Experimental Study On Electrochemical Machining Of The Stem Of The Femoral Prosthesis Of The Hip Joint

As a medical metal implant to replace the failed hip joint,femoral prosthesis stem has the characteristics of difficult material processing and complex surface.At present,the processing methods of femoral prosthesis stem mainly include casting,forging,multi axis NC milling and additive manufacturing.Among them,the processes of casting,forging and other processing methods are cumbersome,multi axis NC processing has high precision,large tool wear and high cost.Additive manufacturing can be customized,but the production cycle is long and the efficiency is low.Electrochemical machining technology has the advantages of wide machining range,no cathode loss and high machining efficiency.Based on this,this thesis proposes a copy electrochemical machining method for the shape of hip femoral prosthesis stem,and carries out simulation and experimental research.The main research contents of this thesis are as follows:(1)Taking the three-axis ECM machine tool as the experimental platform,the ECM process device of femoral prosthesis stem surface is designed,and the electrolyte circulation system is improved.According to the structural characteristics of cementless prosthesis stem,a one-sided feed forming processing method is proposed,and the side flow liquid supply mode is selected.The cathode surface structure is designed by the equal spacing method,and the design and processing of processing blank and tooling fixture are completed.Build the electrolyte circulation system to meet the requirements of sufficient pressure,large flow,high filtration accuracy and stable temperature for the processing of femoral prosthesis stem.(2)The electrochemical machining model of prosthesis stem profile based on electric field model is established.The simulation research is carried out by using COMSOL multiphysics simulation software.The formation process of taper in length direction,the formation process of fillet in width direction and the change of machining gap are analyzed.The electrochemical machining experiments of femoral prosthesis stem profile at different times are carried out.The results show that the change process of anode profile in the experimental process is basically consistent with the simulation analysis,The validity of the model is verified.(3)The influence of different processing parameters on the forming accuracy of prosthesis stem profile is explored.The reliability of the processing device is verified by single factor experiment,and the parameter range of stable processing is determined.Then,taking the machining accuracy and surface quality of femoral prosthesis stem as the evaluation index,the orthogonal experiment analysis shows that the machining voltage and feed speed have a significant impact on the machining accuracy,and the inlet pressure has a significant impact on the surface quality.Under the processing conditions of optimizing the process parameters,the liquid inlet pressure is 0.6 MPa,the machining voltage is 16 V and the feed speed is 0.15 mm/min,the minimum error between the actual size of the sampling surface and the target size is 0.035 mm,the maximum error is 0.153 mm,and the maximum value of surface roughness Ra is 1.044 ?m.The minimum value is 0.884 ?m.