Method of reinforcing an object obtained by additive manufacturing and a reinforced object

Abstract

The present invention relates to a method of reinforcing an object obtained by an additive manufacturing process and a reinforced object obtained by the method. The invention furthermore relates to a reinforced object configured for covering and sealing an end face of a heat exchanger.

Description

[0001]Method of reinforcing an object obtained by additive manufacturing and a reinforced object Field of the InventionThe present invention relates to a method of reinforcing an object obtained by an ad-ditive manufacturing process and a reinforced object obtained by the method. The in-vention furthermore relates to a reinforced object configured for covering and sealingan end face of a heat exchanger. Background of the Invention One challenge related to objects obtained by additive manufacturing is that a strong object made of e.g. a polymer requires a high infill density, i.e., the object must be made of nearly a solid piece of polymer. Additively manufacturing with a high infill den- sity is time consuming, expensive (material and energy wise) and some 3D printersmay not be capable of printing at a 100% infill density. A further challenge when printingwith a high infill density is that the 3D printed part builds up heat, which give a non- uniform time dependent thermal elongation, which increases tolerances on part dimen- sions and may cause severe warping. Therefore, an easier and less expensive method is required. US20220063152 discloses a method of post manufacture processing a 3D printed part. A first step of the method includes to seal the exterior of the 3D printed part by soaking the atmosphere around the part with an aerosol or glue and then place the hollow cavity of the part under vacuum to draw the aerosol or glue into the hollow cavity to seal the exterior of the 3D printed part. A second step of the method includes creating a vacuum pressure inside the hollow cavity with a compressor through a fluid line. Then, the fluid line is exchanged with a second fluid line connected to a container with a glue, wherein the vacuum pressure in the hollow cavity sucks the glue into the follow cavity through the second fluid line. Object of the Invention One objective of the present disclosure is to achieve a method of providing an object obtained by an additive manufacturing process, wherein the object is strong and easy to manufacture. A further objective of the present disclosure is to provide an object for sealing an end face of a heat exchanger, wherein the object is easy to manufacture and made from inexpensive and re-usable materials. Description of the InventionOne objective of the invention is achieved by a method of reinforcing an object obtainedby additive manufacturing comprising an act of providing an object having a surfacedefining an internal volume of the object.The internal volume may comprise a supportive structure supporting the surface.The object has at least one inlet opening in the surface and at least one outlet openingin the surface. The inlet opening is configured for receiving a liquid matrix into the in- ternal volume.The outlet opening is configured to discharge liquid matrix from the internal volume.The method furthermore comprises one or more acts of:- providing liquid matrix into the internal volume through the inlet opening,- filling the internal volume with the liquid matrix by applying a pressure difference be-tween the inlet opening and the outlet opening, so that the liquid matrix fills the internalvolume from the inlet opening to the outlet opening; and- hardening the liquid matrix to obtain a reinforced object.The object obtained by additive manufacturing may be through a 3D printing processand wherein the object may be a 3D printed object. The 3D printing process may bebut is not limited to being material extrusion, fused granulate modelling, digital compo-site manufacturing, digital light processing, stereolithography, selective light sintering,fused deposition modelling, powder bed fusion, digital beam melting, binder jetting,material jetting, multi jet fusion, cold spray, metal 3D printing or any other suitable pro-cess. The object or 3D printed object may be provided in polymer, metals, concrete, resins,photopolymer resin, ceramic or a composite material.In one aspect, the object may be provided in polymer and / or thermoplastic such aspolycarbonate (PC), polypropylene (PP), polyamide (PA), polyvinyl butyral (PVB), ac-rylonitrile styrene acrylate (ASA), acrylonitrile-butadine-styrene (ABS), polylactic acid(PLA) and / or polyethylene terephthalate glycol (PETG). One advantage of providingthe object in a polymer and / or thermoplastic may be that the object is re-usable andhence more environmentally friendly. A further advantage is that the object can be made sufficiently strong and lightweight due to the properties of the polymer and / or thermoplastics.An advantage of the object being provided by additive manufacturing is that thestrength and weight of the object can be optimised by designing the surface with aspecific thickness and the supportive structure with a specific infill pattern