Equipment and methods for 3D printing

Abstract

A 3D printhead including: (a) a print nozzle with a variable aperture size; and (b) a mechanism that adjusts the aperture size. Related hardware and methods are also disclosed.

Description

[0001] TITLE: EQUIPM ENT AND M ETHODS FOR 3D PRINTING

[0002] CROSS REFERENCE TO RELATED APPLICATIONS:

[0003] This PCT application claims the benefit according to 35 U.SC. § 119(e) of USprovisional patent application 63 / 508,269 filed on 15 / Jun / 2023 and having the same title and inventors as the present application; which is fully incorporated herein by reference.

[0004] FIELD OF THE INVENTION

[0005] The invention is in the field of 3D printing

[0006] BACKGROUND OF THE INVENTION

[0007] There are three main types of 3D printing (also known as additive manufacturing): stereolithography (SLA); selective laser sintering (SLS) and fused deposition modeling (FDM ). Although FDM was invented last it has become the leading method of 3D printing, accounting for 46% of the 3D printing market as of 2018. FDM is also referred to as Fused Filament Fabrication (FFF).

[0008] FDM employs a continuous filament (typically thermoplastic polymer but sometimes metal) fed from a spool to a moving extruder which serves as a print head. The extruder includes a heating element to soften the filament to facilitate extrusion through a nozzle. Drops of softened filament are successively deposited at desired locations under the control of a computerized controller operating mechanical elements that move the print head relative to a work surface (or the work surface relative to the print head). Upon completion of one layer, the controller moves the print head up (or the work surface down) by a small increment and provides instructions for deposition of a next layer on the previous layer, giving rise to the term additive manufacturing.

[0009] The initial input for the computerized controller is typically an STL file (stereolithography file format) file generated by a CAD program. STL stores data based on triangulations of the surface of CAD models. Additive M anufacturing File format (AM F) is a newer CAD file format more suitable for 3D printing which stores information using curved triangulations.

[0010] Typically an STLfile is processed by "slicer" software to convert the model into a series of thin layers. The slicer software outputs a G-code file containing instructions tailored to FDM printers. G code serves as the input for 3D printing client software (used by the controller to instruct the print head during the printing process).

[0011] Printer resolution describes layer thickness and X-Y resolution in dots per inch (dpi) or micrometers (pm). Typical layer thickness is in the range of 100 pm (250 DPI) to 16 pm (1 ,600 DPI). X-Y resolution is as good as that of laser printers. The particles (3D dots) are around 50 to 100 pm (510 to 250 DPI) in diameter. For that printer resolution, specifying a mesh resolution of 0.01-0.03 mm and a chord length < 0.016 mm generate an optimal STL output file for a given model input file.

[0012] SUM M ARY OFTHE INVENTION

[0013] One aspect of some embodiments of the invention relates to a 3D printhead with a mechanism that adjusts a diameter of the nozzle. According to various exemplary embodiments of the invention the mechanism is selected from the group consisting of a shutter-leaf arrangement, a piston that applies force to an elastomeric pad with a normally open filament channel, an elastomeric pad with a normally open filament channel surrounded by an inflatable lumen, an elastomeric pad with a normally closed filament channel surrounded by levers that transmit an externally provided opening force, a coiled spring defining a filament channel with a diameter that decreases as the spring is coiled tighter, and a normally open filament channel surrounded by pistons that transmit an externally provided closing force. In some exemplary embodiments of the invention, the mechanism is operated by a same controller running the 3D printing client software. Alternatively or additionally, in some embodiments the instructions for changes in the nozzle diameter reside in the G eode.

[0014] Another aspect of some embodiments of the invention relates to a magnetic switch that engages / releases a base pate of a 3D printer. In some exemplary embodiments of the invention, the switch includes a magnetic rod with a north pole extending axially on one side and a south pole extending axially on an opposite side. According to this embodiment rotation of the rod by 90° releases the base plate and rotation of the rod by an additional 90° in the same direction creates a repulsive force on the base plate.

