CNC Machining parts from pipe stock?

I have designed a large cylindrical part I'd like to have CNC machined. It has an inner diameter of 11", 0.5" thick, and 2.25" tall. It also has many sections machined out for weight reduction (think a flat, thin ladder type shape that has been folded into a loop and joined at the ends).

When considering the stock it will be machined from, pipe stock came to mind. This would reduce waste material and machining time, but I don't know how practical it is for shops to accommodate. It may improve or worsen strength over CNC, I haven't explored the details. I would like to have the part made of 6061-Aluminum.

Is aluminum or steel pipe stock ever used in a CNC operation?

Thanks

Yes. Very often in fact. Another avenue to consider might be a tube laser or waterjet. Depending on your area, these machines are becoming more readily available. And cost comparable.

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I would rather look at it as laser/waterjet cut out flat plate and then rolled.

Is aluminum or steel pipe stock ever used in a CNC operation? Yes, all the time.
If your design allows for truing up the OD/ID, all the better.

It sounds like you need a live tooled lathe, or lathe and then a mill with a 4th.
Both are common, especially since you are in Texas.

Doug.

maxwellhouse72 said:

...Is aluminum or steel pipe stock ever used in a CNC operation?

Click to expand...

Yes, usually because the person designing the part doesn't understand how to select the correct material.

Tubes are structural. Pipes are for moving fluids and air.

Pipe is specified by it's ID, and the OD's are odd sized. Tubes are specified by OD and wall thickness.

You are not going to find a piece of pipe with an 11" ID and 1/2" wall.

You will find 6061 tube 12" OD with 1/2" wall.

Doug,
I recently came from a shop who had a custom 16" OD Round or Square. A Turkish, Fiber Max Laser. If you can find the material, it'll cut it. Head had 80deg. X 360deg. Range of movement. Plus the roll of the tube. If you're cutting out a ladder..... to me seams more practical. But being the machinest I am, my vote it 5 axis CNC. Lol.

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To add on to jancollc's point, I'd recommend going to a local metal supply place and seeing what they stock in different alloys, as far as shape and dimensions. This is best if you go somewhere that has a more "retail" focus, meaning you can go into a showroom or storefront and actually see/handle what they stock without being run over by forklifts zipping around. Friendly salespeople are a plus too. For example, the place close to me like this is a IMS branch. I'm sure there is something similar near you.

While you won't be able to see the absolute full selection of what could be bought and machined, it'll help you understand what things are called ("tube" vs. "pipe") as well as what commonly available dimensions/finishes of stock are in different alloys. For large sizes like your product you could look through their catalog and see what they offer if not in stock at the store. This will help you in communicating material requirements with manufacturers and possibly cost saving in small production/prototype runs as you can design around readily available tube sizes rather than some oddball size that needs to be special ordered or machined from solid round bar. A lot of places will even have a free physical catalog/reference or online catalog you can consult- my EMJ blue handbooks come to mind as being really useful and free, even though I've never bought anything from EMJ.

guest said:

Pipe is specified by it's ID, and the OD's are odd sized.

Click to expand...

If it was only that simple.. ID's based on schedule 40, and even that
doesn't add up.. 1" sch40 has a 1.05ID, 2" sch40 has a 2.07 ID,
4" sch40 has a 4.025 ID.

And then as the Schedule size changes.. The OD remains the same (which
is not the same as the pipe size) and the wall thickness changes...
I do some work with 2" sch160, and the ID is around 1.7"..

At best its a total cluster fuck.. At worst, its a still a cluster fuck.

I don't think I've actually made any parts out of "PIPE" that weren't "PIPE"
related.....Hang on.. That's a lie... I have.. SPACERS, where ID and OD didn't
matter, and the mating parts were made to fit "PIPE", because its cheap and easy
to get (in common sizes)..

You are not going to find a piece of pipe with an 11" ID and 1/2" wall.

You will find 6061 tube 12" OD with 1/2" wall.

Click to expand...

And tubing... OD with some tolerance, and then wall thickness.. And I don't care
what Online Metals tells you.. Wall thickness tolerance is ±10%. I've been bit
in the ass by this before.. A customer of mine was just bit in the ass. .75OD,
.120 wall 304ss.. Online metals says .51 on the ID.. They used to have a tolerance
on there of ±.01.. They don't anymore.. Of course it shows up with the walls right
on the thin side. .109-.112, and the ID was .530... USELESS, it went back (it didn't
actually go back, but he got his money back), and I made the parts from solid.


