The influence of human factors on color difference

The author's factory is a printing and packaging company affiliated to the Yangzijiang Pharmaceutical Group. It specializes in pharmaceutical packaging, printing and post-press processing. According to Yangzijiang Pharmaceutical Group's requirements for printing quality of pharmaceutical packaging (mostly 6-color overprint) and drug packaging equipment (mainly a Guanghua PZ1020B-AL two-color offset printing press and a Taipei PZ4880-B four-color Machine), in the plate-making, the color is made into a spot color version, to reduce the trouble of overprinting requirements and color sequence arrangement, and at the same time facilitate the control of the ink color. However, in the printing process, the color difference is always difficult to avoid and it is very vexing. The following analysis and summarization of color difference control problems are combined with my own work experience and operation.

Chromatic aberration mainly has the same print color difference (ie, local color difference), the same batch color difference and batch color difference. It includes many factors such as man-made, raw materials, environment and equipment, but human factors are decisive. Therefore, several points in this paper are analyzed and summarized from human factors.

1. There is an error in the deployment of spot color inks, resulting in color difference in each batch. The proportion of spot ink is determined at the time of proofing. According to the proportion, it can be precisely weighed and dispensed each time. However, when weighing, human error can cause color differences between batches. In particular, some inks with a small proportion and a small amount of ink, if the weighing is inaccurate, change the hue and show a color difference.
2. When the ink is changed, the car wash is not clean. In the ink fountain, there is residual ink on the ink roller. Especially when the dark ink is changed, the light color ink is changed. The effect is particularly obvious, and the color difference is relatively large. Dark ink printing time is longer. When changing light color ink, water roller and water bucket must be cleaned. For example, the dark color ink of the second color group of our factory is printed for a long time. Every time the yellow ink is changed, we must wash the car several times to clean the water roller. Otherwise, the yellow ink will become blacker and darker, and the darker the Indian.
3, ink adjustment time is short, the ink is not uniform, it is eager to formally print, this situation is the formation of local color difference is an important reason. Such as the barrel box produced by our factory, when the vertical bar is used to change the bar, several groups of small ink teeth must be re-adjusted, otherwise the ink on the ink roller is uneven, and the ink color printed must be deep and shallow.
4, in the uneven ink, the existence of local color, manually manual ink, or blindly tighten the small teeth, very unstable. The best way is to walk through the printing paper to ensure that the ink prints evenly.
5. Frequent machine downtime due to inks, plushs, dirty spots, etc., is an important cause of the color difference in the same batch. The number of shutdowns will surely damage the balance of ink and ink. When the printer is turned on, the ink color is either darker or darker, or dirty or hairy. Therefore, it is necessary to increase the number of overprinted papers when the printer is turned on, and then formally print after the ink is uniform.
6, the normal printing ink will also change, to be adjusted in time, but also to observe the changes after adjustment, can not adjust the excess, so as to avoid the opposite. Therefore, the operator must be diligent about the proofs, dilute the ink fountain, and diligently look at the amount of water.
7, printing time is too long, ink imbalance, the ink prone to emulsification, dim colors, this time can not blindly increase the amount of ink, but should promptly wash the car, re-inking.

(Kaisheng Printing Products Co., Ltd. Shi Huafei)
Reprinted from: "Printing Technology"