Electronic based accuracy enhancement of CNC machine tools

The need for better machine tool accuracy is discussed
together with the factors which can affect machine tool
accuracy. A study is made of the various techniques adopted
for the reduction of errors in machine tools. The concept
of error compensation is discussed and the different
techniques for error compensation are appraised. A critical
appraisal is presented of the work undertaken to date in
the field of error compensation. Based on this appraisal a
criterion is established for a universally applicable error
compensation system. The development of a novel, patented
microprocessor based machine tool error compensation system
which fulfills this criterion is described. This
compensation system, which is based on the precalibrated
compensation technique, utilizes a unique geometric
compensation algorithm. This algorithm allows the
compensation system to compensate for the geometric error
components of any machine tool configuration up to three
axes. The development of this geometric algorithm is
presented. The integration of this compensation system to a
large moving column milling machine is described.
Measurement tests and cutting tests were performed on this
milling machine to establish the effectiveness of the
compensation system. The results from these experimental
tests are presented, and illustrate the significant
improvement in machine tool accuracy achieved through error
compensation.

This is the first attempt at producing a machine tool
error compensation system with universal applicability,
both in terms of the machine geometric model, and the
method of applying the compensation to the machine tool.
The error compensation system developed gives the potential
for compensating for thermally induced and load induced
position errors, and will enable further work in this area
to be commercially exploited.