An Evaluation Method for Two-Dimensional Position Errors and Assembly Errors of a Rotational Table on a 4 Axis Machine Tool

Authors: Jooho Hwang, Chang-Kyu Song, Chun-Hong Park

Abstract:

This paper describes a method to measure and compensate a 4 axes ultra-precision machine tool that generates micro patterns on the large surfaces. The grooving machine is usually used for making a micro mold for many electrical parts such as a light guide plate for LCD and fuel cells. The ultra precision machine tool has three linear axes and one rotational table. Shaping is usually used to generate micro patterns. In the case of 50 μm pitch and 25 μm height pyramid pattern machining with a 90° wedge angle bite, one of linear axis is used for long stroke motion for high cutting speed and other linear axis are used for feeding. The triangular patterns can be generated with many times of long stroke of one axis. Then 90° rotation of work piece is needed to make pyramid patterns with superposition of machined two triangular patterns. To make a two dimensional positioning error, straightness of two axes in out of plane, squareness between the each axis are important. Positioning errors, straightness and squarness were measured by laser interferometer system. Those were compensated and confirmed by ISO230-6. One of difficult problem to measure the error motions is squareness or parallelism of axis between the rotational table and linear axis. It was investigated by simultaneous moving of rotary table and XY axes. This compensation method is introduced in this paper.

Keywords: Ultra-precision machine tool, muti-axis errors, squraness, positioning errors.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1332770

References:

[1] Y. Takeuchi, H. Yonekura and K Sawada, "Creation of 3-D tiny statue by 5-axis control ultraprecision machining," Computer-Aided Design, Vol. 35, No. 4, pp. 403-409, 2003.
[2] S. Gan, H. , Lim, M. Rahman and W. Frank "A fine tool servo system for global position error compensation for a miniature ultra-precision lathe," International Journal of Machine Tools & Manufacture, Vol. 47, No. 7-8, pp. 1302-1310, 2007.
[3] Bono, M. and Hibbard, R., "A flexure-based tool holder for sub-╬╝m positioning of a single point cutting tool on a four-axis lathe," Precision Engineering, Vol. 31, No. 2, pp. 169-176, 2007.
[4] A.C. Okafor, Y.M. Ertekin, Derivation of machine tool error models and error compensation procedure for three axes vertical machining. International Journal of Machine Tools and Manufacture. 2000; 40; 1199-1213.
[5] C. Raksiri,M. Parnichkun, Geometric and force errors compensation in a 3-axis CNC milling machine, International Journal of Machine Tools and Manufacture. 2005; 44; 1283-1291.
[6] A.H. Slocum, Precision Machine Design, Prentice Hall, Englewood Cliffs, NJ, 1992.
[7] ISO230-6, Test Code for Machine Tools-Part 6: Determination of Positioning Accuracy on Body and Face Diagonals (Diagonal Displacement Tests) 2002.
[8] M.A.V. Chapman, Limitations of laser diagonal measurements, Precision Engineering; 2003; 27 ; 401-406.
[9] J. Hwang, C.H. Park, C.H.Lee and S.W. Kim, "Estimation and correction method for the two-dimensional position errors of a planar XY stage based on motion error measurements," International Journal of Machine Tools and Manufacture, 46, pp. 801-810, 2006.