Plastic flexible packaging products are generally printed on various plastic films, and then a composite film is formed by combining a barrier layer and a heat seal layer, and the product is cut and bagged. Printing is the first process of production, and it is also the most difficult process to control. Most of the quality problems of products appear in this process. The quality of a packaging product is measured, and the quality of printing is the first. Therefore, understanding and controlling the process and quality of printing becomes the key to flexible packaging production. Gravure printing is the main printing method for today's plastic film printing. The use of gravure printing for plastic film has the advantages of fast speed, rich colors, clear and bright, moderate contrast, vivid image, and various product specifications. The gravure printing has a high printing resistance, and the large-volume prints with more than one million prints have more advantages.
The quality of the gravure plastic film products is relatively high. The quality standards of the printed appearance are as follows:
1 After the flowering process, the color pattern registration error is not more than 0.3mm.
2 check the specifications of the film, the color pattern registration error is not greater than 0.3mm.
3 Check the ink color of the printed product, and it is required that the hue is correct, bright and uniform, the ink is bright, the ink is soft, and the edges are bright and clean.
4 printing fastness, requires transparent tape stick ink does not decolorize.
5 pattern text lines, requiring clear and complete, not incomplete, no deformation.
6 Textures are rich in requirements, and outlets are clear.
7 The product is clean and tidy, with no visible dirt or knife.
8 Requirements The product has the same color density deviation and the same batch of the same color and other indicators meet the requirements of GB7707-87.
In order to better achieve the above quality requirements, we can control the gravure plastic film process from the following major aspects:
1. Grasp the process points of various plastic packaging film substrates
1BOPP is the most commonly used printing substrate. The main point of its production process is a typical plastic gravure production process; it is printed with polyamide or chlorinated polypropylene ink, with appropriate tension and embossing force, and the drying temperature is controlled below 80°C.
2BOPET printing points: Because PET is usually thin, easy to wrinkle, printing requires greater tension, the ink has a certain degree of selectivity, easy to use the general printing ink layer, the film static, prone to block version (not access to the Internet ), fluffing and knife marks (knife wire) phenomenon, printing workshop humidity is good.
3 BOPA printing points: BOPA is a film that is easy to absorb moisture and deform. Therefore, the printing machine must ensure that the environmental humidity of the printing machine cannot be too high (if the dehumidification measures are not sufficient, the humidity is not suitable for the printing of nylon film); the unprinted film cannot destroy the original aluminum film packaging film and must be printed immediately after opening. Nylon film should be preheated during printing (if the machine does not have a preheating device, the plate can be mounted on the second color, leaving the first color as preheating), and the preheating temperature is 50-80°C; The printing tension should be appropriately reduced; the pressure should be moderate; the ink should be adaptable; depending on the choice of product structure, if it is a cooking bag, cooking ink must be selected; after printing, the product must be tightly packed, stored in the dried-recycled room, and stored as soon as possible. complex.
4K coating film (KOP, KPA, KPET) printing point: Because K coating film is roller or spray type, its thickness uniformity is not very good, the surface is uneven, and PVDC is just brittle, when printing The printing tension and the imprinting pressure cannot be too large, the overprinting is difficult, the ink transferability is poor, and when printing a light screen plate, it is easy to get a flower point (parts of the network points are lost), and a higher hardness press roller is used for printing.
Plastic flexible packaging products are generally printed on various plastic films, and then a composite film is formed by combining a barrier layer and a heat seal layer, and the product is cut and bagged. Printing is the first process of production, and it is also the most difficult process to control. Most of the quality problems of products appear in this process. The quality of a packaging product is measured, and the quality of printing is the first. Therefore, understanding and controlling the process and quality of printing becomes the key to flexible packaging production. Gravure printing is the main printing method for today's plastic film printing. The use of gravure printing for plastic film has the advantages of fast speed, rich colors, clear and bright, moderate contrast, vivid image, and various product specifications. The gravure printing has a high printing resistance, and the large-volume prints with more than one million prints have more advantages.
The quality of the gravure plastic film products is relatively high. The quality standards of the printed appearance are as follows:
1 After the flowering process, the color pattern registration error is not more than 0.3mm.
2 check the specifications of the film, the color pattern registration error is not greater than 0.3mm.
3 Check the ink color of the printed product, and it is required that the hue is correct, bright and uniform, the ink is bright, the ink is soft, and the edges are bright and clean.
