How to calibrate the temperature display of a hot runner temperature control chamber

A very important step in making sure that injection molding processes are steady and product quality is always high is calibrating the temperature display in a hot runner temperature control chamber. The most accurate way to calibrate is to use a standard temperature source to compare the two devices as a whole, and then make changes to both the sensor and the digital display instrument so that the shown value is within ±1℃ of the actual temperature. Here are the exact methods and technical details about how to operate:




I. Getting ready for calibration



Check the status of the equipment



Make sure that the heater, temperature control box, and thermocouples are all connected correctly and are not loose or broken.



Make that the power supply voltage is stable (AC 220V±10%) and that the grounding is good.



Get typical tools ready



Use a portable thermometer or a standard thermometer that has been certified by a metrology lab (accuracy ±0.1℃).



A constant temperature oil bath or normal heat source device is optional, although it will help keep the temperature stable.



Choose calibration points



Choose three points within the normal range of process temperatures, like 200°C, 250°C, and 300°C.



Avoid calibrating at very high or low temperatures to keep equipment from breaking down.











II. Ways to calibrate: the overall method and the split method



1. Overall calibration method (recommended)



Good for quick calibration on-site, showing the whole system fault.



Put the standard temperature probe and the original thermocouple next to each other in the same temperature detecting port, making sure they are in contact with each other.



Set the temperature control chamber to heat up to the desired temperature (for example, 250°C) and wait 10 minutes for the temperature to stabilize.



Check the display value on the temperature control chamber against the standard instrument reading.



If the difference is within the acceptable range (±1°C), write it down.



Change the "Temperature Correction Value" (Offset) in the menu if it goes beyond the limit.



Set the adjustment value to -3° if the display indicates 253° and the standard is 250°.



Check again after calibration to make sure the inaccuracy is less than ±0.5℃.



2. Different Calibration Method (Need for High Precision)



Good for calibrating in a lab or factory, as well as testing the sensor and temperature controller individually.



To calibrate the sensor, put the thermocouple in a standard constant temperature bath and see if its output signal matches the K/J type calibration chart.



Calibration of the temperature controller: Connect a potentiometer to a standard millivolt signal and see if the displayed value is correct.



This procedure needs special tools and is only good for inspections that happen every so often.







III. Changing the temperature through the menu



Most temperature control units can use software to make up for mistakes. The process is as follows:



To enter parameter setting mode, press and hold the "SET" key.



Use the up and down arrow keys to identify the "SV" parameter, which is either "Offset" or "Temperature Correction." Type in the deviation value, such -3 or +2. Press "SET" for a short time to save and leave.



Note: The way things work may be a little different between brands. Please see the "Temperature Calibration" part of the manual.







IV. Checking and recording after calibration



Verification at More Than One Point



To make sure the linearity is good, do the test again at different temperature points.



Check to see if the response time is normal and avoid lag.



Set up the calibration file



Write down the date of calibration, the standard equipment number, the error values before and after calibration, and the name of the person who did it.



It is best to calibrate every 6 to 12 months, or every 3 months for particularly precise situations.



Managing Labels



Put a green label on the item with the expiration date after it has been properly calibrated.



Equipment that isn't qualified should be taken out of service and fixed.