阅读说明：本技术 激光增材制造控制系统和方法 (Laser additive manufacturing control system and method ) 是由 程渤 C·图费尔 于 2020-11-24 设计创作，主要内容包括：提供了激光增材制造控制系统和方法。一种用于控制激光增材制造系统中保护气体对粉末颗粒摄取的计算方法。该计算方法包括接收激光增材制造系统的气体流体域、粉末床域和入口保护气体流速。该方法进一步包括基于入口保护气体流速和气体流体域确定气体流体域内的最大气体流速。该方法还包括基于入口保护气体流速和粉末床域确定气体流体域内的阈值摄取流速。该方法还包括响应于最大气体流速和阈值摄取流速,控制激光增材制造系统中保护气体的粉末颗粒摄取。(Laser additive manufacturing control systems and methods are provided. A computational method for controlling shielding gas uptake of powder particles in a laser additive manufacturing system. The calculation method includes receiving a gas flow field, a powder bed field, and an inlet shielding gas flow rate of a laser additive manufacturing system. The method further includes determining a maximum gas flow rate within the gas flow field based on the inlet shielding gas flow rate and the gas flow field. The method also includes determining a threshold uptake flow rate within the gas flow domain based on the inlet shielding gas flow rate and the powder bed domain. The method also includes controlling powder particle uptake of a shielding gas in the laser additive manufacturing system in response to the maximum gas flow rate and a threshold uptake flow rate.)

1. A laser additive manufacturing system for controlling shielding gas uptake of powder particles, the system comprising:

an inlet configured to introduce a flow of shielding gas;

a main chamber configured to receive a flow of shielding gas;

an outlet configured to discharge a flow of shielding gas;

a base plate located between the inlet and the outlet and configured to support a powder bed having a plurality of particles;

a laser configured to melt a predefined region of the powder bed to form a melt pool; and

a controller having a non-transitory memory for storing machine instructions to be executed by the controller and operatively connected to the portal, the machine instructions when executed by the controller implementing the following functions:

receiving a gas fluid field of the main chamber, a powder bed field of the powder bed, and an inlet shielding gas flow rate;

determining a maximum gas flow rate within the gas flow domain based on the inlet shielding gas flow rate and the gas flow domain;

determining a threshold uptake flow rate within the gas flow domain based on the inlet shielding gas flow rate and the powder bed domain; and

powder particle uptake of a shielding gas in a laser additive manufacturing system is controlled in response to a maximum gas flow rate and a threshold uptake flow rate.

2. The system of claim 1, wherein the first determining function comprises determining a maximum gas flow rate within a gas flow field in a horizontal plane offset from the powder bed field based on the inlet shielding gas flow rate and the gas flow field.

3. The system of claim 1, wherein the control function comprises adjusting the inlet shielding gas flow rate in response to the maximum gas flow rate and a threshold ingestion flow rate.

4. The system of claim 3, wherein the adjustment function comprises decreasing the inlet shielding gas flow rate in response to the maximum gas flow rate being greater than a threshold ingestion flow rate.

5. The system of claim 3, wherein the adjustment function comprises increasing the inlet shielding gas flow rate in response to the maximum gas flow rate being less than a threshold ingestion flow rate.

6. The system of claim 1, wherein the first determining function is performed using Computational Fluid Dynamics (CFD).

7. The system of claim 1, wherein the second determining function is performed using a computational fluid dynamics discrete element method (CFD-DEF).

8. A computational method for controlling shielding gas uptake of powder particles in a laser additive manufacturing system, the method comprising:

receiving a gas flow field, a powder bed field, and an inlet shielding gas flow rate of a laser additive manufacturing system;

determining a maximum gas flow rate within the gas flow domain based on the inlet shielding gas flow rate and the gas flow domain;

determining a threshold uptake flow rate within the gas flow domain based on the inlet shielding gas flow rate and the powder bed domain; and

powder particle uptake of a shielding gas in a laser additive manufacturing system is controlled in response to a maximum gas flow rate and a threshold uptake flow rate.

9. The computing method of claim 8, wherein the first determining step comprises determining a maximum gas flow rate within a gas flow field that is in a horizontal plane offset from the powder bed field based on the inlet shielding gas flow rate and the gas flow field.

10. The computing method of claim 8, wherein the controlling step comprises adjusting the inlet shielding gas flow rate in response to the maximum gas flow rate and a threshold uptake flow rate.

11. The computing method of claim 10, wherein the adjusting step comprises decreasing the inlet shielding gas flow rate in response to the maximum gas flow rate being greater than a threshold uptake flow rate.

