Laser roughening flexographic printing system

Abstract

The invention relates to the technical field of printing, and discloses a laser roughening flexographic printing system. The device comprises at least one color group unit, each color group unit comprises an ink cavity, an anilox roller, a plate roller and a printing roller, lattice points and ink cells are carved on the surface of the plate roller, a laser engraving machine is directly used for engraving, the ink cavity supplies dye to the anilox roller through a closed circulation pipeline, the anilox roller is in press fit contact with the plate roller, the dye is transferred to the plate roller, and the printing roller is used for printing the printing roller. When the plate roller and the printing roller are pressed to make contact, the diameter of the inking dot in the stress direction is increased in the pressed state, and the inking ink cell extrudes the dye and chemical materials under the pressing of dot deformation and transfers the dye and chemical materials to the fabric to be printed wrapping the printing roller. A direct laser engraving machine is used for high-precision engraving of lattice points and ink cells on a plate roller.

Description

Technical Field

[0001] This invention relates to the field of printing equipment technology, specifically to a laser deburring flexographic printing system. Background Technology

[0002] Lasers have advantages such as good directionality, high energy density, and good monochromaticity, making them very suitable for subtractive processing of materials. They are widely used in scientific research, metal cutting, printing plate making and other fields.

[0003] EPDM rubber, or ethylene propylene diene monomer rubber, possesses excellent aging resistance and chemical resistance, making it a cost-effective plate-making material. Laser engraving on EPDM rubber has been widely used in the printing industry, including flexible packaging, paper, and non-woven fabric industries.

[0004] Materials such as paper, film, and even non-woven fabrics have shallow surface textures and low ink absorption, which can usually be met by ink application on rubber surfaces or micro-cavity ink application.

[0005] Fabrics are made by interlacing or looping yarns (silks). The material composition, yarn count, twist, and warp and weft density of the yarns all affect the surface texture of the fabric. Inking on a rubber surface typically only allows ink to reach the prominent and recessed areas of the fabric texture. Lightweight fabrics usually have low basis weight and weak surface texture, requiring less ink, which can be met by an EPDM rubber surface under pressure. However, the more pronounced the fabric's surface texture, the lower the proportion of ink-received area, leading to low color saturation and white showing. Furthermore, printing dark colors and requiring high saturation is very difficult using an EPDM rubber surface.

[0006] Flexographic printing is an extension of flexographic printing into the dyeing and printing industry. It also uses direct laser engraving equipment to perform laser subtractive printing on EPDM rubber rollers. Different substrates will inevitably require adjustments or redesign of the engraving process. Summary of the Invention

[0007] To address the technical problems existing in the prior art, the present invention provides a laser deburring flexographic printing system.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a laser-engraved flexographic printing system, comprising at least one color unit, wherein the color unit includes an ink cavity, an anilox roller, a printing roller, and a substrate roller. The surface of the printing roller is engraved with dots and cells using a direct laser engraving machine. The ink cavity supplies dyes and chemicals to the anilox roller through a closed-loop circulation pipeline. The anilox roller and the printing roller press against each other, transferring the dyes and chemicals to the printing roller, causing the dots to be inked and the cells to store ink. When the printing roller and the substrate roller are in pressure contact, under pressure, the diameter of the inked dots increases in the direction of force, while the ink-receiving cells, under the pressure of the dot deformation, squeeze out the dyes and chemicals and transfer them to the fabric to be printed wrapped around the substrate roller. A direct laser engraving machine is used to engrave the dots and cells on the printing roller with high precision.

[0009] Preferably, the process parameters of the direct laser engraving machine are: engraving resolution: 600–2540 DPI, engraving depth: 0.05–0.5 mm, and roller line count: 635–5080 LPI. High-resolution engraving achieves micron-level control of the cell opening diameter (10–150 μm), and capillary force suppresses ink centrifugal escape when the roller speed is ≤300 rpm; combined with an engraving depth of 0.05–0.5 mm, the ink storage capacity per unit area reaches 2.5–25 BCM, ensuring the accuracy of hair texture and the stability of ink supply.

