R. Duane Smith
Product Manager / Specialty Winding BLACK CLAWSON CONVERTING MACHINERY Davis Standard LLC 46 North First Street Fulton, New York 13069
THE ART OF WINDING GOOD ROLLS
By R. Duane Smith Black Clawson Converting Machinery Davis Standard LLC Fulton, New York What is a good roll? Any baker will tell you that in making a good roll it must be of theright shape, the right size, the right consistency - not too hard and not too soft, it must look good - no blemishes or visual defects, and it must have a good aroma. A slitter winder operator will tell you that a good roll of paper is one that: Is the right shape Is the right size Is of the right consistency It must look good Aroma? - Round and proper width - Not too big or small - Not too hard orsoft - No blemished or visual defects - Well, start shipping your Customers bad rolls and they are going to Raise a Stink
Your customers demand a roll that will run without problems. Most will tell you that, if a roll of material looks and feels good, then it will run without problems. It is a well known fact that you can’t make paper or other products on the slitter winder. Still, it is everywinder operator’s job to insure that the web defects are not amplified or made worse during the slitting and rewinding operation. The purpose of this paper will be to discuss the factors that go into the consistent production of top quality rolls off a slitting and rewinding operation. This article will be centered around roll hardness and visual defects and how they can be controlled forconsistently rewinding good rolls. Roll Hardness Roll density or hardness is probably the most important factor in determining the difference between a good and bad roll. Rolls that are wound too soft will go out of round while winding or will go out of round when they are handled or stored. The roundness of rolls is very important in your customer’s operation. When unwinding out of round rolls, eachrevolution will produce a tight and slack tension wave. These tension variations can distort the web and cause register variations in the process. The only way to minimize the affect of these tension variations is to run the operation at a much lower speed, which greatly affects the production of the process. Rolls that are wound too tight will also cause problems. Tightly wound rolls contain highinwound tension.
These rolls can split open like a watermelon when dropped or squeezed by a roll handling truck. The web will stretch and deform as these stresses are relieved as the roll cures during storage. If this inwound tension becomes too high, bursts can occur inside the wound roll. These cross machine tension bursts are normally well hidden and can not be detected until the roll isunwound. These bursts cause web breaks which cause major production losses on your customer’s production lines.
Cross Machine Tension Burst Since there is no such thing as a perfect web, it is the responsibility of the winder operator to make sure that these slight imperfections do not stand out in appearance and do not cause their customers process problems. Rolls that are wound too tightlywill exaggerate web defects. No web is perfectly flat or the same thickness from one side to the other. Typically webs will have a slight high and low areas in the cross machine profile where the web is thicker or thinner. If the rolls are wound too hard then the web will stretch over these thicker areas causing bumps or ridges. As the web is stretched over these ridges, it deforms in these areas.This causes untensioned areas or baggy paper when the roll is unwound. There may also be moisture streaks where the web is higher in moisture in localized areas across the web. These moisture bands will cause web defects know as corrugations or rope marks in rolls which are wound too tight. Ridges and corrugations cause the customer process problems such as poor registration on a printing line....