Manufacturing apparatus and method

Abstract

A multi-material three-dimensional printer, comprising in combination: a build plate; a first powder dispenser movable over at least portions of said build plate to place a first powder layer above said build plate; a binder jet movable over at least portions of said build plate to place binder and bind the first powder together in locations where the binder is placed; and a device consisting of a cutter that produces a cut in the first powder.

Description

[0001] MANUFACTURING APPARATUS AND METHOD

[0002] 1 TECHNICAL FIELD

[0003] The following invention relates to the printing of three-dimensional items and associated printing methods which print with multiple different materials. More particularly, this invention relates to three-dimensional printers and methods which utilise multiple different materials placed in different parts of a layer, or layers, being formed.

[0004] 2 BACKGROUND

[0005] Advanced manufacture, specifically additive manufacture, can increase industrial productivity and competitiveness by reducing the time required to bring new products to the marketplace and by providing for flexible manufacture of products that cannot economically and robustly be produced by other means, and by providing a range and control of the materials used within the parts. Additive manufacturing holds enormous promise as a manufacturing technique because it replaces the tooling necessary for conventional techniques with a CAD / CAM system directly driving the fixing of material into an object defined in the CAD file.

[0006] All the basic approaches to additive manufacturing are designed to use a single type of material for any portion of an object, and for any object created with the printer. Additive manufacturing printers based on binder jetting hold the greatest promise in terms of flexibility in the materials that are usable, and in the potential for increasing productivity substantially over other types of printers.

[0007] Additive manufacturing, commonly referred to as 3D printing, is a term which encompasses several categories of processes by which 3D objects are formed or "printed". The 3D objects are generally built-up layer by layer, and the processes differ in the way that the layers are formed and in what they are made from.

[0008] Some processes entail polymerising or curing liquid material. For example, in vat photopolymerisation, a platform is lowered into a vat of liquid polymerisable material (e.g. epoxy acrylate resin) so that it is slightly below the surface. Laser radiation is used to polymerise and harden selective parts of the layer above the platform. The platform is then lowered slightly so that a new liquid layer is at the surface (this may be made uniform by using a levelling or coating blade) and the polymerisation process is repeated. This procedure of lowering, coating and polymerising is repeated layer by layer until the desired three-dimensional structure has been formed. The platform may then be raised and the product removed and processed further. Postprocessing typically involves the removal of support structures (which may be formed during the polymerisation steps) and any other residual material, and then high temperature curing following by finishing, e.g. sanding of the product.

[0009] Some other processes entail forming each layer of a 3D structure by extruding a plastic or polymer material (or, less commonly, other material). This is known as extrusion deposition or fused deposition modelling (FDM). Material, e.g. a polylactic acid resin, is fed to an extruder where it is heated and extruded through a nozzle which moves in X and Y directions. The selectively deposited material solidifies on cooling. As with vat polymerisation methods, the structure usually rests on a build platform which typically moves downwards between the deposition of each layer, and support structures are typically required, particularly for overhanging parts of structures. Such extrusion methods are amongst the most common 3D printing processes and used widely in consumer 3D printers.

[0010] Another category of additive manufacturing is material jetting which is similar to extrusion deposition in that material is deposited via a nozzle which moves in X and Y directions. Instead of being extruded, the material is jetted onto a platform. The material (e.g. wax or polymer) is applied as droplets using a print head, similar to conventional two-dimensional inkjet printing. The droplets solidify and then successive layers are applied. Once the structure is formed it may be subjected to curing and post-processing. As with other methods discussed above, support structures may be incorporated during the procedure and then removed during post processing. Powder bed fusion (PBF) methods entail the selective binding of granular materials. This can be done by melting and fusing together part of the powder or particles of a layer of material, then lowering the bed, adding a further layer of powder and repeating the melting and fusing process. The unfused powder around the fused material provides support so unlike some methods discussed above it may not be necessary to use support structures. Such methods include direct metal laser sintering (DMLS), electron beam melting (EBM), selective heat sintering (SHS), selective laser melting (SLM) and selective laser sintering (SLS) . In view of the types of materials which are compatible with such processes (including metals and polymers), functional high strength materials can be manufactured.

[0011] Binder jetting (also known as ink jetting) methods are similar to powder bed fusion methods in that they use layers of powder or particulate material. However, conventional binder jetting methods differ from powder bed fusion methods in that the powder is not initially fused together but instead is held together with a binder which is jetted onto the structure from a print head. The binder may be coloured, and the colour may be imparted to the powder thereby allowing colour 3D printing. Typically, a binder is applied in a specific pattern to a layer of powder, and then the steps of applying a layer of powder and selectively applying binder are repeated.

[0012] In general, binder jetting entails the use of binder as a sacrificial material which is altered or removed in a post-processing step. This is because the adhesive binder typically imparts enough mechanical strength (termed "green strength") to enable the structure to be self-supporting and maintain its shape as it is built up, and to withstand mechanical operations during manufacture, but not enough strength to be functional for the intended end use. Thus, the structure is usually subsequently heated to remove the binder (de-binding process) and to fuse the build material together in a post-processing step to ensure that the product is fit for purpose which may include load-bearing or other applications.

[0013] In general, binder jetting utilises one material powder which is built layer by layer, however, this limits the range of resulting materials that can be formed even when using multiple inks.

[0014] Binder jetting is also referred to as "ink jetting", the "drop-on" technique, "powder bed and inkjet 3D printing", or sometimes just "3D printing", though as summarised here there are many other different types of 3D printing. The binder used in binder jetting is generally liquid and is often referred to as "ink" in view of the inkjet application process. 2.1 DEFINITIONS

[0015] Some definitions of standard terms used in this document are:

[0016] Functional material: A material specifically selected for its functional properties. E.g., resistivity of a certain value enables a specific cross-sectional-area to be used.

[0017] Non-sacrificial binder: Refers to a component of the ink and / or binder which provides some function to the green or brown part but is intended to remain in the final part. It may provide additional useful materials properties.

