Need suggestions on carving blue foam

[asaraca]

This will be my first project on carving a topographic map on blue foam for some of our students project (study of the surface of planet Mars).

Do you have any suggestions on what end mill to use (from the SB starter kit) and what RPM/feed speed to use ?

From the research I did until now, I was going to try the 1/8 ball nose (77-107) at 18 000 RPM and 4 IPS. We have a Buddy 48-12 with a HSD spindle.

Thank you,

Antonio

[dlcw]

The 1/4" ballnose will work great. I did a large (8' long x 4.5' wide) foam sign a few years back and used the 1/4" ballnose. Excellent results. For topographical maps, depending on the resolution and the size of your blank, you might want to look at a 1/8" ballnose. You can carve foam in one pass. No need for a roughing and final pass. Very little danger of breaking the bit.

I think I carved at about 13K RPM at 5 or 6 IPS.

I would suggest using a piece of scrap foam to determine what speed and feed is optimal for your machine. Just remember, you can go pretty fast, unlike in plywood and solid wood. In a classroom environment, optimizing for speed of cutting is important. I volunteer and sub teach at the local highschool woodshop. I am always working with students' designs to help - and teach them - how to optimize/reduce cutting time, as time is at a premium when they only have 50 minutes of class time.

[knight_toolworks]

the only trick in one pass is to make sure the bit has a cutting length as long as the deepest depth. the tick I use in wood is to either raise the bit higher and make the first few passes or make the first pass slow then change the speed back to normal so your not putting a big load on the bit.

[chiloquinruss]

The biggest problem I have when cutting the blue stuff is STATIC CLING! That stuff goes everywhere and sticks! Before I start I empty my dust collector and as soon as I'm done I re-empty. I've even used a shop vac and hand held it close to the bit to catch some of what the DC misses. As far as the actual carving, I also use the 1/4 ball and run at high feed and speed especially doing a lot of material removal IE topo's. If it's a sign with edged letters the speed is slower because sometimes the blue pulls on sharp edged letters. Doing a test piece is always a good idea. Have fun. Russ

[asaraca]

Thank you all for your suggestions. So I used the 1/8 ball nose to carve the planet Mars Gale Crater from a STL file that is available on NASA web site. This result is not too bad for a first try ...

31167

For my second project I'm trying to carve some letters in blue foam. I'm using the Onsrud 48-005 1/4 One Flute Straight bit. The finish is acceptable, but it could be better I guess.

31168

What bit would you suggest to have a better finish on the edges ?

Thanks,

Antonio

[garyb]

The 56-080 will give a much better finish with clean side walls on blue and pink foam
Gary