Analysis of common faults of the hottest offset pr

Analysis of common faults of offset printing

main factors of inaccurate overprint

inaccurate overprint before and after:

1) printing machine

a. the locking screw of the heaven and earth adjusting disk is not fixed, or whether the M5 Allen screw on the paper feeding rocker arm is fixed

b. whether the copper sleeve of the paper pusher is worn

c. the paper feeding teeth are worn

d. the printing pressure is too small

e. the gear is worn, and the rubber blanket is too loose and not tied tightly

2) paper

a. paper cutting accuracy is not high

b. the printing water volume is too large, and the paper has retraction

3) other

a. there is a problem with the printing plate or the original

b. the paper jam is skewed due to the high paper jam stack or the heavy pressure of the paper block

4) incorrect left and right overprinting:

a. whether the left and right baffles are too tight or whether the left and right baffle screws are fixed

b. the length of paper jam is different

c. the drum moves left and right

causes of oil dirt

oil dirt can be divided into two categories: one is through the "double integral" system because the blank part of the page is greasy to the ink, which appears in a greasy state, commonly known as greasy; The other is because the ink is emulsified and evenly distributed in the layout with very fine particles, commonly known as emulsion, which will make the friction between the pendulum shaft bearings dirty

the causes of oil dirt are:

1) printing plate

a. the quality of printing plate itself is not high (poor printing base or recycled version)

b. the exposure time is insufficient when printing, and the developer concentration is too low

c. the protective glue of the printing plate is not cleaned

d. the blank part of the printing plate is oxidized

2) printing press

a. the pressure on the plate is too light

b. the pressure between water rollers is too light

c. the ink viscosity is too low

d. surface aging of rubber part

e. paper powder and paper wool wear plates

f. the pH value of fountain solution is improper

reasons for different ink depths before and after

in actual printing, sometimes it is found that the ink depth before and after the same picture is different, and often the ink depth before and after is mostly deep, and the ink depth before and after is less. The reasons for the different ink depth before and after are:

1) roller part

a. the drum gear or bearing journal is worn after long use

b. the drum journal is not concentric with the drum shell

c. the pressure between the plate roller and the printing plate is too heavy, resulting in jumping

2) ink roller part

a. the surface of the ink roller is aging after long use

b. thus, the purpose of controlling the movement of the beam is achieved. The ink roller has not been cleaned for a long time, and the surface area is inked, resulting in failure to apply ink

c. the ink viscosity is too high