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tion optimisation [6, 7], feed system optimisation [3], moulding
condition optimisation [8], cavity balancing [9], and part thick-
ness optimisation [10]. These optimisation algorithms require
iterative executions of simulation routines. However, for each it-
eration, modification is only made to the CAE analysis model
(mesh model and other input parameters). For example, in gate
location optimisation, the gate location is changed, which can
be implemented by setting a different mesh node of the analy-496
sis model as the new gate location. Part-thickness optimisation
is achieved by modifying the thickness attribute of each mesh
element. For moulding- or processing-condition optimisation,
changes are made to parameters such as melt temperature, mould
temperature, and injection time, which are not relevant to the
part- geometry model.
As such, these optimisation algorithms are not oriented to
part design, especially part-shape design and modification. This
area of research has largely been ignored. In fact, it is not
uncommon that the shape and some features of the initial de-
sign may have to be modified to cater to the manufacturability
requirements.
This paper aims at developing the strategies and methods
for automatic part- shape modification. Modification of a part-
geometry model may be broadly classified into geometric mod-
ification and topological modification [11], or modification and
optimisation in sizing, shape, and topology [12]. This paper will
focus on geometric modification, including sizing of the part and
its features, as well as positional change of the features.
To support the automatic modification of part geometry, it is
essential to have a model that allows the designers to specify the
parameters of the part geometry to be modified and how they
are to be modified. These parameters are referred to as shape
modification variables in this paper. Since the modification vari-
ables are related to the part geometry, the model should be able to
acquire information from the part-geometry model, or to incor-
porate the part geometric model as its integral part. In addition,
the model needs to incorporate information relevant to the CAE
analysis, including the desired criteria for measuring quality. In
our previous work, we have developed a CAD-CAE integration
model [13] and based on this model, a CAD-CAE integrated sys-
tem [14]. This integration model provides a starting point for
part-shape modification. However, it does not support specifi-
cation of shape modification variables of part geometry, thus
does not support automatic part-shape modification. This paper
presents an extension to the model to support automatic shape
modification.
We will begin by briefly introducing the existing CAD-CAE
integration model in Sect. 2. The enhanced integration model
will be presented in Sect. 3. Section 4 describes how this new
model is used to modify the part shape. A software prototype
implementing the strategies and methods is also presented. Sec-
tion 5 studies a few design cases to demonstrate the useful-
ness of the presented work. Finally, the paper is summarised in
Sect. 6.
2 Brief description of CAD-CAE integration model
The CAD-CAE integration model is an object-oriented feature-
based model that incorporates both design and analysis informa-
tion of an injection-moulded part. The model consists of a num-
ber of hierarchically organised features such as part feature, wall
feature, hole feature, rib feature, boss feature, and treatment fea-
ture. The part feature holds the overall information of the part,
while all other features are constituent components of the part,