[0010] Preferably, the laser type is a fiber laser with a spot diameter of 5–40 μm, a single laser energy range of 10–1000 W, and a maximum modulation frequency of less than 10 MHz. The small spot size allows for the engraving of a greater number of dots and cells per unit area, and the single-beam laser energy range and high-frequency modulation maximize engraving efficiency within the tolerance range of the EPDM material.

[0011] Preferably, the printing roller is made of ethylene propylene diene monomer (EPDM) rubber with a surface hardness range of 38–85 HA (Shore Hardness). The EPDM's elastic modulus of 0.5–5 MPa ensures that the hardness gradient of the dot matrix under pressure expansion adapts to the pressure requirements of different fabrics. Different surface hardnesses result in varying degrees of compression on the cells, leading to differences in the amount of extruded dyes and chemicals. Printing rollers with hardness suitable for flexographic printing are generally applicable to laser texturing technology, with 38–85 HA being the preferred range.

[0012] Preferably, the surface material of the anilox roller is ceramic or metal, with an engraving line count of 100-600 LPI and an ink load of 3-30 BCM. High surface material hardness reduces wear. The engraving line count affects the number of dots that penetrate the anilox roller to pick up ink, while the ink load affects the amount of ink picked up each time.

[0013] The beneficial effects of this invention are as follows: High-precision dots and cells are engraved using a direct laser engraving machine. Under pressure, these dots and cells precisely transfer the stored dyes and chemicals onto the fabric to be printed. The high-precision dots and cells can easily handle the surface texture of the fabric, resulting in a uniform printing effect. The engraving depth of the cells can meet the color saturation requirements of fabrics of different weights. Attached Figure Description

[0014] Figure 1 This is a three-dimensional structural diagram of the present invention;

[0015] Figure 2 This is a preset pixel image of the present invention;

[0016] Figure 3 This is a diagram showing the dot shape of the printing roller according to the present invention;

[0017] Figure 4 This is a diagram showing the arrangement of dots and cells on the printing roller of the present invention;

[0018] Figure 5 This is a schematic diagram of the contact point structure between the printing roller and the anilox roller of the present invention;

[0019] Figure 6 This is a schematic diagram of the contact point between the printing roller and the fabric to be printed according to the present invention.

[0020] In the diagram: 1. Ink chamber; 2. Anilox roller; 3. Printing roller; 4. Printing substrate roller; 5. Printing roller dot; 6. Printing roller cell; 7. Anilox roller cell; 8. Fabric to be printed. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0022] Example: A laser-reduced flexographic printing system, such as Figure 1-6 It is used to solve problems such as uneven color, difficulty in controlling saturation, and susceptibility to fabric texture when using rubber materials as printing plates for ink application on fabric surfaces, thereby achieving the effect of "printing instead of dyeing" flexographic printing.

[0023] The system consists of multiple color units, each including an ink chamber, an anilox roller, a printing roller, and a substrate roller. The anilox roller can precisely and controllably transfer the dye and chemicals circulating in the ink chamber to the printing roller, and then the printing roller transfers the dye and chemicals to the fabric to be printed on the substrate roller.

[0024] The core innovation of this invention lies in using a direct laser engraving machine to perform high-precision engraving on the printing roller, forming a dot and cell structure. When the printing roller is pressed into contact with the anilox roller, the dots bear ink, while the cells store ink. When the printing roller is pressed into contact with the printing roller, the inked dots, under pressure, experience a change in force direction, causing their diameter to increase. This forces the dyes and chemicals within the cells to be squeezed out and transferred to the fabric surface.

[0025] Anilox rollers have a constant ink load that is greater than that of printing rollers. Their ink load depends on the number of engraving lines (100-600 LPI) and the material (ceramic or metal), and generally ranges from 3 to 30 BCM.

[0026] The printing roller is directly laser-engraved to form tapered conical dots and continuously distributed cells. This structure allows it to pick up and store ink upon contact with the anilox roller. After multiple contacts, the cells on the printing roller are completely filled, achieving maximum ink storage capacity.

