Printing a model as a hollow object conserves material and decreases print time, but it can also be a functional requirement. Starting with PreForm 3.41.0, you can hollow your models in PreForm.

The hollowing operation is based on the topology of the model. If your model is a union of multiple smaller pieces rather than a single defined body, PreForm hollows each piece, which may lead to unexpected results.

When hollowing a model, add drainage holes to prevent suction cups (SLA) and to prevent material from becoming trapped inside the part (SLA and SLS).

Check the design specifications for 3D models for your printer to find requirements for minimum supported wall thickness.

To hollow models using the Hollow tool:

1. Click Hollow on the toolbar to the left of the 3D scene. The Hollow panel appears.

2. Set your desired Wall Thickness. Model regions thinner than twice the selected Wall Thickness will not be hollowed.
3. Use the Feature Size and Accuracy parameters to set the level of detail for the inner surface of the hollowed model.
   • Feature Size: Reducing it smooths internal surfaces, but PreForm may take longer to hollow the model and generate a larger FORM file.
   • Accuracy: How closely internal features match outer features depending on Wall Thickness. Increasing Accuracy improves the quality of the internal surfaces of the hollowed model, but it may take longer to hollow the model.

4. To hollow all open models, ensure that no models are selected and click Hollow All.
5. Select one or more models and click Hollow Selected to hollow only the selected models.
• Click Reset All or Reset Selected to restore the original models.