| Ultra-precision machining is the basis and key of advanced manufacturing technology,and also one of the important symbols to measure the level of scientific and technological development of a country.High precision,high quality,miniaturized aspheric surface and other micro-structure processing are the peak of ultra-precision micro-nano manufacturing technology.The manufacture of micro grinding wheels(diameter less than 1mm-10mm)used for grinding micro-structures has always been one of the difficult problems to be solved.There are many problems in the traditional fabrication process of micro-diamond grinding wheel,such as serious waste of materials,small space of die cavity,difficulty in forming materials and so on.Therefore,in this paper,pure ABS material will be modified,focusing on the study of micro-diamond composites used in Fused Deposition Molding technology,which is of great significance for saving consumables and preparing diamond grinding wheels with fine and uniform abrasive particles.In this paper,the molecular mechanism and experiment of this kind of resin diamond composite(RDC)are discussed.The main research work includes the following aspects:(1)Molecular dynamics simulation of micro diamond resin composites.Firstly,the raw material molecules of ABS and micro-diamond composites were constructed and optimized.Then,the composites were blended at room temperature,i.e.the composite wire cubic cells were established and a 298 K NVT(constant volume and constant temperature)equilibrium was carried out.Then,the composite crystal cells were obtained by 493 K and 483 K NPT(constant pressure and constant temperature)equilibrium of the blend system.The density cohesion energy density,molecular radial distribution function,mechanical properties and compatibility of the blends were tested with different functional modules.(2)Sample moulds were designed and prepared,and physical properties of composite materials were tested.The die is made of aluminium alloy and consists of upper die,lower die and indenter.The upper die is provided with a guide hole for exhaust and filling.The upper and lower die closing mode adopts shoulder positioning mode.The mixture material was added into the lower model cavity,the mould was closed,and the mould and the mixture material were heated for 40 minutes at 250℃.Samples were prepared by air-cooling with a plunger injection moulding machineunder pressure.The hardness and surface roughness of ABS/PVC/diamond abrasive/DOP samples with different mass fractions were tested.(3)The melt rheological behavior of micro-diamond composites in the printing nozzle and the thermal-structural coupling behavior of micro-diamond grinding wheel were simulated and analyzed.The thickness of 0.1mm,0.15 mm,0.2mm printing layer and the printing speed of 10mm/s,30mm/s and 50mm/s were simulated to prepare grinding wheel,and the temperature and stress-strain nephogram of grinding wheel were analyzed.The wire sheets were heated for 10 min,20 min,30 min,40 min,50 min and prepared by pressure of 20 bar,30 bar and 40 bar at 220℃ respectively.The diameter of the prepared wire was measured to verify whether it meets the requirement of less than the diameter of the inlet of FDM printer.The grinding wheel is printed by means of cross filling and increasing wall thickness in the sand,and the compactness of the grinding wheel is ensured by observation.Using 0.1mm,0.15 mm and 0.2mm printing layer thickness to print grinding wheel,the local view of its outer surface is enlarged 50 times,and the micro-marks are compared and the causes are analyzed.In order to ensure the quality of the outer surface of grinding wheel,the appropriate printing layer thickness is selected. |
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