Study on applicability of touch trigger probes in issues of on-machine measurement of machine tool thermal errors

Straka, M.; Mareš, M.; Horejš, O.; Sulitka, M.; Je, S.; Kim, H.; Kim, Ch.J. CIRP Journal of Manufacturing Science and Technology. 2025, 63 522-532. ISSN 1755-5817.

Machine tool (MT) thermal errors induced by external and internal heat sources are important elements in machined workpiece inaccuracies. In the past few decades, indirect software compensation techniques have been used to address thermal errors due to their economic and ecological advantages. As the sensory equipment of MTs increases, thermal error models can be adapted to regions with higher thermo-mechanical system nonlinearity and inhomogeneity through the introduction of deformation feedback from direct measurements into the model structures. However, adaptive functionalities require discrete interruptions of the MT’s work cycle, which threaten the integrity of the machined surface and complicate the model structure and thus also implementation and industrial deployment possibilities. This research investigates the applicability and validity of touch trigger probe (TTP) measurements for thermal error evaluation on MTs, comparing it with established reference methods. The study examines various operational conditions including no-load, idle heating and machining processes, with particular focus on the method's potential integration into adaptive thermal error compensation systems. Another goal of the paper is to emphasise the need for quality input information for modelling efforts and the industrial applicability of scientific results. Eight experiments were performed on two vertical 5axis milling centres (MT1, MT2) under no-load, idle heating, dry and wet machining, and climate chamber conditions. Results showed that TTP measurements were sufficiently consistent with reference methods under no-load and cool-down transition phases. In spindle idle heating, TTP exhibited nonlinear deviations up to 25 % during the transient part of the behaviour. In case of dry machining, TTP showed a linear deviation of ∼19 % compared to the reference method, which is correctable by a scalar factor. Under wet machining, deviations were negligible due to the homogenising effect of the cutting fluid. Climate chamber tests further confirmed strong ambient temperature dependence and increased error with multiple datum ball (DB) cycles. The study was limited to thermal displacements in the Z-axis. Findings demonstrate that while TTP is not universally reliable, it provides a valuable, industry-relevant approach for updating thermal error models if it is applied in suitable scenarios excluding method's limitations.