Electron beam selective melting powder bed preheating method and electron beam selective melting method

Abstract

The present application relates to the technical field of metal additive manufacturing, and discloses an electron beam selective melting powder bed preheating method and an electron beam selective melting method. The electron beam selective melting powder bed preheating method comprises the following steps: in step S10, based on a three-dimensional model of a part to be printed, the part is sliced in the height construction direction, and cross-section data of a forming area in each layer slice is obtained; in step S20, a preheating area corresponding to each layer slice is constructed, the preheating area is a partial area of the entire forming area, corresponds to a local area of the powder bed, and the preheating area comprises a geometric preheating area fitted based on the shape of the corresponding forming area; and in step S30, a preheating scanning of the local area of the powder bed corresponding to the preheating area is performed by using a preheating electron beam. The electron beam selective melting powder bed preheating method and the electron beam selective melting method can not only meet the forming requirements of parts with variable cross sections, but also have high forming efficiency and low overall energy consumption by reconstructing the preheating area corresponding to each layer slice.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a method for preheating a powder bed and a method for selective electron beam melting. Background Technology

[0002] Selective electron beam melting is an advanced metal additive manufacturing technology that uses a high-energy electron beam as a heat source to selectively scan and melt metal powder along a preset path in a vacuum environment, accumulating layer by layer to form complex metal parts.

[0003] Unlike laser selective melting technology, electron beam selective melting requires preheating of the powder bed before forming and scanning. The preheating process uses an electron beam to heat the powder bed in a defocused or specific scanning mode, raising the powder bed temperature to a specific temperature range. This can effectively reduce the thermal stress caused by the temperature gradient during forming, reduce defects such as warping and cracking of parts, and significantly improve the forming accuracy and quality stability of large-size complex structural parts.

[0004] In traditional electron beam selective melting (EBM) processes, the powder bed is preheated globally before forming scanning. However, in aerospace, energy, and other fields, ring-shaped parts such as turbine guide vanes and bearing housings are characterized by hollow, thin-walled structures, complex internal and external contours, and large radial dimensions. These ring-shaped parts contain large cavities that do not require forming scanning. The aforementioned method of global preheating of the powder bed consumes a significant amount of time and energy; in some cases, preheating time can account for 30% to 45% of the entire forming cycle, which greatly restricts the forming efficiency and energy consumption control of EBM technology.

[0005] Therefore, there is an urgent need for a powder bed preheating method and an electron beam selective melting method to solve the above-mentioned technical problems. Summary of the Invention

[0006] The purpose of this invention is to propose a powder bed preheating method and an electron beam selective melting method. By reconstructing a preheating area that matches the forming area in each slice of the part, it can not only meet the forming requirements of parts with variable cross sections, but also achieve high forming efficiency and low overall energy consumption.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] Electron beam selective melting powder bed preheating method includes:

[0009] Step S10: Based on the three-dimensional model of the part to be printed, slice the part in the height construction direction and obtain the cross-sectional data of the forming area in each slice.

[0010] Step S20: Construct a preheating area corresponding to each layer slice. The preheating area is a part of the entire forming area, corresponding to a local part of the powder bed. The preheating area includes a geometric preheating area, which is fitted based on the shape of the corresponding forming area.

[0011] Step S30: A preheated electron beam is used to perform a preheating scan on a local area of ​​the powder bed corresponding to the preheated area.

[0012] As an alternative solution:

[0013] Step S20 further includes: obtaining a target slice based on the cross-sectional data of the forming region in each layer slice, wherein the target slice is a slice whose cross-sectional data of the forming region has an increased cross-section compared to the cross-sectional data of the forming region of the previous layer slice; taking the layer number of the target slice as a reference, setting a transition preheating zone for all slices whose layer number is less than the layer number m of the target slice, wherein the size and shape of the transition preheating zone correspond to the increased cross-sectional portion of the forming region of the target slice, and the preheating zone includes the transition preheating zone and the geometric preheating zone, where m is a positive integer greater than or equal to 2;

[0014] In step S30, all slices within the layer number m of the target slice are divided into at least two slice groups from bottom to top, and each slice group includes at least one slice. When performing a preheating scan on the local area of ​​the powder bed corresponding to the transition preheating zone of all slices within the layer number m of the target slice, the energy density of the electron beam for the preheating scan is the same for each slice in the same slice group, and the energy density of the electron beam for the preheating scan increases with the increase of the height of the slice group.

