Study on a Ultra-precisely Joining Method using a Shrink Fitter

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 08650168
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 設計工学・機械要素・トライボロジー
• Research Institution: Niigata University
• Principal Investigator: NITTA Isami Niigata University, Graduate School, Science and Techology, Associate Professor, 大学院・自然科学研究科, 助教授 (30159082)
• Co-Investigator(Kenkyū-buntansha): HARA Toshiaki Niigata University, Faculty of Engineering, Professor, 工学部, 教授 (50134953)
• Project Period (FY): 1996 – 1997
• Keywords: Machine Element / Fixing Element / Shrink Fitter / Out-of-Roundness / Polygon Mirror / Self-Acting Air bearing / Ultra Precision

Research Abstract

A shrink fitter was used to join an aluminum polygon mirror and a SiC self-acting air bearing ultra-precisely. It is inevitable that mirror surfaces of the polygon mirror will de wearped by heat gensrated from a motor if conventional joining methods, such as set screws and springs, are taken. The shrink fitter can resolve the deformation problem of the mirror surfaces caused by the temperature rise. The shrinkage fit gives better shaft location than the other joining methods.
Last year we designed dimensions of the shrink fitter by a numerical analysis, in which the mirror surfaces could not be warped over 100nm by the heat generated from the motor. Then the experiment were carried out to check the design of the shrink fitter.
After joining by the shrink fitter, the mirror surfaces of the polygon mirror have to be cut by a ultra-precision lathe to a desirable flatness of 100nm. This is called secondary cut. This year, to omit the secondary cut, we have searched optimum shapes of the poly gon mirror through computer simulation. Usually the mirror surfaces of the polygon mirror in rotation are deformed outwaed to some 300nm by a centrifugal force. However it is thought that special shapes of the polygon mirror can keep this deformation below some 100nm. So we checked some 30 or 40 shapes through the computer simulation and finally found out 2 or 3 optimum shapes which could keep the deformation below tolerable amount (submitted to JSME). Furthermore the effect out-of-roundness ofothe fitting surfaces on the deformation of the mirror surfaces was investigated. Six sets of specimens were prepared and the out-of-roundness of each specimen was measured. The shapes of the mirror surfaces sfter the shrink fit were calculated based on the measured out-of-roundess. In the experiment, the mirror surfaces were measured by the laser interferometer, ZYGO.The calculated values were in good agreement with the measured ones. Thus we could clarify the effect of the out-of-roundness (to be published from JSME). However it was also clear that the secondary cut could not be omitted if the out-of-roundness was 0.