Three-dimensional molding apparatus

Abstract

To provide a technology capable of stabilizing the discharge amount at the time of resumption or immediately after resumption of discharge in a three-dimensional molding apparatus.SOLUTION: A three-dimensional molding apparatus comprises: a plasticizing section that includes a screw and produces a plasticizing material; a nozzle that includes a nozzle opening and discharges the plasticizing material; a discharge amount adjustment mechanism that controls the discharge amount of the plasticizing material from the nozzle opening by adjusting the opening degree of a flow channel communicating with the nozzle opening; and a control unit. The control unit executes at least one of first control and second control, where the first control varies the rotation rate of the screw in a multistep manner during a discharge stop period being a period from the stopping of discharge of the plasticizing material to the resumption of discharge of the plasticizing material, and the second control varies the rotation rate of the screw in a multistep manner during a discharge resumption period being a period from the resumption of discharge of the plasticizing material to the point at which the opening degree of the flow channel reaches the opening degree specified with respect to the discharge amount adjustment mechanism. The control unit raises the rotation rate of the screw after having lowered the rotation rate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a three-dimensional printing apparatus. [Background technology]

[0002] Patent Document 1 discloses a three-dimensional modeling apparatus equipped with a flow rate adjustment mechanism capable of controlling the amount of molten material discharged from a nozzle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-81263 A Summary of the Invention [Problem to be solved by the invention]

[0004] The three-dimensional modeling device disclosed in Patent Document 1 can adjust the discharge amount from the nozzle by adjusting the rotation angle of a butterfly valve as a flow rate adjustment mechanism. However, during the period from when discharge is stopped to when it is restarted, the pressure in the flow path upstream of the butterfly valve is unstable, and the discharge amount may not be stable when or immediately after discharge is restarted. [Means for solving the problem]

[0005] According to a first aspect of the present disclosure, there is provided a three-dimensional modeling apparatus, comprising: a plasticizing unit having a screw and a motor for rotating the screw and plasticizing a material to generate a plasticized material, a nozzle having a nozzle opening and discharging the plasticized material, a discharge amount adjustment mechanism provided in a flow path through which the plasticized material flows and communicating with the nozzle opening and controlling the amount of the plasticized material discharged from the nozzle opening by adjusting the opening of the flow path, and a control unit for controlling the plasticizing unit and the discharge amount adjustment mechanism, and the control unit is configured to stop discharging the plasticized material from the nozzle opening and adjust the opening of the flow path. and performing at least one of the following controls: a first control for changing the rotational speed of the screw in multiple stages during an extrusion stop period, which is a period before the extrusion of the plasticizing material from the nozzle opening is resumed after the extrusion of the plasticizing material from the nozzle opening is stopped; and a second control for changing the rotational speed of the screw in multiple stages during an extrusion restart period, which is a period until the opening of the flow path reaches the opening specified for the extrusion amount adjustment mechanism after the extrusion of the plasticizing material from the nozzle opening is resumed, and the control unit performs the second control by lowering and then increasing the rotational speed of the screw. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic configuration of a three-dimensional printing system. [Diagram 2] FIG. [Diagram 3] Schematic plan view of a barrel. [Figure 4] FIG. 2 is an explanatory diagram illustrating a process in which the three-dimensional printing apparatus prints a model. [Diagram 5] FIG. 1 is an explanatory diagram showing a schematic configuration of an information processing apparatus. [Figure 6] 4 is a flowchart of a modeling process. [Figure 7] 4 is a timing chart showing the process of the first control. [Figure 8] The first figure shows the change in internal pressure over time. [Figure 9] The second figure shows the change in internal pressure over time. [Figure 10]1 is a graph showing the relationship between the maximum internal pressure at each rotation speed and the time it takes to reach 80% of the maximum internal pressure. [Figure 11] FIG. 4 is a diagram showing a change in internal pressure when the rotation speed of the screw is changed stepwise. [Figure 12] A diagram showing the time axis of Figure 11 stretched out. [Figure 13] 10 is a detailed flowchart of a first control in the second embodiment. [Figure 14] 14 is a timing chart of the process in step S55 of FIG. 13. [Figure 15] 14 is a timing chart of the process in step S56 of FIG. 13. [Figure 16] 13 is a graph showing the target value of the internal pressure according to the position of the plunger. [Figure 17] 13 is a flowchart of a formation process according to a fourth embodiment. [Figure 18] 6 is a timing chart showing the processing content of the second control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] A. First embodiment: FIG. 1 is an explanatory diagram showing a schematic configuration of a three-dimensional printing system 10 in the first embodiment. In FIG. 1, arrows indicating mutually orthogonal X, Y, and Z directions are shown. The X and Y directions are parallel to a horizontal plane, and the Z direction is a direction along a vertical upward direction. The arrows indicating the X, Y, and Z directions are also shown in other figures as appropriate so that the illustrated directions correspond to those in FIG. 1. In the following description, when specifying the direction, the direction indicated by the arrow in each figure is indicated as "+" and the opposite direction is indicated as "-", and positive and negative signs are used in combination to indicate the direction. In the following, the +Z direction is also referred to as "up" and the -Z direction is also referred to as "down".

