Non-destructive testing Robot assisted NDT inspection system: reduction of inspection times and additional flexibility

Editor: Alexander Stark

Switzerland — The GKN Aerospace plant in Munich specialises in producing composite aircraft parts. As safety-relevant components, they are subjected to extensive non-destructive testing. Accubot, a multimodal system with high levels of flexibility and dynamism, allowed GKN to significantly increase the productivity and reliability of its non-destructive component testing.

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In ultrasound inspection by through-transmission, signals coupled by water jet must arrive at the receiver from the transmitter with less than 0.3 mm deviation.
In ultrasound inspection by through-transmission, signals coupled by water jet must arrive at the receiver from the transmitter with less than 0.3 mm deviation.
(Source: P. Kemptner)

As a leading supplier of components for the aircraft industry, GKN Aerospace produces aircraft parts exclusively from carbon-fiber composite materials at its Munich plant. Aircraft components are safety-relevant, so they are subject to the strictest quality requirements. GKN subjects 100 percent of the parts to an ultrasonic inspection in order to detect irregularities, such as inclusions of foreign matter, delamination, or porosity. The inspection times for non-destructive component testing (NDT) were as long as 100 minutes on the existing system.

The key criteria in the new tender for the NDT inspection system were a substantial reduction in inspection times and the option for other measurement and testing methods to be implemented on the system, in addition to the intrinsic ultrasonic inspection. The globally active Austrian machine and plant engineering company Fill offered a solution with two articulated robots on linear axes running in parallel.

With two articulated robots on linear axes running in parallel, the ACCUBOT system from Fill can conduct non-destructive testing of composite components in three separate zones.
With two articulated robots on linear axes running in parallel, the ACCUBOT system from Fill can conduct non-destructive testing of composite components in three separate zones.
(Source: Peter Kemptner)

These can inspect workpieces in three separate zones, jointly in one of them. Automatic tool changing with the Fill Flex Change tool changer allows tests to be conducted with different methods, such as phased array pulse-echo testing or through-transmission inspections with squirter technology, in one clamping operation. X-ray, tomography, thermography, and non-contact methods for geometry measurement can also be integrated in the system. Active Tool, an inspection head from Fill with an additional rotatory axis, enables through-transmission inspection in small, highly contorted areas.

Flexibility, precision, and time savings

The system obtains its necessary absolute positioning accuracy through high-precision Fill linear axes and additional rotary encoders fitted on the output side on the rotary axes of the Accubot robots. A robot calibration system based on laser tracker helps achieve and maintain this high precision subsequently. This system has reduced the time required for annual geometrical inspections at GKN from eleven hours to half an hour. The application-independent system software with the Fill Studio programming and operating environment also brings significant gains in efficiency. It contains a digital twin of the entire system, enables offline programming of the robots during machine operation, and features a unique augmented reality interface.

The huge efficiency gain of the Fill Accubot system results from the significantly quicker inspection processes and the possibility to combine them automatically. “Alone with pulse-echo testing by means of phased array, the inspection time is reduced by 93 percent,” reports Dr.-Ing. Jakov Šekelja, Head of Quality Management at GKN Aerospace Deutschland. “In addition, the several hours of tactile wall thickness measurement performed subsequently in the past now occurs automatically as a byproduct of the ultrasonic inspection.”

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