How you can Stop Pitting In EDM Machining

The scene is all as well familiar to anybody connected with EDM machining, aka electrical discharge machining. The scenario goes something 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 factor remaining will be the EDM machining of the details. You've the Graphite Electrode Scraps produced up, which requires a couple more days, and finally every thing is set up inside your CNC EDM machine.

Usually, you may make 4 cavities, which will create 4 precisely identical plastics components when everything is lastly completed. Factor are going nicely, you've run the first 6 different shaped electrodes through the process, now there is just 1 much more. Only an additional 16 hours and you will be done and onto the following project.

So, you get it all setup to run all night, and also you feel confident that everything is as it should be, you are able to sleep peacefully without waking up in a start, wondering in the event you did this or that prior to going house.

The next morning you check in your job the following morning and inspect it while nonetheless within the machine, it all checks out, so you remove it, clean it up and give it to the mold polisher to make it all shiny and good. Quickly, he comes in and tells you he needs to show you some thing. Certain sufficient, right in the bottom from the deepest part, a rib that is there to make the plastic part stronger, is really a pit. Another name for this pit is a DC arc, or zit, or some expletive that is unprintable. What this means is that there is a little hole, or crater in the most inaccessible area of one's 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 repair it, if you can. Generally there is some convoluted way to repair it by cutting out the bad component and creating an insert to replace the pitted region. Sometimes though, it is just not feasible to repair it and the whole piece must be scrapped!

Some producers claim that their machines have software that prevents DC arcing, and to an excellent extent they do. Mostly this is by retracting the electrode out of the cut so flushing can occur. Some possess a higher speed oscillating impact that improves the flushing as well. Then there are some that have improved cutting parameters that will adapt when the machine senses a DC arc.

All of those methods really get down to improving flushing. Even higher tech, new EDM machines will pit. I know because I've had to polish numerous surfaces EDM'd by these machines! You will find a nice searching surface that is not so simple to detect until you begin removing the very first layer of recast.( Broken Baked Electrode)

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