WO2022182594A1

WO2022182594A1 - Material rake assembly for additive manufacturing machine

Info

Publication number: WO2022182594A1
Application number: PCT/US2022/017041
Authority: WO
Inventors: Christopher Sean MARGESON; Yoon Jung JEONG; Lexian GUO; Alton Hugh Phillips
Original assignee: Nikon Corporation
Priority date: 2021-02-28
Filing date: 2022-02-18
Publication date: 2022-09-01

Abstract

A material rake assembly (19) for raking material (12) on a build platform (28A) of a processing machine (10) includes: a mounting assembly (236); a flexible, projection (240) that is coupled to the mounting assembly (236); and a stopper (242). The projection (240) engages and rakes the material (12) on the build platform (28A). Further, the stopper (242) allows for deflection of the projection (240) while inhibiting over-deflection of the projection (240). Moreover, a flexible connector (244) movably connects the projection (240) to the mounting assembly (236). With this design, the material rake assembly (19) scrapes over both small asperities (213C) and large asperities (213D) while accurately leveling the material (12) on the build platform (28A).

Description

MATERIAL RAKE ASSEMBLY FOR ADDITIVE MANUFACTURING MACHINE

RELATED APPLICATIONS

[0001] This application claims priority on U.S. Provisional Application No: 63/154,744 filed on February 28, 2021 , and entitled “MATERIAL RAKE ASSEMBLY FOR ADDITIVE MANUFACTURING MACHINE”. As far as permitted the contents of U.S. Provisional Application No: 63/154,744 are incorporated in their entirety herein by reference.

[0002] As far as permitted the contents of PCT Application No: PCT/US18/67407 entiteld “ADDITIVE MANUFACTURING SYSTEM WITH ROTARY POWDER BED” filed on December 22, 2018, and the contents of PCT Application No: PCT/US18/67406 entiteld “ROTATING ENEGY BEAM FOR THREE-DIMENSIONAL PRINTER” filed on December 22, 2018 are incorporated herein by reference.

BACKGROUND

[0003] Three-dimensional printing systems are used to print three-dimensional objects. One type or three-dimensional printing system is an electron beam additive manufacturing system (“EBAM”). In this system, a material supply deposits material onto a build platform, and a material rake having one or more rake teeth subsequently levels the material to create a material layer. Next, an electron beam or laser system generates a beam that melts the desired portions of the material layer. Subsequently, the material supply deposits additional material onto the previously formed material layer, and the material rake subsequently levels the material to create a new material layer. Next, the electron beam system generates the electron beam that melts the desired portions of the material layer. This process is repeated for multiple material layers until the object is formed.

[0004] Unfortunately, during the melting process, the material can ball up and/or splatter. This can result in asperities in the previously formed material layer. These asperities can adversely influence the leveling done by the material rake on the subsequent material layer(s). This can contribute to poor fabrication quality, and reduce the accuracy of the built object. Further, large asperities can permanently deform and damage one or more rake teeth for the material rake. The deformed rake teeth can lead to uneven material layers and can further contribute to poor fabrication quality.

SUMMARY

[0005] A material rake assembly for raking material on a build platform of a processing machine includes: a mounting assembly; a flexible, first projection that is coupled to the mounting assembly; and a first stopper. The first projection engages and rakes the material on the build platform. Further, the first stopper allows for deflection of the first projection while inhibiting over-deflection of the first projection. With this design, the material rake assembly is able to scrape over both small and large asperities while accurately leveling the material on the build platform. Because the material is accurately leveled, a resulting object will be more accurate. Further, because the material rake assembly scrapes over both small and large asperities, the material rake assembly will not be damaged by these asperities.

[0006] In one implementation, the first projection is at an acute, initial angle relative to normal to the build platform; and the first stopper inhibits deflection of the first projection past a maximum deflection angle relative to normal. The first stopper can include an engagement surface that is at the maximum deflection angle, and the engagement surface can engage the first projection and inhibit the first projection from deflecting past the maximum deflection angle.

[0007] Further, the first projection can include a proximal end that is secured to the first stopper and a distal end that cantilevers away from the first stopper. [0008] Additionally, the material rake assembly can include (i) a flexible, second projection that is coupled to the mounting assembly, the second projection engaging and raking the material on the build platform; and (ii) a second stopper that allows for deflection of the second projection while inhibiting over-deflection of the second projection.

[0009] Moreover, the material rake assembly can include a connector that flexibly couples the first projection to the mounting assembly, the connector allowing the first projection to move relative to the build platform. For example, the connector can allow the entire first projection to move normal to the build platform. In one implementation, the first projection is attached to the first stopper, and the connector connects the first stopper to the mounting assembly. Further, the connector allows the entire first projection and the first stopper to move relative to the build platform.

[0010] The connector can include an actuator that moves the first projection relative to the build platform. Further, the material rake assembly can include a sensor system that senses at least one condition of the first projection and provides sensor feedback that is used to control the actuator. Additionally, or alternatively, the sensor system can sense at least one condition of the material on the build platform and provides sensor feedback that is used to control the actuator.

[0011] Moreover, the material rake assembly can include a flexible second projection that is coupled to the mounting assembly, the second projection engaging the material on the build platform, the second projection being positioned adjacent to the first projection. Additionally, a second stopper can allow for deflection of the second projection while inhibiting over-deflection of the second projection. The second projection can at least partly overlap the first projection.

[0012] In another implementation, the material rake assembly includes a plurality of the first projections that are spaced apart in a first array, and a plurality of the second projections that are spaced apart in a second array. The second projections are at least partly overlapping the first projections.

[0013] In still another implementation, the present invention is directed to a processing machine for building an object from material, the processing machine comprising: a build platform; and the material rake assembly that rakes the material on the build platform. The processing machine can include an energy system that generates an energy beam the melts at least a portion of the material on the build platform.

[0014] In yet another implementation, the material rake assembly includes: a mounting assembly; a plurality of flexible, first projections that are spaced apart in a first array, the first projections being coupled to the mounting assembly, and the first projections engaging and raking the material on the build platform; and a plurality of flexible, second projections that are spaced apart in a second array, the second projections being coupled to the mounting assembly, and the second projections can engage and rake the material on the build platform. In this design, the second projections are at least partly overlapping the first projections.

[0015] Moreover, this implementation, a stopper can be used that allows for deflection of the first projections and the second projections while inhibiting over deflection of the first projections and the second projections.

[0016] Further, each projection can be at an acute, initial angle relative to normal to the build platform; and the stopper can inhibit deflection of the projections past a maximum deflection angle relative to normal. The maximum deflection angle can also be referred to as a predetermined angle or predetermined maximum deflection angle. The stopper can include an engagement surface that is at the maximum deflection angle; and the engagement surface can be adapted to engage the projections and inhibit the projections from deflecting past the maximum deflection angle.

[0017] In yet another implementation, the material rake assembly includes: a mounting assembly; a flexible, first projection that is coupled to the mounting assembly, the first projection engaging and raking the material on the build platform; and a connector that flexibly couples the first projection to the mounting assembly, the first connector allowing the first projection to move relative to the build platform. The connector can allow the entire first projection to move normal to the build platform. Additionally, the connector can include an actuator that moves the first projection relative to the build platform. Moreover, a sensor system can sense at least one condition of the first projection and/or at least one condition of the material layer; and the sensor system can provide sensor feedback that is used to control the actuator. [0018] Additionally, or alternatively, the connector can connect the first projection to the mounting assembly in a kinematic fashion.

[0019] In another implementation, the material rake assembly includes (i) a mounting assembly; and (ii) a projection assembly that is coupled to the mounting assembly, the projection assembly including a first projection and a second projection that is spaced apart from the first projection. In this design, the projections are arranged in series to engage and rake the material on the build platform.

[0020] Further, the second projection is closer to the build platform than the first projection. Moreover, the first projection and the second projection are spaced apart a projection separation distance that is at least 0.01 millimeters. Additionally or alternatively, at least one of the projections has a projection thickness at the distal end that is at least fifty microns.

[0021] Additionally, the material rake assembly can include a stopper having an engagement surface that is at a maximum deflection angle, and the engagement surface is adapted to engage the first projection and inhibit the first projection from deflecting past the maximum deflection angle.

[0022] Moreover, the material rake assembly can include a connector that flexibly couples the projections to the mounting assembly, the connector allowing the projections to move relative to the build platform. In one implementation, the connector allows the entire first projection to move normal to the build platform. The connector can include an actuator that moves the projections relative to the build platform.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The novel features of this embodiment, as well as the embodiment itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:

[0024] Figure 1A is a simplified side illustration of an implementation of a processing machine having features of the present embodiment;

[0025] Figure 1 B is a simplified top illustration of a material bed assembly from Figure 1A; [0026] Figure 2A is a rear view of a material rake assembly from Figure 1A with a build platform;

[0027] Figure 2B is a cut-away view taken on line 2B-2B in Figure 2A with the material rake assembly and the build platform at a first position;

[0028] Figure 2C illustrates the material rake assembly and the build platform of Figure 2B at a second position;

[0029] Figure 2D illustrates the material rake assembly and the build platform of Figure 2B at a third position;

[0030] Figure 3 illustrates a cut-away view of another implementation of the material rake assembly and the build platform;

[0031] Figure 4 illustrates a side view of yet another implementation of the material rake assembly and the build platform;

[0032] Figure 5 illustrates a side view of still another implementation of the material rake assembly and the build platform;

[0033] Figure 6 illustrates a side view of another implementation of the material rake assembly and the build platform;

[0034] Figure 7 illustrates a side view of still another implementation of the material rake assembly and the build platform;

[0035] Figure 8A is a perspective view of yet another implementation of the material rake assembly;

[0036] Figure 8B is an alternative, perspective view of the material rake assembly of Figure 8A;

[0037] Figure 8C is a perspective view of a portion of the material rake assembly of Figure 8A;

[0038] Figure 8D is a perspective view of another portion of the material rake assembly of Figure 8A;

[0039] Figure 9A is a simplified side view of a portion of yet another material rake assembly;

[0040] Figure 9B is a perspective view of a portion of the material rake assembly of Figure 9A;

[0041] Figure 10A is a simplified perspective view of a portion of still another material rake assembly;

[0042] Figure 10B is a simplified side view of the material rake assembly of Figure 10A;

[0043] Figure 10C is a simplified side view of the material rake assembly of Figure 10B with the build platform;

[0044] Figure 11 is a simplified side view of still another implementation of the material rake assembly; and

[0045] Figure 12 is a simplified side view of yet another implementation of the material rake assembly.

DESCRIPTION

[0046] Figure 1 A is a simplified schematic side illustration of a processing machine

10 that may be used to manufacture one or more three-dimensional object(s) 11 (only one is illustrated in phantom). As provided herein, the processing machine 10 can be an additive manufacturing system, e.g. a three-dimensional printer, in which a portion of a material 12 (illustrated as small circles in phantom) in a series of material layers 13 (only one layer is illustrated with small circles in phantom) are sequentially joined, melted, solidified, and/or fused together to manufacture one or more three-dimensional object(s) 11 .

