EDM Finish Qualty Question

4

4Mesh

Guest
In the EDM chambering thread, there was a discussion about quality of finish with EDM vs a reamer. There seemed to be some who thought the EDM might actually make an inferior finish. Some mentioned the HAZ area and roughness thereof. Just going from memory, I thought I had seen where there were EDMs years ago that did really super finishes. (I was recalling Mitsubishi Wire @ 2 Micro).

Also, I sorta remembered folks saying that sinker EDMs were more likely to do a nice finish than wire. That led me to think that the edm should be vastly superior in surface finish to any reamer. But, since I don't use the things I just avoided that discussion.

So, now I go to the Mitsubishi site and see that they've had wire EDMs since 94 that did a 2 micro finish, and later, even better than 1 micro. Wow, that's pretty nice folks. The sinker EDMs they're talking about doing a mirror finish. Hmmm?

So, my question to those who actually use these things is, can these EDMs actually achieve this, or is it just nice marketing that doesn't translate to the real world? I've seen some "nice" edm work (wire) but I don't know what finish they were trying to achieve. I would not have thought it to be even a 16 micro if I was forced to guess. It was nice, but, once you see ground parts go to a profilometer you stop trying to guess!

So, what's "possible"?

BTW, on the subject of chambering, I don't see any of their sinker edm's that have enough part depth to do a long range barrel with a sinker, unless you go to the gantry series. So, I think this might be limited to contender barrels on any affordable edm. Past 17" it looks like you're out of luck. At least with Mistubishi.
 
FWIW
Sirois' process is upside down, the barrel is on top in the Z axis with the breach down. The electrode is below the barrel, facing up. The barrel moves up and down.
 
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I have a Mitsubishi rep comming to my office today to look at one of there sinker machines. They are supposed to bring samples of some "mirror" finshed parts and I will try and post some tonight.
Although I'm buying the machine for carbide bullet die work I need to at least try a chamber.
 
Building a "sinker" to do barrels would be a special but no where impossible. I think the bottom line of this EDM vs reamer discussion is a mute point. Economics will determine the ultimate answer, unless this new "Wonder Congress" ships all barrel chambering to Communist China. Does this mean I have no hope for US economic improvement between now and 2012, it certainly does!!
 
TRA said:
FWIW
Sirois' process is upside down, the barrel is on top in the Z axis with the breach down. The electrode is below the barrel, facing up. The barrel moves up and down.
Click to expand...

Ah, ok, thanks. I was thinking submerged muzzle down and thought wow, that's gonna take a big machine.

Do you happen to know if there's a C axis involved in that process? And, for that matter, would it help the finish? I would think it would, but.

Jerry, I think of it as no different than EDM'ing raceways. If someone wants to pay for it, by all means have at it. I've had more'n a few Bat's in my hand and if that's how rough broaching leaves them, broach'ins fine with me. Folks can do nice work with all different kinds of machines. I suppose if I had one of these machines available, I'd probably have tried something like this already, but I don't.
 
Tom Liakopoulos said:
I have a Mitsubishi rep comming to my office today to look at one of there sinker machines. They are supposed to bring samples of some "mirror" finshed parts and I will try and post some tonight.
Although I'm buying the machine for carbide bullet die work I need to at least try a chamber.
Click to expand...
Thanks Tom, great timing! I'll be interested to know what they say. I was also curious about precisely what you're getting this for. I'd be interested to know if there's still a lot of polishing work to be done after the fact, especially on something that needs a finish like a bullet die.
 
4Mesh

Well the Mitsubishi rep just left. To EDM solid carbide .250 x 3" deep to an 8 rms mirror finish will take about 8hrs of machine time holding the dia spec to .0001.
The polish time afterwards is only about 10min! I will have the machine in 2 weeks at a cost of $180,000 turn key with C axis and 20 position 3R tool changer.
It will run 24 dies at a time "lights out".
Just think carbide dies in less than a week at half the cost of current dies.

Tom
 
4Mesh said:
In the EDM chambering thread, there was a discussion about quality of finish with EDM vs a reamer. There seemed to be some who thought the EDM might actually make an inferior finish. Some mentioned the HAZ area and roughness thereof. Just going from memory, I thought I had seen where there were EDMs years ago that did really super finishes. (I was recalling Mitsubishi Wire @ 2 Micro).

Also, I sorta remembered folks saying that sinker EDMs were more likely to do a nice finish than wire. That led me to think that the edm should be vastly superior in surface finish to any reamer. But, since I don't use the things I just avoided that discussion.

So, now I go to the Mitsubishi site and see that they've had wire EDMs since 94 that did a 2 micro finish, and later, even better than 1 micro. Wow, that's pretty nice folks. The sinker EDMs they're talking about doing a mirror finish. Hmmm?

So, my question to those who actually use these things is, can these EDMs actually achieve this, or is it just nice marketing that doesn't translate to the real world? I've seen some "nice" edm work (wire) but I don't know what finish they were trying to achieve. I would not have thought it to be even a 16 micro if I was forced to guess. It was nice, but, once you see ground parts go to a profilometer you stop trying to guess!

So, what's "possible"?

BTW, on the subject of chambering, I don't see any of their sinker edm's that have enough part depth to do a long range barrel with a sinker, unless you go to the gantry series. So, I think this might be limited to contender barrels on any affordable edm. Past 17" it looks like you're out of luck. At least with Mistubishi.
Click to expand...