and infill density. The supportive structure may be provided in a number of different infill patterns such as but not limited to grid patterns, zig-zag patterns, triangle patterns, tri-hexagon pat- terns, cubic patterns, gyroid patterns, concentric patterns, honeycomb patterns, and / or a combination thereof.The infill density is how much percentage of the internal volume of the object is filledby the supportive structure. The supportive structure must be provided in such a way that the liquid matrix can fill the entire internal volume from the inlet opening to the outlet opening, so that when the liquid matrix is hardened it provides a reinforced object being stronger than the original object. The term being stronger means that the rein- forced object is more resistant to bending and / or breaking when a force or pressure ispushed or put onto a part of the surface or the entire surface of the reinforced objectcompared to the original object. A further advantage of the reinforced object being filled with a hardened liquid matrix in the entire internal volume is that any imperfections in the surface of the reinforcedobject are sealed by the hardened liquid matrix so that the surface becomes more air-and watertight, i.e. air and / or water does not penetrate through the surface of the objectas easily. The at least one inlet opening and the at least one outlet opening are preferably placed so that when the inlet opening receives the liquid matrix and the pressure difference between the inlet opening and the outlet opening is applied the liquid matrix is drawn to the outlet opening and discharged therefrom, and hence the placement of the inletand outlets relative to each other ensures that the liquid matrix fills the entire internalvolume. E.g., if the object is a rectangle or a rod, the inlet opening is placed in one endof the object and the outlet opening is placed in an opposite end of the object. In one aspect where the object may have a complex shape, several inlet openings and outlet openings may be provided in the surface of the object to ensure that the entire volume is filled with the liquid matrix.The pressure difference required is a function of the infill density of the object andviscosity of the liquid matrix. The step of hardening the liquid matrix may be achieved by leaving the object filledwith liquid matrix to rest at room temperature for a long period of time such as 6 to 48hours, any time period there in-between or more. In another aspect, the step of hard-ening is achieved by heating the object filled with liquid matrix in an oven. One ad-vantage of using an oven to harden the liquid matrix is that a higher strength for thereinforced object is achieved and the hardening step is faster. However, use of an ovenis also dependent on whether the 3D printed part can withstand the heating.In another aspect, the object filled with liquid matrix may be put under vacuum pressureduring the step of hardening the liquid matrix. The vacuum pressure may be used toensure that the liquid matrix fills the entire internal volume.A further embodiment of the method is directed at a method of obtaining a cover plate.The method of obtaining a cover plate comprises an act of providing a frame having a surface defining an internal volume. The internal volume may comprise a supportive structure supporting the surface. The frame in the surface has at least one inlet opening configured for receiving a liquid matrix into the internal volume. The frame in the sur- face has at least one outlet opening configured for discharging the liquid matrix from the internal volume. The frame further has a frame surface defining a frame opening and a plurality of mounting holes. The method further comprises acts of:- providing the liquid matrix into the internal volume through the inlet opening;- filling the internal volume with the liquid matrix by applying a pressure difference be-tween the inlet opening and the outlet opening, so that the liquid matrix fills the internalvolume from the inlet opening to the outlet opening;- providing a cover plate made from one or more fibre composite layers and beingconfigured for covering the frame opening;- applying the liquid matrix onto the one or more fibre composite layers so that thecover plate is bonded to the frame during a step of hardening the liquid matrix; and- hardening the liquid matrix to obtain a reinforced object.The aspects and advantages of the method of reinforcing an object obtained by addi-tive manufacturing is applicable to the method of obtaining a cover plate.In a further embodiment of the method, the act of filling the internal volume with theliquid matrix is done by applying a suction force at the outlet opening and / or by applying a pressure to the liquid matrix to inject the liquid matrix into the internal volume through the inlet opening. The suction force applied to the outlet opening may be applied by a vacuum pump or a pressure pump. In one aspect, applying a pressure to the liquid matrix at the inlet opening may beapplied by but not limited to a water pump or liquid pump such as a peristaltic pump,electromagnetic pump, positive-displacement pump, rotary pump, reciprocating pump, piston