WO2018109477A1

WO2018109477A1 - Additive manufacturing

Info

Publication number: WO2018109477A1
Application number: PCT/GB2017/053743
Authority: WO
Inventors: Michael CURTIS-ROUSE; Robert Hardie; Adam SCOTT
Original assignee: Addam Innovation Ltd
Priority date: 2016-12-14
Filing date: 2017-12-14
Publication date: 2018-06-21
Also published as: GB201621285D0; GB2557658A

Abstract

An apparatus and a method of additive manifacturing, such as sintering, for making one or more objects (O₁) from virtual three-dimensional representations, wherein a virtual boundary (VB) at a minimum distance around a virtual three-dimensional object (VO) and a deposition area (D) on a work surface (30) delineated by the virtual boundary (VB) are defined; wherein a first layer of the build material (P), such as a powder, is deposited only on the deposition area (D); wherein a dam or wall (B) and the first slice (S₁) of an Object (O₁) is consolidated, e.g. sintered by a laser (5,50); and wherein the steps are repeated in order to form the subsequent slices (S_n) of the Object (O₁) and the wall or dam (B). The dam or wall (B) acts as a structural wall to retain non-consolidated, e.g. non-sintered, build material (P) within the deposition area (D). Multiple objects (O_n) can be be manufactured by defining multiple deposition areas (D) on the same work surface (30).

Description

ADDITIVE MANUFACTURING

This invention relates generally to the fabrication of one or more objects from virtual 3D representations. More specifically, although not exclusively, this invention relates to apparatus and methods for fabricating one or more objects from virtual 3D representations.

In recent years the manufacture of objects using additive techniques instead of conventional subtractive techniques has become increasingly popular. These additive techniques are commonly known as additive manufacturing or 3D printing. One form of additive manufacturing entails the selective consolidation of sequential layers a build material, for example a powder build material to form a desired object. The consolidation step is controlled to replicate a virtual three-dimensional (3D) map of the object, typically held in a computer. To do so, it is usual for a substantially uniform layer of, say powder build material to be deposited across a work surface, for example using a roller or doctor blade or recoater blade. A first layer of an object is then consolidated within the layer of, say, powder build material, for example using a binder, by sintering or so on. A further uniform layer of, say, powder build material is then deposited across the work surface and consolidated. The process is repeated until the object has been manufactured. The work surface is usually mounted on a stage which is capable of being translated vertically (along the z-axis) to allow successive layers of material to be deposited thereon. The, say, powder build material is located on the stage and spread uniformly thereover using a doctor blade or recoater blade or roller (or other methods) to form a uniform and appropriately thin layer of material. The doctor blade or recoater blade or roller translates in one of the x and y axes to spread the build material, and especially powder build material across the work surface in a single sweep. Once the object has been formed it is removed from the work surface and the remaining build material is removed, for example swept, from the work surface. The work surface is often referred to as a build platform.

Powder build material may be metallic. Some metallic powder build materials are formed from metals or alloys thereof. As will be appreciated, it is desirable for the powder build material to be physically uniform to allow for the deposition and formation of a uniform layer. Some powder build materials are expensive. Clearly it would be beneficial to re-use powder build material.

The process of consolidation may lead to partially consolidated material being formed on the stage. Moreover, the process of consolidation may lead to other contamination of the remaining material. Accordingly, unconsolidated build material, such as powder build material, reclaimed from the stage is often disposed of rather than being re-used for subsequent manufacturing.

This issue is exacerbated where the build material, for example the powder build material, is spread across the entire stage and the footprint of the object to be formed does not occupy a significant portion of the stage. It is therefore a first non-exclusive object of the invention to provide an apparatus and method which at least partially mitigates some or all of the aforementioned issues.

Accordingly, a first aspect of the invention provides a method of making one or more objects from virtual three-dimensional representations, the method comprising:

a) defining a virtual boundary to encompass or encase the periphery of a virtual three- dimensional object viewed in plan;

b) defining a deposition area on a work surface corresponding to, delineated or described by the virtual boundary;

c) depositing a first layer of build material to cover, e.g. only, the deposition area; and d) consolidating build material within the first layer to form a first slice of an object.

Advantageously, depositing build material in order to cover the deposition area instead of to cover the entire work surface reduces the quantity of build material deposited and hence reduces waste thereof. That is the deposition area may cover a minor or major portion of the entire work surface.

Consolidating build material within the first layer may comprise consolidating a dam or wall corresponding to the virtual boundary. The dam or wall may be spaced from the periphery of the first slice of the object, e.g. in order to encase the first slice of the object. The dam or wall may surround the first slice of the object, e.g. encompass the first slice of the object. The dam orwall may comprise a regular or non-regular geometric shape, viewed in plan. The dam or wall provides a volume to retain build material. The cross-sectional area of the dam or wall may be constructed or configured so as to provide sufficient volume of build material within the boundary, for example to effectively conduct heat generated during the consolidation of build material.

The method may comprise defining a further virtual boundary, for example to encompass the periphery of a further virtual 3D object viewed in plan. The method may comprise defining a further deposition area on the work surface, e.g. corresponding to the further virtual boundary. The method may comprise depositing a first layer of build material onto the work surface, for example to cover the further deposition area. The method may comprise consolidating build material within the first layer, e.g. to form a first slice of the further object.

Plural deposition areas may be defined on the work surface. The sum of areas of the deposition areas may be less than the active surface area of the work surface. The active surface area is the proportion of the work surface which could be used for the construction of a part. In some embodiments the active surface area may be the entire surface area of the work surface. In other embodiments the active surface area may be a proportion of the work surface, for example the periphery of the work surface may not be capable of being utilised but may, nevertheless, be coplanar with the active work surface.

Consolidating build material within the first layer of build material in the deposition area may occur at least partially concurrently, for example concurrently, with deposition of the first layer of build material corresponding to the further deposition area.

The method may comprise depositing a second layer of build material onto the first layer and covering the deposition area and/or the further deposition area (where provided), e.g. and consolidating build material within the second layer to form a second slice of the object.

Some additive manufacturing methods entail the consolidation of build material using heat, for example by sintering regions of build material. Such thermal processes generate heat within the deposited layers of powder build material. Improper or incorrect cooling of the work surface and/or the object under manufacture may lead to the manufacture of defective or inaccurate objects.

Advantageously, because only a portion of the work surface (the term 'stage' may also be used) need be covered with build material, corresponding to the virtual boundary, the work surface or stage can comprise sensors or monitoring means.

The method may comprise monitoring, e.g. using sensor means or one or more sensors, one or more characteristics of an object being made on the work surface. The method may comprise determining if the object is defective. The method may comprise terminating the making of the object if it is determined to be defective. Monitoring may comprise generating sensor data by the sensor means or one or more sensors. The sensor means or one or more sensors may be positioned on or in or adjacent the work surface. The deposition area may be defined on an area of the work surface uninterrupted by the sensor means or one or more sensors.

Another aspect of the invention provides a method of making one or more objects from virtual three- dimensional representations, the method comprising generating sensor data using sensor means or one or more sensors in order to monitor one or more characteristics of an object being made, e.g. on a work surface, determining if the object is defective and terminating the making of the object if it is determined to be defective. A further aspect of the invention provides additive manufacturing apparatus, the apparatus comprises a stage upon which an object is to be formed, deposition means to deposit a layer of build material onto the stage and consolidation means for consolidating the layer of build material to form a slice of an object, the stage being translatable along the z-axis and comprising one or more sensors mounted to or on the stage to monitor build progress of the object as it is formed by the consolidation means, the deposition means being controllable to deposit build material in regions non-coincident with said one or more sensors.

