name
phenomenon
the reason
Countermeasure
Poor overprint
In multi-color printing, the ink film is printed on the first printed ink film, and then the ink is repelled, and the second color sticks the first color down, resulting in reverse overprinting.
The ink on the front is not sufficiently dried, the ink on the back is dried too fast, which is caused by the large adhesion during printing, and the general gloss ink is prone to overprinting.
1. Printing plate: (1) The engraved version is more likely to cause malfunction than the corroded version. (2) Increase the depth of the back color version (reverse overprinting occasions). 2. Printing stage: (1) Use quick-drying thinner to make the front ink dry faster. (2) Use a slow-drying thinner to slow the drying of the ink behind, and at the same time reduce the viscosity of the ink without water flow. (3) The position of the scraper of the back color is close to the direction of imprinting, which reduces the imprinting pressure and increases the printing speed.
bubble
Bubbles are generated in the ink tank during printing, the bubbles overflow, hinder the circulation of the ink, and appear mottled or polished, which affects the quality of the printed matter. The previous phenomenon is relatively easy to eliminate, but there are large and many bubbles, and the amount of bubbles is small but it is difficult to eliminate
The ink on the front is not sufficiently dried, and the ink on the back dries too quickly, which is caused by the stickiness during printing. General gloss inks are prone to overprinting
1. Adjust the viscosity of the ink to an appropriate range; 2. Add defoaming agent, but excessive addition will damage the adhesion and complex suitability, pay attention to sometimes there will be a reaction, but it will foam more significantly; 3. Prevent the air in the circulation device from being washed Into the ink; 4. Eliminate the drop of ink in the circulation device and the place where the ink does not flow
mottled
The full version of the printed matter is not smooth, and there are speckles, which reduces the printing effect.
1. The printing speed is slow and the ink drying is slow; 2. The ink is too thin; 3. The ink with large thixotropy is easy to cause mottled impression; 4. The water-based gravure ink has poor wettability to plate roller and paper, and mottled phenomenon is easy to occur; .Electrostatic effect
1. Improve the fluidity of the ink; 2. Use a quick-drying solvent; 3. Increase the printing viscosity within the possible limits; 4. Use pigments with low oil absorption; 5. Reduce the problems caused by static electricity; 6. Select the type of printing plate And screen angle
Block version
The ink in the dots of the printing plate is dry during printing, resulting in the phenomenon of dot defects in the printed matter
1. The ink dries too fast; 2. The resolubilization of the binder in the ink is poor, the ink in the plate roller dots cannot be completely re-dissolved after printing, causing a vicious cycle, and the dust from the paper and film in the printing is mixed into the ink Blocking reasons
1. Use slow drying solvent, but slow drying will affect the post-printing process, it is worth noting; 2. Use a solvent with good solubility
Water absorption deterioration
When printing for a long time, the resin precipitates and gels in the ink, causing gloss deterioration, poor transfer, blockage, etc.
The moisture in the air is slowly mixed into the ink during printing, and the solubility of the ink becomes poor during long-term printing, which is the reason for this phenomenon. Digestive cotton-based inks containing alcohols appear more often, especially in high humidity and small printing area , The ink consumption is easy to cause this phenomenon
1. The ink tank should be well sealed to reduce the area of ​​contact with air; 2. Add a real solvent compatible with water (such as ethyl acetate, cellosolve); 3. Add new ink to avoid the reuse of old ink.
Albino
The ink film is whitened during drying, the gloss of the printed surface, and then the performance such as strength is deteriorated. Once whitening occurs, there is no remedy.
When the ink transferred to the surface of the film is dried, the evaporation balance of the solvent is destroyed, resulting in insolubilization, white turbidity, and partial gelatinization of the resin, which is called resin whitening. At the same time, the solvent volatilizes and absorbs heat during the drying process, the surface of the ink layer is very cold, and the air The water in the ink is mixed into the ink coating to cause gelation, which is called water whitening. Generally, whitening refers to water whitening. The failure mostly occurs in the alcohol-containing digestive cotton ink, which is easy to occur in a high humidity environment.
