Molding system and method for additive metal casting

Abstract

A mold-making system for use in additive manufacturing of metal objects is provided, comprising at least one mold provider controllably operable to form one or more mold regions within a manufacturing layer, each defining one or more respective metal object regions, and a control system for operating the at least one mold provider according to a predetermined build schedule. The mold provider operates according to the predetermined build schedule to build each mold region by sequentially forming a metal-facing zone defining a cavity for forming the metal object region and a metal-non-adjacent zone surrounding the metal-facing zone. The metal-facing zone of the mold region is made of a ceramic-based material and differs from the metal-non-adjacent zone in at least one of material composition and mold deposition process parameters.

Description

[Technical Field]

[0001] The technology of this disclosure is in the field of additive manufacturing of relatively large objects and relates to methods and systems for mold construction for additive metal casting. [Background technology]

[0002] Casting is one of the oldest methods of shaping materials still in use. The main process has remained unchanged since 3200 BC, when bronze was melted and poured into stone molds. Metal casting is defined as the process of pouring molten metal into a mold containing a hollow cavity of the desired geometric shape, where it cools and solidifies to form the part.

[0003] Currently, most of the world's demand for metal castings is met by traditional foundry techniques. While automated solutions are being applied, traditional foundry involves global production of molds and global application of molten metal. For example, additive manufacturing techniques are used in mold production, which involves mold hardening, sintering, or other mold hardening (partial or full) as a global operation before metal injection. Molten metal is poured into the fully fabricated mold.

[0004] Currently available metal AM technologies are suitable for low-volume production of complex designs and relatively small parts. Scaling up from small parts to larger parts weighing hundreds or thousands of kilograms is not easy. With some currently available metal AM technologies, scaling up in size and weight can result in part deformation, distortion, shrinkage, fracture, or cracking.

[0005] Despite the advantages of metal additive manufacturing, the associated high cost, low throughput, and scale-up challenges have prevented the technology from being widely adopted for industrial applications, especially in the production of steel parts.

[0006] Casting is widely used in the industrial production of mass-produced, one-piece products and large components. Metal casting can produce complex shapes, and features such as internal cavities and hollow sections can be easily formed. Materials that are difficult or expensive to produce using other manufacturing processes can also be cast. Compared to other manufacturing processes, conventional casting is inexpensive for medium to large metal quantities, especially for steel casting.

[0007] Modern metal casting also has several drawbacks. Creating patterns and molds is time-consuming and costly. Additive manufacturing processes, such as binder jetting, are typically used to create patterns and molds. However, creating patterns and molds increases lead times and limits design flexibility for modifications and adaptations. Additionally, depending on the application, minor or significant additional post-processing may be required. Furthermore, metal casting is a hazardous operation, operating at very high temperatures and with many manually manipulated and exposed elements, such as furnaces, molds, cooling areas, and additional tooling.

[0008] Commonly assigned U.S. Patent Publication No. 2020 / 0206810 describes a method and apparatus for additive casting of parts, which may include depositing a first portion of a mold on a build table, where the deposition may be layer-by-layer, pouring a liquid material into the first portion of the mold to form a first casting layer, solidifying at least a portion of the first casting layer, depositing a second portion of the mold on the first portion of the mold, pouring a liquid material into the second portion of the mold to form a second casting layer on the first portion of the mold, and solidifying at least a portion of the second casting layer. The method may further include preheating each casting layer before pouring the additional casting layer. Summary of the Invention

[0009] There is a need in the art for new additive metal casting techniques that provide high throughput and mass production.

[0010] To enable high production yields and provide high precision in cast parts, molds produced during additive manufacturing must not only withstand the high hydraulic pressure of the molten metal on the mold walls, but also multiple cycles of heating of the cast metal, which leads to expansion of the metal and therefore further pressure on the mold walls.

[0011] As described in the above-mentioned commonly assigned patent publication US2020 / 0206810, additive metal casting can be performed in conjunction with additive mold casting. The inventors identified another problem related to the need to heat the working area of ​​the object region to a required pre-deposition target temperature before depositing metal in the object region. This heating is necessary to affect bonding between the molten metal and the solidified metal of the preceding metal layer (deposited in a previous casting cycle and already cooled). The pre-deposition target temperature can be lower than, equal to, or higher than the melting temperature of the metal object being produced. Heating already solidified metal in the mold causes a volume change, which exerts pressure on the mold walls during the phase change, creating large stresses within the mold material and potentially leading to mold failure.

[0012] The ceramic-based mold casting process is often the casting method of choice for metal casting because it produces perfect surface quality with intricate detail and dimensional stability. Additionally, ceramic-based molds provide the strength needed to maintain the shape of the cast metal object, permeability to allow hot air or gas to pass through the pores within the ceramic, and thermal stability to prevent cracking upon contact with molten metal.

[0013] The present disclosure presents a novel mold manufacturing system for use during additive casting of metal objects that provides a unique mold area that not only defines the shape of the metal object but is configured to prevent leakage of molten metal during additive casting, thereby maintaining the desired shape of the metal object and improving the yield and safety of the casting process.

[0014] It should be noted that, according to the present disclosure, additive metal casting involves building a mold structure simultaneously with a metal object structure, with this building occurring in a layer-by-layer fashion. The layers are referred to herein as "production layers." Each production layer (except the bottom layer, in some embodiments) defines a respective "object region" of the metal object structure and includes one or more surrounding "mold regions." The closed-loop mold region of a produced production layer defines a cavity into which molten metal for the object region is deposited. Typically, the first layer (bottom layer) includes the closed-loop mold region and a bottom layer of cavities made solely of mold material.

[0015] Therefore, in the following description, the term "mold area" refers to a mold part / portion within a single manufacturing layer. The terms "mold structure" and "mold" are used interchangeably to refer to all or part of a stack of mold areas in all or some manufacturing layers.

[0016] It should be understood that in the general field of 3D printing mold fabrication, the term "mold" is commonly used to refer to a complete mold structure that is fully sintered / hardened prior to pouring metal. The techniques of the present disclosure deal with additive manufacturing of stacks of mold regions (layer-by-layer manufacturing), where within each mold region, additive casting of the stack of respective object regions within the cavity formed by the respective mold region is performed. In this regard, it should be noted that the mold regions of different manufacturing layers may or may not be the same size and shape, depending on the specific shape and size of the respective object regions.

[0017] The mold manufacturing system of the present disclosure is configured to perform a process by forming a stack of multiple manufacturing layers layer by layer. The system is configured to fabricate each manufacturing layer by depositing mold material to form a mold region, and then depositing molten metal into each cavity / object region defined by each of the at least one mold region to form the associated object region. Each subsequent manufacturing layer is formed after the completion of the preceding manufacturing layer. Thus, the mold regions of different manufacturing layers are cured (fully, partially, or not cured at all) at different points during the manufacturing process.

[0018] Additionally, during additive metal casting, each mold zone is subjected to a transient thermal shock. That is, heat is supplied during molten deposition to the connecting object zone; in some embodiments, the temperature of the chamber surrounding the build table is increased after mold deposition and before molten metal deposition, and heat from upper layers is dissipated to lower layers during the fabrication of successive mold zones and object zones in successive fabrication layers. Accordingly, the mold fabrication system of the present disclosure is configured to design the mold zones so that they can withstand said thermal shock.

[0019] Mold region manufacturing systems and methods according to the present disclosure provide mold regions having separate and functionally distinct mold region zones including ceramic-based metal-facing zones connecting with respective object regions and metal-non-adjacent zones surrounding each metal-facing zone.

[0020] Mold region manufacturing systems and methods according to the present disclosure provide mold regions having separate and functionally distinct mold region zones including ceramic-based metal-facing zones connecting with respective object regions and metal-non-adjacent zones surrounding each metal-facing zone.

[0021] The metal-facing zone may have a surface treatment applied to at least its metal-facing surface. For example, the metal-facing surface may be surface-shaped, material-removed (e.g., ceramic deflection), surface-smoothed, coated, hardened, partially hardened, etc. The present invention is not limited by the type of surface treatment technique or system used to apply the surface treatment. For example, techniques and systems such as milling, grinding, polishing, heating, coating, etc. may be used.

[0022] Thus, according to one broad aspect of the present disclosure, there is provided a mold manufacturing system for use in additive manufacturing of metal objects, comprising: The mold manufacturing system includes at least one mold provider controllably operable to form one or more mold regions defining one or more metal object regions within a manufacturing layer, and a control system configured to operate the at least one mold provider according to a predetermined build schedule; the at least one mold provider is controllably operable to create each of the one or more mold regions by sequentially forming, in accordance with the predetermined build plan, a metal-facing zone configured to define a cavity that forms a metal object region, and a metal non-adjacent zone surrounding the metal-facing zone; The metal-facing zone of the mold region is made of a ceramic-based material and differs from the metal-non-adjacent zone of the mold region in at least one of material composition and mold deposition process parameters.

[0023] The non-metallic adjacent zone of the mold region is configured to provide mechanical support to the metallic opposing zone of the mold region. The non-metallic adjacent zone of the mold region may, for example, comprise a ceramic-based material.

[0024] In some embodiments, at least one mold provider is controllably operable to form metallic non-adjacent zones in a mold region having a cross pattern. For example, the mold provider is controllably operable to form metallic non-adjacent zones in the mold region with multiple iterations of material deposition to form the cross pattern. In other embodiments, the mold provider is controllably operable to form metallic non-adjacent zones in a mold region having a curl pattern.

[0025] The mold providing device may be controllably operable to increase the surface area of ​​the metal non-adjacent zone of the mold region, reduce material density to allow rapid transport of heat and vapor from the metal facing zone and metal non-adjacent zone of the mold region, and / or to allow rapid formation of the metal non-adjacent zone of the mold region.

