Dongguan Beite packaging materials Co., Ltd. produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
In the process of gravure printing, some printing faults caused by machinery, process raw materials, working environment and other factors often occur, which will affect the product quality and production progress. Now the practical experience accumulated in gravure printing is introduced to everyone for reference.
Fault - regular and irregular line marks (tool lines)
1. Regular line mark
reason:
(1) The residue in the ink scratched the doctor blade;
(2) The printing plate may be scratched by hard objects;
(3) Plate cylinder wear off chromium, copper layer exposed.
resolvent:
(1) Filter the ink again with 80 mesh copper mesh, and grind the blade with 600 water sandpaper or replace the ink knife;
(2) Grind the scratch with 800 water sandpaper dipped in solvent;
(3) Clean the plate with solvent, fill the scratch with 502 glue and copper powder, and polish it with fine sandpaper.
2. Irregular line mark
reason:
(1) The blade sharpness is not enough;
(2) The inclination of the scraping ink is not enough, and the pressure of the scraping knife is too small;
(3) When the doctor blade is installed, the flatness is poor;
(4) Ink and solvent solubility, liquidity is not good;
(5) The surface treatment of chromium layer of plate cylinder is not smooth and too rough;
(6) When the printing cylinder is printing, the circumferential jump is large;
(7) There is ink residue in the ink, sticking to the back of the blade‘
(8) Ink tube and position is not ideal, ink into the ink tank too fast, resulting in uneven ink.
resolvent:
(1) Grind the blade with 600 water sandpaper;
(2) Increase the pressure of the squeegee blade to make it tilt downward, and move the tool holder according to the actual situation. The ideal contact angle is 50-70 degrees;
(3) When installing the blade, try to use rags to clamp the strip and blade to pull the force outwards. At the same time, tighten the screws from the middle to the outside one by one. However, the tightening screws can not be completed in one step, and it is not necessary to repeat it for two or three times, so that the force on the blade is uniform;
(4) Control the viscosity of the ink (without affecting the printing effect), use deep agent with strong solubility and fast volatilization as far as possible, such as ethyl acetate, ethanol, and adding a small amount of isopropanol to increase the gloss;
(5) Use 800 or 600 water sand paper dipped in solvent to polish the plate cylinder back and forth. Pay attention not to use too much force when grinding to the graphic part. If it is not ideal, contact the plate making factory to make the plate cylinder again;
(6) Check the plate cylinder, drum shaft, bearing and transmission gear for deformation, wear, and may be caused by the seat level is not correct, unstable;
(7) The ink tank and ink box are cleaned, and the ink is filtered in multiple layers;
(8) Move the ink pipe position or reasonably improve the ink groove structure.
Fault two shadow
reason:
(1) Ink dilution filtration, viscosity reduction;
(2) The contact angle between the squeegee and the printing plate is not good, and the blade warping is caused by too much upward tilt or the force of the top knife is too large;
(3) The proportion of gold blending oil and metal powder is not correct;
(4) When the blade is too soft, the distance between the blade and the blade is too large, and the blade extends too long;

(5) The pressure is too high;

resolvent:
(1) Increase the ink viscosity, if the situation is not significantly improved, you can change the ink again;
(2) Adjust the contact angle of the doctor blade downward to reduce the jacking force;
(3) Reduce the amount of gold blending oil appropriately;
(4) Use hard blade with high elasticity, preferably made in Japan, to reduce the elongation distance between blade and pressing strip;
(5) Reduce the pressure of imprint cylinder;
(6) If the tardiness is not serious, it can be eliminated by properly increasing the speed of the aircraft.
Fault three sticky dirty
reason:
(1) The temperature of drying oven is too high or too low;
(2) The cooling circulation system fails and the water flow is too small;
(3) Improper control of temperature and humidity in workshop;
(4) Ink viscosity is too large, drying speed is too slow;
(5) The pressure of the imprint cylinder is not adjusted properly (too heavy or too light).
resolvent:
(1) The temperature of drying oven should be determined according to the speed of the machine and the picture and text situation of the layout. The temperature of large area printing is 60-80 ℃, and the temperature of screen printing is 40-60 ℃.
(2) Increase the cooling roller water flow. Special attention should be paid to the paper guide roller hot, easy to stick with the substrate, need to reduce the oven temperature in time;
(3) The temperature and humidity of printing workshop should be controlled at 18-22 ℃;
(4) Can be timely added in the ink volatile solvent, such as ethyl acetate, reduce ink viscosity, accelerate ink drying;
(5) Increase the printing pressure to make the imprint solid.
The four marks of the fault are false and exposed
reason:
(1) The impression force is insufficient;
(2) Excessive dilution of ink, damage to the fluidity and adhesion of ink;
(3) Too much white ink in ink;
(4) Blocking or printing plate online point wear, off version;
(5) Original ink modulation is not appropriate.
resolvent:
(1) Increase the printing pressure;
(2) Increase ink viscosity;
(3) Ink as little as possible to add white ink (particles more easily damaged version), can be replaced by diluted ink;
(4) Use a brush dipped in solvent to clean the residual ink in the plate hole to improve the transfer rate;
(5) According to the group characteristics of the original ink, reasonable allocation of ink.
Fault five outlets, text printing is not complete
reason:
(1) The ink viscosity is too high, the ink layer on the plate is thick, the positive and negative ions are difficult to pass through the tension, the electrostatic ink absorption effect is reduced, and it is not easy to transfer the ink on the printing plate to the substrate surface;
(2) The smoothness of paper is poor and the fiber arrangement is uneven;
(3) There are ink on both sides of the electrostatic cot, so that it does not form insulation, resulting in current conduction bias leakage, affecting the adsorption force;
(4) The pressure of the doctor blade is too high;
(5) Ink volatilization is too fast, the transfer rate is reduced;
(6) The printing plate in the ink tank is too low.
resolvent:
(1) Reduce the ink viscosity properly;
(2) When purchasing paper, pay attention to check the quality of paper;
(3) Both sides of the electrostatic cot are cut 2mm deep, and the width can be determined according to the long-term printing area to prevent ink sticking;
(4) The contact angle of the doctor blade inclines upward;
(5) Slow drying solvent was added to improve ink transfer performance;
(6) Increase the blade holder, shorten the transfer time and increase the ink storage in the mesh point;
(7) Raise the ink tank to make the plate absorb enough ink.
Fault six spots
reason:
(1) The rubber surface of the imprint drum is damaged or stuck with dirt;
(2) The ink is not completely dissolved;
(3) Improper use of solvent or excessive solvent dilution;
(4) The static electricity of paper is not effectively eliminated.
resolvent:
(1) Replace Su grinding cots to make them smooth;
(2) More confirm whether the use of expired or poor quality ink, and timely replacement;
(3) Improve the viscosity of ink;
(4) Eliminate static electricity and adjust humidity of printing workshop.