With years of experience in printing production and management, the author believes that in terms of process flow, printing color difference control should be divided into three stages: pre-press, printing, and post-printing.

Color control is the core of printing quality control. Color management is at the core of the entire production management of printing companies. With the continuous improvement of customers' requirements for printing quality, the ink color stability of batch products becomes more and more important, and the range of product color difference is getting smaller and smaller.

With years of experience in printing production and management, I think from the perspective of process flow, printing color difference control should be divided into three stages: pre-press, printing and post-printing. In the control process of these three stages, you should pay attention to these points: 1. Reduce the discoloration caused by parking; 2. Select all unqualified products, mark them and handle them centrally; 3. Be diligent, meticulous and focused in your work , Take every small job seriously; 4. All relevant personnel should change bad work habits, so that the operator can implement it in place, and the manager can supervise and coordinate in place.

Prepress control stage

In the prepress control stage, 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, it will produce paper wool and paper slag, which will affect the printing.

2. Try to minimize changes in printability due to changes in environmental temperature and humidity, such as paper. If the paper cannot be cut too early, cover it immediately after cutting and place it near the printing machine; after printing, semi-finished products and finished products should be covered in time and stored near the printing machine to reduce paper deformation, etc.

3. Make sure that the waterway and ink path are not contaminated; the ratio of the wetting fluid is accurate; the water tank and ink roller meet the printing requirements without dirt, emulsification, and crystallization; reduce the ink color caused by the shutdown of the dirty spot and the imbalance of the water and ink Unstable.

4. Adjust the status of the printing equipment to ensure that the pressure of the cylinder, ink roller and water roller is accurate and even. Adjust the double-sheet controller and regulation parts to reduce frequent shutdowns caused by improper adjustment.

5. Choose the appropriate printing color sequence to avoid color differences caused by color sequence changes.

6. When matching spot color ink, add ink auxiliary agent according to the actual situation of graphics and text. Products with large graphics and text area should add debonding agent to reduce ink pulling and paper piles caused by long-term printing and affect the ink transfer.

7. Record the printing parameters and raw material information during the first printing production. Such as ink model, paper specification, varnish model, printing pressure, color sequence, ink and ink volume, production date, machine staff shift, etc.

8. Check the thickness, surface color, and flatness of each batch of paper to determine whether the printing pressure has any effect on the ink color.

9. For products printed multiple times, the previously stored data must be retrieved, but the amount of water and ink must also be adjusted according to changes in ambient temperature and humidity. The printing pressure must be adjusted according to the thickness of each batch of paper to prevent inaccurate printing pressure from causing color difference.

10. For long-term printed products, once the paper and ink are determined, try not to change, otherwise the printing parameters will change accordingly.

Printing control stage

In the printing control stage, the following points should be made:

1. When grading and printing, run more printing paper to make sure that the ink color is even before printing the fixed sample, to avoid color instability caused by the change of the ink on the boot.

2. After confirming the standard samples, the batch printing can be formally carried out. At the same time, a small standard sample that is easy to compare at any time is cut, so that the large sample can be viewed directly, and the details are compared to the small sample.

3. Each spot check should ensure that each location is checked with a small standard sample, so that the operator can find the ink color changes at various locations of the product in time. When the ink color changes, it is necessary to fine-tune the adjustment, the large-scale adjustment must be stopped, and check to determine what factors caused the large-scale change, and can only continue production after a thorough solution.

4. Don't jump fast or slow when starting up, print at a fixed speed to reduce the impact on the ink-water balance.

5. Must do five diligence: diligently check the water content of the layout, check the water tank, adjust the water volume in time, and wipe the water roller with alcohol if necessary; diligently stir the ink to improve the fluidity of the ink and maintain good transfer performance; diligently clean the ink fountain to achieve the ink fountain There are no sundries, paper residues and other debris; wipe the rubber and printing plates frequently to reduce the retention of paper wool, paper powder, ink stains and ink on the rubber and printing plates, but also ensure that they are cleaned and reduce the transfer of ink to the car wash water The effect of ensuring the good transfer of the imprints and providing a reliable basis for judging the supply of ink and ink; sampling samples at least once every 500 sheets, comparing with the standard samples at any time, and finding a new ink and ink balance according to the changes.

6. During the printing process, every time you load paper and ink, you should pay attention to check whether the paper and ink are intact, and reduce the downtime caused by bad paper, paper wool, and ink residue, which affects the quality. The ink in the ink fountain should not be filled with too much ink. Keep the ink volume in the ink fountain moderate.

7. Every time you stop the machine, you must draw more proofs, and try to select all the products with color difference.

8. Once the machine finds some unqualified products such as color difference and dirty spots, the quantity should be counted and stored separately, marked and recorded. After the entire order is completed, the next process will be submitted together for unified storage.

9. For long-print products with large printing volume, pay attention to the ink color change caused by the printing plate being replaced, and replace the new version in time.

Post-printing control stage

In the control stage after printing, the following points should be done:

1. Store the spot color ink remaining after printing in the spot color ink cartridge.

2. Clean all roller surfaces and roller pillows, water rollers, ink rollers, and ink fountains to prepare for the next printing production job.

3. After printing, count the number of products, distinguish the unqualified products, mark them well, and sign with the workshop management personnel to confirm.

4. Unqualified products such as chromatic aberration and dirty spots shall not be allowed to make concessions without permission.

(The author is Heilongjiang Longjiang Media Co., Ltd.)

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