Homogeneous radiant heat source structure and applications thereof

Abstract

The application provides a homogeneous radiation heat source structure and application thereof, and belongs to the field of additive manufacturing, and comprises an infrared lamp, an energy-absorbing shell and an optical homogenizer, wherein: the infrared lamp is arranged in the interior of the energy-absorbing shell and is used for radiating infrared light; the inner side of the energy-absorbing shell is made of an energy-absorbing material and is used for absorbing the non-emitted infrared light; meanwhile, the lower part of the energy-absorbing shell is provided with an opening, and the optical homogenizer is arranged at the opening and is used for converting the incident infrared light into emitted infrared light which is uniform and has a specific shape and is outwardly propagated to form a homogeneous radiation heat source. The application can convert the energy-uniform, direction-unstable infrared light generated by the infrared lamp into emitted infrared light which is direction-controllable, has a specific shape and is uniform, meanwhile, the energy-absorbing shell can absorb the non-emitted infrared light, so that the uniformity of the reflected light is avoided to affect the uniformity of the emitted infrared light, thereby effectively improving the uniformity of the powder bed temperature field in laser selective sintering, and being beneficial to forming a high-temperature polymer component with an ultra-large size.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing, and more specifically, relates to a homogeneous radiative heat source structure and its application. Background Technology

[0002] Selective laser sintering (SLS) is one of the most widely used additive manufacturing technologies. It achieves localized melting and solidification of powder through precise control of a high-energy laser, thereby constructing three-dimensional parts with complex structures layer by layer. During the manufacturing process, the laser beam is controlled to selectively sinter powder layers, tightly binding powder particles together to form effective structural layers. Unsintered powder acts as a support material, providing support for the upper layers. This layer-by-layer deposition and sintering process is precisely controlled, ultimately producing parts with high precision and complex geometries. SLS technology offers advantages such as high manufacturing freedom, high material utilization, and the ability to manufacture complex parts, thus it is widely used in fields such as medical, shipbuilding, and aerospace.

[0003] However, current SLS technology still presents significant challenges for forming some ultra-large parts and high-temperature polymer materials (such as polyetheretherketone, nylon 10T, and nylon 6). The biggest challenge is that the heating system of current SLS equipment struggles to ensure uniformity of the powder bed temperature field under a wide range of high temperatures during the fabrication process. Non-uniformity of the powder bed temperature field can significantly lead to warping, cracking, and even printing failure of the parts.

[0004] Currently, the heating system commonly used in SLS equipment typically consists of multiple infrared lamps. The temperature uniformity of the powder bed is improved as much as possible by increasing the number of infrared lamps and adjusting their arrangement. However, due to the complexity of the energy distribution of the infrared radiation field and the low thermal conductivity of polymer powder, the effect of improving the temperature uniformity of a large-scale powder bed by arranging lamps is very limited. This makes it very difficult to form ultra-large-sized high-temperature polymer components. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a homogeneous radiative heat source structure and its application, aiming to solve the problem that existing heating systems have difficulty in ensuring the uniformity of powder bed temperature under large-scale high-temperature environments.

[0006] To achieve the above objectives, the present invention provides a homogeneous radiative heat source structure, comprising an infrared lamp, an energy-absorbing housing, and an optical homogenizer, wherein: the infrared lamp is disposed inside the energy-absorbing housing for radiating infrared light; the inner side of the energy-absorbing housing is made of an energy-absorbing material for absorbing unemitted infrared light; and the lower part of the energy-absorbing housing is open, at which the optical homogenizer is disposed to convert the incident infrared light into uniform and specific-shaped emitted infrared light and propagate it outward, thereby forming a homogeneous radiative heat source.

[0007] As a further preferred, the power of the infrared lamp is 500W-4000W, and the wavelength of the infrared light is 700nm-2500nm.

[0008] As a further preferred, the outer side of the energy absorption shell is made of a heat-conducting material to conduct the absorbed heat energy to the outside, the thickness of the energy absorption material is 1mm-5mm, and the thickness of the heat-conducting material is 1mm-5mm.

