Laser projection heating device and method

Abstract

The invention belongs to the technical field of laser projection heating, and relates to a laser projection heating device and method. The laser projection heating device comprises a shell, and the shell is provided with a heating laser used for emitting a heating laser beam; the light beam collimator is used for shaping the heating laser beam into a collimated light beam; the light beam focuser is used for modulating distribution of the collimated light beams and forming projection light spots which are projected to the powder bed and have the energy density higher than that of the middle area on the basis of a light emitting lens in the light beam focuser, so that the influence of heat conduction in the powder bed on reduction of the edge temperature of the projection light spots is made up, and a uniform temperature field is obtained; wherein the reflectivity of the edge area of the light-emitting lens is lower than that of the central area of the light-emitting lens. The laser projection heating device can generate a uniform temperature field.

Description

Technical Field

[0001] The present application belongs to the field of laser projection heating technology and relates to a laser projection heating device and method. Background Art

[0002] Laser Powder Bed Fusion (LPBF) is an additive manufacturing (3D printing) technology that uses a high-energy laser beam to scan the part's cross-sectional information layer by layer, sintering and solidifying polymer powder. Layer by layer, the technology builds up into a complete form, ultimately producing parts with complex structures. This technology offers high design freedom, high material utilization, and rapid prototyping speeds, making it suitable for small-batch, customized production of parts with complex geometries. It has widespread applications in medical implants, aerospace, and electronics.

[0003] However, the current LPBF process (laser powder bed fusion) still faces limitations when forming large parts at high temperatures. For example, with high-temperature polymer materials (such as polyetheretherketone and polyetherketoneketone), the temperature uniformity of the powder bed heating area is difficult to maintain during heating, often exhibiting a Gaussian distribution with high temperatures in the center and low temperatures at the edges. This can lead to warping, cracking, and even printing failure of large parts during the forming process.

[0004] For example, Chinese patent publication CN116967478A mentions a homogeneous laser heating device. While this device can emit a relatively uniform laser beam, once the uniform beam spot is projected onto the powder bed heating area, heat conduction occurs between the powder at the edge of the beam spot and the powder outside the beam spot, causing the powder bed temperature at the edge to be lower than that in the middle, leading to an uneven temperature field in the heated powder bed area. For example, Chinese patent publication CN116922769A mentions a homogeneous heat source radiation structure. This technology uses an infrared lamp as a heat source and produces a uniform radiation spot through a homogenizer. However, due to the same heat conduction, the temperature field in the heated powder bed area exhibits an uneven state, with lower temperatures at the edges and higher temperatures in the middle, leading to warping and cracking in the formed parts. Summary of the Invention

[0005] In response to the defects or improvement needs of the existing technology, the present application provides a laser projection heating device and method, which aims to improve the problem of uneven temperature field of the powder bed of large-scale high-temperature LPBF equipment.

[0006] The present application provides a laser projection heating device, comprising a housing, on which is provided: a heating laser, configured to emit a heating laser beam; a beam collimator, for shaping the heating laser beam into a collimated beam; The light beam focus device is used for modulating the distribution of the collimated light beam, and forming a projected light spot with a higher edge light beam energy density than a middle region energy density based on an out-light lens in the light beam focus device, so as to compensate the influence of heat conduction on the temperature reduction of the edge of the projected light spot, and obtain a uniform temperature field. The edge region reflectivity of the out-light lens is lower than the central region reflectivity of the out-light lens.

[0007] As a further preferred, the central region reflectivity of the out-light lens is 1.5%-3.5%, and the edge region reflectivity is 0.15%-0.25%.

[0008] As a further preferred, the central region and the edge region of the out-light lens are both provided with an anti-reflection film, and the number of layers or the thickness of the anti-reflection film of the central region is less than that of the edge region.

[0009] As a further preferred, the heating laser, the light beam collimator and the light beam focus device are internally provided with cooling channels for cooling and cooling the heating laser, the heating laser and the light beam focus device.

[0010] As a further preferred, the laser projection heating device further comprises a protection mirror group for protecting the light beam collimator and the light beam focus device.