[0015] Yet another aspect of some embodiments of the invention relates to use of ferromagnetic material in formation of the base of an object. In some embodiments use of ferromagnetic material obviates a need to heat the base plate during printing. In some embodiments obviation of the need to heat the base plate contributes to a reduction in energy consumption of up to 70%. In some embodiments small bars of ferromagnetic material are employed. In some exemplary embodiments of the invention, these bars are positioned at or near one or more corners of the object to be printed, such as small bars at the corner of the object. Alternatively or additionally, in some embodiments a ferromagnetic raft is employed.

[0016] Yet another aspect of some embodiments of the invention relates to direct measurement of a temperature of melted printing filament as it exits the nozzle of the print head. In some embodiments direct measurement of the temperature of melted printing filament as it exits the nozzle contributes to an increase in printing accuracy.

[0017] It will be appreciated that the various aspects described above relate to solution of technical problems associated with decreasing power consumption.

[0018] Alternatively or additionally, it will be appreciated that the various aspects described above relate to solution of technical problems related to increasing printing accuracy.

[0019] Alternatively or additionally, it will be appreciated that the various aspects described above relate to solution of technical problems related to increasing deposition rate of melted print filament.

[0020] Alternatively or additionally, it will be appreciated that the various aspects described above relate to solution of technical problems related to increasing ease of removal of a base plate from the printer.

[0021] In some exemplary embodiments of the invention there is provided a 3D printhead including: (a) a print nozzle with a variable aperture size; and (b) a mechanism that adjusts the aperture size. According to various exemplary embodiments of the invention the mechanism is selected from the group consisting of a shutter-leaf arrangement, a piston that applies force to an elastomeric pad with a normally open filament channel, an elastomeric pad with a normally open filament channel surrounded by an inflatable lumen, an elastomeric pad with a normally closed filament channel surrounded by levers that transmit an externally provided opening force, a coiled spring defining a filament channel with a diameter that decreases as the spring is coiled tighter, and a normally open filament channel surrounded by pistons that transmit an externally provided closing force. Alternatively or additionally, in some embodiments the system includes a 3D printhead according to claim as above, and a controller running 3D printing client software and providing an output signal that operates the mechanism. Alternatively or additionally, in some embodiments the 3D printing client software translates G code data into instructions for changes in the nozzle diameter.

[0022] In some exemplary embodiments of the invention there is provided a switch including:

[0023] (a) a magnetic rod with a north pole extending axially on one side and a south pole extending axially on an opposite side; (b) a holder accommodating the rod; and (c) a rotational mechanism operatively connected to the rod. In some exemplary embodiments of the invention there is provided a 3D printer including: at least one switch according as defined above; and a base plate including ferromagnetic material, the base plate alternately engaged or released by the switch depending upon an operational state of the switch.

[0024] In some exemplary embodiments of the invention there is provided a method including: (a) depositing at least one layer of ferromagnetic material on a base plate of a 3D printer; and (b) using one or more 3D print heads to print an object on the ferromagnetic material. In some embodiments the depositing at least one layer of ferromagnetic material is performed by a 3D printhead. Alternatively or additionally, in some embodiments the depositing at least one layer of ferromagnetic material is performed without a 3D printhead.

[0025] In some exemplary embodiments of the invention there is provided a 3D printhead including: (a) a print nozzle; and (b) a temperature sensor positioned to measure a temperature of material exiting the nozzle. In some embodiments the temperature sensor produces an output signal, and the printhead includes a heater responsive to the output signal.

[0026] In some exemplary embodiments of the invention there is provided a 3D printhead including: (a) a print nozzle; and (b) a filament channel in the nozzle defined along at least a portion of its length by an elastomeric material. In some embodiments the at least a portion of the filament channel is normally open. Alternatively or additionally, in some embodiments the at least a portion of the filament channel is normally contracted.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although suitable methods and materials are described below, methods and materials similar or equivalent to those described herein can be used in the practice of the present invention. In case of conflict, the patent specification, including definitions, will control. All materials, methods, and examples are illustrative only and are not intended to be limiting.

[0028] As used herein, the terms “comprising” and “including” or grammatical variants thereof are to be taken as specifying inclusion of the stated features, integers, actions or components without precluding the addition of one or more additional features, integers, actions, components or groups thereof. This term is broader than, and includes the terms "consisting of" and "consisting essentially of" as defined by the Manual of Patent Examination Procedure of the United States Patent and Trademark Office. Thus, any recitation that an embodiment “includes” or “comprises” a feature is a specific statement that sub embodiments “consist essentially of” and / or “consist of” the recited feature.

