Additive manufacturing forming method for unsupported powder bed in large-breadth overhanging area

Abstract

The invention relates to the technical field of additive manufacturing, and discloses a large-breadth overhanging area unsupported powder bed additive manufacturing forming method, which is characterized in that an overhanging area is divided into a bonding forming area and a melting curing area, so that structural self-supporting of overhanging area processing is realized, and the tedious step of using an additional supporting structure in a traditional method is avoided; therefore, the problem that the supporting structure is difficult to remove in traditional additive manufacturing is effectively solved; in addition, the binder forming allowance compensation area is designed at the bottom of the binder forming area, and the vertical height of the binder forming allowance compensation area is set, so that the difference between the apparent density of metal powder and the density of the corresponding metal material is ensured; the dimensional deviation generated in the subsequent sintering process after printing of the to-be-machined part is completed is avoided, the stability and the supporting strength of the bonding forming area are guaranteed, and meanwhile the precision and the overhanging surface quality of the overhanging area under the condition that no external supporting exists are further improved.

Description

Technical Field

[0001] The invention relates to the technical field of additive manufacturing and discloses a method for additive manufacturing of a large-scale overhanging area using an unsupported powder bed. Background Art

[0002] Laser powder bed fusion (L-PBF) is an advanced additive manufacturing technology. With its high forming accuracy, excellent comprehensive mechanical properties and the ability to form complex parts, this technology is widely used in the manufacture of integrated lightweight components in the aerospace field and complex components in the mold field. The principle of L-PBF forming is: cut the designed three-dimensional model into thin slices of a certain thickness, and then use the energy of the laser beam to melt the powder into the shape of a thin slice, and then stack the formed slices layer by layer to form a component. In theory, L-PBF technology can form parts of any complexity. However, in the actual printing process, due to the thermoforming characteristics of L-PBF, it is often necessary to add support structures to assist in heat dissipation and prevent warping of the formed parts caused by thermal stress, especially in the forming of low-angle samples. The currently recognized optimal forming angle of L-PBF is 45°. When the forming angle of the sample is less than 45°, it is necessary to add support structures to assist in forming. Although adding support structures can effectively assist in part forming, it is often accompanied by shortcomings such as increased printing time and consumables, increased difficulty in post-processing, and increased support surface roughness. Moreover, for some parts with internal hollowing or complex flow channels, the internal supports cannot be removed, and therefore L-PBF technology cannot be used for forming.

[0003] Some known technologies utilize support-free printing methods, such as those that control laser energy density and scanning strategies. These methods can effectively improve the quality of overhang surfaces by increasing scanning speed and thus reducing laser energy input. Alternatively, by controlling the scanning strategy for overhang samples, the temperature gradient during the forming process can be effectively reduced, thus lowering forming stress and improving the forming stability of overhang samples. However, this method struggles to achieve sufficiently high surface quality when the overhang surface is tilted less than 25° relative to the printing plane, or when the overhang area is large. Summary of the Invention

[0004] The purpose of the present invention is to provide a support-free powder bed additive manufacturing method for large-scale overhanging areas, which can avoid the problem of needing to use additional support structures, and while ensuring the stability and support strength of the bonding forming area, further improve the accuracy and overhang surface quality of the overhanging area without external support conditions.

[0005] In order to achieve the above technical effects, the technical solution adopted by the present invention is:

[0006] A method for forming large-area overhanging areas with unsupported powder bed additive manufacturing, including:

[0007] According to the placement form and position of the part model to be processed on the powder bed of the additive manufacturing forming equipment, the overhang area and the solid support area of the additively manufactured part are identified, wherein the overhang area is a part structure area with an overhang angle of 0 to 20 degrees and a maximum length of the overhang structure projected on the surface of the powder bed of 30 mm or more, and the solid support area is other solid structure areas except the overhang area;

[0008] Dividing the overhanging area into a bonding forming area and a melting solidification area from bottom to top along the vertical height direction of the part model to be processed in the powder bed;

[0009] A binder forming allowance compensation zone is designed on the lower surface of the bonding forming zone. The vertical height of the binder forming allowance compensation zone is obtained according to the analysis of h=D(1-ρ1 / ρ), where h is the vertical height of the binder forming allowance compensation zone, D is the vertical height of the bonding forming zone, ρ1 is the bulk density of the metal powder, and ρ is the metal material density corresponding to the metal powder;

[0010] According to the positional relationship between the solid support area, the overhang area and the binder forming allowance compensation area, powder is laid layer by layer from bottom to top, and a fusion mechanism is used to in-situ melt and solidify the metal powder at the layer processing positions corresponding to the solid support area and the melt-solidification area, and a binder injection mechanism is used to bond and solidify the metal powder at the layer processing positions corresponding to the bonding forming area and the binder forming allowance compensation area, until all the solid support areas and overhang areas of the additively manufactured part to be processed are processed.