The sensors may comprise one or more temperature sensors, strain gauges, position sensors, proximity sensors, image capture and/or comparison means, environmental sensors (e.g. humidity, temperature, pressure and so on), atmospheric composition sensors or means (e.g. monitoring for oxygen, carbon dioxide and/or other compositions). The output from the sensors may be deployable to control the deposition means and/or the consolidation means. Additive manufacturing processes are typically automated processes occurring over an extended period of time which may, for example, be in the order of ten hours or more. Due to the time required to manufacture an object using these processes it is usual for an operator to initiate manufacture and then leave the process to continue unattended until completion. If, for whatever reason, the manufactured object is defective then a significant quantity of build material may have been wasted along with a concurrent waste of manufacturing time. Such defective objects therefore contribute to the expense of manufacture, both in terms of materials costs and in terms of processing time.

Determining if the object is defective or not may comprise calculating the position of the dam or wall on the work surface, e.g. from the sensor data (where provided). Determining if the object is defective or not may comprise comparing the position of the dam or wall with the position of the virtual boundary on the work surface. Determining if the object is defective or not may comprise comparing the sensor data (where provided) with a database of defect data. Monitoring one or more characteristics may comprise capturing image data relating to the object using image capture means or device(s). Monitoring one or more characteristics may comprise capturing temperature data relating to the object, the work surface and/or the environment surrounding the object, for example using temperature sensor means or device(s). Monitoring one or more characteristics may comprise capturing dimension change data, e.g. expansion and/or contraction data, relating to the work surface (for example using a dimension change monitor means or device, such as strain gauges and the like).

Because only a portion of the work surface needs be covered by build material, corresponding to the deposition area, it is possible to build plural objects upon a work surface. If plural objects are being built simultaneously, sensors may monitor the build of each object. If one or more of the objects are considered to be outwith desired build characteristics the deposition of subsequent build material and/or consolidation may be ceased for that or those articles.

The method may comprise generating plural slice images of the virtual 3D object. The first slice of the object consolidated in the first layer of build material may correspond to a first of the plural slice images. Defining the virtual boundary may comprise defining or delineating a virtual boundary, e.g. to encompass the periphery of plural virtual three-dimensional objects viewed in plan. Consolidating build material within the first layer may comprise forming a slice of each of the plurals objects. The method may comprise nesting or tessellation of the plural virtual three-dimensional objects, e.g. relative to one another. Nesting or tessellation in this context refers to orienting three-dimensional objects adjacent one another such that they occupy a minimal total volume whilst remaining spaced from one another. Depositing the first layer of build material may comprise causing a dispenser to move over the work surface, e.g. in an x-axis direction and/or a y-axis direction over the work surface. Depositing the first layer of build material may comprise causing a dispenser with a dispenser container to move (for example to move together) over the work surface, e.g. in an x-axis direction and/or a y-axis direction over the work surface.

Advantageously, the use of a dispenser able to move in both the x and y axis directions enables the dispenser to be directed to other areas of build, for example when the build of an object (for example the build of one or more of plural objects) is ceased due to a fault detection (for example a sensor or one of more of the one or more sensors detects that the build is outwith desired build characteristics) the dispenser may be directed to one or more other object to be built or being built to allow continued build of the other object or objects whilst the build of the 'faulty' object is arrested.

The method may comprise automatically supplying build material to the dispenser or dispenser container. Automatically supplying build material may comprise automatically transferring build material from a storage container to the dispenser or dispenser container.

The method may comprise causing the dispenser, e.g. dispenser with dispenser container, to move to a storage container (or vice versa) for automatically supplying building material from the storage container to the dispenser or dispenser container. The deposition area and/or the further deposition area (where provided) may be defined on the work surface adjacent, e.g. directly adjacent or near to, the storage container.

The build material may comprise two or more different build materials. The build material may comprise a powder, liquid or gel, and so on. Plural storage containers may be provided, for example a first storage container holding a first material and a second storage container holding a second material. The dispenser may be able to be supplied by one or more storage containers. Advantageously, this allows objects to be made from plural materials and may be facilitated by a dispenser translatable in both the x and y axis directions. The build material may comprise a first build material and a second build material. The first build material may comprise a material having a first consolidation characteristic or profile whilst the second build material may comprise a material having a second consolidation profile or characteristic. The first build material may be capable of being consolidated, in use, under different criteria to those suitable for consolidation of the second build material. The different criteria may comprise consolidation at a different temperature, for example the first build material may consolidate at a lower or lesser temperature than does the second build material. The different criteria may comprise consolidation at different electromagnetic wavelengths, for example the first build material may consolidate within a first range of electromagnetic wavelengths whilst the second build material may consolidate within a second range of electromagnetic wavelengths. The first and second ranges may be distinct or may partially overlap. If there is a distinction or minimal overlap between the first consolidation characteristic or profile and the second consolidation characteristic or profile the first build material may be termed an 'active build material' whilst the second build material may be termed an 'inactive build material', or versa vice.

Consolidating build material may comprise sintering. Alternatively, consolidating build material may comprise cross linking, adhering, evaporation, heating, and so on.

One or more steps of the method may comprise the use of an additive manufacturing apparatus and/or may be automated. When referring to spacing of the dam or wall from the periphery of the first slice object, spaced in this context may refer to a minimum separation distance of between 0.1 mm and 10mm, for example between 0.1 mm and 8mm, 7mm, 6mm, 5mm, 4mm, 3mm, 2mm or 1 mm. Additionally or alternatively, spaced in this context may refer to a maximum separation distance of between 0.1 mm and 50mm, for example between 0.1 mm and 45mm, 40mm, 35mm, 30mm, 25mm, 20mm, 15mm or 10mm. Additionally or alternatively, spaced in this context may refer to a separation distance of between 0.1 mm and 50mm, for example between 0.1 mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm or 1 mm and 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm or 50mm.

The method may comprise a further step comprising defining an updated virtual boundary to encompass the periphery of the virtual three-dimensional object viewed in plan. The updated virtual boundary may correspond to the succeeding or one or more of the subsequent plural slice images (for example the slice image subsequent to the slice image which corresponds to the last slice of the object consolidated). The updated virtual boundary may be reduced in size or area relative to the virtual boundary previously defined. The method may comprise defining an updated deposition area on the previous deposition area, e.g. where the updated deposition area corresponds to, is delineated or described by the updated virtual boundary. The method may comprise depositing a subsequent layer of build material to cover, e.g. only, the updated deposition area. The method may comprise consolidating build material within the subsequent layer to form the next or subsequent slice of the object. A further aspect of the invention provides an additive manufacturing apparatus comprising a work surface, a dispenser movable over the work surface and a control means or device configured to cause the dispenser to deposit a first layer of build material to cover a deposition area corresponding to, delineated or described by a virtual boundary encompassing the periphery of a virtual three- dimensional object viewed in plan.

The control means or device may be configured to cause the dispenser to deposit a first layer of build material, e.g. to cover each of one or more deposition areas. The or each deposition area may be delineated, e.g. respectively, by a virtual boundary encompassing the periphery of a virtual three- dimensional object viewed in plan. The dispenser may be movable over the work surface in an x- axis direction and a y-axis direction.

