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answerseek (Mechanical) (OP)
25 Oct 10 1:22
I am designing a piece with rectangular base flange shape (see attached) that will be buttwelded - for a proper model can you suggest a gap dimension  between two flanges?  (the gap on the pdf is exaggerated for better visualization) thanks!
uGlay (Mechanical)
25 Oct 10 9:51
missing a lot of data here.

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gopack13 (Mechanical)
25 Oct 10 10:34
It all really depends.  Is the forming and/or welding being done in house? It's more on the accuracy of the bending operation, as well as the minimum gap that welding would need.

If you are forming it in house, I'd say make the gap as small as your tolerance would allow.  If you are welding it in house, ask welding what size gap they need, or prefer.

If either of these operations are being outsourced, you would need to consult whoever is doing the job what they need.  Or, if someone is doing both operations, just leave it up to them, assuming you give them the critical data for the product you need in return.
rbartz (Mechanical)
26 Oct 10 0:53
I agree that more specific application information is needed. The only thing I can add is recalling a limitation in Solidworks where gaps like this couldn't be 0 or else Solidworks would error(even though in real life I would want them to touch). If you have a situation like this and your application preferrs the pieces to touch use something like .0001 which is small enough to look like its touching but doen't throw off your dimensions.
applejack2 (Mechanical)
26 Oct 10 11:52
I think it's important to consider what you are trying to achieve with this part.  Is something placed inside the tube?  or outside?  it parallelism required between the top and bottom face?  or left and right?

I've seen gaps of 1/2 the material thickness used.  That's close enough to fill with weld and gives some room for tolerance stack up.   
rollupswx (Mechanical)
26 Oct 10 12:33

Quote:

(even though in real life I would want them to touch).

In real life the cuts/bends are going to have a manufacturing tolerance. If digital design is touching and the actual part is on the plus side the sides might buckle/warp.  Depending on the part, manufacturing tolerances.... it might be better to design in a gap such that at the real world maximum material condition the edge just meets or still has minor gap.
DiegoLGraves (Mechanical)
26 Oct 10 13:22
ans, think about what tooling and machine this is formed with too. Your pdf doesn't give any sense of material or scale. Thin steel could be formed to this shape on many press brakes but the part would need to flex in the flat areas to clear the tooling and machine. Stiffer material could cause problems in forming. Qty of parts will affect your approach too.

Too your specific question, I'd use a minimal gap. If the weld joint needs preparation, call that out in your weld symbol.

Diego

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