AR Colleagues,

I recently saw some references to "electrochemical rifling methods" and after doing a bit of research on the Web came up with a few links below. It seems that the process is gaining ground in the industry and has the potential to produce gun barrels with very high tolerances, low stress etc. Smith and Wesson seems to have been the leader in the area at least from the number of hits I came across in a search.

So my next obvious step would be to seek the knowledge of this esteemed body...anybody know anything about the process?
Thanks
Paul


Patent summary


Validation Study of Electrochemical Rifling


Electrolytic Machining and Rifl ing (ECR)


Method of manufacturing an electrode assembly for electrochemically etching rifling in gun barrels

The tooling investment alone is enormous, requiring 1 purpose-machined electrode PER bore/groove/twist rate.

How many barrels of 1 config were ya'll considering here .....

Would this be similar or the same as plunge EDM machining?

It's close to EDM but the process is refined. Because if they can rifle a barrel in one minute they are flying compared to standard EDM.

I reason to guess that on a standard EDM sinker modified to do this would take about five minutes or more per barrel. Although you are not removing much material either

this is pretty cool; should eliminate many of the issues associated with standard rifling methods today.

quote:

Would this be similar or the same as plunge EDM machining?

Ans: No, they are def not the same process - for a rifling application, ECM would only address/work the bore & groove features. Plunge EDM works primarily in the direction of feed, or verticle (much like an ordinary drill bit, which only cuts on it's point end).

quote:

Originally posted by b0400879:

quote:

Would this be similar or the same as plunge EDM machining?

Ans: No, they are def not the same process - for a rifling application, ECM would only address/work the bore & groove features. Plunge EDM works primarily in the direction of feed, or verticle (much like an ordinary drill bit, which only cuts on it's point end).

Not exactly correct.
The EDM process can and does cut on any surface of the electrode. In the correct machine, you can burn in any direction except up. There are also orbiting heads that allow circular motion to be added to a sinker EDM and CNC edm's that have the orbit function built in.

So to say that a EDM only burns in one direction is not correct.

Kerry,
EDM's do not cut, dear fellow. They erode.
Of course there's overburn.

Pls advise which current models of CNC EDMs:

Feed simultaneously in 4 axes
Feed a helical path
Can burn fixed or progressive rifling

Ok they don't "cut" whoppie!!

Agie elox mondo 40 will feed and "erode" in three axes at the same time. that easy that's orbital. but they also can Vector as well. in the control select your job set up and select the type of erosion you wise to perform. Select Vector. The control will then have a "fill in the blanks" GUI and you tell it how many corners you wish to burn and at what angle. Burn at anything other then 0/90/180/270 will result in all three axes in motion at one time. Not move the Z then move the X the move the Y. it's vectoring into the corners moving x,y,z all at the same time. Guess you've never used a CNC EDM??? and I never said 4 axes

Charmilles CNC's will feed a helical path. and have done so for years. How do you think they hard tap a part??? you cut an electrode minus the over burn in the same shape as the threads set up you part and set up the machine come back in a little bit and you now have threads in a part that is 60 RC and if you set up the EDM right it will leave a diamond finish too. so you could fool your friends and say you bought a "special tap" for hard steal

Besides 3 axis motion is only a matter of the function of the control not the EDM. The control can be replaced and set up to do nearly anything the customer desires. I say nearly as you still need to have some sort of a pecking motion to clear the swarf and flush the pocket. And you also need DC arc protection so the control can't do everything or anything you want but it can do a lot.

And fixed or progressive is a electrode design.
Obviously you couldn't erode rifling with a conventional electrode. But with the proper electrode geometry and a correct tool path the electrode will cut Erode a progressive helical path. It's done day in and day out on CNC lathes with square tool bits so the geometry is there.

The area on the electrode just needs to be clearanced to allow it to rotate in a progressive helix with out widening the grooves.

The only problem you run into is the length of feed. The machine would need to be modified to accommodate a long barrel. most machines have about 18" of Z travel at the most

System 3R makes orbiting heads for manual sinkers

It would not be easy and sure as hell would not be cheep

I don't mean to belittle you but ahhh there's tricks to everything. Use your head man

No offense taken, mate.
The OP (Paul) had an inquiry & he got some responses pertinent to sporting arms. The reply defines the approx limit where today's EDM technology hits the wall.

