Thread: How to design/build a sheet metal tube?

Hi all,

I'm designing an enclosure which consists of a sheetmetal tube (1.5mm, about 14 gauge) clamped inbetween 2 3-printed plates.
The only problem is that I have 0 experience with sheetmetal design. I've been reading up a lot, but I struggle with figuring out how to build the tube.
The idea is visualized below:
Tube.PNGSideView.PNG
The tube should be around 250x175mm (10x7"), and about 600mm (2ft) long, the radii of the corners is roughly 17mm (2/3").
Now, I understand the sheet metal can't be folded in one go the way it's drawn here, but in what way would it be possible?
Ideally, the tube should be as smooth as possible (so no overlaps etc.),
Would it be best to fold two U-shapes and weld them together?

Any help would be incredibly appreciated!

Welcome to the forum

TIG welding would be the way to go, start with lots of tacks and then fill in the gaps - there will be some distortion though but a skilled welder should be able to minimise that.

For the folding, I would have the joints on the short sides. Large radii curves like that can be done on a bench (for a one off) by clamping the metal between the bench and a piece of pipe or barstock of around the right diameter and then folding the metal around it. I'd suggest trying it with scraps and a piece of something, just to work out the technique. With the thickness and the length you are talking about it won't be simple, so levers and hammers maybe involved...

Michael

A Magnabend folder (or clone) could easily fold this from one piece of sheet requiring only one weld. A quick look at some YouTube videos will show how it’s done. Don’t know if you’re looking to do this yourself or wanting to pay to,get it made for you. I would think most sheet metal fabricators could do this for you.

Leigh


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Hi Gwalb,
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Welcome

Grahame

Originally Posted by Ambrosia

A Magnabend folder (or clone) could easily fold this from one piece of sheet requiring only one weld. A quick look at some YouTube videos will show how it’s done. Don’t know if you’re looking to do this yourself or wanting to pay to,get it made for you. I would think most sheet metal fabricators could do this for you.

Leigh


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If the material was lighter a Magnabend would do it easily but not with 1.5mm thickness at 600mm long.

=GWalb;1988244 The only problem is that I have 0 experience with sheetmetal design. I've been reading up a lot, but I struggle with figuring out how to build the tube

It might help the responders to your post to help you if we knew the following:

Do you merely want to design the the unit with a view to designing it for the best possible process to be utilised?

Do you design other things and just this time are seeking the how to's with eventual production in mind?

How many units would you like to make. For instance, if you were making hundreds or thousands , 2 halves could be made with a press and die and tig welded or

or

Do you want only to fabricate the unit as a single one off for yourself ? Are you just seeking an insite on the best procedure and the tools to do the job?

With a bender be it magnetic or not, the bending effort increases as the length increases hence the preceding comment from Techo 1.

If you are an absolute newcomer to ( sheet) metal working it would not be a good first project. What you describe can't be made in the average DIY garage or shed.
The tools/equipment are not cheap so the choice of using a sheet metal fabrication shop might be a good choice.

Hi GWalb,

The tools/equipment are not cheap so the choice of using a sheet metal fabrication shop might be a good choice.

I agree !

Two pressed half’s stitch welded together !

That can be done relatively simply from one piece using a sturdy bench and a fairly easy to manufacture former.
600mm of 1.6 over an 8.5mm radius (17mm corner) is not going to be all that difficult (even less so if its R 17mm).

Originally Posted by racingtadpole

That can be done relatively simply from one piece using a sturdy bench and a fairly easy to manufacture former.
600mm of 1.6 over an 8.5mm radius (17mm corner) is not going to be all that difficult (even less so if its R 17mm).

Could you explain this simple method please?

Stitch weld a round bar to a flat bar on edge. Clamp the sheet between the bench and the bar using a couple of clamps, pull the sheet around the round bar. If the bar slips weld a couple of angles on the ends to provide a flatter surface.
If you fold the two corners that have the weld seam between them first you can then fold the other two to form a square.

Same way you do it on a Magna bend, just without 5k worth of machinery to do it.

I have a fixture table with a 30mm thick top that’s gridded with M12, so I just drill the ends of the rods and bolt them down.

Ron Covell did a video demonstrating a similar set up if you search for his radius bending video.

https://www.youtube.com/watch?v=utKpSRpLzCE

Nice a simple.

Thanks everyone! I'm really amazed by the amount of replies.

Also, sorry for not being clear on the purpose of the project.
The idea is to design an enclosure for a special purpose (marine) lithium battery.
First, I'll make 2-3 'prototypes' which I'll sell to a friend.
After that, the idea is to build/sell more (if everything works out).

My first plan was to DIY, but reading your replies makes me inclined to pay a visit to my local metal shop.

The Magnabend looks like it's exactly what I'll need, making 4 folds and the having one tig weld would be perfect. I looked up the specs of the Magnabend, and bending 1.5mm aluminum over 600mm shouldn't be an issue.

I might try the DIY bench setup if my local shop doesn't have a Magnabend (or if it's expensive to have them do it, money's tight), but I'll leave the tig welding to them (with my tig welding skills, it ain't gonna be a clean weld).

Again, thanks a lot! Your replies were incredibly helpful!

You could lay that up in carbon fibre relatively simply also.
Now knowing the application, you could drop material size down to 0.8 or 1mm if you wanted to, 1.6 is overkill for a container like that.

Carbon fiber would be great, but i suppose the costs would be quite a lot higher.
I initially went with 1.5 mm to mitigate denting the enclosure, also the container is quite long (and it carries a 50kg load).
But you might be right, maybe I should drop it to 1 mm, would save some money and weight. Do you think potential denting won't be too bad with 1mm alu?

Hi GWalb, Guys,

Depending upon the grade 1 mm aluminium will take some impact to dent it ! Half Hard is tough stuff, but when it comes to bending, you only get one shot at it because it will crack if you try to bend it a second time. It work hardens where the bend is.