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kNucKlbustr
01-20-2013, 12:31 PM
Not sure what the term would be but, I need to cold form the ID of aluminum pipe. The ID is 0.040-0.060" OOR.
1/4" wall 6061-T6. 2ft- 4ft long
My idea is to hydraulically push or pull a steel ball thru the pipe to form the ID round.
The forming will be only opening up the narrowest section of the OOR pipe.

Any ideas if this will work?

Scottike
01-20-2013, 12:50 PM
I think you may have problems with "springback" and find that you'll
need to find a way to expand the oor section past true round in order
to get your finish round shape.

Toolguy
01-20-2013, 02:57 PM
It should work fine. Make sure to use a good lube. Lanolin might be a good one to try. I agree you will need to go a little bigger on diameter to end up round.

goodscrap
01-20-2013, 04:18 PM
what is the term OOR?

i've seen something similar done in the manufacture of heat exchangers, they use a long rod up the middle of the tube, then draw a 'bullet' back though it to expand the tubes onto the fins. With the hydraulic option you mention, you may need to do it in stages so the ball doesn't lock up and the hydraulic pressure burst the tube. or you could use a press to push a ball through, followed by a slug of material or if there are bends to negotiate then add more balls, slightly smaller to push the first one through?

Brian

Toolguy
01-20-2013, 04:28 PM
I'm thinking OOR means Out Of Round.

LKeithR
01-20-2013, 07:32 PM
Not sure what the term would be but, I need to cold form the ID of aluminum pipe. The ID is 0.040-0.060" OOR.
1/4" wall 6061-T6. 2ft- 4ft long
My idea is to hydraulically push or pull a steel ball thru the pipe to form the ID round.

A lot of unanswered questions. What finished ID do you need? How about the OD? What tolerance do you need to hold on the ID? How straight does the finished part need to be? Is the OOR ID consistent with the OD? In other words, is the OOR condition caused by the tubing being egg-shaped or is it because the wall thickness varies? These are two different problems and could require different solutions.

If you're .040" to .060" OOR now you're probably going to have to expand the tube way more than that to achieve a consistent ID and I'm not sure how 6061-T6 is going to respond to that kind of treatment. You would probably have to anneal the tubing to allow it to expand as much as you need without cracking. You may also have to perform the operation in multiple steps. If you push--or pull--a mandrel through the tube with too much force you could introduce a wave type bend that's hard to get rid of. DOM tubing, which is the closest equivalent to what you're trying to achieve, starts out as an off-size tube and is drawn over--and through--a series of mandrels to get to finish size.


The forming will be only opening up the narrowest section of the OOR pipe.

Ain't gonna happen. There's no way you can get a mandrel to magically slide through the tube and only expand the narrower sections...

kNucKlbustr
01-20-2013, 08:03 PM
The tube is extruded 3.5" ID. Been doing this work for awhile. This is the worst piece Ive had w/ that much tolerance. 24ft. Usually is .015-020" OOR.
I can live with .010" OOR. I use a AN hone on the inside but it cant take that much OOR.
The OD gets taken down a good .020". Didnt measure OD, but wall varies on all extruded.
I can toss it away and buy another $300, 24ft. But, getting extruded is a crapshoot.

LKeithR
01-20-2013, 09:26 PM
The tube is extruded 3.5" ID. Been doing this work for awhile. This is the worst piece Ive had w/ that much tolerance. 24ft. Usually is .015-020" OOR.
I can live with .010" OOR. I use a AN hone on the inside but it cant take that much OOR.
The OD gets taken down a good .020". Didnt measure OD, but wall varies on all extruded.
I can toss it away and buy another $300, 24ft. But, getting extruded is a crapshoot.

Yeah, tolerance range is pretty high on extruded alum. Sounds like you got a real bad piece, though. Sucks to bite the bullet on something like that but sometimes ya gotta do it. I'd ask your supplier to take it back. Mine would.

What are you making? Cylinders?

kNucKlbustr
01-20-2013, 11:23 PM
Not the first time. Its cut up. Ive seen good sections and bad sections in the same length.
Read the extruded pipe and tube tolerances. They use some type of algorithm to get away w/ high tolerances. Even my distributor doesnt understand it.
Even though I cant afford a long run of DOM tube this size, hard to find anyone that does it. Made alot of calls to SAPA, big plants, etc.

But Ill turn my attention to a solution.
A round ball that size is available in hardened steel. Not easy for me to drill a 3/4-1" hole.
Before I get deep in pockets, Ill try a mock up w/ available items using a 12" piece, 3-1/2 bull nose , steel pipe, bottle jack, anchored angle plate , see what happens and post the results.

LKeithR
01-21-2013, 01:13 AM
Keep it simple and don't spend a lot of money on a solution and you haven't got a lot to lose. Sounds like you have lots of material to practice on. One thought that comes to mind is if you use a ball it may tend to follow the inside profile of the tube making it very slightly wavy--the tubing could be on size at any point but not necessarily concentric to the centre line. A bullet-shaped mandrel should transition from highs to lows better and give you a straighter result. Good luck and keep us posted on how the experiment goes...

michigan doug
01-21-2013, 04:53 PM
Use a good lubricant.

Another approach might be to roll the tubing to reduce the out of round condition from the outside if you don't want to increase the id too much.

That's assuming the high points are consistently and conveniently lined up on the outside.

How long is the finished piece?

What's the final use/product??

finest regards,

doug

Rich Carlstedt
01-21-2013, 07:20 PM
Very good suggestion on using Lanolin
Whenever we had a really tough checkout of a new forming die, for thin steel , we used Lanolin for lube as most others failed and the steel would rip open.

If this is a normal occurance, i would opt for a tapered mandrell to insert .
A 4 inch aluminum pipe with a 1/4" wall isn't that bad to reform

Here is a thought
See if your stock will fit inside a 4 1/2 ' or 5 inch square steel tube about 5 feet long
Make a cap removable for one end and tap it for a big thread , like 1.25"
On the opposite end of the tube drill 2 large bolt holes through the tube so the end of the pipe sees them as a stop when bolts are insert.
Make a 6' long threaded rod with socket welded on one end and a 2 inch cup on the other (to contain/follow the ball)
Drop the pipe in, and install the restraining bolts
Put your ball in the other end, followed by the cap, and then use a impact wrech ( air) to drive the ball through

Dont forget to lube the pipe and make sure the cup will turn on the rod, as the ball will not when the threads engage .

Rich

kNucKlbustr
02-01-2013, 10:28 PM
Whomever said the pipe would spring back was correct.

After many hrs/days of frustration, using different jacks, returning a defective jack, splitting an air compressor hose, machining a 3.5"x2" steel die, I ended up using a 20 ton hydraulic press instead.

I found a formula for ciphering compressive strength and came up w/ 15.6 tons needed to overcome the tensile strength of the Al pipe.

Made a steel block jig for the press and formed a 3ft L 0.050" OOR pipe to within .002" round. Takes less than 5 mins. btw-the max OOR manufacturer tolerance is .050"

One thing I did learn was about the crappy jacks sold is in this country.
But thats another thread. :D