Thermal design of the vertical machining centre headstock by the forced cooling method

The headstock thermal drift is a major source of the machining error for a vertical machining centre. However, the research so far reported has been unable to provide a satisfactory method to eliminate the spindle axis dip angle resulting from the thermal drift. In this article, a thermal design is carried out for the vertical machining centre headstock by introducing a dual cooling system, utilizing forced water cooling subsystem and a forced air cooling one. An integrated thermal model of the vertical machining centre headstock has been established by aid of the finite element method, and the appropriate structural parameters of the dual cooling system have been analysed. The theoretical results were verified by an experiment in which the perpendicularity between worktable surface and the spindle axis resulting from the thermal displacement is measured. The results indicate that the thermal behaviour of the vertical machining centre headstock can be improved using the dual cooling method.