[0009] As a further preferred, the optical homogenizer is made of glass, the energy absorption material is made of carbon nanotubes, titanium dioxide or zinc dioxide, and the heat-conducting material is made of one or more of Cu, Ag and Au.

[0010] As a further preferred, the shape of the energy absorption shell is spherical or cubic.

[0011] According to another aspect of the present application, a homogenizing heating system is provided, which comprises a homogenizing radiation heat source unit and a thermal imager and a laser heat compensation unit, wherein the homogenizing radiation heat source unit comprises a plurality of the above-mentioned homogenizing radiation heat source structures, and the homogenizing radiation heat source structures are arranged in an array at a preset distance, for projecting a thermal radiation light field on a powder bed; the thermal imager is arranged above the powder bed to collect the temperature field of the powder bed and determine the heat gap position; and the laser heat compensation unit is used to irradiate laser on the heat gap position to maintain the uniformity of the temperature field of the powder bed.

[0012] As a further preferred, the laser heat compensation unit comprises a laser, a mirror and a galvanometer arranged in sequence along the propagation direction of the laser.

[0013] As a further preferred, the edge distance of adjacent thermal radiation light fields is 0-0.05 times the side length of the thermal radiation light field, and the area of one thermal radiation light field is not more than 1m 2 .

[0014] As a further preferred, the homogenizing heating system further comprises a cooling unit arranged outside the homogenizing radiation heat source unit and the laser heat compensation unit for cooling them.

[0015] As a further preferred, the power of the laser is 20W-200W, the scanning rate is 500mm / s-4000mm / s, and the size of the laser beam spot ranges from 0.5mm to 5mm.

[0016] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following beneficial effects:

[0017] 1.The present application can convert the non-uniform and directionless infrared light generated by the infrared lamp into controllable, specific shape and uniform outgoing infrared light, while the energy absorption shell can absorb the non-outgoing infrared light to avoid the formation of reflected light affecting the uniformity of the outgoing infrared light, and finally the outgoing infrared light as a uniform radiation heat source projects a specific size and shape of infrared thermal radiation field on the powder bed, which can effectively improve the uniformity of the powder bed temperature field in laser selective sintering, and is beneficial to the formation of super large size high temperature polymer components;

[0018] 2.Meanwhile, the present application provides a homogeneous heating system, considering that the direction of the incident infrared light in the homogeneous radiation heat source unit is chaotic, which can cause the edge of the outgoing infrared light to be blurred, and further cause the thermal radiation power of the edge region of the projected thermal radiation field to be lower than that of other regions, so that the thermal radiation power of the edge region of the adjacent thermal radiation field is lower than that of other regions to form a heat gap, by setting a thermal imager to collect the powder bed temperature field and determine the heat gap position, and using a laser heat supplement unit to supplement heat, the uniformity of the powder bed temperature field can be further maintained, compared with the traditional array of ordinary infrared lamp tube heating mode, the maximum temperature difference of the powder bed is greatly reduced, which promotes the SLS technology to form super large parts and sinter narrow window high temperature polymers, greatly expands the application scenarios of SLS technology, and because the infrared thermal radiation field on the powder bed is arranged in an array, the low temperature area is at the junction of adjacent infrared thermal radiation fields, so the low temperature area presents a grid-like distribution on the entire powder bed, which greatly reduces the complexity of path planning and galvanometer control of the laser heat supplement unit, and improves the heat supplement efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a structural schematic diagram of the homogeneous radiation heat source structure provided by the embodiment of the present application;

[0020] Figure 2 is a schematic diagram of the thermal radiation field generated by the homogeneous radiation heat source structure provided by the embodiment of the present application;

[0021] Figure 3 is a structural schematic diagram of the homogeneous heating system provided by the embodiment of the present application;

[0022] Figure 4 is a structural schematic diagram of the laser heat supplement unit in the homogeneous heating system provided by the embodiment of the present application;

[0023] Figure 5 is a schematic diagram of the array-arranged thermal radiation field generated by the homogeneous radiation heat source unit in the homogeneous heating system provided by the embodiment of the present application;

[0024] Figure 6is a scanning range schematic diagram of the heat supplement unit in the homogeneous heating system provided by the embodiment of the present application.