For a good read, research the ECM method by which the M242 (Bushmaster) & other autocannon barrels are rifled/finished. Some of these beasts approach 2m in OAL.

helical decent path, X or six armed cutter.. COULD work .. long Z axis ..

i'd go 2 passes ... one to finalize the bore, making it perfectly round, one to cut the grooves ...

i HEARD TC Icon's are cut with an EDM for the chamber ...

i wonder if it matters in REAL terms of accuracy ...

thinking about it .. it would be faily cheap to build, less the actual EDM power source and tank. ..

IF you could normalize this barrel to where it can be inserted adn KNOWN to be straight .. you could build it from THK rails, some good servoes, USD encoders, $500 bucks for a control+mach2, and being clever with casting an oil sand filled base ..

the inaccuracy would come from the length of the tooling required ... i mean, dang, .225 or so for a .243 barrel ... long skinny tooling would be a tad whippy ...

The method S&W are using is not much different in principle than electro-etching. A method many knifemakers use to apply their name or logo. It works similar to an EDM, but uses AC power with electrolyte where a sinker EDM uses DC power and dielectric oil.

Etching with a stencil produces an accurate and detailed etch up to .02" deep pretty quickly. You can make one with a simple transformer. Couple that with an orbiting head and controled downfeed and you are in business. I am not an engineer, ( Fire Control radar tech in the Navy)but I can see it being done within a reasonable cost for shorter barrels. Rifle length barrels would be another matter.

I have a wire and sinker EDM, and can see how the etching would be much easier than a sinker EDM unless you have a modern machine that can compensate for wear. Of course you could use multiple electrodes to finish, but you will always have wear, and thus taper. Might be less than .0005" over the length of the barrel, but it's still taper. Etching wouldn't produce taper becasue the electrolyteacts like the electrode in an EDM and the bar doesn't wear.

"no ...tool marks left"
What do the forensic people think about this ?

quote:

Originally posted by b0400879:
No offense taken, mate.
The OP (Paul) had an inquiry & he got some responses pertinent to sporting arms. The reply defines the approx limit where today's EDM technology hits the wall.

For a good read, research the ECM method by which the M242 (Bushmaster) & other autocannon barrels are rifled/finished. Some of these beasts approach 2m in OAL.

That's where you are absolutely correct.

Unless highly modified No off the shelf machine has the capacity to do anything more the a short handgun barrel. Yes EDM just hit the wall. And with out a skilled operator well you have a very nice boat anchor. It's the Operator that makes the machine not the other way around

Jeff
a couple of things,
One in chambering: if the electrode was orbited (rotated round it's axis) in the Z motion nearly all run out is removed or at least eliminated as if it was wobbling the high side would do all the cutting. But here's the deal, In nearly all EDM shops electrode are made by tool makers on surface grinders. So the darn thing is super accurate. The surface finish with a Charmilles micro finisher is near a polished finish. It's actually pretty amazing how good of a finish you can get with a micro finisher.

The other thing is with rifling even if the tooling was whippy you can add bushings and I'd have an insulate pilot on the end of the electrode anyway so it would follow the hole. And yes two passes Rough and finish.

But here's the cool thing. All things being equal here you can attain an accuracy of a few millionths of an inch with a Charmilles machine but it takes a very experienced operator to do so. Which I am not. I start to sweat when the boss wants a half thou press fit on the EDM I just don't have the experience on this machine. If it was an Agie elox I could do it no sweat. but not on a D10

And yeah the no tool marks thing is true you'd need 20 to 50 power magnification to see a blemish

Reminds me of Mr. Williams and his illfated receiver. He made the ridiculous statement that he was going to broach the raceways because it gave a better finish than wire EDM. He needs to check the raceways on Jerry Stiller and John Pierce's receivers. The EDM finish on theirs is just great.
Butch

EDM finish is all controlled by the operator not the machine. With the proper set up you can achieve a finish very close to a low degree of polish say a POR 500 grit finish. Or a wet sanded 1200 grit finish.
That's what I meant by a diamond finish. Polish using diamond lapping compound. A Charmilles micro finisher will do it.