Manufacturing apparatus and method

Abstract

A method additive manufacturing a workpiece by providing a first layer of a powder particles and binder jetting the powder an ink where the enthalpy of formation of the resulting material is determined by selecting the powder composition and the ink formulation. The ink formulation can be modified during jetting and / or the ink dosage can be modulated during jetting to form a workpiece with regions of different compositions where interfaces therebetween can either be functionally graded or be abrupt. The method can be used to make workpieces comprising regions of different materials which mechanically interlock or separate when heated to a set temperature as a consequence of different coefficients of thermal expansion. The powder particles can be coated. The ink can comprise surfactants and solvent removeable polymers can be used.

Description

TECHNICAL FIELD The present invention relates to a method of ink jetting and an article manufactured using ink jetting. BACKGROUND 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. It is well understood that the material properties contribute to the part's overall performance. The present invention is focused on the materials microstructure which is the foundation of the materials properties. Such properties include, but are not limited to, conductivity in thermal and electrical sense, mechanical strength and compliance, visual appearance including surface finish. Currently there is a limit set of materials available for use in additive manufacturing and most are based on those used in other more commonly used manufacturing methods. The variability and control of material microstructure enables a greater range of materials than are possible for use in those more commonly used manufacturing methods. When a new material is produced, it is often the case that its properties are determined after it has been used in a part rather than during formulation. Optimisation is a lengthy process as the formulation is altered in small steps which are often associated with just one parameter. A new part is manufactured and then tested. This process is iterated many times before an optimal formulation and manufacturing process control / method has been determined. 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. 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. Post-processing 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. 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. 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. 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 5 binder are repeated. 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 10 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. Binder jetting is also referred to as "ink jetting", the "drop-on" technique, "powder bed and 15 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. SUMMARY A first aspect provides a method of ink jetting, the method comprising: providing a first layer of a powder particles comprising a composition of one or more materials; jetting the first layer of the powder with one or more ink formulations; and controlling the enthalpy of the resulting materials through the selection of powder composition and ink formulation. A second aspect wherein the ink formulation comprises a solvent, a catalyst, a precursor material, a carrier vehicle, and / or a growth agent and / or an inhibitor, and / or particles. A third aspect, wherein the particles comprise nanoparticles. A fourth aspect wherein the resulting materials sinter at a same temperature. A fifth aspect wherein the resulting materials sinter at different temperatures. A sixth aspect wherein the resulting part is printed as one and postprocessed as one. A seventh aspect wherein the particles are coated. An eighth aspect wherein the ink formulation can be modified during jetting. A nineth aspect wherein there is an interlayer heat treatment as specific positions. A tenth aspect wherein regulating forming of the particles from the ink formulation in the first layer of the powder comprises modulating dosing of the ink formulation. An eleventh aspect comprising selecting a particle size distribution of the powder. A twelfth aspect comprising selecting a particle morphology of the powder. A thirteenth aspect where each material within the powder bed is deposited independently to specific locations. A fourteenth aspect employing transition strategies, for example gradient graphs, to define the control the interface between materials within a part. A fifteenth aspect where the permeability of the ink is controlled. A sixteenth aspect where the ink contains surfactants to alter wetting properties. A seventeenth aspect where solvent removable polymers are used to control ink drop bleeding. An eighteenth aspect where surfaces can be made completely hydrophobic, which will repel the aqueous binder for the main part. A nineteenth aspect provides a method of ink jetting, the method comprising: providing a first layer of a powder particles comprising a composition of one or more materials; jetting the first layer of the powder with one or more ink formulations; and multi-material parts can be formed through microstructure grading or abrupt interfacing. A twentieth aspect where mechanically stable interlocking interfaces can be produced including those predesigned to aid material separation during recycling. A twenty-first aspect where layer-by-layer deposition of two materials where a mechanical locking feature is printed. A twenty-second aspect where the difference in thermal expansion coefficients between two materials is employed to create parts that separate when heated to a set temperature. A twenty-third aspect where stresses occurring during sintering are designed into the part. A twenty-fourth aspect consist of a computer comprising a processor and a memory configured to implement, at least in part, a method according to any of claims 1 to 18, a computer program comprising instructions which, when executed by a computer comprising a processor and a memory, cause the computer to perform a method, at least in part, according to any of claims 1 to 18 or a non-transient computer-readable storage medium comprising instructions which, when executed by a computer comprising a processor and a memory, cause the computer to perform a method, at least in part, according to any of claims 1 to 18. A twenty-fifth aspect is an article manufactured at least in part by ink jetting, the article comprising: a first layer of a bound powder comprising a material; wherein the first layer comprises: a microstructure influenced by particles formed from an ink formulation where the enthalpy of the resulting material has been controlled through the selection of powder composition and ink formulation. BRIEF DESCRIPTION OF DRAWINGS Aspects of the present disclosure are described, by way of example only, with reference to the following drawings, in which: Figure 1 schematically depicts a flow diagram of required effect to control; Figure 2 schematically depicts a flow diagram of the steps required for inter layer heat treatment; Figure 3 schematically depicts a flow diagram of consolidation (before and after); Figure 4 schematically depicts permeability control; Figure 5 schematically depicts graded / continuous interface; Figure 6 schematically depicts varied alloy composition: Controlled at the molecular level; Figure 7 schematically depicts doping particles of a different material to interfere with dislocation movement to create high tensile and creep strength at high temperature; Figure 8 schematically depicts a 3D view of the separated test case geometry; Figure 9 schematically depicts Von Mises stress, viewed through a cross section, and planar stress, in the Z-Z plane. Figure 10 schematically depicts optimisation of inter-layer steps for specific materials; Figure 11 schematically depicts a mechanical locking microstructure for materials that will not blend; Figure 12 schematically depicts a mechanical locking structure for materials that will not blend that can be unlocked during recycling; Figure 13 schematically depicts layer-by-layer deposition of two materials where a mechanical locking feature is printed; Figure 14 schematically depicts the component is sintered to the required density; Figure 15 schematically depicts the component is raised to a temperature above the melt temperature of material