pump, diaphragm pump, screw pump, hydraulic pump or a velocity pump. In another aspect, the object may be filled by a liquid matrix with a low viscosity by the use of gravity, in this aspect the first inlet opening is arranged vertically above the outlet opening, so that the liquid matrix may seep downwards inside the internal volume from the inlet opening to the outlet opening.In a further embodiment of the method, the supportive structure fills a volume of theinternal volume in the range of 10% to 65 %, or 15% to 50%, or 20% to 40%. Infill density is the percentage of which the supportive structure fills the internal volume. One advantage of providing a low infill density is that less material is used to provide the object by the additive manufacturing process, and hence the production time for providing the object is also reduced. One further advantage of a low infill density may be that the overall strength of the reinforced object is stronger, because the hardened liquid matrix may provide more strength than the object’s surface and supportive structure to the reinforced object.In a further embodiment of the method, the liquid matrix is resin.In one aspect, the liquid matrix may comprise a resin mixed with a hardener. The resinmay be an epoxy resin and the hardener may be formulated amine, so that when the resin is combined with the hardener it becomes epoxy. A mixing ration between the resin and the hardener may be 100 parts resin and 30 parts hardeners by weight. The hardeners may be chosen based on how fast or slow the resulting liquid matrix may cure. The epoxy resin may be an ultra-low viscosity resin being suitable for quickly infusing into a composite material such as the internal volume of the object and it’s supportive structure. In one aspect the epoxy resin may be IN2 Epoxy Infusion Resin made available byeasycomposite™ (Easy Composites Ltd).To harden the resin, the object filled with the resin may be left at room temperature, e.g., 20-25 degrees Celsius, for at least 24 hours. The hardening time may be reduced to e.g., 6 hours by hardening the object filled with resin in an approximately 60 degrees Celsius oven or 3 hours in an approximately 100 degrees Celsius oven. One advantage of utilizing a long hardening time at room temperature is that the object which may be made from a polymer is not subdued to high temperatures which may degrade the object’s material. Another advantage of hardening at room temperature is energy re- duction because an oven running at high temperatures is not required.In a further embodiment of the method, the object is provided as a frame with a framesurface, where the frame surface defines a frame opening and a plurality of mounting holes, wherein the method comprises a further step of providing a cover plate config- ured for covering the frame opening. The frame may be shaped like a rectangle or square by four frame walls, wherein the frame has a length and a width spanning a frame plane. A frame thickness is definedorthogonal to the frame plane. The frame may be relatively flat, i.e., the frame wallshaving a wall width, measured between an outer frame face and an inner frame facebeing parallel with the frame plane, wherein the frame thickness is smaller than orequal to the wall width. In another aspect the frame thickness is greater than the wallwidth. In another aspect, the frame may be a circular frame, wherein a single frame wall de- fines the circular frame having an inner frame face and an outer frame face. The frame opening is defined between the one or more inner frame faces of the one or more frame walls. The plurality of mounting holes may be arranged parallel to the frame thickness, i.e. perpendicular to the frame plane. The mounting holes may be used for mounting the frame to a flat surface such as a heat exchanger.Like the object, the frame may comprise an internal volume defined between the framesurfaces with a supportive structure supporting the frame surfaces, according to oneor more of the herein disclosed embodiments.The cover plate may be a flat plate extending parallel to the frame plane. The coverplate may be arranged on either side of the frame, i.e. between the frame and a mount-ing surface which the frame is mounted to or the opposite side facing away from themounting surface.In another aspect, the cover plate may extend away from the mounting surface andextend above the frame, so that a volume is provided between the cover plate, the mounting surface and surrounded by the frame. In a further embodiment of the method, the step of providing the cover plate, the coverplate is obtained by additive manufacturing, wherein the cover plate has a surface de-fining an internal volume comprising a supportive structure supporting the surfaces.The cover plate comprising the internal volume comprising a supportive structure maybe provided and configured according to one or more of the herein disclosed embodi-ments of the object. In one aspect, the cover plate may be provided in the same step as the frame is pro- vided. In a further aspect, the internal volume of the cover plate may be in fluid com- munication with the internal volume of the frame, so that the steps of