Features and precautions of screen printing process

Process characteristics

As we all know, the imitation metal etching uses the graininess of the frosted ink itself to print the frosted effect on the gold and silver cardboard. The thickness and feel of the sand depends on the ink used, and the adjustment is limited during operation. Based on the imitation metal etching process, the cloth texture process absorbs some characteristics of the imitation embossing process. Starting from the plate-making film, the original filled background is replaced by a uniformly distributed round or square dot pattern, which is printed during printing. It has a coarse cloth texture effect similar to frosted. At the same time, the size and shape of the texture can be adjusted through the plate-making film, and the autonomy is stronger. The inks used for printing are no longer limited to matte inks, but can also use other types of inks such as dimming inks, pearlescent inks, etc., which show colorful and different effects and have higher aesthetic value.

Plate making

The production of high-quality silk-screen printing plates is an important prerequisite for obtaining exquisite print effects. Therefore, it is very important to control the plate-making process.

First of all, when imposing a large-scale patterned film, the requirements of overprinting during printing should be taken into consideration, and a certain gap should be reserved between the links. Because the cloth film is different from the actual pattern. When using film pre-shrinking, the use of the previous "digging" method to improve overprinting will destroy the integrity of the picture and text. Therefore, the single-piece overall movement method can only be used to improve overprinting. The remaining gap will leave room for the later die cutting process.

Secondly, the tension of the screen should meet the requirements. If the tension of the screen is insufficient, a series of problems such as stretch elongation, inaccurate overprinting, and unstable hue may occur during printing. Generally speaking, the tension of 300 mesh / inch screen should be controlled between 20-23N / cm. In addition, the thickness of the coated photoresist should be moderate to avoid uneven thickness and bubbles on a screen, so as not to have a greater impact on the printing quality. Finally, for the outlets with different numbers of screens, the exact exposure time is measured with a dedicated test strip. Detailed records should be made after each printing, to achieve data management, so that future work can be based.

For cloth products mainly based on bitmaps, if the combination of screen mesh and screen lines is unreasonable, due to the limitations of the screen itself and the existing plate-making system, it is easy to cause the phenomenon of interference with graphics and text. Moreover, the higher the number of screen lines, the finer the picture and text, the higher the chance of moire. Through multiple proofing and printing, on the 300 mesh / inch silk screen, the moire can be overcome by adjusting the printing angle to overcome the 60 lines / inch dot. On this basis, as the number of screens increases, the number of wire meshes used must also increase accordingly to improve accuracy and reduce moire. On the contrary, the mesh number can be appropriately reduced to improve the feel.

If the angle setting is not appropriate, the wire of the screen will interfere with the integrity of the dots and affect the production of the cloth effect. There are two specific methods of operation: one is the "oblique stretch and direct drying method", that is, the screen and the frame are inclined at a certain angle when the net is stretched, and the angle of the film and the frame is kept unchanged when printing; "Straight stretch oblique drying method", that is to maintain a right angle when stretching the net, so that the film is tilted 4-8 degrees in the frame when printing. "Straight stretch oblique drying method" because the tilt angle is not large, the error can be adjusted on the printing machine. The "oblique stretch and straight sun" method is not recommended because it requires the purchase of a specially widened and enlarged wire mesh, and it is difficult to stretch the mesh and the waste of the wire mesh is large. After exposure, the screen should be developed with a high-pressure, low-flow spray gun to prevent the dots from being impermeable due to insufficient water pressure, or the flow rate is too large to cause the dots to be washed away. Before printing on the machine, you should check whether the screen image is complete and the dots are full. Some dots that are suspected of being impervious to ink can be revised by a method of piercing with an embroidery needle under a magnifying glass. [next]

Ink

There are many types of inks that can be used for silk screen printing. Generally, different types of inks can be selected according to different design requirements. For some products that are mainly filled with the base color and supplemented by the texture effect, colored pearlescent ink and color-changing ink can be used to cover the background color, so that when the angle is changed, it will produce a colorful effect such as pearlescent and color changing. . If printing directly on gold and silver cardboard with cloth pattern as the main color, you can choose some colorless matte ink.

When selecting inks, "over-screen rate" is a parameter to be considered. For inks with poor screen passing rate, there are many residues left during printing, and the dots of the printed product just after printing are clear. After a certain amount of printing, the dots will be incomplete and incomplete. Try to choose some uV inks that are not meshed to avoid frequent plate washing in printing and reduce labor intensity. At the same time, UV inks are also safer and more environmentally friendly than solvent-based inks.

Paper

In order to improve the quality of products, more and more packaging choose film-coated gold and silver cardboard. When printing the cloth effect with colorless ink, because the ink particles are colorless and transparent, the hue reflected by the product depends largely on the color of the gold and silver cardboard. If the color of the same batch of paper used is different and the difference is large, then the hue of the printed product is of course inconsistent. Therefore, when purchasing paper, the supply department should not only consider the paper size, thickness, stretch rate and other indicators, but also include the color of the paper into the range of raw material quality inspection, so as to avoid the inconsistency of the same batch of prints due to paper.

Matters needing attention in printing

In the screen printing process, with the increase of the number of scraping and washing, the photosensitive adhesive layer of the screen gradually becomes thinner. When a certain amount of printing is reached, the printed product will be larger in effect than the new version Difference. Therefore, it is necessary to check the proofs in production and replace the screen version in time.

When printing cloth effect, the cleaning ability of the screen itself is worse than that of printed graphics. When printing real-filled graphics, the paper powder may fall off after printing a few sheets, without frequent plate washing. But when printing the cloth effect, the paper powder may still be attached to the screen after printing thousands of sheets, which has a great impact on the quality of the product. If there are more paper wool and paper powder on the surface of the paper, the operator will be tired to cope with it when printing, and will lose sight of each other. Therefore, when cutting paper, the generation of paper wool and paper powder should be avoided as much as possible. The offset printing process that matches the screen printing process should use a UV offset printing process that does not spray powder.

For cloth products printed with matte ink, hot stamping and glazing should be arranged after the offset printing process and before the screen printing process to avoid hot stamping and unequal glazing after screen printing.

The mainfrme adopts solid arm structure, able to be equiped with various types of clmap.
The multi-rotation joint makes extensive scope of workpiece-clamping possible.
It also equiped with brake device, which also can be locked up.
It is widely used in occasions which require accurate positioning,flip,and complex site environment, etc.

Pillar Type Manipulator

Pillar Type Manipulator,Paper Bag Handling Manipulator,Electric Manipulator Arm,Foundry Industry Manipulator

Shandong Sinolion Machinery Corp. Ltd , https://www.packingline.nl

Posted on