Patent Publication Number: US-11034089-B2

Title: Plasticizing device and three-dimensional shaping device

Description:
The present application is based on, and claims priority from, JP Application Serial Number 2018-178937, filed Sep. 25, 2018, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a plasticizing device and a three-dimensional shaping device. 
     2. Related Art 
     For example, JP-A-2010-241016 discloses a plasticizing device which has a rotor having a helical groove formed at an end surface, and a barrel facing the end surface of the rotor where the helical groove is formed and having a communication hole at the center. In this plasticizing device, a material is supplied into the helical groove of the rotor from a hopper at a timing when a material outlet port of the hopper and a material inlet port provided at a lateral side of the rotating rotor overlap each other. 
     In the above plasticizing device, the material is supplied into the helical groove of the rotor from the hopper according to the rotation cycle of the rotor. Therefore, during the period from a timing when the material is supplied into the spiral groove of the rotor from the hopper to the next timing when the material is supplied, the material melted in the spiral groove flows out from the communication hole of the barrel and the amount of the material in the spiral groove decreases. Thus, the applicant of the present disclosure has found that the pressure of the molten material pressure-fed into the communication hole changes, causing a change in the flow rate of the molten material ejected from the communication hole. 
     SUMMARY 
     The present disclosure proposes a plasticizing device in which the change in the flow rate of the molten material ejected from the communication hole is small. 
     According to an aspect of the present disclosure, a plasticizing device plasticizing a material into a molten material is provided. The plasticizing device includes: a drive motor; a rotating unit driven to rotate about a rotation axis by the drive motor and having an end surface perpendicular to the rotation axis and a lateral surface intersecting with the end surface; a barrel having a bottom surface facing the end surface of the rotating unit, and a heater; a case accommodating the rotating unit; and a material supply unit accommodating the material. At least one of the barrel and the case has a sidewall surface facing the lateral surface of the rotating unit and standing up along an outer circumference of the bottom surface of the barrel. At the bottom surface of the barrel, a communication hole through which the molten material flows out and a spiral groove part coupled to the communication hole are formed. The lateral surface of the rotating unit and the sidewall surface together define a supply space where the material is supplied from the material supply unit to the groove part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory view showing a schematic configuration of a three-dimensional shaping device in a first embodiment. 
         FIG. 2  is a perspective view showing a configuration of a flat screw in the first embodiment. 
         FIG. 3  is a top view showing a configuration of a bottom surface of a barrel in the first embodiment. 
         FIG. 4  is an explanatory view showing a schematic configuration of a three-dimensional shaping device in a second embodiment. 
         FIG. 5  is a top view showing a configuration of a bottom surface of a barrel in the second embodiment. 
         FIG. 6  is a cross-sectional view taken along VI-VI of the barrel in the second embodiment. 
         FIG. 7  is a top view showing a configuration of a bottom surface of a barrel in a third embodiment. 
         FIG. 8  is an explanatory view showing a schematic configuration of an injection molding device in another form. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     A. First Embodiment 
       FIG. 1  is an explanatory view showing a schematic configuration of a three-dimensional shaping device  100  in a first embodiment. In  FIG. 1 , arrows along X, Y, and Z-axes orthogonal to each other are shown. The X-axis and the Y-axis are along the horizontal direction. The Z-axis is along the vertical direction. Similarly, arrows along the X, Y, and Z-axes are shown in the other drawings, according to need. The X, Y, and Z-axes in  FIG. 1  represent the same axes as the X, Y, and Z-axes in the other drawings. 
     The three-dimensional shaping device  100  has: an ejection unit  200  including a nozzle unit  60 , a flow rate adjustment mechanism  70 , and a plasticizing device  90 ; a shaping table  310 ; a movement mechanism  320 ; and a control unit  500 . In the three-dimensional shaping device  100  in this embodiment, under the control of the control unit  500 , a shaping material plasticized by the plasticizing device  90  is supplied to the nozzle unit  60 , and the shaping material ejected from a nozzle hole  61  of the nozzle unit  60  is stacked at the top of the shaping table  310 , thus shaping a three-dimensional shaped object. The shaping material may be referred to as a molten material. 
     The movement mechanism  320  changes the relative position between the shaping table  310  and the ejection unit  200 . In this embodiment, the movement mechanism.  320  moves the shaping table  310  relative to the ejection unit  200 . The movement mechanism  320  in this embodiment is formed of a three-axis positioner which moves the shaping table  310  along the three axes of X, Y, and Z by drive forces of three motors. Each motor drives under the control of the control unit  500 . 
     Instead of being configured to move the shaping table  310 , the movement mechanism  320  may be configured to move the ejection unit  200  without moving the shaping table  310 . The movement mechanism.  320  may also be configured to move both the shaping table  310  and the ejection unit  200 . The movement mechanism  320  may have any configuration that can change the relative position between the shaping table  310  and the ejection unit  200 . 
     The control unit  500  is formed of a computer having one or more processors, a main storage device, and an input/output interface to input a signal from outside and output a signal to outside. In this embodiment, the control unit  500  causes the processor to execute a program or command read into the main storage device and thereby controls an operation of the ejection unit  200  and the movement mechanism  320 , thus executing shaping processing to shape a three-dimensional shaped object. The operation includes a movement of the three-dimensional relative position of the ejection unit  200  relative to the shaping table  310 . The control unit  500  may also be configured of a combination of a plurality of circuits, instead of a computer. 
     The plasticizing device  90  has a material supply unit  20  and a plasticizing unit  30 . The material supply unit  20  and the plasticizing unit  30  communicate with each other via a supply path  22 . The plasticizing unit  30  and the nozzle hole  61  of the nozzle unit  60  communicate with each other via a communication hole  55 . The plasticizing device  90  at least partly melts a solid-state material and supplies the resulting paste-like shaping material to the nozzle unit  60 . 
