22" Z capability?

Anybody here able to cut approx 22" thick? Material is 4140, and I need to know how straight of a hole you would be able to cut at this thickness. The hole could be roughed undersize, but the finish would have to be near perfect straight. The finish size hole would be under .375" in all cases.

Not possible to gun drill it?

precisionmetal said:

Not possible to gun drill it?

Click to expand...

I dabble in exteme accurate benchrest shooting. The current method of making gun barrels is to gun drill, ream in a few steps, rifle, then hone. It seems hard to perfect this method. If you were to buy an aftermarket target barrel it is still hit and miss. I read about a life long shooter that bought 34 barrels over his life, only to get 2 great ones. I'm seeing now that wire edm is not without trouble with a lot of "Z" (bowstring effect?). If someone were to come up with a method of making a 'perfectly straight' hole, there may be a great market (military?) for it. Possibly a dedicated wire edm with a very big wire and a ton of wire pressure may make a roughly 22-26 inch long bore 'perfectly straight'. Any thoughts?

These guys can do it, but it's very expensive compared to gun drilling. http://www.adron.com/workpieces/
RJT

I don't think that a so called perfect hole will solve the barrel problem. Some pretty crooked bores have shot incredibly small groups. I think that the stress that remain in the barrel after all the work and stress reliefing is done has more to do with it than a hole that is not perfectly straight.
That being said, it is easier to chamber a straighter barrel.
As you probably know, Crucible steel supplies the best barrel stock at this time. The major barrelmakers buy the 416R stainless with a 24-28RC. Some makers do it a little different, but they normally gun drill and ream first. The bore size for a match barrel will airguage no more than .0002 in size from end to end. The blanks are then stress relieved and then rifled. Some makers stress relieve before final contour and some after.
Butch
Butch

Butch, you are probably correct, even with a perfectly straight bore there are other variables that I'm sure come into play here. Does seem odd that with todays high quality machining methods that one would get a 'great' barrel one out of twelve tries. It would be interesting to compare that great barrel to a mediocre one and really give it a close inspection though. Maybe I'm looking up the wrong tree entirely.

Wich is the tolerance?

Hi to all,

I know a colleague here in spain with 27 inches in Z axis, in this case, which is the tolerance? are you talking about tolerances below from 0.001 inches?

regards.

Yes Roonie, not precision enough. Select match barrels are held to .0002 TIR from end to end. If there is any advantage to another method of blowing the hole out, it is welcome. It needs to be cost effective.
Butch

My experience...

I have cut parts of 23.6 inches, to talk about accuraccy in this thicknesses it could mean talking about tolerances around 0.003" or more even this could be called accuraccy, here edm conditions are the worst posible, the wire bends a lot during roughing and fixing it with finishes is very very complex even more if you don´t have time to research in it.

I think the accuraccy could be better than the one i told you but it needs lot of time and people with a lot of knowledge, i think it should be possible to obtain a maximun acuraccy of .0023, I don´t know if it where suitable for you, "moreover but as i told you it needs time and money!!


Regards.

Yes, Lots of time, and Lots of Money! The best I've seen in tall material on WEDM is .0005" over 18 inches, and that took about a week and a half to dial in. I sure hope it has a start hole....

The BEST we've done at Makino on a U86 machine was 0.0003" total (that's 0.00015" or 3.5um per side) on a 20" tall aluminum punch...with only 2 Pass Machining! It was a simple 1.0" x 0.5" geometry with 4 different corner radii, and was done with custom technology which will repeat the results. This is a great sample part for us that shows the power of our BellyWizard technology, which uses adaptive servo controls to minimize and eliminate belly or bow in a part. Interestingly enough, the size variation of 0.0003" total is actually a straight taper...meaning that the size progressively gets bigger from Top to Bottom, and the part does not have the traditional oversizing or undersizing in the middle of the part.

-Brian

Bluechipx,

Have you tried this company?

http://www.swedm.com/

tall parts

Brian,

i think getting 0.0003" in 20" thick is an incredible mark (sorry for my english , i wouldn´t like to have a missunderstood becouse my language), it seems amazing Brian, but let me ask you a couple of things:
If in that thickness the wire already has a 1 micron of vibration(i think even more), it is imposible to keep it totally vertical, you may need infinite wire balance, so you start with a 2 microns error, then you should have the entire piece in 5 microns, this in (500mm) i think it is near imposible, i don´t know in aluminium but in steel i have some experience (even in taper cut ¡what a headache!), and leaving it into 25 microns (even 35) i think it would be wonderful mark, need to say i don´t know how the aluminium would work.
The power a sparks produces in the middle of the piece in so big tall parts i think is to impossible to fix, near to imposible i mean below from 10 microns per side.

