Wire-cut EDM

This type of EDM is, as mentioned before, for the manufacture of bore holes for later processing by wire-cut EDM (Figure 4.30). This is a variation of die-sinking EDM on special machines. Since the processing of the workpiece is carried out without contact, bore hole diameters of up to 0.2 mm can be created. 

Average removal rate in wire-cut EDM 400 mm (see definition later)... 

Workpiece heights wire-cut EDM 200 to 600 mm (depending on the machine type) Workpiece heights die-sinking EDM 300 to 3,000 mm (depending on the machine... 

Figure 4.37 (on the left) shows pins which were manufactured with an accuracy of 3 pm. The counterpart (Figure 4.37, on the right) was produced using the wire-cut EDM. In the middle, pins and counterpart are combined. 

Figure 4.38 shows a wire-cut EDM machine. The wire runs from a roll in the top left, over to several idler pulleys, by a guide (center), through the workpiece, and into the tool carrier below the workpiece into a tension roll. 

FIGURE 4.38 Wire-cut EDM (without a workpiece, dielectric fluid and clamping system)... 

Only continuous workpieces can be processed in wire-cut EDM since the wire needs to be brought from top to bottom (comparable to a band saw). The contour is produced with the tool table. The wire usually runs in the same axis from top to bottom, wherein the tool table is moved in the XY plane. 

An accuracy of 2 pm (contour) can be reached with wire-cut EDM. The wire diameter is calibrated to 1 pm. EDM wires are usually made from brass with a diameter of 0.2 to 0.25 mm (standard). Wires are available for particularly precise operations, such as with a diameter of only 0.03 mm. These are made from tungsten due to the necessary strength. 

In combination of die-sinking EDM and wire-cut EDM, high precision inserts can be manufactured for the production of micro-plastic parts. Figure 4.43 shows the compiexity and precision of this type of process on the example of micro-stamping. Figure 4.44 iilustrates another combination part. 

The application of EDM is mostly known for steel processing only. But aluminum can easily be processed with EDM with even higher (for the most part) removal rates compared to steel. Eurthermore, the so-called white layer (which is extremely hard for steel) does not form, so that any necessary polishing can be reduced to a minimum. The EDM technologies that are mainly applied in practice are divided into two methods the planetary-EDM (P-EDM process) and the wire EDM (electrical discharge wire cutting or EDC process). 

Wire-EDM (spark erosion cutting, wire erosion). 

Wire-EDM is defined as EDM process using an unwinding wire tool electrode that cuts the workpiece according to a given NC path (CIRP Dictionary 2004). 

Yan J, Uchida K, Yoshihara N, Kuriyagawa T (2009) Fabrication of micro end mills by wire EDM and some micro cutting tests. J Micromech Microeng 19(2) 25004... 

The cutter (a profile tool or cutting wire, forms the anode and the workpiece the cathode, about 40mm apart, separated by a fluid dielectric such as paraffins in the EDM machine. Sub-micron solid impurities in the fluid migrate to form a bridge a spark passes through the fluid, and material is removed from the cathode by melting, evaporation and by... 

For EDM, it has been shown that using electrodes made from very hard graphite or tungsten copper is ideal. Wire EDM is often a very good alternative to complex milling operations for unstable work piece conditions. Material thicknesses up to 200 mm can easily be cut in copper alloys. 

AIWJ is today s state of the art and is worldwide applied in industrial manufacturing with pressures up to 6000 bar. With the AWIJ, all hard materials such as metals, ceramic- and fiber-reinforced composite materials, glass, or stone can be cut. In this field, the abrasive waterjet competes with mechanical sawing, wire sawing, punching, EDM, and laser and thermal cutting techniques. 

Traveling wire EDM wire moves slowly along the prescribed path on the workpiece and cuts the metal with sparks creating a slot of kerf. CNC control is common. 

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