Abstract:
The present invention provides an apparatus for manufacturing multiple color three-dimensional (3D) objects using an additive extrusion type manufacturing build process where the multiple color three-dimensional (3D) object is built layer by layer using a single extrusion nozzle in contact or close proximity to each build layer of the 3D object being manufactured.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates to an apparatus for manufacturing multiple color three-dimensional (3D) objects using an additive extrusion type manufacturing build process where the 3D object is built layer by layer. More particularly, the invention relates to the automatic change of material color and use of a single extrusion nozzle in contact or close proximity with each build layer of the 3D object being built. 
       BACKGROUND OF THE INVENTION 
       [0002]    The use of geometry from three-dimensional (3D) computer aided drafting (CAD) models has been used in conjunction with 3D manufacturing equipment for the purpose of manufacturing prototypes for years. The 3D manufacturing equipment fits into two major categories where the older of two categories involved removal or cutting away of material from a solid block of material such as a CNC machine where the solid block is clamped in place within the CNC machine and material is cut away until the remaining material represents the CAD geometry supplied to the CNC machine. Instead of starting with a volume of material and removing material to create the desired 3D geometry, the newer technology uses an additive process where the 3D CAD model is cut into layers in software and the 3D object is built layer by layer within a build plane until the desired geometry represents the 3D object in the CAD model. The 3D manufacturing equipment (3D Printer) used for this newer technology builds the 3D object by adhering a layer of material to a build plate, then by adhering each consecutive layer to the previous layer in a plane parallel to the build plate within the 3D Printer until the 3D object&#39;s geometry matches the 3D CAD geometry provided to the 3D Printer. 
         [0003]    While this additive build process for 3D Printing is used by several 3D Printing technologies and 3D printing of multiple color objects is common knowledge, the lowest cost technology involving the Fuse Deposition Modeling (FDM) technology, in particular the extrusion type FDM technology is limited with regards to 3D printing of multiple colored objects. The extrusion type FDM technology manufacturers the 3D object as previously described where the 3D object is built layer upon layer but in this specific niche, the additive build process includes feeding a polymeric build material into a material extruder and moving the material extruder and its extruder nozzle as determined by a controller by means of an x-y-z positioning assembly to build the 3D object. During the first build layer of the 3D object, build material is extruded within the build plane (a plane parallel to the build surface where the extrusion nozzle extrudes build material limited horizontally by the x-y-z positioning assembly&#39;s range of motion to move the extrusion nozzle) onto the build plate and more specifically onto the build surface (area specified on the build plate for extruding the first build layer and as determined by the x-y-z positioning assembly&#39;s range of motion to move the extruder nozzle). After the build layer is complete, the build plate and build plane are moved one layer apart by the x-y-z positioning assembly as determined by the controller before the next build layer is extruded and adhered the previous build layer. The build process continues layer upon layer until all layers of the 3D object are built within the 3D printers build volume (3D object&#39;s maximum part volume as determined by the build plane and as determined by the x-y-z positioning assembly&#39;s range of motion to move the build plane relative to the build surface on the build plate). In this first generation of multiple colored 3D printing using this extrusion type FDM technology, the build process stops during each build layer where the color change is required allowing the user to manually change the color of the build material before manually restarting the 3D Printer so it can continue to the next point in the build process where the color change is required. 
