Additive manufacturing process

Abstract

To provide a method of forming a build platform for a powder bed fusion additive manufacturing process.SOLUTION: The method incudes directing a high-energy beam at a first energy level to irradiate a bed of fusible powder and to form a first layer of the build platform. The method also includes forming subsequent initial layers of the build platform, each subsequent layer being formed by directing the high-energy beam to irradiate a distributed layer of the fusible powder to form one of the subsequent initial layers of the build platform. The energy level of the high-energy beam is increased from the first energy level for successive layers of the subsequent initial layers. The build platform may be a sintered build platform where the degree of sintering increases from the bottom layer toward the top layer.SELECTED DRAWING: Figure 6A

Description

[Technical Field]

[0001] This invention relates to additive manufacturing, particularly powder bed melting additive manufacturing processes. [Background technology]

[0002] Additive manufacturing, sometimes called 3D printing, is the process of creating objects (three-dimensional objects) by building them one layer at a time. Powder bed fusion (PBF) is a type of additive manufacturing method (3D printing method). Generally, powder bed fusion works by applying an energy source, such as a laser beam or electron beam, to melt the powder material on a build plate together. The recoater spreads a thin layer of powder across the build surface (powder bed), the energy source selectively melts the material required for that layer, and then the build plate descends for the next layer. [Overview of the project] [Means for solving the problem]

[0003] One aspect of the present disclosure is a method for forming a build platform for a powder bed melt addition manufacturing process, comprising: providing a bed of fusible powder on a worktable in a build chamber; irradiating the bed of fusible powder with a high-energy beam in a first control pattern to form a first layer of the build platform; the high-energy beam being operated at a first energy level to form the first layer of the build platform and forming subsequent initial layers of the build platform; each subsequent layer being formed by lowering the worktable by a predetermined distance and distributing the layer of fusible powder on the worktable; irradiating the distributed layer of fusible powder with a high-energy beam in a second control pattern to form one of the subsequent initial layers of the build platform, wherein the high-energy beam being operated at a second energy level increasing from the first energy level for consecutive layers of the subsequent initial layers. [Brief explanation of the drawing]

[0004] [Figure 1] This shows a conventional build tank configuration for initiating a powder bed melting addition process. [Figure 2] This is a schematic diagram of a powder bed melting addition manufacturing machine. [Figure 3] Figure 2 shows a schematic cross-sectional view of a portion of the build chamber of a powder bed melting additive manufacturing machine used to initiate the powder bed melting additive manufacturing process. [Figure 4] This shows a sintered build platform with a portion formed on it upon completion of a build using a powder bed melting addition process. [Figure 5] This shows a control pattern that can be used for high-energy beams in powder bed melting addition processes. [Figure 6A] Figure 4 is a graph showing the energy levels of the high-energy beam when forming multiple layers of the sintered build platform, illustrating the first energy control method. [Figure 6B] Figure 4 is a graph showing the energy levels of the high-energy beam when forming multiple layers of the sintered build platform, illustrating the second energy control method. [Modes for carrying out the invention]

[0005] The features and advantages of this disclosure are evident from the following description of various exemplary embodiments, as shown in the accompanying drawings, and similar reference numerals generally indicate identical, functionally similar, and / or structurally similar elements.

[0006] The features, advantages, and aspects of this disclosure are described or revealed by the following detailed description, drawings, and claims. Furthermore, the following detailed description is illustrative and intended to provide further explanation without limiting the scope of the claimed disclosure.

[0007] Various embodiments are described in detail below. Certain embodiments are discussed, but this is for illustrative purposes only. Those skilled in the art will recognize that other components and configurations may be used without departing from the spirit and scope of this disclosure.

[0008] Unless otherwise specified herein, terms such as “joined,” “fixed,” “attached,” and “connected” refer to both direct joining, fixing, attachment, or connection via one or more intermediate components or features, as well as indirect joining, fixing, attachment, or connection.

[0009] The singular form "one" or "one" usually refers to multiple things unless the context clearly indicates otherwise.

[0010] Herein, and throughout this specification and the claims, the limitations of scope are combined and interchangeable. Such scopes are identified and include all sub-scopes contained therein, unless the context or expression indicates otherwise. For example, all scopes disclosed herein include endpoints, which are independently combinable with respect to one another.

[0011] Figure 1 is a schematic cross-sectional view of a portion of the build chamber of an electron beam melting (EBM) machine. Figure 1 shows a conventional configuration of a build tank 10 for initiating a powder bed melting addition process. As described above, a high-energy beam 20, such as a laser beam or an electron beam, may be used in the powder bed melting addition process. The high-energy beam 20 selectively irradiates fusible powder 12 placed in a powder bed 14 above a worktable 16. The high-energy beam 20 heats and then melts a portion of the fusible powder 12 to form a layer of the part to be built. This layer is then cooled to solidify the molten particles. Powders such as fusible powder 12 typically have relatively low thermal conductivity, and therefore, in order to efficiently cool the molten powder, the build is conventionally formed on a relatively thick start plate 30, which has a higher thermal conductivity than the fusible powder 12, dissipates heat, and solidifies the molten powder. When the high-energy beam 20 is an electron beam, it is also desirable to avoid charge accumulation in the powder bed 14. The powder, such as the fusible powder 12, also has relatively low conductivity, and the start plate 30, which has higher conductivity than the fusible powder 12, can also effectively guide electrons from the powder bed 14 to avoid charge accumulation.

[0012] The use of a starter plate 30 presents the challenge of increasing the build time of parts manufactured using such a powder bed melting addition process. For example, the starter plate 30 must be placed in the build tank 10, and then the starter plate 30 must undergo a time-consuming leveling process before the build begins. Once the build is complete, the parts may be effectively welded to the starter plate 30, and a machining process may be required to separate the parts from the starter plate 30. The method described herein makes it possible to start a powder bed melting addition process on a powder bed without using a starter plate 30.

