Variable-speed drives retrofitted to watchmaking milling maching

Inverter Drive Systems (IDS), an ABB Authorised Value Provider, has supplied and installed a panel containing two 0.37kW ABB machinery drives, a new fascia with forward and reverse operator controls, and an emergency stop. One drive supplies the three-phase power and speed control for the milling machine, while the other provides three-phase power to the coolant pump.

James Chadburn, a member of the British Horological Institute, repairs and restores timepieces at his workshop in Dunstable, Bedfordshire. He specialises in the restoration of clocks that can be up to 400 years old, making and installing new parts that exactly match original components.

To add to the capabilities of his workshop, Chadburn bought an Aciera F1, a rare Swiss-made milling machine designed to achieve the high accuracies of around 0.0004mm demanded in clock and watchmaking. The challenge was running this three-phase machine from the single-phase supply in the workshop. Chadburn chose IDS to provide a solution to this problem. He comments: "I had contacted a number of companies. Some did not respond to my enquiries but the engineer from Inverter Drive Systems came and took copious notes of what would be needed."

As well as its use in converting the power input from single-phase to three-phase, the main VSD (variable-speed drive) is used to drive the milling head at different speeds to match the work being done. The Aciera F1 has two speed selection dials, one with 125, 250 and 500rpm, and the other with 1000, 2000 and 4000rpm. The milling machine is linked to the VSD so selecting the speed on the Aciera demands the appropriate speed from the VSD.

Chadburn explains: "If I am cutting brass then I would select 4000rpm, certainly nothing under 3200rpm. With multi-tooth cutters, most of the finishing of the piece is achieved during the cut itself, doing up to 80 per cent of the polishing work. Controlling the speed in this way means I can accurately replicate wear on a component, making it look 250 years old.

"For hard steel, the VSD allows me to slow the milling machine right down - if it is too fast, it can destroy the cutters or overheat and scorch the component."

ABB machinery drives are intended for use by the machine building sector and are available in ratings of 0.37kW to 22kW. They are designed to be quick and easy to install and commission, with Chadburn's installation taking less than a day. He concludes: "I was very pleased with the service I received, with the project having only one small hiccup that was sorted out by IDS quickly. I have had no problems with the drives since then."

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