Accuracy Analysis of Newspaper Printing

In recent years, China's newspaper industry has developed rapidly. The number of newspapers has mushroomed and caused fierce market competition. Colorful and colorful newspapers have formed a beautiful landscape. However, due to scientific and technological progress, market competition, and aesthetic requirements of readers, the speed of popularization of color newspapers is unexpected. However, the quality of hurriedly printed newspapers is not always satisfactory. Color newspaper printing is based on the printability of offset rotary printing processes, rewind offset presses and newsprint, reels of printing inks, printing plates, blankets, etc., to achieve color newspaper printing in register, color, sharpness, surface conditions, etc. Aspects of quality and technical indicators. In this paper, the paper analyzes the accuracy of newspaper web offset printing accuracy by referring to the experiences of many years of newspaper printing quality control and the combination of printing teaching practice.

In the case of newspapers offset printing, the main factors influencing color newspaper registration include the factors of tape tension, printing unit factors, newsprint factors, fountain solution factors, and printing environment factors.

1 Effect of tape tension on registration

Different types of high-speed newspaper web offset presses have different methods for controlling the tension of the paper, and the paper feeding route between the printing units of the printing press is also different. Judging from the mainstream equipment currently used in domestic color newspaper printing, the following components will affect the tension of the Zhang Band, which will affect the color newspaper register.

1) Braking device

The roll braking system has two major categories of shaft braking (magnetic powder braking, brake shoe braking) and circumferential braking. The dampness, failure of the magnetic powder, wear of the brake pads, the change of the gap between the brake pads and the brake discs, and the leakage of the brake sealed airbags all have a great influence on the stability of the tension of the tape.

2) Floating roller device

The floating roller is an important component to ensure the stability of the printing tape tension during the printing of newspapers. In actual production, when the paper is accompanied by changes such as paper change, parking, etc., if the tension spring fastening at this site, the bearing and the guide rail work well, and the floating roller is sensitive to changes in the paper tape, the paper tape at the time of printing The tension stability is good; conversely, if the tension spring is loose, the bearing is dry and oil is lacking, or the paper fluff or paper powder accumulates on the guide rail, which makes the floating roller unresponsive to the change of the paper tape, the tension stability of the paper tape is poor.

3) Pre-tension unit (pull roller)

In order to achieve the best printing effect, the different parts of the entire printing production line have different requirements for the tension of the tape. Pulling rollers with independent driving capacity are installed in different parts of the machine to control the tension of the paper path to meet each Part of the tension requirement. The function of the pre-tension unit is similar to that of the paper-pass roller. The function is to further control the tension of the paper tape that enters each printing unit during the printing process, compensates for the influence of the paper-path change on the tension of the paper tape, and stabilizes the tension of the paper-sheet of the printing unit. For better printing results. However, the premise of normal work is that each drawing roller itself must rotate well and the overspeed value is set correctly, otherwise it will inevitably affect the tension of the printing unit tapes, resulting in inaccurate overprinting.

4) Adjustment roller

For a shaft-driven printing press, the registration between the printing units can be achieved by adjusting rollers in addition to the axial and circumferential adjustment of the printing plate and the printing cylinder. The adjustment roller is composed of a fixed roller and a cantilever roller. Under the control of the register motor, the cantilever roller can rotate horizontally around the axis of the roller to change the length of the paper between adjacent printing units. Quasi-problem. Therefore, the horizontality of the cantilever roller and its positional stability in the printing process will directly affect the registration between the printing units, and the stability of the tape tension will also be affected.

5) Paper roller

The transfer roller is the guide roller of the printing paper path. The proper setting of the transfer roller in each part of the printing machine can make the way of paper feeding the best, and it is also conducive to the control of the tension of the paper tape. Therefore, it must be ensured that all the feed rollers have the same level, especially the paper transfer rollers of the adjacent printing units must be horizontally consistent, which is an important factor that affects the register.

6) In addition, the bearings of the above types of rollers must be inspected regularly, and if necessary, new bearings should be replaced to eliminate bearing wear and outer ring phenomenon caused by bearing wear, lack of oil, and jamming, so as to ensure that the bearings work well. Avoid overprinting errors due to bearing problems. In addition, newsprint printability, printing pressure, etc. will also affect the stability of the tape tension.