[0018] Organometallic: Compound / molecule containing at least 1 metal - carbon bond.

[0019] Powder bed: A bed of powder comprising a plurality of particles made up of the desired final part material. Particles are joined together via printed binder to produce the 3D green or brown part.

[0020] Hybrid manufacturing: Utilising both additive and subtractive manufacturing methods.

[0021] Debinding: A heat treatment or part of the sinter cycle where the binder is removed from the green part - ideally as sintering begins.

[0022] Green part: The part (also known as article) as printed. Usually comprised of weakly held together powder bed particles with significantly lower strength than the bulk material.

[0023] Brown part: Heating the green part above a first temperature to remove the binder and generate a brown body part; and when the binder has been crosslinked (or reacted) increasing the part strength compared to the green part. May also refer to where a reactive binder ink has undergone its reaction.

[0024] Ink: The complete liquid formulation that is jetted from the inkjet heads. May include, but not be limited to, carrier, binder, reactive components, particles, gels, viscosity modifiers, surface tension modifiers, anti-flocculation agents, pH modifiers, etc.

[0025] Binder: The component of the ink that causes bed particles to become joined together during the printing process. This can be achieved by deposition of the target print material (i.e. the same material as the powder bed) into the powder bed or by the addition of a different material, such as a polymer, which temporarily joins particles together until sintering.

[0026] Precursor: A chemical component of the ink that has been selected based on its reaction products. E.g., a metal salt or an organometallic compound used to deposit the metal atom after undergoing its reaction.

[0027] Particles: Solid material within the ink used to fill volume in the powder bed, provide reaction surfaces for the binders and or precursors, and to increase the final sintered volume of the part. Particles may be comprised of the bulk target material or an alternative material if specific functionalisation is required (e.g., oxide particles printed onto a metal powder bed to form an ODS alloy).

[0028] Solvent: Any substance capable of dissolving another substance and forming a solution.

[0029] Carrier or carrier vehicle: Fluid used as the bulk component in the ink (by volume) - generally chosen for its properties as a solvent and its evaporation properties when printed.

[0030] Catalyst: A substance used to change the activation energy of a reaction, whilst not being consumed during the reaction.

[0031] Non-binding component: Any component of the ink which does not take part in joining the bed powder particles together after printing.

[0032] Heat treatment stage: A single part of a heat treatment cycle - example cycle broken into 7 stages: 1) loading and atmosphere preparation. 2) ramp up to 1st hold temperature. 3) Hold at 1st temperature for set time. 4) ramp up to 2nd hold temperature. 5) hold at 2nd temperature for set time. 6) cool to unloading temperature. 7) unload.

[0033] Jetting: The controlled ejection of ink from a nozzle in an inkjet head.

[0034] Multiple nozzles: Concerning an inkjet head containing more than one nozzle for ejection of ink.

[0035] Different material delivery methods: The simplest way to deliver a new material is through the printhead. As most of the complicated work is being done in / by the binder, adding extra materials here opens up many more options than purely powder-based methods. Changing the powder bed is still important, as it allows bulk material changes. Voxel control over the powder composition will be the deciding factor in true bulk multi-materials.

[0036] Permeability control: Permeability is the ability of a substance to allow a fluid or gas to pass through. During printing onto a powder bed, the permeability of the ink can be controlled to reduce or increase the distance from the point of drop impact that the ink spreads. This can be controlled during ink formulation by altering either the viscosity or wettability of the ink. Further control can be achieved through control of the powder bed particle surfaces, which can be functionalised to increase or reduce wetting of the ink. Control over the binder wicking and spreading and how it travels through the powder bed. Different materials may produce different wetting characteristics, which are considered. Additional control over the binder wicking and spreading can be achieved by selecting appropriate materials

[0037] Control of enthalpy: Control of ink formulation and material composition used to increase or decrease the reaction rate or reaction temperature at which physical or chemical reactions within the printed part take place. These reactions include, but are not limited to, sintering reactions, metal deposition from the ink, degassing reactions, etc.

[0038] Materials interface: The location where two or more materials are joined. Interfaces can be abrupt (i.e. a transition from one material to another over a small distance), graded (i.e. a gradual transition from one material to another over a larger distance, where the composition of material A reduces continuously or via steps from 100% to 0% and the composition of material B increases as the inverse of material A from 0% to 100%), coherent (i.e. where a similar and aligned crystal structure continues across the interface. Coherent interface can be either strained [with lattice mismatch] or unstrained [without lattice mismatch]), incoherent (where the crystal structure across the interface abruptly changes from one structure to another), bound (where the materials either side of the interface are able to support load) or unbound (where the materials either side of the interface are unable to support load).

[0039] Simultaneous sintering of dissimilar materials: Different materials have different required temperatures for sintering, primarily dependant on their melt temperature. Introduction of nanoparticles of specific sizes can lower the sintering temperature of the higher melt temperature material to bring it into the same range as the lower melt temperature material.

[0040] Ligand: An ion or molecule attached to a metal atom by coordinate bonding.

[0041] Particle size and shape: Particles can be contained in both the ink (nano and micro particles) and in the powder bed (generally microparticles) . Particle shapes may be, but not limited to, spherical, nodular, lenticular, 3D primitive (tetrahedra, cubic, cylindrical, etc), etc. Particle sizes for spherical or near-spherical particles are given as radii or diameters. For collections of particles a distribution of diameters is normally used, with D10, D50 and D90 values given to describe the shape of the distribution.

[0042] Surface control (coating particles): Particles can be coated, or surface treated to alter the way they interact with fluids. Processes to achieve this include, but are not limited to, fluidised-bed atomic layer deposition, plasma treatment, fluidised-bed chemical vapour deposition, and solution processing. These, and other processes alter the surface chemistry of the outermost surface (to depths varying from <lnm up to several pm) and change the wettability, increasing or reducing the oleo / hydrophobicity, and well as the altering the overall contributions of the dispersive and polar components of the surface energy.

