Patent Description:
Conductive liquid three-dimensional printers for building 3D objects from molten aluminum are known in the art. An example of such a system is disclosed in <CIT>. The system works by using a DC pulse applied by an electromagnetic coil to expel molten aluminum drops in response to a series of pulses. The platen to which the drops are targeted translates to allow for the drops to be connected and built up to produce a three-dimensional object.

However, the drops of molten aluminum sometimes do not combine smoothly or with sufficient bonding strength. Further, the 3D object can have an undesirable degree of porosity, as well as uneven build surfaces during fabrication, unwelded drops, and shape inconsistencies. All of these lead to degraded physical properties such as fatigue strength and tensile strength, as well as poor appearance issues with the final object.

Therefore, methods and systems for improving the quality of three-dimensional objects made from conductive liquid three-dimensional printers would be a step forward in the art.

<CIT> discloses a 3D printer using a metal alloy filament, wherein the 3D printer introduces a metal alloy filament through a nozzle formed inside an induction heating coil, melts and extrudes the filament, and laminates the filament three-dimensionally inside a chamber heated to a similar temperature. The 3D printer forcibly introduces a metal alloy filament in a nozzle, heated by an induction heating coil which circularly encloses the exterior of the nozzle and forms a cooling passage therein, by means of a transfer gear connected to a transfer motor. A 3D printer for a metal alloy filament is also provided in which an inert gas is introduced, the outside and heat and air are blocked, and a metal alloy filament that is melted in a nozzle and extruded is laminated one layer at a time on a floor plate installed inside a heated chamber and moving three-dimensionally with respect to the nozzle. <CIT> discloses an additive manufacturing method and system comprising: a nozzle having a nozzle sidewall defining a central channel for allowing a deposition material filament to be dispensed therethrough on a workpiece; a heat source operatively coupled to the nozzle for melting the deposition material filament dispensed through the nozzle to form an additive material layer on a top surface of the workpiece; and an ultrasonic wave generator for providing ultrasonic waves into the melted deposition material in order to break up the oxide layer around the melted deposition material and bond the additive material layer to the workpiece.

An embodiment of the present invention is directed to a three-dimensional printing system. The system comprises a build platform comprising a build surface. The printing system also includes an enclosure system having a side portion extending entirely around the build surface, a top plate portion that abuts the side portion, and a bottom portion. The side portion, the top plate portion and the bottom portion form an enclosed space surrounding the build surface. The top plate portion is moveable so as to adjust a volume of the enclosed space. The bottom portion includes a heat shield that extends from the build platform and abuts the side portion. A 3D printer printhead is disposed adjacent to the enclosure system for depositing a print material onto the build surface, wherein the printhead is configured for ejecting drops of a conductive liquid print material onto the build platform. The printing system also includes a heating system for heating the enclosed space.

Another embodiment of the present disclosure is directed to a method of three-dimensional printing. The method comprises enclosing a build surface of a build platform in an enclosure system. The enclosure system has a side portion extending entirely around the build surface, a top plate portion that abuts the side portion, and a bottom portion. The side portion, the top plate portion and the bottom portion form an enclosed space surrounding the build surface. The top plate portion is moveable so as to adjust a volume of the enclosed space. The bottom portion includes a heat shield that extends from the build platform and abuts the side portion. The method further comprises heating the build surface in the enclosed space. A print material is deposited onto the build surface with a 3D printer printhead to form a 3D object, wherein the printhead is configured for ejecting drops of a conductive liquid print material onto the build platform.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present teachings, as claimed.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate examples of the present teachings and together with the description, serve to explain the principles of the present teachings.

It should be noted that some details of the figure have been simplified and are drawn to facilitate understanding of the embodiments rather than to maintain strict structural accuracy, detail, and scale.

Reference will now be made in detail to embodiments of the present teachings, examples of which are illustrated in the accompanying drawings. In the drawings, like reference numerals have been used throughout to designate identical elements. In the following description, reference is made to the accompanying drawing that forms a part thereof, and in which is shown by way of illustration a specific exemplary embodiment in which the present teachings may be practiced. The following description is, therefore, merely exemplary.

Controlling the temperature of an object during 3D manufacturing can be important for various reasons. The temperature of the 3D object during manufacture can affect the 3D object properties, including the strength of the 3D object, porosity of the 3D object and overall quality of the 3D object appearance, among other things. This can be true for 3D objects made of various materials, including polymer objects, metal objects and so forth.