[0026] In some embodiments, the mold provider is configured and operable to vary one or more of the mold material deposition parameters and conditions for forming the mold region prior to depositing molten metal to form the respective object region of the current manufacturing layer. The varied one or more mold material deposition parameters are selected to form the metal-facing zone and the metal-non-adjacent zone of the mold region with a reduced material density capable of undergoing cyclic thermal shocks associated with the incremental deposition of molten metal in the object region. For example, the reduced material density of each of the metal-facing zone and the metal-non-adjacent zone is defined by the porosity of the mold material, e.g., the reduced material density is defined by porosity having a pore size not substantially exceeding 60 μm.

[0027] Preferably, the ceramic-based material is in an unsintered state.

[0028] For example, the ceramic-based material is characterized by a viscosity of at least 40 Kcps.

[0029] In some embodiments, the metal-facing zone and the metal-non-adjacent zone of the mold region are composed of first and second different mold material compositions, respectively.

[0030] The mold providing apparatus may be configured and operable to provide, by its non-metal-facing side, a mold region configured such that the metal-facing zone is at least partially adhered to the metal non-adjacent zone.

[0031] In some embodiments, the mold region is configured with a metal-facing zone including a first subzone directly bonded to the object region by its metal-facing side and a second subzone opposite and surrounding the first subzone. The first subzone is configured as an inner wall made of a refractory compressible ceramic-based material and serves as a metal-facing thermal insulating wall for the second subzone. For example, the second subzone of the metal-facing zone is made of a plastic material.

[0032] In some embodiments, the mold region further comprises an enclosure around the non-metallic zone, which may be separated from the non-metallic zone by a gap filled with a mold material composition that is more compressible than the non-metallic zone.

[0033] The more compressible mold material composition may include one or more of compressible sand, ceramic-based material, compressible ceramic-based material, porous ceramic, atomized ceramic, spheres, negative thermal expansion material, reversibly compressible plastic, nanostructure, layered material.

[0034] In some embodiments, the mold providing device is controllably operable according to the build plan, which further indicates two or more of the geometric layout of one or more object areas in each manufacturing layer, the materials, geometric properties and arrangements of metal-facing zones and metal-non-adjacent zones of each mold area in each manufacturing layer, surface treatment parameters and surface treatment conditions of the mold areas, and synchronization data for the formation of the mold areas and object areas in the manufacturing layer.

[0035] The mold manufacturing system also includes a surface treatment system configured and operable to apply one or more surface treatments to the mold region, such as applying a temperature treatment to the mold region (e.g., to impart material hardening to the mold region) or applying a mechanical surface treatment to at least a portion of the mold region (e.g., the surface of a metal facing zone connecting with the object region).

[0036] In some embodiments, the mold deposition apparatus comprises one or more traveling depositors, each moving in a horizontal plane according to a predetermined trajectory and associated with one or more reservoirs of mold material.

[0037] The mold deposition apparatus may include one or more extruders in fluid communication with the one or more traveling depositors, respectively.

[0038] The traveling depositor can include at least one of an agitator, a tube, and a tube loop configured to provide continuous circulation of mold material not currently involved in the deposition process.

[0039] The mold manufacturing system can include a build table configured to be placed in a temperature-controlled environment, and the system can be configured to provide relative displacement between the one or more traveling depositors and the build table.

[0040] In some embodiments, the mold manufacturing system is configured and operable to create the mold area of ​​the current manufacturing layer on at least a portion of the previous mold area of ​​the previous manufacturing layer or on at least a portion of the previous object area of ​​the previous manufacturing layer depending on the surface relief of the metal object area to be manufactured.

[0041] According to another broad aspect of the present disclosure, there is provided a manufactured part including a stack of manufacturing layers, each manufacturing layer including one or more object regions of a metal object, each object region surrounded by a mold region, the mold region including a metal-facing zone and a metal-non-adjacent zone surrounding the metal-facing zone, wherein a surface of the metal object within the object region is physically coupled to a metal-facing surface of the metal-facing zone of the mold region, and the metal-facing zone differs from the metal-non-adjacent zone of the mold region in at least one of material composition parameters and mold deposition process parameters.

[0042] According to yet another broad aspect of the present disclosure, there is provided an additive casting system for additively casting a metal object by sequentially fabricating, on a movable build table, a plurality of production layers, up to a top layer, each having a mold region and an object region within a cavity defined by the mold region, the additive casting system including the mold fabrication system described above and an object fabrication apparatus configured and operable to build each current production layer by depositing molten metal into each of one or more object regions defined by a respective one or more mold regions in the current production layer.

[0043] The object manufacturing apparatus may include one or more molten metal depositors and a control system configured to operate the one or more molten metal depositors according to a predetermined build plan indicating the geometric layout of one or more object areas in each manufacturing layer and synchronization data for the formation of mold areas and object areas in the manufacturing layer.

[0044] The object manufacturing apparatus is configured and operable to create an object area of ​​a current manufacturing layer on at least a portion of a previous mold area of ​​a previous manufacturing layer or on at least a portion of a previous object area of ​​a previous manufacturing layer, depending on the surface relief of the metal object area to be manufactured.

[0045] In a broader aspect, the present disclosure provides a method for use in additive manufacturing of metal objects, the method comprising building successive manufacturing layers including a plurality of mold regions each defining a respective number of metal object regions, the building of each manufacturing layer being controllably performed according to a predetermined build schedule, the execution including, for each manufacturing layer, creating the plurality of mold regions prior to depositing molten metal material onto the plurality of object regions, each mold region being created by depositing one or more mold materials to sequentially form a metal-facing zone configured to define a cavity for forming the metal object region and a metal non-adjacent zone surrounding the metal-facing zone, the metal-facing zone of the mold region being made of a ceramic-based material and differing from the metal non-adjacent zone of the mold region in at least one of material composition parameters and mold deposition process parameters.

[0046] As mentioned above, in some embodiments of the present invention, surface treatments are applied to the mold material while it is in the green body state, followed by molten metal deposition. The mold-making techniques of the present disclosure preferably use the mold material in the green body state, which significantly reduces production time. The time required for full sintering is eliminated. The overall mold removal step upon completion of casting is simplified compared to removing a fully sintered mold structure. Some mechanical properties of ceramics, particularly compressibility, are more easily achieved in the green state. However, the use of ceramic mold materials in the green state presents significant challenges, including lower tensile strength and higher porosity than fully sintered ceramics, as well as material sagging during deposition. Aspects of the present disclosure address the challenges of the green state. For example, reduced tensile strength can be addressed by providing support zones or using different materials for different mold zones; sagging in the pre-cured state can be addressed, for example, by surface treatment of the metal-facing zones of the mold region; and increased porosity can be addressed, for example, by surface treatment and / or coating of the metal-facing zones of the mold region.

[0047] In some embodiments, the metal-facing zone is dispensed as a closed-loop, tube-shaped paste (referred to as a "paste tube" or "contour"), and the metal non-adjacent zone is dispensed as a second tube supporting the metal-facing tube (referred to as a "double tube" or "double contour" configuration).

[0048] In some embodiments, larger, wider support zones are required. To improve throughput and other operating parameters, the dispensing plans for the metal-facing zone and the metal-non-adjacent zone have different areal density parameters. The metal-facing zone is dispensed as a closed-loop tube of paste, while the metal-non-adjacent zone is dispensed as a tube in a curled pattern, leaving a predetermined air gap between the paste tube segments.

[0049] In some embodiments, a curly dispensed pattern of metallic non-adjacent zones is arranged in a given direction in one dispense and in a different direction in the next dispense, resulting in a crisscross patterned template structure (denoted as a "Cross" configuration) of successive metallic non-adjacent zones built up in successive repeated dispenses.

[0050] As discussed above, the crisscross or curl pattern of the metal non-adjacent zones (i) provides mechanical support to the metal facing zones, (ii) increases the surface area of ​​the metal non-adjacent zones, thereby allowing for rapid transport of heat and vapor from the mold zones during transient thermal shock and short drying periods of the mold zones, and (iii) allows for rapid construction of the mold zones, thereby reducing overall build time and increasing production throughput. [Brief explanation of the drawings]

[0051] For a better understanding of the subject matter disclosed herein, and to illustrate how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: [Figure 1]Figure 1A is a block diagram illustrating a schematic configuration and operation of a laminated mold manufacturing system according to an embodiment of the present disclosure, and Figure 1B is a diagram illustrating a more specific configuration and operation of the mold manufacturing system according to an embodiment of the present disclosure. [Figure 2] Figure 2A is a flow diagram illustrating a method for building an additive mold according to an embodiment of the present disclosure, which is carried out simultaneously with the construction of a laminated metal object. Figures 2B-2F illustrate the mechanistic principles utilized in the disclosed additive mold manufacturing technique: Figure 2B shows typical stress-strain curves for ceramics, metals, and polymers; Figure 2C shows the stress-strain curve for a brittle material under tensile and compressive stresses; Figure 2D shows the stress-strain curve for a ceramic material that is more resistant to compressive stress than to tensile stress; Figure 2E is a schematic diagram illustrating the pressure exerted by molten metal on the mold wall and the resulting stresses; Figure 2F shows the stress-strain curves for tough, tough, and ductile materials, respectively; and Figure 2G shows the steps of a typical heat treatment of a ceramic-based mold material, including a green stage, debinding, and sintering. [Figure 3] Figure 3A illustrates a timeline of a mold manufacturing process known in the art, and Figure 3B illustrates a timeline of a mold manufacturing process according to the disclosed technique. [Figure 4]4A-4F show examples of mold regions fabricated in accordance with the techniques of the present disclosure, where FIG. 4A illustrates a mold region including a metal-facing zone (defining a cavity that forms a metal object region) and a metal non-adjacent zone surrounding the metal-facing zone, FIG. 4B illustrates a mold region in which the metal-facing zone and the metal non-adjacent zone have a double-contour configuration, FIG. 4C illustrates a mold region including a metal-facing zone and a metal non-adjacent zone, where the metal-facing zone includes two sub-zones, and FIGS. 4D and 4E show partially fabricated mold regions, each including a metal-facing zone and a metal non-adjacent zone, and a spaced apart enclosure around the metal non-adjacent zone with a void (which is filled with a filler material), where the metal non-adjacent zone or its sub-zones are formed in a cross or curl pattern. FIG. 4D shows a mold region having a single metal opposing zone, FIG. 4E shows a mold region including two metal opposing zones defining a cavity therebetween for a ring-shaped metal object region and two respective metal non-adjacent zones, one of which is a mold insert, and FIG. 4F shows a fully fabricated mold region configured generally similarly to FIG. 4D. [Figure 5] FIG. 5 shows some examples of various configurations of metal non-adjacent zones or sub-zones thereof (directly bonded to metal facing zones) formed in a crisscross or curl pattern. [Figure 6] Figure 6 shows a portion of a manufactured part consisting of a stack of manufacturing layers and illustrates that, depending on the surface relief of the metal object area being manufactured, the mold area of ​​the current manufacturing layer may not be perfectly aligned with the mold area of ​​the preceding layer, but rather may be located on at least a portion of the mold area of ​​the preceding manufacturing layer or on at least a portion of the object area of ​​the preceding manufacturing layer. DETAILED DESCRIPTION OF THE INVENTION

