Use "step-by-step clarification" to exclude offset printing faults

Offset printing is a complex and varied process. To enable an offset press to print a qualified product, operators must have the ability to quickly eliminate common failures. As offset printing, there are many causes of failures, some of which are due to the inaccuracy of the machinery and equipment, some are due to improper adjustments by operators, and also due to non-conformity of materials and environmental conditions. There are often the same signs for different reasons and it is very easy to confuse. How to judge the cause of the failure from the characteristics and signs as much as possible, using the "step-by-step clarification method" to exclude the offset press is feasible.
There have been many discussions on the failure analysis of offset presses. Here, the work experience of the operators of small-scale offset presses is not enough. The method for simply handling the faults is not enough for analysis. It is for reference only.
a. One of the faults: creases and tears.
Common treatment methods: knock paper, adjust the open teeth of the fangs.
The "step-by-step clarification method" analyzes the reasons:
The paper is uneven, with lotus leaf edges, upturns and buckles in the mouth; the paper is not positioned at right angles at three points, there is too much paper, and normal transfer cannot be completed; the teeth on both sides are inflexible, and the teeth angle is large and small; the impression cylinder Orthodontic teeth open too late or open angle is not enough; both sides too short, too little paper, etc.; Through analysis, through a variety of phenomena, one by one can be twice as effective;
b. The second failure: Common methods of ghosting: Adjust the grip force, replace the paper, and adjust the pressure between the rollers.
“Step-by-step clarification” analysis: check whether the paper is smooth (with or without curled edges or curls); the pressure of the impression cylinder gripper is not enough, the paper displacement during the imprinting process; slippage between the rollers due to improper lining Excessively large; platen rubber roller shaft, tile sleeve and wall plate hole have a gap to generate vibration; roller axial stringing; machine vibration and so on.
After "step-by-step clarification," find out the crux of the problem and break it down.
c. Failure of three: the lever (strips, roads, ink bars)
Common treatment methods: Adjust the ink roller pressure and check the pressure between the rollers.
"Step-by-step clarification" analysis: distinguish between ink bars and water bars. The ink sticks - irregular or regular dark streaks on the plates and prints. The water bar - an irregular or regular light-colored streak appears on the printing plate and the printed sheet; the ink roller exerts excessive pressure on the printing plate and the ink fountain roller, or the surface of the long-term use is aged and hardened; the roller is not balanced; Printing pressure between rubber, rubber and rubber pressure is too large; ink on the surface of the water roller gradually absorbs ink; the elasticity of the surface of the printing roller is insufficient; the machine vibration is too large and the precision is not enough; printing ink, rubber, pad, printing plate, paper, Potion, color, etc. For example, printed copperplate paper is more prone to ink bars than printed offset paper, and printed blue is easy to get out of ink bars;
The severity of offset presses is an overall assessment of the accuracy of offset presses. The occurrence of “spreads” is not caused by a certain cause, but is caused by a variety of factors. Therefore, some of the taps are complex and difficult to eliminate at one time. To study its laws, it can only prescribe the right medicine;
d. Fault 4: Overprinting is not allowed.
Common treatment methods: Check if the paper is deformed, adjust the paper feeder, check if the pressure is too large, and check if the positioning is accurate.
“Step-by-step clarification” analysis: excessive printing pressure, paper compression and deformation; excessive water supply during printing; unstable paper feeding, inaccurate positioning; inaccurate movement of front and side gauges; Insufficiency; whether the two gaps in the former rule are the same.
The reason why registration is not allowed to occur is very complicated. In general, as long as the conditions are right and the machine is properly adjusted, overprinting is infrequent. When overprinting is inaccurate, you should analyze the cause of the failure calmly and eliminate it step by step. Such as: constant speed, quasi-unequal speed, one side accurate, the other side is not allowed, both sides are not allowed, both sides have no rules are not allowed, the quasi-quasi-trailer is not allowed, the middle of both sides are not allowed and so on. According to the different situations, find out the rules, classify them, and take the best solution to the problems. Otherwise, blindly make judgments. The more adjustments become more chaotic, the old problems will not solve the new failures.
e. Fault No. 5: The printing plate has an Internet access point or text intact, but the printed page cannot be printed on the word or picture.
Common treatment method: pad rubber, but it can not be printed after padding. Check the printing plate is in good condition.
“Step-by-step clarification” analysis: due to the paper folding angle or squeezing rubber in the paper; the printing plate paper is damaged, causing the individual places to not ink; individual images of the rubber roller crush the squeezing rubber; the printing roller partially accumulates ink. Did not clear clean squeezing rubber; printed body quality problems.