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The History of CNC EDM: How CNC EDM Evolution Changed Our Industry
Posted on Dec 24, 2020
Overall, though, the EDM die sinker's fundamental features can give you a feeling as to whether EDM is a decent match for your application. EDM, for example, is usually slower than other methods of machining, but also more predictable, accurate, and repeatable.
Just like the electric telegraph and the jet engine, the die sinker EDM was created independently and almost simultaneously by more than one person. Russian scientists, Boris and Natalya Lazarenko's goal in 1941 was to find ways to boost the service life of tungsten breakpoints. In the course of their study, they discovered that they could control the corrosion of tungsten electrical contacts by immersing them in a dielectric solution. By 1943, Lazarenko's, which eventually became known as the EDM resistor-capacitor (R-C) circuit, developed a spark machining process based on this innovation.
As it stands, the EDM displacement machine is used to manufacture complex cavity shapes such as metal stamping dies and plastic injection molds in instruments and dies. The die flattening method begins by treating the graphite electrode in order to form a "positive" for the target cavity. In the workpiece, this electrode is then deliberately submerged, producing surface sparks,
Hydrocarbon oil is usually used in EDM machines as the dielectric fluid in which the workpiece and the spark are still submerged. They typically use deionized water, in which only the sparking region is immersed, unlike wire EDM devices. The dielectric fluid used in EDM machines performs three essential functions, whether it is oil-based or water-based:
a) Monitor the distance between the electrode's spark gap and the workpiece
b) Shape EDM chips, cooling the heated material
c) Removal from the sparking region of EDM chips
Although much smaller than those produced by processes of milling or turning, EDM produces chips. These small hollow spheres consist of both the electrode and the workpiece's material. As with any chip, by moving a dielectric liquid through a spark gap, it must be separated from the cutting field.
The chance of volatility when the dielectric fluid breaks down, whether as a result of aging or pollution, or discharge increases. To a degree, the control electronics can compensate, but constantly pumping pure dielectric fluid through the cutting zone to wash it is the only real solution. The more conductive the ions in the fluid, the tougher it is for the system within the spark gap to retain steady electrical thresholds.
Although the life of a dielectric fluid depends on several variables, such as its type and EDM fluid filter efficiency and consistency, it does not have an expiry date. However, as a general rule, it generally needs to be replaced if you are using an oil-based solvent and it is over five years old. Your eyesight and smell can also be measured to use and initial fluids, but with a refractometer, the easiest way to decide if a dielectric fluid has to be replaced is.
:: Read More: What Is EDM Manufacturing?
It is not often as straightforward to select the correct dielectric fluid for EDM applications as it might seem. There are many criteria to consider. Some are obvious, such as the degree of metal removal and electrode wear, while others are much more subtle. For example, a crucial aspect for machining efficiency is particle suspension, as the fluid must be able to extract EDM chips and other waste particles from the cutting field. However, these particles will not detach from the fluid during filtration if the particle suspension is too large. Check with the maker of the fluid to make sure that you are using the right dielectric fluid for your unit.
Of course, any workpiece to be machined with EDM must be electrically conductive, but that's not just the material drawbacks associated with EDM. First, relative to normal tool steels, materials such as high nickel alloys, such as those used in the aerospace industry, and carbide materials can pose a higher challenge to EDM. In these examples, however, alternatives to chemical concerns are improvements in electrode formulations and longer EDM cycle times.
In addition, while EDM is technically a smooth method of machining, there is no direct mechanical power applied to the workpiece. It is also a thermal process which through Heat Influenced Zones (HAZs), transformations and microcracks, will change the metallurgy of the workpiece. Any electrically conductive fabrics are also not EDM compliant.
One ideal form has been machined, then one or more heat treatments harden the pieces. This adds time, raises costs, and can modify the measurements of finished pieces, especially if the method of heat treatment is not properly managed. The value of EDM is that while having an outstanding surface finish as a bonus, it will cut hardened materials and rare alloys. The outcome is also a diminished need for any processing after it’s finished.
EDM needs a balance between speed and surface finish, much like all machining processes. For example, to reduce wire deflection, a wire EDM machine also uses quicker, rougher cuts followed by finishing or trowel cuts that use a less violent wash profile. For the majority of jobs using two electrodes, Sinker EDM sees a comparable pattern: one for roughing and one for finishing. EDM's key benefits are that the procedure is very predictable, precise, and repeatable. Both EDM is carried out unattended, because this is the direct labor ratio and output cost, and typically lower for EDM than other processes.
Overall, though, the EDM die sinker’s fundamental features can give you a feeling as to whether EDM is a decent match for your application. EDM, for example, is usually slower than other methods of machining, but also more predictable, accurate, and repeatable. There are other advantages as well: all EDM is done unattended, so the direct labor ratio and cost of production with EDM are typically lower than with other methods. Coupled with comparatively slow machining rates, the combination of predictability, precision, and repeatability explains why EDM is ideally suited for low volume operations with close tolerances, such as in the aerospace and medical industries.
Furthermore, because EDM is a non-contact machining process, compared to regular CNC milling machines, the mounting requirements for cutting small parts are much less strenuous. There is no leverage to cut because you don't need a lot of frames to hold them while you're dealing with little tiny parts. If you've tried to mill them, hold them close enough that they won't be raised or twisted by the machining machine. For example, if you're making mold mandrels and trying to sand them, they're going to shift all over the machining process. You can wire them with the handle that tilts 90 degrees and they come out great.
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