(This article is an original article from Bisheng. It is forbidden to reprint, and reprinting must be corrected)
We often say that the cylinder part is the heart of the offset printing equipment. The actual situation is indeed the same, because the main function of the offset press is to transfer the ink of the graphic part to the surface of the substrate under the pressure, which is the core of the entire machine, and all other institutions are to be able to carry out normally. Imprint service. This shows the importance of cylinders for printing equipment. However, in actual production, we often roll hard objects into the drum due to improper operation or other accidents, causing the surface of the drum to be injured. The direct consequence of this situation is that the machine is unusable, so it is necessary to discuss how to repair the damaged roller surface. Below we will introduce some of the repair solutions.
Repair without removing the roller
Mechanical method without disassembling the drum: This method of repairing the surface of the drum is mainly aimed at the roller surface being depressed by foreign objects rolling into the drum.
Case 1: Roland double-color due to the shedding of the cotter pin, after the roller enters the drum surface, rolled out 15? Long, 2? 3? Wide, and 0.2? 0.3? Deep S-shaped dent.
1. Use a hand drill, 2.5? Drill bit, along the concave line, punch 8 ~ 12? Deep holes on the surface of the drum (the distance between each hole should be close, but can not penetrate).
2. Punch the hole with a small chisel to make it into a dovetail groove shape with a small surface and a large bottom.
3. Knock the copper strip slightly larger than the dovetail groove into the groove with a brass rod, and continue to hit the surface, expand the bottom of the copper strip in the groove, firmly bite the roller, and knock the surface flat, so that the copper and the damage The surface is firmly bonded.
4. Grind it flat with a fine file, and finally smooth it with water sandpaper.
Case 2: The J2108 nut fell into the gap of the drum, causing the surface of the drum to roll out a depression with a diameter of about 10? And a depth of about 0.5 ?.
1. According to the size and shape of the rolling injury, select a drill of 3 to 6? And drill a hole of about 15? In the surface of the drum.
2. Use copper rods of the same diameter, screw in and tighten, and cut off at 0.5 to 1? From the surface of the drum
3. In the same process of beating, filing, grinding and other processes, the surface of the drum is treated flat.
The advantage of the mechanical method is that the required cost is lower and the maintenance time is longer after repair. Normal factories can handle it as long as they have a locksmith, but as long as they are manually operated, the requirements for the operators are relatively high. Even so, it is difficult to completely restore the situation before the damage.
Argon arc welding without disassembling the drum: This method of repairing the surface of the drum, as above, can also deal with relatively serious small surface roll damage on the drum.
Case: In the J2205 printing machine, due to the large tooth spring support rod of the swinging tooth falling off, the longest depression of 3? Is rolled on the surface of the cylinder.
1. Clean the roller surface with gasoline and acetone
2. Use a special argon arc welding machine to spot weld and overlay welding on the damaged part of the drum.
3. Finally, file and smooth the surface with water sandpaper as much as possible.
The advantage is that it can deal with more serious drum surface damage, such as more serious drum surface defects caused by rolling injuries, and because the argon arc welding temperature is relatively low, it is not easy to cause greater deformation of the drum surface. With the protection of argon gas, the surface of the drum is not prone to oxidation.
The disadvantage is that it requires more professional welding equipment, as well as more professional welding technology. In addition, because the subsequent process still relies on manual grinding, it still cannot guarantee the good accuracy of the drum surface.
Filling the drum with glue: This method is more suitable for repairing the depression on the surface of the drum due to wear or corrosion. Generally, this depression will not be very serious, but if not treated, it will have a great impact on printing.
Case: Due to the material problem of the cylinder itself in the J2108B printing machine, the cylinder has corroded and thinned at both ends after several years of use. When printing large-format prints, there will be imprinting at the edges of the prints.
1. First clean the surface of the roller.
2. Use 502 glue mixed with iron powder to coat the depression of the drum. When coating, pay attention to the more precise the coating range, the better. It is better to scrape along the surface of the roller with a relatively long steel sheet just before coating, as far as possible to ensure that the coating place is flush with the surface of the roller.
3. Wrap the gauze on a flat wooden block or iron block with gauze when the 502 glue is half dry, and smooth and polish the filling.
One advantage of this operation method is that it is convenient and fast, and the average machine operator can handle it by himself. However, it usually can not be maintained for a long time, the main reason is that the surface of the drum is often exposed to various organic solvents, and it will slowly fall off during use. Therefore, it is generally only suitable for occasions requiring short-term repair.
(If you use glue to repair the roller, you can also consider epoxy resin and "two in one" glue)
For the repair of cast iron rollers, cast iron repair agent can also be used. In order to ensure that the cast iron repair agent can adhere firmly to the surface of the roller, the roller to be repaired should be cleaned with benzene and acetone before use, and then puncture the repaired area To repair, if the part to be repaired is deep, it is necessary to drill a hole in the drum (a large area can be considered to make a few more holes), tap the thread on the hole, and then use the repair agent. In the process of the repair agent completely dry, continue to sand with sandpaper until flat and smooth.