[0011] As a further preferred, the laser projection heating device further comprises a temperature sensor and a controller, wherein: The temperature sensor is used for detecting the real-time temperature of the powder bed. The controller is used for comparing the real-time temperature with a preset temperature, and dynamically adjusting the laser power of the heating laser based on the comparison result, so that the real-time temperature of the powder bed is adjusted to the preset temperature.

[0012] As a further preferred, the temperature sensor (6) is provided with a plurality of temperature sensors, and the controller (7) compares the average value of the real-time temperatures detected by the plurality of temperature sensors (6) with the preset temperature.

[0013] As a further preferred, the controller adjusts the laser power by using an incremental PID temperature control algorithm, and the control expression of the algorithm is: u(k) = u(k-1)+Δu(k)

[0014] Wherein, u(k) is the control amount of the controller for driving the heating laser to adjust the power at the i th sampling moment, k is the control amount at the i th sampling moment, u(k-1) is the control amount at the i th sampling moment, k-1 is the control amount at the i th sampling moment, Δu(k)is the increment of the control quantity, K p is the proportionality coefficient, e( k ) is the k The temperature error at each sampling moment is K i is the integration coefficient, K d is the differential coefficient.

[0015] The second aspect of the present application provides a laser projection heating method using the following technical solution: A laser projection heating method, based on any one of the laser projection heating devices described in the first aspect, comprises the following steps: After laying the bottom powder raw material to form an initial powder bed, adjusting the power of the heating laser to a first preset power to preheat the powder bed to a preset preheating temperature, and then increasing the power of the heating laser to a second preset power to heat the initial powder bed to a preset pre-processing temperature; After the initial powder bed is heated to a preset pre-processing temperature, the power of the heating laser is increased to a third preset power to heat and sinter the initial powder bed, and the heating laser is turned off when the initial powder bed is completely heated and sintered; After the initial powder bed completes heating and sintering and new powder raw materials are laid to form a new powder bed, the power of the heating laser is increased to a third preset power to heat and sinter the new powder bed. When the new powder bed completes heating and sintering, the heating laser is turned off, and then the steps of laying new powder raw materials, heating and sintering, and turning off the heating laser are repeated to form a cycle.

[0016] As a further preferred embodiment, when the power of the heating laser is increased to the second preheating power or the third preset power, the temperature sensor detects the real-time temperature of the powder raw material, and the controller dynamically adjusts the laser power based on the real-time temperature using an incremental PID temperature control algorithm to adjust the real-time temperature of the powder bed to the preset target temperature.

[0017] In general, the above technical solutions conceived by this application have the following technical advantages compared with the existing technologies: 1. This application utilizes a non-uniform laser projection heating scheme. By making the reflectivity of the edge region of the light-emitting lens lower than that of the central region, a non-uniform light spot is produced, where the energy density of the beam at the edge is higher than that in the central region. This compensates for the effect of heat conduction on the temperature drop at the edge, thereby achieving a more uniform temperature field. Consequently, when using this heating scheme to manufacture formed parts (i.e., components), the formed parts are less likely to warp, crack, or develop problems.

[0018] 2. The laser projection heating device provided by the application adopts an incremental PID algorithm. The traditional heating method has the problem of excessive thermal inertia in the heating process, and the incremental PID algorithm is not prone to integral saturation, can effectively reduce overshoot, has a good regulating effect on the dynamic response of the system, and has relatively small calculation amount and good real-time performance. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a schematic diagram of a laser projection heating device provided by an embodiment of the application; Figure 2 is a schematic diagram of a laser projection heating device provided by an embodiment of the application; Figure 3 is a side view of an outcoupling lens provided by an embodiment of the application; Figure 4 is a bottom view of an outcoupling lens provided by an embodiment of the application; Figure 5 is a schematic diagram of a powder bed temperature field before and after setting a non-uniform antireflection film provided by an embodiment of the application; Figure 6 is a schematic diagram of an incremental PID algorithm provided by an embodiment of the application; Figure 7 is a flowchart of a laser powder bed melting method using the laser projection heating method provided by the application.

