By upgrading its presses to Pilz PMCprotego D servo amplifiers, Schunk Hoffmann Carbon Technology has improved reliability substantially, while also saving energy and maintaining high safety standards.
Schunk Hoffmann Carbon Technology is a leading manufacturer of carbon brushes for automotive starter motors and fuel pumps. After converting from a hydraulic to an electric servo press, the company experienced regular malfunctions due carbon dust short-circuiting the drive controller PCB.
The solution to this problem was to use the Pilz PMCprotego D servo amplifiers that operate reliably even under environmental conditions containing carbon dust; this is possible by virtue of a special coating on the PCB. Operating with third-party motors is no problem for the Pilz servo amplifiers, which can also work with almost any encoder on the market. Dietmar Loidl of Schunk Hoffmann Carbon Technology states: "When we converted the first press to the new drive controller it worked perfectly. The motor was set in the shortest possible time, the Pilz experts were obviously highly trained."
Safe motion control
All relevant safety functions can be integrated into the PMCprotego D servo amplifiers via a plug-in, individually configurable safety card. For the Schunk Hoffmann Carbon Technology application, the following were used, all in accordance with IEC 61800-5-2: STO (safe torque off), SS1 (safe stop 1), SS2 (safe stop 2), SOS (safe operating stop) and SLS (safe limited speed). The safety functions could be implemented seamlessly, independent of the encoder type.
Pilz also developed an emergency stop ramp for this application. This enables the motor to be braked to zero within 50ms, even when it is running at the maximum speed of 1400rpm. As a result, Schunk Hoffmann's requirement to brake the press quickly and safely was successfully met – despite the high number of cycles. The ability to store and reuse brake energy also reduces the machine's peak power requirement thanks to the energy storage system.
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