04.03.2016
The factors influencing the print result of a printing process, especially in offset printing, are a frequent topic of lively discussion among printing technicians. The focus is usually on the printing press and the respective printing process, as this is where all the components required for printing come together. However, the print result also always reflects the interaction between the operating resources used, the materials, and the operating personnel. This series of articles discusses these influencing factors individually and describes them in detail.
The chart below shows the most important influencing factors, although the climate in the printing room—another influencing factor—is not discussed in detail due to significant regional differences.
Each of these influencing factors has a significant impact on the printing result and is directly related to the other influencing factors.
After discussing the influences of the printing plate, the rubber blanket, and the rollers in the printing unit in the last few issues of Gallus In Touch, this article will take a closer look at the influences of the printing press. On the one hand, there are various requirements for an offset printing press; on the other hand, all components come together in the printing press, e.g., the inks, the printing plates, the substrate, etc. They all have a major influence on the print result.
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The most important requirements for an offset printing press:
The colors printed in the printed materials must be precisely matched. The register must be maintained accurately during continuous printing so that a detailed print image can be printed in the correct position and consistently throughout the entire production run. Register differences can also cause color differences.
Color variations during production must be kept to a minimum. Of all printing processes, offset printing is the most susceptible to color variations. This is due to a wide range of factors that can influence the correct balance between ink and dampening solution during printing. Machine manufacturers do everything possible to keep these variations to a minimum. These include, for example, adjusting the number of rollers in the inking unit (ink reservoir), lateral friction, friction temperature control, etc. All settings in the printing unit must be made very precisely and require regular checking.
The printing elements must not cause any shifting in the print image, i.e., the ink transfer between the plate and blanket cylinders must always take place at the same point. Shifting in the print image also causes tone value increase and color differences in the print image.
The print image must be free of any after-effects that may occur after the ink has been transferred from the rollers to the printing form. The inking unit, the number of application rollers, and the printing form have a major influence on this. In addition, the dampening unit settings and the amount of dampening water supplied play a very important role. Offset printing units usually have adjustment options that eliminate these after-effects or reduce them to an acceptable minimum.
The tone value increase in the printed image should be as low as possible. The smaller it is in the printed material, the greater the printable tone value range. There are a number of things that can be done on the machine to reduce tone value increase. This mainly concerns the correct handling of the printing cylinders, the adjustment of the rollers, and optimal pressure control. Of course, all the materials used, such as inks, printing plates, rubber blankets, and substrates, also play a decisive role: film substrates, for example, have increased tone value increase. Optimal machine conditions are therefore a very important factor in this case.
A streak-free print image is a very high requirement for an offset printing unit. It says a lot about the stability of the offset printing unit and the design of the ink and dampening units.
High reproducibility indicates how quickly (in terms of time and waste) the correct coloration (analogous to the template) of the print image can be achieved or how quickly the same coloration as the first print can be achieved for repeat jobs. Modern printing presses use many automatic support functions for this purpose, e.g., remote control of the ink zones, the inking program, stored ink profiles, ink-water curves, etc.
Many of the above points interact and influence the print image and its quality. The materials used, such as substrate, rubber blanket, printing plate (prepress), inks, and roller materials, must be precisely matched to each other and to the printing process in order to achieve the desired print quality. The entire workflow must be standardized in order to achieve the desired consistent quality for every job. Good, regular maintenance of the printing units is also very important.
04.03.2016
The factors influencing the print result of a printing process, especially in offset printing, are a frequent topic of lively discussion among printing technicians. The focus is usually on the printing press and the respective printing process, as this is where all the components required for printing come together. However, the print result also always reflects the interaction between the operating resources used, the materials, and the operating personnel. This series of articles discusses these influencing factors individually and describes them in detail.
The chart below shows the most important influencing factors, although the climate in the printing room—another influencing factor—is not discussed in detail due to significant regional differences.
Each of these influencing factors has a significant impact on the printing result and is directly related to the other influencing factors.
After discussing the influences of the printing plate, the rubber blanket, and the rollers in the printing unit in the last few issues of Gallus In Touch, this article will take a closer look at the influences of the printing press. On the one hand, there are various requirements for an offset printing press; on the other hand, all components come together in the printing press, e.g., the inks, the printing plates, the substrate, etc. They all have a major influence on the print result.
The most important requirements for an offset printing press:
The colors printed in the printed materials must be precisely matched. The register must be maintained accurately during continuous printing so that a detailed print image can be printed in the correct position and consistently throughout the entire production run. Register differences can also cause color differences.
Color variations during production must be kept to a minimum. Of all printing processes, offset printing is the most susceptible to color variations. This is due to a wide range of factors that can influence the correct balance between ink and dampening solution during printing. Machine manufacturers do everything possible to keep these variations to a minimum. These include, for example, adjusting the number of rollers in the inking unit (ink reservoir), lateral friction, friction temperature control, etc. All settings in the printing unit must be made very precisely and require regular checking.
The printing elements must not cause any shifting in the print image, i.e., the ink transfer between the plate and blanket cylinders must always take place at the same point. Shifting in the print image also causes tone value increase and color differences in the print image.
The print image must be free of any after-effects that may occur after the ink has been transferred from the rollers to the printing form. The inking unit, the number of application rollers, and the printing form have a major influence on this. In addition, the dampening unit settings and the amount of dampening water supplied play a very important role. Offset printing units usually have adjustment options that eliminate these after-effects or reduce them to an acceptable minimum.
The tone value increase in the printed image should be as low as possible. The smaller it is in the printed material, the greater the printable tone value range. There are a number of things that can be done on the machine to reduce tone value increase. This mainly concerns the correct handling of the printing cylinders, the adjustment of the rollers, and optimal pressure control. Of course, all the materials used, such as inks, printing plates, rubber blankets, and substrates, also play a decisive role: film substrates, for example, have increased tone value increase. Optimal machine conditions are therefore a very important factor in this case.
A streak-free print image is a very high requirement for an offset printing unit. It says a lot about the stability of the offset printing unit and the design of the ink and dampening units.
High reproducibility indicates how quickly (in terms of time and waste) the correct coloration (analogous to the template) of the print image can be achieved or how quickly the same coloration as the first print can be achieved for repeat jobs. Modern printing presses use many automatic support functions for this purpose, e.g., remote control of the ink zones, the inking program, stored ink profiles, ink-water curves, etc.
Many of the above points interact and influence the print image and its quality. The materials used, such as substrate, rubber blanket, printing plate (prepress), inks, and roller materials, must be precisely matched to each other and to the printing process in order to achieve the desired print quality. The entire workflow must be standardized in order to achieve the desired consistent quality for every job. Good, regular maintenance of the printing units is also very important.