[0029] The phrase "consisting essentially of" or grammatical variants thereof when used herein are to be taken as specifying the stated features, integers, steps or components but do not preclude the addition of one or more additional features, integers, steps, components or groups thereof but only if the additional features, integers, steps, components or groups thereof do not materially alter the basic and novel characteristics of the claimed composition, device or method.

[0030] The phrase “adapted to” as used in this specification and the accompanying claims imposes additional structural limitationson a previously recited component.

[0031] The term "method" refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of architecture and / or computer science.

[0032] Implementation of the method and system according to embodiments of the invention involves performing or completing selected tasks or steps manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of exemplary embodiments of methods, apparatus and systems of the invention, several selected steps could be implemented by hardware or by software on any operating system of any firmware or a combination thereof. For example, as hardware, selected steps of the invention could be implemented as a chip or a circuit. As software, selected steps of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In any case, selected steps of the method and system of the invention could be described as being performed by a data processor, such as a computing platform for executing a plurality of instructions.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying figures. In the figures, identical and similar structures, elements or parts thereof that appear in more than one figure are generally labeled with the same or similar references in the figures in which they appear. Dimensions of components and features shown in the figures are chosen primarily for convenience and clarity of presentation and are not necessarily to scale. The attached figures are:

[0035] Fig. 1 is a perspective view from below of a 3D printhead with an adjustable diameter nozzle according to some exemplary embodiments of the invention, with an inset showing the nozzle in greater detail;

[0036] Fig. 2a is a transverse cross section of a switch based on a rotatable magnetic rod according to some exemplary embodimentsof the invention in a first operational state;

[0037] Fig. 2b is a transverse cross section of the switch of Fig. 2a in a second operational state;

[0038] Fig. 2c is a top perspective view of a group of switches as in Fig. 2a and Fig. 2b with a common operational mechanism according to some exemplary embodiments of the invention;

[0039] Fig. 3a is a top perspective view of a layer of ferromagnetic material deposited on a base of a 3D printer according to some exemplary embodiments of the invention;

[0040] Fig. 3b is a simplified flow diagram of a method according to some exemplary embodiments of the invention.

[0041] Fig. 4a is a schematic representation of a temperature sensor in a 3D print head according to the prior art;

[0042] Fig. 4b is a schematic representation of an external temperature sensor measuring the temperature of extruded melted filament as it exits the nozzle of a 3D print head according to some exemplary embodiments of the invention;

[0043] Fig. 5a is a transverse cross section of a mechanism that adjusts aperture size of a print nozzle in a first operational state according to some exemplary embodiments of the invention; Fig. 5b is a transverse cross section of the mechanism of Fig. 5a in a second operational state;

[0044] Fig. 6a is a transverse cross section of a mechanism that adjusts aperture size of a print nozzle in a first operational state according to some exemplary embodiments of the invention;

[0045] Fig. 6b is a transverse cross section of the mechanism of Fig. 6a in a second operational state;

[0046] Fig. 7a is a bottom perspective view of a mechanism that adjusts aperture size of a print nozzle according to some exemplary embodimentsof the invention;

[0047] Fig. 7b is a transverse cross section of the mechanism of Fig. 7a;

[0048] Fig. 8a is a bottom perspective view of a mechanism that adjusts aperture size of a print nozzle in a first operational state according to some exemplary embodiments of the invention;

[0049] Fig. 8b is a bottom perspective view of the mechanism of Fig. 8a in a second operational state;

[0050] Fig. 9 a is a bottom perspective view of a mechanism that adjusts aperture size of a print nozzle in a first operational state according to some exemplary embodiments of the invention; and

[0051] Fig. 9b is a bottom perspective view of the mechanism of Fig. 9a in a second operational state.

[0052] DETAILED DESCRIPTION OF EM BODIM ENTS

[0053] Embodiments of the invention relate to hardware, systems and methods related to 3D printing.

[0054] Specifically, some embodiments of the invention can be used to increase versatility and / or accuracy of a 3D print head and / or to simplify removal of a printed object from the base plate of a 3D printer.

