阅读说明：本技术 去除构建材料 (Removing build material ) 是由 W·J·克拉索夫斯基 J·M·罗曼 X·阿隆索贝切罗 于 2018-04-27 设计创作，主要内容包括：描述了一种用于从容器去除构建材料的示例性方法。在该示例中,可以在导管中引发脉动气流以便以脉动地从容器吸引构建材料。(An example method for removing build material from a vessel is described. In this example, a pulsating gas flow may be induced in the conduit to draw build material from the vessel in pulses.)

1. A system, comprising:

a conduit having a first open end to remove build material from a vessel when a gas flow is induced in the conduit; and

a controller for controlling components of the system to induce a pulsating gas flow in the conduit to remove build material from a vessel.

2. The system of claim 1, wherein the first and second sensors are disposed in a common housing,

wherein the controller is for controlling a vacuum pump or a valve of the system to induce a pulsating gas flow,

and wherein the pulsing of the gas flow comprises a portion of the substantially unsteady gas flow to remove build material from the vessel.

3. The system of claim 1, further comprising:

a vacuum pump connected at the second open end of the conduit to generate a pressure differential; and

a valve at the conduit between the first open end and the second open end, and the valve is controlled by the controller,

wherein when the valve is controlled closed, a vacuum is generated in the conduit between the valve and the second open end,

and wherein when the valve is controlled to open, a pulsation of the gas flow is induced in the conduit.

4. The system of claim 3, wherein the first and second sensors are arranged in a single unit,

wherein the valve is positioned at the conduit near the first open end.

5. The system of claim 1, wherein the first and second sensors are disposed in a common housing,

wherein the controller is to control components of the system to induce a pulsed gas flow based on a parameter of the build material to be removed.

6. The system of claim 1, wherein the first and second sensors are disposed in a common housing,

wherein the first open end of the conduit is connectable to a build unit comprising uncured build material and a three-dimensional object to remove uncured build material from the build unit.

7. The system of claim 1, wherein the first and second sensors are disposed in a common housing,

wherein the vessel has a gas inlet such that gas can flow into the vessel and the build material can be made airborne when a pulsating gas flow is induced.

8. A method for removing build material from a vessel, comprising:

build material is pulsatory attracted from the vessel.

9. The method of claim 8, further comprising:

inducing a pulsation of a gas flow from the vessel through a conduit connected to the vessel to pulsate draw build material from the vessel,

wherein each pulse of the gas flow has a portion of the gas flow that is unstable.

10. The method of claim 8, further comprising:

generating a pressure differential between the container and the conduit; and

a valve between the vessel and the conduit is opened such that the pulsation of the gas flow entrains build material from the vessel and flows through the conduit.

11. The method of claim 10, further comprising:

when the gas flow from the vessel through the conduit reaches a substantially steady state, the valve between the vessel and the conduit is closed.

12. The method of claim 10, further comprising:

closing the valve between the vessel and the conduit for at least one second such that turbulent gas flow ceases to allow build material to settle in the vessel; and

opening a valve between the vessel and the conduit for a period of at least one second such that build material is drawn from the vessel.

13. The method of claim 10, further comprising:

generating a pressure differential between the vessel and the conduit with the vacuum pump when the valve is closed; and

when the valve is open, gas and build material are drawn from the vessel using a vacuum pump.

14. A non-transitory computer-readable storage medium comprising instructions that, when executed by a processor, cause the processor to:

controlling a vacuum pump to establish a negative fluid pressure in the enclosed conduit; and

a valve is controlled to open a conduit to a build material container such that build material is removed as a function of the pulsation of fluid flow from the container through the conduit.

15. The non-transitory computer-readable storage medium of claim 14, further comprising instructions that, when executed by a processor, cause the processor to:

the valve is controlled to cyclically open and close such that a pulsating fluid flow is induced to remove build material from the vessel.

Background

In 3D printing techniques, three-dimensional objects are generated in a layer-by-layer manner. In some examples, layers of build material are formed continuously, and portions of each layer may be selectively cured to form each layer of the object. In some examples, uncured build material may be removed from the cured object after the printing process so that the cured object may be retrieved.

Drawings

FIG. 1 schematically illustrates an example of a system for removing build material.

FIG. 2 schematically illustrates an example of a system for removing build material.

FIG. 3 schematically illustrates an example of a system for removing build material.

4a-c schematically illustrate examples of the temporal evolution of parameters of a system for removing build material.