4 printing fastness, requires transparent tape stick ink does not decolorize.
5 pattern text lines, requiring clear and complete, not incomplete, no deformation.
6 Textures are rich in requirements, and outlets are clear.
7 The product is clean and tidy, with no visible dirt or knife.
8 Requirements The product has the same color density deviation and the same batch of the same color and other indicators meet the requirements of GB7707-87.
In order to better achieve the above quality requirements, we can control the gravure plastic film process from the following major aspects:
1. Grasp the process points of various plastic packaging film substrates
1BOPP is the most commonly used printing substrate. The main point of its production process is a typical plastic gravure production process; it is printed with polyamide or chlorinated polypropylene ink, with appropriate tension and embossing force, and the drying temperature is controlled below 80°C.
2BOPET printing points: Because PET is usually thin, easy to wrinkle, printing requires greater tension, the ink has a certain degree of selectivity, easy to use the general printing ink layer, the film static, prone to block version (not access to the Internet ), fluffing and knife marks (knife wire) phenomenon, printing workshop humidity is good.
It must be ensured that the environmental humidity of the printing press cannot be too high (if the dehumidification measures are not enough, the humidity is not suitable for printing nylon film); the unprinted film cannot destroy its original aluminum film packaging film, and it must be printed immediately after opening, printing. When the nylon membrane needs to be preheated (if the machine does not have a preheating device, the plate can be mounted on the second color, leaving the first color as a preheating), the preheating temperature is 50 ~ 80 °C; printing tension Should be properly reduced; pressure should be moderate; ink adaptability, depending on the choice of product structure, if it is a cooking bag must choose cooking ink; after the printed product must be sealed, placed in the dry complex indoor storage, and as soon as possible compound.
4K coating film (KOP, KPA, KPET) printing point: Because K coating film is roller or spray type, its thickness uniformity is not very good, the surface is uneven, and PVDC is just brittle, when printing The printing tension and the imprinting pressure cannot be too large, the overprinting is difficult, the ink transferability is poor, and when printing a light screen plate, it is easy to get a flower point (parts of the network points are lost), and a higher hardness press roller is used for printing.
5 Spot inks that are self-provisioned must be accurately recorded and recorded for future reference.
6 try to reach the normal printing speed.
7 If the conditions permit, after confirming the basic color of the sample, first print a certain amount of product (such as a roll of film), then sample and confirm it as a standard sample, and keep it as a file.
8 After confirmation of the standard sample, the attached 2~3m should be taken as the equivalent standard sample, and it should be properly stored in a place with no heat source and no ultraviolet light, and the printed part should be used as a printed sample after each printing.
4. Common troubleshooting
1 dirty version
In plastic gravure, the non-printing surface of the roller is often covered with a layer of resin (entrained pigment in the resin), transferred to the substrate to form a sheet of dirt, or a line of dirt, this is Dirty version. In addition to the hardness of the blade, the blade pressure, the blade contact angle, and the quality of the plate cylinder, the resulting dirty plate phenomenon is also related to the viscosity of the ink. When the printing viscosity is too high, resins, pigments, and other substances have poor fluidity and cannot be uniformly dispersed and accumulated, causing the blade and the plate cylinder to be damaged under high-speed operation, resulting in linear fouling. At the same time, since the resin and the like are also in a supersaturated state, a large amount of resin accumulates together and under the pressure of the doctor blade, the resin adheres to the drum (the pigment is entrained in the resin) due to the affinity of the resin to the drum, and the sheet becomes contaminated. In general, the smaller the ink printing viscosity, the less likely the dirty plate problem occurs.
2 colors are not allowed
It is mainly due to the deviation of the diameter of the gravure cylinder; the deformation of the graphic is caused by the incorrect plate setting; the uneven tooth spacing between the shafts, the large or small gaps, or the overprinting of the top teeth; Balanced or gravure film thickness uneven, flounced edge; uneven pressure between the plate cylinder and the impression cylinder at either end of the multi-color printing or printing plate inconsistencies.
3 dimensional deviation
Insufficient or excessive contraction margin. Due to the influence of the tension of the plastic film and heat drying, the longitudinal dimension of the film changes greatly during printing. Control measures: Adjust the printing tension appropriately to prevent dimensional deviation due to improper temperature setting.