[0015] As an optional approach, in step S30, when performing a preheating scan on a local area of ​​the powder bed corresponding to the preheating region of the same slice layer:

[0016] The defocusing of the preheating electron beam scanning a local region of the powder bed corresponding to the transition preheating zone is greater than the defocusing of the preheating electron beam scanning a local region of the powder bed corresponding to the geometric preheating zone; and / or

[0017] The beam current of the preheating electron beam scanning the local area of ​​the powder bed corresponding to the transition preheating zone is less than the beam current of the preheating electron beam scanning the local area of ​​the powder bed corresponding to the geometric preheating zone.

[0018] As an optional solution, in step S30:

[0019] The defocusing of the preheated electron beam in the local region of the powder bed corresponding to the transition preheating zone of all slices within a layer m less than the layer m of the target slice decreases as the height of the slice group increases; and / or

[0020] The beam current of the preheating electron beam in the local region of the powder bed corresponding to the transition preheating zone of all slices within the layer number m that is less than the layer number m of the target slice increases with the increase of the height of the slice group to which the corresponding slice is located.

[0021] As an optional approach, in step S20, the method for fitting the corresponding geometric preheating zone based on the forming region includes:

[0022] The geometric preheating zone is obtained by adding a preheating offset distance based on the contour of the forming area.

[0023] As an optional approach, in step S20, the method for fitting the corresponding geometric preheating zone based on the forming region includes:

[0024] A preset basic graphics library is provided, which includes a variety of basic graphics.

[0025] Two basic graphics are retrieved from the basic graphics library. One of the basic graphics is set inside the forming area and serves as the inner boundary, while the other basic graphic is set outside the forming area and serves as the outer boundary. The inner boundary and the outer boundary are scaled respectively to fit the geometric preheating area. The two basic graphics may have the same or different shapes.

[0026] As an optional solution, the area within the forming area other than the preheating area is defined as the cold powder area. When performing preheating scanning on the local area of ​​the powder bed corresponding to the preheating area in each slice in step S30, the scanning path of the preheating electron beam avoids the cold powder area.

[0027] As an optional approach, in step S30, when the preheated electron beam performs a preheating scan on a local area of ​​the powder bed corresponding to the preheated area of ​​the same slice layer, a parallel line scan is used.

[0028] The scanning direction of the preheating electron beam scanning the local area of ​​the powder bed corresponding to the preheating region in the next layer slice forms a 90° angle with the scanning direction of the preheating electron beam scanning the local area of ​​the powder bed corresponding to the preheating region in the previous layer slice, wherein the next layer slice and the previous layer slice are two adjacent layers.

[0029] Electron beam selective melting methods include:

[0030] Step S100: Based on the above-mentioned electron beam selective melting powder bed preheating method, obtain the cross-sectional data of the forming area of ​​each layer slice of the part to be printed, as well as the preheating area of ​​each layer slice;

[0031] Step S200: Spread powder on a powder bed;

[0032] Step S300: Obtain the number of layers of the slice corresponding to the powder laid in step S200, retrieve the data of the preheating area corresponding to the slice layer, and perform a preheating scan on the local area of ​​the powder bed corresponding to the preheating area using a preheating electron beam.

[0033] Step S400: Obtain the number of layers of the slice corresponding to the powder laid in step S200, and retrieve the data of the forming area of ​​the slice. Based on the data of the forming area, fill the powder bed with a forming electron beam.

[0034] Step S500, repeat steps S200-S400.

[0035] As an optional solution, the area within the forming plane other than the preheated area is defined as the cold powder area. In step S400, when the powder is being formed and scanned:

[0036] Determine whether the next lower beam point of the shaped electron beam is continuous with the current lower beam point;

[0037] If not, determine whether the line connecting the current lower beam point and the next lower beam point intersects or is tangent to the boundary of the cold powder area;

[0038] If they intersect or are tangent, the jump path of the forming electron beam from the current lower beam point to the next lower beam point is set to at least two segments so that the jump path avoids the cold powder region;

[0039] If they neither intersect nor are tangent, the line connecting the current lower beam point and the next lower beam point is used as the jump path for the shaped electron beam.

[0040] The beneficial effects of this invention are:

[0041] The electron beam selective melting powder bed preheating method of the present invention includes the following steps: based on a three-dimensional model of the part to be printed, slicing the part in the height construction direction and obtaining the cross-sectional data of the forming region in each slice; constructing a preheating region corresponding to each slice, wherein the preheating region is a local area of ​​the corresponding powder bed, and the preheating region includes a geometric preheating region, which is fitted based on the shape of the corresponding forming region; and using a preheating electron beam to preheat and scan the local area of ​​the powder bed corresponding to the preheating region. In this preheating method, the preheating region of each slice is matched one by one based on the cross-sectional data of the forming region in each slice, thereby ensuring the overall forming accuracy and forming quality requirements of the variable cross-section part, and realizing the precise input of preheating energy, avoiding the input of ineffective preheating energy. Compared with the existing scheme of preheating the entire powder bed, this method not only greatly improves the forming efficiency but also significantly reduces the preheating energy consumption.

