阅读说明：本技术 利用气动输送的三维打印机 (Three-dimensional printer using pneumatic conveying ) 是由 小戴维·R·奥蒂斯 凯文·E·斯维尔 杰弗里·L·蒂尔曼 于 2017-07-28 设计创作，主要内容包括：一种三维(3D)打印机和具有用于将构建材料传送至3D打印机的容器的气动输送系统的方法。联接到容器的进给器调节构建材料从容器的排出流动。联接到进给器的密封控制器减少空气流入。(A three-dimensional (3D) printer and method having a pneumatic transport system for transferring build material to a container of the 3D printer. A feeder coupled to the container regulates a discharge flow of build material from the container. A seal controller coupled to the feeder reduces the inflow of air.)

1. A three-dimensional (3D) printer, comprising:

a Pneumatic Conveying System (PCS) disposed within the 3D printer, the PCS for conveying build material to the receptacle, said PCS further comprising:

a feeder coupled to the container, the feeder to regulate a discharge flow of build material from the container; and

a seal controller coupled to the feeder to reduce an inflow of air opposite a direction of build material transport.

2. The 3D printer of claim 1, the feeder further comprising:

a chamber comprising a pocket for receiving a quantity of build material from the container, wherein the pocket moves such that pressure in the PCS is isolated from downstream of the feeder.

3. The 3D printer of claim 1, the feeder further comprising:

a rotatable chamber comprising a plurality of pockets;

an upper shoe including an inlet, wherein the upper shoe is disposed atop the rotatable chamber; and

a lower shoe including an outlet, wherein the lower shoe is disposed below the rotatable chamber such that the chamber is sandwiched between the upper shoe and the lower shoe;

wherein a quantity of build material is received into a first pocket of the plurality of pockets through the inlet.

4. The 3D printer of claim 3, wherein the rotatable chamber rotates such that the first pocket is not disposed below the inlet and above the outlet at the same time;

wherein there is at least one sealing spoke between the inlet and the outlet.

5. The 3D printer of claim 4, wherein the rotatable chamber rotates such that the first pocket is disposed above the outlet;

wherein a certain building material flows downstream out of the feeder.

6. The 3D printer of claim 1, the PCS further comprising:

a centrifugal separator disposed upstream of the vessel, the centrifugal separator receiving build material from the PCS, separating the build material from the conveying air, and discharging separated build material into the vessel;

wherein an air up-flow rate resulting from the feeder receiving build material does not interrupt a downward flow of powder through the centrifugal separator.

7. The 3D printer of claim 3, the seal controller further comprising:

a Direct Current (DC) motor to generate motive force for a feeder wheel of the feeder.

8. The 3D printer of claim 7, the seal controller further comprising:

an encoder for controlling the on and off state of the DC motor.

9. A method of operating a three-dimensional (3D) printer, comprising:

conveying build material to a vessel via a pneumatic conveying system;

dispensing build material from the container into a pocket of a feeder through an inlet of the feeder, the container being disposed above the feeder and the inlet being disposed above the pocket;

controlling rotation of the feeder until the pocket is no longer below the inlet, the inlet being at a first pressure, the outlet being at a second pressure, wherein the first pressure is isolated from the second pressure; and

generating the 3D object from the build material, wherein the conveying is concurrent with the generating of the 3D object.

10. The method according to claim 9, controlling rotation of the feeder further comprising:

activating a Direct Current (DC) motor coupled to a feeder wheel, wherein the DC motor supplies motive force to the feeder wheel to rotate the feeder; and

enabling an encoder to digitally control the on state of the DC motor.

11. The method of claim 9, further comprising:

delivering build material to the vessel through a centrifugal separator that separates build material from the delivery air and discharges the separated build material to the vessel; and

rotating the feeder until the pocket is disposed above an outlet of the feeder, wherein build material drops downstream from the feeder;

wherein air entering the pocket from downstream is isolated from the centrifugal separator to reduce air movement opposite a flow direction of build material from the vessel.

12. A feeder for use by a three-dimensional (3D) system, the feeder comprising:

a chamber comprising a circular rim and spokes disposed inside and orthogonal to the rim, the rim and the spokes forming a pocket in the chamber, wherein rotation of the chamber is controlled by a Direct Current (DC) motor;

an upper shoe plate including an inlet; and

a lower shoe including an outlet, wherein the chamber is sandwiched between the upper shoe and the lower shoe;

wherein the feeder receives build material from an upstream location and deposits build material to a downstream location as follows:

receiving build material through the inlet into a pocket disposed directly below the inlet, the pocket associated with a first pneumatic pressure;

rotating said feeder until the pocket is no longer below said inlet but above said outlet;

depositing build material downstream through the outlet;

wherein the gas pressure in a region upstream of the feeder is isolated from a second region downstream of the feeder, wherein upstream and downstream are referenced to a direction of build material flow.

