What is foam cut and used for?

[WarrenW]

Hi,

I just about finished my first wood cnc router and am just curious what people cut foam for? What is it used for? I can understand the wire for cutting foam for stuff like model airplane wings, etc. But to use a router, what is the foam shapes then used for?

Warren

[JPMach]

I've cut a couple of big pieces of foam in my vmc. The guy I made them for wanted to proof out a computer model of a bike seat and make sure the fit was just right before spending a lot of money on an expensive mold. The foam comes out to less than half the cost of aluminum and you can pretty much go full speed at some incredible depths of cut (.5"+). It is fun to machine but a real mess to clean up.
I get my foam from goldewest mfg out in CA.

JP

[ViperTX]

You could also use foam for "lost foam casting"...check out http://www.buildyouridea.com

[JPMach]

here are some pics of foam being machined

JP

[plexer]

We use foam in school in our cnc router as an inexpensive material for the students to use we got our current stock of it for free and it machines fast so not much waiting around.

Ben

[Geof]

Originally Posted by ViperTX You could also use foam for "lost foam casting"...check out http://www.buildyouridea.com

The foam used for making prototypes such as JPMach shows is most likely polyurethane which can be made in a variety of densities and machines okay.

The foam used for lost foam casting is polystyrene, this quote was copied from a website describing industrial scale: "Lost foam casting is a process in which a polystyrene pattern of a component is produced, coated with a refractory, placed in a flask and surrounded with loose molding media (such as sand) to stabilize it. Then, molten metal is poured into the flask, vaporizing the polystyrene pattern and replacing it to form its exact shape."

[JerryFlyGuy]

Glad to find this thread! I'm actually building a router for only cutting foam. However I'm no machinist and don't really know what feed speeds to design for. Someone passed a link on to me for General Plastics which showed that you could mill their foam at up to 250 ipm. Is this really a realistic number to shoot for? How fast have you guys gone to w/ your systems? Any guess as to a safe number to plan for? Would a 250 ruff cut and 400 ipm rapid machine be ridiculous? The foam I plan to mill is slightly different from the general plastic's stuff [ however I may be doing some of that also] but is should be pretty close to this, its only 2# density].

JerryFlyGuy

[JPMach]

I rough cut 20# density foam with a .75 4 flute @ somewhere around 3500rpm and close to 300 ipm with a .500" depth of cut. I think my finish pass was around 4500 rpm and just under 300 ipm. So you can see that with these chiploads at the spindle speeds you could run in a router you could run around 600-800 ipm. I did hear though with some of the foams that at higher spindle speeds you risk melting the foam and ruining everything.
I have to cut some again in a week or two and am going to try higher speeds and feeds, will let you know how fast I get it to. I think it can handle a pretty fast speed it's just my heart that might not be able to. With that kinda feed in foam you get a pretty thick and long rooster tail coming off the bit. It is also a real mess to clean up as it clings to everything. The higher the chipload you can handle the more the dust turns into shavings that aren't so bad to clean.

JP

[Geof]

JPMach;

Have you ever used a two flute cutter? Double your chipload for the same speed and feed and maybe reduce the dust level? Also if the heavier chip carries off the cutting heat more effectively as it does with solid plastics maybe run both speed and feed higher?

[JPMach]

I haven't yet tried a two flute but I might. The one problem I did notice before is that if you try to get to high of a chipload it is very easy to get chipping on the edge of a part, so you have to watch what you're doing.

JP

[JerryFlyGuy]

Originally Posted by JPMach I rough cut 20# density foam with a .75 4 flute @ somewhere around 3500rpm and close to 300 ipm with a .500" depth of cut. I think my finish pass was around 4500 rpm and just under 300 ipm. So you can see that with these chiploads at the spindle speeds you could run in a router you could run around 600-800 ipm. JP

JPMach, so during these cuts what was your step over? Or were you going the full 3/4"? This is just what I wanted to hear.. I was starting to think that my system was way over on the speed and way under on power to put the tool through the foam.

Can you tell me what your system is running as far as stepper power [ or servo] and your screw pitch as well as is it acme, ball or what ever else type of screw? I can then figure out how many # force it is taking you to push the tool through the foam, I suspect its very little but I just want to confirm this.

Thanks!!
JerryFlyGuy

[JPMach]

My machine is a Haas Vf-4 with 20 hp spindle with two speed gear box. Although when cutting foam the load meter barely moves. It runs on linear ways with ball screws. I believe the ac servomotors are rated for 2500 lbs but they rarely get to full power except when rapiding. As for how much power they were using while cutting I couldn't tell ya but I know it wasn't much. The stepover I was taking I believe was about .730" just enough to ensure a clean cut. I probably could have taken deeper depths of cut but I didn't want that big of steps left on my 3-d surface. I think the ball mill I used for finish was running about .030" step over. Then with just a light hand sanding it was as smooth as glass.

JP