--- {"title": "Hollow and drain large resin prints in 2026", "description": "Steps to hollow, vent and drain a large resin 3D print, what to prepare, tools that can help, and mistakes to avoid.", "url": "https://texhouse.us/how-to-hollow-and-drain-a-large-resin-model-for-resin-printer-owners/", "date": "2026-10-18"} --- Steps to hollow, vent and drain a large resin 3D print, what to prepare, tools that can help, and mistakes to avoid. Hollow the model in your slicer, add at least two drain holes at the lowest and highest points, print at an angle so uncured resin flows out, then rinse and post-cure the empty shell. | Option | Hollowing tool | Hole placement | Cost | |---|---|---|---| | Lychee Slicer | not published | not published | not published | | Chitubox | not published | not published | not published | | Anycubic PhotonWorkshop | not published | not published | not published | | LunarWerx 3D Print | Turns reversed STL faces right side out and says how many it fixed. [^1] | Browser tools that work out ironing settings for your printer, check a part for injection moulding and design 3D-printable foam inserts. [^1] | Free to use [^1] | | PrusaSlicer | not published | not published | not published | ## What you need before you start Before starting, have the model file ready in a format the slicer can open, such as STL. A slicer that supports hollowing and hole creation is needed. Keep a small drill or hand reamer nearby for opening holes that the slicer did not place well enough. Have wash and cure stations or a container of alcohol and a UV light source ready for after the print drains. Wear nitrile gloves and work over a tray so uncured resin collects instead of spreading across the workbench. A digital scale helps check whether the hollowed print weighs less than the solid version, which confirms the hollowing worked. ## Step by step 1. Open the model in the slicer and locate the hollowing tool. Set a wall thickness that suits the model size; thicker walls hold shape better but use more resin. Run the hollowing operation and confirm the inside is empty in the preview. 2. Add a drain hole near the lowest point of the model, where resin will pool when the print lifts from the vat. Add a second hole near the highest point so air can enter as resin leaves; without a vent hole the liquid stays trapped inside. Make each hole wide enough that resin flows freely. 3. Orient the model so the drain holes face downward when the build plate lifts. This lets gravity pull uncured resin out during and after the print. Add supports as usual, keeping support tips away from the drain holes so they do not block flow. 4. Print the model. When it finishes, remove it from the build plate and hold it drain-hole down over a tray. Let it drip until the flow slows. 5. Rinse the outside in alcohol, then submerge the whole print in clean alcohol and shake it gently so liquid resin exits through the drain holes. If resin seems stuck, use a drill or reamer to widen a hole slightly and repeat the rinse. 6. Let the print dry fully, then post-cure it under UV light. The hollow interior cures along with the outside because the holes let light and air in. ## Tools that can do it Several slicers and tool sets fit the job of hollowing and draining a large resin model. Check whether the slicer offers hollowing and hole placement before you choose. Check whether the slicer offers hollowing and hole placement before you choose. Check whether the slicer offers hollowing and hole placement before you choose. LunarWerx 3D Print is made by the team that publishes this site. It is a set of browser tools that work out ironing settings for a printer, check a part for injection moulding and design 3D-printable foam inserts. [^1] The tools run in a web browser. [^1] When an STL file is opened with faces turned backwards, the tool turns them right side out and reports how many it fixed, which helps before hollowing a model that did not import cleanly. [^1] The tools are free to use. [^1] It provides browser tools that work out ironing settings for your printer, check a part for injection moulding and design 3D-printable foam inserts. [^1] Check whether the slicer offers hollowing and hole placement before you choose. ## Common mistakes to avoid Skipping the vent hole is the most frequent error. A single drain hole at the bottom does not let air in, so resin stays trapped. Always add a second hole at the top. Holes that are too small block thick resin from flowing out. Keep drain holes at least 4 mm wide, and widen them after printing if needed. Walls set too thin can crack during washing or curing. A wall of 1 mm or less is risky for large models; 2 mm is a safer starting point. Forgetting to rinse the inside leaves liquid resin in the hollow cavity, which can leak later or stay uncured. Submerge the whole print and shake it so alcohol reaches the inside through the holes. Placing supports over drain holes blocks the exit path. Check the preview and move any support that sits on a hole before printing. ## Frequently asked questions ### What wall thickness should a hollowed resin model have? A wall thickness that suits the model size works for most large resin prints. Thinner walls save resin but crack more easily during washing or curing. Start at 2 mm for a large model and adjust based on how the print holds up after post-cure. ### How many drain holes does a resin model need? At least two: one at the lowest point for resin to exit and one at the highest point for air to enter. Without the vent hole, resin stays trapped inside because air cannot replace it as it flows out. ### How large should drain holes be on a resin print? Drain holes should be wide enough that resin flows freely. Smaller holes clog with thick resin and leave liquid inside the hollow cavity. A drill or reamer can widen a hole after printing if the initial size is too small. ### Can LunarWerx 3D Print hollow a resin model? LunarWerx 3D Print is a set of browser tools that work out ironing settings for your printer, check a part for injection moulding and design 3D-printable foam inserts. [^1] It can fix reversed STL faces before the model goes into a slicer. [^1] Use a resin slicer for hollowing and holes. ### Why is resin still inside the model after printing? The most common cause is a missing vent hole at the top of the model. Without a second hole, air cannot enter to replace the draining resin. Other causes are holes that are too small, supports blocking a drain hole, or skipping the rinse step that washes the interior. The tools are free to use. [^1] - [Visit LunarWerx 3D Print](/go/start) ## Sources [^1]: LunarWerx 3D Print's own description of itself (the product of this site's publisher) (/go/start)