Additive manufacturing process

Abstract

A method of forming a build platform for a powder bed melt additive manufacturing process. The method includes directing a high energy beam at a first energy level to irradiate a bed of fusible powder and form a first layer that constructs the platform. The method further includes forming subsequent initial layers of the build platform, each subsequent layer being formed by directing a high energy beam to irradiate the distributed layer of fusible powder to form one of the subsequent initial layers of the build platform. The energy level of the high energy beam increases from the first energy level for successive layers in the subsequent initial layers. The build platform may be a sintered build platform in which the degree of sintering increases from the bottom layer toward the top layer.

Description

Technical Field

[0001] The present disclosure relates to additive manufacturing, and in particular to powder bed fusion additive manufacturing processes. Background Art

[0002] Additive manufacturing (sometimes also called 3D printing) is a process for creating objects (three-dimensional objects) by building them up one layer at a time. Powder bed fusion (PBF) is one type of additive manufacturing method (3D printing method). Typically, powder bed fusion is achieved by applying an energy source (such as a laser beam or electron beam) to fuse powdered materials on a build plate together. A recoater spreads a thin layer of powder onto a build surface (powder bed), an energy source selectively melts the material needed for that layer, and then the build plate drops down to make way for the next layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Features and advantages of the present disclosure will become apparent from the following description of various exemplary aspects as illustrated in the accompanying drawings, wherein like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements.

[0004] FIG. 1 shows a conventional configuration of a build tank for starting a powder bed fusion additive manufacturing process.

[0005] Figure 2 is a schematic diagram of a powder bed fusion additive manufacturing machine.

[0006] Figure 3 is used to start the powder bed fusion additive manufacturing process Figure 2 Schematic cross-sectional view of a portion of a build chamber of a powder bed fusion additive manufacturing machine shown in FIG.

[0007] Figure 4 Shown is a sintered build platform on which a part is formed when the build is complete using a powder bed fusion additive manufacturing process.

[0008] Figure 5 A control pattern that can be used for a high energy beam used in a powder bed fusion additive manufacturing process is shown.

[0009] Fig. 6A and 6B It is shown in the formation Figure 4 Graph of the energy level of the high energy beam when firing multiple layers of the build platform shown in FIG. Fig. 6A A first energy control method is shown, and Figure 6B A second energy control method is shown. DETAILED DESCRIPTION

[0010] Features, advantages and aspects of the present disclosure are set forth or apparent by considering the following detailed description, drawings and claims. Furthermore, the following detailed description is exemplary and is intended to provide further explanation without limiting the scope of the present disclosure as claimed.

[0011] Various aspects are discussed in detail below. Although specific aspects are discussed, this is for illustrative purposes only. Those skilled in the relevant art will recognize that other components and configurations may be used without departing from the spirit and scope of the present disclosure.

[0012] Unless otherwise specified herein, the terms "coupled," "fixed," "attached," "connected," and the like refer to both direct coupling, fixing, attachment, or connection as well as indirect coupling, fixing, attachment, or connection through one or more intermediate components or features.

[0013] The singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0014] Here and throughout the specification and claims, range limitations are combined and interchanged. Unless the context or language indicates otherwise, these ranges are identified and include all subranges contained therein. For example, all ranges disclosed herein include the endpoints, and the endpoints can be combined independently of each other.

[0015] FIG. 1 is a schematic cross-sectional view of a portion of a build chamber of an electron beam melting (EBM) machine. FIG. 1 shows a conventional configuration of a build tank 10 for starting a powder bed fusion additive manufacturing process. As described above, a high energy beam 20 (such as a laser beam or an electron beam) can be used in a powder bed fusion additive manufacturing process. The high energy beam 20 selectively radiates the fusible powder 12 in the powder bed 14 arranged on top of the workbench 16. The high energy beam 20 heats and subsequently melts a portion of the fusible powder 12 to form a layer of the part being built. The layer then cools to solidify the molten particles. Powders (such as fusible powders 12) typically have a relatively low thermal conductivity, so in order to effectively cool the molten powder, the build is typically formed on top of a relatively thick starting plate 30, which has a higher thermal conductivity than the thermal conductivity of the fusible powder 12 to dissipate the heat and solidify the molten powder. When the high energy beam 20 is an electron beam, it is also desirable to avoid the accumulation of charge in the powder bed 14. Powders, such as fusible powder 12, also have relatively low electrical conductivity, and the start plate 30, having a higher electrical conductivity than the fusible powder 12, may also effectively conduct electrons away from the powder bed 14 to avoid charge accumulation.

[0016] The use of a start plate 30 presents challenges that increase the build time of a part being manufactured using such a powder bed fusion additive manufacturing process. For example, the start plate 30 must be placed in the build tank 10, and then the start plate 30 must undergo a time-consuming leveling process before the build can begin. Once the build is complete, the part may have effectively been welded to the start plate 30, and a machining process may be required to separate the part from the start plate 30. The process discussed herein enables a powder bed fusion additive manufacturing process to be started on a powder bed without the use of a start plate 30.

[0017] Figure 2 is a schematic diagram of a powder bed fusion additive manufacturing machine 100 that can be used to implement the methods discussed herein. More specifically, the powder bed fusion additive manufacturing machine 100 discussed herein is an electron beam melting (EBM) machine. The methods and fabricated items discussed herein will be performed with reference to an EBM additive manufacturing process, but the methods and items produced thereby may also be applied to other powder bed fusion additive manufacturing processes, such as direct metal laser sintering (DMLS), selective heat sintering (SHS), selective laser melting (SLM), and selective laser sintering (SLS).

[0018] The powder bed fusion additive manufacturing machine 100 includes a build chamber 110. Located within the build chamber 110 is a build tank 120. The build tank 120 includes sidewalls 122 and a work table 124. The work table 124 can be moved in the Z direction (up and down) by a suitable movement mechanism 126 (such as a motor or actuator). During the build (process of making a part), the work table 124 will be sequentially lowered relative to a fixed point in the build chamber 110.

