mini sheet metal folder

[dopplershift]

Oh. Ok. Hmmm. Not at all what I was thinking, but yeah, cant see that bending before a sheet of 3mm!

Thanks... will have to think about my design. I'm trying to do it with the handle on a hinge as well so they'll hang vertically when not in use (saving space).

 

[madkayaker]

It wont bend and its easy to hold! And to find usually

 

[dopplershift]

Yeah. Thanks for that! Will have to have a look around and see what I can find.

 

[madkayaker]

post some pics when you get in finished we like pics on here.

 

[dopplershift]

Yeah, will do - if I can work out how! (I know theres a tutorial somewhere... I'll get to that).

I've been lurking for ages and enjoying the pics. I think these forums as a whole are EXCELLENT! Very, very friendly and helpful!

 

[English Steve]

Oh. Ok. Hmmm. Not at all what I was thinking, but yeah, cant see that bending before a sheet of 3mm!

Thanks... will have to think about my design. I'm trying to do it with the handle on a hinge as well so they'll hang vertically when not in use (saving space).

The handle should hang vertically down anyway, without hinging. All of the commercially available machines work that way. If the handle is horizontal before starting to bend you will increase the difficulty in applying sufficient force, and 3mm thick is going to take considerably more effort than you may at first imagine.

 

[dopplershift]

Hi Steve,

Why should the handle hang down anyway? If its not hinged, then you would have to reach down near your knees to reach the handle at the start of the bend??? I'd have thought it would be hard to apply much force in that position?

With hinges, you still bend down to pick up the handle, then lift it into a horizontal position, where it will engage and you can start the bend from there. I know this means the handle will be way up in the air for bends over abour 45', but I have an idea for that too...

I know this thing is going to take ALOT of force. 3mm sheet is no pushover! But with a long enough lever....... (as long as the lever etc are strong enough!)

Thats why i'm interested in the length of Welderpaul's handle (lol!). He managed 2mm sheet, and his handle looks about 60-75cm???

 

[hotrodder]

Doppler, as length of bend increases the forces go up massively (exponentionaly?). Some nice DIY brakes here but at 1m length the top bow is going to need to be VERY stout or it'll bend in the middle. To simply hold a long length (for bending) securly you need many hundred kgs of clamping force

A 1m commercial bender, capable of 16swg mild weighs several hundred kgs! Was using a 10 footer 18swg box and pan folder yesterday- if the bending apron weren't counterweighted i wouldn't even be able to lift it myself, let alone bend something! I know plenty of people that'd have struggled simply operating the hold down lever!

The bend starts as soon as you lift the apron (yep, got to stoop). By the time the apron is horizontal you have around a 90* bend.

To bend 3mm over a 1m length... looking at a press brake AFAIK

 

[dopplershift]

Bugger. Thanks for the info hotrodder!

Couple of questions about your terminology:

top bow? bending apron? Which parts do these refer to?

So far I've been thinking of the bender as a 'table' (stationary, eg in vise) and 'jaws' (the bit with the handle attached that pivots to force the sheet to bend).

 

[hotrodder]

Top bow would be the clampdown bar- bit that holds the metal still for bending
Bending apron, the bit you pull up to bend the metal.

As the sheet has to be able to protrude beyond the top bow (to accomodate different bend leg lengths) it can only be clamped at each end. As the apron is lifted the whole thing is going to want to lift so as the length of bend is increased the top bow needs to be stiffer (to resist bending, result is 'bowed' bend).

Something i should of explained better was the hold down force... generally this sort of kit is designed to produce bends upto 135* so the top bow is angled (hopefully clearer here) which increases the force needed to clamp the metal. Restricting the design to 90* bends lowers the forces a bit

 

[dopplershift]

I see! Thanks for that... photo helped!

Very interesting! So you're saying that the top bow is the component that needs to be strongest (stiff, to prevent bowing in the middle of the bend)? Even stronger than the bending apron?

