Patent Publication Number: US-2021162671-A1

Title: Method of manufacturing three-dimensionally shaped object, and additive manufacturing apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a fused deposition modeling that forms a three-dimensionally shaped object by melting and extruding thermoplastic resin and depositing the resin, and to an additive manufacturing apparatus used for the modeling. In particular, the present invention relates to a technology that improves mechanical strength and rigidity of three-dimensionally shaped objects. 
     Description of the Related Art 
     In recent years, so-called 3D printers are increasingly developed, and various methods are being tried for the development. For example, there are known methods such as powder depositing-and-melting method, stereolithography that uses photo-curable resin, and fused deposition modeling. 
     The powder depositing-and-melting method forms a three-dimensionally shaped object by repeating a process to spread material powder of nylon resin, ceramic, or metal, so as to form a layer of the powder, and a process to selectively melt a portion of the powder layer by irradiating the portion with a laser beam. The powder depositing-and-melting method is also called the SLS method. Recently, for manufacturing products required to have high mechanical strength and good thermal conductivity, a powder depositing-and-melting method that uses metal powder as material powder comes into use. 
     The stereolithography is also called the SLA method, and forms a three-dimensional structure by repeating a process to selectively irradiate a photo-curable liquid resin with ultraviolet rays and form a cured layer. 
     The fused deposition modeling is also called the FDM method, and forms a three-dimensional structure by melting thermoplastic resin, extruding the material from a nozzle or the like, and depositing the material on a target portion for forming the three-dimensional structure. 
     As a specific example of the fused deposition modeling, Japanese Translation of PCT International Application Publication No. JP-2010-521339A discloses a method in which a filament made of a modified ABS (acrylonitrile-butadiene-styrene) is melted and extruded by using an extruding head. In this method, a 3D object is formed by forming one layer, obtained by slicing a CAD model, on another by using the extruding head. 
     In the method described in Japanese Translation of PCT International Application Publication No. JP-2010-521339A, the material is extruded through a nozzle of the extruding head, and deposited on a substrate such that the material forms a continuous line on an x-y plane. The extruded material fuses with the material of a lower layer that has already been deposited, and solidifies as the temperature decreases. Then, the position of the extruding head with respect to the substrate is raised along a z axis orthogonal to the x-y plane, and the next layer is formed. By repeating this process, the 3D object similar to the CAD model is produced. 
     In addition, Japanese Patent Application Publication No. 2005-335380 describes a technique for improving the adhesion strength of the layers. Specifically, when an object is formed by forming layers, an area which is just in front of the extruding head and to which the molten resin is to adhere is heated by using a laser, and then the surface of the molten resin extruded and deposited on the area is cooled by using cool air. 
     However, in the fused deposition modeling disclosed in Japanese Translation of PCT International Application Publication No. JP-2010-521339A, the material having already been deposited and the material extruded additionally after the deposition do not sufficiently fuse with each other. 
     This is because the temperature of the material having already been deposited on the substrate has decreased when the next layer is formed, the material having already been deposited on the substrate is not in a melt state, and thus the adhesion between the material having already been deposited and the newly deposited material is often insufficient. 
     Thus, in three-dimensionally shaped objects formed by using the fused deposition modeling disclosed in Japanese Translation of PCT International Application Publication No. JP-2010-521339A, the adhesion in a planar direction and the adhesion between layers in a vertical direction are insufficient, and the mechanical strength is inferior to that of a molded product made through injection molding or the like. 
     In this point, Japanese Patent Application Publication No. 2005-335380 is intended to increase the adhesion strength in the vertical direction by heating the area which is just in front of the extruding head and to which the molten resin is to adhere, by using a laser when an object is formed by forming layers. 
     However, an area of the layer which is beside a position to which the molten resin is extruded and which has already been formed is not heated. Thus, if it takes time to form one layer, the temperature of the resin of the side area decreases significantly, and solidifies. As a result, sufficient adhesion strength cannot be secured, and the strength in the planar direction becomes insufficient. 
