The overprint accuracy of letterpress prints is one of the important indicators for measuring product quality, which of course has become an important item in quality control in the printing process. However, due to the influence and constraints of various aspects, product overprinting is not allowed to exist in the printing process, which not only reduces product quality, but also brings a lot of trouble to production. Therefore, how to improve the overprint accuracy of products is extremely important.
Throughout the printing process product overprint is not allowed to fault conditions, summed up the reasons are: equipment used to reduce the accuracy of wear; machine adjustment is not good; paper stretching deformation; improper operation process and plate version of the core variation caused by inaccurate and so on .
First, the poor accuracy of the equipment caused by overprinting of the product equipment as an important tool for printing, its accuracy to a large extent determines the product's overprint quality. When the critical components on the equipment wear clearance, loose, it will inevitably produce overprint failure, such as the roller gear on the printing machine, plate rack, connecting rod bearings, track, delivery teeth, cams and linkage before, side When the movements are loosened, it is easy to misalign the “up and down†(ie vertical) and “going†(axial) layouts of the printed product. Product overprinting is not allowed to occur after the failure, should be checked, analyzed and judged to see if it is due to poor equipment accuracy, the identification methods are: air imprinting inspection method, that is, in the case of the normal lining tight, normal The printing speed was successively embossed several times to observe the accuracy of the liner lining on the liner. If the imprinting double-shadow punished, the machine's accuracy was poor, and the parts related to the embossing movement were worn and loosened. In addition, it is also possible to take several sheets of paper with flatness and good stiffness of 70 grams or more. Overprinting is repeated twice with the same layout, and the imprinting is observed. If there is a clear registration on the one side, a clear double printing occurs. It means that the accuracy of feeding the paper or the pre-regulatory or paper feeding mechanism is poor, and corresponding repair and high-speed measures should be taken according to the actual situation. In order to prevent overprinting errors caused by equipment accuracy, equipment should be used scientifically and reasonably. Never allow the machine to run continuously for 24 hours a day, so that the machine does not have a chance to cool, so that the parts are subject to friction and excessive heat, fatigue caused by accuracy and even damage . Usually pay attention to the lubrication of the equipment to prevent the wear of critical components caused by poor lubrication, which is an important measure to ensure accurate overprinting.
Second, improper adjustment of the machine caused by product overprinting is not allowed in the printing process, if the former vision adjustment is too small to make the amount of enamel squeegee paper is too small, bite is not tight when the edge of the imprint is easy to produce slip, causing bite mouth pin position Insufficiency; the lack of pressure on the paper-feeding teeth, the opening and closing of the teeth, and the pressure of the paper-pressing pressure will also make the front sheet of the printed sheet unacceptable; some components of the sheet- feeding system may be misaligned, resulting in insufficient paper feeding or excessive paper-feeding force. The source of the inaccurate needle position. The TY401 type TL2640 "Heidelberg type" four-opening automatic printing press, if the platen adjustment on the side scale is too low, it is easy to produce the side papers when printing thick paper; the DT400 type four-opening automatic platform machine loses. The accumulation of paper dust on the chain under the cardboard will cause the lateral movement to become inaccurate, which will result in inaccurate overprinting of the sheet. In addition, if the flat paper brush wears and causes the elasticity of the press sheet to be uncomfortable, it is easy to make the layout (longitudinal) on the printed sheet larger than the actual plate size. Excessive printing pressure, blind lining thickening and lining loosening are also the reasons for the distortion of the printing layout (larger layout) and the misalignment of overprinting. All of the above situations should be checked and analyzed one by one, and corresponding adjustment measures should be taken to ensure that product overprinting is accurate.
Third, poor paper flatness, telescopic variation caused by overprinting is not allowed When the water content of the paper is abnormal, curling occurs at the edge of the paper, it will inevitably affect the normal feeding and clenching the normal paper, resulting in misprints. For curled paper edges, the method of knocking is generally adopted so that the paper can reach the flatness required for normal printing and the printing accuracy can be ensured. However, it should be noted that knocking on paper should avoid the use of double-sided papers that must be knocked or knocked repeatedly to make the edge of the paper form a “water waveâ€, resulting in inaccurate overprinting. In addition, under the influence of printing pressure, under the influence of printing pressure, due to the influence of temperature and humidity in the printing environment, due to the inevitable absorption of ink, moisture absorption or moisture loss in the printing process, the printed sheets will also have some stretching variation, causing vertical or horizontal misregistration. . In particular, the straight wire and paper with the fiber arrangement parallel to the axial direction of the roller suffer from pressure, moisture absorption, or water loss in the printing process, which may cause longitudinal stretching and variation of the paper. In order to reduce the variation of the paper, the cut paper should be immediately transported to the printing shop, so that the water content of the paper can be balanced with the temperature and humidity of the shop, and the printing shop must be kept at constant temperature and humidity. For printing products that have been misprinted due to print variations, the method of adjusting the thickness of the lining may be used to achieve the quality requirements of the register layout.
