Terahertz spectroscopy augments Fill Accubot NDT system

Spectroscopy by means of ultrashort waves in the terahertz range is reported to be a very promising method for volumetric nondestructive testing (NDT) in non-conductive materials, such as renewable natural materials (wood and cork) and glass-fiber-reinforced plastics (GFRPs). It has been integrated for the first time as an additional technology in a multimodal Accubot NDT system from international machine engineering company Fill Gesellschaft m.b.H. (Gurten, Austria) as part of a three-year ATTIC (Automated TeraherTz Imaging of Composites and tooling profiling) project with international involvement run by EUREKA.

Called THZ-Imaging, the relatively new technique’s frequency band extends from ~100 gigahertz to 10 terahertz (0.05-3.0-millimeter wavelength) and forms the boundary between radio and light waves. According to Fill, THz-Imaging enables contactless examinations of GFRP or wooden parts without any special safety precautions. In addition, it can be used for examining foams or for determining the weld quality of thermoplastics.

The possible applications of terahertz spectroscopy for plastic applications have previously been restricted to laboratory operations. Fill participated in the three-year ATTIC EUREKA project to develop a robot-based automated process for the production and subsequent inspection of drill holes in GFRP. This process involves fully automatic inspection of the material around the drill hole for defects using THz-Imaging. Integration of a THz spectrometer on a FlexChange quick connector flange ensured swift implementation of this technology in a robot-based inspection system from Fill. The flexible system is said to enable use of THz-Imaging for fiber-reinforced composite parts, even if these are contorted or freely formed. The same applies to inspection of the internal supporting structures of complex-formed parts from additive production.

“In the ATTIC project, THz-Imaging achieved technology readiness level (TRL) 5 as another technology for our multimodal automatic NDT systems,” explains Harald Sehrschön, research and development (R&D) team leader at Fill. “Integration of THz-Imaging spectrometry in fully automatic NDT systems would enable a change in methodology in automated nondestructive component testing for many manufacturers. However, there is still much to do before application in a customer project.”

Alongside production systems for the automotive, aviation, sports and construction industries, Fill develops and produces automated solutions for nondestructive materials testing. In addition, the company has developed a solution with the high-precision Accubot robots that can operate independently and jointly on linear axes running in parallel. These systems can perform inspections with different methods. An additional rotatory servo axis at the tool center point also enables component testing in small, highly contorted areas.