1. Improve the drying capacity of the printing press; 2. Increase the temperature and humidity of the printing workshop; 3. Reduce the content of alcohol solvents; 4. Add a small amount of slow-drying true solvent (such as cellosolve, butyl acetate)
Crater phenomenon
Crater-like irregularities on the printed surface or varnished surface, causing rough coating and low gloss
This phenomenon is likely to occur in thermosetting varnishes. In the initial stage of drying, the coating is overheated, which causes the surface layer to form a dry film. The lower layer of solvent cannot escape smoothly and break through the surface film, forming a crater phenomenon.
Excessive hot air drying will only dry the surface layer and produce a reverse effect. The temperature of the oven is preferably a "low temperature-high temperature-low temperature" arch distribution. From the perspective of ink and varnish, the use of slow-drying true solvents can make the surface film difficult to form
Stink
Odor is generated during the printing operation, or the printed material is transformed into odor, which causes the operator to feel uncomfortable
The odors of additives and solvents in resins, the odors of acrylic resins or the odors of active agents in pigments are the reasons for this situation. In printing operations, odors that are different from ordinary conditions can cause unpleasantness, such as esters in publication printing Solvents and ketone solvents in packaging printing; the odor of printed matter is caused by residual solvents, film adhesives, and composite resins
1. Do not use odorous binders and plasticizers; 2. Improve the drying ability, use fresh air to blow away the solvent vapor; 3. Use less slow-drying agent; In case of odor, take the printed matter to dry again, ventilate and other remedies Measures
precipitation
Pigment precipitation causes hue changes and can also cause dirty plate jams
1. Pigment precipitation The dispersion of the connecting material is poor, and the pigment agglomerates; 2. The pigment is not sufficiently dispersed (grinding) and precipitation occurs, in this case the precipitation is hard; 3. The viscosity is too low, the connecting material has no retention of the pigment, stirring Poor effect, causing precipitation
1. Use anti-agglomeration agent; 2. Fully disperse the pigment (grind); 3. Use good miscible pigments and binders; 4. Stir the ink in the tank before use
Full back
Ink penetration in printing
1. Large permeability of printing substrate; 2. Low viscosity of ink; 3. Poor drying of ink; 4. Poor ink fluidity
1. Use quick-drying solvent and increase printing speed; 2. Improve printing viscosity; Improve machine's drying ability; 3. Use fluid ink
polishing
The printing surface is polished due to poor ink transfer
1. High viscosity of ink; 2. Poor scraping performance of scraper; 3. Poor ink transfer due to printing plate with wind
1. Reduce ink printing viscosity; 2. Scraper blade extension; 3. Add slow drying solvent; 4. Confirm the hardness of the pressure roller (hard to soft); 5. Blowing can not be directly or indirectly blown onto the printing plate; 6. Position adjustment of mobile exhaust fan for solvent discharge
beard
Short hair-like ink filaments appear around images and text
Occurs when the viscosity is too low, often caused by static electricity
Anti-static: 1. Film humidification; 2. Use anti-static equipment; 3. Use alcohols, methyl ethyl ketone, acetone, etc. as anti-static addition effect is significant, but the addition of such substances makes the ink adhesion strength worse
Then bad
The ink has no adhesion on the printed substrate
1. Wrong type of ink; 2. Insufficient surface treatment of the substrate; 3. Coating of additives, etc .; 4. Film becoming wet; 5. Ink whitening or moisture deterioration; 6. Insufficient heating during printing
Avoid the above situation
Pinhole
Poor ink transfer in the form of pinholes on the printing surface
1. When the ink is poorly wetted to the film; 2. When the ink uses silicone additives, this phenomenon is likely to occur when excessive addition or insufficient dispersion in the ink (due to the improvement of the current substrate, pinhole failure less)
1. Select a solvent suitable for the substrate; 2. Confirm the amount of additives to maintain an appropriate viscosity
Watermark
The solid part of the ink appears mottled, and the ink overflows from the line drawing part
1. When the viscosity of the ink is too low; 2. When the ink has poor fluidity
1. Add original ink or filler to increase the viscosity; 2. Increase the printing speed; 3. Sharpen the angle of the blade of the scraper; 4. Make the plate shallower if the plate is too deep; 5. Improve the fluidity of the ink
spot
The ink transfer of the gravure dots is poor, the dots of the dots appear on the printed matter, the dots are small and the highlights are more, also known as the snowflake phenomenon
1. The surface of the substrate is uneven and has poor contact with the dots of the plate roller; 2. The printing pressure is low; 3. The ink viscosity is high; 4. The ink dries quickly; Blocking or plate abrasion is large
