A quality hot runner system is critical to the injection molding of consistent, high quality parts. One of the most important performance aspects of a hot runner system is its temperature uniformity. The temperature should be consistent across the hot runner system and should not vary with time. Even slight variations in temperature can have a negative impact on part quality and consistency. Suppliers of high quality hot runner systems are aware of the importance of temperature uniformity and therefore design toward this goal. However, a well-designed hot runner system does not function without an often overlooked component, the temperature controller. Regardless of how well the hot runner system is designed, its temperature uniformity can suffer if paired with an inadequate controller whether or not the controller's display shows any indication of a problem. Properly controlling the temperature of a hot runner system is a dynamic task. During injection, shear heat is generated in varying amounts throughout the hot runner system. How well the temperature controller responds to this sudden non-uniform addition of heat will determine if the various segments of the hot runner are able to consistently return to the same temperature prior to the next shot. Failure to do so will result in shot-to-shot inconsistencies. Although there are many factors that determine how well a temperature controller performs, the most critical factors are the control algorithm, response time, tuning, type of output voltage control and thermocouple resolution.
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