In the injection molding process, the
plastic in the cavity due to uneven cooling and uneven shrinkage and injection
molding structure design is not reasonable, easily lead to various defects of
the product: Shrink, weld marks, stomata, edge, top wound, flash.
In order to obtain high quality injection
molding products, we must fully consider the structural process ability when
designing the products. In the following, the method of avoiding injection
Molding defects is analyzed according to
the main structural features of the injection molding products.
Mold opening direction and parting line
Each injection molding product at the beginning of the design must first
determine the mold opening direction and parting line, in order to ensure
minimize the core pulling mechanism and eliminate the impact of the parting
line on the appearance.
1 mold opening direction is determined, the product stiffener, buckle, bump and
other structures designed to be consistent with the mold opening direction, in
order to avoid pulling the core to reduce the fight seam line, to extend the
life of the mold.
2 For example: bumper mold opening direction is generally χ direction of the
body coordinates, if the mold opening direction is not consistent with the χ
axis, you must indicate the included angle in the product map.
3 mold opening direction is determined, you
can choose the appropriate parting line to improve the appearance and
1 A suitable draft angle to prevent the product from pulling. Smooth surface
stripping slope should be greater than 0.5 degrees, fine skin surface is
greater than 1 degree, rough skin surface is greater than 1.5 degrees.
2 Proper stripping angle to avoid product injury.
3 deep cavity structure product design requirements of the outer surface of the
slope less than the slope of the inner surface to ensure that injection molding
mold core is not biased to get a uniform product wall thickness and ensure that
the material density of open parts of the product intensity.
1 All kinds of plastic have a certain range
of wall thickness, generally 0.5 ~ 4mm, when the wall thickness exceeds 4mm,
will cause the cooling time is too long, resulting in shrinkage and other
issues, should consider changing the product structure.
2 uneven wall thickness will cause surface shrinkage. 3.3 uneven wall thickness
can cause stomatal and weld marks.
1 The rational application of stiffeners, can increase product rigidity, reduce
2 stiffener thickness must be less than 1/3 of the product wall thickness, or
cause surface shrinkage.