Winterthur's R and D in abrasive machining tech

The Winterthur Group, based in Villach, Austria, has reviewed research by its three R and D centres in production abrasive machining technology.

The centres have been working on products such as the plunge grinding of automotive camshafts at grinding wheel surface speeds of up to 200m/s using, typically, 480mm diameter CBN grinding wheels at 8000 rev/min.

Standard camshaft grinding practice before had been at surface speeds of 125-140m/s.

The company is now working on extending the lifetime of CBN wheels through updated dressing procedures.

There have also been developments in automotive gear manufacture.

In the US, for example, automotive plants are now changing from shaving to grinding.

Typically, US plants used two milling and one lapping operation.

This procedure has been replaced, for example, on a Gleason gear hobber using a finish grinding process.

Improvements have also been made in creep feed grinding processes.

'Nanowin' nano particles are now added to the vitreous grinding wheel formulation to reduce the risk of product surface 'burning'.

Winterthur said tests showed that Nanowin wheels reduced grinding time for Module 1.35 gears from 50s to 32s.

A NanoWin wheel can take a 1mm deep cut in one pass.

Wendt, owned by Winterthur, produces super abrasives, having developed ceramic cubic boron nitride (CBN), resin bond and metal bond wheels.

The company has produced a 'hybrid' wheel of metal- and resin-bonded CBN.

Cooling at the grinding wheel/workpiece interface is an important aspect of grinding technology.

Winterthur has also developed internally cooled wheels, typically on tool grinding.

In addition, tests have been carried out on camshaft grinding to eliminate the problem of coolant foaming.

Other developments carried out in the Winterthur R and D centres include: the development of a segmented wheel for camshaft grinding, radial plunge and axial peel grinding, and product cut-off wheels, for example wheels of 2m diameter for the hot cutting of forging billets to be used in a 55MN (5,500 tonf) forging press.

Winterthur said that the wire saw used before took three days to cut a billet compared with 1 hour using the 2m cut-off abrasive wheel.

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