[0011] Furthermore, the fusion mechanism is a laser melting device.

[0012] Furthermore, the vertical height of the bonding forming area is greater than or equal to 4 times the thickness of a single forming layer of the solid support area of the part to be processed during the additive manufacturing forming process.

[0013] Furthermore, the method of using a fusion mechanism to in-situ melt and solidify the metal powder at the ply processing position of the solid support area includes: laying powder layer by layer on the powder bed, scanning the metal powder at each ply processing position layer by layer with a laser with a designed linear energy of the solid support area to complete the processing of the solid support area.

[0014] Furthermore, the bonding forming areas or the bonding agent forming allowance compensation areas at the same vertical height position are formed preferentially.

[0015] Furthermore, during the processing of the solid support area, when the solid support area is in lateral contact with the bonding forming area and the adhesive forming allowance compensation area, the corresponding forming layer of each solid support area is offset by a distance of a light spot toward the corresponding bonding forming area or the adhesive forming allowance compensation area.

[0016] Furthermore, the method for processing the molten solidified zone of the overhanging area includes:

[0017] After the bonding forming area is solidified, the powder bed is lowered to a first layer thickness value, and the powder is spread. The metal powder at the current layer processing position is scanned with a laser at 40% of the design line energy of the solid support area, and sintered to form a first sintered thin layer. The first sintered thin layer is located on the top layer of the bonding forming area;

[0018] The powder bed is lowered by a first layer thickness value, and the powder is spread. The metal powder at the current layer processing position is scanned with a laser at 60% of the design line energy of the solid support area, and sintered to form a second sintered thin layer. The second sintered thin layer is located on the top of the first sintered thin layer;

[0019] The powder bed is lowered by a first layer thickness value, the powder is spread, and the metal powder at the current layer processing position is scanned with a laser at 80% of the design line energy of the solid support area, and sintered to form a third sintered thin layer, which is located on the top of the second sintered thin layer;

[0020] Powder is spread layer by layer on top of the third sintered thin layer, and the metal powder at the current layer processing position is scanned layer by layer with a laser with designed line energy in the solid support area, and the molten solidification area is connected with the adjacent solid support area to form a single-layer cross-section of the part to be processed until the processing of the remaining overhanging area is completed.

[0021] Furthermore, during the scanning process of the solid support area and the molten solidification area, the inter-layer rotation angle of two adjacent forming layers is 67°.

[0022] Furthermore, the thickness of a single forming layer of the solid support area of the additively manufactured part during the additive manufacturing forming process ranges from 20 to 60 μm.

[0023] Furthermore, the thickness of a single forming layer during processing of the bonding forming area and the bonding agent forming allowance compensation area is 40-120 μm.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. By dividing the overhang area into a bonding and forming zone and a melting and solidification zone, the present invention achieves structural self-support during overhang area processing, avoiding the cumbersome steps required to use additional support structures in traditional methods, thereby effectively solving the pain point of difficult support structure removal in traditional additive manufacturing;

[0026] 2. The present invention designs a binder forming allowance compensation area at the bottom of the bonding forming area. The vertical height setting of the binder forming allowance compensation area not only ensures the difference between the loose density of the metal powder and the density of the corresponding metal material, but also avoids the dimensional deviation caused by the subsequent sintering process after the printing of the parts to be processed is completed. While ensuring the stability and support strength of the bonding forming area, it further improves the accuracy and overhang surface quality of the overhang area without external support. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of the part to be processed in Example 1 or 2;

[0028] Figure 2 Schematic diagram of the division of the overhang area and the solid support area of the part to be processed in Example 1 or 2;

[0029] Figure 3 Schematic diagram of laser melting forming of the overhanging area in Example 1 or 2;

[0030] Among them, 1. Powder bed; 2. Overhanging area; 201. Bonding and forming area; 202. Melting and solidification area; 3. Solid support area; 4. Binder forming allowance compensation area; 5. Fusion mechanism; 6. Binder injection mechanism; 7. Scraper. DETAILED DESCRIPTION

[0031] The present invention will be described in further detail below with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the present invention to the following embodiments, as all technologies implemented based on the present invention fall within the scope of the present invention.

