Key points of acrylic bottle combined with silk screen printing process

In the article “Acrylic Bottle Basic Knowledge”, the characteristics and applications of acrylic materials have been introduced in detail. This article is a more in-depth study of acrylic bottles combined with screen printing technology. If acrylic bottles are limited to printing simple lines and text, they cannot meet people’s increasingly demanding requirements for craft products. Today, screen printing of acrylic bottles has begun to dabble in the field of color, and color printing of plexiglass craft products has also become common. The main difference between color printing and general line text printing lies in the dots, which is no different from other printing processes. The evaluation standard is also whether the original manuscript can be truly restored. Screen printing is one of the commonly used processes for acrylic bottle finished products. Therefore, the cost-effectiveness and process characteristics can have a mutually reinforcing effect with acrylic products.

1. Sample analysis

Customers often provide plexiglass samples for plexiglass processors to design solutions. He simply explains his intentions to you, and most of the tasks are completed by you. It is important to understand his intentions. Many disputes are caused by the fact that you do not really understand his true thoughts. You also need to figure out the type of plexiglass sample material and determine the printing process. Sometimes customers know the material type, but most of the time they don’t. You can identify it based on your own judgment. The material type also determines the choice of printing parameters, such as the number of screen lines, screen mesh, pre-press processing, scraper hardness, etc.

2. Choose an ink decolorization tester

Choosing an ink decolorization tester is both difficult and simple. You may be proficient in the adaptability of printing materials and know what kind of resin is good for the adaptability of printing materials. However, the division of labor in society does not care how much you know. You often just need to choose according to the information provided by the manufacturer at hand. You just need to verify the authenticity of the information. It may be suitable in most occasions, but there are exceptions in some special cases. You might as well prepare several more for testing.

The right choice first has a simple understanding in theory. The key is to test according to the existing varieties. There are mainly the following brands of silk screen printing. COA TES is a famous brand produced by Coats Brothers in the UK. It has established the authoritative position of solvent-based in long-term production practice. As an environmentally friendly product, you must be familiar with the product “Dolby UV” of Dolby Company in France. Although Duby is not big, it is the leader in UV. From the initial screen printing and pad printing to UV credit cards and offset printing, Duby has performed well. Apollo is famous for its bright colors. It has won wide acclaim in terms of current varieties and adaptability. If you want to print on metal products and organic glass products, you should choose Apollo first. German quality has always been the best in the world. The leading level of printing technology has created excellent system quality, which of course includes resins and pigments. To this day, Germany still holds the world record for fineness and adhesion. In the field of special printing, you can’t ignore Marabu of Malay Bao Company. “Supreme” is a special product launched by Henghui Industrial Co., Ltd. to develop the mid-range market. We advocate quality, but pay more attention to the effect. Plastic printed products printed with it even make you doubt that it is printed with European ones.

3. Consider the curing process

The vast majority of plastic printing materials are volatile drying type. After the solvent contained in the solvent type evaporates, it is fixed on the printing material. However, some printing requires a drying device to dry before it can be dried, especially for metal, ceramic, and plexiglass printing, which generally requires a drying device. It is very important to configure what kind of drying device. When using UV printing, you must consider the curing device and equipment. UV does not contain solvents and can only be cured under ultraviolet light. Both the drying device and the UV curing machine can dry quickly. If the degree of curing is too low, the ink layer will show poor adhesion and poor gloss; if the curing is excessive, the film layer will be brittle and easily cracked and deformed.

4. About the printing color sequence

Color prints are reproduced by superimposing four primary colors to reproduce the rich colors and layered information of the original. Theoretically, complete transparency can ensure the true restoration of color, but it is composed of resin binders and pigments. The resin cannot be completely transparent, and the pigment itself has a certain covering power. These factors ultimately affect the color.

The color stacking sequence is related to the transparency. The low transparency has strong hiding power and should be printed first. Initially, yellow had the worst transparency, so it should be printed first. Now the situation has changed, and it doesn’t matter whether the yellow ink is printed first or later. Theoretically, except for the difference in hue, the other indicators of the four primary colors should be as close as possible. However, the fact is another situation. The saturation of cyan has a great influence on the color of printing. The high saturation of cyan makes the printed product tend to be cold, so when the saturation of cyan is high, cyan can be placed in the color sequence slightly earlier. The role of black is to increase the outline of the printed product. If the image and text have high requirements for contrast, then print black last. The density of black also has an impact on the printed product. Too high density will cover some layers, so black with higher density can be printed in the first color sequence, and black ink with lower density can be printed last.

5. Determine the number of screen lines

The higher the number of screen lines, the richer the layers can be reproduced, but too high a number of screen lines will bring difficulties to screen printing. To determine the screen count, we must first consider the visual environment, that is, from what distance the image is observed. The visual distance should be the most basic standard for determining the screen count. The closer the visual distance, the higher the screen count can be, which can improve the clarity. The farther the visual distance, the lower the screen count should be, which can reduce the difficulty of printing. Sometimes customers do not understand the characteristics of screen printing and blindly require unnecessary screen counts. You should persuade them to change their minds. The range of screen printing reproduction is usually below 80 meshes. Printing with too high a screen count will cause dot loss in the highlight area and details cannot be reproduced. In addition, too high a screen count will also bring difficulties to the selection of screens. According to the usual selection method, the screen count should be 4 times the screen count of the plate film. Too high a screen count will cause the ink layer to be too thin, and the contrast of the image will be reduced, which will also affect the expressiveness of the image.

