Patent Application
20150165681
Selective laser sintering (“SLS”) is an additive manufacturing technology. SLS is used to manufacture a three-dimensional component (e.g., a part) in a layer-by-layer fashion from a powder such as plastic, metal, polymer, ceramic, composite materials, etc. For example, successive layers of powder are dispensed onto a target surface (e.g., a build surface) and a directed energy beam is scanned over the build surface to sinter each layer of powder to a previously sintered layer of powder. The directed energy beam is typically a laser, which can be modulated and precisely directionally controlled. The scan pattern of the directed energy beam is controlled using a representation such as a computer-aided design (“CAD”) drawing, for example, of the part to be built. In this way, the directed energy beam is scanned and modulated such that it melts portions of the powder within the boundaries of a cross-section of the part to be formed for each layer. For example, SLS is described in detail in U.S. Pat. No. 5,053,090 to Beaman et al. and U.S. Pat. No. 4,938,816 to Beaman et al.
Described herein are devices and methods for providing real-time control of powder sintering processes, which reduce or eliminate defects and internal stresses in components (e.g., parts) produced during the buildup and cooling phases of the powder sintering processes.
An example apparatus for producing a part from a powder using a powder sintering process can include a build chamber including one or more walls and a build piston configured to support the powder and the part. Additionally, the build chamber can enclose a build cylinder and a build surface, and the build piston can be arranged at least partially within the build cylinder. The apparatus can also include a plurality of heat sources distributed in the walls of the build chamber, the build cylinder and/or the build piston, an energy source arranged outside of the build chamber and configured to produce and direct an energy beam to the build surface, and a controller configured to control the heat sources. For example, the controller can control the heat sources to maintain an approximately uniform temperature distribution within the build chamber during the powder sintering process. This disclosure contemplates selectively and individually controlling each of the heat sources. Alternatively or additionally, a size and/or a shape of the build chamber and the arrangement of the heat sources can minimize flow over the build surface.
Additionally, the build cylinder and/or the build piston can include one or more inlet or outlet ports formed therein for accommodating a flow of build chamber gases. Optionally, an inlet port can be a gas inlet port for supplying gas to the build chamber. Optionally, an outlet port can be a gas outlet port for exhausting gas from the build chamber. In addition, the controller can be further configured to control operation of the inlet or outlet ports to adjust a temperature and/or a chemical composition of the build chamber gases, for example, by facilitating supply and/or exhaust of gas to/from the build chamber. This disclosure contemplates selectively and individually controlling each of the inlet or outlet ports.
Alternatively or additionally, the controller can be further configured to control the heat sources and/or the inlet or outlet ports to maintain the part at variable temperatures during the powder sintering process. For example, the variable temperatures can be optimized for powder sintering and annealing of induced internal stresses in the part.
Additionally, the apparatus can optionally include a multi-spectral imaging device configured to acquire images of the build surface, the powder, the part, the walls of the build chamber and/or the build cylinder. The controller can be further configured to receive the images acquired by the multi-spectral imaging device, estimate respective temperature distributions of the build surface, the powder, the part, the walls of the build chamber and/or the build cylinder from the images acquired by the multi-spectral imaging device, and control the energy source (e.g., the operating characteristics and/or scan pattern of the energy beam), the heat sources and/or the inlet or outlet ports based on the estimated respective temperature distributions. For example, the multi-spectral imaging device can be an infrared imaging device. Optionally, the controller can be further configured to calculate a theoretical or computational model for respective temperature distributions for the build surface, the powder, the part, the walls of the build chamber and/or the build cylinder under similar build chamber conditions, compare the estimated respective temperature distributions with the theoretical or computational model, and control the energy source, the heat sources and/or the inlet or outlet ports based on the comparison.
Alternatively or additionally, the apparatus can optionally include a non-optical imaging device configured to acquire images of the powder and the part. The controller can be further configured to receive the images acquired by the non-optical imaging device, determine a condition of the part from the images acquired by the non-optical imaging device, and control the energy source, the heat sources and/or the inlet or outlet ports based on based on the condition of the part. For example, the non-optical imaging device can be an acoustic or electro-magnetic imaging device.
