Board logo

Expanding foam that doesn't expand too much
Mr Whippy - 13/9/23 at 06:42 AM

Hi,

I have a large 3D printed part that is twin walled and to add stiffness was wanting to inject expanding foam into the gap (20mm) but obviously don't want it to balloon the part but just fill it. I have put holes to allow excess foam to escape. Anyone actually used a product they'd recommend?

Thanks.

russbost - 13/9/23 at 08:51 AM

I think pretty much all expanding foam on the market is the builders type product, which, so far as I'm aware is also basically the same stuff as used in fibreglass structures etc. by mixing 2 separate parts that then expand. as long as you've allowed small holes for excess to escape I'd have thought you'd be fine with an ordinary can from any DIY shop/builder's merchant.

If you're really concerned about ballooning you could use something that's solid. but doesn't expand like silicone sealant or Siroflex etc.

SteveWalker - 13/9/23 at 11:35 AM

There are definitely two types - one for filling large voids, that expands a lot and the other for sticking plasterboard too walls and filling cracks. The latter is probably what you want and usually refers to "low expansion" on the can.

nick205 - 13/9/23 at 01:21 PM

Is this a Dalek part?

JoelP - 13/9/23 at 03:06 PM

Soudal plasterboard adhesive foam is what I use. Available at screwfix. It doesn't expand much at all. Window fitters use it to draftproof small gaps.

MikeR - 13/9/23 at 03:15 PM

What about the stuff you buy in separate cans and mix yourself. (Supplied usually from boat builders) You know the expansion ratio so only mix the right amount?

craig1410 - 13/9/23 at 10:47 PM

Just get Screwfix No Nonsense expanding foam and then trim off any excess once cured. It's really easy to cut afterwards and the foam itself is really quite robust in terms of structure and will add real stiffness to your project. I would also recommend the foam which works via a dispenser "gun" rather than the stuff that has its own nozzle but you do carry the extra cost of the gun and maybe some gun cleaner. But it is MUCH more controllable than the self dispensing cans.

Mr Whippy - 14/9/23 at 06:13 AM

quote:
Originally posted by nick205
Is this a Dalek part?


Yes that right, it's the shoulders. I've added a double skin to increase stiffness with a 20mm gap and connecting blocks between the two walls which are 2mm thick. I'm running off a test slice just now which will be ready tomorrow to check for errors and that it actually prints correctly before the 3 weeks to print all the shoulder sections. I like the sound of "Soudal plasterboard adhesive foam" might get some and try it in a small cardboard box and see what it does. Fortunately my office window looks right on a Screwfix super handy!

Description
Description

coyoteboy - 14/9/23 at 11:43 AM

quote:
Originally posted by MikeR
What about the stuff you buy in separate cans and mix yourself. (Supplied usually from boat builders) You know the expansion ratio so only mix the right amount?


This was my thinking, a controlled mix of foaming agent and adhesive.

coyoteboy - 14/9/23 at 11:46 AM

quote:
Originally posted by craig1410
Just get Screwfix No Nonsense expanding foam and then trim off any excess once cured. It's really easy to cut afterwards and the foam itself is really quite robust in terms of structure and will add real stiffness to your project. I would also recommend the foam which works via a dispenser "gun" rather than the stuff that has its own nozzle but you do carry the extra cost of the gun and maybe some gun cleaner. But it is MUCH more controllable than the self dispensing cans.


I think their problem is that when expanding it can do some real expansion damage on thin walled things. I've even had it push up a thin wooden window cill, so a wee 3D printed part will be warped to buggery if the external areas cure first and the expansion keeps going.

harmchar - 16/9/23 at 08:59 PM

Is two part epoxy resin an option. Won’t expand same as foam, but might be too heavy for your purpose.

Mr Whippy - 17/9/23 at 01:17 PM

quote:
Originally posted by harmchar
Is two part epoxy resin an option. Won’t expand same as foam, but might be too heavy for your purpose.


Thanks for the suggestion but yes filling the gap with epoxy would probably make the part very heavy, although bomb proof