How to Use a Hot Runner Temperature Sensor

A hot runner temperature sensor is an important part of injection molding systems that need to control temperature very accurately. Its job is to keep an eye on the melt temperature in the hot runner in real time and send the signal back to the temperature control chamber. This makes sure that the plastic is in the best state for melting. Using the sensor correctly not only makes the quality of the products more consistent, but it also makes the equipment last longer and lowers the amount of scrap. Here is a comprehensive user manual based on how things really work:




I. Getting Ready to Use: Make sure everything is set up and connected correctly



Check the model and specs of the sensor



Make sure the type is a K-type thermocouple or PT100 platinum resistance thermometer that works with the temperature control box's input needs.



Make that the probe's diameter (usually between 1.5 and 3 mm) and length (80, 100, or 120 mm, etc.) fit in the space where the mold will be installed.



Check the dimensions of the mounting holes and the mating surfaces.



To avoid increased thermal resistance that might cause temperature measurement lag, mounting holes should be clean and free of carbon deposits and oil stains.



The hole's diameter must be the same as the sensor's outside diameter. If it's too loose, it will affect how heat moves through it, and if it's too tight, it will break easily.



Check the polarity and wiring method



The red wire is positive and the white wire is negative on the thermocouple. If the connection is reversed, the temperature display will be wrong. The T100 uses three wires to make up for mistakes in wire resistance. Make sure the A/B/C connections are wired correctly.



First Tests:



To measure resistance, use a multimeter. At room temperature (20°C), PT100 is about 109.7Ω. A K-type thermocouple gives off about 4.1mV for every 100°C. Use a megohmmeter to assess the insulation resistance. It should be more than 20MΩ to keep leaks from interfering.







II. Installation and Operation Specifications: Making sure the temperature readings are accurate and the structure is stable



Choose a good place to install it:



Stay away from the edge of the heating coil, the channels for cooling water, and the "dead zones" for melt flow.



Put the placement first at the intersection of the main flow channel and the branch channels to make sure the temperature is accurate.



Do not put it near the pressure ring, sealing ring, or on the outside of the hot runner body.



Make sure the insertion depth is right:



The depth of the insertion should be enough to keep the circuit safe. 8 to 10 times the diameter of the pipe (at least 12mm)



To avoid sluggish reaction because of bad contact, the sensing end must be fully submerged in the molten flow field.



Use methods like angled insertion or counter-current installation.



If there is enough room, a 45° angled insertion can be employed. This will make the insertion longer and less likely to injure the end.



Install against the flow direction while measuring gas temperature to make sure it makes full contact.



It is very important to seal and insulate things correctly.



To stop high-pressure molten material from leaking, use ceramic sealing rings or gaskets that can handle high temperatures.



To keep hot and cold air from compromising the accuracy of temperature measurements, the space between the mounting hole and the protective pipe should be filled with refractory putty or asbestos rope.



To protect against electromagnetic interference, the wiring must be separate.



Signal lines must not be run in the same conduit as heating cables and should utilize double-shielded cables. To keep electrical lines from... Noise Interference Measurement Accuracy, the shielding layer should be grounded at only one location.







III. Keeping an eye on operations and managing maintenance



Verification of Initial Operation



After a frigid start, slowly raise the temperature and see if the trend of the temperature rise stays the same.



If the difference is more than ±1°C, you need to recalibrate the thermometer.



Calibration on a regular basis



Every six to twelve months, it is best to do on-site calibration. Calibration is needed every three months for high-precision production, including making medical and electronic parts. You can calibrate by putting the standard probe and the original sensor next to each other and changing the temperature control box correction value.



Daily Maintenance Tasks



Every three to six months, clean the probe surface of any oil and carbon buildup.



Look for wiring terminals that are loose or have rust on them.



To keep track of status, record calibration data, runtime, and fault history.



Handling that is not normal



Check the circuit continuity when a "open circuit" warning goes off.



When the temperature changes a lot, look into what is causing the electromagnetic interference.



If the response is slow, look for carbon buildup or not enough insertion depth.