Abstract:
A barrel for use in an additive manufacturing machine is disclosed. The barrel includes a sleeve extending along a longitudinal axis. A conduit extends along the longitudinal axis through the sleeve. The conduit is movable relative to the sleeve along the longitudinal axis between a first position and a second position. A nozzle is associated with the conduit. The nozzle is movable with the conduit relative to the sleeve between the first position and the second position.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    The following application claims priority under 35, U.S.C. §119(e) to co-pending U.S. Provisional Patent Application Ser. No. 61/978,400 filed Apr. 11, 2014 entitled RETRACTING EXTRUDER BARREL WITH COOLING FEATURES. The above-identified application is incorporated herein by reference in its entirety for ail purposes. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure generally relates to additive manufacturing, and more particularly to an extruder barrel assembly that extends and retracts along a longitudinal axis of the extruder barrel assembly. 
       BACKGROUND 
       [0003]    Additive manufacturing, also known as 3-D printing and rapid prototyping, is the process of extruding plastic material through a nozzle to form three dimensional models. The models formed by additive manufacturing may be used for functional prototype testing, reviewing fit and function of physical parts, and/or in low volume production scenarios. Additive manufacturing allows for the quick manufacture of physical parts while also reducing cost by eliminating the need for expensive tooling and/or processes that would otherwise be needed to manufacture the parts. 
         [0004]    Another benefit of additive manufacturing is the ability to extrude a variety of different plastic materials. The ability to extrude many different plastic materials allows for the selection of plastic based on the physical and/or mechanical properties of the plastic material. Yet another benefit of additive manufacturing is the ability to extrude the plastic material through a variety of different nozzles. The ability to use different nozzles allows physical models to he created at a slower rate with greater detail using a smaller nozzle, or the physical models can be created at a faster rate with less detail using a larger nozzle. 
         [0005]    Traditionally, additive manufacturing machines have been equipped with a single nozzle. More recent additive manufacturing machines are being provided with two or more nozzles. The additional nozzles provided the benefit of being able to continuously manufacture a physical part utilizing different plastic materials and/or nozzles without having to interrupt operation of the machine to change out the plastic material and/or nozzle. 
         [0006]    The existence of more than one nozzle presents a problem in that each of the nozzles must be elevated the exact same distance over the platform on which the physical part is manufactured in order to ensure accurate manufacture of the physical part. However, elevating all of the nozzles at the same distance creates the risk of one or more of the nozzles coming into contact with the physical part, thereby damaging the part being manufactured. 
         [0007]    Current solutions for the above noted difficulty are problematic in that the current solutions undesirably add cost and complexity to the additive manufacturing machine. 
       SUMMARY 
       [0008]    One aspect of the present disclosure comprises a barrel for use in an additive manufacturing machine. The barrel includes a sleeve extending along a longitudinal axis and a conduit extending along the longitudinal axis through the sleeve. The conduit is movable relative to the sleeve along the longitudinal axis between a first position and a second position. A nozzle is associated with the conduit. The nozzle is moveable with the conduit relative to the sleeve between the first position and the second position. 
         [0009]    Another aspect of the present disclosure comprises another barrel for use in an additive manufacturing machine. The barrel includes a sleeve extending along a longitudinal axis and a conduit extending along the longitudinal axis through the sleeve. An actuating system is associated with the sleeve. The actuating system is configured to move the conduit along the longitudinal axis relative to the sleeve between a first position and a second position. A nozzle is associated with the conduit. The nozzle is moveable with the conduit relative to the sleeve between the first position and the second position. 
