SLS cooldown is dead time every operator wants to shorten. On the Formlabs community forum, a new Fuse 1 owner asked exactly that: the manual warns that skipping the cooling time causes distortion and poorer material properties, but they wanted to pull a job early. “Is there a temperature at which the parts can be removed early without much risk?” The trade-off is warp, and the vendor has published test data on it.
What happens if you unpack too hot?
Formlabs tested this on its Fuse 1+ 30W with Nylon 12 Powder, a fully packed chamber at 15% pack density, unpacking identical builds at temperatures from 100°C down to 25°C. Parts unpacked hotter warped more. Many builds unpacked at 100°C showed double the warp of those unpacked at room temperature.
Is there a safe SLS cooldown threshold?
For that setup, Formlabs found parts unpacked at 50°C weren’t significantly more warped than those at room temperature. Parts unpacked above 70°C warped consistently, and the Fuse Sift warns users who insert a chamber that hot. Formlabs recommends scheduling a full cooldown to 50°C if possible, and between 50 and 70°C at minimum.
Which parts need longer?
Formlabs calls out long, thin parts with their longest dimension in Z. Builds with those parts typically need to stay in the printer until 50°C. It also says shops that print these parts often should test their own threshold, since it varies with pack density, material and geometry.
What did the forum say?
A Formlabs staff reply in that thread pointed to the cooling guide and said the build chamber should be at or below 100°C before handling parts. That’s about safe handling, not warp. For lowest warp risk, Formlabs’ support page says to cool to 50°C or lower, typically about 30–50% of the build time.
What do operators actually do?
In a separate Formlabs forum thread on packing, one production user shared their own thresholds based on the Sift’s display: about 35°C for rush chambers, 29°C for a standard job and 23°C for very delicate parts. They noted the display doesn’t show the core temperature of the powder cake, which is still warm inside. Treat these as one shop’s experience.
Does this apply to other printers?
Not directly. These numbers come from Formlabs’ own printer and powder. Industrial SLS systems have their own cooling procedures, so follow the manufacturer’s guidance and test before changing your process.
How do you get throughput back?
- Cool outside the printer when your system supports removing the chamber, so the next build can start.
- Keep warp-prone parts away from chamber corners.
- Run a test build to find your own unpack threshold per material.
- Schedule unpacking by chamber temperature, not clock time, and build cooldown into quoted lead times.
Related on the Solvi blog: MJF Cooling: Natural or Fast, How Should a Bureau Decide?; SLS Orange Peel: Why It Happens and How to Fix It; SLS Powder Cleanup: How to Keep Dust Under Control.
Sources: Formlabs forum “Fuse 1 cooling time”; Formlabs forum “Can you teach me packing for the Fuse 1+?”; Formlabs “Fuse Series Cooldown Recommendations”; Formlabs “Cooling a build chamber before cleaning prints”.