The use of a single – and two-color offset printing printing multi-color, four-color overprinter deviation is often a headache for the workers.Before two color overprint is generally no problem, but after two color is difficult to control.Usually can only reduce machine speed, reduce ink volume, adjust ink fluidity and dusting and other measures, but the effect is not big, and the above measures will affect work efficiency and product quality, and bring about a doubling of labor intensity.
In fact, we can classify printing as “dry” and “wet”.The so-called “wet printing” is the substrate before and after two overprints for wet pressure wet, that is, before the same color just printed after the beginning of overprint;And “dry printing” is the printing of a color dry and then the next color, such as the use of monochrome machine printing four-color products.
1. Dry printing
The advantage of this printing method is that it can ensure the stable positioning of the paper in the post-sequence printing and the overprinter position is basically fixed.In addition, dry ink overprinter can obtain full color, bright and accurate color.But because there is a certain amount of downtime, easy to cause paper deformation and overprinter, and efficiency is not high, meet urgent work can not be completed.
2. Wet printing
This printing method saves time, and the paper overprints accurately due to small deformation.But it has a lot of problems, such as easy to cause the back rub dirty, printing color gray, ink volume or large printing area, after the printing order color paper is difficult to move paper positioning, affecting the accuracy of overprinter.If there is a four-color offset press there are no such problems, with a single, two-color offset press can only be solved by experience.How to “shrink the time” of wet printing is the goal of our exploration.
Method 1. Check the printing paper to be printed. If the paper with high humidity or air-dried deformation cannot be used, the newly imported paper shall be treated with air drying paper or stored for a certain period of time to ensure the temperature and humidity balance with the printing workshop.Cutting paper to ensure its edge neat, smooth, to ensure that the paper running stability;
Method 2: no or little diluent in the ink, ink blending oil and other fatty oil additives, because it not only affects the color and easy to cause the back smear, printing ink is not easy to dry quickly, resulting in post-sequence color printing paper positioning difficulties, directly affect the accuracy of overprint;
Method 3. Before printing, especially before printing with quick-drying ink on coated paper, make sure that the blanket is dry and clean, in case the blanket sticks to the paper in the semi-dry state and affects the stability of the paper.In the middle of the stop when the same blanket processing clean;
Method four, take measures to speed up the drying of printed semi-finished products in front.Here can be taken out of the paper drum arc protector refit for oil-ting electric sheet, heating processing.In addition, the spray device should be used flexibly.The first two colors do not need powder spray to maintain the air drying effect on the printing, the size of the air volume according to the paper thickness adjustment, the general senior four color printing paper air volume can be appropriately increased, white board printing can adjust the air volume to the maximum, in order to make the printing products to obtain sufficient air drying effect.After installed the hot air drying device, print to paper before the ink is almost dry, neither smearing on the back, and to ensure the order after color printing paper paper feed positioning correctly, and so, wet printing as if into a no time interval of dry type printing, not only have the guarantee accuracy, also can solve the problem of printing quality sticky dirty, poor drying, etc.
The above measures are based on the requirements of conventional printing.Printing operators must operate carefully, master the balance of ink, control the amount of ink, spot check the overprinter at any time, find problems, stop the machine in time to deal with.
Post time: Aug-31-2020