A　class　of　3D　printed　waveguide　structures　is　presented　based　on　the　epoxy　coating.　An　arbitrary　3D　structure　of　a　waveguide　system　is　designed　and　fabricated　by　3D　printing　technique.　Then,　the　whole　structure　is　dipped　into　a　low　viscosity　solution　of　silver　epoxy　and　Isopropanol　in　order　to　coat　a　conductor　layer　on　the　inner　surfaces　of　the　waveguides.　The　ordinary　coaxial　cables　are　used　to　feed　the　system.　As　an　example,　the　coaxial　to　waveguide　adapter　as　a　main　building　block　of　most　waveguide　systems　are　fabricated　in　the　X-band　and　measured　in　a　back-to-back　setup.　In　comparison　with　the　conventional　metal　waveguides,　the　loss　is　slightly　higher　but　the　weight　and　cost　of　are　much　less.　©　2017　Applied　Computational　Electromagnetics　Society.