Analysis and treatment of printing failure of web

Analysis and treatment of printing failure of web offset press

I. poor inking (blind version)

1. The inking part is not inked or slightly blurred

reason: the inking part of the printing plate is worn; The acid of fountain solution is too strong to emulsify the ink; The inking roller pressure is too high

treatment method: replace the printing plate; Adjust the pH value of fountain solution; Spray reducing agent on the inking roller or stop the machine to clean the

inking roller, and readjust the pressure between the inking roller and the plate cylinder

2. The inked part is not inked at all, or shallow printing occurs repeatedly at the same part of each page

reason: the blanket is sunken

treatment method: apply reducing agent on the blanket or replace the blanket

II. Ink spots appear when the whole printing plate surface is stained with ink or color registration

reason: the plate is stained with dry glue during initial operation or the plate is dry when restarting; During normal operation, part of the

of the landing roller is not in contact with the printing plate approaching the production limit at the end of the year, and the water is insufficient due to improper pressure between the brush roller and the bucket roller or serious wear of the brush roller

treatment method: instantaneously increasing the speed of the water supply motor can increase the amount of water, so as to quickly remove the glue from the results of the tensile test. Or check whether the

brush roller is worn, replace the brush roller as appropriate, or readjust the pressure of the brush roller, plate roller and bucket roller

III. at the beginning of printing, the non inking part is stained with a lot of paper powder

reason: at the beginning of printing, if the new ink reaches the plate and the water roller contacts the plate for a long time, the plate

will be polluted at the same time; This phenomenon is particularly likely to occur if printing is started when the ink roller is dry without adjusting the ink in advance

treatment method: stop the machine immediately and wipe the layout. Then change the set time to start printing. Before restarting the machine,

adjust the ink roller first. If we only increase the water volume without stopping the machine, the proportion of water and ink will be out of balance, and the scrap rate

will rise

IV. bad words - words and dots are damaged by ink

reason: excessive ink; Ink viscosity is too high; Excessive pressure of inking roller; After printing plate or rubber cloth lining

the pH value of fountain solution is inappropriate; The printing plate is worn

treatment method: reduce the speed of the ink supply motor or change the gap between the ink bucket and the ink bucket roller to reduce the amount of ink; Reduce

ink viscosity; Adjust the pressure of ink roller and plate roller; Reduce the thickness of printing plate or rubber cloth lining; Change the pH value of fountain solution

replace the printing plate

v. granular - the color of the inking part is thin and weak

reason: the speed of the water supply motor is too high; Insufficient ink; Insufficient pressure of plate roller and rubber roller; Rubber blanket cracked

or contaminated; The inking part of the printing plate is worn; Too much web powder

treatment method: reduce the speed of water supply motor; Increase the gap between the ink bucket and the ink bucket roller to increase the amount of ink; Increase the thickness of printing

plate or rubber cloth lining; Wipe or replace the blanket; Repair or replace the printing plate; Remove the paper powder

on the web

VI. paper fuzzing and circular white spots - there are white spots on the printing surface and black spots on the non inking part

reason: there are dirt on the blanket and inking roller; Foreign matters mixed in the ink; The rubber blanket surface is sticky; Paper fuzzing due to excessive viscosity of ink

; Too much web powder

treatment method: wipe the blanket and inking roller; Replace the ink or add liquid to the ink to eliminate

foreign matters in the ink; Replace the blanket; Reduce the viscosity of ink with reducing agent; Eliminate the paper powder on the web

VII. Dirty plate (dirty) - the non inked part is stained with ink; Ink viscosity is too high or too much ink makes the non

inking part produce ink affinity

reason: poor plate making process; Dirt on the water roller; Jump or slip caused by improper pressure of inking roller;

> rubber cloth is loose or damaged; The pH value of fountain solution is inappropriate or the water quality is too hard; The humidity in the storage place of printing plate is too high

treatment method: change the plate making process; Wipe the water roller; Reset the pressure of the ink roller; Tension blanket or

repair blanket; Adjust the pH value of fountain solution or add softener and ionic agent after inspection; Change the storage conditions of printing plates

VIII. Ghosting - horizontal light color horizontal lines appear on the paper; The common reason is that the shadow points are damaged

reason: the printing plate or rubber cloth lining is too thick; Excessive ink output; The inking part of the printing plate is worn; The pH value of fountain solution is not

good; The ink on the layout is dry; Poor setting of inking roller; The rubber coverage of COTS is uneven

treatment method: reduce the thickness of printing plate or rubber cloth; Reduce the speed of the ink supply motor or change the gap between the ink bucket and the ink bucket

roller to reduce the amount of ink; Repair or replace the printing plate; Adjust the pH value of fountain solution; Increase the speed of the water supply motor, increase the

water volume, and prevent the printing ink from drying; Adjust the inking roller pressure; Check the parallelism of the rubber layer of the ink roller, and replace the rubber roller if necessary

IX. inking failure of inking roller - the ink does not get on the inking roller and the inking part is uneven

reason: the pressure of inking roller is improper; The two ends of the rubber roller are worn or sunken, resulting in poor contact; Ink roller cracking; The coating of ink roller and heavy roller is worn; The acid of fountain solution is too strong to emulsify the ink; The ink composition is wrong

treatment method: if the ink cannot be evenly inked, do not use strong roller pressure to run. The pressure of the sealing line of the roller

shall be uniform as a whole, and the pressure shall be reduced as much as possible within the range that does not affect the printing quality. If the rubber roller is found to be worn, concave

or cracked, it shall be replaced in time; If the coating of inking roller and heavy roller is worn, it shall be repaired in time; Adjust the pH value of fountain solution

or replace the ink

X. floating dirt - irregular light color dirt and whitening on the printing surface as a whole

reason: the blanket cleaning agent flows into the fountain solution; Too much water; The viscosity of ink is too high; Insufficient ink

treatment method: replace with clean fountain solution; Reduce the speed of the water supply motor to reduce the amount of water; Reduce the viscosity of

ink with reducing agent; Increase the speed of the ink supply motor and increase the ink supply

Xi. Paper feeding slack - paper feeding slack between printing press and folding machine

reason: the tension of web is too low; Rubber cloth lining is too thick; Paper powder accumulation on blanket; The paper pulling roller

pressure of the folding machine is too low; The paper cutting roller (RTF roller) and the paper pressing wheel on the folding triangle are set incorrectly

treatment method: adjust the spring or air pressure to increase the tension of web paper; Change the thickness of rubber cloth lining; Scrub rubber

cloth; Adjust the pressure of the paper pulling roller and the paper pressing roller

XII. Paper break

cause: the web tension or brake setting is poor; Excessive fountain solution; Insufficient web tension; The parallelism of the paper guide roller

is abnormal

treatment method: change the web tension by adjusting relevant components to change the braking effect of the brake; Reduce

water volume; Check the parallelism of the paper guide roller; Replace the web

XIII. Paper wrinkles

causes: the blanket is dirty, damaged, loose, and the lining of the rubber drum is inappropriate; Excessive ink and fountain solution

the tension of web paper is too large; The parallelism of the paper guide roller is abnormal or there is ink and dirt on it; Poor adjustment of folding machine

treatment method: scrub and tension the blanket and change the thickness of its lining; Reduce the amount of ink and water; Reduce the tension of roll paper; Scrub the paper guide roller and check its parallelism; Readjust the folding machine; Replace the web