[0043] Changing a blend within a layer: The composition or particle size distribution within a single layer can be changed by using a powder dosing mechanism to deliver different powder materials or different powder size distributions to specified locations in the layer. This could be used to locally increase or decrease the density of that area, or to print multi-materials, or multi-material gradients within a single layer. The ink (type / drop volume / composition) delivered to the same area could either remain constant or could change (type / drop volume / composition) depending on the final material requirements.

[0044] Inter-layer steps: Various treatments can be performed on the upper surface of the powder bed after each layer is completed. These could be performed to degas the surface every layer, to minimise gas evolution and bubble formation during sintering, or to react the active material and increase the green part strength and part density to allow easier handling of the green part. Treatments include, but are not limited to, UV exposure, IR exposure, plasma treatment, atmospheric compositional changes. Depowdering stage: The removal of unbound powder and support / sacrificial powder prior to consolidation.

[0045] Slurry: An extruded material.

[0046] Selective aerosol: A controllable placement of a thin coating of material onto a layer by way of a pressure jet.

[0047] A wound electrical transformer: A electrical device consisting of a winding formed of conductive coils often around a core of material with a high magnetic relative permeability such as iron.

[0048] Bound powder: Powder that has come into contact with the ink binder.

[0049] Unbound powder: Powder that has not come into contact with the ink binder.

[0050] End-turn: traditional radial flux electric motor designs use the conductor parallel to the rotor axle to generate torque, but the winding needs to return to complete the coil requiring the use of end windings. As these end windings (also called end-turns) do not contribute to torque generation, they only add to the overall length of the winding which increases its resistance. They also increase the axial length of the overall motor.

[0051] Skin effect: Is only seen in AC applications and is a phenomenon wherein the electrons preferentially migrate closer to the outside surfaces of the conductor rather than in the centre of the core. This effect is magnified at higher frequencies, typically above 1 kHz.

[0052] Fugitive material: Substance changed during or after a chemical process, becoming partially inert or deactivated. May be used as temporary support material which is removed after the printing stage.

[0053] 3 SUMMARY

[0054] A first aspect is a multi-material three-dimensional printer, comprising in combination: a build plate; a first powder dispenser movable over at least portions of said build plate to place a first powder layer above said build plate; a binder jet movable over at least portions of said build plate to place binder and bind the first powder together in locations where the binder is placed; a device consisting of a cutter that produces a cut in the first powder.

[0055] A second aspect consists of a first powder remover which removes the unbound powder of the current or multiple layers.

[0056] A third aspect provides a cut in the first powder which is adjacent to the bound powder.

[0057] A fourth aspect consists of a flattening surface to flatten the bound powder as the cutter moves.

[0058] A fifth aspect provides a remover to remove unbound powder local to the cutter.

[0059] A sixth aspect where the binder jet consists of multiple jet nozzles which can jet the same or different inks.

[0060] A seventh aspect where the cutter takes the form of a range of shapes to create a range of different interface profiles.

[0061] An eighth aspect where the cutting device can score into layer rather than fully cut.

[0062] A ninth aspect where the cutting device can cut through multiple powder layers.

[0063] A tenth aspect where the printer can start bulk removal of powder before, or after, all cutting on the current layer has completed and / or all ink jetting onto the current layer has completed.

[0064] An eleventh aspect consists of a second powder dispenser movable over at least portions of said build plate to place a second powder layer above said build plate, the second powder different from the first powder.

[0065] A twelfth aspect consists of a second powder that is a temporary structural filler.

[0066] A thirteenth aspect consists of an extruder dispenser movable over at least portions of said build plate used to place a slurry above said build plate.

[0067] A fourteenth aspect consists of a slurry placed in one or more areas where the unbound powder was removed in the current or previous powder layer (s).

[0068] A fifteenth aspect consists of the slurry having material deposited on to it by selective aerosol.

[0069] A sixteenth aspect where the cutting device rotates in any axis.

[0070] A seventeenth aspect where the cutting device depth can be changed while cutting.

[0071] An eighteenth aspect where the cutting device is incorporated into the ink jetting head.

[0072] A twentieth aspect where the printer consists of an energy source such as a UV source or a heater, to selectively cure the binder and / or extruded slurry.

[0073] A twenty-first aspect where the binder jet uses multiple inks to create sections of high insulation and sections of high conductivity.

[0074] A twenty-second aspect where printer prints coil windings where the end-turn geometry has increased surface area while maintaining cross-sectional area. A twenty-third aspect where the printer prints coil windings with high conductor utilisation and higher fill factors.

[0075] A twenty-fourth aspect where the printer prints coils as multistrand either / or braided either / or Litz windings.

[0076] A twenty-fifth aspect where the printer prints coil windings where the conductor material properties are modified at the microstructure to reduce skin effect.

[0077] A twenty-fifth aspect the slurry is printed with laminated layers with optimised planes and structures to reduce magnetic losses.

[0078] A twenty-sixth aspect where the cutting device cuts the bound material.

[0079] A twenty-seventh aspect is a method for multi-material three-dimensional printing, including the steps of: dispensing a first powder in a first powder layer along a major axis over a build plate; first applying binder to combine with portions of the first powder layer; cutting along the interface between the bound and unbound powder; removing first powder from portions of the first powder layer not contacted by the binder.

[0080] A twenty-eighth aspect contains the step of dispensing a second powder in a second powder layer over the build plate, the second powder different from the first powder.

[0081] A twenty-ninth aspect contains the step of extruding material into the sections of the first powder layer from which the unbound powder was removed.

[0082] A thirtieth aspect wherein said first applying step includes jetting at least one binder from a print head.

[0083] A thirty-first aspect wherein the cutting is performed by a device that also smooths the bound powder local to the cutting device.

[0084] A thirty-second aspect wherein the cutting is performed by a device that also removes the bound powder local to the cutting device.