[0042] The electron beam selective melting method of the present invention, by employing the above-mentioned electron beam selective melting powder bed preheating method, can not only greatly improve the forming efficiency, but also significantly reduce the forming energy consumption. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of a three-dimensional model of part one provided in a specific embodiment of the present invention;

[0044] Figure 2 This is a cross-sectional view of part one in the height construction direction provided in a specific embodiment of the present invention;

[0045] Figure 3 These are comparison images of the forming regions of part one in the nth, n-1th, and nmth layers provided in a specific embodiment of the present invention.

[0046] Figure 4 This is a schematic diagram of the geometric preheating zone corresponding to the nm layer slice of part one fitted using the first fitting method;

[0047] Figure 5 This is a schematic diagram of the preheating region corresponding to the nm-n-1th layer slice constructed using the electron beam selective melting powder bed preheating method of the present invention;

[0048] Figure 6 This is a schematic diagram of the geometric preheating zone corresponding to the x-th layer slice of part two, which is fitted using the second fitting method.

[0049] Figure 7 This is a schematic diagram of the preheating scan of the preheating area of ​​the xth layer slice of part two using the electron beam selective melting powder bed preheating method of the present invention.

[0050] Figure 8This is a schematic diagram of the forming area of ​​the xth layer slice of part two when using the electron beam selective melting powder bed preheating method of the present invention for forming scanning.

[0051] In the picture:

[0052] 10. Part 1; 11. Forming Zone 1; 12. Preheating Zone 1; 121. Geometric Preheating Zone 1; 122. Transition Preheating Zone 1;

[0053] 20. Part Two; 21. Forming Area Two; 211. First Model; 212. Second Model; 213. Third Model; 22. Preheating Area Two; 23. Cold Powder Area Two; 24. First Jump Boundary; 25. Second Jump Boundary. Detailed Implementation

[0054] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention and not the entire structure.

[0055] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0056] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0057] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0058] In related technologies, electron beam selective melting (EBM) processes involve global preheating of the powder bed before forming scanning. However, in aerospace, energy, and other fields, annular components such as turbine guide vanes and bearing housings are characterized by hollow, thin-walled structures, complex internal and external contours, and large radial dimensions. These annular components contain large cavities that do not require forming scanning. The aforementioned method of global preheating of the powder bed consumes significant time and energy; in some cases, preheating time can account for 30% to 45% of the entire forming cycle, significantly limiting the forming efficiency and energy consumption control of EBM technology.

[0059] To address this, this embodiment provides a method for preheating an electron beam selective melting powder bed, the method comprising:

[0060] Step S10: Based on the 3D model of the part to be printed, slice the part in the height construction direction and obtain the cross-sectional data of the forming area in each slice.

[0061] Step S20: Construct the preheating area corresponding to each layer slice. The preheating area is a part of the entire forming area, corresponding to a local part of the powder bed. The preheating area includes a geometric preheating area, which is fitted based on the shape of the corresponding forming area.

[0062] Step S30: A preheated electron beam is used to perform a preheating scan on a local area of ​​the powder bed corresponding to the preheating area.

[0063] In the electron beam selective melting powder bed preheating method provided in this embodiment, the preheating area corresponding to each layer of the part is matched one by one based on the cross-sectional data of the forming area in each layer of the part. This ensures the overall forming accuracy and forming quality requirements of parts with variable cross-sections and parts with complex cross-sectional shapes. It also achieves precise input of preheating energy and avoids ineffective input of preheating energy. Compared with the prior art, where each layer of the part preheats the entire powder bed globally, this method not only greatly improves forming efficiency but also significantly reduces preheating energy consumption.

[0064] It should be noted that in this embodiment, "part" refers to the sum of all entities that need to be formed in one electron beam selective melting process. In some cases, a part is a single workpiece, and in other cases, a part is a whole composed of two or more independently set workpieces.

[0065] In some embodiments, the method for fitting the corresponding geometric preheating zone based on the forming region in step S20 includes:

[0066] A preheating offset distance is added to the contour of the forming area to obtain a geometric preheating zone.

[0067] This setup not only ensures that the preheating area can reliably cover the forming area, but also simplifies the calculation of obtaining the geometric preheating area.

