Cleaning during offset printing
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Offset cleaning operation and precautions
Printing plate, blanket, water roller, ink roller and other cleaning work is one of the main contents of the daily operation of offset printing. Proper and timely cleaning operation can not only improve the printing durability of the printing plate and the life of the blanket, but also It is of great significance to ensure the quality of printed matter, compress the auxiliary production time, and make the production go smoothly.
PS version cleaning and protection
First, the purpose of cleaning the plate
Cleaning a plate means applying or scrubbing the surface with water, glue, dampening solution, and gasoline. Its main purpose is to:
1. Protect the plates. When the machine is stopped during printing, the water or glue is coated on the plate to form a water film or film, so that the non-image part of the plate is isolated from the oxygen in the air to prevent the plate from getting dirty. In addition, a plate that has just been dried or a plate that has not been used for a long time can be protected by applying a glue.
2. The layout is dirty. When the oil is dirty in the non-image part of the printing plate, it can be removed with glue, dampening solution, dampening solution, decontamination agent, cleaning solution, gasoline and other materials.
3. Improve the clarity of the graphic. When the layout of the layout is light or enlarged, it can be rubbed with gasoline, dampening solution, glue and other materials to improve the clarity of the graphic.
Second, preparation work
Before the cleaning work begins, various cleaning materials must be prepared to improve the cleaning quality and efficiency.
1. Water. It is mainly used for wetting the surface or cleaning the surface film or cleaning the paper wool, paper powder and other debris. In order to ensure the quality of wetting and cleaning, the water stored in the bucket should be kept as clean as possible without oil, and water should be changed in time.
2. Glue. Also known as hydrocolloid, it is mainly used to coat the surface, to remove dirt or to add to the fountain solution, to protect the printing plate and enhance the hydrophilic properties of the non-image part of the printing plate and improve the clarity of the graphic.
3. Dampening solution. Also known as water bucket solution, it is mainly used to wet the layout or remove the oil from the non-image part of the printing plate, which plays a role of stabilizing and enhancing the hydrophilicity of the non-image part and maintaining the balance of ink and water. The undiluted dampening solution becomes a dampening solution, which can effectively remove the dirty surface.
4. PS version cleaner. It is widely used in many printing houses to effectively remove dirt from the layout and enhance the hydrophilic properties of the blank portion of the plate. The disadvantage is that the cost is too high.
Third, the operation method and steps
1. Select the cleaning wipe.
Wipes are the main tool for cleaning plates. They must be kept as clean as possible and must not contain hard materials such as sand. There are three kinds of cleaning cloths, such as water wipes, rubber wipes and gasoline wipes. You must pay attention to the following four points when choosing a wipe:
1) Water wipes and wipes must be made of soft, hygroscopic cotton gauze, but not with packaging cloth or yarn ends. The water wipes and the wipes can be used together or separately, but must be rinsed in clean water before use.
2) Gasoline wipes can be made of ordinary cotton (such as packaging cloth), but not chemical fiber fabric or yarn ends.
3) Water and rubber wipes must be strictly separated from gasoline wipes.
4) The size of the cleaning wipe should be appropriate. Too large or too small is not conducive to operation. In general, the sum of the length and the width is about 80 mm, and the thin cotton gauze can be slightly larger. Of course, we must also consider the operator himself.
2. Wiping the surface of the plate
1) After the water cloth is repeatedly rinsed in the water, it is taken out, and the cloth is gently rubbed with one hand and the waterless beads are dropped to determine the water content of the cloth. In addition, the downtime is short, the water content of the cloth can be less; on the contrary, it can be more.
2) The wiping method is to hold the four sides and four corners in the palm of your hand and close the palm of your hand (to prevent the corners of the cloth from scratching the plate or getting caught in the machine).
3) Jog the machine or make the machine run at a low speed. Take the “8” shape on the layout and wipe the water on the plate (this will ensure even and rapid application of water to the plate).