[0013] Figure 2 is a schematic diagram of a powder bed melting addition machine 100 that may be used to carry out the methods discussed herein. More specifically, the powder bed melting addition machine 100 described herein is an electron beam melting (EBM) machine. The methods and products discussed herein are described with reference to the EBM (electron beam melting) addition build process, but these methods and products can also be applied to other powder bed melting addition build processes such as direct metal laser sintering (DMLS), selective thermal sintering (SHS), selective laser melting (SLM), and selective laser sintering (SLS).

[0014] The powder bed melting additive manufacturing machine 100 includes a build chamber 110. A build tank 120 is located inside the build chamber 110. The build tank 120 includes side walls 122 and a work table 124. The work table 124 is movable in the Z direction (up and down) by a suitable moving mechanism 126 such as a motor or actuator. During the build (the process of manufacturing parts), the work table 124 continuously descends relative to a fixed point inside the build chamber 110.

[0015] In this specification, a bed of fusible powder 132, referred to as the powder bed 130, is formed on a work table 124 in a build tank 120. Suitable fusible powders 132 that can be used with the methods discussed herein include a variety of thermoplastic polymers and metals. In a preferred embodiment, the fusible powder 132 is a fusible metal powder formed of metal fine particles of a variety of 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 alloys, iron, iron alloys (including iron-aluminum), or high-entropy alloys having a variety of substrates.

[0016] The fusible powder 132 can be stored in a powder hopper 142 (feedstock reservoir) disposed within the build chambers 110 on both sides of the build tank 120. The recoater 144 is arranged to receive or collect the fusible powder 132 from the powder hopper 142 and move between the powder hoppers 134 above the build tank 120. Although the powder hopper 142 is shown as separate from the recoater 144, alternatively, one or more powder hoppers 142 may be integrally formed with the recoater 144 and moved with the recoater 144. As the recoater 144 moves from one side of the build tank 120 to the other, it distributes a layer of the fusible powder 132 over the top of the worktable 124. The recoater 144 can also include smoothing means 146, such as a smoothing roller or a smoothing blade, that smooths the fusible powder 132 on the powder bed 130 as the recoater 144 moves across the powder bed 130 and the worktable 124. Any suitable movement mechanism can be used to move the recoater 144 in the manner described above. For example, the recoater 144 may be movably connected to rails, and a motor moves the recoater 144 in one of the X or Y directions. Movement in the Y direction is shown in FIG. 2, and the X direction is perpendicular to both the Y and Z directions.

[0017] The powder bed melting 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 having an acceleration voltage of, for example, 60 kilovolts (60 kV) to 120 kilovolts (120 kV). The high-energy beam source 150 that generates the high-energy beam 152 is located above the build tank 120, and as will be further described below, the high-energy beam 152 is directed to irradiate the distribution layer of fusible powder 132 in a controlled pattern. The electron beam (high-energy beam 152) can be controlled and directed using various coils, such as one focusing coil (not shown), at least one deflection coil 154, and an astigmatism correction coil (not shown). As described above, the high-energy beam 152 may be any other suitable high-energy beam, such as a laser beam. When the high-energy beam 152 is a laser beam, the high-energy beam source 150 may also be a laser, and the beam may be directed by various suitable means, such as a movable mirror. As will be described in more detail below, the high-energy beam 152 is directed to irradiate a distribution layer of fusible powder 132 to form a sintered build platform 200 and one or more parts 230 formed thereon.

[0018] The environment within the build chamber 110 can be controlled. When an electron beam is used as the high-energy beam 152, the build chamber 110 may be a vacuum chamber in which a vacuum atmosphere can be maintained by means of 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, scroll pump, or ion pump, and one or more valves 164. Additionally or alternatively, an external gas supply source (gas source 172) may be provided by one or more gas bottles fluidly connected to the build chamber 110 by a gas line 174 and a valve 176. When the valve 176 is open, gas from the gas bottle (gas source 172) is supplied to the build chamber 110. The valve 176 may be a flow control valve that can be set to any position between fully open and fully closed to regulate the flow of gas into 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 a predetermined amount of gas into the fusible powder 132 (or the finished three-dimensional article).

[0019] 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 the high energy beam 152, by being electrically and operably coupled to, for example, the high energy beam source 150 and various beam control devices such as a coil (e.g., deflection coil 154) used to control the electron beam. The controller 180 is also communicably and operably coupled to various motors and actuators discussed herein to control the build process. For example, the controller 180 can be communicably and operably coupled to the movement mechanisms 126 of the worktable 124 and the recoater 144. 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). The memory 184 can include one or more computer-readable media including, but not limited to, non-transitory computer-readable media, computer-readable non-volatile media (e.g., flash memory), RAM, ROM, hard drives, flash drives, and / or other memory devices.

[0020] Memory 184 can store information accessible by processor 182, including computer-readable instructions that can be executed by processor 182. Instructions can be any set or sequence of instructions that, when executed by processor 182, cause processor 182 and controller 180 to perform an operation. In some embodiments, instructions can be executed by processor 182 to cause processor 182 to complete any of the operations and functions that constitute controller 180, as will be further described below. Instructions may be software written in any suitable programming language, or they may be implemented in hardware. In addition, and / or alternatively, instructions may be executed in separate logical and / or virtual threads on processor 182. Memory 184 can further store data that can be accessed by processor 182.

