Positive PS version failure analysis - overexposure

Second, overexposure:

(1) The original graphic is of low density and the graphic is light-transmitting during printing. The exposure time should be appropriately reduced. If the original density is too low, the plate should be remastered so that the density of the original ink reaches 3.0 and the density of the dot center is not less than 2.3.

(2) Exposure time is too long: Use the continuous adjustment of the transmission ash ladder to determine the correct exposure time; make the density above 0.8 and 0.8 above all ink, and the density below 0.35 to dry without ink. (line mark)

(3) Layout light leakage: PS version is not properly preserved, light leakage photolysis, should pay attention to avoid storage.

(4) Exposure unevenness: The aging of the printing machine rubber or the vacuum of the suction machine is low, so that the original version and the PS version are not fully sealed, so that some of the graphic texts are scattered by the light and some of the graphic texts do not absorb ink, and the vacuum should be increased. Degree of vacuum in the 700MM mercury column or change the machine pad can also be in the PS plate under the same size of thin hair it can be.

2, over development:

(1) The concentration of the developer is too high and the alkali is so strong that the photosensitive resin film is dissolved and the oxide film is destroyed. Therefore, it is necessary to properly formulate the developer according to the regulations.

(2) The development time is too long: generally should be controlled at 35 ± 10 seconds (line mark), in the case of a higher density of the original blank part, as much as possible to achieve less exposure. This is because the alkali solution has a strong dissolving and destroying effect on the photosensitive layer and the plate oxide layer, so the developing time should be as small as possible, generally not more than 1 minute.

(3) The developer temperature is too high: generally should be controlled at 22 ± 2 °C, if the temperature is too high, it will dissolve the photosensitive layer and oxide layer. The oxidized conjunctiva reduces the activity and does not absorb ink. The solution is that the gauze can be used for a long period of time back and forth on the layout, which can cause the photosensitive layer to be irritated by air.

4, the protection of plastic acid deterioration, wipe rubber uneven, wipe out the rubber track, causing no ink, should pay attention to uniform coating.

5, improper operation of offset press caused by the text is not inked:

(1) When the blanket is aged, blankets and blankets should be replaced. If the offset press is too light, adjust the pressure.

(2) The offset roller is too light and the roller pressure is too heavy. It should be adjusted properly.

(3) The ink used in the offset press is too thick and poor in fluidity. The ink should be adjusted well.

(4) The dampening syrup is not suitable, and the dampening syrup matching the PS version should be used.

(5) The workshop temperature is too low, the workshop should maintain 20-25 °C.
(to be continued)

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