If you ask this question: In order to get a high-quality print, which processes are the most important? The answer may be: the printing process is the most important. This process is a concentrated expression of the quality of each process in printing production. It is a combination of ink, paper and all intermediate processes, creating a superior, general or unqualified printed matter.
The ultimate goal of the printing process is to produce the best possible printed matter with the specified materials, and the product should have stable color reproduction accuracy, contrast and sharpness. For a batch of continuously produced products, the product should have a consistent visual effect, because hundreds of thousands of variables will affect the visual effect of the product, we must measure and control the print quality characteristics that have the greatest impact on the visual characteristics of the product .
The operator of the printing machine must adjust the printing machine under the conditions of the given ink, paper and printing plate, so as to optimize the printing process. These adjustments should minimize the effects of process variables and enable the printing press to produce qualified products that match the qualified proofs. After that, the press operator must control the printing process to produce consistent print products with no changes in color balance, tone reproduction, and registration accuracy.
The first step in optimizing the printing process is to control the printing process. It is difficult to try to control a printer that is not working properly, and the printing process will soon lose control. A working printer can work without problems for a long period of time. It may deviate slightly without producing unqualified products. In order to optimize and control the printing process, you should understand what are the desirable characteristics and which faults are the most typical.
Some obvious harmful printing quality disadvantages are: adhesion, nourishment, color variation, roughening, ghosting, inaccurate overprinting, non-image part inking, poor overprinting, excessive dusting, smudging, shadow failure, back rubbing, white spots Daozi, moire, wrinkles.
The stability of product quality is also very important. It is also meaningful to minimize the loss during the effective printing time. The factory must combine efficiency and quality together.
1. Printing variables
Common printing variables in the operation of lithographic offset printing machines are: dot increase, printing contrast, dot deformation, overprinting, ink layer thickness, and ink hue. Ink temperature, ink emulsification, ink drying speed, paper thickness, paper smoothness, paper surface efficiency, paper relative water content, paper surface strength, paper pH, water bucket pH, blanket hardness, blanket thickness, ambient temperature , Ambient relative humidity, drying device temperature, drying device stop time, cooling roller temperature, printing speed, background color removal, total overprint rate, total ink coverage, roller hardness, liner thickness, roller pressure, roll paper force, printing Edition wear, etc.
The variables listed above are not all the variables that may be generated during printing, but it can be explained that there are a large number of variables in the operation of the printing press. No matter how carefully the press operator works, changes will always happen. In order to ensure the stability of printing. The operator must make judgments about the changes that have occurred and take corresponding adjustment measures.
2. Testing, sampling and adjustment
In order to optimize the work of the printing press to its optimal point, the operator must use the instrument to measure as many variables as possible, such as ink viscosity, plate and blanket lining, printing pressure, hopper solution and its pH, ink Roll hardness, paper relative moisture content, ink roller adjustment, etc. can be measured and controlled, and should also be measured and controlled.
As long as the printing process is optimized with a given set of printing conditions, the press operator can control the stability of product quality by evaluating a sample and adjusting it. Generally, many printing process variables can offset each other, and the printing operator can control the printing process with less adjustment. If adjustments are made when the printing process begins to deviate from the first sign of control, then small deviations in print quality will be insignificant.
The goal of any process control is to correct the deviation of the process by changing the direction of deviation before runaway and non-conforming product.
This requires printing press operators to concentrate on their work, often evaluating products and looking for changes in print quality parameters that indicate runaway variables. The keen eyes of the printing press operator and the process control tools will enable the production of a product to be stable. Even if the printing press deviates slightly during printing, it can be quickly corrected. The impact of the deviation on the printed product will not be obviously.
When many variables affect each other, the following suggested optimization sequence is reliable. The most important variables and their effects will be discussed later.
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