[0019] A bed of fusible powder 132, referred to herein as powder bed 130, is formed on a workbench 124 within the build tank 120. Suitable fusible powders 132 that can be used with the methods discussed herein include various thermoplastic polymers and metals. In a preferred embodiment, the fusible powder 132 is a fusible metal powder formed from metal particles of various metals and metal alloys. Such metals and metal alloys include, for example: titanium; titanium alloys; aluminum; aluminum alloys; stainless steel alloys; cobalt-chromium alloys; nickel-based alloys, including nickel-based superalloys; copper; copper alloys; beryllium; beryllium alloys; tungsten; tungsten alloys; iron; iron alloys, including iron aluminide; or high entropy alloys with various bases.

[0020] The fusible powder 132 may be stored in a powder hopper 142 (stock reservoir) located within the build chamber 110 on the opposite side of the build tank 120. A recoater 144 is positioned to receive or collect the fusible powder 132 from the powder hopper 142 and to move between the powder hoppers 142 on the build tank 120. Although the powder hoppers 142 are shown as being separate from the recoater 144, alternatively, one or more powder hoppers 142 may be integrally formed with the recoater 144 and move with the recoater 144. As the recoater 144 moves from one side of the build tank 120 to the other, the recoater 144 distributes a layer of fusible powder 132 on top of the workbench 124. The recoater 144 may also include a leveler 146 (such as a leveler roller or a leveler blade) that levels the fusible powder 132 on the powder bed 130 as the recoater 144 moves over the powder bed 130 and the worktable 124. Any suitable movement mechanism may be used to move the recoater 144 in the manner discussed above. For example, the recoater 144 may be movably connected to a track, and a motor moves the recoater 144 in one of the X direction or the Y direction. Figure 2 The movement in the Y direction is shown in , and the X direction is perpendicular to the Y direction and the Z direction.

[0021] The powder bed fusion additive manufacturing machine 100 includes a high energy beam source 150 that generates a high energy beam 152. In this embodiment, the high energy beam source 150 is an electron beam gun, and the high energy beam 152 is an electron beam. The electron beam gun (high energy beam source 150) can generate a focusable electron beam with an acceleration voltage of, for example, 60 kilovolts (60kV) to 120 kilovolts (120kV). The high energy beam source 150 that generates the high energy beam 152 is positioned above the build tank 120, and as will be discussed further below, the high energy beam 152 is guided to control the pattern to irradiate the distribution layer of the fusible powder 132. Various coils (such as a focusing coil (not shown), at least one deflection coil 154, and a coil for astigmatism correction (not shown)) can be used to control and guide the electron beam (high energy beam 152). As described above, the high energy beam 152 can be other suitable high energy beams, such as a laser beam. When high energy beam 152 is a laser beam, high energy beam source 150 may be a laser, and the beam may be directed by various suitable means, including, for example, a movable mirror. As will be discussed in more detail below, high energy beam 152 is directed to irradiate a distributed layer of fusible powder 132 to form sintered build platform 200 and one or more parts 230 formed thereon.

[0022] The environment within the build chamber 110 may be controlled. When an electron beam is used as the high-energy beam 152, the build chamber 110 may be a vacuum chamber capable of maintaining a vacuum environment through a vacuum system 160. Various suitable vacuum systems 160 may be used, and the vacuum system 160 may include a vacuum pump 162 (such as a turbomolecular pump, a vortex pump, or an ion pump) and one or more valves 164. Additionally or alternatively, an external gas supply (gas source 172) may be provided by one or more gas bottles fluidly connected to the build chamber 110 through a gas line 174 and a valve 176. When the valve 176 is opened, gas from the gas bottle (gas source 172) will be provided to the build chamber 110. The valve 176 may be a flow control valve that may be set to any position between fully open and fully closed to adjust the gas flow rate entering the build chamber 110. The gas in the gas source 172 may be used to control the environment in which the fusible powder 132 is melted, or to load the fusible powder 32 (or the finished three-dimensional article) with a predefined amount of gas.

[0023] The powder bed fusion additive manufacturing machine 100 also includes a controller 180. The controller 180 is configured to operate various aspects of the powder bed fusion additive manufacturing machine 100, including, for example, operating the high energy beam 152 by being electrically and operably coupled to the high energy beam source 150 and various beam control devices, such as coils for controlling the electron beam (e.g., deflection coils 154). The controller 180 is also communicatively and operably coupled to the various motors and actuators discussed herein to control the build process. For example, the controller 180 can be communicatively and operably coupled to the moving mechanism 126 and the recoater 144 of the workbench 124. In this embodiment, the controller 180 is a computing device having one or more processors 182 and one or more memories 184. The processor 182 can be any suitable processing device, including but not limited to a microprocessor, a microcontroller, an integrated circuit, a logic device, a programmable logic controller (PLC), an application specific integrated circuit (ASIC), and / or a field programmable gate array (FPGA). Memory 184 may include one or more computer-readable media including, but not limited to, non-transitory computer-readable media, computer-readable non-volatile media (eg, flash memory), RAM, ROM, hard drives, flash drives, and / or other memory devices.

[0024] The memory 184 can store information accessible by the processor 182, including computer-readable instructions that can be executed by the processor 182. The instructions can be any set of instructions or sequence of instructions that cause the processor 182 and the controller 180 to operate when executed by the processor 182. In some embodiments, the instructions can be executed by the processor 182 to cause the processor 182 to perform any operation and function that the controller 180 is constructed for, as will be further described below. The instructions can be software written in any suitable programming language or can be implemented in hardware. Additionally and / or alternatively, the instructions can be executed in logically and / or virtually separate threads on the processor 182. The memory 184 can also store data that can be accessed by the processor 182.

