How to Determine the Severity of Hot Runner Cracks

Our previous expertise on the repair, stress management and adaption of hot runner thermal shock cracks permits reliable severity assessment of the cracks using a few basic indicators:

I. Basic Crack Characteristics

Depth Percentage: Cracks that are less than 1/3 the hot runner wall thickness are mild. Cracks that are greater than 1/3 are severe because they can readily penetrate the runner rapidly.

Distribution Location: Cracks on the outer surface solely in non-stressed locations are mild, whereas cracks extending to the inner wall of the runner, bolt holes or other stress sealed locations are severe and directly cause adhesive leakage.

II. Crack Number and Morphology

Morphological Characteristics A single fine linear fracture is minimal. The emergence of the network or several crossing cracks indicates a significant stress. It shows a total internal stress imbalance.

Propagation Trend: A fault identification of only one static microcrack is a mild one. A crack that grows significantly in length and width after two consecutive re-inspections is a severe one, suggesting a rapid propagation.

III. Effect of Operating Conditions

Production Influences: Non-glue leakage, abnormal temperature are small production anomalies. Injection pressure fluctuation, local glue leakage are serious, which affect the normal production.

Repair History: New cracks that emerge for the first time are considered mild. Cracks appearing again after the second repair are deemed serious, suggesting repeated accumulation of residual stress.