WO2022231569A1

WO2022231569A1 - Seals

Info

Publication number: WO2022231569A1
Application number: PCT/US2021/029198
Authority: WO
Inventors: Agusti GARCIA PUJOL; Oscar Lopez Lopez; Marc GUILLAUMET CAMPMANY
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2021-04-26
Filing date: 2021-04-26
Publication date: 2022-11-03

Abstract

In an example, a three-dimensional printed seal comprises a first portion of a layer of fused build material and a second portion of a layer of fused build material. The first portion has a first elastic behavior and the second portion has a second elastic behaviour. The first and second elastic behaviors are different such that the three-dimensional printed seal has a differential elastic profile.

Description

SEALS

BACKGROUND

[0001] Some additive manufacturing systems generate three-dimensional objects on a layer-by-layer basis through the selective solidification of build material.

BRIEF DESCRIPTION OF DRAWINGS

[0002] Examples will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which:

[0003] Figures 1 A and 1 B show a schematic diagram of an example seal;

[0004] Figure 1 C is a schematic diagram showing the performance of an example seal

[0005] Figures 2A is a schematic diagram of an example seal;

[0006] Figures 2B and 2C are different schematic views of an example seal;

[0007] Figure 2D is a schematic diagram of an example seal;

[0008] Figure 3 is a flowchart of an example of a method;

[0009] Figure 4 is a flowchart of an example of a method; and

[0010] Figure 5 is a simplified schematic diagram of an example machine- readable medium in association with a processor.

DETAILED DESCRIPTION

[0011] Additive manufacturing techniques may generate a three-dimensional object through the solidification of a build material. In some examples, the build material may be a powder-like granular material, which may for example be a plastic, ceramic or metal powder. The properties of generated objects may depend on the type of build material and the type of solidification mechanism used. Build material may be deposited, for example on a print bed and processed layer by layer, for example within a fabrication chamber. According to one example, a suitable build material may comprise polymeric (e.g. polyamide, polypropylene, TPU, TPA), ceramic or metallic (e.g. stainless steel) particles.

[0012] In some examples, selective solidification is achieved through directional application of energy, for example using a laser or electron beam which results in solidification of build material where the directional energy is applied. In other examples, at least one print agent may be selectively applied to the build material, and may be liquid when applied. For example, a ‘coalescence agent’ or ‘coalescing agent’ (for example, a fusing agent in examples where the build material comprises a plastics powder, or a binder agent in examples where the build material comprises a metal powder, or, in other examples, a plastics powder) may be selectively distributed onto portions of a layer of build material in a pattern derived from data representing a slice of a three-dimensional object to be generated (which may for example be generated from structural design data). The fusing agent may have a composition which absorbs energy such that, when energy (for example, heat) is applied to the layer, the plastic build material coalesces and solidifies to form a slice of the three-dimensional object in accordance with the pattern. The binder agent may have a composition that, when heated or when UV energy is applied, causes the metal particles of build material to which binder agent is applied to adhere to one another. In other examples, coalescence may be achieved in some other manner.

[0013] According to one example, a suitable fusing agent may be an ink-type formulation comprising carbon black. In one example such a fusing agent may additionally comprise an infra-red light absorber. In one example such a fusing agent may additionally comprise a near infra-red light absorber. In one example such a fusing agent may additionally comprise a visible light absorber. In one example such a fusing agent may additionally comprise a UV light absorber. Examples of print agents comprising visible light enhancers are dye based colored ink and pigment based colored in.

[0014] As noted above, additive manufacturing systems may generate objects based on structural design data. This may involve a designer generating a three- dimensional model of an object to be generated, for example using a computer aided design (CAD) application. The model may define the solid portions of the object. To generate a three-dimensional object from the model using an additive manufacturing system, the model data can be processed to generate slices of parallel planes of the model. Each slice may define a portion of a respective layer of build material that is to be solidified or caused to coalesce by the additive manufacturing system.

[0015] As also noted above, additive manufacturing systems may generate objects through the selective solidification of a build material comprising plastic particles or metal particles (for example a stainless steel powder). This may involve depositing build material in layers on a print bed, or build platform and selectively depositing a fusing agent (in examples where the build material comprises plastic particles) or a binder agent (in examples where the build material comprises metal particles or other suitable types of material), for example using printheads to jet the agent, onto portions of a layer of build material in a pattern derived from data representing a slice of a three-dimensional object to be generated (which may, for example, be generated from structural design data). When heat is applied to a layer of build material, those portions of build material to which a thermal fusing agent has applied will heat and coalesce. When a binder agent is applied to the build material, when heat is applied to the build material (either on a layer-by-layer basis or to a set of layers as a whole, e.g. a volume of build material) this creates a binder matrix that comprises the build material.