A further aspect of the invention provides an additive manufacturing apparatus comprising a work surface, a dispenser movable over the work surface in an x-axis direction and a y-axis direction and a control means or device configured to cause the dispenser to deposit a first layer of build material to cover each of one or more deposition areas each corresponding respectively to, delineated or described respectively by a virtual boundary encompassing the periphery of a virtual three- dimensional object viewed in plan.

The control means or device may be operable or configured to cause the apparatus to carry out the aforementioned method or one or more features or steps thereof.

For the avoidance of doubt the y-axis direction is perpendicular to the x-axis direction. Furthermore, a z-axis direction is also defined as being perpendicular to both the x-axis direction and the y-axis direction.

The apparatus may comprise a base frame. The work surface may be movably attached to the base frame. The work surface may be movable, in use, e.g. in a z-axis direction. The work surface may comprise a substantially flat and/or level surface. The work surface may be for supporting an object during building thereof.

The apparatus may comprise a first gantry, e.g. movably mounted to the base frame (where provided). The first gantry may extend across the work surface, e.g. in the x-axis direction or the y- axis direction. The first gantry may be movable, in use, for example along a length of the work surface (for example in the y-axis direction or the x-axis direction). The dispenser may be movably attached to the first gantry, for example and may be movable, in use, therealong. The apparatus may comprise a consolidation device for consolidating build material, in use, into consolidated build material. The consolidation device may comprise a directing means or device, e.g. for directing the location of consolidation, in use. The consolidation device and/or the directing means or device may be movable, in use, over the work surface. The consolidation device may comprise a sintering device, for example when the build material comprises a powder. The sintering device may comprise a laser source or an E-beam source or a microwave source, etc. Additionally or alternatively, the consolidation device may comprise a source of electromagnetic radiation, for example when the build material comprises a liquid or gel. The source of electromagnetic radiation may comprise a source of ultraviolet radiation and/or any other suitable wavelength of electromagnetic radiation. For example, if the build material comprises an active build material and an inactive build material, the active build material being that which is to provide the article, the inactive build material being that which is to support the article during the build, each layer slice may be consolidated by exposing the entire layer to a consolidation process, for example exposure to a microwave source or UV light source so as to consolidate the active build material whilst leaving he inactive build material unconsolidated.

The apparatus may comprise a second gantry, e.g. movably mounted to the base frame (where provided). The second gantry may extend across the work surface, e.g. in the y-axis direction or the x-axis direction. The second gantry may be movable, in use, for example across a width of the work surface (for example in the x-axis direction or the y-axis direction). The consolidation device or the directing means or device may be movably attached to the second gantry, for example and may be movable, in use, therealong.

The control means or device may be configured to cause the consolidation device or directing means or device (e.g. to move along the second gantry) to consolidate build material within a layer covering a first deposition area to from a slice of an object. The control means or device may be configured to at least partially concurrently cause the dispenser (e.g. to move along the first gantry) to deposit a layer of build material, e.g. to cover a second deposition area. The control means or device may be configured to define the virtual boundary encompassing the periphery of the or each virtual three- dimensional object viewed in plan.

The apparatus may comprise sensor means or one or more sensors, for example operable to detect or measure one or more characteristics of an object being built on the work surface and/or of the work surface and/or of the environment surrounding the work surface. The sensor means or one or more sensors may be located in, on or adjacent the work surface. The work surface may comprise one or more recesses or apertures, e.g. and the sensor means or one or more sensors may be at least partially located within the, one, some or each of the one or more recesses or apertures. The sensor means or one or more sensors may comprise one or more image capture means or device, for example operable to capture, in use, images of an object being manufactured and/or of the work surface.

The apparatus may comprise a storage container for storing build material. The storage container may be fixed, in use, relative to the base frame (where provided). The storage container may be subdivided, for example into separate storage regions each for containing build material. In use, some or each of the separate storage regions may contain different build material, for example different types of build material. The apparatus may comprise a transfer means or device for transferring, e.g. automatically transferring, in use, build material from the storage container to the dispenser. The transfer means or device may comprise a valve means or valve. The transfer means or device may be operably connected to the control means or device, for example which may be configured to transfer build material from the storage container to the dispenser. The dispenser may be movable, in use, to or toward and/or from or away from the storage container. Advantageously, because build material may be transferred from the storage container to the dispenser store, in use, the dispenser store does not need to retain a large mass of build material and therefore may be moved with the dispenser over the work surface accurately and rapidly.

The apparatus may comprise a further dispenser, for example movable, in use, over the work surface. The further dispenser may be movable, in use, in the x-axis direction and the y-axis direction over the work surface. The further dispenser may be movably attached to the first gantry or to a third gantry. The third gantry may extend across the work surface, e.g. in the x-axis direction or the y-axis direction. The third gantry may be movably mounted to the base frame (where provided). The dispenser (and/or the further dispenser, where provided) may comprise or be mounted on or in a carriage. The dispenser (and/or the further dispenser, where provided) may comprise a nozzle, for example and a dispenser container for storing build material. The dispenser (and/or the further dispenser) may comprise a valve means or valve, e.g. for selectively releasing build material from the dispenser container and through the nozzle in order to be deposited. The nozzle may be configured to direct build material toward the work surface, in use.

The control means or device may comprise a memory means or memory and a processor. The memory means or memory may be configured or configurable to store, in use, one or more virtual 3D representations of an object. The processor may be configured or configurable to define a virtual boundary to encompass the periphery of a virtual 3D object viewed in plan.

The build material may comprise a powder. The build material may comprise metal, polymer and/or ceramic. Where the build material comprises metal the build material may comprise an alloy. A further aspect of the invention provides an apparatus for building objects from 3D virtual representations, the apparatus comprising a work surface upon which an object is buildable, a dispenser translatable in the x and y-axis directions relative to the work surface for depositing build material thereupon, a storage container for storing build material and means to transfer build material from the storage container to the dispenser.

Preferably the storage container has an internal volume Vs and the dispenser has an internal volume Vd and Vs>Vd, for example Vd may be less than 95% of Vs, for example Vd<90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, or 10% Vs.

A further aspect of the invention provides an apparatus for building objects from 3D virtual representations, e.g. an additive manufacturing apparatus, the apparatus comprising: a frame; a work surface mounted to the frame; a dispenser movably attached to the frame and movable, in use, in an x-axis direction and a y-axis direction over the work surface for depositing build material thereon; a storage container for storing powder build material fixed relative to the frame; and a transfer means or device for automatically transferring, in use, powder build material from the storage container to the dispenser.

For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention.

