How to 3D print a candle mold (two-part)

To 3D print a candle mold, you turn a candle shape (an STL) into a rigid two-part mold with alignment keys and a pour opening, print it, center a wick inside, and pour wax. The catch that trips people up is heat: molten wax is hotter than PLA can comfortably take, so filament choice matters. Get that right and a two-part printed mold makes clean, repeatable pillar candles.

What you're making

A two-part candle mold is a rigid mold in two halves that clamp together, with a pour opening at what becomes the bottom of the candle and a channel for the wick. You pour wax directly into it, let it set, then open the halves and release the candle. It suits pillar and shaped candles that can pull apart cleanly along a seam.

Design it in the mold generator

Load your candle STL into the two-part box mold generator and set:

• Wall thickness — enough to stay rigid and hold heat without bowing.
• Alignment keys — tongue-and-groove seals liquids best (good for thin wax); pins are simpler for chunkier shapes.
• Pour spout / opening — position it over a flat area so the base pours and sits level.
• Clearance — a touch of clearance so the halves close cleanly and open again after casting.

Heat matters — pick the right filament

This is the make-or-break step. Wax is poured hot — commonly around 57–79 °C for soy and up to roughly 80 °C for paraffin, pillar blends, and beeswax — while PLA starts to soften near 60 °C. So hot wax can warp or distort a PLA mold, especially with paraffin or pillar pours. Your options, safest first:

• Cast a silicone mold from the print (best for hot or repeat pours). Use the printed part as a master to make a flexible silicone mold, then pour wax into the silicone — it easily takes wax temperatures and releases beautifully. See which mold to print for that workflow.
• Print in PETG (or ABS/ASA) for direct wax casting — they tolerate more heat than PLA — and pour at the low end of your wax's range.
• PLA only for cooler pours (low-temp soy), and even then expect limited mold life. For paraffin, don't rely on PLA.

Print the mold

Print the halves flat with the seam faces down for accuracy. Because it holds liquid wax, aim for a watertight print: extra perimeters and solid enough walls that wax can't weep through layer lines — the same watertight habits as a silicone mold box. No supports are needed for a simple two-part mold; a snug key fit keeps the halves aligned.

Wick and pour

1. Center the wick. Thread a wick through the base hole and hold it taut and centered — tie the top to a stick laid across the opening so it stays put while the wax sets.
2. Clamp and seal. Close the halves, band or clamp them, and seal the seam and wick hole with a little removable clay so wax can't leak.
3. Apply release if you're pouring into a rigid printed mold, to ease demolding.
4. Pour at the wax's recommended temperature — follow your exact wax's datasheet, and keep it toward the low end for a PETG mold. Pour steadily to limit air pockets.
5. Cool slowly at room temperature. A second top-up pour fills the sink well that often forms as wax contracts.

Demold and finish

Once the candle is fully set and cool, unclamp and open the halves. Trim the seam line with a knife or gently smooth it, level the base, and trim the wick to length. Let pillar candles cure a day or two before burning for a cleaner flame.

Troubleshooting

• Wax leaks at the seam: add tongue-and-groove keys, clamp tighter, and seal the seam with clay before pouring.
• Mold warped or softened: the wax was too hot for the plastic — switch to PETG or a silicone mold, and pour cooler.
• Sink hole on the base: normal wax shrinkage — do a second top-up pour once the first has partly set.
• Off-center wick: anchor it at the base hole and tie the top across the opening so it can't drift.

FAQ

PLA or PETG for a candle mold?

PETG (or ABS/ASA) for direct wax casting — PLA softens around 60 °C, below many wax pour temperatures. For the most durable option, cast a silicone mold from the printed master and pour wax into that.

How do I keep the wick centered?

Anchor it through the base hole and tie the top to a stick or pencil laid across the pour opening, keeping it taut down the center while the wax cools.

Why did my mold warp?

The wax was hotter than the filament could handle. Pour at the low end of your wax's range, use a heat-tolerant filament, or switch to a silicone mold.