[0016] In the example of a plastics build material, the portions of build material treated with fusing agent absorb energy (e.g. heat energy), coalesce, and solidify to form a slice of the three-dimensional object in accordance with the pattern. Following the application of energy therefore, the portions of build material to which fusing agent was applied heat up, coalesce, and then solidify upon cooling to form the three-dimensional object. Any build material to which fusing agent was not applied (un-coalesced, “loose” build material, or build material remnant), e.g. those parts of the build material that will not form part of the generated object, will not solidify and remain as un-coalesced, loose, excess, build material. Following the application of energy, therefore, the three-dimensional object may therefore be embedded and/or at least partially surrounded by un-coalesced, loose, build material which will need to be separated from the object prior to any subsequent operations (e.g. a post-processing operation such as dyeing). [0017] In the example of a metal build material (or, in one example of a plastics build material), the binder agent may comprise an adhesive element (for example a polymeric concentrate) suspended within a liquid carrier that will cause portions of build material to which binder agent was applied to coalesce during a curing process. For example, following the layer-wise deposition of the metal build material and the selective deposition of the binder agent thereon the build platform and/or the powder contain therein may undergo a curing process during which the build material (including the layers of build material with the binder agent applied and surrounding build material to which no binder agent has been applied) is subjected to energy to cure the build material (for example, using UV light or heat to layer-by-layer cure the build material or using heat to cure a volume (e.g. a set of layers) of build material). During the curing process, the binder agent, applied to portions of the build material, is thermally activated when subject to the curing temperatures, causing adhesive particles (e.g. polymeric particles) to separate from the liquid carrier and adhere to particles of the build material while the liquid carrier evaporates, leaving the portions of build material to which binder agent was applied solidifying and effectively being glued together. Post-curing, any build material to which binder agent was not applied (“loose” build material, or build material remnant), e.g. those parts of the build material that will not form part of the generated object, will not solidify and remain as generally loose, excess, build material. Curing may be performed on a plurality of layers of build material, in other words a whole volume of build material may be subject to heat to cure the whole volume of build material at substantially the same time. For the curing process, the build platform may be moved to a separate curing station comprising a curing oven or similar.

[0018] After curing, the solidified build material (those portions of the build material to which binder agent was applied and have adhered during curing due to the activation of the adhesive) may be referred to as a “green part,” being unfinished but substantially resembling the final part, and being a loosely bound part having a relatively low density. Once cured, to form the final object to be generated from the metal build material, the green part is transferred to a sintering oven in which the green part undergoes a sintering process. During sintering, the green part is exposed to elevated temperatures to sinter the build material particles (of the green part) into the final, solid, three-dimensional object (which will have a higher density than the green part).

[0019] Some examples herein relate to the generation, in an additive manufacturing process of a seal. In examples where a target environment is to be sealed, for example fluidly sealed (to avoid leakages of liquids or gases or build material) or acoustically sealed (to restrict or impede the transmission of sound), or thermally sealed, etc. seals may be manufactured from elastomers and formed by an injection moulding process or an extruded elastomer process. Although, in these processes, it is possible to design and form different shapes, the available shapes are usually non-complex (e.g. having substantially linear profiles) since they are formed from moulds and therefore the design of a seal having a bespoke profile to seal a complex geometry may be difficult, or even not possible, via injection moulding (by complex geometry it is meant to comprise complicated seal profiles such as having 360-degree closure or having undercuts in different axes, etc.). If the seal is to have a more complex profile, e.g. having a 360-degree closure (or a loop), then these parts of the seal may be formed by cutting and then gluing or welding moulded seal segments together to form the final seal. However, in these examples the resulting seal may comprise welding points or parting lines (the juncture between two seal portions that have been joined together). Such welding points or parting lines can reduce the life of the seal as they can present localised points of structural weakness or can even lead unexpected leakages. [0020] According to the examples herein a seal is generated in an additive manufacturing, or 3D-printing, process. Using such a process means that seals having bespoke, and potentially complicated, geometrical profiles, such as including bends, twists, loops, etc. may be made, including profiles that may not be considered possible to manufacture through injection moulding or extrusion, and such profiles may be produced without any welding points or parting lines that could damage the sealings and/or generate leakages. Moreover, some examples herein relate to a three-dimensional seal having a differential elastic profile, or elastic behaviour, or elasticity, or hardness along the geometry of the seal. Example ways of producing such a differential elastic profile will be discussed below but, according to the examples herein, a seal may be generated having different portions of a different parameter value, the parameter being a measure of elastic behaviour, such that a single, one-piece, seal can have different properties along its geometry. In turn, this can mean that the seal responds differently to forces depending on where the forces are applied. For example, the seal may comprise different resonance, or vibration, frequencies along its geometry, or different hardnesses, or a different response to an applied force (e.g. a different compressive or tensile strength), a full parameter list is given below in the discussion of Figure 1. The seal may also have different vibration transmission frequencies, or attenuation properties, along its geometry such that different parts of the seal can have different acoustic properties (e.g. acoustic transmission or isolation properties). There is therefore re-usability, a short lead time, and low costs associated with manufacturing such a seal, in addition to a great amount of design freedom allowing bespoke seals to be easily, cost-effectively, and quickly manufactured.

