Despite the maturity of CTP technology, laser imagesetters still maintain their strong production. In print publications such as commodity packaging and books, there are still quite a few parts that need to be pre-printed, produced, exported, and finally printed out. The quality of the photo-discharge film is directly related to the quality of the final printed product. This shows that there are still many areas in the traditional process that are still to be studied and explored. Below, the author will discuss the experience of quality management of photo film from the perspective of process management.
First, check the quality of the original
From the perspective of total quality management, the quality of control photographs must be checked from the manuscript. Because the quality of the original document determines the quality of the film. Therefore, the original must be carefully checked. A look at the surface of the original whether scratches, dirt, text, lines are complete, with or without missing strokes; Second, see whether the screen color cast. In the natural light or close to the daylight of the standard light source, observe the reflection of the apochromatic parts of white, gray, black and other color interference; three to see if the main color is accurate. In general, the color of reflections (photos, etc.) is slightly exaggerated compared to the actual scene, which is more vivid than the original color. For example, reflections based on characters should be based on the ruddyness of the facial skin. Fourth, whether the contrast is moderate. The contrast of the reflection draft includes luminance difference, color contrast and contrast balance. The brightness difference is moderate, there is a rich transitional color gradation between the high-profile part and the dark tone part; the color contrast is moderate, the reflection text color concentration is large, and the stereoscopic effect is strong; the contrast is good, the same color is in the high-profile part and The tone of the shadow tone will be very consistent.
Second, the pre-press output document quality inspection
The inspection items that need to be performed on the documents to be output are:
1. Check whether the overprint line, color mark and various printing and cutting lines are complete. The register line should be four-color black (ie, C=100%, M=100%, Y=100%, K=100%), and there is no overprinting line. The output four or more color photostrip is equal to one. Heaps of waste.
2, check the image color mode. When the laser imagesetter outputs the color separation film, the color mode of all color images should be CMYK mode. Therefore, before the output, check whether the color mode of the linked image is correct by linking the image table. If the image is still in RGB or Lab mode, the color mode conversion should be performed in the image processing software; otherwise, only the image on the black plate is output when the color separation film is output, or the color separation condition is not ideal or even can not be output; for the black and white image, the image mode Should be grayscale or binary mode, only black dot information is available when outputting.
3, check whether the resolution of the picture used meets the printing requirements.
Ensure that the scanned images, photos, and other raster images have the appropriate resolution, which is necessary to ensure the quality of output photos (the resolution is independent of the Postscript vector, they will print at the output device's maximum resolution). The following are the resolution setting standards for some common different publications:
Newspapers have a scanning resolution of 125-170 dpi. For print images, set the resolution to 1.5 to 2 times the line (lpi) (2 times will make the image more flexible). Newspapers use 85 to 133 lpi.
Journals, magazines, and promotional materials use a scanning resolution of 300 dpi, as magazine printing generally uses 133 or 150 lpi.
High-quality books use a scanning resolution of 350 to 400 dpi because most of the finely printed books use 175 to 200 lpi.
Here we need to explain is: it is best not to use the Internet to download pictures, the resolution of these pictures is generally only 72dpi, some lower, no matter what kind of processing, the output will not be very good.
4. Explain the result of the hair clip by RIP. The RIP interpretation preview is consistent with the final hair print result. By previewing the original or the proof, check whether the linked image of the file is correct, whether the image interpretation is intact (if the image is damaged, the RIP interpretation will be wrong), and whether the image color is Consistent with the manuscript, whether the text is garbled, whether the various elements of the document are misplaced, and whether the black version is overprinted. This is the last check before the output, so be careful to avoid quality problems.
Three, photosetter operation check
After the imagesetter is started, its working status is generally visible in the graphical interface of the control software of the output workstation. The items to be inspected are:
1. Whether the settings of the laser image-setter and the system equipment match and operate normally. In order to ensure the stability of the laser, the laser head should be tested and corrected regularly.
2. The liquid concentration and temperature of the punching machine are normal. According to the photo film and the properties of the liquid, set the values ​​of the developing and fixing parameters, and regularly test with the test strip and the screed. At the same time, do the daily cleaning and maintenance of the punching equipment to prevent the turbid materials from dirty .
3, photo film and the liquid itself is stable. In order to ensure the stability of the quality of photostrips, the use of raw materials should minimize the variable factors, so that the use of raw materials is relatively fixed.
4. Photographic films are easily scratched by the influence of foreign materials during the operation and transmission of the equipment. The transmission components should be cleaned and wiped regularly. When the components are found to be damaged, they should be promptly replaced.
