A method of manufacturing a fin, comprising the steps of:
- preparing a set of sectional molds consisting of a stationary lower mold half having a lower mold cavity, and a reciprocatingly movable upper mold half having an upper mold cavity, the lower and the upper mold cavity together defining a mold cavity for injection molding a blade portion and a foot pocket portion of a fin at the same time;
- a first injection port being provided on the lower mold half within an area of the lower mold cavity for forming the blade portion, and a second injection port being provided at a mold joint of the lower and the upper mold half to communicate with an area of the mold cavity at where the foot pocket portion is to be injection-molded;
- and a first and a second material injecting unit having two different types of molding materials loaded therein being located close to the first and the second injection port, respectively;
- and the first and second material injecting units being independently adjustable in injection time and pressure thereof;
- moving the upper mold half toward the lower mold half to close the set of sectional molds;
- moving the first and the second material injecting unit for them to align with and closely connect to the first and the second injection port, respectively;
- regulated the first and the second material injecting unit independently regulated in advance to the required injection pressure;
- to enable injection of the two types of raw materials to complete at the same time, injecting the molding materials loaded in the first and second material injecting units, respectively, into the mold cavity via the first and second injection ports for injection-molding the blade portion and the foot pocket portion of the fin at the same time, so that the two different types of molding materials are filled into predetermined positions and integrated into one injection-molded body of the fin in the mold cavity;
- wherien the molding materials are different types of materials, they have different flow rates in the semi-liquid molten state, wherein after completion of the injection, the area in the mold cavity of the closed sectional molds for forming the blade portion of the fin is filled with the first raw material, and the area for forming the foot pocket portion of the fin is filled with the second raw material;
- bonding the two types of raw materials injected into the closed mold cavity;
- melting the first and second raw material in a semi-liquid molten state, the first and second raw material being tightly joined at an interface between them to ensure an optimal bonding strength between the blade portion and the foot pocket portion and accordingly an extended usable life of the finished product of fin;
- moving the upper mold half away from the lower mold half to open the set of sectional molds;
- removing the integrated body of the fin from the mold cavity;
- and
- trimming off molded heads formed at the first and the second injection ports to obtain a finished product of the injection-molded fin;
- wherein the two types of molding materials are differently colored.