Experimental Research On Groove In Small Holes By ECM

With the development of aerospace,petrochemical industry,miniaturization and precision of mechanical production,parts with characteristics of small hole,especially with complex internal characteristics of small hole,are used more and more widely.For example,the drum shaped hole,hyperbolic hole and inverted cone hole,which are common used in the special nozzle with different flow properties and injection requirements;Holes with grooves in the inner wall can be used for outer ring of miniature ball bearing;Micro oblique holes are common in the particle filter;Tapered holes are often used as cooling holes;These small holes with complex internal characteristics play an important role in improving the distribution of fluid field,strengthening the cooling and so on.Due to these parts with special holes tend to have high strength,high hardness and easy deformation characteristics,and the size of hole put forward more stringent requirements about tool accessibility and strength,which brought great trouble to machining structure in the hole.Although the inverted cone-hole could be processed with the help of laser drilling and electro-discharge machining drilling,it is easy to produce heat affected zone and recast layer during the processing,which has adverse effects on the performance of the products.As it's difficult to machine the special structure in the small hole,and machining precision or surface quality usually can't be satisfied the requirement of aerospace,chemical and other special occasions with high temperature and high pressure.In the paper,electrochemical machining was put forward to process the groove in small holes of the parts.The completed content mainly including the following aspects:(1)The program of the groove in small holes by electrochemical machining was determined and the machining test apparatus was set up.Including the design of three axis CNC machine,fixtures and tool cathode which can be satisfy machining requests,the preparation of electrolyte and measurement of its electrical conductivity value,the design of suction flow way of electrolyte,selection of pump and power supply.(2)The simulation analysis of the flow field and electric field in the process of the grooves in small holes by electrochemical machining was completed with the help of COMSOL Multiphysics.A two-dimensional simplified model of the grooves in small holes by electrochemical machining was established,and the flow field distribution of different cathodes was analyzed;The electric field in the machining gap of different tool cathode was simulated,and the distribution of current density at different time and voltage was obtained.Analyzing the coordinate data of the boundary of the hole inner surface of the work piece,and the general law of the electrochemical machining was summarized.(3)The electrochemical machining experiment of the grooves in small holes was carried out,and the test work pieces was measured.Experiment based on three aspects of the time,voltage and cathode slit width was designed.Measuring hole inner surface with OLS4100 laser microscope after sectioning the work piece along the hole axes,the forming process of grooves in small holes by electrochemical machining with different machining parameters was analyzed.(4)The influence of different machining parameters on the surface quality of the machined surface was analyzed.The effects of different cathode,time and voltage composition on the surface roughness value was mainly explored.(5)Current efficiency value was figured out and the reliability of the simulation results was verified.After organizing the date of simulation results and the test results under the same machining parameters,and solving the material volume of the actual machining and the simulation in MATLAB,the current efficiency was figured out.Correcting the simulation results according to the obtained current efficiency value,and the reliability of the simulation model was verified comparing the specimen profile coordinate data with the same conditions.