Disclosed herein is a method of electroforming a needle cannula (100) for an injection device, wherein the electroforming method is performed in an electroforming system (1) comprising a cathode (10), an anode (60) and an electrolyte (50) with dissolved metal ions, wherein the method comprises providing a permanent mandrel (10), wherein the mandrel is configured to constitute the cathode. The mandrel (10) comprises a forming portion (20) having a forming surface (21, 22, 23, 24, 25, 26) adapted to form an inner surface of the needle cannula (100), wherein the forming portion (20) comprises a cylindrical axis (A), a longitudinal extension, a first proximal end (16) and a second distal end (17). The method further comprises electrodepositing a metal or metal alloy on the forming surface (21, 22, 23, 24, 25, 26) of the mandrel, where the electrodeposited metal or metal alloy is corresponding to the metal ions dissolved in the electrolyte (50), and whereby the electrodeposited metal or metal alloy is forming a needle cannula (100) on the mandrel (10), and separating the mandrel (10) from the formed needle cannula (100) by moving the mandrel (10) and the electroformed needle cannula relative to each other. Further disclosed is a method of producing different cannula features as composite structures (301, 302, 303, 304, 305) and interlock structures (105, 106, 107, 152, 153).