A focal length thermal effect compensation method for a laser 3D metal printing device

Abstract

The application discloses a focal length thermal effect compensation method of a laser 3D metal printing device, and belongs to the field of laser 3D printing. The optical path system of the device comprises a focusing lens, a focusing lens and a reflecting galvanometer arranged in sequence along the direction of the laser optical path, wherein the focusing lens and the focusing lens are both provided with temperature sensors, and the focusing lens is driven to move along the direction of the optical path by a voice coil motor. The focal length thermal effect compensation is carried out during laser 3D printing, and specifically comprises the following steps: S1. The temperature changes of the focusing lens and the focusing lens are monitored in real time through the temperature sensors; S2. The interval of the focusing lens and the focusing lens is calculated based on the real-time temperature changes of the focusing lens and the focusing lens, and the focusing lens is adjusted through the voice coil motor, so that the interval of the focusing lens and the focusing lens meets the calculation result. The temperature compensation method can solve the problem of imaging focus drift caused by the change of the focal length of the optical lens due to the temperature change, and has the advantages of simple structure and simple adjustment process.

Description

Technical Field

[0001] This invention belongs to the technical field of laser 3D metal printing equipment, and particularly relates to a method for compensating for the focal length thermal effect in laser 3D metal printing equipment. Background Technology

[0002] Laser 3D metal printing (SLM) typically uses fiber lasers ranging from hundreds to thousands of watts for scanning and printing. An example of an optical imaging system for laser 3D metal printing is a 3D printer focusing device disclosed in utility model patent CN215867306U. This device includes a light source, a focusing lens group, a focusing lens group, and a beam adjustment lens group sequentially arranged inside a housing. The centers of the light source, focusing lens group, focusing lens group, and beam adjustment lens group are located on the same straight line. The light source, focusing lens group, and beam adjustment lens group are all fixed to the housing, while the focusing lens group is slidably connected to the housing.

[0003] In the aforementioned optical imaging system, the glass materials of the optical components have a certain absorption rate for high-power lasers. When the laser passes through the imaging lens and other optical components, a small portion of the optical power is lost. This lost laser power causes the related lenses along the optical path to heat up and increase in temperature. Every optical lens glass material has a refractive index temperature coefficient constant (dn / dt). This constant indicates that temperature changes cause changes in the focal length of the optical lens, ultimately leading to temperature drift at the imaging focus.

[0004] Fused silica (FMS) glass, with its excellent physical properties, low light absorption, and very low coefficient of thermal expansion, is the most commonly used glass material for metal laser 3D printing. Currently, both biaxial galvanometer systems using F-Theta lenses and triaxial galvanometer systems with dynamic focusing utilize FMS as the lens material in the optical path. The temperature coefficient of refractive index of FMS is 2.2370E^-005. In a typical triaxial galvanometer system with a focal length of 500mm and a temperature difference of 100℃, the image focus drift caused by temperature variations in the optical material properties is approximately 4mm, which significantly degrades print quality.

[0005] To compensate for focal point drift, the conventional approach is to maximize cooling capacity using methods such as air cooling to limit the rise in the operating temperature of the optical lenses, thereby reducing the focal length change in the optical system caused by lens temperature variations. A more precise solution is to install a temperature sensor near the lens, test its true focal length at different temperatures, and use a control program to change the printed focal length based on the temperature to compensate for the temperature drift caused by temperature changes. For example, Chinese Patent CN215747081U discloses a real-time automatic compensation and stabilization device and system for laser focal point drift. This device includes a focal point compensation module, a driver electrically connected to the focal point compensation module, a feedback control module electrically connected to the driver, and a temperature sensor electrically connected to the feedback control module. The focal point compensation module includes a concave lens and a convex lens that can move relative to each other. The feedback control module adjusts the focal position of the emitted laser by changing the distance between the concave lens and the convex lens through the driver based on the temperature data fed back by the temperature sensor. The above compensation methods require controlling the temperature of the optical path system or setting different focal length values ​​for different temperatures, which leads to a complex optical path system structure, an increase in the size of the entire printing device, and a cumbersome process in which the focal length value needs to be calculated based on different temperatures during the focusing process. Summary of the Invention

[0006] This invention provides a method for compensating for the thermal effect of focal length in laser 3D metal printing equipment, in order to solve the problems in existing optical imaging systems, such as the temperature drift of the imaging focus caused by lens temperature changes, the complexity of the optical path system structure and the cumbersome focusing process caused by the compensation of the image focus drift.

