A flexible 3D printing feedstock material is disclosed. The flexible 3D printing feedstock material includes 45-80 vol % of a powder having at least one of a metal powder and a ceramic powder, 0-5 vol % of a compatibilizer, 10-35 vol % of a soluble flexibilizer, and 5-35 vol % of a non-soluble binder component. Methods of forming the flexible 3D printing feedstock material by melt mixing the components are disclosed. Methods of producing a 3D printed part by operating a fused deposition modeling 3D printer loaded with a filament formed of the 3D printing feedstock material are also disclosed.