As an example, during the printing process of molten metal by a conductive liquid three-dimensional printer, the temperature differential between a molten drop ejected from the printer and a build surface causes inconsistencies with the build strength, porosity and surface finish of the final 3D object. Testing has shown that to properly fuse the molten metal to the base build material the receiving surface temperature can be controlled to a desired deposition temperature. The desired deposition temperature will vary depending on the material being deposited. For aluminum (e.g., pure aluminum or aluminum alloys) this deposition temperature is about <NUM> to about <NUM>, or higher. The conductive liquid three-dimensional printer system uses a heated base plate set to, for example, about <NUM>, to heat the initial layers. However, as the object <NUM> continues to grow from the base plate, the heating from the base plate is unable to maintain the desired temperature on the upper surface so as to ensure a good bond between the molten drop and the 3D object.

The present disclosure is directed to a dynamic thermal containment system employed in conjunction with a 3D printer, such as, for example, a conductive liquid three-dimensional printer. Advantages of the system and method of the present disclosure include one or more of the following: a dynamic thermal containment system that can increase performance of build based on build time, energy used and/or the quality of the final 3D object; improved 3D printed object properties, such as lower porosity, higher yield strength, higher fatigue cycles and/or surface quality; the ability to maintain a desired temperature of the 3D object to improve material bonding during the 3D print; the ability to control the temperature of the printed object independent of the shape, size or material of the object; allow for heating the entire object (e.g., entire volume of the object) being printed regardless of changes in direction of the object during printing; the ability to avoid using high temperature drives systems for the build platform movement; allow a closed system that can maintain an inert gas environment and limit loss of inert gas from the system; and the ability to improve build properties, such as surface appearance and other 3D object properties.

<FIG> illustrates an example of a three-dimensional printing system <NUM>, according to an embodiment of the present disclosure. The three-dimensional printing system <NUM> comprises a build platform <NUM> (an example of which is shown more clearly in <FIG>) including a build surface <NUM> on which a three-dimensional object <NUM> may be built. The build platform <NUM> in <FIG> is shown surrounded by a heat shield <NUM>, which will be discussed in more detail below. The three-dimensional printing system <NUM> further comprises an enclosure system <NUM> that includes a side portion <NUM> extending entirely around the build surface <NUM>, a top plate portion <NUM> that abuts the side portion, and a bottom portion <NUM>. The side portion <NUM>, the top plate portion <NUM> and the bottom portion <NUM> form an enclosed space surrounding the build surface <NUM> that allows an ambient temperature within the enclosure to be maintained at or near a desired deposition temperature. The top plate portion <NUM> can be moveable so as to adjust a volume of the enclosed space, thereby potentially reducing the volume of space to be heated while accommodating 3D object growth during printing. The three-dimensional printing system <NUM> also includes a heating system <NUM> for heating the enclosed space. A 3D printer printhead <NUM> is disposed adjacent to the enclosure system <NUM> for depositing a print material onto the build surface <NUM> through an orifice (not shown) in the top plate portion <NUM>.

In an embodiment, a position of the printhead <NUM> and the top plate portion <NUM> are both adjustable along a z-axis, as shown in <FIG>. In <FIG> the top plate portion <NUM> is shown at a topmost position of the enclosed space, while in <FIG> the top plate portion <NUM> is shown at a lowered position along the z-axis. In an embodiment, a printhead mount plate <NUM> on which the printhead <NUM> is attached is positioned within a region of the top plate portion <NUM>, as shown in <FIG>. Using the printhead mount plate <NUM>, the printhead is attached to the top plate portion <NUM> so that when the print head moves up and down along the z-axis, the top plate portion <NUM> also moves along the z-axis. During printing, the printhead <NUM> and top plate portion <NUM> can be lowered into position over the build surface <NUM> so as to be at a desired distance therefrom. As the 3D object <NUM> is printed, the printhead <NUM> can then be raised to deposit successive layers of the 3D object <NUM> on the build surface <NUM>. As the size of the 3D object <NUM> grows up from the build surface <NUM> during the printing process, the printhead <NUM> and top plate portion <NUM> can be incrementally raised to accommodate the increasing size of the 3D object <NUM>.