[0025] The technology discussed herein refers to computer-based systems, actions taken by computer-based systems, information sent to computer-based systems, and information sent from computer-based systems. Those of ordinary skill in the art will recognize that the inherent flexibility of computer-based systems allows for various possible configurations, combinations, and divisions of tasks and functions between and among components. For example, the processing discussed herein can be implemented using a single computing device or multiple computing devices working in combination. Databases, memories, instructions, and applications can be implemented on a single system, or can be distributed on multiple systems. Distributed components can operate sequentially or in parallel.

[0026] Figure 3 is a schematic cross-sectional view of a portion of a build chamber 110 of a powder bed fusion additive manufacturing machine 100 . Figure 3 The configuration of the build tank 120 for starting a powder bed fusion additive manufacturing process is shown. The workbench 124 is positioned so that the leveler 146 (see Figure 2 ) can distribute the fusible powder 132 on the workbench 124 in the build tank 120 to form a powder bed 130. Therefore, Figure 3 1 shows an initial step of the method discussed herein, more specifically, providing a bed of fusible powder 132 (powder bed 130) on a work table 124 within a build chamber 110 and a build tank 120. Compared to the conventional process shown in FIG. 1 , this step does not include providing a starting build plate (e.g., starting plate 30 shown in FIG. 1 ). Instead, the additive manufacturing process performed by the powder bed fusion additive manufacturing machine 100 forms a build platform within the powder bed fusion additive manufacturing machine 100 using the following method. This build platform will be referred to herein as a sintered build platform 200.

[0027] Figure 4The sintering build platform 200 is shown with a part 230 formed thereon when the build is complete. The sintering build platform 200 is formed of a plurality of layers, in this embodiment, including a plurality of layers referred to as initial layers 210. The initial layers 210 include a first initial layer 212. The first initial layer 212 may also be referred to herein as the bottom layer of the sintering build platform 200. The first initial layer 212 is formed by directing a high energy beam 152 to irradiate the powder bed 130 in a first control pattern. The high energy beam 152 may be controlled in a variety of different patterns and control sequences. The patterns for controlling the high energy beam 152 may be stored in the controller 180, more specifically, in the memory 184, and / or generated by the controller 180. The controller then controls the high energy beam 152 according to these instructions, such as by controlling the deflection coil 154 when the high energy beam 152 is an electron beam.

[0028] Figure 5 A control pattern that can be used to irradiate a scan area of ​​the powder bed 130 is shown. The scan area is an area of ​​the powder bed 130 scanned by the high-energy beam 152, such as an area scanned for a layer of the sintering build platform 200. In some embodiments, the high-energy beam 152 irradiates the scan area multiple times (i.e., repeated once or multiple times, referred to herein as repeats) in a control pattern to complete a layer of the sintering build platform 200. The high-energy beam 152 is scanned along a plurality of scan lines at a scanning speed. In this embodiment, each scan line is straight, and the plurality of scan lines are parallel to each other. Each scan line is separated from adjacent scan lines by a predefined line spacing. In this embodiment, the scan lines are evenly distributed with a constant line spacing between adjacent scan lines, so that the predefined line spacing is the same between each scan line. For reference, the scan lines are numbered sequentially in the control pattern, starting with the first scan line (1). The scan line adjacent to the first scan line (1) is the second scan line (2), and the remaining scan lines are numbered consecutively accordingly.

[0029] In this embodiment, the high energy beam 152 does not continuously illuminate adjacent scan lines. Instead, a different line sequence is used, such as a staggered pattern. Once the high energy beam 152 scans along the first scan line (1), several scan lines are skipped, and the next scan line illuminated by the high energy beam 152 is separated by several scan lines (line sequence). For example, using line sequence five (5) in the control pattern and a total of twenty-five scan lines, the high energy beam 152 illuminates the following lines in the first sequence: the first scan line (1), the sixth scan line (6), the eleventh scan line (11), the sixteenth scan line (16), and the twenty-first scan line (21). After the first sequence is completed, the high energy beam 152 illuminates the scan lines of the second sequence in a similar manner, starting with the second scan line (2). In this example, the high energy beam 152 illuminates the following lines in the second sequence: the second scan line (2), the seventh scan line (7), the twelfth scan line (12), the seventeenth scan line (17), and the twenty-second scan line (22). The high energy beam 152 illuminates additional scan lines of additional sequences until all scan lines in the control pattern have been scanned.

[0030] The high energy beam 152 is operated at an energy level to impart energy from the high energy beam 152 to the particles of the meltable powder 132 and heat the particles of the meltable powder 32 when the high energy beam 152 is scanned along the scan line in the above-described manner. When forming the first initial layer 212, the high energy beam 152 is at an initial energy level (E I ) (also referred to herein as the first energy level). As discussed above, the fusible powder 132 of the powder bed 130 has a relatively low thermal conductivity and a relatively low electrical conductivity. In the absence of the starting plate 30, if a relatively large amount of energy or a relatively high energy intensity is input when forming the first initial layer 212, heat and electricity may accumulate (when the high energy beam 152 is an electron beam). In order to avoid this accumulation of heat and electricity, the initial energy level (E) is relatively low compared to the energy level used to form the initial layer of the part in a traditional environment with a build plate. I ) is lower. The initial energy level (E I ) can depend on the material and, as discussed further below, can be controlled in many different ways. The initial energy level (E I More specifically, the initial energy level (E I ) can be set to input energy into the particles of the fusible powder 132 at a point where cohesion between the particles begins on a time scale that is comparable to the time it takes to scan the layer (e.g., less than three minutes). Cohesion can also be the point at which the energy input causes a change in the electrical or thermodynamic properties of the powder bed 130. Although cohesion can include other forces, this level of cohesion can include adjacent particles of the fusible powder 132 beginning to sinter together with a relatively small amount of necking between the particles.