[0032] Example 1

[0033] See also Figure 1-Figure 3 , a large-area overhang area unsupported powder bed additive manufacturing method, including:

[0034] According to the placement form and position of the part model to be processed on the powder bed 1 of the additive manufacturing forming equipment, the overhang area 2 and the solid support area 3 of the additively manufactured part are identified, wherein the overhang area 2 is a part structure area with an overhang angle of 0 to 20 degrees and a maximum length of the overhang structure projected on the upper surface of the powder bed 1 of ≥30 mm, and the solid support area 3 is other solid structure areas except the overhang area 2;

[0035] The overhanging area 2 is divided from bottom to top into a bonding forming area 201 and a melting solidification area 202 along the vertical height direction of the part model to be processed in the powder bed 1;

[0036] A binder forming allowance compensation zone 4 is designed on the lower surface of the bonding forming zone 201. The vertical height of the binder forming allowance compensation zone 4 is obtained according to the analysis of h=D(1-ρ1 / ρ), where h is the vertical height of the binder forming allowance compensation zone 4, D is the vertical height of the bonding forming zone 201, ρ1 is the bulk density of the metal powder, and ρ is the metal material density corresponding to the metal powder;

[0037] According to the positional relationship between the solid support area 3, the overhang area 2 and the binder forming allowance compensation area 4, powder is laid layer by layer from bottom to top, and the fusion mechanism 5 is used to in-situ melt and solidify the metal powder at the layer processing positions corresponding to the solid support area 3 and the melting and solidification area 202, and the binder injection mechanism 6 is used to bond and solidify the metal powder at the layer processing positions corresponding to the bonding forming area 201 and the binder forming allowance compensation area 4, until all the solid support areas 3 and overhang areas 2 of the additively manufactured part to be processed are completed.

[0038] In this embodiment, by dividing the overhang area 2 into a bonding forming area 201 and a melting and solidifying area 202, the bonding forming area 201 can form a stable support for the metal powder in the melting and solidifying area 202 when it melts and solidifies, thereby realizing the self-support of the structure processed in the overhang area 2, avoiding the cumbersome steps of using additional support structures in traditional methods, thereby effectively solving the pain point problem of difficulty in removing support structures in traditional additive manufacturing; in addition, by designing a binder forming allowance compensation area 4 at the bottom of the bonding forming area 201, the vertical height setting of the binder forming allowance compensation area 4 not only ensures the difference between the loose density of the metal powder and the density of the corresponding metal material, but also avoids the dimensional deviation generated in the subsequent sintering process after the printing of the part to be processed is completed, while ensuring the stability and support strength of the bonding forming area 201, the accuracy and overhang surface quality of the overhang area 2 without external support are further improved.

[0039] In this embodiment, the thickness of a single forming layer of the solid support area 3 of the additively manufactured part during the additive manufacturing process ranges from 20 to 60 μm. The thickness of a single forming layer of the bonding forming area 201 and the bonding agent forming margin compensation area 4 during processing ranges from 40 to 120 μm.

[0040] Example 2

[0041] See also Figure 1-Figure 3This embodiment uses the laser printing process of a large-scale overhanging structural part as an example to explain in detail the process of the unsupported powder bed additive manufacturing method for large-scale overhanging areas of the present invention. The large-scale overhanging structural part is made of GH3635 alloy, and the overhanging portion is 60 mm in size. This embodiment uses a powder bed additive manufacturing device 1 that combines a binder and a laser. A 500W continuous-wave fiber laser with a wavelength of 1070 nm is selected as the laser source. An xy galvanometer scanner is used to guide the laser beam, and an F-θ lens is used to focus the laser beam to selectively melt metal powder particles at specific locations. The device is equipped with a binder jetting mechanism 6, and the nozzles work together to efficiently jet, achieving a printing resolution of 1200 dpi.

