how to manufacture an internally reinforced steel hollow-box beam

[hmalfs]

Dear all,

I´m new in this forum. I don't even know if this section is the most appropriate to post my question.

I want to manufacture a steel beam that is ribbed inside. Basically it´s an hollow-box beam, but it is not bulk along the thickness. It is internally reinforced with steel ribs. I want to know how shall I manufacture the beam. I was thinking about welding. The problem is when I "close the beam" with the outer surfaces, I can´t see the places that I shall weld. I think that by casting is also possible, by using a parget counter-mold and flowing molten metal inside. Any other suggestions about possible manufacturing methods? I would like a reference where I could study this myself, if possible. Sorry to don´t attach the geometry, but I can't really disclose it.

regards,
hmalfs

 

[racookpe1978]

Oh, just a couple of relevant questions:

How long a rib?
What spacing of the ribs?
What is thickness of walls, and of what material?
How many do you need to build?
With what accuracy of every dimension?
Who will make the box, and for what type of client? Toys, bank safes, NASA, bridge beam, building wall, typewriter desk, pipe support, or birdbath? 8<)

 

[hmalfs]

Thanks for the reply,

A rib is between 30-50 cm long. The ribs are not all oriented in the same direction
a beam with section width b=0,2 m and section height h=0,3 m and lenght L=1m has 10-20 ribs in each side.
Material is construction steel. Thickness of the ribs and of the beam is 2-4 mm Total tickness of the reinforced walls is 4-6 cm
I want to build 1 to 3 beams
The geometry tolerance may be in the order of the 1-3 mm
It´s for an industrial laser cutting machine.

I hope I told enough to be able to get a solution.

regards,
hmalfs

 

[MikeHalloran]

I'd start with commercial rectangular structural tube, mill slots through its wall where I want a fin, insert the fin from the outside, leaving a little of the fin projecting out, then just weld all around the fin, only on the outside of the rectangular tube. If the fin is stepped on two edges, so that the part lying outside the tube is a little longer than the slot, it will be basically self-fixturing.

Note that the usual HSS (hollow structural section) will have one or more weld seams on the inside faces, so if you need a perfectly 'flat' bore you'll have to broach it, or buy tube with the weld seam in the corner, like Telespar.



Mike Halloran
Pembroke Pines, FL, USA

 

[rb1957]

not sure if this is the same as mike's suggestion ...
make the tube in segments. weld the stiffeners together (or cut them from plate); stack tube segments either side and weld away ! if things need to be carefully aligned, make a tool for the stiffener pieces to fit over (around) and align the tube segments.

Quando Omni Flunkus Moritati

 

[hmalfs]

Thanks for the reply MikeHalloran and rb1957

To MikeHalloran:

Sorry about my lack of knowledge about technical terms in English but what do you mean by :

-fin
-"mill slots"
"stepped on two edges"
"weld seams"

Do you have any document (.pdf for instance) that you can attach with schemes about your suggestion? Or can you post a link to the document, if it is copyrighted.

To rb1957:

What do you mean by making the tube in segments? do you mean splitting along the length in equal parts?
"stack tube segments either side and weld away"- Where shall I well? on the interface between the ribs and the Hollow-beam?

Do you have any document (.pdf for instance) that you can attach with schemes about your suggestion? Or can you post a link to the document, if if it is copyrighted.



Thanks for your help,
regards,
hmalfs

 

[MikeHalloran]

fin := rib

"mill slots" := use a milling machine to cut slots through the tube wall where you want ribs

"stepped on two edges" := not a single rectangle, but the union of two rectangles like this:

+-----------------------------------------+
| | <-- extends outside tube
+---+ +---+
| |
| | <--- rib/fin inside tube
| |
+---------------------------------+

"weld seams" := Linear projections inside the tube where the longitudinal seam(s) are|is welded in a tube mill. These are customarily removed by a scarfing cutter when making round tube where a full round ID is needed, but are customarily not removed from rectangular tube, where the ID finish is usually unimportant. The projections also occur on the outside of the tube, but are customarily removed from all types of welded tube. The projections are an artifact of the continuous tube welding process, where the seam faces are squeezed together at the weld location and some molten metal is squeezed out.



Mike Halloran
Pembroke Pines, FL, USA

 

[Compositepro]

Machine ribs into four flat plates and weld the plates together to make a rectangular tube.

 

[JStephen]

If the purpose of the ribs is to strengthen the wall, the cheapest way to do this with 1-3 small beams like that is to use a thicker wall where you don't need the reinforcing.

If you have some good welders and a welding shop, sketch out what you need, step out to the shop and ask them "Hey, how would you go about making something like this?"

Without knowing more details, putting corrugations in the walls might accomplish the desired purpose.

 

[MikeHalloran]

ASCII art for "stepped on two edges":

[tt]
+-----------------------------------------+
|                                         | <-- extends outside tube
+---+                                 +---+
    |                                 |
    |                                 | <--- rib/fin inside tube
    |                                 |
    +---------------------------------+
[/tt]

 

[rb1957]

my idea was to divide the tube at the stiffeners. readin that i realise there are two directions for the stiffeners; i assumed they'd be like a "picture frame", dividing the tube at each is an obvious way to make segments for the tube. possibly these stiffeners are axially along the tube ? but if they're axial, then casting is a solution, no?

Quando Omni Flunkus Moritati

 

[Tmoose]

Are you adding the stiffeners because you are attaching components or otherwise applying loads to the tube walls?

I'm not sure I'm correctly picturing the ribs being oriented in different "directions."

http://www.corvair.com/gfx/otto-1.jpg

http://i.ebayimg.com/t/NOS-MONTESA-...jZ/$(KGrHqFHJEgFD26fcvcLBRDWjZrOk!~~60_57.JPG

http://www.steelconstruction.info/images/c/ce/R19_Fig1.png

 

[dvd]

If you end up making this beam with the internal ribs, you should consider laser tube cutting. I have benefited from this on some projects.

http://www.youtube.com/watch?v=QoF1nxKW0vw

I agree with JStephen on the possibility of other solutions. It would be good to know what the intent is and there may be some better solutions which could be suggested by many.

Since this item is not meant for backpacking or air travel, it may be more cost-effective to simply buy some heavier tubing and forget about the stiffeners. In general, machine tools benefit from the mass, but maybe yours is the exception.

 

[IFRs]

Is this possibly a 3D printing application?