Nano-abrasion Machining of Brittle Materials for Ultraprecision Finishing

2000 Fiscal Year Final Research Report Summary

• Project/Area Number: 10450056
• Research Category: Grant-in-Aid for Scientific Research (B).
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 機械工作・生産工学
• Research Institution: Toyohashi University of Technology
• Principal Investigator: HORIUCHI Osamu Toyohashi University of Technology, Professor, 工学部, 教授 (20029185)
• Co-Investigator(Kenkyū-buntansha): IKENO Junichi Saitama Unisersity, Graduate School, Associate Professor, 大学院・理工学研究科, 助教授 (10184441)
• Project Period (FY): 1998 – 2000
• Keywords: Ultraprecision machining / Blasting / Hard and brittle material / Finishing / correcting figuring / Surface roughness / Fine abrasive

Research Abstract

In this study, to improve machining accuracy in ultraprecision machining of hard and brittle materials, nano-abrasion machining has been proposed for finishing and corrective figuring. In the nano-abrasion machining, fine abrasive grains contained in water are ejected under a high pressure from a nozzle and the resulting jet collides with the surface of work materials at a high speed. Then, if the collision energy is low, the abrasion rate may decrease down to a few nanometers per minute and ductile mode abrasion with a few nanometers surface roughness may occur even for hard and brittle work materials. The purpose of this study is to investigate the fundamental characteristics and applicability to corrective figuring of brittle materials.
The experimental apparatus developed was composed of a machining chamber, a high pressure screw pump, a ceramic nozzle, an X-Y table and a numerical controller. The work materials were two kinds of optical glass and single-crystal silicon wafers. Fine abrasives of fused alumina and ultrafine particles of silica were mainly used.
First, a series of fundamental experiments was performed without scanning of the nozzle. The removal spot changed its areal shape from a crescent moon to full moon as the collision angle increased from 30° to 90°. The longitudinal profile along the center line of jet flow had an asymmetric V-shape but the transverse profiles had two different shapes ; parabolic and W-shape. Depth of removal spot and surface roughness tended to increase with an increase of abrasive grain size and ejecting pressure. For a finer abrasives and a lower ejecting pressure, abrasion rates of a few micrometers per hour and surface roughness of a few nanometers were obtained. Therefore this method seemed sufficiently suitable for optical finishing.
Secondly, based on results of computer simulations, circular motion machining were performed. The obtained removal spot had an axis-symmetric UV-shape profile which seemed suitable for local removal in correcting figuring.
As a reslt, this machining method is considered applicable to ultraprecision corrective figuring of hard and brittle materials.