The Sheet Delivery Mechanism as Cause of Paper Curls and Back-Edge Stretch in Sheet-Fed Offset Presses.

Difficulties through paper curling are known when printing heavy forms and long sheets in offset presses. It will be shown that the chain delivery system is the main cause for paper curls because of an existing speed difference in sheet transport. The leading edge sometimes runs slower than the cylinder surface speed. The speed and transport difference depends on the position of the cylinders, chain-leads, height of gripper pads and the length of the sheet. Hints are given how to design sheetfed offset presses without curling effects.