How to control the ink consistency of screen printing machine printing?

The ink viscosity and ink consistency used in the screen printing machine are also different in use:
How to control the ink consistency of screen printing machine printing?
1. Some "sticky" inks used in full-automatic screen printing machines have relatively large viscosity and slightly poor fluidity, which have good adhesion, large intramolecular friction or cohesion, strong adhesion and rapid fixation. Clear, round and solid dots can be obtained by printing with "sticky" inks, and "sticky" inks have good water resistance, are not easy to emulsify, have good "ink collection" and are easy to dry, the dot is bright and clean, the ink color is bright, the color is saturated, and the ink layer is thick. Therefore, this ink is more suitable for the following situations:

(1) for the printing of good gloss, high surface strength of the paper, such as coated paper, glass cardboard, white cardboard and other paper, and gold and silver cardboard and other smooth, non-absorbent paper is also suitable for "sticky" ink;

(2) Suitable for printing fine products with high screen line, easy to obtain strong and clear, full-color images;

(3) printing gold, silver ink, and printing fluorescent ink, also need to adjust the ink sticky some, so that its adhesion is strong and not dirty;

(4) for the phosphorus flake pearlescent ink, also need to adjust the adhesive ink printing.

Since the viscosity of ink is an important factor in dot transfer, in practice, the size of the ink viscosity should be coordinated and adapted to the printing process according to the changes in different conditions, and make appropriate adjustments to increase or decrease the viscosity of the ink. In fact, it is to adjust the cohesion of the ink to meet the requirements of the actual printing conditions,

Specific increase "viscosity" adjustment methods are:

(1) Add appropriate amount of tackifier to increase viscosity, such as No. 0 ink;

(2) adding high viscosity resin oil to increase viscosity;

(3) add the right amount of high viscosity ink viscosity.

Due to the high viscosity of the "sticky" ink cohesion, strong adhesion, in some cases should not be used, such as: in the printing of offset paper, white board paper and other paper with low strength paper, printing speed is faster, the ambient temperature is higher, the layout is mainly large, etc., must use a lower viscosity ink, if the viscosity of the ink is too high, it needs to be reduced viscosity treatment.

The usual methods of reducing "stickiness" are as follows:

(1) add a certain amount of silicone oil;

(2) Add less than 2% and no more than 5% viscosity reducer to reduce viscosity;

(3) Add high boiling point kerosene to reduce viscosity, and the dosage shall be controlled at no more than 10-20ml per kilogram;

(4) adding a certain amount of corn starch, Vaseline and other viscosity reducing substances.

2, consistency is larger, but has a certain viscosity and adhesion of the "thick" ink, due to poor fluidity, ductility is not good, ink is paste, not easy to flow, printing ink film is not easy to spread, graphic transfer more accurate, not easy to deformation, ink color is bright and full. Therefore, "thick" ink is more suitable for the following situations:

(1) Suitable for printing large-scale products with hollow characters or small characters. Because it is not easy to flow and spread, hollow characters or small characters are not easy to produce paste version;

(2) suitable for printing large field with shallow dot products, can obtain a thick field, while the dot is relatively clear, not easy to expand:

A. high ambient temperature, slow speed, dot graphics-based circumstances, the general appropriate to adjust the thick ink for printing;

B. paper surface strength is high, the surface ink absorption is poor, should also be appropriate to adjust the thick ink printing.

In actual production, if there is no ink with corresponding consistency, or the consistency of the ink becomes smaller and cannot meet the requirements of use, then it is necessary to increase the "thickening" treatment to reduce the fluidity of the ink. The specific "thickening" treatment methods are mainly:

(1) Add NaOH, the addition amount is about 1%-3%, this method is effective quickly, it is a simple and effective method for ink thickening;

(2) Add a tackifier, such as No. 0 ink, but pay attention to the appropriate amount, not too much;

(3) If the ink is not viscous enough due to the influence of temperature, the same hue can also be added to the ink.

3. Ink with small consistency and poor viscosity can be extended well under the mutual extrusion of ink rollers due to good flow, good transfer performance and easy ink application. In addition, the ink layer can be quickly leveled and spread between each printing transfer surface, and the ink printing film is smooth and smooth. Therefore, in some cases, the consistency of ink needs to be reduced, such:

(1) The paper is of poor quality, relatively rough, large ink absorption, or low surface strength, easy to pull off the powder, such as the use of poor printing offset paper, book paper, white board paper, etc;

(2) When the layout is dominated by field and large color blocks;

(3) when the workshop temperature is high and the printing speed is fast;

(4) The paper is damaged. If the ink is too thick, it may aggravate the damage. Therefore, ink with greater fluidity should be used for printing.

The main way to reduce ink consistency is:

(1) Add a certain amount of diluent, such as adding low viscosity, high fluidity No. 6 ink, this method is better, but to control the amount, generally not more than 10% of the amount of ink;

(2) frequently stir the ink fountain, because the ink has thixotropy, its flow characteristics will be improved with the increase of the degree of agitation, so that the viscosity of the ink is reduced;

(3) Add less than 2% of the viscosity reducing agent.