[0008] The three-dimensional printing system 10 includes a three-dimensional printing device 100 and an information processing device 400. The three-dimensional printing device 100 of this embodiment is a device that forms a model by a material extrusion method. The three-dimensional printing device 100 includes a control unit 300 for controlling each unit of the three-dimensional printing device 100. The control unit 300 and the information processing device 400 are connected to each other so as to be able to communicate with each other.

[0009] The three-dimensional modeling apparatus 100 includes a head unit 110 that generates and dispenses a plasticized material, a modeling stage 210 that serves as a base for a model, and a movement mechanism 230 that controls the dispense position of the plasticized material.

[0010] Under the control of the control unit 300, the head unit 110 ejects a plasticized material obtained by plasticizing a solid-state material onto the stage 210. The head unit 110 includes a material supply unit 20 that is a supply source of raw materials before being converted into a plasticized material, a plasticizing unit 30 that converts the raw materials into a plasticized material, and an ejection unit 60 that ejects the plasticized material.

[0011] The material supplying section 20 supplies the raw material MR to the plasticizing section 30. The material supplying section 20 is configured, for example, by a hopper that stores the raw material MR. The material supplying section 20 is connected to the plasticizing section 30 via a communication passage 22. The raw material MR is fed into the material supplying section 20 in the form of powder or pellets. As the raw material MR, for example, a resin material such as ABS (acrylonitrile butadiene styrene), PEEK (polyether ether ketone), or PP (polypropylene) is used.

[0012] The plasticizing section 30 plasticizes the raw material MR supplied from the material supply section 20 to generate a paste-like plasticized material that exhibits fluidity, and guides it to the discharge section 60. In this embodiment, "plasticization" is a concept that includes melting, and refers to changing from a solid to a fluid state. Specifically, in the case of a material that undergoes glass transition, plasticization refers to raising the temperature of the material to or above the glass transition point. In the case of a material that does not undergo glass transition, plasticization refers to raising the temperature of the material to or above the melting point.

[0013] The plasticizing section 30 includes a screw case 31, a drive motor 32, a screw 40, and a barrel 50. The screw 40 is also called a flat screw, a rotor, or a scroll. The barrel 50 is also called a screw facing portion.

[0014] The screw 40 is housed in the screw case 31. An upper surface 47 of the screw 40 is connected to the drive motor 32, and the screw 40 rotates in the screw case 31 by the rotational driving force generated by the drive motor 32. The drive motor 32 is driven under the control of the control unit 300. Note that the screw 40 may be driven by the drive motor 32 via a reducer.

