What to do if the printing machine fails Printing machine maintenance

There are four main faults of printing machines: paper breaking faults, watering, inking and embossing troubleshooting, overprinting part failure, and folding part fault analysis and elimination.
1. Paper breakage failure
Paper breakage is a very headache, mainly for the following reasons:
(1) Cracked, tight, bruised or glued on the side. When the paper roll is tight or glued to the side, the paper tape is easy to break, affecting the normal paper supply. If this phenomenon is found, you can use a water brush to wet the tight edge or stick to the glue side, and the fault will be eliminated.
(2) The core of the paper roll itself is not round. The operator can judge whether the eccentricity of the cylinder core is too large based on experience, and change the paper in time or notify the machine administrator to slow down the operation to avoid it according to the situation.
(3) The lifting speed is too fast or the tension is too large. The paper has a tension limit, and when increasing the tension, it should be as far away from the limit tension as possible. At high speeds, a very small change can also create very large stresses that can lead to paper breakage.
(4) The mandrel of the guide roller is loose, the horizontality and parallelism are inaccurate, and the mandrel or bearing is worn. For machines that have been used for a certain number of years, sufficient attention should be paid to them, and maintenance personnel and operators should check the working condition of the paper guide rollers in time.
(5) Too much ink scale is deposited on the guide roller. After a long time of operation, the deposition of ink scale increases the radius of each roller, so that the tension also increases. When the tension reaches the limit value, the machine cutter cuts off the paper protectively. Therefore, the ink stains deposited on the paper guide rollers should be removed in time.
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2. Watering, inking and imprinting failures

(1) Water supply part
Water supply devices can generally be divided into two types: indirect water supply and direct water supply. Regardless of the method of water supply, the purpose is to keep the plate well moistened and the ink balance. The specific manifestations of various faults are: the amount of water will make the ink color lose its luster, gray and dull, the ink color is not full, and in severe cases, ink emulsification will occur; If the water volume is too small, the printing plate will not be fully moistened, resulting in deformation and blurring of the graphics and text. The specific elimination method can be adjusted according to the structure of the water supply mechanism and the function of each component.
If you can check the working condition of the bucket baffle motor or sprinkler solenoid valve, whether the pressure between the water transfer roller, the string water roller, the plate roller and the plate roller is normal to troubleshoot, you should pay attention to the pressure at both ends of the water roller must be adjusted to the balance position. Normally, the water roller and the bucket nozzle should be cleaned in time to check the pressure between the water rollers.
(2) Ink supply part
The ink supply mechanism is composed of ink hopper roller, ink transfer roller, ink string roller and plate ink roller. Common faults include: insufficient ink supply, large ink supply, unstable ink supply, etc. The above faults can be eliminated by checking the working condition of the ink hopper roller and the ink nail and whether the pressure between each ink roller is normal. At the same time, it is necessary to ensure that the pressure of the ink roller is moderate, and the ink collection of the ink roller and the ink output roller are well coordinated, so as to keep the ink absorption of the plate even, and to avoid the inconsistency of the ink color before and after the printed product to the greatest extent, and carefully check whether the surface of the rubber roller is flat and smooth, and whether there are any major hard injuries such as indentations, scratches or poor adjustment of ink and glue caused by local conjunctiva and crystallization. Due to the large temperature difference between winter and summer, the pressure can be appropriately increased in winter and reduced in summer.
(3) Embossed part
The imprint part is the core part of the printing unit, and it is also the most accurate part of design and manufacturing. Printing pressure is an important factor to complete the transfer of ink in the printing process, and moderate printing pressure is a reliable guarantee for the printed layout, text, and pattern to be clear and clean, the text is not deformed, and the ink color is uniform and consistent. The main fault phenomenon is that the ink color is weak, the dots are unclear, and the text is deformed, which is due to insufficient ink transfer, which is caused by the loss of elasticity of the rubber blanket or the lining is too small, as long as the new blanket is replaced or the thickness of the lining can be appropriately increased.
3. Troubleshooting the overprinting part
There are many factors that affect the registration of color prints, such as paper, plate making, dampening fluid, printing process, equipment condition, etc., which may have an impact on the registration. Here we mainly analyze some common registration failures from a mechanical point of view.
(1) Factors affecting the stability of paper tension
The main factors affecting the stability of paper tension are: paper rack, three rollers (infeed), variable speed roller (PIV) and other tension adjustment mechanisms, as well as the working conditions of other paper guide rollers and pulling rollers. The tension adjustment of the tension adjustment mechanism is not suitable, or the parallelism and horizontality deviation of various types of rollers are large, or the paper holder brake pads are worn, the roller bearings are worn and other reasons will lead to tension instability, resulting in inaccurate overprinting.
(2) Factors affecting the accurate transfer of pictures and texts
As a direct printing part for the precise transfer of graphics and text, any mechanical deviation of the printing unit will affect the registration of the printed product. Its failure is mainly caused by the wear of the drum bearing, the serious wear of the copper sleeve or bearing of the clutch pressing rod mechanism, the loose or improper installation of the plate pin, the wear of the registration adjustment mechanism parts, the wear of the transmission parts, the failure of the potentiometer, etc. Although these faults are uncommon, mechanical deviations in these parts should also be carefully examined after the cause of the tension factor has been basically ruled out.
4. Fault analysis and troubleshooting of folding parts
The most common fault manifested by the folding part is blocking, which is caused by many reasons. We analyze the reasons for the blocking of Roland and Gaussian folding machines, mainly as follows:
(1) The rubber strip on the folding roller is used for too long or aged, causing the rubber strip to lose its elasticity or the knife seam is too wide and too deep, which causes the newspaper to be cut continuously, and several newspapers are easy to block at the flower wheel when they are connected together. By replacing the rubber strip with a new one, the problem can be solved.
(2) The cutting knife on the cutting drum is worn or the height of the cutting knife is not in place during installation, resulting in the cutting knife cutting the newspaper continuously during high-speed operation, causing the report to be blocked. The treatment method is generally by raising the knife holder, that is, adding a knife pad under the knife holder.
(3) Severe wear of the reporting needle, folding knife and biting knife, or their corresponding cam roller bearings are stuck, or their corresponding torsion springs are broken, which will cause the folding page to be not in place and cause blockage. By carefully inspecting these parts, the fault can be resolved by adjusting or replacing the corresponding parts as appropriate.
(4) The cutting knife just cuts the adhesive tape for automatic paper splicing but fails to cut it off, causing blockage. This phenomenon is generally rare and there is no suitable way to deal with it.
(5) The paper itself is too wet or the water is too large, resulting in it is not easy to cut and cause blockage. If the paper itself is too wet, replace the paper roll; If the water is too large, turn off the small water volume in time.
(6) Improper adjustment of the diameter of the folding roller or improper adjustment of tension before entering the folding part, resulting in continuous stretching of newspaper or pinhole tearing, may also cause blockage. The treatment method is to check whether the diameter adjustment of the folding roller is appropriate and adjust it according to the situation: check whether the tension adjustment of the variable speed roller is appropriate, whether the press wheel on the variable speed roller is too tight or too loose, etc.
Now I don't think some common faults of the printing machine are easy to solve, but I still have to ask professional maintenance personnel for problems that I am really not sure about. In the next issue, I will introduce you to the maintenance and maintenance of the printing machine, so that the chance of failure is minimized or even not occurring.