     The material supply unit  20  accommodates a material in the state of pellets, powder or the like. The material in this embodiment is ABS resin in the form of pellets. The material supply unit  20  in this embodiment is formed of a hopper. The material accommodated in the material supply unit  20  is supplied to the plasticizing unit  30  via the supply path  22  provided below the material supply unit  20 . 
     The plasticizing unit  30  has a screw case  31 , a drive motor  32 , a flat screw  40 , and a barrel  50 . The screw case  31  is a casing accommodating the flat screw  40 . The drive motor  32  is fixed to a top surface of the screw case  31 . The drive motor  32  drives under the control of the control unit  500  and thus rotates the flat screw  40  about a rotation axis RX. The flat screw  40  may be referred to as a rotating unit. The screw case  31  may be simply referred to as a case. 
     In this embodiment, the flat screw  40  is arranged in the screw case  31  in such a way that the rotation axis RX is parallel to the Z-axis. The drive motor  32  is coupled to a top surface of flat screw  40 . A torque generated by the drive motor  32  causes the flat screw  40  to rotate about the rotation axis RX in the screw case  31 . The flat screw  40  has an end surface  45  perpendicular to the rotation axis RX, at the side opposite to the surface where the drive motor  32  is coupled. The flat screw  40  has a lateral surface  46  intersecting with the end surface  45 . The detailed shape of the flat screw  40  will be described later with reference to  FIG. 2 . 
     In this embodiment, the barrel  50  is fixed to the bottom side of the screw case  31 . The barrel  50  has a bottom surface  51  facing the end surface  45  of the flat screw  40 . In the bottom surface  51 , the communication hole  55  is provided at a position on the rotation axis RX of the flat screw  40 . A spiral groove part  56  is provided around the communication hole  55  in the bottom surface  51 . The barrel  50  has a built-in heater  58 . The temperature of the heater  58  is controlled by the control unit  500 . The detailed shape of the barrel  50  will be described later with reference to  FIG. 3 . 
     In this embodiment, the barrel  50  and the screw case  31  together form a sidewall surface  52  facing the lateral surface  46  of the flat screw  40  and standing up along the outer circumference of the bottom surface  51 . In this embodiment, an upper-side part of the sidewall surface  52  is formed by an inner wall surface of the screw case  31 . A supply port  25  communicating with the material supply unit  20  is provided at the inner wall surface of the screw case  31 . A lower-side part of the sidewall surface  52  is formed by a wall surface standing up from the bottom surface  51  of the barrel  50 . Also, the sidewall surface  52  may be formed by the screw case  31  alone, where the inner wall surface of the screw case  31  extends to the bottom surface  51  of the barrel  50 . The sidewall surface  52  may also be formed by the barrel  50  alone, where the wall surface standing up from the bottom surface of the barrel  50  extends to above the top surface of the flat screw  40 . 
     In this embodiment, the wall surface of the barrel  50  forming the sidewall surface  52  has a slope part  53  at a position intersecting with the bottom surface  51 . The slope part  53  is sloped in such a way as to approach the center of the bottom surface  51  as it goes toward the bottom surface  51 . 
     The lateral surface  46  of the flat screw  40  and the sidewall surface  52  together define a supply space  59  where the material is supplied from the material supply unit  20  to the groove part  56 . The supply space  59  is a space where the material can circulate from the supply port  25  into the groove part  56 . 
     The flow rate adjustment mechanism  70  is provided with a valve mechanism  71 . The valve mechanism  71  in this embodiment is formed of a butterfly valve. The valve mechanism  71  opens and closes under the control of the control unit  500  and switches between communication and non-communication between the communication hole  55  and the nozzle hole  61 . 
     Inside the nozzle unit  60 , a nozzle flow path  62  and the nozzle hole  61  are provided. The nozzle hole  61  is a part that is provided at an end part at the side communicating with the atmosphere and that has a reduced flow path cross section, in the nozzle unit  60 . The nozzle flow path  62  is supplied with the shaping material from the plasticizing device  90  via the flow rate adjustment mechanism  70 . The shaping material supplied to the nozzle flow path  62  is ejected from the nozzle hole  61 . In this embodiment, the diameter of the nozzle flow path  62  is the same as the diameter of the communication hole  55 . However, the diameter of the nozzle flow path  62  may be smaller than the diameter of the communication hole  55 . A nozzle diameter Dn of the nozzle hole  61  is smaller than the diameter of the nozzle flow path  62 . The nozzle diameter Dn is the diameter of the nozzle hole  61  at the end part at the side communicating with the atmosphere. 
       FIG. 2  is a perspective view showing the configuration of the flat screw  40  in the first embodiment. The flat screw  40  shown in  FIG. 2  is in the state where the up-down positional relation shown in  FIG. 1  is reversed in order to facilitate understanding of the technology. The flat screw  40  in this embodiment has a main body part  41 , a flange part  42 , and a plurality of blade parts  43 . In the flat screw  40  in this embodiment, the main body part  41 , the flange part  42 , and the plurality of blade parts  43  are molded as one body. 
     The main body part  41  is substantially cylindrical. The main body part  41  has the foregoing end surface  45 . The diameter of the main body part  41  near the end surface  45  becomes smaller as it goes toward the end surface  45 . 
     The flange part  42  is a disk-like part provided at the side opposite to the end surface  45  in the axial direction of the main body part  41 . The radius of the flange part  42  is larger than the radius of the main body part  41 . 
     The blade part  43  is a part protruding in a radial direction of the main body part  41  from the lateral surface  46  of the main body part  41 . The blade part  43  is provided between the end surface  45  and the flange part  42  in the axial direction of the main body part  41 . The blade part  43  is coupled to the lateral surface  46  of the main body part  41  and to the flange part  42 . A part at the side of the end surface  45 , of the blade part  43 , is sloped so as not to interfere with the slope part  53  of the barrel  50 . In this embodiment, eight blade parts  43  are arranged at equal intervals in the circumferential direction of the main body part  41 . 
       FIG. 3  is a top view showing the configuration of the bottom surface  51  of the barrel  50  in the first embodiment. As described above, the communication hole  55  and the spiral groove part  56  are formed at the bottom surface  51  of the barrel  50 . In  FIG. 3 , the groove part  56  is hatched in order to facilitate understanding of the technology. 
