Causes and solutions for the occurrence of bar marks
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Bar marks are generally caused by the water delivery part, so it is called a water mark. The reasons for this and the ways to overcome them are:
1 Water roller and plate or water roller are over pressure
The pressure between the water roller and the plate or the water roller is too heavy, causing the water roller to jump when it contacts the printing plate, causing friction between the plates to cause streaks.
Overcome the method: Correct the pressure between the water roller and the plate or the water roller, and reduce the water roller to avoid streaking.
2 plate water roller surface area excessive ink
Due to the long-term use of the water roller, the surface accumulated ink dirt is not washed in time, or even dried to form a solid, gradually losing hydrophilicity and affecting the water transfer performance, and at the same time, it is easy to generate friction with the plate surface, lighter, the water roller produces a slight beating, and the heavy one Damage to the base of the pattern and the blisters, both of which cause streaks.
Overcome the method: When the ink is light, remove the washing water roller and renew the water roller when it is heavy.
3 Water roller bearings or shafts are severely worn
The water roller produces a significant axial turbulence, and the beating in contact with the printing plate during operation causes friction to cause streaks.
Overcome methods: Repair or replace bearings and wear parts.
4 layout moisture is too large
The water supply is large, causing the layout moisture to be too large, causing between the ink rollers, between the ink roller and the printing plate.
The formation of water layer isolation hinders the positive transfer of ink. Under the action of pressure, the ink is emulsified seriously, the viscosity is weakened, and the pigment particles of the ink are accumulated on the plate, the blanket and the ink roller, which increases the pressure and friction between each other and causes streaks.
Overcome the method; reduce the amount of water supplied to the blanket and the ink roller.
5 dampening solution is too acidic to clean
The phosphate formed in the plate is dissolved, the inorganic salt layer cannot survive, and the fountain solution does not function. In addition, the acidity is too strong, corroding the screen sand hole, the mesh point is destroyed, the ink emulsification is accelerated, and the layout loses the ink balance and causes streaks.
Overcome the method: the medium and light moisturizing solution is acidic, and the viscosity of the ink is appropriately increased. If necessary, the ink on the ink roller or the cleaning ink roller should be removed. In serious cases, a new printing plate may be considered.
6 bearing wear
The characteristics of streaks in the wear of the roller bearing are that there are several wide streaks at the bite, and a few are equidistant streaks. Due to the long-term use of the roller bearing, the natural wear and tear causes the gap between the journal and the bearing to be too large. The sleeve is loose, the disengagement value is large after the bite is pressed, and the "streak" is caused by the chattering at high speed. In addition, when the roller journal is severely worn and an ellipse appears, a similar situation occurs.
Overcome the method: If it is confirmed that the bearing is seriously worn, a new bearing must be replaced.
7 caused by gear vibration
The gear is embedded with dirt such as paper wool and ink. The machine is used for a long time and is not properly maintained. Some paper wool, dry ink and other dirt will be embedded in the gears. The gears will be pressed into small hard blocks, causing the drum gears to operate. The vibration generated in the middle caused streaks.
Overcome the method: Strengthen the cleaning and maintenance of the machine, thoroughly remove the dirt and ensure the smooth operation of the gear.
8 The pressure of the ink roller is too heavy
The pressure between the printing plate and the ink roller is too large, the plate paper 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.
Overcome the method: Reasonably adjust the plate liner to make it suitable for pressure with water, ink roller and blanket cylinder.
9 caused by the ink system
(1) The pressure of the ink roller is improperly adjusted, and the portion causing the "strip" is generally close to the bite, and its position changes up and down.
(2) The outer circumference of the ink roller is not straight and the bending of the core is not straight, and the position of the "strip" is generally at the bite.
(3) The roller gear is worn or not accurate enough, causing the "strip" to have a pitch equal to the ink gear pitch.
Overcome the method: (1) Adjust the pressure between the ink rollers; (2) Remove the ink roller to grind or replace the ink roller with the flat roller core: (3) If the gear is worn seriously, replace it with a new one.
10 caused by improper ink mixing
Thin ink will not only produce greasy and paste, but also have small cohesive force, which will affect the transfer of ink. Ink roller, printing plate and blanket gradually accumulate ink pigment particles, which increase the surface friction and pressure and cause streaks.
Overcome the method: Add the No. 0 varnish to the ink cow to improve the viscosity and transfer performance of the ink.
11 caused by printability
The surface roughness is poor, it is easy to get rid of the powder, and it accumulates on the printing plate, the ink roller and the blanket, causing the friction force and the pressure to increase and causing streaks.
Overcome method: When printing on paper with poor surface strength, the blanket should be washed frequently, and debonding agent or No. 6 varnish should be added to the ink to reduce the hair loss.
In summary, only some of the factors that cause streaks, and more and more complicated reasons can not be enumerated. Therefore, once streaks are encountered in production, the position of the streak must be
Set, character, analyze the relevant factors, find out the cause of the streaks.