Registration in lithographic screen printing mesh
There are many types of register screen printing in lithographic screen printing mesh, and the screen frame screens are various and can be printed on various products, and lithographic screen printing is only one of them. In flat screen printing, color registration is the most common failure. From the perspective of actual production operations, we take fabric tote printing as an example to discuss the factors affecting the registration of flat screen printing.
1. In general, the registration effect and quality of paper substrates are higher than wood, metal and woven materials. Especially for cloth printing materials, the registration accuracy is the lowest and the quality is the most difficult to control. For example, for thick cloth and other printing materials, the printing pattern of the first color background has little effect on the registration, while the post-order color needs to slightly enlarge the film surface size during plate making, otherwise there will be leakage or sleeve when overprinting. Misalignment.
2. The influence of the quality of the printing plate can be selected from the film, the sulfuric acid paper and the paper printing material, among which the quality of the film is the highest. The direction and position of the film surface during the drying process, as well as the degree of vacuuming and exposure time, will affect the quality of the printing plate. By observing, it is ensured that the film surface is firmly adhered to the exposure device. In addition, to measure the size of the base, place the film face up and center it, and expose it with a professional exposure device. It is worth noting that the film quality of the mesh version is also critical. It is best to use a professional stretcher and film to achieve the production of the screen photographic film surface.
3. Adjustment of the register device
1) When the first color is printed in the first color, the position of the printing material is ensured to be centered by measurement, and the reference surface is fixed by the wood grain tape. When fixing the screen of the first color, pay attention to the flat mouth of the clamping device and ensure that the holder is not swayed. Of course, the proof sheet should also be used to check whether the position of the screen plate corresponds to the position of the substrate, and whether the bite is flush and further debugged. The printing position of the first color is particularly critical. It determines the quality of the entire registration. Generally, small and thin graphics are printed first as the first color. In order to ensure the quality of the first color during printing, the printing material can be placed on several printing platforms at the same time to improve the efficiency and quality of the flat mouth. For the printing of the first color graphic, it is necessary to consider the size of the printing material as much as possible, and fill the corners with graphics for later encapsulation.
2) The principle of flat multi-color screen printing is monochrome overprinting. Therefore, in the plate making process, the registration crosshair should be dried to a reasonable position, and the overprinting should be carried out according to the registration cross line. When overprinting, the position of the substrate is not adjusted, just the position of the plate and screen.
4. The fixing of the substrate is achieved by spraying a professional adhesive on the printing flat, mainly to prevent the substrate from being peeled off from the printing platform due to the excessive adhesion of the ink. Pay attention to the size and even distribution of the amount of glue. At the time of printing, the adhesive and residual ink on the printing platform should be cleaned for reuse.
5. Effect of drying: The drying method can be either a box or a separate drying device, which can be determined according to the quantity and quality requirements of the product. For products that are not very demanding, do not use oven drying, use a small electric dryer. It is worth noting that too long drying time will cause the product to wrinkle, and the time is too short to deink and dirty when overprinting.
This is what we found in the actual production of long-term flat screens. In addition to the above factors, the operator's production experience and operational skills are also important reasons for the impact of registration.
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