[0052] 1A, a block diagram is shown that schematically illustrates a mold manufacturing system 102 that is constructed and operative in accordance with an embodiment of the disclosed technique. The mold manufacturing system 102 is generally part of an additive metal casting system 100 that also includes an object manufacturing system / apparatus 126.

[0053] It should be understood that the construction and operation of object manufacturing apparatus 126 do not form part of this disclosure and, therefore, will not be described in detail herein, except to note the following: the operation of mold manufacturing system 102 to form the mold layer-by-layer is appropriately synchronized with the operating cycle of object manufacturing apparatus 126 (via communication with object manufacturing control system 124) to additively model manufacturing layers, each comprising metal within object areas 130 surrounded by mold areas 132. It should be understood that the object design defines the number of object areas surrounded by each mold area.

[0054] The object manufacturing apparatus is preferably configured and operable as described in the above-mentioned US20200206810 and / or commonly assigned U.S. patent application serial numbers 17 / 744,686 and 17 / 748,069, which are incorporated by reference herein for non-limiting examples of object manufacturing apparatus and associated object manufacturing control systems 124.

[0055] Mold manufacturing system 102 includes, among other things, a control system 104 that controls the operation of one or more mold providing devices 112, and a surface treatment system 114. Control system 104 is a computerized system that includes, among other things, a mold deposition controller 106, a mold layer finish controller 108, and a mold process synchronization circuit 110, the latter in data communication with an object manufacturing control system 124.

[0056] The one or more mold providing devices 112 are controllably operable to deposit mold material to form a mold area 132 that defines an object area 130 in the fabrication layer. The object area 130 is configured to receive molten metal deposited by the molten metal deposition device 128.

[0057] The mold provider 112 is configured and operable by the mold deposition controller 106 according to a predetermined build schedule to sequentially form multiple fabrication layers. In some embodiments, the mold provider 112 is configured to build each mold region 132 of each fabrication layer by performing depositions of variable compositions of mold material in different zones of the mold region (metal-facing zones and metal-non-adjacent zones) before depositing molten metal to form the object region 130 of the current fabrication layer. In some embodiments, the mold provider 112 builds the mold regions by performing one or more iterative mold depositions.

[0058] Each mold provider 112 may include one or more mold material reservoirs 116 connected via supply lines to one or more mobile mold depositors 118. Each mold depositor 118 is driven (by a suitable drive mechanism, not specifically shown) to move in a horizontal plane along a predetermined trajectory according to a production plan.

[0059] The mold depositor 118 can be of any suitable known configuration, does not form part of this disclosure, and will not be specifically described except as noted below. Such mold depositors are typically in the form of one or more extruder / printheads, each in fluid communication with one or more mold material reservoirs 116. Although not specifically shown, it should be noted that because mold material is typically a relatively viscous material, the mold providing apparatus 112 (e.g., the traveling mold depositor 118 and / or supply lines) may include agitators and / or tubing and / or tubing loops configured to provide continuous circulation of mold material not currently involved in the deposition process.

[0060] According to some embodiments of the present disclosure, mold materials include paste, powder, granular, and slurry mold materials, as well as mold materials mixed with binders, release agents, activators, UV-absorbing particles, crosslinking agents, heat-absorbing particles, or other additives to facilitate mold fabrication and use. According to embodiments of the present disclosure, mold materials include, but are not limited to, ceramics (e.g., zirconia, alumina, magnesia, etc.), sand, clay, metal powder, and any combination thereof.

[0061] In the following description, the mold material may be referred to as a ceramic-based material, but it should be understood that the principles of the present disclosure are not limited to this particular example, nor are they limited to any type of mold material. The properties of the mold material used are considered along with the properties and build design of the metal material to design the preferred placement of different zones of the mold area and the preferred placement of metal non-adjacent zones.

[0062] In some embodiments, two material reservoirs 116 may be used for the ceramic-based material. Using two reservoirs may be advantageous for time-efficient mold manufacturing processes if a larger reservoir, which may be located away from the manufacturing area, is configured to provide adequate pre-wetting of a large amount of ceramic-based material at a constant mixture, which may take time. This larger reservoir may be in fluid communication (by a pipe) with a smaller reservoir, which may be kept at a constant mixture, and which may be in communication with the mold depositor 118 and, in some cases, move with the mold depositor 118 on the manufacturing table to form the predetermined mold area 132.

[0063] The mold manufacturing system 102 may further include a surface treatment system 114. The surface treatment system is configured and operable to apply one or more surface treatments to the mold material in the mold region and may include one or more heaters 120, mold treatment equipment 121, and a post-deposition surface finishing system 122.

[0064] The heater 120 is operable to subject the mold material in the mold region to a temperature treatment to harden the mold material, and in some embodiments may be configurable to subject the mold region to a temperature treatment after each of one or more repetitive mold depositions.

[0065] In some embodiments, the heater 120 may be implemented as a common system that provides heating to one or more of the object manufacturing system 126 or portions thereof, a build table (not shown), and manufacturing chambers (not shown) that house the mold manufacturing system 102 and the object manufacturing system, respectively, at least during mold construction and object manufacturing.

[0066] As another example, in embodiments in which the mold material is in powder form, the mold processing device 121 may include a curing system to harden the mold using any known suitable technique, such as thermal curing, UV curing, gas curing, etc. Other mold processes suitable for use in creating the mold may include microwave irradiation, ultraviolet irradiation, arc jet, laser irradiation, ultrasonic vibration, vacuum drying, chemical treatment, exposure to an electromagnetic field, exposure to a gas atmosphere, and combinations thereof.

[0067] The post-deposition surface finishing system 122 may be configured to, for example, perform mechanical surface treatment of at least a portion of the mold region, or mechanical surface treatment of the surface of the mold region facing the object region, e.g., milling, grinding, and / or polishing.

[0068] It should be noted that post-mold deposition surface finishing is not limited to mechanical surface treatments: As will be described below with reference to FIG. 1B, any part of the mold area (i.e., not just the metal-facing walls of the metal-facing zone) can be subjected to several post-mold deposition surface treatments, such as curing with, for example, UV light, smoothing with, for example, laser-induced melting, etc.

[0069] 1B, a more specific illustration of an exemplary configuration and operation of the mold manufacturing system 102 described above, according to an embodiment of the present disclosure, is shown, depicting a cross-sectional view of a portion of an object / mold structure 205 formed by multiple successively fabricated / deposited fabrication layers 202-0 through 202-4.

[0070] Structure 205 contains within its mold structure (enclosed) a metal object 206 undergoing additive casting on a build table 210. The build table is configured to be placed in a temperature-controlled environment (e.g., a chamber, not shown here). Relative movement is provided between build table 210 and components of the manufacturing system used to produce the manufacturing layers (e.g., mold depositor 118 and metal deposition equipment, not shown here).

[0071] This relative movement is provided based on commands from control system 104 (or a control system 124 associated with the metal deposition process) and can be achieved in the left-right (x-direction 224), forward-backward (y-direction), and up-down (z-direction 220) directions, and in some cases can also be rotated clockwise and counterclockwise 222 relative to coordinate system 230. Typically, when casting large, cumbersome, or heavy objects, displacement of build table 210 may be limited to relative movement in the z-direction.

[0072] In some embodiments, the build table 210 is moved along the z-direction between fabrication layers to maintain a working distance between the material depositor and the surface of the work area. In some embodiments, the build table 210 is moved between building the mold area and fabricating the object area of ​​the current fabrication layer. In some embodiments, the XY relative motion can be achieved by keeping the build table 210 fixed and moving the mold depositor 118, heater 120, and mechanical surface finishing unit 122.

[0073] Additive casting of the disclosed technology proceeds according to a predetermined build schedule for the sequential formation of multiple fabrication layers (202-0 through 202-4). In the non-limiting example shown in FIG. 1B, fabrication layers 202-0 through 202-3 accomplish both mold fabrication and metal casting, while in the current fabrication layer (202-4), molten metal 212 is deposited in object region 208 after mold region 204-4 (defining object region 208) of the current fabrication layer is fabricated. Typically, one or more of the bottom fabrication layers (e.g., 202-0) are solely mold material that forms the underside of subsequent fabrication layers.

[0074] In this non-limiting example, layers 202-0 through 202-4 include mold regions 204-0 through 204-4, with the bottom layer 204-0 functioning as a base layer and successive fabrication layers (204-1, 204-2, 204-3, 204-4) including mold regions that define mold cavities that form object regions that receive molten metal. Mold regions 204-0 through 204-4 of layers 202-0 through 202-4 are shown with dotted lines representing the interfaces between them, indicating that the mold regions of the fabrication layers are fabricated in different fabrication cycles and are intimately bonded to one another.

