Improve the quality of flexo printing
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Give you a Ferrari, but you open out the Alto's bumpy feeling, the quality of flexo can't be improved, but you can't blame the equipment. Many times, the quality of flexo printing has a lot to do with the details. After you notice, you earn, pay attention to not Come, this article will save your life! When the 650 type flexographic 6-color printing press was operated, several operational failures occurred, which seriously affected the normal operation of the machine. I am sorting out and I hope that everyone can promote each other.
Question 1: Use of the knife sponge
In general, a high-precision die cutter or a cross-cutting cutter body of a post-press process is provided with a compression sponge, which has various specifications. The knife sponge is rubber on one side and rubber sponge on one side, and its thickness is 1.6mm. After the knife is finished, the blade is invisible. Its main function is: 1 maintain a tension, this tension is achieved by the friction between the knife sponge and the material to be printed, solving the problem of longitudinal die cutting. 2 The flexible knife-blade sponge ejects the die-cut material from the empty portion of the die cutter.
The "Dexin" flexo printing machine has the functions of high-speed glazing and automatic slitting point tracking, as well as non-stop double-station discharge and normal 6-color front and offset marking. The high-speed glazing paper path is 60 meters long and has a high temperature of about 100 degrees. Therefore, the temperature has a serious influence on the service life of the knife sponge on the blade body and the fastening property of the adhesive layer, and the tension of the printing material is randomly generated due to the influence of the quality change of the knife sponge. Compared with the six-cut cutting knife in the post-press die-cutting section, it is very difficult to adjust the tool position under high-speed operation. Sometimes the cutting error is 2mm, and the printed product produces a large amount of waste and defective products.
When adjusting the machine on site, it is found that the operating frequency of the tool position is used: about 6 adjustments per minute after noon every day, which is much larger than the frequency of use in the morning (because the temperature of the whole machine is relatively low in the morning). Therefore, the blade sponge of the cut portion is forcedly air-cooled. As a result, the situation has improved, the use time of the knife sponge has been lengthened, the reject rate has decreased, the frequency of adjustment of the operator has decreased, and the operation intensity has decreased.
Therefore, attention should be paid to the quality and use of the sponge. At the same time, pay attention to the selection of the knife sponge. When using a suitable sponge, test it within the specified time and measure the difference between the height restored by the sponge and the original height. The good sponge is the same as the original. The elastic height, density and hardness are not suitable, and it is difficult to effectively press the paper during die cutting. The sponge should be higher than the blade and can be adjusted according to different materials. In principle, the density is large and the height should be small; the density is small and the height should be large.
The quality characteristics of the sponge are expressed as: 1 rebound speed. 2 long-lasting rebound ability (height difference). 3 compression density.
Question 2: Adjustment of the paper table
In the post-press die-cutting section, the clamp-type high-speed stacking table consisting of double-layer nylon belts, the die-cutting material sent out by the output part, to the slow collecting table for collecting the stacks, the paper is discharged smoothly and neatly and orderly. , the count is accurate.
When the six-card playing card cut-off paper (240 g sandwich paper) was collected, the work surface of the work surface was very messy, and it was impossible to carry out normal collection, which caused great waste of materials and personnel. After analysis, it is considered to be the mess caused by the angle of paper exit. The debugging personnel and the operator are not thorough in the on-site handover, and the angle of the collection table is adjustable, according to the area and weight of the paper. 2 machine speed to carry out.
After adjusting the angle of the collecting table, the operator receives the paper neatly, and the post-order personnel are busy and not chaotic.
Question 3: Adjustment of air pressure
When the "Dexin brand" flexo printing machine was tested for the correctness of the PLC test of the printing plate roll and the anilox roll, it was found that the printing plate roller weighing 80 kg had no action operation function when it was working. The normal bearing linear guides and other mechanical parts slide freely; the electrical PLC program, the inspection is correct; only the cylinder and air pressure to perform the work must be calculated and adjusted.
The result of the calculation is that the cylinder load of the ∮40 should be 60 kg, which is far from the working amount of the plate roller. Finally, after checking the air pressure, it was found that the working pressure was 2 kg, and the requirements for use were not met. Immediately after adjustment to 6 kg, the cylinder of the plate clutch clutch was freely moved and organized.
Question 4: Use of press-fit traction rollers
Frequent use of the same wide range of paper materials, due to the friction of the running speed, will cause local wear and tear in the width direction of the pressure roller, resulting in significant depression. As a result, the diameter of both sides of the rubber roller is higher than the depression, and the normal working pressure is lost on the surface of the pressed paper. When changing the same width, but the weight of the paper material is small, the tension of the paper cannot be maintained due to the depression (the pressure is not tight), and the direct effect is that the precision of the overprint cannot be guaranteed.
In the case of frequent changes in the width of the paper material, the printing factory must repair the surface of the traction rubber roller at all times to ensure that the busbar is straight, so as not to affect the printing work.
Pay attention to the replacement of the traction rubber roller: 1 The traction rubber roller busbar must be parallel with the printing roller, and the force is even, and it cannot produce a single force, or the local busbar is stressed, and the pressure paper is unstable. The paper material tension is fluctuated. 2 If the rubber roller is passive, the main drive roller has a gap, the transmission is unstable, which will affect the tension fluctuation; 3 the pressure of the traction rubber roller determines the printing overprint precision and the return accuracy;
From the above examples, the importance of the printing operator in the entire production process. However, operators must also improve their own quality, and understand in detail the operating performance of the machine, the application of printing accessories and the good habits of normal maintenance (such as lubrication, air filtration, etc.).