To solve the shrinkage problem, the first thing to think about is
to increase the injection pressure and prolong the injection time.
But if the injection speed has been adjusted very fast, it is not
conducive to solve the shrinkage problem. Therefore, sometimes when
the shrinkage is difficult to eliminate, it should be solved by
reducing the injection speed.
Reducing the injection speed can form a large temperature
difference between the melt in front and the inlet, thus conducive
to the sequential solidification and shrinkage of the melt from far
to near, and also conducive to the higher pressure supplement at
the shrinkage level far from the nozzle, which will be of great
help to the solution of the problem.
Because of the lower injection speed, the lower melt temperature in
front and the slower speed, it is not easy for the injection parts
to produce batch fronts. The injection pressure and time can be
further increased and lengthened, which is more conducive to
solving the serious shrinkage problem.
In addition, the effect will be more obvious if the last stage end
filling mode with slower speed, higher pressure and longer time and
the pressure holding mode with gradual slowdown and pressure will
be adopted. Therefore, it is a good remedy to use this method from
the later stage of the injection when the slower speed of the
injection can not be used at the beginning.
However, it is worth noting that filling is too slow to solve the
shrinkage problem. Because by the time the cavity is filled, the
melt has been completely frozen, just as the melt temperature is
too low, there is no ability to compensate for the shrinkage in the
distance.