[0020] In all the drawings, the same reference signs are used to represent the same elements or structures, wherein: 1, housing; 2, heating laser; 3, beam collimator; 4, beam focuser; 4-1, outcoupling lens; 4-2, central region; 4-3, edge region; 4-4, antireflection film; 5, cooling channel; 6, temperature sensor; 7, controller; 8, powder bed; 9, upper protection mirror group. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the application clearer and more apparent, the application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application.

[0022] The application will be further described below with reference to the drawings and embodiments Figure 1-Figure 7 The application will be further described below with reference to the drawings and embodiments

[0023] An embodiment of the application discloses a laser projection heating device. Referring to Figure 1The laser projection heating device includes a housing 1, on which are disposed a heating laser 2, a beam collimator 3, and a beam focuser 4. The heating laser 2 is used to emit a heating laser beam; the beam collimator 3 is used to shape the heating laser beam into a collimated beam; the beam focuser 4 is used to modulate the distribution of the collimated beam and, based on the light-emitting lens 4-1 in the beam focuser 4, form a projection spot projected onto the powder bed 8 in which the energy density of the edge beam is higher than that of the middle region, thereby compensating for the effect of heat conduction in the powder bed 8 on the temperature reduction at the edge of the projection spot and obtaining a uniform temperature field. The reflectivity of the edge region 4-3 of the light-emitting lens 4-1 is lower than that of the central region 4-2 of the light-emitting lens 4-1.

[0024] Preferably, in some specific embodiments, the heating laser 2 is mounted on the upper portion of the housing 1, and the beam collimator 3 and the beam focuser 4 are mounted in the housing 1. The upper end of the beam collimator 3 is connected to the QHB light outlet of the heating laser 2, and the lower end of the beam collimator 3 is connected to the beam focuser 4. In some other embodiments, the positions of the heating laser 2, the beam collimator 3, and the beam focuser 4 on the housing 1 can be adjusted as needed, as long as a complete optical path can be formed.

[0025] In actual use, the heating laser beam output by the heating laser 2 passes through the beam collimator 3 to obtain an ideal collimated beam, and the collimated beam is input into the beam focuser 4, and then the shaping and focusing module in the beam focuser 4 modulates the light intensity distribution of each point of the laser beam on the focusing surface. Finally, these light fields are stacked and accumulated to form a uniform light field, forming a projection spot on the powder bed 8; the shape of the projection spot can be obtained by modulating the shaping and focusing module in the beam focuser 4. The modulation principle is an existing technology and will not be elaborated here.

[0026] Computer simulation results of the temperature field of powder bed 8 show that when the temperature in center region 4-2 reaches 330°C, the edge temperature is around 315°C. By applying uneven coating to the optical focusing lens in beam focuser 4 (e.g., coating the edge of light-emitting lens 4-1 with multiple layers of antireflection coating 4-4) to reduce reflectivity, an uneven light spot with a higher energy density at the edge than in the center region is achieved. This compensates for the effect of heat conduction on the temperature drop at the edge, resulting in a more uniform temperature field. For example, the number of antireflection coating layers 4-4 in center region 4-2 can be set to be less than that in edge region 4-3; or the thickness of antireflection coating 4-4 ​​in center region 4-2 can be set to be less than that in edge region 4-3.

[0027] 作为优选的,如 Figure 3-Figure 4In some embodiments, the optical elements (e.g., lenses) within the lenses of the beam collimator 3 and the beam focuser 4 are primarily made of quartz. The surface of the light-emitting lens 4-1 in the beam focuser 4 has a radius of 0.75 to 0.9 times the center as the central region 4-2, and the remaining area is the edge region 4-3. Both the central region 4-2 and the edge region 4-3 are coated with an antireflection coating 4-4, and the number of layers of the antireflection coating 4-4 ​​in the central region 4-2 is less than that in the edge region 4-3. For example, a single-layer antireflection coating 4-4 ​​is used in the central region 4-2, while a multi-layer antireflection coating 4-4 ​​is used in the edge region 4-3. The coating materials include, but are not limited to, silicon dioxide, titanium oxide, aluminum oxide, or magnesium fluoride. The coating material on the outer surface of the lenses of the beam collimator 3 and the beam focuser 4 is aluminum.