[0075] As shown, the mold manufacturing system 102 includes a control system 104, a mold providing apparatus 112 including mold material reservoirs 116 and mold depositors 118 that receive mold material from these reservoirs 116, and additional mold manufacturing equipment such as a heater 120 and a mechanical surface finishing apparatus 122.

[0076] The primary operation of mold area fabrication is performed iteratively at one or more locations (a single location is shown in the example of FIG. 1B ) within the current fabrication layer by (sequentially) providing relative displacement between the mold provider 112 and the build table 210 and incrementally dispensing mold material to form mold areas (e.g., 204-4) under the control of the mold deposition controller 106. In some embodiments, post-deposition processing (e.g., mold layer hardening, internal surface processing, e.g., milling, grinding, polishing) is performed under the control of the mold layer finishing controller 108, as described above.

[0077] 1A and 1B, the casting system 100 also includes an object build system 126 that includes a molten metal depositor 128. Relative displacement can be provided between the molten metal depositor and the build table 210, for example, the molten metal depositor can be movable. The molten metal depositor 128 can include a crucible, a remote molten metal reservoir, a stock of wire or rod for melting, a powder for melting, or a combination thereof.

[0078] It should be noted that, although not specifically shown, the object manufacturing system 126 also includes a controller therefor (which may be part of or in operative communication with the control system 104 of the mold manufacturing system 102), and a surface treatment device including one or more movable heaters (which provide pre-heating and post-heating of the object area). Generally, in an additive casting process, the movable unit is actuated to move in the x-y plane and in the z direction, and has horizontal, vertical, and rotational degrees of freedom.

[0079] 2A, flow diagram 300 schematically illustrates an additive mold manufacturing method according to an embodiment of the present disclosure, providing mold regions configured as described above, i.e., including a configuration of metal-facing zones and metal-non-adjacent zones configured to have different mechanical properties such that the metal-facing zone has a higher compressibility (higher ability to absorb compressive stress energy) than at least one sub-zone of the metal-non-adjacent zone. This configuration is selected depending on the properties of the metal object to be created and the deposition of molten metal used to create such object.

[0080] The method includes iteratively fabricating a series of vertically stacked fabrication layers (i=0,...,N) based on a mold and object build plan 302 (step 304), until the final fabrication layer is completed to form an entire mold structure surrounding the metal object, after which the mold structure is removed (step 306).

[0081] The mold build plan 302 includes information / parameters necessary to enable the sequential formation of multiple manufacturing layers and, for each manufacturing layer, the formation of one or more iterative mold depositions in each mold area associated with the respective object area. Such mold depositions of mold areas (e.g., in iterations) may be performed entirely before depositing molten metal to form the respective object area of ​​the current manufacturing layer.

[0082] In particular, the mold build plan 302 includes geometric data indicating the geometry / shape of the metal-facing zones of the mold area 308, i.e., the contours of each metal-facing zone determined by the required finished surface of the metal object area, as well as parameters (geometric and material parameters) of the configuration of the metal-facing zones and metal non-adjacent zones, and the geometric layout of the mold area structure 312 (e.g., alignment of the mold area and object area of ​​adjacent manufacturing layers).

[0083] The mold build plan 302 also includes material-related data 310 indicating the properties of one or more materials used to form the mold (e.g., properties of various zones and subzones of the mold region of the fabrication layer). For example, increasing the toughness / compressibility of a mold region may be related to porosity. In this example, porosity is achieved by introducing (e.g., bubbling) a gas into the mold material in a zone or subzone of the mold region, thereby making it more porous and therefore tougher compared to adjacent zones or subzones of the mold region. Additionally or alternatively, porosity in the mold material may be achieved by treating selected portions of the mold region with chemicals. Applicable chemicals may be foaming agents (SDS - sodium dodecyl sulfate, calcium carbonate, etc.).

[0084] Additionally, mold build plan 302 includes data describing a mold deposition process for sequentially forming multiple manufacturing layers, including the number of mold deposition iterations to create the mold area for each manufacturing layer. Typically, the build plan also includes the rate and time 314 of mold material deposition.

[0085] The build plan may also include data indicating temperature parameters / conditions for one or more post-deposition treatments 316. The post-deposition treatments may be of the type aimed at hardening the mold (e.g., by heating), surface treatment, particularly of the interior surfaces of the mold area facing the object area (e.g., by milling, grinding and / or polishing).

[0086] Additionally, the build plan typically includes data 318 indicating temperature parameters / conditions for various steps (including mold deposition steps and post-deposition treatments), including, for example, temperatures of the material reservoir, deposition equipment, and build table during mold deposition, temperatures immediately after mold deposition, etc. Additionally, the build plan typically includes data 318 indicating temperature parameters and other conditions during various steps (including mold deposition steps and post-deposition treatments), including, for example, temperature, pressure, and environmental conditions (gas composition) of the material reservoir, deposition equipment, and build table during mold deposition, and the temperature immediately after mold deposition.

[0087] It should be noted that the mold deposition and metal deposition used to create the mold area and object area, respectively, are performed sequentially during the creation of each fabrication layer and have different process parameters and timing, and therefore the build plan includes or defines synchronization data 320 to properly synchronize the mold deposition procedures and metal deposition processes.

[0088] Typically, fabrication of a fabrication layer begins with fabrication of a base layer (i=0) on the build table 210 (e.g., mold fabrication layer 202-0 in FIG. 1B) (step 322). The fabrication phase 324 of each successive fabrication layer (i=1, ..., N) includes a mold area creation step 325, which begins with depositing mold areas of casting material while creating an arrangement of metal facing zones and metal non-adjacent zones according to a build plan for the current fabrication layer, which may include multiple deposition iterations (step 326), and sequentially applying post-deposition treatments (e.g., milling, polishing, hardening) to each deposited mold area (step 328). Molten metal is then deposited in a synchronized manner into each object area defined by the mold areas of the current fabrication layer (step 330).

[0089] It should be noted that in some embodiments, additional post-processing is used, including at least partial surface finishing of the mold area on which the fabrication layer has been deposited (step 328), which in some embodiments occurs before the mold area cures or solidifies, while in other embodiments, such surface finishing occurs after the mold area has cured.

[0090] In some embodiments, the height of the object area in the fabrication layer is in the range of 4-8 mm, and the height of the corresponding mold area in the fabrication layer is in the range of 6-10 mm. The molded region of the fabrication layer may be achieved in a single deposition, or in two, three, or more repeated depositions. For example, a 6 mm high fabrication layer may be achieved by two repeated mold depositions of a 3 mm high paste tube.

[0091] The appropriate selection of a mold material is generally made according to whether the different mechanical properties of different mold region zones are suitable for the application at hand (e.g., matching the compressibility of the mold material to the expected thermal expansion of the metal object material). Below is a qualitative description of the relevant mechanical properties:

[0092] Figures 2B through 2F provide support for the descriptions and associated terminology used herein, which underlie the principles of the disclosed technology. Figure 2B shows typical tensile / compressive stress-strain curves for three types of materials: ceramic (typically used to create molds), metal (used to create objects), and polymers that can be used as mold materials. Stress-strain curves visually display the deformation of a material under tensile, compressive, or torsional loads. The stress-strain curve of a ceramic material, whether under tensile or compressive stress, is nearly linear up to the yield point, after which it suddenly reaches the fracture point and fractures. While metals are ductile materials and exhibit plastic deformation (a flattened portion of the curve) before fracture, ceramics exhibit negligible plastic deformation under external load (there is almost no flattened portion in the stress-strain curve in Figure 2B). This property of ceramic materials is why they are defined as brittle (the opposite of ductile) materials. Figure 2C shows typical (qualitative) stress-strain curves for a brittle material under tensile and compressive stresses, clearly showing the opposite signs of strain under tensile / compressive stresses.

[0093] However, as a brittle material, ceramics have a compressive strength approximately 10 times greater than their tensile strength (strength is defined as the maximum stress in the appropriate tension / compression quadrant of the stress-strain diagram). The difference between tensile and compressive strength is due in part to the brittle nature of ceramics. When subjected to tensile loads, ceramics, unlike metals, cannot deform to relieve stress. The low tensile strength of ceramics (and glasses as well) is due to the fact that pre-existing defects (internal or surface cracks) act as stress concentration points, causing the material to tend to fracture / crack with little or no detectable prior plastic deformation. However, in compression, defects in ceramic materials do not induce stress concentrations or crack propagation as they do in tension. For example, when subjected to compressive loads, transverse cracks in ceramic materials tend to close and become unable to propagate.

[0094] In some embodiments, ceramic or ceramic-based materials are used as mold materials in metal casting due to their very high elastic modulus (Young's modulus) as well as their ability to withstand the high temperatures of molten metal.

[0095] Figure 2D shows an example of a stress-strain curve for a ceramic material that is stronger (more tough) under compressive stress than under tensile stress, as determined by its high compressibility under compressive stress. The ability of a material to deform under compression (plastic or elastic) is called compressibility. The ability of a material to absorb energy before failure is called toughness. Ductility is a measure of how much a material can deform plastically before failure, but it is important to note that ductility does not necessarily mean that a material is tough. The key to toughness is a good combination of strength (tension / compression) and deformation capacity (under compression and / or tension). A material with high strength (tension / compression) and high ductility will be tougher than a material with low strength and high ductility. Young's modulus represents the stiffness of a material. Stiffer materials have higher elastic moduli. If a material behaves essentially elastically until failure, the material is said to exhibit brittle fracture. Young's modulus is independent of defects (microcracks) in the material. Toughness, on the other hand, is a measure of a material's resistance to crack propagation. Unlike mechanical strength, toughness is independent of defects (microcracks) that cause failure, but is dependent on the material's microstructure.

