Sub-regional thermal error compensation modeling for CNC machine tool worktables

Abstract

For computer numerical control (CNC) machine tools, thermal error is currently compensated according to a single fixed point on the worktable. When the worktable is in motion, the thermal error obviously differs across the worktable due to manufacturing, assembly, and other factors from driving and supporting devices. This causes the thermal error compensation by the single-point (SP) method to have great uncertainty for the whole worktable. To solve this problem, this paper proposes a sub-regional (SR) method to compensate for the thermal error of a worktable. The SR method divides the worktable into different regions and establishes a thermal error compensation model for each region, which are then combined to compensate for the thermal error of the whole worktable. The influence of the number of regions on the compensation effect of the SR method was analyzed theoretically and validated experimentally to provide a basis for determining a reasonable number of regions. The prediction effects of the SR method were compared with the SP method. And the compensation effects of the SR method were compared with a two dimensional thermal error map compensation method. The experimental results showed that the SR method has high prediction accuracy and stability and has better compensation effect in practical application for the whole worktable.