13. The feeder according to claim 12, wherein the DC motor is turned on and off using an encoder.

14. The feeder according to claim 12, further comprising:

a feeder wheel surrounding the chamber, the feeder wheel including teeth that rotate the feeder when moving; wherein the feeder wheel is controlled by the DC motor.

15. The feeder according to claim 12, wherein a pneumatic transport system delivers build material to a centrifugal separator, and build material is received in a pocket of the feeder and discharged from the feeder to a component of the 3D system, wherein the pneumatic transport system and the centrifugal separator are operable during generation of a three-dimensional object by a printer.

Background

Additive Manufacturing (AM) may include three-dimensional (3D) printing to generate a 3D object. In some AM processes, successive layers of material are formed under computer control to fabricate the object. The material may be a powder or powdered material, including metals, plastics, ceramics, composites, and other powders. The object may be of various shapes and geometries, and may be generated via a model such as a 3D model or other electronic data source. Manufacturing may involve laser melting, laser sintering, electron beam melting, thermal fusion, and the like. The model and automated control may facilitate layered manufacturing and additive manufacturing. For applications, additive manufacturing can produce intermediate and end products for aerospace (e.g., aircraft) as well as prototypes, mechanical parts, medical devices (e.g., implants), automotive parts, popular products, structural and conductive metals, ceramics, conductive adhesives, semiconductor devices, and other applications.

Drawings

Certain examples are described in the following detailed description with reference to the accompanying drawings, in which:

1A-1C are illustrations of three separate implementations of a 3D printer according to an example;

FIG. 2 is an illustration of a pneumatic transport system of the 3D printer of FIG. 1C, according to an example;

FIG. 3 is an illustration of a centrifugal separator and a container for use in the 3D printer of FIG. 1C according to an example;

FIG. 4 is an illustration of two types of air leaks overcome by the 3D printer of FIG. 1C according to an example;

fig. 5 is an illustration of a feeder of the 3D printer of fig. 1A-1C according to an example;

fig. 6 is an illustration of a feeder for use in the 3D printer of fig. 1C according to an example;

FIG. 7 is a flow chart of a seal control mechanism used by the 3D printer of FIGS. 1A-1C according to an example; and

fig. 8 is a detailed block diagram of the 3D printer of fig. 1C according to an example.

Detailed Description

The techniques illustrated herein are directed to a three-dimensional (3D) printer having a pneumatic transport system (PCS) to transport build material, such as powder, to enable generation of 3D objects. A feeder inside the 3D printer dispenses build material below the feeder. The chambers within the feeder are operated using a sealing control mechanism to control the upward and downward flow of air. In other words, the feeder has a chamber that reduces the upward flow of air from the feeder and the downward flow of air from the feeder, as described below. Such sealing control may provide that the upward flow of air from the feeder does not cause the powder to be excessively aerated and agitated, which may prevent the downward flow of powder. The sealing control also substantially prevents air leakage (into the feeder) caused by upward gas flow driven by a pressure gradient opposite to the powder flow. Thus, the sealing control enables the feeder to isolate the pressure upstream of the feeder from the pressure downstream of the feeder. This facilitates the 3D printer to simultaneously transport build material and initiate a 3D print job to generate a 3D object, at least for the reason that the upward flow of air does not significantly interfere with the flow of powder or the operation of a centrifugal separator disposed above the container. Furthermore, because the delivery of build material occurs during the print job, the cycle time to complete the 3D print job in the new 3D printer is reduced relative to a 3D printer that completes delivery of build material prior to generating the 3D object.

Fig. 1A, 1B, and 1C are examples of 3D printers 100A, 100B, and 100C, respectively, that may form a 3D object from build material, such as on a build platform. Referring first to fig. 1A, a 3D printer 100A includes a pneumatic transport system (PCS)50A for transporting build material (e.g., powder) 20 to generate a 3D object 90. PCS 50A includes feeder 40 for dispensing build material 20. The printer 100A also includes a seal control mechanism 30 for operating the feeder. The seal control method 30 includes a DC motor and an encoder, as discussed in more detail below.

