A New EDM Method For Square Hole Based On Rotating Electrode

The square hole structure has great torque carrying capacity and high stability.It is widely used in the fields of aerospace,automobile,ship,petroleum and wind power,which have high requirement on the stability of mechanical structure.Milling,casting and other mechanical processing methods can be used to process square holes on ordinary materials.When machining holes with a high aspect ratio on materials of great hardness,non-traditional machining is often used.EDM usually uses square electrodes to process square holes.During processing,machining debris are difficult to discharge from the processing area,causes low processing efficiency and large electrode loss.In order to improve the processing speed and reduce the electrode loss of EDM,this paper presents a method of machining square hole by rotating electrode.The cross section of the tool electrode is designed as Reuleaux triangle,the motion of the Reuleaux triangle electrode rotating in an equal-width square hole is analyzed,the motion form of the center of electrode and the shape and area of the processing area generated by the bottom of electrode have been obtained.According to the analysis results,the square hole machining device is developed,the design work of the parts and assembly of the machining device has been completed.Processing square hole by rotating electrode has been proved feasible by using the square hole machining device.The machining device is simplified,and the simplified machining device is established in Adams/Views software.The space positions of components are determined,and the motion constraints are applied.The effects of length,rotation rate,shape accuracy and clamping error of electrode and the constraint position of the guide mechanism on the shape accuracy of the square hole are investigated by means of motion trajectory simulation.According to the conclusion of the motion trajectory simulation,machining device has been improved and adjusted.According to the rotational movement of the electrode in the square hole,the variation regularity of the flow field in the processing area using the rotating electrode is analyzed.It is found that the rotation of the rotating electrode has a positive effect on the discharge of the machining debris.According to the feasibility experiment and the simulation results,the rotating electrode square hole processing device is optimized to improve the shape accuracy of the square hole.On this basis,single factor experiment is carried out to study the effects of different rotation rates on the machining speed and electrode loss.The square hole machining method by rotating electrode and the square hole machining method by square electrode are compared,The influence of processing conditions,such as open circuit voltage,servo feed speed and detection threshold range,on machining characteristics of two methods is studied.Using two processing methods under the optimal processing conditions,experiments on processing square holes with different depths are finished.With the increase of machining depth,the square hole processing method by rotating electrode is better than square electrode processing method in improving machining speed and reducing electrode loss.