Custom corrugated sheet steel panels for home DIY project. Brake job anyone?

[Robin Hewitt]

or make a helpful suggestion?

First unhelpul suggestions :naughty:

Aren't you rather assuming an even temper throughout the sheet to stop it bending like a banana?

Folding it with a press brake looks a bit labour intensive and fraught.

Lining up for the next fold by pulling it back against the previous fold could be a bit cumulative error wise.

Now a suggestion...

It looks like it needs a custom machine to make it if you want to go commercial.

I'd suggest advancing the plate though a slot then pivoting two bending tools slightly behind the slot exit so one folds on the up stroke, one on the down.

The full 90 degrees would be tricky because there is more metal to spring back.

Lord only knows what shape it would come out, but it could be even with a bit of careful adjustment.

Cleverness would be required gripping it for the advance at sheets end.

This is purely off the top of my head so might be utter gibberish.

[Peter Dow]

First unhelpul suggestions :naughty:

Aren't you rather assuming an even temper throughout the sheet to stop it bending like a banana?

I am assuming the press brake is a good press brake, well designed and strong enough and correctly adjusted and skilfully operated to make consistently straight bends to the same angle along the bend even if the sheet has slight variations in its properties across its area, yes. If there are unavoidable slight differences in sheet properties along the folds causing small differences in spring back across the length then so be it.

I just want the best that can be achieved and looking for someone with a good press brake who knows how to get the best results while I am ignoring the nay-sayers with no press brake or who are not offering to quote but who say "don't try 'cos it'll never be perfect".

Folding it with a press brake looks a bit labour intensive and fraught.

It is a labour intensive job indeed so I am thinking of things to make it easier for one operator to do, such as keeping the sheet light enough to be flipped over 1000+ times. Is a sheet weighing 7.5 Kg light enough for one man to manage do you think?

What else can be done, perhaps in the way of a table to slide the sheet onto for flipping over can be set up to make the job less tiresome?

Lining up for the next fold by pulling it back against the previous fold could be a bit cumulative error wise.

This problem has been mentioned to me from several other people but I think that if the press brake has side stop guides fitted and if they are used to keep the sheet aligned correctly then the bends can be kept square and parallel and accumulative errors can be prevented.

Now a suggestion...

It looks like it needs a custom machine to make it if you want to go commercial.

I'd suggest advancing the plate though a slot then pivoting two bending tools slightly behind the slot exit so one folds on the up stroke, one on the down.

The full 90 degrees would be tricky because there is more metal to spring back.

Lord only knows what shape it would come out, but it could be even with a bit of careful adjustment.

Cleverness would be required gripping it for the advance at sheets end.

This is purely off the top of my head so might be utter gibberish.

I am not going commercial. This is just 12 sheets for my own home DIY. Thanks anyway Robin.

[Robin Hewitt]

I am not going commercial. This is just 12 sheets for my own home DIY.

In that case...

Chronos will sell you a 24" folder for £128. Doubt you could get them folded for less than that.

Lots out folders out there, just avoid the insubtantial cheap stuff. I think there was a nice 12" hand cranked brake complete with guillotine doing the rounds not so long ago for around the £250 mark.

Edit: Try ebay item number: 290446361643 :naughty:

[Peter Dow]

In that case...

Chronos will sell you a 24" folder for £128. Doubt you could get them folded for less than that.

Lots out folders out there, just avoid the insubtantial cheap stuff. I think there was a nice 12" hand cranked brake complete with guillotine doing the rounds not so long ago for around the £250 mark.

Edit: Try ebay item number: 290446361643 :naughty:

Robin, the bends are 2m long...

I have looked at the possibility of using sheet metal folding brakes for this - either paying someone to fold my panels or in the case of the cheaper or second-hand hand brakes, buying or maybe hiring a hand brake and doing the labour myself.

However, all folding brakes seem to have a larger "minimum reverse bend" or minimum separation width between bends than I need.

Some sheet metal folders allow for the use of an "Insert Bar" to achieve smaller reverse bends but those are typically 1/4 inch or 6.35 mm which is still too big for my profiles - I'd need a folding bar width of maybe 5 mm but the "Insert Bar" type of folders does give me the idea that it may be possible to make a custom insert bar which has a thinner edge where it presses the sheet.

Another problem with folders is that the nose bar may not be sharp enough to make the small bends I need. So all in all, the folder approach is looking less likely than the press brake approach at the moment.

Just thinking, but is there any structural reason why the panels have to be done from 1mm thick sheet?
Could you get away with thinner sheet?

1 mm thick stainless steel is surprisingly hard to source with some companies offering so called "1 mm" which is revealed to be 0.9 mm when you actually get hold of it.

So my latest diagrams (see above) assume 0.9 mm and scale all dimensions of the original drawing to 90% of their original values.

I am considering thicknesses down to 0.8 mm thick but no thinner. 0.8 mm thick does not make the folds any easier to make particularly because I would be scaling the size of the folds down in proportion to the thickness used. So a 0.8 mm thick sheet would need a 5 mm V-die to make the smaller "size 80%" folds.


If the nominal sheet thickness is T then profile parameters are

• bend separation width along the path of the sheet (BSW) is 5.5 T,
• the amplitude (A) is 4 T and
• the wavelength (W) is 8.4 T.

So as the sheet gets thinner the profile gets shrunk down in proportion. 0.8 mm is the thinnest acceptable nominal sheet thickness for strength reasons.

As for dies, given the number of parts you want to make, you could probably get away with dies made from untreated steel, and polished up. I've seen a good few homemade dies used, and they're good for short runs where the durability of commercial dies isn't needed. Still need to find somebody with a big enough press though!

Well if anyone wants to quote to home-make me custom corrugating dies for a press brake in their home workshop then please do quote me for that. I don't have a machining workshop at home so it would need to be someone else that makes it. Volunteers please step forward and quote.

I think it would be pointless custom-making standard V-dies from "untreated steel" blanks because the labour involved would cost more than the mass produced V-dies which cost only about £130 to £150 for a 835 mm length and the result would be poorer tools.

Bear in mind, it is not just the Vs and punches which need to be machined but the underside features and all the correct dimensions, holes and screw threads would be needed to attach the die to the press tool holders, according to the Promecam / Amada / Eurotool press brake standard, which is the most common kind of press brake.

Possibly the easiest approach would be to buy second hand V-dies and punches and for the bottom double-V you could machine a new V next to an existing V. For the top tool you could machine a new spring loaded punch section to be bolted (or maybe welded) onto an appropriate top tool.

It might be worth to me perhaps up to £1000 if someone could make 2 metre long press brake corrugating double V-dies and top tools, with one of the top tools spring-loaded as shown here.



But I am not just sending someone £1000 in advance or whatever their "pro forma" quote is.

First, I'd want to see a "proof of principle" length of such corrugating dies made, say the length of a standard bench vice grip, oh 10 cm long or so.

Then a vice could be used to apply the test pressure, so that I could test the vice dies out first. Then if the test section works satisfactorily then I'd be willing to help to fund the costs of the full scale 2 m length production with profits paid only when the final product has been produced and tested to prove it works.