Analysis of Influencing Factors of Rotogravure Overprint Fluctuation Continued

Process factors

Improper process can also lead to overprint fluctuations.

1. Effect of plate making process on overprinting

In fact, each process in the gravure plate making process has an impact on the stability and accuracy of overprinting. The following only discusses some of the major factors.

(1) Plate quality

The blank is the basic material for the printing plate. The mechanical properties of the plate determine the mechanical properties of the finished plate. Therefore, it is required that the surface of the blank is flat, concentric, dynamic and static balanced, and the axis of the plate conform to the machining accuracy.

The concentricity of the plate cylinder is not good, the surface is uneven, and the surface line speed of a certain part of the printing plate will be different from other normal areas, so that the overprinting will change and the overprint fluctuation will occur.

If there is a problem with the dynamic and static balance, it will cause a change in the impulse of the rotating plate cylinder, which will aggravate the wear of the mechanical parts, and the worn out mechanical parts will cause more serious overprint fluctuation problems.

If the plate axis does not meet the machining accuracy, it will cause overprint fluctuations and other printing failures. The large plate axis will bring difficulties to the plate mounting work and damage the components; the plate axis will be too small, which will cause the platen roller to vibrate under the influence of the printing pressure.

(2) Grinding

Grinding machine is to plate the copper plated blank in accordance with the plate diameter requirements. The following two requirements are required:

(1) The axial diameter of the plates after grinding is consistent, otherwise it will cause inconsistence of the surface line speed of the finished plate, leading to overprint fluctuations.

2 After grinding, the copper surface must be smooth and smooth. The purpose is to keep the surface line speed consistent and facilitate the next process of electric carving and chrome plating.

Grinding mills require high processing accuracy. According to the different tensions used on paper and printing, different printing companies use color-incremental version (20-50μm) to ensure the accuracy of overprinting.

(3) Electric carving (corrosion), chrome plating, grinding

Electric carving (corrosion) to make gravure to choose the right carving knife, engraving angle and the number of screen lines, etc., handle the pattern (especially at the color standard block) at the edge. Chromium plating and grinding are also required to meet the printing requirements. Printing defects such as imaginary edges, ink pulls, and edge irregularities at the time of overprinting the color patches are avoided. These failures can cause errors in the scanning signals and eventually lead to overprint fluctuations.

2. Effect of Printing Process on Overprinting

The printing process design mainly includes color arrangement, ink viscosity control, printing speed control, color density value control, and some product quality control. In the process design, we must consider the actual situation of production, comprehensive consideration of the impact of quality control standards on overprint, in particular to consider the impact of printing pressure control overprint. Because if the plate or printing material does not meet the requirements, excessive printing pressure is used, which will lead to increased overprint fluctuations. Therefore, reasonable and stable printing process conditions are an important factor to avoid overprint fluctuations.

Operational factors

The operations that affect overprinting can be divided into two parts, the operation in preparation work and the operation in print production.

1. Prepare the operation

The operations in the preparation work mainly include loading, squeegee loading, machine parameter setting, etc. In response to the problem of overprint fluctuations, the following items should be paid attention to in these tasks:

(1) When installing the plate, check whether the shaft of the plate meets the dimensional requirements. For the size of the plate, take corresponding measures for handling.

(2) Pay attention to checking the plate's dynamic and static balance.

(3) Pay attention to check and keep the transmission parts clean and lubricated. The damaged parts should be repaired in time. replace.

(4) Pay attention to keeping the positioning points and surfaces clean and in place.

(5) The components are in place.

(6) Adjust the horizontal position of the ink car.

(7) The squeegee is mounted flat and installed. According to the conditions of the printing plate and the ink, the appropriate hard and soft blades are used to sharpen the blade so as to prevent the overprint signal from being caused by the failure of the blade to cause ink-drawing, imaginary edge failure, and the like.

(8) Set accurate and appropriate parameters.

2. Operation in print production

In the printing production process, pay attention to the following matters:

(1) Select the appropriate tension and appropriate controllable parameters for different papers.

(2) Keeping it in production. Stable printing speed.

(3) Control printing pressure.

(4) Control ink viscosity, performance, and reduce the occurrence of printing problems.

Implement standardized and standardized operations to minimize overprint fluctuations. At the same time, the operator is required to accurately make judgments after the failure occurs, and take timely measures to solve the problem.

The degree of resolution of overprint fluctuations can reflect the overall management and technical level of a company. Standardization, standardization, and data are the direction of the development of the printing industry, and it is also the fundamental solution to the problem of overprint fluctuations.