The printing process depends on four factors: operator, printer, substrate, and ink. There are some common problems in different printing processes. These problems are related to the formulation of the ink, the manufacturing process, and the method of testing. Only the ink manufacturer strictly controls the production process of the ink, and applies scientifically to the ink. The determination can reduce the problem of the ink in the process of use, and introduce some issues related to the quality of the printing film that may occur in the printing process.
1. Dirty and dirty backsides Because the ink dries too slowly, the ink is too soft, too thin, and the level of ink is too large, causing the ink on a printed surface to become dirty on the back of the upper sheet.
This phenomenon mostly occurs in the field (or low-key) part where the amount of ink on the print is large. Sticking, sticking, and sticking together (as a saying goes, a piece) is the most serious phenomenon of sticking back, which refers to the situation where printed piles of printed matter are stuck together. The second side of the printing press is the second side immediately after the first side is printed. As a result, the printing becomes sticky.
There are several situations that cause this phenomenon: when there are rough-printed paper, more (thick) ink layers are required to print; double-sided glossy paper and some special substrates (such as cellophane, plastic film) Etc.) When they are stacked, they are easily accessible to each other; in the field and dense dots, the amount of ink is too large; when printed on the non-absorbing paper with oxidative drying ink, it is easy to be dirty; desiccant in the ink When the amount is too much, it is easy to oxidize heat in the paper stack, resulting in the ink sticking and making it sticky; the ink is cut when it is not ideally dried, it will cause many ink small stains to be pulled out. Misplaced (taken) misplaced and so on.
The solution is: as long as the printing requirements are met, the smaller the amount of ink on the plate, the better. Use coarser pressure on rough paper, so that it can print more ink, but not too much, so as not to cause the rubbing of the back of another sheet of paper due to protrusions and sticky. A thicker ink should be used, but it should not be too thick so as not to cause pulling of the paper. If you use a new type of ink, you can make a corresponding decision by first printing it out and studying its stickiness. Check if the ink fountain is adjusted properly. If it is color printing, the latter ink should be added with more desiccant than the one printed before to shorten the drying time. Use quick-drying inks instead of general inks, such as wet-curing inks. In the case of paper smooth and poor absorption, using a high concentration of ink can reduce the amount of ink used. This wax or other anti-adhesion agent can also be added to the ink.
2. Flying ink The so-called flying ink (also known as ink flying color) refers to the phenomenon that very small ink particles “fly†out of the operating press. The flying ink particles are drifting. These particles are electrically charged. When the climate is dry, they fly closer. If the ink is placed on a roller that rotates at a high speed, it will never throw (dump) the ink due to centrifugal force. However, when the roller comes in contact with the other roller, flying ink will occur. This is due to the fact that when the ink is transferred, the filaments are drawn between the two rollers, and when the filament breaks, a multi-phase (phase) fracture is formed, except that part of the contraction (extraction) is returned to the roller, and the rest is due to the surface tension. The relationship formed a small droplet and was driven out by the printing press. Drops of ink that fly out can both positively and negatively charge. Due to the splitting of the electric double layer occurring in the ink, the formed small particles can have a single charge. The shrunk (extracted) portion of the broken ink tip (ie, the portion retracted onto the roller and printed on the paper) is also charged. At this point, the charged ink droplets will repel the roller with the same charge and move away from the roller. A study of the charged ink droplets under a microscope revealed that the carbon ink migrated. One was the migration to the periphery of the ink droplets; the other was the migration to the center of the ink droplets. Since the carbon ink particles are always charged, if the ink droplets have an excessive surface charge, the carbon black will undergo electrophoresis, and the ejected ink droplets will easily repel each other and fly away.
Between the two rollers, there are voids, bubbles, etc. which can promote ink flying. The printing speed is fast. Too much ink is given. The relative humidity of the workshop is too low, the temperature is too high, the dielectric constant of the ink is too low, and the air flow influences. Can also cause flying ink.
The solution is: Add a cover as much as possible outside the uniform roller and the transfer roller of the printing press; increase the humidity of the printing room; reduce the speed of the printing press; reduce the amount of ink to be supplied, so that the ink on the roller is as small as possible. Naturally, high-concentration inks should be used; papers with poor surface-absorption properties (the purpose is to reduce the amount of ink supplied); the temperature of the printing room can be lowered; or the press can be equipped with a cooling device; the possibility of all air flow can be eliminated; Ink, because of its conductivity, which can also increase the dielectric constant of the ink, generally speaking, the ink contains 5% of the water, its conductivity is still very low; with anti-adhesive dirty agent to make the ink shorter; Add more viscous binders to inks; for press inks, use good wettability carbon blacks and mineral oils, and use long-chain amines as flow agents; 0.5% inks Glyceryl monostearate or ricinolein alone or with a small amount of defoamer; a mechanical device on the rollers of the machine, such as the use of low-pressure air to blow the particles back out and so on.