     Thus, in the fused deposition modeling, it has been desired to achieve a method and an additive manufacturing apparatus for manufacturing a three-dimensionally shaped object in which each layer has high adhesion strength in the direction parallel to the deposition plane and in the deposition direction perpendicular to the deposition plane, and which has high mechanical strength. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention, a method of manufacturing a three-dimensionally shaped object includes stacking layers on a stage for manufacturing the three-dimensionally shaped object by repeating forming a desired-shape layer while moving a nozzle that injects molten thermoplastic resin. The nozzle moves while locally heating a front area and a side area by using a heating portion. The front area is located in front of the nozzle in a moving direction of the nozzle in a plan view of the stage. The side area is located beside the nozzle in the moving direction in the plan view. 
     According to a second aspect of the present invention, an additive manufacturing apparatus for manufacturing a three-dimensionally shaped object by stacking layers on a stage includes a nozzle and a heating portion. The nozzle is configured to inject molten thermoplastic resin while moving so that the layers are formed. The heating portion is configured to locally heat a front area and a side area. The front area is located in front of the nozzle in a moving direction of the nozzle in a plan view of the stage. The side area is located beside the nozzle in the moving direction in the plan view. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view for illustrating an overall configuration of an additive manufacturing apparatus of a first embodiment. 
         FIG. 2  is a schematic side view for illustrating a configuration of an extruding unit of the first embodiment. 
         FIG. 3A  is a schematic plan view of the (N−1)th layer in a case where the Nth layer is currently being formed. 
         FIG. 3B  is a schematic plan view of the Nth layer alone that is currently being formed. 
         FIG. 4  is a schematic plan view for illustrating an extrusion position, heating, and cooling in the formation of the Nth layer. 
         FIG. 5  is a schematic diagram illustrating an extrusion position, heating, and cooling at a turning point of a trajectory in each stage of the formation of the Nth layer. 
         FIG. 6  is a diagram for illustrating detailed operations of a heating unit and a cooling unit of the first embodiment. 
         FIG. 7  is a control block diagram of an additive manufacturing apparatus of the first embodiment. 
         FIG. 8  is a flowchart illustrating a sequence of steps of an additive manufacturing method of the first embodiment. 
         FIG. 9  is a diagram for illustrating a slice model of each layer. 
         FIG. 10A  is a diagram illustrating a configuration of an extruding unit of a second embodiment. 
         FIG. 10B  is a diagram illustrating a configuration of a valve of the second embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, a method of manufacturing a three-dimensionally shaped object of an embodiment of the present invention and an additive manufacturing apparatus used for the method will be described with reference to the accompanying drawings. 
     Note that in the drawings referred to in the below-described embodiments, a component denoted by an identical reference numeral has an identical function, unless otherwise specified. 
     Note that in the following description, the term “layer” means a portion formed by depositing molten thermoplastic resin once, in a case where a three-dimensionally shaped object is formed by depositing the molten thermoplastic resin more than once in a thickness direction. If the thermoplastic resin is deposited by an extruding head and a stage scanning each other in a relative manner, the term “layer” means a portion formed through a single scanning. 
     The interface between layers may be identified in the observation of a cross section of the three-dimensionally shaped object, but may not be clearly detected if the thermoplastic resin has high uniformity. 
     First Embodiment 
     Configuration of Additive Manufacturing Apparatus 
     With reference to  FIG. 1 , an overall configuration of an additive manufacturing apparatus of a first embodiment will be described.  FIG. 1  is a schematic perspective view illustrating the configuration of the additive manufacturing apparatus. 
     In  FIG. 1 , a forming material  1 , a reel  2 , an extruding unit  3 , a stage  4 , a stage moving apparatus  5 , a control unit  6 , and a computer  7  are illustrated. 
     First, the extruding unit  3  will be described. Since the extruding unit  3  is a mechanism including many components, the configuration of the extruding unit  3  will be described with reference to  FIG. 2 . 
       FIG. 2  is a schematic side view for illustrating a configuration of the extruding unit  3 . In  FIG. 2 , the forming material  1  illustrated in  FIG. 1 , rollers  8 , a material introduction portion  9 , an extruding head  10 , and a molten resin  11  are illustrated. In addition, a heating portion  12 , an extruding opening  13 , a nonrotary gear  14  mounted on the extruding head  10 , a heating unit  15 , and a heating means  16  are illustrated. In addition, a gear  17  mounted in the heating unit  15 , a motor  18  to rotate the gear  17 , a cooling unit  19 , a cooling means  20 , a gear  21  mounted in the cooling unit  19 , and a motor  22  to rotate the gear  21  are illustrated. 
