◆ Concrete
A 150 mm concrete breeze block with four round openings, from a silicone mold you pour yourself. Screens, planter fronts and shelves.
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A silicone mold for a mid-century concrete breeze block, 150 by 150 mm and 50 mm deep, with four round openings 50 mm across and a small diamond in the middle, every edge rounded 3 mm. One block takes 800 ml, about 1760 g in concrete.
Made with our tray mold generator in its flexible silicone tray mode: print one part, a caster, pour silicone into it and peel it out. That silicone is the block mold. The openings are silicone posts 50 mm tall, which would grip a rigid printed mold; silicone peels off them. The block is cast face down, so the front comes off the smooth floor.
Stack and glue a few into a small screen wall, a garden planter front or a tealight shelf, or use one as a book end or a plant stand. The zip carries the printed caster exactly as the tool exported it, the block on its own as an STL, the master uploaded to the tool, and a print and pour sheet with the silicone figure the tool measured.
Shown as a 3D render of the printed caster beside the silicone mold it pours, with a concrete breeze block in front, not a photo.
Print the caster as exported, open side up, no supports. PLA is fine.
Set it on a level surface. Mix 962 ml of silicone in one batch and pour it into one corner in a thin stream until it covers the raised block to the rim. Tap the caster for a minute and let it cure as long as its datasheet says.
Peel the cured silicone out of the caster. That silicone is your mold, with the four openings as posts standing in it.
Brush a little release over the mold, then fill it with a fine concrete with some sand in it. Vibrate it, a sander against the side works, until no more bubbles rise, and strike the back flat.
Cover it and leave it 48 hours, then peel the silicone off the posts first and then off the sides. Let the block cure a week before it carries weight or goes outside.
Print details
| Cast material | Concrete |
|---|---|
| Printed parts | 1 |
| Size (W x D x H) | 171 x 171 x 64 mm |
| Print bed needed | 171 x 171 mm, 64 mm tall |
| Filament | ~658 g |
| Layer height | 0.2 mm |
| Infill | 15% |
| Supports | Not needed |
| Download | ZIP: printed caster (STL) + one breeze block (STL) + tool master (STL) + print and pour sheet |
| Added | 2026-10-30 |
Made with the free Tray mold generator. Upload your own model and get the same kind of mold built around it, in your browser.
ZIP: printed caster (STL) + one breeze block (STL) + tool master (STL) + print and pour sheet
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 ice cube tray mold guide.
For a low decorative screen or a planter front, yes, glued or mortared and on a firm footing. They are 50 mm deep, thinner than a building block, so do not use them as a load-bearing or retaining wall. Seal them for outdoor use.
Lay them in a stack bond (each block straight above the one below) and join them with a thin bed of construction adhesive or a fine mortar, about 5 mm. For more than four rows, run a threaded rod through the openings at the ends for stiffness.
The master is in the zip. Upload it to the tray tool, scale it and download a new caster in a minute. A 150 mm block is the largest that comfortably fits a common printer bed with the silicone wall round it; for bigger blocks, print the caster on a large bed.
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