Screen Printing Common Three Kinds of Issues Notes Continued

Second, repeatedly tensioning the screen

Off-press printing and the use of stretchable screens can also reduce the accumulation of ink on the screen, while the tensioned screen also has a more severe effect on the quality of the print.

All of the mesh fibers are elastic and change with pressure and time, and the degree of change in different materials is also very different. For example, a 110-mesh coarse-mesh screen can be pulled tighter than a 305-wire fine screen, so it is less prone to deformation under heavier pressures.

The new mesh fiber loses 25% of tension within a few hours of tightening, which may not have been printed on the machine yet. During printing, the screen is subjected to a downward force over and over again by the action of the squeegee, deforming the fiber, and we feel it soft.

The best method is to repeat the tension of the screen four times within 24 hours before applying the screen. Every time it is tense, it is found that the speed at which the mesh fiber loses tension slows down until little time has passed since the screen tension was lost.

If the company has stretching equipment, the screen should be placed on the equipment, so that it is always under the role of tension, even if this screen may have to wait a lot of days before printing. The longer the screen is under tension, the greater the possibility of straining the screen on the frame.

Retensioning the screen after printing can easily achieve a higher tension. As a result, the loss of tension will become less and less frequent. Sometimes you will find that an old screen that has been used many times is even better than a new screen.

A hard frame, like a frame made of wood, does not have the advantage of this repeated tensioning of the screen. Excessive tension will cause the wood to deform. Deformed screens are in vain, such as overprinting and uneven ink accumulation.

Some enterprises retain a large number of old wooden net boxes, thinking that this is a fortune, but they do not know that this will cause a great burden. If the company does not plan to purchase some repeatable frames, it should consider replacing all old wooden frames with new wooden frames. Otherwise, the quality and profits of the products will not be guaranteed.

The possible print failures caused by insufficient tension are:

Screen overprinting is not allowed. Ink accumulation under the screen. Printed image appears feathering. Print overprinting is not allowed. The thickness of the ink layer is not uniform. In order to solve the problem of insufficient tension, the operator may reduce the printing speed. As a result, the production efficiency is lowered and the cost is increased.

Insufficient tension will also cause the squeegee to squeegee and will damage the emulsion layer. Some pinholes will be formed in the print. The original role of the emulsion layer is to determine which areas are not inked and which areas are inked.

Older screens that have been on hold for a longer period of time are more prone to pinholes. In order to repair pinholes, production efficiency is greatly reduced, and product quality is a problem. As a result, customers may reject goods and the loss is very serious. It is self-evident that it is light and light.

Third, control the squeegee angle and speed

If the amount of ink on the product is insufficient, the most common method is to increase the pressure applied on the squeegee and print the same image twice. It is recommended that you reduce the angle between the squeegee and the substrate to less than 45 degrees. You can get good results only once. This will not only save half the work, but also double the work efficiency. At the same time, the problem of registration due to insufficient tension will not arise.

Why is it not advisable to directly increase the pressure of the squeegee? The main reason is that the ink's trajectory is the graphic area that goes straight down through the screen. Compared with the 30 degree angle, more ink will be carried by the blade of the squeegee blade at the 60 degree angle, and the trajectory of ink travels downwards, resulting in thick ink accumulation.

The ink is pushed forward by the squeegee blade and is scraped by the doctor blade over the screen. The squeegee pressure is achieved at the moment when the screen fiber and the printing material are in contact with each other. At this time, the ink of different viscosities is in contact with the printing material of the graphic area. Any squeegee pressure that exceeds this critical value will cause the ink to accumulate, damage the screen fibers, and damage the emulsion layer.

The ideal angle between the squeegee and the substrate is 45 degrees. Above 45 degrees, the number of inks driven by the squeegee is less, and vice versa.

In addition, the squeegee speed also affects the amount of ink deposited. Pushing the squeegee at a faster speed, the amount of accumulated ink is smaller because the force applied in the squeegee running direction is greater than the force applied to the printing material. Reducing the angle of the squeegee without slowing down the squeegee will not degrade production efficiency.

The advantage of printing with automatic equipment instead of manual equipment is the angle and speed of the squeegee. When manual equipment is printed, it is artificially pushing the squeegee to mimic the operation of the automatic equipment.

Sometimes the operator initially applies more pressure on the squeegee, and then relaxes the pressure on the squeegee while moving it; sometimes it is lighter and heavier; sometimes it is heavy and light. This change of angle and pressure should be strictly avoided, otherwise it will cause instability in the printing quality.

Fourth, the conclusion

If you visit a mature automatic screen printing operation, you will find that the ink is very thin, like water, very different from the original ink that you just bought. Experience the tension of the screen, and almost no ink accumulates under the screen. The print quality is very good, and the touch is very soft and the production speed is relatively high. This is all worthy of you to learn how to modulate the ink, to understand the impact of screen tension on quality, and how to choose the right squeegee angle and speed, to create favorable conditions for improving the company's profit margins.

If we take a good grasp of these three areas of scale, the company's product quality, production efficiency and corporate reputation will be improved, while the cost will be effectively controlled.