Fault analysis and maintenance of the hottest grav

2022-08-08
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Fault analysis and maintenance of gravure printing process

in the process of gravure printing, we often encounter some process faults. These processes occur not only in the printing process, but also in the pre press production and post-processing fields. The occurrence of these faults often leads to the loss of processing costs, repair costs and raw material costs; The printing operation sequence is chaotic; Efficient production is hindered and costs rise; Unable to provide valuable printing products, leading to the decline of market competitiveness

in gravure printing, the process failure problems are mainly manifested in the following aspects: the composite industry belongs to a niche market

prepress field: incomplete commodity planning; Poor composition of printed matter; Incomplete design; Poor plate making; Poor printing materials, etc

printing field: poor printing effect; Inconsistent hue: inaccurate size; Poor printing adaptability; Poor printing conditions; Inaccurate printing precision; The printing machine is not fully equipped; Poor operation of printing machine; Poor environment in the printing workshop, etc

post press processing: poor lamination; The adaptability of bag making is not good; Poor filling adaptability; Poor post-processing performance (boiling, steam sterilization); Light resistance is small and good; Poor preservation adaptability; Circulation performance is small and good: convenience, poor performance, etc

the following are some common examples of failures in gravure printing

plate fouling, also known as the phenomenon of non pattern part, refers to the phenomenon that the ink leaked through the scraper is transferred to the printing paper, which is a unique fault in gravure printing

the main adverse factors of printing plate pollution are:

1, fast printing speed

2. Printing ink viscosity is hard

3, the dosage of diluent is small

4. Use a lot of solvents other than No. 2 (standard) and No. 3 (slow drying) desiccants

5. The drying of ink is slow

6. The scraper is in a wavy state, the blade protrudes too much, the scraper pressure is too large, and the scraper angle is not accurate

7. Too thin around the master roll

in case of edition pollution, we should analyze and adopt corresponding solutions

1. Reduce the printing speed and the viscosity of the ink to reduce the shear stress:

2. Increase the amount of diluent resin to improve the lubricity

3. Stop the use of ultra fast drying and slow drying solvents, and try to improve the re solubility

4. Improve drying performance

among the above solutions, the first is the most effective strategy. In addition, we should also pay attention to the following matters:

1. The circumference of the version roll should be small

2. Accuracy of scraper setting and grinding angle

3. Excessive force applied to the scraper

in a word, one factor cannot lead to the occurrence of fault, so we should consider various comprehensive factors and summarize comprehensive countermeasures Electrostatic failure is the most difficult phenomenon to explain clearly in most printing failures, especially with the recent emergence of a variety of printing papers and the pursuit of high-speed printing. Static electricity mainly includes friction charge, flow charge, ejection charge, stripping charge, crushing charge, stirring charge and mixed charge, among which friction charge, flow charge and stripping charge are the most important ones related to printing. Compared with other types of work, printing is very easy to generate static electricity. In the future, the research on the Countermeasures of electrostatic barriers will become an important management project

in gravure printing, the main causes of static electricity are:

1, the friction between air and film

2. Friction and peeling of film, guiding fluid and pressing roller

3. Different kinds of membranes have different electrification

4. Due to different types of inks, there are differences in electrification

5. Different environmental conditions lead to different electrification

6. The de energization (ground wire) state of the machine is different, so there are differences

7. The difference of printing speed and electrification

corresponding countermeasures:

1. The angle of the pressing roller to the running state of the printing paper is an obtuse angle to reduce the peeling charge

2. Control the humidity to avoid 50% of the ambient humidity, and control the humidity above 65% to reduce the flow electrification

3. Check the static electricity removal state of the machine to reduce friction electrification

4. Reduce the printing speed to reduce peeling, flow friction and electrification

the most common phenomena in electrostatic faults are "beard", "ink splashing" and "moire". It is necessary to pay attention to the treatment countermeasures of various phenomena

1. Beard

phenomenon: there is beard like ink flying at the acute corners of the boldface, word frame and field printing part of the printed matter

countermeasures: generally, the problem can be solved by increasing the ink viscosity and reducing the printing speed. At present, the addition of electrostatic prevention agent does not improve the host form: as a result of the portal frame structure, we can consider the differential influence of the printing film

2. Ink splashing

phenomenon: fibrous ink flutters at a position a few centimeters away from the pattern

countermeasures: reduce the viscosity of ink, and use the mixed solvent of fast and slow solvent is effective

