WO2020076295A1

WO2020076295A1 - Depowdering a 3d printed object

Info

Publication number: WO2020076295A1
Application number: PCT/US2018/054931
Authority: WO
Inventors: Andrew Lester VAN BROCKLIN; Michael Gabriel MONROE
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2018-10-09
Filing date: 2018-10-09
Publication date: 2020-04-16

Abstract

In one example, a system for depowdering an object printed with a powder based 3D printer includes a depowdering unit to remove powder from the printed object, a scanner, and a controller operatively connected to the scanner to, during depowdering the printed object, iteratively obtain scans of the printed object from the scanner and compare a scan to a 3D model of the object until a comparison is within a tolerance between the scan and the model.

Description

DEPOWDERING A 3D PRINTED OBJECT BACKGROUND

[0001] 3D printers convert a digital representation of an object into a physical object. 3D printers are used to manufacture objects with complex geometries using a variety of materials including thermoplastics, polymers, ceramics and metals. In powder based 3D printing, successive layers of a powdered build material are formed and portions of each layer solidified in a desired pattern to build up the layers of the 3D object. 3D printing is also commonly referred to as additive manufacturing.

DRAWINGS

[0002] Fig. 1 illustrates an example system for depowdering a 3D printed object.

[0003] Fig. 2 illustrates an example implementation for a controller in the depowdering system shown in Fig. 1.

[0004] Fig. 3 illustrates an example implementation for a depowdering system shown in Fig. 1.

[0005] Figs. 4 and 5 illustrate example processes to be performed during depowdering a 3D printed object.

[0006] The same part numbers designate the same or similar parts throughout the figures.

DESCRIPTION

[0007] Metal objects may be printed by selectively applying a liquid binding agent to portions of each of successive layers of metal powder to bind together those portions of the powder corresponding to the solid layer of the 3D object. The binding agent is cured, for example using heat and/or ultra violet energy. The cured object, known commonly as a“green part”, is heated in a sintering furnace to burn off any residual binder and fuse the metal. Polymer objects may be printed by selectively applying a liquid fusing agent to portions of each of successively layers of polymer powder and exposing the treated powder to electromagnetic radiation, causing the treated powder to fuse. [0008] Some of the powder used to print a 3D object may cling to the printed object. The process of removing powder from 3D printed objects is commonly referred to as“depowdering.” Depowdering techniques include vacuuming, vibrating, brushing and air blasting. Different depowdering techniques may be used for different types of printed objects. Higher intensity depowdering may be used on robust, fully fused objects while lower intensity depowdering may be more appropriate for green parts and other fragile objects.

[0009] One of the challenges depowdering 3D printed objects is knowing when depowdering is complete, particularly for fragile green parts in which binder agent, or components of the binder agent, may leak into the surrounding powder and cause the powder to stick to the part after curing. If this unwanted residual powder is not removed before sintering, the sintered, fully fused object may be out of form. In addition, residual unbound or unfused powder may be particularly difficult to remove from holes, recesses, and other internal features. Green parts are fragile compared to a sintered, fused part. Depending on the type of binder agent, some green parts may be easily crushed by hand. Consequently, it may not be possible to use aggressive techniques for depowdering green parts, at least not for the entirety of the depowdering process.

[0010] A new technique has been developed in which a feedback loop is used to help determine when depowdering is complete. In one example, a

depowdering system includes a scanner to scan a 3D printed object during depowdering and a controller to iteratively compare a scan of the printed object to a 3D model used to print the object. When the comparison is within a desired tolerance, depowdering may be deemed complete. The controller may include programming to determine a dimension or group of dimensions from the scans and compare the dimension(s) to the corresponding dimension(s) in the object model. This determination may be made, for example, by the controller creating a 3D model of the printed object from the scans. While it is expected that the comparison usually will be made for pre-selected dimensional tolerances, other recognizable features may be used. The feedback loop may be used to adjust the type and/or intensity of depowdering based on the comparisons. For example, the intensity of depowdering may be lowered when a green part approaches the tolerance to avoid degrading the part itself. For another example, depowdering may be intensified to remove stubborn deposits or targeted to a particular location where the printed object or green part remains out of tolerance.

[0011] These and other examples described below illustrate but do not limit the scope of the patent which is defined in the Claims following this Description.

[0012] As used in this document, "a" and "an" means one or more;“and/or” means one or more of the connected things; a“memory” means any non- transitory tangible medium that can embody, contain, store, or maintain information and instructions for execution by a processor and may include, for example, circuits, integrated circuits, ASICs (application specific integrated circuits), hard drives, random access memory (RAM), read-only memory (ROM), and flash memory; and“scan” means to look at something carefully to detect some feature, for example by measuring or imaging.

