Automotive industry supplier Donnelly Hohe Schleiz relies on theMikron HSM 700 high-speed milling machine to machine dies fordie-cast wing mirrors, exterior and interior door handles andboot catches for a customer base that includes the majorinternational car manufacturers. The company is one of the mainproducers of car mirrors in the world and in 1999, with aworkforce of 290, the company achieved sales of SFr 83 million.Unlike many other automotive suppliers, Donnelly Hohe Schleiz hasnot sub-contracted tool-making, for which it relies on high speedmilling. This creates definite competitive advantages, above allin time and flexibility.

In this fiercely competitive market itis no longer enough to restructure isolated areas of production,only when all the stages in the process are streamlined in aunified structure can maximum productivity be achieved.

Acrossthe board co-ordination, from CAD/CAM to the chucking equipment,provides significant increases in efficiency in die-casting.

Theinjection and die-casting moulds that Donnelly Hohe Schleizspecialises in are extremely complex, with deep, filigreecontours.

'The parts for which we make the moulds,'says Klaus Dietsch, head of the tool-making section, 'aresometimes so complicated that the moulds cannot be manufacturedusing any traditional straightforward technique.' In amarket sector, which is subject to enormous time pressure,imposed by the international car manufacturers on theirsuppliers, the most important things are, in his opinion,'quality and speed'.

For over a year, Donnelly HoheSchleiz has been using a Mikron HSM 700 high-speed millingmachine.

'Even with hard metals we can work without usingspark erosion.

We mill virtually everything,' says Dietsch.The main advantage is that all the machining can be done in onechuck set-up and on just one machine without having to changeprocedures.

That shortens the processing chain, avoidsre-chucking and set-up procedures and increases speed andaccuracy.

Surface quality is also improved because, for example,the thermal damage to the edges which occurs during spark erosionis avoided.

Depending on the mould, there is now a reduction ofabout a third in the spark erosion time, a third in the manualwork required, and of course also a saving in the material forthe electrodes.

Only rarely now, for special moulds with verydeep, narrow contours, does the company fall back on acombination of milling and erosion.

Naturally, the greatpotential of HSM milling for saving both time and money can onlybe fully exploited if the whole processing chain is upgraded.

TheHSM 700 is so fast that at least two NC programmers per shift arerequired.