Graphic Design & Printing TechnologyUnit - 2
Sheetfed Offset Press.....................................................................
Introduction
A printing press is a machine that transfers an image from some sort of plate or
image carrier to a substrate such as paper. Basically the presses are classified
as sheet-fed and Web-fed presses. Four units make a printing press. They are
feeding unit, registration unit, printing unit, and delivery unit. To print an
acceptable finished product, all of the units must be properly adjusted. In this
unit we will discuss in detail about different units of sheet-fed offset press and
its working.
Learning Outcomes
The learner:
- classifies presses based on various aspects.
- understands working principle of an offset press.
- operates different units of an offset machine.
- understands the structure and properties of offset blankets.
Press classification
Offset presses are categorised according to different criteria- maximum sheet
size the press can handle, number of colours that can be applied in a single
pass, whether one or both sides of the paper can be printed in a single pass,
how the paper feeds into the press etc.
Duplicators and Presses:- Small sheet-fed offset presses printing upto a
maximum sheet size of about 11” X 17” are classifed as offset duplicators and
those printing on sheets larger than 11” X 17” are called offset presses. Offset
presses are larger and more sophisticated and capable than duplicators.
Sheet-fed Presses:- Offset presses and duplicators designed to print a single
sheet of paper at a time are referred to as sheet-fed presses. These presses
pickup individual sheets of paper from a feed table. Sheets are delivered one
at a time to the printing unit.
Web-fed Presses:- Presses that feed from a roll of paper is classified as web
offset. These presses are used for work requiring long runs such as magazines,
newspaper and other similar publications.
Multi colour Presses:- Presses that can print more than one colour during a
single pass are referred to as multi colour presses. These presses consist of a