The use of image analysis to measure dimensional changes during paper manufacture

It is demonstrated that the variation and magnitude of cross-direction (CD) shrinkage during paper manufacture can be monitored using image analysis. To move from this stage to online monitoring and automatic control is clearly a big step but the possibility is there in the long term. The paper concerns a project to investigate where exactly the differential CD shrinkage occurs on the paper machine and which of the machine and raw materials variables affect it. This has not been possible previously because of the difficulty in measuring the property. Paper can be removed from any point on the pilot paper machine while it is running without interrupting the continuity of the web. The samples can be restrained to prevent further dimensional change by using a ring and plate clamping system, which is readily available because it is used for standard handsheets. The method, then, is a very useful and practical monitoring tool with prospects for automatic control