[0085] A thirty-third aspect cuts the bound material.

[0086] OBJECTS OF THE INVENTION

[0087] Accordingly, a primary object of the present invention is to provide a mechanism for three- dimensional (3D) printing of objects comprised of more than one material or composite material.

[0088] Another object of the present invention is to provide a binder jetting type of 3D printer capable of incorporating regions of different materials in a 3D printed object.

[0089] Another object of the present invention is to provide a 3D printer with the capability of embedding regions of fugitive materials within an object comprised largely of robust, enduring materials, so the fugitive materials can be later turned into voids in the object.

[0090] Another object of the present invention is to provide a 3D printer with the capability of embedding voids within an object comprised largely of robust, enduring materials, while there is only a tortured path, or no path at all from the empty voids to the outside surface of the printed object.

[0091] Another object of the present invention is to provide a means for creating 3D objects, directly from computer design data, from high performance engineering materials rather than materials chosen to work with a specific 3D printer process.

[0092] Another object of the present invention is to provide a 3D printer that has printing rates that are high enough to be cost competitive with conventional methods of creating objects comprised of multiple materials and void regions within the structure.

[0093] Other further objects of the present invention will become apparent from a careful reading of the included drawing figures, the claims and detailed description of the invention.

[0094] 4 BRIEF DESCRIPTION OF THE DRAWINGS

[0095] Figure 1 schematically depicts an example procedure for production using additive manufacturing.

[0096] Figure 2 schematically depicts prior art powder removal (prior to binding) and replacement of unbound layer.

[0097] Figure 3 schematically depicts prior art removal (after binding) and replacement of unbound layer.

[0098] Figure 4 schematically depicts potential negative issues of prior art methods.

[0099] Figure 5 schematically depicts a simple form of the invention using a cutting stage per layer.

[0100] Figure 6 schematically depicts a simple form of the invention using a cutting stage through multiple layers.

[0101] Figure 7 schematically depicts depositing extruded material in the volume created by removing powder after multiple layers cutting.

[0102] Figure 8 schematically depicts examples of different interface profiles and associated potential cutters.

[0103] Figure 9 schematically depicts the addition of powder flattening paddles.

[0104] Figure 10 schematically depicts the addition of cut material local removal via suction.

[0105] Figure 11 schematically depicts cuts that do not penetrate a layer.

[0106] Figure 12 schematically depicts the use of sacrificial material to back fill the volume created by removing powder.

[0107] Figure 13 schematically depicts an example hybrid manufacturing method.

[0108] Figure 14 schematically depicts a product created by the hybrid manufacturing method.

[0109] Figure 15 schematically depicts cross sections of transformer cores.

[0110] Figure 16 schematically depicts the printing of low inductance and low skin effect multistrand windings.

[0111] Figure 17 schematically depicts the printing of laminations of the transformer or motor pole cores. 5 DETAILED DESCRIPTION

[0112] In general, binder jetting utilises one material powder which is built layer by layer, however, this limits the range of resulting materials that can be formed even when using multiple inks. It is thus advantageous that two of more powders can be used on the same layer.

[0113] Also advantageous would be the inclusion of an extrusion within the powder layer thus combining multiple manufacturing processes.

[0114] The objective of the current invention is to provide a three-dimensional (3D) printer that can create fully free form, 3D objects, with regions within the object comprised of different materials, and with the capability of creating void spaces within such objects, with tortured exit pathways (or even no aperture to the outer surface of the object).

[0115] Objects created with the present invention could be complete after the printing process is complete, but more commonly, the printed object will be treated in a way to densify the powders of different materials to yield components of the object that have properties like those of the solid material from which the powder material is derived. Specifically, for example, powdered alumina ceramic will acquire the same properties as a solid piece of alumina ceramic, and powdered steel alloy will attain the same properties as a bar of that steel alloy created by conventional powder metallurgy techniques. Alternatively, the object may be treated sufficiently to just bind the particles of powder together, while removing the unbound powder material, leaving a void space, or the void spaces may be filled with another material by infusion.

[0116] The present invention utilizes certain aspects of the binder jetting systems employed on current binder jetting systems. Specifically, the present invention incorporates multiple nozzles, ink jet type heads, and associated driver electronics and computers, to dispense a binding material. The current invention may also incorporate a second similar, multi nozzle, head to dispense a different binder material, and / or a volume filling material such as a fugitive material.

[0117] The current invention also utilizes powder coating systems like those used in conventional binder jetting systems to deposit a thin layer of powder that is well controlled to thickness and powder density.

[0118] While the conventional binder jetting systems use one powder coating system to deposit a single material for the whole build, the present invention incorporates more than one powder coating system, each of which deposits a different material. Each of the multiple materials may be deposited on each layer of the object being printed, or any layer may use only one, or a subset of the total number of available materials. Each powder coating system, when it is activated, preferably deposits a uniform and layer of powder over all of the printable surface, or in some cases over only a selected portion of the printable surface that is intended to be patterned with that specific material.

[0119] To facilitate the use of multiple materials on any layer, the powder that is not bound together into the layer of the object, can be removed from the printing area prior to deposition of the next material. Each subsequent material within the layer of the printed object is completed by sequential cycles of powder deposition, patterned binder jetting, cure and removal of the excess powder. When all the materials on a layer have been deposited, bound and cured, the space between the printed object and the inkjet heads is indexed in relation to the previously completed layer to maintain the appropriate relationship between the printing surface and the printer head.

[0120] It is often desirable to change the thickness of any given layer in an object, in consideration of the necessary change in design from one layer to the next, or in consideration of the precision of the pattern needed within a given layer or section, the completed layer thicknesses and thus the amount the partially printed object is indexed relative to the print head, may be different with every completed layer. Binder jetting parameters (print passes, greyscale value, wait times, etc.) may also be changed each layer to compensate and compliment the changes in layer thickness, maintaining final part properties.