3. No ink and ink release roller When the ink in the ink content is too high; ink is too thick, the yield value is too large; ink is too short to become cheese, the ink does not turn with the ink fountain roller, will result in prints lighter and different shades . Offset ink is too emulsified by the fountain solution, causing the ink to lose its interlocking effect; the water is too large; the syrup is too acidic and wets the metal roll.
The solution is: add thin or medium viscosity of the link material to make the ink longer; add a small amount of wetting agent, such as zinc naphthenate, calcium naphthalate, etc.; reduce the amount of fountain solution for the offset printing process; reduce the dampening solution syrup Concentration; In the offset printing ink, add a large and long (that is, good fluidity) of the link material or withdrawal agent.
4. Pull the paper (hair)
In general, the separation in the paper-ink-printing system occurs in the ink film close to the printing plate. If the separation takes place on paper, the surface of the paper will be broken by pull (pull) force. Because the ink is too tacky, the adhesion between the paper and the ink is greater than the adhesion of the coating and the fibers on the surface of the paper. The pulling of the paper or the speed of the machine can also result in pulling.
The solution is: to increase the temperature of the printing shop, or to make the printing press idle for a certain period of time to allow the rollers to preheat; to reduce the viscosity of the ink and to properly remove some, but not excessive, so as not to lose the concentration and hiding power; reduce the printing speed, Therefore, reducing the degree of brushing is directly proportional to the reduction of the separation ratio of the ink film; the use of high-quality coated paper; the ink should be clean, no skin, no particles; check the viscosity, dryness, and fluidity of the ink.
5. There are many ink stains in the non-graphic area of ​​the pasted printed matter. The printed characters such as "mouth", "goods", "crystal", etc. are filled with ink into a solid shape, or the dots are connected into one piece. This phenomenon is due to: the viscosity of the ink is too large, resulting in the coating of small paper or paper, paper hair, concentrated on the plate or dot; ink in the ink fountain has skin or dry particles; ink dried too fast; The ink is too thin, the ink is squeezed out under pressure under pressure; the paper absorbs too much of the binder, resulting in too much pigment in the ink; the roller has ills or its regulation is poor; the layout is uneven and too high; on the glued paper Use too thick ink. The embossing force of the printing press in the offset printing process may destroy the sensitive film on the printing plate to expose the metal, exposing the metal, and the exposed area is affected by trace surfactants, polar substances, free grease and acid in the fountain solution. , Becomes pro-oil, will absorb ink, resulting in non-image areas of the taint, undermine the quality of printed products; ink yield value is too high; water is too low acidity; version of the amount of water is not enough; Cause this phenomenon.
The solution is: using a dry and reasonable and long ink, if the ink is too thick, you can add some of the more dilute varnish to increase the ink distribution performance; if the paste in a high-profile place, you can reduce the pressure; should be based on Paper to use the right ink; fineness of the ink is better, generally should be 20 ~ 25μm. Add some thick binder in offset printing ink; increase the acidity of fountain solution; increase the amount of water supply; support the content of oil and grease in ink formulation; Potion; use quick-drying resin inks.
6. Shadowing Because the ink penetrates the paper too deeply, the pattern or text printed on the front can be seen on the back of the paper.
The solution is: the use of fast-drying ink, and the ink to be thick and low permeability, the link material used in the ink should also be small permeability; you can add some thick varnish and some desiccant in the ink.
7. Crystallized, vitrified, mirrored, printed on the ink printed uneven, or not printed on the whole; overprinted ink in the next color on the bead-like or very weak print, ink film is very poorly linked, there is Can even wipe it off. The reason is due to the fact that the underneath color ink is too hard to reduce the surface free energy; the previous color is printed and the storage time is too long; the desiccant in the ink is too much and so on.
The solution is: cover with a quick-drying ink containing more solvent, the solvent should be able to immerse and soften the underlying ink film; master the overprinting time, and print the second color as soon as the previous color is printed; In the former color ink is added delay drying auxiliaries, such as petrolatum, lanolin, wax additives, etc.; can use fast drying synthetic resin type binder, in order to reduce the amount of desiccant in the ink.