[0021] Figure 1A shows an example seal 100, which comprises a three- dimensional printed seal 100. The seal comprises a first portion 101 of a layer of fused build material having a first elastic behavior and a second portion 102 of a layer of fused build material having a second elastic behavior. The first and second portions 101 , 102 of the layers are schematically indicated in exploded view in Figure 1B. The first and second elastic behaviors are different such that the three- dimensional printed seal has a differential elastic profile, as is schematically indicated by the holes and the exploded views of Figure 1B. The seal 100 therefore comprises asymmetric elastic properties, or asymmetric elastic behaviour.

[0022] The first portion 101 may comprise a portion of a first layer of build material and the second 102 portion many comprise a portion of a second layer of build material, the first and second layers being different, or the first and second portions 101 , 102 may each comprise portions of the same layer of build material. The build material, fused to generate the portions of the layers, may comprise the same build material (or type of build material) such that the seal 100 comprises a substantially identical material composition along its geometry. The first portion 101 and/or the second portion 102 may comprise a portion of the internal volume of the seal 100 and/or a portion of an external surface of the seal.

[0023] The seal 100 may have been generated as part of an additive manufacturing process comprising operating on (e.g. determining or receiving) object model data describing the seal and operating on object generation instructions to generate the seal based on object model data, as will be described with reference to later figures, where the layers of build material may correspond to a slice as defined by the object model data. One or each of the first and second portions may be formed by fusing a layer of a build material using a fusing agent, or binder agent, and each portion may comprise fused build material and a fusing, or binder, agent remnant following evaporation from a solvent from an applied fusing or binder agent. One or each of the first and second portions may also comprise voids, being a portion of the seal absent any (fused) building material (the voids having the same or a different size), as will be explained below.

[0024] The seal 100 of this example is depicted as comprising a tortuous section, or a section with complex geometry, either one of the areas of the seal 100 designated 110, but despite the complex geometry of this portion 110 the seal nevertheless comprises a smooth outer profile, indicating how additive manufacturing can produce a seal 100 having a complex geometry without weld points or parting lines resulting from piecing together seal segments, since the seal 100 of this example may be formed as one single piece. The seal 100 therefore may therefore comprise a continuous (or smooth) external geometrical profile. [0025] The first portion 101 comprises a first elastic profile and the second portion 102 comprises a second elastic profile. The elastic profile may comprise a parameter that comprises a measure of elastic behaviour and/or elasticity and/or compressive strength and/or resilient and/or density and/or tensile strength and/or an ability to withstand, or react to, an applied force and/or an ability to recover its original shape after a force causing deformation has been removed and/or an acoustic property, such as acoustic transmission and/or acoustic isolation and/or attenuation and/or impedance and/or absorption and/or resistance and/or hardness and/or softness and/or brittleness and/or rigidity and/or ductility and/or stiffness and/or flexibility and/or firmness and/or an elastic modulus. The parameter may comprise a “compression set” by which it is meant to comprise a material’s capacity, or ability to recover its original shape following the removal of an applied force causing deformation. The two portions 101, 102 of the seal 100 may therefore comprise different elasticity and/or compressive strengths and/or tensile strengths and/or resiliences and/or densities and/or abilities to withstand, or react to, an applied force and/or abilities to recover their original shape after a force causing deformation has been removed and/or an acoustic property, such as acoustic transmission and/or acoustic isolation and/or attenuation and/or impedance and/or absorption and/or resistance and/or hardness and/or softness and/or brittleness and/or rigidity and/or ductility and/or stiffness and/or flexibility and/or firmness and/or an elastic modulus. In one example, the parameter comprises hardness (or a measure of hardness). Hardness may be measured according to a hardness scale such as Shore hardness or Brinell hardness and may comprise a measure of an ability to react to an applied force. Therefore, in one example, the differential elastic profile of the seal may comprise a differential hardness, e.g. a first portion having a first hardness and a second portion having a second hardness.

[0026] The first portion 112 comprises a different volume of build material than the second portion 114 which may be characterised by each portion comprising a different density, volume of build material or a different number of voids, or holes, producing different elastic behaviour. Nevertheless, the first and second portions may comprise substantially equal geometries (e.g. external geometries), for example substantially equal lengths and/or widths and/or depths.

