Measurement of Motion Accuracy and Improvement of Machining Accuracy on Ultra-high Precision NC Machine Tools by Using Cross Grid Encoder Test

The Cross Grid Encoder is a position detector with a grid which crosses at a right angle, superior to conventional optical linear scales which have not been capable, as the Cross Grid Encoder is, of two-dimensional position detection. When this system is applied in the Circular Motion Test, measurement of behavior on a small radius and high feedrate was conducted with high precision, a capability which the DBB test has not offered. In addition, since it can measure the error of not only the circular interpolation but also the linear interpolation, it is possible to obtain information which is very beneficial for the improvement of machine accuracy. This study investigates the causes of the impediments towards machining accuracy improvements by comparing the accuracy measurement of the double-axis feed motion and actual machining accuracy on the ultra-high precision NC machine tool. Finally, by clearing away the ultimate causes of the impediments the improvement of machining accuracy is confirmed.