<p>Web breaks are considered as one of the most significant runnability problems</p><p>in a pressroom. This work concerns the analysis of relation between various</p><p>parameters (variables) characterizing the paper, printing press, the printing</p><p>process and the web break occurrence. A large number of variables, 61 in</p><p>total, obtained off-line as well as measured online during the printing process</p><p>are used in the investigation. Each paper reel is characterized by a vector x</p><p>of 61 components.</p><p>Two main approaches are explored. The first one treats the problem as a</p><p>data classification task into "break" and "non break" classes. The procedures</p><p>of classifier training, the selection of relevant input variables and the selection</p><p>of hyper-parameters of the classifier are aggregated into one process based on</p><p>genetic search. The second approach combines procedures of genetic search</p><p>based variable selection and data mapping into a low dimensional space. The</p><p>genetic search process results into a variable set providing the best mapping</p><p>according to some quality function.</p><p>The empirical study was performed using data collected at a pressroom</p><p>in Sweden. The total number of data points available for the experiments</p><p>was equal to 309. Amongst those, only 37 data points represent the web</p><p>break cases. The results of the investigations have shown that the linear</p><p>relations between the independent variables and the web break frequency</p><p>are not strong.</p><p>Three important groups of variables were identified, namely Lab data</p><p>(variables characterizing paper properties and measured off-line in a paper</p><p>mill lab), Ink registry (variables characterizing operator actions aimed to</p><p>adjust ink registry) and Web tension. We found that the most important</p><p>variables are: Ink registry Y LS MD (adjustments of yellow ink registry</p><p>in machine direction on the lower paper side), Air permeability (character-</p><p>izes paper porosity), Paper grammage, Elongation MD, and four variables</p><p>characterizing web tension: Moment mean, Min sliding Mean, Web tension</p><p>variance, and Web tension mean.</p><p>The proposed methods were helpful in finding the variables influencing </p><p>the occurrence of web breaks and can also be used for solving other industrial</p><p>problems.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:hh-1144 |
| Date | January 2008 |
| Creators | Ahmad, Alzghoul |
| Publisher | Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Högskolan i Halmstad/Sektionen för Informationsvetenskap, Data- och Elektroteknik (IDE) |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, text |
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