[0028] Under this setting, through differentiated coating design, the reflectivity of the lens edge area 4-3 is reduced, so that the reflectivity of the central area 4-2 is 1.5%-3.5%, and the reflectivity of the edge area 4-3 reaches 0.15%-0.25%, resulting in an uneven light spot with an edge beam energy density 1.3%-2% higher than the energy density in the middle area, thereby overcoming the problem of low edge temperature of the heating area caused by heat conduction, and obtaining a more uniform temperature field on the surface of the powder bed 8.

[0029] Generally speaking, it is better to adjust the size of the projection spot to a circle, but considering the actual needs, the projection spot is often adjusted to a rectangle. Figure 5 As shown, in a certain test, the temperature field of the powder bed 8 without the non-uniform anti-reflection film 4-4 is roughly as follows Figure 5 As shown in (a), the temperature field of the powder bed 8 using the non-uniform anti-reflection film 4-4 is roughly as follows Figure 5 As shown in (b) in .

[0030] Further preferably, in some embodiments, a cooling channel 5 is provided inside the heating laser 2, the beam collimator 3 and the beam focuser 4. By introducing a cooling medium into the cooling channel 5, the heating laser 2, the beam collimator 3 and the beam focuser 4 can be cooled. For ease of understanding, Figure 1 The arrows in the figure indicate the approximate flow direction of the cooling medium.

[0031] Further preferably, in some embodiments, in order to protect various components, the laser projection heating device further includes a protective lens group for protecting the beam collimator and the beam focuser 4, for example, an upper protective lens group 9 (such as Figure 2 As shown), a light-emitting protection lens group (not shown in the figure) is provided below the beam focuser 4.

[0032] Further preferably, in some embodiments, the laser projection heating device further comprises a temperature sensor 6 and a controller 7, wherein the temperature sensor 6 is configured to detect a real-time temperature of the powder bed 8; and the controller 7 is configured to compare the real-time temperature with a preset temperature, and dynamically adjust the laser power based on the comparison result, so that the real-time temperature of the powder bed 8 is adjusted to the preset temperature.

[0033] Specifically, in some embodiments, the temperature sensor 6 is an online infrared temperature sensor, which is provided outside the beam focus 4 and has the characteristics of short response time and strong anti-electromagnetic interference. Preferably, two are provided on each of the opposite sides of the beam focus 4, forming a distributed matrix arrangement. The controller 7 compares the average value of the real-time temperatures detected by the plurality of temperature sensors 6 with the preset temperature.

[0034] In fact, in the conventional high-temperature LPBF process, the powder laying and scanning sintering process will cause fluctuations in the steady-state environment inside the working cavity, resulting in a deviation in single-point temperature measurement. The distributed detection method of the present design can avoid the influence of temperature deviation on a single temperature sensor 6, correct the single-point temperature deviation under the influence of the working cavity environment temperature fluctuation, and thus monitor the overall temperature of the powder bed 8 table.

[0035] As a preferred, the controller 7 is preferably a temperature PID controller. By inputting the real-time temperature data (average temperature data obtained by the four infrared temperature sensors 6) into the temperature PID controller 7, the real-time average temperature and the preset temperature are compared, and the laser power is dynamically adjusted using the incremental PID temperature control algorithm.

[0036] As a preferred, as shown in Figure 6 the controller 7 comprises a proportional element, a differential element and an integral element. During the heating process, the proportional element outputs a control signal proportional to the deviation between the actual temperature and the preset temperature (i.e., the control amount is proportional to the temperature difference), which dynamically adjusts the power of the heating laser 2. The differential element predicts the future temperature change trend according to the rate of temperature change and gives the corresponding control action in advance. When the temperature changes rapidly, the differential element will output a larger control signal to suppress the excessive change of the temperature, so that the system has good stability and dynamic performance (i.e., negative feedback regulation). During the holding process after reaching the preset temperature, the integral element calculates the integral of the temperature difference with respect to time and continuously accumulates the increment (i.e., the control amount increment), so that the system eventually reaches a stable state and eliminates the steady-state error.

