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  1. #1
    Me

    Hi, I have a part-time home DIY project in the planning stage and as part of that I have in mind using a custom design of corrugated sheet stainless steel because the off-the-shelf corrugated sheets are either common and have far too large corrugations or rare and prohibitively expensive and still not all that close to what I would like.

    For me, half the fun of the project is learning how things are best done so I have been researching what tools do this job most easily and cheaply. So I am looking for more than a quote, I am looking for an explanation as to "how?" and "why?" as well.

    I live in Aberdeen in the north of Scotland and a bonus for me would be placing the order with a company within travelling distance so that I could come and see how the panels are made. Alternatively, for companies in southern England if you could video key stages of the production and send me the video that would hopefully satisfy my curiosity and save me a long journey.

    The tooling

    All that follows below about one fabrication method I have researched as I try to source my panels. Before this project, I have never even heard of a "press brake". Before this project, "press brake" is what I did when I wanted to stop a car.

    Maybe some other tools could do this? A box and pan brake maybe?

    The Job

    I'd like to find a manufacturer to bend stainless steel sheets to make some corrugated panels of a custom design of my own, which would be a similar profile but bigger panels than this small sample made by a company in England, though in the end we did not agree a final sample, never mind a price for the job, before the company pulled out from quoting.



    The shape of the corrugations profile would be about this size, or perhaps slightly smaller.



    I think this sample was made using an Amada press brake from flat stainless steel sheet by making bends perhaps using a 6 mm V-die as shown in the diagrams. The sheet had to be manually turned over before each fold, easy enough for the press brake operator making a small sample but turning over before each fold becomes an issue with larger panels.

    This image shows the position of the sheet relative to the 6mm V-die block before the 3rd bend is made. The top tool is not drawn in.


    There would seem to be two alternative possible ways to position the sheet for each fold

    If a CNC press brake is used, the back edge of the sheet could be positioned against the back-gauge which would move under operator sequenced CNC control by a set distance before each fold.

    Or, and this would seem to be the only method for a non-CNC press brake, a strip of steel could be attached (either using a strong epoxy glue such as Araldite, or soldered) along the vertical side of die block which would serve as a shim between the die block and the vertical side of the previous bend and the sheet could be positioned against the shim on the die block.

    Each proposed method of manufacture has its own advantages and disadvantages no doubt.

    This diagram shows the position of the sheet after the 3rd bend is made. Again the top tool is not drawn.



    Not all die blocks with a 6mm V are suitable for this job. The 6mm V does have to be quite close to the edge of the die-block. Fortunately, this is the case with some of the Double V Dies, of the type to fit an Amada press brake.



    There are a few similar Double V-dies listed in the Amada catalogue.


    2 of those 123061 bottom tools would cost 254 which would give me panel length folding of up to 1670 mm.

    3 of those 123061 bottom tools would cost 381 which would give me panel length folding of up to 2505 mm.

    Or, here is a diagram of the 5mm V-die as well, this is straight from the Amada press-brake die catalogue.



    Alternative makes of similar tools might be slightly cheaper to buy, or it might be possible even to hire out those dies and suitable punch tools for this job?

    Not every company with a press brake will have the correct V-dies and punches to do this job in house to begin with so we may need to look at the options to buy or hire the right tooling to do the job.

    This extract from the Amada reference pdf recommends tonnage of 17 per metre and to bend to an inner bending radius of 1mm.



    The appropriate punch or top tool to use we can discuss later but I think many punches would work well enough providing they are 88 degrees or less with a point of 1mm radius or less.

    As you can gather I hope, I have researched this method of manufacture in some detail so I believe these panels can be manufactured this way.

    Possibly there are other methods, perhaps using different tools which would be worth considering so if you can think of another (cheap) way to make this panel please feel free to make suggestions for alternative manufacturing methods to me.

    Mass production of similar architectural facade panels uses roll-forming most often but this is not practical or affordable for a custom design of panel.

    Also there is the question of exactly how big the panels can be made? There is no set size demanded, but I would prefer bigger panels all other matters being equal. Bigger panels are more difficult to make well so there will be an upper limit to the size of panel which can be made which may well be less than the size of the steel sheet as supplied.

    For the sample profile and using a 6mm V-die, I'd like to use 1.0 mm thick stainless steel sheet.

    For a proportionately smaller profile, using a 5mm V-die, I'd suggest around 0.8mm thick stainless steel sheet.

    The total area of sheets to be bent is likely to be about 10 metres squared of 316 grade in total - possibly less if the expense of manufacturing each panel is more than I hope.

    I can certainly afford the sheet steel, the question is how much would it cost to get the corrugated panels manufactured?

    Perhaps you would like to quote for this job, ask for more details or make a helpful suggestion?

    Thank you for your interest in my project.

