Web Inspection Equipment

Web inspection equipment is used for the detection and/or automatic identification of web or web coating patterns and defects or problems such as streaks, blurs, microscopic defects, smudges, fish eyes, coating pin holes, dirt spots, breaks, holes, sags and rips. Typically, these inspection products are used by industries that manufacture or process paper, films, foils, and other roll stock. Web inspection equipment incorporates sensors, cameras, ultrasound technologies, and thickness gauges to take measurements of physical and dimensional properties. In addition to web thickness, these properties include density and surface quality.

Suppliers of web inspection equipment provide many different machine vision, quality control (QC), and quality assurance (QA) technologies for inspecting web materials. Common web inspection technologies include capacitive, resistive, phototransistor, and photomultiplier systems. Capacitive web inspection equipment uses the face or surface of a sensor as one plate of a capacitor, and the surface of the web as the other. Resistive web inspection equipment is also commonly available. Phototransistors are solid-state light detectors with internal gain. They provide analog or digital signals. Photomultiplier tubes are used in web inspection applications where the rapid detection of light is necessary.

Some web inspection equipment uses laser, CCD linear array, streak sensor, or software-based techniques to identify web coating patterns and/or identify defects. Laser-based systems use laser micrometers to measure extremely small distances. Charged coupled device (CCD) linear arrays are used in CCD cameras, devices that contain light-sensitive silicon chips and which detect electrons excited by incoming light. CCD web inspection equipment that uses CCD image sensors is also available. Web inspection systems with thermal sensors are designed to detect heat streaks. Software-based web inspection systems may employ data mining techniques.

Web inspection equipment differs in terms of features, but even basic systems may offer multiple detection methods. Examples include splice and tear-out, missing ply, metallized splice, reject control, and spray marking capabilities. Intermediate web inspection equipment may provide infrared (IR) hole and flaw detection systems, ultraviolet (UV) detectors, and other web inspection methods. With high-speed web inspection machines, line scan technology and coating streak detection technology is used for rapid imaging. Web inspection equipment that is designed for high gloss, high-end coated web materials is also available.

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