- 上一篇：自动束光器传动齿轮注射模设计+CAD图纸
- 下一篇：颚式破碎机英文文献和中文翻译
A mould base is the result of this standardisation.
According to the feature-based and object-oriented assembly
representation, the feature-based solid models for component
parts of the mould base are first constructed; next, the assembly
objects are defined by establishing relationships between
components and encapsulating some functions in the component
parts; then, using these assembly objects, a hierarchical subassembly
object – a mould base – can be formed. This mould
base object can be instantiated by a group of data from the
catalogue database. Figure 4 shows the instantiation of the
mould base object to generate the specified mould base. This
specified mould base instance can be added automatically to
the mould assembly. The structural relations between the mould
base subassembly and top assembly can be expressed by Eqs.
(8) and (9), where Mp and Mr are the unit matrices.
5.2 Automatic Addition of Standard Parts
A standard part is an assembly object. It can be defined
according to Eq. (1) in Section 3.1. In the database, the spatial
constraints are specified by mate, planeFalign and axisFalign,
but unlike the mould base, the position and orientation matrices
of a standard part are left unknown. During instantiation,
the software then automatically infers the explicit structural
relationships by using the simplified symbolic geometric
approach described in Section 4.
5.3 Pocketing for Assembly Objects
One of the important issues for automatic assembly design is
the automation of the pocketing process. Pocketing is an
operation that makes an empty space in corresponding components
to accommodate the inserted components. When an ejector
is added to the assembly, an empty space is required on
the EA plate to accommodate the ejector, as shown in Fig. 5.
Since an object-oriented representation is adopted, each
assembly object can be represented by two solids, the real
object and the virtual object. The virtual object is modelled
according to the space that a real object will occupy. Whenever
an assembly object is added to an assembly, its virtual object
is also added to the assembly. The operation function
pocketFplate() in M of O will subtract the virtual object from
the corresponding components (see Eq. (1) and Table 1).
Moreover, because there are associativities between the virtual
object and real object, the pockets on the corresponding components
will change with the modification of the real object.
This automatic pocketing function further demonstrates the
advantage of an object-oriented representation.
6. System Implementation
Based on the Unigraphics system [13], the proposed featurebased
and object-oriented assembly scheme and automation of
assembly modelling have been implemented in the IMOLD
system [14] developed at the National University of Singapore.
The Unigraphics system provides a user-friendly application
programming interface (API). Through this interface, the users
can call Unigraphics internal functions such as adding parts to
an assembly, modifying parameters, etc. Although Unigraphics
provides functions for mating conditions, the proposed approach
is still needed to infer the component configuration, because
it is necessary to calculate the degrees of freedom, and check
the validity of mating conditions before the component can be
added to the assembly. The proposed synthesised constraints
are compatible with Unigraphics constraints.
Figure 6 shows an injection moulded product, and the
designed injection mould assembly for this product is shown
in Fig. 7(a). The corresponding parent–child relationships for