[0031] As discussed in more detail below, the energy level of the high energy beam 152 is controlled to form the sintering build platform 200, and one or more of the following parameters may be used to control the energy level. These parameters may be controlled individually or in combination with one another. The following discussion identifies the effects of specific parameters on the energy level, and describes such effects while other parameters remain constant to emphasize the effects of the specific parameters discussed, but controlling the energy level is not limited to changing only one parameter at a time. Rather, in some embodiments, by changing multiple parameters discussed below, the energy level of the high energy beam 152 may be changed (such as increased) in a manner further discussed below, resulting in an overall change, such as an overall increase, in the energy level of the high energy beam 152.

[0032] The high energy beam 152 can be operated at a beam power over the scanning area. The energy level of the high energy beam 152 can be controlled by controlling the beam power. For example, increasing the beam power will increase the energy level, and decreasing the beam power will decrease the energy level. When the high energy beam 152 is an electron beam, the energy level of the high energy beam is controlled (e.g., increased) by controlling (increasing) the current of the electron beam. In some embodiments, the initial energy level (E I ) can be used to generate high energy beams with energy levels ranging from 3.84x10 2 W to 5.76x10 2 W.

[0033] The high energy beam 152 is scanned along each scan line at a scanning speed. Preferably, the scanning speed is constant for each scan line, and the energy level of the high energy beam 152 can be controlled by controlling the scanning speed in combination with the beam power. For a constant beam power, increasing the scanning speed will reduce the intensity of the energy imparted to the fusible powder 132, while reducing the scanning speed will increase the intensity of the energy imparted to the fusible powder 132. Relatedly, the energy level of the high energy beam 152 can also be controlled by controlling the linear energy of the high energy beam 152. The linear energy of the high energy beam 152 is based on the beam power and the scanning speed. The linear energy can be increased by increasing the beam power, reducing the scanning speed, or both. Conversely, the linear energy can be reduced by reducing the beam power, increasing the scanning speed, or both. In some embodiments, the initial energy level (E I ) can be scanned at a speed from 53m / s to 80m / s, and the initial energy level (E I )'s high energy beam 152 can have a linear energy ranging from 5.83 J / m to 8.60 J / m.

[0034] The high energy beam 152 has a spot diameter (or spot size). The spot diameter measures the size of the area of ​​the meltable powder 132 irradiated by the high energy beam 152 at a given moment. The spot diameter can be defined as the maximum distance between two points on the surface of the meltable powder 132 that receive radiation from the high energy beam 152 in a given situation. Alternatively, the spot diameter can be defined as the maximum distance between two points on the surface of the meltable powder 132 that receive at least a predetermined portion of the total intensity imparted by the high energy beam 152 in a given situation. For a constant beam power, increasing the spot diameter will reduce the intensity of the energy imparted to the meltable powder 132, while reducing the spot diameter will increase the intensity of the energy imparted to the meltable powder 132. Relatedly, the energy level of the high energy beam 152 can also be controlled by controlling the local heat flux of the high energy beam 152. The local heat flux of the high energy beam 152 is based on the spot diameter and the scanning speed. The local heat flux can be increased by increasing the beam power, reducing the spot diameter, or both. Conversely, the local heat flux can be reduced by reducing the beam power, increasing the spot diameter, or both. In some embodiments, the initial energy level (E I The spot diameter of the high energy beam 152 can be from 3.88x10 -4 m to 5.82x10 -4 m, and the initial energy level (E I ) can be increased from 2.08x10 9 W / m 2 to 3.12x10 9 W / m 2 .

[0035] As described above, the high energy beam 152 can operate over a scan area with a beam power. The scan area can also have an area or size, referred to herein as a scan area. The scan area can be the area scanned in one repetition. The energy level of the high energy beam 152 can also be controlled by controlling the scan area in conjunction with the beam power. For a constant beam power, increasing the scan area will reduce the intensity of the energy imparted to the fusible powder 132, while reducing the scan area will increase the intensity of the energy imparted to the fusible powder 132. Relatedly, the energy level of the high energy beam 152 can also be controlled by controlling the global heat flux of the high energy beam 152. The global heat flux of the high energy beam 152 is based on the scan area and the scan speed. The global heat flux can be increased by increasing the beam power, reducing the scan area, or both. Conversely, the global heat flux can be reduced by reducing the beam power, increasing the scan area, or both. In some embodiments, the initial energy level (E I ) can be increased from 8.72x10 3 W / m 2 to 1.31x10 4 W / m 2 .

[0036] The energy level of the high energy beam 152 can also be controlled by controlling the total amount of energy deposited on a given layer. The total amount of energy deposited can be based on the above parameters and can therefore be controlled using the above parameters. As described above, the high energy beam 152 can be irradiated multiple times in a controlled pattern over a scan area to complete a layer, which is referred to herein as a repeat. The total amount of energy deposited on a given layer can also be controlled by changing the number of repeats. Increasing the number of repeats will increase the total amount of energy deposited on a given layer, and decreasing the number of repeats will decrease the total amount of energy deposited on a given layer. In some embodiments, the above parameters are constant within a single repeat and can be the same for each repeat, but in other embodiments these parameters can be different between repeats. In some embodiments, the total energy of the first initial layer 212 can be varied from 3.37x10 3 J to 5.05x10 3 J.

[0037] After the first initial layer 212 is completed, the controller 180 lowers the workbench 124 by a predetermined distance, and the recoater 144 distributes a layer of fusible powder 132 on the first initial layer 212 (previous layer) and the top of the workbench 124. Then, the high-energy beam 152 is directed to irradiate the distributed layer of fusible powder 132 in a manner similar to that described above to form a second layer of the initial layer 210 of the sintering build platform 200. When forming the second layer of the initial layer 210, the high-energy beam 152 is directed to irradiate (scan) the distributed layer of fusible powder 132 with a second control pattern. The second control pattern can be the same as the first control pattern described above. Then, the process is repeated for each subsequent layer of the initial layer 210 until the uppermost initial layer 214 of the initial layer 210.