12. The computing method of claim 10, wherein the adjusting step comprises increasing the inlet shielding gas flow rate in response to the maximum gas flow rate being less than a threshold uptake flow rate.

13. The computing method of claim 8, wherein the first determining step is carried out using Computational Fluid Dynamics (CFD).

14. The computing method of claim 8, wherein the second determining step is carried out using a computational fluid dynamics discrete element method (CFD-DEF).

15. The computing method of claim 8, wherein the powder bed domain includes one or more powder particle parameters.

16. The computing method of claim 8, wherein the gas flow domain includes one or more inlet shielding gas parameters.

17. A computer-readable medium, comprising:

non-transitory memory for storing machine instructions to be executed by a computer, the machine instructions when executed by the computer implementing the functions of:

receiving a gas flow field, a powder bed field, and an inlet shielding gas flow rate of a laser additive manufacturing system;

determining a maximum gas flow rate within the gas flow domain based on the inlet shielding gas flow rate and the gas flow domain;

determining a threshold uptake flow rate within the gas flow domain based on the inlet shielding gas flow rate and the powder bed domain; and

powder particle uptake of a shielding gas in a laser additive manufacturing system is controlled in response to a maximum gas flow rate and a threshold uptake flow rate.

18. The computer readable medium of claim 17, wherein the machine instructions, when executed by the computer, perform the further function of determining a maximum gas flow rate within a gas flow field in a horizontal plane offset from the powder bed field based on the inlet shielding gas flow rate and the gas flow field.

19. The computer readable medium of claim 17, wherein the machine instructions, when executed by the computer, perform further functions of adjusting the inlet shielding gas flow rate in response to the maximum gas flow rate and a threshold ingestion flow rate.

20. The computer readable medium of claim 17, wherein the machine instructions, when executed by the computer, perform further functions of reducing the inlet shielding gas flow rate in response to the maximum gas flow rate being greater than a threshold ingestion flow rate.

Technical Field

The present disclosure relates to laser additive manufacturing control systems and methods.

Background

Selective Laser Melting (SLM) is a laser additive manufacturing system and process that has attracted a great deal of interest due to its potential to produce high resolution and high density parts from a variety of different metals and alloys. In the SLM process, metal powder particles are melted and fused into a molten pool using a high energy laser beam. Typically, the high local temperatures associated with the SLM process exceed the material vaporization point and cause vaporization. This evaporation process may cause a steam jet effect that results in the generation of emissions from the molten bath. Such emissions may include powder particles within the vapor jet and droplets ejected from the molten bath due to strong surface tension effects. These ejected particles are commonly referred to as splatter. Such spatter may redeposit on the powder particles and the melt pool, thereby limiting the build area and adversely affecting the build quality of the resulting part.

Disclosure of Invention

According to one embodiment, a laser additive manufacturing system for controlling an uptake of powder particles by a shielding gas is disclosed. The system comprises: an inlet configured to introduce a flow of shielding gas; a main chamber configured to receive a flow of shielding gas; an outlet configured to discharge a flow of shielding gas; a base plate located between the inlet and the outlet and configured to support a powder bed having a plurality of particles; a laser configured to melt a predefined region of the powder bed to form a melt pool; and a controller having a non-transitory memory for storing machine instructions to be executed by the controller and operatively connected to the portal. The machine instructions, when executed by the controller, implement the following functions: receiving a gas fluid field of the main chamber, a powder bed field of the powder bed, and an inlet shielding gas flow rate; determining a maximum gas flow rate within the gas flow domain based on the inlet shielding gas flow rate and the gas flow domain; determining a threshold uptake flow rate within the gas flow domain based on the inlet shielding gas flow rate and the powder bed domain; and controlling powder particle uptake of a shielding gas in the laser additive manufacturing system in response to the maximum gas flow rate and the threshold uptake flow rate.

According to another embodiment, a computational method for controlling shielding gas uptake of powder particles in a laser additive manufacturing system is disclosed. The method includes receiving a gas flow field, a powder bed field, and an inlet shielding gas flow rate of a laser additive manufacturing system; determining a maximum gas flow rate within the gas flow domain based on the inlet shielding gas flow rate and the gas flow domain; determining a threshold uptake flow rate within the gas flow domain based on the inlet shielding gas flow rate and the powder bed domain; and controlling powder particle uptake of a shielding gas in the laser additive manufacturing system in response to the maximum gas flow rate and the threshold uptake flow rate.