Fourth, improper operation process caused by improper overprinting of the product 1, poor printing plate bottom, over pressure caused by overprint printing on the letterpress platform printing machine printing large-area color printing products, if the use of multi-layer plastic plate as the bottom of the printing plate On the one hand, because the material is easy to produce imprinting on the one hand; on the other hand, due to the fact that the four sides of the wood tray are difficult to reach the technical requirements of right angles and straight edges, the printing plate is easy to produce arched disease after being fastened, and the printing pressure is inconsistent. A good transfer of the ink layer can be achieved by increasing the printing pressure. If the printing pressure is too heavy, imprinting will easily produce the opposite torsional force of the printed sheet and the clenched teeth. Therefore, the front gauge needle is inaccurate. Therefore, large-format overprinting products with large ink-absorption capacity should be made of metal magnetic platens and aluminum plates. The printing pressure and ink layer effects are good, and overprinting is also more accurate.
2. The color printing products that are not allowed to overprint due to excessive viscosity of the ink layer are large in the ink absorption of the bottom color layout, and the ink layer thickness is also relatively large, so that the ink layer on the printing surface is imprinted on the printing sheet. The sticking force is generated so that the printing paper is easily twisted from the teeth of the roller, causing the front gauge to be misaligned. The ink stickiness is too large, and it is easy to stretch the printed sheet and expand the printing surface, resulting in inaccurate overprinting. Therefore, the large-format background color should be printed as deep as possible, that is, the darkness of the printing ink should be slightly adjusted to make the printing ink thinner, which can satisfy the printing hue requirements and reduce the ink layer. Stickiness, this is one aspect. On the other hand, due to the low temperature, the viscosity of the ink is too large, and additives can be used to properly adjust the ink flow to reduce the viscosity of the ink and prevent relative slippage between the paper and the teeth, ensuring overprinting. accurate.
3, the inconsistent printing specifications caused by the overprint is not allowed to print paper in the cutting process, due to the uneven level of the paper roll appears uneven; the blade edge angle and the paper does not adapt to the characteristics of the paper; blade wear becomes blunt and other bad The situation exists, so that the cut paper will inevitably appear skewed or the "wavy line" whose edges are indistinct from the naked eye, so that the edge of the paper lacks right angles and straight lines. If the cover plate is moved to the lateral position or different Printing machine overprinting (front and side gauge position roller diameter is different), it is very easy to produce overprint not allowed. Therefore, in order to ensure the accuracy of product overprinting, the paper that is required to be cut should reach right angles and straight edges, and the performance and structure of the printer should be the same.
In summary, the reasons for inaccurate product overprinting are various, as long as we are good at conscientiously summing up experience and effectively shutting down operational technology and technology, not only can improve product overlay accuracy, but also promote production efficiency. improve. (Kang Qilai) (From "China Packaging News")
Throughout the printing process product overprint is not allowed to fault conditions, summed up the reasons are: equipment used to reduce the accuracy of wear; machine adjustment is not good; paper stretching deformation; improper operation process and plate version of the core variation caused by inaccurate and so on .
First, the poor accuracy of the equipment caused by overprinting of the product equipment as an important tool for printing, its accuracy to a large extent determines the product's overprint quality. When the critical components on the equipment wear clearance, loose, it will inevitably produce overprint failure, such as the roller gear on the printing machine, plate rack, connecting rod bearings, track, delivery teeth, cams and linkage before, side When the movements are loosened, it is easy to misalign the “up and down†(ie vertical) and “going†(axial) layouts of the printed product. Product overprinting is not allowed to occur after the failure, should be checked, analyzed and judged to see if it is due to poor equipment accuracy, the identification methods are: air imprinting inspection method, that is, in the case of the normal lining tight, normal The printing speed was successively embossed several times to observe the accuracy of the liner lining on the liner. If the imprinting double-shadow punished, the machine's accuracy was poor, and the parts related to the embossing movement were worn and loosened. In addition, it is also possible to take several sheets of paper with flatness and good stiffness of 70 grams or more. Overprinting is repeated twice with the same layout, and the imprinting is observed. If there is a clear registration on the one side, a clear double printing occurs. It means that the accuracy of feeding the paper or the pre-regulatory or paper feeding mechanism is poor, and corresponding repair and high-speed measures should be taken according to the actual situation. In order to prevent overprinting errors caused by equipment accuracy, equipment should be used scientifically and reasonably. Never allow the machine to run continuously for 24 hours a day, so that the machine does not have a chance to cool, so that the parts are subject to friction and excessive heat, fatigue caused by accuracy and even damage . Usually pay attention to the lubrication of the equipment to prevent the wear of critical components caused by poor lubrication, which is an important measure to ensure accurate overprinting.
