Foam

Last Update: 18 September 2019
Foam, being a super soft material, is an easy material to cut. We recommend foam as a starting material to practice CNC programming. Foam also has many useful applications, such as in packaging, RC planes, drones, and more.
Rigid foam is a super easy, soft material to cut. Most of the time, you can cut at full speed and full engagement with no issues, making it a fast way to draft out cuts. Soft foams come in many different densities and softnesses, which can affect cutting. Read more below to learn more. These settings work with both 1/8″ and 1/4″ 2 flute flat end mills.
Material Feed Rate (mm/ min) Plunge Rate (mm/ min) Step Over Step Down (mm) Spindle Speed (RPM)
Foam (rigid closed-cell) 2500 800 0.7 6 10,000

Rigid foams (polystyrene foam insulation)

  • Because polystyrene is so soft, you can typically cut this material at full engagement. Keep your spindle speed low to prevent melting.
  • Since it’s easy to cut, we recommend using it to practice CNC programming or as a drafting material.
  • Foam dust is very fine and sticks to surfaces. It is recommended to use a dust shoe.
  • Keep an eye on melted foam on your bits. You can clean them off with some acetone.

Soft foams (polyurethane)

  • Polyurethane comes in a lot of different hardnesses and densities. Because it is not rigid, it can be pushed out of the way by the end mill rather than be cut. You may need to change your cutting direction, or speeds and feeds to accommodate.
  • Consider using a corn-cob end mill, an end mill with little burred teeth rather than a standard fluted end mill. These bits take little tiny cuts out of your material rather than shaving away chips, preventing the foam from being pushed out of the way.
  • Foam dust is very fine and sticks to surfaces. It is recommended to use a dust shoe. Keep an eye on melted foam on your bits. You can clean them off with some acetone.