Just pointing out that Pipe and Tubing can be a pain in the ass.. Be mindful of what
you are buying, and make sure of what you are getting.

And the other fun part, when you get into the bigger sizes, its not always round either.

I'm always amazed at all the different sizes and shapes of aluminum available. I recently redesigned a major product of mine to save money because it's considerably cheaper to make one part out of 6" 3/4" wall 6061 angle than it is to make two parts from 1.5x5 flat bar and 1/2x2 flatbar like I was doing before.

Could have saved tens of thousands in aluminum over the last few years if I had realized that before.

A friend makes some parts from bigger 6061 tube. The tube sizes are all over the place so he sends them out for honing to size first, then he chops them up and we reference all the machinework off the nice honed ID with mandrels.

Size may be available in billet aluminum

guest said:

You are not going to find a piece of pipe with an 11" ID and 1/2" wall.

You will find 6061 tube 12" OD with 1/2" wall.

Click to expand...

Depending on the material he needs, he can have it spun cast. It's remarkably cheap. Or used to be, like I said I haven't been in the US for a while and lots of those places are gone.

I had a bunch of pieces we used to make out of castings - ended up changing to spun tube (custom size), sliced off then machined from solid. Cost a bit more per part for material but the convenience was waaaaay better, more versatile, fewer problems with porosity, more choice in material, at the end of the day it was cheaper. Didn't look as antique tho ...

Or, depending on what this thing is going to do, castings could be economical. Sometimes castings are nice because people are less likely to copy them.

Just for shits and giggles, I looked for aluminum tubing.. I didn't look all that hard, I just went to speedy metals.

they only go up to 11" OD, and it only comes with a 1" wall.. Its $148.93 an inch. $1522.67 a foot. and $8578.44
for a 6 footer.. The 6 footer weighs 221 pounds, so that's only $40 a pound for $2 a pound material... Speedy
will always give you a discount if you call them.. A bar from somebody else might get you down to $10 a pound..

12" od, 11" id, 2.25 long.. Approximately 8 or 9 pounds.. At unknown $$$$$$ and availability.

so lets look at plate.. 12x12x2.25.. 32 pounds or so... $3 a pound maybe.. $100... Maybe whack it down
yourself, or if you are getting a few, get 'em waterjet and sell the drops for $1.50 a pound on this site, with
certs.

I'm just thinking out loud... I think most of us here have been in similar situations where its an absolute
pain in the ass figuring out the most economical method of getting material... Balance between material cost,
machine time, and possible outside processing (water jet/plasma, forged rings etc.... )... And the PAIN IN THE ASS!!!!
factor <-----Can't forget that, that's the most important one.

just a heads up, I make a family of parts that could be made from 9" thick wall tube, however, the tube is about 10 times the price of the solid round bar.

also with making them out of tube you need to have plugs to keep it round when clamping!

EmanuelGoldstein said:

...I had a bunch of pieces we used to make out of castings - ended up changing to spun tube (custom size), sliced off then machined from solid. Cost a bit more per part for material but the convenience was waaaaay better, more versatile, fewer problems with porosity, more choice in material, at the end of the day it was cheaper.

Click to expand...

I was going to mention castings, but was trying to stick to the OP's question.

I used to make a corner guide for a banding machine. Starting point was a cast tube about 13" in dia. and about a foot long. Chuck it up, turn the OD and ID, put in a face groove and part off 1" wide rings. Then onto the rotary table for the millwork- holes and slots, and finally flip up the rotab to vertical and slit saw 4 pcs. from each ring.

Made'em by the thousands, it was very economical to use the castings.

Now and then I'd hit a piece of sand with the .047" drill. I got pretty good at recognizing whether I had to retract the quill, or if I could push the drill thru as it broke and pull it out from the backside with a needle-nose pliers.

Bobw said:

I think most of us here have been in similar situations where its an absolute
pain in the ass figuring out the most economical method of getting material... Balance between material cost,
machine time, and possible outside processing (water jet/plasma, forged rings etc.... )... And the PAIN IN THE ASS!!!!
factor <-----Can't forget that, that's the most important one.

Click to expand...

Isn't that the truth! It seems all too often I am faced with this dilemma.

doug925 said:

Isn't that the truth! It seems all too often I am faced with this dilemma.

Click to expand...

