How to make screen printing?
1, the choice of screen printing mesh
At present, there are many types of wire mesh on the market, such as silk screen, nylon mesh, polyester mesh, wire mesh, etc., generally considering cost and applicability.
Introduction of nylon mesh features
Nylon mesh has a smooth surface, good ink permeability, good flexibility, high elasticity, strong adaptability, good tensile strength, elasticity and abrasion resistance, high knot fastness, long service life, acid resistance, chemical resistance and organic The solvent has many excellent properties, so it is favored by fine printing, and is widely used in fine line drawing and dot printing.
Precautions for use:
In addition to the above advantages, nylon mesh has some disadvantages, such as high elongation and low heat resistance. Therefore, the following points should be noted when making nylon mesh:
·Because of the high elongation of nylon mesh, it is required to use strong frame and stretcher during printing;
·The disadvantage of low heat resistance of nylon mesh, so do not use hot melt method to fix the screen during printing;
• UV light can also have some effect on nylon mesh, so care should be taken to avoid light when storing nylon mesh or its corresponding screen.
2, the choice of the frame
According to the material, the frame generally has six kinds of wooden frame, aluminum frame, iron frame, plastic frame, stainless steel frame and copper frame. Commonly used are wooden frame, aluminum frame and iron frame.
· Wooden frame: the price is relatively cheap, easy to manufacture, can be stretched by hand and mechanically stretched, but the disadvantage is that it is strong and low, easy to deform, only suitable for printing of low precision products, not suitable for fast high precision network Printing, in addition to the wooden frame pulled out of the NetEase slack, poor recovery.
· Iron frame: Compared with the wooden frame, it has the characteristics of stable size and durability. However, its weight is easy to rust, it is inconvenient to use, and only mechanical stretching can be used.
·Aluminum frame: Although it is only suitable for mechanical stretching, it has the characteristics of small deformation, light weight, rust, and easy movement. Therefore, aluminum frame is the most used frame in printing plate making.
Second, pull the net
In general plate making, the method of pulling the net can be divided into manual, mechanical and pneumatic pulling nets. For example, the silk screen processing factory does not require high precision. Generally, the first two methods can be adopted; if the requirements are higher, the last one can be used. A pneumatic pulling machine, the pneumatic pulling machine is suitable for high-precision screen printing. The utility model has the advantages of uniform pulling force, convenient use, and the tension of the drawing net which can meet different demands, and is particularly suitable for drawing a screen printing of high-precision printing.
Third, wash the net
Printing and plate making generally use special chemicals for washing nets (such as water, thinner, detergent, etc.), but this method consumes time, so for those processing plants that are time-sensitive, this method is slightly Trouble, here is an effective way to share with you: use detergents with strong detergency, such as Tide, wet the mesh, and then use cotton to polish. This method removes the dirt and is also beneficial to the adhesion of the photoresist. Attached, can be described as a sword and double carving. (Note: For the above method, double-sided punching is required during sanding. When grinding the front face, the force should be lighter to avoid the mesh from falling off.) After the washing is completed, the net is placed in the dryer for drying.
Fourth, coating
1, photosensitive material selection
At present, there are two kinds of photosensitive materials used in the market, one is photosensitive adhesive, and the advantage is that the process is simple, economical, practical, and the exposure speed is fast, the screen is durable, the film is easy to remove, and the solvent resistance is excellent. The other is photographic film, which is a pre-sensitized photosensitive material that is attached to the screen before exposure to the screen. It has hydrophilicity, strong resolution, sharp lines, strong durability and excellent performance. In the photosensitive adhesive, it is commonly known as "water film" because of its hydrophilicity.
Generally speaking, the requirement for printing on photosensitive materials is that the printing film formed by the photosensitive material should be suitable for the performance requirements of different kinds of inks, and has a considerable printing durability, can withstand the considerable number of scraping of the squeegee, and the screen The bonding force is good, no filming failure occurs during printing, and it is easy to peel off, which is beneficial to the recycling of the screen plate material.
2, coating
Required items: photosensitive glue, sizing machine (scraper), rack net.
The photosensitive paste on the market needs to be called by itself. The photosensitive powder can be conditioned with hot water, then poured into the photosensitive syrup and thoroughly mixed. It can be used after a few hours. The small factory can be sizing by the plate making workers, while the large factory has an automatic sizing machine with a very uniform thickness.
· Place the dry and ready-to-use net on the coating table, place the screen plate smoothly, and pour the photosensitive glue into the bucket. (Note: appropriate amount)
· Use the scraper to evenly apply the photoresist on the screen, first apply the printing surface (convex surface of the screen), then apply the ink surface (concave surface of the screen), usually three times per side.
• The net is then dried and this process is the first time. (Note: line, character screen printing needs to be double coated)
·If a thick screen is required, it can be applied in multiple times, that is, after the first application, it is immediately put into an oven at 30-40 ° C for drying, and the screen is taken out again, and the coating is determined according to the required thickness. The number of glues, note that the general printing surface (convex surface) is 2-3 times more than the ink surface (concave surface), this operation is the second coating. (Note: This coating is only carried out on the contact surface of the screen)
· Dry with a hair dryer or oven, do not have a dry or dry phenomenon, so as not to affect the quality of the plate. (Note: peeling off the photoresist)
Note: The gluing process is very important. The quality of the screen is good or bad. It depends on the glue, and the thickness of the plate is required to be uniform and uniform.
3, dry
After the silk screen photosensitive adhesive is applied, let it stand for 1-2 minutes, then put the wire mesh into an oven at about 40 ° C for drying, then take it out and put it in a dark frame for use.
Note: The screen must be dried, otherwise it will affect the robustness of the screen.
Five, exposure
The film film of the film is attached to the printing surface (convex surface) of the screen, and then exposed in a vacuum exposure machine. The exposure time depends on the thickness of the photoresist and the energy of the exposure lamp and the requirements of the screen (the general line, solder resist, characters, and screen time required for the screen). Generally, the exposure ruler is used to determine the exposure time. Exposure time, and then fix the exposure time of the screen.
step:
· First, the film will use the magnifying glass to match the latitude and longitude of the screen, and the line should be parallel to the wire. (Note: especially lines, characters)
· Put the good position of the net into the exposure machine, adjust the time, and after vacuuming, turn on the exposure machine switch.
Note: If the exposure time is too short, it will cause the photosensitive adhesive to fall off easily, the line becomes thicker, the solder resist is not strong, and the character number is not strong. When the exposure time is long, it will cause quality defects such as incomplete development or thinning of the line. happened. Therefore, it is especially recommended that the accurate exposure time comes from scientific practice. Before exposure, the exposure time must be measured by the exposure slide rule, and then the exposure time should be fixed. Do not do things by experience and work blindly.
Development
Remove the screen from the exposure machine, remove the negative film, first moisten the two sides of the screen with gentle, non-pressure cold water (warm cold water 20-30 ° C), wet for about 30-60 seconds, then rinse thoroughly with a high-pressure water gun until the image is displayed. Then use an absorbent cloth to blot excess water around, then place the wire into an oven at 30-40 ° C to dry.
step:
· Let the exposed screen water wet on both sides, about 1 minute, and flush the net with high pressure water until it is completely clear;
· Check under the light to see if it is completely clear, whether the plate making is successful, and if it is not good, redo;
· After drying the wet net, place it under the light box and repair the defects such as trachoma and burrs with the sealant.
Seven, check and use
After the screen is dried, check whether the prepared screen is in compliance with the production and processing requirements. If the standard is reached, immediately seal the net to make the production staff ready for use; if it is not suitable, repair or re-manufacture immediately.
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