04/29/2013

TwinServo Technology combines opposites

Schuler’s new development with servo motors in the press bed enables greater force distribution and reduced deflection

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In the TST design, the slide is pulled downward, which makes the force flow much more direct.

Just six months ago, the Göppingen-based press manufacturer Schuler launched a completely new drive concept: TwinServo Technology (TST). This new development of the company’s ServoDirect Technology (SDT), which has since established itself in the marketplace, features two decentralized servo motors in the press bed. This new design now makes it possible to combine properties and characteristics that used to be regarded as contradictory. The result: benefits for the user that cannot be achieved with conventional press designs.

In a traditional press, the slide is pushed downward – therefore closing the die and generating the press force. The resulting reaction force has to be absorbed by the press frame. Due to restrictions caused by part transport considerations, presses are often designed in two parts clamped together by tie rods. The force is then distributed over the entire press frame and the pretensioned tie rods.

In the TST design, the slide is no longer pushed downward, but rather pulled downward: “This makes the force flow much more direct and reduces deflection by around 30%,” explains Thomas Spiesshofer, Technical Manager Automotive Press Technology. “Favorable leverage effects with force application points toward the outer edges result in geometrically enhanced conditions and off-center force applications.” This improves tilting resistance by up to 400% when compared to conventional machines.

Whole clamping surface can be used

Another key benefit is that as the force application points on the slide are located closer toward the edge, the entire clamping surface can now be used: “This means we can achieve both greater excentricities as well as greater off-center loads in absolute terms – which is particularly important for multi-station presses,” explains Frank Viola, Sales Manager Automotive Press Technology.

In addition to the rigid construction of the press, slide tilting can also be actively influenced during strong off-center loads by regulating the two electronically linked drives of the TwinServo press. This also results in shorter tryout times and reduced die wear.

Although the capabilities are the same as with a conventional machine, the external dimensions are much more compact. As a result, the press has a smaller footprint and also fits in spaces that have low ceilings. While the drive has been integrated into the press bed, the foundation dimensions and underfloor space requirements have not increased, enabling easy accessibility for service and maintenance.

Largely oil-free work area

The oil-lubricated drive parts in the press bed are separated by seals, away from working area on the press. As a result, the area is largely oil-free. This also prevents the formation of the dreaded oil mist – which sooner or later causes an oil drop in the work area.

The compact design of the TST means it can be completely enclosed by sound insulation. As this sound enclosure stands freely and is not connected to any machine parts, there is no transmission of   structure-borne sound. Compared to conventional presses, noise emissions are reduced by around 15 decibels – corresponding to a halving of noise pollution for employees.

The stated benefits are greatly increased due to possibilities derived from modern servo drive technology. Such drives enable the user to actively influence the speed of the forming process. In combination with various operating modes, such as full stroke or pendular stroke, users can achieve significant output gains when compared to presses that are operated with flywheels.