Streamlining the airframe fastener management process

  • 16-Nov-2011 08:32 EST

The Fastener Pattern capability in SyncroFIT 2011 incorporates design rules to position fasteners to satisfy edge distance, pitch, and tangent edge requirements while enabling a concurrent approach to part and assembly development.

Thousands of pieces of unmanaged fastener data are generated in the airframe design-to-manufacturing process. Information based on this data must be delivered accurately and completely into assembly sequences aligned with the associated manufacturing systems to build the airframe. The tasks necessary to define and communicate this information are both tedious and complex.

The development team must communicate design information to manufacturing engineers so they can plan the successive assembly states that the airframe goes through while effectively managing production in spite of the huge number of fasteners in these designs (and the volume of information associated with them).

This challenge was difficult enough with traditional aerostructures, but the move toward composite aerostructures makes it even greater because of the interactions between composite designs and the assemblies in which they reside. And, given the fragility of composites, there needs to be precise control of speeds and feeds in the drilling process to avoid the possibility of delamination, splintering, etc., as well as to ensure high throughput.

Vistagy’s SyncroFIT is deployed as a solution to this challenge for a number of airframe manufacturers. It provides key capabilities for addressing the complexities of airframe development by simplifying the process of definition, assuring that a complete definition is created, and streamlining the communication of fastener data to manufacturing systems.

Aircraft are highly efficient structures, meaning the joints in the assemblies must carry loads that are as equally distributed as possible. To achieve this, fasteners must be installed within tight tolerances to ensure there is no mismatch in the joint that would cause one fastener to be more highly loaded than another.

This requires specialized manufacturing methods. There are many rules associated with the design of fastened joints, with some unique qualities specific to airframe design. These include distance to edge, fastener pitch distance, and acceptable grip length ranges. Finally, the holes that the fasteners go into must be defined with special finish operations and variations in assembly states for the design to be manufactured effectively.

The amount of information associated with this very complex kind of design is enormous. Providing an efficient means of transferring data in the correct format to manufacturing systems is a major obstacle to the cost-efficient production.

Previously, the only solution was manual and tedious: grip lengths and edge distances were manually checked, fastener locations were laid out manually, and generating work instructions often led to errors and oversights.

SyncroFIT streamlines this process by enabling engineers to develop a precise definition of the assembly that is specific to the airframe development process and then uses this definition as a basis for building assembly states that map to the manufacturing work cells where the assembly process takes place. The specialized information relating to fasteners and holes must then be transferred directly to automation equipment and to assembly technicians through the use of projection equipment to indicate installation steps via visual work instructions.

SyncroFIT enables the easy definition of fasteners both in terms of specification and layout. It also checks for the ability of machine tools to install the fasteners and conducts the typical checks of fastener pitch and hole-to-edge distances, assuring design rules are met.

After the design is released to manufacturing, the system communicates the specifications and locations of holes and fasteners seamlessly to the automated hole-drilling and fastener-installation systems. This information is grouped by the assigned assembly state, making the task of process planning vastly more efficient. Typically, this information is consumed by off-line programming systems for simulating and programming auto-drilling and fastening machines before being sent to the machine controllers that guide the drilling machines. Having the fastener data grouped appropriately for the programming systems makes the process of planning more straightforward because it captures the logic of how the manufacturing engineer thinks.

This is complemented by optical projection assembly systems that enable manufacturers to install and verify thousands of fasteners quickly without using stacks of drawings and manuals. It avoids the old paper-based approach to the creation of manufacturing planning and work instructions. The net result is a faster, more accurate process that achieves higher measures of quality by removing ambiguity from the overall airframe assembly process.

John O’Connor of Vistagy Inc. wrote this article for Aerospace Engineering.

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