Talking about the daily use and maintenance of the printing equipment rubber roller
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Use of rubber roller
During normal operation, proper pressure and good contact between the rubber rollers should be maintained to ensure the performance of the rubber rollers.
(1) When the rubber roller is installed on the machine, the proper tightness between the roller neck and the bearing should be ensured to avoid sliding or jumping caused by looseness during operation; when disassembling the rubber roller, gently handle it, do not hit the roller neck and The rubber layer is to avoid scratching, bending deformation and damage of the rubber layer. In order to save costs, some customers often require their own bearings. In fact, some models have some small accessories (such as gaskets) between the roller head and the bearing. The function of these accessories is to maintain the dynamic balance of the rubber roller. The rubber roller is better able to express its balanced quality.
(2) The roller neck and bearing of the rubber roller should be kept lubricated at all times, otherwise it will cause the rubber roller shaft to wear and appear gap, which will cause the rubber roller to jump or sway, resulting in uneven printing ink color and causing printing indentation. Long-term non-lubrication will also cause the core to heat up rapidly, causing the rubber to expand due to thermal expansion, which will affect the printing pressure. In addition, the bearings are not reusable, and the removal of the bearings often results in damage to the oil seal and prevents the bearings from slipping smoothly. The outer ring of the bearing is cast iron (harder), the iron core shaft is pig iron (softer), and the bearing will cut the iron core shaft and the wear bearing seat at high speed to cause printing failure.
(3) Correctly adjust the pressure between the roller and the roller, the roller and the plate. We recommend that customers use a special indentation test strip because the pressure of the rubber roller is not proportional to the width of the indentation. After testing, increasing the indentation width by 50% requires an increase of 250% of the pressure; and increasing the indentation width by 100% requires an increase of 725%. If the width of the indentation is too wide, the core shafts at both ends will be subjected to excessive weight, and more power is required to operate the printing press. The rubber roller will be excessively heated, and the adjustment of the ink balance will be more difficult.
When installing a new rubber roller, the spacing must be relaxed because the new rubber roller may be thicker than the old rubber roller. The rubber roller needs to be adjusted up and down and left and right until the entire surface is evenly contacted.
Adjusting the pressure of the rubber roller generally uses 0.15 ~ 0.20mm ink ruler, measuring the pressure of multiple points in the radial direction of the rubber roller to make it uniform, and can also be easily tested with high-strength paper strip. Some models of alcohol water roller because it is differential, its line speed is not the same as the plate roller, this time pay more attention to the pressure adjustment.
Rubber roller cleaning
The roller cleaning products used by current printing manufacturers are roughly divided into two types, one is a conventional cleaning agent, and the other is a new ink cleaning agent.
(1) Traditional cleaning agent
It is generally composed of aliphatic and aromatic hydrocarbons. The cleaning agent has a good cleaning effect on the rubber roller and can dissolve the ink, but the polar material on the ink roller, such as paper powder, paper wool, etc., cannot be thoroughly cleaned. Long-term use will reduce the life of the press, corrode the gel, cause the expansion of the rubber polymer, causing the rubber roll to expand or contract, thus affecting the printing pressure and the transfer of ink and fountain solution. In addition, its low flash point is a flammable substance, which is a fire hazard. It also does not comply with ISO international standards. Volatile substances are anesthetic and can inhibit the central nervous system of humans, which is very likely to cause blood poisoning.
Many manufacturers use a mixture of kerosene and gasoline to clean the rubber roller. This mixed kerosene volatilizes slowly. The long-term retention on the surface of the rubber roller will swell the ink roller rubber layer, causing the rubber roller to change in size, resulting in uneven ink transmission and affecting printing. Quality, the surface of the ink roller is more prone to glaze, can not accurately measure the ink and water delivered, streaks appear during printing (such as: ink bar, water bar, etc.), flat net hair color, color change, rubber hardness change , which affects printing pressure and even shortens the life of the machine.
(2) New ink cleaning agent
It consists of a hydrocarbon with an emulsifier and an anti-corrosion agent and is a safe cleaning agent with a high flash point. It promotes the mixing of water and oil, produces an emulsification effect, and cleans oily and watery dirt. The emulsifier uses the principle of ink emulsification to wrap the surface of the blanket or the rubber roller. In the cleaning process, it must be mixed with water to perform the cleaning action by emulsification. The anti-corrosion agent has the effect of eliminating moisture corrosion and resisting corrosion of the metal roll by moisture. It produces less volatile gas, does not completely evaporate, can hang on the surface of the rubber roller for a long time, in order to maintain the viscosity of the surface of the rubber roller, the cleaning efficiency is higher, the rubber product is not eroded, the usage is reduced, and the storage is safer. .
Use a new ink cleaner to clean the rubber roller, give enough time, usually at a low speed of 4000 ~ 5000 rpm, clean for 3 to 5 minutes; keep the squeegee intact and clean, fully contact with the ink; moderate dosage (flash point The higher the detergent, the more convenient it is).