     The forming material  1  is a raw material used for the additive manufacturing. In the present embodiment, the forming material  1  is a filament of thermoplastic resin. However, another form of material, such as pellet or powder, may be used. 
     The filament used as the forming material has a circular cross section, for example. Preferably, the filament has a diameter of 1.5 to 3.0 mm, and a length of 10 to 1000 m. The forming material  1  is stored, wound around the reel  2 . The forming material  1  can be supplied to the material introduction portion  9  by the reel  2  rotating in a direction indicated by an arrow of  FIG. 1 . 
     The thermoplastic resin used in the present embodiment may be a polycarbonate (PC) resin, an acrylonitrile-butadiene-styrene (ABS) copolymer resin, or a PC/ABS polymer alloy. Alternatively, the thermoplastic resin may be a polylactic acid (PLA) resin, a polyphenylene sulfide (PPS) resin, a polyether-imide (PEI) resin, a polyethylene terephthalate (PET) resin, or a resin in which any of the above-described resins is modified. 
     The extruding head  10  heats and melts the forming material  1  of thermoplastic resin, and extrudes the molten resin  11 . The extruding head  10  includes the material introduction portion  9 , the heating portion  12 , and the extruding opening  13 . 
     The material introduction portion  9  introduces the forming material  1  into the extruding head  10 , and one example of the configuration of the material introduction portion  9  is illustrated in  FIG. 2 . In  FIG. 2 , the number of the rollers  8  is two. 
     Thus, the forming material  1  is nipped by the two rollers  8 . When the rollers  8  rotate in a direction indicated by arrows of  FIG. 2 , the filament is drawn and sent from the reel  2  into the heating portion  12 . 
     The amount of supply of the forming material  1  to the heating portion  12  can be adjusted by the control unit  6  controlling the rotational speed of the rollers  8 . 
     Additive Manufacturing Method 
     Next, an additive manufacturing method of the present embodiment will be described sequentially. 
     The heating portion  12  includes a heater (not illustrated), and heats and melts the thermoplastic resin supplied through the material introduction portion  9 . 
     The molten thermoplastic resin is delivered to the extruding opening  13  by the following material pushing the molten thermoplastic resin; and extruded, as the molten resin  11 , toward a direction opposite to a Z direction in  FIG. 2 , that is, downward in the vertical direction. 
     The extruding opening  13  has a diameter of 0.1 to 5 mm. The molten resin  11  is extruded and deposited on the stage  4 . The width of the molten resin  11  in a planar direction is controlled by the extruding opening  13 , the rollers  8 , the heating portion  12 , and the stage moving apparatus  5 . 
     The molten resin  11  extruded from the extruding opening  13  forms into a pillar-shaped viscous fluid and moves in the vertical direction, that is, toward the stage  4 . 
     In a step to form a single layer, the shape of the layer in the planar direction is formed by arranging a line of the molten resin  11  and making columns. 
     In a case where the first layer of a three-dimensionally shaped object  33  is formed, the molten resin  11  contacts the surface of the stage  4 . In a case where each of the second and the following layers is formed, the molten resin  11  contacts the surface of a lower layer that has already been formed. 
     In both cases, after the molten resin  11  contacts the surface of the lower layer, the temperature of the molten resin  11  decreases to a temperature equal to or lower than a glass transition point (Tg) and the molten resin  11  solidifies. 
     The stage moving apparatus  5  is a mechanism to move the stage  4  in three directions of XYZ, and is controlled by the control unit  6 . 
     An extruding-head moving apparatus (not illustrated) is a mechanism to move the extruding head  10  in the three directions of XYZ, and is controlled by the control unit  6 . 
     When one layer of a three-dimensionally shaped object is formed, the extruding head  10  and the stage  4  scan each other in a relative manner in an XY plane in a state where the distance between the extruding head  10  and the stage  4  is kept constant in the Z direction. 
     When the next layer is formed, the extruding head  10  and the stage  4  scan each other in a relative manner in an XY plane in a state where the distance between the extruding head  10  and the stage  4  is increased by the thickness of one layer in the Z direction. 
     For example, when a cylindrical three-dimensionally shaped object is formed, either one of the extruding head  10  and the stage  4  performs a circular motion in an XY plane while the molten resin  11  is being extruded. In addition, the distance between the extruding head  10  and the stage  4  in the Z direction is gradually increased as the number of layers increases. 