[0021] The techniques described herein refer to computer-based systems, actions performed by computer-based systems, and information transmitted to and from computer-based systems. Those skilled in the art will recognize the inherent flexibility of computer-based systems, which allows for a wide variety of possible configurations, combinations, and divisions of tasks and functionalities among their components. For example, the processes discussed herein can be implemented using a single computing device or a combination of multiple computing devices. Databases, memory, instructions, and applications can be implemented on a single system or distributed across multiple systems. Distributed components can operate sequentially or in parallel.

[0022] Figure 3 is a schematic cross-sectional view of a portion of the build chamber 110 of the powder bed melting additive manufacturing machine 100. Figure 3 shows the configuration of the build tank 120 for initiating the powder bed melting additive manufacturing process. The work table 124 is positioned so that the smoothing means 146 of the recoater 144 (see Figure 2) can distribute fusible powder 132 onto the work table 124 in the build tank 120 to form a powder bed 130. Thus, Figure 3 shows the initial steps in the method discussed herein, more specifically, providing a bed of fusible powder 132 (powder bed 130) on the work table 124 in the build chamber 110 and the build tank 120. Compared to the conventional process shown in Figure 1, this step does not involve providing a start build plate (e.g., start plate 30 shown in Figure 1). Instead, the build platform is formed within the powder bed melting additive manufacturing machine 100 by the additive manufacturing process performed by the powder bed melting additive manufacturing machine 100 using the following technique. This build platform is referred to herein as the sintered build platform 200.

[0023] Figure 4 shows a sintered build platform 200 having a component 230 formed thereon upon completion of the build. The sintered build platform 200 is formed from multiple layers, including multiple layers referred to as initial layers 210 in this embodiment. 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 sintered build platform 200. The first initial layer 212 is formed by irradiating the powder bed 130 with a high-energy beam 152 toward a first control pattern. The high-energy beam 152 can be controlled to various different patterns and control sequences. Patterns for controlling the high-energy beam 152 are stored in a controller 180, more specifically in memory 184, and / or can be generated by the controller 180. The controller then controls the high-energy beam 152 according to these instructions, for example by controlling the deflection coil 154 when the high-energy beam 152 is an electron beam.

[0024] Figure 5 shows a control pattern that may be used to irradiate a scanning area of ​​the powder bed 130. The scanning area is a region of the powder bed 130 scanned by the high-energy beam 152, for example, a region scanned over one layer of the sintered build platform 200. In some embodiments, the high-energy beam 152 is irradiated multiple times (i.e., one or more times, referred to herein as repeats) across the scanning area in the control pattern to complete one layer of the sintered build platform 200. The high-energy beam 152 is scanned along a plurality of scan lines at a certain scanning speed. In this embodiment, each scan line is a straight line, and the plurality of scan lines are parallel to each other. Each scan line is separated from adjacent scan lines by a predetermined line spacing. In this embodiment, the scan lines are evenly distributed with a constant line spacing between adjacent scan lines such that the predetermined line spacing is the same between each scan line. For reference, the scan lines are sequentially numbered 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 sequentially accordingly.

[0025] In this embodiment, the high-energy beam 152 does not irradiate adjacent scan lines consecutively. Instead, different line orders, such as an interlaced pattern, are used. As the high-energy beam 152 scans along the first scan line (1), some scan lines are skipped, and the next scan lines irradiated by the high-energy beam 152 are spaced apart by several scan lines (line order). For example, in a control pattern, the high-energy beam 152 irradiates the lines of 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) in the first sequence, using a five-line order and a total of 25 scan lines. After the first sequence is completed, the high-energy beam 152 irradiates 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 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) in the second sequence. The high-energy beam 152 illuminates additional scan lines for additional sequences until all scan lines in the control pattern have been scanned.

[0026] The high-energy beam 152 is operated at an energy level such that, as it is scanned along the scan line in the manner described above, it transfers energy to the particles of the fusible powder 132, heating them. When forming the first initial layer 212, the high-energy beam 152 is operated at an initial energy level (EI) (also referred to here as the "first energy level"). As described above, the fusible powder 132 in the powder bed 130 has relatively low thermal and electrical conductivity. In the absence of a start plate 30, if a relatively high amount of energy or high energy intensity is input when forming the first initial layer 212, heat and electricity (if the high-energy beam 152 is an electron beam) may accumulate. To prevent this accumulation of heat and electricity, the initial energy level (EI) is set to a lower value compared to the energy level used when forming the initial layer of a component in an environment with a normal build plate. The initial energy level (EI) may be material-dependent and can be controlled in various ways, as described below. An example range of the initial energy level (EI) is described below. More specifically, the initial energy level (EI) is set to input energy at the point where agglomeration begins between the particles of the fusible powder 132. This agglomeration occurs on a timescale comparable to the time required to scan the layer (e.g., less than 3 minutes). Agglomeration may also be the point at which the energy input causes changes in the electrical and thermodynamic properties of the powder bed 130. Agglomeration may also involve other forces, but at this level of agglomeration, adjacent particles of the fusible powder 132 begin to sinter, resulting in relatively small neckings between the particles.

[0027] As will be described in more detail below, the energy level of the high-energy beam 152 is controlled to form the sintered build platform 200, and one or more of the following parameters may be used to control the energy level. These parameters can be controlled individually or in combination with each other. The following discussion identifies the effect of a particular parameter on the energy level, and this effect is described in the context of other parameters, which remain the same to highlight the effect of the particular parameter being discussed, but controlling the energy level is not limited to changing only one parameter at a time. Instead, in some embodiments, the energy level of the high-energy beam 152 may be changed, such as an increase, in the manner further described below, by changing several of the parameters described below, in order to result in an overall change, such as an overall increase in the energy level of the high-energy beam 152.

