Casting mold

Abstract

A casting mold includes: an inorganic or refractory mold, wherein the mold is configured to receive raw material; wherein the raw material is configured to be heated in situ. A reusable mold, a reusable base, and / or a release agent may be incorporated. Methods for manufacturing the mold and methods for casting parts using in-situ heating are also provided.

Description

Technical Field

[0001] This invention relates to casting molds, such as reusable casting molds that can be used for parts production. Background Technology

[0002] Existing technological methods for small-batch production of metal parts can be expensive or slow. When these parts are used for research and development (R&D) or prototyping, it may be desirable to produce them inexpensively, quickly, repeatably, reliably, in a variety of shapes, in a variety of metals or alloys, or scalably. Summary of the Invention

[0003] According to one exemplary embodiment, casting molds, fixture systems, 3D printers, microwave transmitters, systems, parts, and / or methods are provided according to any of the main aspects of this application.

[0004] The implementation method can be implemented according to any of the appended aspects of this application.

[0005] As is well known, the terms "comprise," "comprises," and "comprising" can have an exclusive or inclusive meaning under different jurisdictions. For the purposes of this specification, and unless otherwise stated, these terms are intended to have an inclusive meaning—that is, they will be considered to include the parts listed directly using reference numerals in the drawings, and may also include other unspecified parts or elements.

[0006] References to any document in this specification do not imply an admission that it is prior art that can be effectively combined with other documents, or that it constitutes part of common general knowledge. Attached Figure Description

[0007] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various embodiments of the invention. These drawings, together with the foregoing general description of the invention and the following detailed description of each embodiment, serve to explain the principles of the invention. In the drawings:

[0008] Figure 1 This is a schematic diagram of a system used for metal casting;

[0009] Figures 2 to 7 It is a cross-sectional view of the morphology of the alternative mold;

[0010] Figure 8 It is a cross-sectional view of the combined filling station and microwave oven;

[0011] Figures 9 to 11 It is a three-dimensional diagram of an alternative clamping system;

[0012] Figure 12 It is a cross-sectional view of a mold with conformal cooling; and

[0013] Figure 13 This is a cross-sectional view of the alternative mold and base system. Detailed Implementation

[0014] Figure 1 The illustration depicts a casting system 100 according to an example embodiment. Generally, the casting process can have multiple stages, or these stages can be combined or performed in different sequences depending on the requirements of any given application. A mold 102 is designed for a specific part size. This mold design is then used to print an inorganic semi-permanent mold on a 3D printer 104. The mold is filled with a suitable raw material 106. The filled mold is wirelessly powered to melt the raw material 108 in situ. Alternatively, the raw material can be melted by heating the filled mold using conventional methods, such as 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 if reusability is required by the application, the mold can then be reused for subsequent castings.

[0015] One or more implementations can have the advantage that the mold can be 3D printed faster than the part in question. In any case, once printed, the mold can be used to quickly cast two or more parts.

[0016] In any implementation where the mold can be reused two or more times, the consistent production time for each part can be reduced from 8 hours (or longer for some methods) to as low as 10-15 minutes. For example, in Figure 1 The exemplary system shown can have a small footprint, operate stably, be more efficient, provide acceptable surface finishes, and be quick and easy to train and / or require low maintenance. One or more implementations may be advantageous for the automotive, consumer goods, construction, equipment and machinery, mining, aerospace, shipbuilding, and military industries.

[0017] The following terms will be used throughout:

[0018] The equipment, methods, and / or software used in the casting process.

[0019] Raw materials used in consumable systems may include: ceramics, bases, catalysts, release agents, binders, fluxes, additives, liquids, powders, or metals.

[0020] Molds that are printed and cured.

[0021] Investment casting molds are disposable molds that cannot be opened without damaging the mold itself.

[0022] Permanent molds are molds that can be reused multiple times.

[0023] Semi-permanent molds are molds that can be reused two or more times, also known as reusable molds. The number of times can depend on the requirements of the application, such as the part design, the required alloy, cost, time, and the level of post-mold finishing required (i.e., grinding, filing, cutting, polishing, etc.). A mold may become unusable when it can no longer hold molten metal without leaking. For automotive prototypes, 10 (or more) separate castings may be suitable.

[0024] Multi-part molds are reusable molds with two or more parts.

