Design Out Supports: Three Smart Ways to Make FDM Models Easier to Print

Support Material Starts in CAD

When an FDM printer builds a model, each layer is laid on top of the previous one. A section that extends over empty space may therefore need support. But supports are not always the best first solution: they take time and material, and the surface where support meets the model can be left with marks.

Often, the geometry can be changed to give the printer something better to build on. This does not mean all supports can be avoided, but a few simple design choices can make a big difference.

1. Replace Sharp Undersides with Chamfers

A flat, horizontal underside creates a long span that the printer has to bridge. A chamfer instead breaks the overhang into several gradually offset layers. Each new layer then gets more support from the layer below.

For a bracket or a box, for example, you can replace an internal right-angle corner with a 45-degree chamfer. This is usually easier to print than a long, completely flat underside—and can also reduce the need for support material.

A 45-degree angle is a useful rule of thumb, not a guarantee. The result depends on factors including the printer, nozzle, and settings. Prusa states that overhangs between approximately 45 and 60 degrees can work depending on the equipment, while Ultimaker describes the 45-degree rule as a general guideline for FFF. Test critical geometries with your own machine and material. (help.prusa3d.com)

2. Make Holes Teardrop-Shaped

A horizontal round hole can create a short, flat section at the top where the filament has no support. If the hole does not have to be circular, you can make it teardrop-shaped: keep the rounded bottom, but bring the top to a point or a small roof with sloped sides.

This is useful for features such as cable pass-throughs and screw holes whose shape can be adjusted. The hole will not be identical to a round one, so check the fit if it is intended for a particular screw or shaft. Consider printing a small test piece before printing the entire part.

3. Split or Rotate the Model

Sometimes the easiest way to avoid a difficult underside is to change how the part sits on the build plate. A model printed as one piece may be difficult to support neatly; two parts assembled afterward may each have a more stable orientation.

When choosing an orientation, consider both surface finish and strength. FFF parts are built layer by layer, and orientation affects how loads act across the layers. If the part needs to bear a load, choose the print orientation based on how it will be used—not only on how many supports the slicer shows. Ultimaker highlights both layer orientation and modularity as design considerations for FFF. (ultimaker.com)

A Simple Workflow Before Using the Slicer

Before adding support in the slicer, go through this checklist:

• Look for flat undersides. Could they be replaced with a chamfer or divided into shorter spans?
• Check horizontal holes. Would a teardrop-shaped top work for the part’s purpose?
• Try a different orientation. Could a less visible surface be placed against the build plate?
• Consider multiple parts. Can they be joined with, for example, a screw, snap fit, or adhesive?
• Check the slicer’s preview. See where the model actually lacks support, and print a small test piece if the result is uncertain.

When Supports Are Still the Right Choice

Do not design out supports at any cost. If a geometry must be completely flat, if the appearance requires a particular shape, or if the part will be stronger in a specific orientation, supports may be the sensible solution. Prusa also notes that surfaces above supports can have a different finish from walls and top surfaces, which is worth considering when choosing which side should be visible. (help.prusa3d.com)

The goal is not zero supports on every model. The goal is to use them where they are needed—and let CAD work make the rest of the print easier, cleaner, and more predictable.