One of the common ink failures in the printing process

Flying ink

Flying ink is an ink failure that often occurs in newspaper printing. The so-called “flying ink” means that very fine ink particles are drawn into filaments at the working ink roller, and two or more breaks occur. In addition to partially retracting the ink roller, the remaining parts are formed due to the large surface tension. Drops are thrown by high-speed printing presses and diffuse into the air.

1. cause

There are many reasons for the formation of ink droplets. Incorrect ink transfer roller adjustment, poor quality of the roller surface, rapid printing speed, characteristics of the ink itself, and uncomfortable temperature and humidity in the workshop and environmental conditions can cause ink flying. The following specifically introduces the solution of flying ink.

2. Solution

1) Adjust the ink transfer roller

Operators to adjust the ink roller (flat roller) method is not uniform, such as, some with kraft lamination, some with the ink roller stamping width of the plastic pull law, resulting in the pressure between the roller is not standardized. Too tight adjustment between the ink roller, easy to damage the roller; over-tuned, it will lead to flying ink.

The ink transfer system of a typical printer includes an ink core roller, an anilox roller, two ink transfer rollers, two ink rollers, and two printing rollers. A more specific ink roller adjustment procedure should be:

In the first step, the thickness of the initial ink layer on the ink fountain roller is adjusted uniformly. For machines using a fine anilox roller, the thickness of the ink layer is preferably set to 0.12 to 0.18 mm. With a coarse anilox roller, the initial ink layer thickness is preferably 0.23 to 0.30 mm. The second step is to adjust the anilox roller and ink. The gap of the core roller keeps it balanced. Machines using fine anilox rollers are suitable for gaps of 0.09 to 0.1 mm. For rough textured models, gaps of 0.15 to 0.18 mm are appropriate. The third step is to use an anilox roller and the first transfer roller. Embossing is adjusted to 8mm; In the fourth step, the embossing width between the two transfer rollers and the two ink distributor rollers, the second ink distributor roller and the inner and outer printing plate rollers is maintained at 6-7mm.

In the process of adjusting the ink roller, it is best to adjust the ink roller spacing with yellow ink; the ink of the ink roller must be uniform when adjusting, the smaller the ink volume, the smaller the adjustment error; and the spacing between the rubber rollers should be checked regularly. The spacing is not The specification should be adjusted in time, and the deformed rubber roller should be replaced in time to prevent flying ink.

The adjustment and detection of the rubber roller in the usual production can not only prolong the service life of the rubber roller, but also effectively prevent the occurrence of flying ink.

2) Adjust ink and ink

News ink is mainly composed of non-polar mineral oil. It has low electricity, high solid content, and is not easy to disperse. If the design is unreasonable, it often appears that the silk head is too long and causes flying ink. The ink itself is a pseudo-plastic fluid with poor dispersion (uniform distribution of the pigment in the binder), causing irregular breakage of the ink and the generation of flying ink. The viscoelasticity of the ink is good, the ink is short, and the ink is light, whereas the ink is more heavy.

The solution is to add a thick binder to the ink to increase the viscosity of the ink and increase its cohesion to increase the dielectric constant. Try to use good wettability pigments and mineral oil to make ink, or add anti-rheological additives (such as bentonite, wax, etc.), black ink should be properly increased carbon black content, increase color intensity, but also pay attention to reduce the amount of ink .

In addition to control the temperature and humidity of the workshop, ventilation should not be too strong. The temperature of the printing shop is 20~25°C and the humidity is 50%~60%. If the temperature is too high, the ink's fluidity will increase, the viscosity will decrease, and the flying ink phenomenon will obviously increase.

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