This weeks dilemma.. Just some keys (for keyways).. Little guys.. 4130.. Rectangle or Square is NOT
easy to find in 4130 (not so bad in 4140).. I can get a 12"x12" plate for $50.. Or 3/8" round for $9...
I went with the $9, it'll actually be easier, 3 jaw in the mill and stand 'em up... Real tight chamfers
on the corners and only 2:1 length to width.

It just gets so stupid sometimes..

Bobw said:

...It just gets so stupid sometimes..

Click to expand...

Lol. They must have 4130 because 4140 just won't work?

Do they want them carburized and ground too?

guest said:

Lol. They must have 4130 because 4140 just won't work?

Do they want them carburized and ground too?

Click to expand...

You don't do government work, do you??? Some of it is so STUPID, and some of it is so out of date.

Been doing a lot of C130 stuff lately, and some of it is from 1953...

Shipped a job today (not c130) and had to trace down the paperwork.. BLAH BLAH spec, superceded
by BLAH BLAH, superceded by BLAH BLAH BLAH.... And I'll probably get shit for it.

I had one a while ago, some stupid bronze or brass, and I didn't catch it... Hasn't been common since
just before WWII. I had to have 18 feet of 3/4" dia made... THANKFULLY, I found a place that
did that type of stuff of a lot.. Took about a month, but it was about the cost of buying 6ft lengths of
360 brass from McMaster Carr....

Had another one a while ago. 7075-T78511.. No biggie, I got a bunch of that on the shelf.. Nope,
I had T73511.... Try finding T78511 in anything but a thin wall extrusion.. Can't count the time
I wasted on that.. Turns out that I could have used T651, which I can get ANYWHERE, at ANYTIME, with
no BULLSHIT!!!!! Would have been nice if they told me that the first 3 times I asked if there was any
alternate materials called out in the contract... And they wonder why I won't return their e-mails.

Its just god awful stupid...


Had one a while ago... I was just doing the machining... Aluminum.. Standard alodine or anodize, I don't remember.
Coat of the stinky yellow stuff.. Mil PRF 23377, the normal 2 part zinc chromate, and then some strange spec for paint,
grey.. My customer dug and dug, found the company that the proprietary spec came from, they hadn't made the part in
40 years and had no interest in doing it again... Yeah, its the same normal grey paint that goes on all the ground
support stuff.. "Can you send me a copy of the spec" NOPE... Job got cancelled because of a F'N paint spec.. I got
paid for what I had done, he got paid for what he had done and bought...

Its just SO STUPID!!!!!!

Bobw said:

If it was only that simple.. ID's based on schedule 40, and even that
doesn't add up.. 1" sch40 has a 1.05ID, 2" sch40 has a 2.07 ID,
4" sch40 has a 4.025 ID.

And then as the Schedule size changes.. The OD remains the same (which
is not the same as the pipe size) and the wall thickness changes...
I do some work with 2" sch160, and the ID is around 1.7"..

At best its a total cluster fuck.. At worst, its a still a cluster fuck.

I don't think I've actually made any parts out of "PIPE" that weren't "PIPE"
related.....Hang on.. That's a lie... I have.. SPACERS, where ID and OD didn't
matter, and the mating parts were made to fit "PIPE", because its cheap and easy
to get (in common sizes)..



And tubing... OD with some tolerance, and then wall thickness.. And I don't care
what Online Metals tells you.. Wall thickness tolerance is ±10%. I've been bit
in the ass by this before.. A customer of mine was just bit in the ass. .75OD,
.120 wall 304ss.. Online metals says .51 on the ID.. They used to have a tolerance
on there of ±.01.. They don't anymore.. Of course it shows up with the walls right
on the thin side. .109-.112, and the ID was .530... USELESS, it went back (it didn't
actually go back, but he got his money back), and I made the parts from solid.


Just pointing out that Pipe and Tubing can be a pain in the ass.. Be mindful of what
you are buying, and make sure of what you are getting.

And the other fun part, when you get into the bigger sizes, its not always round either.

Click to expand...

Don't forget that over a certain size (14" or whatever) pipe is suddenly sized by OD, not ID!

To the OP: a smart designer always calls out material that is readily available, inexpensive and easy to make with the tools and equipment available to him and, of course, satisfies the design requirements. Sounds simple but one would be surprised at some of the crazy ideas. I learned my trade working in a shop that was vertically integrated. Purchasing, design and manufacturing all under one roof. The smart engineer consulted both purchasing and manufacturing before deciding on a material or process. What you are doing here is that sort of thing.

Tom