In addition, it is necessary to pay attention to repairing the roller with glue. It is best to only repair the surface of the roller caused by wear and corrosion. There is usually a bulge.
Brush plating thermal spraying technology
Case: Due to the long-term use of quarto paper for printing, this machine has caused the maximum corrosion and collapse of ink and ink outside the quartet to be about 0.15mm. Overprinting is not allowed!
Because the circumferential speed of the rubber cylinder and the impression cylinder is the same when rolling, the method of reducing the printing pressure for full-page solid proofing is used one by one to determine the corrosion depth outside the four quarters by brushing and repairing. The following is a relatively complete process.
1. Pretreatment. First, use a saw blade to shovel away the long-term sludge deposited on the drum, then use a cleaning agent and acetone to initially remove the surface ink, and then use the electrochemical electric net treatment method for further treatment. Considering that the material of the roller is cast iron, and due to the long-term use, there are ink and other dirt in the molecular gaps on the surface of the cast iron, so the activation liquid No. 2 and No. 3 are used to activate twice for the next step of plating.
2. Brushing the entire cylinder for the manual disc printing machine. The overall brush plating is to make the plating layer on the drum as a whole, and reduce the connection of the plating layer, thereby reducing the problems that may be caused by the combination between the two plating layers. Plated until the full-page solid proof has no pits.
3. Repair to the geometric accuracy range. First use profiled tiles, red powder to find the high point of the plated roller, then use oil stone and water sandpaper to grind off the higher part, and repeat until the four rollers are "smooth and synchronous" beating with a magnetic meter Within 0.05mm, the large surface is slightly beating within 0.02mm, use the full version to proof the four-color sample, and the ink color is uniform. Because the four-fold part is overprinted with the grid version, so there is no difference between the overprint and the four-fold after the repair. (This example excludes other causes that cause inaccurate overprinting of printing presses, other reasons are not discussed in this article)
This process accuracy is much higher than the above method. At present, this technology still needs to be done by a professional maintenance department. The cost is relatively high, but it is still more advocated for the process requirements of the printing press.
(Xuzhou Brush Plating Thermal Spraying Company has this technology)
Remove the roller to repair the roller surface
Disassembly drum electroplating repair: This repair is mainly applied to the small trachoma on the surface of the drum. The surface of the drum is uneven due to long-term wear and corrosion.
Steps:
â‘ Position the roller first and then disassemble it.
â‘¡ Grind the surface of the drum with a grinder (about 0.1mm or less per grinding).
â‘¢ Conduct plating treatment on the surface of the drum.
â‘£ Repeat steps â‘¡â‘¢ above until the surface of the drum meets the processing accuracy requirements.
⑤ Install the roller.
This repair method is a very complete repair method for the surface of the cylinder. The repair effect can even be compared with the effect of the new cylinder. Although the process is cumbersome but the effect is very good, the repaired printing machine can print dot prints with very high quality.
In addition, pay attention to the following three problems during the repair process of the roller.
1. Concentric issues. Due to the repair of the old parts, the bearing position of the drum sometimes jumps relative to the center hole due to wear and tear, disassembly and assembly of the bearing, etc., and the grinding machine itself is processed with the center of the two center holes as the center. The two bearing positions are relatively rolling. According to this situation, the method of grinding and grinding the worn bearing positions and the rolling body at the same time is adopted, so that the two bearing positions and the rolling body are "one knife live", so as to achieve "three concentric"!
Second, the taper (ie tip) problem. Due to the requirements of printing, the requirements of the cylinder for its taper are very high. The taper of the cylinder will appear on the printed matter: that is, the ink color of the big head is heavy, the deviation of the overprint and other problems! This requires that the tip of the grinding machine be adjusted as small as possible. In addition, the phenomenon of ellipse (ie flat) cannot appear!
3. Focus on the issue. Due to the requirements of use, the impression cylinder, rubber cylinder and plate cylinder of the offset printing machine are generally not designed as a complete cylinder. Some of the gaps are about one-third, so that when rotating directly on the grinding machine, there will be "large dynamic balance deviation" (commonly known as "biased")! Direct processing of the drum will cause problems such as horizontal ripples, concave belly, and ellipse, which affect the accuracy. Adopt counterweights for different rollers to achieve a certain dynamic balance, and then go to the grinder for processing.
Above we have introduced several ways to repair the drum. In actual production, we choose the repair process of the drum according to different situations and technical requirements. However, the repair of the roller after the rolling injury cannot be the same as before the rolling injury, because once the roller is damaged, including the roller bearings, gears, journals, etc. will be damaged, so the most fundamental The way is to strengthen management, improve the operator's sense of responsibility, and avoid rolling the drum. Because some damages can be repaired and many damages cannot be reversed.Carabiners Climbing is one of the indispensable items for mountaineering enthusiasts. Custom Carabiners will make mountaineering enthusiasts more fashionable. We have various styles of Key Ring Carabiner to choose from, and there is always one that will meet your needs!
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