Graphic Design & Printing Technology

Reference Book

substrate. A second exposure through the negative forms the image on the

plate. As with the sheet materials, the image areas are hardened by this exposure.

The non-image areas remain liquid. Processing removes unwanted liquid in

the non-image areas, leaving raised image areas. A post exposure is then made

to cure the whole plate.

fig. 17.6, 7 IIIrd edn

Computer-to-plate processing transfers images directly from the computer to

the plate, thus eliminating film. Some photopolymer plates can be direclty

imaged by Lasers. In recent years, laser engraved rubber cylinders have been

used to print wall paper and other continuous pattern jobs.

Press types

There are three types of flexographic machine configurations: Stack press,

Central Impression Cylinder (CIC) and Inline presses. Stack presses are the

first type of flexographic presses. In this type of press, the moving web is

unsupported between the printing stations which causes register problems.

Unstretchable substrates such as thick paper or heavier gauge plastics are better

suited for this configuration.

In CIC presses, the web travels from one print station to the next around a

central drum. The moving web is supported between stations, so the press is

ideal for stretchable films needing close register. CIC presses print on one

side only.

Inline flexographic press has separate print stations placed in a straight line.

Each station has its own driers. Two sides can be printed in one pass with the

aid of turner bar. These presses are used to print linear board for corrugated

boxes before corrugation takes place. They are also suitable for printing narrow

web labels and forms that are 6” to 18” wide.

Rubber Plate Liquid Photo PolymerPlate Sheet Photo Polymer

Plate