Talking about the selection of the pad
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: 860681365@qq.com
Pad selection
What kind of pad is chosen depends on the specific situation, but in the same state, there is an optimal state of choice. Let's analyze this best state.
After the pad is installed, it cannot be allowed to slide forward and backward under the blanket. If it slides, it is likely to cause deformation of the print. How can it not slide relative to each other? The outside of the pad is in contact with the blanket, and the inside is in contact with the roller, so that the two contact faces generate friction that hinders the movement of the pad. When this friction is insufficient, the pad may slide relative to each other. Therefore, in order to prevent it from sliding relative to each other, it is necessary to create a sufficiently large friction force. As mentioned earlier, there are two ways to increase friction:
1 The blanket is placed in a tightly and evenly surrounding surface of the drum, i.e., produces sufficient friction.
2 to maximize the friction coefficient of each contact surface:
a. The surface of the blanket should have as large a roughness as possible (with the guarantee of accuracy);
b. The pad surface should have as large a roughness as possible;
c. The surface of the rubber cylinder body should have the maximum roughness (with the guarantee of accuracy).
The way to achieve the first is to increase the tension of the blanket, so that it produces greater pressure in the contact surface; the key to achieving the second is the choice of materials. From the actual situation, the materials of the blanket and the roller are all determined, especially the roller can not be replaced under normal circumstances, and the surface characteristics of the blanket may vary depending on the manufacturer. What the user can choose is the roughness of the pad surface. From the standpoint of increasing the coefficient of friction, the rougher the surface of the pad, the better. There are two reasons for this requirement:
1 From the point of view of the contact surface, the friction coefficient of the gasket and the blanket contact is much larger than the friction coefficient of the contact with the drum, that is, the possibility of the gasket sliding relative to the surface of the drum is large, and this is eliminated. The possibility is only to increase the coefficient of friction.
2 From the inside of the pad, the pad is generally laminated several times, and the contact faces are not allowed to slide relative to each other. The frictional force between them that hinders their relative sliding must be greater than the friction generated by the two outer contact faces (and the blanket, and the roller body). Therefore, the rougher the surface of the pad, the less likely it is to slip relative to each other, and the less the number of layers of the pad, the less likely it is to slip.
In summary, the principle of using the liner is:
1 the friction coefficient is as large as possible, that is, the surface is as rough as possible;
2 the number of layers of the liner is as small as possible;
3 The pad surface should be as flat as possible.
The last point is required by the printing process, otherwise the transfer of the print will be affected. Starting from this principle, we will analyze the selection of three types of liners:
Soft padding: Soft padding is generally made of wool cloth, so the friction coefficient of the surface is absolutely guaranteed. When the pressure is insufficient, the paper can be adjusted with a small amount of paper. In general, the number of layers is small.
Neutral pad: Neutral pad is generally made of rubber cloth plus paper to form a friction coefficient on the surface of the tape is still relatively large. The key issue is the choice of paper. Papers commonly used by printers are: coated paper, newsprint, offset paper, cardboard and kraft paper. The paper jam is inconvenient to use because of its small flexibility. Coated paper has a smooth surface and should not be used. The choices are offset paper, newsprint and kraft paper. These three types of paper surfaces can produce a large coefficient of friction, but from the perspective of the least number of layers, the choice of kraft paper is slightly better. Regardless of which paper is chosen, the third clause of the above principles must be absolutely guaranteed.
The installation method of the gasket is generally placed on the surface of the drum to make it evenly and evenly contacted, and some devices are equipped with a device for clamping the gasket, and the device provides convenience for the installation of the gasket. If the blanket is not tight enough, the paper will pleat forward or backward inside.