[0121] Removal of the excess powder at the end of each material deposition step provides for the application of subsequent materials in the same layer, keeps removed powders of different materials at least largely separate, eliminates the need to remove the excess powder at the end of the printing process, and in general, speeds the overall printing process. It also eliminates the support for the printed structure, and foundations for any portions of the object that were not printed in previous layers. These functions can easily be provided as needed by support structures of one of the functional materials or by a fugitive material that will be removed from the object in subsequent processing, leaving voids.

[0122] In one embodiment of the current invention, the powder coating mechanism will coat an area as wide as the build platform and move in coordination with the print head. In this embodiment each layer of powder is deposited in a single continuous operation, as the coating mechanism traverses the entire build platform. After the deposition of a layer of powder is complete, the coating mechanism retreats to allow access for the print head to the area of the build platform plate.

[0123] For every material to be used in a specific object, a separate powder deposition mechanism is provided. Each of these powder deposition mechanisms is movable to be indexed into position to perform a powder coating operation, and when that layer of powder is complete, moving to a parking spot to clear the way for the binder jet print head or a powder removal mechanism or a subsequent powder deposition mechanism for a different powder to be coated on the current layer. The separate powder deposition mechanisms could be carried together in one embodiment but caused to deposit powder (or not) in sequence.

[0124] In the present invention, 3D parts are printed in a build volume, defined by a build platform / plate that can be virtually any size ranging from a square or rectangular shape (circular, oval or other build platform shapes are also possible) a few tens of centimetres on a side to meters on a side. The build platform is controlled by the computer such that it can be moved down away from the print head as each layer is completed. The build platform serves as the foundation for the first layer of the build of one or more objects and is provided with a mechanism that ensures sufficient adhesion of the build object(s) to the platform during the printing operation and provides for easy removal of the completed object or objects after the build object(s) is complete. Because the present invention is applicable to parts of a wide range of sizes, but very often significantly smaller than the total build volume, many of the same parts, or parts of different design, but requiring the same of materials set, may be printed in a single build. Small parts may be printed in arrays such as to maximally utilize the available area of the build platform, and printed in stacks, to maximally utilize the print volume. Thus, a given build may yield from one to thousands of completed parts, of a single, or multiple designs. The print volume is defined by the area of the build platform times the maximum displacement of the build platform from the starting position relative to the print head.

[0125] Production using additive manufacturing

[0126] Figure 1 schematically illustrates an additive manufacturing process, in this example an ink jetting method. Ink jetting is an Additive Manufacturing process in which a binding liquid is selectively deposited to join powder material together to form a 3D part. An ink jetting procedure generally consists of the following steps, however, those skilled in the art will appreciate that other procedures exist:

[0127] 1. The powder material is spread over the build platform 107 using a roller 103.

[0128] 2. The print head 102 moves on an XY bar 101 and deposits the binder adhesive on top of the powder 106 where required.

[0129] 3. The build platform 107 is lowered by the model's layer thickness 108.

[0130] 4. Another layer of powder 106 is spread over the previous layer. The object is formed where the powder is bound to the liquid.

[0131] 5. The unbound powder 106 remains in position surrounding the object 104.

[0132] 6. The process is repeated until the entire object 104 has been made.

[0133] 7. Un-dosed powder is removed.

[0134] 8. The part is sintered.

[0135] In one embodiment, two inks are used. The use of these two inks in the creation of a structure may control that structure's conductive or insulative properties. In another, the roller is fixed, rotating or counter-rotating, or is replaced by a wiper.

[0136] Prior art methods of powder removal and replacement

[0137] A selective multiple powder deposition procedure generally consists of the following steps made with reference to figure 2, however, those skilled in the art will appreciate that other procedures exist:

[0138] 1. The previous layer (201) has been bound,

[0139] 2. Deposit a first layer consisting of powder one (202),

[0140] 3. Selectively remove powder in specific areas of the first layer (203),

[0141] 4. Jet ink / binder onto specific areas (204),

[0142] 5. Deposit a second layer consisting of powder two (standard methods can be employed) which will fill in specific gaps in the first layer (205),

[0143] 6. Jet ink / binder onto specific areas on the second layer which also permits permeation down to the filled sections in the first layer (205),

[0144] 7. Repeat.

[0145] The completed section of the first layer could be made of sacrificial (dissolvable) material if is intended only for supporting the next layer. In this case, the roller or wiper (shown as 103 in figure 1) would not change height from that used during the deposition of first layer.

[0146] Note that the powder type can be swapped every layer or at other multiples of layers. Note that the powder used in the single layer methods may be a mix of the two powders or a different powder.

[0147] An alternative selective multiple powder deposition procedure from prior art (US690441) consists of the following steps made with reference to figure 3:

[0148] 1. The previous layer (301) has been bound,

[0149] 2. Deposit a first layer consisting of powder one (302),

[0150] 3. Jet ink / binder onto specific areas (303),

[0151] 4. Selectively remove powder in specific unbound areas of the first layer (304) (could be through bulk vacuum),

[0152] 5. Deposit a second layer consisting of powder two (standard methods can be employed) which will fill in specific gaps in the first layer (305),

[0153] 6. Jet ink / binder onto specific areas on the second layer which also permits permeation down to the filled sections in the first layer (306),

[0154] 7. Repeat.

[0155] One negative issue excibited by most prior art methods is the accuracy of the interface between the two powders on a layer which is effected by the definition of the edge when the first powder has been removed from the selected section before the section powder (or filler) is back filled into this section.

[0156] Figure 4 image 400 show the affect of ink diffusion through the last bound layer (407) where the ink has not uniformally diffused in the vertical direction but instead has created overhangs in 407 which will be underminded when the unbound powder is removed by simple vacuum. This lead to the second powder

[0406] filling under the first bound powder layer (407).

[0157] Alternatively the diffusion can create a slope into the unbound section, which again is not the intendend interface between the two powders.

