Bending a closed box tube from flat stock

[z28tt]

Is it possible to bend something to a closed shape? The parts I'm working with are made from 2x1x.125 steel box tubing.

Using a brake (is there one that can handle short lengths (6" or less) of .125 or .093" mild steel?), I figured make the first 90 deg, slide the sheet out an inch, make the next 90, slide it out 2", make a 90, and slide it out the last inch to make the final bend, to as far as the fingers will allow (60 degrees?). Then clamp the part in the bench vise or shop press to close it, and weld.

Currently I'm taking lengths of the box tubing, scribing them, cutting out the corner notches with a saw, bending them (into a roughly M shape /-\_/ ), and TIG welding the open seams closed to keep the shape. It's taking way too long, and I'd like to have this part fabricated by a sheetmetal shop, where the flat can get punched or laser cut, and then bent to shape. Qty would probably be batches of 20 a few times a year, and it takes 2 days to do one batch now. The bend radius must be very tight (2" to centerline), which is why I have the mitered corners, instead of using the tubing bender. Thoughts?

[ViperTX]

Yes it is...but not economically feasible in the home shop.....that is how rectangular steel tubing is made

Can't you find rectangular or square tubing to fit your needs?

[One of Many]

Have you seen an open center upper die with a removable section?

If this applies to your needs.

Either the bottom portion can be removable or one end support can be removable to slide the fully close box off of the die.

The caveat here is that the die must handle the tonnage you plan to place on it during a bend.

For 1/8" A36 air bending it will take about 7 tons/foot. You stated 6" so the die should be designed to handle that at a minimum, yet you will only be pushing 1/2 that.

DC

[massajamesb]

If you can find someone with a hydraulic "finger" brake, they can bend it for you. The finger brake has removable sections in order to make boxes and pans, etc. when working with flat sheet.

Edit: are you trying to bend box tubing or flat stock? The only clean way I know to bend box tubing is through the use of a mandrel bender. The bend radius is determined by the die used.
If you are building this out of flat stock, then a finger brake is the way to go. I have a 3-in-1 sheetmetal worker 52 inches long, and it will brake small sections of .125 wall plate. The brake section is a finger brake design

[schiada96]

You could form two sides of the box slot the third with a laser and hand form. That would double the weld but if the qty is right an easy solution

[ViperTX]

Oh, you're trying to make a complete box....all 6 sides from a single piece of flat stock?

Good luck, you'd be better off caping the ends of some steel tubing....an alternative method is bending 2 U shaped pieces and welding them together...

[z28tt]

Massajamesb - Which 3 in 1 do you have? How do you like it?

schiada96 - Can you explain? I didn't quite understand. Doubling the weld might be worth it, if it's easy to fabricate.

I've attached a screen shot from Alibre Design - pink lines show the bent part, and the grey is the flat that can be used.

All in all - I'd like to make the part as inexpensively as possible. I figured if it was made from one sheet, laser cut, from a place that had CNC bending equipment, and then welded, it could be done quickly by a sheetmetal job shop. This is compared to my time laying out the manual cuts, sawing out the notches, bending, and then TIG welding it together from box tubing. I need to get the cost down somehow. I've thought of welding pieces of box tube together, but now you've added a 4th edge to weld, and more cost, and a need for a more precise jig. Another idea is two 3/4" thick box tubes mandrel bent, and a 1/8" plate stitch welded to the top. I've got the JD Squared mandrel bender, but the bend radius is just too large to make this part. For an idea of scale, it's 1x2" box tubing in the drawing.

Thanks for the ideas. It's great to get outside viewpoints!

Andris

[massajamesb]

[QUOTE=z28tt;226623]Massajamesb - Which 3 in 1 do you have? How do you like it?


I had a 40" one from Northern tool I really liked, and the one I have now is a 52" from Harbor Freight. Honestly, I love it. I am rebuilding a 1951 Mercury coupe right now from the ground up. I think I have pics in my profile of the doorskin I made for it. I brake and roll 18 gauge with minimal effort, anything thinner is a breeze. As I said above, I can also brake .125 sections. I think the largest I ever did would be 6" wide x .125.
You say you have the JD2 bender, which die do you have? I am guessing you have the smallest radius die available for the tubing you use?

[ViperTX]

Thanks for the pic.....I don't think you can do that from flat stock....everytime you do a reverse bend you need to add some material......

[One of Many]

After seeing the pic. I do think the box tubing is your best bet also. If you set up some simple fixtures to nest the tubing in. You could cut all the notches on a vertical bandsaw with consistant dimensions and angles. Make up another fixture to bend and hold it in shape for tack welding.

Making it up out of flat sheet adds a lot of length to your welds. I's suspect the flat would still be turned into a tube with notches prior to the Z bends anyways.

Have you inquired of fab shops, if there is anyone that can do the required angles of punch notching on the tubing for you?

I totally missed the verbal description visualization and the equipment you were using.

DC

[massajamesb]

Honestly, after reviewing that pic, I would say yes it can be done, but...
it would take longer than it does now to make that out of flat stock.
You could do an outlay onto flat .125 sheet, and cut the sheet out, yes.
The problem is that you will spend all day moving it around to do all the brakes, and then you will have a LOT of GTAW to assemble to a finished piece.
IMHO, possible, yes. more efficient, no.

[z28tt]

ViperTX - It's possible to get the reverse bends from from flat stock, if you make the panel from the other side. The right 3 sections are connected by the bottom panels, and where it gets to the reverse bend, it's now connected by the top panel, so there is material to notch for the corners. This was done in Alibre Design Professional, which is can get picky about not generating a feature if the geometry doesn't work.

I don't have a JD^2 die set for the box tubing (bought it for roll cages), but the largest box tube that will fit in the Model 2 Bender is 1.5", with a 5.5" centerline radius. I would need something closer to 2 or 2.5" if possible. Maybe a fab shop with a CNC'd Ercolina mandrel bender can handle tighter radii?

I was hoping an automated solution would be less expensive, but if they're moving the part around by hand in a brake, I could see that taking a while! I haven't spoken to fab shops about this specific part, yet. There was a company I met at a design and manufacturing trade show in NY that suggested making it from flat stock, which is how I got this bug in my ear in the first place! I'm close enough where I can show them something, and at least get an estimate, or get alternative ideas to make it easier to manufacture. Thanks for the ideas everyone.