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Solid "foam" choices

Discussion in 'Electronic Design' started by Don Y, Dec 5, 2013.

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  1. Don Y

    Don Y Guest


    I have several "cases" that I'd like to convert into
    carrying cases for various tools that seem to keep
    multiplying around here. (primarily hand tools)

    I figure all I need to do is find some reasonably stiff
    "foam" in which I can cut holes to set the individual
    tools in, then place these in the cases. Not as good
    as a case made *specifically* for a particular tool
    but a lot better than storing tools in generic cardboard

    Most of the "foam" I've encountered at craft stores is
    just that -- foam. Spongey. It should be easy to
    manipulate but I doubt it will offer much support to
    the tools once the case is closed and carried off.

    [Styrofoam is too "brittle" IMO. But, reasonably "firm"]

    The carrying case for one of my LCD projectors has a "foam
    filler" that seems perfect. *Looks* like styrofoam
    (contrast that with the sort of foam with which you would
    stuff a seat cushion) but rubbery-er. And black.

    I.e., unlike the "seat cushion foam", it has very little "give"
    (just like styrofoam). Unlike styrofoam, it doesn't fall apart
    when abused!

    Suggestions as to what I could use and where I might find it?

  2. Den torsdag den 5. december 2013 19.49.31 UTC+1 skrev Don Y:
    layers of sleeping pad ?

  3. Go to an upholsterer's supplier and buy polyurethane foam of the
    appropriate density.

    Best regards,
    Spehro Pefhany
  5. Don Y

    Don Y Guest

    Hi Clifford,

    I thinnk that is likely to be the same sort of "spongey foam"
    that I've found at craft stores -- various thicknesses, various
    stiffness. But, none would hold up to, for example, cradling a
    10 pound sledge hammer, circular saw, sawzall, etc.

    [yes, they would keep it from bouncing around in the case, but
    the "foam" would quickly show signs of deformation]

    The stuff I'm looking for is more like styrofoam in appearance and
    consistency (your foam looks like a bunch of little bubbles
    welded together; styrofoam looks like a bunch of little *blobs*
    welded together (sorry, I can't come up with a better way of
    describing them -- look at them side by side....). But, the
    stuff I'm after is much rubberier than styrofoam. It doesn't
    "chip off" like styrofoam does when you "pick at it".

    I should see how well it photographs -- though that still wouldn't
    convey its texture, mechanical properties, etc. But, you could
    see how "hard" an edge it holds, that you could pour water on it
    and it wouldn't seep in, that I can set a 10 pound sledge on it
    you'd not be able to tell *where* it sat *while* it was there or
    after it had been removed! (i.e., REALLY stiff)
  6. Don Y

    Don Y Guest

    Hi Spehro,

    The first one I'm sure is the wrong sort of foam -- it's
    very much like the stuff they sell in craft stores to make

    Second one I am assuming is similar -- just sliced and
    diced differently?

    Think of (or, better yet, *hold* a piece in your hand!)
    that sort of foam. Then, think of styrofoam. They are very
    different in terms of their physical characteristics.
    I.e., styrofoam isn't *intended* to be elastic. When you
    exceed a certain pressure, it deforms permanently. The
    other foam "always" deforms under load -- yet returns

    What I'm looking for is closer to styrofoam but less flimsy.
    It feels like it has rubber in it -- though looks much like
    styrofoam (and not at all like the springy/spongey foam.

    Said another way, I could cut styrofoam (and this
    stuff I am looking for) with a sharp knife. The foam you
    cite above would tend to deform under the pressure of that
    knife! (you'd need a heated blade or an *extremely* sharp
    blade to cut along an intended "line")

    I need to see if this photographs well...
  7. Ecnerwal

    Ecnerwal Guest

    And a real upholstery supply has PU foam that is that stiff; not just
    the squishy stuff. Floral supply has another stiff-foam variant, but
    it's generally white or green.

    However, a fully form-fitted stiff solution is also available. Two
    sheets of plastic film larger than the case, and a can of spray PU -
    Great Stuff (tm) or the like. Spray case, lay film, lay tools, lay film,
    spray top of case, close, wait. A few vent holes will make the need to
    judge the proper amount of foam slightly less picky - cut off what boils
    out. You can even get black, if you want it. DON'T get latex "foam."
  8. miso

    miso Guest

    The foam you describe is what I find when I buy military surplus transit
    cases. I have never seen it at a foam shop. But the foam shop I use gets
    pretty close, and I prefer a softer foam anyway.

    I saw the suggestions about an upholstery shop, and that is where I
    wouldn't go. In most industrial areas, they have foam shops that stock a
    variety of foams.

    Granger has foam, but you probably won't like the price. You are better
    off finding a local foam shop and eventually one will have what you want.

    The shop I use cuts to spec. I glue the foam to the case using a 3M
    spray on glue. Super 77 will work.
  9. Martin Brown

    Martin Brown Guest

    The stuff you want is one of the Stratocell polyethylene foams used to
    cushion expensive gear in transit from the likes of UPS jugglers.

