In the pharmaceutical, food and beverage industries, products must be inspected precisely in order to meet the high requirements. For the inspection of rotationally symmetrical objects, Industrielle Sensorsysteme Wichmann (ISW) has developed a new solution with four industrial cameras from Baumer's CX series, whose simultaneously captured images provide a complete picture of a product.

Rotationally symmetrical objects - this term covers many everyday products. For example, spray cans, ampoules or cans, i.e. objects that can be completely imaged if they are rotated around their own axis. They are often found in cylinder form in the pharmaceutical sector and in the packaging industry for food and beverages. Sensitive industries in which it is important to closely monitor the quality and safety-related issues, some of which are prescribed by law, in order to reliably detect possible damage to screw connections, deformation of the packaging, missing spray nozzles or missing labels or even incorrect contents.

New solution for an old problem

Current approaches to checking rotationally symmetrical products concentrate on rotating them once around their own axis on a defined path at a constant speed and with an exact exposure time in front of a camera. The image is then checked using image processing. "The seam areas between the individual images are often unclean, so that in some cases only serial defects, i.e. defects across several products in one stream, can be detected," explains Stefan Tukac, authorized signatory at ISW. However, the engineers at ISW wanted a 100 percent inspection that would also reliably detect one-off product defects while remaining in the production cycle. Six months later, the new inspection system called "4ninety" was ready. The system covers 90° of the circumference of a round body with four cameras. "Exactly the 360°, which also includes unwinding," says Tukac. The four individual images are combined and evaluated by the software without overlapping to form an overall image.

ISW's approach is simple and can be integrated into existing production processes with little effort. The inspection cell can be positioned above any conveyor belt. With the help of various axes, cameras and lighting can be adapted to different conveyor belts and products. Once positioned, aligned and set up on the software side, the system takes on a wide range of inspection tasks. The shapes of products can be checked, for example for integrity, dimensional compliance or lid placement. However, the presence and position of features such as the correct placement of labels and the inspection of applied 1D and 2D codes or texts (OCR/OCV) are also possible. "Our standard library consists of several thousand fonts. This allows us to assign clear customer fonts to our standard fonts for reliable readability," explains Tukac. By simply defining fixed threshold values, faulty products can be sorted out based on the measured deviations in millimetres or degrees. For label detection, ISW relies on a grayscale and contour algorithm that compares the recorded labels with a master. If there are any differences, the product is ejected.