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Title:
CONTROLLING A TEMPERATURE IN A CONDUIT
Document Type and Number:
WIPO Patent Application WO/2019/160534
Kind Code:
A1
Abstract:
An example system comprises a conduit having a first open end to remove build material from a container, when a gas flow is induced in the conduit, a variable flow gas inlet into the conduit and a controller. In that example, the controller is to control the gas flow into the gas inlet in the conduit, so that the temperature of a mixture of build material and gas in a portion of the conduit is maintained below a predetermined temperature.

Inventors:
GARCIA NEBOT, Natalia (Cami de Can Graells, 1-21, Sant Cugat del Valles, Valles, ES)
ANDREA TALLADA, Alex (Cami de Can Graells, 1-21, Sant Cugat del Valles, Valles, ES)
GARCIA GARCIA, Luis (Cami de Can Graells, 1-21, Sant Cugat del Valles, Valles, ES)
Application Number:
US2018/018012
Publication Date:
August 22, 2019
Filing Date:
February 13, 2018
Export Citation:
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Assignee:
HEWLETT-PACKARD DEVELOPMENT COMPANY, L.P. (10300 Energy Drive, Spring, Texas, 77389, US)
International Classes:
B29C64/30; B29C64/393; B33Y40/00; B33Y50/02; B65G51/00
Foreign References:
US20160039148A12016-02-11
US8986767B22015-03-24
US20090068376A12009-03-12
US20040104499A12004-06-03
US9782931B22017-10-10
Attorney, Agent or Firm:
LEMMON, Marcus et al. (HP Inc, 3390 E. Harmony RoadMail Stop 3, Fort Collins Colorado, 80528, US)
Download PDF:
Claims:
Claims

1. A system comprising:

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

a variable flow gas inlet in the conduit to allow gas into the conduit; and a controller to control the gas flow into the gas inlet to control the temperature of a mixture of build material and gas in a portion of the conduit.

2. The system of claim 1 ,

wherein the controller is to control the gas flow into the gas inlet, so that a tem perature of a mixture of build material and gas in a portion of the conduit is maintained below a predetermined temperature.

3. The system of claim 1 , further comprising:

a temperature sensor to measure a temperature within the conduit,

wherein the controller is to receive temperature data from the temperature sen- sor,

and wherein the controller is to control the gas flow into the gas inlet based on the temperature data.

4. The system of claim 3,

wherein the temperature sensor is positioned in the conduit downstream of the gas inlet to measure the temperature of a mixture of build material and gas in a portion of the conduit, and further

wherein the controller is to control the gas flow into the gas inlet using a closed- loop strategy based on the temperature of the mixture of build material and gas in the portion of the conduit.

5. The system of claim 1 ,

wherein the controller is to control the gas flow into the gas inlet by opening and closing a valve of the gas inlet, and wherein the controller is to control the valve to be in one of a fully open state, a fully closed state or an Intermediate state between fully open and fully dosed state.

6. The system of claim 1 , further comprising:

an external gas source to provide gas to the variable flow gas inlet, the external gas source having a lower temperature than the build material,

wherein the external gas source Is ambient air.

7. The system of claim 1 , further comprising:

a vacuum pump to induce a gas flow in the conduit to remove build material from a container,

wherein the controller is to control the gas flow into the gas inlet, so that the temperature of a mixture of build material and gas in a portion of the con- duit is lower than a temperature damage threshold of the vacuum pump or a portion of the conduit.

8. The system of claim 1 ,

wherein the open end of the conduit is to remove build material from a build unit comprising un-solidified build material and solidified three-dimensional ob~ jects,

and wherein another end of the conduit directs build material to a build material separator to separate build material from gas.

9. The system of claim 1 , further comprising a blockage mechanism to pre- vent build material from entering into the gas inlet.

10. The system of claim 1 ,

wherein the portion of the conduit between the open end and the gas inlet is made of a first material, and wherein the first material is heat resistant to a temperature higher than an expected maximum temperature of the build material to be removed from the container.

1 1 . A method to control a temperature within a portion of a conduit comprising: controlling a gas flow into a variable flow gas inlet in the conduit, so that the temperature of a mixture of build material and gas flowing through the con- duit is maintained below a predetermined temperature.