reinforcing the object also reinforces the cover plate.In a further embodiment of the method, in the step of providing the cover plate, thecover plate is made from one or more fibre composite layers and the method comprises a further act of applying the liquid matrix onto the one or more fibre composite layers so that the cover plate is bonded to the frame during the step of hardening the liquid matrix. The step of hardening the liquid matrix applied to the fibre composite layers may be the same process as disclosed in this embodiment regarding the liquid matrix inside the internal volume and / or for the liquid matrix being a resin. In one aspect the fibre composite layers may be a glass fiber, carbon fiber, aramid fiber, boron fiber, polyethylene fiber, ceramic fiber, natural fibers and / or a combination thereof. In the step of providing the cover plate, the one or more fibre composite layers may be laid onto the frame and coated or soaked with the liquid matrix, then by hardening the liquid matrix the cover plate becomes attached to the frame. The hardening of the fibre composite layers and the hardening of the liquid matrix in the internal volume may be done in the same process. In one aspect, the frame and the fibre composite layers may be arranged in a mould, wherein the mould is adapted for the shape of the frame and the intended shape of thecover plate and wherein the mould may be surface treated with a non-stick coating sothat the liquid matrix does not bond the frame and / or the cover plate to the mould.Furthermore, when the frame and the fibre composite layers are arranged in the mould,it may be covered with a container such as a plastic bag, wherein a vacuum pressuremay be applied to the container so that the liquid matrix further soaks into the fibrecomposite layers and the fibre composite layers may conform to the shape of the mould. In a further embodiment of the method, the method comprises a further step of arrang- ing one or more mounting flanges on the fibre composite layers before applying the liquid matrix onto the one or more fibre composite layers.The liquid matrix may be applied to the mounting flanges so that the flanges are bondedto the cover plate in the step of hardening the liquid matrix. In one aspect, bonding the mounting flange to the cover plate may also be that the mounting flange is embedded into the cover plate. The one or more mounting flanges may comprise a flange opening configured to re-ceive a liquid. Furthermore, the mounting flanges may comprise a plurality of fasteningapertures configured to receive fasteners for mounting an object to the mountingflange. The fastening apertures may comprise a thread for receiving a bolt, screw orthreaded rod.In one aspect, the mounting flanges may be configured for mounting inlet and / or outletchannels for supply of liquid through the flange opening into a heat exchanger, whereinthe channels are mounted onto the mounting flanges. The inlet and / or outlet channelsmay be fastened to the flanges through fasteners arranged into the fastening apertures. The mounting flanges may be provided in a metal material. In one aspect, when the mounting flanges are bonded to the cover plate, the one or more flange openings may be covered by the cover plate beneath the mounting flanges. Hence, the method may comprise a further step of cutting or drilling the cover plate directly beneath the flange openings, so that the flange openings are unblocked. In another aspect, the cover plate is configured to receive the one or more mounting flanges at specified positions wherein the cover plate comprises one or more pre-de-fined apertures aligned with the respective flange openings. The pre-defined aperturesmay be defined in the step providing the cover plate, where the one or more fibre com-posite layers are arranged around the pre-defined apertures.In a further embodiment of the method, the mounting flanges are obtained by additivemanufacturing.In one aspect, the mounting flanges may have a surface defining an internal volumecomprising a supportive structure supporting the surfaces. The one or more aspects and / or advantage of providing the object and / or the cover plate by additive manufacturing and hence having a surface defining an internal volume comprising a supportive structure supporting the surfaces are also applicable to the one or more mounting flanges. In a further aspect, the internal volume of the mounting flanges may be filled with a liquid matrix before the step of hardening, so that the mounting flanges are reinforced and may be further bonded to the cover plate by the hardened liquid matrix.In a further embodiment of the method, the method comprises a further act of coatingthe object and / or the cover plate with a waterproof coating. In a further aspect, the one or more mounting flanges may also be coated with the waterproof coating in the step of coating. The waterproof coating may be a surface treatment. One effect of providing the object, the frame and / or the cover plate with a waterproof coating is that the object, the frame and / or the cover plate may be used in conditions wherein contact is made with vapors or liquids.A further objective of