[0047] The type of three-dimensional object(s) 11 manufactured with the processing machine 10 may be almost any shape or geometry. As a non-exclusive example, the three-dimensional object 11 may be a metal part, or another type of part, for example, a resin (plastic) part or a ceramic part, etc. The three-dimensional object

11 may also be referred to as a “built part”. It should be noted with the present design, one or more objects 11 can be simultaneously made with the processing machine 10. [0048] The type of material 12 joined and/or fused together may be varied to suit the desired properties of the object(s) 11. As a non-exclusive example, the material

12 may include metal powder particles (e.g., including one or more of titanium, aluminum, vanadium, chromium, copper, stainless steel, or other suitable metals) or alloys for metal three-dimensional printing. Alternatively, the material 12 may be non- metal material, a plastic, polymer, glass, ceramic material, organic material, an inorganic material, or any other material known to people skilled in the art. The material 12 may also be referred to as “powder” or “powder particles”.

[0049] Particle sizes of the material 12 can be varied. In one implementation, a common particle size is approximately fifty microns. Alternatively, in other non exclusive examples, the particle size can be approximately ten, twenty, thirty, forty, sixty, seventy, eighty, or ninety, or one hundred microns.

[0050] A number of different designs of the processing machine 10 are provided herein. In certain implementations, the processing machine 10 includes (i) a material bed assembly 14; (ii) a pre-heat device 16; (iii) a material supply assembly 18 (illustrated as a box) including a material rake assembly 19; (iii) a measurement device 20 (illustrated as a box); (iv) an energy system 22 (illustrated as a box); (v) a control system 24 (illustrated as a box); and (vi) a mover assembly 25 that causes relative motion between the material bed assembly 14 and the material supply assembly 18. The design of each of these components may be varied pursuant to the teachings provided herein. Further, the positions of the components of the processing machine 10 may be different than that illustrated in Figure 1A.

[0051] Moreover, the processing machine 10 can include more components or fewer components than illustrated in Figure 1 A. For example, the processing machine 10 can include a cooling device (not shown in Figure 1A) that uses radiation, conduction, and/or convection to cool the material 12. Further, the processing machine 10 can include multiple, spaced apart, material supply assemblies 18. Additionally or alternatively, for example, the processing machine 10 can be designed without the pre heat device 16 and/or the measurement device 20.

[0052] As an overview, the material rake assembly 19 is uniquely designed to scrape over both small and large asperities while accurately leveling each material layer 13 on the material bed assembly 14. Because the material 12 is accurately leveled, the resulting object 11 will be more accurate. Further, because the material rake assembly 19 is designed to scrape over both small and large asperities, the material rake assembly 19 will not be damaged by these asperities. A number of different material rake assemblies 19 are described in more detail below.

[0053] The shape and/or thickness of each material layer 13 can be varied to suit the manufacturing requirements. In alternative, non-exclusive examples, one or more (e.g. all) of the material layers 13 can have a layer thickness (along the Z axis) of approximately twenty, thirty, forty, fifty, sixty, seventy, eighty, or ninety, or one hundred microns. However other layer thicknesses are possible.

[0054] A number of Figures include an orientation system that illustrates an X axis, a Y axis that is orthogonal to the X axis, and a Z axis that is orthogonal to the X and Y axes. It should be noted that any of these axes can also be referred to as the first, second, and/or third axes. Further, as used herein, movement with six degrees of freedom shall mean along and about the X, Y, and Z axes.

[0055] It should be noted that the processing machine 10 may be operated in a controlled environment, e.g. such as a vacuum, using an environmental chamber 23 (illustrated in Figure 1A as a box). For example, one or more of the components of the processing machine 10 can be positioned entirely or partly within the environmental chamber 23. Alternatively, at least a portion of one or more of the components of the processing machine 10 may be positioned outside the environmental chamber 23. Still alternatively, the processing machine 10 may be operated in non-vacuum environment such as inert gas (e.g., nitrogen gas or argon gas) environment.

[0056] The material bed assembly 14 supports the material 12 while the object(s) 11 is being built. In the non-exclusive implementation of Figure 1A, the material bed assembly 14 includes a support platform 26 and one or more build platform assemblies 28 (only one is illustrated in phantom in Figure 1 A) that support the material 12 and the object 11 while being formed. The material bed assembly 14 is discussed in more detail below.

[0057] The pre-heat device 16 selectively preheats the material 12. The number of the pre-heat devices 16 may be one or plural. The design of the pre-heat device 16 and the desired preheated temperature may be varied. In one embodiment, the pre heat device 16 may include one or more pre-heat energy source(s) that direct one or more pre-heat beam(s) (not shown) at the material 12. Each pre-heat beam may be steered as necessary. As alternative, non-exclusives examples, each pre-heat device 16 may be an electron beam system, a mercury lamp, an infrared laser, a supply of heated air, thermal radiation system, a visual wavelength optical system or a microwave optical system. The desired preheated temperature may be 50% 75% 90% or 95% of the melting temperature of the material 12 used in the printing. It is understood that different materials have different melting points and therefore different desired pre-heating points. As non-exclusive examples, the desired preheated temperature may be at least 300, 500, 700, 900, or 1000 degrees Celsius. However, other preheated temperatures can be utilized. Energy input may also vary dependent on melt duty of previous layers, specific regions on a layer, or progress though the build.

[0058] The material supply assembly 18 deposits and levels the material 12 onto the build platform assembly 28. The number of the material supply assemblies 18 may be one or plural. With the present design, the material supply assembly 18 includes a material supply 29 (illustrated as a box) that accurately deposits the material 12 onto the build platform assembly 28, and the material rake assembly 19 that levels the material 12 to sequentially form each material layer 13. Once a portion of the material layer 13 has been melted with the energy system 22, the material supply 29 can be controlled to accurately deposit another (subsequent) material layer 13. The material supply 29 can include one or more containers that retain the material 12 that is deposited onto the build platform 28A. In Figure 1A, the material supply 29 is an overhead system that supplies the material 12 onto the top of the material bed assembly 14. Alternatively, the material supply 29 can be at a different location. [0059] A number of alternative material rake assemblies 19 are described in more detail below. In these embodiments, the material rake assembly 19 is positioned above the top of the material bed assembly 14.

[0060] It should be noted that the three-dimensional object 11 is formed through consecutive fusions of consecutively formed cross sections of material 12 in one or more material layers 13. For simplicity, the example of Figure 1A illustrates only the top material layer 13. However, it should be noted that depending upon the design of the object 11 , the building process will require numerous material layers 13.

[0061] The measurement device 20 inspects and monitors the melted (or fused) layers of the object 11 as that are being built, the deposition of the material 12, and/or at least part of the built object 11 . The number of the measurement devices 20 may be none or plural. For example, the measurement device 20 can measure both before and after the material 12 is distributed. As non-exclusive examples, the measurement device 20 may include one or more optical elements such as a uniform illumination device, fringe illumination device (structured illumination device), cameras that function at one or more wavelengths, lens, interferometer, or photodetector, or a non-optical measurement device such as an ultrasonic, eddy current, or capacitive sensor.

[0062] The energy system 22 selectively heats and melts the material 12 to sequentially form each of the layers of the object 11. The energy system 22 can selectively melt the material 12 at least based on a data regarding to the object 11 to be built. The data may be corresponding to a computer-aided design (CAD) model data. The number of the energy systems 22 may be one or plural. The design of the energy system 22 can be varied. In one embodiment, the energy system 22 can direct one or more irradiation (energy) beam(s) (not shown) at the material 12. The one or more energy systems 22 can be controlled to steer the energy beam(s) to melt the material 12.

[0063] As alternative, non-exclusives examples, the energy system 22 can be designed to include one or more of the following: (i) an electron beam generator that generates a charged particle electron beam; (ii) an irradiation system that generates an irradiation beam; (iii) an infrared laser that generates an infrared beam; (iv) a mercury lamp; (v) a thermal radiation system; (vi) a visual wavelength system; (vii) a microwave wavelength system; or (viii) an ion beam system.

[0064] Different materials 12 have different melting points. As non-exclusive examples, the desired melting temperature may be at least 1000, 1400, 1700, 2000, or more degrees Celsius.

[0065] The control system 24 controls the components of the processing machine 10 to build the three-dimensional object 11 from the computer-aided design (CAD) model by successively melting portions of one or more of the material layers 13. For example, the control system 24 can control (i) the material bed assembly 14; (ii) the pre-heat device 16; (iii) the material supply assembly 18; (iii) the measurement device 20; (iv) the energy system 22; and/or (v) the mover assembly 25. The control system 24 can be a centralized or a distributed system. [0066] The control system 24 may include, for example, a CPU (Central Processing Unit) 24A, a GPU (Graphics Processing Unit) 24B, and electronic memory 24C. The control system 24 functions as a device that controls the operation of the processing machine 10 by the CPU executing the computer program. This computer program is a computer program for causing the control system 24 (for example, a CPU) to perform an operation to be described later to be performed by the control system 24 (that is, to execute it). That is, this computer program is a computer program for making the control system 24 function so that the processing machine 10 will perform the operation to be described later. A computer program executed by the CPU may be recorded in a memory (that is, a recording medium) included in the control system 24, or an arbitrary storage medium built in the control system 24 or externally attachable to the control system 24, for example, a hard disk or a semiconductor memory. Alternatively, the CPU may download a computer program to be executed from a device external to the control system 24 via the network interface. Further, the control system 24 may not be disposed inside the processing machine 10, and may be arranged as a server or the like outside the processing machine 10, for example. In this case, the control system 24 and the processing machine 10 may be connected via a communication line such as a wired communications line (cable communications), a wireless communications line, or a network. In case of physically connecting with wired, it is possible to use serial connection or parallel connection of IEEE1394, RS-232x, RS- 422, RS-423, RS-485, USB, etc. or 10BASE-T, 100BASE-TX, 1000BASE- T or the like via a network. Further, when connecting using radio, radio waves such as IEEE 802.1x, OFDM, or the like, radio waves such as Bluetooth (registered trademark), infrared rays, optical communication, and the like may be used. In this case, the control system 24 and the processing machine 10 may be configured to be able to transmit and receive various types of information via a communication line or a network. Further, the control system 24 may be capable of transmitting information such as commands and control parameters to the processing machine 10 via the communication line and the network. The processing machine 10 may include a receiving device (receiver) that receives information such as commands and control parameters from the control system 24 via the communication line or the network. As a recording medium for recording the computer program executed by the CPU, a CD-ROM, a CD-R, a CD-RW, a flexible disk, an MO, a DVD-ROM, a DVD-RAM, a DVD-R, a DVD + R, a DVD-RW, a magnetic medium such as a magnetic disk and a magnetic tape such as DVD + RW and Blu-ray (registered trademark), a semiconductor memory such as an optical disk, a magneto optical disk, a USB memory, or the like, and a medium capable of storing other programs. In addition to the program stored in the recording medium and distributed, the program includes a form distributed by downloading through a network line such as the Internet. Further, the recording medium includes a device capable of recording a program, for example, a general-purpose or dedicated device mounted in a state in which the program can be executed in the form of software, firmware or the like. Furthermore, each processing and function included in the program may be executed by program software that can be executed by a computer, or processing of each part may be executed by hardware such as a predetermined gate array (FPGA, ASIC) or program software, and a partial hardware module that realizes a part of hardware elements may be implemented in a mixed form.