[0027] Figure 1C shows a different view of the seal 100 showing a curve illustrating the differential elastic profile, or behaviour. As can clearly be seen in Figure 1C and in the exploded views of Figure 1B, both the first and second portions 112, 114 comprise portions of fused build material and voids absent fused material. In this example the first and second portions 112, 114 comprise a different number of voids. In this particular example, to illustrate the differing elastic behaviour and differential profile, a set of first and second portions 112, 114, in that the seal 100 comprises two identical first portions 112 and two identical second portions 114, disposed symmetrically about a third portion 116 of the seal 100 such that, along this portion of its geometry, the seal 100 comprises a symmetrical asymmetric profile. The first and second portions 112, 114 of the seal therefore comprise different internal structures, with the first portion 112 comprising a first internal structure and wherein the second portion 114 comprises a second internal structure, wherein the first and second internal structures are different. One or both internal structures may comprise a lattice structure or a mesh structure having fused build material and voids absent build material. The voids of the first portion 112 are of a different size to the voids of the second portion 114. In this way, to produce two seal portions 112, 114 having different elastic behaviours, one portion may have a different number of same-sized voids to the other, or one portion may have the same number of different-sized voids to the other, or (as shown in Figure 1C) one portion may have a different number of different-sized voids to the other. In any example, the size and/or number of the voids may be selected to produce a particular internal structure, such as an internal mesh or lattice, that results in the portions of the seal 100 having different elastic behaviours along its geometry. One portion may therefore comprise fewer voids, or a greater number of voids, than the other. The voids of one portion may be regular and/or symmetric in structure whereas the voids of another portion may be irregular and/or asymmetric. The voids may be entirely bounded by an internal portion of the seal to define a total internal structure, or may comprise a through-hole, extending from a first exterior surface or side of the seal to a second exterior surface or side. The seal may comprise a structure having a regular mesh or lattice (see the exploded view of the first portion 101 of Figure 1B) and/or a structure having an irregular, or irregular mesh or lattice (see the exploded view of the second portion 102 of the Figure 1B). Alternate terminology for the voids may comprise holes, passages, or openings etc. In one example, the seal 100, or any of the other seals described herein, may comprise a gasket.

[0028] Figure 1C shows a curve 111 illustrating the differential elastic profile of the seal along its geometry. As shown by the curve 111, the differing internal structures may be generated to produce a differential elastic profile in the seal, according to which the third portion 116 of the seal 100, absent voids in this example, has a compressive strength F1 whereas the surrounding first portions 114 of the seal have a compressive strength F2 which is less than F1, with the surrounding second portions 112 portion having a compressive strength F3 which is greater than F1, e.g. such that F1 > F2 > F3. Therefore, at the time of manufacturing the seal 100 which is to have a differential elastic profile, or behaviour, the seal 100 may be produced from object model data describing regions having different densities, or volumes, of build material, or different internal structures (such as a lattice structure or mesh structure), or different numbers of voids, or voids of a different size, in order to produce different elastic behaviour at different portions of the seal 100. The different elastic behaviours of the seal 100 may be selected at the stage of generating the object model data describing the seal in order for the seal to react in a set way to a force that is to be applied to the seal. For example, if it is understood that the first portion 114 of the seal 100 is to be struck, in use, with a compressive force where a greater elasticity would cause the seal 100 to deform around an environment to be sealed such that no fluid leakages occurred, then the first portion 114 of the seal may be generated having a greater number of voids, or larger voids, than another portion of the seal (such as the second or third portions 112 or 116) to confer this greater elasticity so that the seal reacts to the applied force in this way. In this example, each of the second portions 112 comprises three voids and each of the first portions 114 of the seal comprise ten voids, the voids of the first portion 114 being smaller than the voids of the second portion 112 to produce a greater compressive strength F3 in the first portion 114 compared to the compressive strength F2 of the second portion 112. [0029] One example in which a greater number of same-sized voids may be used for the seal may be where a large punctual force is to be applied in one area and an elastic profile comprising a particular compression set (ability to recover its original shape once the force is removed) may be used so that the seal deforms to continue sealing when the force is applied but will quickly recover its original shape when the force is removed. For instance, a door of a 3D printer may have a large weight and closing the door may seal the sealing areas near to the door latches to keep the door closed and seal any gaps. These areas may use a higher strength to seal the gaps such that changing the size of the voids in these areas may compromise the integrity of the door seal (since the same level of force is applied to less material), but increasing the number of voids (of the same size) may increase the inertia of the sealing and its deformation rate, and therefore its performance and integrity as a seal without compromising the sealing itself. According to another example, by way of an opposite solution, incrementing the void size may be utilised in examples where a small force is applied and where, if the inertia of the sealing is too high, the response force from the sealing to the surrounding parts may be too high such that the seal is deformed and/or the door cannot close.

[0030] In some examples, part of the first and/or second portions 112, 114 of the fused build material may comprise part of an external surface of the three- dimensional printed seal. Therefore, in examples where the first and/or second portions comprise a void, the void may be part of the external geometry of the seal 100. In other words, any part of the first and/or second portions 112, 114 may comprise part of an internal volume, or both part of an internal volume and part of an external surface.

