| High precision diamond cutting tool, which has high quality cutting edge and minimal corner radius, is crucial in ultra-precision machining. However, due to the high hardness and abrasion performance, diamond cutting tool is difficult to process. In the developed countries, high precision diamond cutting tools and high precision grinding equipments are embargoed towards China. While in our country, the manufacturing technology of cutting tool lags behind the advanced western, and mostly relies on imports. A spindle unit of diamond tool grinding machine has been designed and researched in this paper, and provide the theory base for study of diamond cutting tool machine.First of all, the structure of spindle unit was designed and researched in this paper. The spindle unit includes three parts:the spindle rotation mechanism, the height adjusting mechanism and the angle adjusting mechanism. Taking into account high speed and high rigidity, precision angular contact ball bearings were used in the spindle unit. The height adjustment mechanism adopted screw, and angle adjustment mechanisms adopted worm gear. Particularly, the application of the sleeve and spline connection mechanism dissolved the interference between the two. The spindle unit can fully meet the basic requirements of grinding movement.Second, based on the Hertz elastic theory and calculation formulas of friction heat, the effects of bearing preload on bearing stiffness and thermal behaviors were investigated in detail. It was proved that bearing preload has significant effect on bearing stiffness and thermal performance. According to the design requirements, the optimum value of preloading force was calculated.Then, a finite element model was constructed that taking into account bearing axial and radial stiffness. The dynamic and static performances of the spindle unit, such as modal analysis, static analysis and harmonic response analysis, were analyzed by ANSYS software. The analysis results showed that the spindle unit can meet the requirements of diamond tool grinding. The results also showed that front bearings and wheel is the weak link in the unit, the performances of unit can be improved by improving design. The analysis results under different preload prove that the bearing preload has small effect on dynamic performance, and affirmed the optimum preload is reasonable in this design. Finally, the assembly drawings of the spindle unit have been performed. According to the deficiency of this paper, some suggestions of research were suggested. |