FIG. 5 schematically illustrates an example of a computer-readable storage medium that includes instructions to control a system to remove build material, the instructions being executable by a processor.

FIG. 6 shows a flow chart of an example of a method of removing build material.

FIG. 7 shows a flow chart of an example of a method of removing build material.

FIG. 8 shows a flow chart of an example of a method of removing build material.

FIG. 9 shows a flow chart of an example of a method of removing build material.

Detailed Description

In 3D printing techniques, three-dimensional objects are generated from build material in a layer-by-layer manner. The build material may be powder-based, granular, or granular material, and may include both dry and wet build material. The build material may comprise at least one of a plastic, a thermoplastic, a polymer, an acrylic, a polyester, a silicone, a polyamide, a nylon, an organic material, a metal, or a ceramic. In some examples, the particles forming the build material may have different sizes or shapes, and in some examples, the build material may include different materials, binders, additives, or fillers. The particles constituting the build material may be, for example, spherical, fibrous, elongated, flat, cylindrical, polyhedral, or flaky.

In some examples of 3D printing techniques, successive layers of build material are formed, and portions of each layer of build material are selectively cured, such that the layer-by-layer cured portions of build material form a three-dimensional object. Solidification of the build material may be based on, for example, melting, bonding, sintering, fusing, solidifying, or coalescing. In some examples, an agent is deposited onto a section of the layer of build material, and the section is solidified by applying energy to the layer of build material and the agent.

In some examples of 3D printing techniques, a layer of build material is formed on a platform in a build unit. The building unit may define a three-dimensional space within which the three-dimensional object may be generated. The building unit may be a container and may be open. The platform may be moved parallel to the sides of the build unit so that successive layers of build material may be formed on top of each other and portions of the layers of build material may be selectively cured. In some examples, the build unit contains the solidified three-dimensional object and the uncured build material after the 3D printing process is completed or during the 3D printing process.

In some examples of 3D printing techniques, uncured build material may be removed from a cured object. In some examples, the uncured build material encases the cured object in a so-called cake. For example, uncured bulk build material may be removed from a build unit that includes a cured object and uncured build material so that the cured object may be accessed and removed. In some examples, the uncured build material may be drawn from the build unit with a conduit (e.g., a hose or tube). In some examples, a user may hold the conduit such that the open end of the conduit is within the build unit to remove fugitive build material from the build unit. In some examples, the post-processing station may remove build material from the build unit in an automated or semi-automated manner.

Examples described herein relate to systems and methods of removing build material from a container (e.g., from an element of a 3D printing system such as a build unit). In the examples described herein, build material may be removed from the container by pulsed suction. For example, a pulse of gas flow may be induced in the conduit to remove build material from the vessel, wherein the pulse of gas flow entrains build material in the vessel and the build material is thus conveyed through the conduit with the gas flow. Some examples described herein may reduce the amount of time to remove build material from a container, such as from a build unit, and solidified objects may be de-agglomerated, or otherwise remove uncured build material, and may be more quickly acquired. For example, when a pulsating gas flow is initiated, the gas flow may be turbulent in the vessel and substantially unsteady through the conduit, such that build material in the vessel may become airborne and more build material may be entrained by the gas pulsation than a steady gas flow.

Fig. 1 schematically illustrates an example of a system (010) to remove build material. The system includes a conduit (011) having a first open end for removing build material from the vessel upon initiation of the gas flow, and a controller (012) for controlling components of the system (010) to initiate a pulsed gas flow in the conduit (011) to remove build material from the vessel. The container may be an element of a 3D printer and may contain build material (e.g., uncured build material, such as loose powder) to be removed or transported and a gas, such as air. The container may also be a replaceable element of a 3D printer, or may be a container that stores or holds build material, such as holding a cake of cured and uncured build material, or stores build material in a supply container or storage cavity.

The conduit (011) can be a hose, pipe, conduit, sleeve, or the like to remove build material from the vessel when the gas flow is induced therein. For example, build material may be drawn or attracted from the container through an open end, such as the opening (021) of the conduit (011) schematically illustrated in fig. 2, and may flow through the conduit (011) along with the induced gas flow. The conduit (011) can be connectable to the container (022) and in a fixed position when the build material (023) can be removed from the container (022). In some examples, the conduit (011) can be held by an operator, and the open end of the conduit (011) can be placed within or near the container (022) to remove the build material (023). For example, container (022) can have an outlet, such as opening (024) depicted in fig. 2, through which build material can be removed. In some examples, a first open end (021) of the conduit (011) may be connected, e.g., via an outlet opening (024), to a build unit or vessel including uncured build material and a three-dimensional object to remove uncured build material from the build unit or vessel so that the three-dimensional object may be accessed.

