| High-speed machining (HSM) technology, as one of the advanced manufacturing technical methods, has become the main trend of the development of modern digital-controlled manufacturing technology. It has been applied in the fields of aeronautic, automobile, die & mold, machining of hard-to-cut material, and ultra-precision manufacturing. Due to the lacking of further studies of high-speed machining mechanism and supports by its related technical foundation, there are many problems in practice in high-speed milling, for example, in the machining of hardened steel mold with deep and narrow slots, cutting tools will be easily cracked and broken; in the cutting process of thin-walled workpieces, rebound and vibration will be caused to the cutting tools with the result of worsening of surface finish, deformation of workpieces and failure of cutting tools.This paper aim at Micro-end mill ( φ 2mm) high speed milling hardened die & mould steel. It includes cut-in dynamics, transient analysis and simulation of the cutting process, so as to choose reasonable cutting parameters, reducing tool damage and chatter vibration of cut-in process, high speed machining mechanism is studied in the mean while. It has actualmeanings in reducing the production cost. The main research work include: 1) Dynamic simulation of high speed milling hardened die steel, the contact force between the tool and the workpiece and the flexible deformation characteristic of end mill under impact force is acquired. The study shows the end mill will transform in the cutting process. The transient stress and strain is great on the effect of impact force, and the stress by dynamic loads is several times the static loads, which is the reason of the chip and tool damage in the cut-in process.2) Finite element analysis of micro-end mill under impact force is carried out and the conclusions are drawn. The larger the extended length is, the bigger the stress and strain inside the end mill, by reducing the time effect of the impact loads. The end mill is object to chip. However, the long impact loads time result in the increasing of the high stress, strain rate area and the end mill's displacement, so the tool is object to breakage. Strain rate, stress and displacement are not simply increase and decrease with the change of the extended length. There is an optimal extend length. Simulation results consistent with the tool damage experiments.3) By mode analysis of the micro-end mill, the effect of the end mill's extended length on modes is researched, and the relationship between the tool chatter vibration and the mode is investigated. The mode steps increase with the increase of the extended length, while the corresponding mode steps frequency declines. On the whole frequency scope analyzed, largeextended length is adapt to reduce the chatter vibration. The mode frequency is much close to each other at low frequency range, and the distribution of the mode frequency does not uniform, there is intensive areas and sparse area of the modal frequency. The results of simulation are coincided with the former experiments.4) Through numerical simulation of the orthogonal metal cutting, the forming of the chips, the cutting dynamics and cutting temperature in high speed machining are analyzed. The results illustrate that the plastic yield is begin with the first deformation area, the maximum yield and strain ladder concentrates on the tool-chip interface. In high speed case, with the development of cutting speed, the temperature increases slowly, and leans to steady, which proves the material is in ideal plastic flow state approximately. The higher the cutting speed, the larger the shear angle and the small the deformation and the cutting force is, as well as the equivlent stress. The deformation of the chips is approximately considered as a thermal isolation process. The temperature in the cutting zone exceed 1000 ℃ . HSM has its special advantages, the normal metal cutting theory does not quite adaptive to the high speed machining instance.
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