3 The IKB-MOULD

The IKB-MOULD combines the use of knowledgebased and object-oriented tools with commercial solid modelling software to carry out its function。 The IKBMOULD presented in this paper begins with the plastic part to be moulded and finishes with the generation of a completed mould system with relatively detailed drawings。

The IKBMOULD is composed of the following modules: a product model interface, a mould design module, a knowledge base and some other libraries。

3。1 The product model interface 

The product model is the input to the IKB-MOULD design process。 This model can be a solid, standard engineering interchange, or a surface or wire-frame model。 The IKB-MOULD system provides a product model interface to accept a solid model built in different types of solid modelling software。 It can directly load the product model built in SolidDesigner。 If the product is developed from a CAD system that is other than SolidDesigner, then the product needs to be converted using

STEP, IGES or DXF。

3。2 The mould design module

The injection mould design process of the mould design module in IKB-MOULD covers the pre-moulding process, the initial mould design and the detailed mould design。

3。2。1 The pre-mould process

Product mouldability is evaluated in this pre-mould process。 Some issues to be considered are material thermal expansion, the plastic flow direction and the product draft angle。 The system not only allows experienced mould designers to define the shrinkage of the product model, but also to recommend product

shrinkage using the material library。 This material library is a material database that stores information about the material’s viscosity, temperature sensitivity, and degree of differential shrinkage。 Based on the generic type of material used, IKB-MOULD system retrieves the material shrinkage rate from the material library。 Once shrinkage is determined, the product model is reconstructed to account for material shrinkage that occurs during the mould operation。

3。2。2 The initial mould design

Mould specification is done in the initial stage of the injection mould design。 The requirements of the plastic component are specified at this stage。 Decisions made at this stage include a functional analysis, the number of cavities, the cavities layout and the type of mould configuration。 The initial design plays an important role in the mould design。 Once the initial design stage is completed, the mould structure is determined。 Such an initial design is usually the guideline for the mould quotation, the mould base ordering and the detailed mould design。

– The determination of the cavity number。 The number of cavities can be determined using an empirical formula that considers different factors。 These factors are the period of delivery, the minimum cost, the product precision quality requirement or the machine technical data such as the maximum shot capacity and the clamping force (Menges [25])。 Ye et al。 [26] determined the cavity number based on a mixed consideration of three factors: machine technical data, minimum cost and delivery date。 Often mould designers determine the cavity number based on their experience and suggested empirical calculations with consideration to different factors。

– The determination of the cavity layout。 The cavity layout of an injection mould usually includes the layout pattern andorientation of each cavity in themould。 The layout pattern depends on the cavity number。 A balanced layout pattern is commonly adopted for multiple cavities, such as two-cavity, four-cavity and eightcavity。 Orientation of the cavity affects the position and orientation of the gate system。 In other words, cavity orientation and gate location should be balanced。

– The determination of the mould base。 The projection area of the cavity layout along the ejection direction can be used to determine the minimum mould base size。 The IKB MOULD has a mould base library that stores many standard mould bases (the fixed half and the moving half)。 Design rules and expert knowledge in the initial mould design process are regarded as heuristic knowledge incorporated into the IKB-MOULD。 After the initial design, a mould specification can be generated。