Abstract:
An interdependent dual driver system for advancing and extruding thermoplastic material to be used in 3-dimensional printing applications. The system and process uses a two-driver system where one driver pushes the material through the device while the second driver pulls the material. The material is advanced through a nozzle designed to heat and extrude thermoplastic materials.

Description:
CROSS REFERENCE TO RELATED PATENTS AND APPLICATIONS 
       [0001]    This application claims priority to and the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 62/121,714, filed Feb. 27, 2015, which application is hereby incorporated by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The present disclosure relates to an extrusion system and method, and more specifically to an extrusion system and method for use in additive manufacturing. 
       BACKGROUND 
       [0003]    Material extrusion is a commonly used additive manufacturing technology that involves heating and extruding thermoplastic filament and depositing the extruded material onto a build plate creating a three dimensional model one layer at a time. In these additive manufacturing processes, current methods of extrusion include, but are not limited to, direct drive extrusion and remote drive extrusion. In a direct drive extrusion process, the driving unit is directly connected to the heating component and extrusion nozzle. In an indirect drive extrusion process, the driving unit is mounted remotely and the filament is guided to the heating component and extrusion nozzle via flexible tubing. Feed rate and speed are difficult to optimize in either of these processes due to the need for additional compression of the drive rolls as feed rate and speed increase. Before optimal feed rate and speed can be reached, required drive roll compression can cause damage to the filament. 
         [0004]    U.S. Pat. No. 5,121,329 describes an early apparatus and method for creating three-dimensional objects. The U.S. Pat. No. 5,121,329 sets forth basic principles regarding additive manufacturing and drive systems, and is hereby incorporated herein by reference in its entirety. 
       SUMMARY OF INVENTION 
       [0005]    It has been found to be beneficial to utilize two drivers working in unison to feed the filament during the extrusion process—a static filament driver pushing the filament as a dynamic filament driver pulls the filament. This improved drive system and method allows for optimal feed rate and speed without deforming the filament or allowing slippage of the driver and filament, or causing jamming of filament through the path of extrusion. The drive system and method of the present disclosure is especially beneficial in the fact that it enables the use of a broader variety of materials than either a direct drive or indirect drive system alone. The drive system and method of the present disclosure further allows for more optimal control of the thermoplastic filament as the filament is advanced or retracted through the system, mitigating clogging issues seen with direct and indirect extrusion systems. 
         [0006]    Additionally, by utilizing multiple drivers to feed the filament to the extrusion nozzle, smaller and/or less powerful components can be used than may otherwise be required. For example, two smaller and/or lesser-torqued motors can be used while maintaining quality feed rates. More efficient operating specifications and/or parameters can be obtained, such as lower extrusion temperatures, due to the fact that the driver motors are not being overworked so that there is no need to compensate with high extrusion temperatures, for example. 
         [0007]    In accordance with one aspect of the present disclosure, an extrusion method includes an interdependent dual drive assembly to extrude a thermoplastic filament into layers to form a three-dimensional article or object. The dual drive assembly comprises a static filament driver having a proximal end, a distal end, wherein the proximal and the distal end each include a filament gate, a dynamic filament driver having a proximal end and a distal end, wherein the proximal end is connected to the static drive system through a flexible element and the distal end is attached to a filament extrusion end, and an extrusion nozzle. 
         [0008]    In accordance with another aspect, a method for extruding thermoplastic material to be used in additive manufacturing applications is provided. The method includes a material holder that contains a spool of single stranded thermoplastic filament, an interdependent dual drive assembly comprising a static filament driver having a proximal end and a distal end, wherein a filament gate is disposed at the proximal end and a filament exit gate is disposed at the distal end, and a dynamic filament driver having a proximal end and a distal end. In this embodiment, the proximal end is connected to the static drive system through a flexible element and the distal end is attached to a filament extrusion end. 
         [0009]    In accordance with yet another aspect, a method for extruding a thermoplastic filament to be used in additive manufacturing applications is provided, the method including placing a spool of single stranded thermoplastic filament into a material holder, loading the thermoplastic filament into a static filament driver through a filament gate, pushing the filament through a filament exit gate, flexible tubing and dynamic filament driver, pulling the filament through the dynamic filament driver, pushing the filament from the dynamic filament driver into a heating component and extrusion nozzle, and extruding the filament which deposits in layers to form a three-dimensional object/article. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a side perspective view of a unit for building 3D objects with an interdependent drive system. 
           [0011]      FIG. 2  is a rear perspective view of a unit for building 3D objects with an interdependent drive system. 
