Laser cutting method for optimizing yellowing of edge of cellulose cloth

Abstract

The invention discloses a laser cutting method for optimizing yellowing of the edge of cellulose cloth. The problem that the cellulose cloth becomes yellow during cutting can be solved. The method comprises the following specific steps: placing cellulose cloth needing to be cut in a proper operation space; the size of the cloth needing to be cut is determined, and a proper amount of self-prepared solvent is applied to a notch to enable the solvent to completely soak the cloth; proper laser cutting parameters are set according to the thickness, the components and the structure of the cloth; a laser is turned on to cut the cloth along a set route; the power is adjusted according to color change detection at a notch after complete cutting; the self-configured solvent absorbs laser energy to volatilize and takes away a large amount of heat, so that a laser direct acting part is cut, and meanwhile, the laser energy absorbed by a laser acting point is prevented from conducting heat to surrounding cloth, so that yellowing at a notch is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of laser cutting, and particularly relates to a laser cutting method for optimizing the yellowing of the edges of cellulose fabrics. Background Art

[0002] Cellulose is an abundant natural product that can be extracted from plants such as lignin, cotton, and hemp. Cellulose fabrics are textiles made using cellulose as the main raw material, and they have excellent moisture absorption and breathability, antibacterial properties, and durability. Due to the excellent properties and wide sources of cellulose fabrics, they are widely used in the textile field and other related fields.

[0003] However, in the actual production process, the manufactured cellulose fabrics are often large in area, and it is necessary to cut and engrave the cellulose fabrics according to the actual production and living needs. The traditional method is to directly cut using a knife or scissors. However, these tools are prone to wear and may cause the edges of the cut fabrics to fray. In contrast, laser cutting technology can solve these problems through its flexibility in adapting to various shapes, speed, high accuracy, and repeatability.

[0004] Laser cutting is a method in which a laser beam is focused on the surface of a material after being converted by an optical path, and linear scanning is performed. The scanning line is composed of a series of dense dot matrices combined into a straight line. The material in this area absorbs the laser energy incident on the surface and instantaneously converts it into heat energy, causing the surface temperature of the material to rapidly rise until the material melts or vaporizes, forming a cut seam and cutting the material. In recent years, laser cutting technology has been widely used in the fields of automobile manufacturing, aerospace, etc. to cut some materials with high hardness and brittleness. Laser cutting technology can also be used for the cutting and processing of flexible materials such as fabrics and papers.

[0005] Compared with traditional cutting methods, laser cutting technology has the following advantages: (1) It does not directly contact the material and can perform remote cutting; (2) It can be combined with automated equipment to achieve automation of the cutting process; (3) There is no restriction on the cutting tool, and almost any cutting effect can be achieved; (4) The cutting speed has a great advantage over traditional cutting methods, and a large number of cuts can be completed in a short time; (5) The edges of the cut fabric are flat and smooth, and there will be no burrs, curled edges, etc. like mechanical cutting.

[0006] Laser cutting technology also has certain disadvantages: (1) Smoke, dust, and odors are generated during the cutting process, which may pose hazards to the environment and the health of operators; (2) When cutting thick fabrics or multiple layers of fabrics, the efficiency and quality of laser cutting may decrease.

[0007] During the laser cutting process, due to the temperature gradient between different parts of the object, there will be an exchange of internal energy from the high-temperature part to the low-temperature part, that is, heat conduction. The energy transfer in heat conduction follows Fourier's law: , where is the heat flux density ( ); is the thermal conductivity ]; is the temperature gradient; the negative sign indicates that the heat flows in the direction of decreasing temperature.

[0008] When the laser irradiates the surface of the sample, the absorption of laser energy by the material causes the temperature to rise rapidly. After reaching the melting point or vaporization point, it begins to decompose. The temperature change in this whole stage is a transient heat problem. The temperature distribution of the temperature field changes with time, and it is necessary to solve it using the heat conduction equation derived from the law of conservation of energy and Fourier's law: , where is the laser energy absorbed by the material per unit volume per unit time; is the temperature; is the laser action time; , and are the laser action depths in three directions respectively.

[0009] From the heat conduction in the laser cutting process introduced here, it can be known that when laser cutting fabrics, the laser energy absorbed by the fabrics will be transferred to the surroundings of the laser action point through heat conduction, forming a heat-affected area within a certain range, causing the surrounding materials to heat up. However, when the temperature rise does not reach the complete decomposition temperature of cellulose, cellulose will decompose incompletely, making the cut edge turn yellow. During the laser cutting process, the heat-affected area can be reduced and the yellowing can be reduced by adjusting the laser parameters, but it is very difficult to avoid the yellowing.

