Published on December 5, 2016
1. ELECTROCHEMICAL MACHINING
2. Schematic illustration of the electrochemical machining process.
3. PARTS MADE (a) Turbine blade made of nickel alloy of 360 HB. Note the shape of the electrode on the right. (b) Thin slots on a 4340-steel roller-bearing cage. (c) Integral airfoils on a compressor disk.
4. INTRODUCTION Non-conventional machining system in which metal is removed by electrochemical process. Characterized as ‘Reverse Electroplating’ means it removes metal instead of adding it. Normally used for mass production and for hard materials that are difficult to machine using conventional processes. Both external and internal geometries can be machined.
5. PRINCIPLE Faraday’s law of electrolysis : The Weight of the substance produced during electrolysis process is directly proportional to: Current which passes Length of time of process. The equivalent weight of the material Two dissimilar metals are in contact with an electrolyte and anode loses metal to cathode.
6. PARTS ANODE : Workpiece CATHODE : Tool ELECTROLYTE : An electrically conductive fluid
10. POWER SUPPLY Available in sizes upto 10,000 amp (some circuits are available upto 40,000amp) Range of voltage : 2 to 30 volts d.c. A constant voltage has to be maintained and high density is required
11. ELECTROLYTE Essential for electrolytic process. It cools the cutting zone which becomes hot due to the flow of high current. Neutral salts are used as electrolyte in place of highly corrosive acids and alkalies . Electrolyte solution is pumped between the tool/workpiece gap at about 2.5 N/mm2 and 30 m/s..
12. TOOL REQUIREMENTS OF TOOL FOR ECM : • Good thermal conductivity. • Strong enough to withstand high pressures. • It should be easily machined. MATERIAL FOR TOOL : Copper, Brass & Stainless steel. OUTER INSULATION MATERIAL : Vinyl, Teflon, epoxy, enables or high temperature varnish.
13. CONTROL SYSTEM Control Parameters include: • Voltage • Inlet and outlet pressure of electrolyte • Temperature of electrolyte The current is dependent on above parameters and feed rat .
14. ADVANTAGES ECM is well suited for the machining of complex two-dimensional shapes Delicate parts may be made Difficult-to machine geometries Poorly machinable materials may be processed Little or no tool wear
15. DISADVANTAGES Initial tooling can be timely and costly Environmentally harmful by-products Complicated tool design Large power consumption
16. CHARACTERISTICS Stress free grooves Any groove geometry Any conductive metal can be machined Repeatable accuracy of 0.0005” High surface finish Fast cycle time. The process is economical when a large no. of complex identical products are to be made. Large cavities are more economical on ECM and can be made in 1/10th time in EDM.