         [0004]    The second and current generation of multiple color 3D Printers using the extrusion type FDM technology use multiple material extruders fixed relative to each other within the build plane where the plane of extruders and extruder nozzles is controlled by the x-y-z positioning system to move the plane of extruder nozzles relative the build plate and where both extruders pass through the build volume and pass over the build surface simultaneously. When a change to the material color is required, the current material extruder is turned off, the new color material extruder is turned on to continue the build process. While this color change method eliminates the need for the user to manually change material color in each build layer, the use of multiple extruder nozzles within the build plane simultaneously causes some imperfections in the 3D object being printed. Since the non-extruding extruder nozzle(s) is fixed in the build plane with the extruder nozzle in use, the non-extruding extruder nozzle(s) is moved across the surface of each build layer during the build process. While the non-extruding extruder nozzle(s) moves across the build layer, the non-extruding extruder nozzle(s) scraps the build layer picking up and leaving material of a non-desired material color in the 3D object. Thus it would be advantageous to provide a multiple color extrusion type 3D Printer with a means of printing multiple colors where only one extruder nozzle is in the build plane during the build process. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with the present invention there are disclosed several embodiments of a novel Multiple Color Extrusion Type 3D Printer where a build material is extruded onto a build surface (area specified on the build plate for extruding the first build layer and as determined by the x-y-z positioning assembly&#39;s range of motion to move the extruder nozzle) to build a 3D Object by means of a single extrusion nozzle located in a build plane (plane parallel to the build surface where the extrusion nozzle extrudes build material limited horizontally by the x-y-z positioning assembly&#39;s range of motion to move the extrusion nozzle) during the build process. In the first embodiment, shown are a plurality of material extruders each provided with an extrusion nozzle, each provided with a build material feeder assembly, and each material extruder capable of receiving a given colored build material. All the material extruders and extrusion nozzles are mechanically connected to a x-y-z positioning assembly and moved simultaneously relatively to a build plate. To move each extrusion nozzle in/out of the build plane, this embodiment discloses a material extrusion nozzle positioning assembly capable of moving each extrusion nozzle vertically in and out of the build plane such that only one extrusion nozzle is in the build plane during the build process. When a change is color is required during the build process, the build process is halted and one extruder is turned off, the extrusion nozzle for the color of the build material no longer required is raised out of the build plane, and the extrusion nozzle for the new color build material is lowered into the build plane prior to extruding the new color build material to continue the build process. In the same embodiment an alternate configuration is disclosed showing the x axis of the x-y-z positioning assembly as a means of moving each extrusion nozzle horizontally in and out of the build plane such that only extrusion nozzle is over the build surface and within the build volume during the extrusion process. In this alternate configuration, while the extrusion nozzles are still in the same plane as the build plane, the build plane&#39;s horizontal limits as defined by the build volume (3D object&#39;s maximum part volume as determined by the build plane and as determined by the x-y-z positioning assembly&#39;s range of motion to move the build plane relative to the build surface on the build plate) allows the extrusion nozzles to be moved out of the build plane in a horizontal direction. 
         [0006]    In another embodiment there is disclosed a Multiple Color Extrusion Type 3D Printer where multiple build materials are extruded to build a 3D Object by means of a single extrusion nozzle in the build plane. In this embodiment, a material extruder is provided with a single extrusion nozzle and the material extruder is capable of receiving a plurality of different colored build materials, each build material feed into the single material extruder by a build material feeder assembly. The extruder assembly consisting of material extruder, extrusion nozzle, and build material feeder assemblies is moved relative to the build plate by means of a x-y-z positioning assembly. In this embodiment, when a color change is required during the build process, the build material of the color no longer required is stopped from being fed into the material extruder by the build material feeder assembly associated with the color and the new color build material is fed into the material extruder by the build material feeder assembly associated with the new color build material. This embodiment also discloses two or more build materials feed simultaneously into the material extruder such that colors may be blended to provide a new color at the extrusion nozzle different from the colors of the build materials fed into the material extruder. 
         [0007]    In another alternate embodiment there is disclosed a Multiple Color Extrusion Type 3D Printer where a docking station is provided to receive a plurality of material extruders each material extruder provided with an extrusion nozzle and each capable of receiving a different colored build material controlled by a build material feeder assembly. In this embodiment, the x-y-z positioning assembly is provided with an extruder clamp capable of receiving a material extruder from the docking station and moving the material extruder with its extrusion nozzle relative to the build plate. In this embodiment, when a color change is required during the build process, the build process is halted while the x-y-z positioning assembly returns the material extruder to the docking station moving the material extruder&#39;s extrusion nozzle out of the build plane, then removes the material extruder provided with the new color build material from the docking station before moving the extrusion nozzle associated with the new color into the build plane to continue the build process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is an isometric view of an existing technology extrusion type 3D Printer with a single material extruder and extruder nozzle. 