[0055] The principles and operation of hardware and / or systems and / or methods according to exemplary embodiments of the invention may be better understood with reference to the drawings and accompanying descriptions.

[0056] Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details set forth in the following description or exemplified by the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and is not limiting.

[0057] Exemplary printhead

[0058] Fig. 1 is a bottom perspective view of a a 3D printhead, indicated generally as 100. Depicted exemplary printhead 100 includes a body 110 and a print nozzle 120 with a variable aperture size; and a mechanism that adjusts said aperture size. According to various exemplary embodiments of the invention the mechanism that adjusts the aperture size is selected from the group consisting of a shutter-leaf arrangement, a piston that applies force to an elastomeric pad with a normally open filament channel, an elastomeric pad with a normally open filament channel surrounded by an inflatable lumen, an elastomeric pad with a normally closed filament channel surrounded by levers that transmit an externally provided opening force, a coiled spring defining a filament channel with a diameter that decreases as the spring is coiled tighter, and a normally open filament channel surrounded by pistons that transmit an externally provided closing force. The exemplary embodiment depicted in Fig. 1 employs a shutter-leaf arrangement. Various mechanisms that adjust the aperture size are described in greater detail herein below with reference to Figs. 5a, 5b, 6a, 6d, 7a, 7b, 8a, 8b, 9a and 9b.

[0059] In some exemplary embodiments of the invention, printhead 100 is provided as part of a system that includes a controller running 3D printing client software and providing an output signal that operates the mechanism that adjusts aperture size. In some embodiments 3D printing client software translates G code data into instructions for changes in the nozzle diameter (aperture size).

[0060] Exemplary switch

[0061] Fig. 2a and Fig. 2b are transverse cross sections of a switch based on a rotatable magnetic rod according to some exemplary embodiments of the invention in a first and second operational states respectively.

[0062] The depicted exemplary switch includes a magnetic rod 210 with a north pole extending axially on one side and a south pole extending axially on an opposite side and a holder 220 accommodating rod 210.

[0063] Fig. 2c is a top perspective view of a group of switches as in Fig. 2a and Fig. 2b with a common rotational mechanism according to some exemplary embodimentsof the invention. In some embodiments a rotational mechanism (e.g. levers 240; 250) is operatively connected to rods 210 (not visible in Fig. 2c) in holders 220.

[0064] Some exemplary embodiments of the invention relate to a 3D printer including: at least one switch according as described above and a base plate comprising ferromagnetic material. According to these embodiments, the base plate is alternately engaged or released by the switch depending upon an operational state of the switch.

[0065] Exemplary ferromagnetic layer method

[0066] Fig. 3a is a top perspective view of a layer of ferromagnetic material deposited on a base of a 3D printer according to some exemplary embodiments of the invention.

[0067] In the depicted embodiment, base plate 310 supports a layer of ferromagnetic material 330 to which 3D printing filament 320 has been applied.

[0068] Fig. 3b is a simplified flow diagram of a method according to some exemplary embodiments of the invention. The depicted exemplary method includes depositing 350 at least one layer of ferromagnetic material on a base plate of a 3D printer and using 360 one or more 3D print heads to print an object on the ferromagnetic material. In some exemplary embodiments of the invention, depositing 350 is performed by a 3D printhead. In other exemplary embodiments of the invention, depositing 350 is performed without a 3D printhead.

[0069] Exemplary 3D print head

[0070] Fig. 4a is a schematic representation of a temperature sensor in a 3D print head according to the prior art.

[0071] Conventionally, temperature sensor 440 is mounted within printhead 410. This arrangement provides an estimate of the temperature of print material 430 before it exits nozzle 420.

[0072] Fig. 4b is a schematic representation of an external temperature sensor measuring the temperature of extruded melted filament as it exits the nozzle of a 3D print head according to some exemplary embodiments of the invention.

