Reasons for ink dots in printed matter (2)

Feb. 10, 2023

One. During the paper transmission process, the contact between the printed sheet and the printed sheet, or between the printed sheet and the machine causes smudging.

Packaging boxes

1. Rubbing between sheets.

①Slow drying due to too thick ink layer;

②Because the surface smoothness of the paper is too high or the absorbency is too poor;

③ Serious ink emulsification leads to slow ink drying;

④When the ink layer is not completely dry, the print accumulation is too high...

The above mentioned are generally after printing, the rubbing between the printed sheets on the delivery table can be avoided by the following methods: when the ink layer is thick, spray powder on the delivery end properly; drying rack (every 1000 - About 2000 sheets, add partitions between the piles of paper, of course, this height can also be changed according to the thickness of the paper); before the ink layer is dry, do not apply a large impact to the surface of the pile of paper (such as the operator sitting on the undried on the pile of paper, using heavy objects to knock on the pile of paper, etc.)

1). In the printing color sequence, try to arrange the full plate in the fourth group of printing, so as to reduce the damage of the printed product.

2). Solid inks should be more fluid than normal. In winter, red dry oil and varnish are used in combination, the ratio is about 8%. This ink is used for printing coated paper and white cardboard. Ordinary paper printing ink can be prepared according to the normal ratio.

3). When replacing the new anti-sticking paper still cannot solve the problem, it is recommended to install 3 to 5 springs with a diameter of about 6mm (circumferential direction) on the delivery drum. It is also possible to replace the wire with a diameter of about 2mm, but the effect is slightly worse.

4). The corresponding part of the non-solid part of the printed product that is in contact with the delivery roller is glued with a small piece of foam plastic with a thickness of 5 mm to increase the distance between the delivery roller and the printed product. If the field version is arranged in the first few groups, the thickness of the foam plastic must be controlled within the range that does not affect the overprint.

5). When using the Manroland four-color machine for printing, the plates are arranged in one or two groups truthfully, and the paper feeder row in the middle will also touch dirty prints due to ink accumulation. As long as it is cleaned frequently, the problem can be solved.

6). Some Manroland machines have only a few delivery rollers on the delivery cylinder. If you often print coated paper, it is best to modify it by referring to the delivery cylinder of the domestic 08 machine, and it is easier to do.

Two. Caused by contact between the printed sheet and the machine.

① Some parts on the machine leak oil. The most common is the oil leakage of the mouthpiece, and the oil leakage under the machine when the paper is passed through the lower part of the machine.

Usually the nozzle oil leakage is very easy to judge, as long as the air pump is cleaned accordingly. In addition, keep the bottom of the machine (especially the multi-color machine with more than two colors) clean, and often clean the support rods on the paper transmission line under the machine, and replace the bent and deformed support rods. Modern imported equipment will have an air cushion on the paper path, so ensuring that the air holes on the air cushion are unobstructed is also an important task for daily maintenance.

② Some parts on the paper path are dirty, or the ink on the printed sheet is rubbed by some machine parts on the paper path.

It is more typical for some printing machines of the hem type, such as HDB CD102, when the printed sheet is turned over and printed before it is dry, it is easy to appear. ) rub dirty. In this case, there is generally no good way, only to wait for the printed matter to dry completely before printing.

In multi-color printing, it is not only necessary to check the ink color printed on the front side of the sample, but also to check whether there is dirty ink on the back side. If found, solve the problem in time.

③ There is a pattern on the position where the ball pulled by the side gauge falls. When printing is turned over, the pattern is transferred between the printed sheets by the small ball on the side gauge.

When an experienced master prints some printed matter, he often checks whether the graphics (front and back) on the ruled edge of the paper will be hit by the small ball on the rule. If possible, try to adjust the printing according to the operating equipment The location of the version is avoided.