[0025] A mold cavity is a negative detail or hollow cavity in a mold that is filled with raw material during casting. The mold cavity shapes the outer surface of the part.

[0026] A mold core is a positive feature in a mold that forms a void in the finished part. The core can be reusable or disposable. The mold core shapes the inner surface of the part.

[0027] The mold cavity is the space within the mold formed by the mold cavity, mold core, and any other mold parts.

[0028] The interface between the inner surface of the mold cavity and the mold core, as well as any other mold parts.

[0029] The outer surface of the mold is the visible surface during the assembly of the mold cavity, mold core, and any other mold parts.

[0030] Raw materials include consumables in the form of powders, granules, fine particles, filaments, ingots, or mixtures. For example, raw materials may primarily consist of metal parts.

[0031] Inorganic molds are molds formed from inorganic materials such as refractory materials including metals or ceramics.

[0032] Ceramics include liquids, solids, composite solids, or powders; are capable of withstanding thermal shock; are compatible with metals (unless a barrier layer is used); and are consumables with a maximum operating temperature depending on the material of the part in question. For example, for low-temperature metals, a maximum operating temperature of at least 1000°C may be required.

[0033] Binders, including liquids, solids, or powders, are consumables used to assist in the formation of molds.

[0034] The base includes liquids or powders that assist in generating heat in situ within the mold cavity.

[0035] Release agents, whether liquid or powder, are consumables used to assist in the removal of parts from a mold after the molten material has solidified. They may include or be used as a barrier layer. Alternatively, the barrier layer may be separate.

[0036] Mold identifier: an identifier for the mold or its properties, such as a heat-resistant RFID, heat-resistant NFC, QR code, ID tag or barcode attached to, embedded in or printed on the mold.

[0037] Devices or hardware located at different functional positions in a system, such as printers, metal feeders, microwave ovens, or cooling stations.

[0038] The furnace has a station with one or more wireless power supplies and / or associated cooling drawers for heating.

[0039] Output of the component system.

[0040] Printer: 3D printer and / or related equipment.

[0041] The raw material is heated in situ inside the mold.

[0042] Wireless power sources can include electromagnetic power transmission, microwave power transmission, inductive power transmission, radio frequency power transmission, capacitive power transmission, or dielectric power transmission.

[0043] Microwaves have electromagnetic radiation between 300 MHz and 300 GHz, such as 5.725 GHz and 5.875 GHz, 2.4 GHz and 2.5 GHz, or between 902 MHz and 928 MHz.

[0044] RF has radio frequency electromagnetic radiation with frequencies between 30 Hz and 300 GHz.

[0045] Induction primarily utilizes magnetic fields for wireless power transmission.

[0046] Capacitors primarily utilize electric fields for wireless power transmission.

[0047] The maximum operating temperature is the highest temperature that the material can withstand during the casting cycle without cracking, scorching, shrinkage, deformation, burning, melting, or structural damage. Different temperature values ​​can be used depending on the application requirements. For example, for molds, the maximum temperature might be 1000°C, 1200°C, or 1450°C, while for fixture systems, the maximum temperature might be 200°C.

[0048] Wireless power transmission can transmit wireless power without significant power loss or localized heat generation, depending on the application. In the case of microwave transmission, at least for molds, 10 -3A loss tangent (tanδ) of less than tanδ is considered to be transmittant, although different values ​​may be used depending on the application requirements. For example, a higher tanδ may be acceptable for a fixture system, provided that the fixture system maintains mechanical integrity or does not exceed the maximum operating temperature of the mold. Alternatively, the term wireless power transmission may be used.

[0049] Low-temperature metals are metals or alloys with melting points below 1000°C.

[0050] Density can be an absolute measure, such as mol / mm³. 3 Alternatively, it could be a relative concentration measure, such as the ratio of the molecular weight of the ceramic to that of the substrate at any point on the cross-section of the mold (or at a given distance from the inner surface of the mold), or a comparison with a portion of the total volume of the substrate used in the mold.

[0051] Solidification occurs when molten metal or raw material changes its state to solid.

[0052] Mold Design

[0053] Figure 1 The steps in mold design 102 can be used as follows: Figure 2 The multi-part mold 200 shown can be implemented using a complex, one-time-use design (or investment mold). Complex, one-time-use designs (or investment molds) cannot be made using split molds. In this case, the mold breaks after cooling and the parts are removed. The mold can be designed in CAD software or according to application requirements.

