Delayed cure additive manufacturing

A method for manufacturing a part includes fabricating an object in an additive fabrication stage, the object including a solid mold forming a cavity in the shape of a part with uncured or incompletely cured build material disposed therein. The build material in the cavity is cured in a curing stage that occurs at least partially after the additive fabrication stage. The build material undergoes a phase change mechanism occurring during the additive fabrication stage and a distinct polymerization mechanism occurring during the curing stage and at least partly after the additive fabrication stage of the object and cures the build material by a polymerization process.

BACKGROUND OF THE INVENTION

This invention relates to a manufacturing process with a delayed curing step.

Some manufacturing techniques use molds to fabricate parts. A mold generally has a predefined shape and is filled with a build material (e.g., a molten material such as a molten metal or plastic). The build material solidifies, yielding the part. The part can then be removed, for example, by destroying or otherwise removing the mold.

Molds are often fabricated from metallic material (e.g., steel or aluminum) and are precision-machined to form the features of a desired part. When designing parts for molding, care must be taken to ensure that the parts are compatible with the molding process. For example, the material used for the part, the desired shape and features of the part, the material of the mold, and the properties of the molding machine must all be taken into account when designing a part.

SUMMARY OF THE INVENTION

In a broad aspect, a manufacturing process for fabricating a part uses additive manufacturing techniques to fabricate an object including the part in an uncured or incompletely cured form. In general, the additive fabrication is an iterative process, where the material that forms the object is deposited incrementally, for example, in layers. During an additive fabrication stage of the manufacturing process, the material for the part of the object, referred to as “build material,” is deposited in a liquid phase.

In the additive fabrication stage, additive manufacturing techniques are used to fabricate the object to include a solid mold containing the build material of the part, for example with the solid mold forming a cavity with a shape of the part. Rather than completely fabricating the solid mold and then filling the mold with build material, uncured build material is incrementally added to the object as the mold is fabricated.

In the overall manufacturing process, which includes the additive fabrication stage as well as a subsequent or overlapping part curing stage, the build material for the part of the object undergoes two distinct mechanisms: a phase change mechanism and a polymerization mechanism.

The phase change mechanism occurs during the additive fabrication stage and causes a phase change of the build material from a liquid to a non-liquid (e.g., at least partially solid, semi-solid, and/or quasi-solid), where the phase change is generally not due to polymerization. In this non-liquid form the build material is sufficiently solidified for subsequent incremental deposit of material on to it (e.g., the non-liquid build material can support the weight of incrementally added material and/or the force of the material as it is jetted to, for example, prevent mixing between the build material and the support material).

The polymerization mechanism occurs after, or at least partly after, the additive fabrication of the object during the curing stage. This mechanism cures the build material by a polymerization process. In some examples, the polymerization mechanism is initiated after additive fabrication of the object is complete. In other examples, the polymerization mechanism is initiated before additive manufacturing is complete, for example, being initiated during the phase change mechanism (e.g., with both mechanisms being initiated at the same time, or the polymerization mechanism being initiated during the phase change mechanism).

After the build material is sufficiently cured (e.g., sufficiently polymerized) in the curing stage to allow removal of the mold, the manufacturing process enters a part removal stage for removal of the mold. Removal of the mold yields the fabricated part.

In an general aspect, a method for manufacturing a part includes fabricating, in an additive fabrication stage, an object including build material for the part in an uncured or incompletely cured form and a solid mold forming a cavity with a shape of the part and containing the build material and curing the part, in a curing stage that occurs at least partially after the additive fabrication stage. In the additive fabrication stage, material that forms the object is deposited incrementally including depositing build material for the part in a liquid phase and depositing material for the mold, and during the additive fabrication stage the material for the mold solidifies to form the solid mold. The build material undergoes a phase change mechanism and a distinct polymerization mechanism, the phase change mechanism occurring during the additive fabrication stage and causing a phase change of the build material from a liquid to a non-liquid. The polymerization mechanism occurs during the curing stage and occurs at least partly after the additive fabrication stage of the object, and cures the build material by a polymerization process.

Aspects may include one or more of the following features.

The polymerization mechanism may be initiated after the additive fabrication stage. The polymerization mechanism may be initiated before additive manufacturing stage is complete. The polymerization mechanism may be initiated before completion of the phase change mechanism. The phase change mechanism and the polymerization mechanism may be initiated at the same time.

The method may further include, after the build material is at least partially cured in the curing stage, a part removal stage including removing the mold yield the fabricated part. The material for the mold may solidify by a curing process. Curing the deposited mold material may include causing the deposited mold material to polymerize. The mold material may include a photo-curable material and the curing process includes applying light to the deposited mold material. The material for the mold may solidify by undergoing a physical phase change. Undergoing the physical phase change may include allowing the material for the mold to cool.

The material for the mold may include a wax. Incrementally depositing material for the object may include depositing a number of layers of material. At least some layers of material of the number of layers of material may be deposited using a jetting process. The material for the mold deposited in a second layer of the number of layers may be deposited on the build material deposited in a first layer of the number of layers deposited prior to the second layer. At least some of the layers may be added using two or more print heads.