[0158] Other edge negative issues include splattering of inks near the edge which partial bind powder outside of the intended bound layer section. Simple vacuum may or may not be able to remove this.

[0159] Another negative issue with most prior art methods is in the case that an extruded slurry is used to fill the removed section of layer powder. Most extruded slurries create single layers that are multiples of the layers used by the binder jet on powder method.

[0160] Figure 4 image 401 shows the issue when a slurry fills the removed section of layer powder and sits above the layer. The slurry will have little inherent structural strength initially and tends to slump as shown by 401. Note that 407 is again the bound layer of powder described in image 400.

[0161] Those skilled in the art may believe that removing multiple layers of unbound powder before extruding the slurry would be a credible solution, however, diffusion into multiple layers exacerbates the negative issues with respect to edge accuracy described earlier with image 400. Figure 4 image 402 shows one potential negative effect of diffusion across multiple layers (409).

[0162] An additional negative issue suffered by most prior art methods is the slow speed of the process. Layer by layer selective or bulk removal of unbound (un-inked) powder by vacuum takes time including the moving of the print head away from the layer and the moving in of the vacuum device. The process of bulk removal of unbound or unrequired powder cannot take place until the ink diffusion has completed.

[0163] 5.1 Invention

[0164] The invention disclosed through this application includes a non-obvious edge cutting stage in the selective multiple powder deposition procedure.

[0165] The proposed invention consists of a selective multiple powder deposition procedure of the following steps made with reference to figure 5:

[0166] 1. The previous layer (501) has been bound,

[0167] 2. Deposit a first layer consisting of powder one (502),

[0168] 3. Jet ink / binder onto specific areas (503),

[0169] 4. Cut grove on edge of selectively bound powder (504),

[0170] 5. Selectively remove powder in specific unbound areas of the first layer (505) (could be through bulk vacuum),

[0171] 6. Deposit a second layer consisting of powder two (standard methods can be employed) which will fill in specific gaps in the first layer (506),

[0172] 7. Jet ink / binder onto specific areas on the second layer which also permits permeation down to the filled sections in the first layer (507),

[0173] 8. Repeat.

[0174] Those skilled in the art will appreciate that this cutting stage can also be incorporated in the printing design to permit more accurate interfaces between materials and also enable different interfaces which will be described later. Thus, the invention increases resolution of multimaterial methods.

[0175] An alternative version of this example would be to bind the area into which the cut will be made either by using the first ink of 503 or an alternative ink. This would provide mechanical strength for the cut and bound material right up to the edge.

[0176] Cutting multiple layers

[0177] Another embedment of the invention includes providing the cutting stage after multiple layers of powder have been deposited and bound. An example of this embodiment is given in the procedure of the following steps made with reference to figure 6:

[0178] 1. The previous layer (601) has been bound,

[0179] 2. Deposit a first layer consisting of powder one (602),

[0180] 3. Jet ink / binder onto specific areas of layer one (603),

[0181] 4. Deposit a second layer (604),

[0182] 5. Jet ink / binder onto specific areas of layer two (605),

[0183] 6. Cut grove on edge of selectively bound powder through multiple layers (606),

[0184] 7. Selectively remove powder in specific unbound areas of the first layer (607) (could be through bulk vacuum).

[0185] This method permits better control of the multiple layer edges of the voids selectively created. It also reduced the time to produce a product as the bulk vacuum phase can take place after several layers rather than after every layer. Additionally, it reduces the time by only employing the cutting device after multiple layers.

[0186] Using an extruded slurry

[0187] The selectively removed area could be filled with a second type of powder or alternatively a slurry. An example of this embodiment is given in the procedure of the following steps made with reference to figure 7 building from figure 6:

[0188] 1. Cut grove on edge of selectively bound powder through multiple layers (701),

[0189] 2. Selectively remove powder in specific unbound areas of the first layer (702) (could be through bulk vacuum).

[0190] 3. Selectively extrude material (a slurry for example) into the space produced (703).

[0191] This embedment shows how the invention permits the addition of slurry at the appropriate resolution e.g. after multiple powder layers which are required for binder jet features in part.

[0192] Extruded slurries suffered from the "slumping" problem which can be reduced by cutting and removing multiple layers of unbound powder before adding the slurry.

[0193] Powder cut and removed after multiple layers (with binder jet) will reduce the total part print time. It also creates a deeper depression which offers more support to the slurry particularly when the extruded slurry single layer height is dimensionally greater than that of the powder single layer height.

[0194] Prior art solutions suffer when considering multiple layers as binder will have defused which effects the accuracy of the edges and interfaces. Adding the cutting stage solves this by restoring the require material interface surface.

[0195] Cutter profiles

[0196] The process of employing a cutter permits many opportunities including defining the shape of the interface edge with features hard or impossible to achieve using prior art methods.

[0197] Figure 8 shows three images each with a different cutting profile. Those skilled in the art will realise that the range of possible cut profiles is huge while still linking to the essence of this invention, but only three have been shown here for brevity.

[0198] Figure 8 image 801 shows a simple straight-line profile. Image 802 shows an offset straight line, or inter-locking brick profile. Image 803 shows a contoured interface. Image 804 shows a possible cutter used to create the contour of image 803. Image 805 shows an alternative cutter that would create a similar profile but removing less material.

[0199] Alternatively, the cuter could be a rotating element for example similar to a dental drill or moving point for example similar to needle on sewing machine. Addition of paddles to smooth powder

[0200] In another embodiment the cutter could also incorporate a paddle in order to locally flatten the powder. This would reduce the disturbance from the cutting action. Figure 9 provides an example of how this may be achieved. Those skilled in the art will imagine alternatives that still link to the essence of this invention.

[0201] Image 900 shows the process of cutting in action where the cutter (905) has a paddle (906) so as not to disturb the bound material to the left of the cutter. Image 901 shows three views of the same cutter and single paddle. Front view (907), side view (908), and top view (907).

