Experimental Investigation on ECMM With Nimonic 75 Alloy for Prosthetic Component

Historical Background of Electrochemical Machining

Currently Biomedical instruments are more micro in size and high accuracy. Manufacturing and selecting suitable machining process of such instruments are a challenge for present researchers. Electrochemical process is one of the advanced machining processes and can be possible to manufacture micro sized medical instruments like micro passages for surgical equipment, nozzles and tubes for dentist equipment, etc.

It is a machining process of metal removal generally used in mass production based on electrochemical process. Usually the ECM process machines hard materials, otherwise challenging to machine by conventional method. This method of machining is known as the reverse of anodizing or electroplating as a basic principle. In ECM process, the work piece is machined by controlling anodic dissolution at its atomic level. In which the desired shape of tool as high current at low potential variance through an electrolyte is imprinted on the work piece. The electrolyte is generally water based neutral salt solution. Because of its ability to machine hard materials at greater accuracy, ECM is considered as one of the advanced machining technology and is used in the fields of aerospace, defense, aeronautics, medical equipment. Recently ECM is also finding its application in the field of automobile & turbomachinery because of its inherent advantages low tool wear, lower thermal mechanical stress on work piece and more precision machining in difficult to cut materials by other non-traditional machining processes.

Why Electrochemical Micromachining (ECMM)

As the world is moving towards miniaturized, competent and superiority products, micromachining technique will play a very vital role in realizing the potential the miniaturization era where all products are getting smaller with better efficiency. Micromachining plays a crucial role in technologically demanding industries like medical, electronics, computer, and aerospace industry where complex shapes, holes, slots of micro dimension need to be made on a work piece with high accuracy. Material removal of the dimension ranging between 1.0 micrometers to 999.0 micrometers comes under micromachining. Using conventional micromachining for producing these shapes has its own share of limitations, which include high tool wear rate, thermal stress, and imperfect surface finish. To overcome these limitations, researchers are exploring new non-conventional micromachining technique. One such technique is Electrochemical micromachining (ECMM) having advantages like tool having no wear, stress-free surfaces, machining electrically conductive material regardless of physical as well as chemical property, bright surface finish. ECMM is worked on anodic suspension at atomic level in electrolyte. In spite of having so many advantages, ECMM is not widely used process as it faces some challenges like generating hydrogen bubble which adverse effects on MRR, the impact of variation in tool geometry, the impact of flow of electrolyte on surface finish and rate of machining etc. Researchers are working on how to tackle all these problems in order to get ECMM workable in more area of machining in most optimum way. When the work piece is of simple shape it is easy to define machining variable within IEG but it becomes problematic to define the same when the work piece is of complex shape. This problem can be solved by studying the flow pattern of electrolyte. This information in turn will help to avoid the passivation, which is one of the major problems in ECMM related to complex shape machining. Another problem, which is associated with ECMM, is generation of hydrogen gas at cathode. As electrolyte passes through cathode, it absorbs hydrogen gas generated at cathode. Due to this absorption, electrical conductivity of electrolyte decreases. As MRR and surface finish in ECMM is directly dependent on the electrical conductivity of the electrolyte, a decrease in it will hamper the machining rate and surface finish of work piece. In order to avoid all these, we need to know the source, effects, & pattern of hydrogen bubble generation. How it affect various critical parameters and overall machining performance. As discussed above, there is a lot which needs to be investigated in order to make ECMM more widely used machining technique.