[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0008] This invention relates to a method for compensating for focal length thermal effects in a laser 3D metal printing device. The optical path system of the laser 3D metal printing device includes a focusing lens, a focusing lens, a reflecting mirror, and a printing surface arranged sequentially along the laser optical path. Both the focusing lens and the focusing lens are equipped with temperature sensors. The focusing lens is driven by a voice coil motor to move along the optical path. Focal length thermal effect compensation during laser 3D printing specifically includes the following steps:

[0009] S1. Real-time monitoring of temperature changes in the focusing and adjusting lenses using temperature sensors;

[0010] S2. The distance between the focusing and focusing lenses is calculated based on the real-time temperature changes of the focusing and focusing lenses, and the focusing lens is adjusted using a voice coil motor to ensure that the distance between the focusing and focusing lenses meets the calculation results; the formula for calculating the distance between the focusing and focusing lenses is:

[0011] (1),

[0012] In the formula, △T1 is the temperature change of the focusing lens, △T2 is the temperature change of the focusing lens, D is the calculated distance between the focusing lens and the focusing lens, f1 is the focal length of the focusing lens, and f2 is the focal length of the focusing lens.

[0013] Preferably, the focusing lens is a concave lens and the focusing lens is a convex lens, and both the focusing lens and the focusing lens are made of fused silica lenses.

[0014] Preferably, the focusing lens is mounted on a temperature control base. When adjusting the distance between the focusing lens and the adjusting lens, the temperature of the focusing lens is adjusted by the temperature control base at a fixed ratio according to the temperature change of the adjusting lens.

[0015] Preferably, the temperature control base is a semiconductor cooler or a water-cooled base.

[0016] Preferably, the thickness of the focusing lens and the teleconverting lens satisfies the following:

[0017] (4),

[0018] In the formula, H1 is the thickness of the focusing lens, H2 is the thickness of the focusing lens, and D0 is the distance between the focusing lens and the focusing lens.

[0019] Preferably, both the focusing lens and the focusing lens are mounted on a heat dissipation base, and the thermal conductivity of the heat dissipation base used to mount the focusing lens and the focusing lens satisfies the following requirements:

[0020] (5),

[0021] In the formula, λ1 is the thermal conductivity of the focusing lens, λ2 is the thermal conductivity of the focusing lens, W1 is the light absorption power of the focusing lens, W2 is the light absorption power of the focusing lens, and D0 is the distance between the focusing lens and the focusing lens.

[0022] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0023] 1. The optical path system of the laser 3D metal printing equipment of the present invention includes a focusing lens, a focusing lens, a reflecting galvanometer, and a printing working surface arranged sequentially along the laser optical path. Temperature sensors are provided on both the focusing lens and the focusing lens. The focusing lens is driven by a voice coil motor to move along the optical path. During laser 3D printing, focal length thermal effect compensation is performed. The temperature changes of the focusing lens and the focusing lens are monitored in real time by the temperature sensors. The distance between the focusing lens and the focusing lens is calculated based on the real-time temperature changes of the focusing lens and the focusing lens, and the focusing lens is adjusted by the voice coil motor to ensure that the distance between the focusing lens and the focusing lens meets the calculation result. This temperature compensation method can solve the problem of image focus drift caused by changes in the focal length of optical lenses due to temperature changes. It has a simple structure and a simple adjustment process.

