[gever_tulley]

I'm going to be cutting some foamcore (closed-cell foam sandwiched between two layers of cardstock) and before I buy a full-on router, I wondered if anyone had some ideas about a better way to cut it. I'm looking for very clean edges on the cut, and my concern is that the router will leave substantial fuzz on the soft materials.

Any ideas?

[ger21]

Try it with a handheld router and see what kind of results you get. How about a table saw with a sharp. high tooth-count blade?

[gever_tulley]

Yeah, I tried with a handheld router (and I'm not sure how to mount a circular saw on my practicalcnc table ). I guess a highspeed router might be able to make a better edge, but the cardstock really has a tendancy to fuzz up... now I'm exploring a laser solution.

[Unabiker]

The tooling you use will make all the difference in the world.
Check out www.onsrud.com.
A down-cut type bit would probably give you a better finish, at least on the top layer. Onsrud makes a up/down cut bit that may do the trick.
The propper feed rate and spindle speed will make a big difference too.

[chuckknigh]

How would you cut foam core board, manually? Probably a razor blade or an X-acto knife.

Why not make a drag knife, like the ones for cutting vinyl? Wouldn't that work?

-- Chuck Knight

[cncadmin]

Laser works the best for me

[chuckknigh]

What absorption spectrum is best?

I remember seeing a plan for an IR LASER in Scientific American magazines from the 60s and 70s. A fluorescent tube, your exhaled breath (mostly CO2 with some traces of other gases and water vapor) and some dielectric mirrors. If UV would work, the Blumlein superradiant design is even less demanding, but it is a pulsed LASER.

Maybe we should restart that "homebrew spindle" thread again?



-- Chuck Knight

[Jason Marsha]

Try a standard carbide upcut or downcut bit first, it will cost you about $13.00 for a 1/4" bit. I have cut sign stock that consisted of foam in the center with the outside a thin vinyl layer and the cut was very clean. I used a whiteside upcut 1/4" solid carbide spiral bit at about 30 to 40 inches per min.

Jason

[piratebrian]

I've been doing some experiments with foam-core and the best I have been able to get it was with a 1/4" down cut solid carbide bit running at 100 ft/min. Even that leaves a less than pristine edge. Try to route a .01 channel in your spoil-board prior to routing. Foam-core is super cheap running at $12 per 4x8. For $21 per 4x8 you can get Sintra/Komatex expanded PVC board. Far superior and humidity resistant than card stock foam core. Cuts like butter at 180 ft/min and with a down-cut 1/4" solid carbide you can cut board and vinyl print on top in one go.

[TampaVinyl]

I am cutting 1" foam core with maybe .030 Styrene on the outside. The result I'm getting is **ok**, but I want to get a smoother edge...I'm using a 1/4" fluted mill bit at 16,000rpm on the router.

Anybody have any good ideas on how to get a smooth edge?

[carbon2wheeler]

I run a multicam 1000 series with tangential knife and it works great as long as the curves arent to small.

[TampaVinyl]

How would you cut foam core board, manually? Probably a razor blade or an X-acto knife.

Why not make a drag knife, like the ones for cutting vinyl? Wouldn't that work?

-- Chuck Knight

Yes, you would cut foam core (thin stuff straight cuts) manually with an X-acto, but you would want a new blade and do the cut at a very low angle to reduce the tendency of the foam in the middle from bunching up.

[TampaVinyl]

I run a multicam 1000 series with tangential knife and it works great as long as the curves arent to small.

Let me correct: The foam core is actually 1.5" thick (this stuff: Ultra Board: Foam Board, Ideal for Screen Printing | United Industries), and painted to spec.

I am cutting letters, so a smooth curve is needed. The bit is double fluted, mill end. To get a smooth return, should I increase RPMs and slow it down?

Unfortunately, I don't have much to do a bunch of testing...thought I would get some opinions.

[bzen]

i cut a lot of foam boards ranging from 3/16" to 1" and i would never use a bit for a clean edge, i use a blade attachment (cut guru se 246) and it leaves a prefect edge