Gate
design of Plastic Injection Molding includes gate section shape, gate section size and gate location.
The factors
influence the gate section shape and size, in terms of products, including the
product's shape, size, wall thickness, dimensional accuracy, surface quality
and mechanical analysis, etc. The factors from raw material used in the plastic
properties of the influence gate design are the plastic molding temperature,
viscosity, contractility, and presence of fillers, etc. In addition, at the
time of the gate design, gate should also be considered for processing, mold
release and removal of the difficulty level of the gate.
As usual,
the section size of the gate should be smaller rather than larger. When
determining the gate size, make sure the smaller, and then try to test mould, if
necessary we can revise according to the cavity filling conditions, especially
to a multi-cavity mold, which can be made simultaneously to the cavity filling
evenly through the amendment.
The small
gate can increase molten plastic material flow rate and molten plastic material
through the small gate will have much friction to raise the material
temperatures. Which apparent viscosity decreased and advantageous to the filling.
In addition, due to the small gate of fast curing, which does not produce
excessive feeding and reduce the internal stress of products. At the same time
it can reduce injection molding cycle and improve the gate removal.
Gate should
not be too small for some products, such as thick-walled products, must be more
than two times in the process of injection pressure to meet the requirements of
products. Too small gate will cause the
gate place too early curing, the feeding difficulties will cause the product
defects.
The Gate
location should locate in the thickest area, so that the plastic flow from
thick to thin-walled area and keep the process identical in all parts of the
gate to the cavity,prevent jetting or worming during the filling process.
The gate
location should locate in the main
stress direction, because the plastic flow direction on the highest tensile
stress and compressive stress. When choosing gate location, we should consider
the size requirements of the product. Because the plastic gate mold filling,
the plastic flow direction and perpendicular to the flow direction of shrinkage
varies is not the same. So we need consider the direction of the deformation and
shrinkage.
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