one, but below the melt temperature of material two. Figure 16 schematically depicts a layer-by-layer deposition of two materials where a mechanical locking feature is printed. The two materials have the same enthalpy of reaction; Figure 17 schematically depicts the component sintered to the required density. The two materials sinter at the same temperature; Figure 18 schematically depicts the component raised to a temperature above the melt temperature of ME2m, but below the melt temperature of Elm. This temperature is called the "Recycling Temperature". Figure 19 schematically depicts the layer-by-layer deposition of three materials where two mechanical locking features are printed. The materials cannot be pulled apart without breaking them due to the interlocking posts of material. Figure 20 schematically depicts the component is sintered to the required density. The three materials sinter at the same temperature. The enthalpy modification additives are consumed during the sintering process. Figure 21 schematically depicts the component is raised to a temperature above the melt temperature of M3a, but below the melt temperatures of Mia and M2a. This temperature is called "Recycling Temperature 1". Figure 22 schematically depicts the component is raised to a temperature above the melt temperature of M2a, but below the melt temperature of Mia. This temperature is called "Recycling Temperature 2". Figure 23 schematically depicts layer-by-layer deposition of three materials where two mechanical locking features are printed. The materials cannot be pulled apart without breaking them due to the interlocking posts of material. Figure 24 schematically depicts the component is sintered to the required density. The three materials sinter at the same temperature. The enthalpy modification additives are consumed during the sintering process. Figure 25 schematically depicts the component is raised to a temperature above the melt temperature of M2a, but below the melt temperatures of Mia and M3a. This temperature is called "Recycling Temperature 1". DETAILED DESCRIPTION This disclosure relates to advanced manufacturing including additive manufacturing. In particular, the creation and interfacing of multiple materials (multi-material) as a common part printed / formed / manufactured and postprocessed as one part. The controlled creation of true multi-materials at the microstructural level requires the controlling and blending of elements including inks (including binders) and the powder bed material (including particle size and distribution). This disclosure also covers material by material control of enthalpy to control the interface and enabling simultaneous sintering of dissimilar materials. Several elements require control including, but not limited to: - • Defining ligand, catalyst and particle size and shape. • Carrier vehicle containing ligands or catalysts to force chemical reactions at target temperature. • Inks and binders to work with multiple powders in bed. • Control sintering temperatures independently • Permeability control Interfacing between materials can be graded (continuous) or abrupt (discrete) for materials that are able to blend and abrupt for those that cannot blend. This invention shows how multi-material parts can be formed through grading or microstructure abrupt interfacing. This invention also shows how mechanically useful interlocking interfaces can be produced including those predesigned to aid material separation during recycling. Examples where this invention may be applied include alloy composition. DEFINITIONS Some definitions of standard terms used in this document are: 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. 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. Organometallic: Compound I molecule containing at least 1 metal - carbon bond. 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. Hybrid manufacturing: Utilising both additive and subtractive manufacturing methods Debinding: A heat treatment or part of the sinter cycle where the binder is removed from the green part - ideally as sintering begins. Green part: The part (also known as article) as printed. Usually comprised of weakly held together particles with significantly lower strength than the bulk material. Brown part: Heating the green body 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. Release layer: A specifically printed area at a part edge where printing parameters are altered to reduce the strength in that area. Parameters may include ink composition, drop size, ink saturation. 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. 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) in to the powder bed or by the addition of a different material, such as a polymer, which temporarily joins particles together until sintering. 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. 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). Solvent: Any substance capable of dissolving another substance and forming a solution. Carrier or carrier vehicle: Fluid used as the bulk component in the ink (by volume) - generally chosen for its properties as a solvent its evaporation properties when printed. Catalyst: A substance used to change the activation energy of a reaction, whilst not being consumed during the reaction. Non-binding component: Any component of the ink which does not take part in joining the bed powder particles together after printing. 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. Jetting: The controlled ejection of ink from a nozzle in an inkjet head. Multiple nozzles: Concerning an inkjet head containing more than one nozzle for ejection of ink. 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. 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. 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. 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). 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. Ligand: An ion or molecule attached to a metal atom by coordinate bonding. 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. 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. 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, 5 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. 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, 10 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. Fluid surface tensions and wetting properties: The composition of the ink can be altered, 15 either during the initial formulation or on-the-fly, so that ink with different wetting properties can be printed within a single layer. The following diagrams and descriptions will be used to show how controlling the elements affect the completed part and how the process steps and process variables (time, heat or energy level, atmosphere etc) are also controlled. Figure 1 schematically depicts a flow diagram of required effect to control. The flow diagram in Figure 1 describes the process for printing a multi-material component or components with multiple powders, inks or binders, and inter-layer processing. A CAD model is loaded by the software. The CAD model contains volumetric location-based data specifying either the material to be used or one or more required material properties. The software iterates through the CAD model and generates layer images to be sent to the printer. The software references a database containing reference material properties and the required powder / ink / interlayer processing needed to achieve the material property. The reference data is used to generate layer-by-layer images which are used to control the powder deposition, printing, and in-situ post-treatment for each layer. One set of images determine the type of powder to be dosed onto the build area and the location in x and y for each type of powder. Another set of images determines the ink type and dose volume to be used for each x and y location for each layer. The final set of images determine the layer post-processing - e.g., IR. exposure at a specified temperature and duration at specific locations in x and y. Figure 2 schematically depicts a flow diagram of the steps required for inter layer heat treatment. The flow diagram in Figure 2 shows the steps needed for inter layer heat treatment. Initially the layer-by-layer images are loaded into the printer software. The image stacks contain x and y data for each layer showing the type and volume of powder to dispense, the type and volume of ink to dispense and the interlayer heat treatment requirements. Figure 3 schematically depicts a flow diagram of consolidation (before and after). Image 1201 schematically depicts the part prior to the heat stages. The temperature of the part is controlled, for example, by the parts insertion into a closed volume heater where the volumes atmosphere may be controlled. The parts temperature is taken to the 1st temperature where this temperature is held for the 1st temperature set time. Image 1202 shows the parts internal microstructure has changed during the 1st temperature set time. The parts temperature is taken to the 2nd temperature where this temperature is held for the 2nd temperature set time. Image 1203 shows the parts internal microstructure has changed during the 2nd temperature set time. The final change in microstructure occurs during cooling as shown by image 1204. Figure 4 schematically depicts permeability control. Image 1 shows: Ink mixed in, or just prior to printhead. 