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Maximized throughput is mandatory for film and sheet extruders, but greater speeds can mean greater opportunities for defects, necessitating inline inspection and thickness measurement.

Tony Deligio

February 18, 2009

3 Min Read
Let no defect through your line

Maximized throughput is mandatory for film and sheet extruders, but greater speeds can mean greater opportunities for defects, necessitating inline inspection and thickness measurement.

Many technologies today have closed the loop between inspection and extrusion, adjusting process parameters in response to defects. Vision-system supplier Cognex’s (Natick, MA) SmartView Plastics web-inspection system is customizable based on the film or sheet being produced, with an array of lighting options – collimated, diffused, or side lighting – specified for a product’s translucence or opacity. The company also offers LED (light-emitting diode) light sources, with a greater extended life and lower energy usage.

SRA’s technology is looking for the slightest low-contrast defects, including spots, fish eyes, and contamination.


Cognex's SmartView product offers customizable lighting, including collimated, diffused, or side lighting.

Cognex and other suppliers stress early detection of defects, pointing out that gels, for instance, can indicate issues with upstream filters or extruders. In addition, finding defects and noting their location allows downstream converting to be optimized. Cognex says its SmartView product aims for quality defect imaging and speedy processing of whatever is found.

AccuWeb Inc. (Madison, WI) offers optional software that allows its edge-detection system for blown- and cast-film lines to oscillate the web, measure its width, and monitor the edge position. The company says its ultrasonic WideArray edge-detection system eliminates the need for motorized edge-seeking devices, guiding web into the slitter and windup while simultaneously controlling bubble pressure to keep lay-flat widths within parameters. The company’s edge detectors and line sensors use ultrasonic and infrared technology for sensing and measurement.

AccuWeb’s latest offering is the Accubeam3, which has an improved digital line-guide, as well as an Auto Setup feature that automatically calibrates sensor parameters to their optimum position. This is accomplished through a sensing algorithm that assesses multiple sensing options within its field of view. The company has also gone with LED lighting that it says doubles light intensity compared to previous models, thus improving contrast resolution of the film. The system also allows 25 job recipes to be stored.

NDC Infrared Engineering is also aiming for closed loop inspectionhttps://www.plasticstoday.com/control of film and sheet extrusion, with its Machine Direction and Automatic Target Optimization (ATO) controls. The machine direction system takes the current average scan thickness, compares it to a set target and then, depending on what the user chooses, automatically adjusts either the extruder or the line speed to compensate. The ATO system operates under the same principle, but it dynamically adjusts the target based on current variation in the product as measured by the scanning sensors, aiming to create quality film with the least amount of material needed. For clear and translucent films, as well as coextruded web, NDC offers infrared sensors. For companies running foam and sheet, it can supply gamma ray and X-ray backscatter sensors. For “true thickness” measurement, it can supply single- and dual-sided lasers.

ISRA Surface Vision (Herten, Germany) also emphasizes fully automated inspection systems to optimize manufacturing and maximize output by using precise monitoring and documentation tools. The company has recently sourced systems to Middle Eastern producers of hygienic film and nonwovens. Applied in lines that produce sheets ranging from 2000 to 2250 mm at speeds of 400mhttps://www.plasticstoday.com/min, ISRA says the inspection systems scan surfaces for any relevant defects and then mark them precisely. Products tested include baby diaper backsheets – specifically the embossed outer film used as the diaper’s outer cover and last barrier to leakage, as well as the diaper tape, and in-layer pads. [email protected]

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