1. Choose a substrate with good smoothness, and use electrostatic ink-absorbing printing on the rough surface substrate, which has a good effect; 2. Increase the printing pressure; 3. Reduce the printing viscosity corresponding to the printing speed; 4. Use a slow-drying solvent to reduce drying Speed; 5. Clean the printing plate, redo the heavy-wearing plate
Sieve phenomenon
Originally the same continuous part of the field appeared a screen-like phenomenon
1. Ink: high viscosity, difficult to enter the printing plate dots; drying too fast, losing fluidity; insufficient ink; 2. Plate roller: poor quality plate roller is eccentric; insufficient chrome plating; excessive blade pressure; insufficient printing pressure
1. Use a slow-drying solvent to adjust the viscosity and drying speed. If the ink is insufficient, adjust the ink tank; 2. Due to the difficulties caused by the plate roller, only the printing plate can be improved; 3. Adjust the pressure of the scraper and the pressure roller
curly
Phenomenon of substrate printing surface curling
1. The thickness of the ink film on the substrate is caused; 2. The solid part is prone to curl, the flexibility of the ink connection material, the thickness of the substrate and the water content will affect the curl phenomenon
1. Add plasticizer to increase the flexibility of the connecting material; 2. Use water vapor to increase the moisture of the printed matter; 3. Apply water, water-glycerin solution and other curling inhibitors on the back of the substrate
Static failure
Static electricity is generated when the plastic composite film passes through the printing machine, which causes printing failures. Filamentous whiskers are generated around the line drawing parts, called "whiskers". Causes of sparks or fire due to discharge to a good conductor
High-resistance materials rub or contact with other objects and generate static electricity when peeled off. Paper and plastic films are poor conductors, and they carry static electricity when passing through the printing machine
1. Improve the indoor air humidity; 2. After printing, make the film inside contact with the destaticizer; 3. The guide roller should also remove static electricity; 4. Increase the printing viscosity of the ink
Ploughing
In the ink overprinting part, when the second color ink is transferred to the dry ink layer of the first color, the first color ink is dissolved again, and a part of it is mixed into the second color ink. Ink using polyamide resin is easy to cause this phenomenon due to the resolubility of polyamide
Occurs due to the viscosity of ink, drying speed, and plate depth
1. The depth of the plate will be improved; 2. The printing stage: a. Increase the viscosity of the second color ink; b. Shorten the drying time: You can use a quick-drying solvent, or increase the printing speed, or blow hot air immediately after printing
Poor registration
In the case of multi-color printing, the printing position is not correct, resulting in misalignment and blanking
When there is a problem in the operation process or the automatic registration device itself has a problem
Check the following items: 1. Operation: Whether the rollers are operating normally; whether the brake adjustment is good; whether the plate is loose; whether the left and right printing pressure, the hardness of the printing roller are good; whether the hot air adjustment is good; whether the substrate is uneven in thickness; 2 .Automatic registration device: whether the switch is inserted well; whether the street position is good; whether the tracking mark is clear, such as bad locator, or whether the substrate is wrinkled, whether it is in the shape of a longitudinal snake; check the magnet and fuse; whether the reflector is dirty
Hue change
The hue of the printed matter changes during printing
1. Ink viscosity change: The change in viscosity causes subtle changes in the transfer rate of the ink and the transfer area of ​​the dots, especially in the case of multi-color printing, which will cause changes in color tone; 2. Changes in room temperature and liquid temperature: temperature changes affect the viscosity of the ink, so that The transition state changes to cause the hue change; 3. In the case of mixed color: the difference in the specific gravity of the organic and inorganic pigments in the pale ink is easy to cause failure, especially in the case of poor ink flow in the ink tank and precipitation; 4. The ink absorbs moisture and deteriorates Resulting in low color: during a long period of printing, the solvent composition of the ink changes, and the moisture of the air is mixed into the ink, which damages the normal color development and reduces the concentration; 5. The dot positions overlap: the screen angles of the first color and the second color are the same In occasions, the dots overlap from the highlight part to the middle part, and the polarization is dark and light, and the color tone changes significantly; 6. Others, such as ink whitening, the layout is blown by the wind will also cause the color tone change.