     The communication hole  55  is provided at the center of the bottom surface  51 . The groove part  56  has a center part  151 , a spiral part  152 , and a material inflow part  153 . The center part  151  is a circular depression around the communication hole  55 . One end of the spiral part  152  is coupled to the communication hole  55  via the center part  151 . The spiral part  152  spirally extends about the center part  151  in such a way as to form an arc toward the outer circumference of the bottom surface  51 . The spiral part  152  may be formed in such a way as to extend in the shape of an involute curve or helically. 
     In this embodiment, the cross section of the spiral part  152  perpendicular to the direction of a tangent to the spiral is rectangular. The cross-sectional area of the spiral part  152  in this embodiment is constant. In this embodiment, since the cross section of the spiral part  152  is rectangular, the cross-sectional area of the spiral part  152  can be calculated as the product of the width and depth of the groove of the spiral part  152 . Also, the cross section of the spiral part  152  may be other than rectangular. For example, the cross section of the spiral part  152  may be semicircular. In this case, the cross-sectional area of the spiral part  152  can be calculated using pi (the ratio of the circumference of the circle to its diameter) and the radius of the groove of the spiral part  152 . 
     The other end of the spiral part  152  is coupled to the material inflow part  153 . The material inflow part  153  is a groove-like part provided at the outer circumferential edge of the bottom surface  51  and wider than the spiral part  152 . The supply port  25  of the supply path  22  is arranged above the material inflow part  153 . 
     In the above configuration of the three-dimensional shaping device  100 , as the control unit  500  executes shaping processing to shape a three-dimensional shaped object, the material in the material supply unit  20  travels through the supply port  25  and is supplied into the supply space  59  between the lateral surface  46  of the rotating flat screw  40  and the sidewall surface  52  formed by the screw case  31  and the barrel  50 . 
     In this embodiment, the blade part  43  of the rotating flat screw  40  circles inside the supply space  59 . Therefore, the material supplied from the supply port  25  sequentially fills the space between the respective blade parts  43  of the rotating flat screw  40 . A part of the material filling the space between the blade parts  43  is supplied into the material inflow part  153  at a timing when this space overlaps the material inflow part  153 . In the space between the blade parts  43  where the amount of the material filling the space is reduced as the material is supplied into the material inflow part  153 , the material is additionally supplied from the supply port  25  at a timing when this space overlaps the supply port  25 . Therefore, the inside of the supply space  59  is filled with the material while the flat screw  40  is rotating. 
     The material supplied into the material inflow part  153  is transported into the spiral part  152  by the rotation of the flat screw  40 . The material transported into the spiral part  152  is at least partly melted by the rotation of the flat screw  40  and the heating by the heater  58  built inside the barrel  50 , and thus becomes a fluid paste-like shaping material. The shaping material is transported within the spiral part  152  and pressure-fed into the communication hole  55  by the rotation of the flat screw  40 . The shaping material supplied to the nozzle unit  60  via the communication hole  55  is ejected from the nozzle hole  61  toward the top of the shaping table  310 . 
     In the three-dimensional shaping device  100  in this embodiment described above, the material supplied from the material supply unit  20  is stored in the supply space  59  provided between the flat screw  40  and the barrel  50 . This enables continuous supply of the material from the supply space  59  to the groove part  56 . Therefore, a change in the pressure of the shaping material pressure-fed into the communication hole  55  can be restrained and a change in the flow rate of the shaping material ejected from the communication hole  55  can be restrained. Thus, a change in the flow rate of the shaping material ejected from the nozzle hole  61  can be restrained. 
     Also, in this embodiment, the blade part  43  protruding in the radial direction of the rotating flat screw  40  can stir the material inside the supply space  59 . Therefore, the material can be restrained from adhering to the barrel  50  and closing the supply space  59 . 
     Also, in this embodiment, the material supplied from the supply port  25  provided above the slope part  53  flows along the slope part  53  and smoothly flows into the material inflow part  153 . This facilitates the supply of the material into the material inflow part  153 . 
     In this embodiment, ABS resin pellets are used as the material. However, as the material used in the ejection unit  200 , a material shaping a three-dimensional shaped object which contains various materials such as thermoplastic material, metal material, and ceramic material, as its main material, can be employed. Here, the “main material” means a material mainly contributing to the shaping of the three-dimensional shaped object and means a material whose content in the three-dimensional shaped object is 50% by weight or higher. The shaping material includes the main material melted as a single material, or a paste-like material in which a part of a component contained along with the main material is melted. 
     When a thermoplastic material is used as the main material, the plasticizing device  90  plasticizes the material and thus produces the shaping material. The term “plasticize” means to melt the thermoplastic material by applying heat. 
     As the thermoplastic material, for example, one or a combination of two or more of the following thermoplastic materials can be used. 
     Examples of Thermoplastic Material: 
     Versatile engineering plastics such as polypropylene resin (PP), polyethylene resin (PE), polyacetal resin (POM), polyvinyl chloride resin (PVC), polyamide resin (PA), acrylonitrile butadiene styrene resin (ABS), polylactide resin (PLA), polyphenylene sulfide resin (PPS), polyether ether ketone (PEEK), polycarbonate (PC), modified polyphenylene ether, polybutylene terephthalate, and polyethylene terephthalate, and engineering plastics such as polysulfone, polyethersulfone, polyphenylene sulfide, polyacrylate, polyimide, polyamide imide, polyether imide, and polyether ether ketone 
     An additive such as a pigment, metal, ceramic, wax, flame retardant, antioxidant, or thermal stabilizer may be mixed into the thermoplastic material. In the plasticizing device  90 , the thermoplastic material is plasticized by the rotation of the flat screw  40  and the heating by the heater  58  and thus transformed into a molten state. The shaping material thus produced hardens due to a temperature drop after being ejected from the nozzle hole  61 . 
