How to check the film quality before the prepress

First, the importance of film

Film plays a role in printing and is an indispensable part of printing. We all know that the printing process is: original → plate making → output film → proofing → printing → after processing → finished product. Although the digital direct plate-making technology CTP is developing very fast, it will take some time to popularize the application. Film in the traditional printing process is still one of the key aspects of printing. Without film, it cannot be printed and cannot be printed.

Second, the purpose of checking the film

The earliest printed film was made by photo-engraving. The human factors and technical level have a great influence on the quality of the film. Nowadays, the printed film is generally interpreted as a bitmap image of the digital image through the rip. Then output the results of the finished version to the film. Factors affecting film quality include the perfection of software rip and the work experience of the production staff, as well as the work experience of the dispatchers. The degree of knowledge of the software used by the production staff and the dispatcher determines whether the output film can be printed on the machine normally. The error rate is very high, so checking the film is a must for every printing company and prepress company. The purpose of inspecting film is to eliminate various disadvantages that occur during the printing process or to avoid some printing process errors that may occur.

Third, the tool to check the film

Magnifying glass, scale, standard chromatogram, oily pen, density meter, dot angle ruler

Fourth, the steps to check the film

1. After getting the film, first confirm whether the film quantity is consistent with the requirements of the use. Generally, it includes a monochrome film, a four-color film, a spot color film, and the film of the front cover is insufficient.

2. Under the premise of determining the appropriate amount of film. Check the film fit. Under normal circumstances, on the counter platform, one of the other three films is used as a reference for one of the large-area colors, and no more than half of the line is allowed under the normal thickness of the casing line. Text, lines, and image edges cannot be ghosted.

3. Next, separate the color of each film. Some films have the color standard CMYK, so don't talk about it. Some films do not have a color mark, and can be identified by comparing the color blocks on the color original with the color blocks of the color original, and marked with an oil-based pen. If the film with the problem needs to be re-issued, it should be noted that the first time and the second time should also be marked separately.

4. Check the film size. Check whether the film size is the same as the requirements according to the work order. All the center line, the nesting line and the cutting line should be added when the film is output. If there is a sample, the sample is processed according to the requirements of the finished product. If there are no samples, check the dimensions according to the finished product size. Each relevant size must be checked one by one. If it is an irregular size requirement such as a handbag, envelope or pill box, it is necessary to carefully check whether there is a sticky mouth, a fold, a bottom, a bleeding, and the white side is not enough. Finally check the film size plus the size of the bite can be printed normally (the big flip version has a bite on each side of the 13mm, if the paper does not allow, you have to print two sets).

5. The check of the imposition method is also very important. The imposition method generally has a self-reversing version, a large turning version and a large version. What kind of layout should be tailored to the specific situation, self-revolution and large sets should be symmetric with the center line, it is very important to check whether the distance between the center line and the two sides is equal. The direction of imposition should be symmetrical, and the error of the back cover of the large set should be within 1l, and the corresponding lines can all be aligned. Also note that some work pieces that require back binding or folding must be correct.

6. Check the layout and text content after the imposition is correct. Check whether the customer's change is correct, and then check whether the layout and content are consistent with the original. It should be carefully checked, and the wrong one is wrong. The position of the mosaic must be accurate and the content can be docked.

7. If there is only a plastic sheet with no color proofing, check whether the color of each color version of the four-color film is consistent with the color separation of the color spray. The color on the color spray should correspond to the corresponding film.

8. If it is a re-issue or change the hairline, apply the new film and the old film color version one by one to check, the changed place has been changed or the color density or dot number changes, the new and old film is marked with oily pen.

9. Carefully check the flat screens of each color, the transition network, whether there are scratches, dirty spots, virtual spots, laser lines, creases, noise points, smooth transitions, etc. on the pictures.

10. Using experience If it is not determined whether the density of the film can meet the printing requirements, the film is detected by a densitometer, and the film is 3.4 or more, and the electric film is 3.8 or more.

11. If there is no obvious proof or trace on the proof, the angle of the cable should be checked. In general, the angle of the cable is 0°, 15°, 45°, 75°. If the two-color version of the network cable has the same angle, the moiré must appear, and the angle of the cable must be changed.

12. If you feel that the film cable is rough or the proofing dot is large, check if the number of hairline lines meets the needs of the job. Offset paper printing is generally 130l, newsprint is generally 100l, coated paper is generally 175l, high-grade printing is generally 200l.

13. After the whole film is inspected, if some places are changed, it is best to draw it with a striking pen, clearly indicate the change place. If you can't change it by hand, please re-send the film. Otherwise, it takes a long time for the joint drying, the printing plate is difficult, and it is easy to make mistakes. The customer requirements are high and may not be possible.

14. The excess corners within the finished line must be removed.

15. Some of the above inspections may have been avoided in the production process, some may not be used, too cumbersome, I hope to use my knowledge and experience in the inspection to select uncertain, unsure of several items to do, save inspection time ,Improve efficiency.

16. Under normal circumstances, customers are required to proof, and after proofing, they can find many problems and solve many problems. Combined with film, they can basically ensure normal printing on the machine. The inspection of the film flat net is especially important, and it should be paid attention to. If one point is not suitable, the problem reflected by the printed matter is unevenness or halo.

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Product details
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