[0010] In the existing laser cutting fabric methods, various methods are used by laser devices to avoid the influence of fabric combustion. Patent CN 214831104 U discloses a fabric laser cutting device and method. This device integrates a smoke exhaust and air blowing component in the laser cutting system, which can effectively extract the smoke and quickly extinguish the possible open flames. This utility model patent effectively prevents the combustion of open flames during the cutting process. The present invention is to avoid the yellowing phenomenon of the fabric around the cutting part and ensure that the subsequent use quality of the fabric is not affected.

[0011] Patent CN 107262944 A proposes a medical and nursing clothing cutting machine. By setting cooling components on both sides of the laser emission head, the effect of timely cooling is achieved, avoiding problems caused by the extension and combustion of the fabric. In the present invention, the heat conducted from the laser action point to the surrounding is taken away by the volatilization of the solvent applied around, preventing the surrounding fabric from heating up and achieving fabric cutting without yellowing at the edges.

[0012] Most of the existing laser cutting methods for fabrics only consider avoiding the influence of direct combustion. However, the phenomenon of yellowing at the cutting edge that occurs during the cutting process will affect the subsequent use of the fabric and needs to be avoided. Summary of the Invention

[0013] A laser cutting method for preventing yellowing of excellent cellulose fabrics proposed by the present invention can solve the technical problem of incomplete decomposition and yellowing during the laser cutting of cellulose fabrics.

[0014] To achieve the above object, the present invention adopts the following technical solutions: A laser cutting method for optimizing fabric yellowing includes the following steps: Step 1: Place the fabric to be cut in a suitable operating space, adjust the optical system so that the spot of the laser beam is focused near the surface of the material; Step 2: Determine the size of the fabric to be cut, apply an appropriate amount of self-configured solvent at the cut, and make the solvent completely penetrate the fabric; Step 3: Set appropriate laser cutting parameters according to the thickness, composition and structure of the fabric; Step 4: Turn on the laser, and make it scan the fabric along the set route to ablate the cellulose to achieve cutting; Step 5: Adjust the power according to the change detection at the cut after complete cutting; Step 6: The self-configured solvent absorbs the laser energy and volatilizes, taking away a large amount of heat, so that the directly laser-acted part is cut, and at the same time, the heat conduction of the laser energy absorbed by the laser action point to the surrounding fabric is avoided, thereby reducing yellowing at the cut.

[0015] Among them, the fabric in Step 1 is a textile made mainly of cellulose as the raw material.

[0016] The spot size of the laser beam in Step 1 can be adjusted according to requirements.

[0017] The self-configured solvent in Step 2 is prepared by mixing volatile organic solvents such as ethanol and acetone in proportion, and the specific proportion needs to be adjusted according to the composition of the fabric to be cut.

[0018] The self-configured solvent in Step 2 can absorb a large amount of laser heat, preventing the incomplete combustion of cellulose to produce organic intermediate products such as aldehydes and ketones, resulting in yellowing and blackening.

[0019] The laser cutting parameters in Step 3 include but are not limited to: the average power of the laser, with an adjustment range of 0 W - 10 W; the laser moving speed, with an adjustment range of 0 - 1000 mm / min; and the number of scans being 1 - 100 times.

[0020] In Step 5, the detection of changes at the incision after complete cutting is mainly through visual observation, and at the same time, photos are taken for CIE chromaticity analysis to distinguish. The chromaticity analysis is based on the colorimetric system, and the following formula is used to calculate the color difference value: , where is the brightness value of the displayed color. A positive brightness value indicates white, and a negative brightness value indicates black; is the red - green value of the displayed color. A positive red - green value indicates red, and a negative red - green value indicates green; is the yellow - blue value of the displayed color. A positive yellow - blue value indicates yellow, and a negative yellow - blue value indicates blue. The calculated according to the above formula is the total color difference value for comparing the edges of the fabric before and after cutting. The larger the value, the greater the color difference, indicating that the edge of the cut fabric is significantly yellowed and charred; conversely, it indicates that the yellowing and charring phenomenon of the fabric cutting edge is not obvious.

[0021] The laser power in Step 5 can adjust the surface temperature of the sample within a certain range, within which the cellulose is completely ablated and decomposed without yellowing.

