SLS TPU opens up gaskets, cushioning and grips, but it doesn’t behave like nylon. On the Formlabs community forum, a Fuse 1 operator in Denver described TPU clumping in the hopper so often, sometimes every 5 to 20 minutes, that they couldn’t leave the printer for half an hour without a short feed. Here’s what operators and vendor guidance say about printing and handling TPU powder.
Why does TPU powder clump in the hopper?
Formlabs’ TPU 90A support page says the Fuse 1 is sensitive to powder jams. It recommends filling the hopper with only slightly more powder than the job needs, because extra weight can cause clumping and underdosing. It also recommends printing smaller jobs and stirring the powder before printing. A forum reply noted that the Fuse 1+ has a built-in agitator. For high-volume TPU work, factor the machine generation and job size into your schedule.
Can you tune hardness from one powder?
On the Fuse 1+ 30W, yes, according to Formlabs. Its r/FormlabsOfficial post says the Print Settings Editor can produce parts as soft as 38 Shore A from TPU 90A Powder. Increasing fill hatch spacing has the biggest effect, and lowering fill laser power adds to it. Formlabs publishes downloadable settings for 40A, 50A, 60A and 80A.
What’s the catch with softer settings?
Formlabs warns that softer parts are less dense and more foam-like. That affects mechanical properties and watertightness. At extreme settings, some features may not resolve and surfaces can look fuzzy or crumbly. Test parts for the application before promising a durometer to a customer.
How is depowdering TPU different?
Formlabs’ TPU 90A support page recommends:
- Sifting while the powder cake is still warm but safe to handle, ideally 35–40°C. Unpacking at room temperature can leave powder caked on.
- Using the 150 micron sifter mesh, mesh-clearing balls and a gloved hand to work powder through.
- Blasting with 40–50 grit (313–387 µm) glass media, larger than its usual recommendation, for better finish and faster cleaning.
Formlabs also notes TPU parts don’t form the semi-sintered “Surface Armor” shell that stiffer powders do, so depowdering is simpler, but blasting is still recommended.
Does SLS TPU need separate equipment?
Formlabs says switching a Fuse printer to TPU 90A is possible but recommends a dedicated printer, Sift and build chamber. TPU 90A prints in air without an inert atmosphere.
What about print defects?
For bands and similar defects, Formlabs suggests reducing the bed temperature target in 1–1.5°C steps.
How should this affect scheduling?
Because TPU depowders best warm, plan the unpack for when someone is available. Treat TPU as its own material workflow with its own timing in your schedule, so it doesn’t sit and cool in the chamber.
Related on the Solvi blog: SLS Material Changeover: Is Switching Powders Worth It?; Depowdering SLS and MJF Parts: When Is Automation Worth It?.
Sources: Formlabs TPU 90A support page; Formlabs TPU 90A launch post; Formlabs community forum “TPU clumping in Fuse 1” thread; Formlabs r/FormlabsOfficial softer TPU post.