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SC print quality influenced by fiber length, fabric structures, and machine drainage characteristics.

Application: This study demonstrates the need to use an "engineered approach" to forming fabric design selection.

This paper presents details of an in-depth study of European and North American supercalendered (SC) printing grades. It shows that the final print quality is influenced by headbox fiber length, forming fabric fiber support spans in relation to fiber length, and machine drainage forces and turbulence on each side of the sheet.

Using a unique computer print simulation technique developed by AstenJohnson Research, the study clearly shows that it is the uniformity in the outside 12.5% to 25% of each side of the sheet that directly affects the print quality on that side and not the uniformity of the whole sheet.

This study is based on the analysis of stock samples taken from the headbox, sheets made using that headbox stock, and a detailed analysis of the forming fabric used on each side to form the sheet on that particular machine.

Each sheet was split (lamination technique), first in half, and further into a total of 14 parts. The uniformity of the outside 12.5% of each surface was then examined and compared to the remainder.

The image of the outside 25% was used for the computer print simulation process and compared to a simulation done on the center portion of the sheet.

The conclusion is that in all cases the center of the sheet is almost perfect, while the greater majority of the micro density differences causing poor print quality are in the outside (25%) layer of each side of the sheet. S!

Danby is vice president, forming development, AstenJohnson, Research and Development, 48 Richardson Side Road, Kanata, Ontario K2K 1X2, Canada; email
COPYRIGHT 2002 Paper Industry Management Association
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2002, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Title Annotation:Print Quality
Author:Danby, Roger
Publication:Solutions - for People, Processes and Paper
Date:Nov 1, 2002
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