What are the precautions for sensor installation in hot runner systems?

To ensure precise temperature measurement and long-term stable system operation, precautions for sensor installation in hot runner systems include limiting the distance from the heater, avoiding direct contact, applying thermal grease, making sure the installation is secure, and performing routine inspections.

 

1. Important Installation Safety Measures

An explanation of precautions

Keep the thermal coupling distance between 10 and 20 mm. A distance that is too near can lead to localized overheating, while a distance that is too far would produce a delayed response. The acceptable range is 15 mm ± 5 mm.

Keep the sensor and heater away from one another. Avoid overheating caused by metal-to-metal conduction, which can cause damage or aging of the sensor. Use heat insulation or leave a tiny opening.

Use thermal grease with a high temperature. To increase heat conduction efficiency and decrease temperature measurement latency, apply a tiny bit of thermal grease between the sensor and the mounting hole.

Make sure the installation is tight. To avoid loosening as a result of vibration or thermal expansion and contraction, tighten the fastening threads with the proper torque.

Steer clear of dead-angle and high-stress locations. To guaranty representative temperature reading, the installation site should be remote from dead angles in melt flow and mechanical impact zones.

Practical Tip: Several temperature measuring holes can be set aside for initial installation to facilitate positional adjustment and data comparison during debugging.

 

2. Systems with several cavities and unique operating circumstances

Symmetrical arrangement: To guaranty temperature homogeneity in multi-nozzle systems, the sensor locations in each channel should be the same;

Increased spacing in high-power areas: To avoid thermal shock, spaces with heating power greater than 300 W/in² should be spaced at least 18 mm apart.

Accurate placement in small component systems: Temperature monitoring must be reinforced even if the distance is reduced to 10–12 mm due to space constraints.

Case study: The temperature fluctuation dropped from ±6°C to ±1.8°C and the product yield increased by 12% when the sensor in an automobile part mold was changed from 8mm to 15mm.

 

3. Maintenance Suggestions and Post-Installation Verification

Infrared Thermal Imager Scanning: Use an infrared thermometer to examine the surface temperature distribution and verify that there are no "hot spots" or unusual gradients during the trial molding phase.

TUS Oven Temperature Uniformity Test: To confirm that the sensor locations are representative, conduct multi-point temperature measurements in accordance with the AMS 2750 standard.

Frequent Shutdown Inspection: Every quarter, check the wiring for oxidation and loosening, and reapply thermal grease if needed.

Create Location Records: For simple troubleshooting and process duplication, note the distance, depth, and angle parameters of each sensor.

"Reasonable spacing + good contact + regular verification" is a safety principle that is necessary for long-term, dependable temperature regulation.