System for automated and mechanized additive manufacturing evaporative casting

Abstract

A system for creating a metal casting from a three-dimensional print is provided, the system comprising: a three-dimensional print formed using additive manufacturing; a ceramic coating station configured to coat the three-dimensional print with a ceramic coating to form a pre-cast assembly; and a vibration station having a flask configured to contain the pre-cast assembly packed within one of sand or ceramic beads. The system may optionally include an enclosed pouring system having a furnace configured to melt casting material and configured to pour molten casting material into an interior of the pre-cast assembly.

Description

SYSTEM FOR AUTOMATED AND MECHANIZEDADDITIVE MANUFACTURING EVAPORATIVE CASTINGCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from U.S. Provisional Patent Application No. 63 / 582,083, filed on September 12, 2023, which is incorporated by reference herein in its entirety.BACKGROUND

[0002] It is more efficient to pour molten metal (i.e., casting) to form an integral finished part than welding or assembling multiple components together. The history of foundries dates back to the Bronze Age (3500 BC) and Iron Age (1200 BC), which are named after the predominant foundry technology of the era. At that time and until modern industrial times, there were only two types of casting: (1) greensand casting and (2) lost wax investment casting.

[0003] In greensand casting, the molds are made of a mixture of water, sand, and clay. The molds are made to form a hollow space into which molten metal is poured. The metal cools into a solid piece as a casting in the shape of the cavity in the sand. The mold is dumped out to get the casting, and the sand can be re-used. Tolerances in greensand casting are approximately + / - 1.01 mm per mm (0.040 in. per in.) so in most cases, significant machining may be required to get a finished part.

[0004] Lost wax investment casting, also called investment casting or lost wax, is a much more precision process than greensand casting and maintains tolerances of + / - 0.076 mm per mm (0.003 in. per in.). Investment casting is still used for sculptures and jewelry. It is also used for casting precision parts, such as aircraft engine turbine blades. Investment casting starts by having a piece of wax in the desired shape. The wax can be made by machining, made in a mold, or even hand carved. Pieces are attached to an assembly that feeds the desired shape during pouring. The wax is dipped into a ceramic coating (called the investment) and is allowed to dry. The coating and drying steps are repeated seven to 12 times. Typically, there are 24 hours between each coating step. The coating is typically built up to 6.35 mm to 12.7 mm (0.25 to 0.50 in.) thick. The mold is heated to melt the wax, which is dumped out of the mold. This leaves behind a hollow cavity. Molten metal is poured into the mold. The metal is allowed to cool and solidify. Removing the investment casting mold is difficult. Typical methods include mechanical means such as hammers, shot / grit blasting, waterjets, or chemicalmeans such as acid dissolution. After the investment is removed, the part (casting) is cut off of the gating system. The process takes two weeks or more.

[0005] An improved method of casting is evaporative casting, wherein an additive manufactured part (e.g., a polylactic acid three-dimensional print) is coated with a ceramic coating, which is permitted to harden. Then, a molten cast material is poured onto the additive manufactured part encapsulated by the ceramic coating, wherein the molten cast material causes the additive manufactured part to evaporate, allowing the molten cast material to fdl the cavity formed by the hardened ceramic coating.

[0006] However, it is desired to automate and mechanize this process to reduce the skill, time, and labor associated with this process, while increasing the efficiency of the process.SUMMARY

[0007] In one aspect, a system for creating a metal casting from a three-dimensional print is provided, the system comprising: a three-dimensional print formed using additive manufacturing; a ceramic coating station configured to coat the three-dimensional print with a ceramic coating to form a pre-cast assembly; and a vibration station having a flask configured to contain the pre-cast assembly packed within one of sand or ceramic beads. The system may optionally include an enclosed pouring system having a furnace configured to melt casting material and configured to pour molten casting material into an interior of the pre-cast assembly.BRIEF DESCRIPTION OF THE FIGURES

[0008] The accompanying figures, which are incorporated in and constitute a part of the specification, illustrate various example systems and methods and are used merely to illustrate various example aspects. In the figures, like elements bear like reference numerals.

[0009] FIG. 1 illustrates an example of using 3D printing to print only a hollow shell 100 in 3D of a full-sized target part according to an algorithm.

[0010] FIG. 2 illustrates an example of a pre-cast assembly 240 formed from a hardened coating of ceramic mold 204 over an entire exterior surface of the 3D printed hollow shell.

[0011] FIG. 3 illustrates an example of pouring the selected cast material into a precast assembly while the cast material is in a molten state.

[0012] FIG. 4 illustrates a cutaway view of a pre-cast assembly 440 buried in compacted sand or ceramic beads 414; molten cast material 416 is poured into an inlet to evaporate the material of the 3D hollow shell 100.

[0013] FIG. 5 illustrates cooling to solidify a cast from the molten selected cast material.

[0014] FIG. 6 illustrates an example of a target cast part 620 from the evaporative casting process.

