BACKGROUND

[0001] Additive manufacturing systems that generate three-dimensional objects on a iayer-by-iayer basis have been proposed as a poieniiaiiy convenient way to produce three- dimensional objects in small quantities.

[0002] The efficiency of additive manufacturing systems varies. Generally, three- dimensional objects generated by additive manufacturing systems may have a cooling- down period after manufacture prior to further processing,

BRIEF DESCRfPTiON OF THE DRAWINGS

[0003] Examples are further described hereinafter with reference to the accompanying drawings, in which;

Figure 1 is a diagram of an example of a build material management system for a 3D printing system;

Figure 2 is a diagram of a further example of a build material management system for a 3D printing system;

Figure 3 is a diagram of an example of a transportable container for use in the build material management systems of Figures 1 and 2;

Figure 4 is a diagram of an example of a pumping module of a build material management system for a 3D printing system;

Figure 5 is a diagram of an example of a build material management system for a

3D printing system;

Figure 6 is a simplified illustration of a build material management system according to an example;

Figure 7 is a flow diagram outlining a method of operating a build material management system according to an example; and

Figure 8 is a flow diagram outlining a method of operating a build material management system according to an example.

DETAILED DESCRIPTION

[0004] Figure 1 shows a diagram of an example of a build material management system 100 for a 3D printing system. The build material management system 100 is for use in a 3D printing system. The 3D printing sysiem may comprise a 3D printer {not shown) to generate three-dimensional objects on a layer-by-layer basis, which may be referred to as an additive manufacturing process. The three-dimensional objects are generated from build material which may be in the form of a powder. The build material is selectively fused together, in layers, to form three-dimensional objects. The fusing process may be as a result of the application of directed heat to the build material or as a result of a chemical process in which the build material is bound using chemical binders, and may result in significant amounts of heat within a volume of the build material. The build material may be or include, for example, powdered metal materials, powdered composite materials, powdered ceramic materials, powdered glass materials, powdered resin materials;, powdered polymer materials and the like, in some examples where the build material is a powder-based build material, the term powder-based materials is Intended to encompass both dry and wet powder-based materials, particulate materials and granular materials. It should be understood that the examples described herein are not limited to powder-based materials, and may be used, with suitable modification if appropriate, with other suitable build materials, in other examples, the build material may be in the form of pellets, or any other suitable form of build material, for instance.

[0005] The build material management system 100 comprises a build material management, station 110 to perform build material management operations on build material contained within transportable containers, in the example shown, are three containers in the form of 'hot' mobile build units 130a, 130b, 130c, comprising hot build material and a cooled mobile build unit 132, comprising cooled build material. The build material management station 110 comprises a housing 112 comprising a pumping module 120. The pumping module 120 pumps air and/or build material from the plurality of transportable containers 130a, 130b, 130c, 132 to the material management station 110 and is described in more detail with reference to Figure 4 below. The pumping module 120 is connected to each of the hot mobile build units 130a, 130b, 130c by respective conduits in the form of three cooling connection hoses 114a, 114b, 114c. Each connection hose 114a, 114b, 114c is connected to the respective hot mobile build unit 130a, 130b, 130c at an upper portion thereof via an input port provided between each cooling connection hose 114a, 114b, 114c and the respective hot mobile build unit 130a, 130b, 130c. Similarly, the pumping module 120 is connected to the cooled mobile bulld unit 132 by a conduit in the form of a build material extraction hose 116. The build material extraction hose 116 is connected to the cooled mobile build unit 132 via an unpacking port provided between the build material extraction hose 116 and the cooled mobile build unit132. The structure of the hot mobile build units 130a, 130b, 130c is described in more detail with reference to Figure 3 below. [0006] The mobile build units 130a, 130b, 130c, 132 contain a build matenai volume comprising one or more 3D printed parts, surrounded by a portion of non-fused buiid material Depending on what type of 3D printing operation has been used to create those 3D printed parts, a temperature of the build matenai volume immediately after the 3D printing operation and for some time after may be too high for safe and/or effective removal of the one or more 3D printed parts from the build material volume. The buiid matenai volume may therefore be allowed to cool prior to an unpacking operation in which the one or more 3D printed parts are separated from the surrounding portion of non-fused build material, in this example, the build material volume within the hot mobile build units 130a, 130b, 130c is actively cooled by drawing air through the hot mobile build units 130a, 130b, 130c through the cooling connection hose 114a, 114b, 114c using the pumping module 120. By virtue of the temperature of the ambient air in the airflow being lower than that of the hot build material volume, the build material volume is actively cooled by the airflow. After the active cooling operation, the hoi mobile build units 130a, 130b, 130c each become a cooled mobile build unit, such as the cooled mobile build unit 132. It will be appreciated that rather than drawing the air through the hot mobile build units 130a, 130b, 130c to the cooling connection hose 114a, 114b, 114c by a vacuum pump in the pumping module 120, the air may be caused to flow through the cooling connection hose 114a, 114b, 114c to and through the hot mobile build units 130a, 130b, 130c by a positive pump, such as a fan, in the pumping module 120,

