Electrical Discharge Machining, EDM For Sinker And WEDM

The plastic injection mold making and die making industries both rely heavily on EDM machining, both with the sinker EDM and wire cut EDM machine. The electrical discharge machine is a totally amazing and somewhat mysterious tool, without which, our modern way of life would be much different.

As far as I can gather, two Russian scientists were trying to make hollow ball bearings and came upon the EDM machining process as a result of their experiments. At the time, it was not practical, but later on the Swiss developed it into what it has become today: an essential machine tool for manufacturing. It is no wonder that the Swiss companies, Charmilles, Agie and Erowa are all world leaders in the EDM discharge business. Strange how things get invented and developed sometimes!

Global developments

As time passed, both the USA and Japan became heavily involved in electrical discharge machining, and soon both countries had many excellent companies producing high quality products. The Americans came out with Eltee Pulsitron, which was the most popular machine for many years, and many are still in operation today.

The Japanese came out with Sodick, Makino, and Mitsubishi after the development of the CNC EDM. All 3 of these companies have very high quality machine tools with excellent reputations.

The Swiss are still huge players in this high precision machining arena: Charmilles and Agie are very popular all over the world. Both their wire cut EDM and sinker EDM machines have been in use for many, years and are still accurate.

There are numerous other wonderful brands as well, some from Europe and still others from Asia. Germany, Taiwan and China all produce very good machines that do excellent work.

Accessories

Any tool and die or mold making shop will necessarily have a lot of support for the EDM department. Supplies such as a toolmakers microscope, and optical comparator are essential for inspection. The use of a CMM, or coordinate measuring machine has become an industry standard as well.

The granite surface plate is the foundation of any inspection area. There will also be a surface gage, sine plate, gage block set, pin gage set, dial indicator, various drop indicators, precision vise, tooling ball set, and various electrode holders.

Electrode holders

The sinker EDM requires some type of tooling to mount the graphite or copper electrode, so it can do it's magical work on the injection mold or stamping/forming die. Years ago this was done with angle blocks, vises and homemade fixtures. Today almost all shops use high end, highly engineered systems, such as System 3R and Erowa.

Poco graphite is very popular as an EDM electrode material, but every year a new brand comes out to try and outperform this standby. Graphite has many advantages over it's rival, tellurium copper, but in many cases the copper is the material of choice anyway. Occasionally tungsten carbide is used as well.

EDM jobs

In the USA, the skilled workforce is aging and very few companies are interested or able to train a new generation of EDM toolmakers. A skilled operator will always have a secure EDM job, if he can get the training in the first place!

Automation

Automatic tool changers have made life much easier in the EDM department. This allows the machines to run continuously, sometimes for weeks on end! Now, with a pallet changer system integrated, you can even change the workpiece without human intervention. This requires a great deal of up-front planning, but pays off in the long run.

Electrode manufacturing

As much as possible, the electrodes are made using high speed milling, with a carbide cutter. The carbide tooling is usually coated with a special material to give it high wear properties. It is possible to use conventional vertical milling machines, if they are equipped with a high speed spindle. Haas, Makino, and DMG are all key players in high speed milling.

Mold repair

In the event that something goes wrong in the EDM process, it is usually possible to repair the mold or die by using a laser or micro welder. This process has saved the day, many, many times! Both the laser and micro tig welders are essential for life in an EDM machining environment.