Some Experiences in Offset Quality Management
2018-06-16 16:00:24
Offset products are generally art reproductions, product labels, packaging and decoration, and publications, and the quality of printing will directly affect the social effects of products. The packaging of foreign publications or foreign trade goods also involves our country’s international reputation and influence. Therefore, how to put quality offset printing products in the market is extremely important. Next, the author will talk about the experience of quality control of offset printing products from the perspective of process management.
First, check the quality of the original
From the perspective of total quality management, the quality of offset printing products must start from the original manuscript. Because the quality of the original document determines the quality of the printed product. Therefore, the original (reflective draft) must be checked. A look at the original with or without scratches, dirt, etc., whether the characters and lines are complete, whether there are missing pens or not; second, see if the picture is color cast. Under natural light or a standard light source that is close to daylight, see if there is interference with Other colors in the apochromatic parts such as white, gray, and black on the reflective document. If not, it means there is no color cast in the reflected draft screen; third, 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 people-oriented reflection drafts, facial skin color should be used as the standard; 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 color of the dark tone is very consistent.
Second, the quality of printed semi-finished products inspection
1. Check overprint accuracy. In the general format, three crosshairs are added to the plates on the sides of "relying on the body," "facing outwards," and "dragging." Usually the crosshair should be 2-3mm from the product incision line, the horizontal line is used for the "up and down (ie, vertical)" layout rules, the rigid line is used for "coming (axial)" rules, all kinds of rules Line registration means that the graphic and text are also basically registered. Therefore, it can also be used as a basis for checking the rules and positioning of printed sheets. In order to check whether the gauge lines are consistent between the printed sheets, a stack of products can be taken out, a little diverged, and the “bite†side can be bumped to observe whether the “upper and lower†gauge lines are aligned; when the “pulled paper†is hit, the visual inspection can be performed. Whether or not the overprint of the "going and coming" is correct.
2. The inspection basis and method for the color of each color ink. The color mark on the side of the print can be used to compare whether the ink color is the same as the pay print. Because of the fineness of the dots, the difference in dot size within the pattern range is very large and it is difficult to compare the colors. There is a basis for comparing color patches. The color block can also be used as a basis for inspection of color leaks, white pages, and reverse printing. As soon as the color block is viewed, various waste products are quickly detected. The color standard should generally be in the upper right corner and lower left corner of the printing plate, starting from about 20mm from the corner line of the mouthpiece, and the color patches should be arranged in order, and the top right character's gauge line should be arranged 5mm toward the mouth. The color scale is 4-6mm wide and 10mm long. It is attached to the same edge of the crosshair. When determining the layout, the color mark should be printed to 3-4mm. The reticle should also be on the edge of the paper. The purpose of printing them to the edge is to facilitate the detection of overprint accuracy or waste defective conditions. In order to better control the printing quality, some signal sheets and test strips are printed on the printed sheets (edges or trailing edges). Commonly used are digital signal strips and star circular signs. The most widely used is Bruner's 5 signals and test strips with both functions of signal and test, which can be used together with density measurement and have good effect. If you use a chromatograph, you can also accurately compare the differences in ink hue, lightness, and saturation between the printed sample and the printed sample.
3. Check if the product is dirty. Dirty offset printing products are common problems in the printing process. In general, if the water content of the printing plate surface is controlled to a small extent, the internal quality of the product is better, but it is easy to produce filthy defects. This is worth noting. Therefore, every sampling inspection must first look at the relative positions of the two corners of the printed sheet or the consumption of ink, because if there is dirt, it is often the first time that these parts are dirty.
4. Check the evenness of ink and text on the layout. What is the thickness and uniformity of the ink layer in printed text and field layout products? When the sample inspection is performed, the two sides of the sampled sheet can be compared with the center of the previously sampled proofs, or they can be turned over for comparison to see whether the entire ink layer is printed. Differences in shades. At the same time, it is necessary to carefully observe whether there are ills of “flower paste†in the layout in order to take corresponding measures to eliminate it and ensure the stability of the batch product quality.
