A practical system for 5-axis volumetric compensation

Compensation is a recognised technique for correcting the systematic errors inherent to machine tool positioning systems. It offers a cost effective and flexible solution to the problem of enhancing machine accuracy. In spite of this controller manufacturers provide limited facilities for applying compensation, and in many cases linear positioning compensation only is available. The main reason for this is the potential complexity of a comprehensive compensation system able to cope with the variety of axis combinations and configurations available in the modern machine tool market. This problem is compounded by the demand from industry for precision 5 axis machining. This paper describes a practical geometric error compensation system that can be applied to any machine tool that has up to 5 axes. The system can correct for the effects of all the geometric errors associated with a machine's linear axes, together with the geometric errors associated with a fork type servo head. The system applies compensation dynamically and in real time as the machine moves throughout its working volume.