The cause of the bar mark and its solution

Deflection marks are generally caused by the water delivery section and are called watermarks. The causes and ways to overcome are:

Water roller 1 and the plate string or the water pressure is too heavy roller

The pressure between the water roller and the printing plate or the water roller is too heavy, so that when the water roller comes into contact with the printing plate, a jump occurs, and friction between the plates causes scratches.

Ways to overcome: Correct the pressure between the water roller and the plate or the water roller, and reduce the water roller jump to avoid streaks.

2 plate water roller surface too much ink

Due to the long-term use of the water roller, it does not promptly wash the surface of the accumulated ink dirt, even dry solid, gradually lose the hydrophilicity and affect the water transfer performance, at the same time easy to produce friction with the layout, light, the water roller produces a slight beat, severe Damage to the texture base and trachoma, both of which can cause streaks.

To overcome the method: when the ink is light, remove the washing water roller, and when it is heavy, update the water roller velvet.

3, water roller bearing or shaft wear

The water roller generates a significant axial turbulence. During operation, the pulsation is brought into contact with the plate to cause scratches due to friction.

Ways to overcome: Repair or replace bearings and wear parts.

4, the layout of water is too large

Large amount of water, so that the layout much moisture, causing the ink between the rollers, between the ink roller and the printing plate is generated graphic aqueous layer was isolated, hindered positive transfer ink. Under the effect of pressure, the ink is emulsified seriously, and the viscosity is weakened. The pigment particles of the ink accumulate on the plate, the blanket and the ink roller, and increase the pressure and friction between each other and cause striae.

Overcome the method; reduce the amount of water supply blanket and ink roller.

5, fountain solution is too acidic to clean

Dissolving the phosphate formed on the plate, the inorganic salt layer cannot survive, and the fountain solution does not function. In addition, the acidity is too strong, corrodes the plateau trachoma, the network point is destroyed, accelerates the ink emulsification, the layout loses the water ink balance to cause the striae.

To overcome the method: In the light fountain solution acidity, appropriate to improve the viscosity of the ink, if necessary, should remove the ink on the ink roller or cleaning ink roller, serious, you can consider changing the printing plate.

6, bearing wear

Roller bearing wear produces streaks characterized by several wide streaks at the nip, and a few equidistant streaks. Due to the long life of the roller holder, natural wear results in excessive clearance between the drum journal and the bearing. Loosening of the coupling, relieving the bite after compression, causing chatter during high-speed operation, causing “streaks”. In addition, when the elbow of the drum journal wears elliptically, similar conditions occur.

Ways to overcome: If it is confirmed that the bearing is heavily worn, replace the new one.

7, caused by gear vibration

The gear is embedded with dirt such as paper, ink and skin. The machine is used for a long time and improperly maintained. The gears are embedded with some paper and dried dirt, such as ink and skin, and are pressed into small hard blocks by the gears, causing the roller gear to run. In the shock caused by striations.

Ways to overcome: Strengthen the cleaning and maintenance of the machine, completely remove the dirt, and ensure that the gears run smoothly.

8, caused by the ink roller pressure is too heavy

The pressure between the printing plate and the ink roller is too large, the pad of the printing plate is too thick or the pressure of the ink roller is improperly adjusted, so that the pressure between the printing plate and the ink roller is too large, causing the ink roller to jump and slip, resulting in streaks.

To overcome the method: a reasonable adjustment of the printing plate liner, make it with the water, ink roller and rubber roller pressure.

9, caused by the ink system

(1) Incorrect adjustment of the ink roller pressure, the part that causes the “strip mark” is generally close to the bite opening, and its position is changed up and down.

(2) Outer round of the ink roller The unevenness of the roller core is not straight and the position of the “streak” is generally at the nip.

(3) Insufficient or inaccurate abrasion of the ink roller gear, causing “streaks” whose pitch is equal to the pitch of the ink gear.

Ways to overcome: (1) Adjust the pressure between the ink rollers; (2) Remove the ink roller to perform grinding or replace the ink roller of the straight roller core: (3) If the gear is worn badly, replace it with a new one.

10, caused by improper ink deployment

The thin ink will not only produce greasy and stencil, but also have small cohesion and affect the transfer of ink. The ink pigment particles are gradually accumulated on the ink roller, the printing plate, and the blanket to increase the surface friction and pressure and cause striae.

To overcome the method: In the ink cattle properly added 0 varnish to improve the ink viscosity and transfer performance.

11, caused by printability

The surface roughness is poor, and it is easy to remove the powder off and accumulate on the printing plate, the ink roller, and the blanket, causing the friction and pressure to increase and cause striae.

Ways to overcome: When encountering paper with poor surface strength, the blanket should be washed and the detackifier or No. 6 varnish should be properly added to the ink to reduce the loss of powder.

In summary, it is only part of the factors that produce streak. There are more and more complicated reasons that cannot be enumerated. Therefore, once streak is encountered in the production, it is necessary to analyze the relevant factors and find out the cause of the streak.

Source: China Tinplate Printing Network