Take-out meals: screen printing such as the manufacture of cosmetic packaging materials are very common graphic printing processes, through the combination of printing ink, screen printing screen, screen printing equipment, run the ink through the graphic on the mesh part to the substrates, in the process, the screen printing color change will be influenced by some factors, this document shares several factors affecting the printing color change, content for reference among friends:
The screen printing process is the ink through part of the screen after leaking onto the substrate, the rest of the screen is blocked, the ink can not pass through. The printing ink poured on the screen, without any external force under the action of the ink, will not leak through the screen to the substrate, and when the scraper with a certain pressure and inclination of the corner scraping ink, it will be transferred to the next substrate through the screen to achieve image reproduction.
01 Ink Mfixing
Assuming the pigment in the ink is properly deployed, the usual reason for the color change is the addition of the solvent. In a well-controlled shop, the ink should be available for the press when it is ready, ie the printer should not mix the ink. In many companies, the ink is not matched to the press, but left to the printer, who adds and mixes the ink as he sees fit. In this way, the balance of pigments in the ink is broken. For ordinary water-based ink or UV ink, water in ink the same as solvent in solvent ink, adding water will make the ink film dry thin and will affect the ink color, then reduce the color density. The causes of these problems can be traced further.
In the ink warehouse, ink matching workers do not use weighing devices, rely solely on their own judgment to add the correct amount of solvent, or at the beginning of mixing is not appropriate, or in printing the amount of mixing ink, so that the mixed ink will produce different colors. When the live part is printed again later, the situation worsens and it is almost impossible to reproduce a color unless adequate ink rates are recorded.
02 Screen selection
Wire mesh diameter and weaving mode, whether plain or twill, the thickness of the printing ink film has a great impact. Screen suppliers will provide detailed technical information about the screen, one of the largest theoretical ink volumes, it represents the amount of ink passing through the mesh under certain printing conditions, usually expressed in CM3/ m2. For example, a 150 mesh/cm sieve with a mesh diameter of 31μm will pass through 11cm3/m2 of ink. A sieve diameter of 34 μm, 150 mesh, per square meter will pass through 6 cm3 of ink, which is equivalent to a layer of wet ink 11 and 6 μm thick. It can be seen that 150 mesh this simple representation, will make you get a significantly different ink layer thickness, the result will cause a big color difference.
With the improvement of screen weaving technology, to get a number of twill screens rather than single screens, although it is sometimes possible, but the possibility is very small. Sometimes screen suppliers stock old twill screens, generally speaking, the theoretical ink volume of these screens changes 10%. If you use twill woven screen printing of a fine image level, the fine line breakage phenomenon is more than the use of ordinary screen.
03 Screen Vversion of Jtension
The lower screen tension will cause the screen to slowly separate from the printed surface, which will affect the ink remaining on the screen and the uneven color effect, so that the color seems to change. To solve this problem, it is necessary to increase the screen distance, that is, to increase the distance between the horizontal screen plate and the printing material. Increasing net distance means increasing scraper pressure, which will affect the amount of ink through the screen, causing further color changes.
04 Setting Scrape
The softer the scraper used, the more ink will pass through the screen. The higher the pressure on the scraper, when printing, the wear of the scraper blade will be faster, which will change the contact point of the scraper and the printing, which will also change the amount of ink across the screen, causing color changes. Changing the scraping angle of the ink will also affect the amount of ink adhesion. If the scraper spins too fast, it will reduce the thickness of the attached ink layer.
05 Blet’s go back to Ink KWell Ssetting
The function of the ink knife is to fill the screen hole with a stable amount of ink. Adjusting the pressure, angle and sharpness of the ink knife will make the hole sharp too much or too little ink. The back ink knife pressure is too much, will force the ink through the mesh, resulting in excessive ink fixing. The pressure of the inking knife is not enough, it will lead to ink partially filled with ink, which will lead to insufficient fixing of the ink. The running speed of the ink knife is also very important. If it flows too slowly, the ink will overflow. If run too quickly, it will cause severe ink starvation, similar to the effect of changing the wiper speed.
06 Device Ssetting
Careful process control is the most critical factor. Stable and consistent machine setting means stable and consistent color. If the machine setting is variable, the color may get out of control. This issue usually occurs when the printer changes shifts, or later when the printer changes press settings to suit their own habits, which can cause color shifts. The latest multi-color screen printing presses eliminate this possibility with automatic computer control. These stable and consistent adjustments should be made to the press and should be maintained throughout the printing operation.
07 Printing Mmaterials
An often overlooked aspect of the screen printing industry is the consistency of the substrate material to be printed. The paper, cardboard and plastic used in printing are usually produced in batches. A high quality supplier can guarantee good surface smoothness for the entire batch of materials supplied, but this is not always the case, and any small change in the process can alter the color and surface finish of these materials. Once this happens, the color of the print appears to change, even though nothing is actually changed during the printing process.
Such are the practical difficulties faced by printers when displaying a single image on a variety of media, from corrugated plastic to art board. Another problem we often encounter is that our screen printing catches up with offset printing pictures, if we don’t pay attention to process control, we have no chance. Careful process control involves precise color determination, line color determination with a spectrophotometer, and primary color determination with a densitometer, so users can print images with stable and consistent colors on a variety of media. materials.
08 Llight Ssource
that the pigment used to mix the inks is exactly the same color throughout the printing operation. It could be a disaster if you switch providers. Color determination and perception is a very complex area, and for better control there needs to be a closed loop of ink maker, dispensing, proofing and accurate determination during the printing process. impression.
Sometimes the color changes due to wrong dryer setting. Printing paper or cardboard, if the drying temperature is too high, the general situation is yellow white. The glass and ceramics industry is most troubled by color changes during drying or firing. The pigments used here change from printed to sintered. The color of these frits is affected not only by the firing temperature, but also by oxidation or reduced air quality in the firing zone.
Original source: https://www.fzhgp.com/news/color-changes-of-screen-printing-are-these-factors-paid-attention-to/
Company Name: Fuzhou Huaguang Color Printing Co.,Ltd.
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