[0068] like Figures 1-4 As shown below, taking the geometric preheating region of the nm-th layer slice of part 10 as an example, the direction of the above-mentioned fitted geometric preheating region will be explained in detail, where m is a positive integer greater than 2, n is a positive integer, and n > m. Specifically, the height construction direction of part 10 is as follows: Figure 2 In the Z direction, the forming area in the slice of part 10 is forming area 11, and the preheating area corresponding to the forming area in the slice of part 10 is preheating area 12, and preheating area 12 includes geometric preheating area 121. For example... Figure 4 As shown, the forming region 11 in the nm layer slice of part 10 is annular. The geometric preheating region 121 is obtained by adding a preheating offset distance to the contour of forming region 11. Geometric preheating region 121 is also annular, and the inner diameter of the annulus of geometric preheating region 121 is smaller than the inner diameter of forming region 11, while the outer diameter of the annulus of geometric preheating region 121 is larger than the outer diameter of forming region 11. It is understood that those skilled in the art can set the value of the preheating offset distance according to actual needs, and no specific limitation is made here.

[0069] For parts with varying cross-sections, there may be cases where the forming area of ​​a certain slice has an increased cross-section compared to the forming area of ​​the previous slice (hereinafter referred to as the target slice). Given this increase in the forming area compared to the previous slice, the geometric preheating zone of the target slice will inevitably also increase. When preheating a local area of ​​the powder bed corresponding to the preheating zone of the target slice, if the energy density of the preheating electron beam in the increased cross-section area is the same as the energy density of the preheating electron beam in other preheating areas, it is equivalent to directly performing a high-energy preheating scan on the cold powder area of ​​the powder. Therefore, powder blowing is likely to occur, thus affecting the forming quality of the part.

[0070] In this embodiment, the electron beam selective melting powder bed preheating method further includes step S20: obtaining a target slice based on the cross-sectional data of the forming region in each layer slice, wherein the target slice is a slice whose cross-sectional data of the forming region has an increased cross-section compared to the cross-sectional data of the forming region of the previous layer slice; taking the layer number of the target slice as a reference, setting a transition preheating zone for all slices within m layers where the layer number is less than the layer number of the target slice, wherein the size and shape of the transition preheating zone correspond to the increased cross-section of the forming region of the target slice, and the preheating zone includes a transition preheating zone and a geometric preheating zone, wherein m is a positive integer greater than or equal to 2. Furthermore, in step S30, all slices within m layers of the target slice are divided into at least two slice groups from bottom to top, each slice group including at least one slice. When performing a preheating scan on a local area of ​​the powder bed corresponding to the transition preheating zone of all slices within m layers of the target slice, the energy density of the electron beam for the preheating scan is the same for each slice within the same slice group, and the energy density of the electron beam for the preheating scan increases with the height of the slice group. It should be noted that the number of layers of the slices increases sequentially from bottom to top, and the powder corresponding to each layer of slices is also sequentially laid on the powder bed from bottom to top. Therefore, in this embodiment, "the upper layer slice" refers to the slice located below the target slice, and "all slices within m layers of the target slice" refers to all slices within m layers downwards from the target slice. In addition, the height of the slice group increases as it gets closer to the target slice.

[0071] In this embodiment, by setting transition preheating zones on m layers of slices before the target slice, and increasing the energy density gradient of the electron beam in the transition preheating zone of the m layers of slices, it is equivalent to gradually preheating the increased cross-section portion of the target slice before the formal preheating scan. This avoids the situation of directly performing high-energy preheating scans on the cold powder area, thereby significantly reducing the probability of powder blowing during the preheating process and improving the final forming quality of the part.

[0072] It is understandable that slices whose forming area does not change relative to the forming area of ​​the previous slice, and slices whose forming area has a reduced cross-section relative to the forming area of ​​the previous slice, are defined as slices that do not require transition. The preheating area of ​​all slices within the number of layers m less than the number of layers where slices do not require transition only includes the geometric preheating area and does not set a transition preheating area.

[0073] In some embodiments, during step S30, when performing preheating scanning on a local area of ​​the powder bed corresponding to the preheating region of the same slice layer: the defocusing of the preheating electron beam in the local area of ​​the powder bed corresponding to the transition preheating region is greater than the defocusing of the preheating electron beam in the local area of ​​the powder bed corresponding to the geometric preheating region; and the beam current of the preheating electron beam in the local area of ​​the powder bed corresponding to the transition preheating region is less than the beam current of the preheating electron beam in the local area of ​​the powder bed corresponding to the geometric preheating region. This ensures that the energy density of the electron beam in the local area of ​​the powder bed corresponding to the transition preheating region is less than the energy density of the electron beam in the local area of ​​the powder bed corresponding to the geometric preheating region, thereby reducing the risk of powder blowing during the preheating scanning process.

