# shaping foam rubber



## vicrider (Jun 19, 2010)

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


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## traupmann (Oct 8, 2010)

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.


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## Eric_S (Aug 26, 2009)

If I'm understanding, you could get various sized pieces of foam from a craft store in your area. They have egg crate style and flat foam shapes, hard and soft foam. It can be somewhat pricey though depending on the size and thickness.


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## crank49 (Apr 7, 2010)

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.


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## vicrider (Jun 19, 2010)

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.


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## Dennisgrosen (Nov 14, 2009)

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


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## crank49 (Apr 7, 2010)

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.


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## vicrider (Jun 19, 2010)

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.


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## j_olsen (Sep 19, 2009)

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


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## TopamaxSurvivor (May 2, 2008)

vicrider, I have tried to cut the foam before with the same results. I think you will have to compress it flat on both sides of the cut for best results.


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## 33706 (Mar 5, 2008)

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.


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## FredG (Apr 11, 2008)

Wet the foam, put it in the freezer and when frozen use a router to cut the contour.


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## vicrider (Jun 19, 2010)

Hmmmm, Fred,

I think I'm gonna try that next! have you actually done this?


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## FredG (Apr 11, 2008)

Yes, I have Vic. Not too wet of course, just moist. And a cheap bit.
A Dremel works also.


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## vicrider (Jun 19, 2010)

Thanks for all the ideas, LJ's

awesome responses.


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## LeeBarker (Aug 6, 2010)

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…


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## mtnwild (Sep 28, 2008)

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.


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## crank49 (Apr 7, 2010)

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.


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## Finn (May 26, 2010)

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.


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## Quixote (Jun 9, 2008)

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


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## GFYS (Nov 23, 2008)

electric carving knife…or hot wire


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## MrsN (Sep 29, 2008)

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.


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## KayBee (Jul 6, 2009)

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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## juniorjock (Feb 3, 2008)

Another vote for an electric knife…........ like butter.
- JJ


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## TopamaxSurvivor (May 2, 2008)

*KayBee* What did you use for a heating wire for the cutter?


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## KayBee (Jul 6, 2009)

Basically some heavier gage bell wire that found it's way to my toolbox. Mostly it was handy at the time. To small a wire tends to burn out.


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## TopamaxSurvivor (May 2, 2008)

I made one for one of the kids years ago. Can't rmember how I did it any more )


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## MrsN (Sep 29, 2008)

The wire cutter I have is basically a wire attached to both sides of a little 9-volt battery.


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## LeeBarker (Aug 6, 2010)

Is it a specific type of wire? Seems to me it is.

I found this on ebay.


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## rance (Sep 30, 2009)

Yes, Nichrome wire. As I recall, fumes from foam rubber are much more toxic than typical styrofoam but check before you do it. I wish I could recall the details, sorry.

FredG, clever idea!


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## TopamaxSurvivor (May 2, 2008)

MrsN, how long do you batteries last? Might be better to use a doorbell transformer. I can't remember just how I set the kids up, but I do remember it was adjustable for heat. I suppose I used 24 volts. I remember having an aligator clip to move for adjusting the heat.


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## lilredweldingrod (Nov 23, 2009)

You might try making a template out of 1/4 inch Masonite or plywood, lay it on the foam rubber and compress it and cut the inside with the scalpel.Then contact cement a 1/2 " flat piece on the bottom. I used to be a maintenance mechanic for a foam manufacturer back in the early 70"s. We used dies there much like garment manufactures do today. But for what you are doing, this should work and give you a reasonable finish depending on your skill. Foam needs to be compressed in order to cut it neatly.
Hope this helps. Rand


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## mrg (Mar 10, 2010)

Evening Vicrider,
Here is a link to a company called Uline they sell foam that can be cut to fit any shape. I have used this foam for medical equipment and other fragile equipment. You can use this foam for any shape. Actually it is perforated at certain increments to fit anything.
Hope this helps.
I am not affiliated with this company , just purchased from them.

