(This article is the exclusive contract draft of Bisheng.com. It is strictly prohibited to reprint.
The so-called ink bar is the phenomenon that the dots in the axial strip area appearing on the printed matter increase or decrease.
In the daily work of offset printing, the problem of ink sticks on printed products is often a headache. Because the reasons for the occurrence of ink sticks are multi-faceted, it requires more comprehensive analysis and judgment before they can be effectively solved. Let's analyze the more common ink stick phenomena and causes in production.
In general, the ink bars we can encounter in our work can be roughly divided into four types: vibrating ink bars; geared ink bars; roller ink bars; ink bars produced by other reasons.
Let's discuss the following categories:
1. Vibrating ink bar Vibrating ink bar means that during the printing process, after abnormal vibration of the machine, the contact pressure between the printing plate, blanket, paper, and impression cylinder changes instantly (may increase instantly , May also become smaller instantaneously), resulting in deformation of the dots.
Blanket: The role of the blanket in the printing process is not only to increase the transfer rate of ink to the paper, but also to absorb machine vibration generated during imprinting. When the blanket is hardened, the vibration generated during the operation of the machine cannot be effectively absorbed during imprinting. When this vibration is displayed on the printed matter, the problem of ink sticks will occur. Many domestic printing presses in China use soft padding because of low manufacturing accuracy and large vibration during printing.
Poor oil supply: When the machine's motion mechanism gives poor oil, it will have a certain impact on the stability of the machine's operation. When this effect is large enough, it will cause vibration of the machine. The transfer of the dots is affected to a certain extent, causing local dots to be deformed, and eventually ink bars appear.
Poor embossing force: when the pressure of the roller is too large, the machine will vibrate during the embossing, resulting in ink sticks. Especially when the plate cylinder and rubber cylinder have just entered the impression area (at the mouth), if the pressure is too large, the contact between the rubber cylinder and the impression cylinder will be affected by vibration and a large, regular ink will appear. When the rubber cylinder and the impression cylinder have just entered the impression area from the grip, if the pressure is too large, the effect is the same. A vibration bar will appear in the contact area of ​​the plate cylinder and the rubber cylinder, and then transfer to On paper.
Bearing wear or pressure instability: When the roller shaft head runs out of oil or the machine wears naturally for a long time, the gap between the roller shaft head and the bearing is increased, the cooperation is poor, and the ink stick marks are caused by tremor when the pressure is combined. In this regard, it is advisable to make the grip of the rubber inner liner trapezoidal to reduce the impact during the imprinted state and reduce the degree of ink stick marks. In addition, if the roller shaft head or bearing is seriously worn, it should be considered to repair or replace the new bearing by plating repair to eliminate the trace of ink stick.
Anchor screw is loose: The corner screw is the foundation of the entire printing machine. If the foundation is not stable, of course, the machine runs smoothly. During the installation and commissioning of the machine and the annual maintenance of the machine, it is necessary to specifically check the anchor screws and tighten the loose screws in time to ensure that the machine can run smoothly.
In addition, the reasons that can cause vibrating ink sticks in printing are:
Vibration of the ink transfer roller; vibration caused by each cylinder during imprinting; vibration caused by opening and closing of each gripper; improper motor rectification; uneven rotation; loose chain; loose bolts on the main part of the machine; different wall plate holes Heart; roller unbalance; gear eccentricity and other reasons.
Second, gear-shaped ink sticks Causes of ink sticks: roller gear wear, gear gap is too large or there is foreign matter accumulation between gear teeth. When the roller gears are worn, or there is adhesion of foreign objects between the teeth, during the operation of the machine, the roller gears cannot be accurately meshed, so that the linear speed between the rollers is not consistent. In addition, if the tooth gap is too large, the cylinder is also prone to tremor and jitter, forming printed bar marks, so that there are ink bar marks on the printed board surface that are close to the gear pitch. There is a foreign object obstacle in the tooth gap, and it is easy to cause the roller to tremble due to the "top tooth" phenomenon, so that the horizontal layout of the printed product forms a striped ink bar. In this regard, the center distance between the rollers should be readjusted to reduce the tooth gap; the gears with severe wear should be replaced with new gears; if there is foreign matter adhering between the teeth, they should be cleaned up before the effect of eliminating ink sticks can be achieved.
There are several reasons that can cause the gear bar:
Gear wear; bearing preload is too large or too small; precision is not high; improper chamfering of tooth surface and tooth end; circumferential joint error; tooth error tooth surface finish is not high; gear skew; improper backlash; drive belt tension is too large Or insufficient; there are foreign objects on the tooth surface;
3. Roller Ink Bars There are generally two types of ink bars produced by the rollers. One is the white bar (also called water bar), and the other is the ink bar (for convenience we will refer to them as ink bars). The former is generally caused by the water roller problem, while the latter is caused by the ink roller problem. But whether it is a water roller or ink roller caused by the bar, the reasons are basically the same.
The most common reason for ink sticks in daily production is that the roller pressure is too strong.
