Principle of cold extrusion is similar to that of hot extrusion, which has been shown under hot extrusion in Fig. The dissimilarity is that material in hot working processes should possess the essential ductility with out the application of heat. Impact extrusion is also a cold extrusion process. It is used for making small components from ductile materials. Impact extrusion process is shown in Fig. Impact extrusion of material is accomplished where the work blank is placed in position over the die opening the punch forces the blank through the die opening causing material to flow plastically around the punch. The outside diameter of the tube is same as diameter of the die, and the thickness is controlled by the clearance between punch and die. Collapsible medicare tubes and toothpastes etc. are produced using this impact extrusion. Source A Textbook of Manufacturing Processes and Workshop Technology by Rajender Singh.