How you can Prevent Pitting In EDM Machining

The scene is all as well familiar to anybody connected with EDM machining, aka electrical discharge machining. The situation goes some thing like this:

You spend hours designing an injection mold core or cavity, days CNC milling and grinding to get the size and shape required. The only factor remaining is the EDM machining of the particulars. You've the Graphite Electrode Scraps made up, which takes a couple much more days, and finally everything is setup in your CNC EDM machine.

Usually, you may make 4 cavities, that will create four exactly identical plastics parts when every thing is lastly finished. Thing are going well, you have run the first six different shaped electrodes through the procedure, now there's just one much more. Only another 16 hours and you will be done and onto the following project.

So, you get it all setup to run all evening, and also you really feel confident that every thing is as it ought to be, you are able to sleep peacefully with out waking up inside a begin, wondering if you did this or that before going house.

The following morning you verify in your job the next morning and inspect it whilst still within the machine, it all checks out, so you eliminate it, clean it up and give it towards the mold polisher to create it all shiny and good. Quickly, he comes in and tells you he requirements to show you some thing. Certain sufficient, right at the bottom of the deepest part, a rib that is there to make the plastic component stronger, is really a pit. An additional name for this pit is a DC arc, or zit, or some expletive that is unprintable. What this indicates is the fact that there is a small hole, or crater at the most inaccessible area of your mold that appears like it was bombed whenever you view it through a microscope.( Graphitized Petroleum Coke)

Now you'll need to get creative and fix it, if you can. Usually there is some convoluted way to repair it by cutting out the bad part and making an insert to replace the pitted region. Occasionally although, it's just not feasible to repair it and also the whole piece must be scrapped!

Some manufacturers claim that their machines have software that prevents DC arcing, and to a great extent they do. Mostly this really is by retracting the electrode out of the reduce so flushing can occur. Some have a higher speed oscillating impact that improves the flushing also. Then you will find some that have improved cutting parameters that will adapt when the machine senses a DC arc.

All of these techniques really get down to enhancing flushing. Even high tech, new EDM machines will pit. I know because I have had to polish numerous surfaces EDM'd by these machines! You will find a good looking surface that's not so easy to detect till you start removing the very first layer of recast.( Broken Baked Electrode)

Then you will find numerous, pits, not big sufficient to scrap the component, but definitely big enough to create the polishers’ job much more difficult and possibly changing the dimensional integrity from the steel.