Fourth, the quality of output photos
After the output, it is necessary to check the output photographs, and the inspection of the photographs is the last process before printing. It is necessary to really pay attention to plugging and plugging. The inspection includes:
1. Check the fitting accuracy. In general, continuous output four-color or multi-color photo mating error is very small, if one job requires a one-color or two-color make-up, and the other color photo is a day, two days or longer Previously output, carefully check the alignment accuracy of each color photographing panel. If the fitting error is large, output all color version photographs continuously. Of course, this should be based on the time of use of the imagesetter and the stability of the work. Some image-setters have large errors in arranging four-color images for continuous output. At this time, maintenance or updating of the machine should be considered.
2. Check originals or proofs to check the imprinting relationship of each color version. Sometimes the layout elements will be lost or misplaced due to personnel operation or machine failure. For books and periodicals publications, the best way to check is to attach a photo slide to the original or the proof. If there is any mistake, it will be clearly visible. Of course, in this process, care should be taken to avoid scratching the film and affecting the print quality.
3. Check if the photo film is dirty. Dirty photos are a common problem in the output process. Generally speaking, the washing tank should be cleaned before starting the machine every day. Before the water injection, the water purification equipment of the external water supply switch should be turned on to prevent sediment deposited in the pipeline from being carried into the washing tank, scratching or sticking to the film. According to the platter quality, after the work is finished, the rinsing tank should be drained and carefully cleaned, otherwise impurities may be generated in the water and the rinsing quality may be reduced.
4. Check the angle of the screen angle in each color. In order to avoid collision, theoretically speaking, there should be a difference of 22.5 degrees between the four colors. In the actual production, four-color printing uses 15 degrees, 45 degrees, 75 degrees and 90 degrees. The yellow version of the visual stimuli is relatively weak, and the visual sensation is poor, so it is generally set at 90 degrees. Since human vision is most sensitive to 45-degree angles, the main color of the original document is generally set at 45 degrees. The specific settings should be based on the design of printed products. The angle of the screen can be checked with a magnifying glass for the screen angles of the plates of various colors, or measured with a screen angle measurement tool. In addition to the special requirements of customers, the general network angle settings should not be arbitrarily changed to avoid unnecessary losses.
5. Control row density inspection. Through the transmission density meter check photo film density, the general density value of more than 3.5 can be, but it is best around 4.2, the density is too high, the printing will produce paste phenomenon, the density is too low, for text and field layout products The printed ink was lighter and looked unrealistic. At this time, it is necessary to consider replacing the fixing solution or cleaning the laser head to ensure that the quality of the photolithography film is stable.
In summary, the quality of the photo-discharge film is carefully and accurately checked, and corresponding measures are taken to control it. Not only the quality of the photo-discharge film can be improved, but also the production efficiency can be improved.
First, check the quality of the original
From the perspective of total quality management, the quality of control photographs must be checked from the manuscript. Because the quality of the original document determines the quality of the film. Therefore, the original must be carefully checked. A look at the surface of the original whether scratches, dirt, text, lines are complete, with or without missing strokes; Second, see whether the screen color cast. In the natural light or close to the daylight of the standard light source, observe the reflection of the apochromatic parts of white, gray, black and other color interference; three to see if the main color is accurate. In general, the color of reflections (photos, etc.) is slightly exaggerated compared to the actual scene, which is more vivid than the original color. For example, reflections based on characters should be based on the ruddyness of the facial skin. Fourth, whether the contrast is moderate. The contrast of the reflection draft includes luminance difference, color contrast and contrast balance. The brightness difference is moderate, there is a rich transitional color gradation between the high-profile part and the dark tone part; the color contrast is moderate, the reflection text color concentration is large, and the stereoscopic effect is strong; the contrast is good, the same color is in the high-profile part and The tone of the shadow tone will be very consistent.
Second, the pre-press output document quality inspection
The inspection items that need to be performed on the documents to be output are:
1. Check whether the overprint line, color mark and various printing and cutting lines are complete. The register line should be four-color black (ie, C=100%, M=100%, Y=100%, K=100%), and there is no overprinting line. The output four or more color photostrip is equal to one. Heaps of waste.
2, check the image color mode. When the laser imagesetter outputs the color separation film, the color mode of all color images should be CMYK mode. Therefore, before the output, check whether the color mode of the linked image is correct by linking the image table. If the image is still in RGB or Lab mode, the color mode conversion should be performed in the image processing software; otherwise, only the image on the black plate is output when the color separation film is output, or the color separation condition is not ideal or even can not be output; for the black and white image, the image mode Should be grayscale or binary mode, only black dot information is available when outputting.
3, check whether the resolution of the picture used meets the printing requirements.
Ensure that the scanned images, photos, and other raster images have the appropriate resolution, which is necessary to ensure the quality of output photos (the resolution is independent of the Postscript vector, they will print at the output device's maximum resolution). The following are the resolution setting standards for some common different publications:
Newspapers have a scanning resolution of 125-170 dpi. For print images, set the resolution to 1.5 to 2 times the line (lpi) (2 times will make the image more flexible). Newspapers use 85 to 133 lpi.
