Measuring of positioning, circularity and static errors of a CNC Vertical Machining Centre for validating the machining accuracy

• Laser test is performed to determine the linear positioning accuracy.
• Ballbar test is performed to determine the circularity accuracy.
• Static accuracy test is performed to determine accuracy status.
• The cutting test is performed to determine the actual machine accuracy.
• Machine tool’s errors can be compensated electronically or mechanically.

A CNC machine tool performance depends on the machine accuracy status which is very important to determine the end product compliance to the specification. The accuracy of the machine can be measured and analyzed; hence the errors’ impact can be predicted on a workpiece. This paper presents three types of accuracy tests performed on a CNC Vertical Machining Centre, how the accuracy status affect the end product quality and what are the corrective actions to be taken. First, the laser test to determine the linear positioning accuracy, second the ball bar test to determine the circularity accuracy and third, the static accuracy test to determine the machine current static accuracy status and finally the cutting test to determine the actual machine accuracy effect on a work piece. Machine tool’s errors can be diagnosed and minimize or eliminated by either electronic compensation or mechanical maintenance and sometimes both need to be done.