3. Plate surface adhesive
1) The tape is repeatedly rinsed in water and then unscrewed, and the cloth is pressed with one hand and the waterless beads are dropped to determine the water content of the cloth.
2) The grip of the tape is the same as the grip of the water cloth.
3) According to the area of the printing plate, take a proper amount of glue, so that the glue can not be dripped naturally.
4) The rubbing route is the same as the wiping route. The rubbing glue is generally rubbed 2-3 times to achieve the requirements of flat, thin, uniform and complete adhesive layer.
4. Clean the layout with petrol
The original ink film of the graphic part is washed off with gasoline, and then replaced with new ink to ensure product quality. The operation process is as follows: firstly wash the layout with a water cloth (if the new printing plate should completely wash off the film), then wash the ink of the layout image with a gasoline cloth, and then thoroughly clean the layout 1 to 2 times with a water cloth. The specific operation method of cleaning the layout with gasoline is basically the same as the operation method of wiping the water. (If conditions permit, use a cleaning solution instead of gasoline to clean the layout, but be careful when cleaning the layout, the cloth should be wiped clean with a cloth to avoid missing the plate).
Easy to produce problems and precautions
1. Wash the plate with water or glue (commonly known as wiping or rubbing) to protect the plate. Which method is chosen to protect the plate depends on the length of downtime. Always wipe the glue when the downtime is long.
2. If there is a certain amount of oil on the water wipe, it will make the non-image part of the plate dirty after wiping the water. Therefore, the water should be rinsed in the water before cleaning, and the water in the barrel should be replaced frequently.
3. When wiping the water, the moisture of the layout should be moderate and uniform, and there should be no omissions, otherwise it may cause distressed ink or dirty plates.
4. When rubbing the glue, the film should be as thin, uniform and complete as possible. After a long time stop, apply a dry cloth to wipe the film after rubbing the glue. The film is too thick, which may cause the ink absorption of the dirty plate or graphic to be reduced.
5. When rubbing the glue, avoid dropping the glue onto the blanket; at the same time, the wipe should not touch the ink roller and the roller.
6. When the machine is stopped for a long time, the water roller should not touch the plate to prevent the plate from getting dirty.
7. When cleaning the plate with gasoline, pay attention to the operation sequence; when rubbing the gasoline, the action should be quick; when the cleaning is completed, you should pay attention to the ink and water immediately.
8. After scrubbing the plate with a cleaning solution, be sure to clean the cleaning solution on the plate with a cloth with water to avoid ablation of the plate.
Blanket cleaning
Commonly used materials for cleaning blankets include water, gasoline, kerosene, pumice powder, sulfur powder, talc powder, blanket cleaning agent, blanket reducing agent, and the like.
First, the cleaning of the new blanket
1. The surface of the new blanket has a protective film. Therefore, the protective film must be removed before using the new blanket, otherwise the ink absorption of the blanket will be affected.
2. Pour a proper amount of kerosene onto the blanket or pour the kerosene onto the wipe.
3. Sprinkle pumice powder on the blanket or use kerosene to remove the pumice powder.
4. Repeatly wipe the blanket repeatedly.
5. Pour the petrol and clean the pumice powder with a petrol wipe.
6. Wipe the blanket with a dry cloth.
7. Wrap the talcum powder with 2-3 cotton gauze and spread the talcum powder evenly on the surface of the blanket.
Second, the daily cleaning of the blanket
In the daily printing process, the blanket is continuously in contact with the ink and the paper, and the ink on the printing plate is transferred to the paper, so that certain ink, paper wool and paper powder are inevitably adhered to the blanket (paper) In the filler) and other substances. This sticking phenomenon is more serious when the blanket is sticky, printed on poor paper, or the ink used is thicker, larger than the viscosity and too low in viscosity. Therefore, in the printing process, the rubber should be regarded as the rubber. The accumulation of cloth surface and different work requirements. Regular cleaning of the blanket ensures and enhances the clarity of the graphic and extends the life of the blanket.