     In the present embodiment, both of the stage moving apparatus  5  and the extruding-head moving apparatus can move in the three directions of XYZ. However, both of the stage moving apparatus  5  and the extruding-head moving apparatus may not necessarily move in the three directions of XYZ, for performing the above-described operations. 
     For example, the stage moving apparatus  5  may move in two directions of XY, and the extruding-head moving apparatus may move in the Z direction. In another case, one of the stage moving apparatus  5  and the extruding-head moving apparatus may move in the three directions of XYZ, and the other may not move. 
     With the above-described operations, the molten resin can be deposited for forming a three-dimensionally shaped object. In addition, in the present embodiment, in parallel with the above-described operations, a surface of the object is heated by the heating unit  15 , and cooled by the cooling unit  19 . 
     Next, an area to be heated and an area to be cooled will be described with reference to  FIGS. 3A, 3B, 4, and 5 . These figures are schematic plan views in which a three-dimensionally shaped object that is being formed is viewed from above. 
       FIG. 3A  is a schematic plan view of the (N−1)th layer in a case where the Nth layer is currently being formed.  FIG. 3B  is a schematic plan view of the Nth layer alone that is currently being formed. In the figures, a line  28  denotes a boundary between columns of extruded resin, and an arrow  29  denotes a trajectory (trace of movement) of the extruding opening in the layer. 
     In general, an angle of columns of the molten resin  11  is changed for each layer in a plan view so that the three-dimensionally shaped object does not have anisotropy in strength. In the present embodiment, the angle of columns of one layer is shifted by 90 degrees in a plan view with respect to the angle of columns of an adjacent layer. 
       FIG. 4  is a schematic plan view for illustrating an extrusion position, heating, and cooling in the formation of the Nth layer.  FIG. 5  is a schematic diagram illustrating an extrusion position, heating, and cooling at a turning point of a trajectory in each stage of the formation of the Nth layer. 
     An area P 1  is an area to which the molten resin  11  extruded from the extruding opening  13  of  FIG. 2  contacts (that is, an area on which the molten resin  11  is deposited). An area P 2  is an area to be heated that is located in a direction in which the area P 1  moves relative to the stage  4 . An area P 3  is an area to be heated that is located beside the area P 1 . An area P 4  is an area to be cooled that is located behind the area P 1  in the direction. 
     The heating unit  15  reheats the areas P 2  and P 3  of resin solidified on the stage  4 . The area P 2  is an area of the (N−1)th layer of resin in a case where the Nth layer is currently being formed, and is reheated for increasing the adhesion strength between the Nth layer and the (N−1)th layer. The area P 3  is an area of the (M−1)th column in a case where the Mth column of the Nth layer is currently being formed, and is located beside the area P 1 . The area P 3  is reheated for increasing the adhesion strength between adjacent columns, and thus for increasing the strength of the Nth layer. Preferably, the width of the area P 3  is smaller than the width of the molten resin  11 . This is because if the area P 3  whose width is equal to or larger than the width of the molten resin  11  (that is extruded to the area P 1  and deposited) is heated, columns other than the (M−1)th column may be heated, and a desired shape may be deformed. In addition, the heating is performed locally such that the temperature of a lower layer that has already been formed is equal to or higher than a glass transition temperature of the thermoplastic resin and lower than a glass transition temperature added by 30° C. 
     In addition, when the area P 2  is located at a position at which the distance between the edge of the three-dimensionally shaped object and the area P 2  is smaller than the width of the extruded resin, or the area P 3  is located at a position at which the distance between the edge of the three-dimensionally shaped object and the area P 3  is smaller than the width of the extruded resin, that is, when the outer edge portion (outermost portion) of the three-dimensionally shaped object and its vicinity are heated, the output power of the heating means is reduced for preventing deterioration of the accuracy in shape of the three-dimensionally shaped object, caused by excessive heating. 
     The cooling unit  19  locally cools the area P 4  immediately after the molten resin is deposited on the area P 4 , and speeds up the solidification of the molten resin for increasing stability in shape and size. 
     Next, a method and a mechanism of heating and cooling the resin formed on the stage will be described in detail. 
     A driving mechanism keeps a relative distance between the heating unit  15  and the extruding head  10  and a relative distance between the cooling unit  19  and the extruding head  10 ; and keeps a relative position of the heating unit  15  with respect to the extruding head  10  and a relative position of the cooling unit  19  with respect to the extruding head  10 , while the extruding head  10  is scanning. 