In an embodiment, the top plate portion <NUM> comprises a seal <NUM> (shows as line in <FIG>) disposed at the position where top plate portion <NUM> abuts the side portion <NUM>. The side portion <NUM> and bottom portion <NUM> can also be sealed. Employing such seals can aid in reducing or eliminating unwanted gases from entering the enclosure system, such as between the top plate portion <NUM> and side portion <NUM>, which can be useful for maintaining an inert gas atmosphere within the enclosure system <NUM>. In addition, the seal can allow the top plate portion <NUM> to slide up and down on the z-axis relative to the side portion <NUM>. The seal can comprise a gasket material that can withstand the build temperatures, such as NOMEX ®.

The side portion <NUM> and top plate portion <NUM> can be any suitable materials that can withstand the heat of the 3D print process without degrading while providing the desires structural stability and/or other desired properties, such as thermal insulation and/or air impermeability. Examples of suitable materials include metals, ceramics, glass and so forth. The materials for the top portion <NUM> can be the same or different as the side portion <NUM>. While the enclosure is shown to have a cubic shape, any desired shape can be employed, such as a cylindrical shape.

The bottom portion <NUM> comprises a heat shield <NUM> that extends from the build platform <NUM> and abuts the side portion <NUM>, as shown, for example, in <FIG>. As is well known in the art, the position of the build platform <NUM> is adjustable along the x-axis and the y-axis of an XY plane so as to allow the print material from the printhead to be deposited in a desired location on the build platform during printing. The heat shield <NUM> comprises an orifice that is configured to accept a movable object, such as the build platform <NUM>. The heat shield orifice is capable of two degrees of motion and is movable in any direction within the XY plane so as to match the lateral, angular and radial movements of the build platform <NUM> during printing. In comparative examples, a heat shield <NUM> is not employed, in which case the bottom portion <NUM> of the enclosure system <NUM> can be another surface, such as, for example, a base <NUM>.

The enclosure system <NUM> can include a closed-loop temperature control system for maintaining a desired temperature with the enclosed space. Such a closed loop system may comprise a temperature sensor and feedback loop for controlling the heat output of the heating system <NUM>. As shown in <FIG>, the enclosure system may also include a door <NUM> for providing access to the enclosure system <NUM>.

<FIG>, <FIG> illustrate a heat shield <NUM>, according to an embodiment of the present disclosure. As shown in <FIG>, heat shield <NUM> comprises two or more separate plates <NUM>, such as <NUM> to <NUM> plates, or <NUM> to <NUM> plates, or <NUM> to <NUM> plates. Each of the plates <NUM> comprise a central opening <NUM>. As shown in <FIG>, the plates <NUM> are stacked vertically so that the openings <NUM> align to form an orifice in the heat shield <NUM> through which the build platform <NUM> extends. The plates <NUM> are sized to avoid formation of gaps in the x or y direction between any of the plates regardless of the position of the orifice in the XY plane, thereby forming a continuous shield surrounding the orifice. Referring again to <FIG>, each of the plates <NUM> in the stack has one or more smaller dimensions than the plate <NUM> on which it is stacked, so as to allow the orifice and the build platform <NUM> to move together in any direction within the XY plane. For example, in the case where plates <NUM> are rectangular, as shown in <FIG>, dimensions x', y' of plate 52C will be smaller than x", y" of plate 52B, and x", y" will be smaller than x‴, y‴ of plate 52A. For other plate configurations, one or more of the dimensions of the plates <NUM> may be incrementally decreased with each successive plate. For example, where the plates <NUM> are circles, a diameter of the plates <NUM> may be decreased for each successive plate in the stack. In the case of polygons with <NUM> or more sides, the dimensions of one or more, such as all, of the sides may be decreased for each successive plate in the stack.

Further, the dimensions of each of the plates <NUM> will be large enough to effectively cover the opening <NUM> of the plate <NUM> that is directly below in the stack for the entire range of motion of the plates in the stack. As an example, the dimension x" of plate 52B can be equal to or greater than a width, Wox‴, of the opening <NUM> of plate 52A plus the width, Wps‴, of the side of plate 52A. That way, when the edge, EB1, of plate 52B is positioned all the way to the edge, EA1, of plate 52A, the opposite side B2 of plate 52B will overlap, or at least extend to, the far edge, EOB1 of opening <NUM> of plate 52A. In similar manner, a side of each of the plates <NUM> will cover the far edge of the opening <NUM> of the plate directly below in the stack during the entire range of motion of the stack.

