“Foreign object debris” (FOD) may not be the term that devotees of the Game of Thrones series would use, but most still remember the Starbucks cup that escaped the cutting room floor and made its way to TV screens across the world in the series finale. As an analogy to the problem of foreign object debris in composites fabrication, the cup’s appearance draws some parallels. Despite our best efforts and multiple sets of eyes reviewing production “scenes,” the cup and FOD both manage to escape notice on occasion. Both cause embarrassment and result in costly rework (HBO quietly removed the cup digitally from the scene in subsequent versions of the episode). But the parallels end when one considers the magnitude of the cost – and the seriousness of the consequences.
The problem of foreign object debris has been a perennial concern to end users of composites in critical structures. Thankfully, automatic inspection of large, complex components with LASERVISION not only detects FOD when it can still be removed easily but also helps fabricators to predict when FOD events may occur in future production operations, preventing their occurrence in the first place.
Foreign object debris is somewhat unusual among manufacturing defects: it rarely occurs, but when it does, the impact is highly consequential. “Internal escapes” – FOD events that are detected only during the final inspection process at the end of the fabrication cycle – result in very costly rework, or scrapping of very expensive components if they cannot be salvaged through rework. More concerning are “external escapes” in which undetected FOD can and has resulted in the catastrophic loss of large composite structures, including aircraft. Tragically, loss of life has also resulted.
Automatic inspection presents an opportunity to reduce FOD escapes, eliminate such disastrous events, and raise production rates simultaneously. When you are building large composite structures with complex geometries, an automatic inspection system that is able to “see” fine details across entire surfaces is much more accurate and efficient than manual inspection, and also significantly more efficient and effective than standard “smart cameras” used in some inspection applications. Empirical studies with LASERVISION have demonstrated near-100% accuracy in detecting foreign object debris. Moreover, LASERVISION cuts out 90% or more of the time required for a manual inspection of large composite structures.
How automatic inspection fights FOD
To inspect each and every ply of your large composite structure as it is laid up, LASERVISION initiates a model-directed automatic inspection whenever your work instructions call for it. Mounted above the work-in-progress (WIP) and offering both a large field of view (typically 3m by 3m) and a superior depth of field compared to other vision-based inspection systems, LASERVISION is able to capture highly detailed images across the work surface. The system’s combination of a high-magnification 150 mm lens, high dynamic-range sensor, and AutoFocus provides resolution proven to detect FOD pieces with a 3mm-diameter.
To verify the absence of foreign object debris, the system analyzes the captured images using AI-enabled algorithms. These identify any abrupt changes in optical surface characteristics where none is expected – even a loose piece of black carbon prepreg on a carbon prepreg surface. When FOD is detected, LASERVISION uses its laser projector – with the same best-in-class capabilities as our flagship LASERGUIDE system – to pinpoint its location, making the job of finding and removing it very easy for your operators. In fact, the system will not advance to the next fabrication step until your operator has removed the FOD and LASERVISION has re-inspected that area.
Because it digitalizes the inspection process, LASERVISION’s work in live production is only the beginning. Automatic inspections generate a trove of digital information about your build. This “as-built” data feeds the as-built digital twin, a virtual representation of each actual component, including digital images of each ply in the laminate. This electronic record details any FOD events and the corrective actions taken to ensure a clean build.
Feeding this wealth of inspection data to your enterprise software enables you to perform analytics and identify opportunities for process improvements. For example, by tracing FOD events back through the production process, you may find that prepreg kits coming from one particular cutter generate more FOD events than others, prompting maintenance and/or repair of that cutter. Or, if a high number of FOD events are associated with one work cell, an investigation may uncover an unusual air circulation pattern that tends to carry debris to the work surface in that cell. Analysis of FOD events may even lead to changes in the component’s design or engineering, such as reconfiguring FOD-prone plies.
In this way, automatic inspection takes the battle against FOD well beyond simple detection and removal to analytics, prediction and prevention. Decreasing FOD escapes is critical to both your operating costs and the safety of your products. Decreasing FOD events gives you a competitive advantage both in terms of component quality and in terms of profitability.