A laser milling method for mold surface texture based on heating assistance

Abstract

The present invention discloses a method for laser milling mold surface textures based on heating assistance, comprising the following steps: placing the mold to be laser milled in a nanosecond laser processing system including a heating device; preheating the surface of the mold to be milled to a predetermined temperature by the heating device; setting the laser milling process parameters of the nanosecond laser processing system, turning on the nanosecond laser milling and protective gas system, and performing milling on the mold surface; after completing the laser milling process, regulating the heating parameters of the heating device so that the mold surface temperature gradually cools to room temperature. The present invention promotes the vaporization and removal of the mold surface material during nanosecond laser milling by auxiliary heating of the mold, thereby increasing the milling rate of the nanosecond laser; and can avoid microcrack defects on the mold surface caused by thermal stress; the present invention increases the thickness of the strengthening layer of the laser milling remelting layer by heating assistance, further increasing the service life of the mold.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser processing, and in particular relates to a heating-assisted laser milling method for mold surface texture. Background Art

[0002] Laser milling of mold surface textures involves scanning the mold surface with a high-energy pulsed laser beam, precisely removing material to create surface textures and microchannels. Widely used in molds for leather, plastics, and other applications, this process offers advantages such as environmental friendliness, high precision, and flexibility. Compared to ultrafast laser milling technology, nanosecond laser milling offers lower costs. Laser milling also significantly increases the mold's surface hardness by creating a fine-grained remelted hardening layer.

[0003] However, due to the low single pulse energy, the efficiency of nanosecond laser milling is low; and the laser milling surface will cool rapidly after laser irradiation heating. The laser milling remelted layer often produces microcrack defects due to thermal stress, resulting in a significant reduction in the fatigue life of the mold during use.

[0004] Therefore, it is necessary to further improve the material removal efficiency during nanosecond laser milling, reduce the cooling rate of the surface remelting layer after laser milling, and reduce thermal stress. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for laser milling mold surface texture based on heating assistance, which is more efficient and can avoid micro-crack defects on the mold surface caused by thermal stress.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for laser milling mold surface texture based on heating assistance includes the following steps:

[0008] a. Place the mold to be laser milled in a nanosecond laser processing system including a heating device; preferably, the mold is made of high-alloy mold steel, carbon mold steel or ductile iron; the heating device is a heating table, an induction heating device or a hot air heating device.

[0009] b. Preheat the mold surface to a predetermined temperature by a heating device; preferably, the heating temperature of the heating device is 200-800°C, and the temperature error is less than 30°C; further preferably, the heating temperature of the heating device is 400-650°C, and the temperature error is less than 10°C.

[0010] c. Set the laser milling process parameters of the nanosecond laser processing system, start the nanosecond laser milling and protective gas system, and mill the mold surface; the protective gas in the protective gas system is argon, nitrogen, or helium. Preferably, the laser milling process parameters of the nanosecond laser processing system are: average power of the nanosecond laser 20-1500W; laser pulse repetition frequency 1-70kHz; laser pulse width 1-500ns; spot diameter 20-100μm; fill line spacing 10-120μm; scanning rate 10-2000mm / s. Further preferably, the laser milling process parameters of the nanosecond laser processing system are: average power of the nanosecond laser 70-1000W; laser pulse repetition frequency 20-65kHz; laser pulse width 5-100ns; spot diameter 25-80μm; fill line spacing 20-90μm; scanning rate 30-1000mm / s. More preferably, the laser milling process parameters of the nanosecond laser processing system are: average power of the nanosecond laser 70-1000W; laser pulse repetition frequency 30-60kHz; laser pulse width 8-50ns; spot diameter 30-60μm; filling line spacing 25-50μm; scanning rate 100-700mm / s.

[0011] d. After the laser milling process is completed, the heating parameters of the heating device are adjusted to gradually cool the mold surface temperature to room temperature. Preferably, the cooling rate of the mold surface temperature is less than 20°C / s. More preferably, the cooling rate of the mold surface temperature is less than 5°C / s.

[0012] Compared with the prior art, the advantages of the present invention are:

[0013] 1. The present invention promotes the vaporization and removal of the mold surface material during nanosecond laser milling by auxiliary heating of the mold, thereby increasing the nanosecond laser milling rate;

[0014] 2. After the mold surface is heated, the temperature gradient between the laser milling surface molten pool and the mold base decreases, and the cooling rate is reduced; and the cooling rate is controllable within the range from the mold heating temperature to room temperature, which effectively reduces the thermal stress of the remelting layer during laser milling of the mold and avoids defects such as microcracks.

