OA18778A - 3D printing method and apparatus. - Google Patents

Abstract

A printing apparatus for printing a threedimensional object. The apparatus comprises an operative surface, an energy source for emitting at least one energy beam onto the operative surface and a powder dispensing mechanism for depositing powder onto the operative surface, the powder being adapted to be melted by the or each energy beam. The powder dispensing mechanism is configured to deposit multiple layers of powder onto the operative surface simultaneously.

Description

TITLE “3D PRINTING METHOD AND APPARATUS”

FIELD OF INVENTION

[0001] The présent invention relates to a 3D printing method and apparatus.

[0002] More particularly, the présent invention relates to a 3D printing method and apparatus adapted for manufacturing objects at high speed.

BACKGROUND ART

[0003] Three-dimensional (3D) printed parts resuit in a physical object being fabricated from a 3D digital image by laying down consecutive thin layers of material.

[0004] Typically these 3D printed parts can be made by a variety of means, such as sélective laser melting or sintering, which operate by having a powder bed onto which an energy beam is projected to melt the top layer of the powder bed so that it welds onto a substrate or a substratum. This melting process is repeated to add additional layers to the substratum to incrementally build up the part until completely fabricated.

[0005] These printing methods are significantly time consuming to perform and it may take several days, or weeks, to fabricate a reasonable sized object. The problem is compounded for complex objects comprising intricate component parts. This substantially reduces the utility of 3D printers and is one of the key barriers currently impeding large-scale adoption of 3D printing by consumera and in industry.

[0006] Power is also a significant limiting factor for existing printing methods.

[0007] Whilst sélective électron beam melting can be used as a powerful material fabrication method, this must typically be performed in a vacuum because interaction between charged partîcle beams and air molécules at atmospheric pressure causes dispersion and atténuation of the beams, significantly impairing their power. It is, therefore, known to use an assembly comprising a high-powered électron gun (for Z example, a 150kW électron gun) contained inside a first vacuum housing that is adjoined to a second vacuum housing containing a workpiece to be operated on. Such assemblies, however, resuit in low productivity rates due to the required pumping time for evacuating the housings. The practical size of the workpiece that may be contained inside the second housing is also substantially limited.

[0008] It is, therefore, also known to use a plasma window in conjunction with a high-powered électron gun to perform material fabrication work. Such an assembly comprises an électron gun contained in a vacuum chamber, wherein the vacuum chamber is adjoined to a région of higher pressure (such as atmospheric pressure) containing a workpiece. A beam of charged particles is discharged from within the vacuum chamber and out of the chamber via a beam exit disposed in a wall of the chamber.

[0009] A plasma interface is disposed at the beam exit comprising an elongate channel for bonding a plasma. A plasma-forming gas, such as hélium, argon or nitrogen, that is highly ionized, is injected into the channel. Electrical currents are applied to a cathode and an anode disposed at opposite ends of the channel which causes a plasma to form and bond statically between the cathode and anode. The plasma serves to prevent pressure communication between the higher pressure région and the vacuum chamber whilst permitting substantially unhindered propagation of charged particles from the vacuum chamber to the higher pressure région, via the channel, and onto the workpiece.

[0010] Whilst plasma interfaces constructed in the above manner also serve to pump down the vacuum chamber, this pumping action is weak and of limited effectiveness only. In practice, both the vacuum chamber and the plasma interface’s channel must be pumped such that they are substantially in vacuum prior to the formation of the plasma. This is time consuming and, to implement effectivity, requires equipment that is costly and mechanically cumbersome. Particle gun assemblies that comprise plasma interfaces constructed in this manner are, therefore, not well suited for 3D printîng apparatuses, where the gun assembly is required to be dexterous and flexible in operation.

OBJECT OF THE INVENTION

[0011] It is an object of the présent invention to provide a method and apparatus for printing 3D objects at high speed.

SUMMARY OF THE INVENTION

[0012] In accordance with one aspect of the présent invention, there is provided a printing apparatus for printing a three-dimensional object, comprising:

an operative surface;

an energy source for emitting at least one energy beam onto the operative surface;

a powder dispensing mechanism for depositing powder onto the operative surface, the powder being adapted to be melted by the or each energy beam, wherein the powder dispensing mechanism is configured to deposit multiple layers of powder onto the operative surface simultaneously,

[0013] The powder dispensing mechanism may comprise a plurality of powderdispensing supply hoppers and a supply control mechanism, the supply hoppers and control mechanism being configured to dispense powder from each of the supply hoppers onto the operative surface to form the multiple layers of powder simultaneously.