When the contact pressure between the rubber roller and the printing plate is too large, during the operation of the machine, the inking roller is in contact with the printing plate to roll, it is easy to produce impact and cause tremor, so the increased friction causes streaking. If the pressure of the inking rollers 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. After removing excessive resistance, the ink bar can be better eliminated. In addition, when the pressure between the inking roller and the inking iron roller is too high, the iron roller will squeeze the rubber roller, and the instantaneous temporary deformation caused by the elasticity of the rubber roller will cause sliding friction on the printing plate, causing ink sticks. In addition, because the pressure of the ink collecting roller, the ink roller and the printing plate are different, it is easier to cause the surface linear speed of them to be out of synchronization and cause ink sticks. Therefore, the pressure between the rubber roller and the ink-inking iron roller should be adjusted appropriately to avoid the rubber roller being squeezed, and the resistance and friction increase and the ink stick is prone to occur. There is also a case where the rubber roller is not well-aligned and not straight, and ink sticks are also prone to occur. This is because the contact pressure between the rubber roller and the printing plate is inconsistent during the rolling of the machine. When the machine is rolling, the local friction is increased and the strip bar marks are caused. In this regard, high-precision ink rollers should be replaced for printing full-field and anilox plates.
Similar to the ink bar caused by excessive pressure, there are some reasons in the printing that can cause the roller ink bar. The principle is basically similar to the ink bar caused by excessive roller pressure. Such as: roller bending; roller expansion, cracking; poor cleaning; ink roller, water rubber roller aging; wall hole of ink roller shaft is not concentric; bearing, gear and other wear; roller arrangement problems; roller bearing fulcrum problems.
4. Other Ink Bars In addition to the three situations mentioned above, the reason why ink bars sometimes appear in printing production is really difficult for others to think about. Below we will introduce some reasons that may cause ink bars for reference.
material:
The plate-making paper is wrinkled; the pad under the blanket is wrinkled; the thickness of the plate is uneven; the thickness of the blanket is uneven; the remaining residual varnish;
Machine wear of rollers and bearings; the gap of bearing support is too large, the preload is too large; the bearing is skewed;
The upper plate cylinder or rubber cylinder is too large: if these two conditions exist, the ink line marks will be caused by the inconsistent linear speed on their surface. At the same time, due to the impact vibration of the cylinder during imprinting, the contact between the two cylinder It is easy to produce friction and cause ink stick marks. In addition, sometimes there are not obvious marks on the bite area (the pressure is light), and too many paper pads can also cause ink sticks. In this regard, the thickness of the liner should be accurately adjusted, and the minimum printing pressure should be used as far as possible to make the ink layer transfer evenly, so as to maintain the consistency of the surface linear speed between the rollers as a prerequisite. When adding paper strips to the bite area, the method of adding pads gradually should be adopted. Do not pad more at a time to avoid traces of ink sticks.
The blanket is loose. If the blanket is changed soon, the stretching becomes loose during the printing process, and the tension is not tightened in time, so that it is easy to produce sliding friction when rolling, so there are traces of ink sticks. Therefore, when the blanket is slack, measures should be taken in time to tighten to prevent the printing ink stick.
V. Judgment and exclusion after the appearance of ink sticks As we mentioned at the beginning of the article, the appearance of ink sticks is generally very troublesome. The reasons for the occurrence of streaks are various and the situation is sometimes complicated. It is caused by one reason, and it is composed of many kinds of undesirable conditions; it is caused by the wear of equipment parts, and it is also due to improper operation methods and uncomfortable adjustments. In addition, there are not many opportunities for ink sticks in production, and it is difficult for ordinary operators to accumulate a lot of experience in this area.
However, after careful analysis, we will find that there are certain rules to follow in the creation and elimination of ink sticks.
1. The part where the ink bar appears is lighter than the normal part, and the general problem may be larger on the water roller.
2. When the ink color is darker at the ink bar, priority should be given to whether the ink roller mechanism is normal.
3. When the ink bar is more obvious at the mouth, and it is less obvious when it is dragged, the water roller or ink roller should be given priority.
4. When the full version has streaks of about 1 cm in width, it may be a gear problem (the most likely cause is the wear of gears or the problem of gear spacing).
5. When the width of the ink bar is relatively wide and the position on each print is relatively fixed, it may be due to the wear of the roller bearing or the excessive pressure of the roller.
6. When the ink bar is wider, it may be related to the vibration of the machine.
7. If the appearance of ink sticks is very regular, it may be caused by the periodic vibration of a certain mechanism to a large extent. Further judgment can be made based on the spacing and position of the ink bars.
8. If the appearance of the ink stick is completely irregular, it may be caused by loose bolts or loose and wear of the place where it needs to be tightened.
In fact, after understanding the reasons and rules of the appearance of ink sticks, it will be much easier to solve the problems of ink sticks in production.
In fact, treating disease is worse than preventing disease. In daily production, it is necessary to strengthen the maintenance and maintenance of equipment, use and adjust the machine scientifically and reasonably, and prevent and avoid the chance of ink sticks, which is the best way to deal with the problem.
meeting table,conference table,boardroom table,conference room table,meeting room table
Queen Furniture Co., Ltd. , https://www.queenfurnitures.com