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Abstract

The mold can be an inorganic mold or a refractory mold, and the mold can be configured to receive a feedstock, which can be heated in situ. Reusable molds, reusable susceptors, and / or mold release agents can be incorporated. Also provided are methods for making molds and casting parts using in situ heat.

Description

[Technical Field]

[0001] The present invention relates to molds, eg, reusable molds that can be used to produce parts. [Background technology]

[0002] Prior art methods of short run production of metal parts can be expensive or time consuming. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 5,204,055 [Patent Document 2] US Patent Application Publication No. 2016193653 Summary of the Invention [Problem to be solved by the invention]

[0004] When such parts are used for research and development (R&D) or prototyping, it may be desirable to cheaply, quickly, repeatedly, and reliably produce such parts in a variety of shapes, using a variety of metals or alloys, or to be stretchable. [Means for solving the problem]

[0005] According to an example embodiment, there is provided a mold according to any one of claims 1, 3, 4, 6, 7, 8, 10, 12, 15, 16 or 17, a mold clamping system according to claim 53, a three-dimensional printer according to claim 48, a microwave transmitter according to claim 49, a system according to claim 50 or 51, or a part according to claim 52, or a method according to any one of claims 58 to 62.

[0006] Multiple embodiments may be implemented according to any one of the dependent claims 2, 5, 9, 11, 13, 14, 18-47, and 53-57.

[0007] It is recognized that the terms "comprise," "comprises," and "comprising" can have either an exclusive or an inclusive meaning, subject to jurisdictional variations. For purposes of this specification and unless otherwise specified, these terms are intended to have an inclusive meaning. That is, they are interpreted to mean the inclusion of the recited components to which their use directly refers, and possibly also the inclusion of other components or elements not recited.

[0008] The reference to any document in this specification is not an admission that the document is prior art, may be lawfully combined with other documents, or forms part of the common general knowledge.

[0009] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present invention and, together with the summary of the invention given above and the embodiments given below, serve to explain the principles of the invention. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a system for metal casting. [Figure 2] 10A-10C are cross-sectional views of alternative mold topographies. [Figure 3] 10A-10C are cross-sectional views of alternative mold topographies. [Figure 4] 10A-10C are cross-sectional views of alternative mold topographies. [Figure 5] 10A-10C are cross-sectional views of alternative mold topographies. [Figure 6] 10A-10C are cross-sectional views of alternative mold topographies. [Figure 7] 10A-10C are cross-sectional views of alternative mold topographies. [Figure 8] FIG. 1 is a cross-sectional view of a combination refueling station and microwave device. [Figure 9] FIG. 10 is a perspective view of an alternative clamping system. [Figure 10] FIG. 10 is a perspective view of an alternative clamping system. [Figure 11] FIG. 10 is a perspective view of an alternative clamping system. [Figure 12] FIG. 1 is a cross-sectional view of a mold having conformal cooling. [Figure 13] FIG. 10 is a cross-sectional view of an alternative mold and susceptor system. DETAILED DESCRIPTION OF THE INVENTION

[0011] FIG. 1 illustrates a system 100 for casting, according to an exemplary embodiment. Generally, there may be multiple steps to the casting process, or the steps may be combined or performed in different orders depending on the needs of any given application. A mold is designed to the specifications of a particular part (102). A semi-permanent inorganic mold is then printed with a three-dimensional printer using the mold design (104). The mold is filled with the appropriate feedstock (106). The filled mold is energized with a wireless power source to melt the feedstock in situ (108). Alternatively, the feedstock may be melted by heating the filled mold using conventional means (e.g., a combustion furnace). The mold is cooled and removed from the wireless power source (110). The part within the mold can then be removed (112), and the mold can then be reused in a subsequent casting if the application requires reuse.

[0012] One or more embodiments may provide the advantage that a mold may be faster to 3D print than the part itself, and in either case, once printed, the mold can be used to rapidly cast two or more parts.

[0013] In any embodiment where a mold can be reused more than once, the typical production time for each part can be reduced from 8 hours (or, in some methods, significantly longer) to as little as 10-15 minutes. An exemplary system such as that shown in FIG. 1 has a small footprint, can operate stably, can be more efficient, can provide a meet-standard finish, can be quicker and easier to train, and / or requires less maintenance. One or more embodiments can provide benefits in the automotive, consumer goods, construction, equipment, and machinery industries, mining, aerospace, shipbuilding, and defense industries.

