Differential chucks (also known as ‘slip chucks, or ball chucks’) are fitted to the rewind shafts of slitter rewinders to eliminate tension variances that can develop due to (sometimes very minor) material thickness variations across the parent roll. Differences in the overall material thickness of rolls being slit can result in each slit roll being different diameters and therefore requiring to run at different relative speeds. When rewinding rolls that are shaft-driven if each have a different diameter some of the rolls will be wound loose, tight, or may even cause the web to break. The slipping effect of differential chucks on a rewind shaft helps achieve an even tension profile across all rewound rolls. The chucks are held in place by an air-bladder within the rewind shaft.
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