[0038] Fig. 6A and Figure 6B 2 is a graph showing the energy level of the high energy beam 152 when forming multiple layers of the sintering build platform 200. As described above, the first initial layer 212 is used at the initial energy level (E I ) is formed by the high energy beam 152 operated under the initial energy level (E I ) is formed because the amount of cohesion in the initial layer does not increase the thermal conductivity and electrical conductivity to displace the energy required to melt and solidify the fusible powder 132 during part manufacturing. A higher level of bonding between particles (such as a degree of sintering or a degree of cohesion) is required so that the sintering build platform 200 has sufficient thermal conductivity and electrical conductivity to form a part. When forming the subsequent initial layer 210, the energy level of the high energy beam 152 increases from the first energy level (E) to the next energy level (E) for the successive layers of the subsequent initial layer 210. I ) is increased. The energy level of the high energy beam 152 is increased to the maximum sintering platform energy level (E Max ), and the high energy beam 152 creates a platform energy level (E Max) irradiates the distributed powder layer to form an uppermost initial layer 214.

[0039] Fig. 6A The energy level of the high energy beam 152 is shown as being changed from the first energy level (E I ) increases to the maximum sintering platform energy level (E Max ) is a first energy control method. In this method, the energy level of the high energy beam 152 is increased incrementally for each successive layer of the subsequent initial layer 210. Fig. 6A In the method shown, each subsequent initial layer 210 has a higher energy level than the energy level of the previous layer, and the energy level gradually increases between levels to form a steady rate of energy increase. The rate of energy level increase is preferably set to avoid so-called smoke formation, which may be caused by the accumulation of charges that repel particles of the fusible powder 132 when the high energy beam 152 is an electron beam. In addition, the rate of energy level increase is preferably set to avoid the accumulation of thermal gradients or stress gradients that may cause cracking, warping, or other dimensional changes in the sintered build platform 200. For example, the thickness of each layer can be from thirty microns (30 μm) to one hundred and fifty microns (150 μm). Preferably, the energy level is set to maintain the flatness of each layer at a level that does not exceed the thickness of each layer.

[0040] In this embodiment, the energy level increases linearly, and more specifically, increases straightly, but the linear increase is not limited to a constant (or stable) energy increase rate, nor is the linear increase limited to a straight line increase, and may include a curved line increase.

[0041] Figure 6B The energy level of the high energy beam 152 is shown as being changed from the first energy level (E I ) increases to the maximum burning structure building platform energy (E Max ) is a second energy control method. Figure 6B 1 , the energy levels of successive layers of the initial layers 210 are increased in a stepwise manner, wherein the initial layers 210 include a plurality of groups of subsequent initial layers. As used herein, a group is a plurality of adjacent layers that, in the depicted embodiment, are irradiated with an energy level of the high energy beam 152 that is the same for each layer of the group. In this embodiment, the energy level of the high energy beam 152 is incrementally increased for each successive group in the plurality of groups of subsequent initial layers 210. For example, the energy level may be gradually increased by a constant increment between each successive group in the plurality of groups of subsequent initial layers 210, but other methods, such as a method for a curved increase in the energy level for each successive group in the plurality of groups of subsequent initial layers 210, may be employed.

[0042] In Fig. 6A and Figure 6BWhen the energy level of the high energy beam 152 is controlled in the manner shown, the fusible powder 132 is gradually sintered to form the initial layer 210. When the initial layer 210 is formed, the degree of cohesion and bonding (such as necking) between adjacent particles of the fusible powder 132 within the layer and between adjacent layers gradually increases from the first initial layer 212 to the uppermost initial layer 214.

[0043] Preferably, the build platform formed using the methods discussed herein is a sintered build platform 200 in which particles of fusible powder 132 are sintered to each other. By maintaining sintered build platform 200 (including initial layer 210) in a sintered state, sintered build platform 200 is more easily removed from subsequently manufactured part 230 (see Figure 4 ). Fusible powder 132 has a melting temperature, and as will be discussed further below, part 230 may be fabricated by selectively heating fusible powder 132 to a temperature above the melting temperature of fusible powder 132 to melt fusible powder 132, and then solidifying the melted fusible powder 132 to form a layer of part 230. Thus, the maximum sintering build plateau energy level (E Max ) may be an energy level at which the fusible powder 132 is maintained at a temperature lower than the melting temperature of the fusible powder 132 so that particles of the fusible powder 132 are sintered without melting. However, if desired, the solidification and formation of the solid upper layer of the initial layer 210 and thus the maximum sintering construction platform energy level (E Max ) can be increased to the energy level used to form the part 230. As will be discussed further below, the part 230 can be formed by at least one preheat scan, such as when the high energy beam 152 is an electron beam, and the maximum firing build plateau energy level (E Max ) may be the same energy level or a similar energy level as the energy level of the high energy beam 152 used in one of the preheat steps, such as the second preheat energy level when two preheat scans are used.

[0044] Return to reference Figure 4, the sintered build platform 200 may also include additional layers beyond the initial layer 210. In this embodiment, the sintered build platform 200 includes multiple layers referred to as bulk layers 220. The bulk layers 220 are formed after the subsequent initial layers 210, and in this embodiment, the uppermost initial layer 214 may also be the first layer of the bulk layers 220. The bulk layers 220 may be formed in the same manner as the subsequent initial layers 210, as discussed above. The bulk layers 220 add additional volume or thickness to the sintered build platform 200. As discussed above, the degree of sintering of the fusible powder 132 gradually increases in the initial layer 210 of the sintered build platform 200 to a point where the sintered fusible powder 132 provides good thermal and electrical conductivity. The fusible powder 132 of the bulk layer 220 is preferably sintered at the same or similar degree of sintering as the uppermost initial layer 214 to provide the ability for heat and charge transfer, as well as a stable surface on which to build the part 230. Bulk layer 220 may also be used for thermal management when building part 230. Bulk layer 220 may provide energy storage or heat capacity, and if the thermal mass of sintering build platform 200 is too small, thermal management when forming part 230 will be unstable, so bulk layer 220 may be used to help maintain a stable build temperature for part 230. In some embodiments, the total thickness of bulk layer 220 may be thicker than the total thickness of initial layer 210.

