Design Guidelines for Composite Materials

Specifications, tips and best practices for designing your CNC machined composite materials.

Check out our other guideline pages:


File Setup

Here are the basics you’ll need to know before you send us your first file. If you have any questions, feel free to contact support.

File Format

Prepare and Upload your Design File for Order Custom Metal Parts Online 1

Please upload a “flat” .DXF, .AI or EPS – just as you would for our laser-cutting process.


Tooling diameter and radius

For composite materials, we use a CNC, chip-subtractive method (2-dimensional CNC flatbed machining) to cut your parts. The size of the cutting tool is based on the thickness of your chosen material.

Carbon Fiber: .125” tooling in all thicknesses

  • .125” diameter tooling
  • Allow for a radius of .063” on all internal geometry.
  • Minimum hole size: .125”

Aluminum Composite Material

.125” (~3mm) thickness ACM:

  • .125” diameter tooling
  • Allow for a radius of .063” on all internal geometry.
  • Minimum hole size: .125”

.236” (~6mm) thickness ACM:

  • .250” diameter tooling
  • Allow for a radius of .125” on all internal geometry.
  • Minimum hole size: .250”


Simple, 2-Dimensional, Perpendicular Cuts

  • No V-groves
  • No Threads
  • No 3D Contours
  • No Partial Depth Cuts
  • No Double-Sided Cuts
  • No Counter Bores

Minimum and Maximum Part Sizes

For composite materials, we are limiting the minimum and maximum part sizes in order to provide you with the quickest and most efficient CNC machining possible.

Minimum part size:

  • 3” x 3”

Maximum part size:

  • 22” x 46” (Carbon Fiber) 
  • 46”x38” (ACM)

Internal Geometry Considerations

Inside angles (acute angles) will have a slight radius due to the use of a round cutting tool. The radius will be roughly half of your selected material thickness. For example, in 1/8″ (3mm) material, the inside corner radius would be approximately 1/16″ (1.5mm).

Outside corners are unaffected, but tooling limitations make it impractical for us to produce perfectly square or sharp inside corners.


Material Removal and Design Density Considerations

Parts with large amounts of material removal may be impractical for us to produce. Grills, grates, and perforated patterns are not recommended and may be rejected.

We recommend no more than 50% material removed from a given part. The more material that you remove, the greater the risk that your part will move during the cutting process and become damaged.


Using Dogbone Fillets for Square Corners

If you have been designing in CAD for any length of time, you will be familiar with standard fillets. You may be less familiar with another type of fillet commonly used with CNC milling: The “Dogbone” fillet.

A standard fillet is used to reduce the sharpness of corners. You can modify corners with either a chamfer or curve.

However, for materials that are CNC machined, the inner corners can never be sharper than the diameter of the cutting tool. This is because the tooling is round, and it’s not possible to get perfectly square corners on interior geometry. Instead, these corners will be slightly rounded inwards (approximately .063″ radius). This can cause problems when joining parts, as a part with square edges might not fit in a hole or slot with rounded corners.

The solution: Dogbone fillets!


Ready, set go!

Now that you have the knowledge you are ready to start designing your parts for the CNC mill. Questions? Email us anytime: support@sendcutsend.com

Check out our other guideline pages:
LASER CUTTING GUIDELINES
BENDING GUIDELINES

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