[0027] The specific ink extraction process is as follows: After the printing roller initially contacts the anilox roller under pressure, the dots and cells of the printing roller penetrate into the cells of the anilox roller to extract ink. Under the action of dye tension, the dye fills the cells at the contact points. After the second contact, the cells on the printing roller that have already stored ink will not carry out excess ink due to the constant surface tension of the dye, while the cells that are not yet filled will continue to store ink. After multiple contacts, the cells on the printing roller will be filled with dye.

[0028] Under the condition of constant surface tension of dyes and chemicals, the amount of ink applied to the dots and the amount of ink stored in the cells remain stable.

[0029] The maximum ink capacity of the printing roller is a fixed value, while the amount of dye and chemical transferred to the fabric is related to the pressure of the printing roller, achieving a controllable and proportionally constant transfer.

[0030] When the printing roller rotates back to the anilox roller side, it will be re-inked. Since some dye and chemical residue always remains at the bottom of the cells, the newly added dye and chemical residue can refill the cells under the action of surface tension, restoring the maximum ink storage state.

[0031] During the printing process, the high-precision dots and cells on the printing rollers press against the fabric, and the dyes and chemicals within the cells are squeezed out and transferred to the fabric surface. The areas of the fabric in contact with the dots are directly exposed to ink, while the non-contact areas are mostly covered by the squeezed-out dyes and chemicals.

[0032] If there are still uncovered areas, adjustments can be made in two ways: one is to adjust the pressure of the printing roller, and the other is to adjust the engraving depth of the printing roller to change the maximum ink intake.

[0033] Because the ink load of the anilox roller and the maximum ink capacity of the printing roller remain constant, under the pressure of the anilox roller and the printing roller, the dye and chemical are transferred proportionally from the anilox roller to the printing roller, and then proportionally to the fabric. The system can continuously and stably carry out the ink supply and transfer process.

[0034] The uniformity of color on a fabric surface depends on the roller pressure and the maximum ink absorption. Roller pressure ensures that the dye fully covers the fabric, while the maximum ink absorption determines the color intensity. Both work together to achieve uniform coloring.

[0035] For dyes and chemicals, the ink load of the anilox roller is constant, and the maximum ink load of the printing roller is constant. Under the pressure of the anilox roller and the printing roller, the dyes and chemicals are transferred proportionally from the anilox roller to the printing roller, and then proportionally from the printing roller to the fabric to be printed. After the anilox roller and the printing roller rotate, they can continuously receive and transfer ink, with constant ink intake and transfer volume, repeating the cycle continuously.

[0036] The viscosity of dyes and chemicals significantly affects the printing effect: low-viscosity dyes and chemicals are easy to penetrate and are suitable for "printing instead of dyeing" with the same color on both sides; increasing the viscosity can inhibit penetration and is suitable for back printing or double-sided different color effects.

[0037] Fabric structures are mainly divided into two types: woven and knitted, formed by the interlacing of warp and weft yarns or the looping of loops, respectively. Taking woven fabrics as an example, their thickness is roughly equal to the sum of the diameters of the warp and weft yarns, with warp density and weft density controlling the yarn spacing. Common yarn counts are between Ne10–60, with diameters of approximately 0.12–0.20 mm; long-fiber yarns are approximately 20D–150D, with diameters of approximately 0.01–0.02 mm. The yarn spacing is usually greater than twice the yarn diameter.

[0038] During laser engraving, the laser beam is adjusted to differentially ablate the rubber surface, removing more material from the surface layer than from the bottom layer, thus forming a conical dot structure. The engraving is based on a preset pixel image, ultimately creating a regularly arranged dot and cell structure.

[0039] The pixel image for engraving is preset to a dot-to-cell ratio of 1:1, 2:1, 2:3, or 1:3. The engraving resolution is set between 600 and 2540 DPI, and the laser energy is set to an engraving depth of 0.01 to 0.1 mm. The pixel image shown below has a dot-to-cell ratio set to 2:1.

[0040] The applicable laser type is fiber laser, with a spot diameter of approximately 5–40 μm, a single laser energy range of 10–1000 W, a maximum modulation frequency of less than 10 MHz, and an engraving resolution between 600–2540 DPI.