[0015] FIG. 7 illustrates an upright position of a pre-cast assembly 740 that is connected to an inlet of a conduit 710 into which molten selected cast material 716 is being poured.

[0016] FIG. 8 A illustrates a cutaway view of a pre-cast assembly 840 buried in compacted sand or ceramic beads 814; molten cast material 816 is poured into an inlet to evaporate the material of a 3D hollow shell 800.

[0017] FIG. 8B illustrates a partial magnified view of pre-cast assembly 840.

[0018] FIG. 9 A illustrates an elevation view of a device 942 for increasing the porosity of three-dimensional prints.

[0019] FIG. 9B illustrates a bottom perspective view of device 942 for increasing the porosity of three-dimensional prints.

[0020] FIG. 9C illustrates a top perspective view of device 942 for increasing the porosity of three-dimensional prints.

[0021] FIG. 10A illustrates an elevation view of a device 1042 for increasing the porosity of three-dimensional prints.

[0022] FIG. 10B illustrates a bottom perspective view of device 1042 for increasing the porosity of three-dimensional prints.

[0023] FIG. 10C illustrates a top perspective view of device 1042 for increasing the porosity of three-dimensional prints.

[0024] FIG. 11 illustrates a coating station 1100 for coating a three-dimensional print with a ceramic coating.

[0025] FIG. 12 illustrates a sectional view of an automated vibration station 1254 for settling sand around a hardened ceramic mold within a flask 1255.

[0026] FIG. 13 illustrates an elevation view of an enclosed pouring system 1300 including a furnace 1304 and a flask 1255.

[0027] FIG. 14 illustrates another aspect of a pouring system 1470 including a furnace 1471 and flask assembly 1472.

[0028] FIG. 15 illustrates another aspect of a coating station 1580 for coating a three- dimensional print with a ceramic coating.

[0029] FIG. 16 illustrates an example method 1600 for obtaining a cast part.

[0030] FIG. 17 illustrates a schematic view for an example system 1700 for creating a metal casting from a three-dimensional print.DETAILED DESCRIPTION

[0031] FIGS. 1-6 illustrate a traditional method of manual casting of parts using evaporative casting. However, these casting methods may be integrated into the automated and mechanized process for casting parts described herein.

[0032] FIG. 1 illustrates an example of using 3D printing to print only a hollow shell 100 in 3D of a full-sized target part according to an algorithm. Hollow shell 100 may be fixed to a foam gating member 102. Hollow shell 100 may be fixed to foam gating member 102 via any of a variety of mechanisms, including for example a glue.

[0033] Hollow shell 100 may be used in an evaporative casting process, which involves the use of 3D printing to print only a hollow shell (e.g., hollow shell 100) of a full-sized target part according to an algorithm. Hollow shell 100 may be formed from any of a variety of materials, including for example a polymer material such as polylactic acid (PLA) fdaments.

[0034] The evaporative casting method may incorporate the benefits and capabilities of a 3D printer to print a casting mold prototype (target part) by printing only a hollow shell (e.g., hollow shell 100) in 3D or only an envelope, instead of a solid version of a full-sized target part. Thus, both the amount of PLA materials used and the printing time of the 3D printing are substantially reduced. In addition, a reduction in the amount of PLA materials used to create the 3D hollow shell of the full-sized target part also substantially reduces the amount of PLA materials being burned off or evaporated, thus further reducing the risks of trapping gas bubbles within the solidified cast part. As described further below, gases trapped during evaporation of hollow shell 100 when pouring a molten material may result in forming voids, which are defects on the target part.

[0035] In an example, a 3D printed hollow shell 100 of full-sized target parts may achieve a part tolerance of up to + / - 0.051 mm (0.002 in.) and may achieve a surface finish of up to 0.0016 mm with 0.0051 mm - 0.0076 mm typical (64 microinch with 200-300 typical) root mean square (RMS). The 3D hollow shell may have a first range of wall thicknesses, which is either experimentally determined or mathematically modeled over one or a combination of parameters: for example, surface area pattern and size detail of the cast target part, polymer materials dispensing needle diameter, and physical properties of polymer materials.

[0036] In one aspect, hollow shell 100 may include a range of wall thicknesses of about 0.15 mm (0.006 in.) to about 1.00 mm (0.040 in.). Thicknesses below 0.15 mm may cause hollow shell 100 to lack structural integrity to prevent collapse under its own weight, or the weight of a ceramic coating. Thicknesses above 1.00 mm may result in too much gas being generated during evaporation of hollow shell 100, resulting in defects and possibly explosions. Thicknesses of hollow shell 100, or of specific portions of hollow shell 100, may be selected based upon the minimum material thickness capable of providing hollow shell 100 with the structural integrity necessary to support its own weight and / or be coated with a ceramic. Once hollow shell 100 is printed, the volume of gas expected to be generated during the evaporation of hollow shell 100 may be calculated, and a plan may be developed regarding how to disperse that volume of gas.

