Under a Protolabs video on strong SLS parts, a viewer was unimpressed that 3D Hubs’ SLS ran 100 microns in Z. Other systems, they said, do 50 or even 25, and “at 100 micron it makes it hard to print threads.” I can’t confirm those finer numbers, but the complaint about SLS layer thickness and threads is worth unpacking.
What SLS layer thickness do common machines use?
Around a tenth of a millimeter. Formlabs lists 110 microns for the Fuse 1, Fuse 1+ 30W and Fuse X1. HP’s Jet Fusion 5200 brochure lists a layer thickness of 0.08 mm for its MJF machines. So the viewer’s 100 microns is about normal for powder-bed nylon, not a cheap setting.
Is the layer number fixed?
Not always, and HP’s own spec sheet shows it. The 5200’s headline building speed, up to 5,058 cm³ per hour, is footnoted as based on HP PA 12 at a 0.11 mm layer thickness and 8.45 seconds per layer. That’s a different number from the 0.08 mm in the same table. When a bureau quotes a layer height, ask which mode they’re running before you compare it with another shop.
Why does layer height matter for threads?
Because a thread’s flank is a shallow slope, and slopes show steps. A thread standing upright in Z has its flanks cut into stair steps one layer tall. Lay the same thread horizontally and the steps show around the circumference instead. Thinner layers make the steps smaller, but a 0.08–0.11 mm step is still there on a fine pitch.
It’s also why the hardware question usually comes down to design rather than machine choice. Coarse threads print better than fine ones, and many shops skip printed threads on small sizes entirely.
What should you do instead of chasing thinner layers?
Design for the layer you’ve got. Use a coarser pitch where you can, and model the thread slightly loose so the stepped flanks don’t bind. For anything that has to seal or carry load, print a hole and add a threaded insert or tap it after printing.
How do you check your bureau’s real resolution?
Print a test bar with the thread you plan to use in both orientations, upright and lying flat, and screw a real fastener into each. Pick the orientation that runs smoothly and write it on the drawing so every reorder matches.
Related on the Solvi blog: MJF Threads: Print Them, Tap Them, or Use Inserts?; MJF Tolerances: Clearance for Holes and Nut Pockets; MJF vs SLS Parts: What Should a Bureau Tell Customers?.
Sources: YouTube: SLS strong functional parts hang test (Protolabs), viewer comment; Formlabs Fuse series tech specs; HP Jet Fusion 5200 Series brochure (PDF).