Quoting die-sinker jobs

[Togliatti]

Our company's boss aims to be able to predict die-sinker burn times within 10%. We're burning medical grade stainless and carbide. There are more variables with EDM-ing than there are for milling of turning operations, and quite often, actual burn times don't seem to be logical. For example, we've found that burning 4-up cavities does not take 4x longer than burning one. Are there any experienced EDM-ers on the forum who have achieved an accuracy of 10% on their quotes? If not 10%, what would be a realistic expectation?
Thanks for any help.

[Chopit]

I think the best way to predict sinker burn times is to check the jobs you've done so far and how long it took and then try to categorize them as good as possible; so you, or your boss, can use this information when he's estimating prices:

For example:

(A) Material of the part:
(B) Width and height of the electrode, Or; Area of/in effect simultaneously:
(C) Material of the electrode:
(D) Electrode purpose: Rough/Finish
(E) Depth of the sinking area.

And when you've got all this information you can start figuring out some kind of formula for the feed per minute relative to (A, B, C, D and E).

Theoretically, It's the total area of the electrode that is in effect (simultaneously) that determines the EDM sinking burn time, This of course is relative to the information of (A, B, C, D and E).

Unfortunantly, Theoretically and EDM-machining doesn't seem to like each other that much so it's hard to actually predict anything, Especially since no machine seems to EDM a part as fast as another.

Maybe you should check with the manufacturer of your sinker, They should know how to calculate this stuff, Especially since they built the machine.

However, I know there's some researching going on about EDMin, Concerning feed per minute and why, And also how to determine it. I don't know how far they've come, though. :-P

Ah well, I hope i gave some useful information.

Good luck and take care! :-)

[Togliatti]

Chopit,

Sorry I didn't acknowledge your reply sooner, but I haven't been on this site in a while. I appreciate your many good suggestions. I had planned to start with volume of material to be removed as a key parameter, but I've found it isn't quite so simple. And as you say, theory and actual EDM practice are two different things.

I have found a couple of extremely esoteric papers on this subject, and they're well beyond my ability to make use of in the machine shop.

I think this effort will require a very large amount of empirical data to create a usable database.

Thanks again for your input.
George

[marleecnc]

There are so many variables involved, that it is almost impossible to quote an accurate edm time for a particular job, unless you have done the exact same job already prviously. Flushing, power settings, final surface finish, amount of stock left to remove, material type... the list goes on....
Just placement of a flushing hose for example can be the difference between a 15 minute burn, and a 45 minute burn in many cases. Its all about experience - honestly. Ive been running edms for 20 years, and I never quote times closer than "a half day... a day... or a couple hours for a quick job."