[0007] The unpacking operation in this exampie comprises removing the cooled non- fused build material from the cooled mobile build unit 132 via the build material extraction hose 116. A free end of the build material extraction hose 116 is moveable so as to be manoeuvred about the build volume for placement where suitable for best separation of the cooled non-fused build material from the 3D printed parts. This unpacking operation may be done by an operator manipulating the free end of the build material extraction hose 116 and, optionally, manipulating the build volume. The unpacking operation may be performed by the pumping module 120 operating as an unpacking module, in other words, the build material extraction hose 116 may be connected to the same pump as the cooling connection hoses 114a, 114b, 114c, under appropriate pressure differential routing control The build material extraction hose 118 is connected to a build material container to receive the extracted non-fused build material,

[0008] After the unpacking operation, the 3D printed parts may be removed from the transportabie container, in some examples, the 3D printed parts are removed from the transportable container as part of the unpacking operation. Following the unpacking operation, the transportabie container may be referred to as an empty transportable container. The empty transportable containers may then be re-used in a further cooiing and unpacking operation, after they have received a further hot build material volume. in some examples, the transportable containers are aiso used fo provide build material to the 3D printer for a subsequent 3D printing operation, in this way, the empty transportable container may be filled with non-fused build material and moved to the 3D printer (not shown) for use in a further 3D printing operation. In other examples, the transportable containers may be filled with a build voiume comprising one or more 3D printed parts thai has been produced during a 3D printing operation carried out within a different container.

[0009] The repeated filling with. a build material volume comprising one or more 3D printed parts, cooling the build material voiume and unpacking the build materiaf voiume may be referred to as an operation cycle on the transportable container. In some examples, the operation cycie may also include refilling with non-fused build material and receiving, layer-by-layer, the build material volume from the 3D printer, it will be understood that each operation in the operation cycie may take a different amount of time. in some examples, the active cooling operation may take ionger than other operations in the operation cycle. The material management system 100 can cool build material volumes within a plurality of respective transportable containers to prevent the active cooiing operation presenting a bottleneck in the operation cycle when the operation cycle Is performed with a plurality of 3D printers, ln this example, a single build material management station 110 is connected to a plurality of hot mobile build units 130a, 130b, 130c to perform the active cooling operations on each of the hot mobile build units 130a, 130b, 130c in parallel.

[0010] Many factors may influence the cooiing time for a build material volume, including, but not limited to: the type of build material, the volume of the build material, the quantity, size and shapes of the one or more 3D printed parts within the voiume, the rate of cooiing air flow and the hardness of the voiume of build material {I.e. the resistance to break-up of the voiume of build material). Accordingly, the active cooling operation for each different transportable container may be different. By way of example, the time and or rate at which cooiing air is flowing may be independently controlled for each transportable container. This could be based on knowledge of the contents of a transportable container (for example from data stored on a memory on the transportable container or input from a user,} in examples, the specific active cooiing operation parameters may be determined based on only a single parameter of the voiume of build material, such as size (e.g. a height). Although such an approach may not be completely matched to the exact properties of the voiume of build material to be cooled, this allows for a relatively small number of options from which a user may select, ensuring the user-interface remains simple to use. in another example, the specific active cooling operation parameters may be adjusted based on feedback from a sensor, such as a thermal sensor (e.g. a thermocouple probe) to be embedded within or adjacent to the volume of build material

[0011] In this example, the housing 112 also comprises a filling port 118 for filling an empty mobile build unit 132 with build maieriai after completion of the unpacking operation. The mobile build unit 132 is filled with build material for a further 3D printing operation in the 3D printer.