I am gonna take a shot here, you ride a victory.


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## GFYS (Nov 23, 2008)

foam hot wire 12 v 2-4 amp transformer(or an old 12 v train transformer)...push on/off reostat light switch… .010 wire ..2 pigtails w/gator clips
look on youtube for foam hot wire cutter etc

btw…hot wires work great on ridgid styrofoam and styrene…. not sure on memory foams or foamrubber. Electric carving knife works well on those.


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## vicrider (Jun 19, 2010)

wow, Thanks for all the great ideas!

I will be taking this process up again in the new year and I expect to try several of these methods.

Ain't this site great??!!


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## Rich99 (Sep 18, 2009)

http://www.howtogeek.com/95360/create-custom-tool-drawer-liners-with-a-t-shirt-and-spray-foam/


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## dannelson (Nov 28, 2011)

vicrider we use a product called sign foam this stuff machines well , Im just putting it out there , if you have a specic tool or object that you need nested draw the outline full scale and we can cut it on our cnc.This operation is extreemly easy,accurate and fast.Were not here to make money off you guys just here to help. If this posting is inappropriate in anyway please remove


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## Kickback (Mar 9, 2011)

http://hotwirefoamfactory.com/home.php?cat==


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## ssnvet (Jan 10, 2012)

You want polyethylene foam (PE), It's easy to cut with a thin sharp blade, such as a "clicker" utility knife. You can buy it from U-line.

PE also cuts well on a bandsaw, provided you have the right type of blade (10 - 12 TPI). But you'll have to mend the cut in with adhesive (hot melt works well).

PE is closed cell, so it won't absorb oil or moisture.

Polyurethane foam (PU), is another choice, but you'll want a more dense variant (1.6 to 2 lb/cf) with a "stiff" deflection ( ILD 75 - 100) as the softer and lighter urethanes are tricky to fabricate by hand.

PU is open cell, however, and will absorb and hold moisture and oil.

Fom rubber is actually a different critter, and there are many varieties. Some soft and some as hard as a brick. We only die cut it at work.

Get some 1" thick sheets of black PE, a razor sharp blade and a silver sharpie, trace your pets and cut to the line and you'll be all set. Then laminate you're cut pad to a solid back pad and you'll have a nice foam tray.

Contrast the color of the cut pad and back pad ( I.e. Black on white) and you can sight inventory a large drawer of tools with a quick glance.

Just about any spray contact adhesive will give a great bond…. Just watch the over spray


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## ssnvet (Jan 10, 2012)

Ps. You can also route most foams, but if you don't use the right style bit, feed and speed, you'll likely get hairy edges.


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## ssnvet (Jan 10, 2012)

Pps…. If you hot wire EPS, make sure you do it in a WELL ventilated area as the fumes are wicked nasty.


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## yammi450 (Feb 11, 2011)

Years ago I purchased some foam sheets from sears tool dept. specifically made to cut with a x-acto knife for the tools in their tool boxes. It was 3/8 or 1/2" thick worked out great.


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## Dal300 (Aug 4, 2011)

I've had to cut the sound deadening foam rubber that they use in truck and tractor cabs into odd shapes before. I usually just heat an old paring knife up with the torch and carve out a pre-marked shape. It cuts the foam as smooth as glass. You have to be careful though, when the blade is hot it will go through the stuff as fast as you can move. You'll also have to re-heat the blade often.


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## madts (Dec 30, 2011)

Electric carving knife is the way to go. Use this item for boat upholstery, in my former life.


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## B0b (Jan 13, 2011)

The new oscillating tools cut rigid insulation very cleanly and very easily. I have the dremel multimax and I can't believe how many odd jobs are made easier with this tool. I like the wire idea because you could loop it and bend it to any shape. Are folks saying to use the old telephone wire that is basically just a touch thinner than a small paperclip (or could you use a paperclip)?


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## B0b (Jan 13, 2011)

Oh, and do you have to worry about shorting the battery or transformer?


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