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In the printing process of color boxes, we often encounter problems such as blurred outline of handwriting, corrugated crushing, filling of ink between imprinting gaps, and poor overprinting/overprinting quality. In view of the quality problems that often occur in the production process of color boxes, here are some experiences and lessons accumulated by the peers are shared as follows.
In the printing process of color boxes, we often encounter problems such as blurred handwriting outlines, corrugated crushing, ink filling between imprinting gaps, poor overprinting/overprinting quality, etc. In addition, how to deal with low-weight base paper and how to print large corrugated The problem of color box is also a technical issue that color box companies are very concerned about。
In view of the quality problems that often appear in the production process of color boxes, here are some experiences and lessons accumulated by peers are shared as follows:
The ink part of the paper is roughened or torn
Due to the difference in the material, paper structure and production process of white paper, coated paper, and offset paper, when the temperature is low in winter, the ink viscosity is high, the surface layer or coating layer of the white paper often appears to be sticky or sticky. The phenomenon of breaking seriously affects the appearance quality of printed matter.
Solution
Wetting powder and alcohol can be added to the fountain solution (the ratio is 5% to 20%) to reduce the tension on the edge of the inking part, or according to different types of ink, choose the corresponding ink, detackifier or diluent Reduce the viscosity of the ink.
Control the printing workshop and room temperature, generally control at 19℃～28℃. It is better to heat the ink properly in winter, which will help improve the fluidity of the ink and reduce the viscosity of the ink.
Choose whiteboard paper with strong roughness, and the printing pressure should not be too high.
The backing paper under the blanket should not be too much, the liner should not be soft, and the blanket should be wiped clean after using it for a period of time.
Color paper ink drying speed is slow
This phenomenon is easy to cause the printed matter to be sticky and bring some difficulties to the post-processing. This problem can be controlled from the following three aspects.
Switch to base paper with stronger ink absorption performance: For example, coated white paper has stronger absorption performance than bleached liner paper.
Choose quick-drying ink or add appropriate amount of drying aid according to the characteristics of the ink, and reduce the amount of ink applied to the ink spot.
Properly extend the interval of post-processing or spread the printed product to dry.
In the same batch of printed matter, there are differences in ink shades and differences in color appearance
Use the following methods to control it can get better results:
The ink required by the same batch of products should be prepared at one time. When the ink is formulated, the required ink, as well as the diluent, detackifier, desiccant and other additives must be measured with a weighing instrument, otherwise the ink must be mixed multiple times And random matching of ink will also cause the difference in hue.
The absorption performance, whiteness and thickness of the base paper (white paper) used in the same batch of products should be consistent. The thicker base paper will cause the printing pressure to increase and cause the ink to be thick. The white background of the paper will also cause the ink depth and color. Changes in appearance.
The ink balance on the printing roller should be well controlled, and the empty car should be strictly controlled, because after each run of the empty car, the ink color of the first dozen prints printed out is obviously darker or thicker. If the empty car runs more frequently, Then there are naturally more prints with different shades of ink.
For products that need to be overprinted multiple times, let the previous primer dry thoroughly before performing subsequent overprinting.
Wrinkles when printing on white paper
When printing color-printed face sheets with white paper, if the moisture content of the finished paper is uneven, there are ruffled edges, wavy edges, or tight edges appear due to excessive moisture evaporation at the edges of the paper due to excessive dryness, and the stand-alone overprints color; After repeated printing, wetting will cause the whiteboard paper to wrinkle during the color printing process.
To solve the wrinkling of whiteboard paper in the color printing process, we must first control the entry of moisture in the base paper. And before the whiteboard is printed on the machine, it is best to put it in the offset printing workshop one to two weeks in advance to keep the moisture content of the paper in balance with the humidity of the printing workshop. If the air humidity in the printing workshop is relatively dry, it is best to spray some water on the ground to adjust the air humidity to prevent the paper edge from evaporating more moisture and causing wrinkles due to tight edges. The other is to replace or remove the uneven base paper.
The color-printed veneer is exposed
The causes of color printing veneers are the thickness of the paper, the direction of paper flow, the solid content of the adhesive, the amount of glue on the corrugated peak, the pressure after the veneer, and the moisture content of the cardboard.
The exposure problem can be controlled by the following ways:
Appropriately increase the grammage of the color printing facial paper, and use the characteristics of the horizontal expansion and contraction greater than the longitudinal expansion after the base paper absorbs water, and the longitudinal silk flow and corrugation of the color printing facial paper are cross-fitted into a "+" shape.
Increase the solid content of the adhesive, reduce the moisture in the adhesive, and adjust the gap between the sizing roller and the pressure roller of the veneer (or laminating machine) to ensure that the color printing paper and the corrugated are well bonded In this case, try to reduce the amount of glue on the peak.