1 Channel contains base ink formulation, additional channels contain surfactants to alter wetting properties. Control of composition by regulating reservoir backpressures or flow rates. Image 2 shows: Inks delivered separately via 2 printheads and ink delivery systems. Composition controlled by drop grey scale. Figure 5 schematically depicts graded / continuous interface. The fine dotted line shows the % portion of composition A and the dot-line shows the % portion of composition B. For transitions between materials during printing, strategies can be employed to control the interface between material A and material B. Strategies include, but are not limited to, those shown above. Powder and ink can be dispensed in accordance with the above composition graphs, where the distance value on the x axis corresponds to some multiple of the layer number in the z direction, some multiple of the drop number in the x direction or some multiple of the encoder position in the y direction. Alternatively, either powder or ink can be dispensed as shown above, with the other remaining at a static composition value. Figure 6 schematically depicts varied alloy composition: Controlled at the molecular level. Image 1: Constant composition of powder bed particles used throughout print. Ink composition is varied in one or more directions. Composition variation can be achieved by changing the amount of a single ink delivered (number and / or size of drops per voxel), by changing the composition of the ink prior to ejection, or by dropping multiple different composition inks onto the same volume and changing the drop ratios between the different composition inks. Upon in-situ treatment or during sintering, the ink differences in ink composition throughout the part alter the final microstructure in different areas. Image2: Constant composition of powder bed particles used throughout print. Two different composition inks are used during print to change the binder between layers or voxels. During in-situ treatment or during sintering the different binders promote the formation of different material microstructures at different locations within the part. For example, each of two inks could contain the same fluid composition and both contain nano and / or microparticles of the same material, but the nano and / or microparticles in each ink have a different crystalline morphology. These particles then act as epitaxial seeds during the sintering process to cause the formation of different allotropes of the same composition material. Image 3: Ink composition remains constant throughout the printing process. Powder dispensers are used to deposit different bed powders, in which each different powder particle is of the same material but with different surface coatings. These coatings could be selected to promote or inhibit ink wetting, to provide release layers or to decrease or increase ink permeation into volumes around the printed area; promote or inhibit specific chemical reactions, for example to provide a different surface finish around the boundary of a part and aid depowdering or post processing; promote or inhibit material properties such as electrical or thermal conductivity, part strength, dielectric properties, etc. Image 4: Combinations of different composition inks and selectively different or mixed composition powders to produce varied materials properties throughout the final part. Image 5: Combinations of different composition mixed bed powders with different surface coatings produce varied materials properties throughout the final part. Figure 7 schematically depicts doping particles of a different material to interfere with dislocation movement to create high tensile and creep strength at high temperature. The three images shown schematically depict how the microstructure of the part are controlled by the powder bed particles and ink (left image), including nano and micro particles (middle image) and after sintering or a post sinter heat treatment (right image). Ink is deposited onto metal powder bed particles to bind particles together to define the printed volume. Within the ink nano and micro particles of the same metal material are used to improve the filling density and filling sintered part density. Included within the ink are hard nanoscale particles (e.g. alumina, silica, yttria, boron nitride, tungsten carbide, etc.) which also increase the printed part density. During the sintering cycle or during a post sintering heat treatment, grain growth and recrystallisation can be used to grow the metal grains and densify the part, whilst trapping the hard particles at grain boundaries and within grains to inhibit dislocation movement, thus increasing the fracture toughness and hardness of the final part. Figure 8 schematically depicts a 3D view of the separated test case geometry. Image 1: A requirement for sustainable multi-material additive manufacturing is the ability to separate the different material parts at the end of their life cycle for recycling. One method to achieve this is to exploit the difference in thermal expansion coefficients between two metals to create parts that separate when heated to a set temperature. The image shows a 3D view of the interlocking feature. Image 2: A simple test case was simulated using finite elements methods, solving the linear elasticity and heat equations. The setup geometry consists of two 3D printed parts joined together. One (bottom part) made from copper, 5mm in thickness, which a rounded 10mm diameter post protruding from the top centre, and a second aluminium encasing part, 20mm thickness, with a pocket feature to accept the copper post. The geometry is shown in image. Figure 9 schematically depicts Von Mises stress, viewed through a cross section, and planar stress, in the Z-Z plane. Image 1: Simulation 1 solves the steady state solution where the 6 outer walls are set to a fixed temperature of 300°C, this heat is allowed to propagate through the assembly. The interface between the two materials is fixed in displacement, to simulate the stresses around this interface when the parts are bonded together. Image 2: Simulation 2 solves the steady state solution where the same fixed temperature is applied to the walls however the boundary between the parts is allowed to move, and only the top surface of the aluminum is fixed. This simulates the planar stresses parallel to the material interface, shown in figure 6, cross sectioned. When the brittle fracture stress of the multi-material interface is less than the ultimate tensile strength of the material, along these stress planes, the parts should separate cleanly, requiring minimal cleaning / separation work before recycling. The darker the shading the more stress is present. Figure 10 schematically depicts optimisation of inter-layer steps for specific materials. The image shows the effect on the microstructure of different energy levels or sources when these change between layers. The top and bottom layers have been subjected to a lower level of energy than the middle layer. Energy sources may include UV lamps, IR radiation, heated volume, etc. Figure 11 schematically depicts a mechanical locking microstructure for materials that will not blend. The high level of geometrical microstructure control permits different materials to be interfaced even where they cannot truly blend, at the microstructure level. Images 1 show four examples of mechanical interlock, although many others exist