           [0009]      FIG. 2  is an isometric view of an existing technology extrusion type 3D Printer with dual material extruders and extruder nozzles for the purpose of printing a two color 3D object. 
           [0010]      FIG. 3  is an isometric view of a preferred embodiment of a multiple color extrusion type 3D Printer showing a 3D Printer provided with extrusion nozzle positioning assembly to raise and lower (vertical direction) the material extruders and extruder nozzles where the right extruder nozzle is positioned in the build plane. 
           [0011]      FIG. 4  is an isometric view of the preferred embodiment shown in  FIG. 3  where the left extruder nozzle is positioned in the build plane. 
           [0012]      FIG. 5  is an isometric view of the preferred embodiment shown in  FIG. 3  where the extrusion nozzles are separated in the x axis direction of adequate distance such that the x axis of the x-y-z positioning assembly also serves as the extruder nozzle positioning assembly by moving the unused extrusion nozzle out of the build plane in a horizontal direction. 
           [0013]      FIG. 6  is an isometric view of an alternate embodiment of the invention showing a multiple color extrusion type 3D Printer provided with a material extruder capable of receiving multiple build materials of different colors, and extruding an or all build materials through a single extruder nozzle. 
           [0014]      FIG. 7  is an isometric view of another alternate embodiment of the invention showing a multiple color extrusion type 3D Printer provided with a material extruder clamp on the x-y-z positioning assembly, provided with a material extruder docking station, and multiple material extruders where the material extruder clamp is not loaded with a material extruder. 
           [0015]      FIG. 8  is an isometric view of the alternate embodiment shown in  FIG. 7  where the material extruder clamp is loaded with a material extruder. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    It is well known in the three-dimensional fabricating industry that a three-dimensional object can be created by a apparatus using an additive process that builds the three-dimensional object layer by layer onto a build plate per a CAD model and more specifically uses an extrusion type build process as shown by U.S. Pat. No. 8,282,380 issued Oct. 9, 2012 to MakerBot Industries. It is also well know that 3D Slicer software is used to slice a CAD Model into several layers parallel to the build plate and that the extrusion process used to build the 3D Object takes place starting by extruding a layer of build material onto a build plate in a build plane, then moves the build plane and build plate away from each other to build another build layer on the first layer of extruded build material. This process continues layer upon layer each layer moving the build plane and build plate farther from each other while extruding a layer of build material with the same shape as the corresponding CAD Model Slice until the 3D Object being built matches the original CAD model. 
         [0017]      FIG. 1  shows an existing technology three-dimensional (3D) Printer. As shown in  FIG. 1 , a support structure  1  houses a build plate  2  providing a build surface that is supported by a rigid and stabile leveling assembly  3 . While a leveling assembly is typically provided in the existing technology as shown, the leveling of the build plate  2  is not required as the leveling could be compensated for by means of the x-y-z positioning assembly described below. The support structure  1  also houses a material extruder  4  for receiving a build material  5  which is fed into the material extruder  4  by means of a build material Feeder assembly comprised of a stepper motor  6  and build material feed gear  7 . The material extruder  4  is also provided with an extrusion nozzle  8  located in the build plane. The stepper motor  6  is electrically connected to a controller  9  to control the feed rate the build material  5  is feed into the material extruder  4  and the material extruder  4  is electrically connected to the controller  9  for the purpose of regulating the temperature of the material extruder  4  such that the build material  5  melts and begins to flow (typically 220° C. to 230° C. for use of ABS as a build material  5 ) out of the extrusion nozzle  8  as the build material feeder assembly feeds build material  5  into the material extruder  4 . The material extruder  4  and extrusion nozzle  8  are mechanically supported by a x-y-z positioning assembly comprised of three linear slides with gear-motor assemblies that are attached to the support structure  1  where the x direction linear slide  10  is supported on rails  11  and moved by a x direction gear-motor  12 , where the y direction linear slide  20  is supported on rails  21  and moved by a y direction gear-motor  22 , and where the z direction linear slide  30  is supported on rails  31  and moved by a z direction gear-motor  32 . The controller  9  is electrically connected is electrically connected each of the x-y-z positioning assembly gear-motors  11 ,  21 , and  31  to position the extruder nozzle  8  relative to the build plate  2 . 
