Predictive-adaptive temperature control of molten glass

The temperature of molten glass is critical for the production of glass containers on automated moulding machines. The temperature of the glass determines the quantity of glass in the gob which is placed in the mould and thus affects the quality of the finished container. There are frequent temperature fluctuations in the glass as it exits the main furnace and three PID-controlled heat/cool sections are required to stabilize the temperature before the gobs are cut for the moulds. The long response time of these loops, combined with production rate changes and the physical changes in the glass as a function of temperature, make PID control difficult. This paper discusses the application of a new predictive-adaptive controller for the temperature control. The new controller was able to reduce temperature settling times following set point or production rate changes from 4 to 6 hours to between 2 to 3 hours. This control improvement resulted in a significant reduction in rejected containers as well as less maintenance and controller re-tuning.