Best regards.

Outside of the box - literally

Hi guys,

This is a little off-topic here but on the subject of tall part cutting, I thought you guys might find this application interesting. In the early '90's, I collaborated on many R&D projects with Bill Fricke (an EDM genius with many patents) when he was president of Spectrum Industries (IL).

This particular challenge was to cut a slot into a huge bearing race for a hydroelectric dam. This was a one-off project and was holding up the entire project (never mind the design screw-up that made this operation necessary, another story), so money was not a factor in doing this.

Using waterproof green glass (fiberglass) and phenolic as the insulating framework, an inexpensive C-frame device was constructed and attached to the lower arm of an AGIE equipped with Fast/Track.


Power and grounding cables were made and attached along with flushing hoses. Adapting store-bought and homemade wire rollers and using the machines own guides and nozzles top and bottom, Spectrum was able to wirecut this part and get the dam project (pun intended) back on track.

As I recall, the part setup took almost as long as the machine modification. A wheeled, box-tubing weldment was constructed to support the part (very heavy) and insulated with wooden 4 x 4's. Jackscrews and shims were then used to square the part. It was also wet and messy, using cookie sheets and coffee cans to catch most of the water runoff, but the price they got for cutting this part made any mess incidental.


For the actual cut, the control arms were tipped at 10 degrees and the cut was made. Sorry I don't remember what wire was used or how long it took but again, for the money... who cares? Like most jobshop work, it doesn't have to be pretty, it just has to work.


With the operator for scale, the segment removed was 43" tall and although there was no tolerance call out, in a single pass the slug was straight within an incredible .003" (belly not taper). Amazing!

That's why EDM is so cool... you're only limited by your imagination!

Bud

Outside the box - take two

I don't know what happened to the pictures. Perhaps they were too large. Here's a reposting of them as thumbnails.

Bud

Which bit is moving??

Hi Bud:
I assume this model of Agie has a stationary table and the arms move around in the tank???
Or did Spectrum somehow bolt insulated extension arms to the table and rig some kind of traveling wire feed mechanism to it so power could come from the generator and motion from the table.
It would have been quite the job to fool the machine control into believing the tank doors were closed, the part properly in the circuit, etc etc.
How were the generator settings arrived at?
So many questions, so little time...thanks for giving us a glimpse of what's possible...it's all very cool!
Cheers

Marcus
Implant Mechanix – Design & Innovation - home

Which bit is moving?

Marcus,

Good observations on your part. You made me dust off my memory banks and try to remember more clearly and rethink this application.

Initially, the plan was to use the X & Y movements of the U/V box but this was passed over due to its limited travels and questionable servo response due to the higher torque that would be required to move the entire mechanism. Power and flushing were taken from the lower arm and if I remember correctly, the arm extention was affixed to the table to better support the weight of the long extention and use the travels and sensitivity of the X & Y axes.

I can't answer your question about the door. It either had no saftey interlocks requiring it to be closed or this had been removed by Spectrum. This machine was already highly modified as were several others Spectrum used for similar hairball applications.

Generator settings were totally made-up and were absolutely a cut-and-try event due to the now-unknown impedence from the much longer power cables and the large surface area of the tall cut. Initial cuts were made well inside the final width of the cut until successful settings were developed.

As one would expect, while dialing in the settings wire-breaks were numerous and rethreading was obviously manual and time-consuming, so once a steady cut was made, very soft servos were used to prevent crowding the gap, reducing wire breaks and aiding flushing. Speeds were very slow but speed wasn't at all important... just getting the thing to cut at all was.

I've also realized that the slug shown in the third picture was not from the bearing race, but a similar tall part Spectrum cut with a different machine modification. I'll leave it up with this disclaimer just so you can see how tall some parts have been cut. Sorry for this mix up, my face is red.
(Pssst... hey Bud, when you find yourself in a hole... stop digging!)

This mix-up and my spotty memory has caused me to give Randy Bormann a call today as he worked for Bill and Spectrum and his memory must certainly be better than mine. You may also remember Randy as one of the best speakers on the EDM circuit in the late '80's and early '90's.

If I hear from him, I'll either have him chime in himself or I'll post what he knows.

Also, if the moderator would turn on the "edit" button for me, I'll get rid of the non-pictures that are taking up so much space in my initial post and move the thumbnails into it.

Now I'm gonna go watch the Super Bowl!

Bud

I cannot hold that tolerance on my 24" thick cutting wedm.
I think there is no way around the wire viabrating in the middle of the part , even under the most lightest power setting..