Alternatively or additionally, the apparatus can optionally include a bore-sighted multi-spectral imaging device configured to acquire images of an energy beam-powder interaction region on the build surface. As used herein, the energy beam-powder interaction region includes a point where the energy beam intersects the build surface and can optionally include a melt pool (e.g., at least a portion of the melted powder). The controller can be further configured to receive the images acquired by the bore-sighted multi-spectral imaging device and estimate real-time properties of the energy beam-powder interaction region from the images acquired by the bore-sighted multi-spectral imaging device. The controller can also be configured to calculate a theoretical or computational model for an energy beam-powder interaction region for a similar powder material under similar build chamber conditions, compare the estimated real-time properties of the energy beam-powder interaction region with the theoretical or computational models, and control the energy source, the heat sources and/or the inlet or outlet ports based on the comparison.
Optionally, the apparatus can include an energy beam power meter configured to measure a power of the energy beam, where the energy beam power meter is arranged near the build surface within the build chamber. The controller can be further configured to receive the power of the energy beam, and control the energy source based on the power of the energy beam measured within the build chamber.
Additionally, the apparatus can include a powder feed device arranged outside of the build chamber. The powder feed device can include a powder feed bin configured to store the powder, a powder metering device configured to dispense a measured amount of the powder from the powder feed bin, and a powder drop chute configured to guide the measured amount of the powder into the build chamber. The powder metering device can be arranged between the powder feed bin and the powder drop chute. Optionally, the powder metering device and the powder drop chute are configured to scatter the measured amount of the powder such that the measured amount of the powder undergoes rapid heat transfer as the powder enters the build chamber. For example, the powder can rapidly increase in temperature from an approximate temperature of the powder feed bin to a temperature that minimizes thermal mismatch and part curl when the powder is spread over the build surface. Optionally, the powder drop chute can be configured to deliver the measured amount of the powder to a position near the build surface within the build chamber. In addition, the apparatus can include a strip heater arranged in the build chamber at the position near the build surface.
Alternatively or additionally, the apparatus can include a powder spreading device including a powder spreading roller, a drive system and a thermal box. The powder spreading roller can be arranged within the build chamber, and the drive system and thermal box can be arranged outside of the build chamber. In addition, the drive system can be configured to control at least one of translation and rotation of the powder spreading roller. Further, the thermal box can include one or more thermal seals between the build chamber and components of the drive system. Optionally, the drive system can include a translation drive system configured to control the translation of the powder spreading roller, and a rotation drive system configured to control the rotation of the powder spreading roller.
Optionally, the powder sintering process includes building of the part and subsequent cooling down of the part.
An example method for real-time control of a powder sintering process for producing a part from a powder can include providing a build chamber that encloses a build surface, and acquiring, using a multi-spectral imaging device, images of the build surface, the build chamber, the part and/or the powder. In addition, the method can include, using a controller, estimating respective temperature distributions of the build surface, the build chamber, the part and/or the powder from the images acquired by the multi-spectral imaging device, and controlling the powder sintering process based on the estimated respective temperature distributions. Optionally, the method can further include, using the controller, calculating a theoretical or computational model for respective temperature distributions for the build surface, the build chamber, the part and/or the powder under similar build chamber conditions, comparing the estimated respective temperature distributions with the theoretical or computational model, and controlling the energy source, the heat sources and/or the inlet or outlet ports based on the comparison.
Alternatively or additionally, the method can include acquiring, using a non-optical imaging device, images of the part and the powder. The method can further include, using the controller, determining a condition of the part from the images acquired by the non-optical imaging device, and controlling the powder sintering process based on the condition of the part.