Depositing the build material may include depositing a polymerization initiation catalyst. Depositing the layers may include depositing a number of material components from a corresponding number of print heads, a first print head of the number of print heads depositing the polymerization initiation catalyst. The polymerization initiation catalyst may be mixed with the build material. Incrementally depositing the layers may further include depositing at least some layers including only mold material.

The method may further include removing the solid mold. Removing the solid mold may include at least one of dissolving the solid mold, mechanically removing the solid mold, and liquefying the solid mold. The build material may include a wax after the phase change mechanism. The build material may include a liquid prior to the phase change mechanism. Curing the part may include heating the build material. The build material may undergo a phase change of the build material to a liquid phase during the curing stage.

The build material may include a polymerization precursor. The cured mold material may be substantially stable under a build curing condition. The cured build material may be substantially stable under a mold removal condition. The non-liquid may be sufficiently solidified for subsequent incremental deposit of material onto it during the additive fabrication stage.

In another general aspect, a method receives a model representing a part to be fabricated. The method processes the model to determine characteristics (e.g., shape and material) of a mold that can be used to fabricate the part using the additive manufacturing techniques described above.

Aspects may have one or more of the following advantages.

Aspects advantageously are capable of fabricating parts with shapes and from materials that are not possible with conventional molding techniques (e.g., injection molding).

Aspects advantageously provide a more agile design process as compared to conventional molding processes because the mold can be continuously refined without incurring the costs and efforts associated with making a new mold for conventional molding.

Aspects are advantageously capable of producing polymers that have improved mechanical properties and are more isotropic as compared to those produced by conventional inkjet printed parts.

Without wishing to be bound by theory, it is understood that the methods and materials of the present disclosure may carry one or more potential advantages over the existing methods and materials in the field. For example, the methods and materials may allow for a delayed bulk polymerization of the build materials, which could provide a cured materials containing polymers that are more isotropic and/or have a more uniformed structure, as compared to cured materials prepared by layer-by-layer polymerization. For another example, the methods may be suitable for using a wider range of polymerization conditions, including with slower rates of polymerization than typical.

DETAILED DESCRIPTION

The description below relates to a manufacturing process that uses additive fabrication, for example, using a jetting-based3D printer100as shown inFIG.1. Very generally, the manufacturing process includes three temporal phases: an additive fabrication stage, a part curing stage, and a part removal stage. As is described in greater detail below, in some examples, the part curing stage occurs entirely after the additive fabrication stage. In other examples the additive fabrication stage and the part curing stage partially overlap.

In the additive fabrication stage, additive fabrication is used to fabricate an object104including a solid (e.g., cured) mold structure111that forms a cavity (e.g., closed structure or open vessel) defining a shape of the part112, where the cavity is filled with a semi-solid, uncured or partially cured material in the shape of the part112. The solid mold structure111and/or the semi-solid material are added, layer by layer, to form the object104.

In the part curing stage, at least some of which occurs at a time after completion of the additive fabrication stage, the object104including the filled mold structure111undergoes a curing process for polymerizing the material in the cavity.

In the additive manufacturing stage and the part curing stage, the material used to form the part112(sometimes referred to as “build material) undergoes two distinct mechanisms: a phase change mechanism and a polymerization mechanism.

The phase change mechanism occurs during the additive fabrication stage and causes a phase change of the build material from a liquid to a non-liquid (e.g., at least partially solid, semi-solid, and/or quasi-solid, where these three terms may be used interchangeably herein). In this non-liquid form the build material is sufficiently solidified for subsequent incremental deposit of material on to it (e.g., the non-liquid build material can support the weight or force of incrementally added material).

The polymerization mechanism occurs after, or at least partly after, the additive fabrication of the object104during the curing stage. This mechanism cures the build material by a polymerization process. In some examples, the polymerization mechanism is initiated after additive fabrication of the object is complete. In other examples, the polymerization mechanism is initiated before additive manufacturing is complete, for example, being initiated during the phase change mechanism (e.g., with both mechanisms being initiated at the same time, or the polymerization mechanism being initiated after initiation and during the phase change mechanism).

In the part removal stage, the solid mold structure111is removed, yielding the part112. In some examples, the part removal stage occurs after the part curing stage. But in other examples, the part removal stage may overlap with the part curing stage (e.g., the part112is still curing but is sufficiently cured for removal from the solid mold structure111).

In the additive fabrication stage, the printer100uses jets102(inkjets) to emit material for deposition of layers to form the object104(shown partially fabricated inFIG.1). For the printer illustrated inFIG.1, the object104is fabricated on a build platform106, which is controlled to move relative to the jets (i.e., along an x-y plane) in a raster-like pattern to form successive layers, and in this example also to move relative to the jets (i.e., along a z-axis) to maintain a desired separation of the jets and the surface of the partially-fabricated object104.

As illustrated, there are multiple jets108,110, for example with a first jet108being used to emit a mold material113to form a solid (e.g., cured or semi-cured) mold structure111of the object104, and a second jet110being used to emit build material114to form an uncured or partially cured, semi-solid (e.g., a gel or a wax) part112in the object104. Additional details of the properties of the mold material113and the build material114are described below.