[0024] 2. The focal length thermal effect compensation method for laser 3D metal printing equipment disclosed in this invention monitors the temperature changes of the focusing lens and the focusing lens in real time using a temperature sensor; then, based on the real-time temperature changes of the focusing lens and the focusing lens, the distance between the focusing lens and the focusing lens is calculated, and the focusing lens is adjusted by a voice coil motor to ensure that the distance between the focusing lens and the focusing lens meets the calculation result. Furthermore, by setting the thickness ratio of the focusing lens and the focusing lens of the same material or by setting the thermal conductivity of the heat dissipation base of the focusing lens and the focusing lens, the structure no longer requires an additional temperature control base to adjust the temperature of the focusing lens and the focusing lens, further simplifying the structure and the thermal compensation method. Attached Figure Description

[0025] Figure 1 This is a structural diagram of the laser 3D metal printing equipment involved in the present invention;

[0026] Figure 2 This is an equivalent schematic diagram of the optical path system of the laser 3D metal printing equipment involved in this invention;

[0027] Figure 3 This is a detailed structural diagram of the optical path system involved in Embodiment 1.

[0028] Figure labels: 1-Laser, 2-Focusing lens, 3-Focusing lens, 4-Reflecting galvanometer, 5-Printing working surface, 6-Temperature sensor, 7-Temperature control base, 8-Heat dissipation base. Detailed Implementation

[0029] To further understand the content of this invention, the invention will be described in detail with reference to the embodiments. The following embodiments are used to illustrate the invention, but are not intended to limit the scope of the invention.

[0030] Example 1

[0031] This invention relates to a method for compensating for the focal length thermal effect in laser 3D metal printing equipment, as shown in the attached figure. Figure 1 As shown, the optical path system of the laser 3D metal printing equipment includes a focusing lens 2, a focusing lens 3, a reflecting mirror 4, and a printing working surface 5 arranged sequentially along the laser 1 optical path direction. The focusing lens 2 is a concave lens, and the focusing lens 3 is a convex lens. Both the focusing lens 2 and the focusing lens 3 are made of fused silica. Fused silica has a refractive index temperature coefficient constant of 2.2370E^-005, exhibiting high laser transmittance and extremely low laser absorptivity, making it the most commonly used glass material in high-power laser optical systems. Based on the refractive index temperature coefficient of fused silica, it is known that for a convex lens with a positive focal length, as its temperature increases, the refractive index increases, and the focal length will drift and shorten.

[0032] See attached document Figure 3 As shown, both the focusing lens 2 and the focusing lens 3 are equipped with temperature sensors 6. The focusing lens 2 is driven by a voice coil motor (not shown in the figure) to move along the optical path, while the focusing lens 3 remains stationary. Both the focusing lens 2 and the focusing lens 3 are mounted on heat dissipation bases 8 to reduce their temperature rise. In this embodiment, the two heat dissipation bases 8 have the same thermal conductivity. The thickness of the focusing lens 2 and the focusing lens 3 is not specifically required. Refer to the attached figure. Figure 3 As shown, the bottom of the heat dissipation base 8 of the focusing lens 3 is provided with a temperature control base 7, which is a semiconductor cooler or a water-cooled base.

[0033] When laser 3D printing is performed, the refractive index of the focusing lens increases as the temperature rises, causing the focal length to drift and shorten. Therefore, focal length thermal effect compensation is required. The specific steps for focal length thermal effect compensation include:

[0034] S1. Temperature changes of focusing lens 2 and focusing lens 3 are monitored in real time by temperature sensor 6;

[0035] S2. Calculate the distance between focusing lens 2 and focusing lens 3 based on real-time temperature changes, and adjust focusing lens 2 using a voice coil motor to ensure the distance between them satisfies the calculation result. Assuming the focal length of focusing lens 2 is f1 (f1<0) and the focal length of focusing lens 3 is f2, since the entire optical path focuses an incident parallel beam into a spot at the printing surface 5, the equivalent focal length of the entire optical path is positive, therefore -f1>f2. The equivalent distance between focusing lens 2 and focusing lens 3 is D, and the distance between focusing lens 3 and printing surface 5 is L. Then, the following formula applies:

[0036] ,

[0037] According to the definition of the refractive index temperature coefficient constant of fused quartz, within a certain temperature range, the change in the refractive index of fused quartz is proportional to the change in temperature, that is, the change in the focal length of the lens is proportional to the change in temperature. Therefore, it is assumed that the relationship between the temperature change value ΔT and the focal length change value Δf is as follows, where k is a constant coefficient:

