Electrostatic digital presses and print quality assurance measures
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Digital printing has been rapidly developed and applied in recent years due to its short printing cycle, one printing, on-demand printing, and personalized printing. The business scope is wider and wider, and the business volume is increasing. However, as far as the author's city (Yiwu) is concerned, the overall quality of digital printing is not high, and the overall professional quality of employees is not high. However, with the improvement of people's aesthetics, the quality requirements of printed materials are getting higher and higher, which requires digital printing machine operators to master the corresponding operational skills to ensure print quality. Taking the electrostatic digital printing machine as an example, the author shared the experience of improving print quality accumulated in the work and dealing with printing failures.
Experience 1: Responding to the solution that the electrostatic digital printing machine can't be full version
The electrostatic digital printing machine can't print the full version. Even if the bleeding is set, the paper will have a white edge of 3mm~5mm, which is determined by the characteristics of the electrostatic printing itself. The electrostatic digital printing machine uses toner to print and the toner is heated. Before fixing, it is laid on the substrate. If it is full, the toner will be spread on the edge of the paper. The jitter during the printing process will cause the toner to spill, causing the printed page to be dirty.
Therefore, when printing on paper of the same size as the original, the final finished product size is often smaller than the size of the original supplied by the customer. If the original provided by the customer is A3 (297mm × 420mm), it is printed on the paper of the conventional A3 format. Each side will have a white edge of about 3mm, and the finished product will have a size of 2 9 1mm × 4 1 4mm after cutting off the white edge. This is not a problem when printing a single page, but if you print a magazine or publication with a certain thickness, you should pay attention to the design of the cover size and the choice of the size of the cover paper. I have encountered such an example. The customer prints 50 publications, the internal document 310 pages A4 format, the quantitative amount is 70g/m2 double-adhesive paper, the cover quantity is 200g / m 2 coated paper, the internal printed book The core thickness is 16 mm. The cover original supplied by the customer is 2 9 7mm × 4 2 0mm. The width of the cover original is corrected in consideration of the thickness of the book block. The width is enlarged to 4 3 6mm, and the cover is selected to be 2 9 7mm× 4 4 0mm coated paper, because the printer can not print full version, resulting in 6mm white space, the width of the cover image after printing is 4 3 4mm, after cutting the book cut off 2mm ~ 3mm, the cover just did not appear white, and Not too much cut off the cover will cause the graphic to be missing.
Experience 2: Print color protection measures
1. Color management. The restoration of color is the core of print reproduction. The most ideal state is to maintain color consistency from the input of the original to the output of the print. This requires color uniformity of the input device and output device involved in the whole process, that is, The original intention of color management is to generate ICC profile files for all input and output devices. The PCS connection space in the color management system translates and interprets ICC profile files to achieve color uniformity between different devices. However, as far as the current situation is concerned, most digital printing companies are not particularly demanding and troublesome because of customer requirements. They rarely do color management. Even if they do, there is no professional person responsible for color management. Software engineers to do it. However, in the following two cases, color management must be carried out. First, digital proofing, because this proof is usually used as a proof of offset printing. If the proof is too large, it will not bring accurate proof to subsequent large-volume printing. Standard; Second, when processing in small batches, it is difficult to ensure color consistency without color management, resulting in large losses. Color management must be assigned to a person responsible, over-reliance on software engineers, will seriously affect production efficiency, and it is difficult to make high-quality products.
2. School color. For many companies, not doing color management may have little effect on the product, but if the school color is not done, then the products printed by this company will definitely have a very large color difference with the original, especially the color of the printed products in large quantities. Unstable, the color difference will be larger than before. This is because the digital printing press is affected by the environment, the performance is unstable, the replacement of spare parts, the change of the paper type, etc., the color will constantly change. If there is no calibration, the color stability will not be controlled, and the color correction is mainly to stabilize the printer. s color.
Take the Fuji Xerox Ve rsant T M2 1 0 0 color digital printing machine as an example. When coloring, the EFI-200 color calibration instrument is used to measure the green, yellow and black color targets, and the input and output curves are generated. Value calculation, adjust the output color. Frequently doing school coloring is often to draw the machine input and output relationship curve, so as to constantly match the target value to stabilize the color. If the color is not frequently corrected, the measured value and the target value curve will be too different, not only can not stabilize the color output, but also the color gradient difference, affecting the color output quality and other issues. Therefore, when conditions permit, it is necessary to regularly check the color regularly. The higher the frequency, the better. It is best to do a school color before printing in large quantities. Note on school color:
1) Correct the color according to the paper type and quantity used by the school, instead of arbitrarily selecting the curve paper color that comes out of the factory. 2) Do not check the color when you turn it on. You can print some colors that are not high in color. The manuscript is finished after the standby is stabilized. 3)When the color is correct, 4 to 6 white papers should be placed under the measuring color target of the school color to prevent light transmission; 4) the curves after the color correction can be directly applied. To check whether the measured value is reasonable, first the curve is smooth, there should not be too much fluctuation, and the D-max value is not less than 10% of the target value.
3. Edit the curve. Of course, if you are very familiar with the chromatogram, input and output curves, tone, etc., you can edit the curve directly in the output profile according to the current color output of the press to correct the color output of the current press. It is recommended that the newly edited curve not be applied directly to the color management process, but instead applied directly to the job when setting the print job properties so that it does not affect other jobs.
Experience 3: Troubleshooting and solution to print quality
If the printer can print out normally, there is no error, but the printed screen has various problems: for example, the color of a certain color is light, the color lines of the page appear, and the area of the horizontal width of the page is lighter, and the page is lighter. Black spots, etc., these can be called print quality failure
Experience 4: Preventing and responding to paper jams
Digital printer jams are largely related to paper, such as paper damp, paper curl, paper wrinkles, paper tray settings, and paper mismatch, so pay special attention to paper placement, especially after unsealing. Try to store the paper in the cabinet. After unpacking, wrap the remaining paper and place the paper horizontally to prevent the curl from curling. Coated paper, especially coated paper, has a large internal stress between the papers. If it is wet, it is more likely to have multiple sheets of paper feeding, causing paper jams, especially during the rainy season in the south of the Yangtze River. This problem is more likely to occur. You can use a hair dryer to blow the paper to the side of the stack to loosen the paper, but the temperature of the blower should not be too high, otherwise the paper will curl due to water loss.
Improving the print quality of printed products is the direction of the company's efforts and the responsibility of the printing operators. Every printer should practice, summarize, practice and improve at work.