Study On Machining System Of Precision Micro Abrasive Water Jet And Experiment

This thesis conducts a study on the effect of the cutting process variables of Abrasive water jet (AWJ) on the kerf quality of granite, designs the function principle sketch of the precision micro abrasive water jet and develops the accumulator pulse abrasive supply system and the precision micro abrasive water jet machining system. A primary experimental study on polishing the hard-brittle material is conducted.The effects of the waterjet pressure, the traverse speed and the stand off distance on the striation, the taper angle and the width of the kerf are studied. It is shown that the striation and the taper angle of the kerf decrease and the width of the kerf increases as the waterjet pressure increases and the traverse speed decreases. The effects of the stand off distance on the striation, the taper angle and the width of the kerf are small.Function principle sketch of the precision micro abrasive water jet is designed. Based on the analysis of the machining function, the precision micro abrasive water jet machining system is divided into pressure generation module, jet system module, abrasive supply system module and motion and control system module. A design principle of function model is introduced.The accumulator pulse abrasive supply system and the precision micro abrasive water jet machining system are developed and the jet flux, jet flow velocity and abrasive flow rate are measured. The jet system, which has an orifice with a diameter of 0.08mm, a nozzle with a diameter of 0.3mm and a length of 76.2mm, can form a waterjet with a diameter of 0.3mm. The pressure generation system can generate a jet with a pressure of 2-15MPa, a flux of 0.2-0.55ml/s and a flow velocity of 40-110m/s. The impacting force of the micro jet is 0.02-0.07N. The accumulator pulse abrasive supply system can steadily supply micro abrasive particle by a mass rate of 0.4-0.2mg per pulse. The abrasive rate per plus increases with an increase in the gas pressure and a decrease in the frequency of plus. The flux and the flow velocity increases with an increase in the waterjet pressure. But the increasing ratio is decreased from high to low pressure. The impacting force is increased with an increase in the pressure and decreased slightly with an increase in the stand off distance.Using the micromachining system, a group of polishing experiments is conducted for two kinds of hard-brittle materials such as silicate glass and silicon nitride. Experimental results indicate that the surface roughnesses (Ra) are improved from 0.334μm to 0.080μm for silicate glass and from 0.167μm to 0.069μm for silicon nitride. It is proved the feasibility and the advantage of polishing for hard-brittle material by the precision micro abrasive water jet machining system.