With many years of experience in printing production and management, the author believes that from the process flow, printing color difference control should be divided into three stages: prepress, printing and printing.
Color control is the core of print quality control. In the whole production management of printing enterprises, color management is at the core. As customers' requirements for the quality of printed products continue to increase, the stability of ink color of batch products becomes more and more important, and the range of allowable color difference of products is getting smaller and smaller.
With many years of experience in printing production and management, I believe that from the process flow, printing color difference control should be divided into three stages: prepress, printing and printing. In the control process of these three stages, we should pay attention to these points: 1. Reduce the discoloration caused by parking; 2. Pick out all the non-conforming products, do the labeling and concentrate on the treatment; 3. Be diligent, careful and focused in the work. Seriously treat every small work; 4. All relevant personnel should change bad work habits, so that operators can be put in place, and managers can be supervised and coordinated.
Prepress control stage
In the prepress control phase, the following points should be done:
1. When cutting paper, the paper must meet the requirements. If the paper is skewed or the knife is not fast, paper and paper slag will be generated, which will affect the printing.
2. Changes in the printability of paper and other papers due to changes in ambient temperature and humidity should be minimized. If the paper is not cut too early, it should be covered and placed in the vicinity of the printing machine after cutting; after printing, the semi-finished products and finished products should be covered in time, stored near the printing machine, reduce paper deformation, and so on.
3. Ensure that the waterway and ink path are not polluted; the ratio of dampening liquid is accurate; the water tank and ink roller meet the printing requirements, no dirt, emulsification and crystallization; reduce the ink color caused by the stop of dirty spots and ink imbalance. Unstable.
4. Adjust the state of the printing equipment to ensure that the pressure of the drum, ink roller and water roller is accurate and uniform. Adjust the double controller and the control components to reduce frequent downtime caused by improper adjustment.
5. Select the appropriate printing color sequence to avoid chromatic aberration caused by color sequence changes.
6. When the special color ink is used, the ink auxiliary agent should be added according to the actual situation of the graphic. The product with large graphic area should be added with the detacking agent to reduce the ink transfer caused by the phenomenon of ink extraction and paper pile hair caused by long-time printing.
7. Record the printing parameters and raw material information during the first printing production. Such as ink model, paper size, varnish model, printing pressure, color sequence, ink quantity, production date, machine personnel shifts, etc.
8. Check the thickness, surface color, and flatness of each batch of paper to determine the printing pressure and whether it has an effect on the ink color.
9. The products printed many times should be retrieved from the previously stored data, but the amount of ink should be adjusted according to the change of ambient temperature and humidity. The printing pressure must be adjusted according to the thickness of each batch of paper to prevent the printing pressure from being inaccurate and cause chromatic aberration.
10. For long-term printing products, once the paper and ink are determined to be as small as possible, the printing parameters will change accordingly.
Printing control stage
In the printing control phase, the following points should be done:
1. When the color version is over, run more paper and make sure that the ink color runs evenly before the sample printing can be performed to avoid the color instability caused by the change of the ink on the boot.
2. After the standard sample is determined, it can be officially batch-printed, and a small standard sample that is easy to compare at any time can be cut, so that the large sample can be directly viewed and the details can be sampled.
3. Each sampling should ensure that each position is checked against a small standard, so that the operator can find the ink color change at each position of the product in time. When the ink color changes, it must be finely adjusted. It must be shut down during large-scale adjustment, and check to determine what factors cause large-scale changes, and then completely solve the problem before continuing production.
4. Do not flicker when starting up, you must print at a constant speed to reduce the impact on the balance of ink and water.
5. Must do five diligence: diligently look at the water in the layout, check the water tank, adjust the water volume in time, wipe the water roller with alcohol if necessary; dilute the ink, improve the fluidity of the ink, maintain good transfer performance; clean the ink fountain, do the ink fountain There are no ink slag and other debris in the inside; rubbing the rubber and printing plates to reduce the paper, paper powder, ink stains and ink on the rubber and printing plates, but also to ensure that the cleaning is clean and the car wash water is reduced. The effect is to ensure the good transmission of the imprint, to provide a reliable basis for judging the supply of ink; to sample the samples, check every 500 sheets at least once, compare them with the standard samples at any time, and find a new balance of ink and water according to the changes.
6. During the printing process, each time the paper is fed and inked, it should be checked whether the paper and ink are in good condition, reduce the downtime caused by bad paper, paper wool and ink residue, and affect the quality. The ink in the ink fountain cannot be inked too much, keeping the amount of ink in the ink fountain moderate.
7. Every time you stop the machine, you should take more samples and try to select all the products with color difference.
8. Once the machine finds that there are partial non-conforming products such as color difference and dirty spots, the number of inventory points should be separately stored separately, and the mark should be marked and recorded. After the whole order is completed, the next process will be handed over and stored.
9. Print a large version of the long version of the product, pay attention to the ink color changes caused by the plate version, and replace the new version in time.
Post-printing control phase
In the post-printing control phase, the following points should be made:
1. Store the remaining spot color ink after printing in the spot ink cartridge.
2. Clean all drum surfaces and rollers, water rollers, ink rollers, and ink fountains to prepare for the next print production job.
3. After printing, it is necessary to check the quantity of the products, distinguish the non-conforming products, make the mark, and sign and confirm with the workshop management personnel.
4. Non-conforming products such as color difference and dirty spots shall not be allowed to be released in private.
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