Use of Manufacturing Features for Computer Aided Process Planning and Manufacturing System Design

Abstract

Nowadays the market fluctuation and the fashion ask for designing and manufacturing with reducing delays. So it is necessary to design product by taking into account of the manufacturing requirements and sometimes to design product and manufacturing system simultaneously. We propose, in this paper, an approach of this concept to a particular domain, that of the second tranformation of wood manufacturing industry. This domain closely is linked with market requirements, the added value of the product is quite low and the productivity must be high.

For this objective it is necessary to use structured data bases which can be used by the designer and the manufacturer. We have developped a description model of solid wood furniture pieces. We defined manufacturing features as geometric shapes and a set of specifications for which a machining process is known. The features we have selectionned correspond either to a given cutting operation or to a male female feature or a set of features in accordance to the customs of process planning. The formalization of knowledge is made by using tables, rules, flow charts. A workpiece is defined by a set of manufacturing features.

At first a workpiece is defined by its reference surfaces and some attributes (material, hardness, moisture constent, initial shape,...). Then manufacturing features are defined.

The data base organization is defined by entity-relation formalism. So after that it is easy to deduce workpiece drawings or several sequence operations which take into account all the production constraints.

In the case of wood industry we have a close connection between manufacturing features and fonctionnai features. So by using the same manufacturing features it is possible to design the structure of the manufacturing line which allows to machine the workpieces.

We have developped a prototype software based on a relational data base (MS-ACCESS) which allows to get process planning. From our experience of wood manufacturing we choiced an up-bottom approach using an algorithm treatment based of a mixed system made up of variant and generative methods.