Within the scope of this application it is expressly envisaged that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings and, in particular, the individual features thereof, may be taken independently or in any combination. Features described in connection with one aspect or embodiment of the invention are applicable to all aspects or embodiments, unless such features are incompatible.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a plan view of an apparatus for manufacturing objects from virtual representations according to a first embodiment of the invention;

Figure 2 is a side view of the apparatus shown in Figure 1 ;

Figure 3 is a side view of the dispenser of the apparatus shown in Figure 1 ;

Figure 4 is a schematic flow diagram illustrating a sequence of operation of the apparatus shown in Figure 1 according to an embodiment of the invention;

Figures 5 is a perspective view of a virtual 3D object; Figure 6 is a plan view of the virtual 3D object of Figure 5 shown encompassed by a virtual boundary;

Figure 7 is a plan view of a work surface with a first deposition area defined thereupon; Figure 8 is a schematic perspective view of slice images corresponding to the virtual 3D object of Figure 5;

Figure 9 is a plan view of a work surface with a first layer of build material covering the first deposition area;

Figure 10 is a calculated consolidation path for the sintering device;

Figure 1 1 is a plan view of a work surface on which build material within a first layer of build material has been consolidated;

Figure 12 is a schematic flow diagram illustrating a sequence of operation of the apparatus shown in Figure 1 according to an alternative embodiment of the invention;

Figure 13 is a plan view of an apparatus for manufacturing objects from virtual representations according to a second embodiment of the invention;

Figure 14 is a schematic flow diagram illustrating a sequence of operation of the apparatus shown in Figure 13;

Figure 15 is a schematic flow diagram illustrating a sequence of operation of the apparatus shown in Figure 1 orthe apparatus shown in Figure 13 according to an alternative embodiment of the invention;

Figure 16 is a plan view of a work surface on which objects are being manufactured according to the operation shown in Figure 15;

Figure 17 is a schematic flow diagram illustrating a sequence of operation of the apparatus shown in Figure 1 orthe apparatus shown in Figure 13 according to an alternative embodiment of the invention;

Figure 18 is a plan view of a work surface on which objects are being manufactured according to the operation shown in Figure 17;

Figure 19 is a side view of an apparatus for manufacturing objects from virtual representations according to an alternative embodiment of the invention; and

Figure 20 is a side view of an object being manufactured on a work surface according to an alternative embodiment of the invention.

Referring now to Figures 1 and 2, there is shown an apparatus 1 for manufacturing objects from virtual 3D representations thereof. Such apparatus 1 are also known as additive manufacturing apparatus or 3D printers and in this embodiment of the invention the apparatus 1 is a selective laser sintering (SLS) apparatus.

The apparatus 1 includes a gantry apparatus 2 with a build plate 3 (e.g. a work surface or build platform) movably mounted thereto, a powder dispenser 4 and a consolidation device 5 moveably mounted to the gantry apparatus 2, with a storage container in the form of a powder hopper 6 mounted to the gantry apparatus 2, a housing 7 mounted to the gantry apparatus 2 and a control unit 8 for controlling operation of the apparatus 1 . The storage container 6 preferably has a larger volume than the dispenser 4 which advantageously means that a large volume of build material need not be held within the dispenser 4.

The gantry apparatus 2 includes first and second gantries 20, 21 movably mounted to a base frame 22. The first gantry 20 includes an elongate first spanning member 20a which extends across the build plate 3, thereby defining an x-axis. Supports 20b depend from either end of the first spanning member 20a. The free end of each support 20b engages with a y-axis rail 23, each of which is affixed to the base frame 22 and which extends along the length thereof in a direction perpendicular to the first spanning member 20a. The second gantry 21 includes an elongate second spanning member 21 a which extends across the build plate 3, thereby defining a y-axis. Supports 21 b depend from either end of the second spanning member 21 a. The free end of each support 21 b engages with an x-axis rail 24, each of which is affixed to the base frame 22 and which extends across the width thereof in a direction perpendicular to the second spanning member 21 a. The first and second gantries 20, 21 are disposed above the build plate 3, with the second gantry 21 disposed above the first gantry 20.

The first gantry 20 is movable, in use, along the y-axis rails 23 by a motor (not shown) and is able to traverse the entire length of the build plate 3. The second gantry 21 is movable, in use, along the x- axis rails 24 by a motor (not shown) and is able to traverse the entire width of the build plate 3.

The build plate 3 is rectangular in plan in this embodiment of the invention, however those skilled in the art will appreciate that other shapes may also be suitable. The build plate 3 includes a work surface 30 which is flat and level and extends substantially across the width and length of the build plate 3. The build plate 3 is movably attached to the base frame 22 by a build piston (not shown) which is operable, in use, to lower or raise the build plate 3 relative to the base frame 22 in a z-axis direction. The powder dispenser 4 (as shown in greater detail in Figure 3) includes a dispenser nozzle 40 for dispensing powder build material P and a dispenser container 41 for local storage of powder build material P. A valve 42 is disposed between the dispenser nozzle 40 and the dispenser container 41 . The valve 42 is operable, in use, to selectively allow fluid communication between the dispenser nozzle 40 and dispenser container 41 and hence selectively allow flow of powder build material P from one to the other. The dispenser nozzle 40 is sized and shaped to deposit, in use, powder build material P to a predictable and tightly controlled area of the work surface. The powder dispenser 4 is movably attached to the first gantry 20 and is movable, in use, by a motor (not shown) along the length of the first gantry 20 in the x-axis direction and hence across the width of work surface 30 of the build plate 3, the first gantry being translatable in a direction along the y-axis thereby allowing the powder dispenser 4 to traverse the entire work surface 30. The dispenser container 41 has an internal volume suitable for retaining sufficient powder build material P to provide at least one layer of powder build material. The consolidation device 5 includes a laser outlet 50 to a fibre optic wire (not shown) connected at its other end to a laser source (not shown). The consolidating device 5 is moveably attached to the second gantry 21 and is movable, in use, by a motor (not shown) along the length of the second gantry 21 in the y-axis direction and hence along the length of the work surface 30 of the build plate 3. The laser outlet 50 is directed toward the work surface 30 of the build plate 3.

The powder hopper 6 is mounted to the base frame 22 and is located above and partially over the build plate 3. The powder hopper 6 includes an internal space for retaining a supply of powder build material P. In embodiments the majority or all of the powder hopper 6 may be located over the build plate 3. Advantageously, positioning the powder hopper 6 over the build plate 3 provides an apparatus 1 which has a reduced footprint relative to apparatus in which a store of build material is provided beside a build plate 3. The powder hopper 6 includes a refill device 60 located over the work surface 30. The refill device 60 is provided with a valve (not shown) for selectively allowing a flow of powder build material P from the powder hopper 6. The housing 7 is mounted over the gantry apparatus 2 and sealingly encloses the gantry apparatus 2, build plate 3, powder dispenser 4, consolidation device 5 and powder hopper. The housing 7 is configured to maintain an inert environment therewithin, in use.

The control unit 8 includes a processor 80 and a memory module 81 and is operatively connected to the motors (not shown) for moving the first and second gantries 20, 21 and for moving the powder dispenser 4 along the first gantry 20 and the consolidation device 5 along the second gantry 21 . The control unit 8 is thereby configured to move the powder dispenser 4 and the consolidation device 5 over the work surface 30, each in both the x-axis and y-axis. The control unit 8 is also operatively connected to the valve 42 of the powder dispenser 4 for selectively allowing or preventing flow of power build material therethrough. The control unit 8 is operatively connected to the laser source (not shown) for controlling the generation of a laser, in use. The control unit is also operatively connected to the valve of the refill device 60 for selectively allowing flow of controlled quantities of powder build material P from the powder hopper 6, in use. In this embodiment the control unit 8 is distal from the base frame 22 and other components, however in embodiments the control unit 8 may be mounted to the base frame 22 and/or attached to the housing 7.

The powder build material P is a metallic powder in this embodiment, however a person skilled in the art will appreciate that other powders may be used, for example powder polymers. Referring now to Figure 4, a method of operating the apparatus 1 is shown.

