How to make a 3D printed ice cube tray

The right way to make a 3D printed ice cube tray is not to print the tray you freeze water in — it's to print a master of the cube shape, pour food-grade silicone around it, and use the flexible silicone mold for the ice. That gives you a food-safe, bendy tray that pops cubes out easily and can be any custom shape you like. You can print a rigid tray directly, but it comes with real caveats. Here's both routes, and why the silicone one wins for ice.

Why silicone, not a printed tray

Ice means water sitting against the mold for hours, then flexing to release — exactly where a rigid printed plastic tray struggles:

• Food contact: standard FDM plastic isn't a certified food-contact surface, and the grooves between layers are hard to keep clean (see are printed items food safe).
• Release: ice locks into a rigid cavity — you can't flex a hard tray to pop cubes out, so you end up running it under water.
• Durability: PLA in particular doesn't love constant water and freeze cycles.

Food-grade silicone solves all three: it's a certified food-contact material when you buy a food-safe rated silicone, it flexes so cubes pop right out, and it shrugs off water and freezing. So the printed part becomes a tool to make the silicone tray, not the tray itself.

Route 1 — Print a master, pour food-grade silicone (recommended)

Step 1 — Design the cube master

Model the shape you want your cubes to be — classic cubes, spheres, a logo, whatever — as a solid "positive." In the casting tray generator, upload that shape and switch to Silicone-pour mold mode: instead of a rigid tray, it builds a master with a surrounding trough that you pour silicone into. Give the shape gentle draft (sides that taper slightly) so the silicone — and later the ice — release cleanly.

Step 2 — Set the grid and trough

Choose how many cubes with the rows and columns, the gap between them, and the trough height — how far the walls rise above the master, which is your silicone headroom (a bit over the top of the cubes). Export the STL/3MF and print the trough-and-masters part in any filament; it never touches food, so PLA is fine here.

Step 3 — Pour food-grade silicone

• Use a food-safe / food-grade rated platinum-cure silicone (check the product is certified for food contact — this is the part that matters for ice).
• Mix by the maker's ratio, and consider a light release agent on the print for easy separation.
• Pour slowly into one corner so silicone rises around the masters without trapping air; a gentle tap settles bubbles.
• Let it fully cure, then flex the master out. You now have a soft, food-safe ice tray.

This is the same print-a-form-then-cast-silicone idea as a reusable silicone mold box — just laid out as a multi-cavity tray.

Route 2 — Print a rigid tray directly (with caveats)

If you just want a quick tray for non-food use — freezing paint, wax, resin blanks, or soap embeds — cast-tray's Rigid tray mode makes a printed tray you pour straight into. For actual edible ice it's a compromise: treat the plastic as not certified for food, add plenty of draft so cubes have a chance of releasing, print it watertight (see printing watertight), and expect to twist and run it under warm water to get cubes out. For food, the silicone route above is the honest recommendation.

Freezing and releasing

• Fill the silicone tray, freeze on a flat surface so it doesn't slump.
• To release, flex and push from the base — the whole point of silicone. Let it sit a minute at room temperature first if cubes are stubborn.
• Wash the silicone tray by hand or dishwasher (per the silicone's rating) and dry it.

FAQ

Can I freeze water directly in a 3D printed tray?

You can, but it's not ideal: printed plastic isn't a certified food surface, ice sticks in a rigid cavity, and PLA dislikes constant water. For edible ice, print a master and cast a food-grade silicone tray instead.

Which silicone do I use?

A silicone explicitly rated food-safe / food-grade (typically platinum-cure). That rating is what makes the finished tray safe for ice and food.

What shapes can I make?

Any solid shape you can model or download — cubes, spheres, letters, logos. Upload it as the master, and the tray is built around a grid of that shape.