How to Optimize the Multi-Sensor Average Value Control System for Hot Runners

In order to optimize the multi-sensor average value control for hot runners, four fundamental issues must be addressed: layout, calibration, system adaption, and maintenance. In the end, this enhances control stability and temperature measurement accuracy. The following are specific optimization techniques:

1. Optimizing Sensor Placement: Preventing Spatial Interference and Improving Representativeness

Restricted Use Cases: Only suitable for high-flow molds with runner diameters more than 8 mm and big hot runners. In order to reduce structural weakness and increased shear interference, small runners should prioritize improving single-point installation sites rather than forcing many sensors.

Layered Differentiated Placement: Two sensors per channel are adequate; three sensors are more expensive and provide little value. One sensor is positioned in the main runner's low-shear zone (60%–70% weighting), while the other is positioned close to the nozzle side cavity (30%–40% weighting). To prevent reciprocal interference in heat conduction, keep the distance between the two sensors at least 10 mm.

Strict Symmetry Requirements: To avoid temperature control imbalance brought on by variations in measurement points, all channels in a multi-cavity mold must have the same number of sensors, installation depth, and distance from the heater, with an error regulated within ±1mm.

2. Optimizing Consistency Calibration: Removing Individual Deviations and Guaranteeing Total Accuracy

Unified Screening and Calibration Upon Arrival: All sensors are calibrated using a constant-temperature oil bath following the purchase of a full sensor set. In order to eliminate individuals with severe deviations and eliminate intrinsic deviations at the source, sensors with mutual deviations < ±0.5℃ are chosen for pairing.

Complete Replacement Principle: To prevent mixing old and new sensors and raising deviations, a fresh, calibrated sensor from the same batch is used to replace the complete set when a sensor in a single channel fails due to aging.

Quarterly Pairing Verification: Two sensors in the same channel have their deviations concurrently evaluated during quarterly verification. The complete set must be recalibrated or replaced if the difference is greater than 1°C.

3. Control Logic Optimization: Optimizing Deviation Reduction and Adapting to Various Systems

Give Weighted Average Priority and Use Simplified Arithmetic Average for Older Systems: For more recent temperature controllers with multiple input support (common types like Gene and Master): Reduce the interference from local frictional heat by using a weighted average and setting the weight of sensors in the high-shear zone to 0.3~0.4 and in the low-shear zone to 0.6~0.7; For older temperature controllers without native compatibility, the single-point variation is reduced by about 50% without the need for extra programming changes because just two sensors are required and the arithmetic average is taken directly;

Deviation Compensation Correction: Measure the real temperature using a melt thermometer after deployment. To further control the overall error within +5°C, specify a uniform compensation value in the temperature control system based on the difference between the measured value and the average reading.

4. Optimize Maintenance and Management: Lower Failure Risk and Troubleshooting Expenses

Create a Comprehensive Status Log: To control the overall status and stop individual sensor failures from reducing overall accuracy, note the purchase time, calibration deviation, and verification records of each channel sensor;

Optimize Cabling to Reduce Interference: To minimize fluctuations brought on by signal interference, utilize twisted-pair shielded cables for multi-sensor signal lines and install them independently to avoid parallel routing with power lines;

Batch Centralized Testing: During quarterly verification, use multi-channel temperature recorders to evaluate the deviation of every sensor at once. This eliminates the need for individual point measurements and saves around 60% of maintenance time.