Torque motors eliminate extruder vibration

The latest high-performance torque motors and variable speed drives from Parker Hannifin are playing an important role in a range of extruders manufactured by plastics machinery company, Ghioldi.

The extruders use Parker direct drive technology to offer reductions in energy consumption and also to minimise vibrations that can affect the quality of finished parts.

To date, plastic extrusion machines used for producing profiles, pipes, tracks and tubes for sectors such as construction, automotive and medical, have used traditional motor and gearbox arrangements.

These can be expensive to maintain and are relatively inefficient in terms of energy consumption.

In addition, they can cause excessive vibration, which can be a particular problem in applications where coloured plastics are produced using different resins, as vibration can cause the heavier plastic granules to settle faster in feed hoppers leading to uneven distribution and changes in colour.

To overcome these problems, Ghioldi has developed extrusion machines where the motor and gearbox units are replaced by direct drive systems, using Parker torque motors controlled by variable speed drives.

Filippo Ghioldi, the company's sales director, said: 'Using direct drive technology on our range of extruders of up to 320kW in power has given us and our customers a number of advantages.

'In particular, the systems are easier to produce and assemble, which in turn makes them easier to maintain; they have a smaller footprint and use less energy in operation.

'There is almost no vibration, which also helps to make them far quieter and run below the 80dB threshold.

The Parker torque motors used by Ghioldi are based on a design of permanent magnet, brushless servo motor, which produces high levels of torque at low operating speeds.

Parker offers a range of specialised bearings to enable each motor to be connected directly to an extruder screw, with the motor then being controlled by the variable speed drive.

This allows both torque and speed to be varied infinitely, within the performance envelope of the motor, making each extruder far easier to setup and providing a far more accurate and repeatable method of controlling process parameters, compared with a conventional motor and gearbox arrangement.

'We have recently completed the sale of two machines to a customer in South America, where it is calculated that the energy savings alone will be sufficient to produce a return on investment within just 18 months,' said Ghioldi.

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