Y.-M. Deng

Abstracting and Exploring Functional Design Information for Conceptual Mechanical Product Design

Abstract.The conceptual stage of mechanical product design has been recognised as the most critical product development stage. This is an area which is not addressed by current CAD systems. In this paper, we present our work on the abstraction and exploration of functional design information to support this design area. We consider the exploration of relevant functional design information as an important aspect of design work during this design process. Four aspects of functional design information are abstracted, including function, behaviour, structure and working environment. The working environment information is demonstrated as being useful to the exploration of functional design solutions. The physical behaviour is represented by an input-output flow-of-action, contrary to the commonly-used input-output flow-of-object approach (where object refers to material, energy or signal). Not only is this approach more generic, more importantly, we argue that the input-output flow-of-object is only a physical-level design abstraction, while flow-of-action is a functional-level design abstraction, hence it can capture design intention. Based on this strategy, we explore functional design information by considering the relevant action flows between the design and its working environment, as well as between the different components of the design, including their attributes, attribute expressions, constraints, and so on. Prototype software has been developed to implement the proposed approaches. A simple design example is used to illustrate the various aspects of functional design information and their exploration process.

Feature-based CAD-CAE integration model for injection-moulded product design

One prominent characteristic of product design for injection-moulded parts is that design and analysis (e.g. flow simulation) go hand in hand to ensure that the design is manufacturable by the injection-moulding process. Despite the wide use of CAD and CAE systems, the two processes are still not integrated. There is no generic, unified model that allows both design and analysis information to be specified. In this paper, a feature-based CAD-CAE integration model is proposed to tackle the problem. The model comprises a hierarchy of CAD-CAE features such as part, wall, hole, rib, boss and treatment. The features are defined by their attributes and behaviours. With this model, information relating to both design and analysis can be specified and modified. The specified information from the design process is used to activate relevant CAE analysis routines, thus supporting integration from the CAD to the CAE process. If any of the specified design constraints is not satisfied from the CAE results, the initial model can be modified and the CAE analysis executed again. Hence, the model also supports integration from the CAE to the CAD process. A design case illustrates the bidirectional integration process.

EFDEX: A Knowledge-Based Expert System for Functional Design of Engineering Systems

Abstract.This paper presents a knowledge-based system, ‘EFDEX’, the Engineering Functional Design Expert, which was developed using an expert system shell, CLIPS 6.1, to perform intelligent functional design of engineering systems. On the basis of a flexible, causal and hierarchical functional modeling framework, we propose a knowledge-based functional reasoning methodology. By using this intelligent functional reasoning strategy, physical behavior can be reasoned out from a desired function or desired behavior, and inter-connection of these behaviors is possible when there is compatibility between the functional output of one and the corresponding functional requirement (e.g. driving input) of the next one. In addition, a complicated, desired function which cannot be matched with the functional output of any behavior after searching the object-oriented behavior base, will be automatically decomposed into less complex sub-functions by means of relevant function decomposition rules. An intelligent system for the functional design of an automatic assembly system provides an application of this intelligent design environment, and a demonstration of its methodology. In this paper, a knowledge-based functional representation scheme which integrates two popular AI representation techniques (object-oriented representation and rule-based representation) is also proposed as a prelude to a knowledge-based functional design system

A CAD-CAE Integrated Injection Molding Design System

Abstract. In the injection molding design process, interaction between design and analysis is very intensive. This is to ensure that the plastic part being designed is manufacturable by the injection molding process. However, such interaction is not supported by current computer-aided systems (CAD and CAE), because design and analysis are realized as isolated modules. Although most of CAE systems provide built-in modeling tools, these are only meant for developing an analysis model with very limited CAD functionality. On the other hand, some CAD systems have allowed certain CAE systems to run under their environments, but inherently they use different data models, thus communication between them is poor. This paper presents an innovative, CAD-CAE integrated, injection molding design system. This system uses an integrated data model for both design and analysis. The system is built on top of existing CAD and CAE systems, which not only greatly saves development effort, but also makes full use of the strong functionality of commercial computer aided systems. The system architecture consists of four layers: a CAD and CAE platform layer; a CAD-CAE feature layer; a model layer; and a GUI layer. Two design cases were studied to illustrate the iterative design-analysis process and use of the developed system.

A Design Perspective of Mechanical Function and its Object-Oriented Representation Scheme

The purpose of this paper is to present a functional schema which can be used to develop computer tools to assist designers during the early stages of the mechanical product design process. The schema is based on an analysis of the meaning of function. five main types of mechanical function are described: performance, assembly, manufacturing, marketing and maintenance. The paper focuses on the specification and representation of performance functions. These are defined using a natural language, which is an extension of the verb-noun pair technique. Three levels of performance functions are identified: overall, embodiment and geometric. The relationship between these levels of functions and the physical structures required to implement them is discussed in detail. An architecture to implement the schema using object-oriented technology is described. A research prototype based on this architecture has been developed in the programming language Incr Tcl/Tk.

Guiding functional design of mechanical products through rule-based causal behavioural reasoning

The paper presents a behaviour-driven functional (B-FES) modelling framework for functional design of mechanical products based on a rule-based causal behavioural reasoning step to guide the design process. A new representation scheme called rule-based behavioural representation (causal behavioural rules) was developed to facilitate causal behavioural reasoning, with which the interconnected physical behaviours can be reasoned out from a desired function. The behaviour schema was then used to select and arrange embodiments (abstractions of physical artefacts) to develop a set of potential concept variants. The proposed approach was not only useful in the creation of new configurations (combinations) from a library of standard physical behaviours, but also it might be used to generate specifications of new physical behaviours. A design case study of a terminal feeding unit is presented to demonstrate the practicality of the proposed approach.

Optimization of injection moulding conditions with user-definable objective functions based on a genetic algorithm

This paper applies a Genetic Algorithm (GA) method to optimize injection moulding conditions, such as melt temperature, mould temperature and injection time. A GA is very suitable for moulding conditions optimization where complex patterns of local minima are possible. Existing work in the literature has limited versatility because the optimization algorithm is hard-wired with specific objective function. However, for most of the practical applications, the appropriateness of optimization objective functions depends on each specific moulding problem. The paper develops a multi-objective GA optimization strategy, where the objective functions may be defined by the designers, including using different criteria and/or weights. For parts with general quality requirements, an objective function is also recommended with some quality measuring criteria, which are either more accurately represented or cover more moulding defects than those from existing simulation-based optimization approaches. The paper also elaborates on the effective GA attributes suited to moulding conditions optimization, such as population size, crossover rate and mutation rate. A case study demonstrates the effectiveness of the proposed approach and algorithm. The optimization results are compared with those from an exhaustive search method to determine the algorithms accuracy in finding global optimum. It is found to be favourable.

Modelling functional design information for injection mould design

Injection mould design is a complex process incorporating various aspects of design information and a variety of design activities. Specific requirements such as undercut mould design add difficulties to the problem because they often require innovation, which involves the conceptual stage of design problem solving. Modelling injection mould design from a functional perspective enables a higher level of design abstraction, thus facilitating a wider range of conceptual variants selection. In this paper, the authors discuss the essential aspects of functional design information in injection mould design and how they can be modelled. Functional design knowledge supporting the modelling process is also discussed and formalized, and a number of knowledge libraries are implemented. A side core mechanism design is used as an example to illustrate the proposed method and its usefulness.