[0042] The corresponding forming method process is as follows:

[0043] Step 1: Based on the placement form and position of the part model to be processed on the powder bed 1 of the additive manufacturing forming equipment, the overhang area 2 and the solid support area 3 of the additively manufactured part are identified. The overhang area 2 is a part structure area with an overhang angle of 0 to 20 degrees and a maximum length of the overhang structure projected on the upper surface of the powder bed 1 of ≥30 mm. The solid support area 3 is the other solid structure area except the overhang area 2;

[0044] The part model to be processed in this embodiment is as follows Figure 1 As shown, it includes a vertical portion at the bottom and a horizontal portion at the top. The horizontal portion is a hanging structure, and the angle between its bottom surface and the horizontal plane is 0°. Figure 2 Arrange in this way and identify the overhang area 2 and the solid support area 3.

[0045] Step 2: Divide the overhanging area 2 from bottom to top into a bonding forming area 201 and a melting and solidification area 202 along the vertical height direction of the powder bed 1 along the part model to be processed;

[0046] In this embodiment, the overhanging area 2 is divided into a bonding and forming area 201 and a melting and solidifying area 202 along the vertical direction.

[0047] Step 3: Designing a binder forming allowance compensation area 4 on the lower surface of the bonding forming area 201. The vertical height of the binder forming allowance compensation area 4 is obtained according to the analysis of h=D(1-ρ1 / ρ), where h is the vertical height of the binder forming allowance compensation area 4, D is the vertical height of the bonding forming area 201, ρ1 is the bulk density of the metal powder, and ρ is the metal material density corresponding to the metal powder;

[0048] In this embodiment, GH3536 metal powder with a diameter of 15-53 μm was selected for processing, and the bulk density of the metal powder was measured to be 4.1 g / cm 3 , and the material density of the metal is 8.2g / cm 3In addition, the metal powder in the solid support area 3 is melted and solidified in situ by laying powder layer by layer on the powder bed 1 and using laser scanning to perform melting and forming. The laser scanning parameters are set as follows: the thickness of a single forming layer is 0.04mm, the laser power is 275W, the scanning speed is 980mm / s, the scanning pitch is 0.1mm, and the inter-layer rotation angle is 67°.

[0049] In this embodiment, the vertical height of the bonding forming area 201 is greater than or equal to 4 times the thickness of a single forming layer of the solid support area 3 of the part to be processed during the additive manufacturing forming process. According to the above data, the vertical height of the bonding layer can be set to 0.16 mm, thereby obtaining the vertical height of the adhesive forming allowance compensation area 4 to be 0.08 mm.

[0050] Step 4: According to the positional relationship between the solid support area 3, the overhang area 2 and the binder forming allowance compensation area 4, the powder is spread layer by layer from bottom to top, and the fusion mechanism 5 is used to melt and solidify the metal powder at the layer processing positions corresponding to the solid support area 3 and the melt solidification area 202 in situ, and the binder injection mechanism 6 is used to bond and solidify the metal powder at the layer processing positions corresponding to the bonding forming area 201 and the binder forming allowance compensation area 4, until all the solid support areas 3 and overhang areas 2 of the additively manufactured part to be processed are processed. Among them, since the processing method of the solid support area 3 belongs to conventional processing technology, it will not be repeated here. In this embodiment, the processing flow of the binder forming allowance compensation area 4 and the overhang area 2 is as follows:

[0051] Step 4.1: When the scanned part cross section reaches the position corresponding to the lower surface of the adhesive forming allowance compensation area 4, the adhesive spraying mechanism 6 is used to scan the metal powder at the corresponding layer processing position and thermally cure it to form a first adhesive cured layer;

[0052] Step 4.2: Powder is applied layer by layer on the upper surface of the first adhesive solidification layer. For each layer, the adhesive spraying mechanism 6 is used to scan the metal powder at the corresponding layer processing position and thermally solidify the metal powder until the adhesive forming allowance compensation area 4 and the adhesive forming area of the overhang area 2 are formed. The structural strength and rigidity formed by the adhesive solidification can resist the thermal stress deformation during the subsequent laser forming process above this area.

[0053] In this embodiment, the water-based adhesive BW06SO is selected, the scanning speed is set to 500 mm / s, and the thickness of the single-layer powder coating in the adhesive forming area and the adhesive forming allowance compensation area 4 is 0.08 mm.