[0067] It should also be noted that with the unique designs provided herein, multiple operations may be performed at the same time (simultaneously) to improve the throughput of the processing machine 10. Stated in another fashion, one or more of (i) pre-heating with the pre-heat device 16, (ii) measuring with the measurement device 20, (iii) depositing material 12 with the material supply assembly 18, and (iv) melting the material with the energy system 22 may be partly or fully overlapping in time on different parts of the material bed assembly 14 to improve the throughput of the processing machine 10.

[0068] The mover assembly 25 is controlled to cause relative motion between the material bed assembly 14 and the material supply assembly 18. The design of the mover assembly 25 can be varied to achieve the movement requirements of the processing machine 10. In one implementation, the mover assembly 25 rotates the material bed assembly 14 about a rotational axis 25A (e.g. parallel to the Z axis) relative to the material supply assembly 18, the pre-heat device 16, the measurement device 20, and the energy system 22. The mover assembly 25 can move the support platform 26 at a substantially constant or variable angular velocity about the rotational axis 25A.

[0069] Alternatively, or additionally, the mover assembly 25 can be designed to move the material bed assembly 14 linearly, e.g. along the X axis and/or along the Y axis relative to the material supply assembly 18. Still alternatively, or additionally, the mover assembly 25 can be designed to move the material supply assembly 18 (e.g. rotate and/or move linearly) relative to the material bed assembly 14. The mover assembly 25 can include one or more actuators (e.g. linear or rotary).

[0070] Additionally, the processing machine 10 can include a component housing 30 that retains the pre-heat device 16, the material supply assembly 18 with the material rake assembly 19, the measurement device 20, and the energy system 22. Collectively these components may be referred to as the top assembly. Further, the processing machine 10 can include a housing mover 32 that can be controlled to selectively move the top assembly. The housing mover 32 can include one or more actuators (e.g. linear or rotary) that move the top assembly linearly and/or rotationally. [0071] Still alternatively, one or more of the pre-heat device 16, the material depositor 18, the measurement device 20, and the energy system 22 can be moved relative to the component housing 30.

[0072] Figure 1 B is a simplified top, illustration of one, non-exclusive implementation of the material bed assembly 14 of Figure 1A. In this implementation, the material bed assembly 14 is generally circular shaped, and can be used to make multiple objects 11 (not shown in Figure 1 B) substantially simultaneously. Flowever, the material bed assembly 14 can have a different shape or configuration than is illustrated in Figure 1 B.

[0073] In non-exclusive implementation of Figure 1 B, the material bed assembly 14 includes the support platform 26, a support hub 34, and a plurality of separate, spaced apart, build platform assemblies 28 that are integrated into and supported by the support platform 26. The number of separate build platform assemblies 28 can be varied. In Figure 1 B, the material bed assembly 14 includes three separate build platform assemblies 28. With this design, one or more objects (not shown) can be made on each build platform assembly 28. Alternatively, the material bed assembly 14 can include more than three or fewer than three separate build platform assemblies 28.

[0074] In the non-exclusive implementation of Figure 1 B, the support platform 26 is annular disk shaped and is rotated (with the build platform assemblies 28) about the rotational axis 25A (illustrated with a “+”) in a frame rotational direction 25B (e.g. counter-clockwise in this example) by the mover assembly 25 (illustrated in Figure 1 A) relative to the support hub 34. With this design, the support platform 26 with the build platform assemblies 28 are rotated like a turntable during printing of the objects in the frame rotational direction 25B.

[0075] Additionally, in the non-exclusive implementation of Figure 1 B, each build platform assembly 28 defines a separate build platform 28A that is selectively lowered like an elevator relative to a tubular shaped platform sidewall 28B with a platform mover assembly 28C (illustrated in phantom with a box) into the support platform 26 during the manufacturing process. In Figure 1 B, each build platform 28A is generally disk shaped.

[0076] Fabrication can begin with each build platform 28A placed near the top of the support platform 26. The material supply assembly 18 (illustrated in Figure 1A) deposits and levels the thin layer of material onto each build platform 28A as it is moved (e.g. rotated) below the material supply assembly 18. At an appropriate time, each build platform 28A is stepped down one layer thickness with the platform mover assembly 28C so the next layer of material may be distributed properly. Alternatively, each build platform 28A can be moved in steps that are smaller than the material layer or moved in a continuous fashion, rather than in discrete steps.

[0077] In this Figure, each build platform 28A defines a circular shaped build area that receives the material. Alternatively, for example, each build platform 28A can have a different configuration, e.g. rectangular or polygonal shaped.

[0078] In some embodiments, one or more platform mover assemblies 28C can be used to move (e.g. rotate) one or more of the build platform 28A relative to the support platform 26 and each other about a platform rotational axis 28D (illustrated with a “+”, e.g. along the Z axis) in a platform rotational direction 28E (e.g. the clockwise direction). With this design, each build platform 28A can be rotated about two, separate, spaced apart and parallel axes 25A, 28D during the build process. [0079] In one, non-exclusive example, the support platform 26 can be rotated (e.g., at a substantially constant rate) in the frame rotational direction 25B (e.g. counterclockwise), and one or more of the build platforms 28A can be moved (e.g. rotated) relative to the support platform 26 in the opposite, platform rotational direction 28E (e.g. clockwise) during the printing process. In this example, the rotational speed of the support platform 26 about the frame rotational direction 25B can be approximately the same or different from the rotational speed of each build platform 28A relative to the support platform 26.

[0080] Alternatively, the support platform 26 and one or more of the build platforms 28A can be rotated in the same rotational direction during the three dimensional printing operation.

[0081] It should be noted that in Figure 1A, a separate platform mover assembly 28C is used for each build platform assembly 28. Alternatively, one or more of the platform mover assemblies 28C can be designed to concurrently move more than one build platform assembly 28.

[0082] Figure 2A is a rear view of a material rake assembly 219 that can be used in the processing machine 10 of Figure 1A with a portion of a build platform 228A. Figure 2A illustrates three, formed layers 213A (illustrated with small squares) that have been melted by the energy system 22 (illustrated in Figure 1A), and one, new material layer 213B (illustrated with small circles) deposited onto the formed layers 213A that is being leveled with the material rake assembly 219. The material rake assembly 219 may make the surface of the new material layer 213B parallel to the plane containing the moving direction of the build platform 228 or the plane orthogonal to the rotational axis 25 (illustrated in Figure 1 B) of the build platform 228A. This surface of the new material layer 213B may be the X-Y plane. It should be noted that in this Figure, each formed layer 213A is illustrated as being completely melted. Flowever, depending upon the design of the object 11 (illustrated in Figure 1 A) only a portion of each formed layer 213A may have been melted.

[0083] The design of the material rake assembly 219 can be varied. In the non exclusive implementation of Figure 2A, the material rake assembly 219 includes a rigid, mounting assembly 236, and one or more rake units 238 that engage and level the material 12 on the build platform 228A. In the non-exclusive implementation of Figure 2A, the material rake assembly 219 includes a single, rigid mounting assembly 236 and eight, adjacent rake units 238 that cooperate to level the material 12 on the build platform 228A. Further, the rake units 238 are supported by the common mounting assembly 236. Alternatively, the material rake assembly 219 can be designed to include more than eight, or fewer than eight rake units 238, and/or more than one mounting assembly 236. For example, the material rake assembly 219 can be designed to include a single rake unit 238 that extends across the entire build platform 228A.

[0084] For ease of discussion, the eight rake units 238 can be referred to as a first rake unit 238A; a second rake unit 238B; a third rake unit 238C; a fourth rake unit 238D; a fifth rake unit 238E; a sixth rake unit 238F; a seventh rake unit 238G; and an eighth rake unit 238FI. Any of these rake units 238 can be referred to the first, second, third, etc., rake unit 238

[0085] It should be noted that multiple rake units 238 can be arranged in an adjacent, staggered or overlapping fashion to reduce or eliminate the material 12 that is not leveled by the rake units 238, and/or to rake the material 12 evenly. In Figure 2A, the rake units 238 are positioned side by side. In a different implementation, for example, alternating rake units 238 (e.g. each even numbered rake unit 238B, 238D, 238F, 238H) of the material rake assembly 219 can be positioned in front of and partly overlapping adjacent odd numbered rake units 238A, 238C, 238E, 238G. More specifically, in this example, (i) the second rake unit 238B can be positioned in front of and partly overlapping the first and third rake units 238A, 238C; (ii) the fourth rake unit 238D can be positioned in front of and partly overlapping the third and fifth rake units 238C, 238E; (iii) the sixth rake unit 238F can be positioned in front of and partly overlapping the fifth and seventh rake units 238E, 238G; and etc.

[0086] Additionally, it should be noted that the number and design of the rake units 238 can be varied to correspond to the width of the build platform 228A that needs to be raked. As alternative, non-exclusive examples, the material rake assembly 219 can be designed to have a width (along the X axis) of approximately 10, 50, 100, 500, or 1000 millimeters. Flowever, other widths are possible. [0087] The design of each rake unit 238 can be varied. In the non-exclusive implementation of Figure 2A, each rake unit 238 includes (i) a flexible projection 240 that engages and rakes the material 12 on the build platform 228A; (ii) a stopper 242 that allows for deflection of the projection 240 while inhibiting over-deflection of the projection 240; and (iii) a connector 244 that is movable couples the projection 240 to the mounting assembly 236 and allows the entire projection 240 to move relative to the mounting assembly 236. In certain implementations, the stopper can also be referred to as a hard stop.

[0088] It should be noted, for the first rake unit 238A, (i) the flexible projection 240 can be referred to as the first projection; (ii) the stopper 242 can be referred to as the first stopper; and (iii) the connector 244 can be referred to as the first connector 244. Similarly, for the second rake unit 238B, (i) the flexible projection 240 can be referred to as the second projection; (ii) the stopper 242 can be referred to as the second stopper; and (iii) the connector 244 can be referred to as the second connector 244. This naming structure can be used for the rest of the rake units 238C-238H.

[0089] It should be noted that other designs are possible. For example, the material rake assembly 219 can be designed so that multiple projections 240 cantilever away from a common stopper 242.

[0090] Figure 2B is a cut-away view taken on line 2B-2B in Figure 2A with the material rake assembly 219 and a portion of the build platform 228A. Figure 2B also illustrates the three, formed layers 213A that have been melted by the energy system 22 (illustrated in Figure 1A), and one, new material layer 213B (illustrated with small circles) being leveled on the build platform 228A with the material rake assembly 219. In Figure 2B, the build platform 228A is being moved from right to left relative to the material rake assembly 219 as illustrated with arrow 225. Alternatively, for example, the material rake assembly 219 can be moved relative to the build platform 228A. The relative movement between the material rake assembly 219 can be moved relative to the build platform 228A can also be referred to as the progressing direction of the material rake assembly 219.

