Introduction to wire cutting

Posted on Aug 21, 2020

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Introduction to wire cutting

Wire cutting or Electrical discharge machining (EDM) is a manufacturing process that implements electrical sparks to form a metal shape. Because of these sparks, EDM is also sometimes referred to as spark machining. In this process, the desired shape is cut from the metal when current discharges, or sparks, occur between two electrodes; where the sparking occurs, cuts are made into the metal, creating the desired shape and detaching it from the metal sheet. So this is why it is sometimes referred to as wire cutting.

There are two main types of EDM — wire and sinker — and several other less common methods, but this article will be focusing on wire EDM. Wire EDM uses a wire as the tool electrode. The wire is wound between two spools and when in motion, the active part of the wire continually switches — preventing the material from eroding from the wire itself.

During the EDM process, the metal part is placed in a dielectric fluid and the wire is introduced through the immersed metal part. Electric current is sent through the part to create sparks which will ultimately help form the desired shape of the part.

Reducing the separation distance between the electrodes increases the electric field strength and thus increases the strength of the dielectric fluid. Under these conditions, the current flows more easily between the two electrodes, leading to a separation of the element from the sheet at each spark.

After the currents have passed and the desired shape is achieved, manufacturers sometimes perform a process called "rinsing", using a dielectric fluid to help remove any residual material or waste from the finished product.

:: Read more : A Brief History Of Wire Cut EDM

 

EDM Benefits

Wire EDM machines are able to carefully remove excess material without using much cutting force. The process is often automated, meaning it is less likely to damage the workpiece itself. And since wire EDM machines can machine hard materials, there is no need for additional post-treatment heat treatment. As a result, little or no thermal stress is applied to the shaped part and the surface of the part is less likely to deform.

:: Read more : Let’s look at the Pros and Cons of a EDM Wire Cut Machine

 

EDM applications

Electrical Discharge Wire is most commonly used in mold and die production processes, in particular for extrusion and dies. EDM can be used in everything from prototypes to full production runs, and is most commonly used for the production of metal components and tools. The process is best suited for applications requiring a low level of residual stress.

Wire EDM machining is mainly used to machine various clamps, plastic molds, powder metallurgy molds, etc.which have 2D and 3D surfaces or components combined. It can also cut various sample plates, magnetic steel, silicon steel sheet, a semiconductor material or a noble metal. In addition, it is able to perform fine machining, wrong groove shape or machining standard sample part defects, widely used in electrical engineering, valuable machine tools, light industry, military industry and so on.

:: Read more : Wire Cut EDM Machines - more than just tooling and mold-making equipment

 

Machining of forms

Wire cutting is widely used to process various molds, such as punch die, extrusion die, powder metallurgy mold, bending mold, plastic mold. Among these various types of forms, cutting dies have a significant share in the processing of a cutting punch, and wire EDM processing is an indispensable technology. By adjusting different compensation values ​​during programming, wire cutting EDM can cut terrace die, punch plate, stripper plate and etc, it is easy to meet the requirement of mold fitting clearance and machining accuracy.

Advanced punching dies are characterized by a complex structure, high production difficulty, high accuracy, long service life, high efficiency and low material consumption. This new advanced mold technology also ensures the continuous development of EDM wire cutting technology,

 

Machining of parts

For machining mechanical parts, the wire cutter is suitable for machining parts with large varieties and small quantities, a special material that is not easy to process with conventional machines, special gear, forming cutting tools, various shape holes.

When trying to make a new product, use a wire cutter to cut parts from the workpiece. No need to make molds and the production time is obviously shortened. At the same time the cost is reduced. Besides, because it is easy to adjust the electrical parameters of the wire cut EDM machine, it is possible to overlap thin sheet metal and cut together to increase machining efficiency.

EDM is often the most cost-effective way to machine very hard materials such as tool steel, carbides and exotic alloys such as inconel and hastaloy. It has the advantage that it does not transfer any cutting forces to the workpiece, so there is no distortion, which allows the production of very thin sections. In addition, the wire EDM machine can produce internal corners with radii slightly larger than the radius of the wire itself.

In conventional metal cutting, two passes are usually made to achieve the desired final size and finish. The same goes for wire EDM. Increasing the electrical power erodes the metal faster, but the finish suffers. Reducing the power on the second pass creates a finish that leaves a good surface finish.

Unlike machining processes that produce chips, wire EDM has the potential for increased material utilization. (Something very interesting when cutting high-value materials!) Since the wire removes very little material, there is often a large internal piece left behind. Milling or grinding would turn it into a pile of chips, but with a wire EDM machine, it can be saved and used for another task.

 

Tooling applications for wire EDM

Perhaps the best known application is profile cutting in dies. For aluminum extrusion, they are usually made of H13 tool steel. First, a hole is drilled in the die blank (often also with EDM) and then the wire is threaded through. The CNC moves the blank through the wire to cut the required profile. On modern EDM machines, the wire can be skewed to cut shapes with conical sides.

EDM wire is also useful for making punch tools. The tool steel blank is moved around the wire to cut the required profile. Again, the ability to cut cones is extremely handy.

 

Applications other than instrumentation

Each 2D profile can be cut from a conductive material with wire EDM. In some cases, broaching and milling is possible, but wire EDM has several advantages:

●     Creates sharp inside corners.

●     No cutting forces, allowing very small parts to be machined.

●     Very hard material can be cut at relatively high speed.

●     Suitable for unattended processing.

●     Removes design limitations imposed by conventional metal removal.

●     No special tools are needed.

●     Higher material utilization.

 

One of the application classes of a wire EDM machine is the production of precision machine parts, especially where they are needed in small quantities. Sewing machine components, other gears, and splines would be a good example.

Other categories are medical devices, surgical instruments and small hand tools. In each of these, the ability to cut intricate paths in a very hard material such as stainless steel makes the wire EDM very profitable.

:: Read more : Wire EDM – Today’s Topic | A Complete Look at Today’s Metal Working Industry

 

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