Additionally, the method can include providing an energy source configured to produce and direct an energy beam to the build surface. In addition, the step of controlling the powder sintering process can include adjusting characteristics of the energy beam (e.g., the operating characteristics and/or scan pattern of the energy beam). Alternatively or additionally, the method can include acquiring, using a bore-sighted multi-spectral imaging device, images of an energy beam-powder interaction region on the build surface, e.g., a point where the energy beam intersects the build surface and can optionally include a melt pool. The method can further include, using the controller, estimating real-time properties of the energy beam-powder interaction region from the images acquired by the bore-sighted multi-spectral imaging device, calculating a theoretical or computational model for an energy beam-powder interaction region for a similar powder material under similar build chamber conditions, comparing the estimated real-time properties of the energy beam-powder interaction region with the theoretical or computational model, and controlling the powder sintering process based on the comparison.
Additionally, the build chamber can include a plurality of heat sources distributed therein. Further, the step of controlling the powder sintering process can include energizing or de-energizing one or more of the heat sources. This disclosure contemplates selectively and individually controlling each of the heat sources. For example, the heat sources can be controlled to maintain an approximately equal temperature distribution within the build chamber.
Alternatively or additionally, the build chamber can enclose a build cylinder having a build piston arranged at least partially therein, and the build piston can be configured to support the powder and the part. Further, the build cylinder and/or the build piston can have one or more inlet or outlet ports formed therein. The step of controlling the powder sintering process can include controlling operation of the inlet or outlet ports to adjust at least one of a temperature or a chemical composition of build chamber gases. This disclosure contemplates selectively and individually controlling each of the inlet or outlet ports.
Optionally, the step of controlling the powder sintering process can include maintaining the part at variable temperatures during the powder sintering process. For example, the variable temperatures can be optimized for powder sintering and annealing of induced internal stresses in the part.
Additionally, the method can include providing a powder feed bin configured to store powder, where the powder feed bin is arranged outside of the build chamber, and dispensing a measured amount of the powder from the powder feed bin into the build chamber. In addition, the measured amount of the powder can undergo rapid heat transfer as the powder enters the build chamber between an approximate temperature of the powder feed bin and a temperature that minimizes thermal mismatch and part curl when the powder is spread over the build surface.
Alternatively or additionally, the method can include providing a powder spreading device including a powder spreading roller and a drive system configured to control translation and rotation of the powder spreading roller. The powder spreading roller can be arranged within the build chamber, and the drive system can be arranged outside of the build chamber. A thermal box including one or more thermal seals between the build chamber and components of the drive system can also be provided. The method can further include independently controlling, using the drive system, the translation and the rotation of the powder spreading roller.
Another example method for real-time control of a powder sintering process for producing a part from a powder can include providing a build chamber that encloses a build surface, and acquiring, using a multi-spectral imaging device, images of the build surface, the build chamber, the part and/or the powder. The method can also include, using a controller, estimating respective real-time temperature distributions of the build surface, the build chamber, the part and/or the powder from the images acquired by the multi-spectral imaging device, calculating a real-time physics-based model of the powder sintering process based on the respective real-time temperature distributions, and controlling the estimated powder sintering process based on the real-time physics-based model.
Other systems, methods, features and/or advantages will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be protected by the accompanying claims.
The components in the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding parts throughout the several views.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure. As used in the specification, and in the appended claims, the singular forms “a,” “an,” “the” include plural referents unless the context clearly dictates otherwise. The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms. The terms “optional” or “optionally” used herein mean that the subsequently described feature, event or circumstance may or may not occur, and that the description includes instances where said feature, event or circumstance occurs and instances where it does not. While implementations will be described for providing real-time control of SLS processes, it will become evident to those skilled in the art that the implementations are not limited thereto, but are applicable for providing real-time control of other powder sintering processes.
Referring now to
A plurality of heat sources can be distributed throughout the build chamber 102. For example, heat sources can be distributed in the walls of the build chamber, the build cylinder and/or the build piston. For example, as shown in
The apparatus 100 can also include an energy source 112. As shown in
The build cylinder 104 and/or the build piston 108 can include one or more inlet or outlet ports formed therein for accommodating a flow of build chamber gases. Optionally, an inlet port can be a gas inlet port for supplying gas to the build chamber 102. Optionally, an outlet port can be a gas outlet port for exhausting gas from the build chamber 102.