         [0010]    Yet another aspect of the present disclosure comprises a method of manufacturing a three dimensional model. The method includes the step of providing an additive manufacturing machine having at least two barrels. Each of the at least two barrels is moveable between a first position and a second position. The first barrel of the at least two barrels is provided with a first material and the second barrel of the at least two barrels is provided with a second material. The first barrel of the at least two barrels is moved from the first position to the second position and the first material is advanced. The first barrel of the at least two barrels is moved from the second position to the first position and the first material is retracted. The second barrel of the at least two barrels is moved from the first position to the second position and the second material is advanced. The second barrel of the at least two barrels is moved from the second position to the first position and the second material is retracted. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The foregoing and other features and advantages of the present disclosure will become apparent to one skilled in the art to which the present disclosure relates upon consideration of the following description of the invention with reference to the accompanying drawings, wherein like reference numerals, unless otherwise described refer to like parts throughout the drawings and in which: 
           [0012]      FIG. 1  is a side view of an extruder barrel assembly in a stand-by state; 
           [0013]      FIG. 2  is a sectional view along “A-A” of  FIG. 1 ; 
           [0014]      FIG. 3  is a side view of the extruder barrel assembly of  FIG. 1  in an active state showing some components of the assembly in phantom; 
           [0015]      FIG. 4  is a detail view of area “B” of  FIG. 2 ; 
           [0016]      FIG. 5  is a detailed view of area “C” of  FIG. 2 ; 
           [0017]      FIG. 6  is a side view of a highly schematized additive manufacturing system that may employ the extruder barrel assembly shown in  FIG. 1 ; and 
           [0018]      FIG. 7  is a side view of an extruder barrel assembly according to another aspect of the present disclosure in a stand-by state. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Referring now to the figures wherein like numbered features shown therein refer to like elements throughout unless otherwise noted. 
         [0020]      FIGS. 1-5  show an auto-retracting extruder barrel  10 . The extruder barrel  10  extends along a longitudinal axis  12  between a first end  20  and a second end  22 ,  FIGS. 1 and 2  show the barrel  10  in a stand-by state, and  FIG. 3  shows the barrel  10  in an active state. 
         [0021]    With attention directed toward.  FIGS. 2 ,  3 , and  5 , an upper mounting sleeve  24  is provided at the first end  20  of the barrel  10 . The upper mounting sleeve  24  has a first end  26  and a second end  28 . A cylindrical spring cavity  32  is provided at the first end  26 . The spring cavity  32  extends into the upper mounting sleeve  24  along the longitudinal axis  12 . A collar  30  is provided in the spring cavity  32 . The collar  30  closes off the spring cavity  32  at the first end  26  of the upper mounting sleeve  24 . The collar  30  is movable relative to the upper mounting sleeve  24  along the longitudinal axis  12  in the spring cavity  32 . A compression spring  34  is provided in the spring cavity  32 . 
         [0022]    A cylindrical bearing cavity  36  is provided at the second end  28  of the upper mounting sleeve  24 . The bearing cavity  36  extends into the upper mounting, sleeve  24  along the longitudinal axis  12 . The bearing cavity  36  receives a linear hearing  38 . In one example embodiment an interference fit is used to retain the linear bearing  38  within the bearing cavity  36 . However, any other appropriate retention method may be used. For example, the bearing  38  may be welded to the bearing cavity  36 . Alternatively, an external surface of the bearing  38  may be provided with external threads that interact with corresponding threads provided in the bearing cavity  36 . 
         [0023]    With attention now directed to  FIGS. 2-5 , the extruder barrel  10  farther comprises an inner sleeve  40 . The inner sleeve  40  has a first end  46  and a second end  48 . The first end  46  is attached to the collar  30 . In one example embodiment a set screw is used to attach the first end  46  of the inner sleeve  40  to the collar  30 . However, any other appropriate method may be used. For example, the inner sleeve  40  and the collar  30  may be welded together. 
         [0024]    The inner sleeve  40  extends through the upper mounting sleeve  24  along the longitudinal axis  12  such that the compression spring  34  and the linear bearing  38  surround the inner sleeve  40 . The linear bearing  38  allows the inner sleeve  40  to smoothly slide along the longitudinal axis  12  relative to the upper mounting sleeve  24 . 
