Drives and Controls Magazine

Servo pump system cuts moulding energy use by up to 80%

20 April, 2010

The German automation and drives specialist Baumüller has come up with a servo-based technology which, it claims, could cut the energy used by presses and injection-moulding machines by up to 80%.

Because these machines need more power than most other industrial applications, they have traditionally been driven hydraulically. However, conventional techniques for controlling hydraulic pressure are inefficient, especially as the power requirements of injection-moulding machines and presses can fluctuate widely. For example, closing and injecting operations require much more hydraulic oil and thus much higher flow rates than during dwell pressure applications, which involve high pressures but low flow rates.

Traditionally, these machines have been controlled either by valve-controlled drives, consisting of a motor and constant-volume pump, or by variable electrohydraulic pumps, also driven by standard motors. Both approaches suffer the same disadvantage: the motor-pump combination operates continuously at full speed and does not allow for the wide fluctuations in the machine`s power requirements. This results in inefficient use of energy in the partial load range, raising the machine’s energy and lifecycle costs significantly.

Baumüller’s answer is to combine the advantages of hydraulic power transmission with those of electrical power control using servodrive technology to control the speed of a constant-output pump dynamically and accurately. It says that the technology operates efficiently, with an above-average dynamic response, high precision, and significantly reduced levels of noise and heat. The technology retains the advantages of hydraulic power transmission such as high power density, low inertia, and robust and cost-effective drive elements.

Baumüller says its servo pump technology (shown above) typically cuts energy use by more than 30% compared to conventional systems and that, during extended phases of low power demand, energy savings of up to 80% are possible.