I was going to just use a piece of 100x100x8mm angle, positioned "backwards" so that the max bend would be ~135' rather than 90'..... Will definitely have to think about the top bow some more. Maybe add a 40x40x4mm box section in the L, and then triangular gussets over that to try and stiffen up the bow?

 

[dopplershift]

Oh, forgot to mention:

Was going to put a hole at 50cm in the top bow so that for bends up to 50cm long, I could secure it in the middle too.... reducing the tendancy to bow out in the middle.

 

[hotrodder]

Off the top of my head (it is late) the top bow is going to see the highest loads, at least for designs that allow bends greater than 90* since the leverage is greater- as you bend the sheet it'll try and twist the leading edge of the top beam upwards. Making it triangular in section would help some, heavy wall box or an I beam top bow will be stiffer but limit the apron to 90* movement- not going to get a 90* bend due to material springback

If you look at the link i posted again they talk about the trussed top beam (to stiffen it up). Apron is trussed too but you'll probably have bigger issues with the hinges.

Basically as length of bend and material thickness increase everything gets more massive pretty quickly. 1m 16swg brake, typically use double shear hinges with around 12mm thick sections and 30+mm diameter hingepins. Topbow on a box and pan brake of this capacity is around 12-16mm thick angle, maybe 100mm leg length + stiffeners. The apron is relatively simple on old brakes- big chunk of steel, maybe 20mm x 150mm deep over full length. In the link they've slimmed it dowm and added trusses for efficiency

 

[dopplershift]

Hmm. Thanks. Thats been very, very helpful!

I'll have to see how I go with the top bow. The truss idea apeals to me. Probably end up just making its as strong as possible, and worry about bending the thicker stuff when I come to it (shouldnt be too often, mainly interested in auto panel thickness, but thought 3mm might be nice for some other stuff)

Still interested in handle ideas tho!

 

[English Steve]

Hi Dopplershift, sorry I didn't get back yesterday but I see Hotrodder is better at explaining stuff than I am anyway
The reason for the handle position? If the handle starts the bend in the horizontal position, you are totally reliant on your upper body strength to form the bend as you will be pushing the handle through most of it's working travel. If it starts out hanging vertically, you can also apply your body weight and leg strength as you will be pulling the handle through it's working travel (if that makes sense). You can exert a lot more effort pulling than you can lifting, which is why the commercially available brakes work that way.

Hope that helps, and please post pics when you get it made.

Good luck

 

[dopplershift]

Hmm. I see. I see.

So ideally, you'de have handle that could complete the whole bend, while only moving between vertical down and horizontal (since thats the range in which you have most power from your legs etc)?

Of course, this would mean you could only do up to 90* bends.... unless you did something sneaky with the handle (Which I intend to!).

Thanks everyone! Most enlightening!

And yes, will definitely put some pics up when its done.

Pity i'm arc'ing it all, and my arc welder (cheap!) isnt really up to 8mm+ steel... not the prettiest welds in some places. I've been trying a kindof "root, left, right, zigzag cap" approach to try and deal with the thickness... never done it before tho.

 

[mgarym]

hi doppler

did you every make the sheet bender?

and if so will it bend 3 mm

 

[dannyweld]

sheet bender

made this by milling a V down a piece of bright mild billet. back stop is milled aluminium, have inserted brass bushes for the screw and guides. use standard press brake pieces for the down bits. fits into fly press. could be fitted into slow stroke power press or even a brake press. very accurate tool and good for runs as well.

 

[dopplershift]

hi doppler

did you every make the sheet bender?

and if so will it bend 3 mm

Well... I'm getting there. I've made up the two jaws, and hinges, and the top clamp. They need a bit of reinforcing still.

I haven't been able to afford steel for the handle yet, but hopefully this weekend! Then I can weld that up... need to make some chunky hinges for it too (you'll see later).

And then I just need to get a few holes drilled for the clamping system.

Oh, and I'm going back to uni on the 23rd, so I dont know how much time I will have after that. So all in all... probably a few weeks until I'm finished it

I'll make sure to post photos and do some tests when its done!

 

[mgarym]

I'm thinking of making one for 2mm sheet
so looking forward to seeing your design