Hollowing 3D Models for Resin Printing: Technique and Software
Preparing a file for a resin printer requires an essential technical step: converting a solid volume into a hollow shell. This process, called shelling or hollowing, defines a uniform wall thickness and is fundamental for optimizing work with photosensitive resins. 🧪
Why Hollowing Your Models is Crucial
The main goal is not only to save a significant amount of material, but also to avoid critical problems during printing. A solid model can generate excessive internal pressure when separating from the tank bottom (suction cup effect), leading to layer failures or deformations. By creating a hollow structure, the final weight is reduced and these risks are drastically mitigated.
Key Advantages of Hollowing:- Save Material: You consume less resin, making each piece cheaper.
- Reduce Weight: Final pieces are lighter and more manageable.
- Minimize Failures: Avoids pressure buildup and suction issues that break layers.
A hollow model without drainage holes is like a boat without a bottom: it technically floats, but only until you start using it.
The Critical Importance of Drainage Holes
Creating the shell is only half the job. For the model to print and wash correctly, it is essential to add drainage holes. These openings allow uncured liquid resin to escape from the interior during printing and, afterward, during washing with isopropyl alcohol. If the resin gets trapped, it can expand when curing with subsequent UV light, cracking the piece or leaving soft areas that compromise its integrity. They should be placed in non-visible areas, like the base, and with a sufficient diameter for adequate flow. 🕳️
Software and Practical Steps to Perform Hollowing
Most slicer programs specialized in resin integrate automatic tools for this purpose. Applications like Chitubox, Lychee Slicer, or PrusaSlicer allow defining the wall thickness, which typically ranges between 1.5 and 3 millimeters depending on the model size, and automatically generate the internal shell.
Recommended Workflow:- Use the slicer's hollowing tool, adjusting the wall thickness.
- Add drainage holes manually in strategic locations.
- Verify and repair the mesh with specific tools to ensure it is a "manifold" mesh (without inverted faces or invalid geometry).
It is vital to inspect the resulting mesh. A common mistake is trusting automation without checking. A damaged mesh can cause the slicer to misinterpret the geometry and the print to fail. The mesh should always be repaired before proceeding to slicing. ✅