type of gate depends upon a number of factors including the following:
Are you using hot runner or cold runner? Both runners have a number of gate
types to choose from. For example, commonly used gates for cold runners are tab,
submarine and pin gates. For hot runners hot tip and valve gates.
The shape of the part influences the type of gate. For example, flat parts often
use a tab gate. Flat parts can also use valve gates for hot runners and allow
gating in the centre of the part (such as a lid) and leave a clean flat gate
Part material. Some plastic materials require a larger gate because they are
shear sensitive (such as PET) than other materials so a large tab gate for a
cold runner design or a valve gate for a hot runner design are often used. Pin
gates or hot tip gates should be avoided with shear sensitive materials.
Part cosmetic requirements. Some gates are designed to leave minimal gate
vestige such as a submarine gate.
the type of gate used is very dependent on the application. Every part has
different requirements so each one must be studied on a case by case basis.
The plastic injection mold material
mainly depends upon the annual shot quantity requirement. But it also depends
upon part design and part plastic material.
shot quantity requirements of less than 500,000 prehardened tool steel (called
P20) is most commonly used for cores and cavities and the plastic injection mould base.
mild steel could also be used for the mould base as well.This steel is
aluminium is growing in popularity in the automotive sector.Aluminium is much
easier to machine and handle compared with tool steel so the cost of manufacture
is less.Cycle times are also better but mold maintenance is critical to ensure
part quality – anybuild up of residue will damage the shut off surface and cause
above 500,000 the use of thru hardened tool steels such as H13 or H11 should be
considered for the cores and cavities. These materials will produce quality
parts for much longer than P20 or aluminium because plastic injection mould wear is
corrosive environments such as when molding PVC plastic, stainless steel tool
steels can also be used in mold construction. Stainless steels will minimize
On a more advanced level, cavity filling analysis is useful to predict the
melt front advancement in the cavity and identify the location of knit-lines,
end of fill, and other phenomena before the mold is manufactured and tested.