     It is desirable that the thermoplastic material is heated to its glass transition temperature or more and is ejected in a completely molten state from the nozzle hole  61 . For example, it is desirable that the ABS resin, which has a glass transition temperature of approximately 120° C., is at approximately 200° C. when ejected from the nozzle hole  61 . In order to eject the shaping material in such a high-temperature state, a heater may be provided around the nozzle hole  61 . 
     In the ejection unit  200 , for example, the following metal material may be used as the main material, instead of the above thermoplastic material. In this case, it is desirable that a component which melts when producing the shaping material is mixed with a powder material formed of the following metal material in a powder state and that the mixture is put into the plasticizing device  90 . 
     Examples of Metal Material: 
     A single metal of magnesium (Mg), iron (Fe), cobalt (Co), chromium (Cr), aluminum (Al), titanium (Ti), copper (Cu), or nickel (Ni), or an alloy containing one or more of these metals 
     Examples of Alloy: 
     Maraging steel, stainless steel, cobalt-chromium-molybdenum, titanium alloy, nickel alloy, aluminum alloy, cobalt alloy, and cobalt-chromium alloy 
     In the ejection unit  200 , a ceramic material can be used as the main material, instead of the above metal material. As the ceramic material, for example, an oxide ceramic such as silicon dioxide, titanium dioxide, aluminum oxide or zirconium oxide, or a non-oxide ceramic such as aluminum nitride can be used. When a metal material or ceramic material as described is used as the main material, the shaping material arranged at the shaping table  310  may be hardened, for example, by sintering with laser irradiation, hot air, or the like. 
     The powder material of the metal material or the ceramic material put into the material supply unit  20  may be a mixture material made up of a plurality of types of powder of a single metal, powder of an alloy, or powder of a ceramic material mixed together. The powder material of the metal material or the ceramic material may be coated, for example, with a thermoplastic resin as described above or other thermoplastic resins. In this case, the thermoplastic material may be melted and thus manifest its fluidity in the plasticizing device  90 . 
     To the powder material of the metal material or the ceramic material put into the material supply unit  20 , for example, the following solvent can be added. As the solvent, one type or a combination of two or more types selected from below can be used. 
     Examples of Solvent: 
     Water; (poly) alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether; acetic esters such as ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, and isobutyl acetate; aromatic hydrocarbons such as benzene, toluene, and xylene; ketones such as methyl ethyl ketone, acetone, methyl isobutyl ketone, ethyl n-butyl ketone, diisopropyl ketone, and acetyl acetone; alcohols such as ethanol, propanol, and butanol; tetraalkylammonium acetates; sulfoxide-based solvents such as dimethyl sulfoxide and diethyl sulfoxide; pyridine-based solvents such as pyridine, γ-picoline, and 2,6-lutidine; tetraalkylammonium acetate (for example, tetrabutylammonium acetate or the like); and ionic liquid such as butyl carbitol acetate, or the like. 
     Moreover, for example, the following binder can be added to the powder material of the metal material or the ceramic material put into the material supply unit  20 . 
     Examples of Binder: 
     Acrylic resin, epoxy resin, silicone resin, cellulose-based resin or other synthetic resins or PLA (polylactic acid), PA (polyamide), PPS (polyphenylene sulfide), PEEK (polyether ether ketone), or other thermoplastic resins 
     B. Second Embodiment 
       FIG. 4  is an explanatory view showing a schematic configuration of a three-dimensional shaping device  100   b  in a second embodiment. The three-dimensional shaping device  100   b  in the second embodiment is different from the first embodiment in that an ejection unit  200   b  has a first nozzle unit  60 A and a second nozzle unit  60 B. Also, in the three-dimensional shaping device  100   b  in the second embodiment, the configuration of a plasticizing unit  30   b  of a plasticizing device  90   b  is different from that in the first embodiment. The other configurations are the same as in the first embodiment shown in  FIG. 1  unless stated otherwise. 
     In the first nozzle unit  60 A, a first nozzle flow path  62 A and a first nozzle hole  61 A are provided. The first nozzle hole  61 A is a part that is provided at an end part at the side communicating with the atmosphere and that has a reduced flow path cross section, in the first nozzle unit  60 A. The first nozzle flow path  62 A is supplied with the shaping material from the plasticizing device  90   b  via a flow rate adjustment mechanism  70   b . The shaping material supplied to the first nozzle flow path  62 A is ejected from the first nozzle hole  61 A. In this embodiment, the diameter of the first nozzle flow path  62 A is the same as the diameter of a first communication hole  55 A. However, the diameter of the first nozzle flow path  62 A may be smaller than the diameter of the first communication hole  55 A. A nozzle diameter Dn 1  of the first nozzle hole  61 A is smaller than the diameter of the first nozzle flow path  62 A. 
     In the second nozzle unit  60 B, a second nozzle flow path  62 B and a second nozzle hole  61 B are provided. The second nozzle hole  61 B is a part that is provided at an end part at the side communicating with the atmosphere and that has a reduced flow path cross section, in the second nozzle unit  60 B. The second nozzle flow path  62 B is supplied with the shaping material from the plasticizing device  90   b  via the flow rate adjustment mechanism  70   b . The shaping material supplied to the second nozzle flow path  62 B is ejected from the second nozzle hole  61 B. In this embodiment, the diameter of the second nozzle flow path  62 B is the same as the diameter of a second communication hole  55 B. However, the diameter of the second nozzle flow path  62 B may be smaller than the diameter of the second communication hole  55 B. A nozzle diameter Dn 2  of the second nozzle hole  61 B is smaller than the diameter of the second nozzle flow path  62 B. 
     In this embodiment, the nozzle diameter Dn 1  of the first nozzle hole  61 A is smaller than the nozzle diameter Dn 2  of the second nozzle hole  61 B. A nozzle length Ln 1  of the first nozzle hole  61 A is the same as a nozzle length Ln 2  of the second nozzle hole  61 B. The nozzle lengths Ln 1 , Ln 2  are the flow path length from the end part at the side of the plasticizing device  90   b  to the end part at the side communicating with the atmosphere, in the nozzle holes  61 A,  61 B. 