8. The ink on the powdered product can be wiped off like a dry powder after drying. The reason is due to: a large amount of strong ink in the ink penetrates into the paper, so that the ink loses the adhesive effect; the link material used in the ink is too thin or uses too much non-volatile, non-miscible solvent, and the paper absorbs too fast. Infiltration of the linking material is too deep; the dryness of the ink is too slow and promotes the penetration of the linking material; the quality of the linking material as a binder is too low.
The solution is: to improve the structure and consistency of the link material; use non-reactive resin and linseed oil, mature oil or medium viscosity varnish oil; small amount of varnish or bright oil; ink design When formulating, pigments with relatively low density and high oil absorption are used to replace pigments with relatively high density and small oil absorption, for example, Hansha yellow and benzidine yellow are used instead of chrome yellow.
9. Penetration ink is too thin, oily too much; permeability of the mineral oil is too much or dry too slowly, causing the ink on the print to seep from the paper to the bottom of the paper, and the blot is often brownish oily.
The solution is: to accelerate the dryness of the ink; the ink uses some dry oil or better quality mineral oil; the ink is made (or adjusted) thicker; a small amount of polysiloxane additive can be added to the ink.
10. Stacking ink piled up on the printing press, the pigment was in the form of a powder in a separate state, the dots were pasted, and the colors did not look the same. This is due to poor ink dispersion; the ink used in the relative density of too coarse coarse inorganic pigments; ink film is too thick; ink dilute too much, the linking material is too thin; ink rheological dilatancy performance, so poor distribution; printing pressure Not true, due to poor roller function.
The solution is: check the pressure, roller function and pad lining; give appropriate ink, if the ink is too soft, you can use thicker ink; if the pressure, roller and pad are no problem, you can add some in the ink Viscosity or thin varnish can also be replaced with new ink.
11. The surface of the ink in the bubble ink fountain is covered by a layer of bubbles. The more viscous the ink, the more stable the bubbles. The reason is because the ink is too sticky and the speed of the machine is too fast; the composition of water-based inks with soap components is more likely to happen.
The solution is: add a small amount of solvent to the surface of the ink (do not stir); dilute some ink; add defoamer and so on.
12. The printed product is not brightly diluted with excessive ink, the resin precipitates and loses the linking effect; or the ink deteriorates, causing the print to be dull, dark, and not bright.
The solution is: adding a new ink; or adding bright light to the ink; printing a layer of varnish on the print;
1. Dirty and dirty backsides Because the ink dries too slowly, the ink is too soft, too thin, and the level of ink is too large, causing the ink on a printed surface to become dirty on the back of the upper sheet.
This phenomenon mostly occurs in the field (or low-key) part where the amount of ink on the print is large. Sticking, sticking, and sticking together (as a saying goes, a piece) is the most serious phenomenon of sticking back, which refers to the situation where printed piles of printed matter are stuck together. The second side of the printing press is the second side immediately after the first side is printed. As a result, the printing becomes sticky.
There are several situations that cause this phenomenon: when there are rough-printed paper, more (thick) ink layers are required to print; double-sided glossy paper and some special substrates (such as cellophane, plastic film) Etc.) When they are stacked, they are easily accessible to each other; in the field and dense dots, the amount of ink is too large; when printed on the non-absorbing paper with oxidative drying ink, it is easy to be dirty; desiccant in the ink When the amount is too much, it is easy to oxidize heat in the paper stack, resulting in the ink sticking and making it sticky; the ink is cut when it is not ideally dried, it will cause many ink small stains to be pulled out. Misplaced (taken) misplaced and so on.
The solution is: as long as the printing requirements are met, the smaller the amount of ink on the plate, the better. Use coarser pressure on rough paper, so that it can print more ink, but not too much, so as not to cause the rubbing of the back of another sheet of paper due to protrusions and sticky. A thicker ink should be used, but it should not be too thick so as not to cause pulling of the paper. If you use a new type of ink, you can make a corresponding decision by first printing it out and studying its stickiness. Check if the ink fountain is adjusted properly. If it is color printing, the latter ink should be added with more desiccant than the one printed before to shorten the drying time. Use quick-drying inks instead of general inks, such as wet-curing inks. In the case of paper smooth and poor absorption, using a high concentration of ink can reduce the amount of ink used. This wax or other anti-adhesion agent can also be added to the ink.
