Five-axis machining at Plalite Ltd

Mill-turn centres prove to be a versatile alternative to driven-tool lathes for Kent sub-contractor

Posted on 04 Sep 2018 and read 704 times
Five-axis machining at Plalite LtdTony Bess, director of the sub-contract machinist Plalite Ltd in Sittingbourne, has invested £3 million in capital equipment in the last three years.

Included in the purchases were two Japanese-built Speedio M140X2 30-taper mill-turn centres from Brother.

Supplied by sole UK agent, Whitehouse Machine Tools Ltd, Kenilworth (www.wmtcnc.com), the first of these five-axis machines was installed in mid-2017; it proved so successful that a second was added six months later.

Plalite undertakes a lot of work that requires both milling and turning, so the multi-tasking capability of the M140X2s was attractive to the company, as was their compact footprint on the shopfloor.

Mr Bess said: “On the Brother machines, the number of operations needed to produce a part is minimised.

“Moreover, there are no concentricity issues, blending is perfect and the tolerances that we are able to hold allow us to quote for very accurate work.

“Short set-up times using milling-cutter back ends and the adoption of Lang zero-point quick-change chucks help us to maintain profitability by allowing the machines to be changed over quickly, which is especially important when producing components in small batches.”

When asked why he bought machining centres with turning capability — rather than bar automatics with live tooling — for the one-hit production of what are often predominantly rotational parts, Mr Bess said: “With a turn-mill machine, you get low milling capacity and a limited number of tools, compared with the 22 stations in the Brother turret — added to which, the driven-tool heads on lathes lack rigidity, which tends to cause vibration.

“With a mill-turn machine, you get a quick and very productive prismatic machining capability.

Plalite pic“All the tools are in taper holders that are much more rigid, particularly with the addition of face contact in the case of the M140X2 spindle.

“Moreover, set-up is a lot quicker, and we suffer no issues with holding tolerance.

“There are few restrictions on turning capability, as the direct-drive C axis takes just a third of a second to accelerate from zero to 2,000rev/min, which is a third the speed of a typical lathe but sufficient for many of the jobs we produce.

“If higher revs are needed for turning a particular component, we simply put it on a lathe instead.”

Mr Bess says the relatively limited turning speed is more than offset by ‘high dynamics’ in other areas, notably the 16,000rev/min BIG Plus face-and-taper contact milling spindle (which offers a 0.2sec start/stop time), 50m/min linear rapids and a tool change “that is so fast that it is difficult to see at times”.

In conclusion, Mr Bess said: “We engineer parts differently for production on the M140X2s, to optimise productivity. Cutting strategies are altered and milling routines adapted, with more trochoidal milling when using a machining centre instead of a lathe.

“Provided it is the right kind of mill-turned part, each process route is highly productive on the two Brother machines, making us more competitive.

“We have certainly won new work on the basis of buying them.”

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