[0022] The self - configured solvent in Step 6 instantaneously absorbs a large amount of laser energy during the laser action for its own volatilization, thereby adjusting the energy used for fabric cutting, avoiding the heat conduction of the laser energy absorbed by the laser action point to the surrounding fabric, preventing the surrounding fabric from absorbing energy, increasing the temperature, and undergoing incomplete combustion to produce intermediate organic compounds with chromophoric groups such as aldehydes and ketones, thereby reducing yellowing at the incision: n(ketones ( ) + aldehydes( , ) + + CO, etc.).

[0023] As can be seen from the above technical solutions, an optimized laser cutting method for fabric yellowing of the present invention utilizes the volatile property of the self - configured solvent, and realizes laser cutting without yellowing at the incision of cellulose fabric through processes such as providing energy by high - energy laser, cellulose decomposition, and the absorption and volatilization of laser energy by the self - configured solvent. The present invention can optimize the problem of yellowing at the incision edge caused by incomplete decomposition of cellulose during the laser cutting process of cellulose materials.

[0024] The basic principle of the present invention is that the self-configured solvent volatilizes to take away the energy conducted by heat to the surrounding materials, avoiding their decomposition. Figure 2 This is the model diagram of the present invention. First, the laser acts on the surface of the fabric. The fabric and the solvent absorb the laser energy, the temperature rises, reaching the cellulose decomposition temperature, and the fabric begins to be cut. At the same time, during the process, the solvent continuously volatilizes, taking away the energy, reducing the heat transfer of the fabric to the surrounding of the incision, and avoiding the decomposition and yellowing of the surrounding fabric.

[0025] The present invention uses a fully automatic laser engraving machine to perform laser cutting on cellulose fabric. During cutting, it has high efficiency and automatic control, and achieves no yellowing around the incision while completely cutting the cellulose fabric.

[0026] The present invention also has the following advantages: (1) Only the self-configured solvent is used during the cutting process, with low environmental pollution; (2) The solvent completely volatilizes during the cutting process, without damaging the fabric; (3) High cutting efficiency, capable of automatic control, and suitable for industrial production. Description of the Drawings

[0027] Figure 1 This is the schematic diagram of the method flow of the present invention.

[0028] Figure 2 This is the model diagram of the present invention.

[0029] Figure 3 This is the XRD test diagram of the fabric.

[0030] Figure 4 This is the FTIR diagram of the fabric (a) and the FTIR spectrum of the yellowed part after laser cutting without adding solvent (b).

[0031] Figure 5 This is the macroscopic diagram of the front (a), back (b) and cross-section (c) of the sample after completely cutting the cellulose fabric by laser without adding the self-configured solvent in the embodiment.

[0032] Figure 6 This is the macroscopic diagram of the front (a), back (b) and cross-section (c) of the sample after completely cutting the cellulose fabric by laser with the addition of the self-configured solvent in the embodiment.

[0033] Figure 7 This is the total color difference value between the incision and the original sample after completely cutting the cellulose fabric by laser with and without the addition of the self-configured solvent in the embodiment. Detailed Embodiments

[0034] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives the detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0035] Example

[0036] The example provides a laser cutting method for optimizing the yellowing of the edge of cellulose fabric. The steps include: placing the fabric to be cut in a suitable operating space, adjusting the optical system to focus the spot of the laser beam near the surface of the material; determining the size of the fabric to be cut, applying an appropriate amount of self-prepared solvent at the incision to completely penetrate the fabric; setting appropriate laser cutting parameters according to the thickness, composition and structure of the fabric; turning on the laser and scanning the fabric along the set route to ablate cellulose for cutting; adjusting the power according to the change detection at the incision after complete cutting; the self-prepared solvent absorbs the laser energy and volatilizes, taking away a large amount of heat, so that the directly laser-acted part is cut, and at the same time, the laser energy absorbed by the laser action point is prevented from conducting heat to the surrounding fabric, thereby reducing the yellowing at the incision.

[0037] For the fabric in the first step, we used Swedish towel and conducted XRD (X-ray diffraction) tests on it in advance, and observed the typical diffraction peaks of cellulose: (110 crystal plane) (002 crystal plane), and determined that its main component is cellulose. At the same time, the yellowed part generated by laser cutting without adding solvent was detected. Compared with the original sample, there were 1712 more peaks, corresponding to the stretching vibration of carbonyl (C=O). Thus, it was confirmed that the yellowing was the result of the oxidation of cellulose at this part to produce ketone compounds.

