Screen printing with moiré
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
Moiré is an optical phenomenon first discovered by French researcher Moore in the eighteenth century. From a technical point of view, a moiré fringe is a visual result of interference between two lines or two objects at a constant angle and frequency. When the human eye cannot distinguish between the two lines or two objects, it can only be seen. The pattern of interference, this optical phenomenon is the moire fringe.
Moire fringes are a potential problem for halftone screen printing. The so-called halftone printing is a method of expressing a layer by successively adjusting a document to be decomposed into dots of different sizes by photographing or other methods. The dark call prints a larger dot to express, and the bright call prints a smaller dot to express, and interference between the dots of the same color, especially the multi-color printing or the four-color printing dot, forms a moire fringe.
The moire fringes formed between the dots are a common problem for screen printing at all levels. The dot and the screen can also form another form of moiré, the distribution of such moire on the screen can produce an illegible pattern that is significantly different from the original.
Moire fringes can be produced in three ways:
1. Interference between two or more color dots;
2. Interference between various color dots and screen mesh;
3. As an additional factor, interference occurs due to the nature of the substrate itself. The purpose of using the Moiré stripe protection system is to predict moiré fringes based on the mesh size, number of screen lines, number of lines printed, and screen angle you have selected.
Second, avoid moiré
It is possible to use mathematical calculations to predict and analyze moiré fringes, and the calculation results are only theoretical moiré fringes. The actual moire fringes that affect the screen printing are visible moiré fringes that are harmful to the printing results. The Moir Stripe Protection System provides silk screen workers with a simple visual control tool that will prevent moiré from occurring at any step of the replication process.
Serilor®log contains two sets of tools for predicting moire:
1. Simulated screen mesh, which is a set of films that simulate the number of mesh meshes. The number of simulated meshes depends on the test piece you ordered—Advanced Test and Basic Test. Both sets of test pieces include four mesh numbers: code MG-S -B: 100T / cm, 110T / cm, 120T / cm, and 130T / cm, (255T / inch, 280T / inch, 305T/inch, 330T /inch). The Advanced test piece also contains a detailed series of MG-S-A: 140T / cm, 150T / cm, 165T / cm and 180T/cm (330T / inch, 380T / inch, 420T / inch, 460T / inch). For screen printing of coarse mesh or for screen printing of fabrics, there is MG-S -C: 77T /cm, 81T /cm, 85T /cm and 90T /cm; MG -S -D: 48T /cm, 54T /cm, 61T /cm and 68T/cm.
Test pieces for special purpose and high tension screens are also required to be ordered.
2. The Moiré stripe recognition/indexing instrument can overlap the film and the color separation angle by overlapping the indexing instrument with the film.
The two sets of tools can be used to analyze the mesh number/screen number/mesh angle and the Moire function. You need to install a light-stable glass table in the darkroom to provide a high-intensity, stable light source. The faint light makes it difficult to find moiré.
Moore's two sets of protective tools can help you choose the right screen, and also help you choose the color separation parameters (screening number and angle) and printing parameters - whether it is from the original to the print control, it is important Parameter control.
3. The following examples can help you understand the use of the Mohr protection tool.
(1) For the color separation film provided by the customer, to select the correct mesh mesh number, first place the mesh mesh digital simulation piece on the glass workbench, and then place the color separation film in the selected mesh number area. The color separation film must be completely aligned with the corresponding position of the analog film. When using multi-color or four-color printing, each color separation sheet should be placed on the mesh simulator for inspection.
In some special cases, the moire fringes will appear very clearly in one of the four color separations. Experience has shown that switching this color separation plate to a different mesh screen can solve these problems. The number of meshes that can be used can be selected by the Garnandstandard test piece to select the mesh that is closest but does not produce moire. Note: This is your last resort to solve this problem. In some cases, it will not work, and it will change the amount of ink deposited and cause additional trouble: drying speed, screen definition, color deviation.
(2) The number of meshes cannot be changed but the color separation film can be changed. Due to special technical factors, you may not be able to change the number of meshes (printing parameters and ink deposition amount have been set). In this case, you need to modify the color separation plate parameters. To avoid the generation of moire fringes.
Use the mesh simulation piece matched with the selected mesh mesh number, and cover the moire fringe indexing instrument on the mesh simulation film according to the screening angle of the color separation film, and measure the screening line used by your color separation film. number. When you turn the indexer, different overlays will produce moire fringes. If the moire fringes only appear in the highlight area (below the 10% dot percentage), the printed image will hardly be affected, but when the moire fringes are generated in all grayscale steps or appear at 50% of the dots, you must change the plus. Net angle. When visual moiré appears, replace with a screen line or color separation sheet until all the color separation sheets overlap the screen without moiré.
Check the scanner's recommended value before selecting the screening angle. These screening angles vary for different printing processes (offset, flexo) and are also relevant to the country. For example: the screen angle of North American offset printing and the European standard DIN16547
1 It is almost uniform, but it is divided into different color versions. As shown in the figure (figure omitted):
European flexo screen angle
North American offset printing angle
European DIN16547 standard (1)
European DIN16547 standard (2)
The illustration also shows that it is important to keep the three deepest primary colors at 30° from each other. However, the specific screening angle is not static. Many printers have worked with the color separation to improve the screening angle and use it in screen printing. The biggest help that can be obtained by using the Moiré stripe protection system is to use a visual method to determine the matching relationship between the number of meshes, the number of screen lines, and the angle of the screen.
(3) mesh number and color separation film can not be changed. In some occasions, silk screen workers can neither change the mesh number nor replace the color separation film. At this time, there are two ways to check the moire fringe, one is to change the mesh. Tension—(Adjust the number of meshes), and the other is to change the angle of the stretcher. The Mohr protection system will guide you to change the angle of the stretcher to prevent moiré. Place the indexer on the mesh simulation and turn the indexer until the moiré is generated. The angle of tilt on the indexer is the angle of the mesh that avoids the moire.
4. In other respects, there are several reasons for the occurrence of moiré, which is related to the printing process, although the Moiré stripe protection system is not designed to detect such moiré. It is also able to help you identify these moiré stripes.
(1) screen tension. If the screen tension is too low or the screen tension is unstable during the printing process, the moire fringes will be generated. You will see that the moiré will appear at a fixed position in the pattern, and dot gain and dot loss will occur. To engage in tone printing, the tension of the stretcher must be 20 Newtons/cm.
(2) scraper selection. Moiré can also be produced due to improper selection of the blade angle or hardness. Too much squeegee pressure or poor sharpness of the edge of the squeegee can cause printing distortion. To avoid these problems, it is recommended to use the following three-layer hardness composite squeegee. print.