Analysis Of Thermal Characteristic & Research On Its Experiment On Direct-drive Gear Hobbing Machine Tool

The technology"direct-drive"has been applied in gear hobbing machine tool, so the structure of gear transmission is removed, which not only reduces the effect of the geometry error on the machining precision, but also avoids the effect of the thermal error from the gear transmission structure on the machining precision. The precision and efficiency are raised greatly. But the effect of the heat on the machining precision, which is from electromotor, bearing and so on, can't be eliminated on the machine tool. And the rate of thermal error rises greatly in all the errors, which is from 40%~70% to 60%~80%. The heat source, the way of thermal transfer and so on are analyzed based on the structure of Direct-drive gear hobbing machine YK3610. The effect of the thermal deformation on machining precision is focused on theoretically and experimentally based on the machine tool. Thermal error compensation can be performed by it on the high-speed and high-precision machine tool.Firstly, thermal characteristic of direct-drive gear hobbing machine is analyzed in the paper, including thermal source, the way of thermal transfer, calculation of thermal transfer and calculation of heat. The rotor and stator of motor are the main thermal resource, and the 2/3 of the quantity of heat is from the rotor, which is the primary factor leading to thermal deformation on the machine tool. In addition, bearings are another important thermal resource. The layout and the number of the bearings have a direct effect on the quantity of heat.The effect of thermal deformation on the machining precision based on direct-drive hobbing machine is studied on primarily in the paper. The condition of the thermal deformation on workpeice spindle and hob spindle is analyzed by studying on the heat from the motor and bearings. Then error of the workpiece is calculated theoretically, and the error is from the thermal deformation of the spindles. It is known that the radial thermal deformation has an important effect on the gear direction precision from the analysis former. The radial and axial thermal deformations of the hob spindle have a great effect on the gear distance error and the direction error.The best way to testify the effect of machine tool on the machining precision is experiment. The thermal deformation of the workpiece spindle and the hob spindle is studied experimentally. The experiment indicates that the Y-direction thermal deformation of the workpiece spindle is larger than the X-direction one because of the effect of the thermal structure, and the Y-direction thermal deformation has a great effect on the machining precision of the work piece. The axial thermal deformation is very large, but it has a small effect on the machining precision of the work piece. The X-direction thermal deformation of the hob spindle is larger than the Z-direction one because of the effect of the thermal structure, and the axial thermal deformation is very complicated because of the effect of the trail bracket.At last, the control technology of the thermal deformation on the machine tool, including structure optimization and error compensation is studied in the paper. For example, the betterment of the cooling system of the motor can reduce the effect of the thermal deformation on machining precision. The thermal error compensation is in common use, because the cost is very low and the effect is obvious. The way to build mathematics model and the implementary progress are referred in order to compensate the thermal errors in the paper.