[0037] FIG. 2 illustrates an example of a pre-cast assembly 240 formed from a hardened coating of ceramic mold 204 over an entire exterior surface of 3D printed hollow shell (not shown, but illustrated in FIG. 1 as hollow shell 100). Pre-cast assembly 240 includes a hardened coating of ceramic mold 206 over a foam gating member (not shown, but illustrated in FIG. 1 as foam gating member 102).

[0038] In practice, a layer of ceramic coating may be applied over an entire exterior surface of the hollow shell 100, forming a hardened ceramic mold 204, wherein hardened ceramic mold 204 is fully enclosed and includes an opening at a lower end. As discussed further below, pre-cast assembly 240 may be formed by connecting the opening at the lower end of the hardened ceramic mold to an end of a conduit, while an opposite end of the conduit may be configured as an inlet to the pre-cast assembly.

[0039] In one aspect, ceramic mold 204 may include a range of wall thicknesses of about 0.025 mm (0.001 in.) to about 0.381 mm (0.015 in.). Thicknesses below 0.025 mm may cause ceramic mold 204 to crack during casting, resulting in a “burnt-on sand defect” in which a molten cast material escapes from ceramic mold 204 and contacts the surrounding sand, coating the sand in the molten cast material, which is very difficult to remove from the target cast part. Thicknesses above 0.381 mm may prevent the volume of gas generated during evaporation of hollow shell 100 from escaping through ceramic mold 204 fast enough, or at all. A build-up of the gas may lead to defects in the target cast part and / or explosions.

[0040] FIG. 3 illustrates an example of pouring the selected cast material into a precast assembly while the cast material is in a molten state. FIG. 4 illustrates a cutaway view of a pre-cast assembly 440 buried in compacted sand or ceramic beads 414; molten cast material416 is poured into an inlet of a conduit 410 to evaporate the material of the 3D hollow shell 100 and fdl pre-cast assembly 440. Pre-cast assembly 440 may be contained within a container 412.

[0041] Pre-cast assembly 440 is disposed in an upright, bottom gate position, where the inlet of conduit 410 is bent in such a way to keep at an upright position. Selected cast material 416 in a molten state may flow by gravity down conduit 410 to evaporate the material of hollow shell 100 in a bottom portion, then continue to flow upward (due to a difference in height level of molten cast material 416) to evaporate the material of hollow shell 100 in the enclosed top portion until the entire volume inside the inner surface of pre-cast assembly 440 is fdled with cast material 416, without a void.

[0042] In another example, pre-cast assembly 440 may be disposed in an inverted, top gate position in which the top portion of pre-cast assembly 440 is facing downward and the bottom portion of pre-cast assembly 440 is facing upward, while conduit 410 ’s inlet remains at an upright position to receive selected cast material 416 in a molten state. When disposed in the inverted position, selected cast material 416 in a molten state may flow downward by gravity to start evaporating the material of hollow shell 100 in the bottom portion of pre-cast assembly 440. Cast material 416 may then continue to flow downward to evaporate the material of hollow shell 100 in the enclosed top portion (which is inverted to point downward) until the entire volume inside the inner surface of pre-cast assembly 440 is completely fdled with cast material 416, without a void.

[0043] The decision to bury pre-cast assembly 440 in an inverted position or in an upright position in compacted sand or ceramic beads 414 for pouring of molten cast material 416 may be dependent upon the density of molten cast material 416. Yet alternately, pre-cast assembly 440 may be disposed at an angle (not shown) inside compacted sand or ceramic beads 414.

[0044] FIG. 5 illustrates cooling to solidify a cast from the molten selected cast material. FIG. 6 illustrates an example of a target cast part 620 from the evaporative casting process. Cooling cast material 416 causes cast material 416 to solidify to yield the full-sized target part 620 in a cast from molten selected cast material 416. Left over sand or ceramic beads 414, and any ceramic coating 204, may be removed to yield target cast part 620 from the evaporative casting.

[0045] FIG. 7 illustrates an upright position of a pre-cast assembly 740 that is connected to an inlet of a conduit 710 into which molten selected cast material 716 is beingpoured. Conduit 710 may include a downsprue 729, a runner 730, and an ingate 732. Conduit 710, to include downsprue 729, runner 730, and ingate 732, provide a path (e.g., a tube, after coating with a ceramic mold) through which cast material 716 is ducted into an interior of a ceramic mold 704. Ingate 732 is connected to ceramic mold 704 in a bottom gate configuration. Cast material 716 enters conduit 710, and melts the foam substrate about which ceramic material is formed, allowing cast material 716 to flow through conduit 710 and into ceramic mold 704.

[0046] While cast material 716 enters ceramic mold 704 and evaporates hollow shell 700, the interior of ceramic mold 704 includes a cast portion 733 (making a partially formed casting) and an uncast portion 734. The objective is of course to fill the entirety of the interior of ceramic mold 704 with cast material 716, resulting in the elimination of uncast portion 734. As hollow shell 700 evaporates, gases are generated. The gases escape to uncast portion 734, where gas pressure builds. The gas pressure within uncast portion 734 encounters and acts against metallostatic pressure of cast material 716 within cast portion 733. Gas within uncast portion 734 is able to escape through ceramic mold 704 as described further below.

