Corus drives positioning system accuracy

Deeside, UK - Corus Colors' systems integrator Boulting Technology has installed 0.75kW ABB machinery drives on four positioning systems when pneumatic positioning systems failed to provide the accuracy required by its Shotton Works on Deeside. The positioning systems are part of the coiling operation at the plant.

A major customer wanted Corus to provide its steel coils wound around cardboard tubes, so the steel maker needed to automate the loading of the cardboard inners onto a mandrel ready for winding. In the automated system, the tubes slide onto a saddle-shaped arm, which then swings round to align with the mandrel. Once there, the tubes are pushed into position ready for winding.

The problem was that the rotating system has a non-linear load, which requires additional torque to start the arm moving, according to Nick Bennett, senior project electrical engineer at Corus. "The new drive system control continuously adjusts the torque and speed to achieve the required motion profile," said Bennett. "This is difficult to achieve with an air cylinder because you can only make adjustments to the pneumatic system between operations, not during them."

Each drive at Corus interfaces with two encoders. A TTL encoder monitors the motor and provides the feedback to control the speed of the arm. An absolute encoder on the load side monitors the exact position of the arm, so the drive always knows precisely how far round it has swung.

Most drives would require a separate PLC controller to produce the kind of complex motion and positioning control needed at Corus, but the onboard intelligence and programming capability of the advanced ABB drives eliminated the need for new PLCs.

"We couldn¹t have done it this way without the programming capability," said Boulting Technology's engineer Phil Martin. "The modular programming blocks made the drive easy to use, and it made life much easier to put the control intelligence in the drive."