         [0025]    Although the illustrated example embodiment shows the single compression spring  34  surrounding the inner sleeve  40 , it is contemplated that other spring configurations may be used. For example, the spring cavity  24  may include a plurality of springs having longitudinal axes that are radially outwardly offset from the longitudinal axis  12  of the barrel  10 . 
         [0026]    As clearly shown in  FIGS. 4 and 5 , the inner sleeve  40  includes a first part  42  and a second part  44 . The second part  44  surrounds, and is concentric with, the first part  42 . In one example embodiment the first and second parts  42 ,  44  are manufactured out of stainless steel. However, any other appropriate materials having low thermal conductivity and appropriate strength may be used. The second part  44  is provided with a flared compression fitting  50  at the second end  48  of the inner sleeve  40 . 
         [0027]    The extruder barrel  10  further comprises a liquefier assembly  58  provided at the second end  22  of the barrel  10 . The liquefier assembly  58  includes a nozzle  60  having a first end  62  and a second end  64 . The second end  64  is provided with a nozzle tip  66 . A liquefier block  68  surrounds the nozzle  60  such that the nozzle  60  is substantially covered by the liquefier block  68 . The nozzle tip  66  protrudes from one end of the block  68  along the longitudinal axis  12  of the extruder barrel  10 , The liquefier block  68  houses a thermocouple  74  and a heater  76 . 
         [0028]    As clearly shown in  FIG. 4 , the liquefier block  68  is provided with a connecting portion  70 . The flared compression fitting  50  of the inner sleeve  40  is received in the connecting portion  70 , thereby securing the liquefier assembly  58  to the second end  48  of the inner sleeve  40 . The connecting portion  70  is dimensioned such that a void  72  is created between the liquefier block  68  and the second part  44  of the inner sleeve  40 . The first part  42  of the inner sleeve  40  is in fluid communication with the nozzle  60  when the inner sleeve  40  and the liquefier assembly  58  are connected to one another. 
         [0029]    A lower outer cooling sleeve  52  is provided on the inner sleeve  40 . The cooling sleeve  52  is located along the longitudinal axis  12  between the upper mounting sleeve  24  and the liquefier assembly  58 . The cooling sleeve  52  includes a main portion  54  and a plurality of cooling fins  56 . The inner sleeve  40  extends through the cooling sleeve  52  such that the main portion  54  surrounds, and is concentric with, the inner sleeve  40 . In one example embodiment the cooling sleeve  52  is retained on the inner sleeve  40  by an interference fit. However, any other appropriate retention method may be used. For example, the main portion  54  of the cooling sleeve  52  may be welded to the second part  44  of the inner sleeve  40 . 
         [0030]    The cooling fins  56  extend radially outward away from the longitudinal axis  120  In one example embodiment the main portion  54  and the cooling fins  56  are manufactured as a single integral unit. However, it is contemplated that the main portion  54  and the cooling fins  56  may be manufactured separately and subsequently attached to one another. In the illustrated example embodiment the cooling sleeve  52  is provided with nine cooling fins  56 . However, the cooling sleeve  52  may be provided with fewer or greater cooling fins  56  in order to tailor the performance characteristics of the cooling sleeve  52  for a particular application. 
         [0031]    The extruder barrel  10  is moveable between the stand-by state and the active state. The design of the extruder barrel  10  is such that the extruder barrel  10  is biased to the stand-by state as a default state (i.e. without any external forces acting on the extruder barrel  10 ). 
         [0032]    In the stand-by state the compression spring  34  acts between the collar  30  and the spring cavity  32  to bias the collar  30  along the longitudinal axis  12  toward the first end  20  of the extruder  10 . The inner sleeve  40 , cooling sleeve  52 , and the liquefier assembly  58  are also biased toward the first end  20  of the extruder it) due to the interconnection between the collar  30 , the inner sleeve  40 , the cooling sleeve  52 , and the liquefier assembly  58 . 