           [0012]      FIG. 3  is a front perspective view of a unit for building 3D objects with an interdependent drive system. 
           [0013]      FIG. 4  is a detailed view of the static driver assembly used in the interdependent drive system. 
           [0014]      FIG. 5  is a detailed view of the dynamic driver assembly used in the interdependent drive system. 
           [0015]      FIG. 6  is a schematic diagram of an exemplary system in accordance with the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The interdependent drive assembly in accordance with the present disclosure is designed for additive manufacturing of articles/objects of utility. 
         [0017]    As shown in  FIG. 1 , an interdependent drive assembly includes a main body  1  having a frame that can be open, partially open (shown as an inset in  FIG. 2 ) or fully enclosed (shown as an inset in  FIG. 4 ). The main body  1  can be made of any known material including but not limited to a metal, stainless steel, heavy duty plastic, glass, ceramic, etc. and may be opaque or transparent. In one embodiment the main body  1  includes on its outer or exterior side a material or filament holder  2  to hold a spool of thermoplastic filament  3 , a static filament driver/drive assembly  4 , and a flexible tubing  5  connecting the filament holder/mount  2  and static driver  4 . The static filament driver  4  can be mounted remotely in an ideal location as shown in  FIG. 1 , which is tangent to the thermoplastic filament lead being unwound from the thermoplastic filament spool  3 . On the interior side of the main body  1  is a dynamic filament driver/drive assembly  6 , art known gantry system  11  and a heated build platform  10 . The gantry system  11  is built to transport or move the dynamic filament drive assembly  6 , a filament extrusion head/hot end  7  and the filament extrusion nozzle  8  in the x, y, and z directions. The heated build platform  10  can be made of any known heat retentive materials including but not limited to polyetherimide or aluminum or glass, and is set to a temperature according to the filament specifications. The flexible tubing  5  can be transparent to aid in the visualization of the filament traversing through it or may be opaque. The flexible tubing  5  could be made of any art known materials including but not limited to polytetrafluoroethylene (PTFE). The tubing  5  can be detachable from both static filament driver  21  and dynamic filament driver  6  drivers via ‘push-to-connect’ tubing connectors  22 ,  26  (shown in  FIGS. 4 and 5 ). 
         [0018]    The tubing  5  generally helps to guide the filament pushed from the static filament drive assembly  4  to the dynamic filament drive assembly  6 . The dynamic filament driver  6  then pulls the filament guided by tubing  5  and feeds it into the filament extrusion hot end  7  which is heated by any known means including but not limited to a standard FFF printer filament extrusion hot end according to filament specifications. Because of the increase in temperature that is sufficient to melt the filament, it turns into a more viscous state in the filament extrusion head/hot end  7 , and flows through the filament extrusion nozzle  8 . The spool of thermoplastic filament  3  may consist of any thermoplastic utilized in an additive manufacturing system, including but not limited to acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), high-impact polystyrene (HIPS), polyvinyl alcohol (PVA), etc. The spool of thermoplastic filament  3  which can be colored or colorless is positioned on the main body  1  by means of a filament material holder/mount  2 . 
         [0019]    As shown in  FIG. 2  the spool of thermoplastic filament  3  which resides in the filament material spool holder/mount  2  and the static driver assembly  4  can be permanently attached to the main body  1 . In this embodiment the thermoplastic filament can be manually fed through a filament entry gate  20  (shown in  FIG. 4 ) of the static filament drive assembly  4  until thermoplastic filament is engaged with the drive rolls (not shown) of the static filament drive assembly  4 . The drive rolls that are disposed in the static drive assembly  4  can be controlled by electrical or electromechanical means to engage with a drive motor (not shown) that together makes up the static driver  21  (shown in  FIG. 4 ). Once the thermoplastic filament is engaged with the drive rolls it will then be advanced through the PTFE tubing  5  to pass through an exit gate  23  which can be a product of PTFE tubing  24  connected to static driver  21  by means of a primary push-to-connector  22  (shown in  FIG. 4 ). The thermoplastic filament that is pushed from static driver  21  through subsequent tubing  24  can enter the main body  1  at inlet  25  (shown in  FIGS. 4 &amp; 5 ). 
