Hot Sprue Design Option Prevents the Material Leak

Any reason causes the hot runner material leak in the majority situations, not because error design, because it has not deferred to the design variable in the operation.

Usually, material leaks occur in seal between the hot mouth and the manifold. According to the common hot runner design standard, it has a steel edge in the hot spure; it may guarantee that the hot spure is smaller than highly on the hot runner manifold actual trough is deep. The reason that must design during this size the difference (usually to be called cold gap), the goal is to avoid the heat expansion not damaging the part when in operating.

For example: Regarding a 60mm thick manifold and a 40mm hot sprue (gross altitude is 100mm), when temperature increment to 230c, usually will inflate 0.26mm. If does not have the cold gap, the heat expansion will often create the hot sprue failure. Therefore, the effective seal has not been causes the hot runner under the cooling condition to leak the material the primary cause. Usually, for guarantee systems seal (hot sprue and manifold), must heat up the system to the operating temperature, and thus prevents the injection molding pressure to go against two parts. Generally, operator who lacks experience often cannot wait system to achieve the operating temperature, what will be worse; they even possibly forgot that will open the heating system. Thus, even it has the cold gap, when hot runner before achieved its operating temperature, the pressure from the surface is also unable to prevent to leak the material. Moreover, the material leak also occurs in the overheating situation. As a result of hot sprue edge low expansion compatibility, when system was over heating, once reduces again for the operating temperature time, as a result of the steel distortion's influence, the seal pressure which it produces is unable to prevent divulging. In this kind of situation, not only material leak caused system failure, but also oversized pressure to the hot mouth creates the unrecoverable damage, thus need to transfer hot sprue. Because the hot sprue and the manifold preload is important,  therefore must observe the size  strictly to the hot runner supplier provides, then can prevent the system to leak the material effectively.

 Hot sprue design option prevents the material leak: 

Manifold and hot sprue seal designs to each kind of different hot sprue. It has the steel edge, no ant drip function design. This kind of design seals no own initiative under the cooling condition, also no overheated protects, its operating temperature scope is ±27c. The hot sprue back is fixed on the manifold, fixes the hot sprue on the manifold may prevent leak under the cooling condition divulging. Because the steel edge needs certain expansion space under the normal temperature, therefore this system must have the cold gap. Although this method can prevent the melting stock from the hot sprue to manifold in divulging, but is actually unable to prevent part's heat expansion under the overheated condition, its operating temperature scope is ±27c. One kind way both economy and effective, suitably in locule number system. Because is fixed using the bolt on the hot sprue may movement together with manifold, therefore this kind of design has the smallest length request to the hot sprue, also has the limit to the cavity spacing. The hot sprue edge uses the elasticity, but the non-steel design, the spring edge may provide the preload under the cooling condition, and may prevent the system to damage. If heats up excessively because of the accident, it may also absorb the heat expansion, its operating temperature scope may expand ±110c.

How to discover the material leak:

Usually in situation, the people are very difficult to discover whether the hot runner material leak happened, because is unable to see radically from the mold. But if observes carefully, it can discover through some signs. Generally, when establishes a brand-new hot runner, it may contain injection molding quantity times, for example, if melts the road to be possible to contain three injection molding quantities (each time to inject quantity for melt/cavity's capacity), then after three injections, in the cavity should already have the melting stock. If does not have, the material leak may happen in the manifold. When begins using the hot runner, must guarantee that the injection quantity is established correctly on the machine. In the operating process, another sign is the partial cavities or the product sufficient material is incomplete. It is because the leak in the manifold caused the product injection molding not to be full. On injection molding machines control interface, this kind of situation demonstration for technological parameter sudden change. If the operator suspected that material leak existence, then should close the injection machine immediately, after systems cool, carries on the inspection again. After t cleaning up system and examines leaks the material reason, also should inspect all parts. This is because the overheated temperature or the cleaning up process has the possibility to create part’s damage. If discovered that the part is damaged, should replace the part immediately.