[0073] The depicted exemplary embodiment of Fig. 4b includes a print nozzle 420 attached to a printhead 410 and a temperature sensor 450 positioned to measure a temperature of material 430 exiting nozzle 420. In the depicted embodiment, sensor 450 is an infrared thermometer. In some exemplary embodiments of the invention, temperature sensor 450 produces an output signal and printhead 410 includes a heater responsive to the output signal. Exemplary mechanisms that adjust the aperture size

[0074] According to various exemplary embodiments of the invention the mechanism that adjusts the aperture size is selected from the group consisting of a shutter-leaf arrangement, a piston that applies force to an elastomeric pad with a normally open filament channel, an elastomeric pad with a normally open filament channel surrounded by an inflatable lumen, an elastomeric pad with a normally closed filament channel surrounded by levers that transmit an externally provided opening force, a coiled spring defining a filament channel with a diameter that decreases as the spring is coiled tighter, and a normally open filament channel surrounded by pistons that transmit an externally provided closing force.

[0075] The exemplary embodiment depicted in Fig. 1 employs a shutter-leaf arrangement in which mechanism 122 includes a plurality of leaves 123. The leaves 123 are moved to control the diameter of a central aperture though which extruded filament 122 flows. The mechanical function of the mechanism is analogous to the well-known mechanism for adjusting the light aperture in a camera.

[0076] Each of the following mechanisms can take the place of the mechanism of Fig. 1 .

[0077] Fig. 5a is a transverse cross section of a mechanism that adjusts aperture size of a print nozzle in a first operational state according to some exemplary embodiments of the invention. In the depicted embodiment, central aperture 522 is a normally open filament channel in an elastomeric pad 520. A piston that 510 is free to move up and down in cylinder 512.

[0078] Fig. 5b illustrates that as piston 510 descends in cylinder 512 (in response to an external force) elastomeric pad 520 is compressed. This causes constriction of central aperture 522 from interface 523 (between piston 510 and pad 520) and below. When the piston 510 ascends, central aperture 522 in pad returns to its normally open state.

[0079] Fig. 6a Is a transverse cross section of a mechanism that adjusts aperture size of a print nozzle with an elastomeric pad 622 with a normally open filament channel 622 surrounded by an inflatable lumen 612. In Fig. 6a the lumen is deflated. Upper portion 610 of the mechanism is constructed of a solid inelastic material. A reservoir of compressed fluid (e.g. air) in 614 is connected to lumen 612 by a regulatable valve (not depicted). Fig. 6b depicts Inflation of lumen 612 with fluid from 614 which causes elastomeric pad 622 to compress channel 622 at 623. Release of the fluid from lumen 612 returns channel 622 to its normally expanded state. Fig. 7a is a bottom perspective view of a mechanism that adjusts aperture size of a print nozzle according to some exemplary embodiments of the invention including an elastomeric pad 720 with a normally closed filament channel surrounded by levers 712 that transmit an externally provided opening force. In the depicted embodiment, levers 712 engage pad 720 via rings 730 provided in pad 720.

[0080] Fig. 7b is a transverse cross section of the mechanism of Fig. 7a in which normally closed filament channel 722 is visible. As levers 712 transmit an externally provided outward force (indicated by gray arrows) to pad 720 via rings 730, an aperture at the bottom of normally closed filament channel expands as indicated by the double headed arrow. When the externally provided force is removed, normally closed filament channel 722 constricts and the aperture contracts.

[0081] Fig. 8a and Fig. 8b are bottom perspective views of a mechanism that adjusts aperture size of a print nozzle according to some exemplary embodiments of the invention. In the depicted embodiment, a coiled spring 830 defines a filament channel 822 with a diameter that decreases as spring 830 is coiled tighter. In the depicted embodiment, the mechanism has an upper portion 810 constructed of an inelastic material and an elastomeric portion 820 in which the ring is embedded. In Fig. 8b, spring 830 is more tightly wound and an aperture of channel 822 is narrower. In Fig. 8a, spring 830 is less tightly wound and an aperture of channel 822 is wide.

[0082] Fig. 9a and Fig. 9b are bottom perspective views of a mechanism that adjusts aperture size of a print nozzle according to some exemplary embodiments of the invention. In the depicted embodiment, the mechanism includes and a normally open filament channel 930 with an aperture 932. In the depicted embodiment, channel 930 protrudes from an inelastic base 910. In the depicted embodiment, channel 930 is surrounded by pistons 920 that transmit an externally provided closing force.

[0083] Fig. 9a shows channel 930 with a wide aperture 932 in the absence of externally provided closing force.