[0012] It vvill be understood that an active cooling operation performed using the pumping module 120 may comprise drawing air through one at a time of the plurality of hot mobile build units 130a, 130b, 130c connected to the pumping module 120 via respective cooling connection hoses 114a, 114b, 114c, in a cycling operation, in this way, the pumping module 120 may be controlled to draw air through a first hot mobile build unit 130a and subsequently to draw air through a second hot mobile build unit 130b and further subsequently to draw air through a third hot mobile build unit 130c, The process may then be repeated in order to continue the active cooling operation of ail three hot mobile build units 130a, 130b, 130c in parallel without air being drawn through each of the hot mobile build units 130a, 130b, 130c simultaneously. As discussed above, the time and or rate at which cooling air is flowing may be independently controlled for each mobile build unit, in an alternative method of operation, it will be understood that air may be drawn through each of the hot mobile build units 130a, 130b, 130c simultaneously, although optionally at different rates or for different lengths of time.

[0013] Figure 2 is a diagram of a further example of a build material management system for a 30 printing system. The build material management system 200 shown in Figure 2 is suitable for cooling a plurality of transportable containers in the form of three hot mobile build units 230a, 230b, 230c, The build material management system 200 comprises a piuraiity of pumping modules 220a, 220b, 220c provided as separate standalone stations. In this example, each pumping module 220a, 220b, 220c is to be connected to a singie hot mobile build units 230a, 230b, 230c by a singie respective cooling connection hose 214a, 214b, 214c. Each pumping module 220a, 220b, 22Qc is provided within a simple respective material management station not including an equivalent of the filling port 118 shown in the material management station 110 of Figure 1. In this way, the build material management system 200 is capable of cooling build material volumes within a plurality of transportable containers in parallel without requiring a piuraiity of build material management stations, each having a build material filling capability. Such a build material management system 200 may be particularly cost-effective, ln an example, each pumping module 220a, 220b, 220c of the build material management system 200 is provided to cooi the volume of build material with in the respective hot mobile build units 230a, 230b, 230c. in this way, the pumping modules 220a, 220b, 220c may each be referred to as an active cooiing module, and these may each be operated independently to provide optimal cooling air-How for the respective build material volumes. In another example, as described more fully below with reference to Figure 4, the pumping modules 220a, 220b, 220c are also provided with an unpack module to unpack the volume of build material within the respective hot mobile build units 230a, 230b, 230c through the same respective cooiing connection hose 214a, 214b, 214c,

[0014] Figure 3 is a diagram of an example of a transportable container in the form of a mobile build unit 230 for use in the build material management systems of Figures 1 and 2, The mobile build unit 230 comprises a housing 232 having an upper portion 234 substantially enclosing a volume of build material 236. The housing 232 also comprises a lower portion 238 for containing a supply of build material (not shown) for use in a subsequent 3D printing operation by a 3D printer within a 3D printing system. The build material in the lower portion 238 may be fresh, or a mix of fresh and previously used build material. The upper portion 234 of the housing 232 defines a pair of input ports 240a, 240b to allow air flow into the upper portion 234 of the housing 232 and through the volume of build material 238, In this example, the input ports 240a, 240b are located, one each side, at a lowermost end of the upper portion 234 of the housing 232. The upper portion 234 also defines an outlet 242 to allow air to flow out of the upper portion 234 of the housing 232, The outlet 242 is defined within a top section of the upper portion 234. In this example, the outlet 242 is located within a lid portion of the upper portion 234. The outlet 242 may have fixings (not shown) to connect to a cooiing connection hose as shown in relation to Figures 1 and 2. in this example, the mobile build unit 230 further comprises wheels in the form of caster wheels 244a, 244b to facilitate easy movement of the mobiie build unit 230 between different modules of the 3D printing system. The transportable container shown in Figure 3 is in the form of a mobiie build unit 230 having caster wheels 244a, 244b, but may equally be in the form of a different transportable container for supporting a volume of build material.

