Cracking resin prints (hollow parts and post-curing)
Cracks can show up during the print, a few hours later, or after post-curing. During printing they usually come from suction or trapped resin in hollow parts. After printing, they're commonly linked to trapped uncured resin, stress from over-curing, or leaving parts in alcohol too long.
Most likely causes (in order)
- Trapped resin in hollow parts: Uncured resin sealed inside can push outward or leak and crack the shell.
- Suction during printing: A cavity facing the FEP stresses walls on every peel.
- Over-curing after printing: Long UV post-curing makes many resins more brittle and can add stress to thin or uneven walls.
- Long alcohol soaks: Leaving prints in IPA for a long time can soften the surface and contribute to cracking for some resins.
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. |
| Post-cure time | Follow the resin maker's recommended cure time; avoid long extra curing | Over-curing can make parts brittle. |
| Washing | Wash only as long as needed, then let parts dry fully before curing | Prolonged solvent exposure and curing while wet can cause defects. |
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
- Add drain holes and fully drain/rinse hollow parts
- Reorient so cavities don't face the FEP
- Dry parts completely before UV curing
- Stick to the resin maker's wash and cure times
- Consider a tougher or more flexible resin blend for thin parts
FAQ
Why did my resin print crack days later?
A common cause is uncured resin trapped inside a hollow part. Over-curing and leftover solvent can also contribute.
Does curing longer make resin prints stronger?
Not indefinitely. Past the recommended cure time, many resins just get more brittle.
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
- Lychee Docs: Volcanoes
- Liqcreate: 10 common resin 3D printing fails and how to solve them
- Ameralabs: Resin 3D Printing Troubleshooting Guide
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.