Creep-Feed Grinding Wheel Development for Safely Grinding Aerospace Alloys

Abstract

Creep-feed grinding wheels have been associated with advances in processing difficult-to-cut materials used in the aerospace industry for many years. Since the late 1960s, the development of grinding wheels used for creep-feed grinding (CFG) operations and high-efficiency deep grinding (HEDG) operations has placed great responsibility on grinding wheel manufacturers to produce bonding systems of high strength and bonding bridges with smaller cross-sectional area. The safety of grinding wheels has become very important in recent years due to the increases in porosity (~ 50% vol.) and reductions in bond content (~ 5% vol.). This has necessitated the development of very strong bonding systems that can withstand high rotational, thermal, clamping and contact stresses. The paper not only provides a review of work performed on conventional grinding wheels, but also explains how the use of computational modeling techniques are used to simulate the stresses experienced by superabrasive wheels that are used at high-speeds in creep-feed grinding (CFG), high-efficiency deep grinding (HEDG) and peel grinding (PG) processes. Superabrasive materials of choice for use on difficult-to-machine alloys are typically cubic boron nitride (cBN) and diamond bonded with a vitrified glass-ceramic bonding system. The current work also explains how Weibull statistics are used to characterize the strength of the abrasive-porosity-bond composite structure and how the computational and Weibull statistical analyses are unified through the use of a simple measure of operational integrity known as the safety factor. The paper concludes by showing the reader how computational techniques can be used to design CFG wheels by optimizing abrasive segments bonded to a reinforcing material of high strength operating at a specific peripheral speed. It should be noted that this study is applicable to multi-layered CFG wheels and not to single-layer electroplated grinding wheels that are also used in CFG operations.