[0091] Further, Figure 2B illustrates that the most recently formed material layer 213A can additionally include one or more relatively small asperities 213C (only one is shown), and one or more relatively large asperities 213D (only one is shown). These asperities 213C, 213D can result from the balling up and/or splattering of the material 12 during the melting process in the recently melted layer 213A. In one, non-exclusive example, the small asperities 213C have a small asperity height above the previously formed layer 213A of less than five hundred microns; and the large asperities 213D have a large asperity height above the previously formed layer 213A of greater than five hundred microns. However, the size of the asperities 21 C, 213D can be different than this example.

[0092] In Figure 2B, the build platform 28A is at a first position relative to the material rake assembly 219, and the build platform 228A is being moved right to left relative to the material rake assembly 219. As a result thereof, the material rake assembly 219 is accurately leveling the material 12 on the build platform 228A. Further, the build platform 228A is moving the asperities 213C, 213D towards the material rake assembly 219.

[0093] In the non-exclusive implementation of Figure 2B, the mounting assembly 236 is generally rectangular beam shaped. However, other shapes of the mounting assembly 236 are possible. The mounting assembly 236 can be used to secure the material rake assembly 219 to the rest of the processing machine 10 (illustrated in Figure 1A).

[0094] Figure 2B also illustrates the first rake unit 238A in more detail. It should be noted that the other rake units 238 can be similar or different in design to the first rake unit 238A. As provided above, in one non-exclusive implementation, the first rake unit 238A includes (i) the flexible projection 240; (ii) the stopper 242; and (iii) the connector 244. The design of each of these components can be varied pursuant to the teachings provided herein.

[0095] As an overview, the first rake unit 238A is designed so that (i) the projection 240 can deflect to glide over small asperities 213C encountered by the projection 240; and (ii) the projection 240 can deflect against the stopper 242, and the connector 244 can allow the projection 240 to move upward so that the projection 240 can glide over large asperities 213D. Thus, in this design, the rake unit 238A allows for two ranges of movement, namely, (i) a first range of movement in which the projection 240 deflects within an acceptable range to glide over small asperities 213C; and (ii) a second range of movement in which the connector 244 additionally allows the projection 240 to move upward to glide over large asperities 213D. This inhibits permanent damage to the rake unit 238A and allows the rake unit 238A to accurately level the material 12. A permanently deformed projection 240 can lead to uneven surfaces of the material 12, and may contribute to poor fabrication quality.

[0096] The flexible projection 240 engages and rakes the material 12 on the build platform 228A. In one implementation, the flexible projection 240 is flexible, rectangular plate shaped and includes (i) a distal end 240A that engages material 12 on the build platform 228A and that cantilevers away from the stopper 242: and (ii) a proximal end 240B that is fixedly secured to the stopper 242. In Figure 2B, a plurality of projection fasteners 246 (only one is shown) extend through a support plate 248 and the projection 240, and thread into the stopper 242 to attach the projection 240 to the stopper 242. Alternatively, the projection 240 can be secured to the stopper 242 in another fashion.

[0097] It should be noted that the projection 240 can also be referred to as a tine, a comb tooth, a finger or a blade. Straight lines where the tips of the plurality of projections 240 are located may be parallel to each other. Stated in a different fashion, the distal ends of the projections 240 can be parallel to each other.

[0098] The size, shape, and materials utilized for the projection 240 can be varied to achieve the desired bending characteristics of the projection 240 and the desired area of raking. As a non-exclusive example, the projection 240 can include one or more of the following characteristics: (i) a width (along the X axis) of between approximately 2 millimeters and one meter; (ii) a thickness 240C of between approximately one hundred and five hundred millimeters; and/or (iii) a length (generally along the Z axis) of between approximately five and ten millimeters. As specific, non exclusive examples, each projection can have a width of 2, 5, 10, 25, 50 or 100 millimeters. Further, suitable materials for the projection 240 include, but is not limited to stainless steel, titanium, or nickel alloys.

[0099] In one implementation, the geometry and angle of the projection 240 is selected so that the yield stress of the projection 240 is at least two times the yield stress that the projection 240 will experience from sliding over a small asperity 213C (e.g. deflecting five hundred microns).

[00100] In one implementation, the projection 240 is generally straight. Alternatively, the projection 240 can be curved or arc shaped. Additionally, or alternatively, the thickness 240C of the projection 240 can be tapered.

[00101] Figure 2B illustrates the situation in which the projection 240 is engaging only the loose material 12 on the build platform 228A. At this time, the projection 240 is at an acute, initial angle 250 relative to normal to the build platform 228A. As non exclusive examples, the initial angle 250 can be approximately ten, twenty, thirty, forty, fifty, sixty, or seventy degrees. However, other initial angles 250 can be utilized. [00102] The stopper 242 allows for non-permanent deflection of the projection 240 while inhibiting over-deflection (and permanent deformation) of the projection 240. With this design, the stopper 242 allows for safe bending of the projection 240 to glide over small asperities 213C, while inhibiting unsafe bending of the projection 240 when it engages large asperities 213D. In the non-exclusive implementation of Figure 2B, the stopper 242 has a polygon shaped cross-section and includes (i) a generally straight, stop top 242A that faces the mounting assembly 236; (ii) a generally straight, stop back side 242B that extends perpendicular to the stop top 242A; (iii) a generally straight, stop bottom 242C that spaced apart from and parallel to the stop top 242A; (iv) a mounting side 242D that extends at an angle downward from the stop top 242A; and (v) an engagement surface 242E that extends at an angle between the mounting side 242D and the stop bottom 242C. As non-exclusive examples, the stopper 242 can have a width along the X axis that is approximately equal to or slightly less that the width of the projection 240.

[00103] In one, non-exclusive design, the mounting side 242D engages the proximal end 240B of the projection 240, and the mounting side 242D is an angle that can correspond to the initial angle 250 of the projection 240.

[00104] Further, the engagement surface 242E is at the desired location and/or desired angle to act as a hard, deflection limiting surface that engages the projection 240 to inhibit overbending of the projection 240, while allowing for non-permanent deflection of the projection 240. Thus, the location and/or angle of the engagement surface 242E will depend upon the design and position of the projection 240. In one, non-exclusive implementation, the engagement surface 242E is at an engagement angle 252 of between twenty and sixty degrees relative to normal to the build platform 228A. However, other values are possible, depending on the design and position of the projection 240.

[00105] With this design, the engagement surface 242E (i) inhibits deformation of the projection 240 past the engagement angle 252 to inhibit permanent deformation of the projection 204; and (ii) allows for the deformation of the projection 240 between the initial angle 250 and the engagement angle 252 so that the projection 240 can glide over small asperities 213C. Because, the engagement surface 242E limits the deformation of the projection 240, and the engagement angle 242E can also be referred to as a maximum deflection angle of the projection 240. In one, non-exclusive example, the projection 240 can deflect up to five hundred microns.

[00106] In one specific design, the rake unit 238A can be designed so that the projection 240 flexes sufficiently so that the distal end 240A can glide over a small asperity without the second stage movement associated with the connector 244. In alternative, non-exclusive implementations, the rake unit 238A can be designed so that the projection 240 flexes sufficiently so that the distal end 240A can move at least 100, 200, 500, or 600 microns along the Z axis relative to the build platform 228A without movement with the connector 244 as described below. Stated in another fashion, in this design, the projection 240 can flex so that the distal end 240A of the rake unit 238A has a first range of movement along the Z axis of at least 100, 200, 500, or 600 microns. [00107] In Figure 2B, the projection 240 is inclined to reduce the maximum stress on the projection 240 for a given asperity height, and thereby reduce the risk of deformation and breakage of the projection 240. A stress analysis can be performed on the projection 240 to determine the optimal initial angle 250 and the maximum deflection angle 252 to minimize damage or breakage of the projection 240.

[00108] The connector 244 couples the projection 240 and the stopper 242 to the mounting assembly 236. Further, the connector 224 can allow for the position of the projection 240 and/or the stopper 242 to move (e.g. substantially normal along the Z axis) to the build platform 228A to glide over large asperities 213D. Moreover, the connector 224 can adjust and/or control the position of the projection 240 and/or the stopper 242 normal to the build platform 228A.

[00109] In the implementation of Figure 2B, the connector 244 is a passive connector that passively controls the position of the projection 240 and the stopper 242 relative to the build platform 228A along the Z axis. Further, in this non-exclusive implementation, the connector 244 includes (i) one or more connector fasteners 244A; and (ii) one or more resilient members 244B. In this design, each of the fasteners 244A extends through a corresponding mounting aperture 236A in the mounting assembly 236, and each fastener 244A is threaded into the stop top 242A of the stopper 242. Moreover, the mounting aperture 236A is slightly larger than the diameter of the fastener 244A so that the fastener 244A can slide relative to the mounting assembly 236 in a guided fashion.

[00110] Further, each resilient member 244B is a circular, compression spring that is positioned on a corresponding fastener 244A between the mounting assembly 236 and the stop top 242A of the stopper 242. With this design, the resilient member(s) 244B urge the stopper 242 and the projection 240 downward from the mounting assembly 236 along the Z axis, while allowing the stopper 242 and the projection 240 to move upward along the Z axis when a large asperity is encountered.

[00111] Alternatively, each resilient member 244B can be another type of resilient member that urges the stopper 242 and the projection 240 downward, while allowing for movement upward if necessary. For example, each resilient member 244B can be a blade spring.

[00112] The range of possible movement upward allowed by the connector 244 can be varied to accommodate the size of the possible large asperities. As alternative, non-exclusive examples, the connector 244 can allow for movement (“second range of movement”) of the projection 240 and the distal end 240A along the Z axis relative to the build platform 228A of at least approximately 100, 200, 500, or 600 microns. [00113] In this design, as alternative, non-exclusive examples, (i) the flexing of the projection 240, and (ii) the flexing of the connector 244 can allow of an overall movement of the distal end 240A of at least approximately 200, 400, 1000, or 1200 microns (along the Z axis) relative to the build platform 228A. [00114] The amount of force required to urge the stopper 242 and the projection 240 upward towards the mounting assembly 236 can be varied by changing the design of the resilient members 244B. In certain designs, the projection 240 bends easier than the resilient members 244B. Thus, when a small asperity 213C is encountered, the projection 240 will bend, and the resilient members 244B will bend very little, if any. As alternative, non-exclusive examples, the force required to urge the stopper 242 and the projection 240 upward towards the mounting assembly 236 can be at least two, four, six, eighth or ten times the force required to bend the projection 240.

[00115] Figure 2C illustrates the material rake assembly 219 including the first rake unit 238A, with the build platform 228A at a second position. In Figure 2C, the build platform 228A is being moved from right to left relative to the material rake assembly 219 as illustrated with arrow 225. At this time, the distal end 240A of the projection 240 is engaging the small asperity 213C. Moreover, at this time, the projection 240 is partly deflected at a deflection angle 254 relative to normal of the build platform 228A, and the projection 240 is closer to the engagement surface 242E of the stopper 242. Further, the projection 240 has deflected so that the distal end 240A has moved a first movement distance 256 relative to the build platform 228A. Because, the projection 240 is deflecting at an acceptable level, the projection 240 can glide over the small asperity 213C without damage and/or deforming the projection 240. As a result thereof, the projection 240 will return to the initial angle 250 (illustrated in Figure 2B) after it clears the small asperity 213C, and the projection 240 will return to accurately leveling the material 12.

