PFFC - January 2008 - (Page 43) ROLL ALIGNMENT Are you experiencing web tracking issues, wrinkles in your material, or excessive energy consumption due to roller misalignment? Is the net result unplanned downtime? Here is a course of action that may help prevent these problems. By Jay Tannan, Pruftechnik Service Inc. This article, along with future articles by other authors, is provided as a cooperative effort between PFFC and AIMCAL. Authors contribute to AIMCAL’s technical and education offerings, which include the association’s Fall Technical Conference, Summer School, and Ask AIMCAL. As the unit is swept across the surface of a roll for a minimum of 20 deg, indicated in Figure 3, one laser is lengthened as the other is shortened in each of the gyroscopes. From the change in length, an angular offset is calculated instantaneously to determine the roll’s relative position in space. Measurement Results Figure 3. Simulation of the sweep method across the surface of the roll. The protocol shows the offsets of all the rolls in comparison to a reference roll as displayed in Figure 4. The green side represents the operator side while the red shows the drive side of a roll. The reference roll chosen in Image 1 is Roll ‘A.’ The switch the reference roll as desired. As an example, Image 2 displays Roll ‘C’ as the new reference roll and has all the other roll’s vertical and horizontal values re-calculated. Depending on the industry and machine specifications, the allowable tolerance for the parallelism of each roll normally would be between 0.002 in. and 0.030 in. Roll Misalignment Issues remaining rolls shown have in order for them to be parallel vertical and horizontal offsets with the reference roll. in which adjustments would The flexibility of the softneed to be made at the bearing ware allows the customer to There are several possible web handling issues that can be derived from the sample protocol shown in Figure 4. First, there might be a slight waviness or slack created between Figure 4. Sample protocol that shows two different reference rolls. A: V: 0.000" H: 0.000" C: V: -0.033" H: 0.078" G: V: 0.079" H: 0.040" A: V: 0.033" H: -0.078" C: V: 0.000" H: 0.000" G: V: 0.112" H: -0.037" E: V: -0.096" H: 0.122" E: V: -0.063" H: 0.045" B: V: -0.033" H: -0.083" D: V: 0.000" H: 0.057" F: V: 0.013" H: -0.074" B: V: -0.000" H: -0.161" D: V: 0.033" H: -0.020" F: V: 0.046" H: -0.152" Image 1 — Roll “A” chosen as reference roll. WWW.PFFC-ONLINE.COM Image 2 — Roll “C” chosen as reference roll. JANUARY 2008 | 43 http://WWW.PFFC-ONLINE.COM
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