Greater integrity as vision systems evolve
Inspection and monitoring combined
AUTOMATED PROCESSES in the manufacture of paper products can only be precisely optimised if there is available data about production defects, provision for the collection of analysis of defects, such as web breaks, says Isra Parsytec.
The German company’s compact, smart sensors in its web break monitoring system provide collection and analysis of detailed event information even under harshest environmental conditions, claims the company. The evaluation and compilation of this information is already performed at the sensor unit level.
Event capturing has proven its success in paper manufacturing as it makes it possible to trace back to the defect’s root cause. Process-related critical areas are observed, captured and assessed with a camera system. The relevant evaluation algorithms make conclusions about specific processes and causes of defects in the paper machine. Other event capturing systems are relatively expensive and also difficult to integrate in the production environment.
Isra Parsytec now offers an intelligent web break monitoring system (WBM) to the market consisting of cameras, LED lighting and an embedded PC just in one rugged stainless steel case. Because intelligence is already integrated into the smart sensor, the whole system can be very easily installed directly in the paper machine. Sensors provide all the essential and detailed results, including video data that is provided over a Gigabit Ethernet connection allowing secure transfer over long distances to a remote, central evaluation computer. The staff has the advantage of fewer components installed in the machine since everything is integrated in the sensor unit. The LED lighting is high-intensity with long lifetime guarantee. An optional remote-controlled pan/tilt camera is available for the analysis of specific events, employing zoom optics
Sensors are optimised for the harshest environmental conditions. The screen is cleaned automatically by a flush with windscreen wipers guaranteeing the clearest possible images with low maintenance requirement. Contamination of the visual field is impossible.
The network-enabled systems can be combined and connected. When using several sensors more information can be extracted from various parts of the process in the paper machine. Precise images and events are delivered for the surface regions of interest, allowing for accurate analysis and the ability to draw conclusions “on the run” as defects develop.
Valuable options complement the web break monitoring system. The trim squirt analysis module gives a signal to the operator if contamination of the water nozzles has reached the edge of the contamination section in the screening area of the paper machine such that clumps fall onto the line that could cause line breaks. The release point analysis module monitors the release point of the centre rolls or yankee cylinder. Should the release point no longer be in a specific tolerance area, the operator receives an alarm to prevent paper break. The tail threading analysis module provides for fast and efficient start-up of paper production. The module monitors the quality and progress of tails at critical points and thus provides clear acceleration of the start-up of the paper machine. A further module, the edge analysis unit, provides easy control of paper edges for line fluttering, movement and more.
Coupling the web inspection system (WIS) and the web break monitoring bring additional advantages, as they can be connected to one server on which all information is processed. Completely new on the market: the web inspection and web break monitoring systems are combined into one system. A separate control panel is no longer needed for the event capturing system; single platform includes all monitoring tasks – inspection, analysis, line breaks and events are included in one unit. All information is available through a single operating unit.
A web inspection (WIS) system is generally installed at the end of the production machine in order to monitor the quality of the final product. The WIS captures and catalogues all quality-related paper defects. The relevant video sequences from the WBM cameras are shown from the defects detected by the WIS making it easy to draw conclusions about the defect source. Combining WIS with WBM produces a quicker understanding of where and why the error occurred in the machine providing not only conventional analysis of events such as sheet breaks, but also direct online information about the source and cause of failure. Immediate elimination of the defect makes it possible to more quickly employ preventative measures and web breaks can be reduced by 30 to 70 percent.
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Competes with line scan
CONTACT IMAGE Sensors (CIS) from Stemmer Imaging offer an alternative approach to conventional line scan cameras for industrial web applications such as the inspection of paper and plastics in screen printing, plastic film manufacture and processing and the printing industry.
The technology offers significant advantages in terms of space requirements, ease of alignment, and resolution. With line rates up to 100 kHz, scanning widths up to four metres, very high resolutions and integral light sources, the CIS can be a very cost-effective choice in certain applications.
The CIS head consists of a lens array using graded rod lenses, with each individual lens capturing an image of a very small section of the target object. There is a wide range of resolution options available, from 25 dpi up to 3600 dpi with pixels sizes of 1mm down to 7µm. A clear, sharp image is produced along the narrow line of the sensor ‘head’, which is made up of silicon photodiodes using either CCD or CMOS technology.
Contact Image Sensors have a flat construction, so that they fit into narrow spaces. They come as a system complete with optics, illumination and encoder logic and can be joined together to suit the resolution and width of the web with no reduction of line rate as the width increases. This provides a consistent viewing angle, sharpness and brightness across the width.
Integral LED line lights are pulsed to offer long operating lifetimes and maximise image quality. Built-in timer control includes encoder inputs for triggering and light control and is configured via RS232 or Ethernet. Signal processing allows for high data rates independent of the scanning width. Interface to the image processing system is via industry standard CameraLink or Gigabit Ethernet.
Contact Image Sensors operate with a fixed working distance (typically around 10 mm) and a depth of field of around 2-3 mm so are best suited for inspecting very flat objects where there is no vertical movement of the object at the point of inspection. Conventional line scan cameras, however, remain the preferred option for many applications, so it is important to get independent advice to make the best choice.
Stemmer Imaging claims to be Europe’s largest independent supplier of vision technology and services to industrial and scientific OEMs, system integrators and reseller markets. In addition to a range of Contact Image Sensors, the company also offers cameras in line scan technology and so can provide clear, independent advice as to what is the best solution for any particular web inspection application.
T: +44 1252 780000