[0025] In all the drawings, the same reference signs are used to represent the same elements or structures, wherein:

[0026] 1-homogeneous radiation heat source structure, 11-infrared lamp, 12-optical homogenizer, 13-energy absorption shell, 2-laser heat supplement unit, 21-laser, 22-mirror, 23-vibrating mirror, 3-thermal imager, 4-cooling unit, 5-control unit. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0028] As Figure 1 shown, according to an aspect of the present application, a homogeneous radiation heat source structure is provided, which comprises an infrared lamp 11, an energy absorption shell 13 and an optical homogenizer 12, wherein: the infrared lamp 11 is arranged inside the energy absorption shell 13 for radiating infrared light; the inner side of the energy absorption shell 13 is made of energy absorption material for absorbing the non-emitted infrared light, and the lower part of the energy absorption shell 13 is open, and the optical homogenizer 12 is arranged at the opening for converting the incident infrared light into uniform emitted infrared light and propagating outward to form a homogeneous radiation heat source, and the thermal radiation light field generated by the projection of the homogeneous radiation heat source on the powder bed is as Figure 2 shown.

[0029] The inner side of the energy absorption shell 13 is made of energy absorption material rather than reflective material, mainly because the infrared light radiated by the infrared lamp 11 is relatively complex, and the reflection of the infrared light will affect the uniformity of the emitted infrared light. By arranging the energy absorption material inside the energy absorption shell 13, the diffuse reflection of the infrared light can be greatly reduced, the uniformity of the emitted infrared light of the optical homogenizer 12 can be improved, and the uniformity of the powder bed temperature can be further improved.

[0030] The optical homogenizer 12 is an optical element that can convert the incident infrared light with uneven energy and irregular direction into emitted infrared light with controllable direction, specific shape and uniformity. Its working principle is to disturb the phase of the light beam passing through it, scatter the concentrated light beam, scatter each point on the front end of the light beam to multiple angles, and overlap with the scattering from other points. This overlap produces a uniform intensity distribution. The shape of the optical homogenizer 12 is rectangular, triangular, rhombic, regular hexagonal, etc., to form rectangular, triangular, rhombic, regular hexagonal emitted infrared light.

[0031] Further, the optical homogenizer 12 is made of glass, including but not limited to quartz glass, high borosilicate glass, soda-lime glass, which has a high transmittance to infrared light. The energy-absorbing material is made of carbon nanotubes, titanium dioxide or zinc dioxide, and preferably made of carbon nanotubes, which can greatly absorb unnecessary infrared light and reduce the randomness of the incident infrared light of the optical homogenizer 12 caused by diffuse reflection, thereby improving the uniformity of the outgoing light of the optical homogenizer and further improving the uniformity of the thermal radiation light field on the powder bed. The outer side of the energy-absorbing shell 13 is made of a heat-conducting material, which can be an alloy of one or more of Cu, Au, Ag, and is preferably made of copper to ensure that the energy-absorbing shell 13 has good heat dissipation capability to conduct the absorbed heat to the outside, thereby well conducting the heat absorbed by the energy-absorbing shell 13 to the outside. The thickness of the energy-absorbing material is 1mm-5mm, and the thickness of the heat-conducting material is 1mm-5mm.

[0032] Further, the power of the infrared lamp 11 is 500W-4000W, and the wavelength of the infrared light is 700nm-2500nm, which not only matches the wavelength range of the energy-absorbing material, but also ensures that the powder bed has good absorption efficiency.

[0033] Further, the shape of the energy-absorbing shell 13 is spherical or cubic, and the spherical energy-absorbing shell 13 has better energy-absorbing effect, while the cubic energy-absorbing shell 13 is better assembled.