[0015] 2 is a perspective view showing a schematic configuration of the lower surface 48 side of the screw 40. In order to facilitate understanding of the technology, the screw 40 shown in FIG. 2 is shown in a state in which the positional relationship between the upper surface 47 and the lower surface 48 shown in FIG. 1 is reversed in the vertical direction. The screw 40 has a substantially cylindrical shape in which the length in the axial direction, which is the direction along the central axis, is smaller than the length in the direction perpendicular to the axial direction. The screw 40 is disposed so that the rotation axis RX, which is the center of rotation, is parallel to the Z direction.

[0016] A spiral groove 42 is formed on the lower surface 48 of the screw 40, which is a surface intersecting with the rotation axis RX. The communication passage 22 of the material supply unit 20 described above communicates with the groove 42 from the side surface of the screw 40. In this embodiment, three grooves 42 are formed, separated by a protruding rib portion 43. The number of grooves 42 is not limited to three, and may be one, or two or more. The groove 42 is not limited to a spiral shape, and may be a spiral shape or an involute curve shape, or may be a shape that extends in an arc from the center to the outer periphery.

[0017] 1, the lower surface 48 of the screw 40 faces the upper surface 52 of the barrel 50, and a space is formed between the groove portion 42 of the lower surface 48 of the screw 40 and the upper surface 52 of the barrel 50. Raw material MR is supplied from the material supply section 20 to this space between the screw 40 and the barrel 50 through the material inlet 44 shown in FIG.

[0018] A barrel heater 58 is embedded in the barrel 50 to heat the raw material MR supplied into the groove 42 of the rotating screw 40. A communication hole 56 is provided in the center of the barrel 50.

[0019] 3 is a schematic plan view showing the top surface 52 side of the barrel 50. A plurality of guide grooves 54 are formed on the top surface 52 of the barrel 50, which are connected to the communication holes 56 and extend in a spiral shape from the communication holes 56 toward the outer periphery. Note that one end of the guide grooves 54 does not have to be connected to the communication holes 56. Also, the guide grooves 54 can be omitted.

[0020] The raw material MR supplied into the groove 42 of the screw 40 flows along the groove 42 as the screw 40 rotates while being plasticized in the groove 42, and is guided to the center 46 of the screw 40 as a plasticized material. The paste-like plasticized material that has flowed into the center 46 and exhibits fluidity is supplied to the discharge section 60 through a communication hole 56 provided in the center of the barrel 50. Note that in the plasticized material, all types of substances constituting the plasticized material do not have to be plasticized. It is sufficient that the plasticized material is converted into a state having fluidity as a whole by plasticizing at least some types of substances constituting the plasticized material.

[0021] The discharge unit 60 in FIG. 1 includes a nozzle 61 for discharging the plasticized material, a flow path 65 for the plasticized material provided between the screw 40 and a nozzle opening 62, and a discharge control unit 77 for controlling the discharge of the plasticized material.

[0022] The nozzle 61 is connected to the communication hole 56 of the barrel 50 through a flow path 65. The nozzle 61 discharges the plasticized material produced in the plasticizing section 30 from a nozzle opening 62 at the tip toward the stage 210.

[0023] The discharge control unit 77 includes a discharge amount adjusting mechanism 70 that opens and closes the flow path 65, and a suction mechanism 75 that sucks in the plasticized material and temporarily stores it.

[0024] The discharge amount adjustment mechanism 70 is provided in the flow path 65, and changes the opening degree of the flow path 65 by rotating in the flow path 65. In this embodiment, the discharge amount adjustment mechanism 70 is configured by a valve. The discharge amount adjustment mechanism 70 is driven by a first drive unit 74 under the control of the control unit 300. The first drive unit 74 is configured by, for example, a stepping motor. The control unit 300 can adjust the flow rate of the plasticizing material flowing from the plasticizing unit 30 to the nozzle 61, that is, the discharge amount of the plasticizing material discharged from the nozzle 61, by controlling the rotation angle of the valve using the first drive unit 74. The discharge amount adjustment mechanism 70 can adjust the discharge amount of the plasticizing material and can control the on / off of the outflow of the plasticizing material.

