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Abstract：nIis paper deals with a methodology for single gate location optimization for plastic injecdon mold Theobjective of
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the gate optimization is to minimize the warpage of injection molded pans，because warpage is a crucial quality issue for most
injecdon molded parts while it is influenced greatly by the gate location Feature warpage is defined as the ratio of maximum
displacement on the feature surface to the projected length of the feature surface to describe p',trt wmpage．The optimization is
combined with the numerical simulation technology to find the optimal gate location，in which the simulated annealhag algorithm
is used to search for the optimum Finally，arl example is discussed in the paper and it can be concluded that the proposed method
is effective．Key words：Injection mold，Gate location，Optimization，Feature warpage3767
INTRoDUCTION
Plastic iniection molding is a widely used．tom—
plex but highly efficient technique for producing a
large variety of plastic products，particularly those
with high production requirement，tight tolerance，and
complex shapes．The quailty ofinjection molded parts
is a function of plastic material，part geometry，mold
structure and process conditions．The most important
part of an injection mold basically is the following
three sets of components：cavities，gates and runners，
and cooling system．
Lain and Scow(2000)and Jin and Lam(2002)
achieved cavity balancing by varying the wall tllick-
ness of the part A balance filling process within the
cavity gives an evenly distributed pressure and tem-
perature which can drastically reduce the warpage of
the part．But the cavity balancing is only one of the
important influencing factors of part qualities．Espe·
cially，the part has its functional requirements，and its
thicknesses should not be varied usually．From the pointview ofthe injection mold dcsign．
a gate is characterized by its size and location．and the
runner system by the size and layout．nle gate size
and ruofler layout are usually determined as constants．
Relatively，gate locations and ruiqner sizes are more
flexible，which carl be varied to influence the quality
of the part．As a result，they ore often the design pa-
rameters for optimization．
Lee and Kim n996a1 optimized the sizes of
runners and gates to balance runner system for mul—
tiple inj’ection cavities．The runner balancing was
described as the differences of enhance pressures for
a multi．cavity mold with identical cavities．and as
difbrences of pressures at the end of the melt flOW
path in each cavity for a family mold with different
cavity volumes and geometries．The methodology has
shown uniform pressure distributions among the
cavities during the entire molding cycle of multiple
cavities mold．
Zhai“a1．(2005小presented the two gate loca-
tion optimization of one molding cavity by an effi—
cient search method based on pressure gradlent
(PGSS)，and subsequently positioned weld lines to the
desired locations by varying rumler sizes formulti—gate parts(Zhai et a1．，2006)．As large—volume
part，multiple gates are needed to shorten the maxi—
mum flow path，with a corresponding decrease in
injection pressure．The method is promising for de．
sign of gates and runners for a
single cavity with
multiple gates．
Many of injection molded parts are produced
with one gate，whether in single cavity mold or in
multiple cavities mold．Therefore，the gate location of
a single gate is the most common design parameter for
optimization．A shape analysis approach was pre-
sented by Courbebaisse and Garcia(2002)，by which