Rugged, mid-size milling centres for tough alloys

LB Bentley, based at the Kingfisher Business Park in Stroud, part of the Severn Glocon Group, has identified an ideal platform for producing its subsea valves, and also its filter and dryer equipment, from tough materials. It is the AA1165 VMC with 1,100 x 650 x 600 mm working envelope built by Toyoda joint co-operation company WELE. One was installed at the start of January 2019 and a second is due for delivery in March. The sales and service agent in the UK and Ireland for the Taiwanese machine manufacturer is Whitehouse Machine Tools, Kenilworth.

Although LB Bentley’s existing production equipment has served them well, the company wanted initially to replace two VMCs with new machines capable of meeting the tight positional tolerances and surface finish required when producing components from a range of difficult materials including 625, 718, 725, 825 and 925 nickel alloys and Duplex/Super Duplex stainless steels.

One of the difficulties with the ageing VMC’s was the inability to mill by circular interpolation a sealing surface without four quadrants being visible and lines apparently at each change of axis direction, with the attendant risk of parts being rejected. Quality is paramount, with ± 1.5 µm dimensional accuracy and 0.4 mm Ra surface finish required.

The AA1165 machine, fitted with a high pressure (70 bar) coolant system, has proved itself easily capable of achieving the drawing tolerances when machining nickel and steel alloys. Features of the WELE that secure a combination of heavy cutting performance and precision finishing include two-speed, auto change gearbox drive to the 18.5/15 kW BIG Plus 8,000 rpm spindle, which delivers up to 469 Nm of torque, hand-scraped square-section guideways, rigid construction, up to 10 m/min cutting feed rate and 36 m/min rapids in X and Y, 20 m/min in Z.

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