[0014] The following terminology is used throughout this document: System: The equipment, method, and / or software used in the casting process. Consumables: Raw materials used by the system which may include ceramics, susceptors, catalysts, release agents, binders, fluxes, additives, liquids, powders or metals. Mold: The printed and cured mold. Investment Mold: A disposable mold that cannot be opened without damaging the mold. Permanent mold: A mold that can be reused many times. Semi-permanent mold: A mold that can be reused more than once may also be referred to as a reusable mold. The number of times may depend on the application requirements, such as, for example, the part design, the alloy required, cost, time, and the required level of post-mold finishing (i.e., grinding, sanding, cutting, polishing, etc.). When a mold does not hold the molten metal leak-tightly, the mold may become unusable. For an automotive prototype, 10 (or more than 10) separate castings may be appropriate. Multi-component mold: A reusable mold with two or more parts. Mold Cavity: The concave detail or hollow in a mold that is filled with material during casting. The mold cavity is molded into the exterior surface of the part. Mold Core: The convex feature of a mold that forms the cavity in the finished part. Cores can be reusable or disposable. The mold core is molded onto the inner surface of the part. Mold Impression: The mold void formed by the mold cavity, mold core, and any other mold parts. Inner surface: The contact surface between the mold impression and the mold cavity, mold core, and any other mold parts. Exterior Surface: The surface of the mold that is visible when the mold cavity, mold core, and any other mold parts are assembled. Raw Material: Consumables including powders, particles, granules, wires, ingots, or mixtures. For example, the raw material may be primarily metal components. Inorganic mold: A mold formed from inorganic materials such as metals or refractory materials, including ceramics. Ceramic: A consumable material comprising a liquid, solid, composite solid, or powder capable of withstanding thermal shock compatible with metals (without a barrier layer) and having a maximum service temperature depending on the material of the part. For example, a maximum service temperature of at least 1000°C may be required for low-temperature metals. Binder: A consumable material containing a liquid, solid, or powder that aids in the formation of a mold. Susceptor: A consumable containing a liquid or powder that assists in the generation of heat in situ within the mold impression. Mold Release Agent: A consumable containing a liquid or powder that aids in the release of a part from a mold after the molten raw material has solidified. May contain or also function as a barrier layer. Alternatively, the barrier layer may be detachable. Mold Identifier: An identifier of the mold or a characteristic of the mold, such as, for example, a heat-resistant RFID, heat-resistant NFC, QR code, ID tag, or barcode attached, embedded, or printed on the metal. Station: A device or hardware at a different functional location in a system, such as a printer, a metal feedstock dispenser, a microwave device, or a cooling station. Furnace: A station with one or more wireless sources of heating and / or associated cooling drawers. Part: Something made from a system. Printer: 3D printer and / or related equipment. In-situ heating: The raw material is heated inside the mold. Wireless power source: may include electromagnetic power transmission, microwave power transmission, electromagnetic induction power transmission, RF power transmission, capacitive power transmission, or dielectric power transmission. Microwave: Electromagnetic radiation having a frequency of 300 MHz to 300 GHz, for example, 5.725 GHz to 5.875 GHz, 2.4 to 2.5 GHz, or 902 to 928 MHz. RF: Radio frequency electromagnetic radiation with frequencies between 30 Hz and 300 GHz. Inductive: Wireless power transmission that primarily uses magnetic fields. Capacitive: Wireless power transfer that primarily uses electric fields. Maximum Use Temperature: The maximum temperature that can be withstood during a casting cycle without cracking, charring, shrinking, warping, burning, melting, or structural failure. Depending on the application requirements, different temperature values ​​may be used. For example, for the mold, it may be 1000°C, 1200°C, or 1450°C, while for the clamping system, it may be 200°C. Wireless power transmission: It is possible to transmit wireless power without causing significant power loss or local heating, but depending on the application. In the case of microwave transmission, 10 -3 The following loss tangent (tan δ) is considered at least transmissible to the mold, although different values ​​may be used depending on the application requirements. For example, the clamping system may be able to accept a larger tan δ as long as it maintains mechanical integrity or does not violate maximum mold temperature standards. Alternatively, the term "wireless power transmission" may be used. Low-temperature metal: A metal or alloy that has a melting point below 1000 degrees. Density: The ratio of molecular weight of ceramic to susceptor at any point across the cross section of the mold (or at a given distance from the mold interior surface), or Mol / mm, as compared to a portion of the total volume of susceptor used in the mold. 3 It can be either an absolute measure, such as 0.1% or a relative concentration measurement. Solidification: the state in which molten metal or raw material changes into a solid state

[0015] Mold Design Mold design step 102 of Figure 1 can be performed using a multi-component mold 200 shown in Figure 2 or a disposable complex design (or investment mold) that cannot be made in a split mold. In this case, the mold is broken after cooling and the parts are removed. Molds can be designed in CAD software or according to application requirements.