[0054] Another possibility is the manufacture of tools for the injection molding (PIM) market. One or more implementations could offer the advantage of creating metal tools with integral internal conformal cooling channels compared to CNC machining. The ability to cool metal tools can reduce turnaround time, allow for rapid or controlled cooling of the plastic, and improve part quality and / or production volume. This system could be used to cast PIM molds, or copper could be cast to create EDM electrodes for tool steel molds, both of which are easier to manufacture than CNC machining.

[0055] 3D printers will be able to use multiple printheads to print binders, bases, inks, and possibly release agents, or use a single printhead capable of printing multiple materials. The printed material can include a mold identifier on the mold, which, when scanned by a suitable reader, will inform the user of details such as: ID label, specific raw material, volume / mass of the required raw material, furnace instructions, how many times the mold has been used, the mold's position in the process, and the mold's current condition.

[0056] Mold Printing

[0057] Figure 1 The mold printing step 104 in the example can be achieved using a local 3D printer. The printer can utilize binder jetting technology. Alternatives may depend on the application, such as digital light processing (DLP) printing or selective laser sintering (SLS). This can be achieved according to the disclosures in US 5204055 or US 2016193653, the contents of which are incorporated herein by reference.

[0058] In some implementations, the printer can print a mold from powder that maintains its integrity by undergoing multiple melts at varying melting temperatures within the range of the raw material. Plaster with a powdered PVA binder activated by spraying water through the printhead is one option for the mold. Another option is silica powder with a grain size between 50 and 600 mesh. Spherical grains may flow better on the printhead, but irregularly shaped grains may also perform well. Alumina powder and other powders are also possible, depending on the application requirements. Silica may be more compatible with a wider range of molten metals (resistant to wetting and non-reactive). The silica powder / binder mixture is hygroscopic, and the powder may need to be stored in a sealed container or otherwise protected from moisture absorption. In some implementations, the printer will avoid using nano-aluminum powder, which may be undesirable in some applications.

[0059] Other examples of ceramics include: zircon / zirconium oxide-based, graphite, silicon nitride, or boron nitride.

[0060] To maintain the ceramic powder in the desired shape, a binder can be used. The binder is typically in dry, powder form and mixed into the ceramic powder. Liquid binders can be used in print, rather than as powder on a print bed.

[0061] Other binders may include inorganic colloidal solutions or high-temperature inorganic binders, such as sodium silicate, potassium silicate, aluminum phosphate, silicone resin, and hydraulic cement.

[0062] In some implementations, the printer can be, for example... Figure 3A printing base 302 is shown in the mold part 304. Alternatively, the base can be directly brushed, sprayed, sputtered, dipped, or deposited onto the inner surface of the mold. The base can be printed directly through a printhead using nanoparticles similar to pigments in ink. When exposed to wireless energy delivered by a wireless power source, the base generates a temperature capable of melting the raw material. Furthermore, the base allows the heated surface to remain in contact with the metal, thus allowing the mold to act as an excellent insulator (for safe and faster, more efficient melting, etc.), avoiding the risk of metal particle arcing and damage to the furnace (e.g., in the case of a microwave oven) and / or the mold. Ideally, the base is printed in a manner that reduces the required amount and is heated in a manner that does not damage the mold or the raw material. The base 402 can be as follows: Figure 4 As shown, it is evenly distributed across the entire mold, or as... Figure 5 The altered base distribution 502 shown concentrates the base near the inner surface of the mold and reduces density as the mold moves closer to the outer surface, allowing for controlled heating of the mold body and avoiding thermal shock, or printing in a more complex manner to provide shielding around the part. Figure 6 As shown, a base layer may exist at different locations within the mold at varying depths (compared to the inner surface of the mold) to minimize thermal shock or thermal stress in complex sections of the mold, such as the neck. Figure 7 In another alternative shown, mold 702 may be entirely formed of base material, or ceramic and / or binder may have base properties (at a specific temperature or under normal conditions).

[0063] exist Figure 13 In another alternative example shown, the mold 1300 has one or more voids 1304 printed therein. A base material 1302 can then be placed into the voids. The base 1302 can be in the form of granules poured into the voids 1304, or it can be a solid preform inserted into the voids 1304. Figure 13 In the example shown, the base 1302 is in the form of a rod. In this example, the mold 1300 does not need to include any other base or be printed from a base material. This means that there are more choices of materials for the mold 1300, allowing the base material used to make the mold 1300 to be selected for optimal compatibility with the raw materials. It also allows the use of lower-cost base materials for the mold 1300. This arrangement can also have improved resistance to thermal shock.