1. Maintain a fixed printing speed and printing viscosity; 2. Keep a constant temperature and humidity state in the printing workshop; 3. Fully agitate the ink; 4. Use of real solvents is an important factor to eliminate other failures; 5. Plate making; 6. Note Change of PH value of water-based ink; 2. Hue must change under the following conditions, and must be confirmed during the printing operation: 1. Viscosity change; 2. Scraper replacement; 3. Printing speed change; 4. When replenishing ink; 5. Add Solvent.
Sticky back
The phenomenon that the printed product is wound and accumulated, the ink is transferred to the reverse side of the film or sticks to the film
1. Solvent detachment: The solvent composition of the ink has a greater influence (especially slow-drying solvents). In the case of too deep or multi-color overprinting, the absolute amount of solvent volatilization is large, the surface of the ink dries too fast, and the internal solvent does not volatilize. Come out, which leads to the occurrence of sticky back; 2. temperature: the connection material in the ink is softened by heat, and the presence of a small amount of solvent, the softening point of the ink is lower, the ink is in a softened state due to the heating of the oven during winding, this is due to the heat Caused by sticky back; 3. Pressure: It is easy to cause sticky back when the rewinding pressure is large, especially the film with large thermal stretchability, shrinks after rewinding, the pressure of the winding center becomes very large, and it is easy to cause sticky back; and printed matter When the direction of the pattern is the same as the printing direction, the area with ink after winding is thick, resulting in excessive pressure in the area with ink, causing sticking back; 4. Time: too long storage time of the printed matter is easy to cause sticking back; 5, printing substrate ： The base material contains accelerators, slip agents, antistatic agents, antioxidants, stabilizers and other additives that will cause sticking back. The plasticizer is a non-volatile solvent that can migrate to the ink film to soften the film. This problem Hard However, the slip agent and antistatic agent will migrate to the film surface, making the ink adhesion worse and the ink film softened; 6. Contents: spicy materials in food, animal and vegetable oils, plasticizers for fibers, antistatic agents, Textile additives can be transferred into the ink through the film to soften the ink
1. Select the appropriate thinner; 2. The printed matter must be cooled; 3. The rewinding pressure should be small, the rewinding volume, and the stacking weight should be small; 4. Keep the pressure low during long-term storage (such as vertical stacking); 5. The film plasticizer produced in winter has a large amount of plasticizer and cannot be used in summer. Please indicate it in the film name; 6. Before printing, select the appropriate ink according to the packaging and packaging composition
Omission
Similar to Screening, it seems that the printing surface is not smooth when there is insufficient ink
This phenomenon occurs when there is no ink attached to the printing plate for some reasons
1. Use good quality printing plate; 2. Adjust scraper; 3. Increase printing pressure; 4. Adjust ink viscosity, fluidity drying speed; 5. Eliminate ink bubbles; 6. Use proper film; 7. Change the net Screen angle, narrow the screen edge
Dirty guide roller
The printed matter peels off when it rubs against the guide roller or steering rod, leaving a dirty phenomenon on the substrate
1. Poor drying: The ink drying cannot keep up with the printing speed, the ink is attached to the reversing roller, the ink surface is dry, and the internal drying is insufficient. There are many cases caused by the subsequent failure: the subsequent failure leads to poor friction resistance, so the guide The rotation of the roller is poor, and the printing surface is scratched; 3. The cooling roller is incomplete: the cooling water does not flow normally, and the temperature of the heating increases to soften the ink
1. Adjust the drying suitability of the ink. Insufficient heat, and easy to malfunction when the air volume is too large. Use slow-drying solvent; 2. Solve the problem of ink drying suitability; 3. Confirm whether the cooling water and cooling roller rotate normally
Fly ink
During the operation of the printing press, when the ink is transferred from the printing plate to the object to be printed, there is a phenomenon of mist flying. The occurrence of flying ink is due to the electrostatic adsorption of the substrate, forming a spot-like stain on the pattern part, which is different from the beard phenomenon caused by static electricity