[0016] Another possibility is to create tools that serve the plastic injection molding (PIM) market. An advantage of one or more embodiments over CNC machining can be the creation of metal tools with integrated internal conformal cooling channels. The ability to cool metal tools can shorten turnaround time, allow for rapid or controlled cooling of plastics, and improve part quality and / or yield. PIM molds can be cast by the system, or copper can be cast to create electrodes for electrical discharge machining (EDM) using steel molds, and both PIM and copper casting can be easier than CNC machining.

[0017] 3D printers can print using multiple printheads to print binders, susceptors, inks, and possibly release agents, or using a single printhead capable of printing multiple materials. The printed material can include a mold identifier on the mold, which, when scanned by an appropriate reader, provides the user with detailed information about the material and mold. The details can include an ID tag, the specific material, the volume / mass of material required, furnace instructions, the number of times the mold has been used, where the mold is being processed, and the current state of the mold.

[0018] Mold printing Mold printing step 104 of FIG. 1 may be performed using a local three-dimensional printer. The printer may use binder jetting technology. Alternatives may depend on the application, such as printing with digital light processing (DLP) or selective laser sintering (SLS). This may be performed according to the disclosures in U.S. Pat. No. 5,204,055 or U.S. Patent Application Publication No. 2016193653, the contents of which are incorporated herein by reference.

[0019] In some embodiments, the printer can print molds from powder, which can maintain its integrity by withstanding multiple dissolutions at different dissolution temperatures across a range of raw materials. Plaster of Paris with a powdered PVA binder, activated by spraying water through the print head, is one mold option. Another option is silica powder with a particle size of 50-600 mesh. Spherically shaped particles may flow well on the print bed, while irregularly shaped particles may work significantly better. Alumina powder and other powders are possible, depending on the application requirements. Silica may be more compatible with various molten metals (it is moisture-resistant and non-reactive). The silica powder / binder mixture contains water, so the powder may need to be stored in an airtight container or otherwise protected from moisture absorption. In some embodiments, the printer avoids using nano-aluminum powder, which may be undesirable in some applications.

[0020] Other examples of ceramics include zircon / zirconia, graphite, silicon nitride, or boron nitride.

[0021] Binders may be used to hold the ceramic powder in the desired shape. These are typically in dry powder form and mixed into the ceramic powder. Rather than using a powder form of the binder on the print bed, a liquid binder may be printed.

[0022] Other binders may include inorganic colloidal solutions or high temperature inorganic binders such as sodium silicate, potassium silicate, aluminum phosphate, silicone resins, and hydraulic cements.

[0023] In some embodiments, as shown in FIG. 3 , a printer can print a susceptor 302 for a mold part 304. Alternatively, the susceptor can be painted, sprayed, sputtered, dipped, or deposited directly onto the inner surface of the mold. The susceptor can be printed directly by a printhead using nanoscale particles similar to the pigments in ink. When exposed to radio energy delivered by a radio frequency power source, the susceptor generates temperatures capable of melting the feedstock. Furthermore, the susceptor can also maintain a heat transfer surface in contact with the metal, allowing the mold to act as a high-quality insulator (for safer, faster, more efficient melting, etc.) and avoiding the risk of arcing and generating metal particles that could damage the furnace (e.g., in microwave devices) and / or the mold. Ideally, the susceptor is printed in a way that reduces the amount of susceptor required and avoids damaging heat to the mold or feedstock. As shown in FIG. 4, the susceptor 402 can be evenly dispersed throughout the mold, or as shown in FIG. 5, the susceptor distribution 502 varies. As a result, the susceptor is concentrated near the inner surface of the mold and decreases in density closer to the outer surface, allowing for thermal control of the mold body, avoiding thermal shock or printing in a more complex manner, and providing shielding around the part. As shown in FIG. 6, the susceptor layer can be at different depths (relative to the inner surface of the mold) in different locations of the mold, thereby minimizing thermal shock or thermal stress in complex areas of the mold, such as crevices. In a further alternative, shown in FIG. 7, the mold 702 can be formed entirely of susceptor material, or the ceramic and / or binder can have susceptor properties (either at a specific temperature or at a general temperature).