[0064] The base material may include graphite, magnet, ferrite, silicon carbide, metal oxide, zirconium oxide, aluminum oxide, metallized film, water, molybdenum, stainless steel or any conductive material, depending on the application requirements.

[0065] In some implementations, the release agent can be applied to the innermost surface of the mold. This allows for easy removal of the part, but may also provide a barrier if certain alloys react with the substrate / ceramic. This can be similar to the substrate being printed, coated after printing, or mixed with a liquid substrate to provide a mixed coating. Graphite powder can work well with some metals. Using a release agent on the substrate can improve mold life because the release agent prevents any chemical reaction between some metals and the substrate.

[0066] A dehumidifier / heater can be added to control the temperature and humidity in the printer.

[0067] After printing, the mold can be cured to set the adhesive and expel moisture. This can be done by heating (or UV curing in the case of DLP). Mold curing can affect its integrity, which can be useful for reusable molds.

[0068] raw material

[0069] Figure 1 The raw material filling step 106 can be achieved using a raw material hopper, a vibrating platform, and a weighing scale.

[0070] As in Figure 8 The diagram illustrates an alternative tube-feed arrangement. In this arrangement, the mold 802 can be filled while the microwave oven 804 is inside. A high-temperature resistant tube 806 (which may also be microwave-reflective or microwave-absorbing) is fixed to an orifice in the top of the microwave oven 804. The mold 802 is positioned within the microwave oven 804 and below the tube 806 for filling and subsequent heating. A waveguide 808 outside the orifice cutout ensures no radiation leakage. The tube 806 can be removable and / or slidable, allowing molds of varying heights to be placed below the tube 806. An inert gas, such as argon, can also be dispensed into the tube 806 to reduce oxidation. Furthermore, an IR sensor can be guided axially downward along the tube 806 to directly measure the temperature of the melt.

[0071] The ability to flow will depend on the shape of the raw material particles (e.g., spherical, coarse, or flat) and the particle size, ranging from nanometers to micrometers to pellets. In the case of ingots, cold raw material will not flow into the mold cavity. Ingots can instead be loaded into hoppers. Once the ingots in the hopper melt, the raw material will flow into and fill the cavity. A base around the mold cavity can continue to heat the raw material, keeping it molten until all sections are filled. Keeping the raw material molten until the mold cavity is filled may be more advantageous than existing techniques that require rapid filling of the cavity before the raw material solidifies. This can provide better control over the flow of raw material and / or improve part quality. One or more mold designs can help address the problem of uneven filling, including adding a vibrating table and designing a larger hopper in the mold to accommodate additional raw material for gravity assistance. Different raw materials will have different melting characteristics under different wireless power supplies and other factors, including particle shape and size. A spherical powder shape of a certain size is suitable for most metal alloys. Aluminum, due to its extremely high oxidation properties, may require different processing methods. A mixture of particles of different sizes and shapes can be used to balance flowability and meltability. Trace additives can act as melt and / or flow catalysts or to inhibit oxidation. Electronic scales ensure the correct amount of raw material is filled into the mold.

[0072] Molten raw materials

[0073] Figure 1 The step of melting raw material 108 can be achieved using a furnace such as a microwave oven.

[0074] The filled mold is placed in the microwave oven. The internal metal shape of the microwave oven helps ensure that radiation is focused on the optimal melt and also ensures safe use. We can also use a stirrer to ensure that the microwaves are distributed evenly. The temperature of the outer surface of the mold can be measured so that the operator knows whether the part has solidified and can be removed.

[0075] The mold can be clamped during heating and cooling. After cooling, the operator can open and easily release the part, and then close the mold and repeatedly (two or more times) secure the clamping system.

[0076] The fixture system can be as follows: Figure 9 A portion of the mold 902 shown (e.g., having a ceramic bolt 904 passing through a specific hole 906) can also be independent, such as... Figure 10 As shown, for example, a reusable silicone tape 1002 can be used, or as... Figure 11 As shown, for example, pin 1102 is used, such as spring steel (with rounded ends) and slightly tensioned, or ceramic, or disposable, such as high-temperature strip.