[0031] The seal 100 is to seal against a fluid, for example a fluid type, e.g. a first fluid type. The first or fluid type, e.g. first fluid type, may comprise a liquid or a gas or sound (e.g. acoustic pressure waves) or a build material (e.g. a powder). Hereinafter, the terms “fluid”, “fluid type”, and “first fluid type” should be regarded as interchangeable. Therefore, the seal 100 may comprise a fluid seal (such as a fluid-tight) seal or a hermetic seal or an acoustic seal etc. In examples where the seal 100 comprises an acoustic seal, the structure of the seal 100 (for example an internal or external structure) may be such that acoustic pressure waves incident on a first external surface of the seal 100 are impeded from being transmitted through the seal 100 or attenuated etc. In other words, the seal 100 may comprise a portion having an internal structure comprising an irregular mesh (or lattice) (see for example the exploded view of portion 102) which means that when incident soundwaves propagate through the seal they are caused to break, or collapse, thereby minimising, or eliminating, the soundwaves able to pass through the seal 100, which thereby functions as an acoustic isolator. In other examples, the seal 100 may comprise a thermal seal such that different portions of the seal 100 are to have different thermal properties, or a pressure seal. In another example the seal 100 may comprise a seal to seal against vibrations such that different portions of the seal 100 have different absorptive properties. The first and second portions may therefore comprise different harmonic and/or resonance properties.

[0032] In one example, seal portions may comprise a different hardness such that the seal has a differential hardness profile. In these examples, the first portion of the seal (such as 102 or 114) comprises a first hardness and the second portion of the seal (such as 104 or 112) comprises a second hardness, the first hardness being different to the first (e.g. greater than or less than). In this way, and as indicated in Figure 1C where the first and second portions 114, 112, by virtue of their different internal structures, may comprise different hardnesses, the different hardness of the seal can mean that different areas respond differently to applied forces, in that a different hardness means a different compressive behaviour and ability to react to an applied force or recover its original shape when the force is moved etc. In this way, a portion with a lower hardness may exhibit a greater amount of elastic deformation when compared to a portion with a greater hardness, and this greater amount of elastic deformation may ensure that this portion adequately functions as a seal when it is subject to a given force during use. By way of example, a given torque may cause a portion of the seal with high rigidity (or hardness etc.) to deform away from an environment to be sealed against a given fluid type meaning that the seal portion does not adequately function as a seal when the torque is applied, whereas the same portion of the seal with a low rigidity (or hardness etc.) may, in response to the torque, deform such that the seal portion maintains its sealing capability by deforming in such a way so that the environment remains sealed against the fluid type even when the torque is applied.

[0033] Further seal examples are illustrated in Figures 2A-2D. Figure 2A illustrates an example three-dimensional printed seal 200a, e.g. comprising layers of build material as described above, comprising a number of holes 220 that are for receipt of a fastener to fix the seal 200 to an environment to be sealed. Flowever, the seal 200a of this example has asymmetric elastic properties caused by a different internal structure defined by a number of voids 201-210. Each void 201-210 is provided in a different potion of the seal and may be provided in a different portion of a layer of fused build material used to manufacture the seal 200a or in a different layer of fused build material used to manufacture the seal 200a. As shown in Figure 2A, the seal 200a has various portions exhibiting different internal mesh or lattice structures due to the seal 200a comprising a number of voids of different sizes and shapes. Voids 201 and 205-208 are rectangular in shape (e.g. in cross-section), but of differing sizes, whereas the remaining voids are similar-sized and circular in shape (e.g. in cross-section). In the Figure 2 example (and also in the Figure 1 example for the portion 101) the voids are three-dimensional and comprise constant cross-sections (or cross- sections of constant area) but in other examples the voids may comprise non constant cross-sections. In these latter examples, the voids may comprise irregular, shapes (such as in the Figure 1 example for the portion 102). As also shown in Figure 2A, the seal 200a comprises a number of faces yet it comprises a continuous external profile (e.g. absent weld points or parting lines). The voids of the Figure 2A example are provided on different external surfaces, or faces, of the seal 200a, e.g. voids 209 and 210 are provided on a different external surface to the remainder of the voids 201-208. Therefore, the voids may extend through the seal in different planes, or along different dimensions of the seal (e.g. the voids 209 and 210 may be considered to extend through a width dimension of the seal 200a whereas the remaining voids 201-2018 may be considered to extend through a depth dimension of the seal 201), may extend through the seal in a straight, or curved fashion.

[0034] Figures 2B and 2C depict different views of the same seal 200b. Like the seal 200a, the seal 200b also comprises different sized and shaped voids that are provided on different faces, or surfaces, of the seal 200b and extend through the seal 200b in different geometries (e.g. in a width, length, or depth direction). The seal 200b comprises a first portion 231 of voids that are of a constant rectangular cross-section and extend through the seal 200b in a first dimension (e.g. a width direction) and a second portion 232 of voids that are of a constant circular cross- section extending through the seal 200b in a second dimension (e.g. in a depth direction). The seal 200b further comprises a void 233 that is a void in the external surface of the seal 200b (in this example, the void 233 comprises a void in four external surfaces of the seal), the void 233 in this example forming a cutaway portion of the external surface of the seal 200b. The cutaway void 233 in this example being formed in the seal 200b to accommodate a particular corner.

