A mandrel for molding polymer valve leaflets for heart valve prostheses is disclosed, including a body portion including an outer surface with ridges and contoured surfaces corresponding to the leaflets, the upper edge of the contoured surfaces corresponding to the free upper edge of the leaflets, and the mandrel including a mandrel extension above the body portion, and a gap extending around the mandrel between the upper edge of the contoured surface and the mandrel extension. A process for producing these polymer valve leaflets is also disclosed by dip coating with this mandrel and removing the polymer film created at the gap, preferably by applying suction or blowing thereto.