[0013] Fig. 1 illustrates an example system 10 for depowdering a 3D printed object. Referring to Fig. 1 , depowdering system 10 includes a depowdering unit 12 to remove powder from the printed object, a scanner 14 to scan the printed object during depowdering, and a controller 16 operatively connected to depowdering unit 12 and scanner 14. A scanner 14 in Fig. 1 represents any suitable scanner for imaging, measuring or otherwise detecting the desired feature or features of the object. Scanner 14 may be implemented, for example, as a 3D scanner, a video or still image camera (or group of cameras) and/or a laser measurement tool. A depowdering unit 12 in Fig. 1 represents any suitable depowdering tool or system of tools for depowdering a printed green part or a fully fused object. Depowdering unit 12 may include, for example, a single

depowdering tool or a system of tools and associated processing devices.

Depowdering tools and processing devices include, for example, vacuums, ultrasonic and mechanical vibrators, brushes and air blasters. A depowdering unit 12 may also include sieves, separators and holding, collection and recycling containers. A depowdering system 10 may be implemented, for example, in a depowdering module that is part of a 3D printer or at a depowdering station separate or even remote from the printer. [0014] Controller 16 includes the programming, processing and associated memory resources, and the other electronic circuitry and components to control the operative elements of system 10. In particular, controller 16 includes programming to, during depowdering, iteratively obtain scans of the printed object from scanner 14 and compare the scans to a 3D model of the object until a comparison is within a desired tolerance. Controller 16 can then signal an operator that depowdering is complete and/or automatically stop depowdering. As shown in Fig. 2, controller 16 includes a processor 18, such as a microprocessor or microcontroller, and a memory 20 in communication with processor 18.

Memory 20 includes depowdering instructions 22 which represent programming to make comparisons between the object scans and the object model.

[0015] Fig. 3 illustrates an example depowdering system 10 from Fig. 1.

Referring to Fig. 3, depowdering unit 12 in system 10 includes a support 24 to support green parts or other printed objects 26. In this example, support 24 and thus objects 26 may be rotated in two axes, as indicated by arrows 28, to present objects 26 to the system tools in various aspects in three dimensions. Objects 26 on support 24 are housed in a depowdering chamber 30 along with a vibrator 32 to vibrate objects 26, gas blasters 34 to blow air or another gas at objects 26, and video cameras 14 to scan objects 26. A vacuum may be applied generally to chamber 30, as indicated by arrows 36, to remove powder 38 to a collection tank 40 for recycling or disposal. Also, a vacuum hose may be used to suck powder away from objects 36 in addition to, or as an alternative to, a generalized vacuum.

[0016] Controller 16 is operatively connected to cameras 14 to obtain image scans of objects 26 during depowdering. Controller 16 may also be operatively connected to one or more of the depowdering tools - support 24, vibrator 32, blasters 34, and vacuum 36. For support 24, controller 16 executing instructions 22 (Fig. 2) may control the position of objects 26 for scanning and depowdering. For vibrator 32, blasters 34 and vacuum 36, controller 16 executing instructions 22 (Fig. 2) may start and stop the tool and/or vary the intensity of the tool using feedback from comparisons between the scanned images of objects 26 and the object model. A depowdering unit 12 may include powder (not shown in Fig. 3) surrounding objects 26 in chamber 30 to help transmit vibration to the objects. Tool adjustments by controller 16 may include, for example, vibration intensity and frequency, blaster and vacuum pressure, and the duration and frequency of vibrating, blasting and vacuuming.

[0017] Fig. 4 illustrates an example process 100 to be performed during depowdering a 3D printed green part or other printed object 26. Process 100 may be implemented, for example, by a controller 16 executing depowdering instructions 22. Part numbers in the description of process 100 refer to Figs. 1-3. Referring to Fig. 4, process 100 includes scanning an object 26 during

depowdering (block 102), determining a dimension of the object from a scan (block 104), and then determining if the dimension from the scan is within a tolerance of the corresponding dimension in a 3D object model used to print the object (block 106). If it is determined the dimension from the scan is not within the tolerance, then repeating the process (block 108). If it is determined the dimension from the scan is within the tolerance, then ending the process (block 1 10).

[0018] Depowdering continues (or resumes) each time it is determined the dimension from the scan is not within the tolerance. Each of multiple objects 26 may be scanned at block 102 in process 100 and dimensional determinations and decisions made at blocks 104-1 10 for each object. Multiple dimensions and corresponding tolerances may be used to determine if depowdering is complete.

In one example, process 100 includes terminating depowdering automatically if the dimensions(s) are within tolerance. In another example, process 100 includes signaling an operator that the dimension(s) are within tolerance. Process 100 may be terminated after a threshold number of iterations even if it is determined the dimension is still out of tolerance, for example to handle a defective object. Object 26 may be scanned continuously during depowdering or periodically.

Object 26 may be scanned while the object is actively being depowdered, or active depowdering may be suspended or depowdering intensity reduced temporarily to facilitate scanning the object.