[0028] The high-energy beam 152 can be operated across the scanning region by controlling the beam power. The energy level of the high-energy beam 152 can be controlled by controlling the beam power. For example, increasing the beam power increases the energy level, and decreasing the beam power decreases the energy level. If 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 electron beam current. In some embodiments, the energy level of the high-energy beam 152 for the initial energy level (EI) is 3.84 × 10⁻⁶. 2 W to 5.76 × 10 2 It could be W.

[0029] 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 relation to the beam power. For a constant beam power, increasing the scanning speed decreases the intensity of energy imparted to the fusible powder 132, and decreasing the scanning speed increases the intensity of energy imparted to the fusible powder 132. In connection with this, the energy level of the high-energy beam 152 can also be controlled by controlling the line energy of the high-energy beam 152. The line energy of the high-energy beam 152 is based on the beam power and the scanning speed. The line energy can be increased by increasing the beam power, decreasing the scanning speed, or both. Conversely, the line energy can be decreased by decreasing the beam power, increasing the scanning speed, or both. In some embodiments, the scanning speed of the initial energy level (EI) can be 53 m / s to 80 m / s, and the line energy of the high-energy beam 152 at the initial energy level (EI) can be 5.83 J / m to 8.60 J / m.

[0030] The high-energy beam 152 has a spot diameter (or spot size). The spot diameter measures the size of the area of ​​fusible 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 fusible powder 132 that receive radiation from the high-energy beam 152 in a given example. Alternatively, the spot diameter can be defined as the maximum distance between two points on the surface of the fusible powder 132 that receive at least a predetermined percentage of the total intensity given by the high-energy beam 152 in a given example. For a constant beam power, increasing the spot diameter decreases the intensity of energy imparted to the fusible powder 132, and decreasing the spot diameter increases the intensity of energy imparted to the fusible powder 132. In connection with this, 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, decreasing the spot diameter, or both. Conversely, the local heat flux can be decreased by decreasing the beam power, increasing the spot diameter, or both. In some embodiments, the spot diameter of the high-energy beam 152 relative to the initial energy level (EI) is 3.88 × 10⁻⁶. -4 m~5.82×10 -4 m is possible, and the local heat flux for the initial energy level (EI) is 2.08 × 10⁻⁶. 9 W / m 2 ~3.12×10 9 W / m 2 It is possible.

[0031] As described above, the high-energy beam 152 can be operated over a scanning area with beam power. This scanning area can also have an area or size called the scanning area in this specification. The scanning area may be an area scanned in one repeat. The energy level of the high-energy beam 152 can also be controlled by controlling the scanning area in relation to the beam power. In the case of a constant beam output, increasing the scanning area decreases the intensity of the energy imparted to the fusible powder 132, and decreasing the scanning area increases the intensity of the energy imparted to the fusible powder 132. In relation, the energy level of the high-energy beam 152 can also be controlled by controlling the overall heat flux of the high-energy beam 152. The overall heat flux of the high-energy beam 152 is based on the scanning area and the scanning speed. The overall heat flux can be increased by increasing the beam power, decreasing the scanning area, or both. Conversely, the overall heat flux can be decreased by decreasing the beam power, increasing the scanning area, or both. In some embodiments, the overall heat flux of the initial energy level (EI) is from 8.72×10 3 W / m 2 to 1.31×10 4 W / m 2 and may be.

[0032] 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 parameters described above and can therefore be controlled using those parameters. As described above, the high-energy beam 152 can be irradiated multiple times across a scanning region in a controlled pattern to complete one layer, referred to herein as a repeat. The total amount of energy deposited on a given layer can also be controlled by varying the number of repeats. Increasing the number of repeats increases the total amount of energy deposited on a given layer, and decreasing the number of repeats decreases the total amount of energy deposited on a given layer. In some embodiments, the parameters described above may be constant across a single repeat and the same for each repeat, while in other embodiments, these parameters may differ between repeats. In some embodiments, the total energy of the first initial layer 212 is 3.37 × 10⁻⁶. 3 From J: 5.05 x 10 3 J-Pop.

[0033] After the first initial layer 212 is completed, the controller 180 lowers the worktable 124 by a predetermined distance, and the recoater 144 distributes a layer of fusible powder 132 onto the first initial layer 212 (the previous layer) and the worktable 124. The high-energy beam 152 is then directed to irradiate the distributed layer of fusible powder 132 in the same manner as described above to form the second layer of the initial layer 210 of the sintered 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 in a second control pattern. The second control pattern may be the same as the first control pattern described above. This process is then repeated from each subsequent layer of the initial layer 210 up to the top initial layer 214 of the initial layer 210.

[0034] Figures 6A and 6B are graphs showing the energy levels of the high-energy beam 152 when forming multiple layers of the sintered build platform 200. As described above, the first initial layer 212 is formed using the high-energy beam 152 operating at the initial energy level (EI), but subsequent initial layers 210 are not formed at the initial energy level (EI), and the cohesive force of the initial layers does not increase the thermal and electrical conductivity to replace the energy required to melt and solidify the fusible powder 132 during the manufacturing of the part. A higher level of bonding between particles, such as the degree of sintering or cohesion, is required so that the sintered build platform 200 has sufficient thermal and electrical conductivity to form the part. When forming subsequent initial layers 210, the energy level of the high-energy beam 152 is increased from the first energy level (EI) of the successive layers of the subsequent initial layers 210. The energy level of the high-energy beam 152 is increased to the maximum sintering build platform energy level (EMax), and the high-energy beam 152 irradiates the distribution powder layer at the maximum sintering build platform energy level (EMax) to form the top initial layer 214.