A sensor116(sometimes referred to as a scanner) is positioned relative to (e.g., above) the object under fabrication104and is used to determine physical characteristics of the partially fabricated object. For example, the sensor116measures one or more of the surface geometry (e.g., a depth map characterizing the thickness/depth of the partially fabricated object) and subsurface characteristics (e.g., in the near surface comprising, for example, 10 s or 100 s of deposited layers). The characteristics that may be sensed can include one or more of a material density, material identification, and a curing state. Very generally, the measurements from the sensor116are associated with a three-dimensional (i.e., x, y, z) coordinate system where the x and y axes are treated as spatial axes in the plane of the build surface and the z axis is a height axis (i.e., growing as the object is fabricated).

In some examples, in the context of a digital feedback loop for additive fabrication, the additive manufacturing system builds the object by printing layers. The sensor116captures the3D scan information after the printer100prints one or more layers. For example, the sensor116scans the partial object (or empty build platform), then the printer prints a layer (or layers) of material(s). Then, the sensor116scans the (partially built) object again. The new depth sensed by the sensor116should be at a distance that is approximately the old depth minus the thickness of layer (this assumes that the sensor116is positioned on the top of the of the object being built and the object is being built from the bottom layer to the top layer and the distance between the sensor116and the build platform is unchanged). Various types of sensing such as optical coherence tomography (OCT) or laser profilometry can be used to determine depth and volumetric information related to the object being fabricated.

A controller118uses a model120of the object to be fabricated to control motion of the build platform106using a motion actuator122(e.g., providing three degrees of motion) and control the emission of material from the jets102according to non-contact feedback of the object characteristics determined via the sensor116.

3 Manufacturing Process

Referring toFIG.2, the printer100(only the jets102of the printer100are shown for simplicity inFIG.2) is in the midst of the additive fabrication stage of the manufacturing process where an object104including a three-dimensional, substantially “egg-shaped” semi-solid part112(shown in a two-dimensional cross-section for simplicity inFIG.2) is formed inside a solid mold structure111. In this example, the semi-solid part112remains in an uncured state throughout the additive fabrication stage and the part curing stage begins by initiating the polymerization mechanism after the additive fabrication stage is complete.

As is described above, the semi-solid part112is formed from a semi-solid build material114(e.g., a wax or gel) deposited by the second jet110. In this example, the build material114that is deposited by the second jet110is a curable precursor material including a mixture of a monomer and a polymerization initiation catalyst. The build material114is emitted from the second jet110as a liquid. During deposition, the build material114is sometimes described as being in a build depositing condition. The deposited build material114undergoes the phase change mechanism wherein the build material undergoes a physical phase change to become a semi-solid after being deposited (e.g., by cooling). In this example, the polymerization mechanism is not yet initiated at this stage, and the semi-solid build material114is described as being in a pre-curing condition.

The solid mold structure111is formed from a mold material113(e.g., a UV curable polymer) deposited by the first jet108. In this example, the mold material113is emitted from the first jet108as a liquid. During deposition, the mold material113is sometimes described as being in a mold depositing condition. At some time after the mold material is deposited, curing of the mold material commences. During curing, the mold material113is described as being in a mold curing condition. The mold material113in the mold curing condition undergoes a chemical phase change to become solid after being deposited (e.g., by undergoing a UV curing process). The solid mold material113is sometimes described as being in a mold pre-removal condition.

InFIG.2, a number of layers of the object (some including both semi-solid, uncured build material and solidified mold material) are shown having been deposited such that roughly a third of the egg shaped semi-solid part112is formed in the solid mold structure111.

Referring toFIG.3, as the additive fabrication stage progresses, the egg shaped semi-solid part112begins to take on the appearance of an egg, where some parts of the “egg shell” overhang parts of the interior of the egg. That is, in overhanging areas124of the print surface126, the solid mold structure111is specified to lay on top of the semi-solid part112(i.e., the solid mold structure111overhangs the semi-solid part112). In the overhanging areas124, the mold material113is deposited onto the semi-solid, deposited build material114of the semi-solid part112, which serves as a support surface for depositing the mold material113. The semi-solid, deposited build material114of the semi-solid part112holds the deposited mold material113in place before and during its solidification (e.g. curing).

Referring toFIG.4, eventually the additive fabrication stage of the manufacturing process completes, yielding the fabricated object104including the semi-solid, uncured part112contained in the solid mold structure111.

The semi-solid, uncured part112shown inFIG.4includes a complex structure126. In some examples, the complex structure126is a feature that will still be included in the part112after curing. The complex structure126may be a structure that would be difficult to form using conventional molding techniques. In other examples, the complex structure126is included to compensate for effects of the curing process on the semi-solid part112. For example, the complex structure126may include additional build material114that gravity feeds into the cavity formed in the mold structure111when the build material114of the semi-solid part112shrinks during curing. Alternatively, the complex structure126may be an open space that allows for expansion of the build material114of the semi-solid part112during curing. In yet another example, the complex structure126establishes a vent (not shown) to the environment in the mold structure111to allow gases produced during the curing process to escape. It should be appreciated that any number of other complex structures126can be formed for various other reasons.

