Patent Publication Number: US-2021187843-A1

Title: Print heads for 3d printers

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to, and incorporates by reference, E.U. patent application number EP19461617.3, filed Dec. 18, 2019. 
     FIELD OF THE INVENTION 
     The field of the present invention relates to three-dimensional (3D) printing and, more particularly, to print heads used in connection with 3D printers. 
     BACKGROUND OF THE INVENTION 
     The print heads in 3D printers play a key role in creating and depositing layers of modeling printing material (according to defined arrangements), to produce a desired spatial model. The printing material typically exists in a filament form—and, during a 3D printing process, the printing material is plasticized and extruded from the print head to create a spatial model. There are various known ways for configuring and constructing print heads, which vary in design, range of operating temperatures, internal construction, and printing material compatibility (particularly with those 3D printers that accommodate plasticized printing materials). 
     Most currently-available print heads include a printing nozzle (the aperture through which printing material is extruded) having a diameter up to 1 mm, or more preferably up to 0.4 mm. In such 3D printers, a hot zone exists in which the printing material is plasticized, with the hot zone being preceded by a cold zone in which the printing material is not plasticized. Many currently-available print heads further include a polytetrafluoroethylene (PTFE) tube, which is used to guide printing material through the hot zone (but not the cold zone). Such PTFE tubes have been found to impart low friction to the plasticized printing material and to thermally insulate the melted printing material from print head body. 
     Although the use of PTFE tubes have been somewhat effective, such PTFE tubes do have some disadvantages, particularly with respect to the internal construction of the print head. More particularly, when a print head includes a PTFE tube inside the hot zone, the PTFE tube is often contiguously coupled to a preceding second tube made of another/different material. The second tube is positioned to travel through the preceding cold zone and is often made of a material other than PTFE for a variety of reasons. This type of arrangement and construction sometimes leads to printing material leaks at the joint (i.e., contact point) between the PTFE tube (hot zone) and second preceding tube (cold zone). In addition, the temperature resistance properties of PTFE tubes often do not exceed 270-degrees Celsius, which is too low when it is desired to utilize more specialized printing materials (such as polyether ether ketone or polycarbonate printing materials). 
     Accordingly, in view of the foregoing, it would be desirable to provide a print head for 3D printers that overcomes such disadvantages with currently-available print heads and, specifically, can reliably operate at higher temperatures (such as over 400-degrees Celsius) and, still more preferably, is compatible with a wide variety of printing materials, including metal and polymer composite printing materials. 
     As the following will demonstrate, the print heads and components thereof described herein address such demands in the marketplace (among others). 
     SUMMARY OF THE INVENTION 
     According to certain aspects of the invention, print heads for 3D printers are provided. The print heads generally include a head body, which includes an internal cold zone and hot zone. The print heads include a print nozzle and a tube within the head body. The tube is configured to receive and transport a printing material from a source within the 3D printer to the print nozzle. The invention provides that the tube spans the entire length of the cold zone and the hot zone and, importantly, does not include any joints or locations at which separate tubes connect. The invention provides that the tube and the print nozzle are integrally formed together from a single piece of material—and are preferably made from a metallic material. 
     The print heads further include a heating block attached to the head body. In addition, the invention provides that the heating block is directly connected to the body of the print nozzle. According to such aspects of the invention, the print heads include a screen positioned around the heating block, which is configured to provide thermal insulation to a spatial model being printed below the print head. The screen is preferably made of a material with high thermal radiation insulation capacity. The print heads of the present invention further include one or more vents that are positioned and configured to deliver air flow to a portion of the tube that resides within the cold zone. 
     According to additional aspects of the invention, 3D printers are provided that include the print heads described herein. 
     The above-mentioned and additional features of the present invention are further illustrated in the Detailed Description contained herein. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a cross-sectional view of a print head of the present invention, for use in 3D printers. 
         FIG. 2  is a side exterior view of the print head of  FIG. 1 . 
         FIG. 3  is an oblique exterior view of the print head of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following will describe, in detail, several preferred embodiments of the present invention. These embodiments are provided by way of explanation only, and thus, should not unduly restrict the scope of the invention. In fact, those of ordinary skill in the art will appreciate upon reading the present specification and viewing the present drawings that the invention teaches many variations and modifications, and that numerous variations of the invention may be employed, used and made without departing from the scope and spirit of the invention. 
     Referring now to  FIGS. 1-3 , the present invention relates to print heads used in connection with 3D printers (as well as 3D printers that are equipped with such print heads). In such embodiments, the print heads of the present invention generally include a head body  10 , a print nozzle  12 , and a seamless/joint-free tube  14  for leading a printing material to the print nozzle  12  through a cold zone  16  and a hot zone  18 . The head body  10  is operably connected to a 3D printing machine. More particularly, the invention provides that the upper part of the cold zone  16  of the print head is operably connected to the 3D printing machine. 
