Printing and packaging principle - process - technology articles: How to determine the edge of the mouth when loading the plate? How to determine the width of the edge of the plate when loading? What is a printing positioning system... Here are some common problems and solutions in packaging offset printing. The following content is organized by Xiaobian and is provided for your reference.
Common problems and solutions for packaging offset printing
How to determine the edge of the mouth when loading the plate?
Which side of the original is used as the edge of the mouth should be considered from the needs of printing and finishing.
1 From the specification limit and positioning accuracy of the printing press, the original rectangular original should be the long side as the mouth.
2 From the point of view of the accuracy of overprinting, since the paper deformation at the edge of the cornice is small and the paper on the trailing edge is greatly deformed, the side with the high overprinting requirement on the original plate should be used as the edge of the mouth.
3 From the point of view of saving paper, since the position of 1cm wide on the edge of the mouth is not printed, sometimes the paper format is very tight, and it is necessary to make full use of this part of the white edge, then the blank edge of the finished product or the paper tongue of the paste box is required. When you lick your mouth.
4 From the point of view of post-press processing, the choice of the edge of the mouth should be conducive to die-cutting.
How to determine the width of the edge of the plate when loading?
When installing the plate, the distance between the original image and the edge of the plate is required to be within a certain range. The distance between the image on the original plate and the edge of the plate is c. The distance between the image on the original plate and the edge of the paper is a, and the distance from the edge of the paper to the edge of the plate is b. Then there is c=a. +b. The size of b is determined by the position of the plate cylinder relative to the impression cylinder and the front and back of the front plate. The influence of the adjustment gauge on the b is very small, and the different machines are printed. The position adjustment of the plate cylinder relative to the impression cylinder is different, generally about 5 cm.
The dried printing plate, that is, the case where c has been determined, adjusts the size of b, and can change the front and rear position of the printed image on the paper, commonly known as "borrowing roller". However, if you need to use the "borrowing roller" to adjust the position of the image on the paper during printing, it will obviously affect the production efficiency. It is more reasonable to select a roughly centered b0 value for a certain type of printing press. If you want the image to be printed on the paper at a distance of a from the edge of the mouth, determine the image when printing according to c=a10b0. The distance c from the edge of the plate. Each time in this way, the position of the original plate relative to the edge of the plate at the time of printing is determined, and the "borrowing roller" is not required for printing. If there is a corner on the original, it is usually used as a reference to determine the distance of the original from the edge of the plate.
What is a print positioning system?
From the original to the printed matter, it must be separated, imposition, and copied. Printing, printing and other production processes. In order to ensure that the color separation image can achieve the overprinting accuracy in the fastest way in the production of each process, the coordination pin and the positioning hole can be used to achieve the purpose through a series of operations, and the system is called a printing positioning system. Since the desktop system is generally used for layout production, and the overprinting accurate color separation film can be automatically output, the positioning system is mainly used in the printing and printing process.
What constitutes a positioning system?
The positioning system is mainly made up of printing plates. A film punch, a locating pin and a locating pin on the plate cylinder.
What are the benefits of using a positioning system?
1 greatly shortened the time for loading and editing. If the printing plate can reasonably arrange the position of the original plate relative to the printing plate. And the correct positioning system is used, so that the printing machine can basically achieve the purpose of registration without adjusting the color, so that the production efficiency is greatly improved.
2 The printing plate no longer needs to be repeatedly pulled, which reduces the misregistration caused by the tensile deformation of the printing plate and improves the printing quality of the product.
How to use the positioning system correctly?
At present, the multi-color printing plate and printing positioning system are adopted in China, and the correct use method is as follows:
1 Cut the polyester base, the width should be smaller than the distance of the original edge of the image from the edge of the plate, and use a punch to punch the polyester base.
2 The base of the first color plate is fixed on the base with the perforated edge of the polyester base as the reference of the edge of the printing plate and the long circular hole in the middle of the polyester base as the center line of the printing plate. Note that the base should be attached to the non-film side of the film.