Referring toFIG.5, in the part curing stage of the manufacturing process, the fabricated object104is subjected to a curing process, wherein the polymerization mechanism is initiated to cure the semi-solid part112. The part curing stage yields a cured object504with a cured part512contained in the solid mold structure111. During the part curing stage, the semi-solid build material114of the part112is sometimes described as being in the build curing condition.

The curing process inFIG.5is a heating-based process. Very generally, the heating process activates the polymerization initiation catalyst (i.e., initiates the polymerization mechanism) included in the build material114, which in turn reacts with the monomer included in the build material114to cause polymerization of the build material114of the semi-solid part112, yielding the cured object504with the cured (or sufficiently cured) part512. It should be appreciated that other types of curing processes (e.g., UV curing or curing by a curing agent) can be used. In some examples, the curing process applies different temperatures at different times to control the curing process.

Referring toFIG.6, in the part removal stage of the manufacturing process, the solid mold structure111is removed from the cured object504, yielding the cured (or sufficiently cured) part512. During the part removal stage, the solid mold material113of the solid mold structure111is sometimes described as being in a mold removal condition.

In the example ofFIG.6, the solid mold structure111is soluble (e.g., water or other solvent soluble), and is removed by bathing the cured object504in water130or some other solvent to dissolve the solid mold structure. In other examples, the solid mold structure is physically removed (e.g., by breaking the solid mold structure111off), removed with heat, chemically removed (e.g., by a chemical reaction), or some combination of the aforementioned removal techniques.

Referring toFIG.7, in the example described above two jets are used in the additive fabrication stage of the manufacturing process, one jet for depositing the mold material and another jet for depositing build material that is a mixture of a monomer and a polymerization initiation catalyst. But in the example ofFIG.7, the monomer and the polymerization initiation catalyst are deposited from separate jets and mix at a later time (e.g., when deposited or during the curing process).

That is, inFIG.7, three jets708,709,710are used in the additive fabrication stage of the manufacturing process, with a first jet708being used to emit a mold material713to form a solid (e.g., cured or semi-cured) mold structure711of the object704, a second jet709being used to emit a monomer714as a first component of the semi-solid (e.g., a gel or a wax), uncured part712in the object704, and a third jet710being used to emit a polymerization initiation catalyst715(jetted, for example, in a diluent-solvent) to as a second component of the semi-solid, uncured part712in the object704. In some examples, both the monomer714and the polymerization initiation catalyst715are emitted as a liquid and undergo a phase change mechanism (e.g., cooling) to become semi-solid. Besides this difference in how the build material of the semi-solid part712is formed, the manufacturing process for forming the cured part is much the same as the process described above forFIGS.1-6.

Referring toFIG.8, in another example of the manufacturing process, the printer100(including three jets802in this example) is in the midst of the additive fabrication stage of the manufacturing process where an object804including a three-dimensional, substantially “egg-shaped” semi-solid part812(shown in a two-dimensional aspect for simplicity inFIG.8) is formed inside a solid mold structure811, which is in turn formed inside of (e.g., supported by) a wax support structure817. In this example, the semi-solid part812remains in an uncured state throughout the additive fabrication stage and the part curing stage begins by initiating the polymerization mechanism after the additive fabrication stage is complete.

As was the case in previous examples, the semi-solid part812is formed from a semi-solid build material814(e.g., a wax or gel) deposited in liquid form prior to the phase change mechanism by a second jet810. In this example, the build material814that is deposited by the second jet810is a curable precursor material including a monomer and a polymerization initiation catalyst. The build material814is emitted from the second jet810as a liquid. During deposition, the build material814is sometimes described as being in a build depositing condition. The deposited build material814undergoes the phase change mechanism wherein the build material undergoes a physical phase change to become a semi-solid after being deposited (e.g., by cooling). In this example, the polymerization mechanism is not yet initiated at the stage, and the semi-solid build material814is sometimes described as being in a build pre-curing condition.

The solid mold structure811is formed from a mold material813(e.g., a UV curable polymer) deposited by a first jet808. In this example, the mold material813is emitted from the first jet808as a liquid. During deposition, the mold material813is sometimes described as being in a mold depositing condition. At some time after the mold material813is deposited, curing of the mold material813commences. During the curing process, the mold material813is described as being in a mold curing condition. The mold material813in the mold curing condition undergoes a chemical phase change to become solid (sometimes described as being in a mold pre-removal condition) after being deposited (e.g., by undergoing a UV curing process).

The wax support structure817is formed from a wax support material819(e.g., ester waxes, amide waxes, urethane waxes, or urea waxes) deposited by a third jet809. In this example, the wax support material819is emitted from the third jet809as a liquid and undergoes a physical phase change to become a solid or semi-solid after being deposited (e.g. by cooling).

InFIG.8, a number of layers of the object (some including semi-solid, uncured build material, solidified mold material, and wax support material) are deposited such that roughly a third of the egg shaped semi-solid part812is formed in the solid mold structure811and wax support structure817.