[00116] It should be noted that in this example, that the projection 240 of the first rake unit 328A is only temporarily deformed by the small asperity, and that the projections 240 of the other rake units 328B-328FI (illustrated in Figure 2A) may not be deformed by the small asperity 213C. Thus, the projections 240 of the other rake units 238B-238FI will continue to accurately level the material 12, while the projection 240 of the first rake unit 238A is temporarily deformed.

[00117] Additionally, it should be noted that as illustrated in Figure 2C, the projection 240 can deflect slightly farther prior to engaging the engagement surface 242E. Stated in another fashion, the projection 240 can deflect farther (if necessary) to increase the first movement distance 256. With this design, the projection 240 can glide over slightly larger, small asperities 213C than illustrated in Figure 2C without relying on the second range of movement provided by the connector 244.

[00118] Figure 2D illustrates the material rake assembly 219 including the first rake unit 238A, with the build platform 228A at a third position. In Figure 2D, the build platform 228A is being moved from right to left relative to the material rake assembly 219 as illustrated with arrow 225. At this time, the distal end 240A of the projection 240 is engaging the large asperity 213D. Moreover, at this time, (i) the projection 240 is fully deflected against the engagement surface 242E of the stopper 242, and the projection 240 is at the maximum deflection angle 252 relative to normal of the build platform 228A; and (ii) the connector 244 is compressed to allow the projection 240 (and the distal end 240A) to move a second movement distance 258 along the Z axis. [00119] Because, the projection 240 is deflecting at an acceptable level, and the connector 244 is compressed, the projection 240 can glide over the large asperity 213D without damage and/or deforming the projection 240. As a result thereof, the projection 240 will return to the initial angle 250 (illustrated in Figure 2B) and the connector 244 will expand after the projection 240 clears the large asperity 213D, and the projection 240 will return to accurately leveling the material 12.

[00120] It should be noted that in this example, that the projection 240 and the connector 244 of the first rake unit 228A is only temporarily deformed by the large asperity 213D, and that the projections 240 and the connectors 244 of the other rake units 238B-238FI (illustrated in Figure 2A) are not deformed by the large asperity 213D. Thus, the projections 240 of the other rake units 238B-238FI will continue to accurately level the material 12, while the projection 240 and the connector 244 of the first rake unit 238A are temporarily deformed.

[00121] Additionally, it should be noted that as illustrated in Figure 2D, the connector 244 can compress slightly farther. With this design, the projection 240 can glide over slightly larger, large asperities 213D than illustrated in Figure 2D.

[00122] With reference to Figures 2A-2D, the problem of larger-than-expected asperities 213D breaking the projection 240 is solved by the deflection-limiting stopper 242 and/or the connector 244 that allows for additional motion. When encountering larger asperities 213D, the stopper 242 and the projection 240 may move relative to the mounting assembly 236 to allow the large asperities 213D to pass beneath the projection 240 without damage to the projection 240.

[00123] A non-exclusive list of advantages of the material rake assembly 219 include, but is not limited to, (i) a lower risk of damage to the projection(s) 240 from asperities 213C, 213D; (ii) longer life for the rake units 238; (iii) longer time between maintenance on the material rake assembly 219; and/or (iv) higher overall system reliability.

[00124] Figure 3 is a cut-away view of a portion of the build platform 328A and another implementation of the material rake assembly 319 leveling the material 12. Figure 3 also illustrates one small asperity 313C, and one large asperity 313D on the build platform 328A. In Figure 3, the build platform 328A is being moved from right to left relative to the material rake assembly 319 as illustrated with arrow 325.

[00125] In Figure 3, the material rake assembly 319 includes a mounting assembly 336 that is similar to the corresponding component described above. Further, the material rake assembly 319 includes one or more rake units 338 (only one is visible in Figure 3), with each rake unit 338 including a projection 340, a stopper 342, and a connector 344 that are somewhat similar to the corresponding components described above. Flowever, in the implementation of Figure 3, the connector 344 is an active/passive system that additionally includes one or more connector actuators 360 (illustrated as a box) in addition to the resilient members 344B. For example, the connector actuator(s) 360 can include one or more linear actuators or another type of actuator.

[00126] Further, the material rake assembly 319 can include a sensor system 362 that senses, for example, (i) one or more conditions of the rake units 338; and/or (ii) one or more conditions on the build platform 328A. For example, the sensor system 362 can include (i) a first sensor assembly 362A that monitors the magnitude of deflection of the projection 340; (ii) a second sensor assembly 362B that monitors the layers to measure (estimate) the sizes of any asperities 313C, 313D approaching the rake units 338; and/or (iii) a third sensor assembly 362C that monitors the projection 340, e.g. strain, force, velocity or acceleration. For example, the sensor system 362 can include one or more position sensors, force sensors, strain sensors, stress sensors, velocity sensors, acceleration sensors, contact sensors, optical-reflective sensors, capacitance sensors, and/or eddy current sensors.

[00127] As provided herein, the feedback from the sensor system 362 can be directed to the control system 24 (illustrated in Figure 1A). With this information, the control system 24 can control the connector actuator(s) 360 in a closed loop fashion based on the feedback. As a non-exclusive example, in the event the first sensor assembly 362A senses that the projection 340 is fully deflected (or at a predetermined deflection angle), the control system 24 can control the connector actuator(s) 360 to lift the projection 340 and the stopper 342 relative to the build platform 328A so that the projection 340 clears the large asperity 313D. Additionally, or alternatively, for example, in the event the third sensor assembly 362C senses that the projection 340 is too strained, accelerating quickly, and/or moving quickly, the control system 24 can control the connector actuator(s) 360 to lift the projection 340 and the stopper 342 relative to the build platform 328A so that the projection 340 clears the large asperity 313D. Additionally, or alternatively, for example, in the event the second sensor assembly 362B senses a large asperity 313D is approaching the projection 340, the control system 24 can control the connector actuator(s) 360 to lift the projection 340 and the stopper 342 relative to the build platform 328A. For example, the amount of lifting can be the amount necessary for the projection 340 to safely clear the large asperity 313D while being fully deflected, partly deflected, or not deflected.

[00128] It should be noted, for example, that the rake unit 338 of Figure 3 can be designed without the stopper 342 if the connector actuator 360 is actively controlled with feedback from the sensor system 362.

[00129] Figure 4 is a side view of a portion of the build platform 428A and another implementation of the material rake assembly 419 that rakes the material 12 on the build platform 428A. Figure 4 also illustrates one small asperity 413C, and one large asperity 413D on the build platform 428A. In Figure 4, the build platform 428A is being moved from right to left relative to the material rake assembly 419 as illustrated with arrow 425.

[00130] In Figure 4, the material rake assembly 419 includes a mounting assembly 436 that is somewhat similar to the corresponding component described above. Further, the material rake assembly 419 includes one or more rake units 438 (only one is visible in Figure 4), with each rake unit 438 including a projection 440, a stopper 442, and a connector 444 that are somewhat similar to the corresponding components described above. Flowever, in the implementation of Figure 4, the connector 444 is an active system that includes one or more flexures 444B (resilient members), and one or more connector actuators 460 (illustrated as a box) that connect the stopper 442 to the mounting assembly 436. For example, the connector actuator(s) 460 can include one or more linear actuators or another type of actuator.

[00131] In the design of Figure 4, the connector actuator(s) 460 can be controlled to selectively bend the flexure 444B and selectively pivot the projection 440 clockwise to lift the distal end 440A away from the build platform 428A.

[00132] Further, the material rake assembly 419 can again include a sensor system 462 that senses (i) one or more conditions of the rake units 438; and/or (ii) one or more conditions on the build platform 428A. For example, the sensor system 462 can include (i) a first sensor assembly 462A that monitors the magnitude of deflection of the projection 440; (ii) a second sensor assembly 462B that monitors the layers to measure (estimate) the sizes of any asperities 413C, 413D approaching the rake units 438; and/or (iii) a third sensor assembly 462C that monitors the projection 440. [00133] With this design, the feedback from the sensor system 462 can be directed to the control system 24 (illustrated in Figure 1A). With this information, the control system 24 can control the connector actuator(s) 460 in a closed loop fashion based on the feedback. As a non-exclusive example, in the event the first sensor assembly 462A senses that the projection 440 is fully deflected, the control system 24 can control the connector actuator(s) 460 to lift the projection 440 relative to the build platform 428A so that the projection 440 clears the large asperity 413D. Additionally, or alternatively, for example, in the event the third sensor assembly 462C senses that the projection 440 is too strained, accelerating quickly, and/or moving quickly, the control system 24 can control the connector actuator(s) 460 to lift the projection 440 relative to the build platform 428A so that the projection 440 clears the large asperity 413D. Additionally, or alternatively, for example, in the event the second sensor assembly 462B senses a large asperity 413D is approaching the projection 340, the control system 24 can control the connector actuator(s) 460 to lift the projection 440 relative to the build platform 428A. For example, the amount of lifting can be the amount necessary for the projection 440 to safely clear the large asperity 413D while being fully deflected, partly deflected, or not deflected.

[00134] It should be noted, for example, that the rake unit 438 of Figure 4 can be designed without the stopper 442 if the connector actuator 460 is actively controlled [00135] Figure 5 is a side view of a portion of the build platform 528A and another implementation of the material rake assembly 519 that rakes the material 12 on the build platform 528A. Figure 5 also illustrates one small asperity 513C, and one large asperity 513D on the build platform 528A. In Figure 5, the build platform 528A is being moved from right to left relative to the material rake assembly 519 as illustrated with arrow 525.

[00136] In Figure 5, the material rake assembly 519 includes a mounting assembly 536 that is somewhat similar to the corresponding component described above. Further, the material rake assembly 519 includes one or more rake units 538 (only one is visible in Figure 5), with each rake unit 538 including a projection 540, and a connector 544 that are somewhat similar to the corresponding components described above. Flowever, in the implementation of Figure 5, the connector 544 is an active system that includes a flexure 544B (resilient member) that is integrated into the projection 540, and one or more connector actuator(s) 560 (illustrated as a box) that connect the projection 540 to the mounting assembly 536. For example, the connector actuator(s) 560 can include one or more linear actuators or another type of actuator. [00137] In the design of Figure 5, the connector actuator(s) 560 can be controlled to selectively bend the flexure 544B (and/or the projection 540), and selectively pivot the projection 540 clockwise to lift the distal end 540A away from the build platform 528A. [00138] Further, the material rake assembly 519 can again include a sensor system 562 that senses (i) one or more conditions of the rake units 538; and/or (ii) one or more conditions on the build platform 528A. For example, in Figure 5, the sensor system 562 can include (i) a second sensor assembly 562B that monitors the layers to measure (estimate) the sizes of any asperities 513C, 513D approaching the rake units 538; and/or (ii) a third sensor assembly 562C that monitors the projection 540.