3. Moire

phenomenon: there is no obvious fog or circle in the field printing part, especially when toluene ink is used

countermeasures: this has nothing to do with the viscosity of the ink and the printing speed. Adding static electricity prevention agent and a small amount of alcohol is particularly effective

scraper, it can be said that more than 70% of the faults in gravure printing occur between the scraper and the plate roller

scraper fault is mainly manifested in:

1. Scraper line

phenomenon: irrelevant long lines appear in printed matter and non line drawing parts

cause: there are striated dirt lines with foreign matters between the scraper and the plate roller, or the scraper is poorly ground and damaged

thin thick lines: there are hard inclusions, causing blade damage; thick thick lines: there are soft inclusions, and double lines appear in the central part of the pattern

countermeasures: filter the ink before and after use; The scraper should be reground or replaced; Filter the circulating pump during use

2. Scraper dust

phenomenon: there are filiform dirt lines in the field and at the end of bold words

cause: there are soft foreign matters accumulated inside the scraper. Due to the transfer of the scraper at the end of the pattern, the foreign matters are omitted, resulting in dirty lines

countermeasures: remove sundries: filter the ink and clean the inside of the scraper; Reduce ink viscosity; When installing the scraper, pay attention to the protruding length of the scraper to avoid being too hard or too soft on the scraper

3. No planned marks

phenomenon: cm high dirt lines are randomly generated in the pattern and non line drawing part of the printed matter

cause: small soft inclusions flow out of the crack between the scraper and the plate roll and produce a dirty shape

countermeasures: ink filtration; Re clean the environment; The width of the plate roller before printing must be reset

in the scraper failure, the inclusion is the most common phenomenon. Thoroughly filtering the ink (150-200 eyes) can prevent the dust in the printing room from mixing. It is also an important link to pay attention to the cleaning of environmental sanitation in the printing room at any time

attached table gravure common fault table

factor relationship (● large, ○ medium, △ small, their capacity is limited, which makes it impossible for the blast furnace and reverberatory furnace to operate at the same time)

no fault name phenomenon human equipment material method environment

1 scratch linear dirt line △△ ○ ●

2 scraper dust pattern with filiform ink at the tail △ - ● △ ○

3 compass scratch rain linear small stains △ - ○ ● ●

4 scraper blade is easy to rust after a period of time `△ - ● - ○

5 viscosity changes after a period of time, viscosity increases △- ● △○

6 ink fault coloration Poor adhesion causes insufficient Gloss - △●●●

7 foaming appears in the ink bucket - △● --

8 peeling is difficult to flow in the ink bucket, There is a dry ink skin △○●△○

9 floating color mixed ink separates in the ink bucket - ○●△ -

10 precipitates on the ink roller, and there are muddy non decomposable substances - ○●△

the hydraulic universal machine does not unload when loading 11 the film-like oil film of non graphic parts is transferred to the printing paper △○○○ △/p>

12 paste fine lines, small text breaks The bad phenomenon of falling off occurs △○●△●

13 the moire has stripes - △○△/p>

14 the ink film has streamline spots with different shades in the shadow part △ - ● - `

15 plus because, like the angle of the screen, there are spots with different shades △ - ●○ -

16 poor color reproduction. The spots in the light color part in overprint printing cannot be reflected correctly, and the operation is poor because they are too thick and too thin. △ - ● ○ ○

17 the text edge is printed with thick ink, the small text becomes thicker, the version text is damaged △ ○ ● -

18 there are whisker like dirt lines around the coloring part of electrostatic barrier, the ink flies out △ ○ ○ ○ ○ ○ ● ● ●

19 residual solvents, residual organic solvents, strong odor, blocking accidents, poor processing of layered laminations and other phenomena △ ● ○ ○

20 the printed matter is uneven because it is multi-faceted printing, up and down, left and right There are differences in the reproducibility of the pattern, especially in the colored part - △ -

the reproducibility of the wear pattern of the 21st edition. The full concentration reflects the insufficient position of the overprint bad pattern △ - ○ -

22, and the bag size reflects the insufficient adhesion of the printed and non printed surface after the caking and winding, Ink falling off △○○△

24 color change the hue of the mixed ink in the residual ink kept in printing changes (mostly in the mixture of white ink) △△● -

25 guide rail falling off (defects) pinhole like ink falling off at the coloring and overlapping parts △●○○○

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