Gravure printing common failures and solutions


Published on:

2009-04-18

In the gravure printing process often occurs some printing failure caused by mechanical, process raw and auxiliary materials, work environment and other factors, thus affecting product quality and production schedule. Now the practical experience accumulated in the gravure printing work will be introduced to you, for the reference of peers. Fault a regular and irregular line marks (knife line) 1, regular line marks cause: (1) ink mixed with residue within the scraper knife scratch; (2) printing plate or can be hard objects scratch; (3) printing plate cylinder wear off chrome, copper layer exposed. Solution: (1) with 80 purpose copper mesh to re-filter the ink, and 600 water sandpaper fine grinding knife edge or replace the ink knife;

Gravure printing common failures and solutions

In the gravure printing process often occurs some printing failure caused by mechanical, process raw and auxiliary materials, work environment and other factors, thus affecting product quality and production schedule. Now the practical experience accumulated in the gravure printing work will be introduced to you, for the reference of peers.
Failure a regular and irregular line marks (knife line)
1、Regular line marks
Cause:

(1) ink mixed with residue in the ink scraper scratched;
(2) The printing plate or can be scratched by hard objects;
(3) The printing plate cylinder wear off chrome, copper layer exposed.
Solution:
(1) Re-filter the ink with 80-purpose copper mesh, and fine-grind the blade with 600-gauge water sandpaper or replace the ink knife;
(2) with 800 water sandpaper dipped in solvent fine grinding scratches;
(3) Wash the printing plate with solvent, fill the scratch with 502 glue and copper powder, and take fine sandpaper to gently polish smooth (Note: this method is suitable for short-run products).
2、Irregular line marks
Causes:
(1) Insufficient sharpness of the ink scraper knife blade;
(2) the tilt of the ink scraper is not enough, the pressure of the ink scraper knife is too small;
(3) poor flatness when the ink scraper is installed;
(4) the solubility and fluidity of the ink and solvent is not good;
(5) printing cylinder chrome layer surface treatment is not smooth, too rough;
(6) printing cylinder printing circumferential runout is large;
(7) ink residue within the ink, stick behind the knife edge'
(8) ink tube and location is not ideal, the ink flow into the ink tank too quickly, resulting in uneven ink.
Solution:
(1) Sand the knife blade with 600 grit water sandpaper;
(2) Increase the pressure of the ink scraper to tilt the angle downward, and move the blade according to the actual situation, the ideal contact angle of 50-70 degrees;
(3) on the blade, try to do with rags clamping pressure bar and blade, so that the force to the outside pull, while tightening screws from the middle, one by one outward, but tight screws can not be a step in place, do not need to repeat two or three times to complete, so that the blade is evenly stressed;
(4) control the ink viscosity (without affecting the printing effect), as far as possible, use solubility, volatile fast deep agent, such as ethyl acetate, ethanol, add a small amount of iso ****, can increase the gloss;
(5) with 800 or 600 water sandpaper dipped in solvent back and forth grinding plate cylinder, pay attention to grinding to the graphic part when the force is not too large, such as unsatisfactory contact with the plate manufacturer to re-production plate cylinder;
(6) check the plate cylinder, cylinder shaft, bearings and transmission gear for deformation, wear, may also be caused by the machine seat level is not correct, unstable;
(7) ink tank, ink tank wash, ink multi-layer filter;
(8) move the position of the ink tube or reasonably improve the structure of the ink tank.
Fault two dragging shadow
Causes:
(1) ink dilution filter, viscosity decline;
(2) the contact angle between the ink scraper and the printing plate is not good, too much upward or the top knife force is too large to cause the knife blade warpage;
(3) adjusting gold oil and metal powder deployment ratio is not correct;
(4) the ink scraping blade is too soft, the installation of the pressure strip and the distance between the knife mouth is too large, the blade stretches too long;
(5) the pressure of the embossing cylinder is too large, the ink extrusion;
Solution:
(1) increase the viscosity of the ink, such as the situation is not significantly better, you can change the ink again;
(2) the contact angle of the ink scraper is adjusted downward, the top knife force is reduced;
(3) moderate reduction in the amount of gold transfer oil;
(4) change the use of high elasticity of the hard blade, preferably made in Japan, reduce the blade and pressure bar elongation distance;
(5) reduce the pressure of the embossing cylinder;
(6) such as dragging phenomenon is not serious, you can appropriately increase the speed of the machine to eliminate.
Fault three sticky dirty
Causes:
(1) The drying oven temperature is too high or too low;
(2) cooling circulation system failure, the water flow is too small;
(3) improper temperature and humidity control in the workshop;
(4) ink viscosity is too large, drying speed is too slow;
(5) Improper pressure adjustment of the impression cylinder (too heavy or too light).
Solution:
(1) drying box temperature should be based on the speed of the machine, the layout of the graphics to decide, large-area printing, the temperature of 60-80 degrees Celsius, mesh tone printing, the temperature of 40-60 degrees Celsius.
(2) increase the cooling roller water flow. Special attention should be paid to the paper transfer guide roller hot, easy to stick with the substrate flowers, need to reduce the oven temperature in a timely manner;
(3) printing workshop temperature and humidity control at 18-22 degrees Celsius;
(4) can be added to the ink in a timely manner volatile fast solvent, such as ethyl acetate, reduce the viscosity of the ink to accelerate the drying of ink;
(5) increase the printing pressure, so that the print solid.
Fault four, the print is false, showing the bottom
Causes:
(1) Insufficient imprinting force;
(2) Excessive ink dilution, which destroys the fluidity and adhesion of the ink;
(3) Excessive white ink content in the ink;
(4) blocking the plate or printing plate on the dot wear, falling off the plate;
(5) improper modulation of the original ink.
Solution:
(1) increase the printing pressure;
(2) increase the viscosity of the ink;
(3) the ink as little as possible to add white ink (more particles easy to hurt the plate), available instead of watered down ink;
(4) use a brush dipped in solvent to wash the residual ink in the plate hole to improve the transfer rate;
(5) according to the characteristics of the original ink group, reasonable allocation of ink.
Fault five network point, the text is not printed in full

