Werkstückerwärmung bei trockener Drehbearbeitung

• Workpiece Warming in Dry Turning

Deppermann, Marc Hans; Kneer, Reinhold (Thesis advisor); Klocke, Fritz (Thesis advisor)

Aachen (2017, 2018)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2017

Abstract

Dry machining of metals is one of the most promising innovations inmachining technology by geometrically defined tools. The abstinence ofany cooling lubricant provides economical, ecological and health benefits incomparison to conventional machining, but leads to a significant warmingof the workpiece, tool, and chip. The workpiece warming causes thermallyinduced dimensional deviations as well as profile defects and finally reducesthe manufacturing quality.To overcome the lower quality of dry machining, the workpiece warmingmust be quantified and linked to machining parameters in order todevelop compensation strategies. Therefore, a generic machining process -orthogonal turning - is investigated in three steps:1. Record temperatures and forces,2. Reduce the cutting process to a thermal model of lower complexity and3. Calculate the energy dissipation from mechanical power into heat.The experimental investigation aims at the influence of cutting velocity,feed rate, and a wear resistance layer of titanium nitride onto the tool.The temperature variation of the workpiece is caused by dissipating energyat the interface of tool, workpiece, and chip and therefore, it is necessaryto calculate back from an effect to its cause. An inversed heat conductionproblem has to be solved based on experimental data, forming an ill-posedproblem. To determine the heat flux, a solution algorithm is developedand its stability as well as its numerical performance is verified based onan analytical solution.In order to compare the influence of all experimental variations thePéclet number is introduced and further, a thermal measure is defined: thethermal load. Using both definitions, general conclusions to describe theheat partitioning and to quantify the workpiece warming are made for allcutting parameters and tools with and without the titanium nitride layer.Finally, the cutting parameters are identified that reduce the thermalload and hence, minimize dimensional deviations and profile defects of drymachining. The findings provide a compensation strategy, that increasethe product quality without any need to change the tool path during drymachining.