Sheet Metal Fabrication

If the box has one free opening, the size of the square it is possible with a press tool that fits in the box, long and stiff enough and has a 45 degrees angle to the front and a 90 to bring the ply back in the pressing plane of the press. Tools like

these will do.

For 4 mm material you will need some tools with a strong enough body. The 4 upstanding seems however, need to be weld. e.g. MIG down weld on the outside corners.

If you do not want to weld, you need a deep form press and a molding tool. Here we are talking about heavy presses.

You will need 4 machine operations, not 3.

... and that is assuming an open cube with butted corners. For lapped corners, 4 more operations are required. If it is to be closed, add 4 more, either on the lid or on the top edges (assuming the top is the opening, and the top is to be attached).

Yes, but I won't tell an anonymous author.

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Have you laid it out?

Do you have a clue what you are doing?

If you mean a hollow tube kind, a square tube having 2open ends, then yes. You will need to weld the last edge.

The OP said a box, not a tube. Even if your interpretation were correct, the third bend would require some kind of upper die that could be disassembled to remove from the formed cube. 4mm SS is way too stiff to let it spring out around an upper die strong enough to do the job.

It also requires a press brake whose upper die can be lifted at least 710mm to clear the diagonal of the box.

I am Almost sure that he is talking about a hollow tube which has a square cross section. It is a cube with 2 opposite ends open. Otherwise, how can he be talking about bending a flat sheet in 3 actions only?

In this case, the 3rd bend is the tricky one! for sure. But he could get away with it if he make the 3rd bend and the 1st side could clear the lip etc. then he could cut the extra on the last side.

A box has 6 sides and no openings.

the language might be lacking from the OP! Otherwise how can you exoect him to ask for a 3 bending operation for a 6 sided cube (box)? just a language precision....

Agreed. It's time for the elusive OP to return.

Again, I think no one should be allowed to post without using their user name!

Hiding behind anonymity is cowardly.

Hear! Hear!

Yes it's possible. No special tooling required. Think outside the box.

A sketch or diagram please!

the secret is cutting the one sheet into two sheets and then joining half cubes. soo,, no.

If it has one open side, can be done in one operation (without welding), using proper tool and suitable press. But who ask?

In a press brake?

You just need the proper tool:

No special tooling, and you don't even need three bend operations. A fully enclosed cube can be accomplished with only 2 bend operations in the press brake, though welding and a cutting operation are required in addition.

I'm still waiting for a sketch or diagram from Wrenchtwirler; now I need one from you, please!

I'm puzzled, too.

The original single sheet (as the OP required) measures roughly 3W x 2D (in units of side length of completed cube).

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Two bends are made, each 1W in and parallel to the 2D sides.

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The resulting U channel is cut in half midway down the 2D dimension. To avoid having to make lengthy awkward cuts around corners, most of the cutting could be performed prior to the bending operation, leaving just enough to keep it stable on the brake (and meet the letter of the OP's requirement of starting with just one sheet).

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One of the resulting shorter channels is turned so that the two fit together to form a cube, tacked and welded.

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Mandolin Violin Voilà! One sheet two bends and a box after cutting and welding!

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That brake must be in high demand.