Drying treatment is carried out after the veneer, and the moisture content is controlled at 9±2% to shrink the fibers of the color printing facial paper, which can also reduce the appearance of fluting.
The veneer has cracked glue or corrugated collapse
The veneer adhesives are currently mostly oxidized starch adhesives. If the oxidized starch adhesive is not oxidized enough during the preparation process, or the starch is oxidized too deeply, the quality of the adhesive will be unstable and the glue will be broken. . In addition, if the sizing amount is adjusted too small, too little sizing on the corrugated peaks will also cause cracking. If it is veneered by hand-laminated glue, each layer of tile paper or surface paper is not mounted evenly, which will cause the glue to open.
Laminate on the veneer; or use hand-glued veneer. If the amount of glue applied to the corrugation peak is too large, it will easily cause the corrugation to absorb too much glue and then become soft, and the corrugation will collapse after being pressed with the facial paper. . In addition, too much sizing not only wastes glue, but also makes it difficult to dry the products after the veneer. Therefore, the amount of glue should be strictly controlled.
Color-printed products fade during post-processing, loading and unloading
From the surface phenomenon, the color fading is mainly caused by the friction between the products in the post-processing, handling, loading and unloading. In fact, this problem is also closely related to the ink mixing method. In the production process of color printing products, we often find that the ink is caused by ink. The viscosity of the ink is too large, which causes uneven ink from the ink roller and the printed matter is damaged by the ink sticky hair. In order to solve this problem, a detackifier is often added to the ink. If a detackifier is used for inks with different characteristics, the phenomenon of color fading will be quite serious, because the characteristics of different types of inks are different. Take the Shanghai Ink Factory's 05 and 01 resin inks as an example. If the detackifier is improperly used during ink adjustment, it will cause the ink to crystallize (the ink printed on the product appears powdery) and cause the product to fade seriously. 05 type bright and quick-drying resin ink can only add 0592 type detackifier, and the amount of addition should be controlled within 3%, while 01 type resin ink can use 3% red dry oil and 6# varnish oil. Adjust its viscosity. Under normal circumstances, do not add detackifier, otherwise it will also cause color printing products to fade.
In addition to paying attention to the distribution of ink, in the post-processing and handling of the product, it is also necessary to try to control the discoloration caused by dry friction between the product and the product, the product and the equipment, and the product and the tool, because the ink is not completely dried. In this case, the resistance to dry friction is poor, even if the new renminbi is wiped dry with rough paper, the color will fade.
If the product fades, the remedy is to cover the surface of the printed product with a layer of film or add a bright paste to solve the problem of fade.
In the printing process of color boxes, we often encounter problems such as blurred handwriting outlines, corrugated crushing, ink filling between imprinting gaps, poor overprinting/overprinting quality, etc. In addition, how to deal with low-weight base paper and how to print large corrugated The problem of color box is also a technical issue that color box companies are very concerned about。
In view of the quality problems that often appear in the production process of color boxes, here are some experiences and lessons accumulated by peers are shared as follows:
The ink part of the paper is roughened or torn
Due to the difference in the material, paper structure and production process of white paper, coated paper, and offset paper, when the temperature is low in winter, the ink viscosity is high, the surface layer or coating layer of the white paper often appears to be sticky or sticky. The phenomenon of breaking seriously affects the appearance quality of printed matter.
Solution
Wetting powder and alcohol can be added to the fountain solution (the ratio is 5% to 20%) to reduce the tension on the edge of the inking part, or according to different types of ink, choose the corresponding ink, detackifier or diluent Reduce the viscosity of the ink.
Control the printing workshop and room temperature, generally control at 19℃～28℃. It is better to heat the ink properly in winter, which will help improve the fluidity of the ink and reduce the viscosity of the ink.
Choose whiteboard paper with strong roughness, and the printing pressure should not be too high.
The backing paper under the blanket should not be too much, the liner should not be soft, and the blanket should be wiped clean after using it for a period of time.
Color paper ink drying speed is slow
This phenomenon is easy to cause the printed matter to be sticky and bring some difficulties to the post-processing. This problem can be controlled from the following three aspects.
Switch to base paper with stronger ink absorption performance: For example, coated white paper has stronger absorption performance than bleached liner paper.
Choose quick-drying ink or add appropriate amount of drying aid according to the characteristics of the ink, and reduce the amount of ink applied to the ink spot.
Properly extend the interval of post-processing or spread the printed product to dry.
In the same batch of printed matter, there are differences in ink shades and differences in color appearance
Use the following methods to control it can get better results:
The ink required by the same batch of products should be prepared at one time. When the ink is formulated, the required ink, as well as the diluent, detackifier, desiccant and other additives must be measured with a weighing instrument, otherwise the ink must be mixed multiple times And random matching of ink will also cause the difference in hue.
