Enhanced cycle efficiency thanks to rotary indexing machines

Customers want maximum output with the shortest possible setup time. This is particularly true for price-sensitive mass products such as plug pins, cam discs and cable connectors made of all types of metal materials. However, ancillary times below 0.3s have only been possible up to now thanks to the use of cam-controlled machines, which require compromises in the machining process and often incur setup times of one half to two shifts. With the newly developed RV 10 Flexmaster, which is suitable for small work pieces from 2-13mm in diameter, Winema now boosts productivity by 20 per cent compared with more conventional approaches. The rotary indexing machine boasts a complete setup time of around 1.5h - four to six times faster than comparably equipped cam-controlled machines.

For parts families with an annual volume of five to ten million units, Winema surpasses the speed of cam-controlled alternatives and combine this with the advantages of CNC technology for enhanced flexibility. Up until now, no machine manufacturer has been able to satisfactorily meet these requirements for the entire work piece spectrum. The highly dynamic processes are made possible by the very high rigidity of the load-bearing components and by optimising the masses of the moving parts, as well as very tight manufacturing tolerances.

On account of the compact machine form, only hydraulic drives can be used for linear motions. They enable rapid acceleration and dynamic control response. This means that the use of wearing parts to transfer force is obsolete. In addition, the heat produced by the drive can be easily dissipated at the hydraulic station outside the machine tool - significantly reducing thermal stress.

Rexroth offers the only complete system on the market that provides control units, hydraulic controllers and control valves from a single source. Consequently, Winema is using its IndraMotion MTX CNC system for the first time in their new RV 10 Flexmaster. It meets all requirements for quality of control and dynamics for a large number of axes. In the MTX performance version, it controls the 54 CNC axes of the RV 10 Flexmaster, 27 of which are IndraDrive spindle drives. Thanks to its lean architecture, the CNC core can also execute the Flexmaster's complex tasks in an very short time, thus reducing non-productive periods. The dynamic torque motor increases output even further. It positions the indexing table so precisely that the hydraulically clamped spur gear can engage immediately. This enables unproductive ancillary times to be reduced to less than 0.3s.

Functionality in control, user interface and handling

Rotary indexing machines with a high number of axes place exceptional demands on the functionality of the control system, the user interface and data handling. Transferring Winema's many years of experience to a new control concept and realising further improvements with this step is an enormous challenge. But early in the development phase, multiple laboratory tests at Bosch Rexroth contributed to Winema's progress. By means of simulations, Winema was able to decisively enhance the control technology basis of the mechanical components with regard to the desired quality of control. Not only were all requirements of the specification met, but the constructive and creative collaboration generated additional ideas for further optimising operating convenience and ease of retooling before the start of series production.

The Rexroth HNC100-3X motion control system assumes the micrometer-precise control of the hydraulic feed axes. Its software takes into account all special characteristics of the fluid technology, thus decoupling the drive from the control level. IndraWorks provides the same software tools for the electrical commissioning of the hydraulic axes as for the other drives, which simplifies the work.

Real-time communication cuts cycle time

All electrical and hydraulic drives communicate with the controller via sercos. The Ethernet-based automation bus uses strictly deterministic real-time mechanisms. By combining HNC with sercos and the IndraMotion MTX, output is increased by 20 per cent compared with approaches previously available, and it is even possible to machine two work pieces simultaneously with no difficulties.

It was of course an advantage that the entire automation was supplied by a single source to simplify interface matching. Bosch Rexroth supported Winema intensively throughout the entire development phase and thus significantly reduced time to market. Further information on Bosch Rexroth and the Rexroth HNC100-3X motion control system can be found at www.boschrexroth.co.uk.