What is the difference between a printed water bar and an ink bar?

Water bar: The print is whitish when viewed from left to right.

Ink bar: From left to right, the print is dark (this is the first feeling of straight ** print).

Looking at the outlets, it can also be seen that the water bar outlets are empty and the ink bar outlets are expanding.

Water bars are produced when the pressure is lighter.

In production, we also found that when the pressure between the Tuanwei Xun ink roller and the ink roller is light, the water collapse will occur on this bar.

This is because the pressure between the ink rollers is too light, and the ink cannot be evenly transmitted on the rubber roller and floats on the rubber roller. When the ink is unbalanced, the ink emulsifies due to the thickening of the ink layer on the surface of the rubber roller, and the water bar is easy to appear on the printing sheet.

The quality of the water roller sleeve is poor, the local unevenness, the water roller is not tightly wrapped, the two ends are loose and the middle is tight, the water supply is uneven or the water volume is too large, and it is easy to imitate the water bar at the first two lines of the mouth.

In short, when the ink bar appears in the machine you operate, it must be analyzed from many aspects, clarified step by step, and as long as it is handled properly, it will be able to get a satisfactory solution.

The water bar caused by too much vibration of the water roller swing frame.

01 The water roller swing frame of the machine is controlled by the cam, and the cam is worn after the cylinder repair of the printing machine has been used for a long time. In the neutral place to produce jumping, the water bar is more obvious, most of the printing about 5000 sheets make the water bar, the printing force of the plate is reduced.

In the printing process, sometimes one or several horizontal bars will appear on the printed material layout, which is commonly called printing bar marks in the industry. There are two performance characteristics of printing bar marks: first, the ink color of the horizontal strip shadow part of the printed layout is obviously darker than that of other parts; The second is that the ink color of the bar-shaped bar shadow is significantly lighter than that of other parts.

The former belongs to the ink bar, and the latter belongs to the water bar. The reasons for their emergence are varied.

1. The causes and elimination methods of ink bars.

1. Ink bar caused by rubber roller factors. When the contact pressure between the rubber roller and the printing plate is too large, then during the operation of the machine, when the inking roller and the printing plate contact the roller brush, it is easy to produce impact and cause tremor, so that the friction force increases and causes the streak cross. If the pressure of several of the ink rollers in the format is too high, the density of the bar marks will be greater.

In this regard, the contact pressure between the rubber roller and the printing plate should be adjusted to maintain uniform and moderate contact conditions, and the ink bar can be better eliminated after eliminating excessive resistance.

2. The drum gear is worn, the gear clearance is too large or there is a foreign matter accumulation between the gears. When the drum gears are worn, there is a gap or there are foreign objects adhesion between the teeth, during the operation of the machine, the drum gears cannot be meshed accurately, so that the linear speed between the rollers is not consistent enough. In addition, the tooth gap is too large, and the drum is also prone to tremor and shake, forming printing bar marks, so that the ink bar marks similar to the gear pitch appear on the printed product layout.

There is a foreign body obstacle in the tooth gap, and it is easy to cause it"Top teeth"The phenomenon causes the cylinder to tremble, so that the horizontal layout of the printed product forms a strip-like ink bar. In this regard, the center distance between the rollers should be readjusted to reduce the inter-tooth distance; For the gear that is badly worn, the gear should be replaced with a new one; If there is a foreign matter adhesion between the teeth, it should be cleaned up to achieve the effect of eliminating the ink bar.

3. The roller bearing is greatly worn. When the drum shaft head runs without oil or the machine is used for a long time to produce natural wear, the gap between the drum shaft head and the bearing increases, the fit is poor, and the ink bar traces are caused by tremor when the pressure is combined. In this regard, it is advisable to make the mouth of the rubber liner trapezoidal to reduce the impact during the embossing state and reduce the degree of ink bar marks.

In addition, if the roller bearing is seriously worn, it should be considered to repair it by plating or replace it with a new bearing to eliminate the traces of the ink bar.

4. The lining of the printing plate cylinder or rubber cylinder is too large. If these two situations exist, the linear velocity of their surface will be inconsistent and cause strip-shaped ink bar marks, and at the same time, the impact flutter of the cylinder during imprinting, so the contact between the two cylinders will easily cause friction and cause ink bar marks during fluttering. In addition, in some cases, if the bite is not marked clearly (the pressure is too light), it is easy to cause ink bars if the paper strip is padded too much.

In this regard, the thickness of the lining should be accurately adjusted, and the ink layer should be evenly transferred with the minimum printing pressure as much as possible, so as to maintain the consistency of the surface linear velocity between the cylinders. When adding paper strips to the bite part, the method of gradually heating the pad should be adopted, and it must not be more pads at once, so as not to produce traces of ink bars.

5. The rubber cloth is loose, and it is easy to produce sliding friction when rolling, so there are traces of strip-shaped ink bars. Therefore, measures should be taken in time to tighten to prevent the formation of printing ink bars.

The ink bar refers to the obvious axial deep streaks on the printing plate layout and printing when printing flat screen or solid printing, commonly known as it'Black bars'or'Black striped head'。

The ink bar is the ink bar caused by the ink on the rubber roller sliding for some reason.

The water bar refers to the obvious axial shallow streaks on the printing plate layout and the printed piece when printing flat screen or solid prints, commonly known as it"

White bars"or"

White strip head".The water bar is generally caused by the water conveyance part.

The causes and solutions are:

If the pressure between the water roller and the main ink is too large, the pressure between them should be readjusted to reduce it appropriately. Less stress;

The ink is emulsified, and there is too much ink on the surface of the water roller;

If the moisture on the layout is too large, the water supply should be reduced, the rubber cloth should be cleaned, and the ink roller should be cleaned in serious cases;

The dampening water is too acidic, so the acidity of the dampening water should be reduced.

The ink bar is a kind of fault that is difficult to solve in offset printing production, and most of the operators feel that this is a very tricky problem, and there are many reasons for it, so Tongqi not only needs to flexibly use observation, thinking and judgment to identify the ink bar failure, but also needs to have a high technical foundation and operation skills. In order to obtain a problematic print, we must first observe the special return search of the ink bar, such as thickness, quantity, position and distance between the ink bars, etc., and then analyze the causes according to the characteristics, so as to make a correct judgment.

Hope it works for you.

The water bar refers to the obvious axial shallow streaks on the printing plate layout and the printed piece when printing flat screen or solid prints, commonly known as it"White bars"or"White strip head".The water bar is generally caused by the water conveyance part.

The causes and solutions are:

1) The pressure between the water roller and the main ink is too large, and the pressure between them should be readjusted to reduce it appropriately.

Less stress; 2) Ink emulsification, too much ink on the surface area of the water roller;

3) If the water on the layout is too large, the water supply should be reduced, the rubber cloth should be cleaned, and the ink roller should be cleaned in serious cases;

4) The acidity of dampening water is too strong, and the acidity of dampening water should be reduced.

The ink bar is a kind of fault that is difficult to solve in offset printing production, most of the operators feel that this is a very tricky problem, and there are many reasons for it, so the identification of the ink bar fault should not only flexibly use observation, thinking and judgment, but also need to have a high technical foundation and operation skills. To get a problematic print, we must first observe the characteristics of the ink bar, such as thickness, quantity, position and distance between the ink bars, and then analyze the causes according to the characteristics, so as to make a correct judgment. The world is like this.

Hope it will be useful to you.