[0019] Fig. 5 illustrates an example process 200 to be performed during depowdering a 3D printed green part or other printed object 26. Process 200 may be implemented, for example, by a controller 16 executing depowdering instructions 22. Part numbers in the description of process 200 refer to Figs. 1-3. Referring to Fig. 5, process 200 includes scanning an object 26 in three dimensions during depowdering (block 202), recognizing a feature of the object from the scan (block 204), and locating the object in space using the recognized feature (block 206). Once the printed object is located in space, dimensional comparisons are made between a scan of the printed object and the object model used to print the object. Process 100 includes determining a dimension of the object from a scan (block 208) and then determining if the dimension from the scan is within a tolerance of the corresponding dimension in the 3D object model (block 210). If it is determined the dimension from the scan is not within the tolerance, then repeating the process (block 212). If it is determined the dimension from the scan is within the tolerance, then ending the process (block 214).

[0020] For locating the printed object in space, depowdering may proceed until a feature is recognized at block (204) and then controller 16 executing instructions 22 may generate a 3D model of the printed object from a scan or series of scans and use the model to make the desired dimensional comparisons. Rule sets, deepnets and other suitable feature recognition techniques may be used to recognize features from the 3D object model to locate the printed object while still partly covered with powder.

[0021] A depowdering control process, such as processes 100, 200 shown in Figs. 4 and 5, may take as input a 3D model used to print object 26 along with dimensional tolerances representing the desired precision of form and yield. In addition, control process input may include information representing the effects of various depowdering tools and processes relative to the amount of powder remaining on the object or a particular object feature. Tool information may be used to determine if and when to start and stop a depowdering tool and/or to vary the intensity of a depowdering tool using feedback from the dimensional comparisons between scans and the object model. These and any other inputs may be stored locally in controller memory 20 or retrieved from a remote source “on the fly” during execution of depowdering instructions 22. [0022] As noted at the beginning of this Description, the examples shown in the figures and described above illustrate but do not limit the scope of the patent. Other examples are possible. Therefore, the foregoing description should not be construed to limit the scope of the patent, which is defined in the following Claims

Claims

1. A system for depowdering an object printed with a powder based 3D printer, the system comprising:

a depowdering unit to remove powder from the printed object;

a scanner; and

a controller operatively connected to the scanner to, during depowdering the printed object, iteratively obtain scans of the printed object from the scanner and compare a scan to a 3D model of the object until a comparison is within a tolerance between the scan and the model.

2. The system of Claim 1 , wherein the controller is to determine a dimension of the printed object from a scan and compare the dimension to a corresponding dimension in the 3D object model until a comparison is within a tolerance for the dimension.

3. The system of Claim 1 , wherein the scanner comprises a 3D scanner.

4. The system of Claim 1 , wherein:

the scanner is to scan multiple printed objects simultaneously; and the controller is to iteratively obtain scans of the multiple printed objects from the scanner and compare a scan to a 3D model of the object until a comparison is within a tolerance between the scan and the model for all of the printed objects.

5. The system of Claim 1 , wherein the controller is to signal an end to depowdering when a comparison is within the tolerance.

6. The system of Claim 1 , wherein the controller is to adjust the depowdering unit in response to a comparison that is not with the tolerance.

7. A process to be performed during depowdering a green part printed with a powder based 3D printer, the process comprising:

scanning the green part;

determining a dimension of the green part from the scan;

determining if the dimension from the scan is within a tolerance of the dimension in a 3D model of the part; and

if it is determined the dimension from the scan is not within the tolerance, then repeating the scanning, determining and determining; or

if it is determined the dimension from the scan is within the tolerance, then ending the process.

8. The process of Claim 7, comprising ending the process after repeating the scanning, determining and determining a threshold number of times even if it is determined the dimension from the scan is not within the tolerance.

9. The process of Claim 7, comprising removing unbound powder from the green part each time it is determined the dimension from the scan is not within the tolerance.

10. A memory having processor executable instructions to, during depowdering a printed object, iteratively obtain a scan of the printed object and compare the scan to a 3D model of the object until a comparison is within a tolerance.

1 1. The memory of Claim 10 having instructions to signal an end to depowdering when a comparison is within the tolerance.

12. The memory of Claim 10 having instructions to adjust depowdering in response to a comparison that is not with the tolerance.

13. The memory of Claim 10 having instructions to recognize a feature of the object in a scan of the printed object and wherein the instructions to compare the scan to a 3D model of the object include instructions to compare a recognized feature to the corresponding feature in the model.

14. The memory of Claim 10 having instructions to recognize a feature of the object in a scan of the printed object, locate the printed object in space based on the recognized feature, and thereafter iteratively determine a dimension from a scan of the printed object, and wherein the instructions to compare the scan to a 3D model of the object include instructions to compare a determined dimension to the 3D model until a determined dimension is within a tolerance for the dimension.