Relationship between printing roller and printing pressure
in the printing process, in order to ensure the printing ink transfer rate, printing roller must be maintained between the appropriate pressure, that is, printing pressure. If the printing pressure is too small, the ink can not be fully transferred; printing pressure is too large, it is easy to cause dot distortion and distortion, but also to produce a large printing equipment or deformation. Therefore, to ensure the accuracy and stability of printing pressure is to ensure normal printing.
in the printing process, in order to ensure the printing ink transfer rate, printing roller must be maintained between the appropriate pressure, that is, printing pressure. If the printing pressure is too small, the ink can not be fully transferred; printing pressure is too large, it is easy to cause dot distortion and distortion, but also to produce a large printing equipment or deformation. Therefore, the accuracy and the stability of the printing pressure is the key to guarantee the normal printing. In this regard, it is necessary to study the relationship between the printing roller and the printing pressure. Below, the author summarizes the experience in the work, to talk about the design, assembly and printing of the offset press printing roller, the impact and control of the printing press, and share with colleagues.
one, the printing roller pressure regulating mechanism is usually the case, the offset printing press drum center is fixed. In order to adapt to the change of the thickness of the paper, in general, the rubber roller is designed into the double eccentric mechanism, through rotation of the eccentric sleeve to change the central position of the rubber roller, in order to adjust the printing pressure and in eccentric sleeve rotation can achieve rubber drum of sequential engagement and disengagement. To adjust the eccentric sleeve between the plate and blanket pressure plate cylinder.
press roller pressure regulating mechanism has the connecting rod pressure regulating mechanism, the thread adjusting mechanism, the helical gear adjusting mechanism, the pressure regulating mechanism all have the function of self lock. Main form of on-off pressure mechanism of mechanical type pneumatic type, combined pressure is through the connecting rod mechanism of forming a three-point lock, to ensure the stability of the printing pressure.
two, the influence of design and control in the process of the design of offset press printing roller, to deal with the precision and rigidity of the design, which is the accuracy, uniformity and stability of printing pressure plays a decisive role.
& nbsp; & nbsp; & nbsp; 1. Printing drum precision requirements the size precision of the printing roller is generally controlled at level 6, cylindricity error General requirements in & plusmn; 0.01mm and only allows small mid barrel ends with a big, the barrel beat error in & plusmn; 0.01mm, this may ensure the printing pressure uniformity.
the stiffness of the printing roller is the most effective way is to increase the diameter of the cylinder, but this method will increase the volume of equipment, thereby reducing economic benefits, so the power of the printing roller diameter is generally designed as 270mm, 280mm or 300mm, the whole machine of the printing roller diameter is generally designed as 400mm.
it is worth noting that, in order to facilitate the installation of paper teeth, roll rubber and printing plate, should be designed into the rubber roller gap, the shape of the section as shown in figure 1. And a printing plate drum and nano imprint lithography drum, rubber drum in tension when the rubber blanket need to exert great power and blanket will have a positive pressure on the cylinder body, the rubber roller bending deformation, sometimes deformation degree can reach more than 0.15mm, thus affecting the rubber roller dynamic stiffness and accuracy.
however, the user often does not pay attention to these aspects in the inspection equipment, so in the process of printing, it is possible to cause the printing pressure does not meet the requirements, thereby affecting the quality of printed matter. In order to solve the problem, the structure of the rubber roller has been designed (as shown in Figure 2), that is, the rubber roller of the gap is increased by a smaller diameter of the pull shaft, used to balance the internal stress of rubber roller. Proved by practice, the structure of rubber roller tensioning blanket cylinder body without deformation, in order to ensure the dynamic stiffness and precision of the rubber drum.
3 printing roller material and heat treatment of printing roller material is generally gray iron HT300, better material is ductile iron QT450. If the printing drum body surface material strength is insufficient, the rolling surface depression, commonly known as & ldquo; collapse & rdquo;, it will cause uneven printing pressure. In addition, the printing roller to heat treatment to ensure that its long-term use, and no deformation.
4 printing roller of the shoulder iron can be designed to take the pressure impact of the iron can be buffered printing roller gap, to ensure that the stability of printing pressure, to prevent the emergence of printing products and heavy shadow. To ensure that there is contact pressure between the shoulders and iron to play an effective role.
three, the influence of the assembly process and the control of the general situation, the evaluation index of printing pressure is accuracy, stability and uniformity. In the assembly process, the printing roller related control projects will have an impact on the different indicators of printing pressure, so the control project should be controlled to meet the control standards, and then to control the printing pressure. Control items and control standards for the printing roller assembly process, as shown in table 1.
four, the influence and control of the printing press before printing, the printing pressure is adjusted according to the requirements of the printing equipment. Specific should do the following work: according to the thickness of the paper to adjust the gap between the printing roller; adjust the thickness of the lining, and according to the test printing proofs of the flexible adjustment of printing pressure.
& nbsp; & nbsp; & nbsp; of course, effect of printing roller of printing pressure is far more than the above, because of space in this will not repeat them. To really want to achieve printing pressure stability control and precise adjustment, it is not a simple thing to insiders can communicate more experience, the research, the cylinder of offset printing machine design and manufacture to further enhance the level of, to improve the printing quality of the foundation basis.