The use of edm copper in moldmaking is as old as EDM itself. Copper is much more common than graphite as an electrode material in Europe and Asia, though this is changing.
Copper has many advantages, as well as many disadvantages, when compared to graphite as a material for edm electrodes. A visit to nearly any EDM department will quickly reveal that copper is very much a useful material in sinker EDM.
Deciding which material fits your application is important, and time spent analyzing this can save you many headaches, not to mention time and money.
What are the advantages of edm copper?
- Copper is more efficiently cut on WEDM machines. Copper cuts faster than graphite in WEDM. Highly detailed graphite electrodes, which were formerly manufactured on surface grinders, required many hours of highly skilled labor. The use of copper and WEDM to produce these electrodes has dramatically changed sinker EDM.
- Copper is less likely to cause pits in the steel workpiece. The tendency of any electrode to “DC arc” is the curse of EDM. When the flushing is poor, machining conditions are ripe for a short circuit to occur in the EDM process, causing the tell-tale pits in the workpiece. Copper is much more forgiving and less likely to DC arc.
- Copper is usually used to produce a finer finish in the steel. Copper electrodes are sometimes polished to reproduce the fine finish on the mold surface. Newer EDM machines have polishing settings that can produce mirror finishes, and usually copper is used.
- Copper is the best for small cavities, especially where polishing is difficult. Because of it’s resistance to pitting and the finer finishes attainable, copper is often used in these applications. Adding tungsten to copper increases it’s excellent wear characteristics, but also is very difficult to machine.
- Copper can be machined by coining. In this process, the copper is stamped with an image, just like a coin, and then used as an EDM electrode. This can be an excellent application for designs such as logos.
- Copper is clean to machine and leaves no annoying dust. Also, tellurium copper leaves much less burr than pure copper.
What kind of edm copper should be used?
Tellurium copper (Telco) performs the same as pure copper as an electrode material. It has a huge advantage, however, because of it’s high machinability rating: 90% (free cutting brass = 100%). Pure copper has a rating of 20%.
Telco edm copper is highly recommended for use on machines which have been designed to work best with copper. It’s ease of conventional machining and fast WEDM speeds make it ideal for highly detailed, difficult to flush electrodes.
Why is copper more commonly used in Europe and Asia?
This happened for several reasons. When the first generation of machines were developed in these areas, the power supplies were R-C, or Resistor Condenser. Metallic electrodes such copper and brass were the only materials that efficiently performed in these machines.
Then, as newer generations of machines were developed, the use of edm copper was well established. Plus, EDM grade graphite was simply unavailable.
The use of copper has declined as technology has progressed. Newer EDM machines are designed to use graphite as well as copper. High speed machining centers are equipped with vacuum environments to remove the annoying graphite dust.