Fig. 1B and 1C show further examples of the 3D printer 100, denoted as 100B and 100C, respectively (collectively "3D printer 100"), and having PCS 50B and 50C, respectively (collectively "PCS 50"). In fig. 1B, 3D printer 100B includes PCS 50B and seal control mechanism 30, but further includes build material supply 80 for dispensing build material 20 to PCS 50B. PCS 50B includes a container 60 disposed above feeder 40 to receive build material 20, such as powder, from build material supply 80. In 3D printer 100C, build material 20 is fed into centrifugal separator 70 and then into container 60 before being received into feeder 40. A centrifugal separator 70, coupled to the vessel 60 and also known as a powder catcher or cyclone, more effectively separates the build material 20 from the conveying air.

The 3D printing performed by the 3D printer 100 may include Selective Layer Sintering (SLS), Selective Heat Sintering (SHS), Electron Beam Melting (EBM), thermal fusion, or other 3D printing and AM techniques to generate a 3D object from the build material. The build material may be in powder, powdered or powdered form. The build material may be a variety of materials including polymers, plastics, metals, and ceramics. In operation, the 3D printer 100 employs additive manufacturing of the build material 20 to generate the 3D object 90.

The seal control mechanism 30 is shown as being located outside of the PCS 50. However, the seal controller 30 may be part of the PCS50, and elements of the seal controller 30 may be part of the feeder 40. As discussed in more detail below, in conjunction with the seal control mechanism 30, the feeder 40 does not allow air leakage driven by a pressure gradient opposite the powder flow. Further, during operation of the 3D printer 100, there is a first pressure upstream of the feeder (upstream pressure) and a different pressure downstream of the feeder (downstream pressure), where upstream and downstream refer to the flow of build material 20 in the PCS. As illustrated in more detail herein, the seal controller 30 assists the feeder 40 in isolating the upstream pressure from the downstream pressure. This enables transport of build material 20 within 3D printer 100 to occur while 3D object 90 is being printed.

Pneumatic conveyance is a mechanism by which particles (in this case, build material) are suspended in a conveying air. Particles are obtained from one or more source locations, transported via a conduit (e.g., pipe, tubing, etc.), and received at one or more destination locations. Pneumatic conveying may use positive or negative gauge pressure to convey air. Dilute phase pneumatic conveying is generally characterized by relatively high velocities and low ratios of build material (powder) to gas (air) (e.g., powder to air mass ratios of less than 15). Dense phase pneumatic conveying involves a small amount of gas at high pressure (positive pressure) or high vacuum (negative pressure) and the ratio of material to gas conveyed is relatively high. In one embodiment, PCS50 uses negative (vacuum) pressure to convey build material 20 through 3D printer 100. In a second embodiment, PCS50 uses negative pressure and dilute phase delivery to deliver build material 20. In one example, a typical airflow rate through the PCS50 is about 6-8 cubic feet of air per minute. This corresponds to air velocities between 15 and 19m/sec in a 5/8 "inner diameter tube. In another example, when moving build material or powder, the ratio of powder mass to air mass is less than 2, which allows the powder to move through the conduit 66 at up to 5 g/sec.

Feeder 40 of 3D printer 100 receives build material 20 from PCS50 and dispenses the build material so that 3D object 90 may be generated. The feeder 40 is described in more detail below in conjunction with fig. 6.

PCS50 of 3D printer 100 receives build material 20 from build material supply 80. Build material supply 80 may be a container, such as a hopper, bin, or cassette. In one example, build material supplier 80 is a removable cartridge. This allows the build material supply 80 to be removed from the 3D printer and replaced with a second (full) cartridge if empty. In another example, build material supply 80 includes build material recycled (or recycled) from a previous 3D print job. In another example, build material supplier 80 includes new build material combined with recycled (and/or recycled) build material. In yet another example, build material supplier 80 has a volume that is less than the volume required to generate 3D object 90.

In 3D printer 100, build material 20 delivered by PCS50 is fed into centrifugal separator 70 and then into vessel 60 before being received into feeder 40. Centrifugal separator 70, also known as a powder catcher or cyclone separator, is designed to more effectively separate build material 20 from the conveying air. Like build material supply 80, vessel 60 may be a hopper, bin, or cassette. The container 60 may have a conical or rectangular cross-section with sloped walls so that the powder flows through the container without adhering to the walls and the build material 20 separates from the transport air by gravity.