Causes:
(1) ink viscosity is too high, the ink layer on the printing plate is thick, positive and negative ions are difficult to pass through about the sheet, electrostatic ink absorption is reduced, it is not easy to transfer the ink on the printing plate to the surface of the substrate;
(2) poor paper smoothness, uneven fiber arrangement;
(3) electrostatic rubber rollers on both sides of the ink, so that it has not formed insulation and current conduction bias leakage, affecting the adsorption force;
(4) The pressure of the ink scraper is too large;
(5) the ink evaporates too quickly, the transfer rate is reduced;
(6) the printing plate in the ink tank to absorb too little ink.
Solution:
(1) appropriate to reduce the viscosity of the ink;
(2) paper into the stock, pay attention to check the quality of paper;
(3) electrostatic rubber roller cutting 2mm deep on both sides, the width can be determined according to the long-term printing area, to prevent sticky ink;
(4) squeegee contact angle upward tilt;
(5) Add slow-drying solvent to improve ink transfer performance;
(6) Raise the squeegee holder to shorten the transfer time and increase the ink storage capacity of the screen cavity;
(7) Raise the ink tank to make the printing plate absorb ink sufficiently.
Fault six Spotting
Reason:
(1) The rubber surface of the embossing cylinder is injured or stuck with dirt;
(2) The ink is not completely dissolved;
(3) improper use of solvents or excessive solvent dilution;
(4) not effectively eliminate paper static electricity.
Solution:
(1) Replace the scribing roller to make it smooth;
(2) More confirm whether the use of expired or poor quality ink, and timely replacement;
(3) Increase the viscosity of the ink;
(4) Eliminate static electricity and adjust the humidity in the printing room.
Fault seven ink color thick talk uneven
Causes:
(1) ink tank structure has problems with the ink is prone to precipitation or generate a lot of foam;
(2) drying box air leakage, so that the solvent in the ink evaporates rapidly;
(3) solvent and ink is not completely dissolved.
Solution:
(1) improve the ink circulation system, the release of ink can not be too fast, the appropriate amount of adding defoamer;
(2) find out the drying box air leakage, and remedy it;
(3) Select a solvent with strong solubility.
Fault eight crease
Reason:
(1) Unbalanced pressure of the impression cylinder;
(2) the paper delivery guide roller bearing wear or locking screws loose;
(3) Eccentricity of the printing plate shaft.
Solution:
(1) calibrate both sides of the impression cylinder to make its pressure evenly balanced;
(2) Replace the bearings and reinforce the locking guide roller;
(3) Find out whether the transmission gears are worn, whether the teeth are smooth, whether the plate shaft is deformed, whether the bearings are "burned", and correct them.
Failure of nine sheets on the graphics before and after the overprint is not allowed
Causes:
(1) improper temperature and humidity in the printing workshop, the drying box temperature is too high, the paper shrinkage is serious;
(2) improper arrangement of the printing color group, the front and rear impression cylinder rubber hardness is not the same;
(3) the transmission gear and the plate shaft is not locked, resulting in the displacement of the printing plate cylinder;
(4) automatic tension device failure.
Solution:
(1) Maintain constant temperature and humidity in the printing workshop and reduce the temperature of the drying box;
(2) Correctly arrange the process flow and unify the rubber hardness of the impression cylinder;
(3) draw a line to check whether the transmission teeth and the printing plate slip, and lock it;
(4) If the automatic tension device is malfunctioning, find electrical personnel to repair.
Fault ten imprint crystallization (chalking)
Causes:
(1) Excessive ink dilution;
(2) Insufficient printing pressure, the ink layer is not solid, resulting in easy to fall off the print.
Solution:
(1) Observe whether the ink is cloudy, separated from each other, if the viscosity adjustment still can not be normal printing, you should contact with the ink supplier;
(2) Increase the printing pressure, so that the ink is fully solid.
Failure eleven in the spot color on the gold ink overlay is not real (dew gold)
Reason:
(1) because of coarse gold powder particles, coupled with high ink flow, resulting in too thick ink layer, large ink storage, not easy to dry;
(2) printing pressure is too large, the formation of ink extrusion;
(3) the printing plate cylinder online cavity depth is not enough;
(4) ink drying is not sufficient.
Solution:
(1) in the gold in the right amount of fast-drying solvents, spot colors with slow-drying solvents, such as does not affect the printing effect, the ink viscosity as much as possible to maintain moderate;
(2) printing pressure to maintain a moderate, balanced;
(3) the depth of the screen cavity when making plates should be determined by the situation;
(4) large area printing gold, should reduce the speed of the machine to increase the drying time of the ink between color groups.
Failure twelve sticky mixed color
Causes:
(1) The use of viscosity main ink;
(2) The ink is not sufficiently dry;
(3) incorrect printing pressure;
(4) The adhesion and cohesion of the ink is very poor.
Solution:(1) reduce the viscosity of the ink, control the use of slow-volatile solvent, know the common solvent volatilization rate of gravure printing, adequate heat and air supply, so that the ink fully dry;
(2) Reduce the printing environment temperature;
(3) Appropriately increase the speed of the machine, reduce the color and color overprint, the ink peeling force.