[0074] In other embodiments, it can also be configured such that when performing preheating scanning on a local area of ​​the powder bed corresponding to the preheating region of the same slice: the defocus of the preheating electron beam in the local area of ​​the powder bed corresponding to the scanning transition preheating region is greater than the defocus of the preheating electron beam in the local area of ​​the powder bed corresponding to the scanning geometric preheating region, while the beam current of the preheating electron beam in the local area of ​​the powder bed corresponding to the scanning transition preheating region is equal to the beam current of the preheating electron beam in the local area of ​​the powder bed corresponding to the scanning geometric preheating region. This can also ensure that the energy density of the electron beam in the local area of ​​the powder bed corresponding to the preheating scanning transition preheating region is less than the energy density of the electron beam in the local area of ​​the powder bed corresponding to the preheating scanning geometric preheating region.

[0075] In other embodiments, it can also be configured such that when performing preheating scanning on a local area of ​​the powder bed corresponding to the preheating region of the same slice, the defocus of the preheating electron beam in the local area of ​​the powder bed corresponding to the scanning transition preheating region is equal to the defocus of the preheating electron beam in the local area of ​​the powder bed corresponding to the scanning geometric preheating region, and the beam current of the preheating electron beam in the local area of ​​the powder bed corresponding to the scanning transition preheating region is less than the beam current of the preheating electron beam in the local area of ​​the powder bed corresponding to the scanning geometric preheating region. This can also ensure that the energy density of the electron beam in the preheating scanning transition preheating region is less than the energy density of the electron beam in the preheating scanning geometric preheating region.

[0076] In some embodiments, in step S30: the defocusing of the preheated electron beam scanning the local region of the powder bed corresponding to the transition preheated zone of all slices within m layers of the target slice decreases as the height of the slice group to which the corresponding slice belongs increases; and the beam current of the preheated electron beam scanning the local region of the powder bed corresponding to the transition preheated zone of all slices within m layers of the target slice increases as the height of the slice group to which the corresponding slice belongs increases. This configuration ensures that when preheating scanning the local region of the powder bed corresponding to the transition preheated zone of all slices within m layers of the target slice, the energy density of the preheating scan increases as the number of layers of the corresponding slice increases.

[0077] In other embodiments, the configuration can also be as follows: In step S30, the defocusing of the preheated electron beam in the local region of the powder bed corresponding to the transition preheating zone of all slices within a layer number less than m layers of the target slice decreases as the height of the slice group increases; the beam current of the preheated electron beam in the local region of the powder bed corresponding to the transition preheating zone of all slices within a layer number less than m layers of the target slice remains constant as the layer number of the corresponding slice remains constant. This configuration also ensures that when performing preheating scanning on the local region of the powder bed corresponding to the transition preheating zone of all slices within a layer number less than m layers of the target slice, the energy density of the preheating scan increases as the layer number of the corresponding slice increases.

[0078] In other embodiments, the configuration can be configured such that the defocusing of the preheated electron beam in the local region of the powder bed corresponding to the transition preheating zone of all slices within a layer number m less than the target slice remains constant as the layer number of the corresponding slice increases; while the beam current of the preheated electron beam in the local region of the powder bed corresponding to the transition preheating zone of all slices within a layer number m less than the target slice increases as the height of the slice assembly containing the corresponding slice increases. This configuration ensures that when performing preheating scanning on the local region of the powder bed corresponding to the transition preheating zone of all slices within a layer number m less than the target slice, the energy density of the preheating scan increases as the layer number of the corresponding slice increases.

[0079] like Figures 1-5 As shown, assuming that the forming region 11 of the nth layer to the (n+m)th layer slice of part 10 remains unchanged, the method for constructing the preheating region 12 corresponding to the nmth to (n-1)th layer slices of part 10 is as follows: Figure 3As shown, the forming region 11 in the nth layer slice of part 10 has a cross-sectional increase S compared to the forming region 11 in the (n-1)th layer slice. Therefore, when constructing the preheating region of the nmth to (n-1)th layer slices of part 10, as follows... Figure 5 As shown, in addition to setting the corresponding geometric preheating zone 121, a transition preheating zone 122 is also set. The transition preheating zone 122 and the geometric preheating zone 121 together constitute the preheating area 12 of the slice. The size and shape of the transition preheating zone 122 can be obtained by adding a preheating offset distance to the contour of the added part S.

[0080] This embodiment also provides another method for fitting the geometric preheating zone corresponding to the forming region in step S20, specifically:

[0081] A preset basic graphics library is provided, which includes a variety of basic graphics.

[0082] Two basic graphics are retrieved from the basic graphics library. One of the basic graphics is set inside the forming area and serves as the inner boundary, while the other basic graphic is set outside the forming area and serves as the outer boundary. The inner and outer boundaries are scaled separately to fit the geometric preheating zone.

