METHOD FOR DRAWING GLASS PREFORM

PROBLEM TO BE SOLVED: To provide a method for drawing a glass preform by which the glass preform is drawn to make the deviation of the outside diameter in the longitudinal direction small without causing troubles such as the damage of a grasping part or a dummy rod. SOLUTION: The method for drawing the glass preform is carried out by holding the upper and lower ends of the glass preform 41 respectively with a chuck 47 for feeding the preform and a chuck 55 for receiving the preform, heating and softening the glass preform 41 while moving the chuck 47 for feeding the preform and the chuck 55 for receiving the preform to draw the glass preform 41 to have preliminarily set aimed outside diameter. A control formula including proportional gain for controlling the movement speed of the chuck 47 for feeding the preform and the chuck 55 for receiving the preform corresponding to the difference between the measured outside diameter in the middle of the drawing of the glass preform 41 and the aimed outside diameter is used and the movement speed of the chuck 47 for feeding the preform and the chuck 55 for receiving the preform are controlled to conform the measured outside diameter with the aimed outside diameter and the proportional gain is gradually increased from the start of the drawing of the glass preform 41 to the finishing of the drawing. COPYRIGHT: (C)2011,JPO&INPIT