3 The polyester film base of the first color version of the fixed number is placed on the positioning pin, and the second color negative film and the first color negative film are registered. At the same time, the second polyester sheet base is sleeved on the positioning pin, and in the case of the second and first color version film registration, the second color version of the negative film and the second polyester base are fixed together. The remaining negatives of the other color plates are processed by the method of processing the second color negative film.
4 Punch each plate to be sun-dried, align the film of each color plate and the positioning hole of the plate with the positioning pin, and then print the plate.
5 When installing the plate, firstly, the plates on the edge of the plate cylinder of each unit should be retracted to the same reference position, and the two U-shaped holes on the plate are hung on the positioning pin, so that the u-shaped hole and the positioning pin are closely connected. Then tighten the clip on the side of the tip and tighten the clip on the side of the mouth.
What are the requirements for the exposure light source for the PS version?
1 The spectrum of the light source of the printer should be consistent with the spectrum of the sensitizer of the PS plate. The photosensitive spectrum of the PS plate is about 350-450 nm, and the light source is required to have a high energy peak in this wavelength band to shorten the exposure time and obtain a good exposure effect.
2 The illuminance of the light source should be uniform. The illuminance meter can be used to detect the illuminance of the middle and surrounding points of the printing plate, and the illuminance unevenness of each point of the layout is required to be less than 1 5%.
3 The power of the light source should be around 3000W, and the required voltage fluctuation value is less than 10%. Before the exposure of the plate, the light source should be preheated to ensure the stability of the light intensity during exposure.
How to determine the exposure time of the PS version?
The exposure time of the PS version depends mainly on the sensitization range of the PS plate. Sensitivity and spectral characteristics of the light source, the strength of the light source and other factors. Therefore, each time you change a different brand of PS version or replace the light source, you need to use the test strip to perform a series of tests on the PS version to determine the correct exposure time.
The test method is as follows: select a transmission gray scale with a continuous density difference of 0.15 and a Brunel or other similar test strip with small dots and thin lines, and gradually increase the PS strip with two test strips. The exposure time is exposed, and the corresponding exposure time of each block is recorded. After development, the magnifying glass is used to observe each test strip that is dried, and the exposure time corresponding to the qualified test strip can be used as the normal printing time. When drying ordinary mesh products, the first 4 grades of the gray ladder are required to be sunburned; 1% of the 6 dots are exposed, 2% of the dots are aligned; 11 μm wide thin lines are retained, and 8 μm wide thin lines are dried. .
How to adjust the exposure time of PS version according to specific conditions?
1 There are no outlets, only thicker text. Lines and the original version of the field can increase the exposure time, drying out small dirty spots and dirty marks to reduce the time to remove dirt.
2 The film is stored for a long time, the blank part is yellow, or it is hand-stamped. Two or three layers of blank base are stacked together to increase the exposure time slightly; the original part with a low density in the field can reduce the exposure time.
3 The pressure of the proofing machine is less than that of the printing machine, so the increase of the proofing dot is smaller than that of the printing dot, so the exposure time of the proofing plate should be less than the exposure time of the printing plate. The sun-dried sample is generally done at 0.5% of the outlets, and 1% of the outlets are retained.
Strictly speaking, for the color separation of the layered draft. When determining the tone replication curve, the difference in dot gain in each case should have been taken into consideration and compensated. In fact, the standardization of this kind of process in China is very bad, so it depends on the production conditions of the respective printing plants. Adjust the exposure time. If the factory printing process, the dot gain rate is large. Increase the exposure time. Depending on the substrate to be printed, the exposure time of the printing offset paper should be longer than the printing plate of the coated printing paper.
Why do I need to pump when I get a print?
Take the production of the positive-working PS plate as an example. When printing, the film surface of the film is not closely connected with the photosensitive coating of the PS plate. There is a gap in the middle, and there will be light obliquely from the edge of the blank portion of the film to the photosensitive coating directly below the image portion, causing the edge of the image portion to be decomposed. Make the image sunburn. The dots become smaller, and small dots and thin lines are lost.
Since one side of the printing frame is transparent glass, the other side is a rubber pad. When the vacuum pump draws out the air in the printing frame, the air pressure inside is low, and the rubber pad will be under the external atmospheric pressure, and the PS plate will be used. The original film is placed on the top of the glass and is closely bonded together.
