Holes, craters and cupping in resin prints
'Cupping' is the general name for problems caused by cup-shaped geometry. Any concave area that faces the FEP traps resin and creates suction on every lift. Common results are holes, craters, thin torn walls, or rough over-grown patches.
Most likely causes (in order)
- Cup-shaped areas facing the FEP: Helmets, shields, bowls, and bases printed open-side-down create a vacuum during peel.
- Hollowed models without vents: No path for air means pressure builds on each layer.
- Resin not flowing back in time: Thick or cold resin and no rest time make it worse.
Settings to change
| Setting | Change | Why |
|---|---|---|
| Hollowing | Add at least two drain holes (one near plate, one far) or print solid | Prevents suction cups and trapped resin (Lychee: Volcanoes). |
| Orientation | Orient so no enclosed cavity faces the FEP | Cups create vacuum during peel. |
| Wait before cure (rest after retract) | Add/increase rest time before each exposure (a few seconds; longer for thick resin) | Lets resin flow and the plate settle before curing. |
Exact values depend on your printer and resin. Start from the resin maker's recommended settings and change one thing at a time.
Quick checklist
- Find concave areas facing the FEP in your slicer and reorient
- Add vent/drain holes to hollow or cupped areas
- Add a rest time before exposure
- Warm the resin so it flows back quickly
FAQ
What is cupping in resin printing?
A cup-shaped area, open towards the FEP, that traps resin and creates suction during each lift. It causes holes, craters and blowouts.
How do I stop cupping?
Reorient so the concave side faces up or sideways, or add vent holes so air can get in.
Not sure which one you've got?
Upload 1–4 photos of the failed print and PrintCleric ranks the likely causes and tells you exactly which settings to change, with sources.
Sources
Related fixes
- Layer separation / delamination in resin prints
- Failed supports: model stuck to the FEP, only supports printed
- Nothing on the build plate (print stuck to the FEP)
- Suction cups and blowouts (volcanoes) in hollow resin prints
- Elephant's foot (flared bottom layers)
- Blooming and over-exposure: soft details and rough surfaces
Wear nitrile gloves and eye protection when handling uncured resin, and work in a ventilated space.