[0047] As previously discussed, pre-cast assembly 740 may be buried in various positions including upright, inverted, and tilted at an angle. The selected position may be based on selected cast material 716 for casting, being at least one of: aluminum alloys, brass alloys, copper alloys, bronze alloys, iron alloys, steel, nickel, and stainless steel alloys. If a lower density of the selected cast material 716 is being used for casting, an inverted or a tilted angle burying position may be used. If a higher density of the selected cast material 716 is being used for casting, an upright or the tilted angle burying position may be used. However, it is understood that higher density cast materials 716 may be used in inverted positions, and lower density cast materials 716 may be used in upright positions.

[0048] It may be more desirable to utilize a bottom gate arrangement (e.g., those assemblies illustrated in FIGS. 4 and 7) as a bottom gate arrangement reduces turbulence and leads to more laminar flow of cast material 716 and less potential for defects in the final target part.

[0049] A top gate arrangement may be preferable when casting aluminum, magnesium, and / or beryllium cast materials 716 because those materials’ densities are so low that the metallostatic pressure formed when casting those materials is at times not high enough to push the gas out of uncast portion 734.

[0050] During casting, the head pressure (or metallostatic pressure) of cast material 716 within cast portion 733 of ceramic mold 704 must be greater the gas pressure within uncast portion 734, and additionally must be great enough to push the gas within uncast portion 734 out of the walls of ceramic mold 704.

[0051] The head pressure of cast material 716 within cast portion 733 is a function: f(P) o g * H * V * p, where P is the pressure, g is the gravity constant, H is the height of the column of cast material 716 above the ceramic mold 704’s mold wall, V is the volume of the cast material 716 above the part, and p is the density of cast material 716 and used to calculate the mass being pulled down by gravity.

[0052] The gas pressure of the gas within uncast portion 734, on the other hand, is dependent upon the mass of the polymer (of hollow shell 700) being vaporized, and the ideal gas law, and also varies with temperature. The ideal gas law is written in an empirical form as P V — n R T. To determine the gas pressure, one calculates the mass of polymer to vaporize (i.e., the mass of polymer used to form hollow shell 700) and converts that mass to the number of moles of polymer. One next determines how much the polymer compounds will expand in transitioning from a solid to a gas and how much the polymer compounds will expand due to the temperature increase from room temperature to the molten metal temperature. These expansion calculations allow one to determine the expected gas pressure of gas within uncast portion 734.

[0053] FIG. 8A illustrates a cutaway view of a pre-cast assembly 840 buried in compacted sand or ceramic beads 814; molten cast material 816 is poured into an inlet to evaporate the material of a 3D hollow shell 800. FIG. 8B illustrates a partial magnified view of pre-cast assembly 840. Pre-cast assembly 840 includes a polymer hollow shell 800, coated in a ceramic to form a ceramic mold 804. Hollow shell 800 and ceramic mold 804, bonded as one part, are buried in compacted sand or ceramic beads 814, and cast material 816 is introduced to the interior of hollow shell 800 and ceramic mold 804. Cast material 816 has a temperature that is high enough to vaporize hollow shell 800, causing a temporary shell-free area 836 to form at the junction of a cast portion 833 with an uncast portion 834. Gas generated by vaporized hollow shell 800, as well as any gas previously contained within hollow shell 800 and ceramic mold 804 (e.g., ambient air), can escape through ceramic mold 804 in shell-free area 836. Additionally, any gas previously contained within hollow shell 800 may escape through the wall of hollow shell 800, as illustrated in FIG. 8B. It is understood that cast portion833, uncast portion 834, and shell-free area 836 is constantly changing as cast material 816 is being added to the interior of ceramic mold 804.

[0054] With specific reference to FIG. 8A, a metallostatic pressure Pm acts against a gas pressure Pg. Gas pressure Pg is pressurized, vaporized polymer gas. Metallostatic pressure Pm is hydrostatic pressure for the molten cast material 816. Consideration is given to the design of pre-cast assembly 840 ’s gating (i.e., top gate versus bottom gate) in light of pressure Pm and Pg.

[0055] If pressure Pm is less than pressure Pg, an explosion of molten metal 833 is likely to occur. Molten metal 833 may be forcefully ejected back out of the conduit (including the downsprue) into which it was poured.

[0056] If pressure Pm is equal to pressure Pg, a defect is likely to occur as component only partially fills (that is, cast portion 833 unable to overtake the entirety of uncast portion 834). The defect can occur at any point prior to solidification of the part after casting, or at any localized area in the part geometry.

[0057] Thus, pressure Pm must be greater than pressure Pg for a complete casting. Pressure Pm is calculated from the weight of the metal divided by the cross-sectional area. Pressure Pg is calculated using the following formula: Pg = P vaporized print + P vaporized foam - P exiting gas.

