Frequent ink failure during printing (4-7)

Four piles of ink

The ink stack failure caused by the ink means that the ink accumulates on the ink roller, plate, or blanket, and the ink transferability is poor. In addition to the causes of stacking ink, ink, printing pressure, and plate pressure are the reasons for stacking ink. The ink accumulates on the blanket, the pigment is in the form of powder in a separate state, and the dots are pasted to make the colors inconsistent. This is due to:

(1) The ink is poorly dispersed, and coarse inorganic pigments with relatively high relative densities are used in the ink.
(2) The ink film is too thick.
(3) The ink is diluted excessively and the linking material is too thin.
(4) The printing pressure is not true, and the ink transfer performance of the roller is poor.

Approach:
(1) Check the printing pressure, ink roller performance, and pad.
(2) The amount of ink should be appropriate. If the ink is too soft, some thick ink can be used.
(3) Replace with new ink.

[Related Links]
In the actual printing work, white ink, gold, and silver ink are the inks that are most likely to cause stacking faults.

[Expert Tips]
There are many factors that cause stacking faults. Offset press operators must be clear about the cause of the malfunction. Do not mention that the failure of the stacking ink will be caused by ink.

Five prints with poor gloss, not bright

The gloss of prints is poor and not bright. Except paper factors, the ink is mainly diluted due to excessive dilution of the ink, the resin precipitates and loses the linking effect. The dryness of the ink is slow or the absorption of the paper is too strong. As a result, the ink penetrates into the paper and the print is uneven and dull. Light.

Approach:
(1) Add new ink or add bright light to the ink.
(2) Use high-gloss ink or use poorly absorbent paper.
(3) Add some desiccant as appropriate.
(4) Printed products can be varnished with varnish.

[Related Links]

Another manifestation of poor print gloss is "blushing". This failure is mostly caused by a transparent white ink film that appears during the rapid evaporation of solvents after high-speed printing in the printing process of volatile drying printing inks. This phenomenon is sometimes temporary, but most of it may be long-lasting. This is due to the fact that the cooling (device) blowing or the air in the vicinity of the drying printing ink film is cooled to the dew point, that is, the water (vapor) is absorbed and then returned to the ink film to be condensed. In addition, solvents such as inks or pigments in aqueous systems can also cause a poor gloss of printed ink film.

The prevention method is to adjust the solvent used for the printing ink, reduce the amount of solvent that volatilizes quickly, and control the relative humidity in the air of the workshop to be less than 65%.

Six fading

The color of the ink fades during the printing process, or the color of the ink fades when the print is stacked (during drying). The reasons are:

(1) Heat is generated in the paper stack due to the oxidation of the ink, and this heat causes the ink color to fade.
(2) The desiccant used in the ink contains too much cobalt.
(3) The pigment is not heat-resistant or the pigment content in the ink is too small.
(4) With light color, white ink is not suitable.
Approach:
(1) Reduce the amount of desiccant and use a quick-drying (or fast-setting) ink.
(2) Heat-resistant and light-resistant stable pigments are used in the ink.
(3) Change to white ink.

[Related Links]
Fading is the failure of the printing process or the outdoor aging of printed products. The ink film is exposed in the atmosphere. Due to the effect of ultraviolet rays, the color changes with the atmospheric temperature, humidity, the light intensity of sunlight, and the nature of the printing ink film and ph. Different values. Therefore, try not to use faded lake ink before printing.

Seven poor ink transfer

The main reason for poor ink transfer is poor rheological properties of the ink. If the thixotropy of the ink, the yield value is too large, the viscosity is too small, and the filament head is too short, these rheological characteristics are combined to make the ink Poor flowability, resulting in poor ink delivery to the ink supply system or no ink at all. In addition, the paper de-powdered, lint-fat easy to make ink transmission.

In order to allow offset printing to be performed normally and to obtain high-quality prints, on the one hand, inks with rheological properties suitable for printing should be selected. On the other hand, printing materials should be used in combination with the process conditions at the production site, and at the same time, appropriate amounts of auxiliary agents should be added to the ink. The rheological properties of the ink are adjusted.

[Related Links]
In the normal printing process, the ink occasionally does not rotate with the ink fountain roller. Even the ink accumulates on the ink roller of the printing machine. In particular, after the printing speed is increased, the color tone of the ink is lighter or shaded. This failure was mostly caused by too high a pigment content, a too thick ink, a too high yield value, or a too short ink head. The appearance of these phenomena in recent years is due to the fact that the link material, the pigment acid value in the ink system is too high, or the addition of a single solvent is excessive. There is no problem at the beginning of the printing, and ink is often forced to shut down and change ink when the ink is released from thin to thick, or even flocculent (tofu lumps).

Approach:
(1) Dilution is performed by adding a basic solvent.
(2) Add wet aid.
(3) Diligent ink fountain.

Source: Ke Yin Network