[0083] It should be noted that the types and number of basic graphics included in the basic graphics library can be flexibly set according to actual needs. For example, the basic graphics library can be set as a collection of basic graphics such as circles, squares, rectangles, triangles, regular hexagons, and regular octagons.

[0084] It should be noted that when scaling the inner boundary, the minimum distance between the inner boundary and the inner contour of the forming area can be set to be no less than a first preset value. This first preset value can be flexibly set according to the performance requirements of the formed part, etc., and is not specifically limited here. Similarly, when scaling the outer boundary, the minimum distance between the outer boundary and the outer contour of the forming area can be set to be no less than a second preset value. This second preset value can be flexibly set according to the performance requirements of the formed part, etc., and is not specifically limited here. It is understood that the first preset value and the second preset value can be the same or different.

[0085] like Figure 6 As shown, taking the geometric preheating zone of the x-th layer slice of part 20 as an example, the fitting direction of the other geometric preheating zone mentioned above will be explained in detail. The forming region in the x-th layer slice of part 20 is forming region 21, as shown... Figure 6 As shown, the forming area 21 includes multiple models arranged at intervals. Figure 6Each solid-line box represents a model, and the entire set of all the implementation boxes constitutes the forming region of that layer slice, i.e., forming region 21. When fitting the geometric preheating region of the x-th layer slice, a circle and a regular octagon are retrieved from the basic graphics library. The circle is used as the inner boundary of the geometric preheating region, and the regular octagon is used as the outer boundary of the geometric preheating region. After appropriately scaling the circle and the regular octagon, the geometric preheating region of the x-th layer slice is obtained. Figure 6 (The dashed area in the diagram). In this embodiment, the slices within m layers upwards from the x-th slice (i.e., slices from the x+1-th to the x+m-th slices) do not have an increased cross-section. Therefore, the x-th slice does not have a transition preheating zone, and the geometric preheating zone of this slice is the preheating zone 22.

[0086] In this embodiment, in step S30, when the preheating electron beam performs a preheating scan on a local area of ​​the powder bed corresponding to the preheating region of the same layer slice, a parallel line scanning method is used. It should be noted that parallel line scanning means that within the plane of the powder bed, the entire scanning path includes multiple parallel line segments, and the arrangement direction of the line segments is perpendicular to their extension direction. Optionally, the scanning direction of the preheating electron beam scanning the local area of ​​the powder bed corresponding to the preheating region in the next layer slice forms a 90° angle with the scanning direction of the preheating electron beam scanning the local area of ​​the powder bed corresponding to the preheating region in the previous layer slice. Here, "next layer slice" and "previous layer slice" are vertically adjacent slices.

[0087] In this embodiment, the area within the forming plane excluding the preheating area is defined as the cold powder area. During step S30, when preheating scanning is performed on the local area of ​​the powder bed corresponding to the preheating area in each slice, the scanning path of the preheating electron beam avoids the cold powder area. This design prevents powder blowing during the preheating process, thereby improving the forming quality of the final part.

[0088] like Figure 7As shown, taking the preheating scan of a local area of ​​the powder bed corresponding to the preheating region 22 of the x-th layer slice of part 20 as an example, the cold powder area on the powder bed corresponding to the x-th layer slice is the cold powder area 23. During the scanning process, the scanning electron beam scans laterally, and point A is the current scanning downbeam point, and point B is the next scanning downbeam point after point A. The line connecting points A and B passes through the cold powder area, so the jump path between points A and B can be set to consist of at least two line segments, thereby preventing the preheating electron beam from passing through the cold powder area 23 and effectively preventing powder blowing. Specifically, the method can be as follows: Based on the boundary of the second cold powder region 23, the first offset distance is extended towards the second preheating region 22 to obtain the first jump boundary 24. Points C and D are selected on the first jump boundary 24. The path for the preheating electron beam to jump from the current preheating lower beam point A to the next preheating lower beam point B is set as line segment AC, arc CD, and line segment DB, thereby avoiding the scanning electron beam passing through the part corresponding to the second cold powder region 23. It should be noted that point C can be the intersection of the line connecting point A and the center O of the second cold powder region 23 with the first jump boundary 24, and point D can be the intersection of the line connecting point B and the center O of the second cold powder region 23 with the first jump boundary 24.

[0089] This embodiment also provides an electron beam selective melting method, including:

[0090] Step S100: Based on the above-mentioned electron beam selective melting powder bed preheating method, obtain the cross-sectional data of the forming area of ​​each layer slice of the part to be printed, as well as the preheating area of ​​each layer slice;

[0091] Step S200: Spread powder on a powder bed;

[0092] Step S300: Obtain the number of layers of the slice corresponding to the powder laid in step S200, retrieve the data of the preheating area corresponding to the slice layer, and perform a preheating scan on the local area of ​​the powder bed corresponding to the preheating area using a preheating electron beam.