the invention is achieved by a reinforced object obtained by themethod according to any one or more of the herein disclosed embodiments.A further objective of the invention is achieved by a cover plate obtained by the method according to any of the herein disclosed embodiments and wherein the cover plate is adapted to seal a heat exchanger. A further objective of the invention is achieved by the use of the cover plate accordingto any of the embodiments disclosed herein, wherein the cover plate is mounted to theheat exchanger by a plurality of fasteners arranged through the mounting holes. Description of the Drawing Various examples are described hereinafter with reference to the figures. Like reference numerals refer to like elements throughout. Like elements will, thus, not be described in detail with respect to the description of each figure. It should also be noted that the figures are only intended to facilitate the description of the examples. They are not intended as an exhaustive description of the claimed invention or as a limitation onthe scope of the claimed invention. In addition, an illustrated example need not haveall the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular example is not necessarily limited to that example and can be practiced in any other examples even if not so illustrated, or if not so explicitly described. Exemplary embodiments of the invention are described in the figures, whereon:Fig. 1a illustrates a cross-sectional view of one embodiment of an object obtained byadditive manufacturing.Fig. 1b illustrates one embodiment of an object obtained by additive manufacturing.Fig. 2 illustrates a cross-sectional view of one embodiment of a reinforced objectFig. 3a illustrates one embodiment of an object provided as a frame.Fig. 3b illustrates one embodiment of an object provided as a frame.Fig. 4a illustrates one embodiment of an object provided as a frame with a cover plate.Fig. 4b illustrates one embodiment of an object provided as a frame with fibre com-posite layers arranged thereon. Fig.5a illustrates an end-piece of a heat exchanger.Fig. 5b illustrates one embodiment of a frame and cover plate arranged on a heatexchanger.Fig. 6 illustrates one embodiment of a mould.Fig. 7a illustrates one embodiment of a method of reinforcing an object.Fig. 7b illustrates one embodiment of a method of reinforcing an object and providinga cover plate. Fig.7c illustrates one further embodiment of the method.Fig. 8a illustrates one embodiment of a frame with a cover plate and mountingflanges.Fig. 8b illustrates one embodiment of a frame with a cover plate and mountingflanges. Detailed Description of the Invention Exemplary examples will now be described more fully hereinafter with reference to the accompanying drawings. In this regard, the present examples may have different forms and should not be construed as being limited to the descriptions set forth herein. Ac- cordingly, the examples are merely described below, by referring to the figures, to ex- plain aspects. Throughout the specification, when an element is referred to as being “connected” to another element, the element is “directly connected” to the other element, “electrically connected”, “fluidic connected” or “communicatively connected” to the other element with one or more intervening elements interposed there between. The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting. As used herein, the terms “comprises" "comprising" "includes" and / or "including" when used in this specification specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, oper- ations, elements, components, and / or groups thereof. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this invention pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be inter- preted in an idealized or overly formal sense unless expressly so defined in the present specification. Reference: Referencenumber: Heat exchanger 10Method 100Providing 110Fasteners 12Providing 120Filling 130End face 14Hardening 140Mounting holes 15Providing 150Providing 155Frame plane 16Applying 160Second end 17Coating 170First end 18Object 20Surface 21Frame 22Frame opening 23Internal volume 24Supportive structure 25Mounting holes 26Inlet opening 27Outlet opening 28Frame walls 29Cover plate 30Hollow interior 31Fibre composite layer 32Reinforced object 40Hardened matrix 41Mould 50Mounting flange 60Flange opening 62Fastening apertures 64Figure 1a illustrates a cross-sectional view of one embodiment of an object 20 obtained by additive manufacturing having surfaces 21 defining an internal volume 24. The in- ternal volume 24 comprises supportive structures 25 obtained by the additive manu- facturing process and wherein the supportive structures 25 support the surfaces 21. The object 20 in the cross-section is approximately half of the entire object 20, which is illustrated in fig.1b. The cross-sectional view illustrates how one part of the object 20 is U-shaped and wherein the part has a plurality of mounting holes 26. Between theU-shaped part a cover plate 30 bridges across and defines a hollow interior 31 belowthe cover plate 30. In this embodiment the cover plate 30 is provided by the sameadditive manufacturing