SLS edge flashing is the rough, burr-like lip that sometimes forms along the edges of nylon parts. On the Formlabs community forum, an operator who had run Nylon 12 GF on a Fuse for over a year switched to Nylon 12 and found “major, unfinished looking burrs” on parts that printed cleanly in GF. Here is what the thread and Formlabs guidance point to.
What causes SLS edge flashing?
In this case, the main suspects were a bed temperature that was too hot and the laser exposure at part edges. The operator’s chamber offset was still +0.75 °C from the GF tune. When they finally ran Formlabs’ bed temperature tuning print, the results showed the printer running hot, and they planned to drop the offset to about −1.75 °C. Another experienced operator said they run their Fuse 1+ at −1.5 °C.
Does geometry play a part?
Yes. One forum member explained that an overhanging lip tends to form where an edge tapers to zero. The operator wondered if a small chamfer on sharp design edges would help. In this case, the burrs were on edges facing down in the chamber.
What did Formlabs recommend?
Formlabs’ services team recommended the v5.1 print settings. For finer control, they suggested enabling the Print Settings Editor and creating a custom setting with reduced “Perimeter Upskin” and “Perimeter Downskin” laser powers, which lowers exposure at the edges. Formlabs’ support pages recommend tuning bed temperature before printing Nylon 12 for the first time. The offset adjusts by up to ±5 °C in 0.25 °C steps, and two printers side by side may need different targets.
What should a bureau check first?
- Material change: re-run bed temperature tuning whenever you switch powders. Don’t carry over the old offset.
- Optics: one operator advised cleaning all the optics before calibrating, so dirty glass doesn’t skew the results.
- Print profile: test the current recommended settings before you edit laser powers.
- Design: flag knife edges at quote time and suggest a small chamfer.
How do you keep it from coming back?
Record the offset, profile and refresh rate for each printer and powder, along with the result. When flashing reappears, you can compare against a known-good build instead of starting over.
Related on the Solvi blog: SLS Orange Peel: Why It Happens and How to Fix It; SLS Cooldown: How Hot Can You Unpack a Build?; SLS Powder Cleanup: How to Keep Dust Under Control.
Sources: Formlabs forum “Nylon 12 Burr on edges” thread; Formlabs: Tuning bed temperature for Nylon 12; Formlabs: Adjusting the Bed Temperature Target.