[0084] Fig. 9b shows channel 930 with a narrow aperture 932 in the presence of externally provided closing force. These specific mechanisms are provided as examples only and do not limit the scope of the invention.

[0085] It is expected that during the life of this patent many temperature sensors will be developed and the scope of the invention is intended to include all such new technologies a priori.

[0086] Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, this application embraces all such alternatives, modifications and variations that fall within the broad scope of the appended claims.

[0087] Specifically, a variety of numerical indicators have been utilized. It should be understood that these numerical indicators could vary even further based upon a variety of engineering principles, materials, intended use and designs incorporated into the various embodiments of the invention. Additionally, components and / or actions ascribed to exemplary embodiments of the invention and depicted as a single unit may be divided into subunits. Conversely, components and / or actions ascribed to exemplary embodiments of the invention and depicted as sub-units / i ndividual actions may be combined into a single unit / action with the described / depicted function.

[0088] Alternatively, or additionally, features used to describe a method can be used to characterize an apparatus or system and features used to describe an apparatus or system can be used to characterize a method.

[0089] It should be further understood that the individual features described hereinabove can be combined in all possible combinations and sub-combinations to produce additional embodiments of the invention. The examples given above are exemplary in nature and are do not limit the scope of the invention which is defined solely by the following claims.

[0090] Each recitation of an embodiment of the invention that includes a specific feature, part, component, module or process is an explicit statement that additional embodiments of the invention not including the recited feature, part, component, module or process exist.

[0091] Alternatively or additionally, various exemplary embodiments of the invention exclude any specific feature, part, component, module, process or element which is not specifically disclosed herein.

[0092] Specifically, the invention has been described in the context of FDM printing but might be used in other additive manufacturing protocols as well. All publications, references, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.

[0093] The terms “include", and “have” and their conjugates as used herein mean “including but not necessarily limited to”.

Claims

CLAIM S:

1. A 3D printhead comprising:(a) a print nozzle with a variable aperture size; and(b) a mechanism that adjusts said aperture size.

2. A 3D printhead according to claim 1 , wherein said mechanism is selected from the group consisting of a shutter-leaf arrangement, a piston that applies force to an elastomeric pad with a normally open filament channel, an elastomeric pad with a normally open filament channel surrounded by an inflatable lumen, an elastomeric pad with a normally closed filament channel surrounded by levers that transmit an externally provided opening force, a coiled spring defining a filament channel with a diameter that decreases as the spring is coiled tighter, and a normally open filament channel surrounded by pistons that transmit an externally provided closing force.

3. A system comprising: a 3D printhead according to claim 1 ; and a controller running 3D printing client software and providing an output signal that operates said mechanism.

4. A system according to claim 3, 3D printing client software translates G code data into instructions for changes in the nozzle diameter.

5. A switch comprising:(a) a magnetic rod with a north pole extending axially on one side and a south pole extending axially on an opposite side;(b) a holder accommodating said rod; and(c) a rotational mechanism operatively connected to said rod.

6. A 3D printer comprising: at least one switch according to claim 5; and a base plate comprising ferromagnetic material, said base plate alternately engaged or released by said switch depending upon an operational state of the switch.

7. A method comprising:(a) depositing at least one layer of ferromagnetic material on a base plate of a 3D printer; and(b) using one or more 3D print heads to print an object on said ferromagnetic material.

8. A method according to claim 7, wherein said depositing at least one layer of ferromagnetic material is performed by a 3D printhead.

9. A method according to claim 7, wherein said depositing at least one layer of ferromagnetic material isperformed without a3D printhead.

10. A 3D printhead comprising:(a) a print nozzle; and(b) a temperature sensor positioned to measure a temperature of material exiting said nozzle.

11. A 3D printhead according to claim 10, wherein said temperature sensor produces an output signal, and said printhead comprises a heater responsive to said output signal.

12. A 3D printhead comprising:(a) a print nozzle; and(b) a filament channel in said nozzle defined along at least a portion of its length by an elastomeric material.

13. A 3D printhead according to claim 10, wherein said at least a portion of said filament channel is normally open.

14. A 3D printhead according to claim 10, wherein said at least a portion of said filament channel is normally contracted.-15-RECTIFIED SHEET (RULE 91)

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