[0038] Then, an appropriate amount of self-prepared solvent was applied at the expected cutting position. After laser cutting, multiple experiments were carried out by changing the laser parameters and the ratio of ethanol and acetone in the prepared solvent. Visually observed, the incision of the sample with the added self-prepared solvent changed little or hardly changed compared with that without addition. Then, CIE chromaticity coordinate analysis was carried out on the incision, and it was found that the chromaticity change after adding the solvent was much smaller than that without adding the self-prepared solvent.

[0039] The above examples are only used to illustrate the technical solutions of the present invention, rather than limiting it; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser cutting method for optimizing yellowing of cellulose fabrics, characterized in that: The following steps are involved: Step 1: Place the fabric to be cut in a suitable operating space and adjust the optical system so that the laser beam spot is focused near the surface of the material; Step 2: Determine the size of the fabric to be cut, apply a suitable amount of self-prepared solvent at the cut, and allow the solvent to completely soak the fabric; Step 3: Set appropriate laser cutting parameters according to fabric thickness, composition and structure; Step 4: Turn on the laser to scan the fabric along the set route, ablating the cellulose to achieve cutting; Step 5: Adjust the power according to the change detection at the incision after complete cutting; Step 6: The self-configured solvent absorbs the laser energy and evaporates, taking away a large amount of heat, so that the part directly acted by the laser is cut, and at the same time avoids the laser energy absorbed by the laser action point from being transferred to the surrounding fabric, thereby reducing yellowing at the incision.

2. The laser cutting method for optimizing yellowing of fabric according to claim 1, characterized in that: The cloth in step 1 is a textile made from cellulose as a main raw material.

3. The laser cutting method for optimizing yellowing of fabric according to claim 1, characterized in that: The spot size of the laser beam in step 1 can be adjusted according to demand.

4. The laser cutting method for optimizing yellowing of fabric according to claim 1, characterized in that: The self-prepared solvent in step 2 is a mixture of volatile organic solvents such as ethanol and acetone in a certain proportion, and the specific proportion needs to be adjusted according to the composition of the fabric to be cut.

5. The laser cutting method for optimizing yellowing of fabric according to claim 1, characterized in that: The self-configured solvent in step 2 can absorb a large amount of laser heat, thereby preventing the incomplete combustion of cellulose from producing organic intermediates such as aldehydes and ketones, resulting in yellowing and blackening.

6. The laser cutting method for optimizing yellowing of fabric according to claim 1, characterized in that: The laser cutting parameters in step three include but are not limited to: average laser power, with an adjustment range of 0W-10W; laser moving speed, with an adjustment range of 0-1000mm / min; and scanning times of 1-100 times.

7. The laser cutting method for optimizing yellowing of fabric according to claim 1, characterized in that: In step 5, the change detection of the incision after complete cutting is mainly observed by naked eyes, and photos are taken for CIE colorimetric analysis to distinguish. The colorimetric analysis is based on Color system, use the following formula to calculate the color difference value: ,in, Displays the brightness value of the color. Positive brightness values ​​represent white, and negative brightness values ​​represent black. Displays the red and green values ​​of the color. Positive red and green values ​​represent red, while negative red and green values ​​represent green. The yellow-blue value of the displayed color. A positive value indicates yellow, while a negative value indicates blue. , which is the total color difference between the edges of the cloth before and after cutting. The larger the value, the greater the color difference, which means that the edges of the fabric after cutting are obviously yellowed and burnt; otherwise, the edges of the fabric after cutting are not obviously yellowed and burnt.

8. The laser cutting method for preventing yellowing of fabric according to claim 1, characterized in that: The laser power in step five can adjust the sample surface temperature within a certain range, within which the cellulose is completely ablated and decomposed without yellowing.

9. The laser cutting method for optimizing yellowing of fabric according to claim 1, characterized in that: The self-configured solvent in step 6 absorbs a large amount of laser energy instantly during the laser action process for its own volatilization, thereby adjusting the energy used for fabric cutting, preventing the laser energy absorbed by the laser action point from being thermally transferred to the surrounding fabric, preventing the surrounding fabric from absorbing energy, causing the temperature to rise, and performing incomplete combustion to produce organic compound intermediates such as aldehydes and ketones with chromophore groups, thereby reducing yellowing at the incision: n(ketones( ) + Aldehydes( , ) + + CO, etc.).

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