process, and hence has the same internal volume 24 with sup-portive structures 25.Figure 1b illustrates the same embodiment of the object 20 as fig. 1a, viewed fromabove and in full size. The view illustrates an outside facing surface 21 of the object20, the cover plate 30 and the plurality of mounting holes 26. Figure 2 illustrates a cross-sectional view of a reinforced object 40. The reinforced ob-ject 40 comprises an object 20 with surfaces 21 defining an internal volume 24 with asupportive structure 25. The object 20 has been reinforced into the reinforced object40 by a hardened matrix 41 filling the internal volume 24 of the object 20.The reinforced object 40 may be obtained according to any one of the herein disclosed embodiments of the method 100 of reinforcing an object obtained by additive manu- facturing. Figure 3a illustrates a further embodiment of the object 20, wherein the object 20 is provided as a frame 22. The frame 22 is shaped like a rectangle by four frame walls 29, wherein a frame opening 23 is provided between the frame walls 29. A frame plane 16 (dashed lines) is arranged along a width and a length of the frame 22 and is sub- stantially parallel with the frame opening 23. The frame 22 has a frame thickness meas- ured along the frame wall 29 perpendicular to the frame plane 16. The frame 22 has a surface 21 with an internal volume (24, not shown here), wherein the internal volume comprises a supportive structure (25, also not shown here). The frame 22 comprises an outlet opening 28 arranged in a first end 18 of the frame and connected to the internal volume 24. The outlet opening 28 may be used for draw- ing or sucking a liquid matrix out of the internal volume 24, by e.g. applying a vacuum or suction force to the outlet opening 28. Figure 3b illustrates the same embodiment of the object 20 as fig. 3a, wherein the object 20 is shaped as a frame 22. Figure 3b illustrates a second end 17 of the frame22, wherein the second end 17 is opposite to the first end 18. The frame 22 comprisesa plurality of mounting holes 26 arranged through the frame walls 29, wherein the mounting holes 26 are arranged perpendicular to the frame plane (16, shown in fig. 3a). On the surface 21 of the frame 22 at the second end 17 two inlet openings 27 are arranged and connected to the internal volume (24, not shown here). The inlet open- ings 27 are configured for receiving a liquid matrix, wherein the liquid matrix may be injected or fed into the internal volume 24.The liquid matrix fills the internal volume 24 by a pressure difference being appliedbetween the inlet opening 27 and the outlet opening 28.Figure 4a illustrates one embodiment of an object 20 provided as a frame 22 with aplurality of mounting holes 26 with a cover plate 30 attached to the frame 22. The coverplate 30 is made of fibre composite layers (32, shown in fig.4b), the fibre composite layers 32 are arranged on the frame 22, coated with a liquid matrix and then hardened to form the cover plate 30. As the liquid matrix is hardened, the fibre composite layers 32 may bond together with the frame 22 and become fastened thereto. Figure 4b illustrates one embodiment of an object 20 shaped as a frame 22, wherein fibre composite layers 32 are arranged on one side of the frame 22, before the object 20 and fibre composite layers 32 are processed by the method 100 for reinforcing the object 20 and providing the cover plate 30 made from fibre composite layers 32. Figure 5a illustrates one embodiment of a heat exchanger 10, wherein the heat ex- changer 10 has a plurality of mounting holes 15 arranged along a circumference of an end face 14 of the heat exchanger 10. Figure 5b illustrates one embodiment of a heat exchanger 10 wherein a reinforced object 40 with a cover plate 30 is mounted onto an end face 14 of a heat exchanger 10. The reinforced object 40 is mounted to the heat exchanger by a plurality of fasten- ers 12 being arranged through mounting holes (15,26 shown in fig.5a and 4a). At an opposite end of the heat exchanger 10, another reinforced object 40 with a cover plate 30 comprising two or more mounting flanges 60 (as shown in fig.8a and 8b) may be arranged, wherein the mounting flanges 60 are configured to provide an inlet and an outlet for a liquid. Figure 6 illustrates one embodiment of a mould 50, the mould 50 is configured for re-ceiving fibre composite layers a frame obtained by additive manufacturing and / or anobject obtained by additive manufacturing according to the herein disclosed embodi-ments. The mould 50 may be configured for shaping the fibre composite layers into a cover plate (30, as shown in fig.4a and 5b). The mould 50 may be used according to the method of reinforcing an object and provid- ing a cover plate as disclosed herein. The method may include a step of arranging the fibre composite layers and object in the mould 50, and then soaking the fibre composite layers and object with a liquid matrix. Then the liquid matrix may be hardened at room temperature or in a heated oven. Additionally, before hardening the liquid matrix, themould may be placed in an air-tight container, such as a plastic bag, and then put undera vacuum pressure. The vacuum