Control of melt spinline diameter and birefringence using a novel sensor

Process control techniques have been expanded to include polymer processing operations. This work demonstrated control of melt spinline diameter and birefringence in real-time on an operating spinline. Two control loops have been utilized—diameter and birefringence, respectively, controlled by the take-up velocity of the spinline. Control was accomplished using a prototyped novel sensor for on-line measurement of both diameter and birefringence. The sensor closed the control loop and also indicated spinline position and tension.

The growing awareness of the polymer processing industry to the advantages of applied process control has contributed greatly to the motivation of the project. The lack of process control research in the area of polymer processing, relative to the chemical industry, has given the inspiration for quickly developing new technology. Also, previous work (Lindenmeyer hypothesis) has indicated that energy perturbations of the spinline produce changes of the birefringence, so potential is offered for a new control variable. These changes have been confirmed and explored in this work.

Research on the melt spinline control demanded a minicomputer to serve as a data acquisition facility and controller. The computer interacts with the novel sensor to set parameters for analysis and recording of fiber diameter, birefringence, tension, and position. Also, the computer is used as a research data base for spinline modeling and optimization. Controlling algorithms are encoded in the computer's memory for manipulating a sound wave perturbation and take-up motor to maintain a specific setpoint of diameter or birefringence.

The on-line measurements and capabilities of the novel sensor interfaced with a minicomputer has established a highly functional real time research facility. The real time data acquisition can provide a research data base for process optimization and is a basis for continuing research of the Lindenmeyer hypothesis. Also, the control loop is closed and a research control facility for developing advanced multivariable control strategies has been established. A demonstration of its utility has been made with the successful control of diameter and birefringence.