The apparatus 100 can also include a powder feed device 124 arranged outside of the build chamber 102. The powder feed device 124 is also shown in
The powder metering device 128 and the powder drop chute 130 can be configured to scatter the measured amount of the powder such that the measured amount of the powder undergoes rapid heat transfer as the powder enters the build chamber 102. As described above, the powder is stored in the powder feed bin 126, for example, at a temperature below which the powder does not degrade. Upon entering the build chamber 102, the measured amount of powder can undergo rapid heat transfer (e.g., flash) to a higher temperature. For example, the powder can rapidly increase in temperature from the approximate temperature of the powder feed bin to a temperature that minimizes thermal mismatch between the powder and the build surface 106 when the powder is spread. This minimizes the amount of heat transfer between each successive layer of powder spread over the existing part cake, which minimizes thermal stresses and associated part curl. In contrast, when there is thermal mismatch between the powder and the existing part cake, temperature gradients can induce thermal stresses that might damage the part being built. Optionally, as described above, the strip heater 132 and/or the lamp heater 133 can also be used to heat the powder to the desired temperature before spreading the powder over the build surface 106.
The apparatus 100 can also include an energy beam power meter (e.g., the laser power meter 122 shown in
The apparatus 100 can also include a powder spreading device 134. The powder spreading device 134 can be configured to enable fine control the thickness of each successive layer of powder during the powder sintering process. The powder spreading device 134 is also shown in
The apparatus 100 can optionally include a multi-spectral imaging device 120A configured to acquire images of the build surface 106, the powder, the part, the walls of the build chamber 102 and/or the build cylinder 104. Optionally, the multi-spectral imaging device 120A can be used to acquire images of at least two of the build surface 106, the powder, the part, the walls of the build chamber 102 and/or the build cylinder 104 (e.g., as opposed to acquiring only images of a single region such as the build surface 106, for example). As shown in
Optionally, physics and cyber-enabled manufacturing (“CeMs”) process controls can be implemented to control the powder sintering processes described herein. CeMs process controls use high-fidelity physics-based models, as well as real-time measurements, to control the powder sintering process. For example, the physics-based models can provide a theoretical or computational model(s) of the energy beam-powder interaction region, flow and distribution of thermal energy in the build chamber and/or flow and distribution of thermal energy in the part cake. As used herein, the energy beam-powder interaction region includes a point where the energy beam intersects the build surface (e.g., the build surface 106 shown in
Alternatively or additionally, the apparatus 100 can optionally include a bore-sighted multi-spectral imaging device (e.g., the bore-sighted multi-spectral imaging device 120B shown in
Similar as described above, using a controller (e.g., the controller described below with regard to
Alternatively or additionally, the apparatus 100 can optionally include a non-optical imaging device configured to acquire images of the powder and the part. For example, the non-optical imaging device can be an acoustic or electro-magnetic imaging device. The non-optical imaging device can be arranged outside of the build chamber and can acquire images through the walls of the build chamber, for example. The non-optical imaging device can be used to acquire three-dimensional images of the part, the powder and/or the part cake, which can be used to identify/characterize the three-dimensional properties of the part within the part cake during the powder sintering process. These images can be used to identify/characterize conditions (e.g., defects, non-uniformities, etc.) of the part during the powder sintering process. Similar to above, this information can be used as feedback to provide real-time control the energy source (e.g., the energy source 112 shown in
As described above, the real-time process controls described herein can minimize pre-mature additive manufacturing part failure due to hidden flaws associated with poor process management, as well as can enable additive manufacturing processing at higher environmental conditions while maintaining real-time control to reduce the induction of internal stresses in the manufactured parts. For example, conventional additive manufacturing technologies do not provide adaptive control of the thermal temperature time history at the level of detail enabled by the process controls described herein, which enable higher predictability and performance in resulting manufactured parts.