pressure may further ensure that the liquid matrix fills an internal volume of the object and soaks through the fibre composite layers so that a strong cover plate is obtained.Figure 7a illustrates one embodiment of a method 100 of reinforcing an object by ad-ditive manufacturing comprising the acts of:- providing 110 an object having a surface defining an internal volume of the object,said internal volume comprising a supportive structure supporting the surface, and said object has at least one inlet opening in the surface and at least one outlet opening in the surface, wherein the inlet opening is configured for receiving a liquid matrix into the internal volume and wherein the outlet opening is configured to discharge the liquid matrix from the internal volume;- providing 120 the liquid matrix into the internal volume through the inlet opening;- filling 130 the internal volume with the liquid matrix by applying a pressure differencebetween the inlet opening and the outlet opening, such that the liquid matrix fills the internal volume from the inlet opening to the outlet opening; and- hardening 140 the liquid matrix to obtain a reinforced object.In the step of providing 110 an object, the object may be provided as a frame with a frame surface, where the frame surface defines a frame opening and a plurality of mounting holes.Figure 7b illustrates one further embodiment of the method 100 of reinforcing an objectby additive manufacturing comprising the step of:- a further step of providing 150 a cover plate made by additive manufacturing andconfigured for covering the frame opening; In another aspect, the step of providing 150 the cover plate, the cover plate may be made of one or more fibre composite layers. In this aspect, the method may comprise a further step of:- applying 160 the liquid matrix onto the one or more fibre composite layers so that thecover plate is bonded to the frame during the step of hardening 140 the liquid matrix.Figure 7c illustrates one further embodiment of a method 100 of obtaining a cover platecomprising acts of:- providing 110 a frame having a surface defining an internal volume, said internal vol-ume comprising a supportive structure supporting the surface, where said frame in the surface has at least one inlet opening configured for receiving a liquid matrix into the internal volume and at least one outlet opening configured for discharging the liquid matrix from the internal volume, said frame having a frame surface defining a frame opening and a plurality of mounting holes;- providing 120 the liquid matrix into the internal volume through the inlet opening;- filling 130 the internal volume with the liquid matrix by applying a pressure differencebetween the inlet opening and the outlet opening, so that the liquid matrix fills the in-ternal volume from the inlet opening to the outlet opening;- providing 150 a cover plate made from one or more fibre composite layers and beingconfigured for covering the frame opening;- applying 160 the liquid matrix onto the one or more fibre composite layers so that thecover plate is bonded to the frame during a step of hardening 140 the liquid matrix; and- hardening 140 the liquid matrix to obtain a reinforced object.The method 100 may comprise a further step of arranging 155 one or more mounting flanges on the fibre composite layers before applying 160 the liquid matrix onto the one or more fibre composite layers.The liquid matrix may be applied to the mounting flanges in the step of applying 160the liquid matrix, so that the mounting flanges are bonded to the cover plate in the stepof hardening 140 the liquid matrix.In a further aspect of the step of arranging 155 the one or more mounting flanges, themounting flanges are obtained by additive manufacturing.In a further embodiment of the method 100, the method 100 comprises a further act of coating 170 the object, and / or the cover plate, and / or the mounting flanges with a wa- terproof coating. Figure 8a illustrates one further embodiment of a frame 22 with a plurality of mountingholes 26 with a cover plate 30 attached to the frame 22 as illustrated in fig 4a. Thecover plate 30 may be bonded to the frame 22. This embodiment is further provided with two mounting flanges 60 onto the cover plate 30. The mounting flanges 60 may be bonded to the cover plate 30 by the hardened liquid matrix. The mounting flanges 60 comprise a flange opening 62 and fastening apertures 64. The flange openings 62 are in this illustration blocked by the cover plate 30, the flange openings 62 may be unblocked by cutting out a part of the cover plate30 beneath or inside the circumference of the flange openings 62. Figure 8b illustrates one further embodiment of a frame 22 with a plurality of mounting holes 26 with a cover plate 30 bonded to the frame 22. This illustration shows the op- posite side of the embodiment shown in fig.8a. In this embodiment, two mounting flanges 60 are embedded into the cover plate 30. Each mounting flanges 60 comprise a flange opening 62 and fastening apertures 64. Due to the mounting flange being embedded in the cover plate 30, the flange openings 62 provide a through-going opening through the cover plate 30.