[0038] ,

[0039] When the temperature change value of the focusing lens 2 is ΔT1 and the temperature change of the focusing lens 3 is ΔT2, there is the following formula:

[0040] ,

[0041] Since -f1 > f2, so ΔT1 > ΔT2;

[0042] For any glass material, the proportion of the focal length drift caused by the temperature change is not high either. For example, the refractive index temperature coefficient constant of fused quartz listed above is 2.2370E^-005. That is, when the lens temperature changes by 100 °C, the focal length change rate is only 0.2237%, that is, Δf << f. Therefore, the above formula can be simplified as:

[0043] (1),

[0044] Formula 1 is the calculation formula for the distance between the focusing lens 2 and the focusing lens 3. In the formula, △T1 is the temperature change amount of the focusing lens 2, △T2 is the temperature change amount of the focusing lens 3, D is the calculated distance between the focusing lens 2 and the focusing lens 3, f1 is the focal length of the focusing lens 2, and f2 is the focal length of the focusing lens 3.

[0045] During the real-time dynamic focusing of the focusing lens 2 during the printing process, the value of the distance D between the focusing lens 2 and the focusing lens 3 is in a changing state. During 3D printing or laser processing, in order to be able to match the change in the working distance of the scanning laser spot in real time, it is required that the frequency response of the focusing lens 2 is very high, and it can quickly move the focusing lens 2 in place to compensate for the focal length. Therefore, the moving stroke of the focusing lens 2, denoted as ΔD, cannot be too long. In actual engineering, ΔD generally does not exceed 1 mm, that is, the distance between the focusing lens 2 and the focusing lens 3 changes between D0 and D0 + ΔD, where D0 is the initial distance between the focusing lens 2 and the focusing lens 3.

[0046] According to the characteristic -f1 > f2 of the above optical path system, it can be known that D - f1 > f2. The characteristic value range of f2 is usually 300~1000 mm. Therefore, ΔD << f2. When the focusing lens 2 moves to the other end, the formula for the temperature rise of the focusing lens 3 is as follows:

[0047] [[ID=​

[0048] In the formula, ΔT2' represents the temperature change when the lens moves to the other end, D0 is the distance between focusing lens 2 and focusing lens 3, and ΔD is the change in the distance between focusing lens 2 and focusing lens 3 before and after the adjustment of focusing lens 2. In actual 3D printing optical paths, the value of D-f1 is usually hundreds or even thousands of times greater than ΔD, therefore ΔD < <D-f1。

[0049] Therefore, Formula 2 can be expressed as:

[0050] (3),

[0051] Therefore, it can be seen that the temperature change ΔT1 of the focusing lens 2 and the temperature change ΔT2 of the focusing lens 3 can maintain a stable proportional relationship. When adjusting the distance between the focusing lens 2 and the focusing lens 3, the temperature of the temperature control base 7 under the focusing lens 3 does not need to be frequently adjusted according to the different printing focal lengths. It is only necessary to adjust the temperature of the focusing lens 3 by adjusting the temperature of the focusing lens 2 by adjusting the temperature of the temperature control base 7 at a fixed ratio.

[0052] Example 2

[0053] This invention relates to a method for compensating for the focal length thermal effect in laser 3D metal printing equipment, as shown in the attached figure. Figure 1 As shown, the optical path system of the laser 3D metal printing equipment includes a focusing lens 2, a focusing lens 3, a reflecting mirror 4, and a printing working surface 5 arranged sequentially along the laser 1 optical path direction. The focusing lens 2 is a concave lens, and the focusing lens 3 is a convex lens. Both the focusing lens 2 and the focusing lens 3 are made of fused silica. Fused silica has a refractive index temperature coefficient constant of 2.2370E^-005, exhibiting high laser transmittance and extremely low laser absorptivity, making it the most commonly used glass material in high-power laser optical systems. Based on the refractive index temperature coefficient of fused silica, it is known that for a convex lens with a positive focal length, as its temperature increases, the refractive index increases, and the focal length will drift and shorten.

