Electrodischarge Dressing of Diamond Grinding Wheel for the Finishing Process of Ceramics

1986 Fiscal Year Final Research Report Summary

• Project/Area Number: 60550081
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: 機械工作
• Research Institution: Ibaraki University
• Principal Investigator: KUBOTA Mamoru Ibaraki University, Fuculty of Engineering, Professor, 工学部, 教授 (00007593)
• Co-Investigator(Kenkyū-buntansha): TAMURA Yuji Ibaraki University, Faculty of Engineering, Research Associate, 工学部, 助手 (80007624)
• Project Period (FY): 1985 – 1986
• Keywords: Ceramics / Grinding / Dressing / Electrodischarge dressing / Diamond wheel / Diamond grain / Coefficient of friction / 静摩擦係数

Research Abstract

Finishing process of fine ceramics is grinding usually with a resinoid bonded diamond wheel but low grinding ratio causes high cost of processing. Metal bonded wheel is seldom used because of the troublesome dressing technique though it has high grinding ratio. Electrodischarge dressing (EDD) of metal bonded wheel is easy to dress it to get sufficient chip pocket with firmely fixed diamond grains. Small removal rate necessary for dressing permits using of cheap RC generator. Electrode gap in EDD required to avoid the cutting of the tool electrode by the wheel is found out experimentally. After EDD of a glazed wheel grinding forces of ceramics are measured. As a criterion of dressing effect coefficients of static friction between the wheel and a teflon plate are used. Surface of the ED dressed wheel is investigated with EPMA.
In order to avoid the cutting of the tool electrode by the grinding wheel out put voltage of the generator must be kept high enough in the EDD in tap water. Diamond grains are apprehensive of graphitization or ignition, therefore EDD is recommended to be processed in anoxic fluid with small pulse duration of under 30 us and low peak current of under 8 A. In order to obtain sufficient chip pockets surface roughness of ED dressed wheel should be kept smaller than 10 um Rmax. After EDD of glazed wheel grinding force decrease even to one tenth. Coefficient of static friction between the wheel and a teflon plate is 0.5 after EDD when it was 0.2 before EDD of the glazed wheel. After EDD surface of the diamond grain is covered sometimes with carbon and copper films and iron particles. They may assist electric discharge through the surface of the diamond grains, produce grooves surrounding them, weaken the bonding and increase the wheel wear by shedding.