Pressure Regulation of Printing Machine when Paper Thickness Changes
Pubdate:2018-12-03 09:29:59 Hits:5363
Pressure Regulation of Printing Machine when Paper Thickness Changes
When the thickness of the label printer changes, there are two main changes:
First, the pressure between the rubber drum and the embossing drum has changed, and the original pressure state can not be maintained. When the paper is thinner and thicker, the pressure between the rubber drum and the embossing drum increases; when the paper is thinner, the pressure between the rubber drum and the embossing drum decreases.
Secondly, the size of the image and text (the length of the impression) printed on the impression has changed. When the paper is thinner and thicker, the length of the image and text obtained by the embossing drum is relatively elongated; when the paper is thinner, the length of the image and text obtained by the embossing drum is relatively reduced.
In order to adjust the printing press more accurately when the paper thickness changes, we first understand the adjustment of printing pressure and the relationship between the radius of two drums and the size of the picture and text.
1. Drum pressure
Lithographic offset printing process is to transfer the ink on the plate to the rubber cloth first, and then from the rubber to the substrate. In this transfer process, the surface of the plate drum must be fully contacted with the rubber drum, the rubber drum and the impression drum (printing material). That is to say, there must be a certain contact pressure between the contact surfaces, so that the ink can be fully transferred between them. This contact pressure is the printing pressure. Drum pressure: The interaction between impressions in the printing process.
Printing pressure is the primary condition for lithographic offset printing. Whether the pressure between cylinders is ideal or not is the key to ensure printing quality. Ideal printing pressure is to minimize the printing pressure between cylinders as much as possible on the basis of ensuring good ink transfer (i.e., ensuring that the printed matter is solid, dots are full but not stretched, and tone levels are clear and abundant). It is one of the important indicators to measure the level of technical level and the important condition to ensure high quality and high yield whether the pressure can be low (even if the ideal pressure is used).
Printing pressure too large or too small has a great impact on product quality. Excessive pressure can easily cause dot distortion, paste plate, heavy ink color of products, even image distortion, etc. Excessive pressure can also accelerate plate wear and machine wear; Excessive pressure can cause insufficient or unstable ink transfer, resulting in imprint void, light ink, unclear image outline, inconsistent ink depth and so on.
Method of adjusting printing pressure in actual production:
The printing pressure can be adjusted by adjusting the center distance of the drum.
(2) The printing pressure can be adjusted by adjusting the thickness of the lining (printing plate drum, rubber drum lining).
Note: The center distance is related to the meshing condition of the drum gears. It should be adjusted according to the actual needs of printing process. It is not suitable for regular adjustment. It must be adjusted within the scope indicated by the machine operation and the pressure on both sides must be ensured to be the same.
2. The relationship between the radius of three drums and the size of pictures and texts
General offset press three drum transmission: by three teeth, modulus, spiral angle of the same gear meshing transmission. Therefore, no matter whether the radius of the two drums is equal or not, the angular velocity of the three drums is completely equal.
Ideally, the radius of the cylinder after lining should be equal to the linear velocity of the surface of the cylinder in the printing process, keep the rolling without slip between the cylinders, ensure the accurate coincidence of the particles between the printing surfaces after each operation, and ensure that the dots are not deformed or duplicated. If the three drums are rigid bodies, as long as the radius of the three drums is equal, the surface linear velocity of the three drums can be guaranteed to be equal.
However, the radius of the three drums is different when the material of the three drums is different. In order to keep pure rolling and no slip, the radius of the rubber drum liner should be less than that of the plate drum and the impression drum, which should be equal to the pitch radius in principle.
In order to study the relationship between the radius of three drums and the size of pictures and texts conveniently, we regard all three drums as rigid bodies. Assuming that the area of pictures and texts occupies 180o after the plate is installed, we will study the following situation now:
(1) If the running diameter of the plate drum and the impression drum is equal, and the rubber drum is relatively small (or larger), because the angular velocity is equal, the other two drums also turn 180o when the plate is rotated l80o, that is, the graphic area occupies the same position of 180o on the impression drum. Because the running diameter of the rubber drum and the impression drum is equal, the surface of the plate drum is equal to that of the impression drum. The impression length on the surface of the embossing drum is equal (there is no change in the picture and text).
Conclusion: When the elastic deformation of the rubber drum is neglected, the diameter of the rubber drum does not affect the print length, but affects the printing quality.
(2) If the diameter of the impression drum is smaller than that of the plate drum, then when the plate drum is turned 180o, the other two drums also turn l80o, that is, the area of the image and text occupies the same position of 180o on the impression drum. Because the diameter of the impression drum is smaller than that of the plate drum, the actual length of the image and text obtained by the impression drum is relatively reduced (the figure and text are shortened).
Conclusion: When the diameter of the impression cylinder is smaller than that of the plate cylinder, the pictures and texts are shortened.
(3) If the diameter of the impression drum is larger than that of the plate drum, the area of the picture and text occupies the same position of l80o on the impression drum. Because the diameter of the impression drum is larger than that of the plate drum, the actual length of the picture and text obtained by the impression drum is relatively elongated (the picture and text are elongated).
Conclusion: When the diameter of the impression drum is larger than that of the plate drum, the picture and text are elongated.
