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Handling of hot runner leakage

Date：2024-04-09 Hits：171

Handling of hot runner leakage


 　　


Some of the leaks are not due to poor system design, but rather to failure to operate within the design parameters. Leakage usually occurs at the seal between the hot nozzle and the manifold. According to general hot runner design specifications, there is a steel edge at the hot nozzle that ensures the height of the hot nozzle assembly is less than the actual slot depth on the hot runner plate. The purpose of designing this dimensional difference, often referred to as the cold gap, is to avoid damage to components due to thermal expansion when the system is at operating temperature.


 


1. The back of the hot nozzle is secured to the manifold; the high-temperature bolts that secure the hot nozzle to the manifold prevent leakage under cooling conditions. This system still requires a cold gap, as the steel edges need some room to expand at room temperature. Although this method actively prevents leakage from the hot nozzle to the manifold, it does not prevent thermal expansion of the part under superheated conditions.


 


2. Hot nozzles bolted to the manifold move with the manifold. This design has a minimum length requirement for the hot nozzle and a restriction on the spacing of the mould cavities. It is an economical and effective way to prevent leakage between the nozzle and manifold, and is suitable for systems with fewer cavities.


 


3. The hot nozzle edge is designed to be elastic rather than steel. The elastic edge provides a preload under cooling conditions and prevents damage to the system. It also absorbs thermal expansion if accidentally overheated, extending the operating range to ±110°C.


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