[0093] Step S400: Obtain the number of layers of the slice corresponding to the powder laid in step S200, and retrieve the data of the forming area of ​​the slice. Based on the data of the forming area, fill the powder bed with a forming electron beam.

[0094] Step S500, repeat steps S200-S400.

[0095] The electron beam selective melting method of the present invention, by employing the above-mentioned electron beam selective melting powder bed preheating method, can not only greatly improve the forming efficiency, but also significantly reduce the forming energy consumption.

[0096] Preferably, the area within the forming area excluding the preheating area is defined as the cold powder area. In step S400, during the forming scan of the powder:

[0097] Determine whether the next lower beam point of the shaped electron beam is continuous with the current lower beam point;

[0098] If so, then directly scan the next lower beam point;

[0099] If not, determine whether the line connecting the current lower beam point and the next lower beam point intersects or is tangent to the boundary of the cold powder area;

[0100] If they intersect or are tangent, the jump path of the forming electron beam from the current lower beam point to the next lower beam point is set to at least two segments so that the jump path avoids the cold powder region;

[0101] If they neither intersect nor are tangent, the line connecting the current lower beam point and the next lower beam point is used as the jump path for the shaped electron beam.

[0102] This configuration avoids the forming electron beam passing through the cold powder zone of the powder bed, thereby further reducing the risk of powder blowing during the forming process.

[0103] It should be noted that in some embodiments, the next lower beam point and the current lower beam point belong to the same model. In other embodiments, the next lower beam point and the current lower beam point belong to different models.

[0104] like Figure 8 As shown, taking the forming region 21 in the xth layer slice of the forming scanned part 20 as an example, the path jump during the forming scan is explained. The forming region 21 in the xth layer slice includes a first model 211, a second model 212, and a third model 213 spaced apart. Specifically:

[0105] Point E is the end point of the first forming scan model 211 (i.e., the current end point), and point F is the beginning point of the second forming scan model 212 (i.e., the next end point). Points E and F are discontinuous end points, and the line connecting points E and F intersects the boundary of the second cold powder area 23. When planning the jump path, based on the boundary of the second cooling area 23, the second offset distance is extended towards the second preheating area 22 to obtain the second jump boundary 25. Points G and H are taken on the second jump boundary 25. The jump path of the forming electron beam from the current end point E to the next end point F is set as line segment EG, arc GH, and line segment HF, thereby avoiding the forming electron beam from passing through the second cold powder area 23. It should be noted that point G can be the intersection of the line connecting point E and the center O of the second cold powder area 23 with the second jump boundary 25, and point H can be the intersection of the line connecting point F and the center O of the cold powder area with the second jump boundary 25.

[0106] Point L is the end point of the lower beam in the second model 212 of the shaping scan, and point M is the beginning point of the lower beam in the third model 213 of the shaping scan. When the current lower beam point is point L, the next lower beam point is M. Point L and point M are discontinuous lower beam points, and the line connecting point L and point M does not pass through the cold powder area 23. Therefore, the line connecting the current lower beam point L and the next lower beam point M (i.e., line segment LM) can be used as the jumping path of the shaping electron beam between the second model 212 and the third model 213.

[0107] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, based on the concept of the present invention, there will be changes in specific implementation methods and application scope. The content of this specification should not be construed as a limitation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A method for preheating a powder bed using selective electron beam melting, characterized in that, include: Step S10: Based on the three-dimensional model of the part to be printed, slice the part in the height construction direction and obtain the cross-sectional data of the forming area in each slice. Step S20: Construct preheating areas corresponding to each layer of slices. The preheating area is a part of the entire forming area, corresponding to a local part of the powder bed. The preheating area includes a geometric preheating area, which is fitted based on the shape of the corresponding forming area. Obtain a target slice based on the cross-sectional data of the forming area in each layer of slices. The target slice is a slice whose cross-sectional data of the forming area has an increased cross-section compared to the cross-sectional data of the forming area of ​​the previous layer slice. Using the layer number of the target slice as a reference, set a transition preheating area for all slices whose layer number is less than m layers of the target slice. The size and shape of the transition preheating area correspond to the increased cross-sectional portion of the forming area of ​​the target slice. The preheating area includes the transition preheating area and the geometric preheating area, where m is a positive integer greater than or equal to 2. Step S30: A preheated electron beam is used to preheat and scan a local area of ​​the powder bed corresponding to the preheated region. All slices within a layer number less than the target slice (m layers) are divided into at least two slice groups from bottom to top, each slice group comprising at least one slice layer. When preheating and scanning a local area of ​​the powder bed corresponding to the transition preheated region of all slices within a layer number less than the target slice (m layers), the energy density of the electron beam used for preheating and scanning is the same for each slice within the same slice group, and the energy density of the electron beam used for preheating and scanning increases with the height of the slice group.

