Machining of high-performance materials with ultrasonically modulated cutting speed

为了满足不断增长的对轻量化设计和能源效率的要求，硬质合金、陶瓷和纤维增强塑料等难加工材料变得越来越重要。考虑到传统的加工工艺，这些材料只能在刀具磨损较高的情况下加工。超声辅助加工是解决这一问题的有效方法。在超声辅助加工的情况下，在传统加工过程的运动学上叠加了一个附加的高频振荡。这会在刀具刀具刃口上产生几微米范围内的振荡，从而导致切割速度或进给量的高频变化。因此，可以实现切削力的减少、刀具寿命的增加以及工件质量的改善。在铣削和磨削中，已经表明，在相对于工件的轴向(即垂直于切割方向)上的振动激励的情况下，这些影响已经部分存在。为了进一步提高加工效果，可以在加工方向上叠加振动，从而对高频加工速度进行修正，因此，本课题的研究目的是为超声调速振动辅助磨削提供依据。为此，构造了一种超声驱动器，利用该驱动器可以将铣削和磨具与纵扭超声振动叠加在一起。随后，对振动辅助球磨进行了基础性研究。在球磨过程中，对难加工的钛合金进行了加工。分析了常规工艺参数(速度、进给速度、切削深度和刀具几何形状)和振动参数(频率和振幅)对加工精度的影响。在此过程中，对产生的影响进行了分析，旨在最大限度地减少刀具磨损，提高工件质量。同时，对超声调速下硬脆材料的磨削进行了基础研究，研究了常规参数与振动参数(幅值和频率)之间的相互作用。

In order to meet the constantly increasing requirements with regard to lightweight design and energy efficiency, difficult-to-machine materials such as hard metals, ceramics and fiber-reinforced plastics are gaining in importance. Considering conventional machining processes, these materials can only be machined with high tool wear. Ultrasonic-assisted machining has proved to be suitable to successfully address this issue.In the case of ultrasonically assisted machining, an additional high-frequency oscillation is superimposed on the kinematics of the conventional machining process. This generates oscillations on the tool cutting edge in the region of a few micrometers, thereby causing a high-frequency change in the cutting speed or the feed. Consequently, a reduction in cutting forces, an increase in the tool life as well as an improvement in workpiece quality can be achieved. In milling and grinding it has been shown that these effects are already partially present in the case of a vibration excitation in the axial direction relative to the workpiece, that is perpendicular to the cutting direction. Further improvements of the process results can be achieved by superimposing a vibration in the cutting direction and thus modifying the cutting speed at high frequency.Therefore, the aim of the research project is to provide a basis for vibration-assisted milling and grinding with ultrasonically modulated cutting speed. For this purpose, an ultrasonic actuator is constructed, with which both the milling and the grinding tool can be superimposed with a longitudinal-torsional-ultrasonic vibration. Subsequently, fundamental investigations are carried out for vibration-assisted milling and grinding.During milling, the hard-to-machine titanium Ti-6Al-4V alloy will be machined. The influence of conventional process parameters (speed, feed rate, cutting depth and tool geometry) and oscillation parameters (frequency and amplitude) are evaluated. In doing so, the occurring effects are analyzed aiming at minimizing tool wear and increasing the workpiece quality. At the same time, basic investigations are carried out for the grinding of hard-brittle materials with an ultrasonically modulated cutting speed, in which the interactions between conventional and vibration parameters (amplitude and frequency) are also studied.The milling experiments are carried out on an Ultrasonic linear 40 machine tool, which was provided by the DFG for fundamental studies particularly on vibration-assisted machining.