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the best gate location of injection molding was esti—
mated．Subsequently，they developed this method01．
ogy further and applied it to single gate location op—
timization of an L shape example(Courbebaisse，
2005)．It is easy to use and not time—consuming．while
it only serves the turning of simple flat parts with
uniform thickness．
Pandelidis and Zou f 1 990)presented the opti．
mization ofgate location．by indirect quality measures
relevant to warpage and material degradation，which
is represented as weighted sum of a temperature dif-
ferential term，an over．pack term．and a frictional
overheating term．Warpage is influenced by the above
factors，but the relationship between them is not clear．
Therefore．the optimization effect is restricted by the
determination ofthe weighting factors．
Lee and Kim f 1 996b)developed an automated
selection method of gate location．in which a set of
initial gate locations were proposed by a
designer and
then the optimal gate was located by the adiacent node
evaluation method．The conclusion to a great extent
depends much on the human designer’s intuition。
because the first step of the method is based on the
designer’s proposition．So the result is to a 1arge ex—
tent limited to the designer’s experience．
Lam and Jin(200 1)developed a gate location
optimization method based on the minimization ofthe
Standard Deviation of Flow Path Length(SD『L])and
Standard Deviation of Filling Time(SD[T])during
the molding filling process．Subsequently，Shen et
以仁004a；2004b)optimized the gate location design
by minimizing the weighted sum of flling pressure，
filling time difference between different flow paths，
temperature difference，and over—pack percentage．
Zhai et a1．(2005b)investigated optimal gate location
with evaluation criteria of iniection pressure at theend of filling．These researchers presented the objec．
tive functions as performances of iniection molding
filling operation，which are correlated with product
qualities．But the correlation between the perform．
ances and qualities is very complicated and no clear
relationship has been observed between them yet．It is
also difficult to select appropriate weighting factors
for each term．
A new objective function is presented here to
evaluate the warpage of injection molded parts to
optimize gate location．To measure part quality di—
rectly，this investigation defines feature warpage to
evaluate part warpage。which is evaluated from the
‘‘flow plus warpage”simulation outputs of Moldflow
Plastics Insight(MPI)software．The objective func．
tion is minimized to achieve minimum deformation in
gate location optimization．Simulated annealing a1．
gorithm is employed to search for the optimal gate
location．An example is given to illustrate the effec．
tivity of the proposed optimization procedure．
QUALITY MEASURES：FEATURE WARPGE
Definition of feature warpage
To apply optimization theory to the gate design，
quality measures of the part must be specified in the
first instance．The term“quality”may be referred to
many product properties，such as mechanical，thermal，
electrical，optical，ergonomical or geometrical prop-
erties．There are two types of part quality measures：
direct and indirect．A model that predicts the proper．
ties from numerical simulation results would be
characterized as a direct quality measure．In contrast，
an indirect measure of part quality is correlated with
target quality，but it cannot provide a direct estimate