Cutting Upholstery Foam

[NekoNariko]

Hi, I'm a real newbie to using a shopbot, but there is one at my local Tech Shop. I've taken the courses, so I understand how to use it, but I am wanting to cut out some geometric shapes from upholstery foam for some interesting-shaped pillows. Is this even possible? Can anyone recommend a end mill/bit that would be good for this kind of project? I'm not worried about the sufface being especially smooth or perfect, as it will not be visible, but I do need to be able to have a reasonably sloping angle. Any help/tips/warnings would be very helpful.

[chiloquinruss]

Just my opinion but . . . . . . I wouldn't do it with da' Bot'! I have cut foam but I use a vibrating kitchen knife for cutting out the pieces. The issue with the bot is there would be no way to hold the material and it would be 'grabbed' by any bit and after that well . . . . . Just my 2 cents worth. Russ

[steve_g]

Megan...
I have cut out pockets in charcoal polyester for case linings... what you are doing is controlled ripping out of chunks. All this is only possible if you can figure out a way to hold it while you are doing this violent act! Hot wire cutting is by far the preferred method of cutting flexible foam.

SG

[Brady Watson]

I would not use the bot to cut the foam itself, but if you cut out some templates with the Bot and used an electric knife (like for turkey carving etc), you could compress the foam with the template and use the knife to cut your foam. This kind of foam is just too soft for a rotary tool.

-B

[twelchPTM]

it depends on the desity of the foam. the bot is not the number one choice for cutting soft foams, waterjet or hotwire cnc machines are best but i have had lots of success cutting 3 and 4 lb density cross linked polyethylene foam if the density is to low it will shred and tear instead of cutting. even the electric knife can cause problems with lower density foams but a scalloped band saw blade cuts perfectly through foam and fabric

[Brady Watson]

http://www.youtube.com/watch?v=wqodjNexy7w

-B

[myxpykalix]

One thing we did years ago to make a foam insert for an anvil case for my steadicam was to take the foam and soak it in water then stick it in the freezer till frozen then take it out and carve it with an electric knife. Not sure of whether your foam is the same as what i used...:D

[steve_g]

I have to tell this story that jacks freezer reminded me of... In another life I made tooling and prototypes for a foam packaging company. A mega high-tech electronics company submitted drawings for a foam part with specifications to .001" tolerance. When the QC engineer came to evaluate to part he was very unhappy with the results as every thing was over tolerance... I excused myself, put the part in a freezer for ten minutes and returned with the same part... He left a happy customer!

SG

[NekoNariko]

Well, it sounds like the bot is not the way to go on this. I'd seen several people cut different foams, so I was hoping it would work for my project as well. I'm fine with the surface being torn to shreds as I only really need to have like a 1/4" to 1/8" tolerance. I have cut foam by hand before, but I was having to do a lot of tricky angles and things for this project, so I was really hoping to be able to do this on a shot bot instead. I'll try the freezer thing. That should at least make cutting by hand easier.

[twelchPTM]

I don't mean to repeat my self but a scallopped blade on a band saw can cut even the softest materials effortlessly with out snagging or tearing the material, no freezer needed.

[John David]

You can also grind the foam to shape bit its pretty messy
jd

[steve_g]

FYI...
The wavy bandsaw blades do work well if you can find a supplier... They often have to be bought from a butcher supply company. Technically they're called band knives and are available in wavy, straight and V's.

http://www.yorksaw.com/industrial-machine-knives/band-knives/ (http://www.yorksaw.com/industrial-machine-knives/band-knives/)

A word of caution is in order... they are designed to cut meat and we fit that description. Awkward shapes that are hard to hold at the band saw should be avoided. To get the Bot involved... you can make "ramps" or guides to run a reciprocating kitchen knife against. Also you can put foil tape on this type of ramp and pull a hot wire along them.

SG

[twelchPTM]

[QUOTE=steve_g;145148]FYI...
The wavy bandsaw blades do work well if you can find a supplier...
Mcmaster Carr carries them and yes they are very sharp and will cut through flesh with surgical precision. We keep ours covered and locked to prevent anyone unqualified from even getting near it. We use jigs and guide blocks for odd cuts so nothing is be held free, it will cut without snagging but why risk it.