  2. #2
    ATTENTION PRESS BRAKE OPERATORS - Please read my REQUEST FOR QUOTE!

    I have drawn up a few diagrams showing the appropriate way I believe to produce small-corrugations, "wave profile" panels using a press brake from steel sheet of thickness 0.9 mm, which would I think give a wavelength of about 7.6 mm and an amplitude of about 3.6 mm.

    To make this profile using a press brake, a standard #12306 Amada 6 mm V-die or equivalent needs first to be custom ground to suit.



    The next diagram shows the position of the sheet after two bends have been made and before the 3rd bend is made -



    The above diagram assumes a CNC backgauge stop is being used because I have left a 0.2 mm or thereabouts gap between the vertical side of the sheet and the die.

    The next diagram shows the position of the sheet after the top tool (not drawn) has been pressed down onto the sheet to make the third bend.



    One slight variation on these drawings is simply to use the side of the die as a stop (no CNC back-gauge required) which presumably would produce a 0.2 mm shorter bend separation width than as shown.

    Using the die as a stop might mean a wavelength dimension of about 7.4 to 7.5 mm and an amplitude of 3.4 to 3.5 mm.

    REQUEST FOR QUOTE

    So whether using a CNC back-gauge stop or the die as a stop, will anyone, especially in the UK but I'll consider quotes from elsewhere, with a press brake please now step forward and quote to make 12 panels by bending 12 sheets of stainless steel, grade 316, 0.9 mm thick, sheet size 2 m x 0.5 m, which involves making about 101 bends (using the CNC backgauge stop method and a bend separation width of about 4.95mm) to 105 bends (using the die stop method and a bend separation width of about 4.75 mm) per sheet, to this profile? The bends would be along the longer length of the sheet - 2m long bends in a 2 m x 0.5 m sheet.

    Either that or quote me for what you and your press brake could make something like this plan please.

  3. #3
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 10 Hours Ago Has been a member for 8-9 years. Has a total post count of 1,391. Received thanks 136 times, giving thanks to others 5 times.
    Depending on how many you want to make, it may be more economical to have a custom die made that can do a complete V without having to turn the metal over.
    It would also have the advantage of keeping any score marks from the female die on a single side of the metal.

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  5. #4
    Quote Originally Posted by m_c View Post
    Depending on how many you want to make,
    I am thinking 12 panels will be plenty for now for my own home DIY projects.

    Quote Originally Posted by m_c View Post
    it may be more economical to have a custom die made that can do a complete V without having to turn the metal over.
    Ah you mean these types of corrugating press brake tools?





    Such tools would need to be custom made to the right profile so I think we are talking many thousands for 2 metres of such tooling, maybe even more than 10,000?

    Now, OK, if a company was producing many panels, then such a specialist corrugating tool would be a good investment but I only need 12 panels for just now so a small custom grind of a standard tool is about all I can afford.

    Quote Originally Posted by m_c View Post
    It would also have the advantage of keeping any score marks from the female die on a single side of the metal.
    I believe there is urethane film available which is designed to be inserted under and over the work sheet to protect the sheet against marks from the die.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  6. #5
    Quote Originally Posted by Peter Dow View Post
    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.

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  8. #6
    Quote Originally Posted by Robin Hewitt View Post
    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".

    Quote Originally Posted by Robin Hewitt View Post
    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?

    Quote Originally Posted by Robin Hewitt View Post
    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.

    Quote Originally Posted by Robin Hewitt View Post
    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.

  9. #7
    Quote Originally Posted by Peter Dow View Post
    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:
    Last edited by Robin Hewitt; 05-08-2011 at 03:59 PM.

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  11. #8
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 10 Hours Ago Has been a member for 8-9 years. Has a total post count of 1,391. Received thanks 136 times, giving thanks to others 5 times.
    Robin, the bends are 2m long...


    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?

    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!

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  13. #9
    Quote Originally Posted by m_c View Post
    Robin, the bends are 2m long...
    Blimey, I missed that

    Fading eyesight, large screen, small text, mutter, blah...

    The problems suddenly become clear.

    The job is seemingly easy but labour intensive, especially if he's winding the backstop by tape measure. There is too much potential to go wrong and have everything end in acrimony.

    It is very hard to convince a workshop to take on a tricky job and give it their best shot. They have past experience and simply won't believe you. It is not fun going back to the machine to try again after wasting half an hour placating someone with unreal expectations waving digital calipers in your face.

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  15. #10
    Quote Originally Posted by Robin Hewitt View Post
    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:
    Quote Originally Posted by m_c View Post
    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.


    Quote Originally Posted by m_c View Post
    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.

    Quote Originally Posted by m_c View Post
    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.
    Last edited by Peter Dow; 06-08-2011 at 09:45 PM.

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