This article deals with designing a compact head for 3D printing using Fused Layer Modelling technology, better known as Fused Deposition Modelling (FDM) registered by Stratasys. Technically this technology is an extrusion process, which is very popular e.g. with the RepRap community. The aim is to design a print head based on commercially available basic components for printing two different materials, i.e. to allow control of an extrusion process for each material separately. It also has to be possible to switch nozzles with various diameters. The entire structure of the head should preferably be compact and lightweight to facilitate easy installation into the 3D printer.