How the VIPER grinding process can machine features on big nickel alloy components - like a 1.1m diameter jet engine casing - demonstrated the replacement of milling and lathe-turning.
The largest machine in a series of VIPER grinding demonstrations at Makino UK agent NCMT's technical centre in Coventry - a Makino A100 with 1700 x 1350 x 1400mm travels - showed how the benefits of VIPER grinding are transferrable to big nickel alloy components like a 1.1m diameter jet engine casing. Grinding and other metalcutting functions were combined to show how they can replace conventional milling and lathe-turning. Generally, if bosses are required around the periphery of a casing, the component is OD-turned to leave a band around the outside and the unwanted material is milled away.

Milling is an inefficient way of machining nickel, especially when large volumes have to be removed.

Now, CD grinding can replace milling, resulting in much higher productivity.

Other ground features on the casing included pads, diameters and scallops.

Indeed, VIPER grinding using 100 bar coolant pressure through the PCN and 70 bar through the spindle was used wherever possible, with milling restricted to finishing profiles that were too small for the 150mm diameter wheel to access.

The machining sequence started by showing how 2D contouring with a flat, 50mm wide wheel and roll dresser can perform much of the grinding required on such a part, including coning of an entry angle.

Automatic exchange to load the second, 30mm wide wheel and a V-form dresser was followed by machining of a diameter.

Third operation was milling the profile around the bosses.

Both the PCN and CD tapers were blanked off automatically to prevent swarf ingress.

Operation 4 involved drilling holes through an internal flange.

Such a component would typically require twice as many separate set-ups on a number of machines, and would involve a combined cycle time of between three and six times longer, in addition to handling and fixturing time.