Adjusting the sensor position in a hot runner requires avoiding high-shear zones, maintaining a distance of 10-20mm from the heater, and ensuring a stable and symmetrical installation to reduce frictional heat interference and improve temperature measurement accuracy.
1. Core Adjustment Principles
Avoid High-Shear Zones: Do not install the sensor at the nozzle tip, flow divider cone, or narrow runner inlet (<2mm). These areas generate significant frictional heat due to high-speed melt flow, leading to inaccurate temperature readings.
Choose a Location with Good Temperature Representativeness: Installation is recommended in the middle section of the main runner or the hot runner connection area. Here, melt flow is stable, temperature distribution is uniform, and local interference is minimal.
Maintain a Reasonable Thermal Coupling Distance: Maintain a distance of 15mm ± 5mm from the heater center to avoid conduction overheating or response lag.
Practical Value: In a medical catheter mold, after moving the sensor from the nozzle tip to the middle section of the main runner, the temperature fluctuation decreased from ±6℃ to ±1.8℃, and the product yield improved by 12%.
2. Key Points for Multi-Cavity System Adjustment
Symmetrical Arrangement: The installation depth, angle, and distance from the heater of each channel sensor must be consistent to prevent uneven filling due to temperature measurement deviations.
Use Positioning Fixtures: Use dedicated fixtures or templates to ensure repeatability of installation positions each time, reducing human error.
Reserve Debugging Holes: Multiple temperature measurement holes can be reserved during initial installation to facilitate comparison of data performance at different locations during trial molding.
Note: Asymmetrical arrangement is a common cause of multi-cavity imbalance and requires strict control.
3. Installation and Verification Steps
Operate after shutdown and cooling: Ensure the hot runner is completely cooled to avoid burns or damage to components.
Clean mounting holes: Remove carbon deposits and residues to ensure good heat conduction.
Apply thermal grease:** Apply a small amount of high-temperature thermal grease between the sensor and the hole wall to reduce temperature measurement lag.
Tighten to torque requirements: Use a torque wrench to tighten the fixing nut to prevent loosening.
Record position parameters: Create a record including distance, depth, and angle for easy traceability.
Safety Principles: Reliable temperature control can only be achieved by adhering to the four steps of "avoiding hot spots + maintaining spacing + symmetrical placement + data verification."