[0058] Alternatively, or additionally, one or more vent tube may be added in fluid communication with an interior cavity defined by hollow shell 800 and / or ceramic mold 804, thus permitting the outflow of gas from the interior cavity via the vent tube upon exposure to metallostatic pressure Pm.

[0059] The pressure P vaporized print is the pressure of the vaporized gas generated by the vaporization of 3D printed hollow shell 800. The pressure P vaporized foam is the pressure of vaporized foam within ceramic mold 804, if any (applicable where lost foam casting is used as described herein). Pressure P vaporized print and pressure P vaporized foam are calculated using the Ideal Gas Law.

[0060] The pressure P exiting gas is the pressure of the vaporized polymer gas exiting assembly 840 through ceramic mold 804. Pressure P exiting gas is a function of the surface area of the exposed ceramic mold 804, ceramic mold 804’s permeability, hollow shell 800’s permeability, and vacuum pressure if a vacuum is used.

[0061] In some 3D prints, hollow shell 800 is not permeable enough to allow the vaporized polymer gas to exit assembly 840 at an appropriate rate to maintain the desirablepressure P exiting gas. FIGS. 9A-9C illustrate a device 942 for increasing the permeability of 3D prints. Device 942 includes a body 943 having a hollow cavity 945 opened on one end configured to receive a user’s finger. A piercing element 944 extends from a closed end of body 943 opposite the opened end. Piercing element 944 may be of a sufficient strength and sharpness to pierce the 3D printed hollow shell 800. Piercing element 944 must not have a diameter or thickness so large as to cause hollow shell 800 to crack, or to allow the coating that forms ceramic mold 804 to pass through the wall of hollow shell 800. Device 942 is configured to be worn on one’s finger to facilitate piercing. In another aspect, FIGS. 10A-10C illustrate a device 1042 for increasing the porosity of 3D prints. Device 1042 includes a body 1043 having a hollow cavity 1045 opened on one end configured to receive a user’s finger, and closed on an opposite end. A piercing element 1044 extends from a side of body 1043 and is parallel to the longitudinal aspect of body 1043. Piercing element 1044 may be of a sufficient strength and sharpness to pierce the 3D printed hollow shell 800. Piercing element 1044 must not have a diameter or thickness so large as to cause hollow shell 800 to crack, or to allow the coating that forms ceramic mold 804 to pass through the wall of hollow shell 800. Device 1042 is configured to be worn on one’s finger to facilitate piercing.

[0062] FIG. 11 illustrates a coating station 1100 for coating a three-dimensional print with a ceramic coating. Coating station 1100 includes an enclosure 1102, a plurality of ceramic coating units 1101 A, 1101B that include ceramic coating tanks 1110A, 1110B, a part coating area 1120 including a rack 1106, and a coating output hose 1114.

[0063] At least two coating units 1101A, 1101B are vertically offset from one another, with the upper coating tank 1110A being supported on a shelf 1104 and lower coating tank 1110B being supported on a shelf 1108. Each of ceramic coating tanks 1110A, 1110B includes a cover 1111A, 1111B, respectively. Each of ceramic coating tanks 1110A, 1110B includes a valve 1112A, 1112B, respectively, fixed to an outlet of each of ceramic coating tanks 1110A, 1110B. Coating output hose 1114 is connected to an outlet on upper coating tank 1110A. Flow of ceramic coating from upper coating tank 1110A is controlled by valve 1112A.

[0064] During coating, a 3D print to be coated is placed on rack 1106 in part coating area 1120. Valve 1112A on upper coating tank 1110A is opened, permitting ceramic coating to flow through coating output hose 1114 via gravity. Ceramic coating from coating output hose 1114 is used to coat the 3D print in part coating area 1120. Excess ceramic coating that does not adhere to the 3D print in part coating area 1120 falls through rack 1106 and into lower coating tank 1110B after being collected in a funnel 1116. When upper coating tank 1110A isempty, or sufficiently low on ceramic coating, a user may close valve 1112A, disconnect coating output hose 1114 if necessary, and swap upper coating tank 1110A with lower coating tank 1110B. Output hose 1114 may be connected to lower coating tank 1110B, now supported in an upper vertical position on shelf 1104. In this manner the ceramic coating is recycled as multiple 3D prints are coated.

[0065] Additionally, ceramic coating applied to the 3D print in part coating area 1120 may be dried by hot air blowing onto the coated 3D print from hot air blower 1118. Hot air blower 1118 may be activated after coating of the 3D print and may accelerate the drying of the ceramic coating via application of hot air blown onto the coated 3D print. Once the ceramic coating applied to the 3D print is dried, a hardened ceramic mold is formed.