     In this embodiment, the first communication hole  55 A, the second communication hole  55 B, a spiral first groove part  56 A coupled to the first communication hole  55 A, and a spiral second groove part  56 B coupled to the second communication hole  55 B are formed at the bottom surface  51  of a barrel  50   b  in the plasticizing unit  30   b . The first communication hole  55 A communicates with the first nozzle hole  61 A. The second communication hole  55 B communicates with the second nozzle hole  61 B. The detailed shape of the barrel  50   b  in this embodiment will be described later with reference to  FIG. 5 . 
     In the flow rate adjustment mechanism  70   b , a first valve mechanism  71 A and a second valve mechanism  71 B are provided. Each of the first valve mechanism  71 A and the second valve mechanism  71 B in this embodiment is formed of a butterfly valve. The first valve mechanism  71 A opens and closes under the control of the control unit  500  and switches between communication and non-communication between the first communication hole  55 A and the first nozzle hole  61 A. The second valve mechanism  71 B opens and closes under the control of the control unit  500  and switches between communication and non-communication between the second communication hole  55 B and the second nozzle hole  61 B. 
       FIG. 5  is a top view showing the configuration of the bottom surface  51  of the barrel  50   b  in the second embodiment. In this embodiment, the first communication hole  55 A, the second communication hole  55 B, the first groove part  56 A coupled to the first communication hole  55 A, and the second groove part  56 B coupled to the second communication hole  55 B are provided, as described above. In  FIG. 5 , the first groove part  56 A and the second groove part  56 B are hatched in order to facilitate understanding of the technology. 
     The first groove part  56 A has a first center part  151 A, a first spiral part  152 A, and a first material inflow part  153 A. The first center part  151 A is a circular depression around the first communication hole  55 A. One end of the first spiral part  152 A is coupled to the first communication hole  55 A via the first center part  151 A. The first spiral part  152 A spirally extends about the first center part  151 A in such a way as to form an arc toward the outer circumference of the bottom surface  51 . The other end of the first spiral part  152 A is coupled to the first material inflow part  153 A. The first material inflow part  153 A is a groove-like part provided at the outer circumferential edge of the bottom surface  51  and wider than the first spiral part  152 A. In this embodiment, a first supply port  25 A is arranged at the slope part  53  above the first material inflow part  153 A. The material supply unit  20  and the first supply port  25 A are coupled together via a first supply path  22 A. 
     The second groove part  56 B has a second center part  151 B, a second spiral part  152 B, and a second material inflow part  153 B. The second center part  151 B is a circular depression around the second communication hole  55 B. One end of the second spiral part  152 B is coupled to the second communication hole  55 B via the second center part  151 B. The second spiral part  152 B spirally extends about the second center part  151 B in such a way as to form an arc toward the outer circumference of the bottom surface  51 . In this embodiment, the length along the spiral of the first spiral part  152 A and the length along the spiral of the second spiral part  152 B are the same. The second material inflow part  153 B is a groove-like part provided at the outer circumferential edge of the bottom surface  51  and wider than the second spiral part  152 B. In this embodiment, a second supply port  25 B is arranged at the slope part  53  above the second material inflow part  153 B. The material supply unit  20  and the second supply port  25 B are coupled together via a second supply path  22 B. 
       FIG. 6  is a cross-sectional view taken along VI-VI of the barrel  50   b  shown in  FIG. 5 . In this embodiment, the shape of the first spiral part  152 A and the shape of the second spiral part  152 B are different from each other. Specifically, a width W 1  of the first spiral part  152 A is narrower than the width W 2  of the second spiral part  152 B. A depth H 1  of the first spiral part  152 A is the same as a depth H 2  of the second spiral part  152 B. Therefore, a cross-sectional area A 1  of the first spiral part  152 A is smaller than a cross-sectional area A 2  of the second spiral part  152 B. In this embodiment, the cross-sectional area A 1  of the first spiral part  152 A is constant and the cross-sectional area A 2  of the second spiral part  152 B is constant. 
     In the configuration of the three-dimensional shaping device  100   b  described above, as the control unit  500  executes shaping processing to shape a three-dimensional shaped object, the material in the material supply unit  20  travels through the first supply path  22 A and is supplied from the first supply port  25 A into the supply space  59  between the lateral surface  46  of the rotating flat screw  40  and the sidewall surface  52 . The material in the material supply unit  20  also travels through the second supply path  22 B and is supplied from the second supply port  25 B into the supply space  59  between the lateral surface  46  of the rotating flat screw  40  and the sidewall surface  52 . 
     In this embodiment, a part of the material supplied into the supply space  59  from the first supply port  25 A travels between the blade parts  43  of the flat screw  40  and flows into the first material inflow part  153 A provided below the first supply port  25 A. The material not flowing into the first material inflow part  153 A and remaining in the supply space  59  is transported to the second material inflow part  153 B by the blade parts  43  of the rotating flat screw  40  and flows into the second material inflow part  153 B. The material not flowing into the second material inflow part  153 B and remaining in the supply space  59  is transported again to the first material inflow part  153 A by the blade parts  43  of the rotating flat screw  40  and flows into the first material inflow part  153 A. 
     A part of the material supplied into the supply space  59  from the second supply port  25 B travels between the blade parts  43  of the flat screw  40  and flows into the second material inflow part  153 B provided below the second supply port  25 B. The material not flowing into the second material inflow part  153 B and remaining in the supply space  59  is transported to the first material inflow part  153 A by the blade parts  43  of the rotating flat screw  40  and flows into the first material inflow part  153 A. The material not flowing into the first material inflow part  153 A and remaining in the supply space  59  is transported again to the second material inflow part  153 B by the blade parts  43  of the rotating flat screw  40  and flows into the second material inflow part  153 B. 