It should be appreciated that the logical operations described herein with respect to the various figures may be implemented (1) as a sequence of computer implemented acts or program modules (i.e., software) running on a computing device, (2) as interconnected machine logic circuits or circuit modules (i.e., hardware) within the computing device and/or (3) a combination of software and hardware of the computing device. Thus, the logical operations discussed herein are not limited to any specific combination of hardware and software. The implementation is a matter of choice dependent on the performance and other requirements of the computing device. Accordingly, the logical operations described herein are referred to variously as operations, structural devices, acts, or modules. These operations, structural devices, acts and modules may be implemented in software, in firmware, in special purpose digital logic, and any combination thereof. It should also be appreciated that more or fewer operations may be performed than shown in the figures and described herein. These operations may also be performed in a different order than those described herein.
When the logical operations described herein are implemented in software, the process may execute on any type of computing architecture or platform. For example, referring to
Computing device 700 may have additional features/functionality. For example, computing device 700 may include additional storage such as removable storage 708 and non-removable storage 710 including, but not limited to, magnetic or optical disks or tapes. Computing device 700 may also contain network connection(s) 716 that allow the device to communicate with other devices. Computing device 700 may also have input device(s) 714 such as a keyboard, mouse, touch screen, etc. Output device(s) 712 such as a display, speakers, printer, etc. may also be included. The additional devices may be connected to the bus in order to facilitate communication of data among the components of the computing device 700. All these devices are well known in the art and need not be discussed at length here.
The processing unit 706 may be configured to execute program code encoded in tangible, computer-readable media. Computer-readable media refers to any media that is capable of providing data that causes the computing device 700 (i.e., a machine) to operate in a particular fashion. Various computer-readable media may be utilized to provide instructions to the processing unit 706 for execution. Common forms of computer-readable media include, for example, magnetic media, optical media, physical media, memory chips or cartridges, a carrier wave, or any other medium from which a computer can read. Example computer-readable media may include, but is not limited to, volatile media, non-volatile media and transmission media. Volatile and non-volatile media may be implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data and common forms are discussed in detail below. Transmission media may include coaxial cables, copper wires and/or fiber optic cables, as well as acoustic or light waves, such as those generated during radio-wave and infra-red data communication. Example tangible, computer-readable recording media include, but are not limited to, an integrated circuit (e.g., field-programmable gate array or application-specific IC), a hard disk, an optical disk, a magneto-optical disk, a floppy disk, a magnetic tape, a holographic storage medium, a solid-state device, RAM, ROM, electrically erasable program read-only memory (EEPROM), flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices.
In an example implementation, the processing unit 706 may execute program code stored in the system memory 704. For example, the bus may carry data to the system memory 704, from which the processing unit 706 receives and executes instructions. The data received by the system memory 704 may optionally be stored on the removable storage 708 or the non-removable storage 710 before or after execution by the processing unit 706.
Computing device 700 typically includes a variety of computer-readable media. Computer-readable media can be any available media that can be accessed by device 700 and includes both volatile and non-volatile media, removable and non-removable media. Computer storage media include volatile and non-volatile, and removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. System memory 704, removable storage 708, and non-removable storage 710 are all examples of computer storage media. Computer storage media include, but are not limited to, RAM, ROM, electrically erasable program read-only memory (EEPROM), flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) 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 accessed by computing device 700. Any such computer storage media may be part of computing device 700.
It should be understood that the various techniques described herein may be implemented in connection with hardware or software or, where appropriate, with a combination thereof. Thus, the methods and apparatuses of the presently disclosed subject matter, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other machine-readable storage medium wherein, when the program code is loaded into and executed by a machine, such as a computing device, the machine becomes an apparatus for practicing the presently disclosed subject matter. In the case of program code execution on programmable computers, the computing device generally includes a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. One or more programs may implement or utilize the processes described in connection with the presently disclosed subject matter, e.g., through the use of an application programming interface (API), reusable controls, or the like. Such programs may be implemented in a high level procedural or object-oriented programming language to communicate with a computer system. However, the program(s) can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language and it may be combined with hardware implementations.
Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.
This application claims priority to and benefit of U.S. Provisional Patent Application Ser. No. 61/917,652 filed on Dec. 18, 2013, which is fully incorporated by reference and made a part hereof.
| Number | Date | Country | |
|---|---|---|---|
| 61917652 | Dec 2013 | US |