[0037] In fact, because the energy density of the heating laser 2 is relatively large, rapid heating can be achieved. In the high-temperature LPBF process, the powder spreading process and the laser scanning sintering process will cause certain temperature fluctuations. The traditional heating method has the problem of excessive thermal inertia during the heating process. The controller 7 of this design adopts an incremental PID algorithm. This algorithm is not prone to integral saturation, can effectively reduce overshoot, has a good regulating effect on the dynamic response of the system, and has a relatively small amount of calculation and good real-time performance.

[0038] Specifically, the control expression of the incremental PID temperature control algorithm used is: u(k) = u(k-1)+Δu(k)

[0039] in, u(k) It is k The sampling moment controller 7 is used to drive the heating laser to adjust the power control amount, u (k-1) It is k-1 The control quantity at each sampling moment, Δu(k) is the increment of the control quantity, K p It is the proportional coefficient, which is used to adjust the control amount proportionally according to the size of the current error, so that the system can respond quickly to temperature deviation. K i is the integration coefficient, e( k ) is the k The temperature error at each sampling moment is e(k)=r(k)-y(k) , r(k) is the set temperature, y(k) is the actual temperature. K i e(k) Used to eliminate the steady-state error of the system. K d is the differential coefficient, the differential term K d [ e(k)-2e(k-1)+e(k-2) ]Predict the temperature change trend based on the error change rate and give corresponding control action in advance.

[0040] After obtaining the increment of the control amount, u(k) = u(k-1)+Δu(k) To update the control u(k) , the updated control quantity u(k)This is used to drive the heating laser to adjust the temperature so that the actual temperature gradually approaches the set temperature. During the temperature control process, the incremental PID algorithm continuously repeats the above steps of error calculation, control variable increment calculation, and control variable update, dynamically adjusting the control variable based on the real-time temperature error, thereby achieving precise temperature control.

[0041] Furthermore, in some embodiments, the projection spot of the desired size can be obtained by adjusting the power and wavelength of the heating laser 2, adjusting the specifications and internal optical components of the beam collimator 3 and the beam focuser 4, and adjusting the distance between the entire laser projection heating device and the powder bed 8.

[0042] Generally speaking, the preferred power of the heating laser 2 is 1000W-15000W, and the wavelength of the heating laser 2 is preferably 980nm or 1064nm. The focal length of the beam collimator 3 is preferably 50mm-250mm, and the lens diameter is preferably 25mm-80mm. The focal length of the beam focuser 4 is preferably 700mm-1500mm, and the lens diameter is preferably 65mm-75mm. The working distance of the laser projection heating device (i.e., the distance between the device and the powder bed 8) is preferably 700mm-1500mm, and the side length or diameter of the projected rectangular spot is preferably 150mm-450mm.

[0043] Example 1: This embodiment provides a laser projection heating device primarily for forming small and medium-sized parts. The power of the heating laser 2 ranges from 1000W to 6000W, and the wavelength of the heating laser 2 is 980nm. The focal length of the beam collimator 3 is 65mm, and the lens diameter is 50mm; the focal length of the beam focuser 4 is 600mm, and the lens diameter is 65mm. The resulting projected spot size is 150mm x 150mm.

[0044] The lens materials of the beam collimator 3 and the beam focuser 4 are quartz, the central area 4-2 of the focuser light output lens 4-1 adopts a single-layer antireflection film 4-4, and the edge area 4-3 adopts a multi-layer antireflection film 4-4, and the coating material is magnesium fluoride.

[0045] Example 2: The laser projection heating device provided in this embodiment is mainly used for forming large-sized parts.

[0046] The power of heating laser 2 is 2000W-8000W, and the wavelength of heating laser 2 is 1064nm. By expanding the laser beam, increasing the size of the collimator and focuser, and extending the working distance, a large rectangular spot of 270mm×270mm can be obtained, which is suitable for the high-temperature LPBF process and can realize the forming of large-sized parts.