[0096] To be tough, a material must have both strength and ductility. Therefore, one way to measure toughness is to calculate the area under the stress-strain curve from a tensile test. This value (area under the stress-strain curve) is simply called "material toughness" and has units of energy per volume. The toughness of a material means that the material absorbs energy slowly. Brittle materials tend to have low toughness because they can absorb large amounts of energy through elastic and plastic deformation. Therefore, when a brittle material is subjected to stress, it undergoes little elastic deformation and fractures without significant plastic deformation. Brittle materials, even if they have high strength, absorb relatively little energy before breaking.

[0097] A mold fabricated in accordance with the principles of the technology of the present disclosure (i.e., including a metal-facing zone and a metal-nonadjacent zone) is particularly suitable for use in additive metal casting that involves not only repeating the deposition of molten metal multiple times but also heating a portion of the solidified metal bulk multiple times before depositing the next metal layer. As shown in FIG. 2E, in such a process, the previously deposited molten metal inevitably expands during heating, thereby applying an internal pressure P to the mold region in addition to the pressure applied by a portion of the molten metal during the casting of subsequent production layers. In addition to the axial stresses (tensile stress and compressive stress) generated inside the ceramic mold by the molten metal, it is important to note that circumferential tensile stress is generated along the outer periphery of the mold inside the ceramic mold.

[0098] FIG. 2F shows the strain-stress curves of mold material types MMT1, MMT2, and MMT3, which have different mechanical properties (especially tensile strength TS, toughness TH, and compressibility C). The first type of mold material MMT1 is the strongest / rigid among the three, characterized by the highest tensile strength TS1 and the highest elastic modulus. This material has the lowest toughness TH1 and almost zero (minimal) compressibility C1, as can be judged from the lower strain values obtained under compressive stress compared to the material types of MMT2 and MMT3. The second type of mold material MMT2 has a lower tensile strength TS2 (TS2 < TS1) compared to MMT1 and a higher toughness TH2 (TH2 > TH 1) . The material MMT2 has a significantly higher compressibility C2 (C2 >> C1) compared to the material MMT1, and particularly has both a reversibly elastic region (the linear part of the strain-stress curve) and an almost irreversibly plastic region for compressibility C2. The third mold material MMT3 has approximately the same toughness TH3 (TH3 ≈ TH2) as MMT2 because the regions under the strain-stress curves are approximately the same. However, judging from the non-linear shape of the strain-stress curve, the compressibility C3 of the material MMT3 is almost irreversible.

[0099] Molds constructed in accordance with embodiments of the present disclosure are manufactured by additive deposition of mold material (e.g., ceramic-based material) that is configured to withstand the pressures imposed during metal casting and maintain mold integrity by significantly reducing the number and size of cracks that form in the mold under the pressure of the molten metal.

[0100] The inventors have recognized that a ceramic material suitable for mold manufacturing is one that is highly tough, i.e., possesses an optimal combination of strength and flexibility / ductility. However, this material must also be able to withstand very high temperatures. The additive casting technique of the present disclosure uses a repetitive cycle to produce successive layers of fabrication, each of which involves metal deposition in the mold region and the object region. Such a process involves repeated transient temperature changes, as described in more detail below.

[0101] FIG. 2G illustrates steps in the heat treatment of ceramic-based mold materials according to processes known in the art. Initially, the deposited mold material contains ceramic particles 252, solvent 254, and monomer particles of binder 256. Once extruded, the mold material may undergo various curing stages, indicated by arrows 258, 262, 266, and 268 in FIG. 2G. Curing of the mold material may be active (e.g., heating) or passive (e.g., drying the material). The first curing stage 258 involves partial drying of the mold material, resulting in partial evaporation of solvent 254 and partial polymerization of the binder, which shrinks the mold material and produces polymer dimers 260. The second curing stage 262 involves complete evaporation of solvent 254 and complete polymerization of binder 256, forming polymer network 264. Up until this stage, the mold material is known to be in a "green body" state. Further hardening of the green body, typically during active heating of the mold material, results in debonding, i.e., removal (e.g., burnout) of organic components 266. In the final hardening stage 268, the mold material is sintered, resulting in fusion of the ceramic particles 252 to form a compact, strong mold.

[0102] Because the evaporation or decomposition behavior of organic components varies with temperature, a tailored temperature profile must be used to obtain crack-free ceramics after thermal post-treatment. Sintered ceramic materials are sensitive to sudden temperature changes, which can lead to loss of stability before the casting of the metal object is complete. Generally, the sintering process is lengthy, requiring both heat and time.

[0103] The inventors have discovered that using ceramics in a green state (i.e., before debinding and sintering) is beneficial to the casting process because it can better absorb the strain energy caused by metal expansion during the various stages of casting. However, even during additive metal casting as used in this disclosure (i.e., using green mold material to continuously create mold regions and associated object regions without a sintering step), the mold regions are temporarily exposed to very high temperatures (e.g., 1000-1500°C for gray cast iron), as described in more detail below.

[0104] Figure 3A illustrates the timeline of the additive mold manufacturing process known in the art for forming an overall mold. Typically, in the mold printing process, the ceramic material is made into a paste in a dispenser and maintained at a constant temperature, typically between 16 and 17 °C (Stage 10). It is then printed / deposited onto a surface using an injector / syringe (Stage 12), with both the ceramic and the surface maintained at the same constant temperature, typically between 16 and 17 °C (Stage 13). Special care is taken to ensure steady-state (thermodynamic) conditions so that all physical parameters of the ceramic material (density, texture, viscosity, etc.) are stable during the deposition process. In the next step, the mold is dried at the boiling temperature of the solvent (Stage 14) and sintered at a temperature above the melting temperature of the metal (Stage 16). Once the mold is complete, it is transported to the casting location. Metal is deposited into the mold (Stage 18), and the mold is allowed to cool. The mold is then removed. The lengthy mold preparation process significantly slows down the overall production speed of the casting process.

[0105] A timeline for additive metal casting according to the principles of the present disclosure, specifically the process for mold construction, is illustrated in FIG. 3B. Additive manufacturing of a metal object involves building successive manufacturing layers, each of which involves the formation of one or more mold regions that define one or more respective metal object regions (depending on the configuration of the object being manufactured) prior to depositing molten metal in the object region or regions. The build table, on which both the mold and metal are deposited, is maintained at a relatively high temperature (400-600°C). Metal processing may involve further heating of the metal in the object region. In this way, the successively deposited object regions of cast metal are metallurgically bonded and seamlessly integrated into a single, metallurgically homogeneous object.

[0106] Note that prior to deposition of the mold material (e.g., the first layer in Figure 3B ), the ceramic paste of the mold material is kept at ambient temperature (e.g., 16–17 °C) in the dispenser (stage 10), but as soon as the paste is extruded from the injection nozzle / syringe, it is deposited onto the build table or a previously fabricated fabrication layer (stage 12), and is subjected to thermal shock when it comes into contact with surfaces (previously injected mold material or previously deposited metal) that are kept at or above ambient temperature.

[0107] For example, to shorten the heating and cooling cycles of the fabrication environment, the build table and the fabrication environment containing the previously deposited mold structures or objects may be maintained at predetermined temperatures (e.g., 200–300 °C or 400–600 °C). When defining the desired temperature of the mold structures, the solvent boiling temperature, polymerization rate, thermal conductivity, and mass transfer processes of the mold material must be considered. Temperature changes in the mold material can significantly alter the material properties (e.g., rheology, texture) of the extruded ceramic-based material. For example, rapid heating can cause solvent release, swelling, and crust formation on the surface of the extruded ceramic, which can further adversely affect adhesion with subsequent mold layers.

[0108] In some embodiments, the solvent used in the ceramic-based mold material is water, which evaporates during stage 12 of FIG. 3B. Due to the surface temperature exceeding 100°C, the deposited mold material undergoes a second thermal shock (stage 14), during which it undergoes further hardening, including binder polymerization, as described above with reference to FIG. 2G. Allowing the mold material to dry partially (step 262 of FIG. 2G) is necessary for surface preparation of the mold material (e.g., milling the mold area). Milling (and / or other surface preparation) is necessary to shape the mold surface that contacts the metal, depending on the shape of the metal object being cast. Due to its viscosity, the deposited mold material takes on a tubular shape. As the mold material accumulates, sagging occurs. If the sagging is not removed, the metal will undesirably conform to the shape of the sagging. Furthermore, surface preparation is necessary to compensate for imprecision in dispensing. As previously described, sintering of the mold area is not required (stage 16 of FIG. 3A). After surface preparation of the metal facing walls, the mold area of ​​the current production layer is ready for metal deposition (18).

[0109] The mold area is subjected to a third thermal shock during metal deposition (stage 18) when the temperature temporarily rises to the melting temperature of the metal (approximately 1200-1300°C for gray cast iron, and even higher for other metals). After metal deposition of the first production layer, the mold area and metal object are cooled to a predetermined temperature (e.g., approximately 400-600°C), and additive manufacturing proceeds with the second production layer. In Figure 3B, the temperatures of the first, second, and nth production layers are shown by the solid, dashed, and dash-dot lines, respectively.

[0110] As shown in Figure 3B, while the second layer of mold material (dashed line) undergoes the first cycle of thermal shock, the mold region of the first fabrication layer (solid line) undergoes additional thermal shocks, continuing until the nth fabrication layer (dashed line), after which casting ends and all mold and metal object regions are cooled. From the perspective of thermodynamic conditions, note that this transient mode of mold stacking results in the continuous extraction of solvent from the mold material and continuous drying, causing continuous texture changes.