         [0020]    As the thermoplastic filament travels through the tubing  5  within the main body  1 , it is pushed through a secondary push-to connector  26  into the dynamic filament drive assembly  27  which can also be permanently mounted to the gantry system  11  ( FIG. 3 ). Drive rolls within dynamic filament drive assembly  27  can be powered by drive mechanism engaged with electromechanically controlled drive motor. After engaging the drive rolls (not shown) of the dynamic filament drive assembly  27 , the thermoplastic filament is advanced into the filament extrusion hot end  28  which because of the rise in temperature increases the viscosity of the material allowing it to flow through the filament extrusion nozzle  29  ( FIG. 5 ). The temperature at which the filament is heated depends entirely on the filament material&#39;s melting temperature and glass temperature range and could be provided by the manufacturer. Also, since the filament is fed to the dynamic driver  6  from the static driver  4  at the same rate that the dynamic driver  6  is pushing the filament through the extrusion nozzle, there is no jamming or slipping of the filament and it further allows for better control of the filament feed rate. 
         [0021]    As the thermoplastic filament is extruded and the gantry system  11  moves in the x, y, and z directions the extruded thermoplastic filament is deposited in subsequent layers on the heated build platform  10  to create a 3D printed object  9  (shown in  FIG. 1 ). 
         [0022]    During a typical operation, a spool of single stranded thermoplastic filament is placed in the material holder and the thermoplastic filament can be manually loaded into a static filament driver. The drive rolls present within the static driver and driven by an electromechanical controller pulls the filament into the static drive assembly through a filament entry gate and pushes the filament past a filament exit gate into the flexible tubing. The filament which is then pulled through the flexible tubing, by the force exerted by the drive rolls in the dynamic driver, enters the main body through an inlet. It subsequently travels along the tubing within the main body and enters the dynamic filament driver. The driver rolls within the dynamic driver further aids in pushing the filament through a secondary push connector and feeds the filament into a heating component. Due to a rise in temperature in the filament hot end the filament turns viscous and flows through a nozzle. Further movement of the heated build platform in x, y and z- directions helps the flowing material to deposit in layers to create a final three-dimensioned object. The interdependent dual drive system of the present disclosure can be used for any thermoplastic filament known to be suitable for additive manufacturing. Suitable filament can have a thickness varying in the range of about 1.75 mm to about 3 mm. Since the two drivers operate in unison because of how they are connected to the controller the system prevents any slippage of the material. 
         [0023]    Turning to  FIG. 6 , an exemplary system  60  is illustrated generally including a spool of filament  62 , a static driver  64 , a dynamic driver  66 , an extrusion head  68  including an extruder E, and a controller  70  operably connected to at least one of the static driver  64 , dynamic driver  66 , and/or extruder head  68  for controlling operational aspects of the same. It will be appreciated that one or both of the static driver  64  or dynamic driver  66  can include an electric motor M for driving one or more wheels or other drive elements to advance and/or retract a filament F. Dynamic driver  66  and extrusion head  68  are movable mounted on a gantry  68  in a conventional manner. It will be appreciated that dynamic driver  66  moves relative to static driver  64  during operation of the system  60 . Flexible tube FT extends between the static driver  64  and the dynamic driver  66 . The flexible tube FT guides and/or supports the filament F during relative movement of the drivers, for example. 
         [0024]    It should be appreciated that the advancement rates of the static driver  64  and dynamic driver  66  can be the same. That is, each driver can be operated to advance filament F at a common rate. In other embodiments, it can be desirable to provide different advancement rates for each driver. This may be desirable in certain applications based on printing speed and/or filament characteristics. In some embodiments, one driver may serve as the primary driver for advancing the filament while the other driver is selectively activated to provide secondary advancement under certain predetermined conditions, or when certain operational characteristics are detected (e.g., slippage of the filament, driver motor current draw, etc.). By providing both the static and dynamic drivers, the present disclosure can facilitate feeding of a wider variety of filament materials and/or dimensions than convention drivers. 
         [0025]    To the extent that the term “includes” or “including” is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed (e.g., A or B) it is intended to mean “A or B or both.” When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use. See Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995). Also, to the extent that the terms “in” or “into” are used in the specification or the claims, it is intended to additionally mean “on” or “onto.” To the extent that the term “substantially” is used in the specification or the claims, it is intended to take into consideration the degree of precision available or prudent in manufacturing. To the extent that the term “operatively connected” is used in the specification or the claims, it is intended to mean that the identified components are connected in a way to perform a designated function. As used in the specification and the claims, the singular forms “a,” “an,” and “the” include the plural. Finally, where the term “about” is used in conjunction with a number, it is intended to include ±10% of the number. In other words, “about 10” may mean from 9 to 11. 
         [0026]    As stated above, while the present application has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art, having the benefit of the present application. Therefore, the application, in its broader aspects, is not limited to the specific details, illustrative examples shown, or any apparatus referred to. Departures may be made from such details, examples, and apparatuses without departing from the spirit or scope of the general inventive concept.