[0047] The focal length of the beam collimator 3 is 150 mm, and the lens diameter is 65 mm; the focal length of the beam focuser 4 is 900 mm, and the lens diameter is 70 mm. The lens material of the beam collimator 3 and the beam focuser 4 is quartz, and the central region 4-2 of the light-emitting lens 4-1 in the beam focuser 4 adopts a single-layer anti-reflection film 4-4, and the edge region 4-3 adopts a multi-layer anti-reflection film 4-4, and the coating material is silicon dioxide.

[0048] Embodiment 3: The laser projection heating device provided in the embodiment is used for forming larger parts.

[0049] In the embodiment, the power of the heating laser 2 is 4000 W-15000 W, and the wavelength of the heating laser 2 is 1064 nm.

[0050] In the embodiment, by expanding the laser beam, increasing the size of the collimator and the focuser, and expanding the working distance, a rectangular light spot of 350 mm*350 mm can be obtained, which is used for high-temperature LPBF process and realizes the forming of large-size parts.

[0051] The focal length of the beam collimator 3 is 200 mm, and the lens diameter is 76 mm; the focal length of the beam focuser 4 is 1100 mm, and the lens diameter is 75 mm. The lens material of the beam collimator 3 and the beam focuser 4 is quartz, and the central region 4-2 of the light-emitting lens 4-1 in the beam focuser 4 adopts a single-layer anti-reflection film 4-4, and the edge region 4-3 adopts a multi-layer anti-reflection film 4-4, and the coating material is titanium oxide.

[0052] Embodiment 4: The laser projection heating device provided in the embodiment is used for forming larger parts.

[0053] The power of the heating laser 2 is 6000 W-18000 W, and the wavelength of the heating laser 2 is 1064 nm. By expanding the laser beam, increasing the size of the collimator and the focuser, and expanding the working distance, a rectangular light spot of 400 mm*400 mm can be obtained, which is used for high-temperature LPBF process and realizes the forming of large-size parts.

[0054] Further, the focal length of the beam collimator 3 is 250 mm, and the lens diameter is 80 mm; the focal length of the beam focuser 4 is 1300 mm, and the lens diameter is 75 mm. The lens material of the beam collimator 3 and the beam focuser 4 is quartz, and the central region 4-2 of the light-emitting lens 4-1 in the beam focuser 4 adopts a single-layer anti-reflection film 4-4, and the edge region 4-3 adopts a multi-layer anti-reflection film 4-4, and the coating material is aluminum oxide.

[0055] Embodiment 5: The laser projection heating device provided in this embodiment is suitable for forming particularly large-sized parts.

[0056] The power of heating laser 2 is 6000W-20000W, and the wavelength of heating laser 2 is 1064nm. This embodiment achieves a 450mm×450mm rectangular spot by expanding the laser beam, increasing the size of the collimator and focuser, and extending the working distance. This is suitable for high-temperature LPBF processes and enables the formation of large-scale components.

[0057] Furthermore, the focal length of beam collimator 3 is 250 mm, and the lens diameter is 80 mm; the focal length of beam focuser 4 is 1500 mm, and the lens diameter is 75 mm. The lens materials of beam collimator 3 and beam focuser 4 are quartz. The center region 4-2 of focuser light output lens 4-1 is coated with a single-layer antireflection coating 4-4, and the edge region 4-3 is coated with a multi-layer antireflection coating 4-4. The coating material is silicon dioxide.

[0058] The present application also discloses a laser projection heating method based on any of the above-mentioned laser projection heating devices. The method comprises the following steps: After the bottom layer of powder raw materials is laid to form an initial powder bed 8, the power of the heating laser 2 is adjusted to a first preset power to preheat the powder bed 8 to a preset preheating temperature, and then the power of the heating laser 2 is increased to a second preset power to heat the initial powder bed 8 to a preset preprocessing temperature.

[0059] After the initial powder bed 8 is heated to the preset pre-processing temperature, the power of the heating laser 2 is increased to the third preset power to perform heating and sintering of the initial powder bed 8. The heating laser 2 is turned off when the initial powder bed 8 completes heating and sintering.

[0060] After the initial powder bed 8 has completed heating and sintering, and new powder material has been laid to form a new powder bed 8, the power of the heating laser 2 is increased to a third preset power to heat and sinter the new powder bed 8. When the heating and sintering of the new powder bed 8 is complete, the heating laser 2 is turned off. The steps of laying new powder material, heating and sintering, and turning off the heating laser 2 are then repeated to form a cycle.