[0202] Image 903 shows the top view of a similar embedment with the addition of a second paddle. The paddles are 910 and 911 and the cutter is 912.

[0203] Removing unbound material while cutting

[0204] In another embodiment the cutter could also incorporate a local suction device to remove localised powder during the cutting process.

[0205] Figure 10 shows the front view (image 1000), the side view (image 1001), and the top view (image 1002). The following identifications and descriptions are valid for all images of figure 10. Turning to image 1002, the cutter (1008) has paddles (1007) on each side. The paddles include material guides (1006). When the cutter moves in the direction out of the page, cut material is guided by the material guides (1006) towards the suction / vacuum tube (1005) where it is removed. This localised suction feature helps to keep clear the front face of the cutter.

[0206] When the cutter moves in the direction up the page, cut material is collected by the material guides (1006) and moved towards the suction / vacuum tube (1005) were is removed. This localised suction feature helps to keep clear the rear face of the cutter.

[0207] An additional feature on the paddles (1007) is a profiling, best seen in image 1001. This prevents the build-up of material (powder either unbound or bound) at the leading edge of the paddle.

[0208] Fine cutting (less than a layer)

[0209] In another embodiment the cutter does not penetrate through the entire layer. Turning to figure 11 image 1100, the cutter (1104) with paddle (1103) leaves a small depth (1105) of layer two (1101) rather than fully penetrate the layer. Layer two is above layer one (1102). This enables very fine details to be scored into the layer.

[0210] The cut may be in bound or unbound powder. In all embodiments, the cutter depth can be altered.

[0211] Speeding up the production process

[0212] In all embodiments, the cutting can begin before the ink jetting of the layer has completed. The cutter could be incorporated into the ink jetting head. In all embodiments, the bulk vacuum can begin before the cutting and / or the ink jetting of the layer has completed.

[0213] Replacement powder is sacrificial

[0214] The powder that back fills the removed functional powder may be sacrificial and easily removed after the printing stage. This powder would provide support to the following layers. The use of sacrificial, or packing, powder greatly improves the ease of the depowdering stage which in turn enables the printing of large parts (parts with one dimension greater than 20cm).

[0215] An example of this embodiment is given in the procedure of the following steps made with reference to figure 12:

[0216] 1. The previous layer (1201) has been bound,

[0217] 2. Deposit a first layer consisting of powder one (1202),

[0218] 3. Jet ink / binder onto specific areas of layer one (1203),

[0219] 4. Cut grove on edge of selectively bound powder layer (1204),

[0220] 5. Selectively remove powder in specific unbound areas of the first layer (205) (could be through bulk vacuum).

[0221] 6. Fill the resulting gap in the layer one with support material (1206) (This may require additional ink deposition with same or second ink to bind support volume).

[0222] 7. Deposit a second layer of powder one (1207).

[0223] Examples

[0224] An example embodiment of a product that can be produced using the hybrid manufacturing method described in this invention is a wound electromagnetic device such as an electrical transformer.

[0225] Turning to figure 13 image 1300, the first layer of powder (1304) is deposited on the build surface (1305) before being jetted with ink (1306). A second layer of powder (1307) is deposited and selectively ink jetted with two different inks. Section 1308 with ink one and section 1309 with ink two. Ink one leads to the formation of an insulator and ink two leads to the formation of a conductor. A third layer of powder (1310) is deposited.

[0226] Now turning to 13 image 1301, the third layer of powder has ink selectively jetted (1311). A cutter cuts through the three layers (1312) and the unbound powder removed (1313). The resulting volume is filled with extruded material (1314).

[0227] It will be apparent to those skilled in the art that the extruded material may be deposited in multiple layers within the volume. After each of these layers a thin coating of material can be deposited through, for example, an aerosol. This has the effect of creating laminations of the extruded material which becomes like the stamped metal lamination used during traditional transformer core production.

[0228] Figure 14 gives a schematic representation of the resulting part after depowdering and consolidation. Image 1400 is a side view of a cut through the middle of the part (shown by dotted line 1409 in image 1401). Image 1401 is a plan view of a cut through the middle of the part (shown by dotted line 1408 in image 1400).

[0229] Turning to figure 14 image 1400, the transformer core (1405) is surrounded by an insulator (1406) which itself contains conductors (1407). The conductors (1407) produce a winding, two or which are shown in the plan view in image 1401.

[0230] This embodiment shows how a wound transformer can be printed as one part. Those skilled in the art will appreciate that the manufacturing method detailed in this invention and particularly in this embedment can be used for different parts including, but not limited to, motor stator or rotor windings, air core inductors, metal core inductors, resistive heaters, inductive heaters, IR heaters, etc.

[0231] Those skilled in the art will appreciate that printing the part as one removes stages such as encapsulation or impregnation of the windings. They will also appreciate that this also permits cores to be of shapes that do not readily permit insertion into a preformed winding, for example toroidal or where the pole shoe element in a motor winding has a greater diameter than the winding.

[0232] Figure 15 shows cross sections of transformer cores for which the adding of windings is difficult when using prior art methods. Image 1500 shows a single core (1505) around which there is insulator (1506) and conductive windings (1507). Image 1501 shows a loop core (1508) with insulator (1509) and two sets of conductor windings (1510 and 1511). Image 1502 shows a toroidal core (1512) with insulator (1513) and conductive winding (1514).

[0233] Electric motor design has not yet taken advantage of the design freedom which AM provides and which this invention enables. For example, traditional radial flux electric motor designs use the conductor parallel to the rotor axle to generate torque, but the winding needs to return to complete the coil requiring the use of end windings. As these end windings (also called endturns) do not contribute to torque generation, they only add to the overall length of the winding which increases its resistance. They also increase the axial length of the overall motor.

[0234] An additional embodiment of this invention produces in an end-turn geometry with increased surface area while maintaining cross-sectional area in order to dissipate more heat and fit in a reduced volume.

