Offset Press: General Method for Machine Fault Identification (Part 2)

2. Benchmark test method. All the components on the machine are linked together in the form of a reference, so if we can find absolute and relative benchmarks, we can test their corresponding status based on the benchmark diagrams. If they are inconsistent with the standard status, we should Adjustment. The benchmarks on a machine are generally divided into two broad categories: position reference and time reference. To grasp this essential relationship, many failures will be easily ruled out.
3. Replacement (exclusion method). Due to the intricacies between the cause and the result, this brings great difficulties to fault identification. Therefore, in order to accurately identify the source of the fault, non-fault sources should be eliminated first. An effective method for troubleshooting is the replacement method. No change before and after replacement means that it is not the source of the fault. If there is a change, it is likely to be the source of the fault (of course, there are other sources of the fault).
(1) Paper Replacement The final result of the blot is on the paper, so many trouble spots can be detected by replacing the paper. Here are two examples to illustrate the application of this method.
1 thick paper for thin paper: if the two conditions, the rules are not accurate, then it is likely that the regulation is not appropriate, but has nothing to do with the paper; if the two states are not the same, a set of standards, a set of inaccurate, That shows that the fault is related to paper. According to the standard state adjustment, the rules and the paper are in the best fit.
2 coated paper to replace offset paper: If the ink is still uneven before and after the replacement, it is likely that the ink path is not properly adjusted, and has nothing to do with the paper path; if the change before and after the change, an ink color uniformity, a black ink is uneven, then the paper is likely to be Fault original.
(2) ink replacement method to reduce the ink color, if the paper is still stuck to the blanket after the replacement, it shows that the paper is glued to the rubber market has nothing to do with the viscosity of the ink; if replaced, the paper will no longer stick to the blanket, The ink viscosity is likely to be the fault.
(3) The fountain solution replacement method increases the acidity of the fountain solution. If the plate still wins, it means that the upper plate is not related to the acidity of the fountain solution; if the plate is no longer dirty, it means that The acid of the liquid is likely to be the source of the fault.
(4) Plate replacement method To replace the printing plate, if the ink is still uneven, it means that the failure has nothing to do with the printing plate; if the ink color is changed evenly, the printing plate is faulty.
(5) After Baocun replaces Baocun Village, if the paper is still stuck on the rubber jacket, it means that the paper is stuck on the blanket and has nothing to do with Baocun; if it is replaced, the paper will no longer stick to the blanket. Indicates that the eraser market is the source of the fault. In general, the viscosity of the old eraser market is greater than that of the new eraser market.
The above-mentioned replacement method is a first-level replacement, if you want to further exclude non-fault sources, you need to perform two or more levels of replacement. If the paper is stuck on the squeegee, replace the paper first. If it still sticks on the blanket, it indicates that the paper is not the source of the fault; then change the ink again. If it still sticks on the blanket, it means that the ink is not a source of failure. ; then replace the blanket, if still the same, it shows that the blanket is not a source of failure; in this case can reduce the printing pressure, if it is still no effect, it indicates that the roller row is the source of fault. In the end, what part of the tooth row has failed, and similar methods can be used to detect it.
In short, a failure can be replaced by multiple levels. If the replacement is unchanged, the replacement is eliminated. If there is a change, the reservation is retained, and after debugging, it is replaced. This is the basic guideline for troubleshooting using the replacement method.
4. Symmetry principle. The symmetry principle is a very important method for installing and debugging the machine and troubleshooting. The content of the symmetry principle has been described previously. The following uses several examples of failures to illustrate how to use the symmetry principle.
(1) Check whether the size of the mouthpiece is in a symmetrical state on the lateral side of the printed sheet. If it is in a symmetrical state, it means that there is no relationship between the size of the paper and the size of the paper.
(2) Ink stains on the left and right sides of the print sheet. Check the printing pressure at each contact surface. If all of them are symmetrical, it means that the failure has nothing to do with the size of the printing pressure.
(3) When the printed sheets are fast, check the tightness of the transport belt and the pressure of the rollers above it. If all are symmetrical, it means that the elasticity of the transport belt and the pressure of the pressure roller have nothing to do with the fault. .
The above outlines the use of the symmetry principle. But how to grasp the contents of the symmetry principle during use, this requires the establishment of a symmetric function:

If two places are completely symmetric, then x1=y1, x2=y2,..., Xn=yn. X1,X2,...,Xn and y1,y2,...,yn indicate the contents of symmetry. Taking a tooth row as an example, x1 can be used to indicate the left and right position of the tooth pad, X2 indicates the height of the tooth pad, X3 indicates the friction coefficient of the tooth pad, X4 indicates the hardness of the tooth pad, X5 indicates the time for opening and closing the teeth, and the like.
There are different symmetry functions in different places, so the symmetry function must first be established when using the symmetry principle.
5. Visual method. The amount of water on the surface of the ink roller can be observed visually. If the ink roller reflects light, it indicates that the water is large. There are many faults that can be visually excluded from their non-failure sources.
6. Ear hearing method. Through the ears to analyze whether there is abnormal sound inside the machine, if there is abnormal sound, you need to stop the inspection, this method can be used to find no obvious fault.
7. Touch method. By touching to check the flexibility of the components or the size of the air-suction force, this method is particularly suitable for checking hidden failures in force-closing mechanisms.
8. Signal analysis method. The sensor picks up the vibration signal on the machine, and then uses a computer for analysis to find the source of the fault. When using this method, it is better to collect new and old signals, which is convenient for comparison and analysis.
The general methods used to troubleshoot faults are briefly described above, but of course there are other methods. When troubleshooting, these methods should be integrated to select the best path for troubleshooting. (Finish)