and can be produced using this invention. Image 2 shows a 3D view of a doubled locked interface. Figure 12 schematically depicts a mechanical locking structure for materials that will not blend that can be unlocked during recycling. The high level of geometrical microstructure control permits different materials to be interfaced even where they cannot truly blend, at the microstructure level. Images 1 show two examples of mechanical interlock that permit simple separation as a preparation for the recycling of the part, although many others exist and can be produced using this invention. Image 2 shows a 3D view the single locked T-pin. Figure 13 schematically depicts layer-by-layer deposition of two materials where a mechanical locking feature is printed. Dissimilar Enthalpy Materials: Interlocking geometries are created layer-by-layer to mechanically fix the part together. The inks contain additives to modify the enthalpy of reaction of the materials, allowing them to be co-sintered at the same / similar temperature. Once the parts have been sintered, these additives are no longer present, so the materials will have different enthalpies. This means that the two materials will have different melt temperatures. Therefore, raising the component to the melt temp of the lower material will result in it becoming a liquid and flowing out of the locking mechanism, while the other material remains a solid. Layer-by-layer deposition of two materials where a mechanical locking feature is printed. The materials cannot be pulled apart without breaking them due to the interlocking posts of material. Each ink contains additives to modify the enthalpy of reaction. Ml is a powder bound with an ink that lowers the enthalpy of reaction (effectively lowering the sintering temperature). M2 is a powder bound with an ink that raises the enthalpy of reaction (effectively increasing the sintering temperature) Figure 14 schematically depicts the component is sintered to the required density; The component is sintered to the required density. The two materials sinter at the same temperature. The enthalpy modification additives are consumed during the sintering process. The two materials now revert to their original thermodynamic properties, denoted by the 'a' suffix. Figure 15 schematically depicts the component is raised to a temperature above the melt temperature of material one, but below the melt temperature of material two. The component is raised to a temperature above the melt temperature of M2a, but below the melt temperature of Mia. This temperature is called the "Recycling Temperature". This causes M2a to become a liquid ("M2I") and flow out of the component, The liquid M2I can be collected and solidified for recycling. The solid Mia can be sent for recycling. Examples Any material system with different melt temperatures can be recycled using this method. Material Sintering Temperature (Natural) Sintering Temperature (Modified) Melt Temperature Component 1 Ml Steel 1200 900 1510 M2 Aluminium 600 900 660 Component 2 Ml Steel 1200 1040 1510 M2 Copper 875 1040 1084 Component 3 Ml Copper 875 740 1084 M2 Aluminium 600 740 660 Figure 16 schematically depicts a layer-by-layer deposition of two materials where a mechanical locking feature is printed. The two materials have the same enthalpy of reaction. Similar Enthalpy Materials: Interlocking geometries are created layer-by-layer to mechanically fix the part together. The materials have very similar enthalpies of reaction, so do not need to be modified. The inks contain additives to modify the enthalpy of reaction of the materials post-sinter, changing their mechanical properties after they have been consolidated. This would most likely be by forming a new alloy during the heat treatment phase. These additives can change the melt temperatures of similar materials to move them apart, allowing for a melt-based recycling process to occur. Layer-by-layer deposition of two materials where a mechanical locking feature is printed. The two materials have the same enthalpy of reaction. El is a powder bound with an ink that contains additives that activate post-sinter. E2 is a powder bound with an ink that contains additives that activate post-sinter. Figure 17 schematically depicts the component sintered to the required density. The two materials sinter at the same temperature. The component is sintered to the required density. The two materials sinter at the same temperature. The enthalpy modification additives are activated after the sintering process. The two materials now have modified thermodynamic properties, denoted by the'm' suffix. Figure 18 schematically depicts the component raised to a temperature above the melt temperature ofME2m, but below the melt temperature of Elm. This temperature is called the "Recycling Temperature". The component is raised to a temperature above the melt temperature of ME2m, but below the melt temperature of Elm. This temperature is called the "Recycling Temperature". This causes E2m to become a liquid ("E2I") and flow out of the component. The liquid E2I can be collected and solidified for recycling. The solid Elm can be sent for recycling. Examples Initial Material Sintering Temperature (Natural) Melt Temperature (Natural) Post Treatment Material Melt Temperature (Modified) Component 1 Ml Aluminium 600 660 Aluminium Alloy 1 700 M2 Aluminium 600 660 Aluminium Alloy 2 550 Component 2 Ml Carbon steel 1235 1482 Stainless Steel 1510 M2 Nickel 1000 1453 Chromel 1420 Component 3 Ml Copper 875 1084 Bronze 913 M2 Gold 950 1064 Gold 1064 Figure 19 schematically depicts the layer-by-layer deposition of three materials where two mechanical locking features are printed. The materials cannot be pulled apart without breaking them due to the interlocking posts of material. Scalability: Dissimilar Enthalpies of Reaction There is the option of scaling the process to allow for more materials to be separated out, as long as there is enough difference between their natural melt points. Component can be raised to T1 to melt Ml, T2 to melt M2, T3 to melt M3, etc... until the last material is left and can be recycled on its own. Similar Enthalpies of Reaction There is the option of scaling the process to allow for more materials to be separated out. Each material can be modified to have a specific melt temperature using the enthalpy additives. Then the component can be raised to T1 to melt Ml, T2 to melt M2, T3 to melt M3, etc... until the last material is left and can be recycled on its own. A two-stage melt can be used when: M2 is surrounded by Ml and M3 and does not have a pathway out. M3 has the lowest melt temperature. M2 has the second lowest melt temperature. Layer-by-layer deposition of three materials where two mechanical locking features are printed. The materials cannot be pulled apart without breaking them due to the interlocking posts of material. Each ink contains additives to modify the enthalpy of reaction as required. Ml is a powder bound with an ink that lowers the enthalpy of reaction (effectively lowering the sintering temperature). M2 is a bound powder with the central enthalpy and does not require medication. M3 is a powder bound with an ink that raises the enthalpy of reaction (effectively increasing the sintering temperature). Figure 20 schematically depicts the component is sintered to the required density. The three materials sinter at the same temperature. The enthalpy modification additives are consumed during the sintering process. The component is sintered to the required density. The three materials sinter at the same temperature. The enthalpy modification additives are consumed during the sintering process. The two modified materials revert to their original thermodynamic properties, denoted by the 'a' suffix. Figure 21 schematically depicts the component is raised to a temperature above the melt temperature of M3a, but below the melt temperatures of Mia and M2a. This temperature is called "Recycling Temperature 1 The component is raised to a temperature above the melt temperature of M3a, but below the melt temperatures of Mia and M2a. This temperature is called "Recycling Temperature 1". This causes M3a to become a liquid ("M3I") and flow out of the component, The liquid M3I can be collected and solidified for recycling. Figure 22 schematically depicts the component is raised to a temperature above the melt temperature of M2a, but below the melt temperature of Mia. This