Study On The Key Problems Of The Electric Hot Machining

For a long time, the finishing or semi-finishing of many difficult-to-machine materials have to be machined by means of milling. However, the milling has some disadvantages, such as low efficiency, high consumed power and environment pollution etc. At present, with the development of super-hard tools, hard turning can substitute the milling as the finishing, which is higher efficient, friend to environment and less investment. But current hard turning needs high quality lathe and super-hard tool, which make it difficult to extend. So it provides the urgent need to apply and develop the electric hot machining technology (EHM).As an effective method, electric hot machining can remarkably improve the machinability of hard-to-machine materials and reduce the roughness of machining surface. Although some investigations have shown that electric hot machining is feasible, there exit some inevitable problems interfering in the application of EHM. So this paper mainly concerns with some key techniques in the application of electric hot machining.Based on the basic theory of electric arc, in the process of electric hot machining, the species of electric arc discharge and their developing principles are emphatically analyzed. Meanwhile, the formula of the stabilizing and eliminating condition of direct current arc is derived, and from which the method of eliminating electric arc is presented. In addition, with the use of the transient overvoltage pulse signal and current signal detected between the end of the tool and workpiece to count and control the power supply to be switched off, a new method is proposed to prevent from generating electric spark or arc in the process of the tool retracting from the workpiece. Furthermore, it proved that this method is effective to suppress the discharge of the electric spark or arc and makes possible to cut the discontinuous surface by using EHM.According to the mechanism analysis of conventional tool wear, the wear behaviors of tools used in EHM are researched by experiments. A comparative analysis of four typical tool materials is also performed into EHM to select optimum tool material. Meanwhile, with the control devices of eliminating electric arc, the verification tests are performed and the finer surface quality is steadily obtained, which can decrease the surface roughness to 0.7um or lower. So the results show that electric hot machining can substitute the milling to cut some hard-to-machine materials.The advantages of machining hard-to-machine materials by means of EHM are as following: it can utilize the carbide tool to machine the harden steel in engine lathe, and provides an easy and low cost method to machine hard-to-machine materials, which show that EHM will own a brighter prospect.