10/23/2012

TwinServo Technology: more compact, flexible and silent

New drive concept with two decentralized torque motors / Further development of Schuler’s ServoDirect Technology

It is now five years since Göppingen-based press manufacturer Schuler launched its ServoDirect drive. Thanks to its numerous benefits – such as increased productivity and energy efficiency – ServoDirect Technology (SDT) has established itself as the standard for car manufacturers and their suppliers as well as for the household equipment industry. With its TwinServo Technology (TST), Schuler is now presenting a further development: a new drive concept with two decentralized servo motors in the press bed, which enables a more compact design and greatly reduces noise emissions. It also improves both accessibility and rigidity compared to former servo presses.

“With our TwinServo Technology, we aim to add a further chapter to the success story of ServoDirect Technology,” states Chief Technology Officer Joachim Beyer. In late September, Schuler presented the prototype of a TwinServo press with a force of 1,600 metric tons at its facility in Erfurt, Germany. With a height of six meters, the new transfer press is much lower than previous models. Its footprint is also smaller and the moving bolsters can be placed closer to the machine for die changes. Compared to a conventional SDT press, the total space requirement has been reduced by around 30 percent. In other words, the press takes up less space in the stamping plant and also fits in halls with lower ceilings. As a result, new halls can be planned with correspondingly smaller dimensions.

This compact size also means that the entire press can be insulated with a free-standing sound enclosure. The fact that the drives are located in the foundation already makes sound emissions much lower than with conventional designs. The free-standing sound enclosure reduces process noises and the transmission of structure-borne sound even more completely. Reflections off the hall ceiling are eliminated. Generously proportioned windows provide the operator with a perfect view of the forming process. 

Improved accessibility and greater rigidity

The innovative design of the TwinServo press without uprights also improves access to the die area. The slide movement is handled by four drawrods which apply the press force to the end faces of the slide. Compared to conventional designs, this allows greater eccentric loads. In addition, the maximum press force can be used right up to the bed edge for forming operations.

The 30 percent reduction in deflection which the TwinServo press offers compared to conventional machines has further positive effects: the blanking shock is reduced, thus protecting both die and press. This property is additionally helped by the dampening effect of the increased slide mass. Tilting resistance in the feed direction is almost twice as high, and at right angles to the feed direction as much as four times higher. 

The press bed of the built machine houses two torque motors with a rated force of 503 kilowatts each – as also used in Schuler presses with ServoDirect drive. The two press drives are arranged in the bed in such a way that the draw cushion and scrap chutes can be located almost anywhere near the die clamping area. Synchronization is guaranteed by an electronic control system.

Underfloor space needs unchanged

Although the drives are now located in the foundation, the space requirements are no greater than for existing lines. In the case of the prototype in Erfurt, for example, the foundation is 5.30 meters deep. Accessibility for service operations is also comparable, or even easier in some cases.

Schuler will be using the TwinServo press at UmformCenter Erfurt to produce small batches for customers in the automotive industry as well as to conduct die tests together with its customers. At full stroke, speeds of up to 30 strokes per minute can be achieved, and in pendular stroke operation of up to 40 strokes per minute. It retains the well-known benefits of ServoDirect Technology, such as the freely programmable slide movement, and is capable of the same operating modes. The 25-meter-long line was fitted completely with Schuler’s automation components: the coil line, roll feed, blankloader, electronic tri-axis transfer and press all come from a single source.

Initially, Schuler will be offering its TwinServo Technology for transfer and progressive die presses with forces from 1,000 to 3,500 metric tons. The bed length is between 5,000 and 8,000 millimeters, the width between 2,200 and 3,000 millimeters. The maximum stroke rate per minute ranges from 25 to 40, in pendular stroke operation from 30 to 50.