非共轴螺旋后刀面微钻几何结构优化与刃磨制备研究

非共轴螺旋后刀面微钻相比普通平面后刀面微钻，在刀具刃磨效率及其钻削性能方面具有显著优势。微钻几何结构微小改变将引起钻削性能的重大变化。建立非共轴螺旋后刀面和螺旋槽的数学模型，计算不同几何结构参数下微钻的切削刃形状、前角和未变形切屑厚度，同时建立不锈钢微孔钻削有限元仿真模型，分析螺旋角、钻芯厚度与锋角对钻削力、温度与切屑形态的影响规律，对非共轴螺旋后刀面微钻几何结构进行优化。仿真结果表明：随着锋角增大，轴向力增大，扭矩和温度降低；随着螺旋角增大，钻削力和钻削温度降低，但是当螺旋角增大到40°时，切屑为带状切屑，切屑易阻塞，容易引起刀具折断；随着钻芯厚度增大，钻削力和钻削温度同时增大，切屑宽度减小。结合不锈钢微细钻削过程中钻削力、钻削温度和切屑形态的变化规律，提出优化的微钻几何结构参数。基于六轴数控工具磨床以及所建立的数学模型，磨制出非共轴螺旋后刀面微钻。测量结果表明，其几何参数与设计值基本一致。钻削试验结果表明，该几何结构参数的微钻具有良好钻削性能。

Optimization of Geometric Structure of Non-coaxial Helical Flank Micro-drill and Its Grinding Processing

Non-coaxial helical flank micro-drill has a significant advantage in the tool grinding efficiency and drilling performance compared with the plane flank drill. A slight change in the geometry structure of micro-drill causes a significant change in drilling performance. The mathematical models of non-coaxial helical flank and helical groove are proposed, and the cutting lip shape, rake angle and uncut chip thickness are calculated. The micro-drilling finite element simulation models of stainless steel are established to optimize the geometric structure of non-coaxial helical flank micro-drill, and the effects of helix angle, web thickness and point angle on drilling force, temperature and chip morphology are investigated. The results show that the thrust force increases with the increase in point angle within a certain range of geometric parameters. On the contrary, the torque and temperature decrease with the increase in point angle. The drilling force and temperature decrease with the increase in helix angle. The geometry of chip is continuous chip when the helix angle arrives to 40°, which is easily blocked lead to tool breaking. With the increase in web thickness, the drilling force and temperature increase simultaneously, but the width of chip reduces. The optimized micro-drilling geometric parameters are obtained based on the variation of drilling force, drilling temperature, and chip morphology during the micro-drilling of stainless steel. The non-coaxial helical flank micro-drill is fabricated based on six-axis CNC tool grinder and the mathematical model. The measured results show that the geometrical parameters are basically the same as the designed values. And the experimental results show that the micro-drill with the optimized geometric structure has good drilling performance.