Graphic Design & Printing TechnologyUnit - 5
Press maintenance and Troubleshooting.......................................
Introduction
During offset press operation, when a problem arise the operators skill set
includes the ability to examine the problem and methodically identify the cause-
poor paper, excessive dampening solution, inadequate roller pressure, etc. What
ever the cause the operator is counted on to systematically isolate and eliminate
it. At this point the students learn about basic press maintenance methods and
trouble shooting techniques.
Learning Outcomes
The learner:
- identifies paper problems and suggest remedies
- identifies Ink problems and suggest remedies
- identifies printing problems and suggest remedies
- identifies problems due to blanket and rollers and suggest remedies
- identifies problems due to incorrect cylinder pressure and suggest rem-
edies - understands the importance of preventive maintenance
- demonstrates cleaning and caring the press
- understands the importance of Quality Control Devices in quality print-
ing
Printing problems may arise due to situations involving the substrate, the ink
or the press- or any combination of the three.
Paper problems
Electrostatic Charge on Paper
Printing sheets stick together because they are electrostatically charged. As a
result, several sheets are simultaneously sucked in from the stack, stopping up
the feeder. Static electricity arises from either an electron deficit (positive
charge) or an excess of electrons (negative charge) on the surface of the paper.
An electrostatic charge is especially likely to occur when paper that is too dry
is processed under conditions of low atmospheric humidity.
Remedies:
The moisture content of paper should range between 45% and 55%. The
electrical conductivity of paper, and consequently electrical run off, increases
with increasing moisture content
- Working spaces should be air-conditioned or humidified at a 50% to 55%
level of relative humidity.