Patent Description:
Additive manufacturing, including three dimensional (3D) printing, has constituted a very significant advance in the development of not only printing technologies, but also of product research and development capabilities, prototyping capabilities, and experimental capabilities, by way of example. Of available additive manufacturing (collectively "3D printing") technologies, fused deposition of material ("FDM") printing is one of the most significant types of 3D printing that has been developed.

FDM is an additive manufacturing technology that allows for the creation of 3D elements on a layer-by-layer basis, starting with the base, or bottom, layer of a printed element and printing to the top, or last, layer by heating and extruding thermoplastic filaments into the successive layers. To achieve these results, an FDM system includes at least a print head from which the thermoplastic print filament is fed to a FDM printer nozzle, an X-Y planar control form moving the print head in the X-Y plane, and a print platform upon which the base is printed and which moves in the Z-axis as successive layers are printed.

The FDM printer nozzle heats the thermoplastic print filament received from the print head to a semi-liquid state, and deposits the semi-liquid thermoplastic in variably sized beads along the X-Y planar extrusion path plan provided for the building of each successive layer of the element. The printed bead/trace size may vary based on the part, or aspect of the part, that is being printed. Further, if structural support for an aspect of a part is needed, the trace printed by the FDM printer may include removable material to act as a sort of scaffolding to support the aspect of the part for which support is needed. Accordingly, FDM may be used to build simple or complex geometries for experimental or functional parts, such as for use in prototyping, low volume production, manufacturing aids, and the like in a fraction of the time it would take to manufacture such object using conventional methods.

However, the use of FDM in broader applications, such as medium to high volume production, is severely limited due to a number of factors affecting FDM, and in particular affecting the printing speed, quality, and efficiency for the FDM process. As referenced, in FDM printing it is typical that a thermoplastic filament is heated to a molten state and then squeezed outwardly from the FDM printing nozzle onto either a print plate/platform or a previous layer of the part being produced. The FDM printer nozzle is moved about by the robotic X-Y planar adjustment of the print head in accordance with a pre-entered geometry, such as may be entered into a processor to control FDM printing head movements to form the part desired.

Because of the advances in robotics and high available processing speed, the "choke point" for the FDM printing process is generally the FDM printer nozzle itself. In particular, control over the speed of heating and cooling of the FDM printer nozzle, and in particular refinements in the control and start/stop timing of printing provided by advanced control of heating and cooling of the nozzle, would allow for significant improvements in the printing provided by FDM technologies, but are not presently contemplated in the known art. Accordingly, the ability to provide refined control and sensing of various aspects associated with FDM printing, such as heating and cooling of the print material, pressure on and liquid state of the print material, and the like, would allow for refinement of and improvement to the FDM process.

Notwithstanding the foregoing, currently available nozzles, for the most part, are metallic, and thus conductive, in nature, and have associated therewith a large heating block (such as may include a thermocouple for heating of the nozzle associated therewith) with a significant thermal mass. Thus, because of the large thermal mass of the heating block, refined control of heating and cooling of the nozzle is currently limited due to the permeation of heat to undesired aspects of the metallic nozzle. In addition, current nozzle designs make it difficult to focus heat to areas of the nozzle because of the typically conductive nature of the nozzle, and the slowness of heating and cooling of the nozzle caused by the large thermal mass of the heating block associated with the nozzle from which the control for the heating (and cooling) is provided.

Accordingly, current nozzle designs suffer from significant issues which impede the ability to improve the FDM printing process. A principal one of these impediments is the inability to provide refined control of heating and cooling on the printing nozzle or on particular aspects thereof. Lack of heating and cooling control may cause, for example, inconsistent melting of the thermoplastic material which may lead to low print speeds and nozzle clogging. Lack of cooling control may cause blobs, nipples or mis-printing to occur due to inability to quickly and accurately control the temperature of the nozzle.

Therefore, the need exists for an FDM additive manufacturing nozzle having refined print control and enhanced printing speed.

Conventional 3D printer nozzles comprising a heating element are disclosed in <CIT> and <CIT>.

