In the offset printing process, a flexible blanket is used as a medium between the printing plate and the substrate to realize the transfer of the graphic and the printing process. Although the stability of the use of the blanket and its expiration date are affected by various factors such as paper, ink, dampening solution, cleaning agent, printing pressure, and printing machine accuracy, if the blanket can be used and maintained properly, the rubber can be extended. The service life of the cloth saves the production cost for the enterprise.
The use of the blanket
1. Cutting of the blanket
On the back of the blanket, there is a sagittal or color line indicating the warp position of the blanket. According to the specification data, the required size is cut so that the warp direction is consistent with the running direction of the drum, and the weft direction is parallel to the magazine. Do not bend when cutting, to ensure that the four corners are right angles. If it is skewed, the blanket will be unevenly stressed, easy to creep or twist, causing deformation of the dots during printing.
2. Measurement of thickness
In order to ensure the printing pressure is unchanged, when replacing the new blanket, the blanket and the liner are measured, and the total thickness of the liner is calculated to meet the printing pressure requirement. On the back side of the blanket, the thickness of the blanket is generally nominal, but the nominal thickness of the low-grade blanket is generally not accurate. It is best to measure the four sides of the blanket to check whether the thickness is consistent, so as to take corresponding measures to remedy. When measuring blankets and liners, it is best to measure them by one person, because when using the micrometer, if the operation method is different, the measurement results will be biased. Since the blanket and the pad are elastically moldable, if the micrometer knob is tightened, the measured data will be inaccurate and a large deviation will occur when calculating the pressure.
3. Blanket installation
When the blanket is installed on the clip, the depth of the blanket inserted into the clip should be the same. After tightening the screws on one of the clips, use a ruler to measure whether the two clips are parallel, and then tighten the second version. Clip the screws. After all the screws are tightened, use a ruler to check whether the two clips are parallel to prevent the position of the blanket from changing during the tightening of the screws.
The newly replaced blanket has different degree of tension due to the type of the pad, so press it for 5-10 minutes and then tighten it again, which can reduce the slack caused by the new blanket under rolling. The tightness of the blanket remains stable for a longer period of time.
4. Adjustment of printing pressure
According to the machine pressure requirements and the above measurement results, the thickness of the lining is correctly calculated, and the thickness of the lining is adjusted at any time according to the change of the thickness of the paper, so that the printing pressure is appropriate. The pressure between the blanket cylinder and the impression cylinder is greater than the pressure between the plate cylinder and the blanket cylinder, generally around 0.05-0.10 mm. If the pressure between the plate cylinder and the blanket cylinder is too large, the clarity of the graphics transferred to the blanket will be reduced, which will not conform to the graphics on the printing plate, and cause the printing plate to wear prematurely and reduce the printing. Version life. If the pressure between the blanket cylinder and the impression cylinder is too large, the dot will be deformed, the image level and tone will be affected, and the paper will be excessively stretched and extended, resulting in inaccurate overprinting. At the same time, it will increase the load on the machine, causing excessive wear on the drum shaft. If this state is maintained for a long time, the printing accuracy of the machine will be reduced.
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