Under Vision Miner’s long Fuse 1+ workflow video, one viewer asked what a lot of FDM shops wonder. Is SLS only better for shapes FDM can’t print, and for filling a whole build volume? And is there a strength comparison of FDM nylon 12 against SLS? It’s the right way to frame SLS vs FDM nylon, because geometry is only half of it.
Is SLS nylon actually stronger than FDM nylon?
Mostly in the Z direction, and that’s the part that matters. Formlabs’ Form Now comparison table lists SLS Nylon 12 at 50 MPa tensile strength against 42 MPa for FDM nylon, and 1.8 GPa flexural modulus against 1.2 GPa. The bigger difference is in the layer row. SLS is listed as isotropic, while FDM’s Z-axis layer bond is called a “common failure point.” Keep in mind it’s a vendor table and doesn’t name the FDM filament.
That’s the real answer for a functional bracket. An FDM nylon part can test fine in XY and then split along a layer line once it’s loaded the other way.
Is there more to it than strength?
Yes. Formlabs’ nylon guide points out that nylon filament warps much like ABS and soaks up moisture during long prints. Prusa’s material guide puts PA nozzle temperatures at 240–285 °C with a bed at 70–115 °C, and its PA page recommends an enclosure to fight warping. You’ll dial that in per spool. SLS needs no supports at all, since the powder holds the part up.
The trade is the equipment. Vision Miner quoted another viewer $25k for the Fuse 1+ and manual kit, and $53k for the full setup with Sift and Blast. FDM nylon has nothing like that entry cost.
SLS vs FDM nylon: which should you pick?
The viewer’s instinct was mostly right. SLS earns its keep on two things: parts that take load in every direction, and batches where you can fill a chamber. A one-off jig that’s only loaded flat in XY is an FDM job.
A quick way to decide: sketch the main load on the part. If it pulls across the layers you’d print on FDM, and you can’t reorient it to avoid that, quote it in SLS.
Related on the Solvi blog: MJF vs SLS Parts: What Should a Bureau Tell Customers?; PA11 vs PA12 on MJF: When Is PA11 Worth Running?; MJF Threads: Print Them, Tap Them, or Use Inserts?.
Sources: YouTube: Formlabs Fuse 1+ 30W workflow POV (Vision Miner), viewer question; Formlabs Form Now: Nylon 12 SLS material guide; Formlabs: Nylon 3D printing guide; Prusa filament material guide.