Introduction: Screen printing process is very common in the manufacture of cosmetic packaging materials. The process of screen printing is relatively simple. However, there are many changing factors affecting product quality in the entire screen printing process. This article shares the precautions when printing on the screen printing machine. , The content is for your reference:
Silk screen process
In the screen printing process, the ink passes through part of the mesh of the screen and then leaks onto the substrate. The rest of the screen is blocked and the ink cannot penetrate. When printing, the ink is poured on the screen. Without external force, the ink will not leak through the mesh to the substrate. When the squeegee scrapes the ink with a certain pressure and tilt angle, it will transfer through the screen. To the following substrate to realize the copy of the image.
Precautions for stretched nets
1) Related parameters
In the screen printing machine, the mesh number of the screen, the diameter of the screen, the spinning method of the screen and the selected material directly affect the tension of the stretched screen. When the screen is stretched, the tension of the screen is measured according to these parameters. When measuring tension, the detected tension point should be 10 cm away from the inner edge of the screen frame, otherwise the measured tension will be inaccurate.
2) Tension value
The maximum tension value referred to by the tension is the display of the specific wire mesh strength, that is, the maximum tensile value that can be withstood and rebounded by various meshes and different wire diameters. If it exceeds the given tension value, the mesh will lose its elasticity. It becomes plastic deformation, which should be paid attention to in the stretched net.
3) Tension in warp and weft
The unit of tension: Newton/cm (N/CM), which can be measured with a Newton tensiometer. The tension meter can measure the tension in the warp and weft directions. The so-called warp tension of the screen is the tension in the winding direction of the entire roll of screen, that is, the tension in the edge typing direction; the weft tension of the screen is the tension in the width direction of the screen.
4) Wire mesh material and diameter
Different wire diameters and different meshes made of the same material have different tensions, that is, the same meshes, and their tensions are different, that is, the same meshes, mesh diameters Different, the tension is different, because the tensile strength is proportional to the diameter of the mesh.
Matters needing attention when color mixing
1) Adopt the principle of “from lighter to darker”, regardless of the preparation of light or bright colored inks, when the hue is close to the model, be careful. It is best not to mix inks produced by different manufacturers. Try to use inks of different colors from the same manufacturer for color mixing. Otherwise, uneven tones will occur. In severe cases, agglomeration will occur and the ink will be scrapped.
2) When mixing inks, you should add as few different colors of ink as possible. Generally speaking, the fewer types of color inks you use, the better the mixing effect will be.
3) Some screen printing inks are dried by drying. The light color is lighter after drying than the undried one, and the dark color is darker after drying. In addition, it is easy to overlook whether there is a difference in the color tone of the ink before and after drying during printing. Generally speaking, through natural drying (solvent volatile ink), the substrate is plastic, metal, paper, glass, etc., and the color will not change; but if it is a ceramic color material, the color will only develop after burning and oxidation. , Can only be graded based on experience. For screen printing inks that are dried by thermosetting and light curing, the color changes in depth. When the amount of ink adjustment is large, an ink adjustment machine can be used, and the color adjustment can be completed in a short time.
Technical characteristics of silk screen
1) Screen printing can use many types of inks. Namely: oily, water-based, synthetic resin emulsion, powder and other types of inks.
2) The layout is soft. The screen printing layout is soft and has certain flexibility not only for printing on soft objects such as paper and cloth, but also for printing on hard objects, such as plastic, glass, ceramics, etc.
3) Screen printing has a small impression force. Because the pressure used in printing is small, it is also suitable for printing on fragile objects.
4) Thick ink layer and strong covering power.
5) It is not limited by the surface shape of the substrate and the size of the area. It can be seen from the foregoing that screen printing can not only print on flat surfaces, but also on curved or spherical surfaces; it is not only suitable for printing on small objects, but also suitable for printing on larger objects. It has great flexibility and wide range. Applicability.
Printing elements of screen printing machine
1) Silk screen printing plate
Three methods can be used to prepare the screen printing machine: direct coating method, direct film pasting method, and indirect film pasting method. According to the type of substrate, the screen tension, the number of screen meshes, the thickness of the plate film, the size of the screen frame and other important parameters should be fully considered in the plate making process. Choose water-based or oil-sensitive varnish based on the type of ink.
2) Screen printing ink
The screen printing machine can use solvent-based screen printing inks, UV screen printing inks and various functional pastes. The screen printing inks should be selected and tested according to the material of the substrate.
3) Screen printing squeegee
The screen printing squeegee is the pressure source of the screen printing machine, which plays the role of transferring and pressure leaking ink. Flat substrates usually choose a squeegee with a rectangular cross-section, curved substrates usually choose a squeegee with a triangular cross-section, and special squeegees for CD discs. Choose a softer squeegee for rough surfaces, and a harder one for smooth surfaces. Squeegee.
It is necessary to make a fixture with good stability and good identity to ensure the accuracy of overprinting and the consistency of position. The tangent plane of the highest point of the planar fixture is parallel to the screen plane, while the curved fixture requires that the diameter of the indexing circle of the transmission gear at the shaft end is equal to the diameter of the circular surface of the substrate.