【作者】 刘小莹；

【导师】 吴能章；

【作者基本信息】 西华大学 ， 机械制造及其自动化， 2005， 硕士

【摘要】 由于可转位浅孔钻的两块硬质合金刀片在径向不对称分布在刀体上,导致加工时产生径向合力,从而使钻头轴线产生偏斜,进而影响被加工孔的质量。因此,最大限度地减小加工时的径向合力,就成为浅孔钻设计与制造中要解决的关键问题。为此,建立了浅孔钻在稳定钻削状态下钻削力及扭矩预报的理论模型,该模型包括三个部分:首先采用向量矩阵法建立了浅孔钻切削部分几何参数分析模型,使用该模型可计算出浅孔钻在钻削加工过程中切削刃上各点的刃倾角、法前角、法后角、主偏角及刀片搭接量的大小;其次采用经典的斜角切削理论和经验公式相结合的方法建立了浅孔钻钻削力预报的数学模型,该模型对一种工件材料给出了钻头的几何参数,切削用量及被加工材料的机械物理性能与钻削力和扭矩的关系,它可在较大的范围内分析上述因素对钻削力和扭矩的影响;最后,为了分析不同的工件材料对浅孔钻钻削力与扭矩的影响规律,作者采用了集成单元切削刃上的单位切削力的方法建立浅孔钻钻削力的预报模型。基于上述理论模型,对不同直径、不同切削用量及不同加工材料条件下的浅孔钻钻削力进行了数值仿真研究,并在此基础上,以内、外刀片径向合力与两刀片的扭矩之差为目标函数,以内、外刀片在刀体上的5 个安装参数为设计变量,建立了非线性的多目标、多变量约束优化模型。利用该优化模型对不同加工条件下的浅孔钻进行优化,得到使径向合力及扭矩为最小时的钻头结构参数。同时还对优化结果进行了分析,研究了径向合力随优化参数的变化情况、钻头直径与优化参数间的关系、切削用量与优化参数间的关系、被加工材料与优化参数间的关系以及浅孔钻优化前和优化后所产生的切削力与扭矩的对比。研究结果表明:任意直径的浅孔钻加工时的径向合力,可采用优化刀片在刀体上的五个安装参数使其为零。在刀片的五个空间位置参数中,ψ角的更多还原

【Abstract】 Due to the asymmetrical radial arrangement of the two carbide inserts of the drill with indexable inserts on tool body, the radial cutting forces will be generated during processing, which will lead to the deflexion of the drill axis, and hence affect the quality of the hole machined. Therefore, it is the key issue to be solved in the design and manufacture of the drill to minimize the radial cutting forces in drilling. In this dissertation, a theoretical model for predicting the forces and torque generated in steady drilling state is established. This model involves three parts. First of all, a model of dynamic geometry analysis for the cutting section of the drill using vector-matrix approach is developed, with the help of this model, the cutting edge inclination angle, normal clearance angle,cutting edge angle and the overlapped amount of the inserts can be obtained. Secondly, a mathematical model for drilling forces prediction based on classical oblique cutting theory combined with empirical formulae is built up. The relationship between the drill geometry, cutting conditions and the physical properties of the material to be machined and the drilling forces is given in the model for one type of workpiece material. Using this model, the effect of the factors mentioned above on the drilling forces and torque can be investigated within a broad range. Finally, In order to analyze the influence of different workpiece materials to be machined upon the drilling forces and torque, a predictive model by adding the specific cutting force at each unit cutting edge is established. Based on the model proposed above, numerical emulations for cutting forces and torque in drilling are conducted using different drill diameters, different machining data and different materials to be machined. According to the numerical emulations, a nonlinear and constrained optimization model, with the radial cutting force and torque as the objective function and five setting parameters of the inner and outer inserts on the drill body as design variables is established. With the help of this optimization model, the optimized drill structure, which will generate minimum radial cutting force and torque, can be determined for different cutting conditions. The optimum results are analyzed and how the optimal parameters affect the radial cutting force, the relationship between the drill diameter and the optimal parameters, the relationship between the machining data and the optimal parameters, the relationship between the material to be machined and the optimal parameters, and the comparison between the optimized drills and the drills without optimization are investigated. The research results show that the radial cutting forces generated by drills with different diameters can be reduced to zero by optimizing the five setting parameters of the inserts on the drill body. Among the five parameters, ψhas greatest influence on the radial cutting force while βhas smallest influence on the radial cutting force, thus, when the drills with indexable inserts are designed and manufactured, the tolerance limits for ψshould be strictly controlled. At the same time, the optimal parameters vary with machining conditions, and the five optimal parameters are also different for different drill diameter of the same type. The influence of the physical properties of the workpiece material to be machined upon the optimal parameters are minor. The outcome of the study will provide the theoretical basis and valuable optimized parameters for the design and manufacture of high performance and high quality drills.更多还原