Fig. 2 shows PCS50 in more detail. PCS50 is comprised of conduits 66A-H (collectively "conduits 66") (e.g., tubes, pipes, lines), centrifugal separator 70, vessel 60, feeder 40, air inlet or suction 24, filter 18, and blower 86. The driving force behind PCS50 is a blower 86 that powers air disposed inside duct 66. In fact, once blower 86 is operated, air under negative pressure flows inside conduit 66, transporting build material 20 along the connected conduit in the direction shown by the arrow. The various conduits making up PCS50 may be joined or connected, such as by a conduit tee or other fitting. In an example, the conduit 66 is disposed within a housing of the 3D printer 100.

Conduit 66 of PCS50 feeds build material 20 from build material supply 80 through second feeder 40B. The seal control mechanism 30 controls both the feeder 40 and the feeder 40B. Feeder 40B controls the powder quality relative to the air quality in conduit 66B and thus helps to maintain the quality within certain limits. Build material 20 is dispensed via feeder 40B to conduit portion 66B where it is conveyed via air under negative pressure, in this example via conduits 66B, 66C, and 66D, toward a centrifugal or cyclonic separator 70. The arrows in fig. 2 indicate the direction of the airflow. At cyclone 70, air is separated from build material 20 and the air is drawn through conduits 66E, 66F, 66G, and 66H by negative pressure.

In one embodiment, PCS50 is a negative pressure system. Airflow in PCS50 is established by blower 86 which is located at the downstream end of the pneumatic line and which establishes a negative pressure through the pneumatic line. When blower 86 is activated, a negative pressure is created in PCS50 such that air from air intake (suction) 24 flows through conduit 66A, conduit 66B (also with build material 20), conduit 66C, and conduit 66D where the build material is received into centrifugal separator 70. Where the build material 20 is separated from the air before being received into the container 60 where the build material 20 is discharged by the feeder 40. In centrifugal separator 70, the separated air is drawn by the negative pressure in PCS50 to flow upward to conduit 66E, conduit 66F, conduit 66G, and conduit 66H. In some examples, the air may be filtered before exiting the 3D printer 100.

In one example, blower 86 generates an air flow that provides a velocity sufficient to transport build material 20. The negative pressure through PCS50 causes build material 20 to leak within 3D printer 100 if a leak occurs, so the build material does not leak from the printer. In one embodiment, an airflow rate of up to 5 grams per second (g/sec) of build material may be maintained in PCS 50.

Thus, PCS50 may be characterized as having at least two overall conduit sections, namely an input conveyance ( conduits 66A, 66B, 66C, and 66D) and an output conveyance ( conduits 66E, 66F, 66G, and 66H). The output conveyance of air, which should be free or substantially free of build material 20, may not actually exit PCS50 or printer 100, but may be used, for example, to fill air inlet 24 for subsequent operations. In the event that build material does leak into the output conveyor, the filter 18 disposed along the output conveyor may capture any stray particles.

Thus, PCS50, consisting of conduit 66, air inlet 24, blower 86, filter 18, cyclone 70, vessel 60, and feeder 40, forms a system through which the air stream flows build material 20. The PCS50 may not be a completely closed system, and some leakage may be tolerated. However, leakage below the cyclone separator 70 can be problematic. For example, if the velocity of the air flowing upward through the feeder 40 in the cyclone 70 exceeds a certain velocity, the powder separation of the cyclone may be disturbed, and the separation efficiency of the cyclone may be lost. This principle will be described in more detail below.

The feeder 40 is disposed below (or downstream of) the container 60. Feeder 40 opens to receive build material 20 from upstream and dispense further downstream. Cyclone 70, vessel 60 and feeder 40 are connected and also coupled to PCS 50. This means that when open, the feeder 40 will reduce the separation efficiency of the cyclone and thus impair the efficiency of the PCS 50. Because PCS50 delivers build material by applying air pressure, opening of feeder 40 compromises operation of the PCS.

In one embodiment of 3D printer 100, the average air velocity in build material delivery conduit 66 of PCS50 is between 10 and 20 meters per second (m/sec). For example, for a build material such as polyamide 12(PA12, a nylon), if the air flow rate is less than 6m/sec, the build material may settle in the horizontal duct segments (see, e.g., ducts 66B and 66D).