[0054] Step 4.3: After the bonding forming area 201 is solidified, the powder bed 1 is lowered to a first layer thickness of 0.04 mm and the powder is spread (which can be leveled using a scraper 7). The metal powder at the current layer processing position is scanned with a laser at 40% of the design line energy of the solid support area 3 to sinter and form a first sintered thin layer. The first sintered thin layer is located on the top layer of the bonding forming area 201. The parameters are set as follows: laser power of 110 W, scanning speed of 980 mm / s, scanning pitch of 0.1 mm, and interlayer rotation angle of 67°.

[0055] Step 4.4: Powder bed 1 is lowered 0.04 mm to spread the powder. The metal powder at the current layer processing position is scanned with a laser at 60% of the design line energy of solid support area 3 to sinter the metal powder to form a second sintered thin layer. The second sintered thin layer is placed on top of the first sintered thin layer. The parameters are set as follows: laser power 165 W, scanning speed 980 mm / s, scanning pitch 0.1 mm, and interlayer rotation angle 67°.

[0056] Step 4.5: Powder bed 1 is lowered 0.04 mm to spread the powder. The metal powder at the current layer processing position is scanned with a laser at 80% of the design line energy of solid support area 3 to sinter the metal powder to form a third sintered thin layer. The third sintered thin layer is located on top of the second sintered thin layer. The parameters are set as follows: laser power 220 W, scanning speed 980 mm / s, scanning pitch 0.1 mm, and interlayer rotation angle 67°.

[0057] Step 4.6: Spread powder layer by layer on top of the third sintered thin layer, and use the laser with the designed line energy of the solid support area 3 to scan the metal powder at the current layer processing position layer by layer, and connect the molten solidification area 202 with the adjacent solid support area 3 to form a single-layer cross-section of the part to be processed. The parameters are set as follows: laser power of 275W, scanning speed of 980mm / s, scanning spacing of 0.1mm, and repeat step 4.6 until the processing of the remaining overhang area 2 is completed.

[0058] Step 5. After all the solid support areas 3 and overhang areas 2 of the additively manufactured part are processed, the removed part is cleaned of powder and then degreased and sintered. The degreasing and sintering parameters are as follows: heating to 700°C at 8°C / min under vacuum and holding for 1 hour; then heating to 1170°C at 8°C / min and holding for 2 hours, and then cooling by furnace cooling.

[0059] Step 6: The degreased and sintered parts are hot isostatically pressed at 1175°C / 160MPa to obtain a high-density metallurgical structure.

[0060] In this embodiment, the bonding forming area 201 or the adhesive forming excess compensation area 4 at the same vertical height is preferentially formed. To ensure that the bonding forming area 201 shrinks vertically during the subsequent sintering process, this embodiment employs an embedded connection structure between the solid area and the adhesive forming area. Specifically, during the processing of the solid support area 3, at the position where the solid support area 3 is in lateral contact with the bonding forming area 201 and the adhesive forming excess compensation area 4, the formed layer of each corresponding solid support area 3 is offset toward the corresponding bonding forming area 201 or adhesive forming excess compensation area 4 by a distance of one laser spot. Using a vertical cross-section on the bonding forming area 201 as the XOY plane, a vertical line perpendicular to the XOY plane and passing through the origin O as the Z axis, and the ply stacking direction as the positive Z axis, and employing an O-XYZ spatial rectangular coordinate system, during the sintering process after laser forming, if there are no surrounding constraints, the bonding forming area 201 will shrink along the OX, OY, and OZ directions during sintering. By biasing the light spot, the laser melting area is embedded in the bonding forming area 201, increasing the restrictions in the OX\OY directions; in the OZ direction, there is only a restriction at the top part, and no restriction at the bottom end, and it will shrink along the OZ. The shrinkage is compensated by the adhesive forming margin compensation area 4 to ensure that the size of the overhang area 2 meets the design requirements.

