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High-quality hot runner systems are an essential factor in the injection molding
Nov 09, 2018

High-quality hot runner systems are an essential factor in the injection molding of stable, high-quality components. For hot runner systems, one of the most important properties is temperature uniformity. In a hot runner system with excellent performance, the temperature should be consistent and will not change over time.


However, no matter how well a hot runner system is designed, it can't work properly without a temperature controller. Despite this, the importance of temperature controllers is often overlooked. In addition, if the temperature control system is not matched with the hot runner system, regardless of whether the temperature controller will display the problem in time, it will adversely affect the temperature uniformity of the hot runner system.


Proper control of the temperature of the hot runner system is a dynamic task because during the injection molding process, the entire hot runner system produces varying amounts of shear heat, and the temperature controller handles this sudden, non-uniform heat. How the increment responds directly determines whether the various parts of the hot runner system can return to the same temperature before the next injection.


If the hot runner system does not return to the same temperature as before the next injection, it will affect the consistency between the injections. Although there are many factors that determine the performance of the temperature controller, the relatively key factors mainly include the following aspects.


algorithm


Most temperature controllers use a PID algorithm to adjust the output power to maintain the set temperature. Some controllers use more advanced PIDD control, which can be more quickly after the temperature of the hot runner system is disturbed. Bring the temperature of the hot runner system back to the set point.


Response time


The response time of a temperature controller is determined by comparing the temperature reading to the set temperature and the time it takes to make a power adjustment based on this. The shorter the response time, the faster the temperature controller can react and the smaller the hot runner system is affected by temperature disturbances.


Adjustment


The response produced by different areas of the temperature controller varies widely depending on the portion of the hot runner that they control. Therefore, adjusting the control area and setting the correct algorithm constants has become a very important task.


Some temperature controllers have preset constants, and if there is any area in the hot runner system that is not properly controlled, these constants can be manually changed; others will adjust themselves when they are first turned on; Other controllers can continuously adjust themselves to better control the hot runner system after the hot runner has reached the set point and withstand the temperature changes caused by the molding process.


Output voltage control type


There are two basic types of temperature controller output voltage control. Many temperature controllers use on/off type voltage control, which is achieved by varying the percentage of time that full voltage is applied. This control method can cause temperature fluctuations and shorten the life of the heater.


While other temperature controllers start with a phase angle, such voltage control continues to transmit power and change the output voltage to the desired value.


Thermocouple resolution


The last factor to consider is the resolution of the thermocouple, which determines the increment of the measured temperature reading. Some temperature controllers measure a resolution of 1 ° C, and some temperature controller measurements and response differences can be as small as 0.1 ° C.


In view of the important role of the temperature controller in the operation of the hot runner system, adequate preparation should be done before selecting the temperature controller.


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