ABSTRACT
The fundamental way for identifying the volumetric errors of CNC machine tools is by using a proper method to separate the monomial error from the comprehensive error by measuring the comprehensive displacement errors of lines in the working region. Using the appropriate method for identifying the different types of errors, entire volumetric errors can be obtained concisely, efficiently and precisely. The dual-frequency laser interferometer is the most accurate measurement system used extensively today [1]. There are many methods proposed based on the dual-frequency laser interferometer. Zhang developed a displacement method measuring along 22 lines [2]. This method needed to iterate over the solution and to take strict rules in choosing the measurement points. Thus, the errors propagated seriously. Chen put forward a method measuring along 15 lines [3], which improved the accuracy of the measurement results substantially. However, it was too complex to solve the equations in order to apply this method generally. Fan carried out a method based on the multi-body system measuring along 14 lines [4]. However a non-standard hypothesis was taken into the process which supposed that the sum of all the straightness errors on one axis is zero. Zhao et al. proposed a method only measuring 9 lines [5]. This method had to measure the straightness errors in two vertical directions and one linear error at the same time.