Common problems and solutions for packaging offset printing
How to determine the edge of the mouth when loading the plate?
Which side of the original is used as the edge of the mouth should be considered from the needs of printing and finishing.
1 From the specification limit and positioning accuracy of the printing press, the original rectangular original should be the long side as the mouth.
2 From the point of view of the accuracy of overprinting, since the paper deformation at the edge of the cornice is small and the paper on the trailing edge is greatly deformed, the side with the high overprinting requirement on the original plate should be used as the edge of the mouth.
3 From the point of view of saving paper, since the position of 1cm wide on the edge of the mouth is not printed, sometimes the paper format is very tight, and it is necessary to make full use of this part of the white edge, then the blank edge of the finished product or the paper tongue of the paste box is required. When you lick your mouth.
4 From the point of view of post-press processing, the choice of the edge of the mouth should be conducive to die-cutting.
How to determine the width of the edge of the plate when loading?
When installing the plate, the distance between the original image and the edge of the plate is required to be within a certain range. The distance between the image on the original plate and the edge of the plate is c. The distance between the image on the original plate and the edge of the paper is a, and the distance from the edge of the paper to the edge of the plate is b. Then there is c=a. +b. The size of b is determined by the position of the plate cylinder relative to the impression cylinder and the front and back of the front plate. The influence of the adjustment gauge on the b is very small, and the different machines are printed. The position adjustment of the plate cylinder relative to the impression cylinder is different, generally about 5 cm.
The dried printing plate, that is, the case where c has been determined, adjusts the size of b, and can change the front and rear position of the printed image on the paper, commonly known as "borrowing roller". However, if you need to use the "borrowing roller" to adjust the position of the image on the paper during printing, it will obviously affect the production efficiency. It is more reasonable to select a roughly centered b0 value for a certain type of printing press. If you want the image to be printed on the paper at a distance of a from the edge of the mouth, determine the image when printing according to c=a10b0. The distance c from the edge of the plate. Each time in this way, the position of the original plate relative to the edge of the plate at the time of printing is determined, and the "borrowing roller" is not required for printing. If there is a corner on the original, it is usually used as a reference to determine the distance of the original from the edge of the plate.
What is a print positioning system?
From the original to the printed matter, it must be separated, imposition, and copied. Printing, printing and other production processes. In order to ensure that the color separation image can achieve the overprinting accuracy in the fastest way in the production of each process, the coordination pin and the positioning hole can be used to achieve the purpose through a series of operations, and the system is called a printing positioning system. Since the desktop system is generally used for layout production, and the overprinting accurate color separation film can be automatically output, the positioning system is mainly used in the printing and printing process.
What constitutes a positioning system?
The positioning system is mainly made up of printing plates. A film punch, a locating pin and a locating pin on the plate cylinder.
What are the benefits of using a positioning system?
1 greatly shortened the time for loading and editing. If the printing plate can reasonably arrange the position of the original plate relative to the printing plate. And the correct positioning system is used, so that the printing machine can basically achieve the purpose of registration without adjusting the color, so that the production efficiency is greatly improved.
2 The printing plate no longer needs to be repeatedly pulled, which reduces the misregistration caused by the tensile deformation of the printing plate and improves the printing quality of the product.
How to use the positioning system correctly?
At present, the multi-color printing plate and printing positioning system are adopted in China, and the correct use method is as follows:
1 Cut the polyester base, the width should be smaller than the distance of the original edge of the image from the edge of the plate, and use a punch to punch the polyester base.
2 The base of the first color plate is fixed on the base with the perforated edge of the polyester base as the reference of the edge of the printing plate and the long circular hole in the middle of the polyester base as the center line of the printing plate. Note that the base should be attached to the non-film side of the film.
3 The polyester film base of the first color version of the fixed number is placed on the positioning pin, and the second color negative film and the first color negative film are registered. At the same time, the second polyester sheet base is sleeved on the positioning pin, and in the case of the second and first color version film registration, the second color version of the negative film and the second polyester base are fixed together. The remaining negatives of the other color plates are processed by the method of processing the second color negative film.
