Printing process optimization

If you ask the question: Which processes are the most important in order to obtain 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 of printing production. It is a combination of ink, paper and all intermediate processes, creating a superior, general or unqualified print.

The ultimate goal of the printing process is to produce as good prints as possible from the specified materials. The products should have a stable 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 effects 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 press operator must adjust the press under the given ink, paper, and plate conditions to optimize the printing process. These adjustments should minimize the impact of process variables so that the printer can produce qualified products that match the proofs of the proof. After that, the operator of the printing press must control the printing process to produce consistent print products that do not change in terms of color balance, tone reproduction, correctness of registration, and the like.

The first step in optimizing the printing process is to control the printing process. Trying to control a printer that is not working properly is difficult and the printing process will soon lose control. A working printer can work flawlessly for a longer period of time, and it may experience a slight deviation without producing an unacceptable product. In order to optimize and control the printing process, it should be understood what the desired characteristics are and which failures are the most typical.

Some of the obvious harmful print quality defects are: blocking, nourishing ink, color variation, skeining, ghosting, overprinting, non-image inking, overprinting, excessive dusting, smudging, shadow failure, back stains, white spots, Road, moire, wrinkle.

The stability of the product quality is also very important. It is also meaningful to minimize the losses during the effective printing time. The factory must combine the benefits and quality.

First, the printing variable

The common printing variables in the operation of lithographic offset printing presses are: dot gain, print contrast, dot distortion, overprint, 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, pH value of hopper solution, blanket hardness, blanket thickness, ambient temperature , Relative Humidity, Dryer Temperature, Dryer Stop Time, Cooling Roller Temperature, Printing Speed, Underprint Removal, Total Overprint Rate, Total Ink Coverage, Roller Hardness, Lining Thickness, Roller Pressure, Roll Paper Force, Inking Edition wear and so on.

The variables listed above are not yet all the variables that may be produced in the printing, but it can be stated that there are a large number of variables in the operation of the printing press. No matter how carefully the press operator operates, changes will always occur. In order to ensure the stability of the printing. The operator must make judgments on the changes that have occurred and take appropriate adjustment measures.

Second, detection, sampling and adjustment

In order to optimize the operation of the printing press 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, fountain solution and its pH, ink The roller hardness, the relative water content of the paper, the ink roller adjustment, etc. can both measure the control and also measure the control.

As long as the printing process is optimized with a given set of printing conditions, the press operator can control the stability of the product quality by evaluating a sample and adjusting it. In general, 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, minor deviations in print quality will be insignificant.

The goal of any process control is to correct deviations from the process by changing the direction of deviation before losing control and producing substandard products.

This requires the printer operator to focus on the work, constantly evaluate the product and look for changes in print quality parameters that indicate out-of-control variables. The keen eyes of the press operator plus the process control tools will enable a product to be stable in production. Even if the printer slightly deviates from the press, it can be quickly corrected. The deviation from the printed product will not be affected. obviously.

The following recommended optimization sequences are reliable when many variables influence each other. The most important variables and their effects will be discussed later.