         [0018]    To build a 3D Object, the controller  9  moves the position of the extrusion nozzle  8  in the build plane parallel to the build plate  2  by means of the x-y-z positioning assembly while controlling the rate build material  5  is feed into the material extruder  4  to extrude a layer of material from the extrusion nozzle  8  onto the build surface in the shape of the CAD model&#39;s first slice as determined by the 3D slicer software. After the first build layer is complete, the controller  9  moves the position of the extrusion nozzle  8  to the next build plane away from the build plate  2  by means of the x-y-z positioning assembly to extrude a second layer of material from the extrusion nozzle  8  onto the previous build layer in the shape of the CAD model&#39;s next slice as determined by the 3D slicer software. The process continues extruding layer upon layer of material each layer with the shape of the corresponding CAD model slice until the 3D object matches the original geometry of the CAD Model where the thickness of each layer of extruded material is selected by the resolution the user desires as entered into the 3D slicer software. To print a two color 3D object using the 3D printer of  FIG. 1 , the 3D printer must stop during each layer for user to manually change the color of the build material  5  before restarting the build process. 
         [0019]      FIG. 2  shows an existing technology two color three-dimensional (3D) printer. The 3D printer shown in  FIG. 2  is identical to the 3D printer shown in  FIG. 1  except for the addition of a second material extruder  40  for receiving a second build material  41  of a second material color fed into the second material extruder  40  by means of a second build material feeder assembly comprised of a stepper motor  42  and build material feed gear  43 , and except for revised logic within the controller  9  to control the second material extruder  40  and to control the second build material feeder assembly. The second material extruder  40  is provided with an extrusion nozzle  44  and is electrically connected to a controller  9  for the purpose of regulating the temperature of the material extruder  40  similarly to the first material extruder  4 . The second material extruder  40  and second extrusion nozzle  44  are mechanically supported on the same x-y-z positioning assembly as the first material extruder  4  such that both material extruders extrude into the same build plane. To print a two color 3D object using the 3D printer of  FIG. 2 , the controller  9  changes colors by stopping the build material being fed into one material extruder and starts the other build material being fed into the other material extruder by stopping and starting the stepper motors  10  and  42 . While this technology shown in  FIG. 2  eliminates the need for the user to manually change build material from one color to another, the movement of both extruder nozzles simultaneously in the build plane causes the unused extrusion nozzle to touch parts of the 3D object being built (raised imperfections in the build layer) resulting in extruded material being picked up and dragged such that small amounts of the incorrect color material are dropped in undesired areas of the 3D object. 
         [0020]      FIG. 3  shows the existing technology two color extrusion type 3D printer of  FIG. 2  with a preferred embodiment of the invention showing a extrusion nozzle positioning assembly comprised of two solenoids  50  and  51 . The first solenoid  50  is mechanically connected to the material extruder  4  and extruder nozzle  8  and the second solenoid  51  is mechanically connected to the second material extruder  40  and extruder nozzle  44 . Both solenoids  50  and  51  are electrically connected to the controller  9  such that the controller  9  can raise and lower each extruder nozzle independent of the other extruder nozzle such that only one extruder nozzle is in the build plane during the build process. To print a two color 3D object using the 3D printer of  FIG. 3 , the controller  9  changes colors by stopping the first build material  5  being fed into the material extruder  4  and raising the material extruder  4  and extrusion nozzle  8  out of the build plane by means of the solenoid  50 , lowering the second material extruder  41  and extrusion nozzle  44  by means of the second solenoid  51  into the build plane as shown in  FIG. 4 , then feeding second build material  41  of different color into the second material extruder  40  to continue the build process. To change the color of the build materials  5  and  41  back to the first color, the process is reversed stopping and raising the second material extruder  40  along with lowering and starting the first material extruder  4 . Since only one extrusion nozzle  4  or  44  is in the build plane while extruding during the build process, and since the other extrusion nozzle is raised above the build plane and does not touch the 3D object being built or any imperfections normally associated with the extrusion process, the 3D object being built does not have random bits of the incorrect colored material scattered throughout the 3D object. 