Once stacked, the movement of the build platform <NUM> can force the plates <NUM> to slide relative to each other in any desired direction in the XY plane, such as by a telescoping motion of plates <NUM>. <FIG> illustrate a heat shield <NUM> comprising four sliding plates 52A to 52D that allows freedom of movement in the XY plane while providing protection for the drive systems of the three-dimensional printing system. The top plate 52D includes an orifice <NUM> which can be configured in any desires shape and size to attach to the build platform <NUM> (<FIG>). Bottom plate 52A is attached to the side portion <NUM> and can be held stationary thereby. Plates 52B, 52C and 52D slide relative to each other and to plate 52A when a force is applied by build platform <NUM>, thereby moving the orifice <NUM> from, for example, a first position as shown in <FIG> to a second position as shown in <FIG>. Motion in both the X and Y directions can be completed simultaneously, thereby allowing for complex two dimensional moves by the build platform <NUM>.

The plates are not physically connected in the stack, but are held together by gravity and supported by the bottom plate 52A, which is attached to the side portion <NUM> of the enclosure system and held stationary thereby. A gasket material for providing a seal and/or a lubricant, such as graphite or liquid lubricant, can optionally be disposed between the plates. The plates <NUM> can be made of any desired material that can withstand the processing temperatures, such as one or more materials chosen from ceramics, metals, such as steel, aluminum or other metals, or polymers, such as a high temperature polymer that can withstand temperatures of <NUM> or more, such as <NUM>, <NUM> or <NUM> or more without degrading.

The heat shield <NUM> can act to prevent the drive system for moving the build platform <NUM> from being exposed to high temperatures, which can potentially damage and/or reduce the life of the drive system. In comparative examples where a heat shield <NUM> is not used, high temperature drive systems can be used for moving the build platform <NUM> that are designed to withstand the build temperatures (e.g., temperatures ranging from about <NUM> to about <NUM>). Such high temperature drive systems are well known in the art.

In an embodiment, the heating system <NUM> comprises at least one heat source chosen from a radiant heating system, a conductive heating system and a convection heating system. A radiant heating system comprising infrared ("IR") lamps attached to a surface of the top plate portion <NUM> is illustrated as the heating system <NUM> in in <FIG>. An example of commercially available infrared lamps are nested, curved infrared heating tubes made by Noblelight Heraeus of Hanau, Germany. The IR heating tubes can have any suitable diameter, for example, an <NUM> diameter. Any other suitable type of radiant heating system can be employed, including radiant heating systems attached anywhere inside or outside of the enclosure so as to heat the build platform <NUM> and/or a three-dimensional object <NUM> to be built thereon. Any suitable convection heating system <NUM> (<FIG>) can be employed. For example, the convection heating system <NUM> can flow heated gas, such as an inert gas or air, through the enclosure so as to heat the build platform <NUM> and/or the three-dimensional object <NUM> to be built thereon. Any suitable inert gas can be used, such as argon or nitrogen. The use of inert gas can reduce unwanted reactions of oxygen with the metals, such as magnesium in an aluminum alloy, as an example. Any suitable conduction heating system <NUM> can be employed. For example, a conduction heating system <NUM> can include a system for heating the build platform <NUM>, such as by employing electric coils or other heating mechanisms within or proximate to the build platform <NUM>. Any other suitable techniques for heating the enclosure system <NUM> can be used in place of or in combination with the heating systems discussed herein. In an embodiment, two or more, such as all three, of the radiant heating system, convection heating system and conductive heating system can be employed.

According to the invention, the three-dimensional printing system <NUM> includes a printhead <NUM> that is configured for ejecting drops of a conductive liquid print material (e.g., molten aluminum or other liquid metals) onto the build platform <NUM>. The printhead comprises an electromagnetic coil for applying a DC pulse for ejecting the drops, as is described below. Printheads employing other suitable mechanisms for ejecting drops of conductive liquid print could also be used as printhead <NUM>.

<FIG> illustrates an example of a conductive liquid three-dimensional printing system, referred to herein as a liquid metal 3D printer <NUM>. Drops of liquid metal that are used to form a three-dimensional metal object are produced by a printhead <NUM> supported by a tower <NUM>. The printhead <NUM> is affixed to vertical z-axis tracks <NUM>a and <NUM>b and can be vertically adjusted, represented as movement along a z-axis, on tower <NUM>. Tower <NUM> is supported by a frame <NUM> manufactured, for example, from steel tubing or any other suitable material.

