Wide application of air cushion blanket and its advantages analysis
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The blanket 50 years ago was made of natural rubber (INDIA-RUBBER) and later replaced by synthetic rubber, such as the standard orange blanket of the early Heidelberg GTO, KORD printing press, and the third generation is the air cushion commonly used today. Blanket (appeared around 1960). The first air-cushion rubber was “VULKAN714”, followed by Perfect Dot, which has been used today to become the standard material for most Heidelberg presses. The brand of blankets commonly used in Hong Kong are Meiji of Japan, Phoenix of Germany, VULKAN, PRINTEC, Day of the United States, and so on.
Air cushion blankets can be widely used, mainly because they have the ability to reduce the resilience to paper adhesion and good dot reduction. The surface and structure of the air cushion rubber have a great influence on its characteristics, so the conventional rubber has been rarely used. (Requirements for blankets can be found in DIN 16621).
Air cushion blanket advantages:
First. The linear speed matching of the printing plate and the blanket cylinder is better;
Second, the degree of network restoration is high;
Third, reduce the deformation caused by the substrate;
Fourth, reduce the friction on the layout (offset).
As the foreword, blankets have a great impact on print quality, so they are very important in terms of choice and care. First pay attention to the structure of the blanket such as the fiber layer, the return air cushion; the surface layer is a smooth or rough (hard) surface? Is the surface layer milled or composed of chemical structures? Of course, the structure and organization of the blanket is still the secret of the manufacturer, we can not know.
The blanket has a fiber layer, an air cushion layer and a rubber layer, but we are only interested in the surface layer. About 80% of the rubber is now a 4-layer structure. : top layer (0.35 to 0.4 mm), fiber layer (about 0.25 to 0.3 mm), air cushion layer (0.35 to 0.4 mm), base layer (about 0.25 to 0.3 mm).
The air cushion can be divided into three categories: micro-star treatment (MICROSPHERE) sealed air cushion, BLOWING sealed air cushion, salt filter treatment (SALTLEACH) open air cushion. Today's MSI type air cushion rubber is more common. According to experts' suggestion, the salt filter air cushion can have better printing effect. PERFECTDOT rubber is the blanket of this method.
Most of the printing quality depends on the rubber surface layer, and the surface layer is mostly embossed, ground or high-grinded. The top layer also has other factors that affect printing, such as the viscosity of the paper. What are the benefits of using air cushion rubber? The air cushion is described as the rubber's rebound ability, and the rebound ability can cause the rubber to be deformed without being deformed when it is squeezed, which has a positive influence on the reproduction of the dots. Even so, many people mistakenly believe that because of the resilience relationship, the intensity of printing is greater (corresponding to flexibility), which is not entirely correct. Generally, the corresponding elasticity of the air blanket blanket is 4 to 8%, while the conventional blanket is less than 4%.
The blanket is textured, with one part being tough and the other part being elastic. Basically, the average printer ignores the texture of the blanket, because most of the blankets are already cut. However, if you cut the small size into a small size blanket, you should pay more attention. The blanket must be tough to balance the printing direction. The so-called printing direction usually uses lines as reference lines. In addition, we need to pay attention to cutting the blanket to the right size (not too long, because too long will cause the blanket to loosen on the drum and loosen the blanket, and the aluminum strip or iron of the blanket) For the easy installation, we usually cut a small corner at both ends of the blanket and apply a seal on both sides of the rubber to prevent the water (or car wash water) from rising. Another thing to note is that you should remember to clean the rubber every day and take care of it!
The thickness of the blanket is from 1.35 to 3.00 mm, which is usually 1.95 mm, except for special purposes. The thickness of the blanket is measured by a suitable instrument. Note that the front end of the instrument cannot have sharp edges. According to DIN ISO 12636, the standard of force should be taken when measuring!
What criteria do you use to choose a blanket?
The quality of Perfect Dot from Heidelberg is one of the best. Other brands may have excellent effects on special applications (field, flat screen, adhesive). (If the quality requirements are not too strict or the substrate is rough, consider not using An expensive blanket.).
The rubber with aluminum strips is quick and easy to replace and ensures an even average rubber tension. If you use a clip to tighten the screw, remember not to tighten it from the sides to the middle (the rubber may produce uneven surface or convex hull). The blanket iron must be straight and not bent! Be sure to center during installation. If necessary, press the raised parts on both sides with a small wire cutter. Tensile force of the blanket on the printer (10% of the length of the rubber stamp minus 5 N/m):
SM/CD102 imprint length 70cm pull force 65N/m (maximum)
SM/CD74 imprint length 50cm pull force 45N/m (maximum)
SM/GTO52 blot length 35cm pull force 30N/m (maximum)
The tightening action is repeated two or three times. During the iterative process, the printer needs to be pressed for a while. If the rubber tension is too large, the intermediate fiber fabric will be damaged due to excessive tension, but the rubber tension is too small, and the dot will be deformed. This also requires careful measurement of the actual height of the lining (a high-low measuring device such as HEIDELBERG can be used). Device). The factory has a printing machine with a line of light, and a partial glazing rubber. I recommend using the rubber "VULKAN" which is easy to tear open.