Coorecting steady-state temperature influences on coordinate measuring machines

The use of coordinate measuring machines (CMMs) outside a strictly controlled environment necessitates the management of the temperature-dependent geometry of the machines. This paper presents a thermal error compensation based on physical relations between temperature and deformation, rather than on an empirical model linking inputs and outputs (for example, a regression model or a neural network). Based on an extensive set of laser interferometer measurements, a thermal compensation scheme is composed. A Zerodur hole plate is used to verify the applicability of the model via real measurements. This thermal stable artifact allows monitoring the machine's geometry under various thermal loads. Differet parameters like lengths and angles are measured under various near steady state environment conditions. The developed thermal correction uses only six thermometer inputs. For temperatures different from 20°C, the model reduces the uncertainty of length measurements to the level of the stochastic errors at 20°C. Under spatial temperature gradients, a significant reduction is also obtained.