1. High-speed printing is easy to happen, packaging gravure printing speed is easy to occur above 150-200m / min, low-speed printing is no problem; 2. Ink with high threadability of the connection material, that is, high-molecular-weight resin ink is easy to occur; 3. Ink It is easy to happen when the printing viscosity is high; 4. The dark part of the version is easy to happen; 5. It is easy to happen under low temperature and low humidity environment
1. Emergency treatment: reduce ink viscosity; increase true solvent; reduce printing speed; 2. change ink type
Dirty roller
In the press roller part, ink accumulation occurs during printing. Poor registration is one of the reasons
The pressure roller is wider than the printed material, and the ink film with a very thin printing plate pattern part is transferred to the pressure roller and slowly piled up, which is different from the transfer to the printed material due to the dirty plate; the affinity of the pressure roller rubber and the ink connection material Strong compatibility and easy to occur (such as chlorinated polyethylene ink), nitrocellulose series with low affinity for pressure roller rubber, polyamide-based ink has almost no such phenomenon, dirty version is the root cause of this phenomenon
1. Adopting the countermeasures of the dirty plate phenomenon, the pressure roller is often dirty due to the imbalance between the left and right; 2. The pressure roller using a material that is resistant to the true solvent of the ink; 3. The portion of the pressure roller that is wider than the printed object is taped On; 4. Make the width of the press roller and the printed matter as close as possible (in fact, the width of the printed matter is slightly narrower), this method is the most effective, especially for long-term printing
Scraper line
Multiple vertical lines appear one after another, the number of vertical lines cannot be counted, the width of the line together is equal to the distance the blade moves, the number of lines appears equal to the number of times the blade moves once the plate roller rotates
There is a hard block with a smile on the page. When the scraper moves left and right, the scraper is scratched and changes from a shallow line to a deep line. The plate does not turn once, the deeper the line becomes, and the lines on both sides are thicker
1. When there are hard dirt on the plate surface, grind the scraper and clean the plate roller; 2. When there are hard blocks on the plate surface (generally not pigment particles, but resin particles, the scraper should be as light as possible, use sandpaper to grind the scraper and a little bit on the plate Place, invalid for multiple consecutive times, re-chrome
Wrinkle
During printing, the film is wrinkled, irregularly, or at both ends and in the center
Consider the reasons from three aspects: film, roller and brake. Small glitches in various aspects make the pressure of the film unbalanced, causing wrinkling
1. Check from which roller the wrinkle occurs; 2. Check the condition of the brake (adjust the paper feed brake and tension); 3. Check whether the roller is damaged or dirty. Eccentricity; 4. Check the balance; 5. Check the pressure of the pressure roller and the roller of the pressure roller; 6. Check whether the film has deteriorated; consider the reasons from the above 6 items
Fog Edition
The squeegee failed to completely scrape off the non-graphic part of the ink on the plate roller, resulting in the phenomenon of ink transfer to the printing substrate. Black ink and white ink often occur
1. The precision of the plate roller is insufficient, eccentric, and poor chrome plating; 2. The pressure of the scraper is insufficient, the angle is not suitable; 3. The printing viscosity of the ink is too large; 4. The ink is excessively ground, and the pigment particles are too fine
1. Improve the manufacturing accuracy of the plate roller; 2. Increase the blade pressure, adjust the blade angle to 60-70 degrees, the distance between the two tangent points is 50-60 cm; 3. Reduce the printing viscosity of the ink; 4. Reduce the grinding strength, select Coarse particle pigments; 5. Add 3-5% BaSO4 to the ink formulation
Bite
When multi-color overprinting, the front color is dissolved by the back color, resulting in the change of printing hue
1. The resolubility of the ink is too good; 2. The ink in the front is not sufficiently dried, the ink in the back is dried too fast
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