12. The method of claim 1 1 , further comprising:

measuring the temperature of the mixture of build material and gas within a por- tion of the conduit; and

controlling the gas flow into the variable flow gas inlet based on the temperature measurement and the predetermined temperature.

13. The method of claim 12,

controlling the gas flow into the variable flow gas inlet in a closed-loop manner, so that the measured temperature of a mixture of build material and gas flowing through a portion of the conduit after the gas inlet is maintained be low the predetermined temperature,

wherein the predetermined temperature relates to a damage threshold of the portion of the conduit.

14. The method of claim 12, further comprising:

operating a valve of the variable flow gas inlet when the measured temperature of the mixture of build material and gas in a portion of the conduit is above or below a predetermined temperature.

15. The method of claim 1 1 , further comprising:

applying a pressure differential within the conduit, to enable build material from a container to be removed through an open end of the conduit and so that a mixture of build material and gas is guided through the conduit after the gas inlet,

wherein build material to be removed from a container comprises un-solidified build material.

Description:
CONTROLLING A TEMPERATURE IN A CONDUIT

Background

[001] in 3D printing technology three-dimensional objects are generated in a layer-wise manner. In some examples, layers of build material are successively formed and portions of each layer may be selectively solidified to form each layer of an object. In some examples, 3D printing processes may involve temperatures exceeding room temperature and hot, un-solidified build material may be re moved from solidified objects after a printing process.

Brief Description of the Drawings

[002] Figure 1 schematically shows an example of a system to control a temper ature in a conduit to remove build material.

[003] Figure 2 schematically shows an example of a system to control a temper ature in a conduit to remove build material.

[004] Figure 3 schematically shows an example of a system to control a temper ature in a conduit to remove build material.

[005] Figure 4 schematically shows an example of a system to control a temper ature in a conduit to remove build material.

[006] Figure 5 schematically shows an example of a system to control a temper ature in a conduit to remove build material. [007] Figure 6 schematically shows an example of a system to control a temper ature in a conduit to remove build material.

[008] Figure 7 shows a flow diagram of an example of a method to control a temperature in a portion of a conduit

[009] Figure 8 shows a flow diagram of an example of a method to control a temperature in a portion of a conduit

[010] Figure 9 shows a flow diagram of an example of a method to control a temperature in a portion of a conduit.

Detailed Description

[011] in 3D printing technology three-dimensional objects are generated from build material in a layer-wise manner. Build material may be powder based, par ticulate or grained material and may encompass dry and wet build material. Build material may comprise at least one of plastic, polymers, acrylics, polyesters, sili cones, polyamides, nylon, organic material, metals or ceramics in some exam ples, particles forming the build material may have different sizes or shapes and in some examples build material may comprise different materials, binders, addi tives or fillers. Particles constituting build material may be spherical, fiber-shaped, elongated, flat, cylindrical, polyhedron-shaped or flaked.

[012] in some examples of 3D printing technology, consecutive layers of build material are formed and portions per build material layer are selectively solidified, so that layer-by-layer solidified portions of build material form a three-dimensional object. Solidification of build material may be based, for example, on melting, binding, sintering, fusing, gluing, laminating, curing or coalescing. In some exam ples, an agent is deposited onto a section of a build material layer and by applying energy to the build material layer and agent the section solidifies. [013] !n some examples of 3D printing technology, energy is applied to build materia! layers. For example, an energy source may emit electromagnetic radia tion, heat or electrons. For example, an energy source can be a laser system, an ultra-violet source, an infra-red source, a visible light source, a halogen source, an electron beam source, or a heat source. In some examples, an energy source may apply energy uniformly, or substantially uniformly, to the build materia! layer and in some examples an energy source may apply selectively energy to portions of a build material layer.

[014] in some examples of 3D printing technology, build materia! layers are formed on a platform in a build unit. A build unit may define a three-dimensional space within which three-dimensional objects can be generated. A build unit may be a container and may be open or may have open sides. A platform may be movable parallel to a side of the build unit, so that successively build material layers can be formed on top of each other and portions of build material layers can be selectively solidified. In some examples, a build unit contains solidified three-dimensional objects and un-solidified build material after a 3D printing pro cess is finished or during a 3D printing process.

