1. Poor color accuracy
There are several reasons why plastic film color registration is not allowed:
1. The printing registration changes in the vertical direction (the direction of the transport side).
(1) The tension changes when the film is pulled. Reasons: Improper modulation of the roll brake of the unwinding device; too much roll material, or the diameter of the formed material is too large; improper setting of the speed of the three rollers; the surface friction on the surface of the three rollers decreases; the tension of the rewinder changes. Countermeasure: Check and adjust each control device.
(2) Poor diameter difference of the printing plate cylinder Cause: The increase in the diameter difference during plate making is inaccurate. Countermeasure: Measuring the diameter difference (method: see the plate making section).
(3) The rule line is abnormal. Cause: Insufficient density (dense), offset printing, etc. Countermeasures: Adjust the sensitivity of the photoelectric cell, and manually eliminate the disadvantages such as paste printing.
(4) The diameter of the plate cylinder is small. Reason: The accuracy of overprinting of smaller roller diameter is difficult to control. Countermeasure: If the length of the printing bag is short, the imposition method can be used, that is, more than two bags are printed on one printing roller.
2. The horizontal registration is unstable. the reason:
(1) One side of the film is slack, and the film guide rollers are poorly parallel;
(2) The printing pressure is not uniform;
(3) The plate cylinder and impression cylinder form a taper;
(4) The film tension changes, etc., causing the film to swing left and right. Countermeasure: Check and adjust each element one by one, such as repairing when the horizontal registration device is loose.
2. Poor printing fastness
The reasons for poor printing fastness of plastic film are as follows:
1. Poor corona treatment of polyolefin film. Countermeasure: Check whether the surface tension of PE and PP reaches above 40 dynes / cm.
2. Lin ink has poor affinity with printed materials. The ratio of mixed solvent is poor. Countermeasure: Change the ink and adjust the solvent ratio.
3. The temperature and relative humidity of the printing workshop vary greatly. Countermeasure: Try to control the relative humidity of the workshop between 50% and 60%, but not too low. When it is less than 40%, static electricity is easy to be generated. It is best to control the suffocation temperature at 18 ℃ ~ 23 ℃, and keep the environment clean and air circulation.
4. The plastic film itself is extremely poor in printability and is still unsatisfactory after corona treatment. Countermeasure: Replace printed materials.
3. Pattern size shift
1. When printing, the vertical pattern size shrinks. Reason: insufficient shrinkage margin. Due to the influence of the tension of the plastic film and the heating and drying during printing, the longitudinal dimension of the film is greater than the shrinkage of the printed graphics. Countermeasure: The size of shrinkage should be kept properly during plate making; the film tension should be minimized.
2. When printing, the pattern size in the longitudinal direction is extended. Reason: The gravure size leaves too much for the shrinkage margin. Countermeasure: Increase film tension.
4. Poor reproducibility of printed materials
1. The highlight (bright part) is too deep. Cause: The printing plate is too deep and the ink content is too much.
Countermeasure:
(1) Increase the mesh;
(2) Reduce the color material in the ink;
(3) Increase the angle between the doctor blade and the surface of the printing plate.
2. The highlight is too shallow. Reason: The depth of the printing plate is not enough.
Countermeasure:
(1) Use dark ink;
(2) Properly reduce the angle between the doctor blade and the surface of the printing plate.
3. The dark tone (dark part) is too deep.
Cause: The printing plate is too deep.
Countermeasure: Due to insufficient ink drying, the ink layer may be agglomerated, and if necessary, re-change the plate.
4. Dark tone density is not enough.
Reason: The printing plate depth is not enough.
Countermeasure: Use dark ink.
5. The dark and light junction of the middle tone ink is obvious.
Cause: Poor ink quality.
Countermeasure: Replace the ink with good characteristics.
V. Poor conjunctiva drying after printing
Reasons: 1. Insufficient hot air temperature, wind speed, air volume and exhaust volume.
Countermeasure: Adjust the drying device.
2. The ink layer has the illusion of drying conjunctiva after printing, and the ink layer still contains residual solvent. After the film is wound up, there is still residual heat of about 40 ° C, which is suitable for the solvent to continue to move, and there is a certain pressure during the winding up, thus causing the danger of sticking back.
Countermeasures: (1) The ink layer should be thoroughly dried after printing;
(2) After printing, put the film loosely in the wire basket, wait for the film to cool, and then rewind, cut, and make the bag when it is checked that there is no stick back phenomenon.
Sixth, the gloss of the printed product is thin
Cause: Ink dilution is excessive.
Countermeasure: Control the amount of thinner.
7. The imprinted edges are not smooth, and the background is spotted
Cause: The viscosity of the ink is too low and the solvent is used too much.
Countermeasure: Add new ink to increase viscosity.
8. The printed layer has orange peel marks
Cause: The ink dries too fast, the density is too light, the leveling is poor, the thixotropy is large, there is static electricity, and the printing speed is too slow.
Countermeasures: Find out the reasons and take corresponding measures.
9. The printed layer has scratches
Reason: The guide roller is scratched, the ink is mixed with sand, the scraper is not flat, and the angle between the scraper and the printing plate is inappropriate.
Countermeasure: Corresponding treatment.
Ten, thin tone
Reasons: (1) Thin ink color: (2) Poor color reflection.
Countermeasures: (1) Adjust the ink properties; (2) Use the white ink to lay the background color for printing, and then register the colors in sequence. Inside printing, the gradation version first overprints the three primary colors, and finally lays the background color.
11. Bite color
In overprinting, the second color ink sticks and pulls away the first color ink.
Cause: The ink layer fails to dry completely after the first color printing, the pressure of the second color is too high, or the machine speed is too fast, or the hot and cold air is poor, and the printing suitability of the substrate is poor, which can cause color biting.
Countermeasures: Find out the reasons and take corresponding measures. â‘ Add an appropriate amount of quick-drying agent; â‘¡Slow down the speed of the vehicle; â‘¢Reduce the pressure of the impression cylinder; â‘£Increase the amount of cold and hot air.
Twelve, the print is rough, the blank spots are full, the moiré on the ground, the tone is not full
Reasons: ①Too much solvent; ② The ink is thick; ③ The ink is too thin; ④ The volatilization is too fast; ⑤ The ink has poor fluidity.
Countermeasures: ①Reducing the amount of solvent; ②Replace the ink or re-grind; ③Adjust the ink thinness; ④Appropriately slow the drying solvent; ⑤Replace the ink.
In addition to the blocking phenomenon caused by the chemical reaction caused by the ink itself (rarely rare), the remaining factors can be summarized into five points:
(1) During printing, with a large amount of solvent volatilization, the viscosity of the ink increases, and it is easy to dry inside the network cable. If it is not cleaned in time, it will cause serious blockage.
(2) In the printing process, when the accompanying blade is far away from the printing roller or the angle is unreasonable, the diameter of the plate roller is large, or the depth of the plate cylinder into the ink tank is not enough, the hot air blown from the dryer affects the surface of the plate cylinder, easy Cause serious blockage.
(3) Impurities are mixed in the ink.
(4) The engraving depth of the plate cylinder wire (or the depth of corrosion of the photogravure) is not suitable.
(5) When printing, the temperature is too high, the solvent in the ink volatilizes too fast, and it is also easy to cause blockage of the plate surface.
ChangQingShu BabyToy
ChangQingShu BabyToy
Shantou Chenghai Sweet Baby Toys Firm , https://www.sweetbabytoys.com