Author Topic: Sheetmetal Bending  (Read 4640 times)

Offline Yorkshireman

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Sheetmetal Bending
« on: May 30, 2015, 11:09:11 AM »
Hallo
I am about to start a new model, where a lot bending parts (angle plates of 90 degrees) will be needed.
These will be laser parts from 1mm steel plate.
My idea is now to have the laser cut a dashed line (1 mm cuts and 1 mm spaces) along the bend line.
Will this work? And would this method have any effect on a bending allowance?
The final assembly will be by soldering, so the dashed lines will filled and not be visible (I hope).
Thanks for any hints.
Johannes

Offline Fergus OMore

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Re: Sheetmetal Bending
« Reply #1 on: May 30, 2015, 11:26:05 AM »
My question is 'Why?' As far as I can recall 1mm is quite standard old manganese steel car body thickness and as such will bend on a decent vice failing the availability of something better.
If you Mig weld, you have to be reasonably proficient to do a right angled join and if you skip weld and fill the rest with solder, you will have to use a car body solder, after tinning it with solder paste use tallow  wipe  and then body file it.

I might have got the thing wrong all wrong but it sounds like really hard unnecessary work

Norman

Offline hermetic

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Re: Sheetmetal Bending
« Reply #2 on: May 30, 2015, 11:43:00 AM »
If you mount two similar height vices on your bench, with the jaws in line (clamp a piece of angle iron in both vices before you fit the second one) you can use two pieces of angle iron clamped in both vices with the metal to be bent clamped between them, and the bend line just visible. Perfect bend every time!
Phil

Offline mattinker

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Re: Sheetmetal Bending
« Reply #3 on: May 30, 2015, 11:44:52 AM »
I agree with Norman, why? I would bend them as they are!!

How big are the pieces?

Regards, Matthew

Offline awemawson

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Re: Sheetmetal Bending
« Reply #4 on: May 30, 2015, 11:49:41 AM »
Mark your part, heavily scribe along the inside of your bend line, and bend - like folding card, you'll find the bend bends nice and sharply.

I've been known to cut a groove on sheet with a centre drill when the bend needs to be tight.

Here's an example I did a little while ago:

http://madmodder.net/index.php/topic,9141.msg100540.html#msg100540
Andrew Mawson
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Offline vtsteam

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Re: Sheetmetal Bending
« Reply #5 on: May 30, 2015, 12:02:41 PM »
I just clamp angle iron in a single vise for pieces up to 6" wide in gauge that thin. For wider stuff you can inset a piece of theavy angle iron into your bench edge, with tapped holes, and add a second piece with slots and bolts at convenient spacing as the clamping face.

I do understand, though, if you have invested in a cnc laser capable of cutting metal, you want to get use out of it, so why not? It won't save time, and you'll still need something to keep the bent legs flat, like any of the angle iron or vise suggestions. I don't think it will affect the bend radius which will be determined by the uncut dashes.

I do believe it will weaken your piece, but in model engineering, strength may not matter -- up to you. Well, you say you will weld (or solder) after, so that would not necessarily apply. I would think a groove would be better than dashes for bending through, but maybe that can't be done on your CNC laser. Simplest fastest and strongest would be an unwelded bend as Norman said.

If you are making kits for sale/production, I can see the reason for trying this to make it easier to bend by users wihthout shop equipment, and also pre-marking the cut all in one CNC operation.

Anyway, yes you can do it, no it wouldn't be more efficient for a one off, and would be weaker unless soldered or welded, but perhaps there are other reasons to do it that you have -- including fun with lasers.  :beer:
I love it when a Plan B comes together.

Offline Yorkshireman

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Re: Sheetmetal Bending
« Reply #6 on: May 30, 2015, 12:14:41 PM »
Most of the parts are something like boxes 32 x 16 x 5 mm (26 'spacers' in a model of a rail car).
I think awemason's method will work best. If I scrape a 90 deg. V-groove on the inside, I will get nice sharp bends and reproducible outside dimensions, and 'reproducible' is the keyword here.
Johannes

Offline RussellT

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Re: Sheetmetal Bending
« Reply #7 on: May 30, 2015, 01:02:56 PM »
If someone is doing the laser cutting for you it might be worth asking how deep they could engrave a line on the fold.

Russell

Offline Fergus OMore

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Re: Sheetmetal Bending
« Reply #8 on: May 30, 2015, 01:12:35 PM »
As a 'Manure' student, I picked up double distinctions in City and Guilds Motor Vehicle Restoration and the trick is to fold with sharp edges on your vice or whatever rather than fiddle about. Dammit, it's pan folding, nothing more. The sharper the edges on your former, the better the fold. If you want razor sharp edges, then use the Mig but you'll probably blow holes in the edge until you get enough experience.

Simply settle for the easy pan folding stuff. Joining, by all means use the Mig but with a spot welder attachment if you haven't got a real spot welder. It's a modified Mig nozzle- no more.

What you have got to realise is that if you put too much heat in, your one milli stuff will probably distort and have to be stretched or shrunk which is a whole new ball game.

You've heard of  or heard oil drumming-? That's it.

Regards, good luck and I need that rest!

Norman

Offline Lew_Merrick_PE

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Re: Sheetmetal Bending
« Reply #9 on: May 30, 2015, 07:35:19 PM »
Johannes,

When I need extremely accurate bends in sheetmetal, I place a pair of vee notches on either end of the cut.  Sometimes I place them in "ears" that can later be cut or ground off.  Then, when locating in the bending fixture, I can use a pair of sharps to line everything up.

Unless you are doing vise-based bending I am not sure how much value a dotted line would be.

Offline Will_D

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Re: Sheetmetal Bending
« Reply #10 on: May 31, 2015, 04:37:49 AM »
I can use a pair of sharps to line everything up.

What are a pair of sharps?
Engineer and Chemist to the NHC.ie
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Offline Fergus OMore

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Re: Sheetmetal Bending
« Reply #11 on: May 31, 2015, 07:46:07 AM »
In Britain,  'sharps' can mean surgical instruments and hypodermic needles.

As well as for toffee  :lol:

 Of course, a toffee hammer is the generic term for some panel beating hammers. Originally, it was the hammer used for breaking cinder toffee- which wasn't made from cinders- but the addition of  bicarbonate of soda  which was used as a gel accelerator in CNA glues- which were and are used instead of welding metals.

Got that? Great!




Offline Lew_Merrick_PE

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Re: Sheetmetal Bending
« Reply #12 on: May 31, 2015, 10:31:00 AM »
I can use a pair of sharps to line everything up.
What are a pair of sharps?
Sharps are a piece of steel (hardened, if it is going to be used more than a couple of times) that fit into the vee to locate the part.  The ones I learned to make & use were drilled & reamed (PF) for a dowel pin on one side and slotted (SF) for a dowel pin on the other side.  That way a small cam could be used to "close" the sharps onto the piece being bent.  Otherwise "releasing" the part can be quite a challenge.

When bending in a vise, a pair of low-angle chisels will do the trick.  The only drawback to this approach is that, without magnets to hold things, it quickly becomes a job for Shiva...