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  1. #1
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    Default Budget Conscious Smaller Scale Vacuum Forming - Advice Please

    Hi all,

    I want to make some small scale models of a project I have out of bent ply. I have made a set of what I need and it worked reasonably well using ply bending bucks and curving in one direction (length ways). I now want to develop the models so the curves are two way. I plan to do this by using the existing moulds but vacuum forming as opposed to clamping between the matching forms.

    Can anyone help with advice on how to set up a smaller scale system (max length 400mm and width 200mm).

    Andrew

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    Don't want to disappoint you, but you can't bend ply in both directions. You can have some sections going one way and some going the other way, but not both at once.

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    I have seen 2 directional bendy ply it was very thin like 3mm. Way back in the 1950’s the Eames did do two direction bends in ply for their chairs. They had to use a male female former with built in heating elements and thermosetting glue. Imagine steam bending without the steam and they did it all in a small appartment. Not cheap or simple but it can be done.

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    When I was ordering a sheet of very thin bendy ply to make a cylinder, the guy asked me which way I wanted to roll it - along the long or short dimension, as they were manufactured differently and couldn’t be interchanged.
    So that would match Elan’s post.

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    We tried bending commercially available 3mm bendy ply both ways. Wasn't happening.

    Perhaps with heated moulds, pressure and thermoplastic glue (that's the stuff that softens with heat) like PVA you'd get somewhere, but I still don't think it'd bend very far.

    If you could find a pic of the Eames stuff you're referring to it'd be great; all the chairs I can see only go one way at a time except for this one https://www.wright20.com/auctions/20...ern-design/123 and you can see that the timber shell is joined in multiple segments.

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    4DD69C33-5C59-4DDE-A20B-3487035716AE.png

    Eames leg splint made for the USA navy. It seems to bend in 4 directions? Up on two of the long sides and then it’s seems to have bends going the other way along its centre / bottom.

  9. #8
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    Quote Originally Posted by elanjacobs View Post
    Don't want to disappoint you, but you can't bend ply in both directions. You can have some sections going one way and some going the other way, but not both at once.
    Apologies all. I should have mentioned I'm using laminates of 0.8mm ply.

    Regarding bending in two directions, I'm not that worried about it as the curves I need are quite minor and given the laminate thickness should be ok.

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    The splint bends both ways, but the compound curves are very shallow and have relief cuts made to allow it. There's some more pics here showing the press and components Leg Splint | Eames Office

    I spent a lot of time bending ply into funky shapes in my work making licenced reproduction Featherston chairs, I was also the one tasked with reverse engineering models that hadn't been made since the 50s to revive them. I was given an original chair and had to make both the mould and patterns essentially from scratch. Perhaps Eames had different methods, but I can say categorically that the Featherston stuff only went one way at a time.

  11. #10
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    Default 2d bends

    In my previous life I made a few chairs with bent ply seats made from the local bending ply.
    Was sitting on one reading this thread.
    As you can see in the pic it is possible to get 2d bends.
    They are 500 wide and that’s about 10mm where you sit.
    Its like the slight angle on a chair seat without it the anthropometrics just don’t work.
    Yea I spent two years with George in Canberra.
    Made These once I got going in my own shop here in Sydney.
    probably used urea to glue or maybe epoxy.
    Form (long since chucked out) was ply spider.
    Heaps of clamps, Gross Stabil.The krauts real know how to build em.
    H.
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    Thinking further on this as it was some thing I did research quite a bit a 30 plus years ago before the internet etc.
    What about the wooden aircraft especially the Spruce Goose ( which I checked out in LA on my first US visit). Aircraft sure have 3D shapes.
    Hughes flying boat plus the Dehaviland Mosquito were clad in ply.
    The mossie over balsa, can’t remember about the big boat.
    Theres stuff out there on the net showing the mouldings of the Mossie fuselage halves.
    Probably layers of veneer and glue which ends up as ply on coming out of the mound.
    I found something about the local manufacture of the mossie here in Oz from Coachwood and what glue they used as the Pom curd based Caskimite ? let go in flight due to our high humidity.
    Interesting stuff, especially on a small scale item where microwave steaming or ammonia would help persuade the stuff to behave.
    H.
    Jimcracks for the rich and/or wealthy. (aka GKB '88)

  13. #12
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    Default Use Food Vacuum Sealer

    Good Morning Andrew

    I use a food vacuum sealer for most veneer work, using two different techniques:
    • put veneers in bag, vacuum and seal, then bend freehand or around form,
    • put form inside vacuum bag.

    Different jobs lend themselves to either method.

    I use a vacuum sealer like this - under $200 from any hospitality supplier, department store or kitchenware store.


    In case you haven't done vacuum work before, you cannot use PVA glue as it will not set in a vacuum - it needs oxygen. But epoxy is fine.


    Cheers

    Graeme

  14. #13
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    Quote Originally Posted by GraemeCook View Post
    Good Morning Andrew

    I use a food vacuum sealer for most veneer work, using two different techniques:
    • put veneers in bag, vacuum and seal, then bend freehand or around form,
    • put form inside vacuum bag.

    Different jobs lend themselves to either method.

    I use a vacuum sealer like this - under $200 from any hospitality supplier, department store or kitchenware store.


    In case you haven't done vacuum work before, you cannot use PVA glue as it will not set in a vacuum - it needs oxygen. But epoxy is fine.


    Cheers

    Graeme
    Great tip. I would have been cursing and blinding the PVA for a while if you hadn't mentioned this. Cheers

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