[0111] Mold materials typically contain one or more binders that are responsible for the cohesion of ceramic particles within the mold material. During additive casting according to the principles of the present disclosure, mold deposition is performed layer by layer, with the current mold layer being deposited on top of the previous layer (including the mold region and metal object region) to form a cohesive mold structure with the previous layer. Therefore, the presence of a binder in the mold material of the mold region enhances adhesion between the mold material of the current layer and the mold region of the previous layer. The selection of mold material is also important; if the mold material of the current layer is heated to an excessively high temperature immediately after deposition, not only will it impair adhesion to the previous mold layer, but it will also impair the integrity of the mold region during subsequent milling. The use of inorganic binders that polymerize at relatively high temperatures is advantageous. However, horizontal cracks in the metal-facing zone of the mold region, which can lead to metal intrusion between the mold layers, may not be fully addressed even with the appropriate material and temperature selection. The use of a metal non-adjacent zone adjacent to the metal facing zone can withstand compressive / tensile stresses that arise on the inside of the metal facing wall due to metal expansion.

[0112] Another aspect of providing efficient drying of the mold region relates to the uneven drying of the mold material. Drying of ceramic green bodies involves vapor diffusion within the porous ceramic body. This transport mechanism is sensitive to various parameters, particularly the shape and size of the wet body. While solvent vapor from the mold surface is easily evacuated from the mold region, solvent vapor deeper than the thickness of the mold material becomes trapped and, if it cannot evacuate from the mold quickly enough, forms a crust on the mold surface during the drying stage. This crust further hinders efficient evacuation of the solvent vapor from the mold, causing significant problems during the subsequent milling stage of the mold (the mill may chip off mold pieces). Therefore, according to the techniques of the present disclosure, the metal-free zone is preferably configured in a crisscross or curl pattern, which provides an efficient exit for solvent vapor from the mold region material during the drying stage.

[0113] The inventors have found that using a highly compressible mold material composition (e.g., MMT2 or MMT3 type material) in a portion of a mold region zone or subzone can be advantageous in enhancing the overall mold stability. A relatively compressible mold material can be an elastically compressible material. The shape of an elastically compressible material (in its unsintered state) is partially or completely restored after the applied stress is removed. In other words, an elastically compressible material allows for substantially reversible deformation when released from compressive stress. However, compressible material is a general term and can also refer to materials that exhibit irreversible deformation under compressive stress. Examples of highly compressible materials include compressible sand, ceramic-based materials, compressible ceramic-based materials, porous ceramics, sprayed ceramics, spheres, negative thermal expansion materials, reversibly compressible plastics, nanostructures, and layered materials.

[0114] For ease of explanation, the different mechanical properties of different mold zones will be described with reference to different materials. It should be noted that different mechanical properties of various mold zones can be achieved, for example, by using a single substrate applied in different ways to construct the different mold zones. Porous ceramics are an example of a material whose different structure (pore size distribution, pore location distribution, etc.) results in different mechanical properties. The pores are filled with a gas, such as air, and the material can be considered generally brittle (as opposed to ductile). When pressure is applied, the pores within the ceramic material are compressed by the applied stress and can eventually crack at the limit of the high stresses encountered during metal deposition. However, porous ceramics exhibit limited yield strength (more so than most non-porous ceramics) and can adequately absorb the energy generated by compressive stresses, albeit to a limited extent.

[0115] The following are non-limiting examples of mold region configurations, all constructed in accordance with the techniques of the present disclosure, having a metal-facing zone and a metal non-adjacent zone surrounding the metal-facing zone, and in some embodiments also including an enclosure region. For ease of understanding, the same reference numbers are used to identify components / elements that are common to all examples.

[0116] 4A , an exemplary mold region 132 is shown according to some embodiments of the present disclosure. The mold region 132 includes a metal-facing zone Z1 configured to define a cavity that forms the metal object region 130, and a metal non-adjacent zone Z2 surrounding the metal-facing zone Z1. The metal-facing zone Z1 is formed of a ceramic-based material, such as an MMT1-type material. Generally, according to the present disclosure, the metal-facing zone and the metal non-adjacent zone of the mold region are distinct zones that differ from one another in material composition and / or mold deposition process parameters.

[0117] Thus, in some embodiments, zones Z1 and Z2 of mold region 132 are made from different materials. For example, metal-facing zone Z1 may be a ceramic-based material (e.g., dispensed as a ceramic paste tube), while metal-non-adjacent zone Z2 may be made from sand to provide mechanical support to metal-facing zone Z1. In another example, zones Z1 and Z2 of mold region 132 may be made from two ceramic-based materials having different properties (e.g., different tensile / compressive strengths and / or porosity and / or viscosity).

[0118] In some embodiments, zones Z1 and Z2 of mold region 132 may be made from the same mold material (i.e., ceramic-based material), but applied in separate deposition operations and under different deposition parameters. For example, metal-facing zone Z1 may undergo metal-facing surface processing with a contour / tube shape that defines the shape of the metal object, while metal non-adjacent zone Z2 may be deposited as a second contour surrounding the metal-facing contour (a "dual tube" or "dual contour" configuration).

[0119] In some embodiments, the metal-facing zone Z1 has a contoured / tubular shape that defines the shape of the metal object, while the metal non-adjacent zone Z2 may have a cross or curl pattern (a "cross" configuration) depending on the number of material deposition iterations required for a particular mold region 132.

[0120] As already mentioned above (see FIG. 3B), the additive deposition of molten metal in the object area causes cyclic thermal shocks to the mold material of the previous and current production layers. Therefore, the at least one mold providing device (112 in FIGS. 1 and 2) is configured and operable to deposit mold material to form a cross pattern, for example to reduce the material density in the metal non-adjacent zone Z2, thereby enabling the mold area to withstand said cyclic thermal shocks. 4B, an exemplary mold region 132 according to some embodiments of the present disclosure is shown, which includes a metal opposing zone Z1 and a metal non-adjacent zone Z2 applied in separate deposition operations to form two contour / tube shapes. In this embodiment, the same mold material as well as the same mold depositor (118 in FIGS. 1 and 2) can be used.

[0121] In some other embodiments, metal-facing zone Z1 and metal non-adjacent zone Z2 may be made of the same material but may undergo distinct surface treatment operations, e.g., only metal-facing zone Z1 undergoes a surface treatment. Additionally, mold region 132 may be configured such that its non-metal-facing surface 150 at least partially adheres metal-facing zone Z1 to metal non-adjacent zone Z2.

[0122] Referring to FIG. 4C , an exemplary mold region 132 according to some embodiments of the present disclosure is shown. The mold region includes a metal-facing zone Z1 and a metal non-adjacent zone Z2. In this embodiment, the metal-facing zone Z1 includes a first subzone region SZ1.1 that is directly connected to the object region 130 by its metal-facing surface 160 and a second subzone SZ1.2 that is opposite and surrounds the first subzone SZ1.1. The first subzone SZ1.1 can be configured as an inner wall made of a refractory ceramic-based material that functions as a metal-facing insulating wall for the second subzone SZ1.2. In some embodiments, the second subzone SZ1.2 of the metal-facing zone Z1 is made of a plastic material.

[0123] In some embodiments, the first metal-adjacent subzone is relatively narrower than the outer, relatively wider subzone, by at least a factor of four, such that the mechanical properties (e.g., compressibility, toughness) of the metal-facing zone formed by the relatively narrow metal-adjacent subzone and the relatively wider outer subzone provide the different mechanical properties of the metal-facing zone compared to the non-metal-adjacent zone. For example, the second outer subzone of the metal-facing zone may be constructed of a compressible ceramic-based material, and the first narrow subzone of the metal-facing zone may be constructed as a coating on the metal-facing side of the second outer subzone and may be constructed of a refractory ceramic-based material suitable for the molten metal.

[0124] In the above example, mold region 132 includes a metal-facing zone Z1 made of a ceramic-based mold material, defining a molding contour along its inner surface, which defines each metal object region 130. The porosity of the ceramic-based mold material of the metal-facing zone is configured to efficiently release solvent during the thermal shock described above. Importantly, the pores of the mold material are preferably kept smaller than 60 μm to prevent molten metal from penetrating the mold material during molten metal deposition. The inventors have shown that the surface tension of the molten metal (e.g., iron) is sufficiently high that this pore restriction is sufficient to prevent metal from rupturing / leaking from the mold region.

[0125] Referring to FIG. 4D , an exemplary mold region 400 according to some embodiments of the present disclosure is shown. The illustrated mold region 400 is actually partially fabricated (i.e., an intermediate stage of mold region fabrication). More specifically, the mold region 400 includes a metal-facing zone Z1 and a metal-nonadjacent zone Z2. The metal-facing zone Z1 is in the shape of a paste tube, the apex of which is shown in solid lines. The metal-nonadjacent zone Z2 is comprised of a support subzone SZ2, dispensed in a curled pattern as described above (the apex of the tube-shaped curled pattern is shown in solid lines). The support subzones SZ2.1 of the metal-facing zone Z1 and the metal-nonadjacent zone Z2 are surrounded by a surrounding subzone SZ2.3 of the metal-nonadjacent zone Z2, which is separated from the support subzone SZ2.1 by a space SZ2.2 into which a filler material (e.g., a tensile filler material or a compressible filler material—either mold material MMT2, MMT3, or other types) is filled.

[0126] The mold area 400 in FIG. 4D is shown at an intermediate build stage, i.e., after ceramic paste deposition, creation of the metal-facing zone Z1, the support subzone SZ2.1 and the surrounding subzone SZ2.3 of the metal non-adjacent zone Z2, but before filling the space SZ2.2 with filler material, before surface treatment of the metal-facing zone Z1, and before depositing molten metal in the object area 130.

