A laser selective melting forming device based on dynamic surface exposure

Abstract

The present invention relates to a laser selective melting (SLM) forming device based on dynamic surface exposure. The device comprises a diode laser array homogenizing light unit, a light-addressable light valve imaging unit, and a light source deflection imaging unit, all arranged sequentially along the laser light path. The diode laser array homogenizing light unit is used to emit multiple groups of laser light and homogenize them into a surface light source. The light-addressable light valve imaging unit is used to separate the surface light source into S-polarized light and P-polarized light. The light source deflection imaging unit is used to dynamically adjust the projection position of the S-polarized light to expand the SLM forming area. This SLM forming device based on dynamic surface exposure aims to address the problem that SLM forming based on surface exposure cannot meet the requirements for forming large parts due to the limited exposure range of the surface light source.

Description

Technical Field

[0001] The present invention relates to the technical field of laser powder bed additive manufacturing, and in particular to a laser selective melting forming device based on dynamic surface exposure. Background Art

[0002] Selective laser melting is an advanced manufacturing technology that is data-driven and uses additive materials layer by layer to form solid parts. Compared with traditional subtractive manufacturing, this technology can form lightweight, complex structures and multi-material gradient structures. It has a short process flow, less material waste, and does not require molds. It supports personalized and customized processing and has been widely used in aerospace, biomedicine, automotive and other fields. This technology uses laser sintering to melt the powder pre-laid in the forming area, which is a complex process with multiple mutually coupled and highly dynamic physical fields. The mainstream processing method of traditional selective laser melting systems is to control the laser beam to scan the surface of the powder raw material point by point, and complete the melting of the powder layer "from point to line to surface" according to the slice image. The thin layer of powder in the scanned area undergoes a photopolymerization reaction and melts to form a thin layer of the part.

[0003] With the continuous development of laser and light valve technologies, selective laser melting (SLM) based on surface exposure has become a viable method and is attracting increasing attention. Using a surface light source instead of a traditional point light source bypasses the "point-to-line-to-surface" forming process. A single exposure of the surface light source on the powder bed allows for the formation of a single layer of a part, significantly improving forming efficiency.

[0004] The laser selective melting forming technology based on surface exposure relies on the development of surface laser light source and light valve technology. It is limited by factors such as melting energy, surface light source homogeneity quality, and light valve tolerance. The laser selective melting forming device based on surface exposure is still in the laboratory product stage, and the exposure range of the surface light source cannot be very large. At present, the maximum size of the surface light source can be about 20mm*20mm. It has significant disadvantages when forming large-size parts. Therefore, the limitation of the exposure range of the surface light source has become a bottleneck affecting the further development of this technology.

[0005] Therefore, the inventors provide a laser selective melting forming device based on dynamic surface exposure. Summary of the Invention

[0006] (1) Technical problems to be solved

[0007] The embodiment of the present invention provides a laser selective melting forming device based on dynamic surface exposure, which solves the technical problem that laser selective melting forming based on surface exposure cannot meet the requirements of large-size parts forming due to the exposure range limitation of the surface light source.

[0008] (2) Technical solution

[0009] The present invention provides a laser selective melting forming device based on dynamic surface exposure, comprising a diode laser array homogeneous light unit, a light addressing light valve imaging unit and a light source deflection imaging unit sequentially distributed along the laser light path; wherein,

[0010] The diode laser array homogenous light unit is used to emit multiple groups of lasers and homogenize them into a surface light source, the light addressing light valve imaging unit is used to divide the surface light source into S-polarized light and P-polarized light, and the light source deflection imaging unit is used to dynamically adjust the projection position of the S-polarized light to expand the forming area of ​​laser selective melting.

[0011] Furthermore, the diode laser array homogenous light unit includes a diode laser array and a light homogenizing module, and the multiple groups of lasers output by the diode laser array are homogenized into a surface light source by the light homogenizing module.

[0012] Furthermore, the light-addressable light valve imaging unit includes a projector, a dichroic mirror, a light-addressable light valve and a polarizing prism, the projector is used to project the slice image onto the light-addressable light valve, the dichroic mirror is used to transmit the surface light source and reflect the projection light source of the projector to the light-addressable light valve, the light-addressable light valve is used to divide the projected slices of the surface light source into P-polarized light and S-polarized light, and the polarizing prism is used to transmit the P-polarized light.

[0013] Furthermore, the light-addressed light valve imaging unit further includes a black box, and the black box is used to absorb the S-polarized light.

[0014] Furthermore, the projector is used to divide the light-addressable light valve into two areas, bright and dark, by using the projection light of the slice image.

[0015] Furthermore, the light source deflection imaging unit includes a projection lens system, a reflector and a forming platform. The projection lens system is used to increase the optical path length of the projection surface of the surface light source, and the reflector is used to reflect the surface light source to the powder to be melted placed on the forming platform.