2. Flying ink The so-called flying ink (also known as ink flying color) refers to the phenomenon that very small ink particles “fly†out of the operating press. The flying ink particles are drifting. These particles are electrically charged. When the climate is dry, they fly closer. If the ink is placed on a roller that rotates at a high speed, it will never throw (dump) the ink due to centrifugal force. However, when the roller comes in contact with the other roller, flying ink will occur. This is due to the fact that when the ink is transferred, the filaments are drawn between the two rollers, and when the filament breaks, a multi-phase (phase) fracture is formed, except that part of the contraction (extraction) is returned to the roller, and the rest is due to the surface tension. The relationship formed a small droplet and was driven out by the printing press. Drops of ink that fly out can both positively and negatively charge. Due to the splitting of the electric double layer occurring in the ink, the formed small particles can have a single charge. The shrunk (extracted) portion of the broken ink tip (ie, the portion retracted onto the roller and printed on the paper) is also charged. At this point, the charged ink droplets will repel the roller with the same charge and move away from the roller. A study of the charged ink droplets under a microscope revealed that the carbon ink migrated. One was the migration to the periphery of the ink droplets; the other was the migration to the center of the ink droplets. Since the carbon ink particles are always charged, if the ink droplets have an excessive surface charge, the carbon black will undergo electrophoresis, and the ejected ink droplets will easily repel each other and fly away.
Between the two rollers, there are voids, bubbles, etc. which can promote ink flying. The printing speed is fast. Too much ink is given. The relative humidity of the workshop is too low, the temperature is too high, the dielectric constant of the ink is too low, and the air flow influences. Can also cause flying ink.
The solution is: Add a cover as much as possible outside the uniform roller and the transfer roller of the printing press; increase the humidity of the printing room; reduce the speed of the printing press; reduce the amount of ink to be supplied, so that the ink on the roller is as small as possible. Naturally, high-concentration inks should be used; papers with poor surface-absorption properties (the purpose is to reduce the amount of ink supplied); the temperature of the printing room can be lowered; or the press can be equipped with a cooling device; the possibility of all air flow can be eliminated; Ink, because of its conductivity, which can also increase the dielectric constant of the ink, generally speaking, the ink contains 5% of the water, its conductivity is still very low; with anti-adhesive dirty agent to make the ink shorter; Add more viscous binders to inks; for press inks, use good wettability carbon blacks and mineral oils, and use long-chain amines as flow agents; 0.5% inks Glyceryl monostearate or ricinolein alone or with a small amount of defoamer; a mechanical device on the rollers of the machine, such as the use of low-pressure air to blow the particles back out and so on.
3. No ink and ink release roller When the ink in the ink content is too high; ink is too thick, the yield value is too large; ink is too short to become cheese, the ink does not turn with the ink fountain roller, will result in prints lighter and different shades . Offset ink is too emulsified by the fountain solution, causing the ink to lose its interlocking effect; the water is too large; the syrup is too acidic and wets the metal roll.
The solution is: add thin or medium viscosity of the link material to make the ink longer; add a small amount of wetting agent, such as zinc naphthenate, calcium naphthalate, etc.; reduce the amount of fountain solution for the offset printing process; reduce the dampening solution syrup Concentration; In the offset printing ink, add a large and long (that is, good fluidity) of the link material or withdrawal agent.
4. Pull the paper (hair)
In general, the separation in the paper-ink-printing system occurs in the ink film close to the printing plate. If the separation takes place on paper, the surface of the paper will be broken by pull (pull) force. Because the ink is too tacky, the adhesion between the paper and the ink is greater than the adhesion of the coating and the fibers on the surface of the paper. The pulling of the paper or the speed of the machine can also result in pulling.
The solution is: to increase the temperature of the printing shop, or to make the printing press idle for a certain period of time to allow the rollers to preheat; to reduce the viscosity of the ink and to properly remove some, but not excessive, so as not to lose the concentration and hiding power; reduce the printing speed, Therefore, reducing the degree of brushing is directly proportional to the reduction of the separation ratio of the ink film; the use of high-quality coated paper; the ink should be clean, no skin, no particles; check the viscosity, dryness, and fluidity of the ink.