4 anti-print (ie bite)
Anti-printing means that the ink of the previous color is overprinted onto the latter printing plate during overprinting. Cause: The ink of the previous color was not completely dried; the pressure of the second color was too large, or the speed was too fast, or the hot and cold air was bad; the substrate had poor printability. Improve the adhesion of the ink of the previous color, adjust the viscosity of the ink, increase the amount of hot and cold air, increase the drying speed of the ink, slow the speed of the vehicle, increase the ink supply of the latter color, reduce the viscosity of the latter color, and correctly arrange the color sequence of the printing plate; Reduce impression cylinder pressure, or use a softer rubber roller.
5 whitening
Resin does not dissolve, precipitate; drying too fast. Control measures: Re-inking, appropriate slow-drying solvent. There are many problems in gravure printing. In the actual printing operation, the main reason should be carefully analyzed. It can be considered from the aspects of register control, tension control, ink control, temperature control, etc., and quickly eliminated to ensure smooth production. This requires skilled technology, timely understanding of the causes of the above common quality problems, and decisive measures to solve the problem of gravure quality of plastic film in a timely manner.
6 pattern line incomplete
The hot air is too large, the ink is easy to dry, the ink is dried too quickly in the reticulate lines, and the accumulated ink is solid on the surface of the printing plate; the pressure between the printing plate and the impression cylinder is too small; the angle of the squeegee is not ideal, and the pressure on the plate surface is not enough; Plate uneven print or white spots, plate shallow, burr, ink adhesion; ink is too thin; printing speed is too slow.
Add butanol in a timely manner to clean the printing area; adjust the pressure; adjust the angle of the squeegee and the pressure on the plate; deepen the printing plate to remove burrs; properly add the original ink; adjust the printing speed.
Chromatic aberration refers to the color difference between rolls and rolls during the printing process. Cause: The viscosity of the ink is not well adjusted; the gravure cylinder blocks the plate; the printing staff does not perform properly.
8 block version
During printing, the viscosity of the ink increases with the large amount of solvent volatilization, and the ink is easily dried inside the screen; in the printing process, the position of the doctor blade is far from the printing roller or the angle is not reasonable, the diameter of the printing roller is large, or the depth of the printing roller enters the ink tank When it is not enough, the hot air blown from the drying pipe affects the plate surface of the plate, which can cause serious blockage; the ink is mixed with impurities; the engraving depth of the platen roller line is not suitable; when the printing temperature is too high, the solvent in the ink volatilizes quickly. The process of gravure printing plastic film is more difficult to control, so in the printing, we must sum up some experiences to obtain our own quality control method.
The quality of the gravure plastic film products is relatively high. The quality standards of the printed appearance are as follows:
1 After the flowering process, the color pattern registration error is not more than 0.3mm.
2 check the specifications of the film, the color pattern registration error is not greater than 0.3mm.
3 Check the ink color of the printed product, and it is required that the hue is correct, bright and uniform, the ink is bright, the ink is soft, and the edges are bright and clean.
4 printing fastness, requires transparent tape stick ink does not decolorize.
5 pattern text lines, requiring clear and complete, not incomplete, no deformation.
6 Textures are rich in requirements, and outlets are clear.
7 The product is clean and tidy, with no visible dirt or knife.
8 Requirements The product has the same color density deviation and the same batch of the same color and other indicators meet the requirements of GB7707-87.
In order to better achieve the above quality requirements, we can control the gravure plastic film process from the following major aspects:
1. Grasp the process points of various plastic packaging film substrates
1BOPP is the most commonly used printing substrate. The main point of its production process is a typical plastic gravure production process; it is printed with polyamide or chlorinated polypropylene ink, with appropriate tension and embossing force, and the drying temperature is controlled below 80°C.
2BOPET printing points: Because PET is usually thin, easy to wrinkle, printing requires greater tension, the ink has a certain degree of selectivity, easy to use the general printing ink layer, the film static, prone to block version (not access to the Internet ), fluffing and knife marks (knife wire) phenomenon, printing workshop humidity is good.
3 BOPA printing points: BOPA is a film that is easy to absorb moisture and deform. Therefore, the printing machine must ensure that the environmental humidity of the printing machine cannot be too high (if the dehumidification measures are not sufficient, the humidity is not suitable for the printing of nylon film); the unprinted film cannot destroy the original aluminum film packaging film and must be printed immediately after opening. Nylon film should be preheated during printing (if the machine does not have a preheating device, the plate can be mounted on the second color, leaving the first color as preheating), and the preheating temperature is 50-80°C; The printing tension should be appropriately reduced; the pressure should be moderate; the ink should be adaptable; depending on the choice of product structure, if it is a cooking bag, cooking ink must be selected; after printing, the product must be tightly packed, stored in the dried-recycled room, and stored as soon as possible. complex.