[0015] Figure 4 is a diagram of an example of a pumping module for a 3D printing system. The pumping module 220 comprises a pump 222 to be connected to a

transportable container (not shown) via a cooling connection hose 214 and a pump-to- build material trap conduit 224. The pump 222 is operable to create a pressure differential between the pump 222 and a distal end of the cooling connection hose 214 whereby to draw air info the cooling connection hose 214 from the transportable container. In this example, the pump 222 is a centrifugal pump and causes a pressure below atmospheric pressure upstream of the pump 222 in the cooling connection hose 214. A build material trap 228, such as a cyclonic separator or a filter, is provided between the cooling connection hose 214 and the pump-to-bulid material trap conduit 224. The build material trap 226 prevents build material within the cooling connection hose 214 and moving towards the pump 222 from entering into the pump-to-build material trap conduit 224. The build material extracted by the build material trap 228 is stored within a storage container 228, in an example, the pumping module 220 is to provide cooiing but not an unpacking function to the transportable container connected to the cooiing connection hose 214, and so an amount of build material transported within the cooiing connection hose 214 towards the pump 222 may be small or non-existent in this example, the storage container 228 may be small. When the pumping module 220 is to provide cooing but not an unpacking function, the air flow drawn into the cooling connection hose 214 may be sufficiently iow as not to transport loose build material from the transportable container into the cooiing connection hose 214. in some examples, it will be understood that the build material trap may be located within the transportable container, and so there may be no build material trap 226 in the pumping moduie 220 between the connection hose 214 and the pump 222. ln an alternative example, the pumping module 220 may also be to extract at least a portion of non-fused build material from the transportable container to the storage container 228, ln this alternative example, the storage container 228 may be sized to be Sarge enough to receive the portion of non-fused build material. The pumping moduie 220 further comprises a controller 250 comprising processing circuitry (not shown) to control the operation of the pumping module 220, and in particular to control the operation of the pump 222,

[0016] As with the example described by reference io Figure 1 , the pump may provide a positive pressure differential downstream of the pump to force air to flow from the pump to and through the transportable container, for example via a pump-to-transportable container conduit, in this case, if non-fused build material is to be collected during the cooiing operation, then a separate port for outlet of the non-fused build material wilt be provided, as well as a transportable contalner-to-build material trap conduit,

[0017] Figure 5 is a diagram of an example of a build material management system for a 3D printing system. The build material managemeni system 300 comprises a pumping module 320 substantially as described with reference to the pumping module 220 of Figure 4 previously apart from the hereinafter described differences, and wherein like parts are designated by like reference numerals but with the preceding '2" substituted by a preceding '3' (for example the controller 250 of Figure 4 corresponds to the controller 350 of Figure 5). The pumping module 320 is connected to transportable containers in the form of three mobile build units 330a, 330b, 330c via three respective cooling connection hoses 314a, 314b, 314c. The cooiing connection hoses 314a, 314b, 314c are connected to a build material trap 326 via a valve or manifold 352 and a vaive-to-build material trap conduit 354, The valve 362 is aiso connected to a build material input conduit 318 for supplying build material to the pumping module 320 from a separate moduie of the build material management system 300, The valve 352 is control labie by the controiier 350 to facilitatefluid communication between the vaive-to-build material trap conduit 354 and one or more of the cooiing connection hoses 314a, 314b, 314c and the build material input conduit 318. Hence, the hot mobile build units 330a, 330b, 330c may be cooled in an operation analogous to that described with respect to the hot mobile build units of Figure 1. In this exampie, a material conditioning unit 356 is connected in the path of the valve-to-build material trap conduit 354 to process or filter the build material flowing within the valve-to- build material trap conduit 354 prior to the build material reaching the build material trap 326 and entering the storage container 328. A storage container-to-further module conduit 362 is provided between the storage container 328 and a further module (not shown) of the build material management system 300, An air filter 360 is provided in the pump-to- build material trap conduit 324. A valve 364 is operable to open or close the storage container-to-further module conduit 382. In this way, build material within the storage container 328 can be transported to a further moduie within the build material management system 300 if desired. It will be understood that a further pump (not shown), provided in the further (and separate) moduie of the build material management system 300 may be needed to transport build material from the storage container 328 to the further moduie of the build material management system 300. In an example, it will be understood thai the pumping moduie 320 may be used as the pumping moduie 120 of Figure 1 , with the build material input conduit 316 being the build material extraction hose 118 and the storage container-to-further module conduit 382 being connected to the frlling port 1 18. Therefore, in some examples, the pumping moduie 320 may operate within a single moduie of the build material management system. As with the above-described examples, the active cooiing operations for each mobile build unit 330a, 330b, 330c may be IndependentSy controlled to provide optimal cooiing air-flow for the respective build material volumes.

