Bank Measuring System Helps to Improve the Economics of the Film Production Process and to Improve the Film Quality as Well

摘要

Among extrusion experts it is a well known fact that the quality of polished films is critically determined by the distribution of the bank of material in the nipof the polishing stack. The surface quality, the thickness distribution, the shrinkage, the flatness, the crystal structure of party crystalline polymers and, not least, the forming behavior depend more or less directly on the size of the bank. Despite this insight even new production lines for films polished on both surfaces do not provide any means of measuring the size and distribution of the bank. Although with some lines and modes of operation it is impossible to visually assess the bank in the roll nip by conventional means. During production, dies are operated as close as possible to the roll nip. The main reason for this is to minimise the edge swell and the lateral shrinkage of the melt web. Thus however in the past all attempts to measure the bank directly from the front or from above were thwarted. Due to the above mentioned reasons it is advisable to measure the bank and to keep it constant throughout production.