With the new web inspection system (WIS) on paper machine 2, Sappi is driving forward its plans to continue expanding the centre of expertise for speciality papers and carton board at the Alfeld site. The aim of this investment is to ensure the high quality for which Sappi is known, and to continue raising its quality levels. The investment represents a further step in the expansion of the speciality paper sector at Sappi and follows the approx. € 61 million conversion of the PM2 paper mill in the past year and the commissioning of the new Paper Lab a few months ago.
The new investment in the six-figure euro range is in the installation of a visual WIS web inspection system on PM2. With the help of this system, even the tiniest of production errors can be detected at machine speeds of up to 1200 m/min across the 4700 mm working width. The web inspection system is based on camera inspection in transmission and reflection of the web. Of the three measuring beams that Sappi has installed on PM2, the illumination measuring beam is particularly significant. Its specially optimised camera angle detects even the smallest coating errors such as blade marks, coater smudges, scratches or streaks on the functional side of the special paper with a hitherto unknown degree of precision.
"With the illumination measuring beam for the reflectance test we are offering a world first. Thanks to the new technology we can intervene in ongoing production early on and significantly reduce even the smallest production errors and eliminate defects. This in turn raises our high quality levels even further. Our customers profit from improved processing features of our special papers", explains Klaudia Vandieken, the Project Manager responsible for implementing the new web inspection system at Sappi.
Maximum quality standard raises production reliability
The first of the three measuring beams on PM2 is installed in front of the Speed Coater and checks the raw paper. It detects the web using seven transmission cameras. The second beam has been integrated after the last Bladecoater Station on PM2. This uses 12 illumination cameras to detect coating errors in the oblique light by measuring reflection. In this process the camera bar supports are mechanically adjusted and the camera and light angles are aligned with the web in multiple stages. The result is an outstanding scan of the web. The third measuring beam is located in front of the pope reel and uses seven transmission cameras to detect errors in the finished paper.
Each type of error is detected with excellent quality standards and accurately documented via the web inspection system. A high resolution camera delivers photos of the damaged areas and the specific error location is pin-pointed. The live error map is updated on the inspection screen every five seconds. This is very helpful for Quality Management to identify and correct possible error sources quickly. In subsequent production stages, the faulty paper location can then also be cut out to ensure that customers only receive the highest quality. PM2 is used to manufacture special paper types such as Algro Sol, Algro Finess, Algro Vitess, Parade Prima and many other kraft papers.