[0015] 3. The present invention increases the thickness of the laser milling remelting layer strengthening layer through heating assistance, thereby further increasing the service life of the mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the cross-sectional scan morphology of the mold after laser milling in Example 1 of the present invention;

[0017] Figure 2 This is the morphology of the remelted layer after laser milling of the mold in Example 1 of the present invention;

[0018] Figure 3 This is the cross-sectional scanning morphology of the mold after laser milling in Comparative Example 1 of the present invention;

[0019] Figure 4 This is the morphology of the remelted layer after laser milling of the mold in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0020] Below, with reference to the accompanying drawings and Examples, the specific embodiments of the present invention are described in further detail. Where specific conditions are not specified in the Examples, conventional conditions or conditions recommended by the manufacturer were used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0021] Example 1

[0022] A method for laser milling a mold surface texture based on heating assistance includes the following steps:

[0023] (1) A 5 mm thick Cr12MoV steel sample was selected as the mold material sample to be laser milled. The sample was placed on the heating table surface, and the surface to be milled of the sample was adjusted to the vicinity of the laser beam focus of the nanosecond laser processing system.

[0024] (2) Turn on the heating table and heat the surface to be milled to 400°C in combination with online infrared temperature measurement;

[0025] (3) The laser milling area was set to a 4 mm × 4 mm square area, the laser power was set to 70 W, the spot diameter was set to 30 μm, the pulse width was set to 24 ns, the repetition frequency was set to 55 kHz, the filling method was set to grid filling, the filling line spacing was set to 30 μm, the scanning rate was set to 500 mm / s, and the number of scans was set to 50. The argon shielding gas was turned on at a gas flow rate of 5 L / min.

[0026] (4) After the laser milling process is completed, the heating parameters of the heating stage are adjusted so that the sample temperature drops to near room temperature at a cooling rate of about 5°C / s. Figure 1 and Figure 2 The scanning morphology analysis results of the laser milling interface show that the depth of the laser milling micro-groove is 325μm, the depth of the remelting strengthening layer on the mold surface after milling is 23.1μm, and there is no microcrack defect in the remelting layer.

[0027] Comparative Example 1

[0028] A method for laser milling a mold surface texture comprises the following steps:

[0029] (1) 5 mm thick Cr12MoV steel was selected as the mold material sample to be laser milled, and the surface to be milled of the sample was directly placed near the laser beam focus of the nanosecond laser processing system;

[0030] (2) The laser milling area was set to a 4 mm × 4 mm square area, the laser power was set to 70 W, the spot diameter was set to 30 μm, the pulse width was set to 24 ns, the repetition frequency was set to 55 kHz, the filling method was set to grid filling, the filling line spacing was set to 30 μm, the scanning rate was set to 500 mm / s, and the number of scans was set to 50. The argon shielding gas was turned on at a gas flow rate of 5 L / min.

[0031] (3) After the laser milling process, the sample was directly cooled to room temperature in air.

[0032] Depend on Figure 3 and Figure 4 Scanning morphological analysis of the laser-milled interface revealed a microgroove depth of 203 μm and a remelted layer thickness of 203 μm. Compared to Example 1, where laser milling was performed at an auxiliary heating temperature of 400°C, the material removal efficiency was significantly reduced. Furthermore, due to the rapid heat dissipation from the substrate, the remelted layer produced by laser milling exhibited high thermal stress, resulting in microcracks.

[0033] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

Claims

1. A method for laser milling mold surface texture based on heating assistance, characterized in that: The following steps are involved: a. Place the mold to be laser milled in a nanosecond laser processing system including a heating device; b. Preheat the mold surface to a predetermined temperature through a heating device; c. Set the laser milling process parameters of the nanosecond laser processing system, start the nanosecond laser milling and protective gas system, and perform laser milling on the mold surface; d. After completing the laser milling process, adjust the heating parameters of the heating device to gradually cool the mold surface temperature to room temperature; In step a, the material of the mold is high alloy mold steel, carbon mold steel or ductile iron; The heating temperature of the heating device is 400-650°C, and the temperature error is less than 10°C; In step c, the laser milling process parameters of the nanosecond laser processing system are: average power of nanosecond laser 20-1500W; laser pulse repetition frequency 1-70kHz; laser pulse width 1-500ns; spot diameter 20-100μm; filling line spacing 10-120μm; scanning rate 10-2000mm / s.

2. The method for laser milling mold surface texture based on heating assistance according to claim 1, characterized in that: In step a, the heating device is a heating table, an induction heating device or a hot air heating device.

3. The method for laser milling mold surface texture based on heating assistance according to claim 1, characterized in that: The laser milling process parameters of the nanosecond laser processing system are: average power of the nanosecond laser 70-1000W; laser pulse repetition frequency 20-65kHz; laser pulse width 5-100ns; spot diameter 25-80μm; filling line spacing 20-90μm; scanning rate 30-1000mm / s.

4. The method for laser milling mold surface texture based on heating assistance according to claim 3, characterized in that: In step a, the laser milling process parameters of the nanosecond laser processing system are: average power of the nanosecond laser 70-1000W; laser pulse repetition frequency 30-60kHz; laser pulse width 8-50ns; spot diameter 30-60μm; filling line spacing 25-50μm; scanning rate 100-700mm / s.

5. The method for laser milling mold surface texture based on heating assistance according to claim 1, characterized in that: In step c, the protective gas in the protective gas system is argon, nitrogen or helium.

6. The method for laser milling mold surface texture based on heating assistance according to claim 1, characterized in that: In step d, the cooling rate of the mold surface temperature is less than 20° C. / s.

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