Firmware here: https://github.com/monstermark3d/PrintrbotMultiMaterial Forum location: http://forum.monstercafe.net/ Use this coupling; http://e3d-online.com/Mechanical/Bowden/Threaded-Bowden-Coupling-1.75mm-Filament or purchase from here in the US; https://www.filastruder.com/collections/e3d-spare-parts-and-accessories/products/bowden-couplings-all-types With 9/16" Lamp Nuts (1/8 Pipe thread)...So you dont have to tap your printed part. Like these from Ace Hardware; http://www.acehardware.com/product/index.jsp?productId=22307116&KPID=16230507&cid=CAPLA:G:Shopping_-_Catch_All_-_DT_-_RLSA&pla=pla_16230507&k_clickid=f3e0682e-adbb-4dff-99c4-f47e82ac7146