Alex Noort

Multiple-view feature modelling for integral product development

Abstract To allow a designer to focus on the information that is relevant for a particular product development phase, is an important aspect of integral product development. Unlike current modelling systems, multiple-view feature modelling can adequately support this, by providing an own view on a product for each phase. Each view contains a feature model of the product specific for the corresponding phase. An approach to multiple-view feature modelling is presented that supports conceptual design, assembly design, part detail design and part manufacturing planning. It does not only provide views with form features to model single parts, as previous approaches to multiple-view feature modelling did, but also a view with conceptual features, to model the product configuration with functional components and interfaces between these components, and a view with assembly features, to model the connections between components. The general concept of this multiple-view feature modelling approach, the functionality of the four views, and the way the views are kept consistent, are described.

Integrating part and assembly modelling

Current modelling systems adequately support either modelling of parts or modelling of assemblies, whereas ideal modelling systems should adequately support both. To achieve this, a new modelling system has been developed, which uses enhanced multiple-view feature modelling. This advanced modelling approach provides specialised interpretations of a product for different development phases, by means of so-called feature views, and ways to keep these interpretations consistent, i.e. to make sure that they all represent the same product. The paper concentrates on the views that support detail design of parts and assembly design of the whole product, and the way these views are related and kept consistent. It describes the features and the tools that can be used to build and maintain the feature models of the views. An example modelling session is given to illustrate the benefits of such integrated modelling.

Feature Model Visualization

Feature modelling is now the predominant way of modelling products. Feature visualization is an important aspect here that can still be considerably improved. In this paper, an integrated way of visualizing feature models is presented, using new techniques for both the geometry and the structure of models. For the geometry of feature models, techniques are presented to visualize a selected subset of form features in a way that clearly distinguishes them from the rest of the model, as well as functional information such as closure faces of subtractive form features. For the structure of features models, techniques are presented to visualize several types of graphs. The different visualization techniques are used in an integrated way. Implementation of some of the techniques requires a non‐manifold representation of the geometry of the feature model. This representation, and some other implementation aspects, are briefly described. Throughout the paper, numerous examples of images of feature models are given which show that the new visualization techniques can indeed improve the effectiveness of feature modelling.

Solving Over- and Underconstrained Geometric Models

New approaches to solving underconstrained and inconsistent overconstrained 3D geometric models are described.

Product Development with Multiple-View Feature Modelling

Multiple-view feature modelling can support applications from various phases of product development, by providing an own view on a product for each of these applications. Each view contains a feature model of the product specific for the application. Current approaches to multiple-view feature modelling only deal with form features. Hence, only the later product developments phases, in which the geometry has to be fully specified, are supported. In addition, they only deal with single parts, not with assemblies. A new approach to multiple-view feature modelling is presented here that overcomes these shortcomings. It supports conceptual design, assembly design, part detail design and part manufacturing planning, by providing a view for each of them. The views and the operations that can be applied on them, and the ways the views are kept consistent, are described.

A collaborative framework for integrated part and assembly modeling

An ideal product modeling system should support both part modeling and assembly modeling, instead of just either of them as is the case in most current CAD systems. A good basis for such integration is multiple-view feature modeling, as it allows focusing on different aspects of the product, while at the same time maintaining the consistency among all model views. This paper presents a framework that supports synchronous collaborative sessions via the Internet, among members of a distributed development team, with such a modeling system. The framework provides facilities for creating a hierarchical product structure, with single and compound components, and meanwhile assigning tasks to team members. The actual design of a single component is supported by a web-client specialized in part design, whereas the specification of assembly relations among components is supported by a web-client specialized in assembly design. All clients make use of the same server, which runs a multiple-view feature modeling kernel and maintains the complete product model, guaranteeing the consistency between the part design and the assembly design views. In addition, the server keeps all clients up to date and manages all communication.

Constraint solving for direct manipulation of features

In current commercial feature modeling systems, support for direct manipulation of features is not commonly available. This is partly due to the strong reliance of such systems on constraints, but also to the lack of speed of current constraint solvers. In this paper, an approach to the optimization of geometric constraint solving for direct manipulation of feature dimensions, orientation, and position is described. Details are provided on how this approach was successfully implemented in the Spiff feature modeling system.

Satisfying interaction constraints

In feature modelling, constraints can be used to store design intent in a model. Interaction constraints are an important type of constraints, which limit the extent to which features may interact. This paper describes a solver for constraints on interactions that involve spatial overlap between feature shapes. It searches a model in which such constraints are satisfied, by sampling the parameter space for the model. A Monte Carlo technique is applied to reduce the expected number of samples needed to find such a model.

Enforcing Model Validity by Automatic Adjustment

In current modeling systems, all dimensions in a model have to be fully specified by the user. It is desirable that systems become more flexible in this respect, i.e. that non-critical dimensions in a model can be declared variant, and that the model can be automatically adjusted to enforce its validity when it is invalid. A method to realize this in feature modeling systems is described. The underlying feature model definition and validation approach are introduced. Validation is done by a collection of constraint solvers. An overview of invalid situations in which automatic model adjustment can be applied is given. The constraint solving scheme and, in particular, the automatic model adjustment strategies for different types of constraints are elaborated. Applications to enforce model validity are given for the areas of design by features, creating a member of a family of products, and feature conversion. These illustrate that automatic model adjustment is a very useful concept.

Enhanced multiple-view feature modelling

Multiple-view feature modelling is used in concurrent engineering. A shortcoming of current implementations is that they can only support low-level geometry-based product development phases, because they use form feature models. In order to overcome this shortcoming, we will use enhanced feature models, which are built from features that are defined as an aspect of a product that has some functional meaning. Enhanced feature models are therefore also able to support high-level product development phases.