A vision inspection system using 3D modelling could save composite manufacturers valuable time and money by eliminating the manual inspection process of composite materials and parts, according to researchers at the University of Sheffield Advanced Manufacturing Research Centre.
The strength of a composite component is dependent on the correct alignment of the fibres from which it is made; fibres which are laid incorrectly can result in a range of defects that affect the structural integrity of the final part. While quality checks during the lay-up process are vital they can take 70 per-cent or more of total machine time and is a huge cost.
Detecting such defects, from gaps and overlaps to the presence of foreign objects and debris, at the relatively early lay-up stage of production is much more efficient and cost effective than identifying unacceptable weak points in the material once it is part of a completed component.
The Composite Centre at the AMRC has researched what systems were being successfully employed in related applications which identified the capabilities of the Absolute Arm and its laser scanner options, products developed by Hexagon’s Manufacturing Intelligence division.
Hexagon has developed a composite inspection system especially for measuring fibre orientations, which we believed could be a potential candidate for solving some of our inspection problems. They were able to bring the system to the AMRC to perform a case study – an Absolute Arm with RS5 Laser Scanner and a Vision System 3D.
The Vision System 3D is a camera-based sensor that can accurately detect the orientation of composite fibres using pixel-based algorithms. The system uses a metrological Absolute Arm for position referencing and, combined with scans made using the arm’s laser scanner and camera functionalities, this fibre orientation data can be mapped onto a three-dimensional model of the part being inspected using the dedicated Explorer 3D software platform.
The system lets us validate the design and simulation work that we do at our desks to make sure our design intent is being manufactured, so it becomes a good validation step for our design and manufacture process.
The researchers are primarily using the system for weaving, braiding and preforming processes. Once they perform that initial manufacturing process, they can bring the part to the workstation and use the new inspection system to do a scan of the part to generate the 3D profile of the part.
Using some of the advanced algorithms that are built into the software, they are able to determine fibre orientations that can give an indication of some of the defects that are present in the part.
That information is then taken back into the design and analysis software to update the models with the data from the as-manufactured part in order to perform an analysis which can then be compared against the as-designed part. This provides valuable information for comparing both ‘real’ and ‘virtual’ environments.
This system is one of a number of solutions for composite fibre inspection that has been developed by Hexagon’s Vision and Composites product group in Aachen, Germany. The next stage of the project is to investigate how the technology can be further developed to make them robust enough to pick up some of the more complex defects that we’re hoping to achieve solutions for in the near future.