An investigation of effect of machine loop stiffness

An Investigation of the Effect of Machine Loop Stiffness on Grinding of Ceramics
Bi Zhang (2) University of Connecticut, Storrs, CT 06269, USA Zhang@engr.uconn.edu

Abstract This experimentalstudy deals with the effect of machine structural loop stiffness on grinding of ceramics. The objective of the study is to investigate how the loop stiffness affects grinding forces, wheel actual depth ofcut (ADOC) and workpiece strength. A compliant workholder is specifically designed and attached to a precision grinder to simulate grinding machines of various compliances so that the effect ofmachine loop stiffness can be isolated under otherwise identical conditions. Silicon nitride is used as workpiece material and ground with diamond wheels of two bond types and three grit sizes at machineloop stiffness of four different levels. The ground workpieces are assessed in terms of residual workpiece strength, grinding damage, grinding forces, and ADOC. Theoretical analyses are given toindicate that machine loop stiffness can affect on normal grinding forces and workpiece strength. A discussion is provided to reveal how residual workpiece strength is affected by residual stress andgrinding-induced damage.
Keywords: machine loop stiffness, surface grinding, residual workpiece strength

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INTRODUCTION

Ceramics are difficult to machine because of their extreme hardness and highbrittleness. Grinding has been one of the primary methods used in machining ceramics. However, grinding of ceramics has encountered several problems, such as reduced material removal rate due tomachine deflection, and strength degradation by grinding damage [I]. Machine deflection can be one of the factors contributing to grinding damage, strength degradation, and dimensional inaccuracies ofground parts [2-31. In order to reduce grinding damage, high stiffness machines have been recommended for commercial grinding of ceramics in ductile mode to obtain 'damage-free' workpieces [4]....