Orientation: A Printed Part Is Weakest Between Its Layers

Before orienting anything, ask what the part will actually have to resist. A bracket carries a bending load along its arm; a clip is bent open repeatedly; a spacer is squeezed. Then lay the part so the layers run ALONG the direction the load pulls, not across it. A tensile load pulling layer from layer is the one case where the weld is the only thing holding — and that is the case to avoid. Where the part has to be strong in two directions at once, it may be better printed in two pieces and joined, or printed at 45 degrees as a compromise. Recognising that a single orientation cannot satisfy both is the useful step.

The face touching the plate comes out flat and smooth. Top faces come out smooth if they have enough solid layers. Slanted and curved faces show stepping, because a curve is being approximated by a stack of flat layers. So put the face that matters — the one that will be seen, or that has to seal — flat against the plate or horizontal at the top. Everything else is a compromise made deliberately. Holes are the special case. A hole whose axis is VERTICAL comes out round and accurate; a hole printed with its axis horizontal comes out as an arch that sags at the top and is measurably out of round. Orienting for holes is often worth more than orienting for appearance.

Print the same small part in two orientations and break them both. It takes an hour and it settles the question for your printer, your filament and your settings — which published figures cannot. Break them the same way, with the same lever arm, and note what force it took, even roughly. Two readings that differ by a factor of two are unambiguous; two that differ by 10% are within the noise and need repeating. Keep the broken pieces and look at the fracture. A break that follows a clean layer line across the whole face is a layer adhesion failure; a ragged break through the material is the plastic itself giving way, which means orientation is no longer the limiting factor.