4 Punch each plate to be sun-dried, align the film of each color plate and the positioning hole of the plate with the positioning pin, and then print the plate.
5 When installing the plate, firstly, the plates on the edge of the plate cylinder of each unit should be retracted to the same reference position, and the two U-shaped holes on the plate are hung on the positioning pin, so that the u-shaped hole and the positioning pin are closely connected. Then tighten the clip on the side of the tip and tighten the clip on the side of the mouth.
What are the requirements for the exposure light source for the PS version?
1 The spectrum of the light source of the printer should be consistent with the spectrum of the sensitizer of the PS plate. The photosensitive spectrum of the PS plate is about 350-450 nm, and the light source is required to have a high energy peak in this wavelength band to shorten the exposure time and obtain a good exposure effect.
2 The illuminance of the light source should be uniform. The illuminance meter can be used to detect the illuminance of the middle and surrounding points of the printing plate, and the illuminance unevenness of each point of the layout is required to be less than 1 5%.
3 The power of the light source should be around 3000W, and the required voltage fluctuation value is less than 10%. Before the exposure of the plate, the light source should be preheated to ensure the stability of the light intensity during exposure.
How to determine the exposure time of the PS version?
The exposure time of the PS version depends mainly on the sensitization range of the PS plate. Sensitivity and spectral characteristics of the light source, the strength of the light source and other factors. Therefore, each time you change a different brand of PS version or replace the light source, you need to use the test strip to perform a series of tests on the PS version to determine the correct exposure time.
The test method is as follows: select a transmission gray scale with a continuous density difference of 0.15 and a Brunel or other similar test strip with small dots and thin lines, and gradually increase the PS strip with two test strips. The exposure time is exposed, and the corresponding exposure time of each block is recorded. After development, the magnifying glass is used to observe each test strip that is dried, and the exposure time corresponding to the qualified test strip can be used as the normal printing time. When drying ordinary mesh products, the first 4 grades of the gray ladder are required to be sunburned; 1% of the 6 dots are exposed, 2% of the dots are aligned; 11 μm wide thin lines are retained, and 8 μm wide thin lines are dried. .
How to adjust the exposure time of PS version according to specific conditions?
1 There are no outlets, only thicker text. Lines and the original version of the field can increase the exposure time, drying out small dirty spots and dirty marks to reduce the time to remove dirt.
2 The film is stored for a long time, the blank part is yellow, or it is hand-stamped. Two or three layers of blank base are stacked together to increase the exposure time slightly; the original part with a low density in the field can reduce the exposure time.
3 The pressure of the proofing machine is less than that of the printing machine, so the increase of the proofing dot is smaller than that of the printing dot, so the exposure time of the proofing plate should be less than the exposure time of the printing plate. The sun-dried sample is generally done at 0.5% of the outlets, and 1% of the outlets are retained.
Strictly speaking, for the color separation of the layered draft. When determining the tone replication curve, the difference in dot gain in each case should have been taken into consideration and compensated. In fact, the standardization of this kind of process in China is very bad, so it depends on the production conditions of the respective printing plants. Adjust the exposure time. If the factory printing process, the dot gain rate is large. Increase the exposure time. Depending on the substrate to be printed, the exposure time of the printing offset paper should be longer than the printing plate of the coated printing paper.
Why do I need to pump when I get a print?
Take the production of the positive-working PS plate as an example. When printing, the film surface of the film is not closely connected with the photosensitive coating of the PS plate. There is a gap in the middle, and there will be light obliquely from the edge of the blank portion of the film to the photosensitive coating directly below the image portion, causing the edge of the image portion to be decomposed. Make the image sunburn. The dots become smaller, and small dots and thin lines are lost.
Since one side of the printing frame is transparent glass, the other side is a rubber pad. When the vacuum pump draws out the air in the printing frame, the air pressure inside is low, and the rubber pad will be under the external atmospheric pressure, and the PS plate will be used. The original film is placed on the top of the glass and is closely bonded together.
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