Four step judgment method for the maintenance of t

Printer maintenance: four step judgment method

the author has been engaged in the maintenance of printing machinery for more than ten years. Through continuous practice and exploration, he has summarized a set of methods to judge faults - "look, smell, ask, cut" four methods to judge printer faults

"Wang"

1 Look at the product quality

rely on observation and analysis of the quality of printed matter, find out the rules, and judge the cause of the fault. If the printing is false, you can think of whether the roller pressure is adjusted improperly; White bars are produced by printing products, you can think of whether the water roller of the plate is adjusted improperly; If the ink bar is produced by the printed product, you can think of whether the adjustment by the ink roller is improper; If the paper cutter cuts Skewly, you can think of whether the stacker is adjusted improperly, etc

once, when our factory used Heidelberg four-color offset press to print prints, the prints were partially wrinkled. Observe the pre press paper, the flatness is very good, and then carefully observe the wrinkled part of the print. It is found that except for the first color, the second, third and fourth colors are all wrinkled before printing. According to this judgment, the wrinkling fault occurs in the first color group and the second color, which can also be changed manually; The system can automatically realize the calibration of indication accuracy; Between groups at the end of the experiment. Between the first and second color groups, there is a group of double diameter rear paper transfer rollers and two groups of front paper transfer rollers, with a total of 3 rollers and 4 groups of tooth rows. After careful inspection of the 4 groups of tooth rows, it is found that there is a row of paper teeth on the double diameter roller with inconsistent holding force, and there are individual "dead teeth". After corresponding treatment and adjustment to make the paper teeth have the same force, the wrinkle phenomenon of the printed matter disappears after the machine is tested

2. Check whether the parts have damage marks after the equipment fails

when the equipment fails, observe whether there are scratches, broken marks, friction marks, extrusion marks, etc. on the equipment, analyze the stress condition, and then judge the cause of the failure

a two-color offset printing rotary machine made in Taipei of our factory once had ghosting failure in black group printing, and it could not print normally. Check the printing pressure, lining, machine transmission, bearings, etc. there are no problems. After careful observation, the author found that the chrome coating on the operating surface of the black group cylinder and rubber cylinder was seriously damaged, with obvious extrusion marks. It is judged that the ghosting fault is caused by the vibration caused by the excessive pressure of the shoulder iron on the drum, which indicates that the thickness of the drum lining is wrong. After inspection, it was found that the lining thickness of the printing plate cylinder had not reached the standard for many years due to the nonstandard operation at ordinary times, resulting in the shoulder iron pressure exceeding the standard when the cylinder body pressure reached the standard. The long-term accumulation caused the coating on the surface of the cylinder to be extruded and damaged, and the uneven movement of the cylinder produced ghosting. Based on this analysis, we made a standard configuration for the lining of the printing plate cylinder and the rubber cylinder, and then tried the machine to solve the problem of ghosting

3. Check whether the action of each mechanism is normal during the operation of the equipment

during a printing process, the front gauge tension spring of our Heidelberg four-color offset press suddenly broke, resulting in the dislocation of the positioner support and the cutting of all positioning pins. After the accident, we carried out a comprehensive inspection of all parts and components and restored them to their original state according to the standard. After the test, it was found that the prints were inconsistent and the rules changed. Check the gripper teeth of the positioner, and the gripper force is even. After careful inspection, it is found that the time when the open tooth roller balls on both sides of the paper gripper row of the positioner enter the cam track is obviously out of sync. It is concluded that the left and right closing time of the gripper teeth is inconsistent when the positioner picks up the paper from the paperboard and hands it to the embossing cylinder, resulting in the paper handover error. Therefore, the positioning pin of the open tooth cam track was checked, and it was found that there were obvious shear marks on the surface of the pin. Although it was not cut off, it was enough to cause positioning error. After replacing the pin, try the machine again, and the inconsistency before and after the printing disappears

"smell"

judge whether all parts of the equipment operate normally by hearing. If there is an abnormal sound, find the source of the abnormal sound, so as to identify the cause of the fault and determine a reasonable solution. The key of this method is to judge whether the sound is normal from subtle differences. This method is often used to judge whether the rotating parts of the machine are balanced, whether the fasteners are loose, whether the matching moving parts are well matched, whether there is serious wear, etc

"ask"

"ask" mainly refers to the inquiries of two aspects of personnel

1. Ask the machine operator. There are mainly: ① some abnormal phenomena before the failure; ② The process of fault occurrence; ③ Whether measures have been taken after the failure, what measures have been taken, and what effects have been achieved

2. Inquiries from relevant personnel who have repaired or handled similar faults of this model mainly include: ① the fault phenomenon at that time and the cause of the fault; ② Treatment method and treatment effect at that time

through inquiry, it can be used as a reference to determine the cause of the fault and reduce the detours of fault handling. But at the same time, we should avoid biased belief and listening, and don't let others' thinking limit our ideas and imagination. We can only take some methods and ideas of others as references, and we must not copy them mechanically. In equipment repair, there are often some faults with similar surface phenomena but different causes and mechanisms. "Asking" is only an auxiliary means, and the most important thing is to conduct specific analysis, thinking, judgment and processing through your brain and practice

"cut"

mainly includes three aspects

1. Know whether the equipment has abnormal temperature changes by touching. Abnormal temperature rise can be caused by damage to rolling or sliding bearings, poor operation of electrical circuits, poor cooling or lubrication, etc

2. Know whether the equipment has abnormal vibration by touching. Abnormal vibration may occur if the rotating parts of the equipment are unbalanced, the fasteners are loose or have abnormal impact

3. Judge whether there are signs of wear and damage on some parts that are not easy to see by eyes through touch, so as to check and judge equipment faults

in a word, when the equipment fails, we can conduct comprehensive analysis and judgment through one or more of the above four judgment methods. The metal tensile testing machine is suitable for the mechanical property experiments of metal, non-metal, composite materials and products in the ways of tension, contraction, zigzag, shear, tear, puncture, circulation, etc. to judge the cause of the failure, suit the remedy to the case, and formulate scientific and economic solutions, In order to avoid detours and 2.2. Overall dimension of base: 245 × one hundred and sixty-five × The main disadvantages of the two transmission modes of 60mm dismantling parts and saving time: the former requires regular lubrication and ensures the repair quality

source: Tianji