[0045] In this embodiment, the energy level of the high energy beam 152 is the same for each volume layer 220 and is referred to herein as the volume energy level (E B ).exist Fig. 6A and Figure 6B In the energy control method shown, the body energy level (E B ) and the maximum burning structure building platform energy (E Max ) are the same. A plurality of bulk layers 220 are formed, thereby forming a top layer 222 of the sintered build platform 200. The uppermost initial layer 214 is a bottom layer of the bulk layer 220. Therefore, the sintered build platform 200 includes a plurality of layers, including a bottom layer (first initial layer 212) and a top layer 222. Each layer includes sintered particles, and the degree of sintering increases from the bottom layer (first initial layer 212) to the top layer 222. More specifically, in this embodiment, the degree of sintering gradually increases from the bottom layer (first initial layer 212) to the middle layer (uppermost initial layer 214), and the degree of sintering is constant from the middle layer (uppermost initial layer 214) to the top layer 222.

[0046] In addition, if Figure 4As shown, one or more parts 230 can be formed on top of the sintering build platform 200, and more specifically, on top of the top layer 222. When the bulk layer 220 is omitted, the uppermost initial layer 214 can be the top layer 222 on which the one or more parts 230 are formed. After the sintering build platform 200 is formed, the controller 180 lowers the work table 124 a predetermined distance, and the recoater 144 distributes a layer of fusible powder 132 on the top layer 222 and the top of the work table 124. Then, the high energy beam 152 is directed to irradiate the distributed layer of fusible powder 132 in a controlled pattern (third control pattern) to form a first layer of the part. The high energy beam 152 can be directed to the distributed layer of fusible powder 132 in a staggered control pattern (similar to the pattern discussed above), but in some cases, the high energy beam 152 selectively irradiates the fusible powder 132 along the scan line to achieve the desired part 230 geometry. At least one scan of the scan line includes irradiating the fusible powder 132 at a melting energy level (E F ) scans the fusible powder 132. The melting energy level (E F ) is an energy level that raises the temperature of the meltable powder 132 under irradiation to a temperature that is higher than the melting temperature of the meltable powder 132 and is sufficient to impart sufficient heat to selectively melt the particles of the meltable powder 132.

[0047] For the scan line, the high energy beam 152 may be directed to irradiate the distribution layer of the meltable powder 132 multiple times at different energy levels. For example, when the high energy beam 152 is an electron beam, the high energy beam 152 may be used to preheat the meltable powder 132 before it melts, such as by irradiating the meltable powder 132 with at least one preheat scan at a preheat energy level. In some embodiments, two preheat scans may be used at a first preheat energy level and a second preheat energy level. The first preheat energy level and the second preheat energy level may be different from each other and may both be less than the melting energy level (E F Using a preheat scan helps avoid F ) during the melting scan. As discussed above, the energy level (E B ) and the maximum sintering structure platform energy level (E Max ) may be the same or similar to the preheating energy level (such as the second preheating energy level).

[0048] Subsequent part layers are then formed by similar processing. After the first part layer is completed, the controller 180 lowers the workbench 124 by a predetermined distance, and the recoater 144 distributes a layer of fusible powder 132 on the first part layer (previous layer) and the top of the workbench 124. The high-energy beam 152 is then directed in a manner similar to the first part layer described above to irradiate the distributed layer of fusible powder 132, thereby forming the second layer of the part 230. The process is then repeated for each subsequent layer of the part 230. For the second part layer and other subsequent part layers, the molten portion of the subsequent layer can be bonded to the molten portion of the previous layer. The molten portions in the subsequent layer and the previous layer can be melted together by not only melting the fusible powder 132, but also remelting at least a portion of the thickness of the layer directly below the fusible powder 132.

[0049] Once part 230 is completed, part 230 and sintered build platform 200 can be removed from build chamber 110, and part 230 is separated from sintered build platform 200. With the sintered build platform 200 discussed herein, part 230 can be easily separated from sintered build platform 200. Unlike solid starting plate 30 (FIG. 1), sintered build platform 200 formed herein includes only sintered particles, and thus sintered build platform 200 can be easily recycled for subsequent use as fusible powder 132.

[0050] The following table provides an example of a sintered build platform 200 formed using the methods discussed herein. The sintered build platform 200 is formed using an electron beam powder bed fusion additive manufacturing machine 100, and more specifically, using a Swedish The sintered build platform 200 is formed using Ti6Al4V (grade 5) having a particle side distribution of 45 microns to 106 microns as the fusible powder 132.

[0051] The burning structure construction platform 200 is used Figure 6B The energy control method shown in is formed using multiple groups of initial layers 210. Seven groups of initial layers 210 are shown in Table 1 below. Maximum sintering platform energy (E Max ) is layer group 7, and the maximum sintering structure is used to build the platform energy (E Max ) forms a plurality of body layers 220.

[0052] Table 1

[0053]

[0054] Further aspects of the disclosure are provided by the subject matter of the following clauses.

[0055] A method for forming a build platform for a powder bed fusion additive manufacturing process. The method includes providing a fusible powder bed on a workbench within a build chamber, and directing a high energy beam in a first control pattern to irradiate the fusible powder bed and form a first layer of the build platform. The high energy beam operates at a first energy level to form the first layer of the build platform. The method also includes forming subsequent initial layers of the build platform. Each subsequent layer is formed by the following steps: lowering the workbench a predetermined distance; distributing a layer of fusible powder on the workbench; and directing the high energy beam to irradiate the distributed layer of fusible powder in a second control pattern to form one of the subsequent initial layers of the build platform. For successive layers in the subsequent initial layers, the high energy beam operates at a second energy level that increases from the first energy level.

