Research On Process And Wire Bending Control Of Abrasive-Spark Hybrid Shaping

Hard and brittle materials,especially semiconductor materials,are increasingly used in the fields of photovoltaics,electronics and high-energy optics.At the same time,these new applications place new demands on the machining of hard and brittle materials: high-precision shape cutting.Because the machined surface of shape-cutting is not flat,the traditional machining methods of hard and brittle materials,such as outside diameter blade,inner diameter blade,loose abrasive slurry multi-wire saw,are obviously unable to meet the requirements.The new methods have their own disadvantages when used for shape-cutting of hard brittle materials: the shape accuracy and processing efficiency are very low for fixed abrasive diamond wire sawing(DWS);the wire electrical discharge(WEDM)has a high precision,but the surface damage is serious,and the poor conductivity of semiconductor materials results in low energy utilization rate and low processing efficiency.Aiming at above problems,a novel approach,which combines electric discharge and diamond abrasive grinding into a single process,is proposed for the shape-cutting of hard and brittle materials in this paper.The machine tool was transformed independently to achieve hybrid machining.The material removal mechanism was analyzed.Process experiment was completed to verify the shape-cutting effect.Wire-bending model was explored.The pressure detection and wire bending control system was designed and verified.The main contents of the work are as follows:(1)Transformed the wire traveling mechanism and designed the special guide wheel powering on the diamond wire by Solidworks and Autocad softwares to meet the demands of two methods occurring at the same time.Compiled the components processing technology and processed components to finish the transformation of hybrid processing machine tool.(2)Analyzed the principle and three processing states between diamond wire and workpiece of hybrid machining.Collected the discharge waveform.The rate of three kinds of discharge states are analyzed for the characteristics of hybrid machining.(3)The occurrence and influence of wire bending phenomenon of hybrid machining used for shape cutting are studied.A control method of wire bending detection based on the detection of pressure between diamond wire and workpiece during machining is proposed.The running scheme of control system is designed,including information collection,transmission,processing,feedback control,and so on,which makes it possible for the real-time detection of wire bending.(4)The experiments,testing the cutting quality and shape-cutting accuracy of polycrystalline silicon,are completed with the hybrid machining tool.The cylindricity value polycrystalline silicon cylinder with 20 mm tall and 10 mm in diameter can reach 0.011 mm.The hybrid machining greatly improves the shape-cutting precision of hard and brittle materials.(5)The experiments of polycrystalline silicon are completed to verify the effect of pressure detection and wire bending control system.The result shows that the system detects pressure and adjusts the feed speed well,which results in the approach of the maximum feed speed when the cylindricality meeting the demand.