Tag Archives: inspection

-Automated inspection coming to composites

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Automation of composite manufacturing processes has improved productivity (pounds produced per hour) by roughly a factor of ten or more compared with older manual methods. However, in process inspection of these parts at the layup stage is still performed 100% by eye. The irony of this situation is that some parts produced today by “automated” methods actually take longer to inspect than to produce.

Consider the 787 Fuselage Barrel sections 47 and 48 produced by Boeing using Automated Fiber Placement (AFP). A recent paper co-authored by Boeing (see reference of the article below) describes the challenges and improvements made over several years of AFP production experience.

Cycle time of different elements to produce

Cycle time of different elements to produce the assembly

This figure from the paper breaks down the cycle time elements to produce the assembly. “Program” represents the time spent executing the NC program to lay up the part and comprises 24% of the total cycle time. “Inspect and Rework” consumes 63% of the total cycle time, by far the largest element. In other words, Inspection/Rework takes more than 2.5 times as long to perform as does the layup itself. This even more significant because this time distribution is after several years of process improvements, including Inspection improvements, had been implemented and overall cycle time had been reduced considerably.

The AFRL (US Air Force Research Laboratory), NCDMM and Ingersoll Machine Tools, Inc. are working together to develop and demonstrate an automated system capable of detecting and categorizing defects such as missing tows, fiber twists and gaps commonly found during Automated Fiber Placement (AFP). They are developing Automated Composite Structure Inspection System (ACSIS) designed for AFP layups. The system consists of a camera, lamps and a line scanner mounted on a Gantry that scans the layup to identify and flag flaws. Inspection is performed offline on an AFP layup after it has been produced. For some geometries such as spars made on a dual sided mandrel, one side of the mandrel can be inspected while the opposite side is undergoing layup. In other cases layup and inspection must be performed in series. A prototype system is now operating and beta trials are planned during 2014. ATK has been selected to collaborate with them for a three-month beta site.

Ref.: Harper, R., Halbritter, A., “Big Parts Demand Big Changes to the FP Status Quo”, SME Composites in Manufacturing, Charleston, SC, October 2012)

-“Dark-on-dark”: a machine vision approach for dry carbon fiber inspection

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As automation of dry carbon fiber manufacturing gains more and more momentum across the board, inspection systems become a crucial factor when it comes to assuring the quality of final products and the efficient use of available resources. Due to their ability to detect mistakes and faults at an early stage, it is straightforward to infer the great impact inspection systems can have when suitably integrated in a production line.

The systems presented in this entry are focused mainly in machine vision technology and cover inspection for both dry composite fabrics and post-infusion manufactured pieces. One of the main drawbacks they will need to overcome is the fact that carbon fabric absorbs a wide spectrum of light and presents a black color. Therefore, the design of an adequate lighting system will play a critical role at the task of detecting faults on the material (holes, fuzzballs, foreign-object-debris,etc.) and at providing good performance in the so called “dark-on-dark” scenario where vision systems tend to struggle.

APODIUS VISION SYSTEM

The Apodius Vision System (AVS) is designed to measure the fiber orientation of composite fabrics and, based on the irregularities of the obtained pattern, also detect gaps or impurities that dry composite plies may exhibit. Specifically, it can take orientation angle measurements of 0.1º precision for every 50×50 mm² of both woven and non-woven fabrics thanks to its diffuse lighting technology that minimizes reflections on the fabric’s surface. Also, it is attachable to a robotic arm and, combined with an intuitive software interface the AVS, enables an easy integration of fabric inspection inside a production system.

Apodius inspection head

Apodius´ inspection head

PROFACTOR FSCAN

Another product worth mentioning and highly related to quality control of composite parts is the FScan, designed by the Austrian applied research company Profactor. Instead of using the above mentioned diffuse lighting technique, their machine vision system exploits the reflection model of carbon fiber material and allows to produce high-contrast images. The sensor has a field of view of 60×60 mm² and its capable of scanning a surface with a speed of 1 m/s while detecting in real time all sorts of defects suchs as gaps, inclusions or missing rovings.

Profactor´s high constract carbon fiber images

Profactor´s high constrast carbon fiber images

EDIXIA

This French company with worldwide presence has a very strong background on automation of processes in several industries and is now expanding into the composite market. Their vast experience with different technologies allows them not only to look for defects in several kinds of fabrics, but also to inspect cracks, surface roughness and even fiber orientation of manufactured pieces, after the infusion process is completed. Contrary to 2D systems that infer the presence of defects from irregularities in the observed patterns, Edixia also makes use of 3D technologies which allows them to take direct measurements of the height of a wrinkle, depth irregularities or the 3D location of a cut edge.

Edixia features

Edixia´s features

SURAGUS

Finally, although they do not integrate cameras in their solution, a very original alternative is provided by Suragus. Taking advantage of the conductive properties of carbon fiber, Suragus takes an eddy current approach for this problem, allowing them to successfully leap over the challenging “dark-on-dark” scenario of vision systems. Furthermore, since eddy currents have some penetration in the material, the obtained measurements are not limited to the properties of the surface but also cover a few layers below it. This enables fast inspection for mulitple-layer fabrics (up to 5-7) that otherwise could not be inspected with standard vision systems. Their current  products are able to inspect a square surface of up to 600×600 mm² with a resolution up to 100-200 microns.

Suragus´ Eddy Current Inspection system

Suragus´ Eddy Current Inspection system