Research On EDM Technology Of Internal Gear

The key process in the processing of internal gear is the tooth shape processing after the tooth surface is hardened.Due to the limitation of the structure of internal gear with small and medium modulus,it is difficult to carry out the traditional gear grinding,and the traditional grinding wheel wears fast,while the CBN wheel has good wear resistance but difficult to repair.EDM can process any conductive material without the influence of material hardness and there is no macro cutting force.However,due to the large ratio of the depth and width of the tooth groove of small and medium-sized module gear,when the traditional EDM process is used to process the tooth groove,the discharge debris generated in the process is not easy to discharge,which is easy to form two times of discharge,resulting in low processing efficiency and affecting the surface quality of the workpiece.High speed knife lifting can alleviate this problem,but the control of high speed knife lifting is complex,and a certain amount of pulse energy will be wasted in the process of knife lifting.WEDM can also be used to process cogging,but it is difficult to achieve high precision and high surface quality cogging.The rotating electrode can make the corrosion products better discharged from the pole to pole and promote the cooling between the poles,so as to reduce the concentration of discharge and the abnormal arcing discharge,and improve the state of inter pole discharge.The electrode loss is evenly distributed on the disc shaped electrode due to the change of discharge position at any time,and the forming accuracy is less affected by the electrode loss,so the copper electrode is easier to be modified.In conclusion,this paper puts forward a kind of EDM milling technology and studies the EDM milling technology of internal gear.The research contents are as follows:(1)Firstly,according to the principle and method of machining,the machining device is designed,and the basic law of internal gear forming and milling process is analyzed by single factor experiment.The effects of processing polarity,pulse width,peak current,pulse to pulse width,processing efficiency and surface roughness were studied,and the reasonable and feasible parameter range of each factor was determined.According to the results of single factor experiment,the representative level design orthogonal experiment is selected,and the optimal machining parameters are selected based on the surface quality and machining efficiency of workpiece.(2)Due to the small amount of processing of a single tooth slot,the large discharge volume of the electrode,it is difficult to measure the electrode loss,so a method of measuringthe electrode loss using visual measurement is proposed.The electrode loss is calculated by measuring the size change of workpiece and the size change of sample plate before and after machining.Design experiments to measure the electrode loss of the optimal processing parameters selected in the orthogonal experiment,and check the influence of the electrode loss on the accuracy of the gear.The measured electrode loss parameters are compared with the relevant electrode loss given in the machine tool process manual.The results show that the measurement method has high accuracy.(3)Because the gear is processed by forming method,the indexing mechanism is needed after machining a tooth,while the traditional worm indexing mechanism needs high-precision angle encoder to achieve high indexing accuracy.According to the characteristics of EDM without macro cutting force,the gear dividing mechanism is designed.The mechanical structure is used in the worm dividing mechanism to convert the circular motion into the linear motion,and the high-precision linear grating with good economy is used instead of the circular grating.Through the error analysis of MATLAB,the result shows that it can achieve a higher indexing accuracy.