[0034] According to another aspect of the present application, as Figure 3 , 4As shown, a homogeneous heating system is provided, which comprises a homogeneous radiation heat source unit and a thermal imager 3 and a laser heat compensation unit 2, wherein the homogeneous radiation heat source unit comprises a plurality of the above-mentioned homogeneous radiation heat source structures 1, and the homogeneous radiation heat source structures 1 are arranged in an array at a preset distance, as one of the heat sources of the homogeneous heating system, a specific shape of the thermal radiation light field can be projected on the powder bed, and the entire powder bed can be covered by a plurality of thermal radiation light fields in an array, and then the heat energy is transmitted by the way of radiating infrared light and the temperature uniformity of the powder bed is improved; considering that the randomness of the incident infrared light direction during the working process of the homogeneous radiation heat source unit will cause the edge of the outgoing infrared light to be blurred, so that the heat radiation power of the edge area of the projected thermal radiation light field will be slightly lower than that of other areas, thereby causing the temperature at the junction of adjacent light fields to be slightly lower than that of other areas, therefore the thermal imager 3 is arranged above the powder bed to collect the temperature field of the powder bed and determine the heat gap position; the laser heat compensation unit 2 is the second heat source of the homogeneous heating system, which comprises a laser 21, a mirror 22 and a galvanometer 23 arranged in sequence along the laser propagation direction, the laser 21 emits laser light which enters the galvanometer 23 under the reflection of the mirror 22, and the galvanometer 23 is used to control the size and motion trail of the laser spot to irradiate the heat gap position, thereby maintaining the uniformity of the temperature field of the powder bed, and the number of the laser heat compensation unit 2 can be one or more, which is determined according to the size of the powder bed. As shown in Figure 5 、 6 As shown, through the array arrangement of the thermal radiation light field, the low-temperature area, i.e. the heat gap position, is located at the junction of adjacent thermal radiation light fields, and the low-temperature area presents a grid-like distribution on the entire powder bed, which greatly reduces the complexity of path planning and galvanometer control of the laser heat compensation unit 2, and effectively improves the heat compensation efficiency.

[0035] Further, the number of the homogeneous radiation heat source structures 1 in the homogeneous heating system, the shape of the outgoing infrared light of the optical homogenizer 12 and the distance of the powder bed need to be coordinated to meet the following requirements: 1) the edge distance of the thermal radiation light field projected on the powder bed by adjacent infrared homogeneous radiation heat sources is 0-0.05 times the edge length of the thermal radiation light field; 2) the projection of all infrared homogeneous radiation heat sources can completely cover the powder bed of the laser selective sintering equipment; 3) the projection area of the infrared homogeneous radiation heat source on the powder bed, i.e. the area of the thermal radiation light field, is not more than 1m 2 . Thus, it is ensured that adjacent thermal radiation light fields do not overlap to cause local temperature to be too high, at the same time, it is avoided that the interval between adjacent thermal radiation light fields is too large to affect the working efficiency of the laser heat compensation unit, and it is also avoided that the projection area is too large to cause the energy density per unit area to be too low, thereby reducing the heating efficiency.

[0036] Further, the homogeneous heating system further comprises a cooling unit 4 and a control unit 5, the cooling unit 4 is arranged outside the homogeneous radiation heat source unit and the laser supplementary heating unit 2, and is used for cooling the homogeneous radiation heat source unit and the laser supplementary heating unit 2, the cooling unit 4 is preferably in the form of air cooling, and timely removes the heat in the homogeneous radiation heat source unit and the laser supplementary heating unit 2, so that the whole homogeneous heating system is in a normal use temperature; the control unit 5 is used for collecting the powder bed temperature field information collected by the thermal imager 3, and controls the homogeneous heat radiation unit and the laser supplementary heating unit 2 through algorithm operation to keep the powder bed temperature field consistent, specifically, the control unit 5 can control the power of the infrared lamp 11 in each homogeneous radiation heat source structure 1, and can also control the laser power, the spot size and the scanning path of the laser supplementary heating unit 2; meanwhile, the control unit 5 can also control the cooling unit 4 to make the components of the whole homogeneous heating system in a temperature environment capable of normal working.

[0037] Further, the power of the laser 21 is 20W-200W, the scanning rate is 500mm / s-4000mm / s, and the size range of the laser beam spot is 0.5mm-5mm.