In step S1 the processor 80 defines a virtual boundary VB around the periphery of a virtual 3D object VO (Figure 5 shows one example of such a virtual 3D object VO) when it is viewed in plan. Figure 6 shows the virtual 3D object VO shown in Figure 5 in plan view and surrounded by a virtual boundary VB which encompasses the virtual 3D object VB and is closely spaced from its periphery. The virtual boundary VB is spaced by a minimum distance of 0.5mm from the periphery of virtual 3D object VO viewed in plan. In step S2 a deposition area D corresponding to the virtual boundary VB is defined on the work surface 30, as shown in Figure 7.

In step S3 the processor 80 generates slice image data corresponding to the virtual 3D object, where each slice image Si-S_n represents a horizontal layer of the virtual 3D object VO, as shown in Figure 8. Although only four slice images Si-S_n are shown in Figure 8 this is for illustrative purposes only and in practice any suitable number of slice images Si-S_n may be generated.

In step S4 the powder dispenser 4 is operated to move over the work surface 30 and to deposit thereon a first layer of powder build material P covering the deposition area D, as shown in Figure 9. The depth of the first layer of powder build material P corresponds to the depth of the layer of the virtual 3D object represented by the first slice image Si . The powder dispenser 4 is operated to move across, e.g. to raster back and forth (e.g. follow a serpentine path), over the deposition area, as shown in Figure 10 where one such path is illustrated. In step S5 the consolidation device 5 is operated to move over the deposition area D and the powder build material P is sintered by a laser emitted from the laser outlet 50. Powder build material P within the first layer of powder build material is sintered to form a dam or wall B corresponding to the virtual boundary VB and to form the first slice of the object Oi contained within the first slice image Si, as shown in Figure 1 1 .

Steps S4 and S5 are repeated for each subsequent slice image S2-S_n corresponding to a subsequent layer of the virtual 3D object VO. The build plate 3 is lowered in the z-axis direction following each step S5 by a distance corresponding to the depth of each layer of powder build material P previously deposited. The second layer of powder build material P is deposited over the first layer of build material P (which has been at least partially sintered) and covers the same deposition area D defined on the work surface 30 in Step S2, above.

When the volume of powder build material P within the dispenser container 41 is low or has been exhausted the control unit 8 causes the powder dispenser 4 to move to a location underneath the refill device 60 of the powder hopper 6. The control unit 8 then operates the valve in the refill device 60 in order to allow a flow of powder build material P from the powder hopper 6 into the powder dispenser 4 in order to refill it. The dispenser container 41 includes a sensor (not shown) which is operatively connected to the control unit 8 and sends a signal thereto when the volume of powder build material P within the dispenser container 41 is less than a pre-set threshold volume. In this embodiment the sensor is an optical sensor, however those skilled in the art will appreciate that any suitable type of sensor may be used for this purpose. Additionally or alternatively, the processor 80 may be configured to calculate the volume of powder build material P which has been deposited by the powder dispenser 4 and may initiate refilling of the dispenser container 41 when the volume of powder build material P deposited exceeds a threshold value or the amount of powder build material P previously added to the dispenser container 41 . Manufacturing according to the invention requires only the deposition of powder build material P over a portion of the work surface 30, instead of over the entirety of the work surface 30.

Advantageously, it has been found that objects are manufactured more rapidly using the method of the invention than using prior art methods requiring deposition of powder build material P over an entire work surface. By reducing the area over which powder build material P is deposited the time required for the deposition of material and consequently of the manufacturing process is also reduced. We have surprisingly found that the build time may be reduced by up to 40% using the method of the invention. Powder build material P deposited onto the build plate 3 but not sintered during building of an object is not always reused for subsequent building of a further object. This is because the powder build material P can become contaminated and may no longer be suitable for use. Advantageously, the method of manufacture according to the invention deposits relatively less powder build material P than do prior art manufacturing methods. Consequently, relatively less powder build material P is wasted when manufacturing an object using the method of the invention then in prior art methods, leading to reduced expense of manufacture.

As multiple layers of the object are manufactured the dam or wall B increases in height with each layer. The dam or wall B beneficially acts as a structural wall to retain non-consolidated, e.g. non- sintered, powder build material P therewithin. Consequently, there is always a platform across the entire area of the deposition area on which to deposit a successive layer of powder build material P, where the platform comprises both sintered build material and powder build material P. It has been found that providing a minimum distance of separation between the dam or wall B and the object Oi under manufacture ensures that a minimum volume of powder build material P is retained between the dam or wall B and the object Oi. Clearly, the dam or wall B acts to retain build material within a reduced space compared to the entire build platform. It has been surprisingly found that the dam or wall B helps to generate a finished object Oi which is less liable to show defects than would otherwise be the case and that further benefits are provided. . For example, and without wishing to be bound by any particular theory or belief, the dam orwall B and/or the non-consolidated build material P retained therewithin acts as insulation, e.g. a thermal barrier, mitigating against rapid conduction of heat way from the object Oi and consequently promoting a less rapid cooling of the object Oi post-sintering thereof. Rapid cooling of formed objects Oi post sintering has been found in some circumstances to result in defect formation therein (e.g. crack formation) and so a less rapid cooling is beneficial. Moreover, in prior art systems it has been known to heat the build plate 3 in order to promote more gradual cooling of an object being built to mitigate against formation of such defects. Advantageously, objects Oi being manufactured according to the present invention are thereby cooled more gradually and are therefore less susceptible to being defective. Additionally, heating of the build plate 3 may not be required or may be required to a reduced extent, with consequential savings on expense of heating. Furthermore, provision of a minimum distance of separation between the dam or wall B and the object Oi under manufacture mitigates against unintentional conjoining of the two structures if part of the dam or wall B and/or object Oi are misaligned with respect to their intended location and/or contain one or more defects which would otherwise connect the two structures.

Referring now to Figure 12, there is shown an alternative method of operating the apparatus 1 shown in Figures 1 and 2, wherein like steps to those described in respect of the method shown in Figure 4 have like references preceded by a Ί ' and will not be described herein further. The method shown in Figure 1 1 differs from the method described in respect of Figure 4 in the following respects:

• The deposition area D is first defined on a virtual model of the work surface, in step S12a, prior to being defined on the work surface 30 in step S12; and

• A consolidation path for consolidating the dam or wall B and the first slice of the object Si is calculated by the processor 80 in a step S13a, subsequent to step S13 and prior to step

S15.

Referring now to Figure 13, there is shown a plan view of an apparatus 1 1 according to an alternative embodiment of the invention, wherein like features to those described in respect of the apparatus 1 shown in Figure 1 and 2 are denoted by like references preceded by a T. The apparatus 1 1 shown in Figure 12 differs from the apparatus 1 shown in Figures 1 and 2 in that a camera 19 is also included. The camera 19 is located on the work surface 130 of the build plate 13 and is operatively connected to the control unit 18. The camera 19 is configured to capture image data and to send the image data to the control unit 18. It will be appreciated that the camera 19 may only be located on the work surface 130 because of the method of manufacture according to the invention in which powder build material P is deposited across a deposition area instead of across the entire surface of the work surface 130. Referring now to Figure 14, there is shown a method of operating the apparatus 1 1 shown in Figure 13, wherein like steps to those described in respect of the method shown in Figure 4 in respect of operating apparatus 1 have like references preceded by a '2' and will not be described herein further. The method shown in Figure 14 differs from the method described in respect of Figure 4 by way of the following:

In step S26 the image data of the object under manufacture is captured by the camera and sent to the control unit 8. In step S27 the image data is received by the control unit and is processed by the processor 180 in order to determine the coordinates of points along the dam or wall B. The coordinates of the determined points of the dam or wall B are compared with the coordinates of the virtual boundary VB and a deviation between the dam or wall B and the virtual boundary VB is calculated. If the deviation is less than a threshold value stored on the memory module 181 then the control unit controls the apparatus 1 to perform steps S24 and S25 in respect of a second layer of powder build material P for the second slice image S2 of the virtual 3D object VO. If, however, the deviation is greater than the threshold value then the control unit terminates manufacture of the object and steps S24 and S25 are not performed in respect of a second layer of powder build material P. If the control unit terminates manufacture of the object an alarm or alert may be triggered to alert an operator that termination of manufacture of the object has occurred.

