SLS orange peel is a rough, pitted texture on vertical surfaces that makes a good part look cheap. On the Formlabs community forum, Fuse 1+ owners swap notes on it regularly. The usual question: why does it show up on some builds and not others, and how do you stop it without wasting powder?
What causes orange peel?
Formlabs’ support documentation lists the common causes: incorrect bed temperature, laser output reduced by dirty optics, parts placed too close to the chamber walls, print settings that aren’t tuned for surface finish, and powder degradation from extended use. Research on PA-based SLS powders backs up the powder link. Material that has been repeatedly exposed to heat gets more viscous when it melts, and a higher share of recycled powder raises the risk of an orange-peel surface.
Is refresh rate the main lever?
Often. Formlabs explains that a lower refresh rate (less fresh powder) is cheaper but can raise the defect rate. If maintenance and settings don’t fix the problem, it suggests raising the refresh rate in 10% steps, up to a maximum of 50% or 70% depending on the material. One forum user said they almost always got orange peel printing 100% used powder.
Why do builds with low packing density make it worse?
A forum user explained that when packing volume roughly matches the refresh rate, used powder gets sintered into parts within a few cycles. With low packing density, the same old powder gets recycled over and over. Low-density builds can quietly age your powder supply.
What else causes SLS orange peel?
- Clean the laser windows and the IR sensor housing as part of scheduled maintenance.
- Re-tune the bed temperature for your material.
- Keep cosmetic surfaces away from the chamber walls. One user saw orange peel near the door, where the chamber runs cooler.
How do you stop guessing?
Track the refresh ratio, powder age and surface defects for every build so you can see the trend before customers do. Logging those values against each build in your MES or build records gives you the data to tie defects to their cause.
Related on the Solvi blog: SLS Nylon Yellowing: Why White Parts Turn Yellow; SLS Cooldown: How Hot Can You Unpack a Build?; MJF vs SLS Parts: What Should a Bureau Tell Customers?.
Sources: Formlabs support: orange peel; Formlabs support: diagnosing SLS print failures; Formlabs community forum thread; thesis research on PA3200 orange peel.