Clockmaker saves milling time with ABB drives 13 August 2013

James Chadburn, one of the UK's top flight clock and watch restorers, is using ABB variable-speed drives (VSDs) to control his specialist milling machine.

Dunstable, Bedfordshire-based Chadburn, a member of the British Horological Institute, specialises in restoring clocks up to 400 years old, making and installing new parts that exactly match original components.

To add to the capabilities of his workshop, he bought an Aciera F1 – a rare Swiss-made milling machine, designed to achieve the 0.0004mm accuracies demanded in clock and watch making.

The challenge was running this three-phase machine from his single-phase supply.

"I had contacted a number of companies," says Chadburn. "Some did not respond to my enquiries but the engineer from Inverter Drive Systems came and took copious notes."

IDS 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 of the drives supplies three-phase power for the milling machine long with speed control, while the other powers the coolant pump.

As well as converting the power input, the main VSD 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 500 rpm and the other with 1,000, 2,000 and 4,000 rpm. The machine is linked to the VSD so selecting the speed on the Aciera maps to the VSD.

Says Chadburn: "If I am cutting brass, then I would select 4,000 rpm, certainly nothing under 3,200 rpm. With multi-tooth cutters, most of the finishing is achieved during the cut itself, doing up to 80% 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," he continues.

"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."

Brian Tinham

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