[0061] Furthermore, when the power of the heating laser 2 is increased to the second preheating power or the third preset power, the temperature sensor 6 detects the real-time temperature of the powder raw material, and the controller 7 dynamically adjusts the laser power based on the real-time temperature using an incremental PID temperature control algorithm to adjust the real-time temperature of the powder bed 8 to the preset target temperature.

[0062] In fact, this laser projection heating method is mainly used in the laser powder bed melting process; Figure 7As shown, the laser powder bed melting method using the laser projection heating method includes the following steps: S1. Lay the bottom powder material to form an initial powder bed 8, adjust the power of the heating laser 2 to a first preset power to preheat the powder bed 8, and make the temperature of the powder bed 8 reach a preset preheating temperature.

[0063] In step S1 , the first preset power is preferably 1000W-6000W, and the cooling channel 5 is also enabled to cool down the heating laser 2 and other components by passing a cooling medium.

[0064] S2. Increase the power of the heating laser 2 to a second preset power to heat the powder bed 8 to a preset pre-processing temperature.

[0065] In step S2, the second preset power is preferably between 6000W and 10000W. Once the powder bed 8 reaches the preheating temperature, the power of the heating laser 2 is adjusted to between 6000W and 10000W. Based on the powder bed 8 temperature measured by the temperature sensor 6, the controller 7 uses an incremental PID algorithm to adjust the real-time power of the heating laser 2 to bring the overall real-time temperature of the powder bed 8 to the target temperature (i.e., the processing temperature). The next step is not advanced until the powder bed 8 temperature reaches the preset processing temperature and the maximum temperature difference within the powder bed 8 is less than a preset value (e.g., 5°C).

[0066] S3. The power of the heating laser 2 is increased to a third preset power to heat the powder bed 8 to a preset sintering temperature, and the powder bed 8 is sintered and solidified according to the preset component model cross-section.

[0067] In step S3, the third preset power is preferably between 10,000W and 15,000W. An external power mechanism drives the apparatus along a preset printing path, causing the heating laser 2 in the apparatus to melt a portion of the powder on the powder bed 8 according to the model cross-section based on the third preset power, forming the model's structural layer. Unmelted powder remains as support. Simultaneously, the controller 7 uses an incremental PID algorithm to maintain the temperature of the powder bed 8 at a preset target temperature (in this case, the sintering temperature) during printing.

[0068] S4. Lay the powder raw material layer by layer and repeat step S3 until the component is sintered and solidified.

[0069] In step S3, the powder raw material is laid layer by layer, and after each layer is laid, step S3 is repeated so that the heating laser 2 sintering and solidifying the powder bed 8 according to the corresponding layer section of the component model, and the cycle is repeated until the component is formed layer by layer.

[0070] In this method, the initial powder bed 8 is preheated first, then heated to the pre-processing temperature, and then heated again for sintering. This can improve the problem of excessive thermal inertia in the traditional heating method during the heating process, and the subsequent powder layer can be heated due to the residual heat of the previous powder layer, without the need for additional preheating and other processing; the temperature is monitored by the matching distributed temperature sensor 6, and the power is adjusted in real time by the controller 7 using an incremental PID algorithm, so that the sintering printing process is not prone to integral saturation, which can effectively reduce overshoot. This setting has a good regulating effect on the dynamic response of the control system, and the calculation amount is relatively small, and the real-time performance is good.

[0071] It should be understood that expressions such as "include" and "may include" used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "include" and / or "have" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0072] It should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0073] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0074] In this application, unless otherwise specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0075] It is easy for those skilled in the art to understand that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A laser projection heating device, characterized in that: The invention comprises a housing (1), wherein the housing (1) is provided with: a heating laser (2) for emitting a heating laser beam; a beam collimator (3) for shaping the heating laser beam into a collimated beam; A beam focuser (4) is used to modulate the distribution of the collimated light beam and, based on a light-emitting lens (4-1) in the beam focuser (4), form a projection light spot projected onto the powder bed (8) with an edge light beam energy density higher than that in the middle region, so as to compensate for the effect of heat conduction in the powder bed (8) on the temperature reduction at the edge of the projection light spot, thereby obtaining a uniform temperature field; The reflectivity of the edge region (4-3) of the light-emitting lens (4-1) is lower than the reflectivity of the central region (4-2) of the light-emitting lens (4-1).