[0014] The supply hoppers and control mechanism may be configured to deposit the multiple layers of powder onto the operative surface in a staggered manner such that, when the layers are being worked on by the energy beam, each layer of powder has a topmost surface that is, at least in part, not covered by an overlying layer of powder,

[0015] The energy source may, in use, émit energy beams onto two or more layers of powder simultaneously.

[0016] The energy source may, in use, émit an energy beam onto individual layers of powder in a sequence.

[0017] The printing apparatus may comprise an energy beam splitting means for splitting and directing an energy beam into two or more separate energy beams.

[0018] The supply hoppers and control mechanism may be configured to deposit the multiple layers of powder onto the operative surface in a curved path.

[0019] In accordance with one further aspect of the présent invention, there is provided a method for printing a three-dimensional object, the method comprising the steps of:

depositing a plurality of layers of powder simultaneously onto an operative surface;

using an energy source to émit at least one energy beam onto at least one layer of powder formed on the operative surface to melt the powder and form part of the three-dimensional object; and repeating the steps above until the three-dimensional object is completely formed.

[0020] The layers of powder in the method may be deposited onto the operative surface in a staggered manner such that, when the layers of powder are being worked on by the or each energy beam, each layer of powder deposited has a topmost surface that is, at least in part, not covered by an overlying layer of powder.

[0021] The or each energy beam in the method may be emitted onto two or more layers of powder simultaneously.

[0022] The or each energy beam in the method may be emitted onto individual layers of powder in a sequence.

[0023] An energy beam in the method may be split and directed into two or more separate energy beams using an energy beam splitting means.

[0024] In accordance with one further aspect of the présent invention, there is provided a printing apparatus for printing a three-dimensional object, comprising:

an operative surface;

at least one supply hopper and a control mechanism for depositing multiple layers of powder onto the operative surface simultaneously; and an energy source for emitting at least one energy beam onto at least one layer of powder formed on the operative surface, wherein the or each supply hopper and the control mechanism are adapted to dispense powder onto a heap on the operative surface in a manner such that a plurality of cascading layers of powder form and flow simultaneously over an extemal surface of the heap, each layer of powder having an exposed surface that is, at least in part, not covered by an adjacent layer of powder when the layer is being formed.

[0025] Particles comprised in the powder may each hâve one or more physical properties that cause formation of the cascading layers of powder on the heap.

[0026] The energy source may émit energy beams onto two or more layers of powder on the heap simultaneously.

[0027] The energy source may émit an energy beam onto individual layers of powder on the heap in a sequence.

[0028] The apparatus may comprise a scanning means for determining a position, velocity and/or size of one or more particles comprised in the powder when the, or each, particle is travelling from the supply hopper onto the heap.

[0029] The scanning means may be adapted to measure an airbome density of the powder travelling to the heap.

[0030] The scanning means may be adapted to measure a volume of powder deposited on the heap.

[0031 ] The scanning means may be adapted to measure a shape or profile of the heap.

[0032] The scanning means may be adapted to measure a shape, form, relative position or one or more surface characteristics of the layers of powder formed on the extemal surface of the heap. Λ

[0033] In accordance with one further aspect of the present invention, there is provided a method for printing a three-dimensional object comprising the steps of:

depositing powder onto a heap disposed on an operative surface such that a plurality of cascading layers of powder are formed on and simultaneously flow over an extemal surface of the heap; and using an energy source to émit at least one energy beam onto at least one layer of powder.

[0034] In accordance with one further aspect of the present invention, there is provided a charged particle propagation apparatus comprising a:

generator comprising a vacuum chamber with a gun therein for discharging a charged particle beam from within the vacuum chamber and out of the vacuum chamber through a beam exit disposed in a wall of the vacuum chamber;

higher pressure région adjoining the vacuum chamber at the beam exit that is maintainable at a pressure greater than a pressure of the vacuum chamber;

plasma interface disposed at the beam exit comprising a plasma channel, wherein the plasma channel:

is aligned with the beam exit;

has a first end and a second end; and has at least three electrode plates disposed between the first end and the second end, and wherein:

a sequence of electrical currents are applied to the electrode plates causing at least one plasma to move from the first end to the second end of the plasma channel, thereby pumping down the beam exit; and the charged particle beam is propagated from the vacuum chamber through the, or each, plasma in the plasma channel and into the higher pressure région.

[0035] The sequence may cause a plurality of plasmas to move concurrently from the first end to the second end of the plasma channel.

[0036] A non-plasma région may be formed between two successive plasmas moving concurrently from the first end to the second end of the plasma channel.

[0037] The, or each, non-plasma région may contain residual gas from the vacuum chamber.

[0038] The sequence may be a repeating sequence causîng the beam exit to be pumped down continuously.