[0016] Furthermore, the light source deflection imaging unit also includes an X-axis adjustment lens and a Y-axis adjustment lens, the reflector is used to reflect the surface light source to the center position of the X-axis adjustment lens, the X-axis adjustment lens is used to vibrate around the Y-axis direction to adjust the position of the surface light source in the X-axis direction when it is projected onto the forming chamber, and the Y-axis adjustment lens is used to vibrate around the X-axis direction to adjust the position of the surface light source in the Y-axis direction when it is projected onto the forming chamber.

[0017] Furthermore, the light source deflection imaging unit also includes a field lens, which is used to transmit the surface laser adjusted by the Y-axis adjustment lens to the powder to be melted placed on the forming platform.

[0018] (3) Beneficial effects

[0019] In summary, the present invention uses the design of a diode laser array homogeneous light unit, a light-addressed light valve imaging unit, and a light source deflection imaging assembly to enable the surface light source to directly act on the powder after being projected by the light-addressed light valve. The projection position of the surface light source is dynamically adjusted as the angle of the light source deflection imaging assembly changes, thereby expanding the forming processing area of ​​the surface light source, increasing the applicability of large-size parts formed by surface light source laser selective melting, and effectively improving the processing efficiency of large-size parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 1 is a schematic structural diagram of a laser selective melting forming device based on dynamic surface exposure provided by an embodiment of the present invention;

[0022] Figure 2 This is a structural diagram provided by an embodiment of the present invention.

[0023] In the picture:

[0024] 1-Diode laser array homogenous light unit; 2-Light addressing light valve imaging unit; 3-Light source deflection imaging unit; 4-Diode laser array; 5-Light homogenization module; 6-Projector; 7-Slice image; 8-Dichroic mirror; 9-Light addressing light valve; 10-Polarization prism; 11-Black box; 12-Dark area of ​​projection light; 13-Projection lens system; 14-Reflector; 15-X-axis adjustment lens; 16-Y-axis adjustment lens; 17-Field mirror; 18-Forming platform; 19-Melted powder layer. DETAILED DESCRIPTION

[0025] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are intended to illustrate the principles of the present invention and are not intended to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments and covers any modifications, replacements, and improvements to the parts, components, and connection methods without departing from the spirit of the present invention.

[0026] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0027] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0028] It should also be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "disposed" and "installed" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0029] Figure 1 This is a schematic structural diagram of a laser selective melting forming device based on dynamic surface exposure provided by an embodiment of the present invention. The device may include a diode laser array homogenous light unit 1, a light addressing light valve imaging unit 2, and a light source deflection imaging unit 3 sequentially distributed along the laser light path; wherein,

[0030] The diode laser array homogenous light unit 1 is used to emit multiple groups of lasers and homogenize them into a surface light source. The light-addressed light valve imaging unit 2 is used to separate the surface light source into S-polarized light and P-polarized light. The light source deflection imaging unit 3 is used to dynamically adjust the projection position of the S-polarized light to expand the forming area of ​​the laser selective melting.

[0031] In the above embodiment, the forming device can complete the single-layer powder forming of the slice image of the processed part by splicing multiple surface light sources with the shape of the slice image; the "point-line-surface" scanning method in the existing technology is replaced by a processing method of splicing a single small plane light source, which effectively improves the processing efficiency of laser selective melting and expands the application scope of laser selective melting based on surface light source.

[0032] As an optional embodiment, the diode laser array homogenous light unit 1 includes a diode laser array 4 and a light homogenizing module 5 . The multiple groups of lasers output by the diode laser array 4 are homogenized into a surface light source by the light homogenizing module 5 .

[0033] Specifically, if Figure 1 As shown, the four laser beams emitted by the diode laser array 4 are converged and processed by the light homogenization module 5 before entering the light-addressed light valve imaging unit 2 .

[0034] As an optional implementation, Figure 1As shown, the light-addressed light valve imaging unit 2 includes a projector 6, a dichroic mirror 8, a light-addressed light valve 9 and a polarization prism 10. The projector 6 is used to project the slice image 7 to the light-addressed light valve 9. The dichroic mirror 8 is used to transmit the surface light source and reflect the projection light source of the projector 6 to the light-addressed light valve 9. The light-addressed light valve 9 is used to divide the projection slices of the surface light source into P-polarized light and S-polarized light. The polarization prism 10 is used to transmit P-polarized light.