Cyclonic separation can remove particles from air by vortex separation. Centrifugal separators, commonly known as cyclones, perform this cyclonic separation to separate the received material into two portions, one of which is generally less dense than the other. Referring back to fig. 1C, the 3D printer 100 may include a centrifugal separator or cyclone 70 disposed above the container 60. Once the build material 20 is fed into the airflow of the PCS50, the cyclone separator 70 serves to separate the build material from the conveying air before the build material is received into the vessel 60.

Fig. 3 is one example of a possible configuration of the centrifugal separator 70 and the container 60 of the 3D printer 100. A centrifugal separator or cyclone 70 is provided above the vessel 60 so that in this case the denser material (in this case the build material 20) is separated from the conveying air and received into the vessel 60.

The cyclone separator 70 is comprised of an inner portion 76 and an outer portion 78. Air combined with build material 20 from PCS50 is received into PCS air inlet 82. The shape of the inner portion 76 creates a vortex in the middle of the cyclone separator 70 causing the lighter air to flow upward (see air path arrow 72) while the heavier build material 20 flows downward and centrifugally diffuses toward the wall of the separator (see build material path 74). This causes the build material 20 to fall into the receptacle 60 while the air flows upward and exits the cyclone through the air flow outlet 84.

In one embodiment, the 3D printer 100 has a single cyclone. In another embodiment, a plurality of cyclones are provided in parallel with each other in the 3D printer 100 to perform the above-described separating operation. The efficiency of cyclonic separation can be controlled by, to name a few factors, the size of the build material particles, their density, the velocity of the conveying air, geometric factors, and electrostatic attraction.

In one embodiment, the cyclone separator 70 of the 3D printer 100 is capable of separating 99.95% or more of the build material in the 60 to 80 micron size range, 99.9% or more of the build material in the 45 to 60 micron size range, and 99.5% of the build material in the 10 to 20 micron size range. For build material less than 10 microns (known as fines), the cyclone 70 of the 3D printer 10 is designed to minimize or reduce fines exiting the air flow outlet 84. In addition, other separation percentages and associated particle size ranges are applicable.

Air leakage below the cyclone separator 70 can interfere with the efficiency of the cyclone separator by causing updraft inside the cyclone separator. Such leakage may undesirably carry build material 20 back through air flow outlet 84 to "clean" portions of PCS50 (e.g., output transports 66E, 66F, 66G, and 66H in fig. 2). The seal control mechanism 30 of the new feeder 40 in the 3D printer 100 is designed to prevent or reduce air leakage into the cyclone separator 70.

Fig. 4 is a diagram illustrating the relative positions of components of the 3D printer 200 that may have leakage problems. 3D printer 200 includes cyclone 270, container 260, and feeder 240. The downward spiraling arrow indicates the movement of build material 220 from the cyclone 270 into the vessel 260, while the build material 220 indicates how full the vessel is. PCS250 conveys build material 220 to cyclone 270. Similar to the airflow of the cyclone separator 70 described above in connection with fig. 3, the upward arrows indicate the airflow back into the PCS 250. Feeder 240 is coupled to container 260 and is below container 260. When air leaks into feeder 240, such as through a gap in the housing of feeder 240, outside air may be drawn in. Two possible air leaks from feeder 240 are shown, with the arrows for the first leak (type 1) going upstream toward cyclone 270 and the arrows for the second leak (type 2) going downstream from feeder 240.

Air leaks of type 1 convey unwanted air upstream from feeder 240, such as in the case where the leaking air has a pressure differential opposite the direction of flow of build material 220. This causes unwanted air to move upward through the container 260. If unwanted air leaks into the cyclone 270 above the container 260, the separation efficiency of the cyclone may be compromised. For example, if an unwanted air leakage rate is established by the cyclone cone at an air velocity of about 0.1m/sec or more, the cyclone separation efficiency suffers. Thus, a type 1 leak should be avoided because it would interfere with the powder flow through the cyclone 270.

Type 2 air leaks carry unwanted air downstream from feeder 240. Again, air in the environment surrounding or outside feeder 240 may enter the feeder through gaps in the feeder housing. Unwanted air may move downward through feeder 240. This downstream transport of unwanted air may adversely affect downstream transport and handling of the build material.

Thus, there are at least two different types of leaks that may affect PCS50 and other solids handling of the printer. A given feeder may handle one of these types of leaks at a given time. Leakage of type 1 is of concern for the efficiency of the cyclone. For downstream feeders, such as feeders 440B, 440C, and 440D (fig. 7 below), a type 2 leak may be of concern. A design that eliminates a type 1 leak does not necessarily eliminate a type 2 leak, and vice versa. Both the type 1 and type 2 leaks of the unwanted air shown in fig. 4 can be addressed by the seal control mechanism 30 of the feeder 40 as described in fig. 5 and 6 below.

