Why Hollowing Is the Hidden Key to Big Resin Prints
Solid models waste resin, increase print time and risk excessive shrinkage. Hollowing a model makes large prints affordable, but it only works if you handle drainage holes correctly. Get the holes wrong and you can literally crack a part open with trapped resin.
What a Resin Trap Is
A resin trap is an enclosed pocket inside a hollowed model. Uncured resin or air becomes sealed inside, causing three problems: the pocket acts as a cup that drags against the release film (suction), trapped resin hardens unpredictably, and cleaning the cavity is nearly impossible.
Planning Drainage Holes
- Minimum 2 holes per sealed cavity — one to let resin in/out and one to let air escape.
- Diameter — start with 3–5 mm; larger holes drain faster but leave visible pucks on the surface.
- Placement — put one hole at the lowest point of the cavity (in print orientation) and a vent higher up.
- Avoid support-only pucks — place holes on non-critical faces or where you can blend them later.
Step-by-Step Workflow
| Step | Action |
|---|---|
| 1 | Select the model in your slicer and apply the hollow tool (internal offset 1.5–2 mm). |
| 2 | Enable 'drainage holes' and add 2+ holes per cavity. |
| 3 | Orient the part so at least one hole points toward the build plate. |
| 4 | After printing, flush the cavity with IPA (isopropyl alcohol) and check flow. |
| 5 | Cure, then fill the visible holes with matching resin and post-cure again. |
Thin-Wall Warning
An internal offset below 1 mm can produce thin walls that crack during cleaning or curing. On large parts, bump the offset to 2.2 mm or more, and add internal supports if your slicer offers them.
Recommended Resin
For hollowing experiments we like the forgiving behaviour of ANTINSKY Standard Lite Resin 1 kg. Its low-viscosity formulation drains cleanly through tight holes and cures with crisp detail, making it a great starting point before you move to tougher blends.