4K coating film (KOP, KPA, KPET) printing point: Because K coating film is roller or spray type, its thickness uniformity is not very good, the surface is uneven, and PVDC is just brittle, when printing The printing tension and the imprinting pressure cannot be too large, the overprinting is difficult, the ink transferability is poor, and when printing a light screen plate, it is easy to get a flower point (parts of the network points are lost), and a higher hardness press roller is used for printing.
Plastic flexible packaging products are generally printed on various plastic films, and then a composite film is formed by combining a barrier layer and a heat seal layer, and the product is cut and bagged. Printing is the first process of production, and it is also the most difficult process to control. Most of the quality problems of products appear in this process. The quality of a packaging product is measured, and the quality of printing is the first. Therefore, understanding and controlling the process and quality of printing becomes the key to flexible packaging production. Gravure printing is the main printing method for today's plastic film printing. The use of gravure printing for plastic film has the advantages of fast speed, rich colors, clear and bright, moderate contrast, vivid image, and various product specifications. The gravure printing has a high printing resistance, and the large-volume prints with more than one million prints have more advantages.
The quality of the gravure plastic film products is relatively high. The quality standards of the printed appearance are as follows:
1 After the flowering process, the color pattern registration error is not more than 0.3mm.
2 check the specifications of the film, the color pattern registration error is not greater than 0.3mm.
3 Check the ink color of the printed product, and it is required that the hue is correct, bright and uniform, the ink is bright, the ink is soft, and the edges are bright and clean.
4 printing fastness, requires transparent tape stick ink does not decolorize.
5 pattern text lines, requiring clear and complete, not incomplete, no deformation.
6 Textures are rich in requirements, and outlets are clear.
7 The product is clean and tidy, with no visible dirt or knife.
8 Requirements The product has the same color density deviation and the same batch of the same color and other indicators meet the requirements of GB7707-87.
In order to better achieve the above quality requirements, we can control the gravure plastic film process from the following major aspects:
1. Grasp the process points of various plastic packaging film substrates
1BOPP is the most commonly used printing substrate. The main point of its production process is a typical plastic gravure production process; it is printed with polyamide or chlorinated polypropylene ink, with appropriate tension and embossing force, and the drying temperature is controlled below 80°C.
2BOPET printing points: Because PET is usually thin, easy to wrinkle, printing requires greater tension, the ink has a certain degree of selectivity, easy to use the general printing ink layer, the film static, prone to block version (not access to the Internet ), fluffing and knife marks (knife wire) phenomenon, printing workshop humidity is good.
It must be ensured that the environmental humidity of the printing press cannot be too high (if the dehumidification measures are not enough, the humidity is not suitable for printing nylon film); the unprinted film cannot destroy its original aluminum film packaging film, and it must be printed immediately after opening, printing. When the nylon membrane needs to be preheated (if the machine does not have a preheating device, the plate can be mounted on the second color, leaving the first color as a preheating), the preheating temperature is 50 ~ 80 °C; printing tension Should be properly reduced; pressure should be moderate; ink adaptability, depending on the choice of product structure, if it is a cooking bag must choose cooking ink; after the printed product must be sealed, placed in the dry complex indoor storage, and as soon as possible compound.
4K coating film (KOP, KPA, KPET) printing point: Because K coating film is roller or spray type, its thickness uniformity is not very good, the surface is uneven, and PVDC is just brittle, when printing The printing tension and the imprinting pressure cannot be too large, the overprinting is difficult, the ink transferability is poor, and when printing a light screen plate, it is easy to get a flower point (parts of the network points are lost), and a higher hardness press roller is used for printing.
5 Spot inks that are self-provisioned must be accurately recorded and recorded for future reference.
6 try to reach the normal printing speed.
7 If the conditions permit, after confirming the basic color of the sample, first print a certain amount of product (such as a roll of film), then sample and confirm it as a standard sample, and keep it as a file.