In summary, the quality of offset printing products is controlled through careful and accurate inspections, and corresponding measures are taken to control them. Not only can the quality of the products 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 offset printing products must start from the original manuscript. Because the quality of the original document determines the quality of the printed product. Therefore, the original (reflective draft) must be checked. A look at the original with or without scratches, dirt, etc., whether the characters and lines are complete, whether there are missing pens or not; second, see if the picture is color cast. Under natural light or a standard light source that is close to daylight, see if there is interference with Other colors in the apochromatic parts such as white, gray, and black on the reflective document. If not, it means there is no color cast in the reflected draft screen; third, 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 people-oriented reflection drafts, facial skin color should be used as the standard; 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 color of the dark tone is very consistent.
Second, the quality of printed semi-finished products inspection
1. Check overprint accuracy. In the general format, three crosshairs are added to the plates on the sides of "relying on the body," "facing outwards," and "dragging." Usually the crosshair should be 2-3mm from the product incision line, the horizontal line is used for the "up and down (ie, vertical)" layout rules, the rigid line is used for "coming (axial)" rules, all kinds of rules Line registration means that the graphic and text are also basically registered. Therefore, it can also be used as a basis for checking the rules and positioning of printed sheets. In order to check whether the gauge lines are consistent between the printed sheets, a stack of products can be taken out, a little diverged, and the “bite†side can be bumped to observe whether the “upper and lower†gauge lines are aligned; when the “pulled paper†is hit, the visual inspection can be performed. Whether or not the overprint of the "going and coming" is correct.
2. The inspection basis and method for the color of each color ink. The color mark on the side of the print can be used to compare whether the ink color is the same as the pay print. Because of the fineness of the dots, the difference in dot size within the pattern range is very large and it is difficult to compare the colors. There is a basis for comparing color patches. The color block can also be used as a basis for inspection of color leaks, white pages, and reverse printing. As soon as the color block is viewed, various waste products are quickly detected. The color standard should generally be in the upper right corner and lower left corner of the printing plate, starting from about 20mm from the corner line of the mouthpiece, and the color patches should be arranged in order, and the top right character's gauge line should be arranged 5mm toward the mouth. The color scale is 4-6mm wide and 10mm long. It is attached to the same edge of the crosshair. When determining the layout, the color mark should be printed to 3-4mm. The reticle should also be on the edge of the paper. The purpose of printing them to the edge is to facilitate the detection of overprint accuracy or waste defective conditions. In order to better control the printing quality, some signal sheets and test strips are printed on the printed sheets (edges or trailing edges). Commonly used are digital signal strips and star circular signs. The most widely used is Bruner's 5 signals and test strips with both functions of signal and test, which can be used together with density measurement and have good effect. If you use a chromatograph, you can also accurately compare the differences in ink hue, lightness, and saturation between the printed sample and the printed sample.
3. Check if the product is dirty. Dirty offset printing products are common problems in the printing process. In general, if the water content of the printing plate surface is controlled to a small extent, the internal quality of the product is better, but it is easy to produce filthy defects. This is worth noting. Therefore, every sampling inspection must first look at the relative positions of the two corners of the printed sheet or the consumption of ink, because if there is dirt, it is often the first time that these parts are dirty.
4. Check the evenness of ink and text on the layout. What is the thickness and uniformity of the ink layer in printed text and field layout products? When the sample inspection is performed, the two sides of the sampled sheet can be compared with the center of the previously sampled proofs, or they can be turned over for comparison to see whether the entire ink layer is printed. Differences in shades. At the same time, it is necessary to carefully observe whether there are ills of “flower paste†in the layout in order to take corresponding measures to eliminate it and ensure the stability of the batch product quality.
In summary, the quality of offset printing products is controlled through careful and accurate inspections, and corresponding measures are taken to control them. Not only can the quality of the products be improved, but also the production efficiency can be improved.
Feiaoda Technology Co., Ltd. , http://www.szkitchensilicone.com