The disclosed exemplary apparatuses, systems and methods provide at least heat delivery to enable an FDM printer nozzle for additive manufacturing having refined print control and enhanced printing speed. The heating delivery element includes at least one sheath sized to fittedly engage around an outer circumference of the FDM printer nozzle; at least two nichrome wire coils at least one of which is at least partially partially contacting an inner diameter of the sheath; and at least one energy receiver associated with the at least two nichrome wire coils to increase the efficiency of the FDM printer nozzle.

The at least two wire coils may be at least partially staggered along a longitudinal axis of the FDM printing nozzle. The at least two wire coils may be respectively embedded in at least two sheaths. The at least two sheaths may be concentrically about one another.

Thus, the disclosed embodiments provide a FDM printer nozzle for additive manufacturing having refined temperature control, print control and enhanced printing speed.

The disclosed non-limiting embodiments are discussed in relation to the drawings appended hereto and forming part hereof, wherein like numerals indicate like elements, and in which:.

The figures and descriptions provided herein may have been simplified to illustrate aspects that are relevant for a clear understanding of the herein described apparatuses, systems, and methods, while eliminating, for the purpose of clarity, other aspects that may be found in typical similar devices, systems, and methods. Those of ordinary skill may thus recognize that other elements and/or operations may be desirable and/or necessary to implement the devices, systems, and methods described herein. But because such elements and operations are known in the art, and because they do not facilitate a better understanding of the present invention, for the sake of brevity a discussion of such elements and operations may not be provided herein.

For example, as used herein, the singular forms "a", "an" and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The steps, processes, and operations described herein are not to be construed as necessarily requiring their respective performance in the particular order discussed or illustrated, unless specifically identified as a preferred or required order of performance. It is also to be understood that additional or alternative steps may be employed, in place of or in conjunction with the disclosed aspects.

When an element or layer is referred to as being "on", "engaged to", "connected to" or "coupled to" another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present, unless clearly indicated otherwise. Further, as used herein the term "and/or" includes any and all combinations of one or more of the associated listed items.

Yet further, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the embodiments.

Aspects of the embodiments may provide real time localization, control and targeting of nozzle heating, such as FDM nozzle heating, such as to create improved print control to allow for higher print speed and greater print accuracy. These and other distinct advantages may be provided in accordance with the provided improvements over the known art, such advantages including lower nozzle costs and print costs; provision of the print nozzle as a consumable/disposable good; suitability for nozzle production using known semiconductor and foundry technologies; enhanced design freedom for internal and external nozzle features; and extremely fine control of hot and cold zones for both the nozzle and the printed material.

The disclosed improved printer nozzle may be applied to any type of 3D printing, such as FDM printing that uses thermoplastics, polymers, metals, ceramics, food, and wax printing, by way of non-limiting examples as the print material. More particularly, additive manufacturing can occur via any of various known methods, including the aforementioned FDM printing. By way of example, sintering of powders may be performed in order to additively build layers. Further, for example, resin-based additive printing may be performed.

With regard particularly to FDM printing, current methods are generally fairly slow and inefficient for additive manufacturing, and are presently limited in the number of materials that may be printed. This is in large measure due to the inadequacies of known devices, systems and methods for heating the printer nozzle in FDM systems. Heating elements for additive manufacturing in the disclosed embodiments and equivalents thereto may rectify these inadequacies of known FDM systems.

More particularly, although the disclosed exemplary embodiments may heat and push material for "3D," such as FDM, printing as is known in the art, they also provide refined heating and refined pushing of that material, such as through improved localization of heating. Heating of the print material in an FDM process is the single most important factor in refining FDM printing, and while fast printing is desirable to enhance available FDM printing processes, faster printing speeds require increased heating, and increased heating leads to less refined control over the heating area for known nozzles, such as the presently available metal nozzles that are used in conjunction with large heating blocks. These known heating blocks and nozzles, in combination, also present extreme difficulties in providing the expedient cooling necessary to stop printing, particularly in highly heat-conductive metal nozzles, which expedient cooling is necessary for refined heating control to allow for highspeed FDM printing.