[0035] Figure 6A shows an initial energy control method for increasing the energy level of the high-energy beam 152 from the initial energy level (EI) to the maximum sintered build platform energy level (EMax) in the subsequent initial layers 210. In this method, the energy level of the high-energy beam 152 is increased stepwise with each subsequent initial layer 210. As shown in Figure 6A, each subsequent initial layer 210 has a higher energy level than the layer immediately preceding it, and the energy level increases stepwise, forming a constant energy increase rate. The energy increase rate is desirable to be set to avoid "smoke formation," which occurs due to the accumulation of charge that repels the particles of the fusible powder 132, especially when the high-energy beam 152 is an electron beam. The energy increase rate should also be set to avoid the accumulation of thermal and stress gradients, which can cause cracks, warping, and other dimensional changes in the sintered build platform 200. The thickness of each layer can be, for example, 30 microns (30 μm) to 150 microns (150 μm). The energy level is set to maintain the flatness of each layer, and it is desirable that the level be kept such that the flatness does not exceed the thickness of the layer.

[0036] In this embodiment, the energy level increases linearly, more specifically in a straight line, but this linear increase is not limited to a constant (or stable) rate of energy growth, nor is it limited to a linear increase; it may also include a curvilinear increase.

[0037] Figure 6B shows a second energy control technique for increasing the energy level of the high-energy beam 152 from a first energy level (EI) to the maximum sintering build platform energy (EMax). In Figure 6B, the energy level of successive layers of the initial layer 210 is progressively increased by the initial layer 210, which includes multiple sets of subsequent initial layers. As used herein, a set is multiple adjacent layers irradiated with the same high-energy beam 152 energy level for each layer of the set in the illustrated embodiment. In this embodiment, the energy level of the high-energy beam 152 is incrementally increased with each successive set of the subsequent initial layer 210. For example, the energy level may be progressively increased with a constant increase between each successive set of the subsequent initial layer 210, but other approaches may be taken for each successive set of the subsequent initial layer 210, such as an approach taken for a curvilinear increase in the energy level.

[0038] When controlling the energy level of the high-energy beam 152 in the manner shown in Figures 6A and 6B, the fusible powder 132 is gradually sintered to form the initial layer 210. During the formation of the initial layer 210, the degree of aggregation and bonding, such as necking, between adjacent particles of the fusible powder 132 within the layer and between adjacent layers, progressively increases from the first initial layer 212 to the top initial layer 214.

[0039] Preferably, the build platform formed using the method discussed herein is a sintered build platform 200 having particles of fusible powder 132 that are sintered together. By maintaining the sintered build platform 200, including the initial layer 210, in a sintered state, the sintered build platform 200 becomes easier to remove from the later manufactured part 230 (see Figure 4). The fusible powder 132 has a certain melting temperature, and as will be further discussed below, the part 230 may be manufactured by selectively heating the fusible powder 132 to a temperature higher than the melting temperature of the fusible powder 132 to melt the fusible powder 132, and then solidifying the molten fusible powder 132 to form layers of the part 230. Thus, the maximum sintered build platform energy level (EMax) can be an energy level that maintains the fusible powder 132 at a temperature below the melting temperature of the fusible powder 132, so that the fine particles of the fusible powder 132 are sintered and not melted. However, if necessary, the solidification and formation of the first layer 210 can be used, and thus the maximum sintered build platform energy level (EMax) can be increased to the energy level used to form the part 230. As will be further described below, when the high-energy beam 152 is an electron beam, the part 230 may be formed by at least one preheating scan, and the maximum sintered build platform energy level (EMax) may be the same as or similar to the energy level of the high-energy beam 152 used in one of the preheating steps, such as the second preheating energy level when two preheating scans are used.

[0040] Referring again to 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 a plurality of layers called bulk layers 220. The bulk layers 220 are formed after the subsequent initial layer 210, and in this embodiment, the top initial layer 214 may be the first layer of bulk layers 220. The bulk layers 220 can be formed in the same manner as the subsequent initial layer 210, as described above. The bulk layers 220 add additional bulk or thickness to the sintered build platform 200. As described above, the degree of sintering of the fusible powder 132 is gradually increased in the initial layer 210 of the sintered build platform 200 until the sintered fusible powder 132 provides good thermal and electrical conductivity. The fusible powder 132 of the bulk layer 220 is preferably sintered to the same or similar degree of sintering as the top initial layer 214 to provide capacity for heat and charge transfer, as well as a stable surface for building the parts 230. The bulk layer 220 may also be used for thermal management when the part 230 is built. The bulk layer 220 can provide energy storage or heat capacity, and if the heat capacity of the sintering build platform 200 is too small, thermal management when forming the part 230 will be unstable, and therefore the bulk layer 220 can be used to help maintain a stable build temperature for the part 230. In some embodiments, the total thickness of the bulk layer 220 may be greater than the total thickness of the initial layer 210.

[0041] In this embodiment, the energy level of the high-energy beam 152 for each of the bulk layers 220 is the same and is referred to herein as the bulk energy level (EB). In the energy control method shown in Figures 6A and 6B, the bulk energy level (EB) is the same as the maximum sintering build platform energy (EMax). Multiple bulk layers 220 are formed to obtain the top layer 222 of the sintering build platform 200. The top initial layer 214 is the bottom layer of the bulk layers 220. Thus, the sintering build platform 200 includes multiple layers, including a bottom layer (first initial layer 212) and an top layer 222. Each layer contains 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 intermediate layer (top initial layer 214), and the degree of sintering is constant from the intermediate layer (top initial layer 214) to the top layer 222.

