Thermal test for machine tool volumetric accuracy by a six-degrees-of-freedom laser measurement system

Thermal variations are among the dominant sources of volumetric errors in machine tools. Traditional approaches for evaluating thermal effects, described in ISO 230-3, are limited in capturing complex, position-dependent variations in tool displacement and orientation across the workspace. This study presents an experimental method to investigate the influence of temperature on all linear and angular error motions of a linear axis using a six-degrees-of-freedom (six-DOF) laser measurement system, which can simultaneously record all six linear and angular error components along a single axis in one setup, enabling efficient long-term thermal testing. Unlike conventional thermal tests that measure positioning errors only at a single point, the proposed test can evaluate thermal influence on the six- DOF trajectory of each linear axis. The experiments show observable variations in both positioning and angular errors, particularly along the Y-axis, which are attributed to thermal deformation of the guideways and machine structure. These component errors were incorporated into a geometric model to estimate three-dimensional volumetric errors at any point within the workspace.