         [0033]    Compressing the compression spring  34  results in the extruder moving to the active state, Compression of the compression spring  34  allows the collar  30  to move along the longitudinal axis  12  toward the second end  22  of the extruder  10 . Again, the inner sleeve  40 , the cooling sleeve  52 , and the liquefier assembly  58  move with the collar  30  toward the second end  22  of the extruder  10 . 
         [0034]    Now referring to  FIG. 6 , an additive manufacturing system  100  is shown manufacturing a three dimensional model  126 . A control system  118  is provided to direct the additive manufacturing system  100 . The control system  118  is programmed with instructions for manufacturing the three dimensional model  126 . The additive manufacturing system  100  includes a first extruder  10   a  and a second extruder  10   b.  The first and second extruders  10   a,    101 , are of the type described above and shown in  FIGS. 1-5 . it should be understood that references made to components of the first extruder will he indicated with an “a” suffix, and references made to components of the second extruder  10   b  will be indicated with a “b” suffix. 
         [0035]    The nozzle tips  66   a,    66   b  of the first and second extruders  10   a,    10   b  may be the same or different from one another. For example, the first extruder  66   a  may he provided with a small diameter nozzle tip  66   a  that permits the manufacture of fine details at a slow rate, and the second extruder  66   b  may be provided with a large diameter nozzle  66   b  that permits the manufacture of coarse details at a fast rate. 
         [0036]    The first and second extruders  10   a,    10   b  are fixedly mounted to an extruder head  108 . The extruder head  108  is supported by a gantry  106 . The gantry  106  moves the extruder head  108  and, thus, the first and second extruders  10   a,    10   b  in the “X” and “Y” directions. The three dimensional model  126  is built on a platform  104 . The platform  104  can move in the “Z” direction. A first material  120  is dispensed by a first material source  110 . A second material  124  is dispensed by a second material source  112 . The first and second materials  120 ,  124  may be the same or different from one another. The first and second materials  120 ,  124  are respectively fed into the first and second extruders  10   a,    10   b.    
         [0037]    In use, the control system  118  can select between commanding the first material source  110  or the second material source  112  to dispense material. For the purposes of discussion, the operation of the additive manufacturing system  100  will be explained beginning with the control system  118  commanding the first material source  110  to dispense the first material  120 . 
         [0038]    The first material source  110  feeds the first material  120  through the extruder head  108  and into the inner sleeve  40   a  at the first end  20   a  of the first extruder  10   a.  The material  120  is pushed through the inner sleeve  40   a,  out of the second end  48   a  of the inner sleeve  40   a,  and into the liquefier assembly  58   a,  The first material  120  enters into the liquefier assembly  58   a  via the first end  62   a  of the nozzle  60   a,  The liquefier block  68   a  is heated by the heater  76   a,  The control system  118  monitors the heater  76   a  via the thermocouple  74   a  to ensure the liquefier block  68   a  is heated to an appropriate temperature, Heat transfer between the liquefier block  68   a  and the nozzle  60   a  occurs such that the nozzle  60   a  is heated to substantially the same temperature as the liquefier block  68   a,  The heated nozzle  60   a  heats the first material  120  as the first material  120  travels from the first end  62   a  to the second end  64   a  of the nozzle  60   a,  Heating the first material  120  causes the first material  120  to melt, and the first material  120  is substantially liquefied upon exiting the first extruder  10   a  via the nozzle tip  66   a.    
         [0039]    It should be noted that the void  72   a  provided between the liquefier block  68   a  and the second part  44   a  of the inner sleeve  40   a  minimizes heat transfer between the liquefier block  68   a  and the inner sleeve  40   a.  Additionally, the cooling fins  56   a  of the cooling sleeve  54   a  act as a heat sink and dissipate any heat that may inadvertently be transferred to the inner sleeve  40   a.  Minimizing heat transfer to the inner sleeve  40   a  is critical to ensuring that the first material  120  does not prematurely melt in the inner sleeve  40   a  before the first material  120  enters the nozzle  60   a,  Blockages may occur in the inner sleeve  40   a  if the first material  120  is heated before entering the nozzle  60   a.  Blockages in the inner sleeve  40   a  may result in undesirable operating performance of the additive manufacturing system  100 . 
