Fully-automated inspection of foils for the hygiene market

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1 Multitrack, fast and precise Fully-automated inspection of foils for the hygiene market Manufacturers of foils and products for the hygiene market must ensure the continual improvement of production processes and quality in order to survive the increasingly tough international competition. The effects of rising raw material costs, the diversification of product ranges and smaller batch sizes can only be offset by cutting down on personnel costs, for example, through the realization of production operations by trained employees in low-wage countries. Customers accept nothing less than customized packaging and 100% documented quality. The only solution is fully-automated web inspection systems that are simple to operate and only require a low level of maintenance. It is no longer possible to meet the requirement of 100% visuallyinspected foils with time-displaced random sample inspections. Only electronic systems are capable of coping with large web dimensions and high machine speeds. Every single finished reel must be furnished immediately with a written and/or electronic inspection report so that it can be allocated to A reels, B reels or rejects. The secure knowledge of reel quality alone provides the foil retailer with arguments that support his pricing concept vis-à-vis customers. Only highly efficient inspection systems based on the very latest technology can satisfy these increasingly tough requirements. Company Information Page 1

2 An example of a sophisticated, practical solution A leading manufacturer of foils that are processed into diapers and other hygiene products produces foils in widths of up to 4000 millimeters at web speeds of currently up to 300 meters per minute, which will be increased at a future date to 600 meters per minute. The foils are cut on up to 25 tracks and laminated with nonwoven webs. Holes larger than 0.3 millimeters in size, foreign particles and dirt must be detected. It is also necessary to measure the width of the webs and establish the centered positioning and width of the nonwoven webs that are laminated on the foil. All programmed and acquired data must be stored in a database where it can be accessed by the process control system. A printed protocol is required for each reel immediately after it is changed. Also, any material defects that are found must be marked with a positioning precision of 50 millimeters. The customer required web inspection systems that are simple to operate and can be serviced by the foil manufacturer's maintenance staff. 24-hour operation, seven days a week, necessitates extremely high availability. Maintenance work must be performed on inspection system at the same time as maintenance work on the production line. The solution: an efficient web inspection system ISRA PLASTIC VISION provides the solution: a web inspection system that is based on intelligent line scan cameras. Up to 14 CD (cross-direction) cameras, each with 1000 or 2000 point scanning elements, are necessary to provide a resolution of 0.3 millimeters cross-directionally to the web on webs of 4000 millimeters in width. The cameras work with a pixel frequency of 40 MHz, which produces Company Information Page 2

3 an image repetition rate of up to 37,000 scans per second. At the maximum web speed of 600 meters per minute, the scanning resolution is also 0.3 millimeters in machine direction. This resolution is sufficient to detect holes in the web that are considerably smaller than 0.3 millimeters. Defects that are larger than 0.3 millimeters are allocated to defect categories by the system. The web is laminated with nonwoven strips during the process and divided up lengthways before the web inspection. As a result, the web inspection comprises up to 25 separate webs. The width and the central positioning of the nonwoven strips must be inspected on these webs in addition to the inspection for holes and dirt. This task requires special algorithms to record the low-contrast transition between the nonwoven and the foil, which is almost invisible to the naked eye. The system works with transillumination. The cameras are positioned on one side of the foil web, while the lamp is mounted on the other side. Due to the high light sensitivity of the camera, this process enables the reliable detection of dirt on the opaque foil. Service-friendly and simple to operate The cameras are mounted on plates to enable the service-friendly, fast exchange of cameras by only removing one single thumb screw. To protect them from the high heat loads that are emitted from the nearby equipment modules, the cameras and lamps are housed in closed, air-conditioned casings. To minimize the costs of maintenance, service and replacement part stockkeeping, conventional, low-cost, standard fluorescent tubes are used as lamps. These lamps from various manufacturers are avail- Company Information Page 3

4 able at retail outlets all over the world and no expertise whatsoever is necessary to handle them. The optics are also conventional, high quality standard lenses to simplify the stock keeping of replacement parts. The system is operated via a convenient menu. Parameters such as target widths and the anticipated web positions, as well as the conditional setting of alarm outputs and the allocation of defects to defect categories, can be set on a product-specific basis. All data, including the inspection results, are stored in a database which the process control system can access via an interface. At the beginning of the inspection, the system scans all strips and independently sources their position. The system recognizes any deviations from the operator's entries, such as an incorrect position, and emits a clear alarm signal. Despite this, the inspection commences and automatically adjusts to the situation. Retrofitted defect location marking The material is wound on reels immediately after the inspection line, within a distance of less than six meters of web running length. After the installation of the first four systems, the production facility was pressurized by its customer to retrofit a web marking system to enable maximum defect marking precision. At a web speed of 300 meters per minute, the defects must be labeled with a precision of 50 millimeters. This is the only way to reduce the reject rate during the subsequent end-product packaging process to a minimum. The label dispensing systems for each of the 25 webs were installed at a distance of four meters after the inspection. In collaboration with the customer and the manufacturer of the Company Information Page 4

5 marking system, a highly-effective solution was found. The label dispensers were installed in the existing systems without the need for conversion measures or changes to the inspection concept. This example shows the diversity of foil web inspection applications. In addition to standard solutions, that can in some cases be installed by the customers themselves, ISRA PLASTIC VISION has the know how and flexibility to provide low-cost, customer-specific solutions on the basis of a standard solution. In this way, the company helps manufacturers of foils for the hygiene market to extend and sustain their competitive lead. Company Information Page 5

6 Pictures Inspection system in operation (Bild 1.jpg) Company Information Page 6

7 Multitrack optical inspection ( Bild 2.jpg ) Company Information Page 7