Blanket and Liner Application Questions in Offset Printing (40-47)

40. Anti-aging blankets should take measures?

Anti-aging measures are to enhance the mechanical properties of the blanket, in the surface layer and inner rubber layer of rubber, add some fillers, softeners and anti-aging agents, etc., to prevent aging or prolong the aging period.

(1) The addition of fillers to rubber, in addition to reducing costs, also lies in improving the mechanical strength;

(2) Adding carbon black in rubber has anti-wear effect;

(3) Add antioxidants such as phenyl-β-aniline to prevent or delay aging;

(4) In addition to pigments in rubber, besides facilitating the observation of the blanket on the printing process, it can also play a role of anti-wear.

41. How to maintain the blanket?

Maintain the blanket, extend the aging period and its life, take the following process measures.

(1) Detergents with strong solubility and fast volatile organic solvents should be used as blankets. Slow evaporation of kerosene or other solvent cleaning rubber, easy to rubber swelling.

(2) When washing the rubber, be sure to wash the ink dry, leaving no residue, to prevent the residual traces of oxide dry and accumulated, so that the surface rubber is smooth, hardened, premature aging.

(3) For severe paper lint removal and powder removal, it is necessary to insist on washing the blanket to prevent the build-up of excessively thick and hardened solids. If the time stamping is too long, the rubber layout will lose its elasticity and cause plastic deformation.

(4) After the blanket is washed, the surface should be rubbed with a mixture of talc and sulphur powder (this is the case when the car is not used after the rubber is washed). On the one hand, the surface can be made dry without stickiness. Through the sulfur powder, it can be slightly restored its elasticity.

(5) After each lot or several products have been printed, or when the machine is down for a long time, the tensioner can be loosened and the blanket can be relaxed to gain the chance of internal stress recovery, so as to prevent the tension from taking too long and being under stress. Stress relaxation occurs under stress. Generally, two blankets can be used interchangeably. The rubber removed is filled with gasoline and lightly polished with pumice powder to wash the aging layer. The sulfur powder is rolled up and stored in a cool place for use.

(6) When tension is applied to the blanket, the force should be slow. It is not appropriate to use excessive force to prevent breakage.

(7) The overprinted paper that has been used should be carefully preserved and should not contain sand inclusions, wrinkles or incomplete or sticky joints. At the same time, look at the car well ahead of time, try not to make skew, try to solve the problem, and prevent the crushed blanket.

(8) When blankets and padding linings are used, they must be leveled without inclusions.

(9) The blanket should not be in contact with electromagnetic, light and chemical agents to prevent aging.

(10) The blanket should be protected from high temperatures and should not be placed close to heat or fire. Low temperatures are also detrimental to the blanket.

(11) The printing pressure between the rollers should not be too large and the best printing pressure should be used.

42. What is the role of the roll liner?

The backing material is the filling material of the printing plate—the cutting amount of the rubber roller when correcting the roller pressure, also called the lining material.

First, to fill in the lack of simple cutting, and to equalize the role of equal roller radius;

Secondly, the padding can increase the mutual squeeze force between the rollers and cause pressure between the rollers to ensure the transfer of graphic ink;

Third, the cushion itself has a certain degree of elasticity and is an auxiliary elastic body that increases the elasticity of the blanket.

43. What are the control range and characteristics of rigid cushions?

Hard liners are also called hard liners or hard pads. It is the rubber roller with a few hard cushions, with less pressure, less flexibility to get the correct transfer of graphic ink. In general, there is almost no auxiliary elasticity of the backing material, which depends only on the elastic printing of the blanket itself. The hard pad control process scope is:

(1) Hard liner = Blanket + liner;

(2) The thickness of the blanket of the blanket is less than 2;

(3) Printing pressure (Extrusion deformation value is generally controlled at about 0.04-0.08mm, the maximum limit is not more than 0.10mm.

The characteristics of the hard lining are: With less printing pressure, it can obtain fullness, fullness, small dot gain value and clear level, better than the printing effect of other wrapping trees. However, the manufacturing accuracy of the printing press, the pressure adjustment, the drum line speed, and the flatness of the printing plate and the blanket, and the process conditions are demanding. Its poor flexibility makes it difficult to control and master. Currently, it is rarely used in China. Some foreign-made small roller high-speed machines or contact rollers use hard pad lining.

Domestic machines do not use hard liners. They just need to carefully adjust the pressure. In the printing process, the paper transport is very normal and cannot be skewed. The paper wrinkles will crush the rubber. The paper will not be clean but it can also crush the blanket. Because the blanket has no elasticity other than it, the compressible buffer The effect is small, the rubber is easy to be damaged; due to the reduced elasticity when the pressure is reduced, the rolling friction between the three-roller bearing and the journal is low, the pressure is large, and it is easy to wear.