[0025] The suction mechanism 75 includes a branch flow path 66 connected to the flow path 65, and a plunger 67 disposed in the branch flow path 66. The branch flow path 66 is connected to the flow path 65 between the discharge amount adjustment mechanism 70 and the nozzle opening 62. In the following, moving the plunger 67 in the branch flow path 66 away from the flow path 65 is referred to as "pulling the plunger 67," and moving the plunger 67 closer to the flow path 65 is referred to as "pushing the plunger 67." The plunger 67 of the suction mechanism 75 is driven by a second drive unit 76 under the control of the control unit 300. The second drive unit 76 is, for example, configured by a stepping motor, a rack-and-pinion mechanism that converts the rotational force of the stepping motor into translational motion of the plunger 67, or the like.

[0026] The control unit 300 controls the suction mechanism 75 to temporarily suck the plasticized material in the flow path 65 into the branch flow path 66 by pulling the plunger 67 when the discharge of the plasticized material from the nozzle 61 is stopped. This makes it possible to suppress the tailing phenomenon in which the plasticized material hangs like a string from the nozzle opening 62. Furthermore, when the discharge of the plasticized material from the nozzle 61 is resumed, the control unit 300 adjusts the discharge amount of the plasticized material discharged from the nozzle 61 to be constant by pulling the plunger 67 to suck the plasticized material in the flow path 65 or pushing the plunger 67 to send the plasticized material into the flow path 65. This makes it possible to keep the line width of the plasticized material constant when the discharge is resumed.

[0027] The stage 210 is disposed at a position facing the nozzle opening 62 of the nozzle 61. In the first embodiment, the modeling surface 211 of the stage 210 facing the nozzle opening 62 of the nozzle 61 is disposed so as to be parallel to the X and Y directions, i.e., the horizontal direction. The stage 210 is provided with a stage heater 212 for preventing the plasticized material discharged onto the stage 210 from being suddenly cooled. The stage heater 212 is controlled by the control unit 300.

[0028] The movement mechanism 230 changes the relative position between the stage 210 and the nozzle 61 under the control of the control unit 300. In this embodiment, the position of the nozzle 61 is fixed, and the movement mechanism 230 moves the stage 210. The movement mechanism 230 is configured with a three-axis positioner that moves the stage 210 in three axial directions, that is, the X, Y, and Z directions, by the driving forces of three motors. In this specification, unless otherwise specified, the movement of the nozzle 61 means the movement of the nozzle 61 and the discharge unit 60 relative to the stage 210.

[0029] In other embodiments, instead of a configuration in which the moving mechanism 230 moves the stage 210, a configuration in which the moving mechanism 230 moves the nozzle 61 relative to the stage 210 while the position of the stage 210 is fixed may be employed. Also, a configuration in which the moving mechanism 230 moves the stage 210 in the Z direction and moves the nozzle 61 in the X and Y directions, or a configuration in which the moving mechanism 230 moves the stage 210 in the X and Y directions and moves the nozzle 61 in the Z direction may be employed. Even with these configurations, the relative positional relationship between the nozzle 61 and the stage 210 can be changed.

[0030] 1 shows only one head unit 110, the three-dimensional modeling apparatus 100 may include multiple head units 110. By including multiple head units 110, different types of plasticizing materials can be discharged from each head unit 110. Therefore, for example, the main body of a modeled object and a support structure that supports the modeled object can be modeled using different types of plasticizing materials.

[0031] The control unit 300 is a control device that controls the overall operation of the three-dimensional modeling apparatus 100. The control unit 300 is configured by a computer including one or more processors 310, a storage device 320 including a main storage device and an auxiliary storage device, and an input / output interface that inputs and outputs signals to and from the outside. The processor 310 executes a program stored in the storage device 320 to control the plasticizing unit 30 and the moving mechanism 230 in accordance with modeling data acquired from the information processing device 400, thereby modeling a model on the stage 210. Note that the control unit 300 may be realized by a combination of circuits instead of being configured by a computer.