[0039] In accordance with one further aspect of the présent invention, there is provided a pumping method for pumping down a vacuum chamber comprising the steps of:

disposing a plasma interface at an exit of the vacuum chamber comprising a plasma channel, wherein the plasma channel:

is aligned with the beam exit;

has a first end and a second end; and has at least three electrode plates disposed between the first end and the second end, and applying a sequence of electrical currents to the electrode plates causîng at least one plasma to move from the first end to the second end of the plasma channel.

[0040] The pumping method may comprise the additional steps of applying a further sequence of electrical currents to the electrode plates causîng a plurality of plasmas to move concurrently from the first end to the second end of the plasma channel.

[0041] The sequence of electrical currents used in the pumping method may cause a non-plasma région to be formed between two successive plasmas moving concurrently from the first end to the second end of the plasma channel.

[0042] Residual gas from the vacuum chamber may be contained in the, or each, nonplasma région formed when the pumping method is executed. X

[0043] The sequence of electrical currents used in the pumping method may be repeated causing the beam exit to be pumped down continuously.

[0044] The energy source used in the printing apparatus may comprise a charged particle propagation apparatus as herein disclosed.

[0045] The energy source used in the method for printing a three-dimensional object may comprise a charged particle propagation apparatus as herein disclosed.

BRIEF DESCRIPTION OF DRAWINGS

[0046] The présent invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[0047] Figure 1 is a schematic représentation of a conventional 3D printing apparatus known in the art;

[0048] Figure 2 is a schematic représentation of a 3D printing apparatus according to an embodiment of the invention;

[0049] Figure 3 is a further schematic représentation of the 3D printing apparatus shown in Figure 2;

[0050] Figure 4 is a schematic représentation of a 3D printing apparatus according to a further embodiment of the invention;

[0051] Figure 5 is a schematic représentation of a 3D printing apparatus according to a further embodiment of the invention;

[0052] Figure 6 is a schematic représentation of a charged particle propagation apparatus according to a further aspect of the invention;

[0053] Figure 7 is a schematic représentation of a 3D printing apparatus according to a further embodiment of the invention; Λ

[0054] Figure 8 is a further schematic représentation of the 3D printing apparatus shown in Figure 7;

[0055] Figure 9 is a further schematic représentation of the 3D printing apparatus shown in Figure 7;

[0056] Figure 10 is a schematic représentation of a 3D printing apparatus according to a further embodiment of the invention;

[0057] Figure 11 is a schematic représentation of a 3D printing apparatus according to a further embodiment of the invention;

[0058] Figure 12(a) is a perspective view of a 3D printing apparatus according to a further embodiment of the invention; and

[0059] Figure 12(b) is a top view of the 3D printing apparatus shown in Figure 12(a),

DETAILED DESCRIPTION OF THE DRAWINGS

[0060] Referring to Figure 1, there is shown a schematic représentation of a conventional 3D printing apparatus 10 known in the art. The apparatus 10 comprises a substrate 12 with an operative surface 14 on which a printed object is to be fabricated by 3D printing.

[0061] The apparatus 10 further comprises a supply hopper 16 that is adapted to deposît a single layer of powder 18 onto the operative surface 14.

[0062] An energy source 20 (commonly a laser or électron gun) emits an energy beam 22 onto the layer of powder 18 causing it to melt or sinter selectively to form an individual layer of the 3D object. The process is repeated to add additional layers and incrementally build up the object until it is completed.

[0063] Referring to Figure 2, there is shown a schematic représentation of a 3D printing method and apparatus 30 according to a first embodiment of the présent ol ίο invention. The apparatus 30 comprises a substrate 32 having an operative surface 34 on which a printed object is to be fabricated by 3D printing.

[0064] The apparatus 30 further comprises a powder dispensing mechanism that is configured to deposit multiple layers of powder onto the operative surface 34 simultaneously. In Figure 2, the powder dispensing mechanism is depicted in the form of a plurality of supply hoppers 36. The supply hoppers 36, operating in conjunction with a control mechanism (not shown), are configured to deposit a plurality of layers of powder 38 simultaneously onto the operative surface 34 in a single pass.

[0065] As illustrated in the Figure, the layers of powder 38 are, preferably, deposited by the supply hoppers 36 in a staggered manner such that the formation of each individual layer is commenced slightly later that the individual layer of powder immediately beneath it. This ensures that a surface 40 of each layer of powder 38 will, at least in part, be exposed and not covered by an overlying layer of powder 38 during the simultaneous application of the layers.

[0066] An energy beam 42 is emitted from an energy source 44 and is directed onto the exposed surfaces 40 of each layer of powder 38 to melt or sinter the powder selectively, thereby forming part of the 3D object. This process is repeated for additional passes to add additional layers and incrementally build up the 3D object until it is completed.