[0066] FIG. 12 illustrates a sectional view of an automated vibration station 1254 for settling sand or ceramic beads around the hardened ceramic mold within a flask 1255. Flask 1255 may be a container capable of holding the hardened ceramic mold in a stable position via the settled sand / beads surrounding the hardened ceramic mold. Flask 1255, containing both the hardened ceramic mold and the sand / beads, may be placed upon a vibration table 1256. Flask 1255 may be temporarily fixed to vibration table 1256 by at least one clamp 1257. Flask 1255 may have a protruding flange at its lower end, and the flange may be engaged by at least one clamp 1257 to fix flask 1255 into a desired position. Vibration table 1256 may be supported upon springs 1258 to allow vibration table 1256 to move via input by a vibration motor 1259. Vibration motor 1259 may be mounted to the lower side of vibration table 1256 while flask is connected to the opposite, upper side of vibration table 1256. As a result, sand / beads within flask 1255 may settle around the hardened ceramic mold to hold it in a fixed position within flask 1255 for receiving the molten cast material.

[0067] In another aspect, ceramic coating tank 1110A, 1110B may be placed upon vibration table 1256 to mix ceramic coating contained within ceramic coating tank 1110A, 1110B. Ceramic coating tank 1110A, 1110B may be temporarily fixed to vibration table 1256 by at least one clamp 1257.

[0068] Vibration station 1254 may include a vacuum duct 1260 extending into the interior of flask 1255 from a vacuum source. Vacuum duct 1260 may be used to draw exiting gases formed from the vaporized hollow shell 800 through the ceramic mold 804. Vacuum duct 1260 may be used to extract fumes created during the vaporization of hollow shell 800 away from the system. These fumes may be optionally directed through an activated carbonfilter, through a container of a liquid (e.g., water) where the fumes may resolidify as a polymer for disposal or recycling, or to a flame to ignite and bum the fumes to render them less harmful.

[0069] FIG. 13 illustrates an enclosed pouring system 1300 including a furnace 1304 and a flask 1255. System 1300 may include a frame 1302 (or alternatively, an enclosure) at least partially enclosing additional elements of system 1300.

[0070] Furnace 1304 may be rotationally fixed to a subframe element 1310 by a pivot 1306, whereby pivot 1306 allows furnace 1304 to tilt over and pour its contents (molten cast material) from a spout 1305 arranged in a side of furnace 1304. Pivot 1306 may be a revolute joint. System 1300 may include an electric motor 1308 operatively connected to pivot 1306 (e.g., electric motor 1308 may be connected to a pulley or belt system, which is in turn connected to pivot 1306). Electric motor 1308 may be activated to cause furnace 1304 to rotate to a tilted position (to pour molten cast material from spout 1305) or an upright position (to stop molten cast material from pouring from spout 1305).

[0071] Electric motor 1308 may be activated, deactivated, and otherwise controlled by a programmable logic controller (“PLC”) 1320. PLC 1320 may be operatively connected to electric motor 1308. PLC 1320 may operate at the instruction of a user, as part of a larger system, or be capable of operating in both schemes.

[0072] System 1300 may contain flask 1255. Flask 1255 may rest upon a fume extraction base, or an element of frame 1302. At least one clamp 1257 may temporarily fix flask 1255 to the fume extraction base or the element of frame 1302. Flask 1255 includes an interior for receiving the hardened ceramic mold and surrounding sand / beads described above. The fume extraction base may include a vacuum, an activated carbon filter, or both. Upon application of a molten cast material to the interior of the hardened ceramic mold, the 3D print inside of the hardened ceramic mold evaporates, creating fumes that may be noxious. These fumes may be directed into the activated carbon filter by the vacuum. Alternatively, the fume extraction base may include a burner instead of, or in conjunction with, the activated carbon filter. The burner may safely burn off any noxious fumes produced in the evaporation of the 3D print. The vacuum may direct the noxious fumes to the burner. Alternatively, the fume extraction base may be operatively connected to a container of a liquid (e.g., water) where the fumes may resolidify as a polymer for disposal or recycling.

[0073] Furnace 1304 may heat the cast material to a molten state using resistance heating elements, induction heating elements, or the like. Molten cast material may leave spout 1305 when furnace 1304 is tilted, and may flow down a trough 1312, out a drain 1314 and intoflask 1255. The heating elements within furnace 1304 may be activated, deactivated, or otherwise adjusted under control by PLC 1320. PLC 1320 may be operatively connected to the heating elements within furnace 1304.

[0074] FIG. 14 illustrates an alternative aspect of a pouring system 1470 including a furnace 1471 and flask assembly 1472. In this aspect, furnace 1471 is supported by a frame 1477 (or alternatively, an enclosure) whereby furnace 1471 pivots via at least one pivot point 1475. Furnace 1471 may be pivoted in an automated manner via an actuator, motor, or the like. Alternatively, furnace 1471 may be pivoted via a handle 1476.

[0075] Furnace 1471 may include a furnace bottom 1473 and a furnace lid 1474. A cast material may be heated to a molten state within the interior of furnace 1471 defined by furnace bottom 1473 and furnace lid 1474. Furnace 1471 may be tilted to permit the molten cast material to flow out of furnace 1471 and into the interior of a hardened ceramic mold contained within flask 1255 in flask assembly 1472 oriented below furnace 1471. Flask 1255 may be placed upon fume extraction base 1397 as described above.