Proximate to frame <NUM> is a base <NUM>, formed of, for example, granite or other suitable material. Base <NUM> supports the base platform <NUM> upon which a 3D object is formed. Base platform <NUM> is supported by x-axis tracks <NUM>a and <NUM>b, which enable base platform <NUM> to move along an x-axis. X-axis tracks <NUM>a and <NUM>b are affixed to a stage <NUM>. Stage <NUM> is supported by y-axis tracks <NUM>a and <NUM>b, which enable stage <NUM> to move along a y-axis.

As drops of molten metal (e.g., molten aluminum or other suitable metal) <NUM> fall onto base platform <NUM>, the programmed horizontal movement of base platform <NUM> along the x and y axes results in the formation of a three-dimensional object. The programmed movement of stage <NUM> and base platform <NUM> along x-axis tracks <NUM>a and <NUM>b, and y-axis tracks <NUM>a and <NUM>b can be performed by means of, for example, an actuator <NUM>a and <NUM>b, as would be known to a person of ordinary skill in the art. The actuators 122a and 122b and tracks make up a drive system for the build platform <NUM>. The drive system may or may not be high temperature system as described above. Liquid metal 3D printer <NUM> was designed to be operated in a vertical orientation but other orientations could also be employed.

<FIG> also shows a source of aluminum <NUM> and aluminum wire <NUM>. Alternative embodiments may utilize aluminum in bar, rod, granular or additional forms. In alternative embodiments, any sufficiently conductive liquid or colloidal mixture could be used in place of aluminum with the proper adjustments to the system, as would be understood by one of ordinary skill in the art. The term aluminum as used herein is defined to include both pure aluminum and aluminum alloys, such as, for example, the <NUM> series (e.g., <NUM>), <NUM> series, <NUM> series, <NUM> series (e.g., <NUM>), <NUM> series, <NUM> series (e.g., <NUM>), <NUM> (e.g., <NUM>) series and <NUM> series of alloys, or any other aluminum alloys suitable for 3D printing. Pure aluminum is defined as being <NUM>% by weight aluminum or higher, such as about <NUM>% by weight to about <NUM>% aluminum, and includes, for example, the <NUM> series of aluminum.

Printhead <NUM> includes a nozzle pump <NUM>. Liquid metal 3D printer <NUM> and the method of operating the printer are described in greater detail in <CIT>.

<FIG> illustrates a cross-sectional view of a portion of printhead <NUM>, which includes a cooled wire inlet <NUM>, an outer sleeve <NUM>, and the nozzle pump <NUM> enclosed by an electromagnetic coil <NUM>. In an embodiment, aluminum wire <NUM> is fed into cooled wire inlet <NUM> and a wire guide and gas seal <NUM> made of copper. The aluminum wire <NUM> then passes through an insulating coupler <NUM>, made, for example, of Macor ceramic, where inert gas <NUM> is supplied through the melt shield gas inlet port <NUM>, also made of, for example, Macor ceramic, to apply a protective inert gas <NUM> shield before the aluminum is melted.

Melted aluminum, or other electrically conductive liquid, flows downward under gravity and positive pressure exerted by inert gas <NUM> along a longitudinal z-axis to nozzle pump <NUM>. Electrical heating elements 620a and 620b, made of, for example, nichrome, heat the interior of a furnace <NUM>, made of, for example, firebrick, to a desired temperature (e.g., above the <NUM>° C, which is the melting point of aluminum). The thermally conductive tundish <NUM> transmits heat to aluminum wire <NUM>, as supplied from a source of aluminum <NUM>, causing it to melt as it enters nozzle pump <NUM>. Tundish <NUM> can comprise, for example, boron nitride or other suitable thermally conductive material.

The molten aluminum flows downward to form a charge of molten aluminum <NUM>. Charge of molten aluminum <NUM> is contained primarily within a pump chamber of nozzle pump <NUM>. Electromagnetic coil <NUM> is shaped to surround nozzle pump <NUM>. The pressure on the inert gas <NUM> inside nozzle pump <NUM> is adjusted to overcome surface tension at the nozzle <NUM> in order to form a convex meniscus (not shown). This pressure is determined by Young's law as P=<NUM>×surface tension/orifice radius of the nozzle <NUM>.