5. There are many ink stains in the non-graphic area of ​​the pasted printed matter. The printed characters such as "mouth", "goods", "crystal", etc. are filled with ink into a solid shape, or the dots are connected into one piece. This phenomenon is due to: the viscosity of the ink is too large, resulting in the coating of small paper or paper, paper hair, concentrated on the plate or dot; ink in the ink fountain has skin or dry particles; ink dried too fast; The ink is too thin, the ink is squeezed out under pressure under pressure; the paper absorbs too much of the binder, resulting in too much pigment in the ink; the roller has ills or its regulation is poor; the layout is uneven and too high; on the glued paper Use too thick ink. The embossing force of the printing press in the offset printing process may destroy the sensitive film on the printing plate to expose the metal, exposing the metal, and the exposed area is affected by trace surfactants, polar substances, free grease and acid in the fountain solution. , Becomes pro-oil, will absorb ink, resulting in non-image areas of the taint, undermine the quality of printed products; ink yield value is too high; water is too low acidity; version of the amount of water is not enough; Cause this phenomenon.
The solution is: using a dry and reasonable and long ink, if the ink is too thick, you can add some of the more dilute varnish to increase the ink distribution performance; if the paste in a high-profile place, you can reduce the pressure; should be based on Paper to use the right ink; fineness of the ink is better, generally should be 20 ~ 25μm. Add some thick binder in offset printing ink; increase the acidity of fountain solution; increase the amount of water supply; support the content of oil and grease in ink formulation; Potion; use quick-drying resin inks.
6. Shadowing Because the ink penetrates the paper too deeply, the pattern or text printed on the front can be seen on the back of the paper.
The solution is: the use of fast-drying ink, and the ink to be thick and low permeability, the link material used in the ink should also be small permeability; you can add some thick varnish and some desiccant in the ink.
7. Crystallized, vitrified, mirrored, printed on the ink printed uneven, or not printed on the whole; overprinted ink in the next color on the bead-like or very weak print, ink film is very poorly linked, there is Can even wipe it off. The reason is due to the fact that the underneath color ink is too hard to reduce the surface free energy; the previous color is printed and the storage time is too long; the desiccant in the ink is too much and so on.
The solution is: cover with a quick-drying ink containing more solvent, the solvent should be able to immerse and soften the underlying ink film; master the overprinting time, and print the second color as soon as the previous color is printed; In the former color ink is added delay drying auxiliaries, such as petrolatum, lanolin, wax additives, etc.; can use fast drying synthetic resin type binder, in order to reduce the amount of desiccant in the ink.
8. The ink on the powdered product can be wiped off like a dry powder after drying. The reason is due to: a large amount of strong ink in the ink penetrates into the paper, so that the ink loses the adhesive effect; the link material used in the ink is too thin or uses too much non-volatile, non-miscible solvent, and the paper absorbs too fast. Infiltration of the linking material is too deep; the dryness of the ink is too slow and promotes the penetration of the linking material; the quality of the linking material as a binder is too low.
The solution is: to improve the structure and consistency of the link material; use non-reactive resin and linseed oil, mature oil or medium viscosity varnish oil; small amount of varnish or bright oil; ink design When formulating, pigments with relatively low density and high oil absorption are used to replace pigments with relatively high density and small oil absorption, for example, Hansha yellow and benzidine yellow are used instead of chrome yellow.
9. Penetration ink is too thin, oily too much; permeability of the mineral oil is too much or dry too slowly, causing the ink on the print to seep from the paper to the bottom of the paper, and the blot is often brownish oily.
The solution is: to accelerate the dryness of the ink; the ink uses some dry oil or better quality mineral oil; the ink is made (or adjusted) thicker; a small amount of polysiloxane additive can be added to the ink.
10. Stacking ink piled up on the printing press, the pigment was in the form of a powder in a separate state, the dots were pasted, and the colors did not look the same. This is due to poor ink dispersion; the ink used in the relative density of too coarse coarse inorganic pigments; ink film is too thick; ink dilute too much, the linking material is too thin; ink rheological dilatancy performance, so poor distribution; printing pressure Not true, due to poor roller function.
The solution is: check the pressure, roller function and pad lining; give appropriate ink, if the ink is too soft, you can use thicker ink; if the pressure, roller and pad are no problem, you can add some in the ink Viscosity or thin varnish can also be replaced with new ink.
11. The surface of the ink in the bubble ink fountain is covered by a layer of bubbles. The more viscous the ink, the more stable the bubbles. The reason is because the ink is too sticky and the speed of the machine is too fast; the composition of water-based inks with soap components is more likely to happen.
The solution is: add a small amount of solvent to the surface of the ink (do not stir); dilute some ink; add defoamer and so on.
12. The printed product is not brightly diluted with excessive ink, the resin precipitates and loses the linking effect; or the ink deteriorates, causing the print to be dull, dark, and not bright.
The solution is: adding a new ink; or adding bright light to the ink; printing a layer of varnish on the print;
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