Hockley Pattern & Tool, Halesowen, England, is an example of a company dedicated to the art and science of making perfect tooling.
This article is about how Hockley builds and verifies advanced tooling. Form tooling and fixturing as a manufacturing concept has spanned the ages and today remains the foundation for many advanced parts, including the cockpit canopy for the most advanced aviation platform ever created—the F-35 fighter jet.
The complexity and precision of today’s composite parts rely heavily on the layup tools that make advanced forming possible. These layup tools—and those who design, manufacture, and inspect them—are the unsung heroes behind the many parts and finished products that rely on high-strength, lightweight composites.
As with most manufacturing applications, there is constant improvement in materials and processes that make the manufacturing of high-tech parts faster and cheaper with ever-improving quality. Throughout this ongoing evolution, one thing remains constant: layup tooling is critical for both functionality and quality.
There are many hand-offs in the manufacturing and assembly of composite parts, which often include machining, coatings, finishing, and add-on components. If the layup tooling is not perfect, the foundation is flawed.
At the heart of the UK tooling manufacturing industry for more than 25 years, Hockley Pattern & Tool supplies high quality tools domestically and internationally to major aerospace and automotive manufacturers and their supply chains. “When it comes to designing and making tooling, it can be both a creative and highly technical process,” said Neil Williams, director of Hockley. “Typically, we receive prismatic 3D CAD models that we use to design, build, and inspect finished tooling. But we are often asked to create tooling from an artifact, which can be an organic shape or prismatic part for which there are no CAD models or drawings available. Regardless of how a job comes to our shop, every finished tool includes a quality inspection report tied to a 3D CAD model.”
For Hockley to fulfill its promise of delivering a CAD model-based quality verification report with every finished tool, it relies on Verisurf software and compatible measurement devices from Verisurf Software Inc., Anaheim, Calif. With the operative word being CAD-based, Verisurf was selected on four compelling points:
The flexible combination of an open software platform and a variety of measurement device options allows Hockley to develop and/or maintain digital continuity, or the digital thread, throughout every job.
“Verisurf software has truly raised our quality control levels with its unique set of application tools that speed up our tooling inspection,” said Robin Walton, quality manager for Hockley. “We also use Verisurf Reverse integrated CAD and solid modeler to produce surface models direct from our scanner. The color error mapping and labeling is outstanding and allows us to confirm the accuracy of our work in real time.”
Hockley was tasked with building, inspecting, and delivering tooling for the canopy of the F-35 joint strike force fighter jet. The job required high tolerances given the fact that the canopy, or transparency as the assembly is commonly referred to, comprises a framed windshield and canopy that is produced from a single piece of stretched acrylic, with no steps or gaps in the outside mold line.
The F-35 is the world’s second fifth-generation tactical fighter designed to satisfy four key objectives: lethality, survivability, supportability, and affordability. The concept behind the F-35 Lightning II cockpit is to “return the pilot to the role of tactician,” according to its designers. This is accomplished by using computers to do what computers do best and allowing pilots to do what pilots do best, with optimum pilot/vehicle interface (PVI), manageable single-seat workload, and superior situation awareness.
Pilots never see the outside world through the canopy; they see an image of it. Every manufactured canopy optically distorts the view of the outside world in a unique way. Aerial and ground targets viewed through head-up and helmet-mounted displays can be distorted by imperceptible deviations in canopy thickness, curves, and material. In other words, the canopy can have a direct effect on weapon accuracy. To mitigate this, every canopy is manufactured and verified to extremely tight tolerances. Each canopy is then optically mapped and matched to a specific aircraft as part of the assembly process, with optical deviation data stored in onboard systems to correct the pilot’s view of the outside world, in real-time.
As part of the tool building process for the F-35 canopy, Hockley used several key features of the Verisurf software, combined with appropriate measurement hardware devices, to ensure accuracy and quality verification.
Verisurf Build, also known as the Virtual Gage, displays real-time deviation following the movement of a CMM laser tracker or probe, inspecting the part in relation to the nominal CAD model. Following quick alignment to the CAD model, Build’s live, intuitive interface shows part-to-model deviations.
“The software has been a game changer for us by providing not only clear and decisive tooling verification, but also live digital tooling setup and positioning for advance tooling applications in our aerospace department,” said Paul Squire, engineering manager for Hockley.
In addition to dimensional control, Hockley utilizes the Verisurf Build interface for several additional functions, including:
The F-35 canopy is both an aerodynamic component and a lens that transmits and refracts light. Add to this the aircraft’s performance capabilities and piloting objectives and there is little room for error surrounding the entire transparency system. Identifying and minimizing waviness of the canopy tool surface helps mitigate optical and aerodynamic deviations, maintaining surface performance and lessening the amount of optical correction needed from onboard systems.
A specific analysis feature of Verisurf software is used to determine waviness of the tool surface, both within a local profile and relative to deviations across the entire surface. This provides data to the user to help them correct the tool if necessary. The feature provides:
Verisurf software is an example of integrating modern metrology with traditional manufacturing methods to raise the bar on what is possible. Built on a CAD platform, Verisurf supports the natural progression of model-based design, engineering, manufacturing, and quality verification. This maintains digital continuity throughout every step of the design/build process.
“The evolution of tooling in manufacturing has advanced more in the past 20 years than any other period in history,” said Ernie Husted, president and CEO of Verisurf Software. “High-tech materials have been a critical contributor, but without the experience of expert toolmakers and the integration of CAD, reverse engineering, and metrology solutions, finished platforms such as the F-35 would not be feasible today.”
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