Flexo printing has developed rapidly in China and has become one of the fastest growing printing methods. Flexo printing has unique printing process requirements, understanding the various factors that affect the quality of flexographic printing, and defining the process parameters of flexographic printing to establish a reasonable process flow, which is a prerequisite for doing a good flexo printing.

The main factors influencing the quality of flexo printing are: flexo printing machine, photosensitive resin flexographic plate and plate making, prepress processing, printing materials (web), tape, ink, anilox roller and so on.

First, the mechanical process requirements of flexographic printing machine

In the following, we will discuss the technical requirements of flexo printing on a printing press in combination with a narrow-width flexographic printing press (unit type).

1. Tension control system ensures accurate overprinting;

2. Sensitive pressure and tension adjustment to ensure accurate setting of printing pressure;

3. Plate roller, anilox roller, transfer roller, and embossing roller should have high radial runout accuracy;

4. Efficient and rapid drying system ensures superimposition;

5. Configure the appropriate anilox roller according to the printing material and the number of plate lines.

Second, photosensitive resin flexo and plate making

1. According to the specific printing materials, press structure, determine the thickness of the plate used;

2. According to the characteristics of the printing pattern, consider the exposure latitude of the plate, determine the plate type, and guarantee the reproduction of the fine dots of the high-line number (such as 2% of the dots of the 60 lines/inch image);

3. Wetting performance of the surface ink of the printing plate should be uniform;

4. Ensure that the depth of the convex portion of the printing plate is the same, and the balanced network wall angle and the clear and fine dots are ensured;

5. To ensure the hardness of the plate, control the hardness tolerance range.

The prepress process has a direct impact on the plate making and the final printing results. The following points should be noted:

1. High-resolution image scanning equipment is the key to flexographic copying, making it possible to use high-line fine-flexography;

2. Take full account of the apparent tonal value increase in flexographic printing;

3. Apply accurate dot compensation in prepress processing to ensure the desired printing effect;

4. High quality negative film output, advanced plate making system ensures the quality of plate making;

5. The development and application of CDI technology has further improved the quality of flexo printing.

Third, the process requirements of printing ink

1. With a certain primary color of accurate color, so that the basic color and mixed color can achieve the desired effect after superimposition;

2. Set the ink characteristics (viscosity/surface tension) according to the characteristics of the printing materials;

3. The proportion of toner (pigment) in the ink is high enough so that sufficient color intensity can still be achieved with less ink transfer.

4. The appropriate amount of solvent in the ink is selected, which will not allow the photosensitive resin plate to swell due to immersion, but also can make the ink meet the requirements of firm adhesion and no fading;

5. The ink drying speed should be compatible with the printing speed;

6. The dried ink is resistant to acids, alkalis, water, UV, abrasion, and not affected by alcohol and grease.

Fourth, the printing material should have the performance

1. Good adaptability, only absorb the appropriate amount of ink at the intended site without affecting its normal drying rate;

2. Has a certain degree of smoothness, ink permeability, suitable rheological properties;

3. Has sufficient surface strength to prevent fuzz, shape and size stability;

4. Adhesive dust particles on the surface of the paper.

Fifth, the choice of adhesive tape

The choice of adhesive tape should be based on the characteristics of the printed pattern.

1. Select rigid tape when printing in the field;

2. Neutral tape is selected when field and outlet coexist;

3. Choose soft tape when printing the dots.

The various factors affecting the quality of flexo printing do not exist independently. The influence of other factors should be considered when determining the process parameters. That is, only the factors that affect the quality of flexographic printing can be coordinated to achieve the ideal print. Last but not least, don't ignore the effect of the operator's own level on print quality.

Source: Wuxi Huanyu Printing & Packaging Equipment Co., Ltd.