Under Everything SLS’s video on part orientation for the SLS4ALL Inova, one viewer stated flatly that “the best orientation is 45/45 deg.” The creator pushed back: 45 degrees shows more layer lines and isn’t as strong. The viewer’s reply was more useful than his first comment. Sharp edges face up, curves face down, big flat faces go to 45, “unless strength is more important than a flat surface.” That’s the real answer on SLS part orientation. There’s no single best angle.
Is there one best SLS part orientation?
No. Formlabs says orientation and placement can reduce visible layers, reduce warping or fit more parts in the chamber, and that getting the best print may take a few iterations. You pick the angle for the feature that matters most.
What does each choice buy you?
For looks, Formlabs recommends putting cosmetic surfaces at 0, 45 or 90 degrees to the XY plane. Surfaces at a shallow angle are the ones that show layer lines. Its design guide adds that rounded faces come out smoother facing down, while features that need a crisp edge should face up.
For accuracy, the same guide says holes and pins are most accurate with their axes in Z. Wide, flat, high-aspect-ratio parts should sit at about 20 degrees to reduce warping.
Placement matters as much as angle. Parts near the edges of the build cool fastest and warp most, so thin, flat parts belong near the center of the chamber and the middle of its height. Formlabs also asks for at least 5 mm between parts.
How much strength does orientation cost?
Enough to plan around. In EOS PA 2200 data, as published by the bureau Evology, PA12 printed with the Balance parameter set reaches 48 MPa tensile strength in X and Y but 42 MPa in Z. Elongation at break drops from 18% to 4%. On filled powders the gap matters more: Formlabs warns that Nylon 12 GF is notably brittle across layers and says features needing strength should lie in the XY plane.
How should you decide?
Write down the one property the customer will reject the part for, whether that’s a cosmetic face, a bore or a snap arm, and orient for that. If a snap arm or clip has to flex, lay it flat in XY even if a face ends up at a shallow angle, then fix the look in finishing.
Related on the Solvi blog: MJF Warping: Why Large Flat Parts Warp; SLS Fine Detail: How Small Can Features Go?; SLS Minimum Wall Thickness: How Thin Is Too Thin?.
Sources: YouTube: SLS4ALL Inova part orientation (Everything SLS), viewer comments and replies; Formlabs: Model orientation best practices for SLS printing; Formlabs: Fuse Series SLS design guide; Evology: PA12 Nylon 12 SLS datasheet, EOS PA 2200 values (PDF).