Offset printing blanket requirements and loading skills

First, the three major features of offset printing
1. The offset printing uses the middle roller of the elastomeric blanket to form a unique rolling method for indirect printing.

2. The use of different nature of the selective adsorption of solid surface law, through technical processing, so that the solid surface to meet the needs of the plane printing.

3. Utilizing the natural law of immiscibility of oil and water, both the ink and the water are delivered in the offset printing process.
One of the characteristics of offset printing is the use of an elastomer roller for indirect printing. The use of an elastomeric offset blanket and air blanket has played a decisive role in the transfer of printed graphics. First of all, we need to figure out the transfer process of the offset printing: the original image - text, lines, images of sulfuric acid paper or the output of the film is reversed - the positive image of the PS plate after drying - - Offset printing is reversed from the plate cylinder to the blanket cylinder - the transfer of the blanket onto the paper is positive.

The blanket plays a role in transmitting the printed graphic in printing. The quality of the blanket has a direct relationship with the quality of the transferred graphic.

Second, offset printing on the quality of blankets have what requirements

In the offset printing process, the role of the blanket is to transfer the graphic on the plate completely and clearly to the substrate sheet. In order to strive for the perfect transfer of images and texts, it is necessary that the blanket should have the following characteristics:
1 blanket thickness should be uniform. The uniform thickness will make the printing pressure evenly distributed, and the printed ink shades will also be more symmetrical. In the graphic transfer process, the graphic size will not change easily.

2. Has good flexibility. Ordinary solid rubber elasticity is good. The effect of graphic and text transfer and ink-absorbing performance is also likely to be good. In the imprinting process of ordinary solid rubber blankets, the surface rubber layer tends to produce convex bulges at the leading edge of the nip line. According to the principle of embossing, the hard rubber is presumed. The cloth does not shrink in its compressed state, so it can only be squeezed on both sides of the nip. However, the use of air-cushion blankets does not appear to create a bulge problem at the leading edge of the nip.

3. The blanket has a smaller elongation. The dense structure of the rubber blanket and its high mechanical strength are conducive to the increase of the tensile strength, and thus reduce the amount of deformation of the graphic transfer.

4. The ink absorption performance and transfer performance are good. To ensure that the printing process, ink color uniformity, clear writing.
5. The rubber cloth is oil-resistant, wear-resistant, heat-resistant, and has good anti-aging properties. It has the above properties and can prolong its service life.

6. With acid, alkali and corrosion resistance. The quality of the blanket is directly related to the quality of the graphic transfer. Although there are many factors involved in the quality of graphic and graphic texts, such as mechanics, plate making, materials, and process control, the quality of blankets is one of the important factors. The blankets are penetrated by gasoline, kerosene, and oil during the printing process. Due to the pressure and the relative friction between the drum and the drum, cyclic stretching and squeezing deformation, the blanket becomes sticky, deformed, and lacks good elasticity due to sulfur loss, thereby affecting the transfer quality, in this case , you have to replace the old blanket.

Third, when installing blankets should pay attention to the problem

1. When installing the blanket, pay special attention to the liner can not have any wrinkles. Under normal circumstances, blanket + felt it + paper; or blanket + worsted wool + paper. Felt, worsted wool, paper, etc., lining materials, do not care a little, the shop is not easy to wrinkle.

2. When tensioning the blanket, both sides of the tip and mouth should be carried out at the same time. Do not tighten on one side. Pay attention to safety during operation, avoid inserting the tools and screws into the rollers and rolling off the blanket.

3. The new blanket has good elasticity and good stretchability. Tensile blanket should be gradually stretched and tightened once. After the press of the blanket is pressed for 3~5min, it is tightened again. This can be achieved 2~3 times to achieve the tightening requirement. .

4. Whether the blanket and its cushion is flat, if there is ink or paper debris in the blanket, bumps will appear. Reinstall the blanket.

5. Before the blanket is installed, the blanket lining thickness of blanket+felt or worsted wool+paper should be accurately measured with a micrometer to hear the four-inch micrometer å—’, å—’, å—’, and å—’. Soft lining: blanket+felt+paper, the lining thickness is: 3.35~3.45mm. Neutral lining: blanket + worsted wool + paper or blanket + paper, lining thickness: 3.20 ~ 3.25mm. Hard lining: Blanket + insulating paper or photo paper, with lining thickness of 3.18-3.20mm.

6. Blanket trimming requires the rectangular shape to be upright. Only the direction of the blanket can be selected as the direction of cutting, tightening, and pulling, in order to obtain the desired effect. The warp and weft directions can be known by observing the cylinder shape of the natural roll. The direction of the wire parallel to the core line of the natural roll should be the weft direction, and the direction perpendicular to the weft direction wire is the longitudinal direction. Mainly based on the blanket back (back) plain weave fabric to determine silk.

7. The liner of the rubber blanket lining should be shorter than the rubber blanket so as to prevent the water from infiltrating the paper fibers from swell and deformation and reduce the rust of the drum.

8. Blanket is a kind of elastic body. It will produce elongation after stress during the whole process of clamping, transmission and imprinting. In order to relatively accurately transfer the image size on the printing plate to the paper, the blanket is required to have a low elongation during the entire printing process and must be uniform. The above-mentioned elongation is related to the quality of the blanket itself, and depends on the degree of tightness of the blanket on the drum. The tighter the blanket is, the better it is? This is certainly not the case in practice. The blanket must be stretched tightly and properly. 1 The tighter the blanket is stretched, the lower the elongation during the printing process, and the smaller the size of the graphic. However, if the skin cloth is stretched too tightly, the amount of friction on the plate increases and the plate life decreases. 2 If the blanket is stretched too loosely, then the expansion and contraction rate of the blanket will increase, and the amount of friction on the layout will decrease, which will easily lead to double printing (ghosting).