Journals, magazines, and promotional materials use a scanning resolution of 300 dpi, as magazine printing generally uses 133 or 150 lpi.
High-quality books use a scanning resolution of 350 to 400 dpi because most of the finely printed books use 175 to 200 lpi.
Here we need to explain is: it is best not to use the Internet to download pictures, the resolution of these pictures is generally only 72dpi, some lower, no matter what kind of processing, the output will not be very good.
4. Explain the result of the hair clip by RIP. The RIP interpretation preview is consistent with the final hair print result. By previewing the original or the proof, check whether the linked image of the file is correct, whether the image interpretation is intact (if the image is damaged, the RIP interpretation will be wrong), and whether the image color is Consistent with the manuscript, whether the text is garbled, whether the various elements of the document are misplaced, and whether the black version is overprinted. This is the last check before the output, so be careful to avoid quality problems.
Three, photosetter operation check
After the imagesetter is started, its working status is generally visible in the graphical interface of the control software of the output workstation. The items to be inspected are:
1. Whether the settings of the laser image-setter and the system equipment match and operate normally. In order to ensure the stability of the laser, the laser head should be tested and corrected regularly.
2. The liquid concentration and temperature of the punching machine are normal. According to the photo film and the properties of the liquid, set the values ​​of the developing and fixing parameters, and regularly test with the test strip and the screed. At the same time, do the daily cleaning and maintenance of the punching equipment to prevent the turbid materials from dirty .
3, photo film and the liquid itself is stable. In order to ensure the stability of the quality of photostrips, the use of raw materials should minimize the variable factors, so that the use of raw materials is relatively fixed.
4. Photographic films are easily scratched by the influence of foreign materials during the operation and transmission of the equipment. The transmission components should be cleaned and wiped regularly. When the components are found to be damaged, they should be promptly replaced.
Fourth, the quality of output photos
After the output, it is necessary to check the output photographs, and the inspection of the photographs is the last process before printing. It is necessary to really pay attention to plugging and plugging. The inspection includes:
1. Check the fitting accuracy. In general, continuous output four-color or multi-color photo mating error is very small, if one job requires a one-color or two-color make-up, and the other color photo is a day, two days or longer Previously output, carefully check the alignment accuracy of each color photographing panel. If the fitting error is large, output all color version photographs continuously. Of course, this should be based on the time of use of the imagesetter and the stability of the work. Some image-setters have large errors in arranging four-color images for continuous output. At this time, maintenance or updating of the machine should be considered.
2. Check originals or proofs to check the imprinting relationship of each color version. Sometimes the layout elements will be lost or misplaced due to personnel operation or machine failure. For books and periodicals publications, the best way to check is to attach a photo slide to the original or the proof. If there is any mistake, it will be clearly visible. Of course, in this process, care should be taken to avoid scratching the film and affecting the print quality.
3. Check if the photo film is dirty. Dirty photos are a common problem in the output process. Generally speaking, the washing tank should be cleaned before starting the machine every day. Before the water injection, the water purification equipment of the external water supply switch should be turned on to prevent sediment deposited in the pipeline from being carried into the washing tank, scratching or sticking to the film. According to the platter quality, after the work is finished, the rinsing tank should be drained and carefully cleaned, otherwise impurities may be generated in the water and the rinsing quality may be reduced.
4. Check the angle of the screen angle in each color. In order to avoid collision, theoretically speaking, there should be a difference of 22.5 degrees between the four colors. In the actual production, four-color printing uses 15 degrees, 45 degrees, 75 degrees and 90 degrees. The yellow version of the visual stimuli is relatively weak, and the visual sensation is poor, so it is generally set at 90 degrees. Since human vision is most sensitive to 45-degree angles, the main color of the original document is generally set at 45 degrees. The specific settings should be based on the design of printed products. The angle of the screen can be checked with a magnifying glass for the screen angles of the plates of various colors, or measured with a screen angle measurement tool. In addition to the special requirements of customers, the general network angle settings should not be arbitrarily changed to avoid unnecessary losses.
5. Control row density inspection. Through the transmission density meter check photo film density, the general density value of more than 3.5 can be, but it is best around 4.2, the density is too high, the printing will produce paste phenomenon, the density is too low, for text and field layout products The printed ink was lighter and looked unrealistic. At this time, it is necessary to consider replacing the fixing solution or cleaning the laser head to ensure that the quality of the photolithography film is stable.
In summary, the quality of the photo-discharge film is carefully and accurately checked, and corresponding measures are taken to control it. Not only the quality of the photo-discharge film can be improved, but also the production efficiency can be improved.
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