[0035] Figure 2D shows another example seal 200c which comprises a number of voids 241-245 in its length, one 241 of which comprises a triangular cross- section. The seal 200c of the Figure 2D example also illustrates an example complex geometry that may be generated by generating the seal 200c through additive manufacturing. Despite the complex cross-section of the seal 200c (which may also be non-constant), this design of seal 200c may be manufactured without having to join seal segments together and therefore without producing any weld points or parting lines, the seal 200c thereby having a continuous profile (e.g. external profile) or geometry. Although the examples shown in Figure 2 depict, for illustrative purposes, voids comprising through-holes, in other examples the voids may be totally internal to the seals such that the exterior surface of the seal is smooth, absent voids, yet an internal region comprises a number of voids defining the seal’s internal structure conferring on the seal a differential elastic property.

[0036] Figure 3 shows an example method 300 which may comprise a computer- implemented method. The method 300 may comprise a method of generating a seal, e.g. generating a seal in an additive manufacturing process. The method 300 may comprise a method of generating any of the seals described above with reference to Figures 1A-2D.

[0037] At block 302 the method 300 comprises generating a representation of a seal to seal a representation of an area of an environment against a first fluid type, the seal having a differential elastic profile, wherein the representation of the seal comprises a first portion having a first elastic profile and a second portion having a second elastic profile, wherein the first and second elastic profiles are different. For example, the representation of the seal may comprise seal portions having different internal structures or a different number of voids (e.g. same or different sized voids), e.g. as described above. For example, block 302 may comprise operating on object model data describing the seal according to the representation. The object model data may comprise data representing at least a portion of the seal to be generated by an additive manufacturing apparatus by fusing, or binding, a plastics or metal build material. The object model data may for example comprise a Computer Aided Design (CAD) model, and/or may for example comprise a STereoLithographic (STL) data file, and/or may be derived therefrom. In some examples, the data may be received over a network, or received from a local memory or the like. In some examples, the data may define the shape of the part of an object, i.e. its geometry. In some examples the data may define the seal’s elastic profile and/or behaviour, e.g. at least one mechanical property, for example a measure of elastic behaviour and/or elasticity and/or compressive strength and/or resilience and/or density and/or tensile strength and/or an ability to withstand, or react to, an applied force and/or an ability to recover its original shape after a force causing deformation has been removed and/or an acoustic property, such as acoustic transmission and/or acoustic isolation and/or attenuation and/or impedance and/or absorption and/or resistance and/or hardness and/or softness and/or brittleness and/or rigidity and/or ductility and/or stiffness and/or flexibility and/or firmness and/or an elastic modulus and/or compression set. [0038] At block 304 the method 300 comprises generating, in an additive manufacturing process, the seal based on the representation. For example, block 304 may comprise the deposition of build material and a selective ejection of fusing agent or binder agent to form first and second portions of the seal (as described above with reference to Figures 1A-2D). This will be described in more detail with reference to Figure 4. Block 304 may comprise forming a layer of build material, applying print agents, such as fusing agent or binder agent, in locations specified in the object generation instructions for an object model slice corresponding to that layer, and applying energy, for example heat, to the layer. Some techniques allow for accurate placement of print agent on a build material, for example by using print heads operated according to inkjet principles of two- dimensional printing to apply print agents, which in some examples may be controlled to apply print agents with a resolution of around 600dpi, or 1200dpi. A further layer of build material may then be formed and the process repeated, with the object generation instructions for the next slice.

[0039] Figure 4 shows an example method 400 which may comprise the method 300 of Figure 3. Blocks 402 and 404 of the method 400 respectively comprise blocks 302 and 304 as described above with reference to Figure 3.

[0040] At block 406, the method 400 comprises determining object model data describing the representation of the seal, wherein the first portion of the representation of the seal described by the object model data comprises a first internal structure wherein the second portion of the representation of the seal described by the object model data comprises a second internal structure, wherein the first and second internal structures are different.

[0041] At block 408, the method 400 comprises determining object generation instructions to generate the representation of the seal according to the object mode data by defining a first portion of build material that is to correspond to the first portion of the representation of the seal and a second portion of build material that is to correspond to the second portion of the representation of the seal, wherein the first portion of build material comprises a different volume of build material than the second portion. [0042] In some examples, as part of block 408, according to the object generation instructions, the first portion of build material comprises a first region to which a fusing or binder agent is to be applied and a second region to which no fusing or binder agent is to be applied such that the first region forms part of the seal and the second region forms a void in the seal, and wherein, according to the object generation instructions, the second portion of build material comprises a third region to which a fusing or binder agent is to be applied and a fourth region to which no fusing or binder agent is to be applied such that the third region forms part of the seal and the fourth region forms a void in the seal, and wherein the second region comprises a different volume of build material than the second region such that the first and second portions of the representation of the seal comprise a different number of voids, although in other examples the regions may comprise the same number of voids with the voids of one region being a different size and/or shape to the voids of the other. The voids therefore may be generated in the additive manufacturing process by depositing build material and then applying no print agent (e.g. no fusing or binder agent) such that the build material does not coalesce and does not form part of the 3D-printed seal. In other words, the seal may comprise portions comprises fused build material (e.g. comprising fusing or building agent remnant following part of the additive manufacturing process) and voids absent build material, the voids being formed be depositing build material without applying a print agent.