[0235] Through the design of coils that specifically fit into existing slot geometries, this invention has the potential to create higher fill factors than traditional manufacturing methods. Fill factor is a measure of the percentage of the slot area which is used as a conductor over the total area. An additional embodiment of this invention produces higher conductor utilisation and higher fill factors.

[0236] Turning now to losses in the windings, the skin effect is only seen in AC applications and is a phenomenon wherein the electrons preferentially migrate closer to the outside surfaces of the conductor rather than in the centre of the core. This effect is magnified at higher frequencies, typically above 1 kHz. An additional embodiment of this invention enables multistrand, low inductance and Litz windings to be printed.

[0237] An additional embodiment of this invention modifies the conductor material properties at the microstructure which may be used to reduce skin effect.

[0238] Figure 16 schematically depicts the examples of low inductance and low skin effect multistrand windings.

[0239] Electromagnetic limit is partly governed by geometry, the largest factor for it is defined by the material properties for the soft magnetic components. An additional embodiment of this invention enables prints the transformer core as if laminated using layers with optimised planes and structures which cannot be produced using sheets of material. This enables an optimised grain alignment for radial machines to reduce electromagnetic losses, for example eddy current loss.

[0240] Figure 17 schematically depicts the printing of laminations of the transformer or motor pole cores. Image 1700 shows a single core (1705) around which there is insulator (1706) and conductive windings (1707). The core (1705) has been printed with lamination lines (1708) which could be provided by selectively aerosol or bound powder or selective oxidation for example. Image 1701 shows a toroidal core (1609) with insulator (1710) and conductive winding (1711). The core (1709) has been printed with lamination lines (1712).

[0241] In other products the windings may primarily provide a structural function rather than primarily a conductive one. The core may be produced using binder jetting or another production method rather by way of extruded material.

[0242] This disclosure is provided to reveal a preferred embodiment of the invention and a best mode for practicing the invention. Having thus described the invention in this way, it should be apparent that various different modifications can be made to the preferred embodiment without departing from the scope and spirit of this invention disclosure. When structures are identified as a means to perform a function, the identification is intended to include all structures which can perform the function specified. When structures of this invention are identified as being coupled together, such language should be interpreted broadly to include the structures being coupled directly together or coupled together through intervening structures. Such coupling could be permanent or temporary and either in a rigid fashion or in a fashion which allows pivoting, sliding or other relative motion while still providing some form of attachment, unless specifically restricted.

Claims

6 CLAIMSWhat is claimed is:

1. A multi-material three-dimensional printer, comprising in combination: a build plate; a first powder dispenser movable over at least portions of said build plate to place a first powder layer above said build plate; a binder jet movable over at least portions of said build plate to place binder and bind the first powder together in locations where the binder is placed; a device consisting of a cutter that produces a cut in the first powder.

2. The printer of claim 1, further consists of a first powder remover which removes the unbound powder of the current or multiple layers.

3. The printer of claim 1, where the cut in the first powder is adjacent to the bound powder.

4. The cutting device of claim 1, further consists of a flattening surface to flatten the bound powder as the cutter moves.

5. The cutting device of claim 1, further provides a remover to remove unbound powder local to the cutter.

6. The printer of claim 1, where the binder jet consists of multiple jet nozzles which can jet the same or different inks.

7. The cutting device of claim 1, takes the form of a range of shapes to create a range of different interface profiles.

8. The cutting device of claim 1, can score into layer rather than fully cut.

9. The cutting device of claim 1, can cut through multiple powder layers.

10. The printer of claim 1, can start bulk removal of powder before, or after, all cutting on the current layer has completed and / or all ink jetting onto the current layer has completed.

11. The printer of claim 1, further consists of a second powder dispenser movable over at least portions of said build plate to place a second powder layer above said build plate, the second powder different from the first powder.

12. The second powder of claim 11, is a temporary structural filler.

13. The printer of claim 1, further consists of an extruder dispenser movable over at least portions of said build plate used to place a slurry above said build plate.

14. The slurry of claim 13 is placed in one or more areas where the unbound powder was removed in the current or previous powder layer (s).

15. The slurry of claim 13 has material deposited on to it by selective aerosol.

16. The cutting device of claim 1, rotates in any axis.

17. The cutting device of claim 1, depth can be changed while cutting.

18. The cutting device of claim 1, is incorporated into the ink jetting head.

19. The printer of claim 1, further consists of an energy source such as a UV source or a heater, to selectively cure the binder and / or extruded slurry.

20. The printer of claim 1, uses multiple inks to create sections of high insulation and sections of high conductivity.

21. The printer of claim 20, prints coil windings where the end-turn geometry has increased surface area while maintaining cross-sectional area.

22. The printer of claim 20, prints coil windings with high conductor utilisation and higher fill factors.

23. The printer of claim 20, prints coils as multistrand either / or braided either / or Litz windings.

24. The printer of claim 20, prints coil windings where the conductor material properties are modified at the microstructure to reduce skin effect.

25. The slurry of claim 15 is printed with laminated layers with optimised planes and structures to reduce magnetic losses.

26. The cutting device of claim 1 cuts the bound material.

27. A method for multi-material three-dimensional printing, including the steps of: dispensing a first powder in a first powder layer along a major axis over a build plate; first applying binder to combine with portions of the first powder layer; cutting along the interface between the bound and unbound powder; removing first powder from portions of the first powder layer not contacted by the binder.

28. The method of claim 27 further contains the step of dispensing a second powder in a second powder layer over the build plate, the second powder different from the first powder.

29. The method of claim 27 further contains the step of extruding material into the sections of the first powder layer from which the unbound powder was removed.

30. The method of claim 27 wherein said first applying step includes jetting at least one binder from a print head.

31. The method of claim 27 wherein the cutting is performed by a device that also smooths the bound powder local to the cutting device.

32. The method of claim 27 wherein the cutting is performed by a device that also removes the bound powder local to the cutting device.

33. The cut of claim 27 cuts the bound material.

Images