Improve print quality through optimization of printing process
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If you ask the question: Which process is the most important in order to get a high quality print? The answer may be: the printing process is the most important. This process is a concentrated expression of the quality of each process in the printing process. It is a combination of ink, paper and all intermediate processes, creating an excellent, general or unqualified print.
The ultimate goal of the printing process is to produce the best possible prints with the specified materials. The product should have consistent color reproduction accuracy, contrast and sharpness. For a batch of products that are continuously produced, the product should have a consistent visual effect, because there are hundreds of variables that affect the visual effect of the product, we must measure and control the printing quality characteristics that have the greatest impact on the visual characteristics of the product. .
The press operator must adjust the press for a given ink, paper and plate to optimize the printing process. These adjustments should minimize the effects of process variables, allowing the press to produce qualified products that match the proof proofs. Thereafter, the press operator must control the printing process to produce consistent print products that have not changed in terms of color balance, tone reproduction, and registration accuracy.
The first step in optimizing the printing process is to control the printing process. Trying to control a press that is not working properly is difficult and the printing process will quickly lose control. A properly functioning press can work without problems for a longer period of time, and it can be slightly offset without producing unqualified products. In order to optimize and control the printing process, it should be understood what is the desired characteristic and which are the most typical.
Some obvious harmful print quality defects include: adhesion, ink, color variation, hair pulling, ghosting, overprinting, non-image partial inking, poor overprinting, excessive powdering, smudging, shadow failure, back smear, white spots, Road, turtle, and wrinkles.
The stability of product quality is also important, and it makes sense to minimize losses during effective printing time. Factories must combine efficiency and quality.
First, the printing variable
Common printing variables in the operation of lithographic offset printing presses include dot gain, print contrast, dot deformation, overprint, ink layer thickness, and ink hue. Ink temperature, ink emulsification, ink drying speed, paper thickness, paper smoothness, paper surface efficiency, paper relative moisture content, paper surface strength, paper pH value, water bucket solution pH value, blanket hardness, blanket thickness, ambient temperature , relative humidity of the environment, drying device temperature, drying device stop time, chill roll temperature, printing speed, background removal, total overprint ratio, total ink coverage, roll hardness, lining thickness, roll pressure, web force, printing Version wear and so on.
The above variables are not all the variables that may be produced in the printing, but it can be explained that there are a large number of variables in the printing machine operation. No matter how carefully the printer operator works, changes will always occur. In order to ensure the stability of printing. The operator must make judgments about the changes that occur and take appropriate adjustments.
Second, testing, sampling and adjustment
In order to optimize the press's work to its optimum point, the operator must use the instrument to measure as many variables as possible, such as ink viscosity, plate and blanket lining, printing pressure, water solution and its pH, ink Roll hardness, relative water content of the paper, adjustment of the ink roller, etc. can all be measured and controlled.
As long as the printing process is optimized with a given set of printing conditions, the printer operator can control the quality of the product by evaluating a sample and adjusting it. Often, many print process variables can be offset against one another, and the print operator can control the printing process with fewer adjustments. If the adjustment is made when the printing process begins to deviate from the first indication 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 the deviation before losing control and producing a defective product.
This requires the press operator to concentrate on the work, often evaluate the product and look for changes in the print quality parameters that indicate the runaway variables. The sharp eye of the press operator plus the process control tool will enable the production of a product to be stable. Even if the press is slightly offset during printing, it can be quickly corrected. The deviation from the impact on the printed product will not be obviously.
When many variables affect each other, the recommended order of optimization is reliable, and the most important variables and their effects will be discussed later.