A replacement drives system using ABB variable-speed drives has reduced machine down time to zero and helped a circlip manufacturer save £11,000 a year in energy costs.

Cirteq Ltd, based in Keighley, West Yorkshire, is one of the UK’s leading manufacturers of circlips. The company buys raw, unshaped wire and runs it through various processes before the circlip is cropped, shaped, heat treated and finished. One of the first operations in the manufacturing process is to shape and draw the raw wire.

The machine used to perform this operation originally employed a very early type of DC variable-speed drive (VSD). The two main DC motors on this machine drove the shedding drum (the master drive) and the mill stand (the slave or follower). Used to shape the wire, these are controlled via a dancing arm that maintains tension in the drawn wire. The third motor, an AC motor, is used for the take-up or coiling drum and was controlled via an eddy current drive.

Controlled by a Ward Leonard drive system these DC motors were becoming unreliable and difficult to maintain.  Spares were also a problem, but the biggest problem was they were failing up to three times a week which was having a big effect on production.

Improved machine control with ABB’s DTC

A decision was made to replace the DC drives with two 30 kW ABB industrial drives for the shedding drum and mill stand, controlled in master/slave via the dancing arm and a 7.5 kW ABB industrial drive for the coiling drum.  The drives use ABB’s direct torque control (DTC) to slow the rotation of the coiling drum to compensate for the rising torque as the wire increases the drum’s diameter.

The size of wire used determines the speed the machine, and the previous system used a series of gears to alter the speed in steps.  By changing to AC variable speed drives, speed control was transferred to a dial on the control console giving better overall speed control and improving quality.

The ABB drives are also more efficient, cutting energy costs from £3.36/hour using the Ward Leonard drive system to only £1.47/hour. The machine runs 20 hours per day, six days per week, for 48 weeks a year, giving a saving of £11,000 per year.

Go here for more information on VSDs from ABB UK 

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