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Ch75-I044963.fm Page 371 Tuesday, August 1, 2006 5:58 PM
Tuesday, August
Page 371
5:58 PM
1, 2006
Ch75-I044963.fm
371
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A NEW METHODOLOGY TO EVALUATE ERROR SPACE
IN CMM BY SEQUENTIAL TWO POINTS METHOD
1
2
1
4
2
3
W. M. He , H. Sato , K. Umeda , T. Sone , Y. Tani , M. Sagara and H. Matsuzaki 4
1
Department of Precision Mechanics, Chuo University,
Tokyo 112-8551, Japan
2
Institute of Industrial Science, University of Tokyo,
Tokyo 153-8505, Japan
3
Makino R&D Center, Kanagawa 243-0308, Japan
4
Toshiba Machine, Shizuoka 410-8510, Japan
ABSTRACT
The sequential two points method (STPM), which was developed to identify the straightness motion
of machine tools and cut surface of machined parts, is applied to evaluate the straightness error motion
of the probe in a Coordinate Measuring Machine (CMM). Repeating the measurement on the
objective plane, a method to make a planelike error form is proposed by combining the measured
straightness error motions. If the procedures are made for the respective coordinates, error space can
be evaluated. This could be more easily done by any other conventional method. A compensation
method is proposed, which is possible to improve measurement accuracy without changing the
hardware configuration of the CMM.

KEYWORDS

Coordinate Measuring Machine, Sequential Two Points Method, Straightness, Flatness, Error Space,
Error Compensation, Manufacturing System, Measurement

INTRODUCTION

A Coordinate Measuring Machine (CMM) is indispensable in a manufacturing system as an apparatus
of accurate measurement. It has come to be used in production lines together with machine tools as
well as in specific rooms for measurement. Much effort has been made to develop methods of
calibration and compensation of a CMM (Zhang et al. (1985), Kunzmann & Waldele (1988), Evans et
al. (1996)) and to evaluate accuracy performance of machines (Kunzmann et al. (1995), Balsamo et al.
(1997)). In spite of the effort, it has been difficult to obtain definite and reliable results. One reason
would be that the ballplate which was used as the standard for the calibration was difficult to handle
and to obtain sufficient accuracy.