Compensation of machine tool angular thermal errors using controlled internal heat sources

Thermal errors caused by the influence of internal and external heat sources in machine tool structure can cause up to 70% of total machine tool inaccuracy. Therefore, research on thermal behavior of machine tool structures is crucial for successful manufacturing. This paper provides an insight into the modeling of highly nonlinear (increasing with the complexity of the structure) machine tool thermal behavior using thermal transfer functions. This approach to modeling is dynamic (uses thermal history) and, due to its relative simplicity, it enables realtime calculations. The method uses very few additional gauges and solves separately each influence participating in the thermal error. The main objective of the article is to describe the estimation of angular deformations occurring at the tool center point due to thermal influences. Transfer functions are used for the identification and control of additional internal heat sources. The second aim is to compare modeling effort with approximation quality. A partial objective is to cover other nonlinearities occurring generally in machine tool thermal behavior. The approach has been verified on a closed quill (a simple and symmetrical machine tool part) and applied on a model of a machine tool structure which has been chosen as the least favorable from the thermal point of view.