The Central Impression Press

The Central Impression Press

A central impression press, also known as a drum, common impression, or CI press, arranges all its color stations around a single, large steel impression cylinder mounted in the main press frame. This design locks the web to the cylinder as it passes each station, a fundamental feature that prevents register shift between colors.

Its superior ability to maintain register has made the central impression cylinder press a cornerstone of the converting industry. This stability is particularly vital for complex graphic designs and steady demand for process printing, making the CI press suitable for a wide range of substrates. While the six-color configuration remains the most common, it is increasingly being superseded by eight-color CI presses, with some manufacturers now building ten-color models.

Impression cylinder diameters have evolved significantly. Early four-color presses typically used 30 or 36-inch cylinders. To achieve higher speeds and allow space for interstation drying, diameters up to 60 inches were later adopted for four-color models. The first six-color CI presses employed 83-inch cylinders. The latest eight-color presses feature cylinders up to 94 inches in diameter. However, as drying techniques have improved, reducing the required distance between colors, smaller impression cylinders have regained popularity. The most common eight-color single impression cylinder press now uses an 89-inch (2.26 meter) diameter cylinder.

Advances in between-color drying have rendered the old adage—that larger cylinder presses offer higher speeds—largely obsolete. Nevertheless, larger impression cylinder presses generally still support longer printing repeat lengths than their smaller counterparts.

The central impression press sees limited application for printing both sides of a web in a single pass, with its most common use for this purpose found in tubular film printing.

Central Impression Drum Construction. The drum in a central impression press is constructed from either double-wall steel or cast iron. In both cases, a heating/cooling device controls its temperature. As flexographic market expectations have advanced, press manufacturers must adhere to more demanding tolerances for the CI drum. Digitally controlled heating/cooling elements are now commonly employed to maintain drum temperature within a strict range of ±1°F. This precision is essential for meeting modern print quality demands; temperature variation causes drum size fluctuation, forcing operators to constantly compensate and leading to missed impressions or overimpression.

Regardless of construction method, the CI cylinder must be manufactured to meet high Total Indicated Runout (TIR) specifications. It is standard for new press specifications to require the drum not exceed 0.0003" TIR, with an ideal, lower actual number. Since the drum's TIR depends on the supporting journal and bearings, press manufacturers now favor printer-quality roller bearings with a TIR of approximately 0.0002". The use of custom hand-fit bronze bushings, once prevalent, is declining. Bronze bushings require constant lubrication, usually from a pump, whereas printer-quality roller bearings manufactured to acceptable tolerances can be lubricated via an enclosed oil bath or grease pack similar to a gearbox.

Looking toward 2026, the flexographic printing industry continues to prioritize automation and precision. Enhanced drying technologies and smarter temperature control systems allow for more compact press designs without sacrificing speed or quality. Sustainability remains a key driver, with a focus on reducing energy consumption and material waste throughout the printing process.