[0038] The working process of the homogeneous heating system provided by the application comprises the following steps:

[0039] S1: after the powder raw material is laid on the powder bed, the homogeneous radiation heat source unit and the cooling unit 4 are started, and the power of the infrared lamp 11 is limited to 500W-2000W;

[0040] S2: when the powder bed temperature reaches the preheating temperature of the powder, the power of the infrared lamp 11 is adjusted to 2000W-3000W, the laser supplementary heating unit 2 is started, the control unit 5 determines the spot size and the motion trajectory according to the powder bed temperature field information obtained by the thermal imager 3 through an algorithm, and uses the galvanometer 23 to drive the laser to scan the heat gap position of the powder bed to improve the temperature and reduce the maximum temperature difference of the powder bed, and when the maximum temperature difference is less than 0.5℃, the printing is started;

[0041] S3: the power of the infrared lamp 11 is adjusted to 3000W-4000W, after one layer of printing is completed, the next layer of powder laying and printing is started, and the process is repeated until the printing is completed, and the scanning path of the laser supplementary heating unit 2 is adjusted through an algorithm to avoid intersection with the laser sintered powder forming during the printing process.

[0042] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the application, and is not used to limit the application, and any modification, equivalent replacement and improvement made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A homogeneous heating system, characterized in that, The homogeneous heating system includes a homogeneous radiation heat source unit, a thermal imager (3), and a laser heating unit (2). The homogeneous radiation heat source unit includes multiple homogeneous radiation heat source structures (1). Each homogeneous radiation heat source structure (1) includes an infrared lamp (11), an energy-absorbing housing (13), and an optical homogenizer (12). The infrared lamp (11) is located inside the energy-absorbing housing (13) and is used to radiate infrared light. The inner side of the energy-absorbing housing (13) is made of an energy-absorbing material to absorb the unexposed infrared light. The lower part of the energy-absorbing housing (13) has an opening, and the optical homogenizer (12) is located at this opening to convert the incident infrared light into uniform and specific-shaped emitted infrared light and propagate it outward to form a homogeneous radiation heat source. The outer side of the energy-absorbing housing (13) is made of a thermally conductive material to conduct the absorbed heat energy to the outside. The thickness of the energy-absorbing material is 1 mm to 5 mm, and the thickness of the thermally conductive material is 1 mm to 5 mm. mm; the power of the infrared lamp (11) is 500 W to 4000 W, the wavelength of the infrared light is 700 nm to 2500 nm, the optical homogenizer (12) is made of glass, and the energy-absorbing material is made of carbon nanotubes, titanium dioxide or zinc dioxide; and the homogenized radiation heat source structure is arranged in an array at a preset distance to project a thermal radiation light field on the powder bed; the thermal imager (3) is used to be set above the powder bed to collect the temperature field of the powder bed and determine the location of the heat gap; the laser heating unit (2) is used to irradiate the heat gap location with laser to maintain the uniformity of the temperature field of the powder bed.

2. The homogeneous heating system as described in claim 1, characterized in that, The thermally conductive material is one or more of Cu, Ag, and Au.

3. The homogeneous heating system as described in claim 1, characterized in that, The energy-absorbing shell (13) is spherical or cubic in shape.

4. The homogeneous heating system as described in claim 1, characterized in that, The laser heating unit (2) includes a laser (21), a reflector (22) and a galvanometer (23) arranged sequentially along the laser propagation direction.

5. The homogeneous heating system as described in claim 1, characterized in that, The edge distance between adjacent thermal radiation light fields is 0 to 0.05 times the side length of the thermal radiation light field, and the area of ​​one thermal radiation light field does not exceed 1 m². 2 .

6. The homogeneous heating system as described in claim 1, characterized in that, The homogeneous heating system also includes a cooling unit (4), which is located outside the homogeneous radiation heat source unit and the laser heating unit (2) for cooling them.

7. The homogeneous heating system as described in claim 4, characterized in that, The laser (21) has a power of 20 W to 200 W, a scanning rate of 500 mm / s to 4000 mm / s, and a laser beam spot size of 0.5 mm to 5 mm.

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