Spindles in precision boring machines usually operate without internal cooling, and thermal error in such spindles is nonnegligible and can severely affect the end-processing quality of the machines. This study aims to investigate the effects that external cooling exerts on the thermal behavior of such spindles. A helical tube cooler is taken for external cooling. An analytical thermal resistance model for the grease-coated cooler-housing joint surface, which considers the pressured cambered-flat contact pair and rough metal surface-grease contact, is presented and validated, and a numerical thermal–fluid–solid coupling model for the cooler-spindle system is then established. An evaluation method is put forward to obtain the stability of the thermal error, which determines the boring processing accuracy and thermal equilibrium time, from experimental data. Then, the external cooling was optimally designed based on the simulation results from the numerical model. Experiments show that the designed cooler reduced the thermal equilibrium time by 47.13% and the maximum thermal error by 81.7%, and the proposed model can accurately predict the cooling effect on the spindle thermal behavior. This study not only provides a thermal error control method for the spindle but is expected to advance the theoretical basis of cooling design for complex electromechanical systems.

中文翻译：

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带涂层接头外部冷却的精密镗床主轴热误差控制

精密镗床中的主轴通常在没有内部冷却的情况下运行，此类主轴中的热误差是不可忽略的，并且会严重影响机器的最终加工质量。本研究旨在调查外部冷却对此类主轴的热行为的影响。采用螺旋管冷却器进行外部冷却。提出并验证了润滑脂涂层冷却器-外壳接合面的分析热阻模型，该模型考虑了受压弧形平面接触对和粗糙的金属表面-润滑脂接触，并提出并验证了用于润滑脂涂层的冷却器-外壳接合面的数值热-流体-固体耦合模型。然后建立冷却主轴系统。提出了一种评价方法，以获得决定镗孔加工精度和热平衡时间的热误差稳定性，从实验数据来看。然后，根据数值模型的模拟结果对外部冷却进行了优化设计。实验表明，所设计的冷却器使热平衡时间减少了47.13%，最大热误差减少了81.7%，所提出的模型可以准确预测冷却对主轴热行为的影响。该研究不仅为主轴提供了一种热误差控制方法，而且有望推进复杂机电系统冷却设计的理论基础。并且所提出的模型可以准确地预测冷却对主轴热行为的影响。该研究不仅为主轴提供了一种热误差控制方法，而且有望推进复杂机电系统冷却设计的理论基础。并且所提出的模型可以准确地预测冷却对主轴热行为的影响。该研究不仅为主轴提供了一种热误差控制方法，而且有望推进复杂机电系统冷却设计的理论基础。