[0035] Specifically, after exposure to projection light, the light-addressed light valve 9 in the light-addressed light valve imaging unit 2 is divided into two regions: the portion covered by the projection light from projector 6 is the bright region; the portion not exposed to the projection light is the dark region. Under the influence of the photoelectric effect, the bright region of the light valve dynamically adjusts the orderly arrangement of the liquid crystal material molecules based on the distribution of the projection light, resulting in different refractive indices along and perpendicular to the molecular long axis. After the light valve liquid crystal material molecules are redistributed, the light from the diode laser surface light source passing through the bright region of the light valve is adjusted to P-polarized light, while the light from the surface light source passing through the dark region of the light valve is adjusted to S-polarized light. In other words, after passing through the light-addressed light valve 9, all slice images to be projected are converted to P-polarized light, while all other portions not required for projection are converted to S-polarized light.

[0036] As an optional implementation, Figure 1 As shown, the light-addressed light valve imaging unit 2 further includes a black box 11, which is used to absorb S-polarized light. The black box 11 is set to absorb useless light other than the projected image in the surface light source.

[0037] As an optional implementation, the projector 6 is used to divide the light-addressable light valve 9 into two areas, bright and dark, through the projection light of the slice image 7 .

[0038] As an optional implementation, Figure 1 As shown, the light source deflection imaging unit 3 includes a projection lens system 13, a reflector 14 and a forming platform 18. The projection lens system 13 is used to increase the optical path length of the projection surface of the surface light source, and the reflector 14 is used to reflect the surface light source to the powder to be melted placed on the forming platform 18.

[0039] Specifically, a specific structural form of the light source deflection imaging unit 3 is given above, which is used to dynamically adjust the incident angle of the laser polarization light, thereby expanding the forming area of ​​the surface light source.

[0040] As an optional implementation, Figure 1As shown, the light source deflection imaging unit 3 also includes an X-axis adjustment lens 15 and a Y-axis adjustment lens 16. The reflector 14 is used to reflect the surface light source to the center position of the X-axis adjustment lens 15. The X-axis adjustment lens 15 is used to vibrate around the Y-axis direction to adjust the position of the surface light source in the X-axis direction when it is projected onto the forming chamber. The Y-axis adjustment lens 16 is used to vibrate around the X-axis direction to adjust the position of the surface light source in the Y-axis direction when it is projected onto the forming chamber.

[0041] Specifically, the X-axis adjustment lens 15 can vibrate around the Y-axis direction, thereby adjusting the position of the surface light source in the X-axis direction when it is projected onto the forming chamber, and the Y-axis adjustment lens 16 can vibrate around the X-axis direction, thereby adjusting the position of the surface light source in the Y-axis direction when it is projected onto the forming chamber.

[0042] As an optional implementation, Figure 1 As shown, the light source deflection imaging unit 3 further includes a field lens 17 , which is used to transmit the surface laser adjusted by the Y-axis adjustment lens 16 to the powder layer 19 to be melted placed on the forming platform 18 .

[0043] Specifically, the function of the field lens 17 is to adjust the focal height of the surface light source when projecting at different positions.

[0044] Example 1

[0045] according to Figure 1 The optical path diagram of the device is shown. The specific adjustment of the optical path in actual application is as follows:

[0046] Diode laser array 4, laser wavelength 1064nm, 6-bar array, each bar has 104 light spots;

[0047] The light homogenization module 5 is composed of multiple optical components. The diode laser array is homogenized into a planar homogeneous light source through the light homogenization module. The light source size is a square homogeneous light spot of 15mm*15mm;

[0048] Projector 6, which uses a projection laser of 472nm to project the slice image to be formed onto the light valve;

[0049] The dichroic mirror 8 can transmit a light source with a wavelength of 1064nm and reflect a light source with a wavelength of 472nm. Therefore, the surface light source from the laser can pass through the dichroic mirror and enter the light valve, and the projection light source from the projector can be reflected by the dichroic mirror and then enter the light valve.

[0050] The optically addressable light valve 9 has a light aperture of 15mm*15mm. An adjustable AC voltage with an average voltage of approximately 4V is applied across both ends of the light valve. Under the action of this voltage, the light valve 9 dynamically adjusts the liquid crystal material properties at the corresponding positions of the light valve 9 based on the distribution of the projected image. This adjusts the light from the surface light source projecting through the light valve to P-polarized light, while the light from the surface light source projecting through the dark area of ​​the light valve is adjusted to S-polarized light.

[0051] The polarizing prism 10 can transmit P-polarized light and reflect S-polarized light; therefore, the P-polarized light used to project the slice image in the surface light source can pass through the polarizing prism, and the remaining S-polarized light that does not need to be projected is reflected to the black box and absorbed;

[0052] The black box 11 is used to absorb the S-polarized light of the surface light source other than the projected image;

[0053] The projection lens system 13 is a 4F projection lens system, which is used to increase the optical path length of the projection surface of the surface light source. The focal plane of the diode laser is 200 mm, and the focal plane of the laser after passing through the 4F projection lens is 400 mm.