In short, the high speed, high quality FDM printing provided in certain of the embodiments requires the transfer of as much controllable energy to the print material as is possible, at the greatest mass flow rate, to thereby allow for the desired increased printing speeds. Accordingly, the refined heating systems and methodologies disclosed herein improve print speed and control in FDM printers.

That is, aspects of the disclosed embodiments may be employed on a nonconductive or a conductive, such as a metal, nozzle. For example, dielectric layer(s), such as glass, may be deposited, such as via vacuum deposition, CVD, PVD, or sputtering, onto a metal nozzle, thereby providing an intermediate dielectric substrate onto which conductive layers and/or coils may be placed.

For example, the disclosed embodiments thereto may help to prevent nozzle clogging More specifically, one of the main dynamics that promotes clogging in the known art is that a traditional nozzle must be run at a significant temperature-rise over the melting point of the thermoplastic. Once the print material flow is stopped, the print material and the (over)heated nozzle then come to equilibrium, which causes the print material to approach the nozzle temperature in the current art. This degrades the print material, making it brittle and thereby causing clogging. In certain of the disclosed embodiments, the providing of `slow' and 'fast,' such as zoned, heating allows for the use of the `slow' mode to maintain the nozzle inner temperature below the degradation temperature of the print material, and use of the 'fast' mode may be used only at flow condition. Thus, when the print material flow stops in the disclosed embodiments, the 'fast' mode may be turned off quickly, thus preventing a temperature rise above degradation temperature.

<FIG> is a block diagram illustrating an exemplary FDM printer <NUM>. In the illustration, the FDM printer <NUM> includes an X-Y axis driver <NUM> suitable to move the print head <NUM>, and thus the print nozzle <NUM>, in a two dimensional plane, i.e., along the X and Y axes. Further included in the FDM printer <NUM> for additive manufacturing are the aforementioned print head <NUM> and print nozzle <NUM>. As is evident from <FIG>, printing may occur upon the flow of heated print material outwardly from the nozzle <NUM> along a Z axis with respect to the X-Y planar movement of the X-Y driver <NUM>. Thereby, layers of printed material <NUM> may be provided from the nozzle <NUM> onto a build plate <NUM> along a path dictated by the X-Y driver <NUM>.

<FIG> illustrates with greater particularity a print head <NUM> and nozzle <NUM> system for an additive manufacturing device, such as a FDM printer. As illustrated, the print material <NUM> is extruded via the print head <NUM> from a spool of print material 110a into and through the nozzle <NUM>. As the nozzle <NUM> heats the print material <NUM>, the print material <NUM> is at least partially liquefied for output from an end port 106a of the nozzle <NUM> at a point distal from the print head <NUM>. Thereby, the extruded print material <NUM> is "printed" outwardly from the port 106a via the Z axis along a X-Y planar path determined by the X-Y driver <NUM> (see <FIG>) connectively associated with the print head <NUM>.

<FIG> illustrates an exemplary nozzle <NUM>. The nozzle <NUM> may be, for example, constituted of steel, ceramic, glass, or of any other suitable material to achieve the desired thermal properties. For example, a glass nozzle may reduce local thermal capacity. For example, Cp*rho*V for glass = <NUM>*<NUM>*<NUM> = <NUM>. 0825J/C, but for steel, the same calculation yields <NUM>*<NUM>*<NUM> = <NUM>. 1794J/C, which represents more than twice the joules needed, for heating or cooling, for a steel nozzle per degree Celsius as is needed by the glass nozzle.

For heating of the nozzle <NUM>, the nozzle <NUM> is wrapped in one or more wire windings <NUM>. The nozzle <NUM> includes at least one sheath <NUM> about nozzle <NUM>. The nozzle <NUM> may also include an additional layer or multiple layers between the wire winding <NUM> and the nozzle <NUM> outer diameter, and/or between the sheath <NUM> (where present) and the windings <NUM>, such as in order to enhance thermal coupling, redistribute heat, insulate from overheating, or the like.

