You can’t just convert a CNC drawing to STL and send it to a powder bed fusion machine. DfAM is a completely different engineering discipline—it requires you to think about how material gets deposited, where supports are needed, how powder flows, and what happens during post-processing.
DMLS and SLM can achieve approximately 0.4mm minimum wall thickness, but that assumes the wall is supported, you’re not expecting fatigue performance from that thin section, and your post-processing plan accounts for the tolerance band. In practice, 0.6mm is the real design minimum for any wall that matters. At 0.4mm you’re fighting the process—laser spot size, powder layer thickness, and thermal management all conspire against you. For unsupported walls, thickness jumps to 0.8–1.0mm minimum.
EBM runs thicker powder layers, so minimum wall thickness is roughly 0.7–0.8mm. The larger melt pool means you can’t get away with thin walls that DMLS allows, but EBM is faster and more forgiving of slightly out-of-spec powder. DED is coarser still—expect 1.5–2.0mm minimum walls. DED is better suited to larger features, thicker walls, and repair work where you don’t need micro-detail.
Overhangs are the single biggest headache in powder bed AM. The conventional wisdom says don’t design unsupported overhangs steeper than 45 degrees from horizontal. That’s directionally correct, but it oversimplifies. Avoid 30–45 degree unsupported overhangs. If you must have an aggressive angle, either make it steeper than 50 degrees, use a support structure, or design it to be post-machined with 0.5–1.0mm stock added.
Supports anchor the part to the build platform, manage thermal gradients to prevent distortion, and hold up overhangs. Support density matters—too few and the part warps off the platform mid-build, too many and you’re wasting material and creating scars during removal. For DMLS, space supports 8–15mm apart depending on material. Inconel needs denser support than titanium because it shrinks more. Linear supports are fastest to design and remove. Lattice supports distribute loads better but take longer.
Z-direction is weakest—layer bonding is imperfect, so parts built tall in Z have lower strength in that direction. If your part carries a critical load in Z, consider rotating it. XY tolerance is typically ±0.3–0.5mm while Z tolerance is ±0.5–1.0mm. If you need a tight-tolerance hole, orient it in XY. Thin walls should face the scanner—walls perpendicular to the laser scan direction are harder to control.
You design a part with an internal cavity for weight savings. The printer pours powder into that cavity during setup. It prints, gets cleaned, and you realize the internal powder can’t come out. Rule: any internal void must have at least one hole of 2mm diameter minimum to allow powder escape. If you truly need a sealed cavity, print it open, machine a hole, then have it welded closed.
If your part will be machined, add 0.5–1.0mm stock to those features. Don’t expect the AM machine to hold 0.1mm tolerance. Design datum surfaces that are flat, accessible, at least 15mm x 15mm for clamping, and perpendicular or parallel to critical features. For holes tighter than ±0.2mm, leave them undersized and machine to final size. Print a counterbore and tap threads by hand—don’t try to print internal threads.
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