[0054] The reflector 14 adjusts the angle of the reflector so that the surface light source is incident on the X-axis to adjust the center position of the lens;

[0055] The X-axis adjustment lens 15 can vibrate around the Y-axis direction, thereby adjusting the position of the surface light source in the X-axis direction when projected onto the forming chamber;

[0056] The Y-axis adjustment lens 16 can vibrate around the X-axis direction, thereby adjusting the position of the surface light source in the Y-axis direction when projected onto the forming chamber;

[0057] The light transmission area of ​​the field lens 17 is 62 mm*82 mm.

[0058] Specifically, the distance between the X-axis adjustment lens and the Y-axis adjustment lens is 50 mm, and the distance between the Y-axis adjustment lens and the forming platform is 100 mm. When the X-axis adjustment lens and the Y-axis adjustment lens are both in the initial position, the surface light source is vertically incident on the forming platform. At this time, the lower left end point of the surface light source is defined as the origin of the coordinate system, as shown in FIG. Figure 2 As shown. The exposure area of ​​the surface light source is 15mm*15mm. The squares marked ①, ②, ③, ④, ⑤, and ⑥ in the figure represent the six moving positions of the surface light source. The moving trajectory of the surface light source is marked with the lower left endpoint of each square, marked as O1, O2, O3, O4, O5, and O6 respectively. These six moving positions correspond to the X-axis adjustment lens deflection angle θ x and Y axis to adjust the lens deflection angle θ y As shown in the following table:

[0059]

[0060]

[0061] It should be noted that the various embodiments in this specification are described in a progressive manner. References to the same or similar parts between the various embodiments are sufficient. Each embodiment focuses on the differences from the other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and technologies are omitted here.

[0062] The above are merely embodiments of the present application and are not intended to limit the present application. Various modifications and variations are possible for those skilled in the art without departing from the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A laser selective melting forming device based on dynamic surface exposure, characterized in that: It comprises a diode laser array homogeneous light unit (1), a light addressing light valve imaging unit (2) and a light source deflection imaging unit (3) which are sequentially distributed along the laser light path; wherein, The diode laser array homogenizing light unit (1) is used to emit multiple groups of lasers and homogenize them into a surface light source, the light addressing light valve imaging unit (2) is used to separate the surface light source into S-polarized light and P-polarized light, and the light source deflection imaging unit (3) is used to dynamically adjust the projection position of the P-polarized light to expand the forming area of ​​laser selective melting and form large-sized parts; The light source deflection imaging unit (3) comprises a projection lens system (13), a reflector (14) and a forming platform (18); the projection lens system (13) is used to increase the optical path length of the projection surface of the surface light source; the reflector (14) is used to reflect the surface light source to the powder to be melted placed on the forming platform (18); The light source deflection imaging unit (3) further comprises an X-axis adjustment lens (15) and a Y-axis adjustment lens (16); the reflector (14) is used to reflect the surface light source to the center position of the X-axis adjustment lens (15); the X-axis adjustment lens (15) is used to vibrate around the Y-axis direction to adjust the position of the surface light source in the X-axis direction when projected onto the forming chamber; and the Y-axis adjustment lens (16) is used to vibrate around the X-axis direction to adjust the position of the surface light source in the Y-axis direction when projected onto the forming chamber.

2. The laser selective melting forming device based on dynamic surface exposure according to claim 1, characterized in that: The diode laser array homogenous light unit (1) comprises a diode laser array (4) and a light homogenizing module (5); multiple groups of laser light output by the diode laser array (4) are homogenized into a surface light source via the light homogenizing module (5).

3. The laser selective melting forming device based on dynamic surface exposure according to claim 1, characterized in that: The light-addressing light valve imaging unit (2) comprises a projector (6), a dichroic mirror (8), a light-addressing light valve (9) and a polarizing prism (10); the projector (6) is used to project a slice image (7) onto the light-addressing light valve (9); the dichroic mirror (8) is used to transmit the surface light source and reflect the projection light source of the projector (6) to the light-addressing light valve (9); the light-addressing light valve (9) is used to divide the projected slices of the surface light source into P-polarized light and S-polarized light; and the polarizing prism (10) is used to transmit the P-polarized light.

4. The laser selective melting forming device based on dynamic surface exposure according to claim 3, characterized in that: The light-addressed light valve imaging unit (2) further comprises a black box (11), and the black box (11) is used for absorbing the S-polarized light.

5. The laser selective melting forming device based on dynamic surface exposure according to claim 3, characterized in that: The projector (6) is used to divide the light-addressable light valve (9) into two areas, bright and dark, through the projection light of the slice image (7).

6. The laser selective melting forming device based on dynamic surface exposure according to claim 1, characterized in that: The light source deflection imaging unit (3) further comprises a field lens (17), and the field lens (17) is used to transmit the surface laser adjusted by the Y-axis adjustment lens (16) to the powder to be melted placed on the forming platform (18).

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