Automotive industry supplier Donnelly Hohe Schleiz relies on the Mikron HSM 700 high-speed milling machine to machine dies for die-cast automotive components.
Automotive industry supplier Donnelly Hohe Schleiz relies on the Mikron HSM 700 high-speed milling machine to machine dies for die-cast wing mirrors, exterior and interior door handles and boot catches for a customer base that includes the major international car manufacturers. The company is one of the main producers of car mirrors in the world and in 1999, with a workforce of 290, the company achieved sales of SFr 83 million. Unlike many other automotive suppliers, Donnelly Hohe Schleiz has not sub-contracted tool-making, for which it relies on high speed milling.

This creates definite competitive advantages, above all in time and flexibility.

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

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

The injection and die-casting moulds that Donnelly Hohe Schleiz specialises in are extremely complex, with deep, filigree contours.

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

For over a year, Donnelly Hohe Schleiz has been using a Mikron HSM 700 high-speed milling machine.

'Even with hard metals we can work without using spark erosion.

We mill virtually everything,' says Dietsch.

The main advantage is that all the machining can be done in one chuck set-up and on just one machine without having to change procedures.

That shortens the processing chain, avoids re-chucking and set-up procedures and increases speed and accuracy.

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

Depending on the mould, there is now a reduction of about a third in the spark erosion time, a third in the manual work required, and of course also a saving in the material for the electrodes.

Only rarely now, for special moulds with very deep, narrow contours, does the company fall back on a combination of milling and erosion.

Naturally, the great potential of HSM milling for saving both time and money can only be fully exploited if the whole processing chain is upgraded.

The HSM 700 is so fast that at least two NC programmers per shift are required.