[0032] 4 is an explanatory diagram showing a schematic diagram of the three-dimensional modeling apparatus 100 modeling a model. In the three-dimensional modeling apparatus 100, as described above, the raw material MR in a solid state is plasticized to generate the plasticized material MM. The control unit 300 discharges the plasticized material MM from the nozzle 61 while changing the position of the nozzle 61 relative to the stage 210 in a direction along the modeling surface 211 of the stage 210, while maintaining the distance between the nozzle 61 and the modeling surface 211 of the stage 210. The plasticized material MM discharged from the nozzle 61 is continuously deposited in the movement direction of the nozzle 61.

[0033] The control unit 300 forms layers ML by repeatedly moving the nozzle 61. After forming one layer ML, the control unit 300 moves the position of the nozzle 61 relative to the stage 210 in the Z direction, which is the stacking direction. Then, a further layer ML is stacked on the layer ML that has been formed so far, thereby forming a modeled object.

[0034] The control unit 300 may temporarily suspend the discharge of the plasticizing material from the nozzle 61, for example, when the nozzle 61 moves in the Z direction after completing one layer ML or when there are multiple independent modeling regions in each layer. In this case, the control unit 300 may, for example, close the flow path 65 using the discharge amount adjustment mechanism 70 to stop the discharge of the plasticizing material MM from the nozzle opening 62, and temporarily suck the plasticizing material in the nozzle 61 using the suction mechanism 75. In addition, the control unit 300 may, for example, change the position of the nozzle 61, and then open the flow path 65 using the discharge amount adjustment mechanism 70 while discharging the plasticizing material in the suction mechanism 75, thereby resuming the deposition of the plasticizing material MM from the changed position of the nozzle 61.

[0035] 5 is an explanatory diagram showing a schematic configuration of the information processing device 400. The information processing device 400 is configured as a computer in which a CPU 410, a memory 420, a storage device 430, a communication interface 440, and an input / output interface 450 are interconnected via a bus 460. An input device 470 such as a keyboard or a mouse, and a display unit 480 such as a liquid crystal display are connected to the input / output interface 450. The information processing device 400 is connected to the control unit 300 of the three-dimensional printing apparatus 100 via the communication interface 440.

[0036] The CPU 410 executes a program stored in the storage device 430 to function as a data generation unit 411 .

[0037] The data generating unit 411 generates modeling data. The modeling data is data that represents information on the movement path of the nozzle 61 relative to the stage 210, the amount of plasticizing material discharged from the nozzle 61, the rotation speed of the screw 40, and the like. The data generating unit 411 reads shape data that represents the shape of a three-dimensional object created using three-dimensional CAD software or three-dimensional CG software, and divides the shape of the three-dimensional object into layers of a predetermined thickness. As the shape data, data in STL format, AMF format, or the like is used. The data generating unit 411 generates modeling data by determining the movement path of the nozzle 61 and the amount of plasticizing material so as to fill each divided layer with the plasticizing material. The modeling data is represented by G code, M code, or the like.

[0038] 6 is a flowchart of the modeling process executed by the control unit 300 of the three-dimensional modeling device 100. In step S10, the control unit 300 acquires modeling data generated by the information processing device 400.

[0039] In step S20, the control unit 300 performs modeling control. In this modeling control, the control unit 300 controls the plasticizing unit 30 to start discharging the plasticizing material, and models a three-dimensional object. The control unit 300 controls the plasticizing unit 30, the discharge control unit 77, and the moving mechanism 230 in accordance with the modeling data, thereby forming a three-dimensional object on the stage 210, as described in FIG. 4.

