joint in half to allow access to the test point. The solution provided by Indentec removes this time consuming operation and enables tests to be performed immediately after the component leaves the heat treatment furnace. This leads to a reduction in wastage and therefore increased productivity. Tests can now be performed in less than 20 seconds as opposed to 10 minutes with the previous test method.

The Indentec ZHV30 micro and macro Vickers hardness testers are used to check the hardened case depth of the CV joint. The component is first cut in half and polished to a high quality before mounting into bespoke support fixture which ensures the part is securely held in place during the application of the Vickers test force.

The instrument is supplied with an XY table fitted with high accuracy micrometers, each with 50 mm of travel. The hardened case of the CV joint has a precisely defined profile to ensure optimum performance. The Indentec system provides an easy, fast and accurate means of verifying the integrity of the hardened layer.

A CCD camera and automatic indentation measurement software was supplied in order to both reduce uncertainty associated with manual measurement and to significantly increase the accuracy of the result. Vickers impressions are now measured in less than 1 second.

The Rockwell and Vickers instruments were manufactured in accordance with Indentec’s UKAS accredited ISO 17025:2005 Quality Assurance system and calibrated to the relevant ISO and ASTM standards, thus providing direct traceability to National Metrology Institutes such as NIST, PTB and IMGC.

 www.zwick.com
  
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Rob Tremain Photographer
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