Study Of The Methods Removing The Craters And Resolidified Materials Of WEDM Surface

When the workpiece is sliced by using wire electrical discharge machining(WEDM),the materials are removed by melting and evaporation.Owing to the material removal mechanism,the surface of the workpiece after WEDM is covered with recast layer,which is composed of numerous discharge craters and re-solidified materials,leading to the low surface roughness.The recast layer also can deteriorate the materials property such as fatigue strength,resistance to corrosion,and service life.In order to solve this problem,this paper studies the methods of removing the craters and re-solidified materials on the surface of WEDM to improve the surface quality of the workpiece.Aiming at metal conductive materials are cut by WEDM,a wire electrical discharge-electrochemical machining(WEDCM)method is proposed,which combines WEDM'and ECM removes craters and re-solidified materials generated by WEDM,and improve the surface quality.The mechanism for improving the surface topography and roughness is analyzed and verified by the experiments.The influence of the feed rate of the wire electrode in the electrolysis stage and the movement distance between the two feeds of the wire on the final surface quality of the workpiece are analyzed.A method of improving the surface quality of a workpiece in the electrolysis stage using high speed and multiple feeds is explored.Aiming at the complicated process of the WEDCM method,low wire feed rate-WEDCM method is proposed to simplify the process,and it is studied by the experiments.The differences between WEDCM and low wire feed rate-WEDCM for improving the surface quality of workpieces are compared.Following that,the analytical models about WEDCM and low wire feed rate-WEDCM,which are based on the double layer model and Faraday's law of electrolysis,are developed.In the WEDCM method,the model is developed to identify the appropriate feed rate of the wire electrode during the stage of electrochemical dissolution.The study shows the relationship between the wire feed rate in the electrolysis stage and the movement distance of the workpiece under the condition that the re-solidified materials of the same thickness needs to be dissolved.The influence on the surface quality of the workpiece are also studied and obtained.The reasonable value range of the wire feed rate in the electrolysis stage and the movement distance of the workpiece is obtained to get a good surface quality of the workpiece.In low feed rate-WEDCM,the model is developed to find the suitable feed rate of wire electrode,with which the re-solidified material can be removed by electrochemical dissolution and surface quality improved.The effect of wire feed rate on the surface quality of workpiece are studied and the reasonable value range of value also obtained.The composition and causes of stipes on workpiece surface are analyzed,and the methods and principles of removing the stripes are also discussed.The experiments are carried out to verify the two models and the calculation errors are also discussed.The results show that the calculation model can reflect the appropriate feed rate of the electrode wire in the two processing methods.The calculation errors mainly come from the instability of the machining process caused by the wire vibration.Since semiconductor materials cannot be machined by using ECM.Therefore,aiming at semiconductor materials are cut by WEDM,the wire saw-WEDM hybrid machining method(W-WEDM)is proposed to remove the craters and re-solidified materials.In the cutting process,the wire with diamond abrasive is used as a tool,and the wire electrode and the workpiece are in contact with each other.The sparks and the diamond abrasive grains are combined together to remove the craters and re-solidified materials produced by the WEDM.Firstly,the principle of W-WEDM is theoretically analyzed.Then the feasibility is verified by experiments.The material removal mechanism of W-WEDM is analyzed.It is the sparks and diamond abrasive grains together that remove the materials.Owing to the grinding action of the diamond abrasive grains,the W-WEDM method can remove the spark craters and re-solidified materials generated by WEDM,and reduce the surface roughness of WEDM workpiece.At the same time,combined with relevant experiments,the three cutting methods,namely,W-WEDM method,wire saw cutting and WEDM,are compared in terms of cutting efficiency,surface element residue,kerf width,and tool wear.