Getting a good surface finish milling foam with cnc


Has to be very careful when sanding, just som light sanding to take out minor artifacts, it is impossible to sand a the hole ting without damaging it , thus the idea of applying some sort of primer and then cnc rout into this more compact layer with a less spongy surface.

Time is also of the essence, I deliver within 3-4 workingdays.


We use Eba from Svas Kjemi at NTNU for milling, it finishes well enough for international architectural exhibitions, easy to paint, etc. However, the lightest one (grey) wont stand up to transportation too well and will get dents in rough use. The other irritating part with Eba is that the dust/chips can easily become statically charged, depending on your setup. It will stick to you, your mill, your dog, your life, everyone around you. Make sure you have really good airflow for getting the chips off and try to keep the chips a bit big.


Thank you, good information.

I have a seperate cyclone used for routing artificial materials with a capacity of around 1200m3/hour and
a dust cap with long brushes, which helps alot.

Hate to work with materials that get statically charged, but some times you have to bite the bullet.

I talked with Svas kjemi, and they have material in stock.


Hi Henrik,

My experience with foam on CNC routers is limited though I have met with several individuals over the last three decades and they all said the same thing, Industrial Design, Surfcraft Shapers, Boat Hull Blanks etc.
“we never use milling or routing cutters the positive rake angles drag the foam into the cutter. So we use rotary burrs that are specifically designed for foam cutting or we use abrasive coated lollipop cutters” I’ve seen many beautiful surfaces.


Hi Aussie

Thanks, I will check this out.


Rotary Burrs with End Cut, Ball burrs and Lollipop burrs all work awesome on EPS foam. I think our “flute” count is somewhere around 30 for each burr and we only use single cut burrs. Frankly, I have not found a need to deviate from a standard burr geometry, I just adjust my feeds and speeds based on the tool.

I use type XV EPS foam (3lb density) but lower densities do work, its all in your feeds and speeds. If you can get Type C bead for any density its even better.

There will be some pockets in the EPS because of how its formed but they are super easy to fill in with a variety of materials. If I can find some good images Ill upload them later to show you what you can expect



Thanks for the tip, for the moment there is no large pockets in the finish after milling, the foam I use is easier to machine than standard EPS, however I think using a rotary burr will make for a smoother surface finish overall.


Here is and example of work I did for DroidWorx Drones. Using a high density foam and a 3" two blade bit (1/2" diameter).