[0042] Furthermore, as shown in Figure 4, one or more parts 230 may be formed on the sintered build platform 200, more specifically, on the top layer 222. If the bulk layer 220 is omitted, the top initial layer 214 may be the top layer 222 on which one or more parts 230 are formed. After the sintered build platform 200 is formed, the controller 180 lowers the work table 124 by a predetermined distance, and the recoater 144 distributes a layer of fusible powder 132 onto the top layer 222 and the work table 124. The high-energy beam 152 is then directed to irradiate the distributed layer of fusible powder 132 in a control pattern (third control pattern) to form the first layer of the part. The high-energy beam 152 can be directed to the distributed layer of fusible powder 132 in an interlaced control pattern, as with the patterns described above, but in some examples the high-energy beam 152 selectively irradiates the fusible powder 132 along a scan line to achieve a desired geometric instance of the part 230. At least one scan of the scan line includes scanning the fusible powder 132 at a melting energy level (EF). The melting energy level (EF) is an energy level that raises the temperature of the fusible powder 132 during irradiation to a temperature higher than the melting temperature of the fusible powder 132, and is sufficient to provide enough heat to selectively melt the fine particles of the fusible powder 132.

[0043] The high-energy beam 152 may be directed to irradiate the distribution layer of the fusible powder 132 multiple times for scanning lines 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 fusible powder 132 before melting by irradiating the fusible powder 132 with at least one preheating scan at a preheating energy level. In some embodiments, two preheating scans may be used at a first preheating energy level and a second preheating energy level. The first and second preheating energy levels may be different from each other and may both be below the melting energy level (EF). Using preheating scans helps to avoid smoke during melting scans at the melting energy level (EF). As described above, the bulk energy level (EB) and the maximum sintering build platform energy level (EMax) may be similar to or comparable to the preheating energy levels, such as the second preheating energy level.

[0044] Subsequent component layers are formed by a similar process. After the first component layer is completed, the controller 180 lowers the worktable 124 by a predetermined distance, and the recoater 144 distributes a layer of fusible powder 132 onto the first component layer (previous layer) and the worktable 124. The high-energy beam 152 is then directed in the same manner as for the first component layer above, and irradiates the distributed layer of fusible powder 132 to form the second layer of component 230. This process is then repeated for each subsequent layer of component 230. For the second and other subsequent component layers, the molten portion of the subsequent layer may be combined with the molten portion of the preceding layer. The molten portions in the subsequent and preceding layers may be melted together not only with the fusible powder 132, but also by remelting at least a portion of the thickness of the layer directly beneath the fusible powder 132.

[0045] Once part 230 is completed, part 230 and the sintered build platform 200 can be removed from the build chamber 110, and part 230 can be separated from the sintered build platform 200. Using the sintered build platform 200 described herein, part 230 can be easily separated from the sintered build platform 200. Unlike the solid start plate 30 (Figure 1), the sintered build platform 200 formed herein contains only sintered particles, and therefore the sintered build platform 200 can be easily recycled for subsequent use as fusible powder 132.

[0046] The following table provides an example of forming a sintered build platform 200 using the method discussed herein. The sintered build platform 200 was formed using an electron beam powder bed melting additive manufacturing machine 100, more specifically an EBM Q10+ v2.1 manufactured by G. Additive GmbH in Märnrike, Sweden. The sintered build platform 200 was formed using Ti6Al4V (grade 5) with a particle size distribution of 45 microns to 106 microns as the fusible powder 132.

[0047] The sintered build platform 200 was formed using multiple sets of initial layers 210, employing the energy-controlled approach shown in Figure 6B. Seven sets of initial layers 210 are shown in Table 1 below. The maximum sintered build platform energy (EMax) was for layer set 7, and multiple bulk layers 220 were built using the maximum sintered build platform energy (EMax).

[0048] [Table 1]

[0049] Further aspects of this disclosure are provided below.

[0050] A method for forming a build platform for a powder bed melt addition manufacturing process. The method provides a bed of fusible powder on a worktable in a build chamber, and in a first control pattern, directs a high-energy beam to irradiate the bed of fusible powder to form a first layer of the build platform. The high-energy beam is operated at a first energy level to form the first layer of the build platform. The method also forms subsequent initial layers of the build platform. Each subsequent layer is formed by lowering the worktable by a predetermined distance, distributing the layer of fusible powder onto the worktable, and in a second control pattern, directs the high-energy beam to irradiate the distributed layer of fusible powder to form one of the subsequent initial layers of the build platform. The high-energy beam is operated at a second energy level, increasing from the first energy level, for consecutive layers of the subsequent initial layers.

[0051] The above method, which involves providing a bed of fusible powder on the build platform within the build chamber, does not include providing a starting build plate.

[0052] Any of the above methods, comprising controlling the energy level of the high-energy beam to gradually sinter the fusible powder and form a sintered build platform.

[0053] The method described above, wherein the fusible powder is a fusible metal powder.

[0054] The subsequent initial layer comprises a plurality of sets of subsequent initial layers, and the energy level of the high-energy beam is progressively increased with each successive set of the sets of subsequent initial layers, in any of the above methods.

[0055] The fusible powder has a melting temperature, and the energy level of the high-energy beam is gradually increased from the first energy level to the maximum sintering build platform energy level, in any of the above methods. The maximum sintering build platform energy level is the energy level that maintains the fusible powder at a temperature below its melting temperature.

[0056] Any of the above methods, wherein the high-energy beam has beam power, and the energy level of the high-energy beam is controlled by controlling the beam power.

[0057] The method of directing the high-energy beam to form the first layer and the subsequent initial layer of the build platform includes scanning the high-energy beam at a scanning speed, wherein the energy level of the high-energy beam is controlled by controlling the scanning speed.

[0058] Any of the above methods, wherein 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.

[0059] The energy level of the high-energy beam is controlled by controlling the line energy, in any of the above methods.

