20.09.2005

New perspectives in the production of micro-precision components

Linear motor press: Stanzrapid

Stamping Days/Pforzheim - With the increasing trend towards miniaturization, precision micro-components are becoming more and more important in electronics, precision engineering, micromechanics and medical technology. At the same time, the requirements regarding accuracy, complexity and economic efficiency of production are also increasing. Schuler’s new linear motor press "Stanzrapid" opens up completely new perspectives in the production of precision micro-components. This new type of linear drive technology features freely programmable displacement-time and force-displacement motions for slide travel, high achievable stroke rates and a high degree of precision. The machine can be used for flexible production as a stand-alone press, or as a compact and modular multi-stage machine. The "Stanzrapid" was developed by a consortium of companies and research institutes as part of a project sponsored by the German Ministry for Science and Education ("Key components for the production of precision micro-components").

Conventional technology – high stroking rates

Due to the high output levels for micro-components, they are generally formed by highly accurate, mechanical high-speed blanking presses, which can reach the appropriate stroking speeds. The world’s fastest press at present – a Schuler Yamada Omega F1 – can achieve up to 4,000 strokes per minute at a stroke length of 6 mm. This type of press converts the rotary motion created by the electric motor into a linear motion of the press slide with the aid of mechanical transfer elements. The characteristic sinus-shaped, displacement-time motions can only be changed by sophisticated lever kinematics, such as those of the Schuler Yamada NXT range. In contrast to conventional high-speed blanking presses, the NXT machines can significantly reduce working speed in the forming area thanks to their transverse-shaft, double-knuckle link drive.

Freely programmable displacement/time and force/displacement

It is also a particular advantage in deep drawing processes to be able to determine the displacement/time and force/displacement motions completely as required. The complex material handling involved with micro-components and the integration of other manufacturing technologies, such as milling, laser cutting, gluing etc., into the forming tool all call for freely programmable slide travel. This demand for more stroke path flexibility can only be met by the new linear drive concept. As the slide is not coupled mechanically to a rotation movement, the displacement/time and force/displacement behavior can be individually defined and programmed for every phase. Disrupting factors, such as the play of gear elements, no longer apply. The press force is available at any given point of the stroke. In this way, the new press combines the advantages of mechanical and hydraulic presses and greatly enhances both quality and accuracy. At the same time, the reduction in wear and tear results in reduced maintenance needs and raises both reliability and lifetime. On the other hand, however, the press force is currently limited to a maximum of 40 kN – due to the linear motors currently available. The lack of an energy reserve also means that the machine is less efficient than conventional presses. Stroking rates of up to 1,200 per minute are currently possible.

Economic manufacture of small batch sizes

For manufacturing processes with several forming operations and higher total forces, Stanzrapid modules can be easily joined in a line to form a compact unit. The individual slides can be operated either individually or synchronously. Material handling is also carried out by grippers driven by linear motor technology, which can feed the sensitive material according to a programmable displacement-time motion. All machine axes are controlled by a common and user-friendly control system. By exchanging individual units, lines can be quickly reconfigured. With this flexibility in manufacturing processes and product ranges, the Stanzrapid is able to economically produce high-quality products even in small batch sizes.

Modular design: new manufacturing perspectives

With the Stanzrapid, the project’s development partners have presented a production unit whose innovative concept and flexible use leaves the economic and qualitative boundaries of conventional technology far behind. Thanks to its precisely programmable stroke characteristics, new classes of materials, material combinations (compound materials) or several materials together can be processed simultaneously. Additional processing units (e.g. milling or laser cutting) can be integrated into the individual modules of a Stanzrapid line. This enables users to manufacture parts which were previously not possible on conventionally driven presses.

New production concepts

The capabilities of linear motor presses open up new application possibilities for metalforming processes – especially for micro-forming, where the relatively low press forces which this technology provides are generally quite sufficient. Whereas in the past, the forming process had to be adapted to the prevailing slide kinematics, the Stanzrapid now enables the machine operator to adjust the stroking motion to the respective manufacturing task. For the first time, it is now possible to keep a programmed slide speed constant over the entire stroke. This opens up new opportunities especially in deep drawing, as in this process the important friction coefficients between material and active parts are dependent on the speed. The control possibilities allow completely new manufacturing and die concepts. One example: by varying the bottom dead center (BDC) when using a die with offset punches, perforation dies can be greatly simplified. A punched strip which would normally require a die with 177 punches, can be produced on a linear motor press using a much cheaper die with just 20 punches.

Technical data

Maximum force 20 kN or 40 kN
Max. stroke speed 1,200 per minute
Max. stroke length 85 mm
Slide area 490 x 200 mm
Bed surface (w x d) 520 x 400 mm
Die space 230 mm
Ext. dimensions (w x d x h) 690 x 400 x 2,700 mm