CAD for additive manufacturing (DfAM) basics

Design for additive manufacturing (DfAM) means designing around how parts are actually built: layer by layer.

Think in layers FDM parts are anisotropic — strongest within a layer, weakest between layers. Orient the part so the main loads run along the layers, not across them.

Minimise supports - Overhangs up to roughly 45 degrees usually print without supports - Use chamfers instead of horizontal ledges on downward-facing features - Bridges (horizontal spans between supports) work over short distances but sag over long ones - Holes along the build direction print rounder than horizontal holes; teardrop-shaped horizontal holes print cleanly

Use features that FDM does well - Ribs instead of thick solid sections - Fillets at internal corners to spread stress - Built-in alignment features for assemblies - Captive nuts or heat-set inserts instead of printed threads for repeated assembly

Avoid what FDM does poorly - Very thin walls and pins - Large flat areas prone to warping - Tight sliding fits without test prints

Plan for post-processing If you'll sand, paint or insert hardware, add the allowances to the CAD rather than relying on the print to be exact.