[0076] FIG. 15 illustrates another aspect of a coating station 1580 for coating a three- dimensional print with a ceramic coating. Coating station 1580 may include a housing 1581 containing a coating vat 1583, a coating output hose 1582 for transporting coating from coating vat 1583 to a 3D print to be coated, and controls 1584 for controlling the operation. In practice, a 3D print to be coated is placed within housing 1581 on a rack or the like, suspended above coating vat 1583. Ceramic coating is pumped out of coating vat 1583 and through coating output hose 1582 to pour down onto the 3D print.

[0077] Coating station 1580 may include a mechanism to stir the ceramic coating within coating vat 1583 (e.g., a magnetic stirrer). Coating station 1580 may include one or more dryer. The pump, stirrers, driers, and the like can be controlled via controls 1584. Excess ceramic coating that does not adhere to the 3D print is able to fall back into coating vat 1583 via gravity.

[0078] FIG. 16 illustrates an example method 1600 for obtaining a cast part. Method 1600 begins with obtaining a 3D computer-aided design (“CAD”) model for a given design of a part (step 1602).

[0079] Next, method 1600 includes determining the number of 3D printed parts required to obtain the total hollow shell 3D print (step 1604). Sometimes the hollow shell can be a single 3D printed part, and other times the hollow shell must be formed from multiple 3Dprinted parts assembled together. The volume of the print material is minimized by modifying the wall thickness and minimizing infill. The mass of the print material is determined.

[0080] Next, method 1600 includes 3D printing the additive manufacturing evaporative casting part and assemble the parts where necessary (e.g., where multiple 3D printed elements were required to form the whole 3D printed part) (step 1606). Any support structure(s) and excess printing material is removed. Assembly of multiple 3D printed elements may include a compression fit, or fitting using an adhesive or polymer welding. Any adhesives used are kept at a minimum as the adhesives will produce gas when vaporized during casting.

[0081] Next, method 1600 includes attaching an ingate to the gating system (step 1608)

[0082] Next, method 1600 includes applying a masking material, such as masking tape, to areas not to be coated with ceramic (step 1610). One example is the downsprue attachment point.

[0083] Next, method 1600 includes applying a ceramic coating to the gating system, ingate, and part(s) (step 1612). This step may be completed using any of the coating stations described above, including coating stations 1100 and 1580.

[0084] Next, method 1600 includes removing masking materials and adhering a downsprue to the assembly (step 1614). The downsprue is the vertical funnel-like portion of the conduit. The downsprue may be a preformed ceramic item. The downsprue is adhered to the downsprue attachment point that was covered by a masking material during ceramic coating. The top (inlet) of the downsprue may be covered (e.g., with a paper cover) to prevent sand and / or ceramic beads from entering the top of the downsprue.

[0085] Next, method 1600 includes placing the assembly in a flask and packing sand and / or ceramic beads around the assembly (step 1616). An initial base of at least 50.8 mm (2.0 in.) of sand and / or ceramic beads is provided in the bottom of the flask before placement of the pre-cast assembly inside of the flask. The ceramic beads may be ID40 ceramic beads. Beads between AFS Grain Fineness Number (“AFN”) 20 and 80 may be used. Silica, olivine, or other types of natural or synthetic sands may be used. The sand and / or ceramic beads are vibrated into the flask using automated vibration station 1254 around the pre-cast assembly until at least 254 mm (10 in.) of sand and / or ceramic beads cover the highest point of the ceramic mold, while the top of the downsprue extends above the level of the sand and / or ceramic beads.

[0086] Next, method 1600 includes pouring molten casting material into the top (inlet) of the downsprue (step 1618). Any covering of the top (inlet) of the downsprue (e.g., the papercover) is removed, or perforated, prior to pouring. The casting material is heated to a temperature at least 65.6 degrees C (150 degrees F) above the casting material’s melting point. The casting metal is poured into the downsprue as fast as possible, with a target rate of about 45.4 kg (100 lbs.) per second. The pouring should be continuous (without interruption) to avoid defects. Either of pouring systems 1300 or 1470 may be used to bring the casting material to a molten state and pour the molten casting material into the hardened ceramic mold.

[0087] Next, method 1600 includes allowing the cast part to solidify, removing the assembly from the flask, removing gating, and removing the ceramic coating (step 1620). Solidification of the part typically takes at least one hour. The gating is removed by either knocking it off, or cutting it off. The ceramic coating may be removed by shotblasting, wire brush, rinsing, or the like.

[0088] FIG. 17 illustrates a schematic view for an example system 1700 for creating a metal casting from a three-dimensional print. In the first stage of system 1700, a three- dimensional print 100 is formed using an additive manufacturing / 3D printer. In the second stage of system 1700, three-dimensional print 100 is coated with a ceramic coating in coating station 1100, forming a pre-cast assembly (such as pre-cast assembly 840). In the third stage of system 1700, pre-cast assembly 840 is packed in a flask (such as flask 1255) in automated vibration station 1254, with a vacuum duct (such as vacuum duct 1260) being oriented with its distal end near pre-cast assembly 840. In the fourth stage of system 1700, pre-cast assembly 840, packed within a flask (such as flask 1255), is cast with molten casting material in enclosed pouring system 1300.