[0054] See attached document Figure 2 As shown, both the focusing lens 2 and the focusing lens 3 are equipped with temperature sensors 6. The focusing lens 2 is driven by a voice coil motor (not shown in the figure) to move along the optical path, while the focusing lens 3 is stationary. Both the focusing lens 2 and the focusing lens 3 are mounted on a heat dissipation base 8 to reduce their temperature rise.

[0055] When laser 3D printing is performed, the refractive index of the focusing lens increases as the temperature rises, causing the focal length to drift and shorten. Therefore, focal length thermal effect compensation is required. The specific steps for focal length thermal effect compensation include:

[0056] S1. Monitor the temperature changes of the focusing lens 2 and the focusing lens 3 in real time through the temperature sensor 6;

[0057] S2. Calculate the distance between the focusing lens 2 and the focusing lens 3 based on the real-time temperature changes of the focusing lens 2 and the focusing lens 3, and adjust the focusing lens 2 through the voice coil motor so that the distance between the focusing lens 2 and the focusing lens 3 meets the calculation result; Assume that the focal length of the focusing lens 2 is f1 (f1 < 0), and the focal length of the focusing lens 3 is f2. Since the entire optical path focuses an incident parallel beam into a spot at the printing working surface 5, the equivalent focal length of the entire optical path is a positive focal length. Therefore, -f1 > f2. The equivalent distance between the focusing lens 2 and the focusing lens 3 is D, and the distance between the focusing lens 3 and the printing working surface 5 is L. Then there is the following formula:

[0058] ,

[0059] According to the definition of the refractive index temperature coefficient constant of fused quartz, within a certain temperature range, the change in the refractive index of fused quartz is proportional to the change in temperature, that is, the change in the lens focal length is proportional to the change in temperature. Therefore, assume the relationship between the temperature change value ΔT and the focal length change value Δf is as follows, where k is a constant coefficient:

[0060] ,

[0061] When the temperature change value of the focusing lens 2 is ΔT1 and the temperature change of the focusing lens 3 is ΔT2, there is the following formula:

[0062] ,

[0063] Since -f1 > f2, so ΔT1 > ΔT2;

[0064] For any glass material, the proportion of the focal length drift caused by temperature change is not high either. For example, the refractive index temperature coefficient constant of fused quartz listed above is 2.2370E^-005. That is, when the lens temperature changes by 100 °C, the focal length change rate is only 0.2237%, that is, Δf << f. Therefore, the above formula can be simplified as:

[0065] (1),

[0066] That is, formula (1) is the calculation formula for the distance between the focusing lens 2 and the focusing lens 3. In the formula, △T1 is the temperature change amount of the focusing lens 2, △T2 is the temperature change amount of the focusing lens 3, D is the calculated distance between the focusing lens 2 and the focusing lens 3, f1 is the focal length of the focusing lens 2, and f2 is the focal length of the focusing lens 3.

[0067] In this embodiment, the two heat dissipation bases 8 have the same thermal conductivity, both being λ, and no additional heat dissipation device is added, ensuring that the heat dissipation thermal conductivity of the lens group is the same. The equivalent thicknesses of the focusing lens 2 and the focusing lens 3 are H1 and H2, respectively, and the laser power is W. Therefore, the following formula applies:

[0068]

[0069]

[0070] Therefore:

[0071] (4),

[0072] In the formula, H1 is the thickness of focusing lens 2, H2 is the thickness of focusing lens 3, and D0 is the distance between focusing lens 2 and focusing lens 3.

[0073] When the thicknesses of the two sets of lenses satisfy the above formula, the two sets of lenses will generate different temperature rises when the same laser beam passes through, and ultimately the imaging focus will not drift.

