Four-step judgment of the printer failure method
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The author has been engaged in the maintenance of printing machinery for more than ten years. Through continuous practice and exploration, he has summed up a set of methods for judging faults - "Watch, smell, ask, cut" to determine the four methods of printer failure.
"Look"
1. Look at product quality
Rely on observation and analysis of print quality, find out the law to determine the cause of the failure. If the printed matter is imaginary, it is conceivable whether the roller pressure is improperly adjusted; if the white bar is produced by the printed product, it is conceivable whether the plate roller is improperly adjusted; if the ink bar is produced by the printed product, it is conceivable whether the adjustment by the plate roller is improper; If the paper machine is cut and skewed, it is conceivable whether the stacker is improperly adjusted.
Once, when printing on a Heidelberg four-color offset press, the print was partially wrinkled. Observing the pre-press paper, the flatness is very good, and then carefully observe the wrinkles of the printed product, and found that except for the first color, the second, third and fourth colors are printed after being wrinkled. Based on this, the wrinkle failure occurs between the first color set and the second color set. There is a set of double-diameter rear transfer roller and two sets of front transfer rollers between the first and second color groups. There are 3 rollers and 4 groups of teeth. The 4 rows of teeth are carefully inspected. It is found that there is a row of rafts on the double-diameter roller. Paper teeth are inconsistent, and there are individual "dead teeth." After the corresponding treatment is carried out, the tension of each of the grippers is adjusted, and the wrinkling phenomenon of the printing machine disappears.
2. Look for signs of damage to parts after equipment failure
When the equipment fails, observe whether there are any scratches, broken marks, friction marks, crushing marks, etc. on the equipment, and analyze the force condition to judge the cause of the failure.
A Taipei-made two-color offset rotary press, the black group printing once had a ghosting failure and could not be printed normally. Check the printing pressure, lining, machine transmission, bearings, etc. are no problem, after careful observation, the author found that the surface of the black plate cylinder and rubber roller operating surface chrome plating is seriously damaged, there are obvious extrusion marks. It is judged that this ghosting fault is caused by the vibration of the shoulder iron to the drum pressure too much, indicating that the thickness of the drum liner is incorrect. After inspection, it was found that the thickness of the lining of the plate cylinder was not standardized due to the normal operation, and the shoulder iron pressure had exceeded the standard when the pressure of the drum body reached the standard. The long-term accumulation caused the coating on the surface of the roller to be crushed and damaged. Unhealthy movement produces a ghost image. Based on this analysis, we have standard configuration of the lining of the plate cylinder and the blanket cylinder, and then test the machine to solve the problem of ghosting.
3. See if the actions of the various mechanisms in the equipment are normal.
In a printing process, the front gauge spring of the Heidelberg four-color offset press suddenly broke, causing the positioner bracket to be misaligned and the positioning pins to be all cut. After the accident, we thoroughly inspect all parts and restore them to their original condition. After the test, I found that the prints were inconsistent and the rules changed. Check the keeper's gripper for even force. Upon careful inspection, it was found that the time when the opener balls on both sides of the squeegee row of the locator entered the cam track was obviously out of sync. It is concluded that the positioner is inconsistent in closing the left and right sides of the paper when the paper is fed from the paperboard and delivered to the impression cylinder, resulting in paper transfer errors. Thus, the positioning pin of the open cam track was inspected, and it was found that the surface of the pin had obvious shear marks, and although it was not cut, it was enough to cause a positioning error. After replacing the pin, re-test the machine and the inconsistency of the printed product disappears.
"smell"
It is judged by hearing whether the components of the equipment are operating normally. If an abnormal sound is emitted, find the source of the abnormal sound, so as to identify the cause of the malfunction and determine a reasonable solution. The key to this method is to determine if the sound is normal from the nuances. This method is often used to judge whether the rotary parts of the machine are running smoothly, whether the fasteners are loose, whether the mating moving parts are well matched, and whether there is serious wear.
"Ask"
"Q" mainly points to the inquiry of two people.
1. Ask the machine operator. There are mainly: 1 some abnormal phenomena before the fault occurs; 2 the process of the fault occurrence; 3 whether the measures have been taken after the fault occurs, what measures have been taken, and what effect.
2. The inquiries from the relevant personnel who have repaired or disposed the similar faults of this model mainly include: 1 the fault phenomenon at the time and the cause of the fault; 2 the treatment method and treatment effect at that time.
By asking, you can make a reference for judging the cause of the fault and reduce the fault handling detour. But at the same time, we must avoid bias and partiality. Don't let other people's thinking limit their own ideas and imaginations. They can only use other methods and ideas of others as a reference. In the repair of equipment, there are often some faults with similar surface phenomena but different causes and mechanisms. “Q” is just an aid. The most important thing is to analyze, think, judge and deal with it through your own brain and practice.
"Cut"
There are three main aspects.
1. Touch to see if the device has abnormal temperature changes. Abnormal temperature rise can occur due to damage to rolling or sliding bearings, poor operation of electrical circuits, and poor cooling or lubrication.
2. Touch to see if the device is vibrating abnormally. Abnormal vibration may occur due to unbalanced rotating parts of the equipment, loose fasteners or abnormal impact.
3. Touch to determine if there are any signs of wear and damage on parts that are not easily visible to the eye to check and judge equipment failure.
In short, when the equipment fails, we can conduct comprehensive analysis and judgment through one or more of the above four judgment methods, quickly and accurately determine the cause of the fault, prescribe the right medicine, and formulate a scientific and economic solution to avoid detours. Reduce parts and time, and ensure the quality of repairs.