[0067] As shown in Figure 3, in the first embodiment of the invention the energy source 44 is adapted to operate as a raster such that while the layers of powder 38 are being simultaneously deposited by the supply hoppers 36, the orientation of the energy source 44 is adjusted such that the energy beam 42 is directed selectively onto each of the exposed surfaces 40 in a sequential manner.

[0068] For example, the energy beam 42 may initially be directed onto a first exposed surface 46 of a lowermost layer of powder 48. After the first exposed surface 46 has been sufficiently worked on by the energy beam 42, the orientation of the energy source 44 is then adjusted such that a second energy beam 50 is directed onto a second exposed surface 52 of a second layer of powder 54. This process is continued until ail layers of X powder deposited in the pass of the supply hoppers 36 hâve been worked on sufficiently before the next pass is conducted.

[0069] In the embodiment where the energy source 44 opérâtes as a raster, the energy beam 42 may be applied to each exposed surface 40 of each powder layer 38, as necessary, for a sufïicient period of time such that the powder is heated or energised causing it to melt or sinter before the energy source 44 is re-orientated for the next layer.

[0070] Alternatively, the energy beam 42 may be applied to each exposed surface 40 of powder 38 for a lesser period of time such that the powder is only partially heated or energised before the energy source 44 is re-orientated for the next layer. In this method, the energy source 44 is cycled repeatedly through the plurality of layers 38 in a rapid manner such that additional energy is applied to each exposed surface 40 on each itération. This causing the température or energy of each surface 40 that is worked on to increase incrementally until it reaches a point at which the powder melts or sinters.

[0071] Referring to Figure 4, there is shown a further embodiment of the printing apparatus 30 according to the present invention. In this embodiment, the printing apparatus 30 comprises a plurality of energy sources 56. Whilst four energy sources 56 are used in the embodiment shown, it will be appreciated that an alternative number may be used.

[0072] The energy sources 56 are arranged in an array and, in contrast to the abovedescribed raster approach, are adapted to émit a plurality of energy beams 58 simultaneously onto exposed surfaces 40 of the layers of powder 38.

[0073] Referring to Figure 5, there is shown a further embodiment of the printing apparatus 30. In this embodiment, the printing apparatus 30 comprises a single energy source 44 adapted to émit a single energy beam 42 onto an energy beam splitting means

60.

[0074] The energy beam splitting means 60 splits the single energy beam 42 into a plurality of separate directed energy beams 62. The energy beam splitting means 60 opérâtes in conjunction with a splitting control mechanism (not shown) which ensures that each directed energy beam 62 emîtted from the energy beam splitting means 60 is directed, simultaneously, onto a different exposed surface 40 of a layer of powder 38.

[0075] In the embodiments shown in Figure 2 to 5, five supply hoppers 36 are used to deposit five layers of powder 38 onto the operative surface 34 simultaneously. This yields a five-fold increase in printing productivity levels compared to the conventional printing apparatus and methodology shown in Figure 1.

[0076] It will be appreciated, however, that an alternative number of supply hoppers may be used in the présent invention (for example, ten supply hoppers). More generally, «

N supply hoppers (where N > 2) may be used for simultaneously depositing N layers of powder, leading to an N-fold increase in printing productivity.

[0077] The energy source 44 or sources 56 used in the présent invention can comprise any one of a laser beam, a collimated lîght beam, a micro-plasma welding arc, an électron beam, a particle beam or other suitable energy beam.

[0078] In embodiments of the invention that make use of électron beam energy sources, the printing apparatus 30 (including the operative surface 32) may be contained and operated wholly inside a vacuum chamber to facilîtate propagation of the électron beam onto the layers of powder.

[0079] Alternatively, the energy source 44 may comprise a charged particle propagation apparatus that has been conceived by the applicant, which will obviate the need for housing the entire printing apparatus 30 inside a vacuum chamber.

[0080] Referring to Figure 6, there is shown a particle propagation apparatus 64 which forms a further aspect of the présent invention.

[0081] The particle propagation apparatus 64 comprises a generator 66 comprising a vacuum chamber 68. Inside the vacuum chamber 68, there is disposed a gun 70 for dischargîng a charged particle beam 72. The gun 70 may, for example, comprise a highpowered 150kW électron beam gun.

[0082] As shown in the Figure, the charged particle beam 72 is discharged from within the vacuum chamber 68 and out of the vacuum chamber 68 through a beam exit 74 disposed in a wall 76 of the vacuum chamber 68.

[0083] A région of higher pressure 78 adjoins the vacuum chamber 68 which is maintainable at a pressure greater than a pressure of the vacuum chamber 68. Preferably, the région of higher pressure 78 will be maintained at atmospheric pressure.