[0074] Example 3

[0075] This invention relates to a method for compensating for the focal length thermal effect in laser 3D metal printing equipment, as shown in the attached figure. Figure 1 As shown, the optical path system of the laser 3D metal printing equipment includes a focusing lens 2, a focusing lens 3, a reflecting mirror 4, and a printing working surface 5 arranged sequentially along the laser 1 optical path direction. The focusing lens 2 is a concave lens, and the focusing lens 3 is a convex lens. Both the focusing lens 2 and the focusing lens 3 are made of fused silica. The refractive index temperature coefficient constant of fused silica is 2.2370E^-005, which has very high laser 1 transmittance and extremely low laser absorptivity, making it the most commonly used glass material in high-power laser optical systems. According to the refractive index temperature coefficient of fused silica, for a convex lens with a positive focal length, as its temperature increases, the refractive index increases, and the focal length will drift and shorten.

[0076] See attached document Figure 2 As shown, both the focusing lens 2 and the focusing lens 3 are equipped with temperature sensors 6. The focusing lens 2 is driven by a voice coil motor (not shown in the figure) to move along the optical path, while the focusing lens 3 is stationary. Both the focusing lens 2 and the focusing lens 3 are mounted on a heat dissipation base 8 to reduce their temperature rise.

[0077] When laser 3D printing is performed, the refractive index of the focusing lens increases as the temperature rises, causing the focal length to drift and shorten. Therefore, focal length thermal effect compensation is required. The specific steps for focal length thermal effect compensation include:

[0078] S1. Monitor the temperature changes of the focusing lens 2 and the focusing lens 3 in real time through the temperature sensor 6;

[0079] S2. Calculate the distance between the focusing lens 2 and the focusing lens 3 based on the real-time temperature changes of the focusing lens 2 and the focusing lens 3, and adjust the focusing lens 2 through the voice coil motor so that the distance between the focusing lens 2 and the focusing lens 3 meets the calculation result; Assume that the focal length of the focusing lens 2 is f1 (f1 < 0), and the focal length of the focusing lens 3 is f2. Since the entire optical path focuses an incident parallel beam into a light spot at the printing working surface 5, the equivalent focal length of the entire optical path is a positive focal length. Therefore, -f1 > f2. The equivalent distance between the focusing lens 2 and the focusing lens 3 is D, and the distance between the focusing lens 3 and the printing working surface 5 is L. Then there is the following formula:

[0080] ,

[0081] According to the definition of the refractive index temperature coefficient constant of fused quartz, within a certain temperature range, the change in the refractive index of fused quartz is proportional to the change in temperature, that is, the change in the focal length of the lens is proportional to the change in temperature. Therefore, assume the relationship between the temperature change value ΔT and the focal length change value Δf is as follows, where k is a constant coefficient:

[0082] ,

[0083] When the temperature change value of the focusing lens 2 is ΔT1 and the temperature change of the focusing lens 3 is ΔT2, there is the following formula:

[0084] ,

[0085] Since -f1 > f2, so ΔT1 > ΔT2;

[0086] For any glass material, the proportion of the focal length drift caused by the temperature change is not high either. For example, the refractive index temperature coefficient constant of the fused quartz listed above is 2.2370E^-005, that is, when the lens temperature changes by 100 °C, the focal length change rate is only 0.2237%, that is, Δf << f. Therefore, the above formula can be simplified as:

[0087] (1),

[0088] That is, formula 1 is the calculation formula for the distance between the focusing lens 2 and the focusing lens 3. In the formula, △T1 is the temperature change amount of the focusing lens 2, △T2 is the temperature change amount of the focusing lens 3, D is the calculated distance between the focusing lens 2 and the focusing lens 3, f1 is the focal length of the focusing lens 2, and f2 is the focal length of the focusing lens 3.

[0089] In this embodiment, neither of the two heat dissipation bases 8 has any additional heat dissipation device, but the two heat dissipation bases 8 have different thermal conductivity. Assuming that when laser 1 passes through the focusing lens 2 and the focusing lens 3, the absorption power of laser 1 by the two sets of lenses is W1 and W2 respectively, these values ​​are calculated based on the power of the incident laser 1, the total thickness of the lenses, and the absorptivity of the glass material. Assuming that the equivalent heat dissipation thermal conductivity of the focusing lens 2 to the external environment is λ1, and the equivalent heat dissipation thermal conductivity of the focusing lens 3 to the external environment is λ2, then the following formula applies:

[0090] ,

[0091] ,

[0092] According to this formula, when λ1 and λ2 satisfy the following relationship, laser 1 passing through the lens group will not affect the focal length of the final imaging position when the lens temperature rises:

[0093] (5),

[0094] In the formula, λ1 is the thermal conductivity of focusing lens 2, λ2 is the thermal conductivity of focusing lens 3, W1 is the light absorption power of focusing lens 2, W2 is the light absorption power of focusing lens 3, and D0 is the distance between focusing lens 2 and focusing lens 3.