1. Prepare the materials used for cleaning and prepare a piece of water wipe, gasoline wipe, and clean dry cloth.
2. The grip of the wipe is the same as the grip when wiping the water.
3. Jog the machine or make the machine run at a low speed, starting from the mouth of the blanket and wiping a bit of water.
4. Jog the machine from the blanket to the mouth or when the machine is running to the mouth, scrub the blanket with gasoline to dissolve the ink on the blanket.
5. When jogging the machine or when the machine is running again to the crevice, remove the oil and impurities from the surface of the blanket with a clean cloth.
Third, the special cleaning of the blanket
If the blanket is used for too long or because of improper maintenance, the surface of the blanket will form a smooth film or stickiness, which will not only affect the sharpness of the printed image, but also cause the printing work to not proceed smoothly. Therefore, it is necessary to wash off the smooth film layer or apply a sticky bond to the blanket.
1. Handling of the smooth layer of the blanket: Remove the blanket from the machine together with the splint and lay it flat on a smooth surface. The cleaning method is the same as the cleaning of the new blanket; or it can be washed with water on the machine. Wipe with pumice powder from petrol.
2. The remedy of the sticky coat of the blanket: the blanket is sticky, mainly due to the poor durability and the swelling or the aging of the blanket. Severe stickiness can cause the blanket to continue to be used. Mild stickiness can also cause the printed paper to adhere to the blanket. Therefore, the stickiness should be detected as soon as possible and the blanket should be cleaned in time.
3. The cleaning method is: first wash off the ink layer on the surface of the blanket with gasoline, and wipe it with a dry cloth; then use a strong solvent gasoline or a small amount of industrial alcohol in the gasoline (also use rubber reducer) Wipe the blanket and then wipe the surface of the blanket with talc powder mixed with sulfur powder to reduce the stickiness of the blanket.
Fourth, easy to appear problems and precautions:
1. When using pumice powder, be sure to avoid the pumice powder contacting the plate or falling into the padding material, otherwise it will accelerate the wear of the corresponding parts of the plate.
2. The interval between daily cleaning of blankets should be based on the accumulation of blankets and different work requirements. The general rule is: cleaning must be done once when changing colors; in formal printing, every 3000-5000 sheets should be cleaned once; It should be cleaned once a day before work (after shutdown); the test process should be cleaned at least once.
3. When the machine is jogged, the finger should be light and the hand holding the blanket should leave the surface of the roller; after the jog is completed, the finger should leave the button during the scrubbing process.
4. When cleaning, do not touch the solvent on both sides of the blanket.
5. The liner lining the blanket should be narrower than the blanket to prevent penetration of solvents such as gasoline.
6. Blank or unused blankets should be cleaned, put on talcum powder, covered with protective paper, stored in a closed container or in a well-ventilated, cool, dry place, avoid oil, acid, alkali, salt And other chemicals are in contact and avoid being squeezed. When printing on the machine, it must be cleaned like a new blanket.
7. When cleaning the blanket daily, kerosene cannot be used.
8. When using a device that automatically cleans the blanket, strictly control the amount of cleaning agent.
Cleaning of water transfer roller and water roller (water roller type)
In the printing process, due to the repeated contact between the water roller and the printing plate, after using for a period of time, on the one hand, the ink and the like may be adhered from the printing plate, and on the other hand, the velvet structure on the surface of the water roller may be damaged, and the water is transferred. During the water transfer process, the surface velvet structure will be damaged by the same; at the same time, the ink on the water roller will pass through the water roller to the water transfer roller. Therefore, the water roller must be cleaned or replaced in time to restore and maintain water absorption and water transfer performance.
First, prepare cleaning materials and tools
1. Cleaning materials: gasoline, water (preferably a pool with taps);
2. Tool nylon brush and steel sheet.
Second, cleaning
Place the removed water roller on the bracket (or wooden pillow) of the water roller, pour the gasoline on the roller surface, and brush evenly in one direction (the direction of the water roller of the water roller) with the plate brush; After the ink is dissolved, it is washed with water until there is no dissolved ink on the roll surface; finally, the excess moisture is scraped off with a steel sheet.
