Three sliding-headstock lathes equipped with high-pressure coolant have revolutionised SS component production at one of the UK's leading aircraft engine pipe assembly suppliers.

Three Star sliding-headstock lathes equipped with high-pressure coolant (HPC) delivered at 2,000 lb/in2 (140 bar) have revolutionised stainless steel component production at B and D Patterns in the West Midlands, UK, one of the leading European suppliers of pipe assemblies to aero engine manufacturers. The Hinckley company supplies around 100,000 pipe assemblies a year in 1,300 variants to Rolls-Royce, requiring the manufacture of 500,000 individual components in 850 variants of which 25 are different types of union nuts, threaded adapters and ferrules. They are machined from S80 stainless (EN57), a corrosion-resistant aircraft steel, high in nickel and chromium, which is challenging to turn as it produces long, stringy swarf that is difficult to chip.

B and D had been soldiering on with the problem for many years, producing half of its requirement of these components in-house in batches of 200- to 500-off using a selection of its 28 fixed-head lathes without HPC; the remainder it subcontracted out.

However, against a background of increasing orders the company decided to upgrade production, opening a satellite unit in nearby Narborough in the first half of 2005 and installing its first three sliding-headstock lathes - two SV-32s and an SR-20R from Star Micronics GB - all with HPC equipment as part of the turnkey solution.

The benefits were immediate and dramatic.

As B and D managing director Ian Burton explained, 'Whereas our operators previously had to interrupt the turning cycle on each machine every hour to prise off swarf that had wrapped itself around the component and tools, this no longer has to be done on the Stars with HPC.

Consequently, higher speeds and feeds can be used.

There is no need, for example, to waste time centring, drilling a pilot hole and then drilling a hole to full diameter using three successive tools.

An 18 mm indexable-insert drill can be fed straight down the centre of a 32mm diameter, S80 bar in one operation without fear of swarf clogging the hole.

Burton added: 'A further advantage is that, whereas the old cutting conditions invariably created large burrs on the components that needed removal by hand at a bench, the minimal burrs that are now left can be removed by rumbling batches of components, saving considerably on second-operation work.' In the case of the nuts and adapters, such deburring was in fact a third operation, as the twin-spindle fixed-head lathes formerly used had a single turret without live tooling.

So although parts could be turned at both ends in one set-up, they had to go onto a machining centre for second-op cross hole drilling and milling.

With the Star multi-axis mill-turning centres, all operations are completed in one hit.

The result is that the larger nuts and adapters can be mill-turned on any of the Stars in cycle times that are on average 25% less and there is no re-fixturing on a machining centre for prismatic operations.

Ferrules are turned in half the time as they do not need to be milled or drilled.

B and D's original intention had been to retrofit HPC to some of its existing lathes and to invest in fixed-head mill-turn centres, two initiatives that it has in fact started in order to improve production of other parts.

However, when they visited Star's open house in Melbourne, Derbyshire, UK, last year they discovered that, for the production of nuts, adapters and ferrules, the sliding-headstock configuration with HPC was capable of faster cycle times than an equivalent fixed-head, twin-spindle lathe with driven tooling.

Mr Burton says that the Star sliders resulted in like-for-like cycle time savings of 25 to 50%t compared with those offered by fixed-head mill-turn lathes they investigated.

Currently the Narborough shop is running 13h/day, but production will be ramped up to 24h/day, five days a week by the end of 2005.

The two SV 32mm bar machines are devoted to the larger sizes of union nut and threaded adapter while the SR 20mm capacity lathe produces the smaller varieties and ferrules.

The three machines were delivered by Star as total turnkey packages with all ancillary tooling and cutting tools, and program suites fully proven prior to delivery.

At Star GB's open house in June this year, B and D placed an order for two more Star machines for delivery in September to cope with increased demand.

The extra lathes combined with the implementation of 24h operation will create spare sliding-headstock mill-turning capacity that Burton is currently looking to fill.

He believes that their experience in machining exotic materials well qualifies them to carry out subcontract work for the medical industry in particular.

In conclusion, Burton commented, 'We looked at other sliding-headstock lathe suppliers but liked the robust build of the Star machines.

We took up references from a number of customers and were particularly interested in comments from 'mixed users', i e, firms using sliders from two or more different suppliers, whose comments steered us towards the Stars.'