The controller (012) may be a microcontroller, an integrated circuit, an embedded system, or any combination of circuits and executable instructions, such as a control program representative of performing control operations, which will be described in more detail with reference to fig. 5. The controller (012) can include circuitry to control components of the system (010) to induce a pulsating gas flow in the conduit (011). For example, the controller (012) can control a vacuum pump, a valve, a gas inlet, a gas outlet, a fan, a source of pressurized gas, a vacuum component, or another component of the system that induces a pulsating gas flow in the conduit (011). For example, the controller (012) can control the operation, electrical power, frequency, or input signals of the components of the system (010) to induce a pulsating gas flow. For example, the controller (012) can modulate the input signal of a component such that the component operates in a pulsed or cyclic operation. For example, the controller (012) can control the components to operate at a duty cycle such that a pulsating gas flow is induced. In some examples, the controller (012) may receive signals from components of the system (010), and may control the components to induce a pulsating gas flow based on the received signals, e.g., in a feedback loop.

In some examples, the system to remove build material may include a vacuum pump (025), for example as shown in fig. 2. The vacuum pump (025) may be connected to a second open end (027) of the conduit (011), such as to a second open end (027) opposite the first open end (021) of the conduit (011). The vacuum pump (025) may be used to induce a pressure differential through the conduit (011), and the vacuum pump (025) may be sealed to the second open end (027). For example, the vacuum pump (025) may apply suction and may induce a gas flow in the conduit (011). In some examples, the controller (012) can control the vacuum pump (025) to induce a pulsatile gas flow in the conduit (011).

For example, the vacuum pump (025) may be controlled to induce gas flow to cyclically start and stop, or the vacuum pump (025) may be controlled to cyclically change between at least two modes of operation such that a pulsating gas flow is induced in the conduit (011). In some examples, the mode of operation of the vacuum pump (025) may be reversed, such as operating like a fan or blower, for example to induce a suction pulsation of the air flow and a puffer pulsation of the air flow flowing in opposite directions. The controller (012) can control the vacuum pump (025) to abruptly trigger a gas flow or to abruptly induce a pressure differential such that a surge of gas flow is induced from the container (022) through the conduit (011). For example, the surge of gas flow may be a pulsating gas flow comprising a portion of a substantially unsteady gas flow to draw build material from the vessel (022). The vacuum pump (025) can be controlled to operate with a duty cycle such that a pulsating gas flow can be induced in the conduit (011). In some examples, the vacuum pump (025) may be controlled to induce a gas flow in the conduit (011), and the gas flow may be interrupted or blocked, e.g., by a gate, valve, or the like, such that a pulsating gas flow is induced.

In some examples, a system to remove build material may include a valve (026) at a conduit (011), such as shown in fig. 2. The valve (026) may be, for example, a pressure valve, a butterfly valve, or other suitable valve that permits or regulates gas flow through the conduit (011). A valve (026) can be positioned between the first open end (021) and the second open end (027) of the catheter (011). The controller (012) can control the valve (026) to be in one of a fully open state, a fully closed state, or an intermediate state between fully open and fully closed. For example, the valve (026) may be controlled by the controller (012) to induce a pulsating gas flow.

For example, the controller (012) can control the valve (026) to be closed such that a vacuum is generated between the valve (026) and the second open end (027) within the catheter (011). For example, vacuum pump (026) can be controlled to generate a pressure differential between container (022) and the closed portion of conduit (011) while valve (026) is controlled to close. The controller (012) can then control the valve (026) to open such that a pulsation or surge of gas flow is induced in the conduit (011). For example, the controller (012) can control the valve (026) to open abruptly, or substantially instantaneously, as compared to a full duty cycle of the valve. For example, the controller (012) can control the valve (026) to alternately cycle (e.g., in a duty cycle) open during a first time period and close during a second time period to induce a pulsating gas flow. The duty cycle may not be constant during build material removal. The pulsation or surge of airflow induced by the opening of the control valve (026) can induce periods of substantially unsteady airflow.