Referring toFIG.9, as the additive fabrication stage progresses, the egg shaped semi-solid part812begins to take on the appearance of an egg, where some parts of the “egg shell” overhang parts of the interior of the egg. That is, in overhanging areas824of the print surface826, the wax support structure817is specified to lay on top of the solid mold structure811(i.e., the wax support structure817overhangs the solid mold structure811), and the solid mold structure811is specified to lay on top of the semi-solid part812(i.e., the solid mold structure811overhangs the semi-solid part812). In the overhanging areas824, the mold material813is deposited onto the semi-solid, deposited build material814of the semi-solid part812, which serves as a supporting surface for depositing the mold material813. Similarly, the wax support material819is deposited onto the solid mold material813of the solid mold structure811in the overhanging areas824. That is, the semi-solid, deposited build material814of the semi-solid part812holds the deposited mold material813in place before and during its solidification (e.g., curing) and the mold material813of the solid mold structure811holds the wax support material819in place as it cools.

Referring toFIG.10, eventually the additive fabrication stage of the manufacturing process completes, yielding the fabricated object804including the semi-solid part812contained in the solid mold structure811, which is in turn contained in the wax support structure817. The semi-solid, uncured part812of the fabricated object804at this stage is sometimes described as being in a build pre-curing condition.

Referring toFIG.11, the fabricated object804is then subjected to a combined part removal/curing stage of the manufacturing process to remove the wax support structure817and cure the semi-solid part812. In the curing aspect of the part removal/curing stage, the polymerization mechanism is initiated to cure the semi-solid part812. The part removal/curing stage yields a cured part912contained in the solid mold structure811. In some examples, the part removal/curing stage substantially simultaneously removes the wax support structure817and cures the semi-solid part812. In other examples, the removal and curing occur in two sequential steps. While the semi-solid part812undergoes the curing process in the part curing stage, it is sometimes described as being in a build curing condition.

The curing process shown inFIG.11is a heating-based process. Very generally, the heating process melts away the wax support structure817and activates the polymerization initiation catalyst (i.e., initiates the polymerization mechanism) included in the build material814, which in turn reacts with the monomer included in the build material814to cause polymerization of the build material814of the semi-solid part812. This yields the cured (or sufficiently cured) part912contained in the solid mold structure811.

In some examples, the heating process operates at a single temperature that is sufficient to both melt the wax support structure and cure the build material814. In other examples, the curing process applies different temperatures at different times to control the melting and/or curing process. It should be appreciated that other types of curing processes (e.g., UV curing or curing by a curing agent) can also be used.

Referring toFIG.12, in the part removal stage of the manufacturing process, the solid mold structure811is removed from the cured (or sufficiently cured) part912. During the removal stage, the solid mold material813of the solid mold structure811is sometimes described as being in a mold removal condition.

In the example ofFIG.12, the solid mold structure811is soluble (e.g., water or other solvent soluble), and is removed by bathing the cured part912contained in the solid mold structure811in water830or some other solvent to dissolve the solid mold structure811. In other examples, the solid mold structure811is physically removed (e.g., by breaking the solid mold structure811off), removed with heat, chemically removed (e.g., by a chemical reaction), or some combination of the aforementioned removal techniques.

Referring toFIG.13, in another example of the manufacturing process, the printer100(only the jets1302of the printer100are shown for simplicity inFIG.13) is in the midst of the additive fabrication stage of the manufacturing process where an object1304including a three-dimensional, substantially “egg-shaped” semi-solid part1312(shown in a two-dimensional cross-section for simplicity inFIG.13) is formed inside a solid mold structure1311. In this example, the semi-solid part1312begins the curing stage, including undergoing the polymerization mechanism, during the additive fabrication stage. The curing stage continues after the additive fabrication stage is complete.

As is described above, the semi-solid part1312is formed from a semi-solid build material1314(e.g., a wax or gel) deposited by the second jet1310. In this example, the build material1314that is deposited by the second jet1310is a curable precursor material including a mixture of a monomer and a polymerization initiation catalyst. The build material1314is emitted from the second jet1310as a liquid. During deposition, the build material1314is sometimes described as being in a build depositing condition. The deposited build material1314undergoes the phase change mechanism wherein the build material undergoes a physical phase change to become a semi-solid after being deposited (e.g., by cooling). In this example, the polymerization mechanism is initiated either simultaneously with the phase change mechanism or at sometime soon thereafter (e.g., by application of UV light or some other trigger) such that the part curing stage commences. In the event that the polymerization mechanism is initiated after the phase change mechanism, the semi-solid build material1314is described as being in a pre-curing condition when the phase change mechanism is complete and the polymerization mechanism is not yet initiated. Once the polymerization mechanism, the build material1314is described as being in a build curing condition.

The solid mold structure1311is formed from a mold material1313(e.g., a UV curable polymer) deposited by the first jet1308. In this example, the mold material1313is emitted from the first jet1308as a liquid. During deposition, the mold material1313is sometimes described as being in a mold depositing condition. At some time after the mold material is deposited, curing of the mold material commences. During curing, the mold material1313is described as being in a mold curing condition. The mold material1313in the mold curing condition undergoes a chemical phase change to become solid after being deposited (e.g., by undergoing a UV curing process). The solid mold material1313is sometimes described as being in a mold pre-removal condition.