[00139] With this design, the feedback from the sensor system 562 can be directed to the control system 24 (illustrated in Figure 1A). With this information, the control system 24 can control the connector actuator(s) 560 in a closed loop fashion based on the feedback. As a non-exclusive example, in the event the third sensor assembly 562C senses that the projection 540 is too strained, is too strained, accelerating quickly, and/or moving quickly, the control system 24 can control the connector actuator(s) 560 to lift the projection 540 relative to the build platform 528A so that the projection 540 clears the large asperity 513D. Additionally, or alternatively, for example, in the event the second sensor assembly 562B senses a large asperity 513D is approaching the projection 540, the control system 24 can control the connector actuator(s) 560 to lift the projection 540 relative to the build platform 528A. For example, the amount of lifting can be the amount necessary for the projection 540 to safely clear the large asperity 513D while being fully deflected, partly deflected, or not deflected.

[00140] It should be noted, for example, that the rake unit 538 of Figure 5 is designed without the stopper. Alternatively, the rake unit 538 can be designed to include the stopper.

[00141] Further, it should be noted that the distal end 540A of the projection 540 can be curved as illustrated in Figure 5 or have another shape.

[00142] Figure 6 is a side view of a portion of the build platform 628A and still another implementation of the material rake assembly 619 that rakes the material 12 on the build platform 628A. Figure 6 also illustrates one small asperity 613C, and one large asperity 613D on the build platform 628A. In Figure 6, the build platform 628A is being moved from right to left relative to the material rake assembly 619 as illustrated with arrow 625.

[00143] In Figure 6, the material rake assembly 619 includes a mounting assembly 636 that is somewhat similar to the corresponding component described above. Further, the material rake assembly 619 includes one or more rake units 638 (only one is visible in Figure 6), with each rake unit 638 including a projection 640, and a connector 644 that are somewhat similar to the corresponding components described above. In the implementation of Figure 6, the connector 644 is an active system that includes a flexure 644B (resilient member) that is integrated into the projection 640, and one or more connector actuator(s) 660 (illustrated as a box) that connect the projection 640 to the mounting assembly 636. For example, the connector actuator(s) 660 can include one or more linear actuators or another type of actuator.

[00144] Moreover, in Figure 6, the distal end 640A of the projection 640 includes a roller that engages the material 12 on the build platform 628A.

[00145] In the design of Figure 6, the connector actuator(s) 660 can be controlled to selectively bend the flexure 644B (and/or the projection 640), and selectively pivot the projection 640 clockwise to lift the distal end 640A away from the build platform 628A. [00146] Further, the material rake assembly 619 can again include a sensor system 662 that senses (i) one or more conditions of the rake units 638; and/or (ii) one or more conditions on the build platform 628A. For example, in Figure 6, the sensor system 662 can include (i) a second sensor assembly 662B that monitors the layers to measure (estimate) the sizes of any asperities 613C, 613D approaching the rake units 638; and/or (ii) a third sensor assembly 662C that monitors the projection 640.

[00147] With this design, the feedback from the sensor system 662 can be directed to the control system 24 (illustrated in Figure 1A). With this information, the control system 24 can control the connector actuator(s) 660 in a closed loop fashion based on the feedback as described above.

[00148] It should be noted, for example, that the rake unit 638 of Figure 6 is designed without the stopper. Alternatively, the rake unit 638 can be designed to include the stopper.

[00149] Figure 7 is a side view of a portion of the build platform 728A and still another implementation of the material rake assembly 719 that rakes the material 12 on the build platform 728A. Figure 7 also illustrates one small asperity 713C, and one large asperity 713D on the build platform 728A. In Figure 7, the build platform 728A is being moved from right to left relative to the material rake assembly 719 as illustrated with arrow 725.

[00150] In Figure 7, the material rake assembly 719 includes a mounting assembly 736 that is somewhat similar to the corresponding component described above. Further, the material rake assembly 719 includes one or more rake units 738 (only one is visible in Figure 7), with each rake unit 738 including a projection 740, and a connector 744 that are somewhat similar to the corresponding components described above. In the implementation of Figure 7, the connector 744 is an active system that includes a flexure 744B (flexible member) that is integrated into the projection 740, and one or more connector actuator(s) 760 (illustrated as a box) that connect the projection 740 to the mounting assembly 736. For example, the connector actuator(s) 760 can include one or more linear actuators or another type of actuator.

[00151] Moreover, in Figure 7, the distal end 740A of the projection 740 is rounded, and the projection 740 has a curved and tapered configuration. The curved design allows for the projection 740 to be longer. This will increase the deflection range of the projection 740. It should be noted that these features of the projection 740 can be implemented into the previously described embodiments.

[00152] In the design of Figure 7, the connector actuator(s) 760 can be controlled to selectively bend the flexure 744B, and selectively lift the projection 740 along the Z axis to lift the distal end 740A away from the build platform 728A.

[00153] Further, the material rake assembly 719 can again include a sensor system 762 that senses (i) one or more conditions of the rake units 738; and/or (ii) one or more conditions on the build platform 728A. For example, in Figure 7, the sensor system 762 can include (i) a first sensor assembly 762A that monitors the projection 740 and/or the connector 744; (ii) a second sensor assembly 762B that monitors the layers to measure (estimate) the sizes of any asperities 713C, 713D approaching the rake units 638; and/or (iii) a third sensor assembly 762C that monitors the projection 740. [00154] With this design, the feedback from the sensor system 762 can be directed to the control system 24 (illustrated in Figure 1A). With this information, the control system 24 can control the connector actuator(s) 760 in a closed loop fashion based on the feedback as described above.

[00155] It should be noted, for example, that the rake unit 738 of Figure 7 is designed without the stopper. Alternatively, the rake unit 738 can be designed to include the stopper.

[00156] Additionally, it should be noted that any of the sensor systems 362, 462, 562, 662, 762 described herein can be designed to include three position sensors to read the topology of the surface prior to deposition of the material 12, and spreading to map the contour and make use of the actuators 360, 460, 560, 760 to adjust tension between the projection(s) and the material 12 on the build platform 328A, 428A, 528A, 628A, 728A.

[00157] Figure 8A is a perspective view of yet another implementation of a material rake assembly 819 that rakes the material 12 (illustrated in Figure 1A). In Figure 8A, the material rake assembly 819 includes a mounting assembly 836 that is somewhat similar to the corresponding component described above. Further, the material rake assembly 819 includes a single rake unit 838 having a plurality of projections 840, and a connector 844 that connects the projections 840 to the mounting assembly 836. Alternatively, for example, the material rake assembly 819 can be designed to include multiple rake units 838.

[00158] Figure 8B is an alternative perspective view of a portion of the material rake assembly 819 of Figure 8A.

[00159] In the implementation of Figures 8A and 8B, the connector 844 is an active system that includes (i) a lower frame 866 that retain the projections 840; (ii) an intermediate frame 868 that is secured to the lower frame 866; (iii) an upper frame 870 that is secured to the intermediate frame 868; (iv) a first connector actuator assembly 872; (v) a second connector actuator assembly 874; and (vi) a kinematic coupling assembly 876 that kinematically couples the actuator assemblies 872, 874 to the upper frame 870. The design of each of these components can be varied pursuant to the teachings provided herein.

[00160] Each frame 866, 868, 870 is rigid. Further, one or more of the frames 866, 868, 870 can be made of a dielectric material, e.g. a ceramic or other material. In one implementation, the lower frame 866 retains the projections 840 at an inclined angle relative to the build platform 28A (illustrated in Figure 1 B).

[00161] The connector actuator assembly 872, 874 are controlled to move and accurately position the frames 866, 868, 870 and the projections 840. For example, the first connector actuator assembly 872 can include a linear mover 872A that is secured to the mounting assembly 836, a shaft 872B, and a transverse frame 872C that is secured to the shaft 872B. In this design, the linear mover 872A is controlled to selective move the shaft 872B, and the transverse frame 872C. Somewhat similarly, the second connector actuator assembly 874 can include a linear mover 874A that is secured to the mounting assembly 836, and a shaft 874B that is selectively moved and positioned with the linear mover 874A.

[00162] The kinematic coupling assembly 876 kinematically couples the actuator assemblies 872, 874 to the upper frame 870. In one non-exclusive implementation, the kinematic coupling assembly includes (i) three, spaced apart, coupling spheres 876A, (ii) three, spaced apart, coupling pads 876B that are secured to the top of the upper frame 870, and (iii) a resilient assembly 876C. In this design, two of the coupling spheres 876A are positioned in two, semi-spherical shaped apertures (not shown) in the bottom of the transverse frame 872C, and one of the coupling spheres 876A is positioned in a semi-spherical shaped aperture in the distal end of the shaft 874B of the second connector actuator assembly 874. Further, each coupling pad 876B includes a “V” shaped slot and is positioned to receive one of the coupling spheres 876A.

[00163] Further, the resilient assembly 876C urges the upper frame 870 towards the mounting assembly 836, and urges (biases) the coupling pads 876B against the coupling spheres 876A. The resilient assembly 876C can include one or more springs or other type of resilient members. It should be noted that the resilient assembly 876C can be designed to provide the required preload forces to maintain the spheres 876A properly positioned during operation of the material rake assembly 819.

[00164] Further, the material rake assembly 819 can again include a sensor system 862 that senses (i) one or more conditions of the rake unit(s) 838; and/or (ii) one or more conditions on the build platform 728A (illustrated in Figure 7). For example, in Figure 8, the sensor system 862 can be similar to the corresponding components described above and can be used for closed loop control of the connector actuator assemblies 872, 874.

[00165] Additionally, as provided above, the sensor system 862 can be used to properly position the projections 840 relative to the material 12. For example, the first connector actuator assembly 872 can lower the projections 840 until a conductive path is established with the build platform 728A as determined by the sensor system 862. The first connector actuator assembly 872 can then be retracted (reversed) the desired thickness of the material layer (e.g. 200 microns). Next, the second connector actuator assembly 874 can lower the projections 840 until a conductive path is again established with the build platform 728A as determined by the sensor system 862. Subsequently, the second connector actuator assembly 874 can then be retracted (reversed) the desired thickness of the material layer (e.g. 200 microns).

[00166] Figures 8C and 8D illustrate the lower frame 866 and the plurality of projections 840 in more detail. In this design, as illustrated in Figure 8C, the plurality of projections 840 include a first row 880 of first projections 840A, and a second row 882 of second projections 840B that are positioned behind the first row 880. Further, the first row 880 and the second row 882 are fixedly secured to the lower frame 886 with one or more projection fasteners 846. In this design, the second row 882 is against the lower frame 866 and the first row 880 is positioned over the second row 882. It should be noted that the projections 840A, 840B can have the same stiffness, or the stiffness of the first projections 840A can be different from the stiffness of the second projections 840B.

[00167] In this non-exclusive implementation, the first row 880 of first projections 840A includes a frame that defines the plurality of spaced apart, first projections 840A that cantilever from the lower frame 866. In this design, each of the first projections 840A have a first projection width 880A along the X axis; and adjacent first projections 840A are spaced a first projection gap 880B.

