A Method of Testing Position Independent Geometric Errors in Rotary Axes of a Five-axis Machine Tool Using a Double Ball Bar

Research output: Contribution to journalArticlepeer-review


Colleges, School and Institutes


Ensuring that a five-axis machine tool is operating within tolerance is
critical. However, there are few simple and fast methods to identify whether
the machine is in a \usable" condition. This paper investigates the use of
the double ball bar (DBB) to identify and characterise the position indepen-
dent geometric errors (PIGEs) in rotary axes of a five-axis machine tool by
establishing new testing paths. The proposed method consists of four tests
for two rotary axes; the A-axis tests with and without an extension bar and
the C-axis tests with and without an extension bar. For the tests without an
extension bar, position errors embedded in the A- and C-axes are measured
first. Then these position errors can be used in the tests with an extension
bar, to obtain the orientation errors in the A- and C-axes based on the given
geometric model. All tests are performed with only one axis moving, thus
simplifying the error analysis. The proposed method is implemented on a
Hermle C600U five-axis machine tool to validate the approach. The results
of the DBB tests show that the new method is a good approach to obtaining
the geometric errors in rotary axes, thus can be applied to practical use in
assembling processes, maintenance and regular checking of multi-axis CNC
machine tools.


Original languageEnglish
Article number89
Pages (from-to)151–158
Number of pages8
JournalInternational Journal of Machine Tools and Manufacture
Early online date5 Nov 2014
Publication statusPublished - Feb 2015

ASJC Scopus subject areas