Molding device and molding method for optical fiber preform

A molding method for an optical fiber preform, the molding method comprising:

• preparing:
• enabling a cylinder mold to pass through a heating jacket, connecting and fixing a first end of the cylinder mold to a first driving shaft of two driving shafts through a first annular fastener, and placing an end cylinder in the cylinder mold, turning on the heating jacket, performing heat preservation at 200-350° C. for 0.5-1 h, and placing a second driving shaft of the two driving shafts in an electric furnace for heat preservation at 200-350° C. for 0.5-1 h;
• melting:
• melting cladding glass and core glass successively in a melting furnace, wherein the cladding glass is weighed quantitatively based on a core diameter of the optical fiber preform;
• pouring the molten cladding glass:
• placing the cylinder mold with an opening at a second end of the cylinder mold facing upwards vertically after the first end of the cylinder mold is connected and fixed, pouring the molten cladding glass into the cylinder mold, taking out the second driving shaft, and connecting and fixing the second driving shaft to the second end of the cylinder mold through a second annular fastener;
• rotating:
• maintaining the cylinder mold and the two driving shafts in a vertical state, and rotating the two driving shafts at a rotational speed of 3000 r/min, waiting for 5-10 s and laying the cylinder mold and the two driving shafts stably, continuing to keep the cylinder mold for heat preservation at 200-350° C., and turning off the heating jacket to enable the cylinder mold to be cool naturally after the cylinder mold is rotated for 3-60 min, wherein, upon rotation of the cylinder mold, a bottom die and an extrusion head are put into the electric furnace for heat preservation at 400-600° C. for 0.5-1 h in advance;
• mounting an annular gasket and a heat resisting cylinder:
• dismounting the first annular fastener and the second annular fastener at two sides of the cylinder mold, taking out the cylinder mold and placing the cylinder mold horizontally, pushing a cladding sleeve to the first end of the cylinder mold to replace the end cylinder with the annular gasket and enabling the annular gasket align with the first end of the cylinder mold, cutting off a narrow protrusion structure of the cladding sleeve to ensure that two ends of the cladding sleeve are of opening structures;
• and placing the heat resisting cylinder in the second end of the cylinder mold, and then placing the cylinder mold as a whole in the electric furnace for heat preservation at 200-450° C. for 0.5-1 h;
• mounting a top die, the extrusion head and the bottom die:
• taking out the bottom die from the electric furnace, pouring the molten core glass into the bottom die, taking out the extrusion head from the electric furnace and mounting the extrusion head on the bottom die, and taking out the cylinder mold and enabling the first end of the cylinder mold which is provided with the annular gasket to face upwards, placing the cylinder mold wholly and vertically, mounting the extrusion head at the second end which is a bottom end of the cylinder mold, and placing the top die at the first end which is a top end of the cylinder mold;
• extruding:
• transferring the cylinder mold installed with the top die, the extrusion head and the bottom die to a hydraulic machine, turning on the hydraulic machine and setting an extrusion speed to be 0.4-5 mm/s;
• extruding the molten core glass reversely into the cladding sleeve stably;
• stopping extruding in response to observation through the top die that the molten core glass overflows;
• remaining a position of the hydraulic machine unchanged, waiting for 30-300 s and taking out the cylinder mold;
• and transferring the cylinder mold into the electric furnace to be annealed for 3-6 h, and cooling the cylinder mold to room temperature in the electric furnace;
• and
• taking out a product:
• disassembling the cylinder mold and taking out the optical fiber preform.