According to yet another embodiment, a computer-readable medium is disclosed. The computer readable medium includes a non-transitory memory for storing machine instructions to be executed by a computer. The machine instructions, when executed by a computer, implement the following functions: receiving a gas flow field, a powder bed field, and an inlet shielding gas flow rate of a laser additive manufacturing system; determining a maximum gas flow rate within the gas flow domain based on the inlet shielding gas flow rate and the gas flow domain; determining a threshold uptake flow rate within the gas flow domain based on the inlet shielding gas flow rate and the powder bed domain; and controlling powder particle uptake of a shielding gas in the laser additive manufacturing system in response to the maximum gas flow rate and the threshold uptake flow rate.

Drawings

Fig. 1A and 1B depict schematic side views of an SLM build chamber showing ideal gas flow and non-ideal shielding gas flow, respectively.

FIG. 2 is a schematic diagram of a computing platform that can be utilized to implement the computing method of one or more embodiments.

FIG. 3A depicts a schematic perspective view of an SLM build chamber configured for use with the computing method of one or more embodiments.

FIG. 3B is a schematic side view of an SLM build chamber depicting a flow of shielding gas from an inlet rail towards an outlet.

FIG. 3C is a schematic side view of an SLM build chamber showing gas flow domains and powder bed domains configured for use with one or more steps of a computational method to simulate interactions between a shielding gas flow and metal powder particles.

Fig. 4A depicts a schematic perspective view of different sized metal powder particles falling under gravity into a container.

Fig. 4B depicts a schematic perspective view of a settled powder bed after different sized metal powder particles have fallen into the container under gravity (g).

FIG. 5A depicts a schematic perspective view of an SLM chamber showing vertical and horizontal velocity planes of a flow of shielding gas using a predetermined flow rate and CFD calculation method, according to one embodiment.

Fig. 5B depicts a schematic plan view of the horizontal flow velocity plane of fig. 5A.

Fig. 5C depicts a schematic plan view of the vertical flow velocity plane of fig. 5A.

FIG. 6 is a graph depicting the functional relationship between maximum velocity (m/s) based on inlet gas flow rate (L/m) at a predetermined distance of 1 mm above the powder bed, according to one embodiment.

FIG. 7A is an image of a velocity profile within the gas flow field 152 taken in a vertical velocity plane in response to a predetermined inlet flow rate according to one embodiment.

Fig. 7B is an image of a velocity profile taken in a vertical velocity plane in a region between the powder bed field and a predetermined distance above the powder bed field according to one embodiment.

Fig. 7C is an image of particles being ingested from the particles of the powder bed domain according to one embodiment.

Fig. 8A, 8B and 8C are images of powder beds in which different inlet gas velocities have been applied.

Fig. 9A illustrates an image of velocity profiles within the gas flow field and over the powder bed field 154 taken in the vertical velocity plane in response to a predetermined inlet flow rate based on certain powder particle and gas parameters, according to one embodiment.

Fig. 9B shows an image of powder particle uptake in response to a predetermined inlet flow rate based on certain powder particle and gas parameters, according to an embodiment.

Detailed Description

Embodiments of the present disclosure are described herein. However, it is to be understood that the disclosed embodiments are merely examples and that other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As one of ordinary skill in the art will appreciate, various features illustrated and described with reference to any one of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combination of features illustrated provides a representative embodiment for a typical application. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations.

In connection with one or more embodiments, a group or class of materials is described as being suitable for a given purpose, implying that a mixture of any two or more of that group or class of members is suitable. Description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily preclude chemical interactions among the constituents of a mixture once mixed.

Except where expressly indicated, all numerical quantities in this description indicating amounts of material or properties of size or material are to be understood as modified by the word "about" in describing the broadest scope of the present disclosure.

The first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation. Unless expressly stated to the contrary, measurement of a property is determined by the same technique as previously or later referenced for the same property.

Reference is now made in detail to the compositions, embodiments, and methods of the embodiments known to the inventors. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

The term "substantially" or "about" may be used herein to describe disclosed or claimed embodiments. The term "substantially" or "about" may modify a value or relative characteristics disclosed or claimed in this disclosure. In such cases, "substantially" or "about" may indicate that the value or relative property modified is within ± 0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or 10% of the value or relative property.

Selective Laser Melting (SLM) is a non-limiting example of a powder bed based additive manufacturing process. In the SLM process, the complex shaped metal components are manufactured in a layer-by-layer manner. In one example, a relatively thin layer of metallic powder particulate material is deposited on a solid substrate or previously solidified material. Subsequently, the laser beam may be used to scan and melt one or more predefined areas of the layer of relatively thin metallic powder particle material. The steps of melting and solidifying the layered metal powder particle material are repeated to produce a part, such as a complexly shaped metal component.

