FDM 3D Printing

Rules of thumb

Printing using an FDM machine is an iterative process. The following guidelines are general rules of thumb and may need to be tweaked for your specific application.

Remember when designing your part that simply because something can be made in CAD does not mean it can be 3D printed.


  • Remember that material cannot be printed in thin air. New material must be fully supported or at least partially supported by material underneath it in order to print.

  • Supports must be added to surfaces that are angled more than 45 degrees away from the vertical direction. These surfaces will often have a rougher surface finish.

Wall thickness

  • Features should be at least half the size of the filament (we use 1.75mm filament). Additionally, features that are as small or smaller than the filament size will be weak and may break.


  • Holes should have a diameter greater than 1mm (0.04in) to maintain their circular shape.

  • Holes are best printed normal to the X-Y plane (center axis is vertical) because the circular path is continuous on a single layer. Holes printed with a horizontal center axis will not be as circular because of discontinuities at every layer. Additionally horizontal holes will most likely require supports.

  • Holes may be drilled out after printing for higher accuracy.

Image courtesy 3D Hubs


  • Orienting a part properly has a significant impact on the success and quality of your print.

    • Orient circular features to be on the X-Y plane.

    • Keep fragile features parallel to the X-Y plane.

    • Think about how the direction of the layers in your part affect its strength, as shown below.

Image courtesy 3D Hubs


  • Fillets can greatly increase the strength of your part. They can also reduce the need for support material.


  • Ribs are another way of increase the strength of your part and typically provide more support than fillets. They can also reduce the need for supports. Keep your ribs at least 1.5mm (0.06 in) thick.


  • The recommended minimum thickness and height for text is 1mm (0.04in). This is true for both extruded and cut-out text.

  • Text is best printed on the X-Y plane because it avoids the letters looking "squished" by the discontinuities in the layers.

Layer Steps

  • Steps between layers are most noticeable on shallow curved surfaces. Orient your part such that low-angled curved surfaces grow parallel to the X-Y plane to minimize this effect or increase the surface angle.


  • FDM filament is heated and then cooled during the printing process. This can cause your part to warp. This is especially prominent with ABS plastic, as it needs to be heated to a higher temperature during printing.

  • Large, flat surfaces are especially prone to warping. Adding the correct

Warping on the bottom left corner. Image courtesy 3D Hubs


  • FDM 3D printing can be used with a variety of plastics. Lab64 provides PLA filament, but also has some ABS and NinjaFlex filaments in assorted colors.

    • ABS: strong, cheap,

    • Polycarbonate: industrial thermoplastic, high tensile and flexural strength

    • Nylon: used in industrial manufacturing, high impact strength