     In the present embodiment, the nonrotary gear  14 , the gear  17  mounted in the heating unit  15 , and the motor  18  that transmits power to the gear  17  are provided. The nonrotary gear  14  is mounted on the extruding head  10  such that the central axis of the nonrotary gear  14  is equal to the central axis of the extruding head  10 . In addition, the gear  21  mounted in the cooling unit  19 , and the motor  22  that transmits power to the gear  21  are provided. The gears  17  and  21  mesh with the gear  14 . Thus, when the gears  17  and  21  rotate, they pivot on the gear  14 . 
     Although the gears that pivot on the extruding head  10  are used as the driving mechanism in the present embodiment, another mechanism such as a disk or a robot arm may be used as long as the mechanism can keep the relative distance between the extruding head  10  and the heating unit  15  and the relative distance between the extruding head  10  and the cooling unit  19 , and the relative position of the heating unit  15  with respect to the extruding head  10  and the relative position of the cooling unit  19  with respect to the extruding head  10 . 
     The heating unit  15  heats the area of the resin located in the direction toward which the extruding opening moves with respect to the stage, and the area of the resin located beside the extruding opening. The resin of the areas has been extruded from the extruding opening, and cooled and solidified by the outside air. Preferably, the heating means of the heating unit  15  has a short startup time for the heating. This is because if the time in which the temperature of the solidified material rises to a target temperature is long, the extruding head have to move at slow speed to wait the rise of temperature of the solidified material, possibly causing the forming time to increase. 
     In addition, if another approach that cannot locally heat the area is used, another area of the solidified material other than the desired area will be heated. As a result, the viscosity of the solidified forming material will decrease, possibly deforming the shape of the object. 
     Thus, it is preferable that the heating means can start the heating in a short startup time, and locally heat the area. For example, the heating means may be a laser or a near-infrared heater with a condensing or masking function. 
     For heating the front area and the side area, a plurality of heating means may be used. However, for preventing the apparatus from being upsized, it is preferable that a single heating means be used to limit or control areas to be heated. 
     In the present embodiment, a heat-condensing near-infrared heater is used. The heat source of the heater is a half-ring-shaped halogen lamp, and the heat from the heat source is condensed and shielded so that the heat is applied to a semicircle focal point whose diameter is equal to or smaller than three times the diameter of the molten resin deposited in the planar direction. 
     The cooling unit  19  cools the resin that has been extruded from the extruding opening. 
     Preferably, the cooling unit  19  uses a cooling means that cools the resin in a noncontact manner. This is because if the cooling means contacts the forming material in the cooling, the forming material will adhere to the cooling unit, and may cause trouble in the forming operation. Thus, in the present embodiment, a fan is used to send cool air. 
     The control unit controls the operation of the driving means, and thereby controls the position of the heating unit  15  so that the heating unit  15  is located in front of the extruding head  10 . In the sequence control, since the difference between the position of the heating unit  15  determined in the system and the actual position of the heating unit  15  may be accumulated, correction (calibration) is performed regularly for correcting the difference. Thus, in the present embodiment, feedback-control is performed by using an absolute encoder. 
     Configuration of Control Unit 
     The control unit  6  is a control circuit for controlling each unit of the additive manufacturing apparatus. 
     The control unit  6  includes a CPU, a ROM, a RAM, and an I/O port. The ROM is a nonvolatile memory that stores a control program and a control numerical table. The RAM is a volatile memory used for computation or the like. The I/O port is used for communicating with a device located outside the apparatus and each component of the apparatus. 
     Note that the ROM stores a program used for controlling a basic operation of the additive manufacturing apparatus. 
     The computer  7  is an electronic computer including a storage device, a computing device, and an input/output device; and can execute a three-dimensional shape editing program. The computer  7  creates a multilayer model, depending on the information on a three-dimensional model to be formed. The multilayer model is a model suitable to form by using the extruding head. The computer  7  sends instructions to the control unit  6  for sequentially forming layers of the model. 
     The computer  7  may be a computer included in the additive manufacturing apparatus, or may be an external computer that can be connected with the additive manufacturing apparatus via a network or the like. 
     Next, with reference to  FIG. 6 , forming operations of the heating unit  15  and the cooling unit  19  in the present embodiment will be described in detail. 