The sheath <NUM> may about the nozzle <NUM> as referenced, and may be over, underneath, or have embedded therein wire windings <NUM>. The sheath <NUM> may be press fit, plasma vapor deposited or plated, rolled foil, or the like in its application to the shank of the nozzle <NUM>. In the illustration of <FIG> and by way of non-limiting example, the sheath <NUM> encompasses the one or more coils <NUM>.

By way of non-limiting example, the nozzle <NUM> may comprise a shank 106b and port tip 106a, comprised of steel, having at least partially thereabout the one or more wire windings <NUM>, such as nichrome wire windings wrapped thereabout, wherein the windings <NUM> may be at least partially enclosed within sheath <NUM>. The wire winding <NUM> may serve as a heating coil to heat the print material <NUM> within the inner diameter of the nozzle <NUM>. Of note, the delivery of heat by the heating coil <NUM> may change the resistance of the heating coil <NUM>. Accordingly, the resistance change in the heating coil <NUM> maybe sensed in order to assess the level of heating being delivered to the nozzle <NUM>. Further, the sheath <NUM> may be employed to refocus the heat from coil <NUM> back into nozzle <NUM>.

The coil <NUM> and/or multiple coil aspects or coils, and the proximity of those coils <NUM> to the nozzle <NUM> such as in conjunction with the small thermal mass of sheath <NUM>, may allow for highly refined and targeted control of heat delivered to the print material printed through the nozzle106. This may allow for expedited heating and cooling, such as near-immediate heat up and cool down/shut off, which provides the pushing of much more significant an amount of print material <NUM> through the nozzle port 106a than can be pushed in the known art.

More specifically, the speed and amount of print material <NUM> exiting the hot end of the nozzle <NUM> at port 106a may be determined by a variety of factors. Such factors may include, by way of non-limiting example, the material printed, the extrusion rate, the rate of motion of the X-Y driver, and the heat applied to the extrusion material. The latter factor, i.e., the heat applied to the extrusion material, may be selectively employed in certain of the embodiments, such as using windings <NUM>, in order to obtain substantially optimal and efficient printing in light of others of the aforementioned print factors.

<FIG> and <FIG> illustrate the comparison of a prior art nozzle (shown in <FIG>) to an exemplary resistive hot end <NUM> according to the embodiments, such as may be comprised of the nozzle <NUM>, windings <NUM>, and/or sheath <NUM> as shown in <FIG>. More particularly, the comparison of <FIG> is illustrative of the differences, such as the significant difference in thermal mass, between the prior art heating block <NUM> of <FIG>, and the combination of the sheath <NUM> and windings <NUM> of the hot end <NUM> of <FIG>.

As shown in <FIG>, the current art includes a large heating block <NUM> which integrates a heating cartridge <NUM> and a thermocouple <NUM>, each of which are plugged into the heating block <NUM>. Upon actuation of thermocouple <NUM>, the heating block <NUM> begins to heat, and passes the heat through the heating block <NUM> to the so-called "hot end" of the nozzle, which in turn heats the print material <NUM> within that portion of the nozzle <NUM> receiving the delivered heat just above the distal tip of the nozzle <NUM>. As shown, the nozzle <NUM> threads into or otherwise connectively integrates with the heating block <NUM>.

In sum, the foregoing forms a "hot end" having a significant thermal mass in the known art. This thermal mass corresponds to a characteristic thermal momentum, which carries with it a particular heating and cooling ramp rate. Because of this ramp rate, the heating block of the known art can neither be turned on nor off quickly and efficiently, thereby causing bumps and nipples in the printed material path, as well as nozzle bleeding and clogging.

In stark contrast to the known art and as illustrated in <FIG>, the thermal mass of the disclosed embodiments for hot end <NUM> is significantly reduced over the thermal mass provided by the known art. Accordingly, the disclosed embodiments of the hot end <NUM> heat more expediently than the known art, and cool more expediently than the known art. That is, the minimal thermal capacity provided by certain of the disclosed embodiments of the hot end <NUM> provides a lower temperature capacity than the known art, and consequently is appreciably more responsive to application of or removal of energy to the hot end <NUM>.