In some examples, the valve (026) can be positioned near the first open end (021) of the catheter (011). For example, when a higher pressure differential is generated prior to opening, or when a larger portion of conduit (011) is evacuated prior to opening valve (026), the pulsating gas flow initiated by controlling valve (026) to open may entrain more build material particles. In some examples, the induced pulsation of the gas flow may include a longer period of unsteady flow when a higher pressure differential is generated within the closed conduit (011) or when a larger portion of the conduit (011) is evacuated. For example, the valve (026) can be positioned at the first open end (021), or about 1 cm, 2 cm, 5 cm, 10 cm, or about 20 cm from the first open end (021) of the catheter (011).

In some examples, the vessel (022) may or may not be gas tight, such that gas may flow into the vessel (022) and may cause the build material (023) to become airborne when a pulsating gas flow is induced therein. For example, as shown in fig. 3, container (022) may have gas inlets (031a, 031b) at a lower portion of container (022) or at another portion of container (022). A gas inlet in the vessel (022) can facilitate the attraction of build material (023) when a pulsating gas flow is induced. For example, ambient gas, such as air from the environment surrounding vessel (022), may flow into vessel (022) through inlet (031) when drawn by the pressure differential generated through conduit (011), and may swirl, disperse, or lift build material (022), such as loose powder, in vessel (022), and thus build material (023) may become airborne. When the controller (012) controls, for example, a valve to close after one duty cycle, the lifted, airborne, or dispersed build material (022) may settle or fall. Thus, pulsating attraction of build material may induce turbulent motion of airborne build material in the vessel (022) and may facilitate build material removal.

In some examples, when the pulsed gas stream is directed through conduit (011) to remove build material through first open end (021), the other end of conduit (011), e.g., second opening (027), can direct a mixture of build material and gas of the pulsed gas stream to a build material separator (not shown) to separate build material from gas, e.g., prior to vacuum pump (025). The build material separator may include a screen, filter, barrier, or may be based on the principle of cyclonic separation to separate build material from the gas. For example, the separator may separate materials, gas molecules, or particles according to different weights, momentums, loads, sizes, or velocities. In some examples, the uncured build material may be partially separated from the gas. In some examples, the uncured build material separated from the gas may be stored in another container, such as a storage container or a supply container, and may be recycled.

In some examples, the open end (021) of the conduit (011) can include several open ends at, for example, several arms or branches of the conduit (011) to remove build material from a plurality of containers (not shown in the figures) by pulsed attraction. For example, each arm or branch of the conduit (011) can be connected to the outlet of the vessel. A vacuum pump, for example, attached at the second end of the conduit, can be controlled to generate a pressure differential, such as to constantly apply suction through the conduit and the arms or branches leading to the plurality of containers. In some examples, a plurality of valves, e.g., each valve positioned at an arm or branch of the conduit (011), may be controlled to induce a pulsed gas flow from each vessel and, e.g., through each arm or branch of the conduit, to remove build material from each vessel using the pulsed gas flow.

For example, the controller (012) can control to close all valves so that a vacuum is established within the enclosed portion of the conduit. The controller (012) can control to open at least one valve to induce a surge or pulsation of gas flow from at least one vessel such that build material is removed from the vessel through a respective arm or branch of the conduit (011). In some examples, the controller (012) can control to close all valves again so that vacuum is again established, and then can open at least one other valve to induce pulsation of gas flow from another vessel to remove build material. In some examples, pulsing of the gas flow from each of the plurality of vessels through the arm or branch of the conduit (011) can be induced by operating each valve with a duty cycle. In some examples, components of the system (010) can induce a substantially unsteady airflow pulsation for each container connected to an open end of the conduit (011).

In some examples, the controller (012) may be used to control components of the system (010) to induce a pulsed airflow based on parameters of build material to be removed from the container (022). For example, the build material type, rate of build material removal, temperature of build material in vessel (022) or conduit (011), flow rate, pressure, mass or volume of build material to be removed or that has been removed, or another parameter of the build material or gas flow may be determined or measured, and a corresponding signal may be received by controller (012). The controller (012) can control components of the system (010) in a closed-loop manner to induce a pulsating gas flow based on the received parameters. For example, the duty cycle of the components may be controlled by the controller (012) based on the received signals. For example, if the build material removal rate decreases or falls below a threshold, the duty cycle of the components used to induce the pulsating gas flow may be modified. In some examples, the controller (012) controls the components to induce a pulsating gas flow based on previous measurements or observations (such as based on empirical data). For example, the controller (012) can control the valve to open and close during a duty cycle based on previous tests to improve build material removal.