Cleaning of water bucket sticks and water rollers
The more common bucket rollers are chrome-plated. During the printing process, the ink on the water roller is also transmitted to the water roller and the water roller, which reduces the water permeability. In addition, when the downtime is long, even if there is no ink stain on the water fountain roller and the ink roller, an oxide film is formed on the surface, and the roller surface adsorbs oil mist, dust and the like in the air to make them original. Some hydrophilic properties have changed. Therefore, the water bucket roller and the water roller must be cleaned in a timely and regular manner to restore the hydrophilicity and uniform water transfer.
Cleaning materials: pumice powder, dampening solution, glue, and wipes.
1. Draw the dampening solution, then pour the pumice powder, then wipe back and forth on the surface of the water roller and the water roller. When the ink and oxide film are removed, quickly wipe the surface with a damp cloth.
2. Jog the machine, turn to the remaining unscratched parts, and wipe according to the appeal method until all the water rollers are cleaned.
3. Dip the glue with water and wipe the surface of the water roller.
Water bucket cleaning
The water bucket is generally made of a copper alloy material. Long-term use of water buckets will inevitably fall into dust and other debris, while the water bucket roller will also bring paper powder, paper wool, ink stains, etc. into the water bucket, which will not only reduce the wetting properties of the fountain solution. And will directly affect the printing quality of printed products.
Cleaning step
1. Prepare clean water and a piece of cloth, a brush, and a plastic tube.
2. Remove the bucket roller
3. Pour water into the water bucket, and use a brush to stir up the dirt at the bottom of the bucket, and then use a conduit (the principle of the connector) to suck the liquid in the water. While watering, brush and guide the water until the water bucket is basically clean. Finally, clean the water bucket with a cloth.
4. Install the bucket roller
Easy to produce problems and precautions
1. Take care when disassembling the water roller. If the removed water roller does not need to be used or installed immediately, it should be placed on the water roller bracket.
2. When cleaning the water transfer roller and the water roller, the direction of brushing and scraping should be as close as possible to the direction of the wire of the water roller.
3. When cleaning the water roller and the water roller, the amount of pumice powder should be minimized, and the pumice powder should be prevented from falling into the surface of the water bucket or water roller.
4. The water roller should be cleaned in time, otherwise the water delivery performance of the water delivery components will be reduced, resulting in defects such as dirty plates. The time for cleaning the water roller and the water bucket should be determined by the degree of fouling and the specific conditions. The general rule is:
1) When stopping the machine for a long time or replacing the fine product, the water roller and the water bucket should be thoroughly cleaned before starting the machine.
2) During the normal printing process, if the ink layer of the layout is thicker, the water roller should be cleaned every day; if the layout is thin or the general product is printed, the cleaning times can be appropriately reduced.
3) The ink on the water roller and the water roller should be cleaned in time. Otherwise, the local water supply of the printing plate will be insufficient, causing malfunctions such as dirty plates, and the water roller is also very easy to get ink.
4) When changing dark ink to light ink, be sure to clean or replace the water roller.
5) Before the new water roller is printed on the machine, apply a clean wet cloth to the wire in the direction of the water roller to remove the floating fluff on the surface of the water roller. Then, wipe the surface of the water roller with a cloth with water or a dampening solution, so that the new water roller has a certain water content before the machine to facilitate printing. When the new water roller is on the machine, the machine can be idling for 10-20 minutes to replenish the water content of the water roller, and then the machine will wipe off the fluff on the water roller and the water roller.
Ink fountain and ink path cleaning
Cleaning of the ink fountain:
1. Prepare ink knife, container for residual ink, petrol and two quick wipes
2. Scrape the ink: Use an ink knife to shovel the ink in the ink fountain.
3. Disassemble the ink fountain
4. Clean the ink roller: use a cloth to pick up the gasoline, scrub the ink on the ink roller, and completely dissolve it. Then use a clean cloth to wipe the ink to make it look shiny.
5. Cleaning the ink fountain