Wire-cut metal cutting for high-quality finishing
Nov. 26, 2021
Electric discharge machining or EDM is a method primarily used to machine hard metals, especially those that are difficult to machine using other techniques. It is a machining method that is only applicable to materials that can conduct electricity. In EDM, the cutting tool is the discharge of the wire.
The material of the wire corrodes and causes it to break, so in EDM the wire is wound on a spool that rotates to continuously expose the different parts of the wire that are active in the desired process.
How EDM finishing differs
The EDM surface finish is different from the surface finish produced by machining with carbide and other hardened tools. In these cases, each cutting process produces a finish that is influenced by the direction and motion of the cutting tool. Sliding friction in the direction of the tool is lower than sliding friction in the direction of the tool. In EDM, there is no direction per se. Therefore, the surface finish with EDM wire cutting can be mirror-like.
EDM wire cutting works by creating tiny lightning bolts between the tool, the wire and the metal part being machined. These arcs touch the workpiece and generate intense heat that evaporates the material and removes it from the surface, creating a small crater. These craters may be micron deep, but thousands of these craters are created every second. As a result, the workpiece is subjected to progressive erosion.
The material removed by this erosion is achieved by an insulating fluid, a flowing dielectric. Dielectrics are very poor electrical conductors and no current flows through them. This flowing dielectric is filtered out at different points in the EDM wire cutter.
As you increase the power and frequency through the wire, it creates a more powerful arc, which enables more material to be removed. This requires higher flushing pressure to remove the resulting material debris, which can lead to larger pits and rougher surfaces. Therefore, by controlling the power and frequency of the flow through the wire, a high quality finish or a rougher finish can be obtained.
The hardness of the material is not a factor in its ability to be cut by the EDM wire, which allows the EDM wire cutter to be used to machine even the hardest and toughest materials, as long as they are good conductors of electricity. Thus, EDM wire cutting can be used to cut tungsten carbide and tool steel.
EDM wire cutting has a very high degree of precision and accuracy
In conventional metal cutting, the surface roughness achieved is inversely proportional to the power and speed of the cut. In other words, a higher quality surface finish can be achieved with a slower cut. With EDM wire cutting, the subsequent process is often faster than the previous process.
When you need to use an EDM wire cutter for high quality cutting and finishing, it is normal procedure to put the workpiece through roughing and one or more cutting passes. With each pass, less and less material is removed as the material gets closer to the finished edge.
For example, if we use 0.010" diameter wire, the first pass may remove 0.013" of overburned material. The next skim will remove 0.0015". The next would require 0.0004" and finally 0.0001". Obviously, more passes can produce a very smooth surface, but it is also related to the density of the material being cut. The denser the material, the fewer passes the smoother the finish will be.
By passing through the wire cut several times, any secondary processes, such as grinding, can be completely avoided, as many metal products need to be passed through when cut by other means.
EDM wire EDM is the tried and true method for creating complex, precise and technical components when cutting conductive metals. While other types of machining often require customers to accept a certain level of error in the final product, this is not the case with EDM. Experts who use EDM understand the importance of every detail to the customer. If small gaps or curves are not achieved at the correct angle or size, certain prototypes will not work as expected.
Most metrics show that using this type of EDM produces better than 99.99% accuracy compared to the original specifications. In addition, many have found that highly technical procedures such as internal cutting operations can only be achieved through the use of wire EDM. In this type of machining, almost all metrics are unmatched in terms of accuracy and precision. Therefore, EDM should be the first choice for anyone who needs the most defined prototypes.
Because wire EDM can achieve such precise cuts and the cuts are not directional, it is a good choice when you need a high quality surface finish.
High efficiency and quick turnaround
Many customers find that the quick turnaround time for creating prototypes using EDM wire cutting is perfect for meeting deadlines for investor and stakeholder presentations and meetings. Most companies requiring prototyping services follow very tight schedules, as they are often dependent on developing presentable models of future products for investors in a short period of time. Of all the possible manufacturing options, EDM wire cutting has the fastest turnaround rate without compromising accuracy by a single percentage point.
The high efficiency is achieved by the inherent characteristics of EDM, such as the fact that it requires the least amount of tooling procedures. Many other production methods used for prototyping follow archaic and clumsy procedures that require a lot of time for setup. In contrast, EDM wire cutting is a cutting-edge technology that allows for minimal setup. In turn, the turnaround time using such technology is very fast.
For companies interested in prototyping, the two most important metrics of accuracy and efficiency reach their highest degree when using EDM wire cutting. Accuracy and precision ensure that the accuracy of the final model is virtually error-free compared to the original design and blueprints. In addition, to meet strict deadlines and schedules, this type of machining ensures that prototypes are made as quickly as possible without compromising accuracy. Overall, wire-cut EDM should be the first and only choice for any prototyping needs.