Thermal error compensation of dry hobbing machine tool considering workpiece thermal deformation

Dry hobbing is a new gear tooth forming process, which would replace the traditional wet hobbing process due to its high efficiency and environmental friendliness. However, due to the absence of metal cutting fluid in dry hobbing, temperature of hobbed workpiece is relatively high, which will lead to the increase of dimension errors, especially tooth thickness errors. In this paper, the features of workpiece thermal deformation errors are identified and an error compensation model is developed to compensate both machine tool thermal errors and tooth thickness errors which is induced by workpiece thermal deformation. In this model, the representative temperature variables of a dry hobbing machine tool are obtained based on experimental data with fuzzy clustering method. A compensation model is proposed to map the relationship between representative temperature variables and compensation value. In a series of experiments, the tooth thickness errors ranged from -22 to -59 mu m. After implementing compensation of machine tool thermal errors, the tooth thickness errors ranged from -18 to -28 mu m, which demonstrates that workpiece thermal deformation has a great influence on tooth thickness errors in dry hobbing. Furtherly, the tooth thickness errors ranged from -4 to 8 mu m, after implementing compensation of both machine tool thermal errors and workpiece thermal deformation errors, which demonstrate that the compensation model is effective.