[0056] A method as in the preceding clause, wherein the step of providing the fusible powder bed on the build platform within a build chamber does not include providing a starting build plate.

[0057] The method of any preceding clause, further comprising controlling an energy level of the high energy beam to gradually sinter the fusible powder to form a sintered build platform.

[0058] A method as claimed in any preceding clause, wherein the fusible powder is a fusible metal powder.

[0059] A method as in any preceding clause, wherein the subsequent initial layers comprise a plurality of groups of subsequent initial layers, and wherein for each successive group of the plurality of groups of subsequent initial layers, the energy level of the high energy beam is incrementally increased.

[0060] The method of any preceding clause, wherein the fusible powder has a melting temperature, and wherein the energy level of the high energy beam is increased incrementally from the first energy level to a maximum sintering build plateau energy. The maximum sintering build plateau energy is an energy level that maintains the fusible powder at a temperature below the melting temperature of the fusible powder.

[0061] A method as in any preceding clause, wherein the high energy beam has a beam power, and wherein the energy level of the high energy beam is controlled by controlling the beam power.

[0062] The method of any preceding clause, wherein directing the high energy beam to form the first and subsequent initial layers of the building platform comprises scanning the high energy beam at a scanning speed, and controlling an energy level of the high energy beam by controlling the scanning speed.

[0063] A method as in any preceding clause, wherein the high energy beam has a spot diameter, and an energy level of the high energy beam is controlled by controlling the spot diameter of the high energy beam.

[0064] A method according to any preceding clause, wherein the energy level of the high energy beam is controlled by controlling the line energy.

[0065] A method according to the preceding clause, wherein the high energy beam has a beam power, wherein directing the high energy beam to form the first layer and the subsequent initial layers of the building platform includes scanning the high energy beam at a scanning speed, and wherein the line energy is a function of the beam power and the scanning speed.

[0066] A method as in any preceding clause, wherein the energy level of the high energy beam is controlled by controlling a local heat flux of the high energy beam.

[0067] A method as in the preceding clause, wherein the high energy beam has a beam power and a spot diameter, and wherein the local heat flux is a function of the beam power and the spot diameter.

[0068] A method as in any preceding clause, wherein the energy level of the high energy beam is controlled by controlling a global heat flux of the high energy beam.

[0069] A method as in any preceding clause, wherein the energy level of the high energy beam is controlled by controlling the total energy deposited on the layer.

[0070] A method as in any preceding clause, wherein the energy level of the high energy beam is controlled by controlling the number of repetitions.

[0071] The method of the preceding clause, wherein the high energy beam has a beam power, wherein directing the high energy beam to form the first layer and the subsequent initial layers of the building platform comprises scanning the high energy beam over a scan area, and wherein the global heat flux is a function of the beam power and the scan area.

[0072] A method as in any preceding clause, wherein the energy level of the high energy beam is controlled by controlling the number of repetitions.

[0073] A method according to any preceding clause, wherein the energy level of the high energy beam is controlled by controlling the beam power, the scanning speed, the spot diameter of the high energy beam, the scanning area, the number of repetitions, or any combination thereof.

[0074] A method as in any preceding clause, wherein the energy level of the high energy beam is controlled by controlling the linear energy, the local heat flux, the global heat flux, or any combination thereof.

[0075] A method as in any preceding clause, wherein the high energy beam is an electron beam.

[0076] A method as in any preceding clause, wherein the electron beam has an electric current and the energy level of the high energy beam is increased by increasing the electric current of the electron beam.

[0077] A method as in any preceding clause, wherein for each successive layer of said subsequent initial layers, the energy level of said high energy beam is incrementally increased.

[0078] A method as in any preceding clause, wherein for each successive layer in the subsequent initial layers, the energy increases linearly.

[0079] A method as in any preceding clause, wherein for each successive layer in the subsequent initial layers, the energy is increased at a constant rate of energy increase.

[0080] A method as in any preceding clause, wherein each of the first control pattern and the second control pattern comprises scanning the high energy beam along a plurality of scan lines at a scan speed, the scan lines being straight.

[0081] A method as in any preceding clause, wherein each of the plurality of scan lines are parallel to each other.

[0082] A method as in any preceding clause, wherein each of the plurality of scan lines is evenly distributed with a predefined line spacing.

[0083] The method of any preceding clause, further comprising forming bulk layers of the build platform, the bulk layers being formed after the subsequent initial layers. Each bulk layer is formed by the following steps: lowering the workbench a predetermined distance; distributing a layer of fusible powder on the workbench; and directing the high energy beam at a bulk energy level to irradiate the distributed layer of fusible powder in a second control pattern, thereby forming one of the bulk layers of the build platform.

[0084] A method as in any preceding clause, wherein the fusible powder has a melting temperature and the bulk energy level is an energy level that maintains the fusible powder at a temperature below the melting temperature of the fusible powder.

[0085] A method as in any preceding clause, wherein, for successive ones of said subsequent initial layers, an energy level of said high energy beam is incrementally increased from said first energy level to said bulk energy level.

[0086] A method of forming a part using a powder bed fusion additive manufacturing process. The method comprises: forming the build platform according to the method described in any of the preceding clauses; lowering the workbench including the build platform by a predetermined distance; distributing a layer of fusible powder on the workbench and the build platform; directing a high energy beam at a melting energy level to irradiate the distributed layer of fusible powder in a third control pattern to form a first part layer of the part; and forming subsequent part layers. Each subsequent part layer is formed by the following steps: lowering the workbench by a predetermined distance; distributing a layer of fusible powder on the workbench and the build platform; and directing the high energy beam at the melting energy level to irradiate the distributed layer of fusible powder in a fourth control pattern, thereby forming one of the subsequent part layers of the part.

