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How to choose the right temperature controller for the hot runner?
Jun 05, 2018

For injection molding a stable and high-quality part, a good hot runner system is an essential and critical factor. One of the most important properties for hot runner systems is the temperature uniformity. In a good hot runner system, the temperature should always be consistent and not change over time.


However, no matter how well a hot runner system is carefully designed, normal operation cannot be performed without a temperature controller. Despite this, the importance of temperature controllers is often overlooked. In addition, if the temperature controller matched with the hot runner system is not matched, the temperature uniformity of the hot runner system will be adversely affected regardless of whether the temperature controller will promptly display the problem.


Reasonably controlling the temperature of the hot runner system is a dynamic task because during the injection molding process, the entire hot runner system will produce different amounts of shear heat, and the temperature controller will respond to this abrupt, non-uniform heat. How the increment responds directly determines whether parts of the hot runner system can return to the same temperature as they had before the next injection.


If the hot runner system cannot return to the same temperature as before, the consistency between injections will be affected. Although there are many factors that determine the performance of the temperature controller, the relative key factors mainly include the following aspects.

300s controller for hot runner.jpg

1.algorithm

Most temperature controllers use a PID algorithm to adjust the output power to maintain the set temperature, and some controllers use more advanced PIDD control. This temperature controller can be more quickly after the temperature of the hot runner system is disturbed. Return the hot runner system temperature to the set point.

2.Response time

The response time of a temperature controller is determined by comparing the temperature reading with the set temperature and based on the time taken for power adjustment. The shorter the response time, the faster the temperature controller can react and the less affected the thermal runner system is by the temperature disturbance.

3.Adjustment

The response generated by different areas of the temperature controller varies greatly, depending on the portion of the hot runner 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. If any area in the hot runner system is not properly controlled, these constants can be changed manually; other controllers will adjust themselves when they are turned on for the first time; There are also some controllers that have reached the set point in the hot runner and are able to continuously adjust themselves to better control the hot runner system after undergoing temperature changes caused by the molding process.

4.Output voltage control type

There are two basic types of output voltage control for temperature controllers. Many temperature controllers use on/off type voltage control. This type of control is achieved by changing the percentage of time the full voltage is applied. This control method may cause temperature fluctuations and shorten the life of the heater.

Other temperature controllers start with phase angle. Such voltage control will continue to send power and change the output voltage to the desired value.

5.Thermocouple resolution

The last factor to consider is the resolution of the thermocouple, which determines the increment of the temperature reading measured. Some temperature controllers have a resolution of 1°C, and some temperature controller measurements and responses 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, sufficient preparation should be made before selecting the temperature controller

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