01. Paper fluffing, off powder reasons and solutions
Paper surface strength has a greater impact on offset printing, offset printing paper surface strength is too low in the printing process is prone to printing sheet hair, powder, paper sticky rubber phenomenon. But the paper caused by a variety of factors, and sometimes a combination of factors, the main reasons are as follows.
① paper surface strength is too low
② the supply of fountain solution is too large
③ ink viscosity is too high or the workshop temperature is too low
④ printing speed is too high.
In the actual printing process from the paper off the fiber, paint particles, etc. and ink mixed together on the rubber blanket, then the rubber blanket pile of ink failure. Pile of ink first make the image becomes coarse, serious when prematurely make the printing plate wear occurs in the blank at the paste version of the text at the drop of the phenomenon (but this pile of ink problem is different from the simple pile of ink, if the blanket is not paper hair, paper powder, it is a simple pile of ink phenomenon, may be due to insufficient blanket lining thickness, or insufficient printing pressure, the ink can not be well transferred and caused by).
ecause of the factors that cause the paper to fall out of a variety of factors, the corresponding reduction in the paper to fall out of a variety of methods and sometimes multiple methods to use together, the main methods are as follows.
① printing, select the surface strength of high paper. If the paper surface strength is too low, the printing process, paper hair, paper powder was stripped down in large quantities, mixed with the ink piled up on the blanket, triggering the blanket pile of ink failure. If purely to digest unqualified paper, in order to ensure the quality of printing, formal printing can be pressed once before the water or in the printing of fine products before printing a varnish.
② from the process point of view, the first should strictly control the amount of fountain solution, in the case of not paste the plate, not on the dirty to make the minimum amount of water, to prevent the amount of ink due to the amount of water is too large and cause paper sticky rubber failure.
③ appropriate to reduce the viscosity of the ink, to ensure that the ink has good fluidity. Especially in the printing environment is poor, the winter temperature should pay more attention to this problem, the solution is mainly baked ink, adding the right amount of withdrawal of viscous agent or thinner to the ink.
④ appropriate to reduce the printing speed to reduce the stripping tension, to avoid or slow down the paper table off powder, hair phenomenon.
⑤ in multi-color offset printing machine, such as redundant units should be the first unit empty, and select "empty pressure", and to often clean the blanket.
02. Paper stick blanket reasons and solutions
Offset printing large field large amount of ink printing, if the workshop workshop temperature is too low, there may be frequent paper sticky sticky blanket, resulting in the normal start printing phenomenon.
The main reason for the ink viscosity is too large, coupled with the winter workshop temperature is very low, just start when the temperature of the rubber roller is also very low, so it is easy to cause the paper sticky rubber phenomenon.
It is recommended to bake the ink first, so that the ink becomes soft, viscosity correspondingly reduced, and then add more dry oil (for ordinary ink) to thin the ink, so that the ink viscosity and then reduce the normal start-up temperature of the rubber roller will slowly rise, the ink viscosity is correspondingly reduced, so that the normal printing.
It should be noted that, although you can add the withdrawal of viscous agent to reduce the ink viscosity, but the withdrawal of too much viscous agent will create the back of the stacked color register can not be printed; you can also add thinner to reduce the ink viscosity, but too much thinner will affect the ink layer drying, especially in the case of very low temperatures in winter. Therefore, here I suggest adding dry oil to reduce the ink viscosity.
In addition, to avoid the phenomenon of paper sticky rubber, in addition to the above methods can also take the following measures.
① appropriate to improve the workshop environment temperature, when the ambient temperature increases, the ink viscosity will be relatively lower.
② in the case of ensuring uniform printing pressure, appropriate to reduce the printing pressure.
③In the formal printing before the equipment according to the normal printing speed idle for a period of time, in order to make the rubber roller in the high-speed friction process of rapid warming, so as to achieve the purpose of reducing the ink viscosity (ink in the process of roller movement under the action of shear stress will also be reduced viscosity).
④ using the "deep ink thin printing" method, the appropriate ink color deeper, in the case of ensuring the color phase and the same as the original sample to properly reduce the thickness of the printing ink layer.
