Best filament for molds: rigid and smooth

The short answerPETG for easy molds. ABS for smooth molds.

A mold must be rigid, smooth, and release cleanly. PETG is the easy pick for a rigid mold. ABS gives the smoothest surface and acetone smoothing. PLA is too brittle for a mold you reuse.

What a mold asks of a filament

A mold holds its shape under pressure and releases the cast cleanly, so it needs rigidity and a smooth surface. Layer lines transfer to the cast, so a smooth print matters. PLA is too brittle for a reuse mold.

How the materials compare

When to pick PETG

Pick PETG for an easy, rigid mold. It prints without a heated chamber at 240 to 260 °C and holds its shape. Sand and seal the surface before you cast, because layer lines transfer to the part.

When to pick ABS

Pick ABS for the smoothest mold. It takes acetone smoothing, which melts the layer lines into a glass surface that releases cleanly. The Polymaker ABS sheet lists a nozzle of 245 to 265 °C, and ABS prints the rigid walls a mold needs.

For the materials, read the PETG guide or ABS guide. For other functional parts, see best filament for functional parts.