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In practical operations, besides using elastic pads to absorb force, greater emphasis should be placed on adjusting and balancing the press pressure. Generally, the pressure should be adjusted until dot expansion and edge effects are minimized.
1. Apply Appropriate Printing Pressure
The recommended printing pressure for flexographic printing typically ranges between 1–3 kg/cm², while for corrugated boxes, it is usually between 1–2 kg/cm². Due to the pressure exerted by the plate and the reaction force from the impression cylinder, issues such as light ink color and color deviation may occur during printing. When insufficient ink coverage is perceived, operators often increase the pressure in an attempt to improve ink density. However, this frequently results in severe edge effects, such as dot gain and blurred text, pushing the limited ink to unintended areas.
When printing on corrugated substrates, excessive pressure on the raised areas of the flutes may cause washboarding. Fortunately, this can be mitigated to some extent by using elastic padding to fill the gaps. In halftone printing, significant dot gain may cause the entire image to shift toward higher tones, with shadow areas becoming solid and leading to color imbalance. As a result, the overall image may appear flat with poor gradation and reduced three-dimensionality. Solid areas, lines, and text may exhibit edge effects, appearing thin and blurred. Therefore, applying the correct impression force is crucial.
In actual operation, besides using elastic pads for buffering, more attention should be paid to adjusting and balancing the press pressure. Generally, the pressure should be adjusted until dot expansion and edge effects are not visually apparent.
2. Maintain Stable Ink Transfer Volume
The viscosity of water-based ink, the type of anilox roller used, the ink transfer method, and the printing speed all influence the ink transfer performance.
1) Ensure the anilox roller is clean and free from wear.
2) Maintain a consistent and stable printing speed to ensure stable ink transfer and color consistency.
3) Ink transfer volume is inversely related to printing speed-slower speeds yield higher ink transfer, while faster speeds reduce it. A stable speed ensures consistent ink transfer.
4) Ink viscosity is directly proportional to ink transfer volume. For large solid areas, slower speeds, higher-viscosity ink, and lower-line-count anilox rollers are recommended. For halftone printing, faster speeds, lower-viscosity ink, and higher-line-count anilox rollers are preferred.
5) Generally, higher-line-count anilox rollers deliver less ink, while lower-line-count rollers deliver more.
6) Slower printing speeds and higher ink viscosities result in increased ink transfer volumes.
7) For solid or block printing, it is advisable to use anilox rollers with lower line counts, higher-viscosity ink, and slightly slower speeds. For high-resolution halftone and color gradation printing, higher-line-count anilox rollers, lower-viscosity ink, and faster speeds are recommended. These settings should be adjusted according to actual production conditions.