[00168] Figure 8D illustrates the second row 882 without being covered by the first row 880. Similarly, the second row 882 of second projections 840B includes a frame that defines the plurality of spaced apart, second projections 840B that cantilever from the lower frame 866. In this design, each of the second projections 840B have a second projection width 882A along the X axis; and adjacent second projections 840B are spaced a second projection gap 882B.

[00169] With reference to Figures 8C and 8D, in one, non-exclusive implementation, (i) the first projections 840A of the first row 880 are evenly spaced apart; and (ii) the second projections 840B of the second row 882 are evenly spaced apart. Further, the first projections 840A of the first row 880 are staggered with the second projections 840B of the second row 882 so that the second projections 840B overlap the first projections 840A as view from a progressing direction (e.g. along the Y axis) of the material rake assembly 819. Moreover, in certain implementations, (i) the second projection width 882A is greater than the first projection gap 880B; (ii) the first projection width 880A is greater than the second projection gap 882B; and (iii) the second projections 840B are positioned behind and partly overlap the first projections 840A. Stated in another fashion, (i) the plurality of first projections 840A are aligned in a first direction (e.g. along the X axis) that intersects the progressing direction (e.g. along the Y axis) of the material rake assembly 819; (ii) the plurality of second projections 840B are aligned in a second direction (e.g. along the Y axis) that intersects a progressing direction (e.g. along the Y axis) of the material rake assembly 819; and (iii) the first direction and the second direction are the same. In this example, (i) the first projections 840A are spaced apart and aligned along a first axis 840Aa; (ii) the second projections 840B are spaced apart and aligned along a second axis 840Ba; and (iii) the first axis 840Aa and a second axis 840Ba are spaced apart and parallel to each other. As a result thereof, there is no gap in the combined rows 880, 882 and the material 12 will be evenly distributed.

[00170] Moreover, in this design, if one of the first projections 840A encounters an asperity 713C (illustrated in Figure 7), that first projection 840A and the second projections 840B on either side will deform to clear the asperity 713C. Alternatively, if only one of the second projections 840B encounters an asperity 713C, then only that second projection 840B will deflect.

[00171] As alternative, non-exclusive implementations, (i) the first projection width 880A can be two hundred, three hundred, four hundred, five hundred, or six hundred microns; (ii) the first projection gap 880B can be two hundred, three hundred, four hundred, five hundred, or six hundred microns; (iii) the second projection width 882A can be two hundred, three hundred, four hundred, five hundred, or six hundred microns; and (iv) the second projection gap 882B can be two hundred, three hundred, four hundred, five hundred, or six hundred microns.

[00172] Figure 9A is a simplified side view of a portion of yet another implementation of the material rake assembly 919. More specifically, Figure 9A illustrates the lower frame 966, the first row 980 of first projections 940A, and the second row 982 of second projections 940B. In this design, the first row 980 is again stacked on top of the second row 982.

[00173] Further, in this embodiment, the lower frame 966 defines a stopper 942 that is positioned at the desired location and/or desired angle to act as a hard, deflection limiting surface that engages the projections 940A, 940B to inhibit overbending, while allowing for non-permanent deflection. The stopper 942 and projections 940A, 940B can be similar in design to the corresponding components described above. It should be noted that the projections 940A, 940B can have the same stiffness, or the stiffness of one or more of the first projections 1040A can be different from the stiffness of one or more of the second projections 1040B.

[00174] It should be noted that in the non-exclusive implementation of Figure 9A, the second projections 940B extend longer than the first projections 940A so that both projections 940A, 940B equally engage the material 12 (illustrated in Figure 1A). [00175] Figure 9B is a perspective view of the first row 980 of first projections 940A and the second row 982 of second projections 940B a portion of the material rake assembly of Figure 9A.

[00176] In summary, the material rake assemblies 19, 219, 319, 419, 519, 619, 719, 819, 919 disclosed herein solve the problem of potential damage to the projection(s) caused by the asperities during spreading of the material 12. Further, in the implementations, feedback from the sensor system is used to actively control the position of the projection(s) to control spreading the material 12, to glide over the asperities, and to actively control the compression between the projections and the material 12 that is being spread.

[00177] With the use of the sensor system, the connector actuators can be controlled to react “on-the-fly” and make adjustments to successfully dispense a uniform (or whatever desired thickness/topology) layer of material 12. This also allows the rake units to correct for variations in previous layers or zones that may have been disturbed. [00178] Figure 10A is a simplified perspective view of yet another implementation of a material rake assembly 1019 that rakes the material 12 (illustrated in Figure 10C) on the build platform 1028A (illustrated in Figure 10C). In Figure 10A, the material rake assembly 1019 includes a mounting assembly 1036 that is rigid. Further, the material rake assembly 1019 includes a single rake unit 1038 having a projection assembly 1040 with a first projection 1040A, and a second projection 1040B that cantilever downward from the mounting assembly 1036. With this design, the projections 1040A, 1040B are arranged in series to engage and rake the material 12 on the build platform 1028A. Alternatively, for example, the material rake assembly 1019 can be designed to include multiple rake units 1038 and/or more than two projections 1040A, 1040B in series. For example, the material rake assembly 1019 can include 3, 4, 5, 6, or more projections 1040A, 1040B. It should be noted that the projections 1040A, 1040B can have the same stiffness, or the stiffness of the first projection 1040A can be different from the stiffness of the second projection 1040B.

[00179] Figure 10B is an end view of the material rake assembly 1019 of Figure 10A including the mounting assembly 1036 and the projections 1040A, 1040B.

[00180] Figure 10C is a simplified end side view of the material rake assembly 1019 of Figure 10B with the build platform 1028A. Figure 10C also illustrates the three, formed layers 1013A that have been melted by the energy system 22 (illustrated in Figure 1A), and one, new material layer 1013B (illustrated with small circles) being leveled on the build platform 1028A with the material rake assembly 1019.

[00181] In Figure 10C, the build platform 1028A is at a first position relative to the material rake assembly 1019, and the build platform 1028A is being moved left to right relative to the material rake assembly 1019. As a result thereof, the material rake assembly 1019 is accurately leveling the material 12 on the build platform 1028A. In Figure 10, the build platform 1028A is being moved from left to right relative to the material rake assembly 1019 as illustrated with arrow 1025. Alternatively, the material rake assembly 1019 can be moved relative to the build platform 1028A.

[00182] As provided herein, when spreading the material 12 at high speeds (high relative movement between the build platform 1028A and the material rake assembly 1019), it is common to get a wavy surface which may not be desirable. This phenomenon gets worse when (i) a larger amount of material 12 is needed, and (ii) the spread speed is increased. By utilizing multiple, spaced apart projections 1040A, 1040B in series, the material rake assembly 1019 essentially achieves the effect of spreading a smaller amount of material 12, thereby reducing the cause of “wave” on the spread surface. Stated in another fashion, in this design, the first projection 1040A is used to roughly level the material 12, while one or more subsequently projections 1040B do a thin, fine removal (and spreading) of the material 12. By placing additional, spaced apart projections 1028A, 1028B, out-of-phase relative to the period of the wave (which is system dependent), the material rake assembly 1019 achieves a smoother surface by cutting the peaks of the wave from the previous projection 1028A.

[00183] The proposed material rake assembly 1019 creates a simple method of generating good quality material 12 spread at high speeds. This allows the system to build objects faster. Thus, as provided herein, the problem of creating smooth material 12 spread at high speed is solved by using the material rake assembly 1019 having multi, spaced apart projections 1040A, 1040B.

[00184] As provided herein, the number, size, shape, and spacing of the projections 1040A, 1040B can be based on the dynamics of the system, including the material spread speed, layer thickness, and supply amount.

[00185] As highlighted in Figure 10B, the projections 1040A, 1040B are spaced apart a projection separation distance 1040D. As alternative, non-exclusive examples, the projection separation distance 1040D can be approximately 0, 0.1 , 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 , 2, 3, 4, 5 millimeters or any other number.

[00186] Further, each of the projections 1040A, 1040B has a distal end 1040C, and in certain implementations, the distal end 1040C of the second projection 1040B is closer to the build platform 1038A than the distal end 1040C of the first projection 1040A. Stated in a different fashion, the second projection 1040B is longer than the first projection 1040A by a length difference 1040E. As alternative, non-exclusive examples, the length difference 1040E between any two projections 1040A, 1040B is at least 0, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 microns or any other suitable number.

[00187] Moreover, as alternative, non-exclusive examples, one or each of the projections 1040A, 1040B can have a projection thickness 1040F of at least 0.05, 0.1 , 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 , 2, 3, 4, 5 millimeters or any other suitable number. [00188] The design of each of the projections 1040A, 1040B can be varied. In Figures 10A and 10B, each projection 1040A, 1040B is rigid beam shaped with a curved (rounded) distal end 1040C. Alternatively, each projection 1040A, 1040B can have a different configuration, such as (i) a curved, flexible beam, (ii) a flat distal end, or (iii) a triangular shaped distal end. Still alternatively, one or both of the projections 1040A, 1040B include a plurality of adjacent teeth.

[00189] Further, one or more of the projections 1040A, 1040B can be made of stainless steel, silicone, rubber, plastic, aluminum, or any other suitable material. [00190] Figure 11 is an end view of yet another implementation of the material rake assembly 1119. In this design, the material rake assembly 1119 is similar to the corresponding component described above in reference to Figures 10A-10C. Flowever, in this implementation, the material rake assembly 1119 includes three spaced apart projections 1140A, 1140B, 1140C that are arranged to rake the material 12 (illustrated in Figure 10C) in series.

[00191] Figure 12 is an end view of still another implementation of the material rake assembly 1219. In this design, the material rake assembly 1219 is similar to the combination of the implementations of Figure 3 and Figures 10A-10C. In this implementation, the material rake assembly 1219 includes two spaced apart projections 1240A, 1240B that are arranged rake the material 12 (illustrated in Figure 10C) in series.

[00192] In Figure 12, the material rake assembly 1219 includes a mounting assembly 1236 that is somewhat similar to the corresponding component described above. Further, the material rake assembly 1219 includes a stopper 1242 having an engagement surface 1242E for each projection 1240A, 1240B, a connector 1244, and one or more connector actuators 1260 that are somewhat similar to the corresponding components described above. In this implementation, the connector 1244 is an active/passive system.

[00193] Moreover, the material rake assembly 1219 can include a sensor system 1262 that senses, for example, (i) one or more conditions of the projections 1240A, 1240B; and/or (ii) one or more conditions on the build platform 28A (illustrated in Figure 1 B). For example, the sensor system 1262 can (i) monitor the magnitude of deflection of the projections 1240A, 1240B; (ii) monitor the layers to measure (estimate) the sizes of any asperities 313C, 313D (illustrated in Figure 3); and/or (iii) monitor the projections 1240A, 1240B, e.g. strain, force, velocity or acceleration.

[00194] It that this design, can be modified to remove the stopper 1242, the connector 1244, and/or the connector actuator 1260.

[00195] Those of ordinary skill in the art will realize that the following detailed description of the present embodiment is illustrative only and is not intended to be in any way limiting. Other embodiments of the present embodiment will readily suggest themselves to such skilled persons having the benefit of this disclosure. Reference will now be made in detail to implementations of the present embodiment as illustrated in the accompanying drawings.