     The material flowing into the first material inflow part  153 A is transported into the first spiral part  152 A by the rotation of the flat screw  40 . The material transported into the first spiral part  152 A is at least partly melted by the rotation of the flat screw  40  and the heating by the heater  58  built inside the barrel  50   b , and thus becomes a fluid paste-like shaping material. The shaping material is transported within the first spiral part  152 A and pressure-fed into the first communication hole  55 A by the rotation of the flat screw  40 . 
     The material flowing into the second material inflow part  153 B is transported into the second spiral part  152 B by the rotation of the flat screw  40 . The material transported into the second spiral part  152 B is at least partly melted by the rotation of the flat screw  40  and the heating by the heater  58  built inside the barrel  50   b , and thus becomes a fluid paste-like shaping material. The shaping material is transported within the second spiral part  152 B and pressure-fed into the second communication hole  55 B by the rotation of the flat screw  40 . 
     In this embodiment, to shape the outer shape of the three-dimensional shaped object that needs a higher dimensional accuracy than the inner shape, the control unit  500  causes the second valve mechanism  71 B to close and the first valve mechanism  71 A to open and thus causes the shaping material to be ejected from the first nozzle hole  61 A with the smaller diameter toward the top of the shaping table  310 , thereby shaping the three-dimensional shaped object. The outer shape refers to a site visible from outside, of the three-dimensional shaped object. The inner shape refers to a site of the three-dimensional shaped object other than the outer shape. Meanwhile, to shape the inner shape of the three-dimensional shaped object, the control unit  500  causes the first valve mechanism  71 A to close and the second valve mechanism  71 B to open and thus causes the shaping material to be ejected from the second nozzle hole  61 B with the larger diameter toward the top of the shaping table  310 , thereby shaping the three-dimensional shaped object. 
     In the three-dimensional shaping device  100   b  in this embodiment described above, the material is plasticized by the pair of the flat screw  40  and the barrel  50   b  and the shaping material can be ejected from the first communication hole  55 A and the second communication hole  55 B. Therefore, the shaping material can be supplied to the first nozzle unit  60 A and the second nozzle unit  60 B without complicating the configuration of the three-dimensional shaping device  100   b  having the plasticizing device  90   b  incorporated therein. 
     Also, in this embodiment, the first groove part  56 A formed in the barrel  50   b  has the first spiral part  152 A, and the second groove part  56 B has the second spiral part  152 B. Therefore, the material can be melted in the first groove part  56 A and transported toward the first communication hole  55 A more easily by the rotation of the flat screw  40 . Also, the material can be melted in the second groove part  56 B and transported toward the second communication hole  55 B more easily by the rotation of the flat screw  40 . 
     Also, in this embodiment, since the shape of the first spiral part  152 A and the shape of the second spiral part  152 B are different from each other, the shaping material can be ejected from the first communication hole  55 A and the second communication hole  55 B at different flow rates and with different pressures. Particularly, in this embodiment, the cross-sectional area A 1  of the first spiral part  152 A communicating with the first communication hole  55 A is smaller than the cross-sectional area A 2  of the second spiral part  152 B communicating with the second communication hole  55 B. Therefore, the pressure of the shaping material pressure-fed into the first communication hole  55 A communicating with the first nozzle hole  61 A with the smaller diameter can be made higher than the pressure of the shaping material pressure-fed into the second communication hole  55 B communicating with the second nozzle hole  61 B with the larger diameter. Thus, a drop in the amount of the shaping material ejected from the first nozzle hole  61 A having a higher resistance than the second nozzle hole  61 B can be restrained. 
     Also, in this embodiment, the blade part  43  can stir the material in the flat screw  40  and the barrel  50   b . This enables the material to flow easily into the first material inflow part  153 A and the second material inflow part  153 B. 
     Also, in this embodiment, the nozzle diameter Dn 1  of the first nozzle hole  61 A is smaller than the nozzle diameter Dn 2  of the second nozzle hole  61 B. Therefore, the outer shape, which needs higher quality in terms of dimensional accuracy and surface roughness than the inner shape of the three-dimensional shaped object, can be finely shaped by ejecting the shaping material from the first nozzle hole  61 A with the smaller diameter. Also, the inner shape of the three-dimensional shaped object can be shaped in a short time by ejecting the shaping material from the second nozzle hole  61 B with the larger diameter. 
     Also, in this embodiment, the first valve mechanism  71 A can switch on and off the ejection of the shaping material from the first nozzle hole  61 A, and the second valve mechanism  71 B can switch on and off the ejection of the shaping material from the second nozzle hole  61 B. Therefore, when the shaping material is ejected from the first nozzle hole  61 A to shape a three-dimensional shaped object, the shaping material can be restrained from leaking from the second nozzle hole  61 B. When the shaping material is ejected from the second nozzle hole  61 B to shape a three-dimensional shaped object, the shaping material can be restrained from leaking from the first nozzle hole  61 A. 
     Also, in this embodiment, the first supply port  25 A is arranged at the slope part  53  above the first material inflow part  153 A, and the second supply port  25 B is arranged at the slope part  53  above the second material inflow part  153 B. This enables the material to be supplied into the supply space  59  from a position near each material inflow part  153 A,  153 B and therefore enables the material to flow into each material inflow part  153 A,  153 B more easily. 
     C. Third Embodiment 
       FIG. 7  is a top view showing the configuration of the bottom surface  51  of a barrel  50   c  in a third embodiment. In a three-dimensional shaping device  100   c  in the third embodiment, the configuration of the barrel  50   c  in an ejection unit  200   c  is different from that in the second embodiment. Specifically, a first communication hole  55 A, a second communication hole  55 B, a third communication hole  55 C, and a fourth communication hole  55 D communicating respectively with separate nozzle holes  61  are formed at the bottom surface  51  of the barrel  50   c . Also, a first groove part  56 A coupled to the first communication hole  55 A, a second groove part  56 B coupled to the second communication hole  55 B, a third groove part  56 C coupled to the third communication hole  55 C, and a fourth groove part  56 D coupled to the fourth communication hole  55 D are formed at the bottom surface  51  of the barrel  50   c . A first supply port  25 A supplying the material to the first groove part  56 A, a second supply port  25 B supplying the material to the second groove part  56 B, a third supply port  25 C supplying the material to the third groove part  56 C, and a fourth supply port  25 D supplying the material to the fourth groove part  56 D are formed at a part forming the sidewall surface  52  of the barrel  50   c . The other configurations are the same as in the second embodiment unless stated otherwise. In  FIG. 7 , the groove parts  56 A,  56 B,  56 C,  56 D are hatched in order to facilitate understanding of the technology. 