[01 S] in some examples, 3D printing processes include temperatures exceeding room temperature. For example, temperatures above 100 °C can be reached within a build unit comprising solidified and un-solidified build material, e.g. by application of energy to melt or coalesce build material. For example, build mate rial like Polyamide 12 has a melting temperature of about 190 °C and a tempera ture within a build unit comprising solidified objects and un-solidified build mate rial, such as Polyamide 12 powder, may exceed 130 °C.

[016] in some examples of 3D printing technology, un-solidified build material may be removed from the solidified objects in some examples, un-solidified build materia! encloses solidified object in a so called cake. For example, un-solidified, loose build materia! may be removed from the build unit comprising solidified ob jects and un-solidified build material, so that the solidified objects can be ac cessed and extracted. In some examples, un-solidified build material may be sucked from a build unit with a conduit, e.g. a hose or a tube. In some examples, a user may hold the conduit so that an open end of the conduit is within the build unit to remove lose build material from the build unit. In some examples, a post- processing station may remove build material from the build unit in an automated or in a semi-automated manner.

[017] in some examples, un-solidified build material in the build unit has temper atures too high to be removed because components may be damaged when re moving the un-solidified, hot build material. For example, the temperature of the build material may exceed a damage threshold of a conduit or a part of a post processing station when getting in thermal contact with the un-solidified build ma terial. In some examples, the temperature of the build material to be removed may be too high for the user to hold a conduit to suck out lose build material from a build unit.

[018] The examples described herein are related to a system and a method to control a temperature in a conduit to remove build material from an element of a 3D printing system. Some examples described herein may reduce the amount of time to remove build material from a container, such as a build unit, and solid ified objects may be de-caked, or otherwise have any non-solidified build mate rial removed, and may be accessible faster. This may be possible, for example, as build material at a relatively high temperature may be removed, without hav ing to wait for the build material to cool below a predetermined temperature. Some examples described herein may increase life-time of components, such as of a conduit to remove build material, because damage due to high tempera tures may be reduced or avoided.

[019] Figure 1 shows an example of a system (010) to remove build material. System (010) comprises a portion of a conduit (01 1 ) having a first open end (014) to remove build material from a container, when a gas flow is induced in the con duit (011 ). in that example, the system (010) comprises a variable flow gas inlet (012) to allow gas into the conduit (011 ) and a controller (013) to control the gas flow into the gas inlet (012) to control the temperature of a mixture of build materia! and gas in a portion of the conduit (01 1 ).

[020] A conduit (01 1 ) may be a hose, a tube, a pipe, a sleeve, or the like, to remove build material from a container when a gas flow is induced therein. For example, build material may be sucked from a container through an open end (014), such as an opening, of the conduit (01 1 ) and may flow through the conduit (01 1 ). For example, a vacuum pump (not shown) may induce a gas flow through the conduit (01 1 ) to remove build material from a container and build material flows with the induced gas flow through the conduit (01 1 ). A container may con- fain un-soiidified build material, such as loose powder. For example, a container may be a build unit and may comprise solidified objects, un-soiidified build mate- rial and air or a container may be a supply container comprising loose build ma terial. For example, when a gas flow is induced in the conduit (01 1 ) build material may be removed from a build unit through an open end (014) of the conduit (01 1 ) and solidified objects may remain in the build unit.

[021] A variable flow gas inlet (012) allows gas into the conduit (01 1 ). The vari able flow gas inlet (012) may allow gas into the conduit (01 1 ) downstream after the open end (014) of the conduit (01 1 ) through which build material can be re moved from a container. In some examples, a variable flow gas inlet (012) may be positioned in proximity to the open end (014) of the conduit (011 ). A variable flow gas inlet (012) may comprise hoses, tubes, valves, gates or further compo nents to vary the gas flow into the conduit (01 1 ) at the gas inlet (012). A variable flow gas inlet (012) may be controllable to vary the amount, volume, mass, speed or pressure of gas flowing from the gas inlet (012) into the conduit (01 1 ). Gas introduced via the variable flow gas inlet (012) into the conduit (01 1 ) may have a different, e.g. lower, temperature than build materia! removed through an open end (014) of the conduit (01 1 ).

[022] A controller (013) is to control the gas flow into the variable flow gas inlet

(012) in the conduit (01 1 ) The controller (013) is to control the gas flow into the gas inlet (012) to control the temperature of a mixture of build material and gas in a portion of the conduit (01 1 ). For example, the controller (013) is to control the gas inlet (012) to allow, stop or vary gas flow into the conduit (01 1 ) of gas having a lower temperature than build material to be removed from a container through an open end (014) of the conduit (01 1 ).

