Hollow models: when they make sense and when infill is enough

Why a cavity is made

In resin printing a part is hollowed to save expensive resin and reduce stress. With FDM you do not need to. The slicer makes the outer walls and fills the inside with a sparse pattern set by the infill percentage. In practice it is the same cavity, only with a lattice that holds the walls up.

So you can upload a solid model as it is and choose the strength in the calculator.

Our strength settings

• Light, 10% infill: the least material, suited to decorations and light objects.
• Standard, 15% infill: ordinary objects, boxes, holders.
• Strong, 40% infill: parts that carry a load, such as handles and levers.

When a cavity is worse

If you hollow out the inside yourself and leave thin walls, you get a hollow part without infill, whose strength depends only on the wall thickness. With a thin wall under 1 mm it is fragile. A closed cavity without an opening is fine for FDM, since the printer bridges it. But if the roof of the cavity is wide, it needs supports, and they cannot get out of a closed cavity, so they stay inside.

The drain holes for letting out uncured resin that you know from SLA are not needed here. We do not print resin.

A common mistake is to hollow the model yourself and leave the walls thin. You end up with a part whose strength depends only on the wall thickness, and with a wall under 1 mm it is fragile. If you want to save material, choose light strength rather than trying your own cavity.

What to do when ordering

Send the model solid, as it is. If you want to save material, choose light strength with 10% infill. If you want a hollowed shape for a function, such as a container, look at wall thickness and check it is strong enough. You see the price per piece right after uploading and it is based on real grams.