[0084] A plasma interface 80 is disposed at the beam exit 74 that comprises a plasma channel 82. Preferably, the plasma channel 82 is substantially aligned with the beam exit 74 such that the particle beam 72 may pass through an elongate length of the plasma channel 82.

[0085] The plasma channel 82 has a first end 84 and second end 86 and a plurality of electrode plates 88 are disposed between the first end 84 and the second end 86. Each electrode plate 88 has a central aperture (not shown) coaxially aligned with the plasma channel 82 which the particle beam 72 may pass there through.

[0086] Each electrode plate 88 is separated from the others in the plurality by an insulator 89 disposed between adjacent electrode plates 88. Each insulator 89 also has a central aperture (not shown) coaxially aligned with the plasma channel 82 which the particle beam 72 may also pass there through. Each insulator 89 is made from a material having electrical insulating properties such as, for example, aluminium oxide, highdensity polyethylene, mica or polytetrafluoroethylene. The dimensions of each insulator 89 is adapted to minimise the distance between adjacent électrodes plates 88 while preventing electrical interférence the électrodes plates 88.

[0087] In the exemplary embodiment shown in Figure 6, the plasma channel 82 comprises nine electrode plates 88. However, it will be appreciated that an alternative number of plates may be used, provided always that a minimum of three plates is used.

[0088] In use, a plasma-forming gas, such as hélium, argon or nitrogen, that is highly ionized and contains positive ions and électrons, is injected into the plasma channel 82 X using an injection means known in the art such as, for example, a supply tube and mechanical gas pump (not shown).

[0089] Once the gas has sufficiently filled the plasma channel 82, electrical currents are applied to the electrode plates 88 causing a first plasma to form at the first end 84 of the plasma channel 82 and be maintained at a high pressure, which may be atmospheric pressure, for example. This may be achieved by supplying a high voltage, low current power supply to a first plate 90, thus causing the first plate 90 to form a cathode, followed by supplying a low voltage, high current power supply to a second plate 92, thus causing the second plate 92 to form an anode and thereby boundîng a plasma between the first plate 90 and the second plate 92.

[0090] A pre-deteimined sequence of electrical currents are then applied selectively to the other electrode plates 88 in the channel 82 thereby causing the first plasma to move from the low pressure région at the first end 84 of the plasma channel 82 to the high pressure région at the second end 86 of the plasma channel 82.

[0091] After the first plasma has propagating through the plasma channel 82 towards its second end 86 by a sufficient length, further electrical currents may be applied to the first and second electrode plates 90,92 causing a second plasma to form at the first end 84 of the plasma channel 82. The second plasma is then, similarly, propagated through the plasma channel 82 towards its second end 86 by selectively applying a sequence currents to the other electrode plates 88.

[0092] This process may be repeated to cause further plasmas to be generated and travel simultaneously along the elongate length of the plasma channel 82 in succession. The movement of the, or each, plasma through the plasma channel 82 towards its second end 86 in this manner causes a substantial pumping down to occur at the beam exit 74. This process can be used to create the vacuum in the vacuum chamber 68 rapidly and maintain the same once formed.

[0093] Further, the sequence of currents applied to the electrode plates 88 may be adapted such that a non-plasma région is formed between two plasmas that are traveling simultaneously along the elongate length of the plasma channel 82. Λ

[0094] In embodiments of the plasma channel 82 comprising a high number of electrode plates 88, a high number of plasmas and corresponding non-plasma régions may travel simultaneously along the elongate length of the plasma channel 82.

[0095] The, or each, non-plasma région may contain residual gas from the vacuum chamber. This substantially increases the power and effectiveness of the pumping down that is performed at the beam exit 74.

[0096] The particle beam 72 propagates from the vacuum chamber 68, through the beam exit 74 and through the, or each, plasma that may be present in the plasma channel 82, without dispersion or atténuation, and onto a workpiece 94 disposed in the région of higher pressure 78. This arrangement provides for substantially unhindered transmission of charged particles from the gun 70 to the workpiece 94.

[0097] Each plasma that is formed within, and propagating through, the plasma channel 82 may reach a high température of approximately 15,000° K. Stabilizing means are used to stabilize each plasma preferably by providing a lower température boundary around each plasma. The stabilizing means may comprise a plurality of coaxially stacked together annular cooling plates 96 with the plates 96 collectively having a central bore which defines the plasma channel 82 therethrough.

[0098] Cooling fluid or gas is circulated under pressure through each of the cooling plates 96 for removîng heat therefrom for stablishing a lower température boundary around each plasma. During operation, heat is transmitted radially outwardly by conduction through the cooling plates 96 and is removed by the cooling fluid circulating therethrough. Accordingly, by circulating the cooling fluid or gas around the plasma channel 82, heat is removed therefrom for stabilising each plasma.