         [0040]    The diameter of the nozzle tip  66   a  is substantially smaller than the diameter of the rest of the nozzle  60   a  and the first part  42   a  of the inner sleeve  40   a,  The reduced diameter of the nozzle tip  66   a  creates an area in the nozzle  60   a  that restricts the flow of the first material  120 . As additional first material  120  is fed into the first extruder  10   a,  the flow restriction created by the nozzle tip  66   a  results in a downward force in the “Z” direction that is exerted upon the nozzle  60   a,  The downward force is transmitted to the collar  30   a  via the inner sleeve  40   a.  The collar  30   a  exerts the downward force on the compression spring  34   a,  thereby causing the compression spring  34   a  to compress. As the compression spring  34   a  is compressed the collar  30   a  moves downward in the “Z” direction. Movement of the collar  30   a  also causes the inner sleeve  40   a  the cooling sleeve  52   a,  and the liquefier assembly  58   a  to move downward in the “Z” direction, thereby moving the nozzle tip  66   a  into the active state. 
         [0041]    When it is necessary to switch to the second material  124  the control system  118  first commands the first material source  110  to slightly retract the first material  120  away from the second end  22   a  of the first extruder  10   a.  Retracting the first material  120  away from the second end  22   a  prevents the inadvertent release of the first material  120  from the nozzle tip  66   a.  Additionally, retracting the first material  120  removes the force exerted upon the nozzle  60   a.  The compression spring  34   a  is able to expand once the force exerted upon the nozzle  60   a  is removed. The expanding compression spring  34   a  moves the collar  30   a  upward in the “Z” direction, thereby also moving the inner sleeve  40   a,  the cooling sleeve  52   a,  and the liquefier assembly  58   a  upward in the “Z” direction. Moving the collar  30   a,  the inner sleeve  40   a,  the cooling sleeve  52   a,  and the liquefier assembly  58   a  upward in the “Z” direction returns the first extruder  10   a  to the stand-by state. 
         [0042]    With the first extruder  10   a  in the stand-by state the control system  118  commands the second material source  112  to dispense the second material  124 . The second material  124  is fed through the extruder head  108  and into the inner sleeve  40   b  at the first end  20   b  of the second extruder  10   b.  The operation of the second extruder  10   b  is identical to the operation of the first extruder  10   a  set forth above. 
         [0043]    When it is necessary to switch hack to the first material  120  the control system  118  commands the second material source  112  to slightly retract the second material  124  away from the second end  22   b  of the second extruder  10   b,  thereby returning the second extruder to the stand-by state. 
         [0044]    Switching between the first material  120  and the second material  124  is accomplished in the manner set forth above. When the additive manufacturing system  100  completes the manufacture of the three dimensional model  126  the control system commands both the first and second material sources  110 ,  112  to retract the materials out of the nozzles  60   a,    60   b  and into the inner sleeves  40   a,    40   b,  This moves the first and second extruders to  10   a,    10   b  to the stand-by state, thereby completing the manufacturing process. 
         [0045]    In yet another example embodiment, movement of the collar  30 , the inner sleeve  40 , the cooling sleeve  52 , the liquefier assembly  58  and the nozzle  66  between the active state and the state-by state can be effectuated by an actuating system  202  (shown schematically in  FIG. 7 ). The actuating system can be a solenoid actuator, a servo actuator, or any other suitable actuator. The compression spring can optionally be omitted if the barrel  10  is provided with an actuating system  202 . Alternatively, the compression spring&#39;s spring constant can be sized to act as an assist to actuating system  202 . 
         [0046]    What have been described above are examples of the present disclosure. It is of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present disclosure are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.