temperature is called "Recycling Temperature 2". The component is raised to a temperature above the melt temperature of M2a, but below the melt temperature of Mia. This temperature is called "Recycling Temperature 2". This causes M2a to become a liquid ("M2I") and flow out of the component, The liquid M2I can be collected and solidified for recycling. The solid Mia can then be sent for recycling. Examples Material Sintering Temperature (Natural) Sintering Temperature (Modified) Melt Temperature Component 1 Ml Stainless Steel 1300 875 1510 M2 Copper 875 875 1084 M3 Aluminium 600 875 660 Component 2 Ml Titanium 1200 1000 1670 M2 Nickel 1000 1000 1453 M3 Gold 950 1000 1064 Component 3 Ml Tantalum 1300 1150 3017 M2 Stainless 1300 1150 1510 M3 Copper 875 1150 1084 Figure 23 schematically depicts layer-by-layer deposition of three materials where two mechanical locking features are printed. The materials cannot be pulled apart without breaking them due to the interlocking posts of material. A single-stage melt can be used under the following conditions: The central material M2 has a pathway out of the component. Ml and M3 do not mechanically lock with each other. M2 has a lower melt temperature than Ml and M3. Layer-by-layer deposition of three materials where two mechanical locking features are printed. The materials cannot be pulled apart without breaking them due to the interlocking posts of material. Each ink contains additives to modify the enthalpy of reaction as required. Ml is a powder bound with an ink that lowers the enthalpy of reaction (effectively lowering the sintering temperature). M2 is a bound powder with the central enthalpy and does not require medication. M3 is a powder bound with an ink that raises the enthalpy of reaction (effectively increasing the sintering temperature). Figure 24 schematically depicts the component is sintered to the required density. The three materials sinter at the same temperature. The enthalpy modification additives are consumed during the sintering process. The component is sintered to the required density. The three materials sinter at the same temperature. The enthalpy modification additives are consumed during the sintering process. The two modified materials revert to their original thermodynamic properties, denoted by the 'a' suffix. Figure 25 schematically depicts the component is raised to a temperature above the melt temperature of M2a, but below the melt temperatures of Mia and M3a. This temperature is called "Recycling Temperature 1 The component is raised to a temperature above the melt temperature of M2a, but below the melt temperatures of Mia and M3a. This temperature is called "Recycling Temperature 1". This causes M2a to become a liquid ("M2I") and flow out of the component, The liquid M2I can be collected and solidified for recycling. Mia and M3a are now separated and can be sent for individual recycling. Examples Material Sintering Temperature (Natural) Sintering Temperature (Modified) Melt Temperature Component 1 Ml Stainless Steel 1300 875 1510 M2 Aluminium 600 875 660 M3 Copper 875 875 1084 Component 2 Ml Titanium 1200 1000 1670 M2 Gold 950 1000 1064 M3 Nickel 1000 1000 1453 Component 3 Ml Tantalum 1300 1150 3017 M2 Copper 875 1150 1084 M3 Stainless 1300 1150 1510 ASPECTS CONTROLLING ENTHALPY Defining ligand, catalyst and particle size and shape. Control enthalpy of reaction by attaching a range of ligands which protect the metal centre from reacting until necessary. Passive or reactive ligand. Falls apart at a certain temp, comes off as gas or solid. Used to make two materials have the same enthalpy of reaction so they react at the same temp to create a true multi-material interface. Optional, ligands on one material can separate and move to second material to from a secondary reaction during temp. Carrier vehicle contains ligands or catalysts to force chemical reactions at target temperature For inks containing binders with different "binding" material and different activation / decomposition temperatures, catalysts can be added to one or both inks to bring the activation temperatures closer together, to allow the curing / decomposition reactions to happen simultaneously. E.g., Al from dimethyl ethylamine alane decomp[position temp reduced from ~150C to 55C with addition of Ti isopropoxide. Inks and binders to work with multiple powders in bed Option of using binders that leave components in the part until the sintering cycle, like the normal binder jet process. The components could even act as sinter agents, microstructural modifiers, or have other useful characteristics. Different materials will sinter at different energy levels. This can be controlled by adding sintering agents to the materials. These agents could be part of the ink composition or be a coating on the powder particles. Some alloys have components in them just to help with the process, such as LPBF alloys having melt pool stabilisers. Nanoparticles act as sinter temp reduction agents (any size up to 500nm). % ranges of size and composition add. Any solid, e.g., Silver, Copper, Titanium. Sizes, under lnm to 500nm Control sintering temperatures independently For bimodal or multimodal bed powders, the smaller particle size range can be selected to promote sintering at lower temperatures. This could be done in cases where the material from the ink (deposition products and suspended / dispersed particles) sinters at a different temperature to the bed powder material, thus bringing the sintering initiation temperatures closer together. For multi-material powder beds, the same can be applied, with the smallest particles from the powder bed are selected based on their size to reduce the sintering initiation temperature of the higher melt point material closer to that of the lower melt point material. For multi material inks (either in together in one ink, or jetted separately as two or more inks), the suspended particles in the ink could be selected based on their size to initiate sintering at similar, or the same, temperatures. E.g. for Al and Cu, a sintering temp of ~500C could be used (no size selection required for the Al particles) if the Cu particles are around 5nm. PERMEABILITY CONTROL 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. Tailored fluid surface tensions and wetting properties (polar / non-polar components) allow ink to spread desired distances in powder bed. Surface functionalisation of powder bed particles to promote or inhibit fluid wetting. The composition of the ink can be altered, either during the initial formulation or on-the-fly, so that ink with different wetting properties can be printed within a single layer. Three methods of stopping ink bleed with a coating: • First is to have a reaction that solidifies / increases the viscosity of the ink at the edge of the part. • Second is to render the edge particles inadmissible, so that the coating repels the ink. • Third is to functionalise the particles within the part boundary to draw the binder inwards. Oleophobic surfaces can be jetted around the part boundary, this will prevent the ink from bleeding past this point. It can also be jetted inter-layer to prevent binder mixing between layers in the bed. Oleophilic surfaces can draw the binder down and increase the binder permeation through the part. It can also be used as the inverse of the oleophobic binder, where the particles within the part boundary are made oleophilic and draw the binder in to prevent bleed. Superabsorbent polymers will react with aqueous solutions to prevent the ink from bleeding through. The polymer reacts to form a gel, which could either prevent aqueous solutions travelling further through absorption, or the gel could block the pore throats between the powder particles. This may be used inter- or intra-layer to prevent binder movement and mixing. When inks are next to each other we may wish to stop an ink drop bleeding through to the adjacent material to control the interface between the resulting materials. May use solution-based coating, where the polymer is dissolved in a solvent, jetted over the micron particles, and then the solvent is evaporated, leaving behind a polymer coating on the micron particles. For example, sodium polyacrylate, cellulose, or starch polymers, dissolved in water / organic solvent, NMMO / DMAc, or water, respectively. • Sodium polyacrylate dissolved in water / organic solvent such as ethanol / acetone. • Cellulose dissolved