Machining, Measurement, and Control Laboratory
 

2 0 0 1    J o u r n a l    P a p e r

 
 
 
 
Theoretical analysis of circular interpolation contouring error at quadrant changing position in NC machine tools
 
Jun Fujita (Toshiba Machine Co., Ltd.)
Sadaji Hayama (Toshiba Machine Co., Ltd.)
Minoru Hamamura (Toshiba Machine Co., Ltd.)
Kazuhiro Shiba (Toshiba Machine Co., Ltd.)
Atsushi Matsubara (Kyoto University)
Yoshiaki Kakino (Kyoto University)
Satoshi Owaki (Kyoto University)
 
 
 
Abstract

This project focuses on the analysis of circular interpolation contouring errors in NC machine tools. It is well known that the quadrant change in circular interpolation often introduces various contouring errors, such as the stick motion, lost motion, and exponential-type lost motion. Such motion control issues became of more importance due to the recent trend of high-speed machining. In particular, the stick motion is due to the friction between a slide table and guideways, and results in a spike-shaped error at quadrant changes. The exponential-type lost motion is due to the nonlinear spring characteristics of a rolling ball guideway.

More detailed theoretical analysis of the generation mechanism of the stick motion and the exponential-type lost motion is presented. For the analysis purpose, a dynamic model of a feed drive system is proposed that includes the nonlinear spring characteristics of a rolling ball guideway and the Coulomb friction between a ballscrew and its support bearings. Motion errors at quadrant changes due to the stick motion and the exponential-type lost motion can be estimated by using the proposed mathematical model. Several experimental tests are conducted on a test stand of a vertical-type machining center to show that the measured amount of motion errors coincide well with estimated results based on the proposed model.

 
 
 
 
 
 
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