Electrical discharge Machining (EDM)

[1] Electrical discharge machining removes metal by controlled electrical arcing (sparking) between the tool and workpiece. The EDM process is valued for its ability to machine complex shapes in metals of any hardness. It is used widely in making injection and compression molds for rubber and plastic molding, molds for die-casting metals, and dies for forging and metal stamping .EDM can also be used to remove broken taps and studs and to drill holes as small as 0.05mm. Because no tool pressures are involved, the process is ideal for machining delicate workpiece.

Electrochemical Machining(ECM)

[2] In electrochemical machining, the tool is the cathode and the workpiece is the anode. A gap is 0.0254mm to 0.76mm is maintained between the tool and workpiece. This provides space for the flow of electrolyte and keeps the electrical circuit from shorting out. A low-voltage, high amperage direct current passes from the workpiece to the tool through electrolyte. This current dissolves metal particles from the workpiece into the electrolyte by electromechanical reaction. The ECM process can be used to machine any metal that conducts electricity, regardless of hardness. The absence of tool pressures on the workpiece makes the process ideal for machining thin metals and fragile workpieces.

Electrochemical Machining(ECM)

[3] In ultrasonic machining, also called impact grinding, fine abrasive particles suspended in a fluid (usually water) are pumped in a gap between the workpiece and the tool. The tool is made to vibrate a few hundredths of a millimeter at ultrasonic frequencies ranging from 19kHz to 25kHz. The rapid pumping action of the tool hurls the abrasive particles at the workpiece at high velocith,thus grinding the workpiece to the shape of the tool. A major advantage of USM is that it can machine materials that cannot conduct eclectricity and which, therefore cannot be machined by EDM of ECM. However tool wear is high in USM, due to the abrasive cutting action. One or more roughing tools and a finishing tool are usually required for each job. Tools made of cold-rolled steel or stainless steel provide the best wear ratios.

Laser Beam Machining (LBM)

[4] The energy source for laser beam machining is a highly conce3ntrated beam of light When the beam is focused to a small spot, its power density is raised to produce sufficient heat to vaporize any material. However, the rate is metal removal is very small, which limits the use of lasers to hole-drilling and cutting operations in relatively thin materials. Two types of lasers are now in common use:(1)solid lasers,which are capable only of providing shortr bursts of power,and (2)gas lasers, which produce a continuious laser beam.