Fig. 4a schematically shows an example of a duty cycle of a valve, such as valve (026) of system (020) in fig. 2, to induce a pulsating gas flow in conduit (011). Fig. 4a schematically shows the state of the valve over time, e.g. open or closed. The state of the valve may be controlled by a controller, for example by a control input signal or power supply, to induce a pulsating gas flow. The following examples of a duty cycle of a valve for inducing a pulsating gas flow may be applicable to any other component of the system (010) to remove build material, wherein the component is controllable in the duty cycle or in a cyclical or periodic mode of operation to induce the pulsating gas flow as described herein.

Figure 4b schematically shows an example of a pulsating gas flow induced in the conduit by the duty cycle of the valve shown in figure 4 a. The gas flow depicted in fig. 4b is an example of a flow parameter curve describing the pulsation of the induced gas flow. The controller (012) can control the components to induce pulsations in the gas flow depicted by various curves different from the flow parameter curve depicted in fig. 4 b. The gas flow through the conduit may be described by flow parameters such as an average velocity of gas particles making up the gas flow, a mass rate of flow through the conduit, a volume of gas flowing through a portion of the conduit per unit time, a number of gas particles flowing through a portion of the conduit per unit time, or a combination thereof. The flow parameters that induce the gas flow may be related to a duty cycle of a valve controlled by the controller (012) or to a duty cycle or controlled operation of components of the system (010) to remove build material.

FIG. 4c schematically shows an example of a build material removal rate through a conduit when a pulsed gas flow is induced. For example, the build material removal rate may be measured, or may be determined based on the mass or volume of build material extracted per time interval. In some examples, the build material removal rate may be related to or may be dependent on a flow parameter of the induced pulsed gas flow for delivery of build material, for example related to a flow parameter of the pulsed gas flow induced by a duty cycle of a valve as shown in fig. 4a and 4 b. In some examples, the build material removal rate may further depend on parameters such as the mass or volume of build material in the vessel, the build material type, temperature, environmental conditions, mechanical components, humidity, and the like.

For example, the valve may be controlled to open for a first period of time (T1) and may be controlled to close for a second period of time (T2). Accordingly, a pulsed gas flow (041a) may be initiated within a pulse length (T3), and during a cycle (T5) when the valve is open, build material may be pulsed (046a) with substantially no gas flow for a duration (T4) thereafter or previously, and with no build material removal for a duration (T6) when the valve is closed. In some examples, the valve opening time (T1), the pulse length of the gas pulse (T3), and the cycle of powder removal (T5) may be related, e.g., may begin at substantially the same time or may continue at substantially the same time. In some examples, the closing time of the valve (T2), the time span without gas flow (T4), and the time span without powder removal (T6) may be correlated. In some examples, the pulsing (041a) or powder removal cycle (046a) of the gas flow may be delayed in time relative to the opening of the valve, e.g., due to the inertia of the gas particles and the inertia of the build material. In some examples, the pulsing (041a) of the gas flow and the powder removal cycle (046a) may be initiated substantially instantaneously by opening a valve, such as depicted in fig. 4 a-c.

The controller may control the valve to open and close in a duty cycle such that multiple gas pulses (041a, 041b) may be initiated and build material (046a, 046b) may be pulsed. For example, the valve may be controlled to open once, twice, three times, four times, five times or more per minute, or once, twice, three times, four times, five times or more per ten minutes. Each duty cycle of the valve may be defined by an open time (T1) and a closed time (T2). In some examples, the opening and closing times may be controlled to be constant along various duty cycles. In some examples, the open time (T1) may be about one second, about five seconds, about ten seconds, about twenty seconds, about forty seconds, or about one minute. The off time (T2) may be about one second, about five seconds, about ten seconds, about twenty seconds, about forty seconds, about one minute, about two minutes, about four minutes, about six minutes, or about eight minutes. In some examples, the open time (T1) may be about 1%, 2%, 5%, 10%, 20%, 40%, 60%, 80%, 100%, 120%, 150%, or 200% of the close time (T2). In some examples, the controller may modify the duty cycle of the valve, for example, based on a feedback signal or measurement, and the duty cycle may not be constant, but may vary over time. In some examples, the pulse length (T3) and the powder removal cycle (T5) of the gas pulse may correspond to or may be substantially the same as the opening time (T1) of the valve that triggers the pulse (041a) of the gas flow and the pulse (046a) of the powder removal. In some examples, the pulsing of the induced gas flow may be controlled by controlling a duty cycle (010) of a valve or a component of the system.