[0041] Different lasers have different engraving depths at different energies. In this patent, the laser energy is set to engrave a depth of 0.01 to 0.1 mm.

[0042] For example, when the laser spot size is controlled at 20μm, the size of the dots and holes is approximately 30μm × 30μm.

[0043] The number of network lines added is: 25.4 * 1000 / 30 = 846 LPI;

[0044] LPI is defined as the number of alternating transparent and opaque halftone dots distributed evenly per inch. As can be seen from the pixel diagram, the number of dots and cells per inch corresponds to the number of mesh holes (pores).

[0045] When the spot diameter is 5μm, the ratio of dots to holes in the pixel image is set to 1:1, and the equivalent screen ruling is 5080 LPI.

[0046] When the spot diameter is 40μm, the ratio of dots to holes in the pixel image is set to 1:1, and the calculated screen ruling is 635 LPI.

[0047] At this size, the surface of a single yarn can be covered by 4–9 dots or cells. Therefore, by adjusting the dot engraving depth (typically 0.05–0.50 mm) and pressure of the printing roller, complete coverage of the fabric surface can be achieved.

[0048] Increasing the engraving depth enhances the ink storage capacity of the cells, thereby transferring more dyes and chemicals; increasing the pressure of the printing roller allows the dots to contact deeper into the fabric layers and extrudes more ink. The rubber hardness of the printing roller is generally controlled between 38–85 HA. Lower hardness helps improve ink adhesion and dot deformation ability, with around 55 HA being generally optimal.

[0049] When the dyes and chemicals can basically cover the fabric surface, the system can achieve high-quality "printing instead of dyeing", presenting a printing effect with uniform color and small color difference between the left, center and right sides.

[0050] The above content is a further detailed description of the technical solution provided in conjunction with the preferred embodiments of this patent. It should not be considered that the specific implementation of this invention is limited to the above description. For those skilled in the art to which this patent pertains, several simple deductions or substitutions can be made without departing from the concept of this patent, and all of these should be considered to fall within the protection scope of this patent.

Claims

1. A laser-based flexographic printing system, characterized in that: It includes at least one color unit, the color unit including an ink cavity, an anilox roller, a printing roller and a printing substrate roller, the surface of the printing roller is engraved with dots and cells, which are directly engraved by a laser engraving machine; The ink chamber supplies dyes and chemicals to the anilox roller through a closed circulation pipeline; The anilox roller presses into contact with the printing roller, transferring the dye and chemical material to the printing roller, causing the dots to be inked and the cells to store ink. The printing roller and the substrate roller press into contact, and the dyes and chemicals are transferred to the fabric to be printed by the expansion of the dots and the squeezing of the cells.

2. The laser deburring flexographic printing system according to claim 1, characterized in that: The process parameters of the direct laser engraving machine are as follows: engraving resolution: 600-2540 DPI, engraving depth: 0.05-0.5 mm, and roller line count: 635-5080 LPI.

3. The laser de-texturing flexographic printing system according to claim 1, characterized in that: The laser type of the direct laser engraving machine is fiber laser, with a spot diameter of 5-40 μm, a laser energy range of 10-1000 W for a single laser, and a maximum modulation frequency of less than 10 MHz.

4. The laser deburring flexographic printing system according to claim 1, characterized in that: The printing roller is made of ethylene propylene diene monomer (EPDM) rubber, and its surface hardness ranges from 38 to 85 HA according to the Shore hardness scale.

5. The laser deburring flexographic printing system according to claim 1, characterized in that: The surface material of the anilox roller is ceramic or metal, with an engraving line count of 100-600 LPI and an ink load of 3-30 BCM.

6. The laser de-texturing flexographic printing system according to claim 1, characterized in that: The ratio of dots to cells in the pixel image to be engraved is preset to 1:1, 2:1, 2:3, or 1:

3. The engraving resolution is set to a range of 600–2540 DPI. The laser energy is set to engrave a depth of 0.01–0.1 mm.

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