I'd be interested in seeing just how they got a "2" micro out of a wire! Maybe a six or eight, but most grinders won't do a good two micro. Typical machine ways that are ground are often in the six to seven range with four being considered super slick. I did have some folks up in Hammond Indiana make me several sets of ways twelve feet long that ground them on kind of a grinder that looked like a SIP on steriods. They claimed .0003" in over twenty feet, and a very low micro. I held them to .00025" parallelism and .0002" max on flatness with a four micro. They did it! Perhaps Mitsubishi knows something nobody else knows?
gary
 
Mtek said:
4Mesh

Well the Mitsubishi rep just left. To EDM solid carbide .250 x 3" deep to an 8 rms mirror finish will take about 8hrs of machine time holding the dia spec to .0001.
The polish time afterwards is only about 10min! I will have the machine in 2 weeks at a cost of $180,000 turn key with C axis and 20 position 3R tool changer.
It will run 24 dies at a time "lights out".
Just think carbide dies in less than a week at half the cost of current dies.

Tom
Click to expand...

What you using the C axis for (rotation about the Z axis)? You could take a sinker for a 30BR and make a really fat 30mmBR!!

With a BeCu electrode can you take the C-axis and compensate for the wear of the electrode??
(See, I know just enough about EDM to ask stupid questions!!!)
(I've written postprocessors for wire EDM's but never programmed one)
 
Tom, thanks for the info. And btw, congrats on the new toy!

That's interesting the sinker does an 8rm finish cause I was thinking with the C axis, it could be better. It certainly appeared so from the marketing literature. Well good luck on the die endeavor, I bet it's going to be fun.

Gary,
That's precisely why I asked. When I think of 2 micro and better, I start visualizing gage blocks. I know you can't go by how glossy the part is and tell what the finish will measure, but, well, you know what I mean. Going from what Tom's saying about the sinker, it appears that 2rm (or <1) is a bit optimistic with wire. They do say though, this is only with multiple passes, but I did not see anywhere that it specifies how many. I seem to recall 2, but it's been almost a decade since I had that conversation and I could be mistaken.
 
JerrySharrett said:
What you using the C axis for (rotation about the Z axis)?
Click to expand...
I'd have thought it almost a requirement for making a round hole Jerry. No?
I'm imagining uneven burn on the electrode (very slight, but,uneven nonetheless).

Maybe C is overkill, but, so is everything we do in shooting. We'll spend decades trying to reduce group sizes another 3%... :D :D
 
Correct the C axis is rotation about the Z axis. Rotation is required as well as orbital movement of the correct undersized tool. The orbital motion also helps with the flushing of the cut.
The samples I looked at today were great looking mirror finish with no post polish. For the curious the electrode was "poco" carbon/copper.
 
Tom Liakopoulos said:
Correct the C axis is rotation about the Z axis. Rotation is required as well as orbital movement of the correct undersized tool. The orbital motion also helps with the flushing of the cut.
The samples I looked at today were great looking mirror finish with no post polish. For the curious the electrode was "poco" carbon/copper.
Click to expand...

Makes sense now. We had some Agietron (French) EDMs but I never needed to learn about them since they were in a captive operation, making textile spinarettes. Thanks
 
Mtek said:
4Mesh

Just think carbide dies in less than a week at half the cost of current dies.

Tom
Click to expand...

Tom,

Are you going to be offering these dies? And can you do them from a fired case or are you thinking of running 24 dies at a time from some production spec?

thanks

al
 
Al,

It's a little early for all the details but.... The plan as it stands is to start with bullet dies, then move on to sizing dies as well as a progressive bullets presses.
I don't mean to completey de-rail this thread, But in the next few weeks as the equipment gets installed I'm going to be comming here to discuss some of the options for dies and presses. (ie. should the die be threaded?, should they be allowed to float in relation to each other?)

Tom
 
It's been a long time since I ran a wire. Over ten years now. I do remember though being able to fiddle and get a surface finish that was pretty impressive. The head programmer guy was screwing around one day and used a block of D-2 (about a 2" cube of the stuff) to cut a clover leaf on the wire. He then did the mirror image in another piece of material. After offseting the wire width and after a few tries we were able to get the "male" piece in the pocket. When assembled the edges were kissed with a surface grinder and the seam completely disappeared. The plug would rotate to any position and retain the fit-although you could see the grinder marks change direction once this was done.

The sides were silky smooth and as nice as any lapped finish I've ever seen.

This also took a few hours to do. Back then a wire was good for about 1/16-minute on the feedrate. I'm betting that hasn't changed much.

I know sinkers are often used for mold work. I have some here in the shop done this way and the finish is quite nice. Exceptional in fact.

As for chambering I have no doubt it would work. However, unless a guy hits the powerball and just wants to be different I don't see a practical application for chambering. The plug needs to be machined so your still have that operation. It's going to erode which means it'll need to be routinely cleaned up or replaced. Now the process gets complicated from a repeatability perspective because from one job to the next your going to have to take additional measures to ensure the chambers are consistent.

Hope this helped to answer your question.
 
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I'm assuming you are talking "sinker" for a chamber. I don't see how it would be possible to use wire for a chamber.
Made a lot of electrodes out of Poco graphite in the olden days. They have had a plant in Decatur, Texas for years.
Are you sure Bat doesn't wire their raceways?
Butch
 
Perhaps Mitsubishi knows something nobody else knows?
Click to expand...

Reminds me about a story told by old guy employees of Morse Twist Drill down here in New Bedford, MA...........Back in the 60s, MTD developed a drill for drilling holes in micro circuit boards. It was claimed as the thinnest drill in the world. About the diameter of a human hair...............A Japanese company bought a couple and sent them back to MTD with a hole drilled down the center...........That, was the beginning of the end!
 
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