[0043] As stated above, the object model data may define the representation of the seal as having first and second portions of differing elasticity, or elastic behaviour, such that the seal has a differential elastic profile (or differential elastic behaviour). The object model data may define a seal having any of the properties discussed above with respect to Figures 1 and 2. For example, the object model data may define a seal having first and second positions that comprise different internal structures, different external profiles, a different number of voids, and/or voids of a different size resulting in the different elastic profiles, or different elastic behaviours, of the first and second portions. [0044] Figure 5 shows an example non-transitory and machine-readable medium 500 associated with a processor 502. The medium 500 (which may comprise a computer-readable medium) comprises machine-readable instructions 504 stored thereon which, when executed by a processor 502, may the cause the processor 502 to perform the method 300 or 400 as described above (e.g. any one or combination of the blocks thereof). For example, the instructions 504 are to cause the processor 502 to generate a representation of a seal to seal a representation of an area of an environment to be sealed against the first fluid type, the seal having a differential elastic behaviour along a geometry of the seal, wherein the representation of the seal comprises a first elastic behaviour and a second portion having a second elastic behaviour different to the first, and generate, in an additive manufacturing process, the seal based on the representation.

[0045] The instructions 504 that are to cause the processor 502 to generate the representation of the seal may be to cause the processor 502 to determine object model data describing the representation of the seal, wherein a first portion of the representation of the seal having the first elastic behaviour described by the object model data comprises a first internal structure wherein the second portion of the representation of the seal having the second elastic behaviour described by the object model data comprises a second internal structure, wherein the first and second internal structures are different, for example as described above with reference to block 406 of the method 400.

[0046] The instructions 504 that are to cause the processor 502 to generate the seal based on the representation may be to cause the processor 502 to determine object generation instructions to generate the representation of the seal according to the object mode data by defining a first portion of build material that is to correspond to the first portion of the representation of the seal and a second portion of build material that is to correspond to the second portion of the representation of the seal, wherein the first portion of build material comprises a different volume of build material than the second portion, for example as described above with reference to block 408 of the method 400. [0047] In some examples, according to the object generation instructions determined by the processor, the first portion of build material comprises a first region to which a fusing or binder agent is to be applied and a second region to which no fusing or binder agent is to be applied such that the first region forms part of the seal and the second region forms a void in the seal, and wherein, according to the object generation instructions, the second portion of build material comprises a third region to which a fusing or binder agent is to be applied and a fourth region to which no fusing or binder agent is to be applied such that the third region forms part of the seal and the fourth region forms a void in the seal, and wherein the second region comprises a different volume of build material than the second region such that the first and second portions of the representation of the seal comprise a different number of voids, or may, in some examples, comprise the same number of voids but of a different size and/or shape.

[0048] Examples in the present disclosure can be provided as methods, systems or machine readable instructions, such as any combination of software, hardware, firmware or the like. Such machine readable instructions may be included on a computer readable storage medium (including but is not limited to disc storage, CD-ROM, optical storage, etc.) having computer readable program codes therein or thereon.

[0049] The present disclosure is described with reference to flow charts and/or block diagrams of the method, devices and systems according to examples of the present disclosure. Although the flow diagrams described above show a specific order of execution, the order of execution may differ from that which is depicted. Blocks described in relation to one flow chart may be combined with those of another flow chart. It shall be understood that each flow and/or block in the flow charts and/or block diagrams, as well as combinations of the flows and/or diagrams in the flow charts and/or block diagrams can be realized by machine readable instructions.

[0050] The machine readable instructions may, for example, be executed by a general purpose computer, a special purpose computer, an embedded processor or processors of other programmable data processing devices to realize the functions described in the description and diagrams. In particular, a processor or processing apparatus may execute the machine readable instructions. Thus, functional modules of the apparatus and devices may be implemented by a processor executing machine readable instructions stored in a memory, or a processor operating in accordance with instructions embedded in logic circuitry. The term ‘processor’ is to be interpreted broadly to include a CPU, processing unit, ASIC, logic unit, or programmable gate array etc. The methods and functional modules may all be performed by a single processor or divided amongst several processors.

[0051] Such machine readable instructions may also be stored in a computer readable storage that can guide the computer or other programmable data processing devices to operate in a specific mode.

[0052] Such machine readable instructions may also be loaded onto a computer or other programmable data processing devices, so that the computer or other programmable data processing devices perform a series of operations to produce computer-implemented processing, thus the instructions executed on the computer or other programmable devices realize functions specified by flow(s) in the flow charts and/or block(s) in the block diagrams.