InFIG.13a number of layers of the object (some including both semi-solid, uncured build material and solidified mold material) are shown having been deposited such that roughly a third of the egg shaped semi-solid part1312is formed in the solid mold structure1311.

Referring toFIG.14, as the additive fabrication stage progresses, the egg shaped semi-solid part1312begins to take on the appearance of an egg, where some parts of the “eggshell” overhang parts of the interior of the egg. That is, in overhanging areas1324of the print surface1326, the solid mold structure1311is specified to lay on top of the semi-solid part1312(i.e., the solid mold structure1311overhangs the semi-solid part1312). In the overhanging areas1324, the mold material1313is deposited onto the semi-solid, deposited build material1314of the semi-solid part1312, which serves as a support surface for depositing the mold material1313. The semi-solid, deposited build material1314of the semi-solid part1312holds the deposited mold material1313in place before and during its solidification (e.g. curing).

Referring toFIG.15, eventually the additive fabrication stage of the manufacturing process completes, yielding the fabricated object1304including the semi-solid, partially cured part1312contained in the solid mold structure1311.

Referring toFIG.16, the part curing stage of the manufacturing process continues and eventually yields a cured object1604with a cured part1612contained in the solid mold structure1311.

Note that there is no additional curing process inFIG.16—the polymerization mechanism initiated during the additive fabrication stage simply continues without any additional influence. However, it should be noted that there could be additional steps taken to cure the partially cured part1312after the additive fabrication stage is complete. For example, the fabricated object1304including the partially cured part1312could be subjected to a heating step (as described above) after the additive fabrication stage is complete.

Referring toFIG.17, in the part removal stage of the manufacturing process, the solid mold structure1311is removed from the cured object1604, yielding the cured (or sufficiently cured) part1612. During the part removal stage, the solid mold material1313of the solid mold structure1311is sometimes described as being in a mold removal condition.

In the example ofFIG.6, the solid mold structure1311is soluble (e.g., water or other solvent soluble), and is removed by bathing the cured object1604in water1730or some other solvent to dissolve the solid mold structure. In other examples, the solid mold structure is physically removed (e.g., by breaking the solid mold structure1311off), removed with heat, chemically removed (e.g., by a chemical reaction), or some combination of the aforementioned removal techniques.

4 Material Properties

Very generally, the build and mold materials described above are chosen such that an uncured or partially cured part can be fabricated, where at least some of the curing of the fabricated part occurs in the solid mold at some time after fabrication of the part.

4.1 Build Materials

In some examples, the build material is a mixture of a precursor and a polymerization initiation catalyst and possibly a “gelling” component (e.g., a wax). The build material is deposited in the build depositing condition (e.g., as a liquid) and, by a phase change mechanism, “gels” to form a semi-solid material (sometimes described as a pre-cured condition). The gelling of the build material is caused by a physical state change (e.g., cooling) and is not caused by chemical changes such as polymerization or partial polymerization (though in some examples, it is caused by a non-polymerization chemical change). In some examples, at a time during the additive fabrication stage or after the additive manufacturing stage is complete, a part curing stage initiates a polymerization mechanism, causing the precursor and the polymerization initiation catalyst of the build material to react, curing the build material in the build curing condition (e.g., by polymerization). In some examples, the curing process of the part curing stage causes liquification of the build material.

In some embodiments, the build material is deposited (e.g., jetted) under a build depositing condition (e.g., build jetting condition).

In some embodiments, the build material is cured under a build curing condition.

In some embodiments, the build material is a liquid under the build depositing condition (e.g., the build jetting condition).

In some embodiments, the build material is a wax when in the pre-curing condition.

In some embodiments, the build material has a melting point being the same or lower than the temperature of the build depositing condition.

In some embodiments, the build material has viscosity ranging from about 5 cp to about 100 cp at the temperature of the build depositing condition.

In some embodiments, upon deposition, the build material is converted to a solid, semi-solid, or quasi-solid (e.g., via a phase change).

In some embodiments, upon deposition, the build material is converted to a solid, semi-solid, or quasi-solid by cooling.

In some embodiments, the build material is converted to a solid by a non-polymerization chemical change.

In some embodiments, the build material is UV curable.

In some embodiments, the build material is thermally curable.

In some embodiments, the build material is chemically curable by a curing catalyst or a curing agent.

In some embodiments, the build material is substantially stable (e.g., chemically and/or physically) toward the mold material.

In some embodiments, the build material is substantially stable (e.g., chemically and/or physically) under the mold curing condition (e.g., when exposed to UV radiation).

In some embodiments, the build material is substantially stable (e.g., chemically and/or physically) toward the cured mold material.

In some embodiments, the build material comprises a precursor (e.g., a monomer or a protected monomer) for a polymer.

In some embodiments, the precursor is a precursor for a polyamide (e.g., polyamide 6).

In some embodiments, the precursor is a precursor for a polyethersulfone (PES).

In some embodiments, the precursor comprises an epoxide, a polyepoxide, or a combination thereof.

In some embodiments, the precursor comprises a benzoxazine.