44. What are the control range and characteristics of neutral cushions?

Neutral liners are called neutral liners or mid pads. It is a combined package tree with a certain thickness and elasticity of the blanket cylinder, and has elasticity that assists the elasticity of the blanket. The control process range is:

(1)Materials of neutral material=blanket+vinyl rubber+paper

Neutral liner = blanket + blanket + paper

(2) The lining thickness of the blanket cylinder is between 3mm and 3.5mm;

(3) The printing pressure (squeeze deformation value) is generally controlled between 0.15-0.2mm.

Neutral liner due to moderate hardness, printed dots clear, smooth spots, low expansion, due to the flexibility of the choice of lining material is relatively large, generally can be divided into: neutral soft liner and neutral hard liner Pad two. Neutral soft lining, most of them are not used in contact with the pillow, for example, domestic J2108, J2203 lithographic offset printing machine.

Neutral soft: rubber + felt + liner + pressure (0.2mm)

Neutral hard: rubber + clip rubber + liner + pressure (0.15mm)

Neutral hard: rubber + insulation paper + liner + pressure (0.15mm)

45 . What are the control range and characteristics of soft cushions?

Soft tree mats are also called soft linings or cushions. The blanket cylinder uses a thicker tree mat, greater pressure (extrusion deformation value), and greater elasticity to obtain the transfer of the printing ink. The range of cushion control is:

(1) soft pad = blanket + felt it ten liner

= blanket + two thin + liner

(2) The lining thickness of the blanket cylinder is about 4mm or more.

(3) The printing pressure (extrusion deformation value) is controlled between 0.20-0.25mm, and some reach 0.35mm.

This lining method can only be changed to a neutral lining and cannot be changed to a hard lining. The soft lining surface is flexible, large in deformation, and wide in contact with the arc. The level of the worn printing plate is poor, and ink blemishes are not easy to occur. The dots are easy to spread and expand, and the dot shape is not correct. The printing quality is slightly poor. Therefore, the soft lining is more suitable for use on machines that are worn out too much. Soft lining has been seldom applied, and it is generally changed to soft offset medium soft lining and soft neutral neutral lining. The thickness of the rubber lining is controlled between 3.25mm and 3.50mm because of its liner thickness. Large, rough surface paper, printing pressure up to 0.3mm or more, soft neutral neutral lining printing performance secret change fruit, similar to the neutral soft lining.

46. What are the advantages and disadvantages of rigid cushions?

(1) The outlets are clear, bright and clean, and reproducible. It is most appropriate to print fine art reproductions.

(2) The paper surface receives less ink, and the thickness of the ink layer is thinner than that of the soft package. Once it exceeds the allowable thickness, the low-profile part is easy to paste.

(3) The geometric shape of the graphic text changes little, and the increase in the width of the special graphic text is relatively small.

(4) Adding a reduced amount of padding has a greater impact on the degree of graininess of the imprinting pad. It is easier to harden the pad when filling the rubber pad (the edge of the pad has a high and low position, where the pressure is significant, and it is called the hard port on the printed sheet. In this case, there is a transition to gradually thinning the pad edge.

(5) The surface is subject to more friction and the printing plate is not wear-resistant to the detriment of the printing plate. If it is not a multi-layered metal plate or a PS plate, the printing plate is less resistant to printing.

(6) Bucket fountain solution, the original liquid used to increase properly.

(7) It is easy to squash the blanket in case of paper skew, discounts, or multiple sheets.

(8) The flatness of the blanket is required to be high, the pressure is small, and it is difficult to master the printing process.

(9) The requirements for machine accuracy are relatively high, otherwise it is easy to produce partial pastes, strips and other problems of the printing plate.

Visible hard mats are superior to other mats, but demanding.

47. What are the pros and cons of Chinese mattresses?

(1) The outlets are brighter and fuller, the levels are clear and rich, dark outlets are not merged, and high-profile small spots are not lost.

(2) Good ink transfer fracture performance, strong ink application, low ink consumption, and less smear on the back of the ink layer.

(3) The deformation of the blanket is less, the change of the fan shape is less affected by the paper drag, and overprinting is accurate and accurate.

(4) Adding a reduced amount to discuss the effect of mat thickness on the degree of imprinting, and it is not obvious that the shimming rubber plays a hard mouth.

Source: Guanhua Printing Network