A common problem with SLM and other powder bed based laser additive manufacturing processes is that metal powder particles are ejected from and around the melt pool formed during the melting step. During the SLM process, a large number of ejected particles (otherwise known as splatter) may fall back to the powder bed or onto an area of the particles that has been scanned and solidified due to gravity and/or particle-gas flow interactions. The redeposited spatter may contaminate the surface of each layer and negatively affect part quality, such as introducing porosity due to insufficient melting of the relatively large size spatter. A flow of shielding gas having an inlet flow rate may be used to remove splatter inside the SLM building chamber. The flow of shielding gas attempts to entrain the spatter and move it away from the main build area (e.g., powder bed) before it falls back onto the build area (e.g., powder bed and/or molten bath).

While the shielding gas may be utilized to remove spatter from a build area of a powder bed based additive manufacturing system, it may be difficult to determine an appropriate flow rate or range of flow rates to achieve the necessary spatter removal without causing other negative effects. For example, the shielding gas flow rate should be carefully determined because a relatively low shielding gas flow rate may not effectively remove the spatter, while a relatively high shielding gas flow rate may ingest metal powder particles from the powder bed. The uptake of metal powder particles can adversely affect the quality of the resulting part by redistributing the metal powder particles in unwanted areas of the melt pool or powder bed. Furthermore, once the powder particles are blown off the substrate, the laser beam may directly irradiate the resulting thinner powder bed or the substrate supporting the powder bed.

What is needed is a powder bed based laser additive manufacturing control system, a calculation method, and a computer readable storage medium having computer readable instructions thereon for causing a processor to perform the calculation method to effectively mitigate powder bed particle uptake. In one or more embodiments, the present disclosure discloses a computational method of determining a threshold gas flow rate based on powder uptake phenomena such that an inlet gas flow rate of an additive manufacturing build chamber is determined. In one or more embodiments, the inlet gas flow rate determined using the calculation methods of one or more embodiments may be used to control a powder bed based laser additive manufacturing system. The computing method may be implemented using a computer-readable storage medium having computer-readable program instructions thereon for causing a processor to perform the computing method.

As mentioned above, the SLM process is a non-limiting example of a powder bed based additive manufacturing process. Fig. 1A and 1B depict schematic side views of an SLM build chamber 10 showing ideal and non-ideal shielding gas flows, respectively. The SLM build chamber 10 includes a laser assembly 12 and a build platform 14. A powder bed 16 is supported on the build platform 14. During the SLM process, the laser assembly 12 scans a predefined area of the powder bed 16 in a scan direction 18 to form a melt pool 20. The scanning may be performed on a layer-by-layer basis of the powder bed 16.

The SLM building chamber 10 further comprises a gas flow inlet channel 22 and a gas flow outlet 24. The gas flow inlet channel 22 may include one or more gas flow inlet nozzles for the flow of shielding gas therethrough. The shielding gas may be an inert gas, such as argon. The shielding gas flows from the gas inlet channel 22 towards the gas outlet 24, as depicted by the arrows 26. As depicted by arrows 28, the shielding gas ingests the spatter 30 to be removed from the powder bed 16 and the molten bath 20. According to the embodiment shown in fig. 1A, this uptake is a result of the ideal shielding gas flow, since the removal of the spatter 30 does not affect the powder bed 16. On the other hand, as depicted by the arrow 32 on fig. 1b, the shielding gas additionally takes up metal powder particles 34 of the powder bed 16. According to the embodiment shown in FIG. 1B, this ingestion is a result of the non-ideal shielding gas flow, as the removal of the spatter 30 also ingests the metal powder particles 34, moving them to the powder bed 16 and/or other areas of the molten bath 20. In one or more embodiments, a computational method is utilized to determine the threshold gas velocity above the powder bed 16 and the inlet gas flow rate associated therewith.

In one embodiment, the calculation method is configured to determine the inlet gas flow rate to achieve an efficient spatter removal rate while preventing and/or minimizing metal powder particle uptake. The effective spatter removal rate may be any one of or within a range of any two of the following values: 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% and 100%. The minimized metal powder particle uptake may be at any one of the following values or within a range of any two of the following values: 0%, 0.01%, 0.1%, 0.5%, 1% and 2%. As part of the calculation method, the interaction between the shielding gas fluid and the metal powder particles is examined and a threshold velocity of the shielding gas flow above the powder bed 16 is determined to prevent or minimize metal powder particle uptake during the spatter removal process.

