Just ask anyone who has an electrical discharge machining job, and you will quickly find out that you must be as picky as picky gets. A fuss-budget, 5 star, exacting, detailed perfectionist would make a pretty good EDM operator. Then add a bit of mechanical ingenuity, daring, endurance and sheer willingness to hang in there and you have it.
Guess that eliminates just about everybody. Yet nearly every single thing you pick up that is made by plastic injection mold making was largely made by the electrical discharge machining process. Not many people know that, and even fewer people have any idea whatsoever EDM is. It is one of those hidden jobs that everybody is glad for, but is just unaware of.
Electrical discharge machining is one of those unheard of jobs that effects everybody.
What is electrical discharge machining, a.k.a EDM?
To avoid technical jargon and lengthy explanations, just think of the process like this:
Press a coin, such as a nickel, into some silly putty or bread dough until it leaves an impression. It will look just like the coin, except that it is a mirror image of the design.
That is how electrical discharge machining works in one picture. Now, imagine that you use highly sophisticated computer controlled machines to cut the picture on the nickel into a piece of copper, or graphite. Graphite such as in you pencil lead. You can buy high grade graphite blocks and cut shapes into them very easily, and this is actually the most common material used for EDM.
Of course it is cut as a mirror image of what you see on the coin so the end result is correct. Now instead of silly putty, you use a piece of steel. You put it on a special table, clamp it down, and put the graphite block above it in a holder, much like an old fashioned printing press. So the graphite rests about the steel, which is securely fastened to a machine table.
Now you see the electrode, now you don’t
Now, you submerge all of this in an oil bath and turn on the electrical supply to make the graphite charged with electricity. Gradually it is lowered close to the steel until millions of tiny sparks jump back and forth between the steel and the graphite.
After some time, you will see the shape that was cut in the graphite reproduced perfectly in the steel! It seems as if it would never work, but it actually works very well. In real life, the current and movement of the graphite is highly controlled so that a predictable result follows. It is no uncommon to maintain accuracies of one/eighth of a human hair!
Why does the EDM operator have to be so picky?
This process is mostly a matter of setting things up properly. The location of the graphite in relation to the steel must be perfect, the electrical settings must be exact and the oil must be controlled in an exact manner as well. If any of these aspects are wrong, you will end up with scrap metal. Not only that, but you might not know it for many hours or days because the process is slow and it is all submerged in oil!
Once you make your set up correctly, eventually you must push the button to begin the process. Usually though, you can’t see much because of the oil, so it is often a tense time in the beginning.
Another reason for the pickiness is that usually an electrical discharge operator is responsible for several machines at the same time. Keeping track of the multitude of details requires a high degree of carefulness and diligence.
EDM can be a very rewarding career job, for the right person. You must be very determined, highly detailed, able to accept defeat and correction, be willing to work long hours and enjoy technology. The job security for a highly qualified electrical discharge machining operator can be very good.
What about the pay?
This depends on your level of experience and where you live. In California you are going to make a lot more than in Mississippi, for example. Or Germany compared to Romania. Generally, if you can find out what a plastic injection mold maker or mold designer earns, you can estimate that an EDM operator will make about 85% of that rate.
If you are a mold maker, then it is an easy step into the EDM department and your pay should remain the same. You already have the skills with dial indicators, surface plates, sine plates, roll dimensions, height gages, surface gages and understand the entire mold making process.
One of the “benefits” is the amount of overtime most EDMer’s work. It is quite common to work 45-60 hour weeks, so, if you are willing to work smart, be diligent, pay close attention to everything you do, and work many hours, you can earn a very good annual income without going to a university.
Other aspects of injection mold making