WIRE 2012
Image processing for all elevations Inside the AUTOCONTROL system software project, GEFRA
has continuously developed crack detection tools for both transmitted and reflected light applications. Whenever a crack or its impact on the contour of the part is visible under transmitted light both tools for measuring and contour control can be applied to detect it. This is possible also for non-circular shapes and can be realised with an accuracy of +/-0.02mm in general. Not all crack types and localisations can be found using
transmitted light. Especially cracks upside of the outer contour and on different part levels need another kind of image acquisition and processing. At this point two imaging methods in combination with several types of part specific illuminations can be applied. First, the top and, if possible, the bottom view delivers an
image of the outer contour and other contour lines on the part. In principal the same idea for contour control algorithms is applied here on grey level structures. Figure 4 shows a so-found crack. This tool is not limited to circular structures as shown in Fig. 2 and 4. Other shapes like squares and hexagons (as shown in Fig. 3) can be controlled. A tool for free shapes is also available. In addition to this contour based method, the surface of
the part can be analysed by special tools for crack detection. Developed in particular for the common characteristics of cracks on different surfaces, various classifications for the quantitative and qualitative properties like shape, dimension, orientation, number can be specified. Also users can define the regions of interest on annuli like parts, as shown in Fig. 4.
As an example, Fig. 6 shows a line and a rectangle as the
region of interest and the computed result. In this case, the part would be guided to the reject container.
Fig. 6: Side view on a cracked screw head: line and rectangle surface tool applied
In certain cases and with nearly all fixed part dimensions a
simultaneous top and side view image can be generated using a special objective mirror instead of five cameras. As shown in Fig. 7 tools can be applied in one step on one image by covering nearly the whole part.
Fig. 7: Top and side view by a mirror objective
In this way both the number of images to compute and so
Fig. 4: Top view on a cracked screw head: tool for outer contour (green) and surface (yellow) applied, crack (red)
Very often the view from top and bottom of a part is not
sufficient to cover all possible cracks and other damage. Here, as the second transmitted light imaging method a 360° surround view technology can be applied. Using four cameras at 90° angle distances (as shown in Fig. 5)
a complete image set of the part’s side view is generated. On these images all the tools for crack detection on surfaces can be used.
the data rate per item can be reduced and the number of parts controlled per second can be increased. At the end, all the mentioned software tools based on reflected light images can be applied more than one time to an image. In this way, different kinds of crack types and localisations in one part can be covered.
No end in sight Driven by every new and unsolved customer problem and also
by considering the next and prospective development in both image-processing based quality control and customer sorting tasks, GEFRA’s development team will continue to increase the variety of tools and their application opportunities. GEFRA, with its highly qualified and experienced staff
members and partners in the field of mechatronics, electro techniques, engineering, informatics and natural sciences, is working continuously at the further optimisation and development of its products and technologies. The main focus lies on the further increase of the control
performance, on the integration of new concepts for illumination, image acquisition, processing, and also on the development of multiple sensor systems. The integration of other imaging media like X-ray and other non-invasive inspections like fast eddy current tests for material hardness will be the next step. In this field GEFRA will work in collaboration with
Fig. 5) 360° image acquisition position
external partners and research institutions. GEFRA will continue to offer its national and international customers reliable, flexible, and robust state-of-the- art solutions for their quality control applications.
www.gefragmbh.de
156 Fastener + Fixing Magazine • Issue 73 January 2012
Hall 15 Stand G26
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