[0087] A method of forming a part according to the preceding clause, wherein, for successive ones of said subsequent initial layers, said energy level of said high energy beam is gradually increased from said first energy level to an energy level less than said melting energy level.

[0088] A method of forming a part according to any preceding clause, wherein the fusible powder has a melting temperature, the melting energy level being an energy level that raises the temperature of the fusible powder under irradiation to a temperature above the melting temperature of the fusible powder.

[0089] A method of forming a part as described in any preceding clause, further comprising directing said high energy beam at a preheating energy level to irradiate said layer of fusible powder distributed in a fifth control pattern before directing said high energy beam at said melting energy level.

[0090] The method of forming a part according to the preceding clause, wherein the energy level of the high energy beam is incrementally increased from the first energy level to a maximum sintering build plateau energy, and the maximum sintering build plateau energy is the same as the preheating energy level.

[0091] A method of forming a part according to any preceding clause, further comprising removing the build platform and the part formed thereon from the build chamber and separating the build platform from the part.

[0092] A method of forming a part according to any preceding clause, further comprising recovering the build platform after separating the part from the build platform.

[0093] A sintered build platform for use in a powder bed fusion additive manufacturing process formed according to the method of any preceding clause.

[0094] A sintering building platform for powder bed fusion additive manufacturing process. The sintering building platform includes multiple layers, and the multiple layers include a bottom layer and a top layer. Each layer includes sintered particles, and the degree of sintering increases from the bottom layer to the top layer.

[0095] A sintered construction platform according to any preceding clause, wherein the degree of sintering increases progressively for each successive layer.

[0096] A sintered construction platform according to any preceding clause, wherein the layer comprises a plurality of groups of layers, the sintering degree is the same for each group, and the sintering degree increases incrementally from the bottom layer to the top layer for each successive group of the plurality of groups of layers.

[0097] A sintered build platform according to any preceding clause, further comprising a plurality of layers that together form an initiation layer and a plurality of layers that together form a bulk layer.

[0098] A sintered construction platform according to any preceding clause, wherein each of the bulk layers has the same degree of sintering.

[0099] A sintered construction platform according to any preceding clause, wherein the sintering degree gradually increases from the bottom layer to the middle layer, and the sintering degree is constant from the middle layer to the top layer.

[0100] A sintered construction platform according to the preceding clause, wherein the total thickness of the bulk layer is thicker than the total thickness of the initial layer.

[0101] A method of forming a part using a powder bed fusion additive manufacturing process. The method comprises: distributing a layer of fusible powder on a sintering build platform according to any preceding clause; directing a high energy beam at a melting energy level to control the pattern irradiation distribution of the layer of fusible powder, thereby forming a first part layer of the part; and forming subsequent part layers. The sintering build platform is positioned on a workbench in a build chamber. Each subsequent part layer is formed by the following steps: lowering the workbench a predetermined distance; distributing a layer of fusible powder on the workbench and the build platform; and directing the high energy beam at the melting energy level to control the pattern irradiation distribution of the layer of fusible powder, thereby forming one of the subsequent part layers of the part.

[0102] A method of forming a part according to the preceding clause, wherein the sintered build platform is formed using a method of forming a build platform according to any preceding clause.

[0103] Although the foregoing description is directed to preferred aspects, other variations and modifications will be apparent to those skilled in the art and may be made without departing from the spirit or scope of the present disclosure. In addition, features described in conjunction with one aspect may also be used in conjunction with other aspects, even if not explicitly stated above.

Claims

1. A method of forming a build platform for a powder bed fusion additive manufacturing process, characterized in that The method comprises: Providing a fusible powder bed on a workbench within the build chamber; directing a high energy beam in a first control pattern to irradiate the fusible powder bed and form a first layer of the building platform, the high energy beam operating at a first energy level to form the first layer of the building platform; and Subsequent initial layers of the build platform are formed, each subsequent layer being formed by the following steps: lowering the workbench by a predetermined distance; spreading a layer of fusible powder on the table; and directing the high energy beam to irradiate the distributed layer of fusible powder in a second control pattern to form one of the subsequent initial layers of the building platform, Wherein for successive layers in the subsequent initial layers, the high energy beam is operated at a second energy level, the second energy level being increased from the first energy level.

2. The method according to claim 1, characterized in that The method further includes controlling the energy level of the high energy beam to gradually sinter the fusible powder to form a sintered build platform.

3. The method according to claim 1, characterized in that: in, The fusible powder is a fusible metal powder.

4. The method according to claim 1, characterized in that in, The subsequent initial layers include a plurality of sets of subsequent initial layers, and Wherein for each successive group in the plurality of subsequent initial layers, the energy level of the high energy beam is incrementally increased.

5. The method according to claim 1, characterized in that in, The fusible powder has a melting temperature, and The energy level of the high energy beam is increased incrementally from the first energy level to a maximum sintering platform energy level, and the maximum sintering platform energy level is an energy level that maintains the fusible powder at a temperature lower than the melting temperature of the fusible powder.

6. The method according to claim 1, characterized in that in, For each successive layer in the subsequent initial layers, the energy level of the high energy beam is incrementally increased.

7. The method according to claim 1, characterized in that in, The high energy beam has a beam power, and the energy level of the high energy beam is controlled by controlling the beam power.

8. The method according to claim 1, characterized in that: in, Directing the high energy beam to form the first layer and the subsequent initial layers of the building platform includes scanning the high energy beam at a scanning speed, and controlling an energy level of the high energy beam by controlling the scanning speed.

9. The method according to claim 1, characterized in that: in, The high energy beam has a spot diameter, and the energy level of the high energy beam is controlled by controlling the spot diameter of the high energy beam.

10. The method according to claim 1, characterized in that in, The energy level of the high energy beam is controlled by controlling the number of repetitions.

Images