2. The laser projection heating device according to claim 1, characterized in that: The reflectivity of the central area (4-2) of the light-emitting lens (4-1) is 1.5%-3.5%, and the reflectivity of the edge area (4-3) is 0.15%-0.25%.

3. The laser projection heating device according to claim 1, characterized in that: The central area (4-2) and the edge area (4-3) of the light output lens (4-1) are both provided with antireflection films (4-4), and the number of layers or thickness of the antireflection films (4-4) in the central area (4-2) is less than the number of layers or thickness of the antireflection films (4-4) in the edge area (4-3).

4. The laser projection heating device according to claim 1, characterized in that: The heating laser (2), the beam collimator (3) and the beam focuser (4) are provided with cooling channels (5) for cooling the heating laser (2), the beam collimator (3) and the beam focuser (4).

5. The laser projection heating device according to any one of claims 1 to 4, characterized in that: The laser projection heating device further comprises a temperature sensor (6) and a controller (7), wherein: The temperature sensor (6) is used to detect the real-time temperature of the powder bed (8); The controller (7) is used to compare the real-time temperature with the preset temperature, and dynamically adjust the laser power of the heating laser (2) based on the comparison result, so that the real-time temperature of the powder bed (8) is adjusted to the preset temperature.

6. The laser projection heating device according to claim 5, characterized in that: A plurality of temperature sensors (6) are provided, and the controller (7) compares a real-time temperature average value detected by the plurality of temperature sensors (6) with a preset temperature.

7. The laser projection heating device according to claim 5, characterized in that: The controller (7) uses an incremental PID temperature control algorithm to adjust the laser power. The control expression of the algorithm is: u(k) = u(k-1)+Δu(k) in, u(k) It is k The controller (7) is used to drive the heating laser (2) to adjust the power control amount at each sampling moment. u(k-1) It is k-1 The control quantity at each sampling moment, Δu(k) is the increment of the control quantity, K p is the proportionality coefficient, e( k ) is the k The temperature error at each sampling moment is K i is the integration coefficient, K d is the differential coefficient.

8. The laser projection heating device according to any one of claims 1 to 4, characterized in that: The laser projection heating device also includes a protective lens assembly for protecting the beam collimator (3) and the beam focuser (4).

9. A laser projection heating method, based on the laser projection heating device according to any one of claims 1 to 8, characterized in that: The following steps are involved: After laying the bottom powder raw material to form an initial powder bed (8), adjusting the power of the heating laser (2) to a first preset power to preheat the powder bed (8) to a preset preheating temperature, and then increasing the power of the heating laser (2) to a second preset power to heat the initial powder bed (8) to a preset preprocessing temperature; After the initial powder bed (8) is heated to a preset pre-processing temperature, the power of the heating laser (2) is increased to a third preset power to heat and sinter the initial powder bed (8), and the heating laser (2) is turned off when the initial powder bed (8) is completely heated and sintered; After the initial powder bed (8) completes heating and sintering and new powder raw materials are laid to form a new powder bed (8), the power of the heating laser (2) is increased to a third preset power to heat and sinter the new powder bed (8), and the heating laser (2) is turned off when the new powder bed (8) completes heating and sintering, and then the steps of laying new powder raw materials, heating and sintering, and turning off the heating laser (2) are repeated to form a cycle.

10. The laser projection heating method according to claim 9, characterized in that: When the power of the heating laser (2) is increased to the second preheating power or the third preset power, the temperature sensor (6) detects the real-time temperature of the powder raw material, and the controller (7) dynamically adjusts the laser power based on the real-time temperature using an incremental PID temperature control algorithm, so that the real-time temperature of the powder bed (8) is adjusted to a preset target temperature.

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