针对难加工材料钛合金在采用普通麻花钻传统钻削过程中存在钻削力和扭矩较大使得钻孔困难，刀具使用寿命低，连续长切屑易缠绕刀具、划伤孔加工表面、增大刀具-切屑-工件孔壁之间的摩擦以及排屑差引起堵屑和卡刀具的问题，引入一种新刃型刀具（即八面钻），并结合超声振动钻削技术，进行了钛合金旋转超声辅助钻削试验。分析了旋转超声辅助钻削和普通钻削中切屑形成原理，采用文中所设计的旋转超声振动钻削主轴结合BV100立式加工中心平台、测力系统和非接触激光测量系统进行了无冷却条件下基于八面钻的钛合金旋转超声辅助钻削和普通钻削试验以及钻削力、扭矩和切屑形态的研究。试验结果表明：相比于普通钻削，超声钻削明显降低钻削力和扭矩分别为19.07%~20.09%和31.66%~34.3%，明显增强了钻头横刃和主切削刃的切削能力，获得了良好的断屑和排屑效果，提高了切削过程的稳定性，能够极大改善钛合金钻孔过程钻削困难、刀具使用寿命低和孔加工质量差的问题。
To solve the problems consisted of big thrust force and torque that led to the difficulty in drilling operation of machined hole, low tool life, as well as continuous long chip that easily caused the tool entanglement, surface scratches of machined hole, increased frictional effect between the tool, chip and hole wall, and poor removal effect of chip evacuation that easily resulted in the chip jamming and tool jammed after the traditional drilling process of the difficult-to-cut materials like titanium alloys (Ti6Al4V) using the common twist drill, a novel tool (i.e., 8-facet drill) is introduced and the rotary ultrasonic-assisted drilling (RUAD) technology is combined so as to carry out the RUAD experiments of Ti6Al4V. The principles of chip formation in RUAD and common drilling (CD) process are analyzed. And then, the drilling experiments of RUAD and CD of Ti6Al4V based on the 8-facet drill under no cooling condition are performed, which combined with a designed RUAD spindle unit, BV100 vertical machining center platform, measurement system of thrust force and non-contact laser measurement system; meanwhile, the thrust force, torque and chip type in RUAD and CD are studied. The experimental results indicate that compared with the CD of Ti6Al4V, in the RUAD process, the thrust force and torque decreased by 19.07% to 20.09% and 31.66% to 34.3%, respectively, the cutting abilities of chisel edge and major cutting edge are enhanced significantly, the excellent effects of chip breakability and evacuation are obtained, the cutting stability of drilling process is increased, as well as the problems comprised of the big drilling difficulty, low tool life and poor hole quality can be greatly improved.
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