8 After confirmation of the standard sample, the attached 2~3m should be taken as the equivalent standard sample, and it should be properly stored in a place with no heat source and no ultraviolet light, and the printed part should be used as a printed sample after each printing.
4. Common troubleshooting
1 dirty version
In plastic gravure, the non-printing surface of the roller is often covered with a layer of resin (entrained pigment in the resin), transferred to the substrate to form a sheet of dirt, or a line of dirt, this is Dirty version. In addition to the hardness of the blade, the blade pressure, the blade contact angle, and the quality of the plate cylinder, the resulting dirty plate phenomenon is also related to the viscosity of the ink. When the printing viscosity is too high, resins, pigments, and other substances have poor fluidity and cannot be uniformly dispersed and accumulated, causing the blade and the plate cylinder to be damaged under high-speed operation, resulting in linear fouling. At the same time, since the resin and the like are also in a supersaturated state, a large amount of resin accumulates together and under the pressure of the doctor blade, the resin adheres to the drum (the pigment is entrained in the resin) due to the affinity of the resin to the drum, and the sheet becomes contaminated. In general, the smaller the ink printing viscosity, the less likely the dirty plate problem occurs.
2 colors are not allowed
It is mainly due to the deviation of the diameter of the gravure cylinder; the deformation of the graphic is caused by the incorrect plate setting; the uneven tooth spacing between the shafts, the large or small gaps, or the overprinting of the top teeth; Balanced or gravure film thickness uneven, flounced edge; uneven pressure between the plate cylinder and the impression cylinder at either end of the multi-color printing or printing plate inconsistencies.
3 dimensional deviation
Insufficient or excessive contraction margin. Due to the influence of the tension of the plastic film and heat drying, the longitudinal dimension of the film changes greatly during printing. Control measures: Adjust the printing tension appropriately to prevent dimensional deviation due to improper temperature setting.
4 anti-print (ie bite)
Anti-printing means that the ink of the previous color is overprinted onto the latter printing plate during overprinting. Cause: The ink of the previous color was not completely dried; the pressure of the second color was too large, or the speed was too fast, or the hot and cold air was bad; the substrate had poor printability. Improve the adhesion of the ink of the previous color, adjust the viscosity of the ink, increase the amount of hot and cold air, increase the drying speed of the ink, slow the speed of the vehicle, increase the ink supply of the latter color, reduce the viscosity of the latter color, and correctly arrange the color sequence of the printing plate; Reduce impression cylinder pressure, or use a softer rubber roller.
5 whitening
Resin does not dissolve, precipitate; drying too fast. Control measures: Re-inking, appropriate slow-drying solvent. There are many problems in gravure printing. In the actual printing operation, the main reason should be carefully analyzed. It can be considered from the aspects of register control, tension control, ink control, temperature control, etc., and quickly eliminated to ensure smooth production. This requires skilled technology, timely understanding of the causes of the above common quality problems, and decisive measures to solve the problem of gravure quality of plastic film in a timely manner.
6 pattern line incomplete
The hot air is too large, the ink is easy to dry, the ink is dried too quickly in the reticulate lines, and the accumulated ink is solid on the surface of the printing plate; the pressure between the printing plate and the impression cylinder is too small; the angle of the squeegee is not ideal, and the pressure on the plate surface is not enough; Plate uneven print or white spots, plate shallow, burr, ink adhesion; ink is too thin; printing speed is too slow.
Add butanol in a timely manner to clean the printing area; adjust the pressure; adjust the angle of the squeegee and the pressure on the plate; deepen the printing plate to remove burrs; properly add the original ink; adjust the printing speed.
Chromatic aberration refers to the color difference between rolls and rolls during the printing process. Cause: The viscosity of the ink is not well adjusted; the gravure cylinder blocks the plate; the printing staff does not perform properly.
8 block version
During printing, the viscosity of the ink increases with the large amount of solvent volatilization, and the ink is easily dried inside the screen; in the printing process, the position of the doctor blade is far from the printing roller or the angle is not reasonable, the diameter of the printing roller is large, or the depth of the printing roller enters the ink tank When it is not enough, the hot air blown from the drying pipe affects the plate surface of the plate, which can cause serious blockage; the ink is mixed with impurities; the engraving depth of the platen roller line is not suitable; when the printing temperature is too high, the solvent in the ink volatilizes quickly. The process of gravure printing plastic film is more difficult to control, so in the printing, we must sum up some experiences to obtain our own quality control method.
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