Sinker EDM head??

Hello. I don't know if this exists, or for that matter, even possible....here it goes; does anyone make a sinker EDM "attachment" that would go into a CAT50 tool holder that I could then "burn" threads into a part? I realize that this may cause damage to spindle bearings and the like...but is it possible?

Thanks,
Mark

Are you trying to use a milling machine as a sinker edm?

Yes, that is the thought. We manufacture a difficult material to machine, but is doable with PCD tooling...threading is a real PIA...it eats taps, the thought was if I could save from setting up the part in another machine....

M. Roberts said:

Yes, that is the thought. We manufacture a difficult material to machine, but is doable with PCD tooling...threading is a real PIA...it eats taps, the thought was if I could save from setting up the part in another machine....

Click to expand...

Why not see if you can get PCD thread mills? Google returns at least a couple results. First hit: CUSTOMIZED PCD THREAD MILLING TOOLS - Tommasin Utensili Speciali

TM,

Thank you for the response. Obtaining a small PCD thread mill is a challenge in itself; I am in the process of having some made for M5 x 0.8 pitch. The issue that seems to be the case is that the bond joint between the PCD wafer and the carbide becomes small and weak. We have tried all of the special coatings, and nothing except EDM produces a respectable thread. I have sent material to OSG, Kennametal, Brubaker, and a few others....they just give up.

Hi M. Roberts:
There is a fundamental difficulty with what you're proposing, and that is that the motion control for a sinker operates differently from the motion control for a VMC.
The difference is complicated, but essentially the sinker needs feedback about the gap conditions between electrode and workpiece, and bases its motion response on what those conditions are.
The interrogation and response is pretty much continuous with a very short sampling interval (microseconds).
This is not like a mill where you give it a feedrate and just go.

Also there are practical difficulties associated with flooding the workpiece in dielectric oil and managing the currents without trashing anything etc etc.

Now there ARE self contained orbiting heads available for manual sinkers that enable them to vector in directions other than Z- and they could possibly be adapted if they are paired with a spark generator.
Gromax is a brand I'm familiar with and Charmilles made one way back when too.
This is all obsolete technology since no one pursuing commercial sinker work would dream of using these old clunkers for anything serious, but you could probably still find a used one and bodge it to your machine.

However, a far better solution presents itself, and that is to put a mill and a sinker right next to each other, and stick a robot between them to pass the part back and forth.
Yeah it's expensive but it's guaranteed to work and it's probably no more expensive than screwing around with an orbiter, a spark generator, a dielectric tank and a big clusterfuck trying to do this the hillbilly way.

So, to answer your question...YES (sort of) but NO, not in any practical way.

Cheers

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

Well, the only stupid question is one that isn't asked. I didn't think such a beast existed, but...I didn't think about the dielectric...I was thinking water like with a wire EDM. Some of the parts that is in manufacturing are roughly 27" square x 4" thick, with features on all four edges, and both faces...with threaded holes from a M16, down to an M3...yes, the larger threads are more akin to thread milling, but the smaller threads, definitely a challenge.

Mark

Hi again M. Roberts:
Yeah, with parts that big I can see why you're highly motivated to avoid trying to set up on two machines.

So could you do this?
Well if you can tailor the spark characteristics to a dielectric that is water soluble coolant based rather than a straight dielectric oil and still get the finish and accuracy you want along with trode wear you can live with, the orbiter is a theoretical way forward, so long as you have a spark generator too.
The business end of an orbiter weighs less than a decent sized facemill and is about the same dimensions too, but it's got cables and wires hanging off it.

If this is a long term proposition, you could embark on the path and make it work, provided you recognize you'd be building essentially from scratch.
Your predicate device is any manual sinker or a tap buster...both are pretty primitive but work, so there is no essential reason you cannot make this work too.

Do you think it's worthwhile for your company to commit to a year of pain and a couple of hundred thousand dollars to solve this well enough that you can rely on it?
That's my most conservative guess on what it would take.
I may well be wrong by an order of magnitude though, and if so, that robot (well actually a pallet transfer system for parts this size) starts to sound pretty attractive too, and if it shits the bed, you can just call someone to fix it.

Cheers

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

M. Roberts said:

Hello. I don't know if this exists, or for that matter, even possible....here it goes; does anyone make a sinker EDM "attachment" that would go into a CAT50 tool holder that I could then "burn" threads into a part? I realize that this may cause damage to spindle bearings and the like...but is it possible?

Thanks,
Mark

Click to expand...

Got a edm I sell you
Roboform 31
13,000.00
New powersupplies
New monitor
New relays
Ready to burn baby threads
The nice thing about 31 is I sits on frame control and machine are 1 part
Easy to setup
Easy to move with pallet jack



Sent from my SM-G975U using Tapatalk

As Marcus said (you beat me to it again ), the complexities of a sinker edm are many. Along with filtered dielectric fluid needed at all times, electrical isolation is key. Something that is also of concern is electrical noise and it's isolation and suppression.

It's a novel idea, and I'm sure a one off could be made, but the amount of time and money could well pay off a good used sinker.

Does anyone make a sinker with an indexer that would accommodate a part of this size? I never said this was going to be easy....unless someone has a better idea on how to produce the threads...

Mark

Hi again M. Roberts:
You wrote: " Some of the parts that is in manufacturing are roughly 27" square x 4" thick, with features on all four edges, and both faces"
"Does anyone make a sinker with an indexer that would accommodate a part of this size?"

No, a 27" x 27" x 4" plate of just about any metal is going to be a beast for weight, and you'll have a very hard time finding an EDM indexer for something that huge.
You'd also need enough dielectric oil to fill a big tank, and that stuff is EXPENSIVE!

However, the beauty of CNC sinkers is that you do not need to flip the part to orient it to the Z axis of the machine...you can burn in any orientation.
So you could just make your electrode kind of like a Renishaw star probe and use it to burn your threads on the top and all four sides without ever moving the block.
Since EDM is a non contact process, you don't even need to clamp the block down...its own weight will hold it just fine.

You can also index the trode at will with the C axis so you have a roughing trode and a finishing trode simply by saving one trode for only the finishing burns and indexing it into working position when you need it.
If the pitches are all the same you can make a single diameter trode that drops into the smallest hole and just orbit it out to whatever thread diameter you want...just like a threadmill.

27" x 27" x 4" is still a pretty big block and needs a big machine, but it's not impossible big.
I would do a simple test:
Contact Reliable EDM in Texas and get them to burn one for you.
They specialize in big stuff and can do a block like this no sweat.
Find out how expensive it will be and how well it works for the threads you want to make.
Now you can make an informed decision about whether to continue to farm them out, whether to invest in the goodies you need to do it yourself with EDM, or whether to find another way (like accepting one threaded hole per tap and just chucking lots of taps and billing the customer)

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com