Unlike screen printing, in offset printing the image of the design is transferred to plates rather than a screen. Each plate is individually engraved for every color used; the ink is then transferred to a rubber “blanket.” Blankets are attached to a rotating wheel, and each blanket contains one color. Whereas in screen printing a separate pass is required for each color, in offset printing, the entire process is done in a single pass. Offset printing can be “dry” or “wet,” which refers to the type of ink used. This method is best-suited to round containers but can be adapted to square or irregularly shaped containers, although production will be at a lower speed.
Offset printers are a simple way of printing a continuous, repeating message on moving products like pipe and tube, metal conduit, and extruded plastics. Standard units print at speeds up to 700 feet/minute (210 meters/minute), and the optional high-speed inking system increases print speed to 1500 ft/min (450 m/min). Character sizes range from 1/16″ to 1″ high (16 to 25 mm).
Advantages of offset printing:
Precise replication of even delicate designs and artwork
When artwork has halftone printing demands
High-speed production on round containers or plastic and metal tubes