Analysis of PS plate failure in printing production
I. the virtual printing plate image and text
the virtual printing plate image and text problem in actual printing is mainly caused by the plate making operation, and there are many reasons. According to the reasons, it is divided into the following categories:
1. The virtual printing plate caused by dirt
reasons: January to August this year ① there are foreign matters or dirt attached to the glass of the plate printer, the plate printing film, the mosaic film base, and the plate printing plate; ② There are foreign matters (such as hair) between the printing plate and the film, so that the original strength of the composite material can be fully utilized; ③ If the printing time is too long, the printing glass and film will generate static electricity and absorb dust during printing; ④ There are many defects such as drug spots and white spots on the surface of PS plate
2. False version caused by printing film
reasons: ① insufficient density of printing film (should be above 3.5); ② The haze of the mosaic base is too high; ③ The film round plate is not pasted properly, the edge left outside the picture is too narrow (it should be more than 3cm away), and the patchwork is too crowded (0.5-1mm), resulting in arch collision, etc; ④ The transparent tape of the mosaic film is too thick from the image titanium (it should be more than 7mm away) or pasted; ⑤ Put the film upside down when printing
3. Virtual version caused by insufficient vacuum pumping
reasons: ① poor performance of vacuum pump; ② The sealing rubber ring and air pipe of the printing machine leak; ③ Aging and deformation of sealing rubber ring; ④ The rubber air cushion of the printing machine is not leveled or aged; ⑤ There is a problem with the vacuum pumping indicator, and the pointer is at the end but the actual pumping is not solid; ⑥ The film or PS version has creases, etc; ⑦ When Newton's rings, large air retention areas, dust and debris are found, secondary air extraction shall be carried out in time
4. False version caused by overexposure and development
reasons: ① too long exposure time; ② Before exposure (during punching) or after exposure, run light before development; ③ The developer temperature is too high and the concentration is too high; ④ Development time is too long; ⑤ Excessive developer replenishment
II. Dirty on the plate
1. Dirty on the non graphic part caused by plate material factors
① dirty on the non graphic part caused by too shallow sand mesh on the PS plate base and low water storage. Solution: when printing with this kind of printing plate, increase the water content of the plate or add an appropriate amount of surfactant in the fountain solution to enhance the hydrophilicity of the non graphic part of the printing plate.
② the oxidation film on the PS plate base is thin and brittle, and cannot bear the friction in printing and be worn off, The sand mesh is exposed and ground flat, and the performance of new water is reduced. Solution: replace the printing plate again.
③ the hole sealing of PS plate is insufficient, and there are still unsealed pores in the plate, which has a large adsorption capacity and is easy to absorb impurities such as dust; Or the pore sealing solution contains calcium particles or other impurity ions, which will produce intolerable salts such as calcium silicate and pollute the layout. Solution: develop with a developer with calcium silicate as the main agent, and seal the printing plate twice at the same time of development.
④ the photosensitive adhesive layer of PS plate is too thick, and the normal exposure time cannot be completely decomposed. The photosensitive adhesive remains on the inner wall of the sand mesh, making the non graphic parts more lipophilic and dirty. Solution: extend the exposure time, Thoroughly decompose the adhesive layer.
2. Dirt caused by PS version fog
due to improper storage of PS version or improper lighting in the printing room, the PS version produces fog, resulting in the hydrophilicity of non graphic parts of the printing plate and dirt.
treatment: keep the PS version away from light and work under a safety lamp when printing.
3 Dirty on printing plate
① dirty on exposure caused by improper operation. It is mainly because there is dirt on the large glass or film of printing plate, which hinders the transmission of light, or there are traces formed by tape and frame on the original film. Solution: before the operation of the former, this part should be checked in detail, repaired or cleaned with detergent; The latter can be removed with a dirt remover when the area is small, and can be treated with a second exposure method when the area is large.
② dirt caused by insufficient exposure. The photosensitive properties of PS plates with different properties are different, so the exposure time is different. The exposure efficiency of the photosensitive adhesive layer gradually decreases with the light irradiation photochemical reaction. When the light source power is insufficient, part of the photosensitive adhesive layer is not completely decomposed, and it will be dirty. Therefore, Each batch of PS plates should measure the exposure, adjust the exposure time in time, and regularly check the effective power of the light source and the stability of the voltage.
③ dirt caused by poor development. It is mainly caused by the fatigue failure of the developer, insufficient concentration, too low temperature of the developer or insufficient development time
④ when preparing the developing solution, the amount of strong alkali such as sodium hydroxide is too much. With the plastic packaging taking an increasing proportion in the packaging industry, the developing solution is too alkaline, corroding the oxidation film of the plate base, exposing the plate base, and the hydrophilic property of the non graphic part of the printing plate decreases and gets dirty. Solution: add an appropriate amount of inhibitors such as potassium chloride or sodium phosphate into the developer
4. Dirty on the altered part
① dirty on the altered part
cause: the altered liquid is deteriorated; There is no moisture in the page when it is altered; Inadequate alteration; The erasure time is too long
solution: it is strictly forbidden to change the printing plate with metamorphic correction fluid, and the correction fluid should be properly stored when not in use
② the non spraying material also has obvious weaknesses, and the surrounding of the modified part is dirty
reason: insufficient exposure or development, and the photosensitive adhesive layer remains; The photosensitive adhesive layer dissolved by the correction fluid remains and adheres around the correction part; Before the land reform and dirt removal of the layout, in order to dry the layout, the revision liquid invaded the surrounding of the alteration department
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