[023] The controller (013) may comprise circuitry to control the gas inlet (012) to allow gas into the conduit (01 1 ). For example, the controller (013) may control the gas inlet (012) in the conduit (01 1 ) to increase or decrease, or to allow or to stop gas flow via the gas inlet (012) into the conduit (01 1 ). in some examples, the controller (013) may be a microcontroller and may comprise a processing system, e.g. CPU, and a computer readable storage medium comprising instructions to control the gas inlet (012). In some examples, the gas inlet (012) may be con- trolled by an appropriate electronic circuit controller (013).

[024] Figure 2 shows an example of a system (020) to control a temperature in a conduit (01 1 ) to remove build material and indicates with arrows examples of mass, volume or material flow, when a gas flow is induced in the conduit (01 1 ), e.g. by applying a pressure differential through the conduit (01 1 ). Figure 2 indi cates a flow of build material (021 ) removed, e.g. sucked, through an open end (014) of the conduit (01 1 ) and guided through the conduit (01 1 ). In some exam ples, build material (021 ) removed, e.g. from a container may comprise un-solid- ified, loose build material and gas, such as air from e.g. a container or within the conduit (01 1 ) upstream of the gas inlet (012).

[025] in the example shown in Figure 2, a variable flow gas inlet (012), control lable by controller (013), may allow a variable gas flow (022) into the conduit (01 1 ). The gas flow (022) may have a different e.g. lower, temperature than build material (021 ) removed through the open end (014) of the conduit (01 1 ). The gas flow (022) may depend on a size of the gas inlet (012), such as a diameter of the inlet (012), or may depend on a gas pressure. A mixture (023) of build material and gas may flow through the conduit (01 1 ) away from the open end (014) and downstream of the gas inlet (012). The mixture (023) of build material and gas may flow through the conduit (01 1 ) away from the gas inlet (012), when a gas flow is induced, e.g. by applying a pressure differential through the conduit (01 1 ), to remove build materia! (021 ) in some examples, the mixture (023) of build ma terial and gas may be a substantially constant flow of mass, volume or material, when a gas flow is induced, consisting of varying portions of build material (021 ) and gas (022).

[026] in the example of Figure 2, the controller (013) may be to control the gas flow (022) into the gas inlet (012) to control the temperature of the mixture (023) of build material and gas in a portion of the conduit (01 1 ) downstream of the gas inlet (012). In some examples, the temperature of the mixture (023) of build ma terial and gas may be controlled to be lower than the temperature of build material (021 ) removed through an open end (014) due to thermal mixing with gas flow (022) having a lower temperature and due to varying the ratio of build material flow (021 ) and gas flow (022) by controlling the gas inlet (012) with controller (013) to allow gas flow (022) into the conduit (011 ).

[027] Figure 3 shows an example of a system (030) to control a temperature In a conduit to remove build material comprising a conduit (01 1 ), a gas inlet (012), a controller (013) and a temperature sensor (031 ). The temperature sensor (031 ) may be to measure a temperature within the conduit (01 1 ). In that example, the controller (013) may comprise circuitry to receive temperature data of the temper ature sensor (031 ) and the controller (013) may be to control the gas flow into the gas inlet (012) based on the temperature data, e.g. using a closed-loop strategy. A temperature sensor (031 ) may sense the temperature of a portion of the conduit (01 1 ), a temperature of a mixture of build material and gas downstream of the gas inlet (012) or a temperature of build materia! removed from a container up stream of the gas inlet (012).

[028] in some examples, the temperature sensor (031 ) is positioned in the con duit (01 1 ) downstream of the gas inlet (012), as shown in example system (040) to control a temperature in a conduit to remove build material in Figure 4. The temperature sensor (031 ) positioned downstream of the gas inlet (012) is to measure the temperature of a mixture (023) of build material and gas in a portion of the conduit (01 1 ). In that example, the controller (013) may control the gas flow (022) via the gas inlet (012) into the conduit (01 1 ) using a closed-loop strategy based on the temperature measurement of the mixture (023) of build material and gas in a portion of the conduit (01 1 ). For example, the controller (013) may control the gas flow (022) to increase or decrease, or to allow or stop gas flow (022) through the inlet (012) Into the conduit (01 1 ), depending on the temperature data measured by the sensor (031 ) For example, the controller (013) may control the gas inlet (012) to allow or increase gas flow (022) into the conduit (01 1 ), when the measured temperature is above a predetermined value or the controller (013) may control the gas inlet (012) to stop or decrease gas flow (022) into the conduit (01 1 ), when the measured temperature is below a predetermined value. In that example, gas introduced via the gas inlet (012) into the conduit (01 1 ) may have a lower temperature than build material removed through an open end (014) of the conduit (011 ).