In some examples, the pulse (041a) of the induced gas flow may have a peak (043a), such as schematically illustrated in the example of fig. 4b, and the powder removal rate may have a peak (047a), such as schematically illustrated in fig. 4 c. In some examples, the peak of the gas flow (043a) may be correlated to the peak of the powder removal rate (047 a). In some examples, the no-flow duration (T4) may be characterized by a lower-flow parameter (043b), such as an average of the flow parameter during the no-flow duration (T4), e.g., the lower-flow parameter (043b) may be zero, such as when the valve is closed. In some examples, the valve may be partially closed during a period of time (T2) such that a reduced amount of gas may flow through the conduit, e.g., such that the lower flow parameter (043b) may be non-zero and the lower build material removal rate (047b) may be non-zero.

For example, the pulse (041a) of the induced gas flow triggered by opening the valve may have a peak flow parameter (043a) or an average flow parameter over the pulse length (T3) that is at least 50%, at least 100%, at least 500%, at least 1000%, or at least 10000% higher than a lower flow parameter (043b) describing, for example, a reduced gas flow after or before when the valve is not fully closed. In some examples, the build material removal rate may have a peak (047a) triggered, for example, by the induced gas flow, and the peak of build material removal (047a) or average build material removal rate over the cycle length (T5) may be at least 50%, at least 100%, at least 500%, at least 1000%, or at least 10000% higher than a lower powder removal rate (047b) described after or before the time period (T6) (e.g., when the reduced gas flow is induced). In some examples, the build material removal rate may decrease over time as the volume of build material in the vessel decreases, such as at the end of the build material removal when substantially no more build material remains to be removed.

In some examples, the controller (012) may control components of the system (010) to induce the pulsation (041a) of the substantially unsteady airflow, or the induced pulsation (041a) of the airflow may have (e.g., over a period of time) a portion of the substantially unsteady airflow (044). The flow parameters of the unsteady gas flow may not be substantially constant over time. For example, during the pulse length (T3), the flow parameter may decrease from a peak value (043a) to a steady or constant value (043c), such as shown by the example flow curve of fig. 4 b. In some examples, the induced pulsed gas flow (041a) may have a portion of the gas flow (045) that is substantially stable (e.g., over a period of time). The flow parameter of the steady gas stream may be constant over time, for example, the flow parameter (043c) may be constant for the portion of the steady gas stream (045).

In some examples, the controller (012) may control components of the system (010) to induce the pulsation (041a) of the gas flow having a portion (044) of the unsteady gas flow that may be more than 25%, more than 50%, more than 75%, or 100% of a pulse length (T3) of the pulsation (041a) of the gas flow. For example, the controller may control the valve to close when a steady flow plateau (045) is reached. In some examples, the controller may minimize the portion of the steady flow (045), such as in a feedback loop or based on empirical knowledge. In some examples, the build material removal rate may stabilize or decrease when a substantially steady state gas flow is achieved. In some examples, the build material removal rate is higher during an unsteady flow of pulsations (041a) of the gas flow. For example, an unsteady gas flow may induce turbulence, and the build material may become airborne in the vessel. In some examples, additional aspects may modify the removal rate of build material, such as build material type, density of agglomerates of cured and uncured build material, humidity, temperature, and the like.

In some examples, the valve may be controlled to open or close relatively abruptly or substantially instantaneously, or the controller (012) may control another component of the system (010) to start or stop a duty cycle or change an operation mode relatively abruptly or suddenly. For example, the valve may open or close (e.g., from a closed state to a fully open state) within less than 10%, less than 5%, or less than 1% of the total open time (T1). In some examples, a component (010) of the system may be controlled to change between two modes or states of operation within less than 10%, less than 5%, or less than 1% of the total duty cycle. In some examples, the pulsation of the gas flow (041a) or the pulsation of build material attraction (046a) may be initiated by opening the valve, and may delay less than 10%, less than 5%, or less than 1% of the total opening time (T1) of the valve relative to opening the valve. In the example of fig. 4a-c, the pulsing of the gas flow (041a) and the build material removed with the pulsing of the gas flow (046a) may be substantially instantaneously activated when the valve is opened, and may be substantially instantaneously intermittent when the valve is closed.

Fig. 5 schematically illustrates a controller, such as controller (012) of system (010), that includes instructions for removing build material from a container. The controller (012) can include circuitry for controlling a vacuum pump (025) and a valve (026) of the system (010). In some examples, the controller (012) may include circuitry to control or receive a signal from a component of the 3D printer or from the system (010) to remove build material. The controller (012) includes a processor (051) having any suitable circuitry capable of processing (e.g., computing) instructions, such as one or more processing elements, e.g., a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), a semiconductor-based microprocessor, a Programmable Logic Device (PLD), or the like. The processing elements may be integrated in a single device or distributed across multiple devices.

