Most shops inspect parts going out the door. Far fewer inspect incoming SLS powder. A Fuse user on the Formlabs forum learned why that’s backwards when a fresh Nylon 12 GF delivery showed up looking wrong.
What should you check on incoming SLS powder?
The seal, the powder and anything that isn’t powder. In this case, all 20 containers had gold-discolored aluminum foil seals that looked heat-exposed, and two seals weren’t bonded to the container at all. Opening them got worse: 15 of 20 had visible clumps, which the user had never seen in earlier GF deliveries. Four had foreign material in them. Only five looked acceptable at first glance.
Another member did the math. At 3 kg per container, that’s well over $5,000 of powder that could fail builds if it went into the hopper.
What was the foreign material?
Probably bits of the seal. One commenter thought the flecks looked like aluminum foil that tore and crumbled on opening. The user suspected the seals were overheated during sealing, leaving the backing too brittle to peel cleanly. Nobody in the thread could explain the clumps.
How did it get resolved?
Better than you’d fear. The user opened a support case, and Formlabs arranged a free replacement shipment. It then found that all its remaining stock came from the same batch, blocked that batch from distribution, and started a root-cause investigation. Clean stock was expected in about three weeks. The user praised the support team for being open and quick this time.
Three weeks is a long gap if you run GF every day. Keep enough sealed stock from a known-good lot to cover that.
How do you store it once it passes?
Sinterit’s storage guidance for its PA12 Smooth works as a baseline for any nylon. Keep it around 23 °C and 50% humidity, and lower is better. Store it in a sealed dry box, don’t leave containers open, and don’t let powder sit in the printer for more than a couple of hours. Sinterit also suggests a few moisture absorbers in the storage container, but not in the printer.
What does a receiving check look like?
It takes five minutes per delivery. Photograph every seal before opening, write the lot number on your job traveler, and pour a scoop from each container onto a dark tray to look for clumps and flecks. If anything looks off, quarantine the whole lot and send the photos with your claim. A sealed container you didn’t open is your strongest evidence.
Related on the Solvi blog: SLS TPU: How to Print and Depowder Flexible Parts; MJF Humidity: How Room Conditions Affect Your Builds; SLS Material Changeover: Is Switching Powders Worth It?.
Sources: Formlabs forum Nylon 12 GF delivery thread; Sinterit PA12 Smooth storage guidance.