Second, improper adjustment of the machine caused by product overprinting is not allowed in the printing process, if the former vision adjustment is too small to make the amount of enamel squeegee paper is too small, bite is not tight when the edge of the imprint is easy to produce slip, causing bite mouth pin position Insufficiency; the lack of pressure on the paper-feeding teeth, the opening and closing of the teeth, and the pressure of the paper-pressing pressure will also make the front sheet of the printed sheet unacceptable; some components of the sheet- feeding system may be misaligned, resulting in insufficient paper feeding or excessive paper-feeding force. The source of the inaccurate needle position. The TY401 type TL2640 "Heidelberg type" four-opening automatic printing press, if the platen adjustment on the side scale is too low, it is easy to produce the side papers when printing thick paper; the DT400 type four-opening automatic platform machine loses. The accumulation of paper dust on the chain under the cardboard will cause the lateral movement to become inaccurate, which will result in inaccurate overprinting of the sheet. In addition, if the flat paper brush wears and causes the elasticity of the press sheet to be uncomfortable, it is easy to make the layout (longitudinal) on the printed sheet larger than the actual plate size. Excessive printing pressure, blind lining thickening and lining loosening are also the reasons for the distortion of the printing layout (larger layout) and the misalignment of overprinting. All of the above situations should be checked and analyzed one by one, and corresponding adjustment measures should be taken to ensure that product overprinting is accurate.
Third, poor paper flatness, telescopic variation caused by overprinting is not allowed When the water content of the paper is abnormal, curling occurs at the edge of the paper, it will inevitably affect the normal feeding and clenching the normal paper, resulting in misprints. For curled paper edges, the method of knocking is generally adopted so that the paper can reach the flatness required for normal printing and the printing accuracy can be ensured. However, it should be noted that knocking on paper should avoid the use of double-sided papers that must be knocked or knocked repeatedly to make the edge of the paper form a “water waveâ€, resulting in inaccurate overprinting. In addition, under the influence of printing pressure, under the influence of printing pressure, due to the influence of temperature and humidity in the printing environment, due to the inevitable absorption of ink, moisture absorption or moisture loss in the printing process, the printed sheets will also have some stretching variation, causing vertical or horizontal misregistration. . In particular, the straight wire and paper with the fiber arrangement parallel to the axial direction of the roller suffer from pressure, moisture absorption, or water loss in the printing process, which may cause longitudinal stretching and variation of the paper. In order to reduce the variation of the paper, the cut paper should be immediately transported to the printing shop, so that the water content of the paper can be balanced with the temperature and humidity of the shop, and the printing shop must be kept at constant temperature and humidity. For printing products that have been misprinted due to print variations, the method of adjusting the thickness of the lining may be used to achieve the quality requirements of the register layout.
Fourth, improper operation process caused by improper overprinting of the product 1, poor printing plate bottom, over pressure caused by overprint printing on the letterpress platform printing machine printing large-area color printing products, if the use of multi-layer plastic plate as the bottom of the printing plate On the one hand, because the material is easy to produce imprinting on the one hand; on the other hand, due to the fact that the four sides of the wood tray are difficult to reach the technical requirements of right angles and straight edges, the printing plate is easy to produce arched disease after being fastened, and the printing pressure is inconsistent. A good transfer of the ink layer can be achieved by increasing the printing pressure. If the printing pressure is too heavy, imprinting will easily produce the opposite torsional force of the printed sheet and the clenched teeth. Therefore, the front gauge needle is inaccurate. Therefore, large-format overprinting products with large ink-absorption capacity should be made of metal magnetic platens and aluminum plates. The printing pressure and ink layer effects are good, and overprinting is also more accurate.
2. The color printing products that are not allowed to overprint due to excessive viscosity of the ink layer are large in the ink absorption of the bottom color layout, and the ink layer thickness is also relatively large, so that the ink layer on the printing surface is imprinted on the printing sheet. The sticking force is generated so that the printing paper is easily twisted from the teeth of the roller, causing the front gauge to be misaligned. The ink stickiness is too large, and it is easy to stretch the printed sheet and expand the printing surface, resulting in inaccurate overprinting. Therefore, the large-format background color should be printed as deep as possible, that is, the darkness of the printing ink should be slightly adjusted to make the printing ink thinner, which can satisfy the printing hue requirements and reduce the ink layer. Stickiness, this is one aspect. On the other hand, due to the low temperature, the viscosity of the ink is too large, and additives can be used to properly adjust the ink flow to reduce the viscosity of the ink and prevent relative slippage between the paper and the teeth, ensuring overprinting. accurate.
3, the inconsistent printing specifications caused by the overprint is not allowed to print paper in the cutting process, due to the uneven level of the paper roll appears uneven; the blade edge angle and the paper does not adapt to the characteristics of the paper; blade wear becomes blunt and other bad The situation exists, so that the cut paper will inevitably appear skewed or the "wavy line" whose edges are indistinct from the naked eye, so that the edge of the paper lacks right angles and straight lines. If the cover plate is moved to the lateral position or different Printing machine overprinting (front and side gauge position roller diameter is different), it is very easy to produce overprint not allowed. Therefore, in order to ensure the accuracy of product overprinting, the paper that is required to be cut should reach right angles and straight edges, and the performance and structure of the printer should be the same.
In summary, the reasons for inaccurate product overprinting are various, as long as we are good at conscientiously summing up experience and effectively shutting down operational technology and technology, not only can improve product overlay accuracy, but also promote production efficiency. improve. (Kang Qilai) (From "China Packaging News")
Gym Equipment,Gym Machine,Body Building Equipment
DDS Trade Co., Ltd. , http://www.lijiujia-sports.com