The absorption performance, whiteness and thickness of the base paper (white paper) used in the same batch of products should be consistent. The thicker base paper will cause the printing pressure to increase and cause the ink to be thick. The white background of the paper will also cause the ink depth and color. Changes in appearance.
The ink balance on the printing roller should be well controlled, and the empty car should be strictly controlled, because after each run of the empty car, the ink color of the first dozen prints printed out is obviously darker or thicker. If the empty car runs more frequently, Then there are naturally more prints with different shades of ink.
For products that need to be overprinted multiple times, let the previous primer dry thoroughly before performing subsequent overprinting.
Wrinkles when printing on white paper
When printing color-printed face sheets with white paper, if the moisture content of the finished paper is uneven, there are ruffled edges, wavy edges, or tight edges appear due to excessive moisture evaporation at the edges of the paper due to excessive dryness, and the stand-alone overprints color; After repeated printing, wetting will cause the whiteboard paper to wrinkle during the color printing process.
To solve the wrinkling of whiteboard paper in the color printing process, we must first control the entry of moisture in the base paper. And before the whiteboard is printed on the machine, it is best to put it in the offset printing workshop one to two weeks in advance to keep the moisture content of the paper in balance with the humidity of the printing workshop. If the air humidity in the printing workshop is relatively dry, it is best to spray some water on the ground to adjust the air humidity to prevent the paper edge from evaporating more moisture and causing wrinkles due to tight edges. The other is to replace or remove the uneven base paper.
The color-printed veneer is exposed
The causes of color printing veneers are the thickness of the paper, the direction of paper flow, the solid content of the adhesive, the amount of glue on the corrugated peak, the pressure after the veneer, and the moisture content of the cardboard.
The exposure problem can be controlled by the following ways:
Appropriately increase the grammage of the color printing facial paper, and use the characteristics of the horizontal expansion and contraction greater than the longitudinal expansion after the base paper absorbs water, and the longitudinal silk flow and corrugation of the color printing facial paper are cross-fitted into a "+" shape.
Increase the solid content of the adhesive, reduce the moisture in the adhesive, and adjust the gap between the sizing roller and the pressure roller of the veneer (or laminating machine) to ensure that the color printing paper and the corrugated are well bonded In this case, try to reduce the amount of glue on the peak.
Drying treatment is carried out after the veneer, and the moisture content is controlled at 9±2% to shrink the fibers of the color printing facial paper, which can also reduce the appearance of fluting.
The veneer has cracked glue or corrugated collapse
The veneer adhesives are currently mostly oxidized starch adhesives. If the oxidized starch adhesive is not oxidized enough during the preparation process, or the starch is oxidized too deeply, the quality of the adhesive will be unstable and the glue will be broken. . In addition, if the sizing amount is adjusted too small, too little sizing on the corrugated peaks will also cause cracking. If it is veneered by hand-laminated glue, each layer of tile paper or surface paper is not mounted evenly, which will cause the glue to open.
Laminate on the veneer; or use hand-glued veneer. If the amount of glue applied to the corrugation peak is too large, it will easily cause the corrugation to absorb too much glue and then become soft, and the corrugation will collapse after being pressed with the facial paper. . In addition, too much sizing not only wastes glue, but also makes it difficult to dry the products after the veneer. Therefore, the amount of glue should be strictly controlled.
Color-printed products fade during post-processing, loading and unloading
From the surface phenomenon, the color fading is mainly caused by the friction between the products in the post-processing, handling, loading and unloading. In fact, this problem is also closely related to the ink mixing method. In the production process of color printing products, we often find that the ink is caused by ink. The viscosity of the ink is too large, which causes uneven ink from the ink roller and the printed matter is damaged by the ink sticky hair. In order to solve this problem, a detackifier is often added to the ink. If a detackifier is used for inks with different characteristics, the phenomenon of color fading will be quite serious, because the characteristics of different types of inks are different. Take the Shanghai Ink Factory's 05 and 01 resin inks as an example. If the detackifier is improperly used during ink adjustment, it will cause the ink to crystallize (the ink printed on the product appears powdery) and cause the product to fade seriously. 05 type bright and quick-drying resin ink can only add 0592 type detackifier, and the amount of addition should be controlled within 3%, while 01 type resin ink can use 3% red dry oil and 6# varnish oil. Adjust its viscosity. Under normal circumstances, do not add detackifier, otherwise it will also cause color printing products to fade.
In addition to paying attention to the distribution of ink, in the post-processing and handling of the product, it is also necessary to try to control the discoloration caused by dry friction between the product and the product, the product and the equipment, and the product and the tool, because the ink is not completely dried. In this case, the resistance to dry friction is poor, even if the new renminbi is wiped dry with rough paper, the color will fade.
If the product fades, the remedy is to cover the surface of the printed product with a layer of film or add a bright paste to solve the problem of fade.