     In an operation C 1  to form a straight portion, the gear  17  mounted in the heating unit  15  and the gear  21  mounted in the cooling unit  19  are moved so that the heating unit  15 , the extruding head  10 , and the cooling unit  19  are arranged upstream in this order in the moving direction of the stage  4  (in parallel with the moving direction of the stage  4 ). While such an operation is performed, the molten resin  11  is extruded from the extruding opening  13 . 
     In an operation C 2  to form a curved portion, when the heating unit  15  is reaching a turning point at which the moving direction of the stage  4  changes, the relative angle of the heating unit  15  to the extruding head  10  is changed so that the next area that the extruding head  10  will pass is heated. In the operation C 2 , the gear  17  mounted in the heating unit  15  is rotated by the motor  18 , and thereby pivoted on the nonrotary gear  14  mounted on the extruding head  10 . 
     In an operation C 3  to form a curved portion, when the extruding head  10  is reaching a turning point at which the moving direction of the stage  4  changes, the relative angle of the cooling unit  19  to the extruding head  10  is changed so that the area that the extruding head  10  has passed is cooled. In the operation C 3 , the gear  21  mounted in the cooling unit  19  is rotated by the motor  22 , and thereby pivoted on the nonrotary gear  14  mounted on the extruding head  10 . 
     In the operations C 1  and C 3 , if the turning point has an angle (40 degrees or less in the present embodiment) that causes the cooling unit  19  to interfere with the heating unit  15 , the cooling fan is positioned at a position at which the cooling unit  19  does not interfere with the heating unit  15 , to give priority to the operation C 2 . 
     In this manner, the three-dimensionally shaped object is formed by forming a planar shape by using the operations C 1 , C 2 , and C 3 , then lowering the stage by the thickness of one layer, and then repeating the above-described operations. 
     Configuration of Control Blocks 
     Next, with reference to  FIG. 7 , a configuration of control blocks of the additive manufacturing apparatus of the present embodiment will be described.  FIG. 7  is a simplified block diagram illustrating a relationship of connection of control lines for components of the apparatus. In  FIG. 7 , the stage moving apparatus  5 , the computer  7 , the motor  18 , the motor  22 , a roller driving unit  23 , and an extruding-head moving apparatus  24  (not illustrated in  FIG. 1 ) are provided. The motor  18  is illustrated in  FIG. 2 , and used for rotating the gear  17 . The motor  22  rotates the gear  21 . In addition, a heater driving unit  25 , and a cooler driving unit  26  are provided. 
     Functions of the stage moving apparatus  5 , the extruding-head moving apparatus  24 , the control unit  6 , and the computer  7  are as descried above. 
     The roller driving unit  23  is a circuit to drive the two rollers  8  disposed adjacent to the material introduction portion  9  of the extruding head  10 , and includes a circuit to receive a driving command from the control unit  6  and a driver circuit to drive a roller driving motor. 
     The heater driving unit  25  is a circuit to drive a heater included in the heating portion  12  of the extruding head  10  and the heating means  16  of the heating unit  15 , and includes a heater power source, an energization control circuit, and a circuit to receive a heating command from the control unit  6 . 
     The cooler driving unit  26  is a circuit to drive the cooling means  20  of the cooling unit  19 , and includes an air-blowing power source, an energization control circuit, and a circuit to receive a cooling command from the control unit  6 . 
     Additive Manufacturing Process 
     Next, an additive manufacturing process of the present embodiment will be described sequentially.  FIG. 8  is a flowchart illustrating a sequence of steps of an additive manufacturing process of the present embodiment. 
     In Step S 1 , three-dimensional shape data of a three-dimensional model to be formed is stored in the computer  7 . The three-dimensional shape data may be created by the computer  7 , or may be created by using CAD or a three-dimensional shape measurement instrument and sent to the computer  7  via a network or a storage medium. The three-dimensional shape data format may be the STEP format, the Parasolid format, or the STL format, but may be another format as long as the other format can express the three-dimensional shape by using digital data. 
     In Step S 2 , the computer  7  creates shape data of each layer from the three-dimensional shape data. The shape data of each layer is used when the three-dimensional model is formed by placing one layer on top of another. In Step S 2 , the computer  7  uses a computing device included in the computer  7  and a three-dimensional shape editing program, and creates a divided model obtained by dividing the three-dimensional model. The thickness of the divided model is a thickness of one layer that the additive manufacturing apparatus of the present embodiment can place on top of another. 