[0040] In step S30, the control unit 300 determines whether or not to stop the discharge of the plasticizing material from the nozzle opening 62. In step S30, the control unit 300 analyzes the modeling data, and determines to stop the discharge of the plasticizing material in the case where, for example, any of the following (A) to (D) applies. When it is determined not to stop the discharge, the control unit 300 returns the process to step S20, and continues modeling of the three-dimensional object until it is determined to stop the discharge. (A) Printing of all layers is complete. (B) The nozzle 61 is moved along the Z direction to build the different layers. (C) The nozzle 61 is moved to a different position within the same layer. (D) When the three-dimensional modeling apparatus 100 includes a plurality of head units 110, the head unit 110 to be used is switched.

[0041] When it is determined in step S30 that the discharge is to be stopped, the control unit 300 determines whether or not the modeling of all layers is completed in step S40. When it is determined that the modeling of all layers is completed, the control unit 300 ends the modeling process.

[0042] If it is not determined in step S40 that modeling of all layers has been completed, the control unit 300 executes a first control in step S50. The first control is a control for changing the rotation speed of the screw 40 in multiple stages during a discharge stop period, which is a period from when the discharge of the plasticizing material from the nozzle opening 62 is stopped until when the discharge of the plasticizing material from the nozzle opening 62 is resumed. "Changing the rotation speed of the screw 40 in multiple stages during a discharge stop period" means changing the rotation speed of the screw 40 one or more times during the discharge stop period.

[0043] FIG. 7 is a timing chart showing the processing contents of the first control in the first embodiment. FIG. 7 shows a timing chart of a signal indicating the target rotation speed of the screw 40 output from the control unit 300 to the plasticizing unit 30. In the first control, the control unit 300 increases the rotation speed of the screw 40 to a second rotation speed, which is a rotation speed higher than the first rotation speed in the period before the discharge stop period, and then decreases it to a third rotation speed, which is a rotation speed lower than the first rotation speed. The first rotation speed is the rotation speed of the screw 40 during the formation of the three-dimensional object. The second rotation speed, the third rotation speed, and the duration of the second rotation speed are determined in advance by performing simulations and experiments so that the pressure in the flow path 65 upstream of the discharge amount adjustment mechanism 70 becomes an appropriate pressure when discharge is resumed. Hereinafter, the pressure in the flow path 65 upstream of the discharge amount adjustment mechanism 70 is referred to as the "internal pressure". The first rotation speed, the second rotation speed, the third rotation speed, and the duration of each rotation speed may be variable depending on the type of material being used, and the first rotation speed and the second rotation speed may be the same rotation speed.

[0044] After executing the first control, in step S60 of Fig. 6, the control unit 300 controls the discharge amount adjustment mechanism 70 to resume the discharge of the plasticizing material from the nozzle opening 62. At this time, as shown in Fig. 7, the control unit 300 increases the rotation speed of the screw 40 from the second rotation speed to the first rotation speed in the period before the discharge stop period. Thereafter, the control unit 300 returns the process to step S20 and continues the formation of the three-dimensional object.

[0045] The three-dimensional modeling apparatus 100 of the first embodiment described above executes a first control in which the rotation speed of the screw 40 is changed in multiple stages during a discharge stop period, which is a period from when the discharge of the plasticizing material is stopped until when the discharge of the plasticizing material from the nozzle opening 62 is resumed. Therefore, when the discharge is resumed, the internal pressure, which is the pressure in the flow path upstream of the discharge amount adjustment mechanism 70, can be quickly stabilized to an appropriate pressure. As a result, it is possible to stabilize the discharge amount when the discharge is resumed, and to maintain a constant line width.

[0046] Hereinafter, the experimental results regarding the first control will be described with reference to Figures 8 to 12. In this experiment, ABS resin was used as the material.

