Ink uniformity and application of eight-wire ink stick

In the gravure printing production, because of the volatilization of the solvent in the ink tank, the uniformity of the ink is reduced, and the surface is easily formed into ink skins and ink sticks. After the printing roller is brought on, the scraping knife is not easy to scrape clean, so that the printing product produces paste plates, knife lines, etc. defect. How to solve this problem, let the ink "flow" together, keep mixing, can naturally avoid this situation.

There are two means to move the ink: one is to use an ink circulating pump to let the ink circulate; the other is to place an ink stick in the ink tank to allow the ink to flow in the ink tank. The former is the external circulation of the ink, the cost is high, and the factors that cause failures are increased. Generally, the addition of the solvent and the automatic viscosity control system are not included in this article. From the point of view of uniform ink, the latter is the most economical and effective measure.

Agitating rods are generally hollow rods made of aluminum alloys, with spiral-shaped continuous protrusions on the surface, so-called "ripples" or unwinding lines, with magnetic material at both ends, which can be adsorbed on a plate roller. During the printing, the agitating rod floats on the surface of the ink, and when the printing roller rotates, it rotates in the reverse direction by the adsorption effect. When rotating, the corrugation drives the surface layer of the ink to allow the ink on the surface to move, thereby evening the ink and avoiding the corresponding quality problems of the printed product.

The following are the two main factors that determine the quality of agitating sticks:

1, effect. The ink mixing of the agitating stick mainly depends on the unwinding line, which is called ripple, and the size, angle, structure, and rotational speed of the agitating rod determine the agitating effect. In general, the faster the agitating rod rotates, the better the agitating effect. The bigger the development line is, the larger the angle is and the better the ink mixing effect is. However, if the developing line is too large, the magnet part is far from the platen roller, the magnetic force is weakened, and the magnetic force is not easy to be absorbed. The rotation speed of the ink stirring rod is reduced (discarded), but the effect is poor. In addition, the smaller the specific gravity is, the better the floating effect of the agitating rod in the ink is.

2, life. The agitating rod needs to float on the surface of the ink and is generally hollow. If the seal leaks, the solvent enters the interior of the agitating rod and will sink and lose the stirring effect. Therefore, the seal at both ends should be resistant to corrosion. In addition, the surface wear resistance is better.

3, magnetic. The adsorption of the ink roller to the plate roller mainly depends on the magnetic strength. On the one hand, the internal magnet is preferably larger, and the magnet cannot be large because of its large proportion. It is a good idea for manufacturers to add a rubber ring to control the distance when they are used, but they should pay attention to the problem of rubber swelling.

4, distance. The agitator should have a suitable distance from the plate roller. Too close, the ink at the seam is too small to stir; too far, the magnetic force is reduced, and it is easy to throw away.

At present, the commercially available ink agitating stick generally has the following kinds.

1, plastic stirring rods. Commonly used in imported products, the surface is made of abrasion-resistant plastic sheeting. The inner core is used. The quality is quite good, and the price is relatively high. Generally, it is about 1,000 yuan per meter. It is said that at present some people in China have already imitated it, but because there is no better friction-resistant plastic material, the life expectancy is relatively poor. In addition, the effect of ink mixing is also not very good.

2, around the rope stirring ink sticks. Generally made of general aluminum tube, the surface of a wire wound around the line to develop the line, this product has two defects: 1 because the use of wire rope winding, the angle of the line is relatively small, 2 lines will be infiltrated with ink, dry formation when the machine stops When used again, dry agglomerates may be mixed with ink, causing print marks.

3, single-line aluminum alloy corrugated ink sticks. The structure is similar to the roving agitator, except that the string is changed to an aluminum alloy spiral protrusion because only one deployment line has a small angle and the ink mixing effect is relatively poor.

4, eight-wire aluminum alloy corrugated ink rod. Aluminium alloy rotary extrusion profiles have 8 lines of development on the surface and have a large angle, which is the best product for current ink mixing. In addition, these products are not only more corrosion-resistant seal at both ends, and wear resistance is also relatively good, if the timely cleaning of iron powder and other impurities absorbed by the ink stick, the life expectancy is generally 2-3 years, it really saves the manufacturers even Ink costs. This is also the product that most color printing plants currently choose. At present, Beijing RAND Meike's LB-03 eight-wire ink sticks and Nanning's eight-wire ink stick are such products.


Frequently, customers have asked the author the ink return direction of the eight-line corrugated ink stick. The actual problem is whether the corrugation has an interface. If the left and right spirals meet in the middle, the ink will flow from the middle of the ink tank to both ends or both ends of the work. Flow in the middle (needs to reverse the orientation); if the ink stick is striated (ie, no interface, left or right), the ink will flow from one end of the ink tank to the other during operation. According to the author's experience, the two ink-return methods basically have no effect on the uniformity of the ink.

(Author/Wang Jiaxuan)