[0060] The high-energy beam has beam power, and directing the high-energy beam to form the first layer and the subsequent initial layer of the build platform includes scanning the high-energy beam at a scanning speed, wherein the line energy is a function of the beam power and the scanning speed, in any of the above methods.

[0061] The energy level of the high-energy beam is controlled by controlling the local heat flux of the high-energy beam, in any of the above methods.

[0062] The high-energy beam has beam power and spot diameter, and the local heat flux is a function of the beam power and the spot diameter, in any of the above methods.

[0063] The energy level of the high-energy beam is controlled by controlling the global heat flux of the high-energy beam, in any of the above methods.

[0064] The energy level of the high-energy beam is controlled by controlling the total energy deposited in the layer, in any of the above methods.

[0065] The energy level of the high-energy beam is controlled by controlling the number of repeats, in any of the above methods.

[0066] The high-energy beam has beam power, and directing the high-energy beam to form the first layer and the subsequent initial layer of the build platform includes scanning the high-energy beam across a scanning region, wherein the global heat flux is a function of the beam power and the scanning region, in any of the above methods.

[0067] The energy level of the high-energy beam is controlled by controlling the number of repeats, in any of the above methods.

[0068] The energy level of the high-energy beam is controlled by any of the above methods, by the beam power, the scanning speed, the spot diameter of the high-energy beam, the scanning area, the number of repeats, or any combination thereof.

[0069] The energy level of the high-energy beam is controlled by the line energy, the local heat flux, the global heat flux, or any combination thereof, in any of the above methods.

[0070] The high-energy beam is an electron beam, by any of the methods described above.

[0071] 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, in any of the above methods.

[0072] The energy level of the high-energy beam is gradually increased with respect to each subsequent layer of the initial layer, in any of the above methods.

[0073] The energy is increased linearly with respect to each subsequent layer of the initial layer by any of the above methods.

[0074] The energy is increased at a constant energy increase rate for each subsequent layer of the initial layer, by any of the above methods.

[0075] The first control pattern and the second control pattern include scanning the high-energy beam along a plurality of scanning lines at a scanning speed, wherein the scanning lines are straight lines, in any of the above methods.

[0076] In any of the above methods, each of the plurality of scan lines is parallel to the others.

[0077] In any of the above methods, each of the plurality of scan lines is evenly distributed at predetermined line intervals.

[0078] Any of the above methods further comprises forming a bulk layer of the build platform, wherein the bulk layer is formed after the subsequent initial layer. Each bulk layer is formed by lowering the work table by a predetermined distance, distributing the layer of fusible powder onto the work table, directing the high-energy beam at the bulk energy level, irradiating the distributed layer of fusible powder in a second controlled pattern, and forming one of the bulk layers of the build platform.

[0079] Any of the above methods, 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.

[0080] The energy beam of the high-energy beam is gradually increased from the first energy level to the bulk energy level for successive layers of the subsequent initial layer, in any of the above methods.

[0081] A method for forming a part using a powder bed melting addition process. This method involves forming the build platform by any of the above methods, lowering the work table including the build platform by a predetermined distance, distributing the fusible powder layer onto the work table and the build platform, directing a high-energy beam at a melting energy level, and irradiating the distributed layer of fusible powder in a third control pattern to form a first part layer of the part and subsequent part layers. Each subsequent part layer is formed by lowering the work table by a predetermined distance, distributing the fusible powder layer onto the work table and the build platform, directing the high-energy beam at a melting energy level, and irradiating the distributed layer of fusible powder in a fourth control pattern to form one of the subsequent part layers of the part.

[0082] The component forming method described above, wherein the energy level of the high-energy beam is gradually increased with respect to successive layers of the subsequent initial layer, from the first energy level to an energy level below the melting energy level.

[0083] The above-mentioned method for forming a component, wherein the fusible powder has a melting temperature, and the melting energy level is an energy level that increases the temperature of the irradiated fusible powder to a temperature higher than the melting temperature of the fusible powder.

[0084] Any part forming method, further comprising directing the high-energy beam at a preheating energy level so as to irradiate the distribution layer of the fusible powder in a fifth control pattern before directing the high-energy beam at the melting energy level.

[0085] A part forming method, wherein the energy level of the high-energy beam is gradually increased from the first energy level to the maximum sintering build platform energy, and the maximum sintering build platform energy is equivalent to the preheating energy level.

[0086] A method for forming a component, comprising removing the build platform and the component formed on the build platform from the build chamber, and separating the build platform from the component.

[0087] A part formation method comprising separating the part from the build platform and then recycling the build platform.

[0088] A sintered build platform for a powder bed melting addition process, formed by one of the methods described above.

[0089] A sintered build platform for a powder bed melt addition manufacturing process. The sintered build platform comprises multiple layers, including a bottom layer and an top layer. Each layer contains sintered particles, and the degree of sintering increases from the bottom layer to the top layer.

[0090] The degree of sintering is gradually increased for each successive layer in any of the above sintering build platforms.

[0091] The layer is any of the above sintering build platforms, comprising multiple sets of layers. The degree of sintering is equivalent for each set and increases progressively for each consecutive set of layers from the bottom layer to the top layer.

[0092] A sintering build platform, any of the above, comprising multiple layers that collectively form an initial layer and multiple layers that collectively form a bulk layer.

[0093] A sintered build platform, wherein each layer of the bulk layer has the same degree of sintering.

[0094] A sintering build platform, wherein the degree of sintering gradually increases from the bottom layer to the intermediate layer, and the degree of sintering remains constant from the intermediate layer to the top layer.

[0095] A sintered build platform of any of the above, wherein the total thickness of the bulk layers is greater than the total thickness of the initial layers.