     According to such preferred embodiments, the print heads of the present invention further include a heating block  20  that is attached to the head body  10  (within the hot zone  18 ). In addition, according to certain preferred embodiments, the heating block  20  is directly connected to the body of the print nozzle  12 . The invention provides that when the heating block  20  of the print head is affixed and attached to the head body  10  (and the print nozzle  12 ), such configuration enhances the mechanical strength of the print head. Such configuration also enables the use of a much larger heating block  20  (compared to various prior art print heads in which a heating block is mounted to a tube for guiding printing material). During operation, when using the print heads described herein, the temperature within the cold zone  16  may range from 30-degrees Celsius to 90-degrees Celsius; whereas, in the hot zone  18 , the operating temperature may range from 70-degrees Celsius to 400-degrees Celsius. The invention provides that the heating block  20  may be made of aluminum, steel, stainless steel, copper, brass, and combinations and alloys of such materials. 
     The invention provides that at least one heating element (e.g., an electrical heating coil) is preferably mounted to or integrally formed within the heating block  20  (within the hot zone  18 ). The invention provides that parameters relating to the heating element (e.g., duration and amount of heat to be applied during a printing procedure) is preferably controlled through a user interface of the 3D printer. The hot zone  18  also preferably includes a temperature sensor, which is configured to monitor and report the temperature within the hot zone  18  to a processor and user interface associated with the 3D printer. The invention provides that the heating block  20  is preferably attached to the head body  10  using, e.g., screws, rivets, or other mechanical attachments, which preferably exhibit a small diameter (such as less than 1.5 mm) in order to minimize heat loss. 
     As illustrated in  FIG. 1 , and as mentioned above, the invention provides that the tube  14  extends through the cold zone  16 , through the hot zone  18 , and to the nozzle  12 . Importantly, according to certain preferred embodiments of the present invention, the tube  14  and print nozzle  12  are integrally formed together (and are made from the same material), such that the tube  14  forms a single, seamless tunnel from the cold zone  16 , through the hot zone  18 , and to the print nozzle  12 . In such embodiments, the tube  14  is preferably constructed without any joints (e.g., it is constructed without separate tubes adjoining each other, as otherwise included in various prior art printers), which eliminates the possibility of printing material leaks (which are sometimes observed in prior art print heads). In certain preferred embodiments, the integrally formed joint-free tube  14  and nozzle  12  are manufactured from metal materials. Non-limiting examples of such metals include steel, stainless steel, titanium, brass, copper, ceramic sinters, Teflon, and combinations and alloys of such metals. In such embodiments, the print head further includes a leading sleeve  28 , which is positioned and configured to supply the printing material to the tube  14 . 
     According to such preferred embodiments, the print heads of the present invention further include a heat shield  24 , which is mounted to the print nozzle  12 . More specifically, the heat shield  24  is mounted to the print nozzle  12 , such that it forms a thermal barrier between the print head and a spatial model that is being printed below the print nozzle  12 . The heat shield  24  may be constructed from, e.g., a polytetrafluoroethylene (PTFE) material. The invention provides that the heat shield  24  is configured to minimize the amount of disadvantageous heat radiation that emanates from the print head from contacting the spatial model being printed. That is, the heat shield  24 , which is preferably positioned around the heating block  20 , provides thermal insulation to the spatial model being printed. In certain embodiments, the heat shield  24  may exhibit a circular dimension, as illustrated in  FIGS. 2 and 3 . 
     Still further, according to certain preferred embodiments, the print head will include a screen  26  located around (and that encapsulates) the heating block  20 . In such embodiments, the screen  26  is preferably made of a material with high thermal radiation insulation capacity, e.g., a metal having low heat capacity, low thermal conductivity, and high heat reflectivity. Non-limiting examples of such metals include steel, stainless steel, copper, brass, aluminum, and combinations and alloys of such metals. 
     The invention further provides that, within the cold zone  16 , the joint-free tube  14  is preferably cooled by air flow. The invention provides that the portion of the tube  14  within the cold zone  16  is subject and exposed to free air flow. For example, the invention provides that one or a plurality of vents  30  may provide such air flow to that portion of the tube  14 . In addition, in certain embodiments, the 3D printer may utilize and/or incorporate one or more fans (or other means) for generating air flow, which may preferably be applied to the cold zone  16  through the one or more vents  30 . 
     The invention further encompasses 3D printers that include and are equipped with the print heads described herein. More particularly, the invention provides that the print heads may be constructed and sold separately or, in other embodiments, the invention encompasses 3D printers that include the print heads described herein. 
     There are many advantages of the print heads (and 3D printers) described herein. For example, as mentioned above, one advantage of the invention is that the construction of the print head prevents unwanted leaks of printing material (which cause print failures) within the seamless and joint-free tube  14  that spans both the hot zone  18  and cold zone  16 . Another advantage is that the print head is configured to accommodate unique printing materials with associated operating temperatures that exceed 400-degrees Celsius (e.g., such print heads may accommodate metal and high-temperature polymer composite printing materials). In addition, the use of air ventilation within the cold zone  16  allows for effective removal of excess heat from the print head, while not compromising the ability of the printing material to be plasticized within the hot zone  18 . 
     The many aspects and benefits of the invention are apparent from the detailed description, and thus, it is intended for the following claims to cover all such aspects and benefits of the invention that fall within the scope and spirit of the invention. In addition, because numerous modifications and variations will be obvious and readily occur to those skilled in the art, the claims should not be construed to limit the invention to the exact construction and operation illustrated and described herein. Accordingly, all suitable modifications and equivalents should be understood to fall within the scope of the invention as claimed herein.