Norbar Torque Tools, the world's leading torque specialist, chose a Stark Zero Point system from Roemheld to achieve the desired improvements in quality and repeatability, while also reducing set-up times at its Banbury plant.
Banbury-based Norbar, which manufactures torque wrenches from 0.3 Nm up to 1,500 Nm and gearboxes up to 300,000 Nm in capacity, had installed two new Gleason machines and was looking to reduce wasted time through all aspects of the gear shaping process: from starting with an accurate gear blank, through to fitting to an accurate fixture mounted to an accurate base plate. In particular, Norbar wanted to avoid having to clock and adjust every fixture and gear part shaped.
The company had used Roemheld zero point mounting technology before on different machines, so was aware of its capabilities. After consulting with Roemheld on the project, Norbar purchased Stark Zero Point mounting plates for both machines. To increase accuracy while reducing loading times, the new machines employ drawbar automatic clamping. All fixtures were then fitted with the Stark zero point nipples, allowing fixturing to fit straight onto the base plate with no adjustment required.
Norbar also introduced a colour code system on the Stark Zero Point bases to indicate the best loading position for each fixture to minimise runout. This allowed fixtures to be mounted with a 10-15 micron accuracy and repeatability within 5 microns.
Norbar also reduced first-off quality check down-time by introducing as much in-process checking as possible. This led to the company being able to produce almost four times as many components than with the previous set-up.
In addition, Norbar asked Reomheld to supply adaptor plates to mimic the old machines so the company can still use the original fixturing. These too were fitted with the Stark Zero Point nipples for the required accuracy and repeatability. These improvements have resulted in excess capacity on the machines in anticipation of Norbar's planned future expansion.
Tim Bloor, design engineer at Norbar UK, who headed up the project, says: "My aim was to minimise setup times with the introduction of two new gear shapers. We were raising the bar in terms of the expected quality and accuracy of geared parts coming off these machines. The Stark plates have provided a solid foundation for mounting all gear shaping fixturing, and we have a high level of confidence the fixturing we fit to the Stark base plates will be accurate, so subsequent clocking of the fixture and component will just be a simple confirmation of its accuracy and consistency. It is early days, but we have seen a big improvement in gear quality and consistency, much quicker run times and greatly reduced setup times. So the expenditure was well worth it for the long term."
The introduction of this new technique of using drawbolts and fixturing together was a major culture change for the setters and operators, as it was so different from the old style of fitting and adjusting fixtures and clamping components. As a result, Norbar has made use of Roemheld's ongoing technical support to help it maximise the technology's potential for accuracy and repeatability.
Norbar Torque Tools is planning a phased move to a new factory in the town that will triple its manufacturing space. The move to the new factory will also include the setting up of a department dedicated to developing new products and customer solutions. Adds Mr Bloor: "With this factory expansion, we will be increasing our machining capacity and will be looking to make the machining process as lean as practical. This could well involve using the Stark system for other processes away from the gear shaping where they have proved to be so successful. "
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