[0061] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for additive manufacturing of large-scale overhanging areas without support in a powder bed, characterized in that: include: According to the placement form and position of the part model to be processed on the powder bed of the additive manufacturing forming equipment, the overhang area and the solid support area of the additively manufactured part are identified, wherein the overhang area is a part structure area with an overhang angle of 0 to 20 degrees and a maximum length of the overhang structure projected on the surface of the powder bed of 30 mm or more, and the solid support area is other solid structure areas except the overhang area; Dividing the overhanging area into a bonding forming area and a melting solidification area from bottom to top along the vertical height direction of the part model to be processed in the powder bed; A binder forming allowance compensation zone is designed on the lower surface of the bonding forming zone. The vertical height of the binder forming allowance compensation zone is obtained according to the analysis of h=D(1-ρ1 / ρ), where h is the vertical height of the binder forming allowance compensation zone, D is the vertical height of the bonding forming zone, ρ1 is the bulk density of the metal powder, and ρ is the metal material density corresponding to the metal powder; According to the positional relationship between the solid support area, the overhang area and the binder forming allowance compensation area, powder is laid layer by layer from bottom to top, and a fusion mechanism is used to in-situ melt and solidify the metal powder at the layer processing positions corresponding to the solid support area and the melt-solidification area, and a binder injection mechanism is used to bond and solidify the metal powder at the layer processing positions corresponding to the bonding forming area and the binder forming allowance compensation area, until all the solid support areas and overhang areas of the additively manufactured part to be processed are processed.

2. The large-scale overhang area unsupported powder bed additive manufacturing forming method according to claim 1 is characterized in that: The fusion mechanism is a laser melting device.

3. The large-scale overhang area unsupported powder bed additive manufacturing method according to claim 2, characterized in that: The vertical height of the bonding forming area is greater than or equal to 4 times the thickness of a single forming layer of the solid support area of the part to be processed during the additive manufacturing forming process.

4. The large-scale overhang area unsupported powder bed additive manufacturing method according to claim 2, characterized in that: The method of using a fusion mechanism to in-situ melt and solidify the metal powder at the ply processing position of the solid support area includes: laying powder layer by layer on the powder bed, scanning the metal powder at each ply processing position layer by layer with a laser with a designed linear energy of the solid support area, and completing the processing of the solid support area.

5. The large-scale overhang area unsupported powder bed additive manufacturing method according to claim 4, characterized in that: The bonding forming area or the bonding agent forming allowance compensation area at the same vertical height position is formed first.

6. The large-area overhang area unsupported powder bed additive manufacturing method according to claim 5, characterized in that: During the processing of the solid support area, the solid support area is in a position where it is in transverse contact with the bonding forming area and the adhesive forming allowance compensation area layer, and the corresponding forming layer of each solid support area is offset by a light spot distance toward the corresponding bonding forming area or adhesive forming allowance compensation area.

7. The large-scale overhang area unsupported powder bed additive manufacturing method according to claim 2, characterized in that: The method for processing the molten solidification zone of the overhanging area includes: After the bonding forming area is solidified, the powder bed is lowered to a first layer thickness value, and the powder is spread. The metal powder at the current layer processing position is scanned with a laser at 40% of the design line energy of the solid support area, and sintered to form a first sintered thin layer. The first sintered thin layer is located on the top layer of the bonding forming area; The powder bed is lowered by a first layer thickness value, and the powder is spread. The metal powder at the current layer processing position is scanned with a laser at 60% of the design line energy of the solid support area, and sintered to form a second sintered thin layer. The second sintered thin layer is located on the top of the first sintered thin layer; The powder bed is lowered by a first layer thickness value, the powder is spread, and the metal powder at the current layer processing position is scanned with a laser at 80% of the design line energy of the solid support area, and sintered to form a third sintered thin layer, which is located on the top of the second sintered thin layer; Powder is spread layer by layer on top of the third sintered thin layer, and the metal powder at the current layer processing position is scanned layer by layer with a laser with designed line energy in the solid support area, and the molten solidification area is connected with the adjacent solid support area to form a single-layer cross-section of the part to be processed until the processing of the remaining overhanging area is completed.

8. The large-area overhang area unsupported powder bed additive manufacturing method according to claim 2, characterized in that: During the scanning process of the solid support area and the molten solidification area, the inter-layer rotation angle of two adjacent forming layers is 67°.

9. The method for large-scale overhang area unsupported powder bed additive manufacturing according to any one of claims 1 to 8, characterized in that: The thickness of a single forming layer in the solid support area of the additively manufactured part during the additive manufacturing process ranges from 20 to 60 μm.

10. The method for large-scale overhang area unsupported powder bed additive manufacturing according to any one of claims 1 to 8, characterized in that: The thickness of a single forming layer during processing of the bonding forming area and the bonding agent forming allowance compensation area is 40-120 μm.

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