Perfecting Press

Most sheetfed presses print on one side of a sheet per pass, requiring the entire paper pile to be turned over and run through again to print the reverse side. A perfecting press, however, accomplishes this in a single operation. The process of printing at least one color on both sides of a sheet in one pass is known as perfecting, and any press capable of this is termed a perfecting press or perfector.

The most common type is the convertible perfector, illustrated in Figure 3-5. It employs special reversing cylinders that tumble the paper end-for-end between printing units, allowing the second unit to print the opposite side. This design enables versatile output; for instance, a two-color convertible perfector can print either two colors on one side (2/0) or one color on each side (1/1) in a single pass. Presses with four or more units offer further combinations, such as a six-unit perfector printing 6/0 or 4/2, depending on the unit configuration and the perfecting cylinder's location.

Another, less common type is the blanket-to-blanket sheetfed perfecting press. Here, the blankets from two printing units make direct contact, with the paper passing between them. This eliminates the need for an impression cylinder, as each blanket acts as the impression surface for the other. This method is standard on most web offset presses.

Sustainability remains a key driver, with efficient perfecting presses reducing paper waste and energy consumption per sheet. These technological refinements support the demand for shorter runs and faster turnaround times in both commercial and book printing applications.