Research On The Key Technologies Of Micro-milling And Micro-cutter

In recent years, with the rapid development of micro/nano technology, thedevelopment and manufacturing of highly accurate and miniaturized componentswith complex shape has potential in widespread application in such fields asnational defense, aerospace, biological and medical treatment, automotiveelectronics, and communication systems. Micro-milling technology featuring highprocessing efficiency and diverse in processing material is characterized byfabricating complex real three-dimensional3D. Meanwhile, it has the advantage oflow processing cost and high flexibility. Up to now, the micro-milling technologyhas increasingly played an important role in manufacturing all these microproducts.Due to shrinking of cutting tool and its cutting parameters, micro-milling isdifferent from traditional machining in micro scale effect, such as temperaturedistribution, easy wearout of cutting tool, low removal rate, poor quality of surfaceprocessing and hard burr elimination, which seriously restrict the micro-millingtechnology applications in the processing of microproducts. In view of the abovequestions, key technologies such as temperature field distribution, burr control,micro-cutter wear and effect to cutting tool run-out have been investaged in thispaper. The detailed contents of this thesis contain:The study of micro-milling temperature field is significant in reducing toolwear, improving machining accuracy and surface quality. In this paper, thetemperature distribution of the micro-end-milling process has been investigated bynumerical simulations approach. Micro-end-milling processes are modeled by thethree-dimensional finite element method coupling thermal–mechanical effects. Thetemperature field is analysised during micro-milling process. The effect of varioustool edge radii, spindle speed, feed rate, depth of cut on cutting temperaturedistribution during micro-end-millingprocess are investigated. The simulationresults show that with increase of tool edge radius, the maximum cuttingtemperature region of the micro-cutter occurs from the rake face to the corner onthe tool edge and the flank face. The tool edge radius has been found to be themajor factor affecting micro-cutter temperature distribution, with a distinct obvioussize effect.Experiment is the effective means to research cutting temperature. Infrared (IR)temperature measurement systems are used to measure transient cutting temperaturefield in micro-milling process. The influence factors of tool edge radii, feed rate,spindle speed and depth of cut on cutting temperature field are investigated in detail.The experiment results agreed well with simulated results. Based on control volume method, the thermal partition proportion of micro-cutter, workpiece and chip arecalculated. It is found that the thermal partition proportion of chip is too more, thethermal partition proportion of workpiece and micro-cutter are too less.Burr is an important influence factors for evaluation of the miniaturizedcomponents surface quality. The three dimensional finite element model of themicro-milling was developed to dynamically simulate the burr formation process.The mechanism of burr formation is analyzed with the effect of cutting edge effect.The influence of feed per tooth, depth of cut, tool edge radius and cuttingtemperature on burrs formation are analyzed. The simulation results are verifiedthrough micro-end-milling experiment of microstructure grooves. The effect ofinfluence factors on the dimensions of top-burrs height are obtained in numericalsimulation and experiment respectively, with the maximum error within20%. Theexperimental results also show that the model is suitable for studying themechanism of burr formation and predicting the dimensions of burrs.The investigation of micro-cutter mechanism is helpful to prolong the micro-cutter life and improve the processing quality of workpiece. Micro-cuttermechanism and effect of run out on micro-cutter wear are investigated in micro-milling process. Micro-milling experiments are conducted on micro-machine wearmorphologies and wear mechanism of micro-cutter are analyzed. Based onoxidation analysis of micro-cutter, it is found that the oxidation reaction happenedin tool-tip region with oxygen, it can prove that the tool tip oxidation reaction withlocal high temperature occurs. The main failure modes of micro-cutter were coldwelding, abrasion wear and tool nose breakage. The three-dimensional micro-milling finite element models were built to analyze the wear mechanics of micro-cutter considering tool run out effect. The simulation results show that tool run outis found to have a significant influence on the mechanics behaviors and wear ofmicro-cutter. A small deflection angle will cause high cutting force, stress, and weardepth of micro-cutter. It is recommended that the micro-cutter axis should be asconsistent as possible with spindle axis and micro-cutter should be installed as thatthe deflection plane is perpendicular to the cutting edges.