         [0021]    While the two color extrusion type 3D printer shown in  FIG. 3  shows two solenoids  50  and  51 , it is understood that stepper motors, gear-motors, or any variety of motion control devices and mechanical assemblies could be used to provide the mechanical motion necessary to control the height of the both material extruders and extrusion nozzles relative to the build plane such that only one extrusion nozzle is in the build plane during the build process. While only two material extruders  4  and  40 , two build materials  5  and  41 , two extrusion nozzles  8  and  44 , and two solenoids  50  and  51  are shown, two or more material extruders, build materials, extrusion nozzles and a mechanical motion control system could be provided to limit one extrusion nozzle in the build plane during the build process including a mechanical motion control system that requires only a single motion control device. For example, a gear-motor and a cam could be used to control a plurality of material extruders and extrusion nozzles such that only one extrusion nozzle is in the build plane during the build process. Additionally, a single motion control device could be coupled with the z axis of the x-y-z positioning assembly such that a single solenoid could be used to raise and lower one material extruder and extrusion nozzle above and below a material extruder and extrusion nozzle that is fixed to the x-y-z positioning assembly. In the example, swapping extrusion nozzles in the build plane requires raising or lowering the z axis to move the extrusion nozzle fixed to the x-y-z positioning assembly and lowering or raising (opposite z direction of x-y-z-positioning assembly) twice the distance the z axis moved to position the other extrusion nozzle in or above the build plane. 
         [0022]    It is further understood that while a x-y-z positioning assembly is shown to position the extrusion nozzle(s) relative to the build plate  2 , a robotic arm commonly used in the motion control industry to move parts within a given three-dimensional space could be used to replace the x-y-z positioning assembly. Additionally, while a variety of motion control devices could be used to raise and lower extrusion nozzles in and out of the build plane, use of one axis of a robotic arm (such as the rotation of a wrist) could be used to raise and lower extrusion nozzles. For example, mechanically connecting one extrusion nozzle to the thumb and connecting a second extrusion nozzle to the little finger would allow rotating of the robotic arm&#39;s wrist to raise and lower the extrusion nozzles such that only one extrusion nozzle is in the build plane during the build process. 
         [0023]      FIG. 5  shows and alternate configuration of the preferred embodiment of  FIG. 3  where the extrusion nozzle positioning assembly comprised of solenoids  50  and  51  is replaced with spacers  52  and  53  to provide adequate distance between material extruders  4  and  40  and adequate distance between extrusion nozzles  8  and  44  such that only one extrusion nozzle is in the build plane during the build process. While both extrusion nozzles are in the same plane parallel the build surface, the spacers  52  and  53  provide adequate distance between the extrusion nozzles such that one extrusion nozzle is located horizontally outside the build plane and outside the build volume. In  FIG. 5 , the x axis of the x-y-z positioning assembly is used to move the extrusion nozzles horizontally in and out of the build plane and the build surface and build volume are limited dimensionally in the direction of the x axis to a maximum distance of the distance provided between the extrusion nozzles  8  and  44 . Any distance between the extrusion nozzles  8  and  44  shorter than the length of the build plane or build volume in the same direction would allow both extrusion nozzles  8  and  44  to be in the build plane simultaneously during all or part of the build process resulting in extruded material being picked up and dragged such that small amounts of the incorrect color material are dropped in undesired areas of the 3D object. 
