How to Stop Pitting In EDM Machining

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

You invest hours designing an injection mold core or cavity, days CNC milling and grinding to obtain the size and shape required. The only thing remaining will be the EDM machining from the particulars. You've the Graphite Electrode Scraps made up, which requires a couple much more days, and finally every thing is set up in your CNC EDM machine.

Typically, you may make four cavities, which will produce four exactly identical plastics parts when every thing is finally completed. Thing are going nicely, you have run the very first 6 various shaped electrodes through the process, now there is just one much more. Only an additional 16 hours and also you will probably be carried out and onto the following project.

So, you get it all set up to run all evening, and also you feel confident that everything is as it should be, you are able to sleep peacefully without waking up inside a begin, questioning if you did this or that prior to going home.

The next morning you verify in your job the next morning and inspect it while nonetheless in the machine, it all checks out, so you remove it, clean it up and give it towards the mold polisher to create it all shiny and nice. Soon, he comes in and tells you he needs to show you some thing. Sure sufficient, correct at the bottom of the deepest component, a rib that is there to create the plastic component stronger, is really a pit. Another name for this pit is a DC arc, or zit, or some expletive that is unprintable. What this indicates is that there's a little hole, or crater in the most inaccessible region of your mold that appears like it was bombed whenever you view it via a microscope.( Graphitized Petroleum Coke)

Now you'll need to obtain inventive and fix it, if you can. Usually there's some convoluted method to fix it by cutting out the bad component and making an insert to replace the pitted area. Occasionally though, it is just not feasible to repair it and the whole piece should be scrapped!

Some manufacturers claim that their machines have software program that prevents DC arcing, and to a great extent they do. Mostly this really is by retracting the electrode out from the cut so flushing can happen. Some have a high speed oscillating effect that improves the flushing also. Then there are some that have enhanced cutting parameters which will adapt when the machine senses a DC arc.

All of those techniques truly get down to improving flushing. Even higher tech, new EDM machines will pit. I know simply because I have had to polish many surfaces EDM'd by these machines! You'll find a good searching surface that's not so easy to detect until you start removing the very first layer of recast.( Broken Baked Electrode)

Then you will discover numerous, pits, not big enough to scrap the component, but certainly large enough to create the polishers’ job much more tough and possibly altering the dimensional integrity from the steel.