     The first groove part  56 A has a first center part  151 A, a first spiral part  152 A, and a first material inflow part  153 A. The first center part  151 A is a circular depression around the first communication hole  55 A. One end of the first spiral part  152 A is coupled to the first communication hole  55 A via the first center part  151 A. The first spiral part  152 A spirally extends about the first center part  151 A in such a way as to form an arc toward the outer circumference of the bottom surface  51 . The other end of the first spiral part  152 A is coupled to the first material inflow part  153 A. The first material inflow part  153 A is a groove-like part provided at the outer circumferential edge of the bottom surface  51  and wider than the first spiral part  152 A. The first supply port  25 A is arranged at the slope part  53  above the first material inflow part  153 A. 
     The second groove part  56 B has a second center part  151 B, a second spiral part  152 B, and a second material inflow part  153 B. The second groove part  56 B has the shape of the first groove part  56 A rotated clockwise by 90 degrees about the center of the bottom surface  51 . The second supply port  25 B communicating with the material supply unit  20  is arranged at the slope part  53  above the second material inflow part  153 B. 
     The third groove part  56 C has a third center part  151 C, a third spiral part  152 C, and a third material inflow part  153 C. The third groove part  56 C has the shape of the second groove part  56 B rotated clockwise by 90 degrees about the center of the bottom surface  51 . The third supply port  25 C communicating with the material supply unit  20  is arranged at the slope part  53  above the third material inflow part  153 C. 
     The fourth groove part  56 D has a fourth center part  151 D, a fourth spiral part  152 D, and a fourth material inflow part  153 D. The fourth groove part  56 D has the shape of the third groove part  56 C rotated clockwise by 90 degrees about the center of the bottom surface  51 . The fourth supply port  25 D communicating with the material supply unit  20  is arranged at the slope part  53  above the fourth material inflow part  153 D. 
     In this embodiment, the material supply unit  20  and the respective supply ports  25 A,  25 B,  25 C,  25 D are coupled together via four supply paths  22 A,  22 B,  22 C,  22 D. Also, four material supply units  20  may be provided, and the respective supply ports  25 A,  25 B,  25 C,  25 D may communicate with the respective material supply units  20  via the respective supply paths  22 A,  22 B,  22 C,  22 D. For example, the first supply port  25 A may communicate with a first material supply unit via the first supply path  22 A. The second supply port  25 B may communicate with a second material supply unit via the second supply path  22 B. The third supply port  25 C may communicate with a third material supply unit via the third supply path  22 C. The fourth supply port  25 D may communicate with a fourth material supply unit via the fourth supply path  22 D. Different types of materials may be accommodated in the respective material supply units  20 . 
     In the three-dimensional shaping device  100   c  in this embodiment described above, each supply port  25 A,  25 B,  25 C,  25 D is arranged at the slope part  53  above each material inflow part  153 A,  153 B,  153 C,  153 D. This enables the material to be supplied into the supply space  59  from a position near each material inflow part  153 A,  153 B,  153 C,  153 D and therefore enables the material to flow into each material inflow part  153 A,  153 B,  153 C,  153 D more easily. 
     D. Other Embodiments 
     (D1) In the three-dimensional shaping devices  100 ,  100   b ,  100   c  in the above embodiments, the blade part  43  of the flat screw  40  is provided parallel to the rotation axis RX. However, the blade part  43  may have a surface sloped with respect to the rotation axis RX. Specifically, the surface of the blade part  43  at the front side in the direction of rotation of the flat screw  40  may be sloped with respect to the rotation axis RX in such a way that the material is pushed out toward the end surface  45  when the material comes in contact with the surface at the front side in the direction of rotation of the flat screw  40 , of the blade part  43  of the rotating flat screw  40 . In this case, the blade part  43  of the rotating flat screw  40  can pressure-feed the material between the flat screw  40  and the barrel  50  toward the bottom surface  51  of the barrel  50 . This can further facilitate the supply of the material to the groove part  56 . 
     (D2) In the three-dimensional shaping devices  100 ,  100   b ,  100   c  in the above embodiments, the cross-sectional area of the spiral part  152  is constant. However, the cross-sectional area of the spiral part  152  may become smaller as it goes toward the communication hole  55 . For example, the spiral part  152  may be formed with a width decreasing as it goes toward the communication hole  55 , or may be formed with a depth decreasing as it goes toward the communication hole  55 . In this case, the pressure of the shaping material pressure-fed into the communication hole  55  from inside the spiral part  152  can be increased. 
     (D3) In the three-dimensional shaping devices  100 ,  100   b ,  100   c  in the above embodiments, the flat screw  40  has the blade part  43 . However, the flat screw  40  may not have the blade part  43 . Even in this case, the material can be continuously supplied to the groove part  56 . 
     (D4) In the three-dimensional shaping devices  100 ,  100   b ,  100   c  in the above embodiments, the sidewall surface  52  has the slope part  53 . However, the sidewall surface  52  may not have the slope part  53 . Even in this case, the material can be continuously supplied from the supply space  59  to the groove part  56 . 
     (D5) In the three-dimensional shaping device  100   b  in the above second embodiment, the length Ln 1  of the first nozzle hole  61 A and the length Ln 2  of the second nozzle hole  61 B are the same. However, the length Ln 1  of the first nozzle hole  61 A and the length Ln 2  of the second nozzle hole  61 B may be different from each other. For example, the length Ln 1  of the first nozzle hole  61 A may be longer than the length Ln 2  of the second nozzle hole  61 B. 
