Analysis and treatment of printing failure of the

2022-08-04
  • Detail

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

cause: 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 completely not inked or the same part of each page repeats light printing

reason: the blanket is sunken

treatment method: apply reductant on the blanket or replace the blanket

II. Oil appears when the whole printing plate surface is stained with ink or chromaticity. The annual output of China's daily-use plastic products is about 3.2 million tons of ink spots

reason: the plate is stained with dry glue during initial operation or the plate is dry when it is restarted; During normal operation, a part of the landing roller is not in contact with the printing plate, and the water volume is insufficient due to improper pressure between the brush roller and the bucket roller or serious wear of the brush roller

treatment method: increasing the speed of water supply motor instantaneously can increase the water volume, so as to quickly remove the glue. 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

cause: when starting printing, if the new ink arrives in front of the plate and the water roller contacts the plate for a long time, the plate will be polluted; This phenomenon is particularly likely to occur if printing is started when the ink roller is dry without prior ink adjustment

handling method: stop the machine immediately and clean the page. 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

cause: 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 not appropriate; 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 ink volume; Reduce ink viscosity; Adjust the pressure of ink roller and plate roller; Reduce the thickness of printing plate or rubber cloth; Change the pH value of fountain solution

change the printing plate

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

cause: the speed of water supply motor is too high; Insufficient ink; Insufficient pressure of plate roller and rubber roller; The rubber blanket is cracked or contaminated; The inking part of the printing plate is worn; Too much web paper 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 ink volume; Increase the thickness of printing plate or rubber cloth; Clean or replace the blanket; Repair or replace the printing plate; Remove the paper powder from 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

cause: 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 ink viscosity; Too much web paper 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; Remove the paper powder from the web

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

reason: poor plate making process; Dirt on the water roller; Jump or slip caused by improper pressure of inking roller; The rubber blanket 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 plates is too high

treatment method: change the plate making process; Clean the water roller; Reset the pressure of the ink roller; Tension or repair the 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 - the paper has horizontal light color horizontal lines; The common reason is that the shadow points are damaged

cause: the printing plate or rubber cloth is too thick; Excessive ink output; The inking part of the printing plate is worn; Poor pH value of fountain solution; The printing ink on the plate is dry; Poor setting of inking roller; The rubber coverage of the rubber roller 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 as long as it meets the specified mandrel diameter and has sufficient hardness; 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. ink roller inking failure - the ink does not get on the ink roller, and the inking part is uneven

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

treatment method: if the ink cannot be evenly inked, do not use strong roller to operate. The pressure of the sealing line of the roller shall be uniform as a whole, and the pressure shall be as small as possible within the range that does not affect the printing quality. If it is found that the rubber roller is 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 the fountain solution or replace the ink

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

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

treatment method: replace with clean fountain solution; Reduce water supply motor speed to reduce water volume; Reduce ink viscosity with reducing agent; Increase the speed of the ink supply motor to increase the ink supply

Xi. Paper feeding slack - paper feeding slack between the printer and the folding machine

cause: the web tension is too low; Rubber cloth lining is too thick; Paper powder accumulation on the blanket; The pressure of the paper pulling roller of the folding machine is too low; The paper cutting roller (RTF roller) and the paper pressing roller on the folding triangle are set improperly

treatment method: adjust the spring or air pressure to increase the tension of web paper; Change the thickness of rubber cloth; Wipe the rubber blanket; 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 the relevant components, and change the braking effect of the brake fan blade industry, which consumes more than 1million tons of composite materials every year; Reduce water volume; Check the parallelism of the paper guide roller; Replace the web

XIII. Paper wrinkle

cause: the blanket is dirty, damaged, loose, and the rubber drum is not properly lined; Excessive ink and fountain solution; The tension of the web 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 ink volume and water volume; Reduce web tension; Scrub the paper guide roller and check its parallelism; Readjust the folding machine; Replace the web

Copyright © 2011 JIN SHI