[0089] To the extent that the term “includes” or “including” is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed (e.g., A or B) it is intended to mean “A or B or both.” When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use. See Bryan A. Gamer, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995). Also, to the extent that the terms “in” or “into” are used in the specification or the claims, it is intended to additionally mean “on” or “onto.” To the extent that the term “substantially” is used in the specification or the claims, it is intended to take into consideration the degree of precision available in manufacturing. To the extent that the term “selectively” is used in the specification or the claims, it is intended to refer to a condition of a component wherein a user of theapparatus may activate or deactivate the feature or function of the component as is necessary or desired in use of the apparatus. To the extent that the term “operatively connected” is used in the specification or the claims, it is intended to mean that the identified components are connected in a way to perform a designated function. As used in the specification and the claims, the singular forms “a,” “an,” and “the” include the plural. Finally, where the term “about” is used in conjunction with a number, it is intended to include ± 10 % of the number. In other words, “about 10” may mean from 9 to 11.

[0090] As stated above, while the present application has been illustrated by the description of embodiments and aspects thereof, and while the embodiments and aspects have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art, having the benefit of the present application. Therefore, the application, in its broader aspects, is not limited to the specific details, illustrative examples shown, or any apparatus referred to. Departures may be made from such details, examples, and apparatuses without departing from the spirit or scope of the general inventive concept.

Claims

CLAIMSWhat is claimed is:

1. A system for creating a metal casting from a three-dimensional print, comprising: a three-dimensional print formed using additive manufacturing; a ceramic coating station configured to coat the three-dimensional print with a ceramic coating to form a pre-cast assembly; and a vibration station having a flask configured to contain the pre-cast assembly packed within one of sand or ceramic beads.

2. The system of claim 1, wherein the three-dimensional print forms a hollow shell.

3. The system of claim 1, wherein the three-dimensional print is formed from polyactic acid.

4. The system of claim 1, wherein the ceramic coating station further comprises an enclosure with two ceramic coating tanks aligned vertically relative to one another with a part coating area vertically between the two ceramic coating tanks.

5. The system of claim 4, wherein a coating output hose extends from an upper ceramic coating tank into the part coating area and wherein the coating output hose is configured to coat the three-dimensional print with the ceramic coating.

6. The system of claim 5, wherein excess ceramic coating falls into a lower ceramic coating tank.

7. The system of claim 1, wherein the ceramic coating tanks include outlets with valves through which the ceramic coating flows.

8. The system of claim 1, wherein the ceramic coating station further comprises a hot air blower configured to blow hot air over the pre-cast assembly.

9. The system of claim 1, wherein the vibration station further comprises a vibration table upon which the flask is placed, and wherein a vibration motor is mounted to the vibration table and configured to cause the vibration table to vibrate.

10. The system of claim 9, wherein the vibration table is supported upon springs configured to allow the vibration table to move via input by the vibration motor.

11. The system of claim 9, wherein the vibration table includes at least one clamp to temporarily fix the flask to the vibration table.

12. The system of claim 1, wherein the vibration station further comprises a vacuum duct extending into an interior of the flask from a vacuum source.

13. The system of claim 12, wherein the vacuum duct is configured to draw exiting gases formed from vaporization of the three-dimensional print through the ceramic coating during the application of a molten casting material.

14. The system of claim 12, wherein the vacuum duct is configured to extract fumes formed from vaporization of the three-dimensional print during the application of a molten casting material.

15. The system of claim 1, further comprising an enclosed pouring system having a furnace configured to melt casting material and configured to pour molten casting material into an interior of the pre-cast assembly.

16. The system of claim 15, wherein the enclosed pouring system further comprises a frame, and wherein the furnace is rotationally fixed to a subframe element of the frame by a pivot configured to allow the furnace to tilt causing molten casting material to pour from the furnace.

17. The system of claim 16, wherein the enclosed pouring system includes an electric motor operatively connected to the pivot, and wherein the electric motor is configured to cause the furnace to rotate between an upright position and a tilted position.

18. The system of claim 16, wherein the enclosed pouring system includes a programmable logic controller, and wherein the programmable logic controller is operatively connected to the electric motor.

19. The system of claim 15, wherein the flask containing the pre-cast assembly is contained within the enclosed pouring system, and wherein the flask is temporarily constrained by at least one clamp.

20. The system of claim 15, wherein the enclosed pouring system includes a trough configured to route molten cast material from the furnace into the interior of the pre-cast assembly.

21. The system of claim 15, wherein the enclosed pouring system includes a programmable logic controller, and wherein the programmable logic controller is operatively connected to heating elements within the furnace.

Images