What are the process parameters that affect flexo printing?
The main factors affecting the quality of flexo printing are: flexo printing machine, photosensitive resin flexographic plate and plate making, prepress processing, printing materials (rolled paper), plate adhesive tape, printing ink, anilox roller, etc.
(1) Flexo printing machine
The process requirements for the narrow flexo press (unit type) include: ① The tension control system guarantees accurate overprinting. ② sensitive pressure and tension adjustment to ensure accurate printing pressure setting. ③The plate roller, anilox roller, transfer roller and embossing roller should have high radial runout precision. ④ efficient and fast drying system to ensure the overprinting effect. ⑤ Configure the appropriate anilox roller according to the printing material and the number of screens.
(2) Photosensitive resin flexographic plate and plate making
① Determine the thickness of the plate to be used according to the specific substrate and the structure of the printer. ② According to the characteristics of the printed pattern, consider the exposure latitude of the plate, determine the plate model, and ensure the fine dot reproduction of the high number of lines (such as 2% of the 60 line / inch image). ③The wettability of the ink on the surface of the plates is uniform and uniform. ④ Ensure that the convex parts of the plate have the same depth, ensuring a balanced mesh wall angle and angular points. ⑤ to ensure the hardness of the plate, control the hardness tolerance range.
(3) Prepress processing
The prepress process directly affects the plate making and the final printing effect. The following points should be noted: ① The high-resolution image scanning device is the key to the flexo color separation, making it possible to fine-tune the high-screen number. ② fully consider the obvious color value increase phenomenon in flexographic printing. ③ Pre-press processing with accurate dot compensation to ensure the desired printing results.
(4) Printing materials
① good suitability, only absorb the right amount of ink in the predetermined part, does not affect its normal drying speed. ② has a certain degree of smoothness, ink bleed, and suitable rheological properties. ③ has sufficient surface strength to prevent fuzzing, shape and size stability. ④ There is no sticky dust particles on the surface of the paper.
(5) Adhesive tape
The choice of the adhesive tape should be based on the characteristics of the graphic to be printed. ① Select hard tape when printing on the ground. ② When the field and the network point coexist, choose neutral tape. ③ Select soft tape when printing dots.
(6) Printing ink
① It has a true color of a certain color tone. ② Set the ink characteristics (viscosity/surface tension) according to the characteristics of the substrate. ③ The proportion of the colorant (pigment) in the ink is sufficiently high to achieve sufficient color strength with less ink transfer. ④ The amount of solvent used in the ink is appropriately selected, which does not cause the photosensitive resin plate to expand due to immersion, and enables the ink to meet the requirements of firm adhesion and no fading. ⑤ ink drying speed should be compatible with the printing speed. ⑥ After drying, the ink can be resistant to acid, alkali, water, ultraviolet and abrasion, and is not affected by alcohol and grease. The various factors affecting the quality of flexo printing are not independent. The influence of other factors should be considered when determining the process parameters. That is to say, only the various factors affecting the quality of flexographic printing can be coordinated to obtain the desired printed product. Also consider the impact of the operator's level of operation on print quality.
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