[0095] According to the basic knowledge of thermal conductivity, thermal conductivity λ is inversely proportional to the heat dissipation area of ​​the material and directly proportional to the equivalent thickness between the heat source and the external environment. Therefore, when designing the heat dissipation base 8 of the focusing lens 2 and the focusing lens 3, the area of ​​the heat dissipation base 8 of the two sets of lenses and its equivalent thickness for heat dissipation relative to the external environment can be designed based on the calculation results of the above formula, or simulation software can be used to simulate the heat dissipation coefficient of the heat dissipation base 8 of the two sets of lenses to meet the requirements of the above formula. The above is the general knowledge of heat dissipation base 8 design, which will not be elaborated here.

[0096] The present invention has been described in detail above with reference to the embodiments, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made in accordance with the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A method for compensating for the focal length thermal effect in a laser 3D metal printing device, characterized in that: The optical path system of the laser 3D metal printing equipment includes a focusing lens, a focusing lens, a reflecting galvanometer, and a printing surface arranged sequentially along the laser optical path. The focusing lens is a concave lens, and the focusing lens is a convex lens. Both the focusing lens and the focusing lens are made of fused silica. Temperature sensors are installed on both the focusing lens and the focusing lens. The focusing lens is driven by a voice coil motor to move along the optical path. Focal length thermal effect compensation is performed during laser 3D printing, specifically including the following steps: S1. Real-time monitoring of temperature changes in the focusing and adjusting lenses using temperature sensors; S2. The distance between the focusing and focusing lenses is calculated based on the real-time temperature changes of the focusing and focusing lenses, and the focusing lens is adjusted using a voice coil motor to ensure that the distance between the focusing and focusing lenses meets the calculation results; the formula for calculating the distance between the focusing and focusing lenses is: （1）， In the formula, △T 1 represents the temperature change of the focusing lens. △T 2 represents the temperature change of the focusing lens. D To calculate the distance between the focusing lens and the teleconverting lens, f 1 represents the focal length of the focusing lens. f 2 represents the focal length of the focusing lens.

2. The focal length thermal effect compensation method for laser 3D metal printing equipment according to claim 1, characterized in that: The focusing lens is mounted on a temperature-controlled base. When adjusting the distance between the focusing lens and the adjusting lens, the temperature of the focusing lens is adjusted by the temperature-controlled base at a fixed ratio according to the temperature change of the adjusting lens.

3. The focal length thermal effect compensation method for laser 3D metal printing equipment according to claim 2, characterized in that: The temperature-controlled base is a semiconductor cooler or a water-cooled base.

4. The focal length thermal effect compensation method for laser 3D metal printing equipment according to claim 1, characterized in that: The thicknesses of the focusing lens and the teleconverting lens satisfy the following requirements: （4）， In the formula, H 1 represents the thickness of the focusing lens. H 2 represents the thickness of the focusing lens. D 0 represents the initial distance between the focusing lens and the telephoto lens.

5. The focal length thermal effect compensation method for laser 3D metal printing equipment according to claim 1, characterized in that: Both the focusing lens and the focusing lens are mounted on a heat dissipation base. The thermal conductivity of the heat dissipation base used to mount the focusing lens and the focusing lens meets the following requirements: （5）， In the formula, λ 1 represents the thermal conductivity of the focusing lens. λ 2 represents the thermal conductivity of the focusing lens. W 1 represents the light absorption power of the focusing lens. W 2 represents the light absorption power of the focusing lens. D 0 represents the initial distance between the focusing lens and the telephoto lens.

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