Claims

CLAIMS1. A method (100) of obtaining a cover plate (30) comprising acts of:- providing (110) a frame (22) having a surface (21) defining an internal volume (24),said internal volume (24) comprising a supportive structure (25) supporting the surface(21), where said frame (22) in the surface has at least one inlet opening (27) configuredfor receiving a liquid matrix into the internal volume (24) and at least one outlet opening(28) configured for discharging the liquid matrix from the internal volume (24), saidframe (22) having a frame surface defining a frame opening (23) and a plurality ofmounting holes (26);- providing (120) the liquid matrix into the internal volume (24) through the inlet opening(27);- filling (130) the internal volume (24) with the liquid matrix by applying a pressure dif-ference between the inlet opening (27) and the outlet opening (28), so that the liquidmatrix fills the internal volume (24) from the inlet opening (27) to the outlet opening(28);- providing (150) a cover plate (30) made from one or more fibre composite layers (32)and being configured for covering the frame opening (23);- applying (160) the liquid matrix onto the one or more fibre composite layers (32) sothat the cover plate (30) is bonded to the frame (22) during a step of hardening (140)the liquid matrix; and- hardening (140) the liquid matrix to obtain a reinforced object (40).

2. The method (100) according to claim 1, wherein the act of filling (130) the internal volume (24) with the liquid matrix is done by applying a suction force at the outlet open- ing (28) and / or by applying a pressure to the liquid matrix to inject the liquid matrix into the internal volume (24) through the inlet opening (27).

3. The method (100) according to claim 1 or 2, wherein the supportive structure (25) fills a volume of the internal volume (24) in the range of 10% to 65 %, or 15% to 50%, or 20% to 40%.

4. The method (100) according to any one of the preceding claims, wherein the liquidmatrix is a resin.

5. The method (100) according to claim 1, wherein the step of providing (150) the coverplate (30), the cover plate (30) is obtained by additive manufacturing wherein the coverplate (30) has a surface (21) defining an internal volume (24) comprising a supportivestructure (25) supporting the surfaces (21).

6. The method (100) according to any one of the preceding claims, wherein the methodcomprises a further step of arranging (155) one or more mounting flanges (60) on thefibre composite layers before applying (160) the liquid matrix onto the one or more fibre composite layers (32).

7. The method (100) according to claim 6, wherein said mounting flanges are obtainedby additive manufacturing.

8. The method (100) according to any one of the preceding claims, wherein the method (100) comprises a further act of coating (170) the object (20) and / or the cover plate (30) with a waterproof coating.

9. A cover plate (30) obtained by the method (100) according to any one of claims 1 to8 adapted to seal a heat exchanger (10).

10. Use of the cover plate (30) according to claim 9, wherein the cover plate (30) ismounted to the heat exchanger (10) by a plurality of fasteners (12) arranged throughthe mounting holes (26).

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