         [0024]      FIG. 6  shows the existing technology two color extrusion type 3D printer of  FIG. 1  with a alternate embodiment of the invention showing a single material extruder  60  mechanically connected to the x-y-z positioning assembly. In this embodiment, the material extruder  60  is capable of receiving two different colored build materials  61  and  62 . The first build material  61  is fed into the material extruder  60  by means of a build material feeder assembly comprised of a stepper motor  63  and build material feed gear  64 . The second build material  62  is fed into the same material extruder  60  by means of a second build material feeder assembly comprised of a second stepper motor  65  and second build material feed gear  66 . Both stepper motors  63  and  65  are electrically connected to the controller  9  to control the feed rate each build material  61  and  62  is fed into the material extruder  60 . The material extruder  60  is provided with a single extrusion nozzle  67  and the material extruder  60  is electrically connected to the controller  9  for the purpose of regulating the temperature of material extruder  60  such that the build materials  61  an  62  melt and begin to flow out of the single extrusion nozzle  67  as the build material feeder assemblies feed build materials  61  and  62  into the material extruder  60 . 
         [0025]    In the embodiment shown in  FIG. 6 , the two build material feeder assemblies can be operated by the controller  9  independently or simultaneously or at different feed rates such that changing the color extruded from the single extrusion nozzle  67  may be changed by stopping the first build material  61  from being fed into the material extruder  60 , then starting the second build material  62 . The color extruded from the single extrusion nozzle  67  may be changed by starting a second build material  62  feed into the material extruder  60  while the first build material  61  continues to be feed into the material extruder  60  resulting in a blend of the two build materials  61  and  62  being extruded from the single extrusion nozzle  67 . The color extruded from the single extrusion nozzle  67  may also be changed by stopping one of the build materials  61  or  62  from being feed into the material extruder  60 . The color extruded from the single extrusion nozzle  67  may also be changed by changing the feed rate of the build materials  61  and  62  such that the color extruded from the single extrusion nozzle  67  is a blend of the two build materials  61  and  62  with a mix ratio other than a one to one mixture. 
         [0026]    While the two color extrusion type 3D printer shown in  FIG. 6  shows two build materials  61  and  62 , and two build material feeder assemblies comprised of stepper motors  63  and  65  and build material feed gears  64  and  66 , it is understood two or more build materials could be fed into the single material extruder  60  for the purpose of extruding any single build material or a blend of any combination of build materials from the single extrusion nozzle  67  where the single extrusion nozzle  67  is the only extrusion nozzle in the build plane during the build process. Also, while the build material feeder assemblies are shown feeding build materials into the single material extruder  60 , material colorants could be provided in place of one or more build materials such that a build material(s) could be combined with any combination of colorant materials in the single extruder  60  and extruded from the single extrusion nozzle  67  as commonly found in plastic molding industry. Additionally, material colorants such as the primary colors (red, blue and green) could be feed into the single material extruder  60  and blended in a multiple combination of mix ratios to extrude multiple colors from the single extrusion nozzle  67 . 
         [0027]    While a x-y-z positioning assembly is shown in  FIG. 6  to position the extrusion nozzle  67  relative to the build plate  2 , a robotic arm could be used to replace the x-y-z positioning assembly. 
