Error Compensation of Coordinate Measuring Machines

• Published in: CIRP annals Vol. 34; no. 1; pp. 445 - 448
• Main Authors: Zhang, G., Veale, R., Charlton, T., Borchardt, B., Hocken, R.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1985; Elsevier
• Subjects: Applied sciences; Exact sciences and technology; Industrial metrology. Testing; Mechanical engineering. Machine design; Measuring instrument; Measurement; Length; Coordinate measuring machine; Metrology; Error correction; Measurement error
• ISSN: 0007-8506
• DOI: 10.1016/S0007-8506(07)61808-3

The methods and results are presented for applying software error compensation to a commercial three axis coordinate measuring machine. The technique incorporates compensation for geometric positioning errors and some thermal effects. Geometric error computation is based on a rigid body model of workpiece motion in the machine coordinate frame. Complete kinematic equations of the error motions are presented. The measurement method only requires taking a small set of data for each axis to compute the errors throughout the full workzone. To achieve the desired accuracy, squareness is determined using linear displacement measurements along selected machine diagonals. The dominant thermal effects in the machine are removed by introducing the concept of an “effective” nominal differential expansion coefficient. The entire error compensation computation is incorporated into the machine position reading subroutine to automatically produce compensated readings. The effectiveness of this method is tested by measuring linear displacement along arbitrarily oriented lines through the workzone and by measuring the length of a 500 mm gage block in several orientations. The results show a factor of ten performance improvement (limited by measurement repeatability) over 0.5 C range in temperature.