Small volume sliding head work
Some of the medical instruments produced by Kirkstall Precision on the Star machines
Twin-spindle sliding head mill-turning centres help Kirkstall Precision produce finished parts from bar – allowing tight tolerances to be maintained while reducing costs to the customer by saving on labour and materials.
The supply of surgical instruments and other high precision medical components accounts for 90% cent of turnover, according managing director John Thornton, with other sectors covered including the nuclear, aerospace, petrochemical, textile and electronics industries.
Component complexity is increasing all the time, but batch sizes tend to stay the same or decrease, which means that more and more time was being spent repeatedly setting up jobs on conventional machine tools. It was not unusual for a component to visit, for example, a milling machine, a wire eroder, a 4-axis machining centre and a lathe before it was finished.
Since the arrival of two twin-spindle, sliding-head, multi-axis mill-turning centres from Star, an SR-20RIII in 2009 and an SB-16E, parts that previously needed multiple operations are produced from bar in one operation. Not only is productivity increased, but also the frequent changeovers for producing batches as low as 10-off are much faster when there is one machine to set rather than four.
"The advantages of one-hit machining are significant, both for us and our customers," says Mr Thornton.
"For a start, we achieve the required accuracies easily without tolerance build-up between ops. We regularly hold the position of a cross-hole to a shoulder, for instance, to within 25 microns total.
"The rigidity of the Stars and the absence of play in the axis movements allows very fine features to be machined accurately; we currently have a job going through that needs a 0.19 mm hole drilled.
"Labour savings are considerable due to the reduction in set-ups, so we are able to hold down prices, and there is no work-in-progress to manage.
"Material savings are also evident. Whereas to produce a batch of 50 we often lost 10 to 20% in the process, now every part is good."
www.kirkstallprecision.co.uk
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