Returning to fig. 2, recall that PCS50 of 3D printer 100 is a negative gage pressure system. Any portion to which the PCS50 is connected is sealed so that the negative pressure of the PCS operates effectively and efficiently. Thus, the other components of the PCS (e.g. cyclone 70, vessel 60 and feeder 40) thus form a larger system which is subjected to negative pressure. While leakage in some portions of PCS50 can be tolerated, leakage below cyclone 70 is of particular concern and can affect cyclone efficiency.

Fig. 5 is a detailed illustration of the feeder 40 of the 3D printer 100 for transferring the build material 20 from an upstream position to a downstream position. The feeder 40 includes an upper shoe (shoe)34A, a lower shoe 34B (collectively "shoes 34"), and a housing 46 sandwiched orthogonally between the shoes. Inside the housing 46, a chamber 42 is provided below the upper shoe 34A and above the lower shoe 34B. The chamber 42 is made up of a circular rim 46 and spokes or ribs 48 that form the various pockets 44. The number of spokes 48 forming the same number of pockets 44 may vary. In one embodiment, the chamber includes six spokes and six equally wide pockets. In a second embodiment, the chamber comprises at least three spokes and three pockets. In a third embodiment, the number of pockets is sufficiently large to make the volume of each pocket small so that the air upflow velocity from an empty pocket is below a threshold (e.g., 0.1m/sec) that would cause problems with the cyclone separator. In a fourth embodiment, each feeder pocket 44 has a volume between 4 and 10 cubic centimeters.

Surrounding the feeder 40 is a feeder wheel 94 adjacent the gear train 92. The feeder wheel 94 has a plurality of teeth that can mesh with adjacent teeth in the gear train 92. The gear train is a mechanical system formed by mounting gears in such a manner that teeth of the gears mesh with each other. In fig. 6, the gear train has a plurality of gears (four in this example) that are neatly distributed to smoothly transfer rotation from one gear to the next. As shown in fig. 6, the gear train 92 that drives rotation of the feeder wheel 94 causing rotation of the feeder 40 is controlled by the seal controller 30.

In one embodiment, as shown in FIG. 6, the seal control mechanism 30 utilizes a DC motor 96 that is activated and controlled by an encoder 98. By digitally controlling the on and off state of DC motor 96, encoder 98 provides control of the Revolutions Per Minute (RPM) of feeder wheel 94 to be tightly controlled. Due to the gear train 92 between the feeder wheel 94 and the motor 96, the motor operates at a speed that is faster than the desired RPM of the feeder wheel 94. In one example, the feeder wheel 94 moves between 2 and 20 RPM. In another example, the rotation of the feeder wheel 94 may be operated continuously for a period of time before closing. Further, the sealing control mechanism 30 may control more than one feeder in the 3D printer 100. The operation of the seal control mechanism 30 for multiple feeders is described in more detail below in fig. 8.

An inlet (e.g., opening, slot, hole, etc.) 32 is provided in the upper shoe 34A, and an outlet (e.g., opening, slot, hole, etc.) 38 is provided in the lower shoe 34B. Both the inlet 32 and the outlet 38 may be hinged doors, variable sized holes, chutes, etc. In one embodiment, the inlet 32 and outlet 38 are generally open. In this example, the feeder 40 is cylindrical. In operation, the upper shoe 34A seals against the top surface of the rim 46 of the chamber, while the lower shoe 34B seals against the bottom surface of the rim, thereby substantially sealing the chamber 42 and the pocket 44 of the chamber. Although the feeder 40 is depicted as being substantially cylindrical in shape, the feeder may be a shape other than that depicted in the figures.

Build material 20 flows from an upstream location (e.g., a container, hopper, or build material supply) to feeder 40. Through inlet 32, a bolus (e.g., a quantity or portion) of build material 20 drops by gravity into one of pockets 44 of chamber 42 that is directly below inlet 32. In one example, a bolus of about 5 grams. Each pocket 44 will typically contain something, air, build material 20, or a combination of build material and air. Thus, the drop operation is a trade-off. When a bolus of build material 20 drops into a designated pocket opening 44, air within the pocket opening moves upwardly out of the pocket opening.

