How to determine if frictional heat error affects product quality?

Observing the discrepancy between the temperature readings and the actual molding results, as well as doing a thorough analysis in conjunction with process fluctuations and defect features, are crucial to determine whether frictional heat error affects product quality.

 

1. Crucial Indicators of Judgment

The phenomenon

Justification

The product has short shoots or inadequate filling, yet the hot runner temperature display is excessively high.

Temperature control misjudges "overheating," automatically cooling down due to frictional heat, which results in an inadequate real melt temperature.

Short shots are improved by raising the set temperature.

shows that the system's actual heat output is too low and needs to be manually adjusted.

Stable quality at low speed, increased faults at high speed.

Inaccurate temperature control is the result of frictional heat produced by high shear.

The actual melt temperature, as determined by infrared thermography, is far lower than the value shown on the hot runner display.

verifies the presence of frictional heat inaccuracy directly (the discrepancy frequently reaches +10~30°C).

Practical Example: The hot runner in a connection production process showed 300°C, yet the short shot rate at high speed filling was 15% and there were no flaws during low speed filling. Only 278°C was the actual melt temperature. The primary reason was determined to be a frictional heat error of +22°C.

 

2. Quick On-Site Verification Techniques

Comparison Test for High-Speed and Low-Speed:

Run at a slow speed (less than 50 mm/s) and note the product quality and stable temperature;

Run at a high speed (>200 mm/s) and check if faults and temperature jumps occur at the same time;

Frictional heat interference is indicated if the temperature increases as the quality rapidly declines.

Melt Temperature Measurement and Comparison:

Use an insertion-type melt thermometer to determine the material's actual temperature at the output;

Check the temperature controller reading for the hot runner. A considerable influence is indicated by a difference more than 10°C.

Scanning with an infrared thermal imager:

Scan the hot runner surface as soon as the mold opens to find "hot spots" in the unheated area;

Severe frictional heat accumulation is indicated if the temperature of the flow divider cone or nozzle tip rises abnormally.

Note: This mistake is most noticeable in parts with thin walls, small sections, and materials with high viscosity (such PC/ABS).

 

3. How Can the Impact of Quality Be Verified? Defects happen in tandem with temperature changes: flash or brief shots follow each temperature change;

The problem can be mitigated by changing the set temperature: short shots diminish after raising the temperature by 5–10°C, suggesting that the initial temperature control was too low;

The same issue keeps coming up in several batches; it is confirmed to be a systematic error after random causes are checked out.

Safety principle: To prevent misinterpreting it as equipment failure, a three-step confirmation procedure called "phenomenon correlation + data comparison + process verification" is employed.