[0099] Referring now to Figures 7 to 9, there is shown a schematic représentation of a 3D printing method and apparatus 100 according to a further embodiment of the present invention. The apparatus 100 comprises a substrate 102 having an operative surface 104 on which a printed object is to be fabricated by 3D printing.

[00100] The apparatus 100 further comprises a single supply hopper 106. The supply hopper 106 is adapted such that it dispenses powder onto a heap 108 on the operative surface 104.

[00101] As shown in Figure 7, in use the heap 108 is, initially, small and contains a corresponding small volume of powder. As additional powder is dispensed from the supply hopper 106, the size of the heap 108, and the corresponding volume of powder that the heap 108 contains, increases in a commensurate manner, as is illustrated by Figure 8.

[00102] Like the embodiments illustrated in Figures 2 to 5, in this embodiment of the invention the supply hopper 106 is also configured to deposit multiple layers of powder onto the operative surface simultaneously. To achieve this, as the powder is progressively dispensed from the supply hopper 106 onto the heap 108, the powder flows down an extemal surface 110 of the heap 108 in a staggered manner such that a plurality of cascading layers of powder 112 form and flow simultaneously over the extemal surface 110.

[00103] In Figure 7, the heap 108 is shown with two layers of powder (112.1, 112.2) that hâve formed and are flowing simultaneously along the extemal surface 110. In Figure 8, the heap 108 is shown with four layers of cascading powder (112.1, 112.2, 112.3 and 112.4) that hâve formed and are flowing simultaneously on the extemal surface 112. It will be appreciated, however, that at any point in time during use of the apparatus 100, an alternative number of cascading powder layers 112 may be layered and be flowing simultaneously along the extemal surface 110 of the heap 108.

[00104] The cascading layers of powder 112 are formed as a resuit of one or more means operating in isolation or unison. For example, the apparatus 100, preferably, comprises a flow control mechanism that causes powder to be released from the supply hopper 106 in a staggered manner thereby causing the powder to form into the cascading layers 112 as it flows simultaneously down the extemal surface 110. o?

[00105] Alternatively, the powder is formed into the cascading layers 112 as a resuit of one or more physical properties of the particles comprising the powder such as, for example, the surface roughness, adhesion and/or friability of the particles.

[00106] Dispensîng the powder in cascading layers 112 provides that at any point in time during operation of the apparatus 100, each individual layer of powder 112 on the heap 108 has an extemal surface 114 that is, at least in part, not covered by an adjacent layer of powder. Referring to Figure 8, for example, whilst the first layer of powder

112.1 shown in the Figure is substantially covered by the second 112.2, third 112.3 and fourth 112.4 layers of powder, at least part of its extemal surface 114.1 remains uncovered.

[00107] The apparatus 100 further comprises an energy source 116. An energy beam 118 is emitted from the energy source 116 and is directed onto the exposed surfaces 114 of each layer of powder 112 on the heap 108 to melt or sinter the powder selectively, thereby forming part of the 3D object.

[00108] The energy beam 118 is applied to the heap 108 progressively as the heap 108 increases in size in order to incrementally build up the 3D object until it is completed.

[00109] As shown in Figure 9, the energy source 116 may be adapted to operate as a raster such that while the layers of powder 112 simultaneously flow down the surface 110 in a cascading manner, the orientation of the energy source 116 is adjusted such that the energy beam 118 is directed selectively onto each of the exposed surfaces 114 in a sequential manner.

[00110] For example, the energy beam 118 may initially be directed onto a first exposed surface 114.1 of the first layer of powder 112.1. After the first exposed surface

114.1 has been sufficiently worked on by the energy beam 118, the orientation of the energy source 116 is then adjusted such that a second energy beam 120 is directed onto a second exposed surface 114.2 of a second layer of powder 112.2. This process is repeated for the third and fourth powder layers 112.3, 112.4.

[00111] In embodiments where the energy source 116 opérâtes as a raster, the energy beam 118 may be applied to each exposed surface 114 of each powder layer 112, as necessary, for a sufficient period of time such that the powder is heated or energised causîng it to melt or sinter before the energy source 116 is re-orientated for the next layer 112.

[00112] Altematively, the energy beam 118 may be applied to each exposed surface 114 of powder for a lesser period of time such that the powder is only partially heated or energised before the energy source 116 is re-orientated for the next layer 112. In this embodiment, the energy source 116 will be cycled repeatedly through the plurality of layers 114 in a rapid manner such that additional energy is applied to each exposed surface on each itération. This causîng the température or energy of each surface that is worked on to increase incrementally until it reaches a point at which the powder melts or sinters.