In one embodiment, the calculation method includes first and second calculation steps. The first computational step may be a full-scale Computational Fluid Dynamics (CFD) method configured to simulate gas flow characteristics in the SLM build chamber 10. The full-scale CFD method can model a relatively large-sized domain, e.g., 100 to 900 millimeters in the X, Y and Z directions. In one or more embodiments, the full-scale CFD method of the first calculation step does not model the metal powder particles, as the metal powder particles may be less than 100 microns. This significant size difference may make the full-scale CFD method unsuitable for modeling metal powder particles. In these cases, the full-scale CFD method does not model the metal powder particles. Instead, a second calculation step of reduced scale may be utilized.

The second calculation step may be a reduced-scale CFD method (CFD-DEM method) integrated with a fully coupled Discrete Element Method (DEM) configured to simulate the effect of gas flow characteristics on the movement of the metal powder particles. The downscale CFD-DEM method can model a domain of relatively reduced size, e.g., 1 to 3 millimeters in the X, Y and Z directions. In one or more embodiments, the metal powder particle motion may be modeled using a reduced scale CFD-DEM method. The second calculation step may be configured to determine the maximum gas flow velocity at a predetermined height above the powder bed 16 based on different inlet flow rates in the SLM build chamber 10. The predetermined position above the powder bed 16 may be any one or within a range of any two of the following values: 0. 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 mm. The second calculating step may be configured to determine a metal powder particle uptake threshold velocity at a predetermined height above the powder bed. Based on the output of the first and second steps of the calculation method, the calculation method is configured to determine a relationship between the metal powder particle uptake threshold velocity and the inlet gas flow rate of the SLM building chamber.

The computational methods and steps of one or more embodiments, including but not limited to the CFD computational method and the CFD-DEM computational method, are implemented using a computational platform, such as computational platform 50 illustrated in fig. 2. Computing platform 50 may include a processor 52, memory 54, and non-volatile storage 56. Processor 52 may include one or more devices selected from a High Performance Computing (HPC) system, including a high performance core, microprocessor, microcontroller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, or any other device that manipulates signals (analog or digital) based on computer-executable instructions residing in memory 54. Memory 54 may include a single memory device or multiple memory devices including, but not limited to, Random Access Memory (RAM), volatile memory, non-volatile memory, Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), flash memory, cache memory, or any other device capable of storing information. Non-volatile storage 56 may include one or more persistent data storage devices, such as hard disk drives, optical drives, tape drives, non-volatile solid-state devices, cloud storage, or any other device capable of persistently storing information.

Processor 52 may be configured to read into memory 54 and execute computer-executable instructions that reside in CFD software module 58 and/or CFD-DEM software module 60 of non-volatile storage 56 and that embody the computational method techniques of one or more embodiments. Software modules 58 and/or 60 may include an operating system and applications. Software modules 58 and/or 60 may be compiled or interpreted from computer programs created using a variety of programming languages and/or techniques, including without limitation, Java, C + +, C #, Objective C, Fortran, Pascal, JavaScript, Python, Perl, and PL/SQL, either alone or in combination.

When executed by processor 52, the computer-executable instructions of CFD software module 58 and/or CFD-DEM software module 60 may cause computing platform 50 to implement one or more of the computing method techniques disclosed herein. The non-volatile storage 56 may also include CFD data 62 and CFD-DEM data 64 that support the functions, features, calculations, and processes of one or more embodiments described herein.

Program code embodying the algorithms and/or method techniques described herein may be distributed as a program product in a variety of different forms, both individually and collectively. Program code may be distributed using a computer readable storage medium having computer readable program instructions thereon for causing a processor to carry out aspects of one or more embodiments. Inherently non-transitory computer readable storage media may include volatile and non-volatile, and removable and non-removable tangible media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Computer-readable storage media may further include RAM, ROM, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other solid state memory technology, portable compact disc read-only memory (CD-ROM) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be read by a computer. The computer-readable program instructions may be downloaded from a computer-readable storage medium to a computer, another type of programmable data processing apparatus, or another device, or to an external computer or external storage device via a network.

The computer readable program instructions stored in the computer readable medium may be used to direct a computer, other type of programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function, act, and/or operation specified in the flowchart or illustration. In some alternative embodiments, the functions, acts and/or operations specified in the flowcharts and illustrations may be reordered, processed serially and/or processed simultaneously consistent with one or more embodiments. Further, any flow diagrams and/or illustrations may include more or fewer nodes or blocks than those illustrated consistent with one or more embodiments.

FIG. 3A depicts a schematic perspective view of an SLM build chamber 100 configured for use with one or more embodiments of a computing method. SLM building chamber 100 has a width (W), a length (L), and a height (H). In one embodiment, W, L and H are 450 mm, and 400 mm, respectively, but these sizes can be very significantly based on the design of the SLM build chamber. W may be any one of the following values or within a range of any two of the following values: 100. 200, 300, 400, 500, 600, 700, 800 and 900 mm. L may be any one of or within the range of any two of the following values: 100. 200, 300, 400, 500, 600, 700, 800 and 900 mm. H may be any one of the following values or within the range of any two of the following values: 100. 200, 300, 400, 500, 600, 700, 800 and 900 mm. W, L and H can be independently selected based on these values and ranges.

