USING A DESIGN BY FEATURES CAD-SYSTEM FOR PROCESS CAPABILITY MODELING

Process capability modelling offers a method of matching the shape, te chnological and cost capabilities of manufacturing equipment to the re quirements of components, singly or as groups. This provides the basis of planning tools useful in the capital intensive business of the con struction of new manufacturing facilities or the reconfiguration of ex isting ones. The success of this modelling approach is dependent upon having an appropriate representation of the design geometry. The repre sentation must be such that all geometric inquiries raised by the proc ess capability modelling are either explicitly held within some data r epresentation or alternatively can be derived algorithmically by refer ence to a geometric model. The representation must also be capable of withstanding the rigours of use within the wider context of implementi ng an important part of the CAM interface within a CIM environment. Th is paper describes a feature-based representation based on a feature t axonomy which uses External Access Directions (EAD) as the characteriz ing aspect of geometry. These EADs become potential machining directio ns for a collection of features on a component, and are used as an ess ential link into generative process planning activities. The represent ation has been used in conjunction with process planning and process c apability modelling applications. This paper concentrates on the latte r, where the feature representation has been embedded within a proprie tary geometric modeller which has been provided with a purpose-built u ser interface. A feature-based component model is created by the geome tric modeller and accessed by functions which enable flexible componen t grouping and matching to process capability through the concept of a composite component. Subsequent process component grouping within the context of particular manufacturing systems strategies (cellular manu facture, flow-line, etc.) ultimately results in functional machine des criptions and variants.