VMC machines vaporiser bodies from extruded stock

Anaesthesia equipment manufacturer, Penlon, is using a Daewoo vertical machining centre to produce vaporiser bodies from aluminium extrusions in-house.

Abingdon-based anaesthesia equipment manufacturer, Penlon, has achieved rapid success with the launch onto world markets of its Sigma Delta vaporisers, the outer bodies of which are machined from aluminium extrusion rather than being produced by metalforming.

A Daewoo vertical machining centre has been installed exclusively to produce this part, while a horizontal-spindle model machines various internal components from solid.

Both machines were supplied by sole agent, Mills Manufacturing Technology.

The ACE-V500 vertical machining centre was the first installation, in early 1999.

Penlon's Manufacturing Manager, Max Kelly, had intended that this machine would bring the production of all vaporiser parts in-house.

Volumes grew so quickly to its current level of between 1,000 and 1,500 per month that the machine is devoted to the body and two variants made for other anaesthetic machine manufacturers.

Said Mr Kelly, "At the time we were looking to produce several different components on this machine and reduce our reliance on subcontractors.

So we wanted a VMC with a long bed on which we could fixture several parts, and a large tool magazine to minimise tool exchange during set-up.

The Daewoo one-metre bed machine offered 30 tools, whereas most machining centres of this capacity at the time had 20 or 24 tools." Other desirable specifications included automatic tool change time of less than two seconds, 30m/min rapid feeds, swarf augers for evacuating the copious aluminium chips into trays beneath the machine, and Fanuc control to match those fitted to other machines in the factory.

These factors, combined with competitive price, decided the selection of the V500.

Three vaporiser bodies of 200 x 100 x 100mm nominal dimensions are fixtured along the bed.

At the first station, one end of a pre-cut length of polished aluminium extrusion is pocketed, drilled, tapped and has two recess features milled.

At station 2, the machined part from station 1 is inverted before undergoing a similar sequence on the reverse end.

Finally, the part is clamped on a vertical indexing head for milling openings on two opposing sides.

All three operations are completed in one continuous cycle before the doors are opened and the parts moved along, with a new extrusion entering at station 1 and a finished body leaving from station 3 each time.

The Daewoo ACE-H400P horizontal machining centre was installed in January this year (2001) when it became clear that 100 per cent in-house production volumes of the body would swamp the vertical-spindle machine, even working 24 hours a day, five days a week.

All other critical parts such as the valve block and back bars will be machined on the twin-pallet machine, there being no requirement to continue subcontracting out any of these critical parts.

Components are machined on all six faces and require two set-ups.

Max Kelly has arranged that two sides of a cube fixture on one pallet carry parts for first-operation machining while the second operation is performed on the other two cube faces.

This leaves the second pallet free to produce an entirely different part, maximising flexibility, although production demand has dictated that only valve blocks have been produced to date on this machine.

Three valve blocks are fixtured per cube face.

Operation 1 involves face milling the top; rough and finish profiling around four sides; then drilling, thread milling, boring, reaming and form drilling.

Operation 2 requires holes to drilled and tapped in the sides, followed by interpolation of a 5mm wide, 10mm deep spiral in four passes.

Here, Paul Toplis, Team Leader in charge of the Daewoo cell, has a useful tip as regards tooling to avoid swarf retention in the spiral and consequent tool breakage.

He uses nearly the full 12,000 rpm spindle speed of the machine with a Dormer single-flute carbide end mill and, surprisingly, the first tool Paul tried several months ago is still being used without any loss of performance.

Penlon opted for Daewoo again when buying the horizontal machine, having looked at two or three other suppliers, because the price was competitive and service with the VMC had been exemplary - Mills are usually on site the same day if there is a problem, or the next day at the latest.

"Confidence in a vendor's back-up is a big part of machine tool acquisition these days," commented Paul.

The nominal half-metre-cube, 7.5 second APC pallet-change machine specification is ideal for the applications.

Penlon wanted 40 or 50 tools and the H400P has 60 in the magazine.

The company was looking for speed and found it in the 40m/min rapid feeds and 4.0 second chip-to-chip ATC.

Coolant delivery and chip removal are efficient, consistent with the large amount of aluminium being cut.

Fanuc control is again standard.

Supplied by Mills as part of the H400P package was a Renishaw NC1 laser system for setting tool length and the diameter of boring bars.

It also detects tool breakage and shuts the machine down automatically.

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