SLM building chamber 100 includes an inlet rail 102 configured to receive a flow of shielding gas and direct the flow of shielding gas through a cylindrical nozzle 104. The diameter of the entrance track 102 may be any one of or within a range of any two of the following values: 35. 36, 37, 38, 39, 40, 41, 42, 43 and 44 mm. The axial centerline of the entrance track 102 may be located approximately 50 mm above the bottom of the SLM building chamber 100. The axial length of the inlet rail 102 may be any one or within a range of any two of the following values: 320. 330, 340, 342, 350, 360 and 370 mm. Cylindrical nozzle 104 is configured to direct a flow of shielding gas into main chamber 106 of SLM building chamber 100 above powder bed 108 and towards outlet 110. In the embodiment shown in fig. 3A, the number of cylindrical nozzles 104 is 13. The number of cylindrical nozzles 104 may be any one of or within a range of any two of the following values: 10. 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20. In the embodiment shown in fig. 3A, each nozzle has a diameter of 12 mm. The diameter of each cylindrical nozzle 104 may be any one of or within a range of any two of the following values: 10. 11, 12, 13, 14 and 15 mm. In the embodiment shown in fig. 3A, the center-to-center distance is 18 mm. The center-to-center distance of adjacent cylindrical nozzles 104 may be or be within a range of any one or two of the following values: 15. 16, 17, 18, 19 and 20 mm.

The outlet 110 is partially surrounded by an outlet housing 112. The width (W) of the outlet housing may be any one of or within a range of any two of the following values: 45. 50, 55, 60, 65, 70 and 75 mm. The length (L) of the outlet housing may be any one of or within a range of any two of the following values: 280. 290, 300, 310, 320, 330 and 340 mm. The flow of shielding gas exits main chamber 106 through outlet 110.

In one or more embodiments, the calculation method simulates the flow of the shielding gas in the main chamber 106 by assuming that the shielding gas is transient, incompressible, and/or turbulent. In one or more embodiments, turbulent flow behavior may be modeled using a k-e turbulence model. According to one or more calculation methods disclosed herein, the inlet boundary condition for the flow of shielding gas through the inlet rail 102 may be referred to as a volumetric flow rate, and the outlet boundary condition for the flow of shielding gas exiting through the outlet 110 may be referred to as an outflow (outflow). The flow of the shielding gas in the main chamber 106 may be simulated using a CFD method.

The simulated shielding gas flow is then utilized to simulate the shielding gas flow and metal powder particle interaction. Reduced-scale fluid particles (e.g., CFD-DEM methods) may be used to simulate the interaction of the shielding gas stream and the metal powder particles. FIG. 3B depicts a schematic side view of the SLM build chamber 100 shown in FIG. 3A. As shown in fig. 3B, the flow of shielding gas from the inlet rail 102 begins within a predetermined value for the inlet boundary condition as indicated by arrow 114. The shielding gas flows over the powder bed 108. The shielding gas flows toward the outlet 110 as indicated by arrow 116. The metal powder particles of the powder bed 108 initially settle in the powder bed 108 as shown in fig. 3B.

Fig. 3C depicts a schematic side view of SLM build chamber 150 showing gas flow field 152 and powder bed field 154 configured for use with one or more steps of a computational method to simulate the interaction between a shielding gas flow and metal powder particles. The powder bed region 154 is located at the bottom of the gas flow region 152, as shown in fig. 3C. The length (L) of the gas flow field 152 may be about 30 mm. The height (H) of the gas flow field 152 may be about 30 mm. The width (W) of the gas flow field may be about 0.4 mm. The length (L) of the powder bed field 154 may be about 4 mm. The height (H) of the powder bed field 154 may be about 0.2 mm. The depth (D) of the powder bed field 154 may be about 0.4 mm. In one or more embodiments, the volume of the gas flow field 152 is relatively much larger (e.g., 90, 92, 94, or 96% larger) than the powder bed field 154 to ensure that the flow of shielding gas maintains a steady flow over the powder bed.