It has been found that, through use of the above-described method, it is possible to terminate manufacture of objects at an early stage of their manufacture if they display signs that they are defective. Hence, powder build material is not used to continue building these defective objects with a consequential reduction in waste of powder build material P. Moreover, one or more further objects may continue to be built. The time of manufacture of these one or more further objects may be relatively reduced due to cessation of manufacture of the object determined to be defective.

Steps S26 and S27 may occur prior to, concurrent with or subsequent to lowering of the build plate 3 in the z-axis direction. Steps S26 and S27 may occur after every step S25 in which build material within a layer is sintered. Alternatively, in embodiments steps S26 and S27 may occur only at preset times during manufacture of the object. Additionally or alternatively, in embodiments steps S26 and S27 may occur after a pre-set number of layers have been built.

In embodiments one or more other sensors may be located in, on or adjacent the work surface 130 for measurement of characteristics of the work surface 130, the environment around the work surface 130 and/or an object under manufacture on the work surface 130. For example, a thermocouple may be located on the work surface 130 for measurement of the temperature of the work surface 130 during manufacture of an object thereon. Advantageously, temperature data from such a thermocouple may be used to monitor, in use, the temperature of the work surface 130 during manufacture of an object thereon. Whether or not to continue manufacture of the object and/or whether or not to commence manufacture of a further object on a different portion of the work surface 130 may be determined based on temperature data from the thermocouple. A person skilled in the art will appreciate that other sensors may also be suitable, for example one or more strain gauges or one or more gas flow sensors. Advantageously, provision of such sensors in, on or adjacent the work surface 130 may provide real-time data concerning the temperature, expansion and/or deformation of the work surface 130 and/or the temperature and/or gas flow rate in the environment adjacent the work surface 130. As will be appreciated, provision of this data, beneficially, allows for a more advantageous positioning of one or more deposition areas on the work surface and of the timing of commencement and/or continuation of manufacture of objects.

Referring now to Figure 15, there is shown a method of operating the apparatus 1 shown in Figures 1 and 2 or the apparatus 1 1 shown in Figure 13 to manufacture two objects, wherein like steps to those described in respect of the method shown in Figure 4 in respect of operating apparatus 1 have like references preceded by a '3'.

The method of manufacturing two objects shown in Figure 15 differs from the method of manufacturing an object shown in Figure 4 by way of the following:

• The method of manufacturing two objects shown in Figure 15 includes a preliminary step S30 in which first and second virtual 3D objects are nested with respect to one another. As will be apparent to one skilled in the art, nesting in this context refers to orienting the first and second virtual 3D objects relative to one another such that they are closely spaced and require a relatively reduced footprint on the work surface 30, 130 during manufacture.

• In step S31 a virtual boundary VB is defined around the nested first and second virtual 3D objects viewed in plan. The virtual boundary VB encompasses both of the 3D virtual objects and is closely spaced from the periphery of both virtual 3D objects.

• In step S33 slice image data is generated of the nested first and second virtual 3D objects.

• In step S35 build material within the first layer is sintered in order to form a first slice of the first object 0i and the second object O2 and a dam orwall B therearound, as shown in Figure 16.

Steps S34 (deposition of powder build material P to cover the deposition area D) and S35 may be repeated any suitable number of times in order to manufacture the two objects. Although the method shown in Figure 15 is described as being for the manufacture of two objects it will be appreciated that this need not be the case and that any suitable number of objects may be manufactured according to this method.

Advantageously, manufacturing objects according to the method shown in Figure 15 provides enhanced protection of relatively delicate and/or relatively small objects. Furthermore, nesting of objects in the above-described manner results in an increased efficiency in use of space on the work surface 30, 130.

Referring now to Figure 17, there is shown a method of operating the apparatus 1 shown in Figures 1 and 2 or the apparatus 1 1 shown in Figure 13 to manufacture two objects, wherein like steps to those described in respect of the method shown in Figure 4 in respect of operating apparatus 1 have like references preceded by a '3'.

The method of manufacturing two objects shown in Figure 17 differs from the method of manufacturing two objects shown in Figure 15 by way of the following:

• The method shown in Figure 17 includes a preliminary step S41 in which a first virtual boundary is defined around a first virtual 3D object viewed in plan and a second virtual boundary is defined around a second virtual 3D object viewed in plan.

• In step S42 a first deposition area corresponding to the first virtual boundary is defined on the work surface and a second deposition area corresponding to the second virtual boundary is defined on the work surface 30, 130. The first and second deposition areas are defined at non-overlapping areas of the work surface 30, 130.

• In step S43 slice image data corresponding to first virtual 3D object and slice image data corresponding to the second virtual 3D object is generated.

• In step S44 the powder dispenser 4, 14 is operated to deposit a first layer of powder build material P to cover the first deposition area D1 and to cover the second deposition area D2.

• In step S45 the consolidation device 5, 15 is operated to move over the first deposition area D1 and to sinter powder build material P corresponding to the first slice image of the first 3D virtual object and a wall or dam B1 therearound. Additionally, in step S45 the consolidation device 5, 15 is operated to move over the second deposition area D2 and to sinter powder build material P corresponding to the first slice image of the second 3D virtual object and a wall or dam B2 therearound. Figure 18 shows first and second objects under manufacture on the work surface 30, 130.

Steps S44 and S45 may be repeated any suitable number of times in order to manufacture the two objects. In embodiments, the first and/or second deposition area may be located, in step S44, on the work surface 30, 130 adjacent the powder hopper 6. Advantageously, manufacturing times are reduced by locating at least one of the deposition areas on the work surface 30, 130 at a location adjacent the powder hopper 6. In this way, the time required for refilling the dispenser container 41 with powder build material P from the powder hopper 6 is beneficially reduced with a consequential reduction in overall manufacture time. In embodiments, the first and second deposition area may be located on the work surface 30, 130, in step S44, in a closely spaced arrangement, e.g. relatively nested together. Advantageously, nesting of the first and second deposition area in this manner provides a relatively more efficient use of the work surface 30, 130 available area and may allow the consecutive manufacture of an increased quantity of objects at any given time. In embodiments, the first and second deposition area may be located on the work surface 30, 130, in step S44, in spaced arrangement, for example such that the first and second deposition areas are spaced apart. Advantageously, spacing apart of the first and second deposition areas provides for controlled cooling of the first and second objects during manufacture thereof.