[0127] The support subzone SZ2.1 may be made of the same mold material as the metal-facing zone Z1, or it may be made of a different mold material. This support material is selected to provide mechanical support to the metal-facing zone Z1. The spaced crisscross (or curl) pattern increases the surface area, thereby allowing rapid transport of heat and vapor from the mold material of both the metal-facing zone Z1 and the non-metal-adjacent support subzone SZ2.1 during cyclic thermal shocks of the mold area. The vapor can come from evaporation of the mold solvent (e.g., water) or from organic / inorganic binder residues that are continuously released as a result of repeated mold drying and metal placement over multiple production layers. As previously mentioned, efficient vapor transport is important to prevent swelling of the mold area and the formation of crusts on the mold area surface.

[0128] Referring to Figure 4E, another exemplary mold area 402 is shown according to some embodiments of the present disclosure. Similar to the example of Figure 4D, the example of Figure 4E shows an intermediate stage of mold area fabrication.

[0129] The mold area 402 comprises metal opposing zones Z1, Z1', a metal non-adjacent zone SZ2.3 including support sub-zones SZ2.1, SZ2.1', and a surrounding sub-zone SZ2.3 separated from the other sub-zones by a space SZ2.2 which is filled with ceramic molding material (not shown) or other filler (e.g., sand) (not shown) to complete the mold area 132.

[0130] 4E, mold region 402 is configured to define a ring-shaped cavity for ring-shaped object region 130. Mold region 402 thus includes two metal-facing zones Z1, Z1′ that define opposing surfaces of ring-shaped cavity 130, and two corresponding metal-non-adjacent zones (zone Z2′ in the form of a mold insert in the center of the ring, and zone Z2 around metal-facing zone Z1).

[0131] The metal non-adjacent zones Z2, Z2' have a crisscross pattern (or curl pattern) that supports the metal facing zones Z1, Z1'.

[0132] The metal non-adjacent zones Z2, Z2' are formed by applying the tube-shaped paste in a curled pattern in a predetermined direction. The crest line of the paste tube is shown in FIG. 4E by a solid line. In some embodiments, a cross pattern is achieved by depositing the mold paste in a curled pattern such that the direction of the curl pattern in one deposition iteration intersects the direction of the curl pattern in a subsequent mold deposition iteration. This is indicated in FIG. 4E by the marking CC, which represents several curls in a cross pattern formed in a previously deposited mold area. This indicates the interleaving of curls. This allows for air gaps to be created between mold tube sections in the same deposition iteration and between mold tube sections in successive deposition iterations. The cross pattern can be created within a fabrication layer or stack of fabrication layers, and air gaps can be distributed along the support structure to improve evaporation and drying of the mold material components.

[0133] As discussed above, a spaced crisscross pattern (typically produced with multiple iterations of material deposition) or curl pattern (discontinuities in mold material) significantly reduces the deposition time of a mold region compared to a non-adjacent zone of metal completely filled with mold material (continuity in mold material). This time savings is important in additive manufacturing according to the present disclosure, where each manufacturing layer of multiple manufacturing layers provides a mold region defining one or more respective object regions and is configured to receive molten metal deposited in each of the one or more object regions.

[0134] FIG. 4F illustrates the complete mold area 132 in the general configuration of FIG. 4D.

[0135] More specifically, mold region 132 includes metal-facing zone Z1, metal-nonadjacent zone Z2 surrounding metal-facing zone Z1, and surrounding zone Z2. The structure formed by the metal-nonadjacent zone and surrounding zone can be described as multiple subzones of metal-nonadjacent zone Z2, including a first subzone SZ2.1 that abuts metal-facing zone Z1, a second subzone SZ2.2 that surrounds subzone SZ2.1 and is made of a relatively compressible mold material, and an outer subzone SZ2.3 that surrounds subzone SZ2.2.

[0136] It should be noted that, although not specifically shown, the first sub-zone SZ2.1 of the metal non-adjacent zone is preferably made in a cross pattern (or curl pattern) that provides support to the metal facing zone Z1.

[0137] FIG. 5 shows in a self-explanatory manner non-limiting examples of various configurations of zones / subzones around a metal facing zone. 6 shows a cross section of a mold structure including multiple mold regions 132 and object regions 130 in multiple manufacturing layers, with five manufacturing layers shown: (i-2), (i-1), i, (i+1), and (i+2). The mold regions in all manufacturing layers have metal-facing zones Z1 and metal-non-adjacent zones Z2. In this example, the metal object has a specific surface relief along its outer surface, resulting in different alignments between the mold regions in different manufacturing layers.

[0138] As illustrated for fabrication layers (i-2) and (i-1), each mold area 132 i-1 and 132 i-2 are perfectly aligned vertically and mold area 132 i-1 Metal facing zone Z1 i-1 and metallic non-adjacent zone Z2 i-1 Both of the mold area 132 of the preceding manufacturing layer (i-2) i-2 Each of the Z1 i-2 Zone and Z2 i-2In the manufacturing layer i, the surface shape of the object area changes, correspondingly changing the shape of the mold area 132. i Metal facing zone Z1 i The shape of the metal facing zone Z1 has changed. i The mold material of the preceding fabrication layer (i-1) is deposited on / aligned with the deposited metal (part of the object area) of the preceding fabrication layer (i-1) as dictated by the narrowing profile of the metal object in the build plan. In particular, the metal deposition of fabrication layer (i+2) is performed in part on the mold material deposited during the build of the mold area of ​​layer (i+1). Thus, in fabrication layer i, the mold area 132 i is the so-called "mold over metal" portion, and the object area 130 of fabrication layer (i+2) i+2 Part of this is the so-called "metal overmolded" part.

[0139] As noted above, the configuration of a mold region and the relative accommodation of mold regions in adjacent fabrication layers are dictated by the mold structure and the configuration of the object being fabricated simultaneously. For ease of illustration, mold regions are illustrated as two-zone structures with simple designs, such as circular or annular cross sections. In such illustrations, the metal-facing zone faces the metal in the same fabrication layer, as shown, for example, in Figures 4A-4F. However, as is evident from Figure 6, in some production scenarios, the metal-facing zone in fabrication layer i may face the metal in the next fabrication layer (i+1) ("metal-over-mold" manufacturing scenario).

[0140] Thus, the surface treatment applied to the metal facing zone may be applied to the inner walls of the cavity formed in the mold region of fabrication layer i. The surface treatment may also be applied to the top surface of the mold region, which defines the cavity that forms the metal object region to be deposited in the subsequent fabrication layer i+1.

[0141] In other production scenarios, the metal facing zone of production layer i may face metal present in the previous production layer (production layer i-1) ("mold over metal" production scenario). The temperature of the metal area of ​​production layer i-1 may be higher than the temperature of the mold area part of production layer i-1.

[0142] As a result, different parts of the mold area of ​​the fabrication layer I may experience different temperatures during deposition.

[0143] The use of two (or more) zones of mold regions that differ from one another in at least one of material composition and mold deposition process parameters has been described primarily with reference to different mechanical properties of the different mold region zones. Implementation of two (or more) zones of different mechanical properties has been illustrated with respect to improving stress absorption of the mold structure.

[0144] The invention is not limited to the illustrated embodiments, and other embodiments are possible within the scope of this disclosure.

[0145] The metal non-adjacent zone (e.g., the support subzone SZ2.1 shown in Figure 4D) can be deposited in various configurations and shapes, each resulting in different mechanical behavior. For example, crack deflection can be achieved by spiral printing, which changes the deposition direction depending on the tube radius. Making the metal non-adjacent zone wavy around the metal facing zone may improve longitudinal resistance to tension.

[0146] Additional material parameters may be used separately for the metal-facing and non-metal-adjacent zones, for example, different concentrations of inoculant in different mold zones may be used to control metal properties and potentially improve deposition throughput.

[0147] As used throughout this specification, the terms "metal" and "metallic" refer to any metal and / or metal alloy suitable for melting and casting, such as, for example, iron alloys, aluminum alloys, copper alloys, nickel alloys, magnesium alloys, etc.

[0148] References herein to a method should apply mutatis mutandis to a system capable of performing the method, and should also apply mutatis mutandis to a non-transitory computer-readable medium storing instructions that, once executed by a computer, result in the performance of the method. References herein to a system should also apply mutatis mutandis to a method that may be performed by the system, and should also apply mutatis mutandis to a non-transitory computer-readable medium storing instructions that may be executed by the system.

[0149] Terms such as "front," "rear," "top," "bottom," "upper," "lower," and the like, used in this specification and claims are used for descriptive purposes and are not necessarily used to describe permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances, and that the embodiments of the disclosure described herein are, for example, operable in orientations other than those shown or described herein.

[0150] The subject matter which is regarded as the technology of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. However, the technology of the present disclosure, both as to organization and method of operation, together with its objects, features, and advantages, may best be understood by reference to the detailed description taken in conjunction with the accompanying drawings.

[0151] It should be understood that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

[0152] In the claims, reference signs placed between parentheses shall not be construed as limiting the scope of the claim. The word "comprising" does not exclude the presence of elements, operations, or steps other than those recited in a claim. Furthermore, as used herein, the terms "a" and "an" are defined as one or more. Furthermore, the use of an introductory phrase such as "at least one" or "one or more" in a claim shall not be construed as implying that the introduction of another claim element with the indefinite article "a" or "an" limits a particular claim containing such introduced claim element to inventions containing only one such element, even if the same claim also contains an introductory phrase such as "at least one" or "one or more" and an indefinite article such as "a" or "an." The same applies to the use of definite articles. Unless otherwise noted, the terms "first" and "second" are used arbitrarily to distinguish between the elements they describe. Therefore, these terms are not necessarily intended to indicate a chronological or other priority of such elements. The mere fact that certain measures are recited in different claims does not indicate that a combination of these measures cannot be advantageously used.

[0153] While certain features of the technology of the present disclosure have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and variations as fall within the true spirit of the present disclosure.