In some embodiments, the precursor is a precursor for ring opening polymerization

In some embodiments, the precursor comprises a cyclic olefin (e.g., ring opening metathesis polymerization).

In some embodiments, the precursor comprises an acrylate.

In some embodiments, the precursor is a precursor for thiol-ene polymerization.

In some embodiments, the precursor comprises a thiol agent, an alkenyl agent, or a combination thereof.

In some embodiments, the precursor is a precursor for bulk polymerization.

In some embodiments, the build material comprises a curing catalyst.

In some embodiments, the curing catalyst cures the build material but does not cure the mold material.

In some embodiments, the build material comprises a curing agent (e.g. an agent that co-polymerizes with the polymer precursor, modifies the polymer, or cross-links the polymer).

In some embodiments, the curing agent cures the build material but does not cure the mold material.

In some embodiments, the curing agent comprises an amide, an anhydride, or a combination thereof.

4.1.1 Build Curing Conditions

In some embodiments, the build curing condition comprises or is initiated by irradiation (e.g., visible light or UV).

In some embodiments, the build curing condition comprises or is initiated by an elevated temperature condition.

In some embodiments, the build curing condition results from adding a curing catalyst.

In some embodiments, the build curing condition results from adding a curing agent (e.g. an agent that co-polymerizes with the polymer precursor, modifies the polymer, or cross-links the polymer).

In some embodiments, the build curing condition is substantially free of air (e.g., oxygen).

In some embodiments, the build curing condition is substantially free of water.

4.1.2 Cured Build Materials

In some embodiments, the cured build material is substantially stable (e.g., chemically and/or physically) toward the cured mold material

In some embodiments, the cured build material is substantially stable (e.g., chemically and/or physically) under the mold removal condition.

In some embodiments, the build material comprises a polymer.

In some embodiments, the polymer is a polyamide (e.g., polyamide 6).

In some embodiments, the polymer is a polyethersulfone (PES).

In some embodiments, the polymer is formed by polymerization of epoxide.

In some embodiments, the polymer is formed by co-polymerization between epoxide, and an amide or anhydride.

In some embodiments, the polymer is a benzoxazine polymer.

In some embodiments, the polymer is formed by ring opening polymerization (e.g., ring opening metathesis polymerization).

In some embodiments, the polymer is an acrylate polymer.

In some embodiments, the polymer is a thiol-ene polymer.

4.2 Mold Materials

In some examples, the mold material is curable during the additive fabrication stage such that the solid mold structure can be at least partially cured (e.g., via a chemical change such as polymerization) as it is built. In some examples, the mold material is deposited in a mold depositing condition (e.g., as a liquid). The deposited mold material is sometimes described as being in a mold pre-curing condition. The deposited mold material enters a mold curing condition when solidification of the mold material is triggered by an excitation signal. In some examples, the excitation signal includes ultraviolet illumination emitted by a curing signal generator (e.g., the UV lamp115ofFIG.1), which triggers curing of the mold material shortly after it is emitted. In other examples, an excitation signal (e.g., optical, RF, etc.) is not necessarily used. Rather, the curing is triggered chemically, for example, by mixing multiple components before jetting, or jetting separate components that mix and trigger curing. In some examples, the cured mold material is described as being in a mold pre-removal condition.

In general, when the mold material of the solid mold structure is in the mold pre-removal condition, it is able to resist the process used to cure the part (e.g., heating) without deformation or break-down. The mold material is removable from cured part after curing is complete by subjecting the mold material to a mold removal condition.

In some embodiments, the mold material is deposited (e.g., jetted) under a mold depositing condition (e.g., mold jetting condition).

In some embodiments, the mold material is cured under a mold curing condition.

In some embodiments, the mold material or the cured mold material is removed under a mold removal condition.

In some embodiments, the mold material is a liquid under the mold depositing condition (e.g., the mold jetting condition).

In some embodiments, the mold material is a wax.

In some embodiments, the mold material has a melting point being the same or lower than the temperature of the mold depositing condition.

In some embodiments, the mold material has viscosity ranging from about 5 cp to about 100 cp at the temperature of the mold depositing condition.

In some embodiments, upon deposition, the mold material is converted to a solid (e.g., via a phase change).

In some embodiments, upon deposition, the mold material is converted to a solid by cooling.

In some embodiments, upon deposition, the mold material is converted to a solid by curing.

In some embodiments, the mold material is UV curable.

In some embodiments, the mold material is thermally curable.

In some embodiments, the mold material is curable toward a curing catalyst or a cuing agent.

In some embodiments, the mold material is substantially stable (e.g., chemically and/or physically) toward the build material.

In some embodiments, the mold material comprises a polymer precursor (e.g., a monomer).

In some embodiments, the mold material comprises a non-reacting compound (e.g., a wax).

In some embodiments, the mold material comprises a curing catalyst.

In some embodiments, the curing catalyst cures the mold material but does not cure the build material.

In some embodiments, the mold material comprises a curing agent (e.g. an agent that co-polymerizes with the polymer precursor, modifies the polymer, or cross-links the polymer).