The feeder 40 is then rotationally moved under the control of the seal control mechanism 30 such that the pocket 44 is no longer directly below the inlet 32. For each rotation of feeder 40 below upper shoe 34A, inlet 32 is disposed above an adjacent pocket 44. In one example, the width of the inlet is less than the width of each pocket. At this time, the upstream pressure of the feeder 40 is isolated from the downstream pressure of the feeder. Once pocket 44 is disposed over outlet 38, a bolus of build material drops from chamber 42 (e.g., by gravity) and moves downstream from feeder 40. Again, drop is an exchange in which the build material in the pockets 44 is now replaced with air. Because the air pressure in the pockets 44 is fluidly isolated from the upstream passages, and in particular the cyclone separators 70, the incoming air will generally not travel upward causing problems. Instead, seal controller 30 of feeder 40 prevents or reduces backflow of air from the access point of the feeder mechanism, which in turn enables the negative pressure of PCS50 to move build material 20 within conduit 66. In the example of fig. 5, the inlet 32 and outlet 38 are similarly shaped, but the shape and size of these openings may be different. In another example, chamber 42 is rotated at least twice between receiving build material 20 from inlet 32 and depositing build material through outlet 38. In other words, there is at least one spoke-to-shoe seal or sealing spoke between inlet 32 and outlet 38 at a given location of feeder 40; otherwise, there would be a direct leakage path for build material 20 to fall through the feeder.

Further, build material may be accidentally disposed between the upper shoe plate 34A and the wall 46, between the wall and the lower shoe plate 34B, and between other components that make up the feeder 40. In these cases, the amount of air leaked is typically small enough not to affect the operation of the PCS. Thus, the escape of air from the feeder, whether upstream or downstream, may occur unintentionally.

In some examples, the seal control mechanism 30 and the encoder 98 can include or be associated with a computing device having a processor and a memory storing code executed by the processor to adjust operation of the feeder. The computing device may be a controller. The controller may include a processor, microprocessor, Central Processing Unit (CPU), memory storing code executed by the processor, integrated circuits, Printed Circuit Boards (PCBs), printer control cards, Printed Circuit Assemblies (PCAs) or Printed Circuit Board Assemblies (PCBA), Application Specific Integrated Circuits (ASICs), Programmable Logic Controllers (PLCs), components of Distributed Control Systems (DCS), Field Programmable Gate Arrays (FPGAs), or other types of circuitry. Firmware may be used. In some cases, if firmware is employed, the firmware may be code embedded in the controller, such as code programmed into, for example, Read Only Memory (ROM) or flash memory. The firmware may be instructions or logic for the controller hardware and may facilitate control, monitoring, data manipulation, etc. by the controller.

Fig. 7 is a flowchart showing the operation of the seal controller 30 in the feeder 40 of the 3D printer 100. Operation of feeder 40 follows the conveyance of build material 20 from PCS50 to cyclone 70 where the build material is separated from the conveying air. Build material 20 flows downstream to container 60 and is then received in feeder 40. At this point, the operation of fig. 7 begins.

A quantity or dose of build material 20 is dispensed through an inlet 42 located on an upper shoe 34A of a chamber 42 covering a feeder 40, where it is received into one of the pockets 44 (block 302). At this point, air within pocket 44 is displaced by incoming build material 20 and flows upward through inlet 32. By keeping the pocket size small, the 3D printer 100 manages the upward airflow without completely avoiding the upward airflow. In one example, the amount of air displaced in the pockets 44 (although flowing upward toward the cyclone separator 70) is not small enough to negatively impact the performance of the cyclone separator. In other words, the resultant air upflow rate will not exceed the problem-causing threshold and will therefore not impede the downward flow of powder through the cyclone outlet to the receptacle.

Next, feeder wheel 94 is rotated such that inlet 32 is no longer positioned over the pocket containing build material (block 304). In one example, the upstream pressure is now completely isolated from the downstream pressure. The feeder chamber wheel 94 is again rotated until the pocket 44 is disposed over the outlet 38 in the lower shoe 34B (block 306). In one example, the feeder wheel rotates at a rotational speed proportional to the grams per second delivery rate of the build material. Once so positioned, a quantity or dose of build material 20 is dispensed from pocket 44 through outlet 38 and fed downstream (block 308). Thus, the operation of the sealing function 30 is completed.

