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the possibility of analyzing large frequency components; the sensor system does not disturb the production; the measurements are performed real-time and can be adjusted without delays; the measurement concerns the entire production, not just small sample values. It must be possible to distinguish between the machine-directional and cross-directional deviation and the residual deviation as the control system handles these three deviations separately and in different ways. The earlier systems calculated a long-term average profile to filter the profile. As several quality profiles can be adjusted automatically it is important to get the right profile data with high resolution quickly to the control system. This is especially important during changes, after breaks and during grade changes. In advanced systems, algorithms are used to calculate the profile data.
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web. The measurements are taken on the diagonal line and act as basis for profile (machine and cross-direction) and variation calculations. This value is subject to integration depending on the machine speed. If the measurement signal sampling frequency is in size range 2000/s, then the smallest measurement element is about 0.2 cm in cross-direction. The measurement data is integrated to eliminate a small-scale formation variation from the measurement result.
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goal is maintaining the exact respective position of the upper and lower measurement platforms in relation to their distance from each other, in MD and in CD . This is achieved through a robust construction and by reducing the effects of temperature and other environmental effects and through a moving mechanism with minimized backlash of the measurement platform.
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The QCS scanner beam is an essential part of a QCS system. Wide machines and accurate profile calculations require beam stability and accuracy of mechanical movement. As high accuracy in demanding and variable conditions is required, the sensitive sensors must be securely fastened. The most important
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The requirements for an ideal paper machine online sensor include the following: the sensor is calibrated to a natural constant during the measurement; the sensor and the related electronics include fault diagnostics; digital processing of the signal is possible from the start without destroying
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Online sensors are set on the scanner beam to scan across the web. Typical crossing time of the web in new systems is 10–30 s (8m web, 60 cm/s). If the web speed is 1200 m/min and web width 8.5 m, the web moves 280 m during a scan, and the sensor moves the same distance diagonally across the
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Sensors measuring the paper quality (online meters) are attached to a sensor platform that move across the web guided by the scanner beam. A typical crossing time for a sensor platform is 10–30 s (an 8 m web, 60 cm/s). The sensor platform scans across the paper web and continuously measures
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The measurement value is averaged so that each sensor gives one measurement value per one data box which is typically from 5 mm to one centimeter of web width. For a 1 meter wide web, for instance, 100 - 200 measurement values are taken. These measurement values from a single scan (profile
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refers to a system used to measure and control the quality of moving sheet processes on-line as in the paper produced by a paper machine. Generally, a control system is concerned with measurement and control of one or multiple properties in time in a single dimension. A QCS is designed to
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continuously measure and control the material properties of the moving sheet in two dimensions: in the machine direction (MD) and the cross-machine direction (CD). The ultimate goal is maintaining a good and
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Other commonly used continuous measurements include: ash content, color, brightness, smoothness and gloss, coat weight, formation, porosity, fiber orientation, and surface properties (topography).
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Other commonly used continuous measurements include: ash content, color, brightness, smoothness and gloss, coat weight, formation, porosity, fiber orientation, and surface properties (topography).
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points) are called 'raw profiles'. In modern quality control systems, the width of these data boxes can be changed, and accurate profiles can be formed using several thousands profile data boxes.
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Usually the scanner beam also contains all the cables and the air, cooling liquid and protection gas pipes. The base of the scanner beam contains elements that dampen vertical vibration.
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and moisture profile measurements and in addition average basis weight of the paper web and moisture control related to these variables. Caliper is also one of the basic measurements.
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and moisture profile measurements and in addition average basis weight of the paper web and moisture control related to these variables. Caliper is also one of the basic measurements.
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paper characteristics from edge to edge. It can also be directed and stopped to a specific, fixed point on the web to measure the machine-direction (MD) variation at a single point.
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quality and meeting users' economic goals. A basic quality measurement system generally includes
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Quality
Control Systems Education Common Interest Group of the Process Control Division (2012).
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Quality
Control Systems Education Common Interest Group of the Process Control Division (2012).
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Machine Quality Control Systems - Volume 1: Measurement Systems and Product Variability
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Machine Quality Control Systems - Volume 1: Measurement Systems and Product Variability
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A basic quality measurement system generally includes
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In modern systems QCS applications can be embedded to
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342:Safety instrumented system
331:Distributed Control System
285:Variables to be measured
80:Industrial technologies
421:. Tappi Organization.
396:. Valmet Corporation.
392:Nuyan, Seyhan (1997).
371:. Tappi Organization.
459:Industrial automation
44:Manufacturing methods
449:Control engineering
316:Sensor requirements
300:Measurement process
72:Agile manufacturing
249:, board machines,
67:Lean manufacturing
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118:Six Sigma
325:See also
21:a series
19:Part of
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251:tissue
149:ISA-95
144:ISA-88
344:(SIS)
338:(PLC)
188:SCADA
163:B2MML
423:ISBN
398:ISBN
373:ISBN
183:DCS
178:PLC
154:ERP
123:TQM
113:TOC
108:QRM
103:VDM
98:TPM
93:RCM
88:PLM
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