Figure 72 is a schematic diagram of a manufacturing process. The diagram shows a cube shaped tank three quarter filled with liquid polymer. Two sides of the tank have been cut away to reveal what is happening inside the liquid. About half way down there is a platform, perforated with holes, with vertical direction arrows underneath it pointing down. A partially constructed model of a boat's propeller is shown resting on the platform. Imagine the propeller resting on the platform such that its axis of rotation is vertical and the level of liquid polymer only reaches part way up the sides of the blades and central cone. The parts of the propeller above this level do not exist. A rectangular shaped object is shown sweeping to and fro across the surface of the liquid polymer. It is not labelled. Situated above the tank there is a cylindrical objected labelled 'Laser', two discs labelled 'Lenses' and an inclined rectangle labelled 'Steerable mirror'. There is a double headed direction arrow indicating that the mirror can be tilted at different angles. The laser, lenses and steerable mirror are in a horizontal row above the tank. A line representing the laser beam is shown leaving the laser, going through the lenses and then reaching the mirror. The beam is reflected from the mirror down to the surface of the liquid in the tank where it makes contact with the model of the propeller.