With the continuous development of the label printing industry, it has evolved from the previous common jobs to multi-color multi-color, and the self-adhesive printing machine has also turned from single-sheet paper to full-automatic web color printing. There are two processes for printing plate making in self-adhesive printing machines: flat pressing and round pressing. Flat press is used for both hard and soft substrates (polyester base) in the selection of plate materials, but for round flattening, only plates with polyester base can be used to achieve the best printing effect . The following describes the plate-making process of the resin plate.
First introduce the equipment for plate making. The resin plate making machine is composed of four systems: exposure, vacuum, plate washing and constant temperature drying. The light source of the plate-making machine is usually a side-by-side black light group, and the output power of the light source is about 360 nm. The purpose of the vacuum of the plate-making machine is to make the film closely match the plate material, and the resin plate after exposure will not be distorted. The plate-making machine washing system is composed of a stainless steel washing tank and a soft and hard brush and a motor. Bidirectional plane rotation. The drying box of the plate-making machine requires uniform heating, good circulation, and an automatic constant temperature device to avoid overheating.
1. Film production
Film production uses a camera to take pictures, or uses a computer to typeset, and uses a laser phototypesetting machine to print. Usually, a negative picture, that is, a negative picture of a positive character (negative film) is seen when the medicine film is facing upward. The density of the light-transmitting part of the film should be less than 0.05, and the density of the light-shielding part should be greater than 3. If it is lower than this standard, it will cause the exposure of ultraviolet rays to penetrate the film, so that the graphics will not be processed to the end. Do not crease the film. Color network cable jobs usually use electrical extension, or laser phototypesetting machine to release film.
2. Plate making process
(1) First cut the plate material according to the size of the film. The plate material should be larger than the film by 2-3mm. The vacuum film must be cleaned. If there is dust and stains, clean it with absolute ethanol. Remove the protective film on the plate, so that the drug film surface of the film and the drug film of the plate face each other. Open the vacuum suction to line up the air between the film and the plate. Order the required exposure time. (This time is determined by the light source intensity of the plate-making machine lamp and the size of the plate-making font. If a plate has both large and small fonts, the exposure time should be determined separately: the exposure time for large characters is short, and the exposure time for small characters and thin lines is long. The large part is covered with a mask. When covering, the vacuum pump cannot be turned off to prevent the plate from drying out.
(2) Rinse The double-sided tape is attached to the automatic washing plate with double-sided tape for two-way automatic washing, and the plate is washed to the base of the plate (clean water must be injected into the washing tank before washing to set the washing temperature)
(3) Drying Use the sponge to absorb the floating water on the surface of the plate, and put it in a drying box for drying. The temperature is generally set between 60-70 ℃. The time is 10-20 minutes.
(4) Post-exposure The plate after drying should be exposed again, so that the parts with insufficient light sensitivity and incomplete curing are completely cured in this process, so that the plate can reach the required hardness standard. [next]
Table: Common faults and treatment methods
Fault phenomenon
cause
Solution
Flush
1. The water temperature is too low
1. Raise the water temperature
2. Low film density
2. Recopy
3. Plates expire or see light
3. Replace the plate
Thin wire bending
1. Short exposure time
1. Increase exposure time
2. The water temperature is low and the rinsing time is too long
2. Straighten slightly after drying, increase the water temperature, and wash by air
3. The density of the light transmitting part is high or there is fog
3. Recopy the film
The layout is incomplete
1. Smear the film while drawing ink
1. Be careful when drawing ink, and then print after drying
2. There is stolen goods on the cover film of the plate-making machine
2. Before printing, you should check the cover film for stolen goods
Small prints, independent points fall off
1. Short exposure time
1. Increase exposure time
2. The density of the transparent part of the film is too high
2. Recopy
3. Improper drying and thermosetting treatment
3. Follow the correct method of operation
4. The plate is not well bonded
4. Replace the plate
The washed-out part can not be washed to the end, showing a patchy pattern
1. Low water temperature
1. Increase water temperature
2. The density of the light shielding part of the film is low
2. Recopy
3. Plate quality problems
3. Replace the plate
Pieces of patterns or scars appear on the base version
1. No talc powder or glycerin before exposure caused air bubbles between the film and the layout
1. Apply talcum powder before printing
2. Insufficiency
2. Absorption when re-dried
3. Scrape the film with a knife
3. Only wipe clean or trim with thinner
Stripping between the photosensitive layer of the solid plate and the substrate
1. The drying time is not enough, the high temperature heat solidifies to form bubbles
1. Heat curing after drying thoroughly
2. The plate is not well bonded
2. Replace the plate
The plate is curled severely dry and the heat curing time is too long, soak in water for 5 to 10 minutes and then dry again
The layout is brittle
1. The drying time is too long
1. Follow normal operation
2. The finished version is not dried, but exposed to the air
2. Drying
3. Excessive printing pressure
3. Reduce printing pressure
The above plate-making process is the plate-making method of the resin plate for flattening and flattening. The resin plate is made of hard-edged domestic plate material. Of course, the imported polyester version can also be made with this model. The following describes the plate-making process of the round flattened polyester plate, that is, the fully automatic label printing plate.
The difference between the process of making round flat polyester version and flat flat resin version is mainly the equipment. The roller-type rotary exposure machine for making a round flattened polyester version is based on the diameter of the roller of the automatic adhesive labeling machine. This plate-making machine rotates the drum for exposure, and the lamps are arranged in an arc shape. After the negatives are made, the cut plates are placed on a circular drum for vacuum adsorption. Exposure is carried out after the application is completed. After the exposure is completed, the subsequent plate-making process is the same as the lithographic process.
See the table above for the common faults and treatment methods in the above plate making process. Welcome colleagues to discuss with us the technical essentials of the plate making process.
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