Even though composites are seemingly mainstream on commercial aircraft, fastener components remain indispensable in aircraft assembly. An aircraft contains fasteners by the millions, in enormous variety and complexity. That makes them an important consideration for all manufacturing process steps—from development to planning to assembly. The advantages of a consistent fastener infrastructure are thus self-evident: consistent data and associativity permit quick recognition of changes and allow early responses in downstream processes.
Designers and developers agree: An ideal aircraft structure would be a single entity consisting of just one material and created in just one manufacturing process. That is just not feasible. There simply is no getting around subdivided sections, subassemblies, and individual parts being joined.
Each fastener needs to be managed along the aircraft’s entire product life cycle—from design to process planning to assembly. Since in most cases fasteners are standard parts, the data must be managed and processed along the entire supply chain as well.
Today’s product life-cycle management (PLM) systems—such as CAD, CAPP, and CAM—do not provide dedicated fastener objects that can be managed along the entire process chain. In the past, this shortcoming drove many aircraft industry OEMs and their suppliers to develop a bewildering variety of individually defined fasteners. Even today, these definitions lack uniformity, 3-D representation, and consistency along the process chain.
To compound the problem, 2-D design drawings often continue to serve as the master documents for fastener information. But at the same time, the CAD data relevant to manufacturing is frequently managed via a separate design-for-manufacturing 3-D CAD model. This redundancy increases administrative work.
The lack of standardization for fasteners in today’s 3-D CAD systems is reflected in a lack of associativity in downstream processes within and beyond the enterprise.
Modern product design paradigms distinguish between shape definition via a 3-D CAD model and engineering data definition via a 2-D CAD drawing. A product model’s engineering data directly influences process planning and manufacture. Actually, an engineering data object such as a tolerance or a part definition can be viewed as an engineering requirement that must be fulfilled by the corresponding manufacturing process. An example would be the drilling and reaming process by which a hole is created in accordance with its specific tolerance requirements, and as a result of which a specific fastener can be installed in accordance with the fastener specification requirements.
Hence an engineering requirement is linked to its corresponding manufacturing process. Following this approach, an engineering requirement object can be linked to a corresponding process planning step in an associated process planning application. This linkage is a prerequisite for an automated reconciliation of process planning following an engineering change. The basic objective of “model-based definition” is to incorporate all engineering-relevant information—i.e., the 3D-geometric shape and the engineering data—into a single model: the 3-D model. This model fulfills the prerequisites that enable automated data processing in downstream processes while simultaneously avoiding data redundancy and media breaks.
The methodology of model-based definition and the configuration requirement approach form the basis for the development of the application for fastener management.
In terms of an across-the-board product life-cycle management concept, fastener data management comprises all aspects of handling fastener data along the value chain of aircraft design and production. This would include the authoring of fasteners in airframe assembly, the planning of an airframe assembly process through automated or manual fastening operations, as well as offline programming of automated fastening operations or development of work instructions for manual fastening operations.
A number of requirements must be met in order to reap the full benefits of PLM-integrated fastener data management. In assembly engineering, a structured allocation of fastener data facilitates administration and re-use of fasteners. A high-performance application for fastener authoring would support engineers in defining and modifying the wide range of fasteners they have to manage.
The greatest benefits of a consistent fastener data set manifest themselves in process planning and offline programming. Since an airframe assembly can easily run to several thousand fastener positions, avoiding the manual entering of process-relevant information that is already contained within the engineering model means a major boost in efficiency.
To address all the defined requirements, Cenit, a participant in the recent SAE 2009 AeroTech Congress & Exhibition in Seattle, has developed a software called FASTJOINT to author and manage fasteners. Since the PLM system CATIA V5 has become the industry norm in aerospace engineering, FASTJOINT is seamlessly integrated into the CATIA V5 system architecture. To help engineers define fasteners easily, FASTJOINT is designed as an intuitive add-on to the V5’s assembly design. In this way, each engineer receives a fully CATIA V5-integrated environment that allows quick and simple authoring and management of fasteners.
Fasteners defined during this phase can be readily re-used in process planning and offline programming. But process planners and offline programmers view fasteners from a different perspective than engineers do. For this reason, a specific view of the fasteners is allocated to each of the different applications. In addition, the preset modes of fastener representation for process planning and offline programming enable automatic reconciliation when engineering changes occur. This associativity means that the planning process can start at a very early stage; in fact, it can now be implemented parallel to design and efficiently manage modifications as they become necessary. As a result, the overall process is decisively accelerated, and time-consuming iterations during the implementation of the productive process are reduced.
Nikolai D'Agostino of Cenit wrote this article for Aerospace Engineering.