Research On In-situ Preparation Technology Of Micro-milling Cutter Based On WEDG

Micro-milling technology plays a very important role in the manufacturing of complex 3D miniaturized parts,which are made of various materials and in submillimeter and micrometer sizes,since it has the advantages of high efficiency,high flexibility,high-precision,low cost and wide material adaptability.Micro-milling has become one of the key technologies for making micro-structure components,such as THz folded waveguide slow wave structure,code lock with counter meshing gears,and inertial confinement fusion.Micro-milling cutter is the most critical and the most active factor in micro-milling process,With the characteristics of the above-mentioned micro-structure components getting smaller and smaller because of the miniaturization tendency of manufacturing,the micro-milling cutter is facing a number of problems.Since the micro-milling cutter is getting smaller,the manufacturing cost of the cutter becomes higher,the cutter service life reduces,and the tool runout caused by set-up errors contributes more significant impact to the machining accuracy in micro-milling process.Those problems have stunted the development and application of micro-milling technology.Aiming at reducing the manufacturing and operating cost of micro-milling cutter and the tool runout at high spindle speeds,firstly the mechanisms of the tool runout caused by set-up errors were reviewed,and then a novel on-machine fabrication method of micro-milling cutter using wire electro discharge grinding(WEDG)was proposed.The on-machine fabrication method of micro-milling cutter could avoid the existence of setup errors of spindle-axis offset and tool tilt caused by re-stallment of the micro-milling cutter,and even accomplish on-machine repairing of the cutter.In this way,the cost of micro milling could be reduced,in the mean time,the machining accuracy could be improved.Therefore,the development and application of micro-milling technology will be promoted.The main contents of this paper are as follows:(1)The amplifying function of the tool runout caused by the centrifugal force,which comes into being because of the existence of setup errors,was analyzed.And the importance of controlling and even eliminating set-up errors was proved.The basic theories of WEDG and the realization conditions of fabricating micro-milling cutter using WEDG were reviewed.The fabrication of the micro-milling cutter with diameter less than 100?m was realized,and this proved that fabricating micro-milling cutter using WEDG was feasible.The principle of on-machine fabrication method and their specific requirements for the micro-milling cutter and experimental platform system were proposed,(2)The design principle and design flow of the micro-milling cutter were put forward,and the material selection and preliminary design of the micro-milling cutter were completed.Based on the characteristics of the micro-milling cutter,the suspension of micro milling cutter was simplified as a cantilever beam model,and the finite element model of the micro-milling cutter was established.The stress-deformation analysis and modal analysis of the micro-milling cutter were carried out by ANSYS software,and the strength,stiffness and natural frequency of the micro-cutter were studied.The results showed that the composite mechanical properties of D-shaped cross-section were better than those of triangle,"one"shape,traditional double-edged spiral and other blade cross-sectional shapes.It was available for increasing extended length and cone angle to decrease the first order natural frequency of the micro-milling cutter,while increasing the cutter shank diameter would enhance the first order natural frequency of the micro-milling cutter.The influence of the length to diameter ratio of tool bit for the the first order natural frequency of the micro-milling cutter was very small,but when the length to diameter ratio was greater than 6:1,the high natural frequency would be greatly affected.The geometrical parameters of the micro-milling cutter could be optimized according to the actual requirements,(3)The experimental platform system with both micro-milling and micro-EDM functions were built.The experimental platform system achieved a stable discharge of a single pulse with a minimum energy of 10-7J,and a maximum speed of 150000rpm and a minimum speed less than thousands rpm.The detailed route and parameters of the complete maching process of the proposed on-machine fabrication method were drew up.And the detection methods of geometric precision and cutting edge quality of the micro-milling cutter were proposed.Then the fabrication of micro-milling cutters with the D-shaped cross-section were accomplished.The minimum diameter of those cutters was 100?m,menawhile the geometric precision reach to micron-level and the blunt circle radius no more than 2?m.According to comparison of the experimental results between the fabricated micro-milling cutter and the commercial micro-milling cutter,the on-machine fabricated micro-milling cutters using WEDG had good cutting performance and could effectively control the tool runout.Therefore,the machining accuracy of micro-milling would be improved.