3. Pressure Regulation of Printing Machine when Paper Thickness Changes
Take paper thickness from thin to thick as an example
If the paper changes slightly from thin to thick, the drawing and text will be extended.
When the thickness of the label printer changes, there are two main changes:
First, the pressure between the rubber drum and the embossing drum has changed, and the original pressure state can not be maintained. When the paper is thinner and thicker, the pressure between the rubber drum and the embossing drum increases; when the paper is thinner, the pressure between the rubber drum and the embossing drum decreases.
Secondly, the size of the image and text (the length of the impression) printed on the impression has changed. When the paper is thinner and thicker, the length of the image and text obtained by the embossing drum is relatively elongated; when the paper is thinner, the length of the image and text obtained by the embossing drum is relatively reduced.
In order to adjust the printing press more accurately when the paper thickness changes, we first understand the adjustment of printing pressure and the relationship between the radius of two drums and the size of the picture and text.
1. Drum pressure
Lithographic offset printing process is to transfer the ink on the plate to the rubber cloth first, and then from the rubber to the substrate. In this transfer process, the surface of the plate drum must be fully contacted with the rubber drum, the rubber drum and the impression drum (printing material). That is to say, there must be a certain contact pressure between the contact surfaces, so that the ink can be fully transferred between them. This contact pressure is the printing pressure. Drum pressure: The interaction between impressions in the printing process.
Printing pressure is the primary condition for lithographic offset printing. Whether the pressure between cylinders is ideal or not is the key to ensure printing quality. Ideal printing pressure is to minimize the printing pressure between cylinders as much as possible on the basis of ensuring good ink transfer (i.e., ensuring that the printed matter is solid, dots are full but not stretched, and tone levels are clear and abundant). It is one of the important indicators to measure the level of technical level and the important condition to ensure high quality and high yield whether the pressure can be low (even if the ideal pressure is used).
Printing pressure too large or too small has a great impact on product quality. Excessive pressure can easily cause dot distortion, paste plate, heavy ink color of products, even image distortion, etc. Excessive pressure can also accelerate plate wear and machine wear; Excessive pressure can cause insufficient or unstable ink transfer, resulting in imprint void, light ink, unclear image outline, inconsistent ink depth and so on.
Method of adjusting printing pressure in actual production:
The printing pressure can be adjusted by adjusting the center distance of the drum.
(2) The printing pressure can be adjusted by adjusting the thickness of the lining (printing plate drum, rubber drum lining).
Note: The center distance is related to the meshing condition of the drum gears. It should be adjusted according to the actual needs of printing process. It is not suitable for regular adjustment. It must be adjusted within the scope indicated by the machine operation and the pressure on both sides must be ensured to be the same.
2. The relationship between the radius of three drums and the size of pictures and texts
General offset press three drum transmission: by three teeth, modulus, spiral angle of the same gear meshing transmission. Therefore, no matter whether the radius of the two drums is equal or not, the angular velocity of the three drums is completely equal.
Ideally, the radius of the cylinder after lining should be equal to the linear velocity of the surface of the cylinder in the printing process, keep the rolling without slip between the cylinders, ensure the accurate coincidence of the particles between the printing surfaces after each operation, and ensure that the dots are not deformed or duplicated. If the three drums are rigid bodies, as long as the radius of the three drums is equal, the surface linear velocity of the three drums can be guaranteed to be equal.
However, the radius of the three drums is different when the material of the three drums is different. In order to keep pure rolling and no slip, the radius of the rubber drum liner should be less than that of the plate drum and the impression drum, which should be equal to the pitch radius in principle.
In order to study the relationship between the radius of three drums and the size of pictures and texts conveniently, we regard all three drums as rigid bodies. Assuming that the area of pictures and texts occupies 180o after the plate is installed, we will study the following situation now:
(1) If the running diameter of the plate drum and the impression drum is equal, and the rubber drum is relatively small (or larger), because the angular velocity is equal, the other two drums also turn 180o when the plate is rotated l80o, that is, the graphic area occupies the same position of 180o on the impression drum. Because the running diameter of the rubber drum and the impression drum is equal, the surface of the plate drum is equal to that of the impression drum. The impression length on the surface of the embossing drum is equal (there is no change in the picture and text).
Conclusion: When the elastic deformation of the rubber drum is neglected, the diameter of the rubber drum does not affect the print length, but affects the printing quality.
(2) If the diameter of the impression drum is smaller than that of the plate drum, then when the plate drum is turned 180o, the other two drums also turn l80o, that is, the area of the image and text occupies the same position of 180o on the impression drum. Because the diameter of the impression drum is smaller than that of the plate drum, the actual length of the image and text obtained by the impression drum is relatively reduced (the figure and text are shortened).
Conclusion: When the diameter of the impression cylinder is smaller than that of the plate cylinder, the pictures and texts are shortened.
(3) If the diameter of the impression drum is larger than that of the plate drum, the area of the picture and text occupies the same position of l80o on the impression drum. Because the diameter of the impression drum is larger than that of the plate drum, the actual length of the picture and text obtained by the impression drum is relatively elongated (the picture and text are elongated).
Conclusion: When the diameter of the impression drum is larger than that of the plate drum, the picture and text are elongated.
3. Pressure Regulation of Printing Machine when Paper Thickness Changes
Take paper thickness from thin to thick as an example
If the paper changes slightly from thin to thick, the drawing and text will be extended.
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