In some embodiments, the curing agent cures the mold material but does not cure the build material.

4.2.1 Mold Curing Conditions

In some embodiments, the mold curing condition comprises or is initiated by irradiation (e.g., visible light or UV).

In some embodiments, the mold curing condition comprises or is initiated by an elevated temperature condition.

In some embodiments, the mold curing condition results from adding a curing catalyst.

In some embodiments, the mold curing condition results from adding a curing agent (e.g. an agent that co-polymerizes with the polymer precursor, modifies the polymer, or cross-links the polymer).

In some embodiments, the mold curing condition is substantially free of air (e.g., oxygen).

In some embodiments, the mold curing condition is substantially free of water.

4.2.2 Cured Mold Materials

In some embodiments, the cured mold material is substantially stable (e.g., chemically and/or physically) toward the build material

In some embodiments, the cured mold material is substantially stable (e.g., chemically and/or physically) under the build curing condition.

In some embodiments, the cured mold material comprises a polymer.

4.2.3 Mold Removal Conditions

In some embodiments, the mold removal condition comprises adding a solvent, thereby dissolving the cured mold material.

In some embodiments, the mold removal condition comprises mechanically removing the cured mold material.

In some embodiments, the mold removal condition comprises converting the mold material from a solid to a liquid (e.g., via a phase change).

While the above examples are described in the context of a feedback based additive fabrication process, it is noted that the described process is equally applicable to non-feedback based or conventional additive fabrication processes.

The egg-like structures described above are simple examples of parts that can be fabricated using the described processes. But it should be noted the described processes are not limited to fabricating these simple shapes. Indeed, many other types of parts with more (or less) complex shapes can be (and likely would be) fabricated using the described processes.

In the examples described above, the build material is assumed to be homogenous. But it is possible that non-homogenous build materials could be used to fabricate the semi-solid part. For example, an “egg yolk” of a different build material could be included in the semi-solid part.

In the examples described above, the build material assumes a semi-solid state after it is deposited. But it is possible that the build material could be in a liquid state after being deposited. In such cases, surface tension of the liquid build material would be able to support any mold material deposited on the liquid build material before it is polymerized.

In some examples, the solid mold structure and the semi-solid, uncured or partially cured part are formed at the same time, layer-by-layer. In some examples, multiple layers of the solid mold structure are deposited and then the cavity formed by the multiple layers of the solid mold structure is filled with build material.

The approaches described above can be implemented, for example, using a programmable computing system executing suitable software instructions or it can be implemented in suitable hardware such as a field-programmable gate array (FPGA) or in some hybrid form. For example, in a programmed approach the software may include procedures in one or more computer programs that execute on one or more programmed or programmable computing system (which may be of various architectures such as distributed, client/server, or grid) each including at least one processor, at least one data storage system (including volatile and/or non-volatile memory and/or storage elements), at least one user interface (for receiving input using at least one input device or port, and for providing output using at least one output device or port). The software may include one or more modules of a larger program. The modules of the program can be implemented as data structures or other organized data conforming to a data model stored in a data repository.

The software may be stored in non-transitory form, such as being embodied in a volatile or non-volatile storage medium, or any other non-transitory medium, using a physical property of the medium (e.g., surface pits and lands, magnetic domains, or electrical charge) for a period of time (e.g., the time between refresh periods of a dynamic memory device such as a dynamic RAM). In preparation for loading the instructions, the software may be provided on a tangible, non-transitory medium, such as a CD-ROM or other computer-readable medium (e.g., readable by a general or special purpose computing system or device), or may be delivered (e.g., encoded in a propagated signal) over a communication medium of a network to a tangible, non-transitory medium of a computing system where it is executed. Some or all of the processing may be performed on a special purpose computer, or using special-purpose hardware, such as coprocessors or field-programmable gate arrays (FPGAs) or dedicated, application-specific integrated circuits (ASICs). The processing may be implemented in a distributed manner in which different parts of the computation specified by the software are performed by different computing elements. Each such computer program is preferably stored on or downloaded to a computer-readable storage medium (e.g., solid state memory or media, or magnetic or optical media) of a storage device accessible by a general or special purpose programmable computer, for configuring and operating the computer when the storage device medium is read by the computer to perform the processing described herein. The system may also be considered to be implemented as a tangible, non-transitory medium, configured with a computer program, where the medium so configured causes a computer to operate in a specific and predefined manner to perform one or more of the processing steps described herein.

A number of embodiments of the invention have been described. Nevertheless, it is to be understood that the foregoing description is intended to illustrate and not to limit the scope of the invention, which is defined by the scope of the following claims. Accordingly, other embodiments are also within the scope of the following claims. For example, various modifications may be made without departing from the scope of the invention. Additionally, some of the steps described above may be order independent, and thus can be performed in an order different from that described.

A number of embodiments of the invention have been described. Nevertheless, it is to be understood that the foregoing description is intended to illustrate and not to limit the scope of the invention, which is defined by the scope of the following claims. Accordingly, other embodiments are also within the scope of the following claims. For example, various modifications may be made without departing from the scope of the invention. Additionally, some of the steps described above may be order independent, and thus can be performed in an order different from that described.