The controller (012) includes a computer-readable storage medium (052) including instructions (053) for controlling the vacuum pump (025) to establish a negative fluid pressure in the closed conduit (011), such as when the valve (026) is closing a portion of the conduit (011), and for controlling the valve (026) to open the conduit (011) to the build material container (022) such that build material is removed with pulsations of fluid flow from the container (022) through the conduit (011). The computer-readable storage medium (052) may include volatile (e.g., RAM) and non-volatile components (e.g., ROM, hard disk, CD-ROM, flash memory, etc.) and may be an electronic, magnetic, optical, or other physical storage device capable of containing (i.e., storing) executable instructions (053). The storage medium (052) may be integrated with the processor (051) in the same device, or it may be separate but accessible to the processor (051). The instructions (053) comprise instructions executable by the processor (051), and the instructions (053) may implement a method of removing build material.

In some examples, the computer readable storage medium (052) may also include instructions to control the valve to open and close in a cycle, such that a pulsating fluid flow is induced to remove build material from the vessel. For example, the instructions may include instructions to control a valve to induce a pulsating fluid flow as described in the sections of fig. 4 a-c. The fluid may comprise a gas, air, a liquid composition, or humidified air. The vacuum pump (026) can be a pump for pumping liquid through the catheter.

Fig. 6 schematically shows a flow chart of an example of a method (060) of removing build material from a vessel. The method (060) may be implemented as instructions of the controller (012) to control the system (010), as shown in fig. 1 or fig. 5. The method (060) comprises pulsatory drawing of build material (061) from a container. For example, the method may include inducing a pulsation of a gas flow from the vessel through a conduit connected to the vessel to pulsate draw build material from the vessel. The induced pulsation of the gas flow may induce turbulence in the vessel and the build material may become airborne such that the pulsating gas flow may entrain the build material and transport the build material from the vessel through the conduit. In some examples, each pulse of induced airflow may have a portion of unsteady airflow, such as described in portions of fig. 4a-c, for example.

Fig. 7 schematically illustrates a flow chart of an example of a method (070) of removing build material. The method (070) may also include generating a pressure differential between the container and the conduit (071). As shown in fig. 2, a vacuum pump may be attached to the conduit, for example, and may apply suction such that when the conduit is opened, the enclosed portion of the conduit is evacuated, or may draw gas and build material from the vessel. The method (070) may also include opening a valve between the container and the conduit such that the pulsing of the gas flow entrains build material from the container and flows through the conduit (072). For example, as shown in fig. 2, a valve may be positioned at the conduit and may trigger a pulse of gas flow from the container through the conduit. The pulsing of the gas flow may be non-steady or may have a non-steady portion of the gas flow. For example, as described in the sections of fig. 4a-c, the valve may open abruptly or substantially instantaneously.

Fig. 8 schematically shows a flow chart of an example of a method of removing build material (080). The method (080) may further comprise closing a valve (081) between the vessel and the conduit when the gas flow from the vessel through the conduit reaches a substantially steady state. For example, as discussed in the section describing fig. 4a-c, the pulsed flow parameter of the gas flow may reach a constant value after opening the valve for a period of time. Based on previous measurements, testing, or based on a feedback signal from the system, the valve may close before, after, or while the flow parameter of the gas flow reaches a substantially constant state. In some examples, build material removal may be more efficient during the time of the pulsed unsteady gas flow of the induced gas flow.

In some examples, the method of removing build material may further comprise closing the valve between the vessel and the conduit for at least one second, about five seconds, about ten seconds, about twenty seconds, about forty seconds, or about one minute such that turbulent airflow ceases to allow build material to settle in the vessel, and opening the valve between the vessel and the conduit for a period of at least one second, about five seconds, about ten seconds, about twenty seconds, about forty seconds, or about one minute such that build material is drawn from the vessel, for example as described in the section of fig. 4 a-c. In some examples, the valve may operate in a duty cycle, e.g., periodically open and close, to induce a pulsating gas flow until the end of build material removal from the vessel. The duty cycle may not be constant and may vary from cycle to cycle.

