Abstract
This study presents a multiphysics simulation analysis that was performed for the cooling channel of a built-in spindle. The design of experiments (DOE) method was employed to optimize the dimension of the cooling channel, and a practical machining experiment was performed to validate the effect of the design. In terms of the temperature, pressure drop, thermal deformation, manufacturing cost, and initial cost considerations, the paralleling type cooling channel of the front bearing and the helical type cooling channel of the motor were adopted in the study. After the optimal design of the cooling channel was applied, the bearing temperature was reduced by a maximum decrease of 6.7 °C, the spindle deformation decreased from 53.8 μm to 30.9 μm, and the required operational time for attaining the steady state of the machine tool was shortened from 185.3 min to 132.6 min. For the machining validation, the spindle with the optimal cooling channel design was employed for vehicle part machining, the flatness of the finished workpiece was increased by 61.3%, and the surface roughness (Ra) was increased by 52%. According to the findings for the optimal cooling channel, when the spindle cooling efficiency is increased by the optimal cooling channel design, the thermal deformation and warm-up period can be reduced effectively, and the machining precision can be enhanced. This method is an efficient way to increase the accuracy of a machine tool.
Highlights
40% to 70% of the machining errors of a machine tool are induced by thermal deformation
A multiple physical coupling simulation analysis was performed for the cooling channel design of a built-in spindle, and the design of experiments (DOE) method was adopted to optimize the critical dimension of the cooling channel
A comparison of the theoretical calculation and experimental results indicates that the heat generation of the front bearing and rear bearing was higher than the built-in motor at a spindle rotating speed of 12,500 rpm
Summary
40% to 70% of the machining errors of a machine tool are induced by thermal deformation. In the ball-screw of a machine tool feeding system, cooling channels are designed to remove generated heat and reduce thermal error [6,7,8]. Huang et al [16] performed experiments and a simulation to investigate the effect of cooling channels on the temperature rise and deformation of a built-in spindle at a rotating speed of 18,000 rpm and 10 min of operation. Adopted a high-speed built-in spindle to analyze the heat convection coefficient variation of the cooling channel at different cooling flow rates by simulations and experiments. The on–off operation of a cooling system was employed to experimentally attain the minimum thermal deformation of the vertical machine tool and lathe-milling machine tool and indicate that the proposed method could effectively increase the efficiency of the cooling system. Practical machining experiments were conducted to verify the machining accuracy enhancement by the optimized cooling channel design
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