[00113] The apparatus 100, preferably, also comprises a scanning means (not shown) adapted to déterminé a position, velocity and/or size of one or more particles comprised in the powder 108 when the, or each, particle is travelling from the supply hopper 106 to the heap 108.

[00114] The scanning means is, preferably, also adapted to measure the airbome density of the powder.

[00115] The scanning means is, preferably, also adapted to measure a volume of powder deposited on the heap 108.

[00116] The scanning means is, preferably, also adapted to measure a level or profile of the powder deposited on heap 108.

[00117] The scanning means may make use of an ultra-sonic, laser or other appropriate known scanning or positioning technology.

[00118] Information and data collected using the scanning means is used, in conjunction with control electronics and software, to déterminé the volumétrie flow rate, direction and/or velocity of powder emitted from the supply hopper 106 and/or the direction and intensity of the energy beam 118 to optimise fabrication of the part being printed.

[00119] The energy source 116 can be any one of a laser beam, a collimated light beam, a micro-plasma welding arc, an électron beam, a particle beam or other suitable energy beam.

[00120] In embodiments of the invention that make use of électron beam energy sources, the printing apparatus 100 (including the operative surface 104) may be contained and operated wholly inside a vacuum chamber to facilitate propagation of the électron beam onto the layers of powder.

[00121] Altematively, the energy source 116 may comprise the charged particle propagation apparatus described above, which will obviate the need for housing the entire printing apparatus 100 inside a vacuum chamber.

[00122] Dispensing multiple powder layers 114 onto the operative surface 104 simultaneously, and operating on the layers, in this manner substantially increases in printing productivity levels compared to the conventional printing apparatus and methodology shown in Figure 1.

[00123] Referring to Figure 10, there is shown a further embodiment of the présent invention. This disclosed embodiment is identical in ail material respects to the embodiment illustrated in Figures 7 to 9 save that the printing apparatus 100 comprises multiple energy sources and, in particular, a first 116 and a second 122 energy source. The energy sources 116,122 are adapted to émit two energy beams 118, 124 simultaneously onto exposed surfaces 114.1,114.2 of the first and second layers of powder 112.1,112.2. The energy sources 116,122 work on the cascading powder layers 114 comprised in the heap 108 two at a time simultaneously.

[00124] Whilst two energy sources 116,122, and two corresponding energy beams 118,124, are used in this embodiment, it will be appreciated that N number of energy sources and energy beams may be used to simultaneously work on N layers of powder 114 in the heap 108 simultaneously.

[00125] Referring to Figure 11, there is shown a further embodiment of the présent invention. The disclosed embodiment is also identical in ail material respects to the embodiment illustrated in Figures 7 to 9 save that the supply hopper 106 is configured to deposit powder substantially onto individual sides, or individual parts, of the powder heap 108 in sequence or succession.

[00126] For example, in the Figure the supply hopper 106 is shown depositing powder onto a far right side 126 of the powder heap 108 thereby forming first and second cascading layers of powder 112.1 and 112.2 at the right side 126. The energy source 116 is configured to direct its energy beam 118 onto respective exposed surfaces 114.1,114.2 of the two powder layers 112.1 and 112.2 to melt or sinter the powder selectively to fabricate part of the 3D object at the right side 126.

[00127] The supply hopper 106 and energy beam 118 will then, subsequently, be directed onto further individual sides or parts of the power heap 108 in order to form further cascading layers and parts of the 3D object at the sides or parts until the 3D object has been formed completely.

[00128] The scannîng means described above is used to measure, in real-time, the shape, form, surface characteristics and/or relative positions of the individual powder layers 112.1, 112.2 being formed on sides of the heap 108. This information is used by the apparatus 100, in conjunction with control electronics and software, to détermine and continuously control the direction and power of the energy beam 118, and the corresponding position of résultant weld pools, such that individual layers 112.1, 112.2 formed are melted, sintered and/or fused correctly in order to fabricate the 3D object.

[00129] Referring to Figures 12(a) and 12(b), there is shown a further embodiment of the printing apparatus 30 according to the present invention. In this embodiment, the supply hoppers 36 and control mechanism of the printing apparatus 30 are configured to deposit layers of powder 38 simultaneously onto the operative surface 34 in a curved path. This provides that the embodiment is particularly adapted to fabricate 3D objects having a generally circular or curved form.

[00130] Preferably, the multiple layers of powder 38 are deposited in a stepwise or helical manner. This provides that when the supply hoppers 36 hâve finished a complété rotation and the batch of layers 38 deposited hâve been worked on by the energy source <·Χ

2l sufïïciently to form a first layer of the 3D object, then the supply hoppers 36 will subsequently deposit the next batch of multiple layers immediately above the previous batch to form the next layer of the object incrementally.

