◆ Concrete
Hexagon concrete planter mold
A hexagon planter, 90 mm across the flats, to cast in concrete with even 8 mm walls. A silicone mold kit from printed parts.
◆ Concrete
A hexagon planter, 90 mm across the flats, to cast in concrete with even 8 mm walls. A silicone mold kit from printed parts.
A hexagonal planter 90 mm across the flats at the rim and 76 mm at the foot, 80 mm tall, with rounded corners and a small chamfer round the rim. The well follows the hexagon with an even 8 mm wall over an 11 mm floor, and a 10 mm drainage hole runs through the middle.
Made with the box mode of our silicone mold maker in its round shape, the mode the tool itself suggests for this low, wide pot. Print the base with the planter fused onto it, the two walls and the two clamps, and pour about 1130 ml of silicone. It fills the well and becomes the core, with a pin that forms the drainage hole, so each cast comes out hollow and drained.
The pot widens toward the rim, so the cured block gets one straight slit down its side to let each cast out, and the printed walls hold it shut for the next pour. Hexagons stand flat against each other, so a set of three in different pigments makes a tidy windowsill group. The zip carries every printed part, the planter master as its own STL, the tool's own print-settings sheet and a recipe file for the generator.
Shown as a 3D render of the printed mold parts pulled apart around the master, not a photo.
Print the base with the master fused onto it, the two walls and the two clamps.
Stand the base on the table. Set each wall down a few centimetres out from it and slide it in over the table until the ridge round the base sits in the groove at its foot, then slide the clamps down over the seams. Once they are on, the walls cannot lift, and the ridge seals the bottom.
Mix 1210 ml of silicone in one batch and pour it in a thin stream down the inside of a wall, letting it rise round the master and into its well until it covers the top.
Once it has cured, take the clamps off and slide the walls straight out. The planter is wider higher up than at its foot, so cut one straight slit down the side of the block with a sharp knife, from the open face to about 10 mm short of the top, open it like a book and lift the master out.
Turn the block over and stand it back inside the walls with the clamps on, which hold the slit shut. The opening is the foot of the planter, with the silicone core standing up in the middle and the drainage pin on its tip.
Mix a fine concrete or Jesmonite a little wetter than for a slab, pour it slowly down one side of the ring round the core, and tap the walls for a minute to raise the air. Fill level with the opening and strike it flat, wiping the tip of the drainage pin clean.
Leave it to cure for a day, take the walls off, open the slit, peel the silicone off the outside and twist the planter off the core. Sand the foot flat and seal it.
Print details
| Cast material | Concrete |
|---|---|
| Printed parts | 5 |
| Size (W x D x H) | 130 x 130 x 118 mm |
| Print bed needed | 153 x 130 mm, 118 mm tall |
| Filament | ~357 g |
| Layer height | 0.2 mm |
| Infill | 15% |
| Supports | Not needed |
| Download | ZIP: 5 printed parts (STL) + planter master (STL) + print sheet + recipe |
| Added | 2026-09-26 |
Pro early access until October 26, 2026, then free with any account.
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Free for personal use. Selling the pieces you cast needs a commercial licence (Pro or Founder); passing on the file itself is not permitted on any plan. Full terms.
New to casting? Read the silicone mold maker guide.
Yes, flat to flat. Each one is 90 mm across the flats at the rim, so a row or a cluster of three meets rim to rim, with the gaps opening toward the foot where each pot narrows to 76 mm. Cast them in two or three pigments and raise one on a board for a staggered display.
Because the well is the same hexagon, 8 mm in from the outside and drafted with it. An even wall cures evenly, so it is less likely to crack at a thick corner, and it takes 405 g of concrete where a round well inside a hexagon would leave heavy corners.
Add a powder pigment for concrete at 2 to 5% of the cement weight and mix it into the dry mix before the water, or use Jesmonite pigment at the rate on the tub. For a marbled look, fold a second colour in with two or three strokes just before you pour.
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