In the offset printing process. To use a flexible blanket as a medium between the plate and the substrate, in order to achieve the transfer of the text. Finish the printing process. Although the stability of the blanket used and its effective period, by the paper, ink, fountain solution. Cleaning agents, printing pressure, printing press accuracy and other factors affect. However, if you can use and maintain the blanket properly, you can extend the life of the blanket for the company to save production costs.
The use of blankets
Blanket cutting
4. A sagittal mark or color line indicates the warp position of the blanket on the back of the blanket. Cut the required size according to the specification data. Make the warp direction the same as the drum running direction. Latitude parallel to the plate. When cutting is not allowed to skew to ensure that the four corners are right-angle if skewed, the blanket will be subject to uneven force easily creep or twist. Causes dot distortion during printing.
2. Measurement of thickness
In order to ensure that the printing pressure is unchanged. When replacing a new blanket. To make measurements on blankets and pads. Calculate the total thickness of the lining to meet the printing pressure requirements. On the back of the blanket. The nominal thickness of the blanket is generally stated. However, the nominal thickness of a typical low-grade blanket is not accurate enough. It is best to measure the four sides of the blanket. Check the consistency of the thickness in order to take appropriate measures to remedy. When measuring blankets and pads. It is best to measure by one person because if you use a micrometer, you have different methods of operation. The result of the measurement will be biased. Because blankets and pads are elastic. So if you screw the micrometer knob hard. The measured data will be inaccurate. Large deviations occur when calculating pressure.
3 blanket installation
When the blanket is installed on the plate. The depth of the blanket inserted into the clamp should be the same after tightening the screws on one clamp. Use a ruler to measure if the two plates are parallel. Then tighten the screws of the second plate clamp. After all the screws are tightened, use a ruler to check if the two plates are parallel. To prevent the position of the blanket from changing during tightening the screw.
Newly replaced blankets due to the type of pad. The degree of tension is different. So first press and print for 5-10 minutes and then tighten it again can weaken the relaxation phenomenon of the new blanket under the rolling action, so that the tightness of the blanket will remain stable for a long time.
4. Adjustment of printing pressure
According to the pressure requirements of the machine and the above measurement results. Correctly calculate the thickness of the lining and adjust the thickness of the lining at any time according to the change of the paper thickness to make the printing pressure suitable. 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 to 0.10 mm.
If the pressure between the plate cylinder and the blanket cylinder is too high, the resolution of the graphic transferred to the blanket will be reduced. Inconsistent with the graphic on the plate. It also causes premature wear of the printing plate and reduces the plate life. If the pressure between the blanket cylinder and the impression cylinder is too large, it will cause the dot deformation. The image hierarchy and tone are affected. Excessive pressure to extend the paper, resulting in overprinting is not allowed. At the same time, it will increase the load on the machine. Causes the roller shaft to wear excessively, if keep this state for a long time, will reduce the printing precision of the machine.
Blanket use matters needing attention
(1) When using a micrometer to measure the blanket and liner thickness, care should be taken when the micrometer screw approaches the blanket and liner. Instead, rotate the force measuring device. After hearing the humming sound, twist three times. The resulting reading is the thickness of the blanket and pad. If you screw the micrometer knob hard. The data obtained will be inaccurate.
(2) Do not mistake the latitude and longitude direction of the blanket when installing the blanket. Generally, there is a marking on the back of the blanket indicating the tightening direction. It can also be judged by hand. The direction of easy stretching is latitudinal, and the direction of easy stretching is longitudinal. Once the direction is wrong. It is not tense when it is taut like a leather cloth. Especially in the use of open or full open blanket retired due to rigid damage reduced to a small open size use. More attention should be paid to its directionality.
(3) When taut the blanket. The power should be moderate. If it is too loose and imprinted. The blanket will be displaced under the effect of the squeeze force and cannot be reset in time. Cause ghosting failure;
If it is too tight, the surface of the blanket will be thinned. Reduced elasticity. It will accelerate the creep and aging of the blanket and shorten its service life.
(4) In storage. Avoid bumping with hard objects during the installation of the blanket.
(5) When cleaning the blanket. To use blanket cleaning agent. When cleaning, prevent the cleaning agent from penetrating into the base cloth of the blanket. Inflate the edge of the blanket.
(6) It is best to prepare two (sets) blankets. A piece (set) for printing large size paper. Another (set) is used to print small size paper. Avoid indentation left on the blanket on the edge of the small size paper to affect the transmission of large-scale graphics and text. Spare blankets should be cleaned. And apply a layer of talcum powder. Avoid light and hang it up or place it flat on a countertop.
The Effect of Blanket Aging on Print Quality
Physical damage to the surface of the blanket can easily detect the impact on the quality of the printed matter. A slight damage to the blanket can be restored by using the recovery fluid. The more serious damage is to use paper to make up the blanket. In addition to hard injuries. After long-term use blanket. On the surface of the glass, vitrification occurs. The surface of the blanket becomes very smooth. The absorption and transfer of ink are impaired. Virtual. flower. This effect of aging on the quality of the product is not easy to find, and often mistakenly assumes that it is under pressure or the plate has problems when the blanket ages. Wipe your fingers on the surface of the blanket. If the finger is slippery, replace the new blanket. If you don't have a new blanket and you have a tight time, you can wipe the blanket with detergent pumice powder until you feel the surface of the blanket is not slippery, so as to ease the vitrification phenomenon, but this is not a long-term solution. Should also replace the new blanket in a timely manner.
Blanket maintenance
The purpose of maintaining the blanket is to scientifically maintain it according to its physical and chemical characteristics. To maintain its stable mechanical properties, chemical properties and printability. Extended service life. Use and maintain the blanket properly. It is the most effective and economical technical measure to delay the aging of the blanket.
(1) Because the blanket has the characteristics of heat aging of light aging. So the rubber
The cloth should be stored away from light. cool. Dry place. And placed vertically or horizontally.
(2) Wash and dry the blanket when cleaning the blanket. No residue. Remnants are easily oxidized and dried on the one hand. To prematurely age the blanket. on the other hand. In the next printing. Remnants are prone to uneven ink at the beginning.
(3) When printing paper that is easy to lose powder. Be diligent in cleaning the blanket. Excessive accumulation of dirt will not only affect product quality. It will also increase the pressure of the rubber layout department. Make more local deformation.
(4) If the downtime is longer, loosen the tensioning device of the blanket. Keep the blanket in a relaxed state. To facilitate its restoration.