[0053] Further, the teachings herein may be implemented in the form of a computer software product, the computer software product being stored in a storage medium and comprising a plurality of instructions for making a computer device implement the methods recited in the examples of the present disclosure. [0054] While the method, apparatus and related aspects have been described with reference to certain examples, various modifications, changes, omissions, and substitutions can be made without departing from the spirit of the present disclosure. It is intended, therefore, that the method, apparatus and related aspects be limited only by the scope of the following claims and their equivalents. It should be noted that the above-mentioned examples illustrate rather than limit what is described herein, and that those skilled in the art will be able to design many alternative implementations without departing from the scope of the appended claims. [0055] The word “comprising” does not exclude the presence of elements other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims. [0056] The features of any dependent claim may be combined with the features of any of the independent claims or other dependent claims.

Claims

1. A three-dimensional printed seal comprising a first portion of a layer of fused build material having a first elastic behavior and a second portion of a layer of fused build material having a second elastic behavior, wherein the first and second elastic behaviors are different such that the three-dimensional printed seal has a differential elastic profile.

2. The three-dimensional printed seal of claim 1 , wherein the first portion of the layer comprises a different volume of build material than the second portion of the layer.

3. The three-dimensional printed seal of claim 1 , wherein the first portion of the layer comprises a different density of build material than the second portion of the layer.

4. The three-dimensional printed seal of claim 1 , wherein the first portion of the layer of fused material comprises portions of fused material and voids absent fused material, wherein the first portion comprises a different number of voids than the second portion.

5. The three-dimensional printed seal of claim 1 , wherein the seal comprises a continuous external geometrical profile.

6. The three-dimensional printed seal of claim 1, wherein the first and/or second portions of the fused build material are part of an external surface of the three-dimensional printed seal.

7. The three-dimensional printed seal of claim 1, wherein the first portion comprises a first internal structure of the seal and wherein the second portion comprises a second internal structure of the seal, wherein the first and second internal structures are different.

8. A method comprising: generating a representation of a seal to seal a representation of an area of an environment to be sealed against a fluid, the seal having a differential elastic profile, wherein the representation of the seal comprises a first portion having a first elastic profile and a second portion having a second elastic profile, wherein the first and second elastic profiles are different; and generating, in an additive manufacturing process, the seal based on the representation.

9. The method of claim 8, wherein generating representation of the seal comprises determining object model data describing the representation of the seal, wherein the first portion of the representation of the seal described by the object model data comprises a first internal structure wherein the second portion of the representation of the seal described by the object model data comprises a second internal structure, wherein the first and second internal structures are different.

10. The method of claim 9, wherein generating the seal based on the representation comprises: determining object generation instructions to generate the representation of the seal according to the object model data by defining a first portion of build material that is to correspond to the first portion of the representation of the seal and a second portion of build material that is to correspond to the second portion of the representation of the seal, wherein the first portion of build material comprises a different volume of build material than the second portion.

11. The method of claim 10, wherein, according to the object generation instructions, the first portion of build material comprises a first region to which a fusing or binder agent is to be applied and a second region to which no fusing or binder agent is to be applied such that the first region forms part of the seal and the second region forms a void in the seal, and wherein, according to the object generation instructions, the second portion of build material comprises a third region to which a fusing or binder agent is to be applied and a fourth region to which no fusing or binder agent is to be applied such that the third region forms part of the seal and the fourth region forms a void in the seal, and wherein the second region comprises a different volume of build material than the second region such that the first and second portions of the representation of the seal comprise a different number of voids.

12. A non-transitory machine-readable medium comprising a set of machine- readable instructions stored thereon which, when executed by a processor, cause the processor to: generate a representation of a seal to seal a representation of an area of an environment to be sealed against the fluid, the seal having a differential elastic behaviour along a geometry of the seal, wherein the representation of the seal comprises a first elastic behaviour and a second portion having a second elastic behaviour different to the first; and generate, in an additive manufacturing process, the seal based on the representation.

13. The medium of claim 12, wherein the instructions that are to cause the processor to generate the representation of the seal are to cause the processor to: determine object model data describing the representation of the seal, wherein a first portion of the representation of the seal having the first elastic behaviour described by the object model data comprises a first internal structure wherein the second portion of the representation of the seal having the second elastic behaviour described by the object model data comprises a second internal structure, wherein the first and second internal structures are different.

14. The method of claim 13, wherein the instructions that are to cause the processor to generate the seal based on the representation are to cause the processor to: determine object generation instructions to generate the representation of the seal according to the object model data by defining a first portion of build material that is to correspond to the first portion of the representation of the seal and a second portion of build material that is to correspond to the second portion of the representation of the seal, wherein the first portion of build material comprises a different volume of build material than the second portion.

15. The medium of claim 14, wherein, according to the object generation instructions determined by the processor, the first portion of build material comprises a first region to which a fusing or binder agent is to be applied and a second region to which no fusing or binder agent is to be applied such that the first region forms part of the seal and the second region forms a void in the seal, and wherein, according to the object generation instructions, the second portion of build material comprises a third region to which a fusing or binder agent is to be applied and a fourth region to which no fusing or binder agent is to be applied such that the third region forms part of the seal and the fourth region forms a void in the seal, and wherein the second region comprises a different volume of build material than the second region such that the first and second portions of the representation of the seal comprise a different number of voids.