Fig. 8 is an illustration of a 3D printer 400 implementing the sealing function 30 described in fig. 5 and 6 above. In 3D printer 400, there are five feeders 440A, 440B, 440C, 440D, and 440E (collectively "feeders 440"), one or more of which may benefit from use of seal controller 30. In one embodiment, the seal control mechanism 30 controls all five feeders 440. In addition to the feeder 440 and sealing function 430, the PCS 450 also includes a conduit 466, an air intake or aspiration 424, a blower 486, and a filter 418 as before, but in this example also features a venturi 422 located directly in front of the blower 486 at the end of the output delivery portion of the PCS. Recall that the output delivery portion of the PCS should contain air, not the build material. However, some build material may be found in the output delivery portion of the PCS. The filter 418 captures these migratory build materials. In one example, the filter 418 is accessible to a user of the 3D printer 400 and may be removed and replaced after, for example, a recommended number of 3D print jobs. The venturi is a passive device for measuring a differential pressure that is used to identify the volumetric flow rate of air in the conduit 66.

Upon activation of blower 486, the negative vacuum draws air from suction 424, carrying the air through the input feed of PCS 450. The 3D printer 400 includes two hoppers or containers containing build material 420, a build material container 480 and a recycled material container 416. Each of which includes a feeder 440C and 440D, respectively, that dispense build material 420 to a conduit 466. Build material container 480 may include fresh or "new" build material, while recycled material container 416 contains recycled or "recycled" build material. The 3D printer 400 may receive new build material, recycled build material, or a combination of both into the PCS 450 for use in generating the next 3D object.

In one embodiment, the build material cartridge 412 is connected to a build material container 480. The build material cartridge 412 can be removed by a user and replaced with a new cartridge. Similarly, recycled material cartridge 414 is coupled to recycled material container 416 to allow a user to remove and replace the cartridge as desired.

The cyclone 470 is connected downstream to a container or hopper 460 and a feeder 440A controlled by a seal control 430. Feeder 440A dispenses build material 420 to powder processing system 402. Build material 420 is then dispensed into build chamber 404. The 3D object is generated in build bucket 406. A feeder 440E, also controlled by seal control mechanism 430, is disposed below build drum 406 to sequentially convey unused build material downstream. Operation of the powder processing system 402, build chamber 404, and build barrel 406 is beyond the scope of this disclosure.

PCS diverter valve 424 allows build material 420 to be diverted to second cyclone and vessel 408 coupled to second feeder 440B. Similar to feeder 440A, feeder 440B may be controlled by seal control 430. The pressure isolation achieved by seal control 430 prevents or reduces the undesirable air from adversely affecting the efficiency of cyclone separator 408 and adversely affecting the downstream flow of build material. In an example, build material 420 received into feeder 440B flows to recycled material cartridge 414 or recycled material container 416.

In the example, 3D printer 400 includes two additional feeders 440C and 440D, one for dispensing fresh build material from build material supply 480 and the other for dispensing recycled build material from recycled material container 416. Both feeders 440C and 440D may be controlled by seal controller 30 to ensure that the pressure between the upstream device and the feeder is isolated and the pressure between the feeder and downstream PCS 450 is isolated.

Feeders 440A and 440B are disposed below the cyclones 470 and 408, respectively. Both feeders will benefit from the use of the seal control 430 because this mechanism prevents leakage from class 1 from affecting the operation of the individual cyclones. For feeders 440C, 440D, and 440E, the focus is to avoid type 2 leakage. The sealing mechanism 430 will also prevent type 2 leakage from adversely affecting the flow of powder downstream. Thus, the seal control mechanism 430 can mitigate the effects of both type 1 and type 2 leaks.

In an example, the seal control 430 may establish a continuous rotation of the lower feeders 440C and 440D for a period of time (e.g., 25 seconds) and then the lower feeder stops for a second period of time (e.g., 10 seconds). A container of the 3D printer 400, such as the upper container 460, for example, may include a sensor that indicates how full the upper container is. The seal control mechanism 430 can use this information to open and close the feeder. This allows time for PCS50 to transfer the powder to upper feeders 440A and 440B. The feeder may stop because a receiving unit downstream of the feeder has received an adequate supply of build material.

The above example illustrates the use of the feeder 40 and the seal control mechanism 30 in a 3D printer. The feeder 40 and seal controller 30 may also be used in a powder management station to maintain a desired powder flow.

While the examples discussed above have been shown by way of example, the present techniques may be susceptible to various new modifications and alternative forms. It should be understood that the present technology is not intended to be limited to the particular examples disclosed herein. Indeed, the present technology includes alternatives, modifications, and equivalents falling within the true spirit and scope of the appended claims.