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FLEXO Magazine : August 2013
Smart Value: State-of-the-art today may not be competitive tomorrow. Technology is advancing at an exponential pace pushing conver ters’ demands for quicker ROI. Stay ahead of the curve with European component quality equipment at a lower investment. *Value=Affordable Euroflex Flexo CI 8/10c Press *HighSpeed1500+f.p.m. *Short&LongRuns *Mono-blockFrame *FullyServo *AutoPre-register&Impression *AutoWashSystem Call 630-681-2521 email@example.com www.kymcamerica.com roll and the distance that its mass center is displaced from the rotational axis. The general formula for centrifugal force is: FORCE=w2xRx(W/g) or FORCE = w2 x DYNAMIC UNBALANCE Where: W = roll weight g = gravitational constant R = radius of rotation w= angular speed of rotation We must therefore measure imbalance as the product of weight and displacement, expressed in terms of ounce- inches. An imbalance of two ounce-inches is produced by a two-ounce weight displaced 1 inch from the rotation axis. For example, a roll weighing 125 pounds (2,000 oz.) with its center of mass 0.001-in. from its rotational center as deter- mined by its bearings, is 2 (2,000 x 0.001) ounce-inches out of balance. The magnitude of the centrifugal force produced by a two-ounce unbalanced condition is a function of the speed of rotation or in other words, the revolutions per minute of the roll. This force, which produces vibrations, increases as the square of the rotational speed. For example, consider again the roll that has an unbal- anced condition of two ounce-inches. When this roll is oper- ated at 500 revolutions per minute (rpm), it will produce a centrifugal force of approximately 0.9 pounds. However, when we increase the speed to 1,000 rpm, we create a centrifugal force of 3.6 pounds, or 4 times the force at 500 rpm. The example illustrates that there is a much greater need for accuracy of balance at higher speeds than at lower speeds. The degree of balance required in a roll can only be deter- mined after consideration is given to the operating speed in rpms and the conditions under which the roll will be used. 40 FLEXO august 2013 www.flexography.org Image 2: Centrifugal force as a function of roll speed. Image 1: Dynamic Imbalance.