How to Reduce Errors in Hot Runner Sensor Verification

Preparation, operation, judgment, and verification are the four processes in which control can be implemented step-by-step to minimize errors in hot runner sensor verification. The following are specific, doable strategies:

 

1. Prior to Verification: Make sure everything is ready to remove mistakes at their source.

Clean the test area completely: Use a brush and a high-pressure air cannon to remove any remaining material and oxide residue from the hole's bottom. To avoid debris rising the probe and creating measurement errors of 0.05mm or more, wipe the probe with a fresh cotton cloth prior to verification.

Calibrate and choose appropriate instruments: Prior to verification, make sure the push-pull force gages and vernier calipers/micrometers are calibrated within their validity period. Push-pull force gages must have an accuracy of at least 0.1N and length measuring instruments must have an accuracy of at least 0.01mm. Use thin lead foil that is between 0.05 and 0.1 mm thick for uniformity verification to prevent excessive thickness from hiding off-center loading.

Preventive troubleshooting and interference removal: First, look for aging sensors and loose wiring. Before disassembling the mold, resolve any non-pre-tightening or contact force issues to prevent invalid verification.

 

2. To prevent human error during operation, standardize measurement procedures.

To calculate the average, determine the measurement reference point and repeat the measurements: Preload calculations must closely follow the mold mounting face and sensor mounting thread face as references; flange faces should not be confused. To minimize random errors from individual measurements, take three measurements at the same spot and average them.

Standardize Contact Force Testing Procedures: When using the push-pull force gage to draw the sensor, keep the pulling direction perpendicular to the sensor's coaxial axis, pull steadily and slowly, and take a reading as soon as the sensor starts to move. To prevent force variances of 1-3N brought on by skewed or fast pulling, repeat three times and average the results.

Verify Contact Uniformity Completely: Examine the indentation on the whole probe end face, not just a specific spot, following lead foil imprinting. To prevent overlooking isolated off-center loads, make sure the indentation depth is constant throughout.

 

3. Judgment: To prevent making poor decisions, match scenario criteria.

Steer clear of using universal standards in a one-size-fits-all manner. Choose the proper permissible range according to the production scenario and installation structure:

Structure and Scenario of Installation

Requirements for Acceptable Range

Control of Tolerance

Type of Threaded Clamping (Conventional)

Preload: 0.15–0.25 mm; Contact Force: 8–12 N

±0.05 mm

Type of Ejector Screw Fixing

Preload: 0.1–0.2 mm; Contact Force: 5–10 N

±0.03 mm

Big Injection Mold with High Pressure

Preload: 0.2–0.3 mm; Contact Force: 10–15 N

±0.05 mm

Injection Molding at High Temperatures (>300°C)

Preload/Contact Force regulated at the middle of the range

The tolerance was reduced to ±0.03mm.

Supplement: In order to counteract the preload increase brought on by mold expansion at high temperatures, the preload during room temperature verification may be 0.02–0.03 mm lower than the standard value due to high-temperature thermal expansion and deformation.

 

4. Post-Adjustment: Additional Confirmation to Guaranty Correctness

The mold cannot be sealed promptly after correction; a second check is required:

Use a feeler gage to remeasure the gap around the sensor mounting face; the gap difference around the entire circle should be ≤0.02mm, confirming that the mounting end is straight and without skewing; after startup, check the production data to ensure that the temperature rise time difference is <30%, the stable production temperature fluctuation is ≤±3°C, and there are no temperature-related product defects. Remeasure the preload and contact force to ensure that the values fall within the corresponding acceptable range and that uniformity meets requirements. Lastly, verify that the verification results are accurate.