The electromagnetic coil <NUM> are shaped around nozzle pump <NUM> in such a way as to focus magnetic field lines vertically through the charge of molten aluminum <NUM>. Nozzle pump <NUM> is transparent to the magnetic field. The electromagnetic coil <NUM> applies forces to the charge of molten aluminum <NUM> to pump liquid metal based on the principles of magnetohydrodynamics. A step function direct current (DC) voltage profile applied to the electromagnetic coil <NUM> causes a rapidly increasing applied current to electromagnetic coil <NUM>, thereby creating an increasing magnetic field that follows magnetic field lines. The optimal range of voltage for the pulse and current strength, as well as the range of time durations for the pulse, for effective operation vary depending on the electrical resistivity of the fluid, viscosity and surface tension. The possible effective range is wide, where alternative embodiments could optimally range from <NUM> to <NUM> volts (V) and <NUM> to <NUM> amperes (A).

According to Faraday's law of induction, the increasing magnetic field causes an electromotive force within the pump chamber, which in turn causes an induced current in molten aluminum <NUM> to flow along circular paths through the charge of molten aluminum <NUM>. The induced current in molten aluminum <NUM> and the magnetic field produce a resulting radially inward force on molten aluminum, known as a Lorenz force, in a ring shaped element through the charge of molten aluminum <NUM>. The radially inward force on molten aluminum is proportional to the square of the DC voltage applied.

A peak pressure occurring at the inlet to the nozzle <NUM> is also proportional to the square of the DC voltage applied. This pressure overcomes surface tension and inertia in the molten aluminum to expel the drop of molten aluminum. At the same time, a computer causes stage <NUM> to move to deposit the drop of molten aluminum in the desired location on base platform <NUM> (e.g., on the 3D object being printed).

An embodiment of the present disclosure is directed to a method of three-dimensional printing. The method comprises enclosing a build surface of a build platform in an enclosure system, such as any of the enclosure systems described herein. The enclosure system has a side portion extending entirely around the build surface, a top plate portion that abuts the side portion, and a bottom portion. The side portion, the top plate portion and the bottom portion form an enclosed space surrounding the build surface. The top plate portion is moveable so as to adjust a volume of the enclosed space. The build surface is heated in the enclosed space. A print material is deposited onto the build surface using a 3D printer printhead to form a 3D object. The method comprises depositing the print material, such as by, for example, ejecting a first drop of a molten metal from the printhead so as to deposit the first drop on a preheated drop contact point at a first deposition temperature, as described herein above. The method further comprises adjusting the position of the top plate portion and the printhead along a z-axis. The method further comprises adjusting the position of the build surface along an x-axis, a y-axis or both the x-axis and the y-axis. An orifice of a heat shield, as described herein, can move within the XY plane so as to match one or more of the build platform lateral, angular and radial movements.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein.

While the present teachings have been illustrated with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from scope of the appended claims. In addition, while a particular feature of the present teachings may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms "including," "includes," "having," "has," "with," or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term "comprising. " Further, in the discussion and claims herein, the term "about" indicates that the value listed may be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the illustrated embodiment. Finally, "exemplary" indicates the description is used as an example, rather than implying that it is an ideal.

Claim 1:
A three-dimensional printing system (<NUM>), the system comprising:
a build platform (<NUM>) comprising a build surface (<NUM>);
an enclosure system (<NUM>) having a side portion (<NUM>) extending entirely around the build surface (<NUM>), a top plate portion (<NUM>) that abuts the side portion (<NUM>), and a bottom portion (<NUM>), the side portion (<NUM>), the top plate portion (<NUM>) and the bottom portion (<NUM>) forming an enclosed space surrounding the build surface (<NUM>), the top plate portion (<NUM>) being moveable so as to adjust a volume of the enclosed space;
the bottom portion (<NUM>) comprising a heat shield (<NUM>) that extends from the build platform (<NUM>) and abuts the side portion (<NUM>);
a 3D printer printhead (<NUM>) disposed adjacent to the enclosure system (<NUM>) for depositing a print material onto the build surface (<NUM>), wherein the printhead (<NUM>) is configured for ejecting drops of a conductive liquid print material onto the build platform (<NUM>); and
a heating system (<NUM>) for heating the enclosed space.