Help Cutting 1" thick Soft Foam for Cases

[wolfsmagic]

Hey Folks,
Any tips on Cutting 1" thick Soft Foam for Cases etc.?
Is this even possible?
I need to create compartments within an ATA case for components to be stored using the typical soft black foam you find in cases.
I know this is typically die-cut but I am in need of smaller quatities and the die-cut set up fees will kill my profit margin.
Any help would be great.
Thanks
Chance Wolf
Wolfs Magic

[myxpykalix]

We did this several years ago and not with a bot, to make a custom foam case for my Steadicam.

We took regular soft foam and put it in a freezer and let it get hard then cut it with a knife.
I can't imagine you could cut anything like that with a router on a bot. I have seen where they have used(I forget the term used) a hot wire to cut foam.

[wolfsmagic]

Thanks Jack. I figured it may be wishful thinking but maybe someone else has found a trick for this.
Any help would be appreciated.
Thanks
Chance

[ljdm]

An electric carving knife works pretty well.

[benchmark]

I just cut a vacuum hose adaptor out of some hard black foam with a 1/4" upcut, it did the trick but the edges were a bit ragged.

What about a Zip bit ?

Paul

[myxpykalix]

I believe that any bit trying to cut soft foam is just going to catch and wrap the material around the bit or just rip it.

I don't remember if we did this when i cut mine but if you get the foam wet enough before you stick it in the freezer that might help it have enough structural strength to withstand cutting with a bit, but i doubt it. Its like trying to use the bot to cut a sponge, sometimes it just isn't the right tool for the job. Lou's idea about the electric knfe is a good one. Just make sure you clean out the foam before thanksgiving or the turkey is likely to take a bit rubbery.

[knight_toolworks]

Just mash it down with a ruler and use a sharp razor fast and easy.

[wolfsmagic]

Thanks for the input folks.
I have cut plenty of foam with the electric knife etc basically for straight block cuts.
My need is for more complicated inner cuts for odd shaped parts to fit within and time is a factor so hand cutting would be a bit much as they are pretty intricate parts.
Looks like I will have to sub it out to a foam die-cutting operation.
rats!
Thanks again,
Chance

[Brady Watson]

Chance,
You might want to investigate a very high RPM spindle that could be mounted on a ShopBot & used to cut the softer foams. The characteristics of soft foam require a very low chipload, and therefore, a very high RPM spindle. Pneumatic spindles come to mind, preferably something in the 100,000+ RPM range would be worth investigating. High RPM & multi-flute (4 or more) cutters are the key.

Your next challenge will be holding the foam to the machine while cutting. One cut/hold-down solution might be a tangential rotary knife. You should contact ShopBot directly and speak with their engineering dept, as I believe that that have built a similar type of machine for cutting leather. (RE: 'ThinLine Pads' on this (http://www.shopbottools.com/fromshops.htm) page)

-B

[wolfsmagic]

Thanks Brady. Sounds like a good start!
Chance

[gene]

Do you know anyone with a laser

[matt_conklin]

It is tricky business cutting soft foam on a laser. Your cuts wont be true due to the over melting of the foam. We use a hotwire to cut foam all the time. Make a tracing template to put top and bottom on your piece and use it to cut out your shapes. If you need help making a hotwire let me know.

[br928]

Hmmmmm....waterjet for this one. Just water with no abrasive. Hey...they cut bread with it.

[rcnewcomb]

Liquid nitrogen?

[dana_swift]

Randall LN2 at -321F can be a hazardous substance and difficult to keep contained when you pour it in or on the foam (lots of fun to play with I have to admit!) and large dewars are not cheap.. however dry ice (-109F) might be a grand idea, being a solid its much easier to handle (with gloves). Not that its "safe" to work with either, at least you can buy it at your local grocery store.

If the foam can be converted to a "solid" for a while a standard router bit would probably be worth trying. Then you can make more than the generic straight cuts typical of a hot wire.

Another idea is to shape a hot wire "router bit" in the shape of a loop and guide it through the room temperature foam with the bot. Then you might be able to cut any arbitrary shape.

I can imagine a rectangular loop oriented in the Y plane so you can make X cuts. Then another oriented in the X plane so you can make Y cuts.

If anybody gives that a try, I would love to know how it comes out.

D

[matt_bernhardt]

I've tried what Dana is suggesting - we bought a rather inexpensive hot knife, hoping for high-resolution cuts through wallmate insulation board (the blue board you get from Lowe's). Maybe it was the knife we bought, but we couldn't get any sort of quality on the cuts - the tip of the knife seemed to be much hotter than the rest of the blade, so the foam melted away much more significantly (i.e the blade cut a swath 1/8" in size, the tip cut 1/4").

Maybe a home-built hotwire would be better - it almost certainly wouldn't be worse. We have also now have a CNC hotwire from Foamlinx, and the quality of its cuts are light years beyond what we could achieve with the knife.

[david_white]

Just thinking out loud ,but could you mash the foam in the center of two 3/4 inch pices of ply wood. Screw four corners and the inside of the profile so it dosent fly off.

Dave

[mikek]

Use a hot wire kit. We make display cases for salesguys all the time with it. I cut the foam blanks on a bandsaw (knife and straitedge will do if you hold the cutter straight up!) to fit inside the case, then use the hot wire to hollow out the spaces for "objects". I use a drill press to put quick holes in the foam to feed the wire through and hot wire out the parts you don't want. Use a CAD program to draw your template and print it out 1 to 1. Use sizzors or xacto knife to cut out template from thicker than normal paper and use a fine point Sharpie to outline your cutout area. Hot wire just outside the lines and you are done. Here is a cheap source. It will cut most types of foam.

http://hotwirefoamfactory.com/product.php?productid=16140&cat=3&page=1

[allegheny]

How about sandwiching the foam between two pieces of 1/2' plywood or mdf and then screwing the assembly to the the table to compress the heck out of the foam? Then simply cut trough to the lower plywood.

Brian

[donchandler]

We cut pockets in Ethafoam that is used for padding in shipping. It is fairly soft. We use a straight bit and move at 1"ps. Cuts real well.