Concrete Tetrapod Moulds

thingiverse

These are refined moulds for casting concrete tetrapods, based on the work of steyrc in https://www.thingiverse.com/thing:1845255. These versions are in four parts, not twelve, for ease of use and cleaner lines on the resulting castings, but the tradeoff is that it is harder to release them from the mould. I recommend using a resin printer with a very thin layer height, to maximise how smooth the inside of the mould is, and then spraying a release agent in there before you pour the concrete (I used Pol-Ease 2300). No supports should be needed - these have no serious overhangs when printed in the orientation they are provided in. For each tetrapod, print 3 "closed" parts and one "open" one, fasten the pieces together using six M5 or #10 machine screws and nuts, mix up your favourite concrete mix (I recommend a fine one with minimal or no aggregate - I used the US brand CementAll), pour, and wait for it to set. If you wait until the concrete is mostly set rather than completely, it's easier to demould the tetrapods and trim off any flashing that occurred around the joints. You'll need to figure out how long that is based on your mix, though!