[029] In some examples, the controller (013) is to control the gas flow into the gas inlet (012) based on empirical data to control the temperature of a mixture of build material and gas in a portion of the conduit (01 1 ). For example, the controller (013) may control the gas flow Into the gas inlet (012) in an open-loop strategy without measuring or disregarding measured temperature data in those exam ples, it may be known from previous temperature measurements or observations how to control the gas inlet (012) so that a temperature of a mixture of build ma terial and gas is controlled.

[030] In some examples, the controller (013) is to control the gas flow into the gas inlet (012), so that a temperature of a mixture of build material and gas in a portion of the conduit (01 1 ) is maintained below a predetermined temperature. In that example, gas introduced via the gas inlet (012) into the conduit (01 1 ) may have a lower temperature than build material removed through an open end (014) of the conduit (01 1 ). For example, as shown in Figure 2 the temperature of a mixture (023) of build material and gas downstream of the gas inlet (012) is con trolled to stay below a predetermined temperature. For example, the predeter mined temperature may be a damage or safety threshold of a portion of the con duit (01 1 ), a post-processing station or for a user. [031] !n some examples, the controller (013) is to control the gas flow into the gas inlet (012) by opening and dosing a valve of the gas Inlet (012) The controller (013) may control the valve to be in one of fully open state, a fully dosed state or an intermediate state between fully open and fully closed. In that example, a fully closed state may stop a gas flow through the gas inlet (012) in the conduit (01 1 ) and a fully open state of the valve may allow gas flow through the gas inlet (012) in the conduit (01 1 ). Correspondingly in some examples, closing the valve may increase build material flow through an open end (014) of the conduit (01 1 ), when a gas flow is induced, and opening the valve may decrease build material flow through an open end (014) of the conduit (01 1 ), when a gas flow is induced, so that a mixture (023) of build material and gas, as indicated in Figure 2, may be a substantially constant flow of mass, volume or material consisting of varying por tions of build material (021 ) and gas (022). In some examples, the controller (013) may control the valve to be in a plurality of intermediate states between fully open and fully closed state to allow gas flow through the gas inlet (012) in the conduit (01 1 ). For example, a valve may be a pressure valve, a butterfly valve or another suitable valve to allow gas flow into the gas inlet (012) in the conduit (01 1 ).

[032] A valve of the gas inlet (012) may be controlled to control the temperature of a mixture of build material and gas in a portion of the conduit (01 1 ). For exam ple, a valve may be controlled by the controller (013) in a closed-loop manner, so that a measured temperature of a mixture of build material and gas in a portion of the conduit stays below a predetermined temperature. For example, the con troller (013) may control the valve to be in a fully open state when a measured temperature, for example measured with sensor (031 ) shown in Figure 3, is above a predetermined value and the controller (013) may control the valve to be in a fully closed state when a measured temperature, for example measured with sen sor (031 ) shown in Figure 3, is below a predetermined value. In that example, gas introduced into the conduit (01 1 ) by controlling the valve may have a lower tem perature than build material removed through an open end (014) of the conduit (01 1 ). [033] Figure 5 shows an example system (050) to control a temperature in a conduit to remove build material comprising an external gas source (051 ) The external gas source (051 ) may be to provide gas to the variable flow gas inlet (012). in some examples, the external gas source (051 ) may be a gas bottle or pressurized gas. The gas of the external gas source (051 ) may have a lower temperature than the build material (021 ) to be removed from a container in some examples, the external gas source (051 ) may be ambient air at room temperature and may have about standard atmosphere pressure. For example, a controller (013) may control a gas flow of ambient air, e.g at room temperature, into the gas inlet (012) in the conduit (01 1 ), when e.g. a gas flow is induced through the conduit (01 1 ). For example, a controller (013) may control a valve to be in one of fully open state, a fully dosed state or an intermediate state between fully open and fully closed to control a flow of ambient air into the conduit (01 1 ), when e.g. a gas flow is induced though the conduit (01 1 ) or a pressure differential applied by a vacuum pump (not shown). In that example, the temperature of a mixture (023) of build material and air downstream of the gas inlet (012) may have a tem perature lower than the build material (021 ) removed from a container.

