Causes and Countermeasures of Common Faults of Gravure Printing (2)

Second, the color registration accuracy of poor plastic film color is not allowed to have the following () reasons:
(1) Longitudinal direction (direction of travel) Printing register change 1 Tension variation during film pulling.
Cause: The reel brake of the uncoiling device is not properly prepared; the reel material is too much, or the diameter of the reel material is too large; the three roller speeds are set incorrectly: the surface friction of the three roller surfaces is reduced; the tension of the rewinding machine is changed.
Countermeasures: Check and adjust each control device.
2 The difference in the diameter of the plate cylinder is poor.
Cause: The growth of the diameter difference during the platemaking process is inaccurate. Countermeasure: Measuring the diameter difference.
3 abnormal rules line. Cause: Insufficient density, printing offset, etc.
Countermeasures: Adjust the sensitivity of photocells, and artificially eliminate defects such as plate stencils.
4 The diameter of the plate cylinder is small.
Reason: The smaller roller diameter overlay accuracy is difficult to control:
Countermeasures: If the length of the bag is short, the imposition method may be used, ie, two or more bags may be printed on one roller.
(2) The lateral register device is unstable.
Causes: 1 The film is loose on one side and the guide roller is in parallel.
2 printing pressure is not uniform;
3 Plate cylinder and impression cylinder form taper;
4 Film tension changes, etc., and the film swings left and right.
Countermeasures: Check and adjust each element one by one, such as when the lateral register device is loose.
Third, printing fastness bad plastic film printing fastness has the following reasons:
(1) The corona treatment of the polyolefin film was poor.
Countermeasures: Check whether the surface tension of PE and PP reaches 40 dynes/cm or more.
(2) The affinity of the printed ink and the printed material is poor. This is a poor mixture ratio. Countermeasures: Replace the ink and adjust the solvent ratio.
(3) The temperature and relative humidity of the printing shop vary greatly.
Countermeasures: As far as possible, the relative humidity of the workshop should be controlled between 50% and 60%, but it should not be too low. Below 40%, static electricity is easily generated. Room temperature is best controlled at 18 °C ~ 23 °C is the best, and keep the environment clean and air circulation.
(4) The printability of the plastic film itself is very poor, and is still undesirable after corona treatment.
Countermeasure: Replace the printed material.
Fourth, the pattern size shift
(1) The length of the longitudinal pattern shrinks during printing. Reason: Insufficient shrinkage margin. Due to the tension of the plastic film and heat drying during printing, the longitudinal dimension of the film is larger than the shrinkage of the printed image.
Countermeasures: The amount of shrinkage should be properly left when making plate, and the tension of the film should be minimized.
(2) The length of the pattern in the longitudinal direction is elongated during printing.
Cause: The plate size has left too much of the shrinkage margin.
Countermeasures: Increase the film tension.
Fifth, the print product level is poor
(1) The highlight (light part) is too deep.
Cause: The printing plate is too dark and contains too much ink.
Countermeasures: 1 increase the number of mesh lines; 2 reduce the ink color; 3 appropriately increase the angle of the squeegee and the surface of the printing plate.
(2) The light is too shallow.
Cause: The depth of the plate is not enough.
Countermeasures: 1 Use dark-toned ink; 2 properly reduce the angle between the squeegee and the plate surface. (3) Dark tone (dark part) is too deep.
Cause: The plate is too deep.
Countermeasures: Due to the lack of ink drying, the ink layer may be agglomeration, and if necessary, it must be reprinted.
(4) Shadowing density is not enough.
Cause: The plate is not deep enough.
Countermeasure: Use dark color ink.
(5) The depth of the intermediate tone ink is clearly at the junction.
Cause: Poor ink.
Countermeasure: Replace ink with good characteristics.
Sixth, the Indian ink dried conjunctiva is bad
(1) Insufficient hot air temperature, wind speed, air volume, and exhaust air volume.
Countermeasure: Adjust the drying device.
(2) After printing, the ink layer has the illusion of dry conjunctiva. The ink layer still contains residual solvent. After the film has been rewinded, there is also residual heat at about 40° C., which is suitable for the solvent to continue its activity, and the pressure at the time of rewinding has a certain amount of pressure, thereby causing the danger of back tackiness.
Countermeasures: 1 After printing, the ink layer should be thoroughly dried; 2 After printing, the film should be loosely collected in a wire basket. After the film cools, the film will be rewinded, cut, and bagged when it is tested for no stickiness.