[0077] In addition, the fixture system can be entirely external, like a feature in the floor of a furnace, or a wedge-shaped box that holds the mold together.

[0078] For metal parts, the way the raw material is cooled in the mold can affect how the metal molecules align, which can influence its strength properties, namely tensile, shear, torsional, compressive, and hardness. Controlling the cooling of metal parts will allow the parts to have the desired strength properties. Conformal cooling in mold 1200 can be used to control cooling, such as... Figure 12 As shown in the diagram. Alternatively, selectively melting a region of the mold and then moving the molten area to another region can provide additional control. Forced air cooling can rapidly cool the mold while it is still in the microwave oven. Forced air extraction and filtration (most likely activated carbon) to remove any harmful gases that may be released during the melting cycle can be useful.

[0079] Once the part is cast, it is allowed to cool to a safe temperature before processing.

[0080] Remove parts

[0081] Figure 1 The step of removing the part from mold 112 can be achieved using an inspection station.

[0082] Remove the clamping system and separate the mold parts. If the mold is an investment mold, in this case, the mold is physically removed (e.g., with a hammer or vibratory tool). The part is then pulled out of the mold.

[0083] The funnel and any other cast artifacts are cut—usually with a hacksaw or band saw. If necessary, the parts are then sanded, filed, fine-ground, or polished to an acceptable surface finish. The parts may then be coated, painted, or treated in some other way.

[0084] Inspect the mold for damage (visually, by machine, or using some calibration device). Then, close the mold (manually) and tighten it back together, and refill it with raw material before returning it to the furnace. If the mold has been in use for a long time, another curing cycle may be required to remove any moisture that may be present. If the mold fails the inspection, remove it from production.

[0085] Although the invention has been described by way of description of various embodiments, and although the embodiments have been described in detail, the applicant does not intend to limit the scope of the appended claims or in any way to such details. Other advantages and modifications will be readily apparent to those skilled in the art. Therefore, the invention is not limited in its broader aspects to the specific details, representative devices and methods, and the illustrative examples shown and described. Thus, these details may be omitted without departing from the spirit or scope of the applicant's overall inventive concept.

Claims

1. A casting mold, comprising: An inorganic mold, the inorganic mold being configured to receive a raw material, the raw material including a metal; and A base, located on or within the inorganic mold, is configured for in-situ heating to melt the raw material. The inorganic mold is 3D printed, and the base is a 3D printed base.

2. The casting mold according to claim 1, wherein, The inorganic mold is a multi-part mold.

3. The casting mold according to claim 1, wherein, The inorganic mold can be reused to cast two or more parts.

4. The casting mold according to claim 1, wherein, The inorganic mold used in 3D printing comprises ceramics and a binder.

5. The casting mold according to claim 1 further includes a hopper or funnel.

6. The casting mold of claim 1 further includes one or more conformal cooling channels located within the casting mold, the conformal cooling channels being configured to assist in cooling the part formed from the molten raw material.

7. The casting mold according to claim 1, wherein, The base is made of silicon carbide, graphite, or a magnet.

8. The casting mold of claim 1 further includes a release agent configured to assist in the removal of a part from the casting mold after the molten raw material has solidified.

9. The casting mold according to claim 1, wherein, The raw material is a low-temperature metal.

10. The casting mold according to claim 9, wherein, The low-temperature metal raw material includes at least one selected from the group consisting of Al, Mg, Zn and any combination or alloy thereof.

11. The casting mold according to claim 1 further comprises a binder selected from the group consisting of sodium silicate, inorganic colloidal solution or high-temperature inorganic binder.

12. A casting system, the casting system comprising a casting mold according to claim 1 and a wireless power source outside the inner cavity of the casting mold, wherein, The in-situ heating is provided by the wireless power source.

13. The casting system according to claim 12, wherein, The wireless power source is selected from the group consisting of microwave transmitters, inductive power transmitters, capacitive or dielectric power transmitters, RF (radio frequency) power transmitters, and any combination thereof.

14. A method for casting a part, comprising: Receive the casting mold according to claim 1; Select the amount of raw materials, including metals; Fill the casting mold with the raw material; and The raw material is heated in situ to form the part, wherein... The casting mold is powered by a wireless power source to melt the raw material in situ, and the base generates a temperature capable of melting the raw material when exposed to the wireless energy delivered by the wireless power source.

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