[0047] FIG. 8 is a diagram showing the change in internal pressure over time when the rotation speed of the screw 40 is 6 rpm. FIG. 9 is a diagram showing the change in internal pressure over time when the rotation speed of the screw 40 is 0.5 rpm. The horizontal axis in these diagrams indicates the elapsed time from the stop of discharge. The vertical axis indicates the internal pressure of the flow path 65 upstream of the discharge amount adjustment mechanism 70. At the rotation speed shown in FIG. 8, the internal pressure after the stop of discharge becomes excessive compared to the internal pressure at the time of the stop of discharge, and when the discharge is resumed, the discharge amount of the plasticized material increases significantly, making it difficult to keep the line width constant. In contrast, at the rotation speed shown in FIG. 9, the internal pressure can be prevented from becoming excessive, but it takes time for the change in internal pressure to stabilize. Therefore, if the discharge stop period is short, there is a possibility that the internal pressure will be insufficient when the discharge is resumed, and the discharge amount of the plasticized material will be insufficient.

[0048] FIG. 10 is a diagram showing the relationship between the maximum internal pressure Pmax at each rotation speed and the time required to reach 80% of the maximum internal pressure Pmax. The maximum internal pressure Pmax is the internal pressure at the time when the pressure change becomes almost zero due to the passage of time from the stop of discharge. According to the experimental results shown in FIG. 10, it was confirmed that the maximum internal pressure Pmax exceeds the appropriate pressure even when the rotation speed is set to 1 to 2 rpm in order to shorten the time required for the internal pressure to reach the maximum internal pressure Pmax. The appropriate pressure is, for example, a pressure that is 2 to 3 times the internal pressure during modeling, and is a pressure that allows the line width to be kept constant by operating the plunger 67 when the discharge is resumed. According to the experimental results shown in FIGS. 8 to 10, it was confirmed that it is difficult to suppress the internal pressure from becoming excessive while shortening the time required for the internal pressure to stabilize when the rotation speed of the screw 40 is controlled to be kept constant without changing it during the discharge stop period.

[0049] FIG. 11 is a diagram showing the change in the internal pressure when the rotation speed of the screw 40 is decreased from 6 rpm to 0.5 rpm 0.3 seconds after the discharge is stopped. FIG. 12 is a diagram in which the time axis of FIG. 11 is extended. As shown in these FIGS. 11 and 12, when the rotation speed of the screw 40 is changed in multiple stages after the discharge is stopped, it is possible to instantly increase the internal pressure to the appropriate pressure range shown by the broken line, and the pressure can be stabilized in a short period of time. In other words, it was confirmed that the control unit 300 can reduce the time until the internal pressure is stabilized while suppressing the internal pressure from becoming excessive by executing the first control. Therefore, according to the first embodiment, the discharge amount at the time of resuming discharge can be stabilized regardless of the length of the discharge stop period.

[0050] B. Second embodiment: The configuration of the three-dimensional printing system 10 in the second embodiment is the same as that in the first embodiment. In the second embodiment, the content of the first control executed by the control unit 300 in the printing process is different from that in the first embodiment.

[0051] 13 is a detailed flowchart of the first control executed by the control unit 300 in the second embodiment. In step S51, the control unit 300 determines whether the reason for stopping the discharge is the above (B), that is, whether or not the nozzle 61 is to move along the Z direction.

[0052] In step S51, when it is determined that the discharge stop is the above (B), the control unit 300 increases the rotation speed of the screw 40 to a second rotation speed, which is a rotation speed higher than the first rotation speed, which is the rotation speed before the discharge stop period, in step S52, and then decreases the rotation speed to a third rotation speed, which is a rotation speed lower than the first rotation speed, and ends the first control. The control content in step S52 is the same as the first control in the first embodiment shown in FIG.

[0053] If it is determined in step S51 that the reason for stopping the discharge is not the above-mentioned (B), the control unit 300 determines in step S53 whether the reason for stopping the discharge is the above-mentioned (C), i.e., whether or not the nozzle 61 is to be moved to a different position within the same layer.

[0054] If it is determined in step S53 that the reason for the stop of discharge is (C) above, the control unit 300 determines in step S54 whether the movement distance of the nozzle 61 in the same layer is shorter than a predetermined distance. If it is determined that the movement distance of the nozzle 61 is shorter than the predetermined distance, the control unit 300 executes the process of step S55. The predetermined distance is, for example, 1 to 10 mm.