in N-methylmorpholine-N-oxide (NMMO) or lithium chloride / dimethylacetamide (LiCI / DMAc). • Starch dissolved in water. In-situ Polymerisation: To produce the polymer coatings, the surface of the metal particles can be functionalised, a monomer layer produced on the surface, and then the monomer polymerised into a polymer. Example method: 1. Make a binder that has a molecule containing a reactive functional group at one end, e.g. a thiol, and a hydroxyl / carboxyl / amino group at the other end (mercaptoethanol or mercaptoundecanoic acid for the first two for example) dissolved in a solvent 2. Jet this binder onto the micron particles in the bed. The molecules could attach to the surface and have the hydroxyl / carboxyl / amino group facing outwards 3. Introduce a polymerisation initiator to the surfaces 4. Apply a monomer solution on to the initiator to form a monolayer 5. Polymerise the surface to get a cross-linked polymer coating 6. That polymer coating will now react with the aqueous solution to prevent bleed The area with the polymer can be separated from the actual part prior to sintering, so there are no unwanted elements in there. Binder which is a solution of the polyacrylate monomer, 2-hydroxyethyl acrylate (HEMA), in ethyl acetate with a coupling agent, 3-aminopropyltriethoxysilane (APTES). Jet onto aluminium powder and allow the monolayer to form. Jet a second binder containing benzoin methyl ether (BME) and ethyl acetate solution. Use UV light to begin polymerisation. Solution of sodium polyacrylate and water. Concentration of sodium polyacrylate can determine the coating thickness. Jet this solution onto the aluminium particles. This is formed through ionic interactions with the surface. No initiator is needed as it does not need to be polymerised. Solution of acrylic acid in ethanol, with N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-Hydroxysuccinimide (NHS). The EDC and NHS activate the carboxyl groups in the acrylic acid. Jet the solution onto copper particles. The acrylic acid should react with the copper surface to form a self-assembled monolayer with the carboxyl groups facing outwards. Dissolve 2,2'-Azobis(2-methylpropionitrile) (AIBN) in water. AIBN is a thermal initiator. Jet the AIBN solution onto the coated copper particles. Remove oxygen (which can inhibit the reaction) and heat to 60-80°C. Once the superabsorbent polymer has coated the particles, it can be used to form a barrier to the ink bleed: If the ink is aqueous, then it will react with the polymer and form a gel that prevents the ink moving past this point If the ink is not aqueous, then water can be jetted onto the coated particles to form the gel. The gelled polymer will close the pore throats and the binder cannot bleed past it. The border could be offset from the part, so that later in the build when the weight of the binder and powder on the layers above forces the binder outwards, it cannot go past this point. The partial curing by this point should stop the polymer from contaminating the part. Hydrophilic / phobic Polymer Coatings: This can be performed using the same methods as the superabsorbent polymer deposition, but the polymers will be different. Hydrophilic: PEG, PVA, PAA PEG coating on aluminium to make it hydrophilic. Dissolve the PEG in water, ethanol, or methanol. Jet this solution onto aluminium particles. The PEG will adsorp onto the surface of the aluminium. Hydrophobic: PTFE, PDMS PTFE coating on copper to make it hydrophobic. Etch the copper with dilute acid or a copper etchant to activate the surface. This can be jetted. Dissolve the PTFE in a fluorocarbon solvent or a mixture of organic solvents. Jet the PTFE solution onto the activated copper. Nanoparticle Solution Coatings: Can coat micron particles with nanoparticles by mechanically mixing them. Suspending the nanoparticles in liquids of different pH levels can affect how the concentration on the surface of the micron particles, e.g. amount of Y2O3 nanoparticles adsorbed by steel micron particles is lower at higher pH levels, pH of 7 adsorbs all, pH of 9.5 is a small amount. This is determined by the isoelectric point (IEP) of the two materials. Can control the pH of the binder that is jetted to change the number of nanoparticles absorbed Can do this to modify the cohesion of the powder, change the wettability, or allow the second binder to react with the first (e.g. the earlier jetting of functional groups) Any type of functional group that can be attached to the surface of the particles can be used. INK FORMULATION AND MATERIAL COMPOSITION 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. 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 many more options than purely powder-based methods. 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. 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. 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. Plasma flashing / clean selected areas. Reactive species such as ions, electrons, and excited atoms are part of plasma. These species are highly reactive and can break down organic contaminants and oxidize inorganic contaminants. Plasma activates the top few molecular layers of a surface. It is possible to jet precursors onto the particles, then plasma treat those areas to functionalise the surface. These precursors can be fluoro-, amines, and acids, and can join together to form functional polymers or materials on the surface. Surfaces can be made completely hydrophobic, which will repel the aqueous binder for the main part. Plasma Polymerisation of Superabsorbent Polymers Could pair this with the earlier idea of superabsorbent polymers. Use acrylic acid (a superabsorbent polymer precursor) in a precursor gas to coat steel particles. When the acrylic acid is excited by the plasma, it will polymerise, and deposit a thin film on the surface of the steel particles. Hydrophobic Surfaces Produce a hydrophobic coating on the particles at the part boundary, this will prevent the ink from bleeding past this point. Hydrophilic surfaces Plasma surface activation, whereby radicals bind to the surface. Following treatment, the surface is rich in polar molecules, which render the surface hydrophilic. This can draw the binder to these particles and increase the binder permeation through the part. It can also be used as the inverse of the hydrophobic binder, where the particles within the part boundary are made hydrophilic and draw the binder in to prevent bleed. For example, copper particles can be made hydrophilic by using a precursor gas that contains a functional group, such as Oxygen or Nitrogen. When this gas turns to plasma, it will react with the surface of the copper, and leave it hydrophilic. Then the structural, aqueous binder will be drawn to this point. Plasma Cleaning Can clean the surfaces of the particles with plasma to remove organic impurities and oxides. For example, aluminium particles exposed to oxygen or argon plasma. There are various cleaning methods such as the reactive species dislodging contaminants and oxides from the surface of the particles. Plasma Passivation May want to passivate the surface of a reactive metal. For example, aluminium, by reacting a nitrogen or oxygen plasma with the particles to form a nitride or oxide layer. Plasma-Enhanced Chemical Vapour Deposition Depositing materials onto the surface of the particles. For example, coating aluminium particles in alumina. Particles be put in a chamber with aluminium alkoxides or organometallic compounds, and oxygen or water vapor. The gasses provide the aluminium and oxygen required for the alumina. Plasma activates the precursor gasses, aluminium and oxygen species react and form alumina on the particles surface. INTERFACES • Graded / continuous interface may include annealing If graded interfaces are used, these could sinter at different rates, resulting in high stresses along the interfaces. These stresses would need to be mitigated or removed afterwards. Sintering agents would change the enthalpy of the reactions of the different materials and can be used to reduce these stresses. The stresses could also be designed into the part and used afterwards for some purpose. Using two different materials for the bed powder and / or the inks could allow predesigned stresses to be built into the final part after sintering. A material with a lower coefficient of thermal expansion is printed around a material with a higher coefficient