Claims

1. 1. A mold manufacturing system for use in additive manufacturing of metal objects, the mold manufacturing system comprising: at least one mold provider controllably operable to form one or more mold regions defining one or more metal object regions within a manufacturing layer; and a control system configured to operate the at least one mold provider according to a predetermined build schedule; the at least one mold provider is controllably operable to create each of the one or more mold regions by sequentially forming, in accordance with the predetermined build plan, a metal-facing zone configured to define a cavity that forms a metal object region, and a metal non-adjacent zone surrounding the metal-facing zone; The system, wherein the metal-facing zone of the mold region is made of a ceramic-based material and is distinct from the metal-non-adjacent zone of the mold region in at least one of material composition and mold deposition process parameters.

2. The system of claim 1 , wherein the metallic non-adjacent zone of the mold region is configured to provide mechanical support to the metallic opposing zone of the mold region.

3. The system of claim 2 , wherein the non-metallic adjacent zone of the mold region comprises a ceramic-based material.

4. The system of claim 1 , wherein the at least one mold provider is controllably operable to form metal non-adjacent zones of the mold region having a cross-shaped pattern.

5. 5. The system of claim 4, wherein the at least one mold provider is controllably operable to form non-adjacent zones of metal in the mold region in multiple iterations of material deposition to form the cross pattern.

6. The system of claim 1 , wherein the at least one mold provider is controllably operable to form metal non-adjacent zones of the mold region having a curl pattern.

7. 7. The system of claim 4, wherein the at least one mold provider is controllably operable to form a metal non-adjacent zone of the mold region with an enlarged surface area and reduced material density to enable rapid transport of heat and vapor from the metal-facing zone and the metal non-adjacent zone of the mold region.

8. 8. The system of claim 4, wherein the at least one mold provider is controllably operable to form metal non-adjacent zones in the mold region configured to enable rapid formation of metal non-adjacent zones in the mold region.

9. 9. The system of claim 1, wherein the at least one mold providing device is configured and operable to vary one or more mold material deposition parameters and conditions to form a mold region prior to depositing molten metal to form each object region of a current manufacturing layer, the varying one or more mold material deposition parameters being selected to form the metal-facing zone and the metal-non-adjacent zone of the mold region having a reduced material density capable of undergoing cyclic thermal shocks associated with the additional deposition of molten metal in the object region.

10. The system of claim 9 , wherein the reduced material density of each of the metal-facing zone and the metal-non-adjacent zone is defined by the porosity of the mold material.

11. The system of claim 10 , wherein the reduced material density is defined by porosity having pore sizes not substantially exceeding 60 μm.

12. 12. The system of claim 3, wherein the ceramic-based material is in a green state.

13. 13. The system of claim 3, wherein the ceramic-based material is characterized by a viscosity of at least 40 Kcps.

14. 14. The system of claim 1, wherein the metal-facing zone and the metal-non-adjacent zone of the mold region comprise first and second different mold material compositions, respectively.

15. 15. The system of claim 1, wherein the at least one mold provider is configured and operable to provide, by its non-metal-facing side, a mold region configured such that the metal-facing zone is at least partially adhered to the metal non-adjacent zone.

16. 16. The system of claim 1, wherein the metal-facing zone includes a first subzone that is in direct contact with the object area by its metal-facing surface and a second subzone that is opposite the first subzone and surrounds the first subzone, the first subzone being configured as an inner wall made of a refractory compressible ceramic-based material that acts as a metal-facing thermal insulation wall for the second subzone.

17. 17. The system of claim 16, wherein a second subzone of the metal-facing zone is made of a plastic material.

18. 18. The system of claim 1, wherein the mold region further comprises an enclosure around the non-metallic zone, the enclosure being spaced from the non-metallic zone by a gap filled with a mold material composition having a higher compressibility than the non-metallic zone.

19. 20. The system of claim 18, wherein the highly compressible mold material composition comprises one or more of compressible sand, ceramic-based material, compressible ceramic-based material, porous ceramic, atomized ceramic, spheres, negative thermal expansion material, reversibly compressible plastic, nanostructures, and layered material.

20. 20. The system of claim 1, wherein the at least one mold provider is controllably operable according to the build plan, the build plan further indicating two or more of the geometric layout of one or more object areas in each manufacturing layer, the materials, geometric properties and arrangements of metal-facing zones and metal-non-adjacent zones of each mold area in each manufacturing layer, surface treatment parameters and surface treatment conditions of the mold areas, and synchronization data for mold area and object area formation in the manufacturing layer.

21. 21. The system of any one of claims 1 to 20, further comprising a surface treatment system configured and operable to apply one or more surface treatments to the mold area.

22. 22. The system of claim 21, wherein the surface treatment system is configured and operable to apply a temperature treatment to the mold region.

23. 23. The system of claim 21 or 22, wherein the surface treatment system is configured and operable to apply a temperature treatment to the mold area to impart material hardening to the mold area.

24. 24. The system of any one of claims 21 to 23, wherein the surface treatment system is configured and operable to perform a mechanical surface treatment of at least a portion of the mold area.

25. 25. The system of claim 24, wherein the surface treatment system is configured and operable to perform a mechanical surface treatment on a surface of a metal-facing zone that interfaces with the object region.

26. 26. The system of any one of claims 1 to 25, wherein the at least one mold deposition device comprises one or more mobile mold depositors, each moving in a horizontal plane according to a predetermined trajectory and associated with one or more mold material reservoirs.

27. 27. The system of claim 26, wherein the at least one mold deposition device comprises one or more extruders in fluid communication with the one or more traveling depositors, respectively.

28. 28. The system of claim 26 or 27, wherein each of the one or more traveling depositors includes at least one of an agitator, a tube, and a tube loop configured to provide continuous circulation of mold material not currently involved in a deposition process.

29. 29. The system of any one of claims 1 to 28, including a build table configured to be placed in a temperature controlled environment.

30. 30. The system of any one of claims 26 to 29, including a build table configured to be located in a temperature controlled environment, the system configured to provide relative displacement between the one or more traveling depositors and the build table.

31. 31. The system of claim 1, configured and operable to create a mold area of ​​a current manufacturing layer on at least a portion of a previous mold area of ​​a previous manufacturing layer or on at least a portion of a previous object area of ​​a previous manufacturing layer depending on the surface relief of the metal object area to be manufactured.

32. 1. A manufactured part comprising a stack of manufacturing layers, each manufacturing layer comprising one or more object regions of a metal object, each object region surrounded by a mold region, the mold region comprising a metal-facing zone and a metal-non-adjacent zone surrounding the metal-facing zone, wherein a surface of the metal object in the object region is physically bonded to a metal-facing surface of the metal-facing zone of the mold region, the metal-facing zone differing from the metal-non-adjacent zone of the mold region in at least one of material composition parameters and mold deposition process parameters.

33. 33. The manufactured part of claim 32, wherein the metallic non-adjacent zone is configured to provide mechanical support to the metallic facing zone.

34. 34. The manufactured part of claim 32 or 33, wherein the non-metallic adjacent zone comprises a ceramic-based material.

35. 35. The manufactured part of any one of claims 32 to 34, wherein the non-adjacent zones of metal are formed in a crisscross pattern.

36. 1. An additive casting system for additively casting a metal object by sequentially fabricating, on a movable build table, a plurality of fabrication layers, up to a top layer, having a mold region and an object region within a cavity defined by the mold region, the system comprising: A mold manufacturing system according to any one of claims 1 to 35; and an object manufacturing apparatus configured and operable to build each current manufacturing layer by depositing molten metal into each of one or more object regions defined by a respective one or more mold regions within the current manufacturing layer.

37. 37. The additive casting system of claim 36, wherein the object manufacturing apparatus comprises one or more molten metal depositors and a control system configured to operate the one or more molten metal depositors according to a predetermined build plan that indicates a geometric layout of one or more object regions in each production layer and synchronization data for the formation of mold regions and object regions in that production layer.

38. 38. The system of claim 36 or 37, wherein the object manufacturing apparatus is configured and operable to create an object area of ​​a current manufacturing layer on at least a portion of a previous mold area of ​​a previous manufacturing layer or on at least a portion of a previous object area of ​​a previous manufacturing layer, depending on the surface relief of the metal object area to be manufactured.

39. 1. A method for use in additive manufacturing of a metal object, comprising:

1. A method comprising: building successive manufacturing layers including a plurality of mold regions each defining a respective number of metal object regions, the building of each manufacturing layer being controllably carried out according to a predetermined build schedule, the execution including, for each manufacturing layer, creating the plurality of mold regions before depositing molten metal material in the plurality of object regions, each mold region being created by depositing one or more mold materials to sequentially form a metal-facing zone configured to define a cavity in which the metal object region is formed and a metal non-adjacent zone surrounding the metal-facing zone, the metal-facing zone of the mold region being made of a ceramic-based material and differing from the metal non-adjacent zone of the mold region in at least one of material composition parameters and mold deposition process parameters.

40. 40. The method of claim 39, wherein the metallic non-adjacent zone of the mold region is configured to provide mechanical support to the metallic opposing zone of the mold region.

41. 41. The method of claim 39 or 40, wherein the non-metallic adjacent zone of the mold region comprises a ceramic-based material.

42. 42. The method of any one of claims 39 to 41, wherein the metal non-adjacent zones of the mold region comprise a cross pattern.

43. 43. The method of claim 42, wherein the metallic non-adjacent zones of the mold region are created in multiple iterations of material deposition to form the cross pattern.

44. 42. The method of any one of claims 39 to 41, wherein the metal non-adjacent zone of the mold region comprises a curl pattern.

45. 45. The method of any one of claims 42 to 44, wherein the metal non-adjacent zone of the mold region is formed with an enlarged surface area and reduced material density to allow rapid transport of heat and vapor from the metal facing zone and metal non-adjacent zone of the mold region.

46. 46. ​​The method of any one of claims 42 to 45, wherein the metallic non-adjacent zones of the mold region are created to allow for their rapid formation.

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