[034] in some examples, the portion of the conduit (01 1 ) between the open end (014) and the gas inlet (012) is made of a first material. In that example, the first material may be heat resistant to a temperature higher than an expected maxi- mum temperature of the build material to be removed from a container. For ex ample, temperatures of build material removed from a build unit may have an expected temperature about 80 °C, 100 °C, 150 °C or about 180 °C and the first material may be heat resistant to temperatures above 80 °C, 100 °C, 150 °C or about 180 °C. In some examples, a portion of the conduit (01 1 ) downstream of the gas inlet (012) may be made of a second material with a lower heat resistance than the first material. The controller (013) may control the gas flow into the gas inlet (012) in the conduit (01 1 ), so that a temperature of a mixture of build material and gas in a portion downstream of the gas inlet (012) is lower than a damage threshold of the second material. [03S] Figure 6 shows an example system (060) to remove build material from a container through a conduit (01 1 ), when a gas flow is induced in the conduit (01 1 ), and to control the temperature in a portion of the conduit (01 1 ). In some exam- pies, system (060) may comprise a vacuum pump (062) to induce a gas flow in the conduit (01 1 ). In some examples, the controller (013) may control the vacuum pump (062), for example to turn the vacuum pump (062) on or off. in some exam ples, the controller (013) may be to control the gas flow into the gas inlet (012), so that the temperature of a mixture (023) of build material and gas in a portion of the conduit (01 1 ) is lower than a temperature damage threshold of the vacuum pump (062) or a portion of the conduit. For example, the vacuum pump (062) or a portion of the conduit (01 1 ) downstream of the gas inlet (012) may have a dam age threshold lower than an expected temperature of build material to be re moved from a container, e.g. build material flow (021 ) indicated with arrows. The controller (013) may control the gas inlet (012) to allow gas flow, such as gas flow (022) indicated by arrows, into the conduit (01 1 ), such that, due to a lower tem perature of the gas flowing via the gas inlet (012) into the conduit (01 1 ) than the build material (021 ) removed from a container, a mixture (023) of build material and gas has a temperature lower than a damage threshold of components down stream of the gas inlet (012).

[036] in some examples, an open end (014) of the conduit (01 1 ) is to remove build material from a build unit (061 ) comprising un-solidified build material and solidified three-dimensional objects. For example, during or after a 3D printing process of three-dimensional objects a build unit (061 ) may comprise solidified objects and un-solidified, loose build material and possibly air or gas. Un-solidified build material, e.g. sucked out with e.g. air, may be removed from a build unit (061 ), so that solidified objects can be accessed and un-solidified build material may be recycled.

[037] For example when a gas flow is induced through the conduit (01 1 ), another end of the conduit (011 ) may direct a mixture (023) of build material and gas to a build material separator (065) to separate build material (063) from gas (064), as shown in example system (060) and indicated by arrows in Figure 6. A build ma terial separator (065) may comprise a sieve, a filter, an obstacle, a barrier or may be based on a cyclonic separation principle to separate build material (063) from gas (064). For example, a separator (065) may separate material, gas molecules or particles due to different weight, momentum, charge, size or speed. In some examples, build material (021 ) removed from a container may comprise un-solid- ified build material and gas, such as air, from a container or within the conduit (01 1 ) upstream of the gas inlet (012). A build material separator (065) may sepa rate un-solidified build material from gas introduced into the conduit (01 1 ) via the gas inlet (012) and from gas, such as air, from upstream of the gas inlet (012), such as from a container when a gas flow is induced through the conduit (01 1 ). In some examples, un-solidified build material may be separated partially from gas. In some examples, un-solidified build material separated from gas may be stored in another container, such as a storage container or supply container, and may be recycled.

[038] In some examples, an open end (014) of a conduit (01 1 ) may comprise several open ends to remove build material from a container or a plurality of con tainers. In some examples, another end downstream of the gas inlet (012) may comprise a plurality of ends. For example, another end downstream of the gas inlet (012) may comprise at least two ends to separate build material from gas.