of thermal expansion, and the two materials are joined either via a coherent interface (graded or sharp) or by mechanically locked features in the print design. When the part is cooled after sintering, the internal volume printed in high thermal expansion coefficient will contract more per unit volume than the outer, low coefficient material. The interface between the two materials would transfer stresses across the interface and would leave the outer material under compressive strain and the inner material under tension. These strains would reduce further away from the interface. Alternatively, the materials could be the other way around (I.e., low expansion internally, high expansion externally) to result in tensile strain in the outer layer and compressive strain in the inner layer. VARIED ALLOY COMPOSITION For example, ODS (oxide dispersion strengthened) type alloys. ODS type alloys can be made by including hard oxide nanoparticles in ink and jetted onto a powder bed. When sintered they do not sinter but stay in material, they block deformation under stress by stopping slipping of dislocations and crystal planes. Two most common ODS catalysis are Alumina (AI2O3) and Yttria (Y2O3) when added as nanoparticles. Examples Include C15715 (AI2O3), Fe-Cr-AI (Y2O3), and Ni-Cr-AI (Y2O3). Typically, mechanically mixed for oxide dispersion. EXAMPLES Examples of products that can be manufactured using the methods disclosed in this invention include, but are not limited to: Cutting edges on parts, for example, a strong metal with a sharp ceramic blade surface. These two materials are printed as one and interface. Surface treatment, for example: aluminium and copper instead of plating in preparation for soldering. This saves multiple process steps which are currently required. Miniature Gas turbine blades, which are currently produced using multiple stages including, for example, casting, crystal growth, surface milling and finishing. These require pressure, heat, energy, a lot of time and extremely precise process controlled. The current invention can remove many, if not all, steps to create the part. Solid oxide fuel cells can be produced in a single print using the methods disclosed. Ceramic jacket around heatsink to direct the heat flow. Print two materials, one is a ceramic with low thermal conductivity, the other is copper with a high thermal conductivity. Conventional AM heatsinks are single material, which will uniformly radiate heat from all surfaces that are not coupled to the item to be cooled. The cooling can be augmented with active cooling using fans or fluid streams. With multi-material printing, it is possible to build a partial ceramic jacket around the copper heatsink to direct the heat emission. The ceramic jacket will prevent heat from being radiated from the surfaces it contains, allowing the heat to be emitted at a chosen location (e.g., away from heat sensitive components or electronics). This selective heat dissipation can be applied to many different devices, and the geometry customised to provide optimum heat flow away from sensitive areas. Solar panels can be printed as one converter element. In addition, while a particular feature or aspect of an embodiment of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Furthermore, it should be understood that embodiments of the disclosure may be implemented in discrete circuits, partially integrated circuits or fully integrated circuits or programming means. Also, the term "exemplary" is merely meant as an example, rather than the best or optimal. It is also to be appreciated that features and / or elements depicted herein are illustrated with particular dimensions relative to one another for purposes of simplicity and ease of understanding, and that actual dimensions may differ substantially from that illustrated herein. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof. ASPECTS OF THE DISCLOSURE Non-limiting aspects of the disclosure are set out in the following numbered clauses. 1. A method of ink jetting, the method comprising: providing a first layer of a powder particles comprising a composition of one or more materials; jetting the first layer of the powder with one or more ink formulations; and controlling the enthalpy of the resulting materials through the selection of powder composition and ink formulation. 2. The method according to any previous claim, wherein the ink formulation comprises a solvent, a catalyst, a precursor material, a carrier vehicle, and / or a growth agent and / or an inhibitor, and / or particles. 3. The method according to any previous claim, wherein the particles comprise nanoparticles. 4. The method according to claim 1, wherein the resulting materials sinter at a same temperature. 5. The method according to claim 1, wherein the resulting materials sinter at different temperatures. 6. The method according to any previous claim, wherein the resulting part is printed as one and postprocessed as one. 7. The method according to any previous claim, wherein the particles are coated. 8. The method according to any previous claim, wherein the ink formulation can be modified during jetting. 9. The method according to any previous claim, wherein there is an interlayer heat treatment as specific positions. 10. The method according to any previous claim, wherein regulating forming of the particles from the ink formulation in the first layer of the powder comprises modulating dosing of the ink formulation. 11. The method according to any previous claim, comprising selecting a particle size distribution of the powder. 12. The method according to any previous claim, comprising selecting a particle morphology of the powder. 13. The method according to any previous claim where each material within the powder bed is deposited independently to specific locations. 14. The method according to any previous claim employ transition strategies, for example gradient graphs, to define the control the interface between materials within a part. 15. The method according to any previous claim where the permeability of the ink is controlled. 16. The method according to any previous claim where the ink contains surfactants to alter wetting properties. 17. The method according to any previous claim where solvent removable polymers are used to control ink drop bleeding. 18. The method according to any previous claim where surfaces can be made completely hydrophobic, which will repel the aqueous binder for the main part. 19. A method of ink jetting, the method comprising: providing a first layer of a powder particles comprising a composition of one or more materials; jetting the first layer of the powder with one or more ink formulations; and multi-material parts can be formed through microstructure grading or abrupt interfacing. 20. The method according to any previous claim where mechanically stable interlocking interfaces can be produced including those predesigned to aid material separation during recycling. 21. The method according to any previous claim where layer-by-layer deposition of two materials where a mechanical locking feature is printed. 22. The method according to any previous claim where the difference in thermal expansion coefficients between two materials is employed to create parts that separate when heated to a set temperature. 23. The method according to any previous claim where stresses occurring during sintering are designed into the part. 24. A computer comprising a processor and a memory configured to implement, at least in part, a method according to any of claims 1 to 18, a computer program comprising instructions which, when executed by a computer comprising a processor and a memory, cause the computer to perform a method, at least in part, according to any of claims 1 to 18 or a non-transient computer-readable storage medium comprising instructions which, when executed by a computer comprising a processor and a memory, cause the computer to perform a method, at least in part, according to any of claims 1 to 18. 5 25. An article manufactured at least in part by ink jetting, the article comprising: a first layer of a bound powder comprising a material; wherein the first layer comprises: a microstructure influenced by particles formed from an ink formulation where the enthalpy of the resulting material has been controlled through the selection of powder composition and 10 ink formulation. Amendments to the claims have been filed as follows:

Claims

1. A method of ink jetting, the method comprising:providing a first layer of a powder particles comprising a composition of one or more materials, wherein the particles are coated;jetting the first layer of the powder with one or more ink formulations; andcontrolling the enthalpy of the resulting materials through the selection of powder composition and ink formulation.

2. The method according to any previous claim, wherein the ink formulation comprises a solvent, a catalyst, a precursor material, a carrier vehicle, and / or a growth agent and / or an inhibitor, and / or particles.

3. The method according to any previous claim, wherein the particles comprise nanoparticles.

4. The method according to claim 1, wherein the resulting materials sinter at a same temperature.

5. The method according to claim 1, wherein the resulting materials sinter at different temperatures.

6. The method according to any previous claim, wherein the resulting part is printed as one and postprocessed as one.

7. The method according to any previous claim, wherein the ink formulation is modified during jetting.

8. The method according to any previous claim, wherein there is an interlayer heat treatment at specific positions.

9. The method according to any previous claim, comprising selecting a particle size distribution of the powder particles.

10. The method according to any previous claim, comprising selecting a particle morphology of the powder particles.

11. The method according to any previous claim, where the powder particles comprise a composition of more than one material and where each material within the layer of powder particles is deposited independently to specific locations.

12. The method according to any previous claim employ transition strategies, for example gradient graphs, to define the control the interface between materials within a part.14 11 2413. The method according to any previous claim where the permeability of the ink is controlled by altering the viscosity and / or wettability of the ink or by functionalising the powder particle surface to increase or reduce wetting.

14. The method according to any previous claim where the ink contains surfactants to alter wetting properties.

15. The method according to any previous claim where solvent removable polymers are used to control ink drop bleeding.

16. The method according to any previous claim further comprising treating the upper surface of the layer of powder particles after jetting.

17. The method according to any previous claim wherein mechanically stable interlocking interfaces are produced, including those predesigned to aid material separation during recycling.

18. The method according to any previous claim comprising layer-by-layer deposition of two materials, wherein a mechanical locking feature is printed.

19. The method according to any previous claim where the difference in thermal expansion coefficients between two materials is employed to create parts that separate when heated to a set temperature.

20. The method according to any previous claim where stresses occurring during sintering are designed into the part.

21. A computer comprising a processor and a memory configured to implement, at least in part, a method according to any of claims 1 to 20, a computer program comprising instructions which, when executed by a computer comprising a processor and a memory, cause the computer to perform a method according to any of claims 1 to 20 or a non-transient computer-readable storage medium comprising instructions which, when executed by a computer comprising a processor and a memory, cause the computer to perform a method according to any of claims 1 to 20.

22. An article manufactured at least in part by ink jetting, the article comprising:a first layer of a bound powder particles, the powder particles comprising one or more materials, wherein the particles are coated;wherein the first layer comprises:a microstructure influenced by particles formed from an ink formulation where the enthalpy of the resulting material has been controlled through the selection of the powder particles and the ink formulation.Application No: GB2315898.3 Examiner: Matthew LawsonClaims searched: 1-18, 24 &25 and 20-23 in Date of search: 12 April 2024partPatents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance v A 1-6,10-16,24,25 US 2020 / 0338819 Al (HINCH) - the whole document. X 1- 4,6,9,11- 13,15,16, 24,25 US 2021 / 0154924 Al (ERICKSON) - paragraphs [0006] &00132] and figures 1A-1C. v A 1-4,6,11-13,15,16, 24,25 US 2021 / 0371619 Al (NATARAJAN) - paragraphs [0089] &[0095], X 1,2,4,6,11 13,15,24, 25 US 2021 / 0053116 Al (SELEZNEV) - paragraphs [0123], [0128] &[0134], X 1,2,5,6,8, 10- 16,24,25 US 2017 / 0056138 Al (ZANDINEJAD) - paragraphs [0009], [0011] &[0082]-[0083],Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of same category. before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:International Classification:Subclass Subgroup Valid From B22F 0010 / 14 01 / 01 / 2021 B22F 0010 / 38 01 / 01 / 2021 B33Y 0080 / 00 01 / 01 / 2015

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