If a linear encoder is used to record the slide position, the position control loop covers the entire feed drive mechanism. This is known as closed loop operation. Mechanical transmission errors can thus be detected by the linear encoder on the feed axis and adjusted via the control electronics. This rules out an array of potential sources of errors:
- Positioning errors due to the heating up of the ball screw
- Reversal errors
- Kinematical errors due to slope errors with the ball screw
Direct linear encoders are thus essential for machines that require high positioning accuracy and machining speeds. All HEDELIUS machining centres are fitted with direct Heidenhain measuring systems as standard.