In certain of the embodiments and in order to optimize the foregoing lower temperature capacity over the known art, the winding or windings <NUM> may vary by type, length, and/or actuation timing and manner in accordance with the location of the windings <NUM> along the geometry of the hot end <NUM>. For example, high density windings may be put at the nozzle taper approaching the port 106a in order to provide maximum heat and maximum heating control at the exit port 106a for the print material.

Additionally, although the example illustrated in <FIG> may include a heating block, such as in the form of sheath <NUM>, which may include a thermocouple, the skilled artisan will appreciate that such a heating block may or may not be present with the heating methodologies provided throughout, by way of non-limiting example. That is, windings <NUM> may reside directly on nozzle <NUM>, such as being wet wound thereon, may have one or more layers between windings <NUM> and nozzle <NUM>. In addition, the windings <NUM> may or may not be surrounded by sheath <NUM>.

The embodiment illustrated in <FIG> and other like embodiments may thus allow for faster ramping of heat application to the extruded print material, and may allow for shutoff of extrusion of the print material at a notably faster rate, than in the known art. This is due, in part, to the refined control provided by the wire winding <NUM> about the nozzle, and the improved thermal coupling thus provided between the heat available from the wire winding <NUM> and the print material <NUM> within the nozzle <NUM>. It should be noted that thermal mass concerns may also be addressed by control software, and, in an exemplary embodiment, a servo drive, such as a <NUM> servo drive, that at least partially provides energy to the wire winding <NUM>.

Different power formats may be employed to provide heating energy to the wire winding <NUM> in certain of the embodiments. For example, as illustrated in <FIG>, certain power sources <NUM> may be matched with particularity to certain types of wire windings <NUM>, certain types of nozzles <NUM>, and so on. By way of example, Newtonian heating, i.e., providing current to the wire winding to generate heat, may be performed in conjunction with any of various types of nozzles and/or with various types of wire windings <NUM>, such as the wire windings <NUM> embedded in sheath <NUM> of <FIG>. Other energy types <NUM> may be employed to provide thermal excitation to the wire windings <NUM>, such as irradiation, radio frequency excitation, ultrasonics, microwaves, or any other power provision techniques understood to the skilled artisan. Moreover and as referenced above, certain types of power sources <NUM> may be specifically matched to certain types of wire windings <NUM> and nozzles <NUM>, such as wherein infrared excitation may be employed with a glass nozzle for improved thermal coupling and ramp time, or such as wherein the wire winding comprises a bulk element rather than individual windings.

In additional alternative and exemplary embodiments, such as that illustrated in <FIG>, a distinct wire winding may not be provided as wire winding <NUM>, but rather distinct characteristics may be provided around or embedded in nozzle <NUM> to serve effectively as windings <NUM>, as that term is used herein. By way of example, the sheath <NUM> may be provided about the nozzle <NUM> to provide thermal coupling to a particular heating source, such as to receive microwave energy for heating. That is, the sheath <NUM> may be embedded or otherwise formed with characteristic materials that are thermally excited by bombardment using microwaves, which will thereby allow the sheath <NUM> to impart heat directly to the nozzle <NUM>.

Of course, the wire windings or like heating elements <NUM>, rather than being wound onto or otherwise directly applied to nozzle <NUM>, may reside within sheath <NUM> separate and apart from nozzle <NUM>. The providing of the sheath <NUM> as a secondary physical element from nozzle <NUM> but as a primary thermal coupling thereto allows for fitting of the thermal coupling element onto a nozzle <NUM> after creation of the nozzle <NUM>, i.e., sheath <NUM> having therein windings <NUM> or the equivalent thereof may be provided as a "bolt on," post-manufacture component to the nozzle <NUM>.

By way of non-limiting example, the windings <NUM> may take the form of bulk element <NUM>, as shown in <FIG>. This bulk element may be subject to structure <NUM> that is also embedded within sheath <NUM>, such as to maintain the bulk element <NUM> at a given distance from nozzle <NUM> so as to maintain a certain level of heating. Moreover, sheath <NUM> may include, for example, an embedded reflective cavity <NUM>, such as to redirect heat from element <NUM> back toward nozzle <NUM> for optimized heating.

