detailed description of web offset press
operation is beyond the scope of this
publication or training. However, the
growth of web printing for books, newspapers,
magazines, business forms, etc. has made
the process a major part of the printing
industry. The following information will
give you a brief introduction and understanding
of the workings of a web offset press.
printing refers to the printing on a continuous
roll of paper (or some other substrate)
rather than printing on individual sheets
as a sheetfed press does. There are two
basic types of web presses with two sub
types. These include:
web - heat dries the ink
to blanket - prints both sides of
the web at the same time.
web - ink dries by air and absorption
to impression - only prints one
side at a time
web press is similar to the sheetfed press
in that it contains an infeed section,
printing units and delivery section. However,
because the web prints rolls the various
sections are different from those used
on a sheetfed press.
are differences between the various web
presses not only in web width but speed,
configuration, etc. Web press widths can
vary from 11" up to 56". Speeds can vary
from 300 feet/minute to 3,000 feet/minute.There
are basically two types of web presses:
speed commercial web
mostly for high volume printing such
as publication, newspaper, book, advertising,
900 - 3000 ft/min
- ink dries by heat
sheeters and folders
both sides of the web at the same time.
meaning web widths in the 25" range
meaning web widths in the range between
33" - 56"
mostly for lower volume printing such
as business forms, small publications,
300 - 900 ft/min
- ink dries by air and absorption (into
to roll or roll to sheet or roll to
to perforate, punch, etc.
ranges from 11" to 25"
web presses have some commonaities such
as an infeed, printing units and delivery.
Paper is delivered to the press by the
infeed section. The infeed section typically
contains a roll stand to hold the paper
rolls; a splicer which automatically splices
the end of one web to the beginning of
another (except on small business forms
presses), a web-steering device which
controls the sidelay (side-to-side position)
of the infeeding web; and a tensioner
that maintains the proper tension on the
web as it enters the press.
Web presses are made up of several printing
units usually numbering from 3 up to or
more than 9. Like sheetfed, each printing
unit contains an inking system, a dampening
system, a plate cylinder, a blanket cylinder,
and an impression cylinder.
delivery section can consist of a variety
of devices, from a simple sheeter, which
cuts the moving web into sheets of the
required size, to a combination sheeter
and folder, which can both fold the web
into final signatures (group of pages)
and trim the signatures to size. Small
business forms presses can print from
a roll into another roll for future processing.
there are similarities between the various
web presses, there are also many differences.