[0018] Figure 6 is a simplified illustration of a build material management system 400 according to an exampie of the present disciosure. The system 400 comprises a controller 450 that controls the general operation of the build material management system 400, In the exampie shown in Figure 8 the controiier 450 is a microprocessor-based controiler that is coupled to a memory 410, for exampie via a communications bus (not shown). The memory stores processor executable instructions 412, The controiier 450 may execute the instructions 412 and hence control operation of the build material management system 400 in accordance with those instructions.

[0019] ln one example, the controller 450 controls the pumping module 220 to implement the cooling operation described hereinbefore.

[0020] Figure 7 is a flow diagram outlining a method of operating a build material management system according to an example of the present disclosure, in the method 500a of Figure 7, at 502a, at ieast two transportable containers in the form of mobile build units are received by the build material management system. Each transportable container comprises a volume of build material. At 504a, the transportable containers are connected to an active cooiing module of the build material management system. At 506a, the active cooling module is controlled to cool the volume of build material within each transportable container.

[0021] Figure 8 is a flow diagram outlining a method of operating a build material management system according to an example of the present disclosure, in the method 500b of Figure 8, at 502b, one or more transportable containers are received by the buiid material management system. The or each transportable container comprises a voiume of build material. At 506b, an active cooling module of the build material management system is controlled to cool the volume of build material within the or each transportable container. At 508, the build material management system is controlled to ftll a further transportable container with further build material using a filling module, separate from the active cooiing module of the build material management system, it will be understood that the further transportable container may be the same as one of the one or more transportable containers in some examples,

[0022] It will be understood that although the specific description has used the example of the transportable containers faking the form of mobile build units such as trolleys, other types of transportable container are envisaged, including those without wheels and those without a portion for containing a supply of fresh build material, in some circumstances, it may be desirable to transfer the contents of a transportable container that has been used in a 3D printing operation to another transportable container, for example to decouple the build process from the cooling and unpacking processes.

[0023] it will be appreciated that examples described herein can be realised in the form of hardware, or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device iike a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a GO, DVD, magnetic disk or magnetic tape, it will be appreciated that the storage devices and storage media are examples of machine-readabie storage that are suitable for storing a program or programs that, when executed, implement examples described herein. Accordingly, examples provide a program comprising code for implementing a system or method as described herein and a machine readable storage storing such a program.

[0024] Throughout the description and ciaims of this specification, the words "comprise" and "contain" and variations of them mean "including but not Simited to", and they are not intended to (and do not) exciude other components, integers or steps. Throughout the description and ciaims of this specification, the singuiar encompasses the plural uniess the context otherwise requires, in particuiar, where the indefinite article is used, the specification is to be understood as contemplating piuraiity as weii as singularity, uniess the context requires otherwise,

[0025] Features, integers or characteristics described in conjunction with a particuiar example of the disclosure are to be understood io be appiicable to any other example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at ieast some of such features and/or steps are mutually exclusive. The disclosure is not restricted to the details of any foregoing examples. The disclosure extends to any novel one. or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.