[00196] In the interest of clarity, not all of the routine features of the implementations described herein are shown and described. It will, of course, be appreciated that in the development of any such actual implementation, numerous implementation- specific decisions must be made in order to achieve the developer's specific goals, such as compliance with application-related and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure.

Claims

What is claimed is:

1. A material rake assembly for raking material on a build platform of a processing machine, the material rake assembly comprising: a mounting assembly; a flexible, first projection that is coupled to the mounting assembly, the first projection engaging and raking the material on the build platform; and a first stopper that allows for deflection of the first projection while inhibiting over deflection of the first projection.

2. A material rake assembly for raking material on a build platform of a processing machine, the material rake assembly comprising: a mounting assembly; a flexible, first projection that is coupled to the mounting assembly, the first projection engaging and raking the material on the build platform; and a first stopper that has an engagement surface that contacts the first projection.

3. The material rake assembly of claim 2 wherein the engagement surface of the first stopper contacts the first projection if a deflection angle of the first projection is more than a predetermined angle.

4. The material rake assembly of claims 1 or 2 wherein the first projection is at an acute, initial angle relative to normal to the build platform; and wherein the first stopper inhibits deflection of the first projection past a maximum deflection angle relative to normal.

5. The material rake assembly of claim 1 wherein the first stopper includes an engagement surface that is at the maximum deflection angle, and wherein the engagement surface is adapted to engage the first projection and inhibit the first projection from deflecting past the maximum deflection angle.

6. The material rake assembly of claims 1 or 2 wherein the first projection includes a proximal end that is secured to the first stopper and a distal end that cantilevers away from the first stopper.

7. The material rake assembly of claims 1 or 2 further comprising (i) a flexible, second projection that is coupled to the mounting assembly, the second projection engaging and raking the material on the build platform; and (ii) a second stopper that allows for deflection of the second projection while inhibiting over deflection of the second projection.

8. The material rake assembly of claims 1 or 2 further comprising a connector that flexibly couples the first projection to the mounting assembly, the connector allowing the first projection to move relative to the build platform.

9. The material rake assembly of claim 8 wherein the connector allows the entire first projection to move substantially normal to the build platform.

10. The material rake assembly of claim 8 wherein the first projection is attached to the first stopper, and wherein the connector connects the first stopper to the mounting assembly.

11. The material rake assembly of claim 10 wherein the connector allows the entire first projection and the first stopper to move relative to the build platform.

12. The material rake assembly of claim 8 wherein the connector includes an actuator that moves the first projection relative to the build platform.

13. The material rake assembly of claim 12 further comprising a sensor system that senses at least one condition of the first projection and provides sensor feedback that is used to control the actuator.

14. The material rake assembly of claim 12 further comprising a sensor system that senses at least one condition of the material on the build platform and provides sensor feedback that is used to control the actuator.

15. The material rake assembly of claims 1 or 2 further comprising (i) a flexible second projection that is coupled to the mounting assembly, the second projection engaging the material on the build platform, the second projection being positioned adjacent to the first projection; and (ii) a second stopper that allows for deflection of the second projection while inhibiting over-deflection of the second projection.

16. The material rake assembly of claims 1 or 2 further comprising a flexible second projection that is coupled to the mounting assembly, the second projection engaging the material on the build platform, and the second projection at least partly overlapping the first projection.

17. The material rake assembly of claim 16 further comprising a plurality of the first projections that are spaced apart in a first array, and a plurality of the second projections that are spaced apart in a second array; wherein the second projections are at least partly overlapping the first projections.

18. A processing machine for building an object from material, the processing machine comprising: a build platform; and the material rake assembly of claims 1 or 2 that rakes the material on the build platform.

19. The processing machine of claim 18 further comprising an energy system that generates an energy beam the melts at least a portion of the material on the build platform.

20. A material rake assembly for raking material on a build platform of a processing machine, the material rake assembly comprising: a mounting assembly; a plurality of first projections that are spaced apart in a first array, the first projections being coupled to the mounting assembly, and the first projections engaging and raking the material on the build platform; and a plurality of second projections that are spaced apart in a second array, the second projections being coupled to the mounting assembly, the second projections engaging and raking the material on the build platform, and wherein the second projections are at least partly overlapping the first projections.

21. A material rake assembly for raking material on a build platform of a processing machine, the material rake assembly comprising: a mounting assembly; a plurality of first projections that are spaced apart in a first array, the first projections being coupled to the mounting assembly, and the first projections engaging and raking the material on the build platform; and a plurality of second projections that are spaced apart in a second array, the second projections being coupled to the mounting assembly, the second projections engaging and raking the material on the build platform, and wherein the first projections and the second projections are placed in staggered arrangement.

22. The material rake assembly of claims 20 or 21 wherein the second projections are at least partly overlapping the first projections when the first and second projections are viewed from a progressing direction of the material rake assembly.

23. The material rake assembly of claims 20 or 21 wherein the plurality of first projections are aligned in a first direction that intersects a progressing direction of the material, and the plurality of second projections are aligned in a second direction that intersects a progressing direction of the material.

24. The material rake assembly of claim 23 wherein the first direction is the same as the second direction.

25. The material rake assembly of claims 20 or 21 wherein the first and second projections are flexible.

26. The material rake assembly of claims 20 or 21 further comprising a stopper that allows for deflection of the first projections and the second projections while inhibiting over-deflection of the first projections and the second projections.

27. The material rake assembly of claims 20 or 21 wherein each projection is at an acute, initial angle relative to normal to the build platform; and wherein the stopper inhibits deflection of the projections past a maximum deflection angle relative to normal.

28. The material rake assembly of claims 20 or 21 wherein the stopper includes an engagement surface that is at the maximum deflection angle, and wherein the engagement surface is adapted to engage the projections and inhibit the projections from deflecting past the maximum deflection angle.

29. The material rake assembly of claims 20 or 21 wherein each projection includes a proximal end that is secured to the stopper and a distal end that cantilevers away from the stopper.

30. The material rake assembly of claims 20 or 21 further comprising a connector that flexibly couples the projections to the mounting assem bly, the connector allowing the projections to move relative to the build platform.

31 . The material rake assembly of claim 30 wherein the connector includes an actuator that moves the projections relative to the build platform.

32. The material rake assembly of claim 31 further comprising a sensor system that senses at least one condition of the projections and provides sensor feedback that is used to control the actuator.

33. The material rake assembly of claim 31 further comprising a sensor system that senses at least one condition of the material on the build platform and provides sensor feedback that is used to control the actuator.

34. A processing machine for building an object from material, the processing machine comprising: a build platform; and the material rake assembly of claims 20 or 21 that rakes the material on the build platform.

35. The processing machine of claim 34 further comprising an energy system that generates an energy beam the melts at least a portion of the material on the build platform.

36. A material rake assembly for raking material on a build platform of a processing machine, the material rake assembly comprising: a mounting assembly; a first projection that is coupled to the mounting assembly, the first projection engaging and raking the material on the build platform; and a connector that flexibly couples the first projection to the mounting assembly, the first connector allowing the first projection to move relative to the build platform.

37. The material rake assembly of claim 36 wherein the first projection is flexible.

38. The material rake assembly of claim 36 wherein the connector allows the entire first projection to move normal to the build platform.

39. The material rake assembly of claim 36 wherein the connector includes an actuator that moves the first projection relative to the build platform.

40. The material rake assembly of claim 39 further comprising a sensor system that senses at least one condition of the first projection and provides sensor feedback that is used to control the actuator.

41. The material rake assembly of claim 39 further comprising a sensor system that senses at least one condition of the material on the build platform and provides sensor feedback that is used to control the actuator.

42. The material rake assembly of claim 36 wherein the connector connects the first projection to the mounting assembly in a kinematic fashion.

43. The material rake assembly of claim 36 further comprising a stopper that allows for deflection of the first projection while inhibiting over-deflection of the first projections; wherein the stopper includes an engagement surface that inhibits the first projection from deflecting past the maximum deflection angle.

44. The material rake assembly of any of one of claims 36-43 further comprising a flexible, second projection that is coupled to the mounting assembly, the second projection engaging and raking the material on the build platform.

45. The material rake assembly of claim 44 wherein the second projection at least partly overlaps the first projection.

46. The material rake assembly of claim 44 further comprising a plurality of the first projections that are spaced apart in a first array, and a plurality of the second projections that are spaced apart in a second array; wherein the second projections are at least partly overlapping the first projections.

47. A processing machine for building an object from material, the processing machine comprising: a build platform; and the material rake assembly of claim 36 that rakes the material on the build platform.

48. The processing machine of claim 47 further comprising an energy system that generates an energy beam the melts at least a portion of the material on the build platform.

49. A material rake assembly for raking material on a build platform of a processing machine, the material rake assembly comprising: a mounting assembly; and a projection assembly that is coupled to the mounting assembly, the projection assembly including a first projection and a second projection that is spaced apart from the first projection, wherein the projections are arranged in series to engage and rake the material on the build platform.

50. The material rake assembly of claim 49 wherein the first projection and the second projection are aligned in a progressing direction of the material rake assembly.

51 . The material rake assembly of claim 49 wherein the second projection is closer to the build platform than the first projection.

52. The material rake assembly of claim 49 wherein each projection has a distal end, and wherein at least one of the projections has a projection thickness at the distal end that is at least fifty microns.

53. The material rake assembly of claim 49 further comprising a stopper that includes an engagement surface that is at a maximum deflection angle, and wherein the engagement surface is adapted to engage the first projection and inhibit the first projection from deflecting past the maximum deflection angle.

54. The material rake assembly of claim 49 further comprising a connector that flexibly couples the projections to the mounting assembly, the connector allowing the projections to move relative to the build platform.

55. The material rake assembly of claim 54 wherein the connector allows the entire first projection to move normal to the build platform.

56. The material rake assembly of claim 54 wherein the connector includes an actuator that moves the projections relative to the build platform.

57. A material rake assembly for raking material on a build platform of a processing machine, the material rake assembly comprising: a mounting assembly; a first projection that is coupled to the mounting assembly, the first projection engaging and raking the material on the build platform; and a sensing system that senses a condition of the first projection or the material on the build platform.

58. The material rake assembly of claim 57 wherein the sensing system includes at least one of a position sensor, a force sensor, a strain sensor, a stress sensor, a velocity sensor, an acceleration sensor, a contact sensor, an optical- reflective sensor, a capacitance sensor, and an eddy current sensor.

59. The material rake assembly of any of one of claims 57-58 wherein the condition sensed by the sensing system includes at least one of a magnitude of deflection of the first projection and a size of asperity in the material.

60. The material rake assembly of any of one of claims 57-59 further comprising a feedback system that controls an actuator of the material rake assembly based on the condition sensed by the sensing system.

61. A processing machine for building an object from material, the processing machine comprising: a build platform; and the material rake assembly of claim 57 that rakes the material on the build platform.

62. The processing machine of claim 61 further comprising an energy system that generates an energy beam the melts at least a portion of the material on the build platform.