         [0028]      FIG. 7  shows the existing technology two color extrusion type 3D printer of  FIG. 2  with a an alternate embodiment of the invention showing a material extruder  70  for receiving a build material  71  feed into the material extruder  70  by means of a build material feeder assembly comprised of a stepper motor  72  and build material feed gear  73  for the purpose of extruding the build material  71  through an extrusion nozzle  74  along with a second material extruder  80  for receiving a second build material  81  of different material color feed into the second material extruder  80  by means of a second build material feeder assembly comprised of a second stepper motor  82  and second build material feed gear  83  for the purpose of extruding the build material  81  through an extrusion nozzle  84 . Both stepper motors  73  and  83  are electrically connected to the controller  9  to control the feed rate the building materials  71  and  81  are fed into the material extruders  70  and  80 . The material extruders  70  and  80  are electrically connected to the controller  9  to regulate the temperature of the material extruders  70  and  80  such that the build materials  71  and  81  melt and start to flow out of the extrusion nozzles  74  and  84  as the build material feeder assemblies feed build materials  71  and  81  into the material extruders  70  and  80 . In this embodiment of the invention, the material extruders  70  and  80  along with the extrusion nozzles  74  and  84  are supported by a docking station  90  but not permanently connected mechanically to the docking station  90 .  FIG. 7  also shows a extruder clamp  91  mechanically connected to the x-y-z positioning assembly the extruder clamp  91  capable of receiving the material extruders  70  and  80  from the docking station  90 . The x-y-z positioning assembly as determined by the controller  9  is capable of moving such that the extruder clamp  91  snaps onto a material extruder  70  or  80  and such that the material extruder  70  or  80  along with the extrusion nozzle  74  or  84  is lifted out of the docking station. As shown in  FIG. 8 , the material extruder  70  is received by the extruder clamp  91  and removed from the docking station  90 . To print a two color 3D object using the printer of  FIGS. 6 and 7 , the controller  9  changes colors by moving the x-y-z positioning assembly to lower the material extruder and extrusion nozzle into an empty location in the docking station  90 , moves the extruder clamp  91  away from the docking station to release the material extruder and extrusion nozzle from the extruder clamp  91 , then moves the extruder clamp  91  horizontally to the material extruder and extrusion nozzle fed with the desired color build material to receive the material extruder and extrusion nozzle before lifting the material extruder and extrusion nozzle out of the docking station  91  before continuing the build process. In this embodiment the build surface, build plane, and build volume may be dimensionally limited by the volume the docking station  90  as the 3D object being built cannot be built in the same volume used by the docking station  90 . Additionally, the build plane may change dimensionally as the distance between the build plane and build plate change during the build process. In this embodiment involving the docking station  90  and extruder clamp  91 , only one extrusion nozzle is in the build plane during the extrusion process while the docking station  91  houses the other material extruder and extrusion nozzle. 
         [0029]    While the two color extrusion type 3D printer shown in  FIGS. 7 and 8  show two material extruders  70  and  80 , two build materials  71  and  81 , and two extrusion nozzles  83  and  84 , it is understood that two or more material extruders, two or more build materials, and two or more extrusion nozzles may be supported by the docking station  90 . 
         [0030]    While  FIGS. 7 &amp; 8  show a docking station  90  capable of supporting two material extruders  70  and  80 , two build materials  71  and  81 , and two extrusion nozzles  83  and  84 , the 3D printer shown may be modified such that the docking station  90  receives individual build materials instead of the assembly consisting of a material extruder, build material feeder assembly, and extrusion nozzle with build material fed into the material extruder. In this alternate configuration of the embodiment shown in  FIGS. 7 and 8 , the x-y-z positioning assembly is mechanically connected to a single material extruder, single build material feeder assembly, and connected to a single extrusion nozzle and the color of the material extruded from the extrusion nozzle is changed by the controller  9  moving the x-y-z positioning assembly to park the existing build material in an empty location in the docking station  90 , then disconnects the existing build material from the material extruder by backing the existing build material out of the material extruder by reversing the stepper motor in the build material feeder assembly, then repositioning the material extruder in line with the build material of the desired material color before feeding the new build material into the material extruder using the build material feeder assembly connected to the x-y-z positioning assembly. In the same manner, the docking station  90  could be modified to receive any part or all parts of the extrusion equipment described including material extruder, build material, build material feeder assembly, and/or extrusion nozzle such that all parts as shown in  FIGS. 7 and 8  are supported by the docking station  90 , or the build material and part of the extrusion equipment is supported by the docking station  90 , or only the build material is supported by the docking station  90  as previously described. 
         [0031]    While a x-y-z positioning assembly is shown in  FIGS. 7 and 8  to position the extrusion nozzle  74  or  84  relative to the build plate  2 , a robotic arm could be used to replace the x-y-z positioning assembly. 
         [0032]    While several preferred embodiments of the present invention have been described, it should be understood that various changes such as but not limited to moving the build plate relative to the extrusion nozzles, various adaptations, and various modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims.