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APPH Nottingham has bought a nine-axis Star SV-32 sliding-head lathe to mill-turn components from stainless steel and titanium bar.

Most of the components APPH makes are for the aerospace sector and include landing gears.

APPH chose the Star sliding-head lathe, mainly because of its rigidity, heavier construction and high-power drive to the live cross-working and end-working tools.

The Star SV-32 weighs 3.8 tonnes.

An FMB Turbo 3-36 magazine feeds bar up to 3.2m long into the working area.

The machine has turret-mounted tooling as well as a gang toolpost and has been equipped with high-pressure coolant delivery for improved chip control and tool life when producing safety-critical components from exotic aerospace metals.

The SV-32 is used for one-hit mill-turning of parts up to 32mm diameter, mainly stainless steel and high-carbon steel plungers.

Each is subsequently match-ground to fit the bore in the body of a hydraulic actuator.

The SV-32 also regularly produces titanium alloy vortex tubes in batches of 2,000-off, 27 of which fit into a titanium ring that forms part of the fuel-distribution system in an aircraft.

The remainder of the sliding-head lathe’s time is spent on mill-turning intricate sleeves, connectors and other components to tight tolerances.

Formerly, such parts had to visit two, three or even four machines.

These were typically a fixed-head lathe, a CNC milling machine for adding prismatic features and sometimes a manual machine for hole drilling at compound angles and a wire-cut or die-sinking EDM machine for adding serrations.

In addition, a part number is engraved on some components, which is also performed in-cycle on the Star lathe, saving a further separate operation.

Consolidating repeated set-ups on several different machines into a single operation causes: faster turnaround; the elimination of tolerance build-up, improving component accuracy; and reduced operator involvement and work-in-progress, which results in lower costs.

Accuracy of parts run on the Star SV-32 is verified on Hommel optical inspection equipment, which checks the profiles against DXF files derived from the original CAD data.

Dave Fell, APPH’s manufacturing engineer, said: ‘We opted for a sliding-head mill-turning centre rather than a fixed-head CNC lathe with counter-spindle and live tooling because of the large variety of shaft-type components we produce, up to 14 times longer than their diameter.

‘Having said that, some of our parts are relatively short, say twice their diameter, and these are produced just as efficiently on the SV-32.

‘The other benefit of the sliding-head configuration is that three tools are often in cut simultaneously, so productivity tends to be higher than on fixed-head lathes, few of which can deploy more than two tools cutting at the same time.

‘Irrespective of shape, complexity and material, provided that it is of 32mm diameter or less, a component can usually be machined more efficiently on the Star sliding-headstock lathe.’ Machine operator Dave Broadfoot added that there had been no problems with either the SV-32 or the FMB bar magazine in nearly two years of operation.

He added that, even though APPH Nottingham was new to sliding-head turning at the outset, on-site training for one week was sufficient to ensure proficiency in machine programming and operation.

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