High speed rotary gravure printing has the
advantages of high speed and long printing paper path. Once there is a fault,
whether it is to stop the adjustment or start the adjustment, the waste is
amazing in China printing. There are
many reasons for the failure. Firstly, it is affected by the physical and
chemical changes of the ink; secondly, it is affected by the wetting condition
between the printing plate and the squeegee; thirdly, it is affected by the
physical and chemical properties of the paper surface and the electrostatic
inking system; thirdly, it is also affected by the operation of the machine and
the change of printing environment.
Small text printing plate ink transfer is
not good, there is an obvious lack of pen
It was a summer night, the weather was
sultry, the temperature and humidity in the workshop were very high, and the
relative humidity was close to 100%. In the process of shift change, the paper
breaks suddenly and stops. The next captain connected the paper and then turned
on the machine. After sampling, it was found that the black version of the
small text was light in color, and there was a serious lack of strokes. The
captain lowered the speed of the plane and asked the deputy to wipe the black
plate carefully. After speeding up, the captain took a few more samples and
looked at them, but he was still not satisfied. All the small words were
"blocked".
Generally speaking, the black version of
small text area, small ink consumption, long time does not need to add ink.
With the evaporation of solvent in the ink, the solubility of the ink becomes
poor, and the version is blocked slowly. In addition, the shutdown time was too
long when the shift was over, and the ink in the mesh hole dried up. Dip in the
solvent to wipe the plate, the solvent volatilizes rapidly, takes away the huge
heat, the moisture in the air condenses to the plate, especially in the
environment temperature and humidity is not ideal state performance is
particularly obvious. Ink mixed with water and - solubility is poor, you have
to print out all the ink, clean the plate thoroughly with detergent, and clean
the plate with dry cloth. Redistribute the ink and add a small amount of butyl
acetate into the ink. As soon as the machine is turned on, the speed is
increased to more than 100 meters, and the small text in the black version is
normal.
2. Poor transfer of fine dot in
hierarchical printing of China printing
Whether the ink transfer of fine dot is
normal is the key to the success or failure of printing. This is the second
printing product. The paper used is 230g / m2 white cardboard. When the
printing speed was increased after the printing was started, the captain found
that the fine dot loss was serious and there were too many white dots in the
cyan plate, and the effect of adjusting the ink viscosity was not obvious. The
captain first compared the paper used, and found that the surface of the
printing paper was slightly rough. After the paper roughness reached a certain
degree, it was difficult to transfer the ink from the small mesh holes to the
paper by electrostatic leveling, so there were more white spots in the
highlight part. Then the captain looked at the cyan printing unit and found
that the embossing roller was not an electrostatic inking roller. Then, the
whole electrostatic ink leveling system was checked comprehensively. He found
that the brush had agglomerated, and the brush in some places could not contact
the electrostatic roller. So he took the brush down and cleaned it, checked
whether the electrostatic generator was normal, replaced the non-static inking
roller and replaced the paper. Everything is ready, adjust the ink viscosity,
turn on again, speed up to more than 100 meters, small dot transfer normal,
white dot also disappeared in process of China printing.
3. How can a good overprint version
suddenly run away
Printing registration stability is
maintained by tension control system and cursor tracking. The printing status
of cursor has a great influence on the stability of overprint. In addition,
printing pressure, drying temperature, ambient temperature and humidity also
have great influence on the stability of overprint in China
printing.
This is a transition period from summer to
autumn. It is still very hot during the day and cool at night. In addition, the
humidity is greatly reduced after a gust of north wind. This time, the printing
on the machine is 80 g / m2 wide coated paper, and the product is beer label.
The thinnest part of multi position typesetting is only half line (about
0.15mm). After the handover, the captain found that the middle group of
printing units had run out of print, so he adjusted the overprint deviation in
a hurry, but there was no response. The captain checked the unwinding tension,
winding tension and the tension between the printing units, and found no
abnormal tension.
Later, when checking the cursor of the
printing sample sheet, it was found that the cursor imprinting of a printing
unit in the middle was not real, and half of the front part of the cursor was
dry. In this way, there was an error in the cursor signal read out, followed by
the cursor errors in turn, so that the plate was run out.
