Wire EDM Basics
A wire electrical discharge machining or WEDM is a metal wire that is a single strand, thin, and normally is made out of brass which is fed through a work piece then put in a tank of dielectric fluid which is usually deionized water. This will control electrical properties with de-ionizer units and filters and the resistivity to the water. The debris from the cutting zone will be flushed away. This is extremely important, as it will determine the feed rate for the thickness of the material. WEDM is also known as wire cutting and wire cut EDM.
WEDM is normally used when residual stresses are low because cutting forces are not high for removing material. If the pulse’s energy is very low, the material’s mechanical properties will hardly change because of the low stresses.
Wire cut EDM are used for tools, punches, cutting plates as thick as 300mm, and metals that are hard and hard are to machine by using other methods. The wire spools are quite long. A 0.25 mm wire 8 kg spool is 19 kilometers long. The diameter of the wire can be as little as 20 micrometers and the geometry precision is extremely close to +/- 1 micrometer.
From a spool, the wire is fed constantly and is held between a lower and upper diamond guides. Normally CNC controlled, the guides will move in the x-y plane. The upper guide on most machines can move by itself in the z-u-v axis. This means that it can cut shapes that are transitioning and tapered or a bottom square with a circle. It can be computer programmed to cut very delicate and intricate shapes. The guide also controls the axis movements of x-y-u-v-i-j-k-l.
The cutting Kerf or path of the guides is 0.335 mm and uses 0.25-brass wire. This is the most cost effective and saves machining time. The guides can cut as small as 0.12 mm and uses 0.1 mm wire and can be extremely accurate to 0.004 mm. The width of the wire is smaller than the cutting width because erosion or sparking occurs from both sides of the wire that is connected to the work piece. This is a very normal procedure and the over cutting is necessary.