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It’s just a fastener…or is it? (Part 2)

Siemens Dreamer Siemens Dreamer
Siemens Dreamer

In part 1 of this blog, Steve Peck, director of product & market strategy, aerostructures, for the Specialized Engineering Software (SES) business segment of Siemens PLM Software, discussed just how much trouble an airframe fastener can cause in the design and production of an aircraft. In part 2, he’ll look at ways to get better control of these mischievous little parts.

Part sizing and fastener definitions are closely coupled through design rules. Changes throughout the design often result in violations of these rules.


The fastener challenges start early in the airframe design process. Fasteners and associated holes often dictate the size of an airframe component and vice versa. Rules that establish the distance a fastener is positioned relative to the edge of a part and to an internal tangent edge of a flanged part are based on the size of the fastener. Therefore, it is critical to start capturing and tracking details of the fasteners and holes from the outset since that information is so closely coupled with the overall design.

The problem is that in the early stages of design there is little control of the fastener information. A designer usually makes some quick calculations on a scrap of paper during the initial layout and this information is never captured.  Given this informality and the evolution of part thicknesses and overall dimensions during the course of a program, it’s no wonder there are typically numerous engineering change orders (ECOs) and a lot of shop floor rework.



These frequent changes are part of the reason that detailed fastener definitions are left until late in the design process. Our studies have found that on average a designer spends six minutes per fastener on the initial definition and placement, and three minutes to implement each change. Given the sheer quantity of fasteners on an aircraft, you can see why engineers wait until a design has stabilized to begin defining fasteners. Unfortunately, by that time, detail parts have often been released and resolving the  hole misalignment, edge distance violations and assembly collisions means implementing  costly ECOs.

Many air framers have sought to improve their processes and productivity by creating home grown macros or basic knowledge-based tools that help calculate the grip length of a fastener or instantiate and position the 3D fastener models in the assembly. Although these macros help automate some tedious tasks, it is a broad problem that requires numerous point solutions.

A list of fasteners grouped by the joint association in Sycnrofit allows quick navigation of the multitude of fasteners in an airframe assembly.


This is where the Syncrofit™ portfolio of software for airframe assembly from Siemens PLM Software comes in. Syncrofit was developed by Vistagy (now known as SES) prior to being acquired by Siemens to address the design-to-manufacturing requirements for airframe assemblies. It is a 3D CAD-integrated solution that is quickly becoming the de facto standard for many aircraft OEMs and suppliers.

Syncrofit facilitates authoring design data for joints, fastener and holes to create complete 3D product definitions. It stores the design data and links to the associated geometry inside the CAD model (NX or Catia®). Syncrofit interacts with Teamcenter to retrieve the fastener models directly from the vault when they are being placed in the assembly. Syncrofit provides powerful tools for automating repetitive design tasks, such as laying out fastener patterns, calculating grip lengths, loading fasteners and creating holes. It also helps engineers generate critical information, such as model-based definition formats and Bill of Material (BOM) reports for assembly hardware.

Syncrofit facilitates creation, management and communication of multiple manufacturing states required for assembling airframes. It enables you to easily consume requirements into assembly states – including the condition of supply – to support process planning. It also aids in tracking fastener consumption and delivers information for programming automated drilling and fastening equipment.

The result? A highly efficient process for delivering world-class aircraft on schedule and on budget.

Read about how GKN Aerospace uses Syncrofit to enhance its fastener manager processes.