As the number of lines increases, the dot size continues to decrease until the dot cannot be printed. Unlike offset printing, which can copy 3% to 98% of dots, screen printing can only copy 15% to 85% of dots strictly speaking. Dots above 15% will be lost, and dots below 85% will be enlarged to become solid. For originals with very fine layers, they need to be corrected and compressed after scanning into the computer to be restored. The highlights and dark dots of the compressed image are easy to reproduce at a given line number. Of course, excessive compression of the tonal range will cause some loss of image details.

6. Determine the output resolution of the film

If the output resolution (dpi) is set too low, the film will have jagged edges. If the resolution is too high (the number of lines remains unchanged), the layers of the exposure film will certainly be richer, but the number of gray levels will increase exponentially, and the copying ability of screen printing is limited, which even makes screen printing impossible. Practice has proved that it is difficult for screen printing to copy prints with more than 100 lines. Of course, the development of technology is driving the progress of screen printing, and such a conclusion is not absolute.

7. Selecting a screen

The screen should have a consistent number of threads and balanced tension in the warp and weft directions, otherwise it will cause moire and misregistration. Screen parameter indicators should include screen diameter, screen mesh, tension curve and screen thickness.

(1) For rough graphic printing, choose a low-mesh screen, and for fine graphics and layered printing, choose a high-mesh screen;

(2) The selection of screen mesh should match the screen line count of the exposure soft plate, generally 4 times the screen line count of the exposure soft plate as the screen mesh;

(3) For UV, considering the curing effect, the screen mesh should not be too low.

(4) For fine graphics and layered printing, dyed screens are preferred, and the resolution of dyed screens is much higher than that of white screens.

(5) Selecting a screen calculator can help you obtain data support and determine the relationship between static screen mesh and dynamic screen mesh.

8. Set the stroke of the printing machine

First install the substrate, then hold the scraper with your hand and move it on the surface of the substrate. When the position is suitable, fix the block. For curved screen printing machines, the stroke of adjusting the screen movement should exceed the circumference of the plastic bottle. Appropriate stroke can save time, increase printing speed, reduce the discontinuity of ink supply, and print good dots.

9. Choose a scraper

Generally, the length of the scraper is about 5~10mm longer than the length of the image. The selection of the scraper involves hardness and shape. A scraper with higher hardness can perform very fine graphics and layered printing; a softer scraper is suitable for substrates with very rough printing surfaces, and the printing ink layer is also relatively thick. A pointed scraper is often used for curved printing, and a scraper with a rectangular cross-section is often used for flat printing.

10. Select the screen frame

The screen frame material should preferably be aluminum products, which are relatively light and have high strength. They are suitable for printing layered images, especially for four-color printing. A screen frame with good rigidity must be selected. Many screen frames used in the special printing industry are non-standard parts. This is because the substrates of special printing have various shapes. It is very important that many special screen frames can complete the screen printing task without being restricted by the screen printing machine. An important aspect of selecting the screen frame is to be able to maintain tension balance in the printed image area.

Screen frame manufacturing is also an aspect to consider. The screen frame should be as hard as possible and have good bending and twisting resistance.

11. Determine the screen spacing

The screen spacing is the distance between the screen and the surface of the substrate. Setting the screen spacing too large or too small will change the size and accuracy of the image.

Regardless of the tension, a high screen spacing will cause the image to expand. Under high tension, the separation speed of the screen and the substrate is faster than the running speed of the scraper, which will cause the scraper to deform. A high screen spacing is also very damaging to the screen. The sticky screen slurry is not perfect, and it may also fall off due to excessive tension.

Too low a screen spacing will cause the screen and the substrate to be difficult to separate. The separation speed of the screen and the substrate is slower than the speed of the scraper, which will leave screen marks and cause smudges. The correct screen spacing should ensure the rapid separation of the screen and the substrate. The selection of screen spacing is related to the screen tension. A high-tension screen can choose a lower screen spacing, and a low-tension screen should choose a higher screen spacing. Generally, this data is between 2 and 3mm.

12. Printing

Color screen printing must first pay attention to the overprint problem. Only accurate overprinting can obtain good prints. To achieve accurate overprinting, the tension of the screen should be basically consistent, and the error should be less than 1N/cm. The tension of each plate should be measured with a screen tension meter and should be maintained at 18N/cm. The uniformity of the positioning device is very important. Each substrate must have the same position when entering the printing, otherwise it will cause inaccurate overprinting. Four-color printing is four primary colors. Choosing one that meets international standards can avoid the problem of color misalignment.

Establishing testing standards for color products is conducive to implementing institutionalized management and avoiding disputes between manufacturers and customers. It should be said that very little work has been done in this area in the special printing industry. I believe that this situation will change one day.