Built a CNC router to specifically machine styrofoam patterns for aluminum
casting.
But I now have a couple of questions after several machining attempts.
(I'm using a trim router as my cutting head)
1. Is Polystyrene (Lowe's pale green insulation board) the same chemical
formulation as construction styrofoam (blue)?
2. Is one better than the other?
3. Does high speed cutting release cyanide gas?
4. Does high speed cutting release microscopic dust? (I run a vacuum during
cutting, but micro particles can probably get through the vac's filter...)
5. After about 1-1/2 hrs of cutting, my 1/16" cutter developed a ball of
polystyrene on it's tip, ruining the project. A problem after 1-1/2 hours
sound more like an exception than a rule. IF a rule, how do I avoid it?
The whole concept of machining foam to make an aluminum casting seemed so
simple and straight-forward.
But now little problems keep creeping in...
Chet

In article ,
"Chet" wrote:

2. Is one better than the other?

There are different densities of foam. Some foams are specifically made
for the sign cutting industry - they may work better for holding fine
detail.

XPS (extruded, waterproof - the typical blue or pink, you'd have to ask
Lowes about green) works much better than expanded (white, coffee-cup
foam - crumbles.) Generally denser is better for holding fine detail,
but may also cut harder/hotter...

5. After about 1-1/2 hrs of cutting, my 1/16" cutter developed a ball of
polystyrene on it's tip, ruining the project.

Too hot - try directing a compressed air stream (or other coolant - that
one is at least dry) at the cutter, or change your program to allow the
cutter to cool - ie, take breaks.

I mostly cut wood, but the various cnc router fora are full of
signmakers who cut a lot of foam.

--
Cats, coffee, chocolate...vices to live by

--Howzabout switching to machinable wax? Or are you doing 'lost
foam' casting?

--
"Steamboat Ed" Haas : Imagine what I could do if
Hacking the Trailing Edge! : I knew what I was doing...
www.nmpproducts.com
---Decks a-wash in a sea of words---

On Sun, 20 Sep 2009 18:13:32 -0400, Ecnerwal wrote:

In article ,
"Chet" wrote:

2. Is one better than the other?

There are different densities of foam. Some foams are specifically made
for the sign cutting industry - they may work better for holding fine
detail.

XPS (extruded, waterproof - the typical blue or pink, you'd have to ask
Lowes about green) works much better than expanded (white, coffee-cup
foam - crumbles.) Generally denser is better for holding fine detail,
but may also cut harder/hotter...

5. After about 1-1/2 hrs of cutting, my 1/16" cutter developed a ball
of polystyrene on it's tip, ruining the project.

Too hot - try directing a compressed air stream (or other coolant - that
one is at least dry) at the cutter, or change your program to allow the
cutter to cool - ie, take breaks.

I mostly cut wood, but the various cnc router fora are full of
signmakers who cut a lot of foam.

Folks that hot-wire cut foam for model airplane and UAV wings generally
prefer the extruded stuff over the white beaded foam, although some like
the beaded foam better.

They all say that if you use the beaded stuff you want to ask for virgin
foam -- apparently the stuff for insulation is often recycled. This is
fine for insulation, but it leaves hard bits in the foam that messes up
the machining process, even if you're doing it with a hot wire.

--
www.wescottdesign.com

Thanks for tips, guys!
As far as re-cycled styrofoam, THAT may be my problem. I got sheet of
Lowe's house brand 1/2" insulation. Since it's a house brand it may very
well be made with recycled products. Ironically, for the same price I could
have had a 1/2" sheet of the pink stuff from Home Depot.
And, yes, I'm doing lost foam... Just wish I hadn't lost as much foam as I
have experimenting! ; - )

"steamer" wrote in message
...
--Howzabout switching to machinable wax? Or are you doing 'lost
foam' casting?

--
"Steamboat Ed" Haas : Imagine what I could do if
Hacking the Trailing Edge! : I knew what I was doing...
www.nmpproducts.com
---Decks a-wash in a sea of words---