High Resolution Residual Stretch Profile Measurement, 1997 Process & Product Quality Conference Proceedings
Through-out the winding process of a roll, the sheet is stretched greatly in the machine direction. During that process, through interlayer slippage on the top of the roll, the sheet will usually relax. This interlayer slippage has been well demonstrated using the J-line test. The compression within coefficient of friction, winder’s running tension, etc. prevent the sheet from returning to a totally unstretched state. At this phase the sheet maintains a residual stretch. Since 1963, when the Cameron Gap Strain was first introduced as a TAPPI routine control method’ to measure the devoted to slitting, measuring, calculating and charting. With 40 + readings per roll, the resolution of the profile is low. invaluable information would have become apparent. Influences of the winding parameters and/or paper machine process related signatures would have been uncovered which could possibly be detrimental to pressroom runnability. Since paper mills still use the Cameron Gap test today to confirm winder operation, it was just a matter of time before a more in-depth analysis was invented. Still it took over 30 years. Unless a mill is running into specific pressroom runnability issues, if the paper meets the quality, strength, roll size and width, why test the roll after winding? When mills run into misregistration problems in pressrooms, or increased break where the problem originated. Adjustments would then be made in the paper making process or winding parameters to try to eliminate the pressroom problems. There was no way, however to confirm if the adjustments corrected the problem, until the paper was sent back to the pressroom and run in large quantities. This paper will explain the workings and results of a new test instrument which measures the residual stretch profile of the known Cameron Gap Test, painting a roll stretch profile in very high resolution and precision.