Referring now to Figure 19, there is shown a side view of an apparatus 101 according to an alternative embodiment of the invention, wherein like features to those described in respect of the apparatus 1 shown in Figures 1 and 2 are denoted by like references preceded by a '10' and will not be described herein further. The apparatus 101 shown in Figure 19 differs from the apparatus 1 shown in Figures 1 and 2 in that the powder hopper 106 is subdivided into plural compartments 1060a, 1060b, 1060c. The refill device 1060 is configured, in use, to selectively allow flow of powder build material from one, some or all of the plural compartments 1060a, 1060b, 1060c through use of a valve (not shown). In use, the apparatus 101 may be operated according to any of the above-described methods. Additionally, however, the powder hopper 106 is provided with plural different types of powder build material. A different type of powder build material is stored in each of the plural compartments 1060a, 1060b, 1060c. The control unit 108 is operable, in use, to cause the powder dispenser 104 to move to the powder hopper 106 and be refilled by the refill device 1060 with any of the different types of powder build material stored in the powder hopper 106. In this way, the apparatus 101 is operable to deposit different types of powder build material in different layers of an object. Additionally, the apparatus 101 is operable to deposit different types of powder build material within a single layer of an object.

Referring now to Figure 20, there is shown a side view of an object O being manufactured on a work surface 23 according to an alternative method of operating the apparatus 1 , 10, 101 . The object is surrounded by a wall or dam B_a, Bb retaining non-consolidated build material P therewithin. The wall or dam B_a extends orthogonally relative to the work surface between the work surface 30 and a plane parallel thereto defined by the line F-F. From the plane defined by the line F-F the wall or dam B_a extends in a sloped or angled manner with respect to the work surface 30 (e.g. non-orthogonal relative to the work surface 30). The wall or dam Bb extends, over its entire height, orthogonally relative to the work surface 30.

The method of manufacture is generally as described in respect of any of Figures 4, 12, 14, 15 or 17 for each of the layers between the work surface 30 of the build plate 3 and the plane defined by line F-F. At the plane defined by line F-F the method of manufacture is amended with respect to the methods of manufacture described in respect of Figures 4, 12, 14, 15 or 17. In the amended method of manufacture the layer is begun by defining a new virtual boundary around the virtual 3D object viewed in plan. This new virtual boundary is reduced in size relative to the previous virtual boundary. The remainder of the steps of the aforementioned methods then proceed as previously described, using the new virtual boundary in order to define a new deposition area. Subsequent layers may be manufactured according to the same modified method or according to any of the methods previously described in respect of Figures 4, 12, 14, 15 or 17.

Advantageously, a reduced quantity of build material P is required when utilizing this alternative method of operating the apparatus 1 , 10, 101 with consequential savings on expense of materials. In particular, the reduction is shown by the dotted area G in Figure 20.

It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention. For example, although the consolidation device 5 is described as including a laser outlet 50 of a fibre optic this need not be the case and instead the consolidation device 5 may include a laser source, which may be movably mounted to the second gantry. Additionally or alternatively, the consolidation device 5 may include directing apparatus, for example one or more mirrors and/or prisms configured to direct a laser generated by a laser source at or to specific positions on the work surface 30. The laser source may be located at any suitable location, for example beneath the work surface 30, 130. Additionally or alternatively, although the apparatus 1 , 1 1 , 101 is described as including a second gantry 21 this need not be the case and instead the apparatus 1 , 1 1 , 101 may include a support structure positioned above the work surface, for example and above the first gantry 20. The support structure may be configured to support directing apparatus of the consolidation device 5. The support structure may be mounted to the base frame 22. Additionally or alternatively, although the apparatus 1 , 1 1 , 101 is described as including first and second gantries 20, 21 , 1020, 1021 this need not be the case and instead the apparatus 1 , 1 1 , 101 may include one or more robotic arms, for example to which the dispenser 4 and/or the consolidation device 5 may be mounted. The one or more robotic arms may comprise a 6-axis robotic arm or any other suitable type of robotic arm. The one or more robotic arms may be attached at one end to the base frame 22. Additionally or alternatively, the consolidation device 5 may include an e-Beam generator or a binding agent deposition device. Where the consolidation device 5 includes a binding agent deposition device the consolidation device 5 may be configured to deposit a binding agent, for example an adhesive, onto the build plate 3. The binding agent may be cured subsequent to deposition, for example through application of ultraviolet radiation and/or thermal energy thereto. Subsequent to complete manufacture of all the required layers of the object it may be necessary, where a binding agent has been used, to further treat the manufactured object, for example to heat the manufactured object in order to sinter the layers of powder build material. The consolidation device 5 may be configured to heat and/or evaporate and/or cross-link the build material.

Additionally or alternatively, although the apparatus 1 , 1 1 , 101 is described above as using a powder build material P this need not be the case and instead the build material may be a liquid or a gel. Additionally or alternatively, the build material may comprise plural build materials, e.g. a first and second build material. The first build material may be susceptible to consolidation whilst the second build material may be non-susceptible to consolidation. Alternatively, the first build material may be more susceptible to consolidation than is the second build material. Additionally or alternatively, the first build material may be susceptible to consolidation under a first condition whilst the second build material may be susceptible to consolidation under a second condition, for example the first build condition may comprise a first consolidation temperature, whilst the second build condition may comprise a second consolidation temperature. The first consolidation temperature may be relatively lower than the second consolidation temperature. In this way, when the build material is exposed to a temperature equal to or greater than the first consolidation temperature but less than the second consolidation temperature the first build material may be consolidated whilst the second build material may not be consolidated. The first build material may therefore form a slice of the object under manufacture whilst the second build material may provide a support material (e.g. for further layers of the object). Additionally or alternatively, the first build condition may comprise a first range of electromagnetic radiation under exposure to which the first build material may be consolidatable (e.g. ultraviolet or microwave radiation). The second condition may comprise a second range of electromagnetic radiation, e.g. different to the first range of electromagnetic radiation. Where the first and second build materials are susceptible to consolidation under different conditions the first and second build material may be deposited across a greater area of the build plate 3. The first build material may be deposited over the area required to form a slice of the object whilst the second build material may be deposited over the remaining area of the deposition area or over the remaining area of the build plate 3. The consolidation device 5 may then apply consolidation (for example in the form of heat or electromagnetic radiation) to both the first and second build materials. Subsequently, only the first build material may be consolidated whilst the second build material may be non- consolidated. Additionally or alternatively, although the method of manufacture described above in respect of Figure 17 describes the processes for both the first and second object in each of steps S42, S43, S44 and S45 as occurring at the same time this need not be the case and instead the process or processes for the second object described in one, some or all of the steps S42, S43, S44 and S45 may occur at any suitable time. For example, in embodiments the first layer of build material may be deposited to cover the first deposition area D1 prior to deposition of the first layer of build material to cover the second deposition area D2. The first layer of build material may be deposited to cover the second deposition area simultaneously with the sintering of build material within the first layer to form the first slice of the first object and a wall or dam B1 therearound. Advantageously, performing operations from different steps on the different objects simultaneously results in relatively reduced overall manufacturing times.

Additionally or alternatively, a first object may be partially built through multiple passes through steps S44 and S45 prior to commencement of building of the second object. Additionally or alternatively, building of the first or second object may cease prior to ceasing of building of the other object, for example where building of one object has been completed or terminated. Advantageously, powder build material P is not deposited over the object for which building has ceased, thereby reducing waste of powder build material P. Additionally or alternatively, the powder hopper 6 need not be mounted to the base frame 22, 1022 but may instead be separate therefrom and/or may comprise its own support frame.

