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Problems in bending sheet aluminium to a 90 deg angle

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Greensands07/08/2021 14:04:33
250 forum posts
43 photos

Hi - Can anyone offer advice/assistance on just how to achieve a 90 degree bend in sheet stock. The photos illustrate my (home made) bending machine at work and the results obtained when attempting to achieve a 90 degree bend in 1.5mm aluminium sheet. As I see it the bending arms need to move through 90 plus degrees in order to to end up with the required 90 degree angle but I am not sure what modifications are required to the bending gear to achieve the desired effect.

img_9951.jpgimg_9952.jpg

Brian H07/08/2021 14:13:30
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2230 forum posts
113 photos

Most bending operations will require the metal to be overbent and allowed, or made, to spring back.

With aluminium in particular, the amount will depend on wether the material is pure aluminium or one of the heat treated alloys.

I would suggest removing the piece of angle iron and keeping a check on the angle with some sort of angle gauge until the correct angle is reached.

Brian

John Haine07/08/2021 14:14:02
4189 forum posts
242 photos

I think that the bit the metal bends against should have a bevelled edge at say 45 degrees rather than 90 as you have it. This allows you to bend for the "plus" bit to allow for springback.

John Haine07/08/2021 14:14:03
4189 forum posts
242 photos

I think that the bit the metal bends against should have a bevelled edge at say 45 degrees rather than 90 as you have it. This allows you to bend for the "plus" bit to allow for springback.

noel shelley07/08/2021 14:19:48
770 forum posts
19 photos

You will never make a 90* bend unless you over bend by a small amount 3-5*. Youngs modulus of elasticity or some such ! So having a a stop at 90* will always give a smaller bend. If you measure the bend you have, then add the short fall to 90* you will be pretty close. Good luck, Noel.

pgk pgk07/08/2021 14:28:06
2324 forum posts
293 photos

The simplest mod I can think of (will it work?) would be to turn your rt angle steel to apex uppermost with appropriate mounting holes (perhaps little flat topped V blocks so you can dog down) and then make up a stop each end of the bend area so you can adjust for repetition.

pgk

Gary Wooding07/08/2021 14:30:56
873 forum posts
227 photos

I reckon that the purpose of the angle-iron is to securely clamp the workpiece, but you are using it as a bend stop. I suggest to reverse the angle-iron and machine a bevel on the edge close to the bending point. Then make a separate stop to limit the bend amount.

br07/08/2021 14:54:42
697 forum posts
3 photos

Ours was similar with a flat clamp strip instead of the angle, front edge chamfered at 60 degrees.

Bends up to 115 degress were achievable

bill

Steviegtr07/08/2021 15:06:21
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2244 forum posts
311 photos

I assume the angle iron is locked down with the 2 screws to hold the plate in place, to be bent. Once you have done the bend. Release the hold down angle iron & draw the angle bent piece through a little further. Clamp down & re-bend. You will achieve the angle you want.

Only problem with this method is the radius of the bend will be greater & allowance will have to be made with sizing the material.

Steve.

Greensands07/08/2021 15:22:22
250 forum posts
43 photos

The angle plate is currently serving as both a holding down clamp and backing plate held in position by two 1/4 dia socket screws permitting a 12" maximum sheet width. I rather like the idea of retaining the angle as the means of clamping and to then consider machining an angle on the front face. Problem is just how to go about milling the angle. Current thoughts are to use two milling table vices which permits holding long lengths but just how to set up the angle is the problem.

Oven Man07/08/2021 15:29:58
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158 forum posts
31 photos

Most DIY benders have the clampling angle "upside down" so that the two edges clamp the part and then there is room to over bend the part.

Peter

John Haine07/08/2021 15:34:27
4189 forum posts
242 photos

You won't be able to machine a very large slope on the angle because it isn't very thick. You could replace it with a rectangular bar perhaps? Make the bevell / chamfer perhaps by milling with a dovetail cutter. Or for a 45* chamfer, mount the bar by clamping in a couple of vee blocks.

Nicholas Farr07/08/2021 15:35:25
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3002 forum posts
1371 photos

Hi, I made a 1M long one in my last job, Which had a piece of 100 x100 x 12mm angle and like pgk pgk says, the apex was uppermost so it had a 45 degree backwards fence. The two outside edges were machine back though where it clamped the sheet being folded, so it had just a very small radius for the bend. The angle also had a 30 x 70mm piece of flat bar tack welded inside the angle, which helped it from bowing during folding and a block was welded on each end of the angle for a sloppy 24mm bolt hole for clamping it down, the sloppy hole made for a bit of adjustment for different thickness metal. We could, with a bit of a grunt, bend a piece of 1mm 306 stainless steel, about 800mm wide in it, but it would do ally up to 1.5mm thick the full 1M wide. It was made to be bolted down to a heavy steel bench. Yes you will always get a bit of spring-back, even on a break press.

Regards Nick.

P.S. on reflection, the clamping blocks welded on each end of the angle, were in fact thick oblong box sections.

Edited By Nicholas Farr on 07/08/2021 15:55:29

Roger Best07/08/2021 15:53:22
306 forum posts
36 photos

Gary has it. smileyyes

JasonB07/08/2021 16:23:39
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Moderator
21468 forum posts
2455 photos
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Yep what Garry says, the angle is really only to stop the clamping bar bowing, rotate 180deg so vertical leg is away from the bend and mill or file a chamfer on the edge of the flat leg

It won't mean a larger bending radius.

Edited By JasonB on 07/08/2021 16:27:30

Edited By JasonB on 07/08/2021 17:08:21

Sam Longley 107/08/2021 18:32:39
860 forum posts
30 photos

I would now lay a piece of wire or thin rod  in the angle right in the bend & then push the upright just over centre. The wire acting as a radiused packing off the 90 degree former

Edited By Sam Longley 1 on 07/08/2021 18:33:18

Howard Lewis07/08/2021 20:34:53
5348 forum posts
13 photos

+1 for overbending, so that then metal springs back to 90 degrees.

A bit of "suck it and see" until you get to know how much to over end to get the required angle.

Will probably vary from material to material, and the thickness..

File under "Experience", unless you are like me and have a good ability to forget.

Howard

Hillclimber08/08/2021 07:46:36
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200 forum posts
52 photos

Check out the layout of the bending machine photo that JasonB has posted.

You will see that the angle is used as the bending bar, and is mounted to the moving component of the tool. The workpiece is held with a flat clamping bar, the leading edge of which is bevelled.

That bevel is only essential if you need a sharp fold, and you are going to set the leading edge back very slightly from the machine fold, to accommodate the material.

Good luck.

Cheers, Colin

JasonB08/08/2021 07:55:33
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21468 forum posts
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Posted by Hillclimber on 08/08/2021 07:46:36:

Check out the layout of the bending machine photo that JasonB has posted.

You will see that the angle is used as the bending bar, and is mounted to the moving component of the tool. The workpiece is held with a flat clamping bar, the leading edge of which is bevelled.

No, The work is clamped by the larger angle on the top held down by the two extended wing nuts, bevel can be seen on this angle.

The smaller angle on the moving part is just the way the bender is made.

Full details of that folder here

John Haine08/08/2021 09:26:52
4189 forum posts
242 photos

Another way to bevel the edge of the clamping angle is to use a 90* countersink as a milling cutter. Makes an awful noise but does the job if you take it slow.

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