     For example, as illustrated in  FIG. 9 , if the three-dimensional model to be formed is a rectangular parallelepiped  27 , the three-dimensional model is divided into slice models each having a thickness of t. The thickness t is a thickness of one layer that the additive manufacturing apparatus can place on top of another. For convenience of description, in the present embodiment, the three-dimensional model is divided into N layers. Thus, the slice models are a layer  27 - 1 , a layer  27 - 2 , . . . , and a layer  27 -N, arranged upward in this order in the vertical direction. 
     In Step S 3 , the computer  7  creates an instruction set necessary for the additive manufacturing apparatus to form the three-dimensional model, in accordance with the divided model created in Step S 2 ; and sends the instruction set to the control unit  6 . Note that the computer  7  may send the divided model to the control unit  6 , and the control unit  6  may create the instruction set necessary for forming the three-dimensional model. The instruction set includes procedure for forming the first to the Nth layers stacked one after another, and instructions related to areas to be heated and cooled. 
     In Step S 4 , the control unit  6  operates each component of the apparatus and performs the formation of a single layer, the heating, and the cooling, in accordance with the instruction set. The operations in Step S 4  are as described above. In Step S 4 , the divided model created in Step S 2  is three-dimensionally formed as one layer. 
     In Step S 5 , the control unit  6  determines whether the whole of N number of primary divided models is three-dimensionally formed. Then the control unit  6  executes Step S 4  again if the whole of the divided models is not formed, or ends the additive manufacturing if the whole of the divided models is formed. 
     The present embodiment can form a three-dimensionally shaped object having high strength in the planar direction and the deposition direction and high shape stability, compared to conventional methods in which the heating and the cooling are not performed. 
     Second Embodiment 
     Hereinafter, a second embodiment will be described with reference to the accompanying drawings. The present embodiment differs from the first embodiment in configuration and operation of the extruding unit  3 . Thus, the description for a component identical to a component of the first embodiment will be omitted. 
     A configuration of the extruding unit of the present embodiment will be described with reference to  FIGS. 10A and 10B . In the present embodiment, as illustrated in  FIG. 10A , one or more heating means are disposed on a circle around the extruding head  10 , and valves  30  corresponding to the respective heating means are disposed. Thus, when an area to be heated on a top surface on which the deposition is performed is changed in accordance with the forming operation, and when the output power is changed, the valves  30  are opened or closed. 
     In a first specific example of the second embodiment, a ring-type halogen lamp is used as the heating means  16 .  FIG. 10B  illustrates a planar shape of each valve  30 . As illustrated in  FIG. 10B , the valve  30  includes a round plate  31  that has an arch-shaped long hole  32  formed on a circle around the extruding head  10 . Specifically, the valve  30  is constituted by two round plates  31 , and the two plates  31  are completely overlapped with each other such that each plate can rotate independently around the extruding head  10 . Since each of the two round plates  31  is rotated in accordance with the forming operation, the position at which the arch-shaped long holes  32  overlap with each other can be controlled. With this control, the shape and position of an opening through which the near-infrared light from the halogen lamp passes are changed, and thereby the area to be locally heated on a surface on which the forming operation is performed is changed. 
     In a second specific example of the second embodiment, eight hot-air torches are used as the heating means  16 . The eight hot-air torches are disposed at regular intervals on a circle around the extruding head  10 , and on-off valves are attached to the corresponding hot-air torches. By operating the on-off valves, the area to be heated on a surface on which the forming operation is performed is changed. 
     In the present embodiment, since a valve is provided for each of the heating means for controlling the local heating, the position of the area to be locally heated and the amount of heat can be precisely controlled. Thus, the present embodiment can form a three-dimensionally shaped object having high strength in the planar direction and the deposition direction and high shape stability. 
     The present invention can also be embodied by supplying a program that achieves one or more functions of the above-described embodiments, to a system or a device via a network or a storage media, and by causing one or more processors of a computer of the system or the device to read and execute the program. In addition, the present disclosure may be embodied by a circuit (such as an ASIC) that achieves one or more functions. 
     Other Embodiments 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2019-217176, filed Nov. 29, 2019, which is hereby incorporated by reference herein in its entirety.