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I need to fly with some delicate and slightly heavy equipment that is going to have to be checked in. I have hard-sided cases I can put it in that came with convoluted open cell foam. Given the weight, I'd like to put a sturdier foam in, as I've seen the equipment shift in the convoluted foam just from regular day-to-day travel. I assume the airline baggage handlers will drop-kick it.

Polyethylene foam seems like the popular option for custom cut case foam, but while looking at the selection at the local hardware store website I saw they also have closed cell EPDM (ethylene propylene diene monomer) foam, which is much cheaper.

Has anyone attempted to cut/glue EPDM before? Does it work well as a case foam?


Same question for upholstery foam. Is it too soft/malleable?

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EPDM and similar foams can be glued quite well. You can glue them with contact adhesive (the sort you apply to both surfaces, allow to go tacky, then stick together, no chance of adjustment). This works for large flat areas. Hot glue also sticks them but getting the thin even layer you need for laminating sheets won't be easy as it will set before you've finished.

In both cases the bond is weakest against pealing, so try to avoid a construction that has you pulling against thin edges.

Thin sheets can be cut with a sharp knife, but over about 15mm (1/2") a hot wire cutter or hot knife is better. Short cuts can be done by heating up a craft knife but there are heated knives made for this. EPDM might not smell pleasant, and you can get fumes if too hot, so ensure good ventilation.

All the same techniques can be used for open cell foam as well, and a sandwich construction using stiffer and softer foam can be effective. Upholstery foams come in different firmness ratings. All but the softest should be good here, and will be a great improvement on the built-in one-size-fits-none stuff you have now. Sharp scissors or a knife will go up to about 25mm (1") with an imperfect edge, again, hot wire is better beyond that.

EPDM has a downside - it's heavy. I've comes across it as sound-absorbing foam, and it's noticeably denser than alternatives like EVA.

One other option to consider, depending on how often you'll be repacking, is the packaging foam that moulds in situ to the item you're protecting. It's essentially the same as builders' foam filler, blown into a bag while liquid. There are expensive systems for custom packing, or DIY solutions. Neither is as visually appealing as a well-made cut foam insert.

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  • Molded-in place foam will have the disadvantage that the item contained cannot be exposed (for Security or Customs) without seriously impairing or destroying the enclosing foam. Jan 17, 2023 at 23:57
  • @DavidSupportsMonica that's wrong. If done properly, that's simply not an issue. With the packaging system I used to use, you'd fill a bag, then place it in the container still soft. After a second or two, place the well-wrapped items, then another bag to expand on top (or shut the lid, lined with flat foam) . Most items could be simply lifted out for inspection, and put back in again. But they do have to be sealed as the process releases steam. Jan 18, 2023 at 7:34
  • ... This is how I often used to pack for precisely this task. The harder part at customs was the inner packaging for optical assemblies - we didn't want them getting dust on the optics by opening too much Jan 18, 2023 at 7:37
  • Yes, thanks. Constructing the packing in two pieces (top and bottom, to fit around the shipped item) would certainly make exposing the item possible. Jan 18, 2023 at 15:55
  • "Upholstery foams come in different firmness ratings. All but the softest should be good here, ..." I've found a few different rating systems for upholstery foams online, one system starting with 'T##', another with 'HD##', and another that just lists the foam density. Is there a particular rating system and threshold I should look for?
    – Huckle
    Jan 20, 2023 at 1:29

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