The computational method for simulating the interaction of the shielding gas flow and the metal powder particles may include a first step and a second step. The first step may include generating a powder bed. One method of producing the powder may include a raindrop method, in which a predetermined number of different sized metal powder particles are free to fall into a container under the force of gravity. Fig. 4A depicts a schematic perspective view of different sized metal powder particles 200 falling under gravity (g) into a container 202, indicated by the downward arrow 204. As depicted by legend 206, different sized metal powder particles 200 may have diameters of approximately 2.000e-03 to 6.000 e-03. Fig. 4B depicts a schematic perspective view of the settled powder bed 208 after different sized metal powder particles 200 have fallen into the container 202 under gravity (g). In one embodiment, the settled powder bed 208 is introduced into the powder bed 108 of fig. 3A as an initial state for determining the interaction between the shielding gas stream and the metal powder particles. The predetermined flow properties are assigned to the shielding gas. Based on these predetermined flow properties, the shielding gas enters the inlet and exits from the outlet. This flow of shielding gas may cause metal powder particles to be removed from the powder bed if the flow rate exceeds a threshold flow rate.

In one or more embodiments, metal powder particles of different sizes are considered to be perfect spheres having different diameters. According to the calculation method disclosed herein, newton's second law of motion may be used to determine X, Y and Z-direction velocities (including, without limitation, translational and rotational components) of individual metal powder particles. The calculation methods disclosed herein may also determine and account for drag forces due to the volume fraction of powder particles and particle-fluid interactions.

In one embodiment, the density and viscosity of the shielding gas for use with the one or more calculation methods are about 1.225 kg/m, respectively³And about 0.00001781 kg/m-s. In certain embodiments, the shielding gas density may be any one of or within a range of any two of the following values: 1.0, 1.2, 1.4, 1.6, 1.8 and 2.0 kg/m³. In certain embodiments, the shielding gas viscosity may be any one of or within a range of any two of the following values: 0.00001700, 0.00001800, 0.00001900, 0.00002000, 0.00002100 and 0.00002200 kg/m-s. In one embodiment, the metal powder particles for use with the one or more calculation methods have a density of about 7710 kg/m³. In certain embodiments, the density of the metal powder particles may be any one of or within a range of any two of the following values: 2000. 4000, 6000, 8000, 10000 and 12000 kg/m³. In one embodiment, the size distribution of the metal powder particles is in the range of about 18.8 μm (D10) to about 60.3 μm (D90), which has an average diameter of 36.7 μm.

FIG. 5A depicts a schematic perspective view of SLM build chamber 100 showing a vertical flow velocity plane 118 and a horizontal flow velocity plane 120 of a flow of shielding gas within main chamber 106 of SLM build chamber 100 using a predetermined inlet shielding gas flow rate and CFD calculation method, according to one embodiment. Fig. 5B depicts a schematic plan view of the horizontal flow velocity plane 120. Fig. 5C depicts a schematic plan view of the vertical flow velocity plane 118. The differently shaded areas in the velocity planes 118 and 120 represent different velocities in m/s. Legend 122 shows the different shading associated with speeds in the 0.000e +00 and 1.300e +00 ranges. As shown in fig. 5A, the horizontal flow velocity plane 120 is taken at a predetermined distance above the powder bed 108. According to the calculation method shown in fig. 5A, the predetermined distance is about 1 mm. In certain embodiments, the predetermined distance may be any one of or within a range of any two of the following values: 0. 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 mm.

The velocity planes 118 and 120 of fig. 5A were generated using an inlet shielding gas flow rate of 250 liters/minute. In other embodiments, the predetermined inlet shielding gas flow rate may be or be within a range of any one or both of the following values: 10. 100, 1000 and 10000 l/min. As can be seen by fig. 5A, the flow rate of the inlet shielding gas is not evenly distributed within the main chamber 106. In one embodiment, the calculation method determines the interaction between the metal powder particles in the powder bed 108 at regions where the flow rate is in a relatively high range (e.g., 1, 2, 3, 4, 5, 10, or 20% of the maximum flow rate). If the metal powder particles in the powder bed 108 are unaffected by the gas flow at the high velocity regions, the metal powder particles at the low velocity regions are also unaffected by the gas flow.

As shown in FIG. 5B, the maximum flow velocity above the powder bed 108 is about 1.3 m/s. When the maximum gas flow rate reaches a threshold, the metal powder particles in the region of maximum velocity may undergo uptake due to gas flow-particle interactions. The maximum flow velocity at a predetermined distance above the powder bed 108 determines the powder particle uptake condition. If the maximum flow velocity at the predetermined distance above the powder bed 108 is less than the threshold velocity for powder particle uptake, then no powder bed 108 is subjected to the powder uptake condition.