    See for example:
  10. You're thinking of latex foam. It's rubbish.
    Ask for high-density PU foam and you'll get what you want.
  11. Here in Australia, it's about a half the price, and three times the
    quality of what you can get elsewhere. It's where good auto trimmers and
    professional re-upholsters go, so it's sold at trade prices.
  12. Don Y

    Don Y Guest

    I've never bought any military surplus cases. But, this would be
    in the same category as an "equipment case" for a relatively high
    end piece of kit. *Heavy* kit. E.g., I have carrying cases for
    professional microphones that are filled with the "spongey"
    foam that I mentioned. It's appropriate, there, as the microphones
    are pretty lightweight.
    I will contact some of the hits google turned up for "foam" later
    today. I can always bring in what I have as a sample and say,
    "Gimme some of this" or "Can you tell me what the heck this is?"
    However, I don't expect to get much in terms of results.
    There's a Grainger in the general part of town I'll be in. I can
    always stop in and see if they have the equivalent product, regardless
    of price. Then, jot down what they *call* it and use that to locate
    another vendor.
    This stuff is so rigid that I suspect I can almost *wedge* it in place!
    E.g., When I pulled it out (despite the adhesive), I've been able to
    push it right back into place, turn the case upside down, shake it, etc.
    It *really* doesn't like being compressed so squeezing it just a little
    (to get it past whatever "lip" surrounds the case top/bottom) and then
    letting it return to its normal size seems to hold it in place well.
  13. Hi Don, We have use this stiff but 'plasticy' white foam.
    It's easy to cut, but holds up to all sorts of pressure.

    No sledge hammers here, but some pictures

    I can't find the name of the foam right away.. but if that's what you are looking for I can contact our packaging people and see what's it's called. It comes in various thicknesses and we sometime 'glue' pieces together.

    George H
  14. Don Y

    Don Y Guest

    Hi George,

    Yeah, I think that's the stuff Martin (?) was talking about.
    It's kinda "shiney" (has a glossy finish vs. the matte finish
    that styrofoam can be thought of having)? And almost feels
    "wet"? I've frequently seen that as a "skeleton" around items
    that are packed in cardboard boxes.

    (I.e., when styrofoam was used for that, you typically had large
    conformal fitting blocks of styrofoam being used. The stuff you
    are talking about seems to be used more sparingly and, as you
    say below, almost like it is glued together from more nominally
    dimensioned "stock" pieces (instead of the more "custom"
    approach used by styrofoam)
    This is a photo of the stuff I'm looking for. That's a 10lb sledge
    sitting "end on" the foam. Note that there is virtually no deflection
    (I was tempted to take a picture with me *standing* on it to really
    illustrate how firm it is)

    Note that it isn't as homogenous looking as your stuff or the stuff in
    the second photo, below. I describe it as looking like (black) "large
    curd" cottage cheese! :-/ And, where styrofoam feels "dry" and your
    stuff "wet", this stuff feels like "rubber" (but I don't think it is)

    By contrast, below is some of the foam that Spehro had mentioned (I
    think). Note that you can't even *see* the end of the hammer as
    it has sunk so far into the foam!

    I'll start calling foam places this afternoon. Too early to be
    working! :>
  15. Don Y

    Don Y Guest

    I deliberately didn't downsample the photos so you can zoom in to see
    a bit more detail. Black on black tends to be a bit vague...
  16. Don Y

    Don Y Guest

    Hi Clifford,

    I'm not hopeful -- but I will try. I can't imagine this stuff
    being used in any sort of "compressible" application! It's
    just too stiff. (Can you imagine using styrofoam in that way?)
  17. Don Y

    Don Y Guest

    Hi Joe,

    I'm not sure. I thought polyethylene foam was more homogenous.
    See my photos elsewhere this thread.

    I'm not sure if the color isn't just for cosmetic reasons (?)
  18. miso

    miso Guest

    The problem is upholstery shop foam is too soft. We can get that foam at
    Wal-Mart. For light stuff, that is what I use.

    For a lot of mobile radios/scanners, the USAF night vision transit boxes
    are just about the right size as is. I have half a dozen of these cases. I got them at a swap meet for $6,
    but Murphy's price isn't all that bad. Every one I got is air tight. I
    can barely open them after dropping in altitude.
  19. The stuff I bought for lining a flight case is 1.5" thick, and the kind
    of stuff that you could stand on one-legged all day without it going
    completely flat, and when you hop off, within 5 seconds there'll be no
    sign that you did it. And that's not the densest stuff they make.

    Upholsterers need and use all grades, often with lower density glued
    over higher density foam. I've seen the light stuff that miso talks
    about too, but a trade supplier - especially that supplies pleasure
    boat chandleries and trimmers - will have the good stuff.

    But it seems you like questions more than you like answers...
    Find a proper trade supplier and don't take "no" for an answer.

    Clifford Heath.
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