2. The electron beam selective melting powder bed preheating method as described in claim 1, characterized in that, In step S30, when performing a preheating scan on a local area of ​​the powder bed corresponding to the preheating region of the same slice: The defocusing of the preheating electron beam scanning a local region of the powder bed corresponding to the transition preheating zone is greater than the defocusing of the preheating electron beam scanning a local region of the powder bed corresponding to the geometric preheating zone; and / or The beam current of the preheating electron beam scanning the local area of ​​the powder bed corresponding to the transition preheating zone is less than the beam current of the preheating electron beam scanning the local area of ​​the powder bed corresponding to the geometric preheating zone.

3. The electron beam selective melting powder bed preheating method as described in claim 1, characterized in that, In step S30: The defocusing of the preheated electron beam in the local region of the powder bed corresponding to the transition preheating zone of all slices within a layer m less than the layer m of the target slice decreases as the height of the slice group increases; and / or The beam current of the preheating electron beam in the local area of ​​the powder bed corresponding to the transition preheating zone of all slices within the layer number m that is less than the layer number m of the target slice increases with the increase of the height of the slice group to which the corresponding slice is located.

4. The electron beam selective melting powder bed preheating method as described in claim 1, characterized in that, In step S20, the method for fitting the corresponding geometric preheating zone based on the forming region includes: The geometric preheating zone is obtained by adding a preheating offset distance based on the contour of the forming area.

5. The electron beam selective melting powder bed preheating method as described in claim 1, characterized in that, In step S20, the method for fitting the corresponding geometric preheating zone based on the forming region includes: A preset basic graphics library is provided, which includes a variety of basic graphics. Two basic graphics are retrieved from the basic graphics library. One of the basic graphics is set inside the forming area and serves as the inner boundary, while the other basic graphic is set outside the forming area and serves as the outer boundary. The inner boundary and the outer boundary are scaled respectively to fit the geometric preheating area. The two basic graphics may have the same or different shapes.

6. The electron beam selective melting powder bed preheating method according to any one of claims 1-5, characterized in that, The area within the forming area other than the preheated area is defined as the cold powder area. When performing preheating scanning on the local area of ​​the powder bed corresponding to the preheated area in each slice in step S30, the scanning path of the preheated electron beam avoids the cold powder area.

7. The electron beam selective melting powder bed preheating method according to any one of claims 1-5, characterized in that, In step S30, when the preheating electron beam performs preheating scanning on the local area of ​​the powder bed corresponding to the preheating area of ​​the same slice layer, parallel line scanning is used. The scanning direction of the preheating electron beam scanning the local area of ​​the powder bed corresponding to the preheating region in the next layer slice forms a 90° angle with the scanning direction of the preheating electron beam scanning the local area of ​​the powder bed corresponding to the preheating region in the previous layer slice, wherein the next layer slice and the previous layer slice are two adjacent layers.

8. An electron beam selective melting method, characterized in that, include: Step S100: Based on the electron beam selective melting powder bed preheating method according to any one of claims 1-7, obtain the cross-sectional data of the forming area of ​​each layer slice of the part to be printed, and the preheating area of ​​each layer slice; Step S200: Spread powder on a powder bed; Step S300: Obtain the number of layers of the slice corresponding to the powder laid in step S200, retrieve the data of the preheating area corresponding to the slice layer, and perform a preheating scan on the local area of ​​the powder bed corresponding to the preheating area using a preheating electron beam. Step S400: Obtain the number of layers of the slice corresponding to the powder laid in step S200, and retrieve the data of the forming area of ​​the slice. Based on the data of the forming area, fill the powder bed with a forming electron beam. Step S500, repeat steps S200-S400.

9. The electron beam selective melting method as described in claim 8, characterized in that, The area within the forming plane, excluding the preheated area, is defined as the cold powder area. In step S400, during the forming scan of the powder: Determine whether the next lower beam point of the shaped electron beam is continuous with the current lower beam point; If not, determine whether the line connecting the current lower beam point and the next lower beam point intersects or is tangent to the boundary of the cold powder area; If they intersect or are tangent, the jump path of the forming electron beam from the current lower beam point to the next lower beam point is set to at least two segments so that the jump path avoids the cold powder region; If they neither intersect nor are tangent, the line connecting the current lower beam point and the next lower beam point is used as the jump path for the shaped electron beam.

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