[039] In some examples, a system to control the temperature within a portion of a conduit to remove build material from a container may comprise a blockage mechanism to prevent build material from entering into the gas inlet (012). For example, a sieve, a filter or a barrier may prevent build material to enter the gas inlet (012). For example, a blockage may prevent build material to accumulate at the gas inlet (012).

[040] Figure 7 shows a flow diagram of an example of a method to control a temperature within a portion of a conduit. The method comprises controlling a gas flow into a variable flow gas inlet in the conduit, so that the temperature of a mix ture of build material and gas flowing through the conduit is maintained below a predetermined temperature (071 ) in some examples, build material may be re- moved via the conduit from a container, such as a build chamber, when a gas flow is induced therein and gas flow introduced into the conduit via the gas inlet may have a different temperature than the build material to be removed from a container.

[041] In some examples, a gas flow into the gas inlet may be controlled based on an open-loop or a closed-loop strategy, so that the mixture of build material and gas downstream of the gas inlet may have a temperature below a predeter mined temperature, e.g. below a damage or a safety threshold. In those exam- pies, gas of lower temperature than the temperature of build material may be controlled to flow into a conduit via a variable flow gas inlet, so that the mixture of build material and gas has a lower temperature than the temperature of build material.

[042] Figure 8 shows a flow diagram of an example of a method to control a temperature within a portion of a conduit. The method may comprise measuring the temperature of a mixture of build material and gas within a portion of the con duit (081 ). In some examples, the mixture may flow through the conduit when a gas flow is induced through the conduit, for example to remove build material from a container. The gas flow into the variable flow gas inlet may be controlled based on the temperature measurement and a predetermined temperature (082). For example, the gas flow into the gas inlet may be controlled such that the measured temperature of a mixture of build material and gas in a portion of the conduit stays below the predetermined temperature. For example, the gas flow into the gas inlet may be controlled in a closed-loop manner based on the temperature measure ment and the predetermined temperature. For example, the predetermined tem perature may relate to a damage threshold of a portion of the conduit, a vacuum pump or a build material separator to separate build material from gas.

[043] Figure 9 shows a flow diagram of an example of a method to control a temperature within a portion of a conduit. The method to control a temperature in a portion of a conduit to remove build material may comprise, measuring a tem perature of a mixture of build material and gas flowing within a portion of a conduit (081 ) when a gas flow is induced. For example build material may be removed from a container when a gas flow is induced. The method may comprise closing a valve of a variable flow gas inlet into the conduit when the measured tempera ture is below a predetermined temperature (091 ) and opening a valve of the var iable flow gas inlet into the conduit when the measured temperature is above a predetermined temperature (092). For example, gas introduced into the conduit when opening a valve may have a lower temperature than build material flowing through the conduit when a gas flow is induced.

[044] in some examples, a method comprises applying a pressure differential within the conduit, to enable build material from a container to be removed through an open end of the conduit and so that a mixture of build material and gas may be guided through the conduit after the gas inlet. In some examples, build material to be removed from a container may comprises un-solidified build material and may comprise gas, such as air, within the container. In some exam ples, applying a pressure differential may enable a substantially constant flow of material, mass or volume through the conduit with varying portions of build mate rial and gas after the gas inlet in some examples, a pressure differential may be applied through the conduit, e.g. by a vacuum pump, before, after or during mov ing an open end of the conduit info a container or build unit of build material so that build material can be removed from therein in some examples, a pressure differential may be applied through the conduit, e.g. by a vacuum pump, and a gas flow may be allowed into a variable flow gas inlet in the conduit before moving an open end of the conduit to a container or build unit in that example, a portion of the conduit may be cooled before moving an open end of the conduit into a container or build unit so that hot build material is to be removed.

[045] The following terminology is understood to mean the following when re cited by the description or the claims. The word“comprising” does not exclude the presence of elements other than those listed, the word“including” or“having” does not exclude the presence of elements other than those listed,“a”,“an” or “the” does not exclude a plurality and a“series” or“plurality” does not exclude a singularity. The words“or” and“and” have the combined meaning“and/or except combinations of listed features where at least some of such features and/or ele ments are mutually exclusive within the context

[046] All of the features disclosed in the claims and description (including draw- ings), and/or ail 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.