[0024] In another alternative example, as shown in FIG. 13 , a mold 1300 is printed with one or more voids 1304 therein. A susceptor material 1302 can then be placed into the voids. The susceptor 1302 can be in the form of a particulate that is applied to the voids 1304, or it can be a preformed solid shape that is inserted into the voids 1304. In the example shown in FIG. 13 , the susceptor 1302 is rod-shaped. In this example, the mold 1300 does not need to include any other susceptor or be printed from a susceptor material. This means that there are more options for the material of the mold 1300, and consequently, the substrate for making the mold 1300 can be selected for optimal compatibility with the raw material. This may also allow for the use of a lower-cost substrate for the mold 1300. This arrangement may also result in improved resistance to thermal shock.

[0025] Susceptor materials may include graphite, magnetite, ferrite, silicon carbide, metal oxides, zirconia, alumina, metallized films, water, molybdenum, stainless steel, or any conductive material depending on the application requirements.

[0026] In some embodiments, a release agent can be applied to most of the mold's inner surface. This allows for easy extraction of the part, but can also provide a barrier if certain alloys react with the susceptor / ceramic. This can be printed, like the susceptor, coated after printing, or mixed with the liquid susceptor to create a hybrid coating. Graphite powder can work well with some metals. Mold life can be improved by using a release agent applied to the susceptor, thereby preventing any chemical reaction between some metals and the susceptor.

[0027] A dehumidifier / heater can be added to control the temperature and humidity of the printer.

[0028] After printing, the mold can be cured to attach the binder and release moisture. This can be done with heat (or, in the case of DLP, by applying UV). Mold curing can affect its integrity, which can be useful for reusable molds.

[0029] raw material The ingredient loading step 106 in FIG. 1 may be performed using an ingredient hopper, a vibrating table, and a weigh scale.

[0030] An alternative tube-feed arrangement can be used, as shown in FIG. 8 . In this arrangement, the mold 802 can be filled while inside the microwave device 804. A high-temperature refractory tube 806 (which can also reflect or absorb microwaves) is attached to the top opening of the microwave device 804. The mold 802 is filled and then positioned below the tube 806 within the microwave device 804 for continued heating. A waveguide 808 across the opening cut ensures no radioactive material leaks. The tube 806 can be removable and / or slidable, allowing molds of different heights to be installed below the tube 806. An inert gas, such as argon gas, can also be dispensed into the tube 806 to reduce oxidation. Additionally, an infrared sensor can be pointed down the axis of the tube 806 to directly measure the temperature of the melt.

[0031] Flowability is determined by the shape of the feedstock particles (e.g., spherical, irregular, or flat are all possible) and the particle size, ranging from nano to micro to pellets. In the case of ingots, the cold feedstock does not flow into the mold impression. Instead, the ingots may be loaded into a hopper. Once the ingots in the hopper are melted, the feedstock flows into the cavity, filling it. A susceptor around the mold impression may continue to heat the feedstock, so that the feedstock remains molten until the entire part is filled. Maintaining the feedstock molten state until the mold impression is filled may offer advantages over prior art techniques that require rapid filling of the cavity before the feedstock solidifies. This may result in more precise control of feedstock flow and / or improved part quality. One or more mold designs may help address uneven filling, including the addition of a vibrating table to hold additional feedstock and provide gravity assistance, and the design of a larger hopper for the mold. Different raw materials have different melting characteristics, taking into account different radio power sources and other factors including particle shape and size. A spherical powder shape of a certain size works well for most metal alloys. For aluminum, its exceptionally high oxidation properties may require a different approach. A mixture of different particle sizes and shapes may be used to balance flow and solubility. Trace additives may act as melt and / or flow catalysts or inhibit oxidation. Electronic balances may ensure that the mold is filled with the correct amount of raw material.

[0032] Dissolving raw materials The step 108 of melting the raw materials in FIG. 1 may be performed using a heating furnace such as a microwave device.

[0033] The filled mold is placed in a microwave device. The internal metal features of the microwave device may be used to ensure that the radiation is optimally focused on the melt, ensuring safe use. A "stirrer" may also be used to ensure even distribution of the microwaves. The temperature of the exterior surface of the mold may be measured, informing the operator when the part has solidified and can be removed.

[0034] The mold may be clamped during heating and cooling, and after cooling, the operator may be able to open the part, easily release the part, then close the mold and lock the clamping system repeatedly (twice or more times).