FIG. 6 is a graph 250 depicting the functional relationship between maximum velocity (meters per second or m/s) based on inlet gas flow rate (liters per minute or L/m) at a predetermined distance of 1 mm above the powder bed 108. The data points 252 are determined using one or more embodiments of the computational method. Dashed line 254 is a fit line through data points 252. As can be seen in fig. 6, the maximum velocity increases linearly with increasing inlet flow rate. The linear relationship shown in FIG. 6 is that y (maximum velocity in m/s) is equal to 0.0055x (inlet gas flow rate (L/m)) minus 0.0925. The functional relationship shown in fig. 6 may be used to correlate gas flow rates that do not create a powder particle uptake condition with inlet flow rates in response to an identified threshold velocity.

Fig. 7A is an image of a velocity profile 156 within the gas flow field 152 taken in a vertical velocity plane in response to a predetermined inlet flow rate. In the calculation method used in FIG. 7A, the inlet flow rate was 9 m/s. As shown in fig. 7A, a steady flow stream 158 is formed over the powder bed region 154. The legend 160 indicates that, due to turbulence and other factors, the velocity of the steady flow stream 158 is approximately less than an inlet flow velocity of 9 m/s. Fig. 7B is an image of the velocity profile 160 taken in the vertical velocity plane in the region between the powder bed region 154 and a predetermined distance 162 above the powder bed region 154. As shown in fig. 7B, the predetermined distance 162 is 1 mm. Fig. 7C is an image of particles 164 being ingested from the particles of the powder bed field 154. As shown in the legend 163 of fig. 7B, the maximum gas velocity at the predetermined distance is 7.34 m/s, and at this maximum gas velocity, the particles 164 are ingested from the particles of the powder bed field 154. Legend 166 shows shading for different particle sizes. According to the calculation method of one or more embodiments, the particle uptake condition is controlled.

Different maximum velocities at predetermined distances may be obtained by varying the inlet gas velocity of the calculation method of one or more embodiments. Fig. 8A, 8B and 8C depict images of the powder bed 300 at different inlet gas velocities of 6.53 m/s, 7.34 m/s and 8.19 m/s. Fig. 8A, 8B, and 8C include legends 302 that illustrate shading for different particle sizes. As shown in fig. 8A, no particles in the powder bed 300 are ingested by the inlet gas stream. As shown in fig. 8B, particles 304 are ingested from the powder bed 300. As shown in fig. 8C, particles 306 are ingested from the powder bed 300 and the area 308 is almost exposed in the underlying substrate. Thus, with increasing gas velocity, individual powder particles may be gradually blown away from their initial position, and the powder bed becomes thinner, and the surface morphology of the powder bed 300 changes significantly. In addition, some regions (e.g., region 308) may be free of powder particles on the underlying substrate. As shown in fig. 8A, 8B, and 8C, a maximum velocity of 7.34 m/s at a predetermined distance of 1 mm shows an early stage of the powder particle intake condition via the calculation method of one or more embodiments. According to the calculation method of one or more embodiments, the maximum velocity may be used as a threshold velocity for the powder particle uptake condition in response to the particular powder material and shielding gas parameters used.

The calculation method can be applied to varying powder and gas parameters. Fig. 9A shows an image of a velocity profile 350 within the gas flow field 152 and over the powder bed field 154 taken in a vertical velocity plane in response to a predetermined inlet flow rate based on certain powder particle and gas parameters. In this example, the shielding gas had a mass of 1.6228 kg/m³And a viscosity of 0.00002125 kg/m-s. In this example, the powder particles had a particle size of 4420 kg/m³And the size distribution of the powder particles is between 25 μm (D10) and 53 μm (D90), which has an average diameter of 38 μm. A legend 352 shows different shading of different velocities within the velocity profile 350. Fig. 9B shows an image of the powder particle bed 354 within the powder bed region 154 when the velocity profile 350 is applied. As shown in fig. 9B, the particles 356 were ingested from the powder particle bed 354 at a maximum velocity of 6.523 m/s from an inlet volume flow rate of approximately 1000 to 1500 liters/minute. According to the calculation method of one or more embodiments, the input speed may be reduced to determine a threshold speed of the powder particle uptake condition so that the condition may be controlled.

The following applications are related to the present application: U.S. patent application serial No. 16/592, 250 filed on 3/10/2019. The identified application is incorporated by reference herein in its entirety.

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously mentioned, the features of the various embodiments may be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments may have been described as providing advantages over or being preferred over other embodiments or prior art implementations in terms of one or more desired characteristics, those of ordinary skill in the art realize that one or more features or characteristics may be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, and the like. As such, to the extent that any embodiment is described as being less desirable in one or more characteristics than other embodiments or prior art implementations, such embodiments are not outside the scope of the present disclosure and may be desirable for particular applications.