FIG. 9 schematically illustrates a flow chart of an example of a method (090) of removing build material. The method (090) may also include generating a pressure differential between the container and the conduit with the vacuum pump when the valve is closed (091), and drawing the gas and build material from the container with the vacuum pump when the valve is open (092). For example, a vacuum pump, such as vacuum pump (025) shown in fig. 2, may constantly apply suction through the conduit. Thus, when the valve is closed, the conduit may be evacuated and a pressure differential generated between the conduit and the vessel, and when the valve is open, a pulse of unsteady gas flow may be induced to compensate for the generated pressure differential, and additional gas and build material may be drawn by the suction of the vacuum pump.

The examples as described herein may be implemented according to the following clauses:

clause 1: a system comprising a conduit having a first open end to remove build material from a vessel when a gas flow is induced in the conduit; and a controller for controlling components of the system to induce a pulsating gas flow in the conduit to remove build material from the vessel.

Clause 2: the system of clause 1, wherein the controller is to control a vacuum pump or valve of the system to induce a pulsating gas flow, and wherein the pulsation of the gas flow comprises a portion of the substantially unsteady gas flow to remove build material from the vessel.

Clause 3: the system of any preceding clause, further comprising a vacuum pump connected at a second open end of the conduit to generate a pressure differential and a valve located at the conduit positioned between the first open end and the second open end, and controlled by the controller, wherein when the valve is controlled to be closed, a vacuum is generated in the conduit between the valve and the second open end, and wherein when the valve is controlled to be open, a pulsation of gas flow is induced in the conduit.

Clause 4: the system of clause 3, wherein the valve is positioned at the conduit proximate the first open end.

Clause 5: the system of any preceding clause, wherein the controller is to control components of the system to induce the pulsed gas flow based on a parameter of the build material to be removed.

Clause 6: the system of any preceding clause wherein the first open end of the conduit is connectable to a build unit comprising uncured build material and a three-dimensional object to remove uncured build material from the build unit.

Clause 7: the system of any preceding clause wherein the vessel has a gas inlet such that gas can flow into the vessel and build material can be made airborne when a pulsating gas flow is induced.

Clause 8: a method of removing build material from a container includes pulsating draw of build material from the container.

Clause 9: the method of clause 8, further comprising inducing a pulsating gas flow from the vessel through a conduit connected to the vessel to pulsate draw build material from the vessel, wherein each pulse of the gas flow has a portion of the unsteady gas flow.

Clause 10: the method of any preceding clause, further comprising generating a pressure differential between the container and the conduit and opening a valve between the container and the conduit such that the pulsation of the gas flow entrains build material from the container and flows through the conduit.

Clause 11: the method of clause 10, further comprising closing a valve between the vessel and the conduit when the flow of gas from the vessel through the conduit reaches a substantially steady state.

Clause 12: the method of clause 10, further comprising closing the valve between the container and the conduit for at least one second such that turbulent airflow ceases to allow build material to settle in the container, and opening the valve between the container and the conduit for a period of at least one second such that build material is drawn from the container.

Clause 13: the method of clause 10, further comprising generating a pressure differential between the vessel and the conduit with the vacuum pump when the valve is closed, and drawing the gas and build material from the vessel with the vacuum pump when the valve is open.

Clause 14: a non-transitory computer readable storage medium comprising instructions that, when executed by a processor, cause the processor to control a vacuum pump to establish a negative fluid pressure in a closed conduit, and control a valve to open a conduit to a build material container such that build material is removed with a pulsation of a fluid flow from the container through the conduit.

Clause 15: the non-transitory computer readable storage medium of clause 14, further comprising instructions that, when executed by the processor, cause the processor to control the valve to cyclically open and close such that a pulsed fluid flow is induced to remove build material from the vessel.

The following terms, when recited in the specification or claims, shall be understood to have the following meanings. The word "comprising" does not exclude the presence of elements other than those listed, the word "comprising" or "having" does not exclude the presence of elements other than those listed, the words "a", "an" or "the" do not exclude a plurality, and the word "series" or "a plurality" does not exclude a singular. The words "or" and "have a combined meaning" and/or "except where at least some of such features and/or elements are mutually exclusive in context with a combination of the listed features.

All of the features disclosed in the claims and the specification (including the drawings), and/or all of the elements of any method or process so disclosed, may be combined in any combination and order, except combinations where at least some of such features and/or elements are mutually exclusive.

In the examples described herein, the techniques and methods of removing build material may be applied in various additive manufacturing techniques, as will be apparent to those skilled in the art. For example, the 3D printer may relate to, for example, a rapid prototyping system, a selective laser sintering system, a selective/direct laser melting system, an electron beam melting system, a binder jetting system, an inkjet 3D printing system, and the like.