<FIG> illustrates with particularity an exemplary nozzle <NUM> having a thermal coupling element <NUM>. In the illustration, the thermal coupling element <NUM> is included in a sheath <NUM>, and also includes, embedded therein, a resistive wire wrapping <NUM>. As such, an electric current may be "plugged into" sheath <NUM> to resistively and thermally excite the sheath <NUM>, thereby causing element <NUM> to heat the print material <NUM> within the nozzle <NUM> at locations adjacent to the element <NUM>.

More particularly, the windings <NUM> may thus be provided on the nozzle <NUM>, in a ring/sheath around the nozzle <NUM>, or at both positions, by way of non-limiting example, such as to provide convection, conduction, and/or radiative heating focused on the nozzle <NUM> and the printing material <NUM> therein. By way of example, wire winding <NUM> may be of nichrome resistance wire as mentioned above, and may use ceramic (silicate) adhesive. Moreover and as referenced herein, various insulators, such as glass fabric, may be included on-board the nozzle as a shield from the winding <NUM> or sheath <NUM>, or as a shield between the winding <NUM> and the sheath <NUM>, or between the winding <NUM> or sheath <NUM> and the external environment. Such insulators may also include reflectors, by way of non-limiting example, and may thus be used on the inner diameter of the sheath <NUM> to redirect heat back toward nozzle <NUM>. By way of particular example, an exterior surface or surfaces, either integrated on-nozzle or as a separate sheath, may be highly-reflective such that, for IR power is produced at the nozzle <NUM>, that IR power that would otherwise be lost is redirected back into the nozzle <NUM> by the insulating layer.

By way of further example, a direct-wind onto the nozzle <NUM> of a coil <NUM>, such as of nichrome wire, may be solidified with the aforementioned silicate adhesive, whether or not further structurally supported by placement of a surrounding sheath <NUM>. Moreover, multiple layers may be wound onto the nozzle to form windings <NUM>, and may be separated by a thin layer of glass fabric, which may also provide additional strength and stability. Yet further, matrix material around the heating elements <NUM>, whether or not heating elements <NUM> are embedded in a sheath <NUM>, such as the silicate adhesive above, may be colored, such as with black, to increase emissivity, thereby increasing IR emission power. Of note, although a fast heating method, IR generally has little heating capacity, and hence may be best used to provide modulation of flow unless enhanced in the manners discussed herein, i.e., using increased emissivity and/or physical separation from the nozzle inner diameter to allow maximum IR power delivery.

In embodiments, the length of the sheath <NUM> may be varied, as may be the relative length of the nozzle <NUM>. Variations in nozzle length may accommodate different elements <NUM>, such as to allow for different elements <NUM> to serve different purposes, such to allow for the most efficient heating of particular print materials. By way of non-limiting example, a nozzle <NUM> in the embodiments may be longer than in the known art, and includes a particular taper at the nozzle tip 106a, such as to enhance the heating properties of heating elements <NUM> that may be employed, particularly such as to improve the temperature gradient provided by the element <NUM> to the nozzle <NUM> to correspondingly enhance the maximum feed rate of the particular print material <NUM> in the nozzle <NUM>.

As was mentioned above in relation to measuring heat delivered based on resistance (or other electrical characteristic) change in winding <NUM>, the characteristics of element <NUM>, such as the resistance or conductance thereof, may be readily sensed in order to assess the heat being delivered to nozzle <NUM>. More particularly, element <NUM> and/or sheath <NUM> may be provided with sensors <NUM> that are embedded in or otherwise associated with sheath <NUM>. The data related to changes in, for example, the resistance or conductance of sheath <NUM> may then be directly or indirectly indicative of the temperature of the element <NUM> at the measured point or points, thereby allowing for very precise temperature sensing and control at the nozzle tip 106a.