[0096] A method for forming a part using a powder bed melting addition process. The method involves distributing a layer of fusible powder onto one of the sintering build platforms described above, directing a high-energy beam at a melting energy level to irradiate the distributed layer of fusible powder in a controlled pattern to form a first part layer of the part, and forming subsequent part layers. The sintering build platform is located on the work table of a build chamber. Each subsequent part layer is formed by lowering the work table by a predetermined distance, distributing the layer of fusible powder onto the work table and build platform, and directing the high-energy beam at the melting energy level to irradiate the distributed layer of fusible powder in a controlled pattern to form one of the subsequent part layers of the part.

[0097] The sintered build platform is formed using any of the above-described methods for forming a build platform, and the component forming method is any of the above-described methods.

[0098] While the foregoing description pertains to preferred embodiments, other variations and modifications will be obvious to those skilled in the art and may be made without departing from the spirit or scope of this disclosure. Furthermore, features described in relation to one embodiment may be used in conjunction with other embodiments, even if not explicitly stated above.

Claims

1. A method for forming a build platform for a powder bed melt addition manufacturing process, A bed of fusible powder is provided on the worktable inside the build chamber. In the first control pattern, a high-energy beam is directed to irradiate the bed of fusible powder to form the first layer of the build platform. The high-energy beam is operated at a first energy level to form the first layer of the build platform. Forming the subsequent initial layer of the build platform, Each of the subsequent layers is, Lower the work table by a predetermined distance, The fusible powder layer is distributed onto the work table, In the second control pattern, the high-energy beam is directed to irradiate the distribution layer of the fusible powder, forming one of the subsequent initial layers of the build platform. It is formed by, The high-energy beam is operated at a second energy level that is increased from the first energy level for successive layers of the subsequent initial layer. The aforementioned subsequent initial layer includes multiple sets of subsequent initial layers, The energy level of the high-energy beam is gradually increased with each successive set of the subsequent initial layers. A method for forming a build platform.

2. The energy level of the high-energy beam is controlled to gradually sinter the fusible powder and form a sintered build platform. A method for forming a build platform according to claim 1, further comprising the following:

3. The fusible powder is a fusible metal powder. A method for forming a build platform according to claim 1.

4. The fusible powder has a melting temperature, The energy level of the high-energy beam is gradually increased from the first energy level to the maximum sintering build platform energy level. The maximum sintering build platform energy level is the energy level that maintains the fusible powder at a temperature below the melting temperature of the fusible powder. A method for forming a build platform according to claim 1.

5. The aforementioned high-energy beam has beam power, The energy level of the high-energy beam is controlled by controlling the beam power. A method for forming a build platform according to claim 1.

6. Directing the high-energy beam to form the first layer and subsequent initial layers of the build platform includes scanning the high-energy beam at a scanning speed. The energy level of the high-energy beam is controlled by controlling the scanning speed. A method for forming a build platform according to claim 1.

7. The high-energy beam has a spot diameter, The energy level of the high-energy beam is controlled by controlling the spot diameter of the high-energy beam. A method for forming a build platform according to claim 1.

8. The energy level of the aforementioned high-energy beam is controlled by controlling the number of repeats. A method for forming a build platform according to claim 1.

9. The energy level of the high-energy beam is controlled by controlling the line energy. A method for forming a build platform according to claim 1.

10. The aforementioned high-energy beam has beam power, Directing the high-energy beam to form the first layer and subsequent initial layers of the build platform includes scanning the high-energy beam at a scanning speed. The line energy is a function of the beam power and the scanning speed. The method for forming a build platform according to claim 9.

11. The energy level of the high-energy beam is controlled by controlling the local heat flux of the high-energy beam. The aforementioned high-energy beam has beam power and spot diameter, The local heat flux is a function of the beam power and the spot diameter. A method for forming a build platform according to claim 1.

12. The energy level of the high-energy beam is controlled by controlling the global heat flux of the high-energy beam. The aforementioned high-energy beam has beam power, Directing the high-energy beam to form the first layer and subsequent initial layers of the build platform includes scanning the high-energy beam across a scanning region. The global heat flux is a function of the beam power and the scanning region. A method for forming a build platform according to claim 1.

13. Further includes forming the bulk layer of the build platform, The bulk layer is formed after the subsequent initial layer, Each bulk layer is, Lower the work table by a predetermined distance, The fusible powder layer is distributed onto the work table, The high-energy beam is directed at the bulk energy level, and the distribution layer of the fusible powder is irradiated in a second control pattern to form one of the bulk layers of the build platform. Formed by, A method for forming a build platform according to claim 1.

14. The fusible powder has a melting temperature, The bulk energy level is the energy level that maintains the fusible powder at a temperature below the melting temperature of the fusible powder. The method for forming a build platform according to claim 13.

15. A method for forming a part using a powder bed melting addition process, The build platform is formed by the build platform formation method described in claim 1, Lower the work table, which includes the build platform, by a predetermined distance. The layers of the fusible powder are distributed onto the work table and the build platform. A high-energy beam is directed at the melting energy level, and the distribution layer of the fusible powder is irradiated with a third control pattern to form the first component layer of the component. Forms a subsequent component layer, Each subsequent component layer is: Lower the work table by a predetermined distance, The layers of the fusible powder are distributed onto the work table and the build platform. The high-energy beam is directed at the melting energy level, and the distribution layer of the fusible powder is irradiated in a fourth control pattern to form one of the subsequent component layers of the component. Formed by, Method for forming parts.

16. The energy level of the high-energy beam is gradually increased from the first energy level to an energy level below the melting energy level of the subsequent layers of the initial layers. The part forming method according to claim 15.

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