Lakhasly

An ECM machine tool consists of four main subsystems: the power source, the electrolyte cleaning and supply system, the tool and tool feed system and the work and work holding system. The power source supplies a low-voltage (5–30 V) high-current (as high as 40 kA) rectified DC power supply. Figure 11.14 shows a photograph of a simple low-capacity ECM machine. The electrolyte supply and cleaning system consists of a pump, filters, piping, control valves, heating/cooling coils, pressure gauge and a tank/reservoir. These elements should be made of anti-corrosive materials because the electrolyte used is corrosive in nature. Tools are also required to operate in a corrosive environment for a long period of time. Hence, they should also be made of anti-corrosive material having high thermal and electrical conductivity, and easy-to-machine characteristics (high machinability). Copper, brass and stainless steel are commonly used materials for making ECM tools. It is important to know that only electrically conductive materials can be machined by this process. However, work holding devices are made of electrically non-conducting materials having good thermal stability, corrosive resistance and low moisture absorption. Glass-fibrereinforced plastics (GFRP), Perspex and plastics are some such materials that can be used to fabricate work holding devices. To exploit the full potential of the process, many allied processes/operations have been developed using the principle of anodic dissolution described above.
316 V.K. Jain
Some of the allied ECM operations are electro-chemical boring, electrochemical broaching, electro-chemical ballizing, electro-chemical drilling, electro-chemical deburring, electro-chemical die sinking, electro-chemical milling, electro-chemical sawing, electro-chemical micromachining, electro-chemical turning, electro-chemical trepanning, electro-chemical wire cutting, electrostream drilling and shaped tube electromachining (STEM) [1]. Shaped tube electro-chemical drilling (STED) has been successfully used to drill smalldiameter high-aspect-ratio holes in difficult to machine materials such as nimonic alloys (Figure 11.15) [14]. To enhance the capabilities of the base process (here ECM), two or more processes are combined together to make it a hybrid process. Some of these hybrid processes are electro-chemical grinding (ECG) [15], electro-chemical honing (ECH) [16], and electro-chemical spark machining [17–22]. Such hybrid processes give better performance than the constituent processes (ECM + grinding, or ECM + honing or ECM + EDM).