Title

A study of the wheel wear and thermal limitations in creep feed grinding with particular reference to coolant application, and the grinding of vertical faces and slots

Date of Completion

January 1996

Keywords

Engineering, Aerospace|Engineering, Industrial|Engineering, Mechanical

Degree

Ph.D.

Abstract

The critical limitations of wheel wear and thermal damage to the workpiece were investigated for alumina and CBN wheels. The research consisted of three related efforts: coolant optimization, workpiece oscillation to improve coolant application to the sidewall and reduce thermal damage to the workpiece, and characterization of the source and nature of grinding wheel wear.^ Optimized coolant nozzle and coolant system conditions were verified in three ways: (1) by using a specially designed power flux rig in which an electrical heating element was employed to simulate heat input to the workpiece; (2) by grinding flat surfaces on test billets; and (3) by grinding production-run, profiled components considered most difficult to grind by Pratt & Whitney. Optimization results were used to demonstrate a reduction in wheel use of 27% relative to the current baseline production level during continuous-dress, creep feed grinding of profiled components.^ Transverse oscillation of an M-2 tool steel workpiece during the grinding of a vertical face, at a peak-to-peak amplitude of 0.381 mm (0.015 in.) and frequencies of 0, 0.2, and 2 Hz, showed that thermal damage to the workpiece can be reduced by employing workpiece oscillation directly through the grinding machine bed at a frequency of 2 Hz.^ The profiled production components ground during the coolant optimization study revealed that these parts were a limiting case of creep feed grinding, particularly on their vertical faces. Grinding tests performed to investigate this type of creep feed grinding showed that the corner of the grinding wheel, within the first 2.5 mm (0.1 in.), is responsible for all the grinding forces. Wheel corner wear was also observed during continuous-dress, creep feed grinding tests with alumina wheels, but may be hidden by the effect of continuous dressing, which begins to restore the corner profile as the wheel breaks through the trailing edge of the workpiece during reduced maximum normal infeed. These findings concerning the nature of wheel corner wear led to the development of a wheel corner wear model. ^