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.
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 thehotsprue 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 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
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.