More particularly, a sensor <NUM> may be embedded in or on, or otherwise physically associated with, a sheath <NUM> placed around a print nozzle <NUM>. The sheath <NUM> may include therewithin a heating coil <NUM>. Thus, the sensor <NUM> may receive, directly or indirectly, a heat reading of the heat delivered by the heating coil <NUM> to nozzle <NUM>. In addition to sensor <NUM> as shown, the sensor may comprise embedded traces or other inter- or intra-connective elements, as will be understood to the skilled artisan.

In additional and alternative embodiments, a thermocouple (not shown) may also be included in the sheath <NUM> provided around the nozzle <NUM>, as may be one or more expedited cooling mechanisms. For example, <FIG> illustrates, by way of non-limiting example, a cooling tube <NUM>, wherein a small amount of air (or another gas) forced into the tube <NUM> or being vented from the tube <NUM> may increase or decrease the rate of which heat delivered to the nozzle <NUM>. The cooling tube <NUM> may include one or more valves (not shown) to allow for limitations on air or other gases released or received. Moreover, other cooling methodologies may be employed using the tube <NUM>. By way of example, inlet and outlet tubes maybe provided to enable a closed looped cooling system, such as wherein cooling liquid or gas, such as water or air, may be circulated into one tube and out of the other.

Experientially, a <NUM>-up <NUM> nichrome wire winding with L~=<NUM> gives ~<NUM>. 6ohms and an <NUM>. 3ohm swing over a 250C swing in <NUM> PLA inside of a 7mmOD/3mmID glass tube, with a resistance per temperature gain of <NUM> ohms/C. Higher gain may be achieved by increasing the nominal coil resistance, although that also requires higher voltage. Accordingly, in the embodiments, temperature may be discerned based on amperage-that is, temperature measurement of the coil may be tracked based on coil resistance. Of course, on-board thermocouples, RTDs, or other contact-sensing technologies, and/or optical sensing technologies, to assess heating may be employed as sensor(s) <NUM> in embodiments.

<FIG> illustrates that nozzle <NUM> heating may be provided in one or several "zones" or "phases". For example, provided may be a first heating zone <NUM> for heating the length of the print material melt <NUM> within nozzle <NUM>; a second heating zone <NUM> for "high speed" melts, such as may necessitate added power for taller melts; and a third heating zone <NUM> specifically for the nozzle tip 106a, at which point the highest power density is needed for the melt exiting port 106a into the pattern. Moreover, the zones <NUM>, <NUM>, <NUM> may be provided by providing overlapping windings 204a, 204b, 204c, and/or by providing one or more concentric or staggered sheaths 202a, 202b, 202c that each include discrete windings. Alternatively, one or more staggered or concentric sheaths may be provided over multiple overlapped zone windings, i.e., the layers may comprise winding <NUM>, winding <NUM>, then sheath <NUM>; or may be concentrically provided successively over each winding, i.e., the layers may comprise winding <NUM>, sheath <NUM>, winding <NUM>, sheath <NUM>, etc..

In short, multiple zones of coils with differing power densities allows for the presentation of different levels of power to different areas of the melt. Of note, the multiple resistors of the multiple coil zones may share one common leg, thus reducing the number of wires coming off the heater.

As discussed throughout, for optimal control and power expenditure impact, it may be desirable to use direct resistive heating (and cooling) as close as is practicable to the print material within the nozzle. Accordingly, the heating element may be a winding, a sheet material or bulk material (collectively "winding" throughout, unless otherwise indicated) highly adjacent to the print material within the nozzle.

Claim 1:
A 3D printer nozzle (<NUM>) comprising a heating element, the heating element comprising:
a first sheath (<NUM>) comprising a first inner diameter and a first outer diameter, the first sheath (<NUM>) sized to engage around an outer circumference of the 3D printer nozzle (<NUM>);
at least two nichrome wire coils, at least one of which is at least partially contacting the first inner diameter of the first sheath (<NUM>); and
at least one energy receiver (<NUM>) associated with the at least two nichrome wire coils,
whereby the at least two nichrome wire coils comprise a high density winding at a taper portion of the 3D printer nozzle (<NUM>) at an exit port (106a) and a lower density winding along a non-taper portion of the 3d printer nozzle (<NUM>).