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Posted on Nov 18, 2020
Imagine a band saw, except there is a thin wire instead of a saw blade, positioned vertically or at an angle that can be sliced at any direction x-y. It is a method of EDM cutter (EDM machining) that can cut either hard or soft, even carbide or diamond, electrically conductive material.
Contactless electrical discharge wire cuts, without burrs. You can cut internal corners with a wide radius and also narrow holes because the wire is so thin. As the wire never touches the workpiece, there are no grinding forces, because there are no cutting forces Thin fabrics, fine ribs or very delicate shapes may be sliced.
In the industry, EDM wire has been used for about 50 years. As well as built-in sensors and intelligence, modern EDM cutter machines implement CNC control, making them more powerful and easy to use.
The English physicist Joseph Priestly found in the 18th century that, using electrical discharges, he could erode metal. However, when two Russian physicists, the Lazarenko couple, created a regulated method of extracting metal using electricity, this technique became useful only during World War II.
EDM was mostly used at the beginning to remove missing taps and drills By placing an electrode into the middle of the damaged instrument. The same idea is currently used in an EDM or vertical EDM system, in addition to the EDM cutter machine, which produces a cavity in the workpiece with a copper or graphite electrode of the desired form.
A tubular electrode is used by an EDM drill to "burn" a hole through the conductive material.
As an electrode, a EDM cutter system that entered industrial use in the 1960s utilizes extended and taut wire. Usually, in deionized water, the workpiece and wire are immersed. Until an electric discharge occurs, water serves as a dielectric (electrical insulator).
As the wire approaches the workpiece, at some point the distance becomes small enough and the voltage large enough that the dielectric is destroyed and allows the discharge of electricity - a spark - between the wire and the workpiece.
A small portion of the workpiece is heated to thousands of degrees by an electrical discharge. Under high pressure, the dielectric becomes an ionized gas or plasma, exiting. The plasma bubble collapses, forcing the molten substance onto the dielectric fluid to dissipate, leaving the workpiece with a small crater.
A fragment of wire is being eroded at the same time. This method of discharge is quickly replicated, up to 250,000 times per second. The metal near the wire is stripped in this way and an incision is made along the wire. The rinsing of a clear stream of deionizing water keeps it and cools the wire and removes any particles formed.
As the wire also undergoes some erosion in this process, the EDM cutter continuously feeds fresh wire from the spool. The machine shreds the used wire and leaves it behind a bin for recycling.
You need to have a pilot hole to cut the inner mold. For a traditional drill or EDM drill, this can be achieved. To start off, the wire is threaded through the hole. Automatic threading is supported by advanced wire-EDM devices. The wire is guided through the workpiece by a jet of water or air.
The computer makes the requisite mechanical and electrical connections automatically. The machine senses the break if the wire breaks while cutting the part, rewinds the wire, and continues cutting where the wire broke.
The critical components of the EDM process are wire and dielectric water. The wire is available in several materials and diameters, the most commonly used being 0.010 "or 0.012".
The wire used in most applications is made of brass. If you need more performance, you can choose galvanized wire, which gives more speed and better surface finish. The zinc coating allows the wire to tolerate higher heat and helps maintain spark integrity.
Annealed, annealed wire - zinc enriched brass wire - can tolerate more heat when cut. To make EDM wire of a thick part that would not get much of the wire rinse water in the center of the workpiece, use high efficiency wire. It can withstand heat, keep consistency when cutting, and resists cracking.
Today's EDM machines detect wire and cutting conditions and adjust the cutting speed accordingly. By simply changing the wire, the speed can be improved without making any other adjustments.
For example, in one application, a brass wire was cut within 10 hours. But the scattered annealed wire cut that time to seven hours without changing any settings. The process can be optimized by adjusting the settings on the machine.
The upgrade is very application dependent. Some get better, some get less, but there's always a dramatic change. Even a 5 percent improvement can make it worthwhile. Each type of wire will only cost a few dollars an hour, and high-performance wire can pay off with increased production.
For particular uses, other forms of EDM wires are available. For example, copper can not be used in implantable medical devices, so molybdenum wire is used. In applications where the wire is under high voltage, crack-resistant brass wire with a steel core is used.
To get the best performance from your EDM cutter machine, you need to keep the water clean and conductive. In EDM, some of the metal ends up in the water as small particles and some dissolves in the water.
The water is recirculated through a two-part water treatment - filter to remove particles and re-deionization to remove metal atoms from the solution. Good maintenance practice includes periodically replacing the filter cartridges and sending the deionization resin for regeneration.
Automatic threading of 0.25 mm wire into a 0.7 mm hole. Thus, EDM cutter enters applications that have been used before, such as "fir" slots where turbine blades attach to the hub in power generation applications.
They can get an EDM machine for one specific project - inside corner they couldn't cut, or high nickel alloy parts. The new EDM machine can only run a third of the time, said Bond, and then someone realizes it can run at night for $ 25 or $ 50 and get the part produced. You can load an EDM table with a punch and die on one side and a piece of carbide on the other, and work unattended all night.
The process can be regulated by a shop that performs its own EDM cutter. For a finer finish or more consistency, if you have a simulator at home, you can make more passes. You sometimes get the chance to build items that are better for a client than what you have provided in the past.
A jab or a dice, for instance, which would last longer. You will get timetable flexibility for in-house EDM cutter and do not have to contend with EDM shop lead times, so you can quote shorter delivery times.
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