Reference Book
side edge of the top sheet, as the front blowers separate the sheet from the
stack.
Sheet separation Blowers :- They are air
producing device that separates the top most
sheet from the rest of the pile in the feeding
system.
In the feeding unit paper is stacked on the
pile board. The pile must be positioned in
correct relationship with the settings of the
register and insertion device. An air blast is used to seperate the top most
press sheet from the rest of the pile. The blast can be adjusted for papers of
different weight. Heavy and coated papers require stronger air blast than light
and uncoated papers. The air blast must be strong enough to float the topmost
piece of paper above the pile at a specified height below the sucker feet. The
pile table automatically raises and maintain the correct feeding height as sheets
are removed from the top. The sucker feet grab the floating top sheet and send
it down the registration board where the registration unit takes over.Registration Unit
Functions of Registration unit
Registration is the process of controlling and directing the sheets as it enters
the printing unit. The goal of registration is to ensure absolute consistancy of
image positions on every sheet printed.
Parts of Registration unit
Double sheet detector, Registration board, front lay, side lay, conveyor tape,
running in wheels, two point guide system, three point guide system, transfer
cylinder system.
Double sheet detector :- It is a control device that prevents more than one
sheet of paper from entering the press. Double sheet detectors sense the paper
thickness. When the sensor detects excess thickness, indicating multiple sheets,
the feeding of paper automatically stops.
Registration board :-It is a platform that accepts a sheet from the feeder unit
and inserts it in register, ready for print.