When cleaning the alcohol water roller, do not use an oil-soluble solvent to wipe the alcohol water roller. Use a special water roller cleaning agent to minimize the amount of ink on the water roller to maintain stable printing. Clean the ink on the alcohol water roller in time. . There are many reasons for the difficulty in cleaning the rubber roller. The ability of the rubber itself to cooperate with the chemical will affect the cleaning effect; the cleaning agent volatilizes slowly, and the operator washes off the cleaning agent when the cleaning agent has not fully functioned, which may cause cleaning difficulties; Some cleaning agents contain volatile, decomposable components such as alcohol, which make cleaning poor.
Daily maintenance and maintenance of rubber rollers
When we visited our customers, we found that there were several problems in the use of rubber rollers, such as surface crystallization, glazing, difficulty in cleaning, dimensional changes in rubber rollers, and glazing maintenance of ink rollers. In response to these phenomena, how to do a full range of rubber roller maintenance and maintenance? We generally recommend customers to do the following: de-calcium maintenance of the ink roller; cleaning and maintenance of the ink roller color change; idle maintenance of the ink roller; softening maintenance of the dead ink; regular gel reduction maintenance; glaze maintenance of the water roller And regular maintenance of the water circulation system.
(1) Crystallization
Crystallization is mainly caused by calcium and magnesium plasma in water systems, ink binders, and paper surface coatings. Although crystallization is almost inevitable, it can be prevented, such as cleaning the rubber roller regularly (once a week), or frequently. Apply calcium oxide crystal remover before paper change printing, then wash it off, and prevent crystallization for about 12 hours without affecting normal water transfer, ink transfer and drying.
(2) Glaze
After the glaze, the surface area of the rubber roller is lost, and the hardness is increased, and the elasticity is lowered, which seriously affects the water transfer performance. When deglazing occurs on the surface of the rubber roller, some manufacturers prefer to clean the surface of the rubber roller with gasoline, and then mix the surface of the roller with a 5% aqueous solution of sodium hydroxide and talc. In this way, although the transferability of the rubber roller is improved on the surface, the surface structure of the rubber roller and the geometrical size of the rubber roller are destroyed. Moreover, since the hardness changes in various parts of the rubber roller due to glazing, the grinding may cause different grinding depths at different positions, thereby affecting the mechanical properties of the rubber roller when it is used again. At the same time, the use of particulate matter grinding, due to manual control can not be precisely controlled, it will also cause size in and out. Especially for alcohol water rollers, some imported models of alcohol water rollers have a certain degree of curvature in the radial direction in order to balance their transfer ability. The surface of the rubber roller is slightly higher in the middle and the ends are slightly lower. Manual or mechanical grinding will destroy this special. Construction, affecting the water balance of the water roller. Therefore, when maintaining the alcohol water roller, a special alcohol cleaning agent should be used, and the water circulation system should be cleaned regularly to ensure the hydrophilicity and transmission capacity of the water roller.
The method of avoiding severe glazing is also frequent treatment and regular maintenance. Use the “water accumulation” or “accumulation cream” to treat the rubber roller without damage to the rubber roller. (Note that the latter must be used after the roller is removed, and after application To stand for 8 to 10 hours and then wash with warm water), we recommend that customers use a special enamel remover, preferably a cleaning agent approved by the printer manufacturer. Cleaning according to the correct method of operation will reduce the problem of crystallization and glazing.
(3) color change
In the case of color change, it is often found that the cleaning of the rubber roller is particularly difficult. In the case of dark to light color or spot color printing, the cleaning agent cannot be deeply cleaned. At this time, you should use a quick-cleaning agent or a color-changing paste to remove residual substances in the inner layer of the gel.
(4) Expansion and contraction
The main reasons for the expansion and contraction of the rubber roller are that the rubber roller has poor solvent resistance and poor heat resistance, and the second is caused by the use of an incorrect cleaning agent. So what is the impact of the size change of the rubber roller?
It can be seen from Tables 1 and 2 that in the case of dimensional changes, the width and pressure of the indentation have undergone large changes, especially the change in pressure is most obvious.
Table 1 The rubber roller expands
Table 2 The rubber roller shrinks
Under normal printing pressure, the oily solvent in the poor quality cleaning agent will enter the rubber and dissolve with the liquid plasticizer, causing the rubber roller to expand. After a period of time, this material will precipitate under the printing pressure. The rubber, which in turn causes the rubber roller to shrink. At the same time, high-speed printing increases the cohesive heat of the rubber, destroying the molecular cross-links, and also changing the size of the rubber roller.
In general, the use of a good rubber compound can improve the solvent resistance and heat resistance of the rubber roller; the use of a new ink cleaning agent can prevent the precipitation of rubber plasticizer; when running an empty car, apply it on the rubber roller of the empty color group. The empty car protection paste can greatly reduce the cohesive heat and prevent the rubber roller from aging too quickly. Try to control the size change of the rubber roller, avoid the physical resistance and chemical resistance change of the rubber roller, prevent the frequent adjustment of the printing pressure, and reduce the waste of paper ink.