High Speed High Precision Indexing



90° Index in 300ms with Ultra High Accuracy

+/- 0.4 arc min, +/-0.02mm at Working Radius

Electrical control equipment operating handles are automatically assembled at EATON production, with a critical element of the process being the insertion of an M2 machine screw that holds the components together. Turntable Image If this screw does not correctly engage or cross threads, then the component is rejected causing costly rework.

When EATON contacted Cornfield Engineering Solutions they were suffering from high reject rates due to the insertion of the M2 machine screw. They had identified that the precision on the turntable index was at the root of the problem and required a solution to reduce the reject rate and also reduce the maintenance demand of resetting the position of the turntable. The new solution needed to have an index time of 300ms and provide an index accuracy of +/- 0.02mm at the working radius. Alongside this the solution also needed the ability to apply a 45° Offset when a product change is made to utilise an alternative set of 4 chocks that were positioned at 45° from the primary set of chocks. The solution needed to be a turnkey solution encompassing all mechanical, electrical and control requirements, from design to manufacture to assembly and commissioning.

The solution devised utilised a zero stop globoidal cam unit as the final stage. This gave support for the turntable and a zero backlash final stage gearbox, owing to the mechanical construction of the unit. To this was added a high precision planetary gearbox with a backlash of less than 3 arc min. Finally a Lenze MCS servo motor with high precision multi-turn absolute encoder was used as the driving force. A Lenze L-Force 9400 servo drive controlled the motion with the existing Moeller PLC modified to coordinate the turntable index with the main machine cycle.

The Lenze servo drive was packed into a new enclosure which was mounted to the frame of the machine and all installation work, both mechanical and electrical, was completed before final commissioning.

The solution achieved all of the objectives with an index distance of 90° in a time of 300ms with a final accuracy of +/- 0.02mm at the working radius. The 45° Offset, to allow an alternative set of 4 chocks on the turntable to be used for a different product, was achieved whilst maintaining full accuracy. The existing PLC program was modified and a new set of electrical drawings produced and supplied to EATON.

The reject rate of the machine has reduced significantly with the majority of rejects being due to the component parts and not the assembly process.


Call us on 01782 511161

Cornfield Engineering Solutions Ltd, Unit 5, Brindley Court, Victoria Business Park, Brown Lees, Stoke-on-Trent, ST8 7PP