[00131] The embodiment depicted in the Figures has four supply hoppers 36 that are configured to deposit four layers of powder 38 simultaneously in a curved path along the rotational direction indicated by reference numéral 128. This advantageously yields a four-fold increase in printing productivity for 3D objects having a circular or curved form compared to prier art printing apparatuses and methods. It will be appreciated that, more generally, N supply hoppers (where N > 2) may be used for simultaneously depositing N layers of powder in a curved path, leading to an N-foId increase in printing productivity for circular or curved objects.

[00132] Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the présent invention.

[00133] In the daims that follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims (17)

1. A printing apparatus for printing a three-dimensional object, comprising:

an operative surface;

an energy source for emîtting at least one energy beam onto the operative surface; and a powder dispensing mechanismfor depositinga plurality oflayers of powder onto the operative surface, the powder being adapted to be melted by the energy beam, wherein the powder dispensing mechanismis configured to deposit the layers of powder such that the layers of powder are formed simultaneously on the operative surface;

each layer of powder in the plurality overlays a subjacent layer of powderin the plurality or, for the bottommost layer in the plurality, the operative surface; and the layers of powder are formed in a staggered manner such that, when being worked on by the energy beam, each layer of powder in the plurality has an exposedtopmost surface section that is not covered by an overlying layer of powder; and wherein the energy source is configured to émit anenergy beam onto each of the exposedsurface sections simultaneously or sequentially.

2. The printing apparatus according to claim 1, wherein the powder dispensing mechanismcomprisesa plurality of powder-dispensing supply hoppers and a supply control mechanism, the supply hoppers and control mechanism being configured to dispense powder from each of the supply hoppers onto the operative surface to form the plurality of layersof powder simultaneously.

3. The printing apparatus according to claim 1 or 2, wherein the printing apparatus further comprises an energy beam splitting means for splitting and directing an energy beam into two or more separate energy beams.

4. The printing apparatus according to any one of preceding daims, wherein the supply hoppers and control mechanismareconfigured to deposit the plurality of layers of powder onto the operative surface in a curved path.

5. The printing apparatus according to claim 1, wherein the powder dispensing mechanismcomprises at least one supply hopper, the or each supply hopper beîng adapted to dispense powder onto a heap on the operative surface in a manner such that a plurality of cascading layers of powder form and flow simultaneously over an extemal surface of the heap, each layer of powder having an exposed surface that is, at least in part, not covered by asuperjacent layer of powder while the layer is being formed.

6. The printing apparatus according to claim 5, wherein the energy source emits energy beams onto two or more layers of powder on the heap simultaneously.

7. The printing apparatus according to claim 5, wherein the energy source emits energy beams onto individual layers of powder on the heap in a sequence.

8. The printing apparatus according to any one of daims 5 to 7, wherein the printing apparatus further comprises a scanning means for determining a position, velocity and/or size of one or more particles comprised in the powder when the, or each, particle is travelling from the or each supply hopper to the heap.

9. The printing apparatus according to claim 8, wherein the scanning means is adapted to measure an airbome density of the powder travelling to the heap.

10. The printing apparatus according to claim 8 or 9, wherein the scanning means is adapted tomeasure a volume of powder deposited on the heap.

11. The printing apparatus according to any one of claims8 to 10, wherein the scanning means is adapted to measurea shape or profile of the heap.

12. The printing apparatus according to any one of daims 8 to 11, wherein the scanning means is adapted tomeasure a shape, form, relative position or one or more surface characteristics of the layers of powder formed on the extemal surface of the heap.

13. The printing apparatus according to any one of preceding daims, wherein the energy source is configured to émit a laser beam.

14. The printing apparatus according to any one of claims source is configured to émit a collimated light beam.

to

12, wherein the energy

15. The printing apparatus according to any one of claims source is configured to émit a micro-plasma welding arc.

to

12, wherein the energy

16.

The printing apparatus according to any one of claims 1 to

12, wherein the energy source is configured to émit an électron beam.

17. A method for printing a three-dimensional objecte the method comprising the steps of:

depositing a plurality of layers of powder simultaneously onto an operative surfacesuch that each layer of powder in the plurality overlays a subjacent layer of powder in the plurality or, for the bottommost layer in the plurality, the operative surface;

and the layers of powder are formed in a staggered manner such that, when being worked on by an energy beam, each layer of powder in the plurality has an expos ed topmost surface section that is not covered by an overlying layer of powder, using an energy source to émit an energy beam onto each of the exposed surface sections simultaneously or sequentiallyto melt the powder and form part of the three-dimensional object; and repeating the steps above until the three-dimensional object is completely fonmed.