Electrode overburn

[MAKINOPAT]

I need some advice as to the best way to cut overburn on an electrode! Have tried changing cutter diameters and using tip, as well as using cutter diameter(actual size) with center as tip comp with negative stock to leave. On angles the amount of actual stock removed changes depending on the sidewall angle. the closer to vertical the closer to actual desired undersize. I know I can make changes with my EDM spark gap settings, but want trodes right out of my CNC.

[Hardmill]

Negative stock with surf machining or have

them modeled with the proper spark gap.

 

 

PEACE

[MAKINOPAT]

I am pulling the trodes out in mastercam from surface files, even using negative stock it doesn't cut the angles with proper overburn. The cut will vary depending on the angle, it appears everything is adjusted from center of cutter and not from the tangent point. We are also experimenting with some diffrent orbits on the sinker to see if we can come up with the right combination.

[Matt Berube at Ferron Mold]

Hi Pat,

 

I can assure you that cutting with negative stock will yield perfectly accurate results as long as you use a spherical orbit in the EDM.

 

When I am burning features that need to be exactly right I use negative stock. When I have room to cheat I lie about cutter size.

[Redfire427]

We use negative stock on a surface model without modifying cutter dia. and we also CMM the finishing electrodes where we are shooting for tenths on the final burn with no problem at all, regardless of sidewall angle. I see by your forum name that maybe you are using a Makino. If so, do you have a laser where you can scan the tool to get its "real" geometry. We make electrodes day-in, day-out, on our Makinos.

[Mjölnir]

I aways comp to tip, never center. There was a time when Mastercam couldn't do anything but comp to center but those days were gone long ago.

 

For spherical orbits, I use negative stock only. For continuous (2d) orbits, I use negative stock for spark gap only (typically .001 to .002 thou) and cheat the cutter diameter (bull nose) for actual orbit amount.

 

In any case orbiting never nets "perfect" shape even if the electrodes are dead nuts to size. There are a few exceptions, round hole - round trode, etc) Almost aways you end up "steel safe". If working to very close tolerances (e.g. shut offs on an injection mold for nylon or polypropylene which will flash in a half thou gap) it is suggested to make a couple extra trodes to either straight sink or use a very minimal amount of orbit.

[MAKINOPAT]

Well negative stock using tip comp seems to be give the best results. I think it is up to the edm dept to get the orbits figured out now! Yes I am running Makino machines, they have only been here for a few months so still trying to work out all the bugs, but are extremely happy with them so far and are already looking to add more soon!

thanks for the advice