I began building a proof of concept to print concrete in a sand matrix but never got that device working properly. It had a 6x6 array of 2“ square nozzles but I

I began building a proof of concept to print concrete in a sand matrix but never got that device working properly. It had a 6x6 array of 2“ square nozzles but I ran into problems with the mechanism to switch the nozzles between sand and concrete. I designed a second version that would have had better switching mechanism, but couldn't afford to build it.