Super abrasive peel grinding bests Inconel turning

Holroyd has employed its super abrasive machining technology to reduce the cycle time for producing turbo charger stators from 5½ minutes to just 46 seconds. These improvements have been achieved using Peel Grinding of the stator shaft, removing as much as 5 mm a side in a single cut. In addition, the super abrasive wheel used in the Holroyd process lasts up to 200 times longer than tool inserts used with in twin turret turning, providing a life of at least 10,000 parts to minimise tooling and machine set-up costs. “We are not surprised by these findings,” said Neil English, sales director of Holroyd. “In every case where we have performed machining trials with our Edgetek machines we have achieved at least a 40 to 50 percent increase in throughput, and in many cases it is much, much more.” The stators comprise an Inconel impeller attached to a mild steel shaft. Previously, the time to machine the shaft and the faces and OD of each impeller was 5½ minutes, using twin turret lathes. However, there were a number of problems with this machine set-up. First, the cycle time was too long to enable the manufacture to achieve his desired component cost. Second, although a twin turret lathe was used to ensure full depth of cut on the shaft - without bending, this did not account for the resulting upset of the shaft during the deep machining process. Third, the depth of cut required – 5 mm a side - from the twin turret lathe, and the resulting chattering of the tools in operation, meant that the life of tool inserts was extremely poor, with commensurate high costs for replacement.