Selecting a used sinker EDM for a small die-making task

From time to time, we make dies for our own use to produce little parts on a punch press, typically with the longest dimension smaller than 1/2" across. Up until now, these have always been very simple and we could finish everything with a surface- and jig-grinder. We're working on a new design that requires a slightly more complicated die set that could be made on a sinker EDM but we don't have experience with these machines.

Supposing we want to dip our toes in the pool and find a used, manual EDM:
1. What are the better options among the used EDM machines?
2. How does a guy inspect a sinker EDM?
3. What are the show-stoppers with EDM?

Hi Borealis:
When I think "Punch Die" I normally think "Wire EDM" so I'm surprised to see "sinker EDM" in your post.
What features do you feel need sinker EDM as opposed to wire?
Are there going to be draw stations for example?

With regard to buying a sinker, there are lots of posts written by me and by others over the years on here, so a search under the name implmex will probably get you some useful information to start you off.

The Cole's Notes version though is pretty simple and pretty basic.

From worst to best:
Hydraulic ram manual sinker
Hydraulic ram manual sinker with CNC orbiter.
Stepper or servo driven ram ZNC sinker
Basic CNC sinker
Sophisticated CNC sinker
Brand spankin' new CNC sinker.

Hydraulic machines are a crap shoot because they depend on a hydraulic servo valve to respond to the spark gap conditions.
They are both un-fixable and irreplaceable if they go down, and they do so on old machines with distressing frequency once they've got enough miles on them.
Also, If you don't have the burn tables for the machine you have a boat anchor.

CNC is absolutely wonderful for sinker work...there are a bazillion reasons why.
Orbiting, adaptive control, C axis, vector burning etc etc.

A new high end CNC sinker can run rings around an older, more primitive machine and it will do it better and more accurately too.
Modern adaptive controls try to jigger the settings continuously (there are a LOT of settings all of which interact) and find the best combination to meet the stated goals in the best time possible...I can burn for ten hours on my 1996 Hansvedt Foreman sinker to do a burn that a new Sodick can do in under an hour, and the Sodick burn will be better and more accurate too with less electrode wear.

That's the ultra short version, I encourage you to scroll through the archives and find out more.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

We've off and on debated picking up a used sinker here also. It wouldn't see a whole bunch of use so we would buy used. Do you have any recommendations on what a solid used cnc sinker would be? I've always heard the Sodick sinkers are nice because of the linear motor Z drive, but I don't really know any specifics about that.

Hi wdevine:
So far as I know, Sodick was the first to market with linear motor sinkers, and the benefits became apparent very quickly.
The principal one is that you can move the ram really fast and really precisely, so you can "jump flush" better than with a ballscrew ram.
Jump flushing (there are other names for it too) relies on using the electrode almost like a piston to force dirty dielectric fluid out of the spark gap and draw fresh fluid in, so no more flushing holes in the trode (most of the time).

That's a really big deal, so Sodick has a great sinker reputation for that reason.
Others have copied it since, so the choice is much broader now.

With regard to buying used, the biggest thing is that you don't inadvertently buy a dog.
There are two kinds of dog you could buy:
One is a worn out clunker that's not worth fixing.
Two is an orphan you can't get parts for.

Once you get past that, you have to decide how much you're willing to pay to get better features.
Sinker technology really changed the game when CNC came on the market, enabling burns in any orientation.

It changed again when adaptive controls came into general use, allowing the machine to pick the settings for the spark generator and to do it on the fly.

It's been slowly getting more and more convenient for inexperienced guys to use, so no more crusty old farts who carry the secrets of their arcane wizardry to the grave with them.
But if you buy one of the old ones, you have to learn all the "old fart secrets" because the machine won't help you.

That's why a 1980's manual hydraulic ram machine, even if it's in great shape, is an unwise purchase for the unwary.
So if you have the cash, splash the cash and save yourself some pain.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining