How much is the packaging offset? (198-209)

198. What is the point pressure, total pressure, line pressure, surface pressure?

Offset printing due to the use of round pressure round embossing method, the embossing surface of the rubber roller blanket lining the compression of different, the resulting pressure is also different, a little pressure on the embossed surface is called point pressure. The sum of the pressure on each point on the embossing surface is called the total pressure. Because the imprinted embossing surface is longer in the axial direction and the circumferential arc length is shorter, if the embossing surface is considered as an axial straight line, the average pressure in this direction is called line pressure and the unit is usually expressed in kg/cm. The total pressure on the embossing surface is divided by the embossed area, which is called the average pressure. The unit is usually expressed in kg/cm2. It is the most commonly used method for expressing pressure at home and abroad.

199. What is the maximum amount of compression?

After the offset press is pressed, the rubber roller is mainly compressed and deformed. In the circumferential direction of the embossing surface, the blanket cylinder is concaved in an arc, and the maximum value of the depression is the maximum amount of compression, which is denoted as λ, and is a method commonly used in offset printing to indirectly indicate the printing pressure, and the unit is mm.

200. What is the width of the embossing surface?

The width of the embossing surface is the arc length in the circumferential direction of the embossing surface, denoted as b, and the unit is mm.

201. What is the role of printing pressure?

1 Because of mechanical manufacturing accuracy errors and the rough surface of the paper, blanket, and plate surface, a certain pressure must be applied to make the printing surface completely contact to complete ink transfer.
2 The printing pressure makes the ink be pressed into the fiber gap on the surface of the paper quickly and forcibly, which is beneficial to the fixing and drying of the ink on the paper.

202. What is the material of the plate cylinder liner?

It is usually a paper or hard plastic film, which has a large elastic modulus, a thin thickness, and little auxiliary elasticity.

203. The blanket lining is usually divided into several types?

The blanket lining method of the blanket cylinder does not strictly distinguish the boundary, and can generally be divided into three kinds, namely: rigid liner, neutral liner and soft liner.

204. What is a hard liner? What are the characteristics?

Hard lining means that the lining on the squeegee consists only of blanket and backing paper. The elastic modulus of the backing paper is large, and elastic deformation mainly occurs in the blanket itself. The maximum compression of the hard liner is small (usually less than 0.1mm), the width of the embossing surface is small, the maximum point pressure is large, and the dot reproducibility is good, but the manufacturing precision and the printing process of the printing press are demanding, otherwise the ink sticks are prone to occur.

205. What is a soft lining? What are the characteristics?

Soft lining means that the lining on the squeegee consists of a blanket with a softer liner (usually wool, felt, and liner). The maximum amount of compression of the soft liner during printing is large (about 0.20 to 0.25 mm), but because of its small elastic modulus, the maximum point pressure is small, and the width of the embossed surface is large. The use of a soft lining makes it easy to expand the layout of the outlets, affecting the reproduction and sharpness of the gradation. However, it requires less mechanical precision and is less prone to ink bars.

206. What is a neutral lining? What are the characteristics?

Neutral lining means a lining with an elastic modulus between the rigid lining and the soft lining, usually consisting of a blanket plus a rubber pad and a backing paper that are specially used as a bottom lining. Its maximum compression is generally controlled at 0.15-0.20mm, and its dot reproduction performance and mechanical precision requirements are also between rigid liner and flexible liner.

207. What are the commonly used offset blankets?

Divided into ordinary blankets and air blankets two.

208. What is the difference between the structure of ordinary blankets and air-cushioned blankets?
Ordinary blanket is composed of surface rubber layer (synthetic rubber), elastic rubber layer (natural rubber) and cotton cloth skeleton layer. The air-cushion blanket is composed of a surface rubber layer, a microbubble sponge layer (consisting of a myriad of extremely closed air spheres dispersed in the adhesive layer), an elastic adhesive layer, and a cotton cloth skeleton layer.

209. Compared with ordinary blankets, what are the characteristics of air-cushioned blankets?

1 Because the rubber has a volume incompressible characteristic, when the ordinary blanket is pressed, it will be convex around the pressure area. At the same time, since the blanket cylinder is impressed in the axial direction, the blanket protrudes from the front and rear sides of the embossing area, and the convex hull makes the maximum radius (convex) at the circumferential arc of the embossing area and the minimum The difference in radius (the midpoint of the arc) increases, causing an increase in slippage between the blanket cylinder and the plate cylinder and between the blanket cylinder and the impression cylinder, resulting in an increase in the dot size and a decrease in the correctness of graphic and text transfer. After the air-cushion blanket is pressed, the air spheres in the microbubble sponge layer shrink their own volume under the action of pressure, so that the blanket is vertically compressed, and no convex bulges are formed on the front and rear sides of the embossing area, thereby reducing the press gap. The slippage, the correctness of the transfer of images and texts has been improved. For color products with a high number of screens and screens, the use of air-cushioned blankets can reduce the increase in the number of dots, reduce the loss of gradation, and improve the clarity and tone of products and the correctness of color reproduction.
2 Because the elastic recovery of the micro-bubble sponge micro-holes is fast and good, the air-cushion blanket has better sensitivity and elasticity than the ordinary blanket. For products that often require changing specifications, air-cushioned blankets are less prone to uneven plastic deformation due to uneven compression and pressure non-uniformity when printed on other specifications.
3 air cushion rubber has good impact resistance. During printing, due to the existence of a roller gap, vibrations and shocks are generated, which makes it easy for ordinary blankets to produce insufficient pressure due to a large amount of plastic deformation at the ink bars and the rinsing port. Due to the shock absorption and shock absorption of the microbubble sponge layer, the air-cushion blanket is not prone to the phenomenon of insufficient pressure on the ink sticks and fistulas.
4 The air-cushion blanket has high tensile strength and low elongation, and the adhesive layer thinning, elasticity reduction and pressure unevenness caused by stretching are lighter.
5 For high-speed printers, in the case of high frequency of alternating stress, because the internal friction of the air-cushion blanket is smaller than the ordinary blanket, besides being conducive to maintaining the stability of the printing pressure, it can also reduce the speed of aging and prolong The life of the blanket.
However, the price of air-cushion blankets is much higher than that of ordinary blankets, which increases production costs. Only when used on high-speed machines and when using high-quality products such as hard-lining or hard-liner printing, can the air-cushion blankets have the advantages of high image transfer accuracy and good sensitivity and flexibility. If soft liners are used to print common products, there is no need to adopt flexible liner linings because of the large amount of compression, the wide embossing area, and the easy expansion of outlets, which offsets the advantage of high accuracy in the transfer of airborne blankets. Air-cushion blanket.

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