[0035] The clamping system can be any part of the mold 902 as shown in FIG. 9 (e.g., with ceramic bolts 904 passing through specific holes 906), or a separate part such as shown in FIG. 10 using, for example, a silicone band 1002 that may be reusable, or as shown in FIG. 11 using pins 1102 such as spring steel (with rounded ends), or tape (e.g., high temperature tape) that is slightly tensioned or ceramic or disposable.

[0036] Also, the clamping system may be completely external, such as a feature on the furnace floor, or may be a wedge box that holds the molds together.

[0037] For metal parts, the method of cooling the feedstock within the mold can affect how the metal molecules align, which can affect its strength properties (i.e., tension, shear, torsion, compression, and hardness). Controlling the cooling of the metal part allows for a desired strength cross-section. As shown in FIG. 12, a conformal cooling section 1200 of the mold can be used to control cooling. Alternatively, selectively melting areas of the mold and then moving the melting zone to another area can provide additional control. Forced air cooling can quickly cool the mold while stationary within the microwave device. Forced air extraction and air filtration (likely utilizing activated carbon) to remove any toxic vapors that may be released during the melting cycle can be useful.

[0038] Once the part is cast, it is allowed to cool to a safe temperature before being manipulated.

[0039] Removing parts Step 112 of removing the part from the mold in FIG. 1 may be performed using an inspection station.

[0040] The clamping system is removed and the mold parts are separated (if the mold is an investment mold, then the mold is physically removed (e.g., with a hammer or vibrating tool)). The part is then ejected from the mold.

[0041] The ventilators and any other casting artifacts are typically cut with a hacksaw or bandsaw. If necessary, the parts are then sanded, filed, finished, or polished to an acceptable surface finish. The parts may then be coated, painted, or treated in some manner.

[0042] The mold is inspected (visually or mechanically, or with some calibration device) for damage. The mold is then closed (manually), clamped together again, and refilled with material before being placed back into the furnace. If the mold has not been used for a long time, it may require another cure cycle to remove any moisture that may be present. If the mold fails the inspection, it is removed from production.

[0043] While the present invention has been illustrated by the description of several embodiments, and several embodiments have been described in detail, applicants do not intend to restrict or in any way limit the scope of the appended claims to such details. Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the present invention in its broader aspects is not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicants' general inventive concept.

Claims

1. an inorganic mold configured to receive a feedstock comprising a metal; a susceptor on or in the mold, the susceptor configured to heat the feedstock in situ to melt the feedstock; The mold and the susceptor are three-dimensionally printed.

2. The template of claim 1 , wherein the template comprises a plurality of elements.

3. The mold of claim 1 , wherein the mold is reusable for casting two or more parts.

4. The mold of claim 1 , wherein the three-dimensional printed mold comprises a ceramic and a binder.

5. The mold of claim 1 further comprising a hopper or ventilator.

6. The mold of claim 1 , further comprising one or more conformal cooling channels within the mold configured to assist in cooling a part formed from the molten feedstock.

7. The mold of claim 1 , wherein the susceptor is silicon carbide, graphite, or magnetite.

8. The mold of claim 1 , further comprising a mold release agent configured to aid in removing a part from the mold after the molten feedstock has solidified.

9. The mold of claim 1 , wherein the raw material is a metal having a melting point of less than 1000° C.

10. 10. The mold of claim 9, wherein the metal having a melting point of less than 1000 degrees includes at least one selected from the group consisting of Al, Mg, Zn, and any combination or alloy of Al, Mg, and Zn.

11. The mold of any one of claims 1 to 10, further comprising a binder selected from the group consisting of sodium silicate, an inorganic colloidal solution, or a high temperature inorganic binder.

12. 10. A casting system comprising the mold of claim 1 and a wireless power source external to the mold impression, the wireless power source providing in situ heating.

13. 13. The casting system of claim 12, wherein the wireless power source is selected from the group consisting of a microwave transmitter, an electromagnetic induction power transmitter, a capacitive or inductive power transmitter, an RF (radio frequency) power transmitter, and any combination of the foregoing transmitters.

14. 1. A method of casting a part, comprising: receiving the mold of claim 1; selecting an amount of metal-containing raw material; filling the mold with the feedstock; heating the feedstock in situ to form the part; Including, the mold is energized by a wireless power source to melt the feedstock in situ, and the susceptor, when exposed to wireless energy delivered by the wireless power source, generates a temperature capable of melting the feedstock.

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