     (D6)  FIG. 8  is an explanatory view showing a schematic configuration of an injection molding device  110  as another form. An ejection unit  200   d  may be used in the injection molding device  110  as well as in the three-dimensional shaping devices  100 ,  100   b ,  100   c . In the injection molding device  110  shown in  FIG. 8 , the ejection unit  200   d  has an injection unit  600  in addition to the plasticizing device  90  and the nozzle unit  60 . The configuration and functions of the plasticizing device  90  are as described above. In  FIG. 8 , the illustration of the material supply unit  20  and the supply path  22  is omitted. The injection unit  600  measures the molten material supplied from the plasticizing device  90  and injects the material from the nozzle unit  60  into a space demarcated by an upper mold  710  and a lower mold, not illustrated, in a mold-clamped state. The injection unit  600  has an injection cylinder  610 , an injection plunger  620 , a check valve  630 , and an injection motor  640 . As the injection motor  640  drives the injection plunger  620  to slide to the side opposite to the side of the communication hole  55 , the molten material in the communication hole  55  is drawn into the injection cylinder  610  and measured. As the injection motor  640  drives the injection plunger  620  to slide toward the communication hole  55 , the molten material in the injection cylinder  610  is pressure-fed toward the nozzle unit  60  and injected into the space demarcated by the upper mold  710  and the lower mold. 
     E. Other Forms 
     The present disclosure is not limited to the foregoing embodiments and can be implemented in various forms without departing from the spirit and scope of the present disclosure. For example, the present disclosure can be implemented in the following forms. A technical feature in the embodiments corresponding to a technical feature in each of the following forms can be replaced or combined with another according to need, in order to solve apart or all of the problems in the present disclosure or in order to achieve a part or all of the effects of the present disclosure. Also, the technical feature can be deleted where appropriate, unless described as essential in this specification. 
     (1) According to a first aspect of the present disclosure, a plasticizing device plasticizing a material into a molten material is provided. The plasticizing device includes: a drive motor; a rotating unit driven to rotate about a rotation axis by the drive motor and having an end surface perpendicular to the rotation axis and a lateral surface intersecting with the end surface; a barrel having a bottom surface facing the end surface of the rotating unit, and a heater; a case accommodating the rotating unit; and a material supply unit accommodating the material. At least one of the barrel and the case has a sidewall surface facing the lateral surface of the rotating unit and standing up along an outer circumference of the bottom surface of the barrel. At the bottom surface of the barrel, a communication hole through which the molten material flows out and a spiral groove part coupled to the communication hole are formed. The lateral surface of the rotating unit and the sidewall surface together define a supply space where the material is supplied from the material supply unit to the groove part. 
     In the plasticizing device of this configuration, the material can be continuously supplied to the groove part. Therefore, a change in the pressure of the molten material pressure-fed into the communication hole can be restrained. Thus, a change in the flow rate of the molten material ejected from the communication hole can be restrained. 
     (2) In the plasticizing device according to the above aspect, the sidewall surface may have a supply port through which the material supply unit and the supply space communicate with each other. The material may travel through the supply port and flow into the supply space. 
     In the plasticizing device of this configuration, the material can be supplied from a position near the groove part. This can facilitate the supply of the material to the groove part. 
     (3) In the plasticizing device according to the above aspect, the rotating unit may have a plurality of plate-like blade parts protruding from the lateral surface toward the supply space. The material may travel between the blade parts and flow into the groove part. 
     In the plasticizing device of this configuration, the blade parts of the rotating unit that is rotating can stir the material between the rotating unit and the barrel. Therefore, the material can be retrained from adhering to the barrel and closing the space between the rotating unit and the barrel. 
     (4) In the plasticizing device according to the above aspect, the blade parts may have a surface sloped along the rotation axis. 
     In the plasticizing device of this configuration, the blade parts can pressure-feed the material between the rotating unit and the barrel to the bottom surface of the barrel. This can facilitate the supply of the material to the groove part. 
     (5) In the plasticizing device according to the above aspect, the sidewall surface may have, at a position intersecting with the bottom surface, a slope part sloped in such a way as to approach a center of the bottom surface as it goes toward the bottom surface. 
     In the plasticizing device of this configuration, a flow of the material along the slope part toward the groove part can be formed. This can facilitate the supply of the material to the groove part. 
     (6) In the plasticizing device according to the above aspect, the groove part may be reduced in cross-sectional area as it goes toward the communication hole. 
     In the plasticizing device of this configuration, the pressure of the molten material pressure-fed from inside the groove part into the communication hole can be increased. 
     (7) According to a second aspect of the present disclosure, a three-dimensional shaping device is provided. The three-dimensional shaping device includes: a nozzle ejecting a shaping material; a plasticizing device plasticizing a material into the shaping material and supplying the shaping material to the nozzle; and a control unit controlling the plasticizing device. The plasticizing device includes: a drive motor; a rotating unit driven to rotate about a rotation axis by the drive motor and having an end surface perpendicular to the rotation axis and a lateral surface intersecting with the end surface; a barrel having a bottom surface facing the end surface of the rotating unit, and a heater; a case accommodating the rotating unit; and a material supply unit accommodating the material. At least one of the barrel and the case has a sidewall surface facing the lateral surface of the rotating unit and standing up along an outer circumference of the bottom surface of the barrel. At the bottom surface of the barrel, a communication hole through which the shaping material flows out into the nozzle and a spiral groove part coupled to the communication hole are formed. The lateral surface of the rotating unit and the sidewall surface together define a supply space where the material is supplied from the material supply unit to the groove part. 
     In the three-dimensional shaping device of this configuration, the material can be continuously supplied to the groove part. Therefore, a change in the pressure of the shaping material pressure-fed into the communication hole can be restrained. Thus, a change in the flow rate of the shaping material ejected from the communication hole can be restrained. 
     The present disclosure can be implemented in various forms other than the plasticizing device. For example, the present disclosure can be implemented as a three-dimensional shaping device, an ejection unit, and the like.