Written By Mark Batson Baril
What is EDM (Electric Discharge Machining) and why should we know about this technology as manufacturers and finished part buyers? This is one of those areas of producing cut parts that is incredibly interesting. Let's explore…
Electric Discharge Machining (EDM) was first introduced in the 1940's as a crude device used to cut broken machining tools from expensive in-process parts. Since that time EDM has become a sophisticated and indispensable technology, revolutionizing the tool, die, and mold making industries, and making significant inroads into the production of highly accurate, intricate, and difficult to machine production parts.
EDM is a process that removes material by generating intense heat in a highly localized area of a workpiece. Material is removed by a controlled electrical spark generated in the machines power supply and released from the electrode to the workpiece. The workpiece may be of any material, no matter how hard or tough, so long as it is electrically conductive.
One terminal of the power supply is connected to the electrode and the other to the workpiece. The two terminals or connecting points are held in close proximity by the machine, yet they remain separated by a small gap throughout the process.
What is the electrode? The electrode is the part of the machine that the power is discharged through. It can take the form of a single thin wire that passes through the material as a straight line. It can be angled as related to the part. It can also take the form of a solid custom shape that will make a cut to match this shape as it passes through the material.
The gap between the two terminals is always filled with a circulating dielectric fluid which acts as an insulator. The fluid also acts as a cooling agent in the cutting area and flushes away the particles of material that have been eroded from the part. When the power is first applied, there is no current flow because of the insulating dielectric fluid, yet an electrical field begins to build in the gap at the point of minimum clearance. The conductive particles begin to form a bridge focusing on this point. By narrowing the gap, the voltage, the shape of the electrode, and the shape of the workpiece we cause the bridge to ionize at the point where the field is strongest. This is where a discharge channel forms and the negative particles flow toward the positive, and current begins to flow. As the particles begin to move, extremely high temperatures and pressure are generated causing the particles to melt and vaporize in a very localized area of the part being cut. The initial charge of the current tends to be the most important part of the cutting process and so parameters must be set that will pulse the power on and off at very high speeds as the electrode is moved through the material. As is the case with all machining, the operator control, and final adjustments of all parameters involved are directly related to the quality of the parts being cut.
By combining this electrical process with a extremely accurate movement system, an incredible diversity of machining can be done with EDM.
Some of the areas that die makers and die cutters are effected include:
- Specialty Cutting Punches used in die cutting
- Machined Rotary Dies used for many industries like labels, gaskets, high production folding carton …
- Bases for Highly accurate and intricate flat-bed Steel Rule Dies.
- Matched Metal (Male and Female) and/or Combo tooling used for diecutting, stamping, and forming of parts for almost all specialty die cutting applications.
- Rapid production and prototyping in many materials of the actual parts. This is one of the alternatives to making tooling at all.
By learning more about processes like this, it allows us to explore areas and ideas that may help us to better our products and manufacturing methods. Being in the business of cutting makes this process a related and extremely important process to all of us.
We hope you enjoyed the article. Please contact Cut Smart if you would like more information on this subject.
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