Additionally or alternatively, although a camera 18 is shown in the apparatus 1 of Figure 13 and described in the method of Figure 14 this need not be the case and the camera 18 may be replaced or supplemented by one or more other suitable sensor, for example a proximity sensor. Additionally or alternatively, although the camera 18 of apparatus 1 1 is described as being located on the work surface 130 this need not be the case and instead the camera may be located in the work surface 130, for example projecting or partially projecting through an aperture or recess in the work surface, or located adjacent the work surface 130, e.g. mounted to the base frame 22.

Additionally or alternatively, although the apparatus 101 shown in Figure 19 is described as having a powder hopper 106 which is subdivided into plural compartments 1060a, 1060b, 1060c this need not be the case and instead the powder hopper 106 may include plural separate containers, for example which may be positioned adjacent one another or at discrete locations.

Additionally or alternatively, although the apparatus 101 shown in Figure 19 is described as being operable to refill the powder dispenser 104 with plural different types of powder build materials from the powder hopper 106 this need not be the case and instead the apparatus 101 may include plural powder dispensers which may each be refilled with a specific type of powder build material from the powder hopper 106. Where plural powder dispensers are provided they may each be movably attached to the first gantry 1020 or, alternatively, they may each be movably attached to additional gantries, each of which may be movably mounted to the base frame 1022 in a similar manner to the first gantry 1020.

It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.

Claims

A method of making one or more objects from virtual three-dimensional representations, the method comprising:

defining a virtual boundary to encompass the periphery of a virtual three-dimensional object viewed in plan;

defining a deposition area on a work surface delineated by the virtual boundary;

depositing a first layer of build material to cover the deposition area; and

consolidating build material within the first layer to form a first slice of an object.

A method according to Claim 1 , comprising consolidating a dam or wall corresponding to the virtual boundary, spaced from the periphery of the first slice of the object.

A method according to Claim 2, comprising defining a further virtual boundary to encompass the periphery of a further virtual 3D object viewed in plan, defining a further deposition area on the work surface corresponding to the further virtual boundary, depositing a first layer of build material onto the work surface to cover the further deposition area, and consolidating build material within the first layer to form a first slice of the further object.

A method according to Claim 3, wherein consolidating build material within the first layer of build material in the deposition area occurs at least partially concurrently with deposition of the first layer of build material corresponding to the further deposition area.

A method according to any preceding Claim, comprising monitoring using sensor means one or more characteristics of an object being made on the work surface, determining if the object is defective, and terminating the making of the object if it is determined to be defective.

A method according to Claim 5, wherein monitoring comprises generating sensor data by the sensor means which are positioned on or adjacent the work surface and wherein the deposition area is defined on an area of the work surface uninterrupted by the sensor means.

A method according to Claim 5 or 6 when dependent on Claim 2, wherein determining if the object is defective or not comprises calculating the position of the dam or wall on the work surface from the sensor data and comparing the position of the dam or wall with the position of the virtual boundary on the work surface.

A method according to Claim 6 or 7, wherein determining if the object is defective or not comprises comparing the sensor data with a database of defect data.

9. A method according to any of Claims 5 to 8, wherein monitoring one or more characteristics comprises capturing image data relating to the object using image capture means.

10. A method according to any preceding Claim, comprising generating plural slice images of the virtual 3D object.

1 1 . A method according to Claim 10, wherein the first slice of the object consolidated in the first layer of material corresponds to a first of the plural slice images.

12. A method according to any preceding Claim, wherein defining the virtual boundary comprises defining a virtual boundary to encompass the periphery of plural virtual three-dimensional objects viewed in plan.

13. A method according to Claim 12, wherein consolidating comprises forming a slice of each of the plural objects.

14. A method according to any preceding Claim, wherein depositing the first layer of build material comprises causing a dispenser to move in an x-axis direction and/or a y-axis direction over the work surface.

15. A method according to Claim 14, comprising causing the dispenser to move to a storage container for automatically supplying building material from the storage container to the dispenser.

16. A method according to any preceding Claim, wherein the build material comprises two or more different build materials.

17. A method according to any preceding Claim, wherein the build material comprises a powder and wherein consolidating build material comprises sintering.

18. An additive manufacturing apparatus comprising a work surface, a dispenser movable over the work surface in an x-axis direction and a y-axis direction and a control means configured to cause the dispenser to deposit a first layer of build material to cover each of one or more deposition areas each delineated respectively by a virtual boundary encompassing the periphery of a virtual three-dimensional object viewed in plan.

19. An apparatus according to Claim 18, comprising a first gantry movably mounted to a base frame and extending across the work surface in the x-axis direction, where the first gantry is movable, in use, along a length of the work surface in the y-axis direction, and where the dispenser is movably attached to the first gantry, and is movable, in use, therealong.

20. An apparatus according to Claim 19, comprising a consolidation device for consolidating build material, in use, into consolidated build material, wherein the consolidation device comprises a directing means and wherein the consolidation device or the directing means is moveable, in use, over the work surface.

21 . An apparatus according to Claim 20, comprising a second gantry movably mounted to the base frame and extending across the work surface in the y-axis direction, where the second gantry is movable, in use, across a width of the work surface in the x-axis direction, and where the consolidation device or the directing means is movably attached to the second gantry, and is movable, in use, therealong.

22. An apparatus according to either of Claims 20 to 21 , wherein the consolidation device comprises a sintering device and the build material comprises a powder.

23. An apparatus according to Claim 22, wherein the sintering device comprises a laser source or an E-beam source.

24. An apparatus according to any of Claims 21 to 23, wherein the control means is configured to cause the consolidation device or directing means to consolidate build material within a layer covering a first deposition area to from a slice of an object, and to at least partially concurrently cause the dispenser to deposit a layer of build material to cover a second deposition area.

25. An apparatus according to Claim 24, wherein the control means is configured to define the virtual boundary encompassing the periphery of the or each virtual three-dimensional object viewed in plan.

26. An apparatus according to either of Claims 25, comprising sensor means operable to detect one or more characteristics of an object being built on the work surface and/or of the work surface and/or of the environment surrounding the work surface.

27. An apparatus according to Claim 26, wherein the sensor means is located in, on or adjacent the work surface.

28. An apparatus according to Claim 27, wherein the work surface comprises a recess or aperture and the sensor means is located at least partially within the recess or aperture.

29. An apparatus according to any of Claims 26 to 28, wherein the sensor means comprises an image capture means configured to capture, in use, images of an object being manufactured and/or of the work surface.

30. An apparatus according to any of Claims 19 to 29, comprising a transfer means for automatically transferring, in use, build material from a storage container to the dispenser, where the storage container is fixed, in use, relative to the base frame.

31 . An apparatus according to Claim 30, wherein the dispenser is movable, in use, to the storage container.

32. An apparatus according to any of Claims 18 to 31 , wherein the dispenser comprises a nozzle, a dispenser container for storing build material and a valve means for selectively releasing build material from the dispenser container and through the nozzle in order to be deposited.

33. An apparatus according to any of Claims 19 to 32, comprising a further dispenser movable, in use, in the x-axis direction and the y-axis direction over the work surface, wherein the further dispenser is movably attached to the first gantry or to a third gantry extending across the work surface in the x-axis direction or the y-axis direction, where the third gantry is movably mounted to the base frame.