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shaping foam rubber

12K views 45 replies 28 participants last post by  B0b 
#1 · (Edited by Moderator)
Does anyone have any experience forming or shaping foam inserts to fit specific items? I would like to nest small tools in a shaped foam insert in a box. I have tried using poly foam seal, various sizes of weather strip adhesive backed foam, and a few other messy methods that were all abysmal failures. I haven't been able to find any good google search results.

Any and all ideas will be gladly accepted.

thanks,
vicrider
 
#2 ·
I once used Saran Wrap around an item held it up with bamboo skewers from the kitchen put a heavy weight on it, and used spray foam that expands. then cut it with a hand saw. Worked OK, but I wasn't expecting much perfection, just shipping it across country.
 
#4 ·
If you are talking about cutting foam rubber to fit a tool, I assume you don't want to use the expanding type foam. The best tool for cutting foam, short of a CNC water jet of course, is a surgical scapel. If you can apply a slight pressure to the foam surface then slice with the scapel it's too easy. Just please be very careful. Those blades are so sharp you can slice your hand wide open and never feel a thing. Been there, done that. Scapels are wonderful tools that can do amazing jobs, but they are very dangerous if you get careless.
 
#5 · (Edited by Moderator)
Thanks, guys,

I have been attempting to make a form fitted indentation in the foam. Is there any way to pour a foam mixture over a mold?

I did try the same thing with plastic wrap and polyurethane foam (sealer), but the result was creased and looked terrible. I wonder how manufacturers do it?

I do have a set of scalpels, but my attempt to cut a recess with those looked worse than the poly expansion foam. very ragged.
 
#6 ·
I´m alittle curios about why and where you want to use foam becourse if its
to hold the tools in a drawer or stray then is the traditionel way makining a french insert
corvered with some feltclothe
and if you look over to the photho section they use a foam in the hardcases thats already
cut in 1inch sheets and every sheet is allso precut in small squares so its possiple to
make holes thats fit the single camera , objectiv ,blitz and this technic is used in many
different trades

just my 3cent

Dennis
 
#7 · (Edited by Moderator)
I obviously can't see what your scapels look like and therefore can't say they are, or are not, the type I am speaking of, but there is no way a true scapel with a new blade will make a ragged cut. These blades come wrapped in a little strip of cardboard, sealed in a sterile foil pack. Mine were made in Sheffield England. The blade style I use is called a #11. These things make a "scary sharpe chisel" feel like a putty knife. I'm talking beyond sharp. You can't touch the edge of the blade without producing blood. I cut rubber molds for jewelry patterns all the time with these little buggers; and have the scars to prove it.
 
#8 ·
Hi Crank49,

as an ex-medical tech, I have real scalpels. the ragged edge comes from being unable to carve a molded shape in the bottom of the foam under the item I am capturing.

It appears that I may be trying too hard to get that custom recess look. Perhaps making a wood pattern of the object, then compressing the 1/2" foam under the pattern and cutting the foam in a compressed state may give a more professional look.

I make lots of small boxes for gifts and occasionally like to add unique items specially selected for that person. Rather than have the item rattling around in the box, my thought was to use some sort of foam to make a custom recess within the box. I also have a few long-time friends that have requested custom fitted boxes for larger items, really not suited for hand carved foam.

Thanks for all the thoughts, LJ's, and I will keep this thread going for more ideas.
 
#9 · (Edited by Moderator)
Vicrider

When I was in the Navy (aviation eletronics tech) we used a closed cell foam and made cutouts for our tool drawers so we could quickly invetory tools before buttoning up the repaired equipment-as you can imagine a tool being loose in a a radar conrtol box wouldn't be a good thing

the material is similar to the pads that they use when gardening to kneel on-cuts easy and holds it's shape
even the material they use for a sleep pad when camping

just a thought

Jeff
 
#11 · (Edited by Moderator)
I remember watching an episode of "Overhaulin" where they would rebuild custom cars. They's send their interiors out to a custom upholstery shop where a very talented guy would 'shave' the contours into the foam before reupholstering. The bolsters on the bucket seats, custom sculpted dashes and contours on the arm rests were perfectly shaped before the vinyl went on. I just can't seem to remember what tool he used, but I believe it was similar to an electric knife like for carving a turkey.
 
#16 ·
On some foams I have successfully used an electric knife. Usually two bucks at a thrift store, and easy to sharpen. Not good for the inside cuts you're talking about, but I'll go with the freezing idea and a grapefruit knife, also available, for less that two bucks, at a you-know-what store…
 
#17 ·
I once saw a guy use a tool for that. I think he made it himself.

It was shaped like a hacksaw but instead of a blade, he had a hot wire rigged in there. He could slide that hot wire any which way. Cut real nice. He really sculpted the foam.

Some big sharp scissors would probably work for some cuts. The big nice scissors are expensive though.
Surgical knife cuts it, but small messy cuts.
 
#18 ·
Vicrider,
I guess I forgot how many of those molds I had to cut to develope the technique, but it was a lot for sure.

I think the freezing idea FredG suggested sounds like it would work; might not be real smooth however.

You mentioned you tried layers of adhesive backed weather strip foam with bad results, but might I suggest using the closed cell sleeping pad foam that Jeff suggested, cutting it in layers with your scapel, and then gluing the layers together with a few spots of polyurethane glue (like Gorilla glue). Dont forget to mist a little water on one layer for the glue to react with.
 
#19 ·
I have cut hundreds of holes in foam rubber to hold "test tubes" for shipping. I made a "drill" for this by putting a sharpened brass tube in a drill press and it cut through the foam like butter. Maybe you can use this idea somehow. I see there is a motorised rotary knife on the market now.
 
#20 ·
SEM and 3M make an expanding foam that we use inside door skins and other automotive panels for sealing and sound deadening. It is a two part foam, requires a special gun and mixing tube to use. Investment of around $200 for the dispensing gun, about $1 for disposable mixing tube and about $50 a cartridge.

http://www.shop3m.com/60980036473.html?WT.ac=POW_3MAAD_List

It will form around your part for a great fit, you may have to trim upper overflow, but it is a great filler if you need something that is exact.

But it's pricey, and for display, you will end up trimming some of the topside anyway.

For my tools I have built the foam rubber pad up in layers, that way I have a perfectly formed or faced bottom pad, and each layer has a clean razor cut side panel for each step up.

Q
 
#22 ·
I have used styrofoam insulation covered in felt with some sucess. It would be as "cushy" as a foam rubber but it may be easier to shape. I have used dremels, knifes, hot knifes, even melted it with hot glue. Once the shape was right I covered it with the sticky backed felt. The felt has just enough stretch to cover the shape as long as it isn't too drastic.
 
#23 ·
Use an foam cutter-wire with low current run through it to cut foam. You can make them pretty easy, if you're comfortable working with electricity even a little bit. Cut the profile out, slightly oversized for any felt covering etc. THEN, you glue it on to a solid, thinner bottom piece. Looks like you cut a 'pocket' out of foam and much easier with better results. Hope that gives you some ideas you can use.
 
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