In order to produce stable and high-quality parts through injection molding, a high-quality hot runner control system is a crucial factor. One of the most important characteristics of a hot runner control system is temperature uniformity. In a well-performing hot runner system, the temperature should remain consistent and not fluctuate over time.
However, no matter how well-designed a hot runner control system is, it cannot operate properly without a hot runner controller. Additionally, if the hot runner controller paired with the system is not compatible, it will adversely affect the temperature uniformity of the hot runner controller system, whether or not the hot runner controller displays any issues in time.
Properly controlling the temperature of the hot runner controller system is a dynamic task because, during the injection molding process, the entire hot runner control system generates varying amounts of shear heat. How the hot runner controller responds to this sudden, non-uniform heat increase directly determines whether the different parts of the hot runner controller system can return to the same temperature before the next injection.
If the hot runner controller system does not return to the same temperature before the next injection, it will affect consistency between injections. Although many factors influence the performance of a hot runner controller, the key factors include the following:
Most hot runner controllers use a PID algorithm to adjust the output power to maintain the set temperature, while some controllers use more advanced PIDD control. This type of hot runner controller can restore the hot runner controller system temperature to the set point more quickly after it is disturbed.
The response time of a hot runner controller is determined by the time it takes to compare the temperature reading with the set temperature and adjust the power accordingly. The shorter the response time, the faster the hot runner controller can react, thus reducing the impact of temperature disturbances on the hot runner controller system.
The response of different areas of the hot runner controller can vary significantly depending on the part of the hot runner it controls. Therefore, adjusting the control areas and setting the correct algorithm constants is a very important task.
Some hot runner controllers come with preset constants, and if any part of the hot runner controller system is not properly controlled, these constants can be manually adjusted. Other controllers automatically adjust themselves when powered on for the first time. Some controllers can continuously adjust themselves after the hot runner reaches the set point and undergoes temperature changes due to the molding process, allowing for better control of the hot runner controller system.
There are two basic types of output voltage control for hot runner controllers. Many hot runner controllers use on/off type voltage control, which achieves control by changing the percentage of time the full voltage is applied. This method may cause temperature fluctuations and shorten the heater's lifespan.
Other hot runner controllers use phase angle starting, where this type of voltage control continuously sends power and adjusts the output voltage to the required value.
The final factor to consider is the resolution of the thermocouple, which determines the temperature reading increment. Some hot runner controllers measure with a resolution of 1°C, while others measure and respond with differences as small as 0.1°C.
Given the important role of the hot runner controller in the operation of the hot runner controller system, thorough preparation should be done before selecting a hot runner controller.