[0055] FIG. 14 is a timing chart of the process of step S55. In step S55, the control unit 300 increases the rotation speed of the screw 40 to a second rotation speed, which is a rotation speed higher than the first rotation speed, which is the rotation speed before the discharge stop period, and then returns it to the first rotation speed, and ends the first control. In this way, even if the movement distance of the nozzle 61 in the same layer is short and the discharge stop period is short, the internal pressure can be quickly increased to an appropriate pressure. Note that the control unit 300 may return the rotation speed from the second rotation speed to the first rotation speed immediately after the discharge is resumed after the first control ends, instead of during the first control.

[0056] When it is determined in step S54 of FIG. 13 that the movement distance of the nozzle 61 is longer than a predetermined distance, the control unit 300 executes the process of step S56.

[0057] FIG. 15 is a timing chart of the process of step S56. In step S56, the control unit 300 increases the rotation speed of the screw 40 to a second rotation speed, which is a rotation speed higher than the first rotation speed, which is the rotation speed before the discharge stop period, and then gradually decreases the rotation speed to a third rotation speed, which is a rotation speed lower than the first rotation speed, and ends the first control. In this way, the internal pressure can be brought close to the target internal pressure in a short time, and the time until the internal pressure is stabilized can be shortened. Note that "gradually decreasing" includes decreasing the rotation speed in multiple stages and decreasing the rotation speed gently or linearly, as shown in FIG. 15.

[0058] In the above step S53, when it is determined that the reason for the discharge stop is not the above (B) or (C), that is, when it is determined that the reason for the discharge stop is not the movement of the nozzle 61 along the Z direction or the movement of the nozzle 61 to a different position in the same layer, the control unit 300 stops the screw 40 in step S57, and after a certain period of time has elapsed, returns the rotation speed of the screw 40 to the first rotation speed, which is the rotation speed before the discharge stop period. When the reason for the discharge stop is not the movement of the nozzle 61 in the Z direction or the movement of the nozzle 61 to a different position in the same layer, for example, it is a case where the head unit 110 to be used is switched or emergency maintenance is performed on the head unit 110 during the modeling process. Note that the control unit 300 may reduce the rotation speed of the screw 40 instead of stopping it in step S57. In addition, the timing for returning the rotation speed of the screw 40 to the first rotation speed may be immediately before or at the time of resuming discharge.

[0059] According to the second embodiment described above, the control of the rotation speed of the screw 40 during the discharge stop period is switched depending on the reason for the discharge stop. Therefore, even if the discharge stop period varies in length depending on the reason for the discharge stop, the internal pressure can be appropriately controlled.

[0060] In the second embodiment, the control unit 300 switches the control contents depending on the reason for the ejection stop. Alternatively, the control unit 300 may calculate the length of the ejection stop period and switch the control contents depending on the length. For example, the control unit 300 may execute the process of step S57 when the ejection stop period is 5 minutes or more, execute the process of step S52 when the ejection stop period is 10 to 20 seconds, execute the process of step S56 when the ejection stop period is 1 to 10 seconds, and execute the process of step S55 when the ejection stop period is less than 1 second.

[0061] In the second embodiment, the control unit 300 switches the control content to one of four depending on the reason for the stop of discharge in the first control as shown in Fig. 13. In contrast, the control unit 300 may execute any one of the processes of step S55, step S56, and step S57 in the first control regardless of the reason for the stop of discharge.

[0062] C. Third embodiment: The configuration of the three-dimensional printing system 10 in the third embodiment is the same as that in the first embodiment. In the third embodiment, the content of the first control executed by the control unit 300 in the printing process is different from that in the first embodiment.

[0063] In the first control in the third embodiment, the control unit 300 changes the rotational speed of the screw 40 in multiple stages as shown in FIG. 7, while controlling the second rotational speed according to the position of the plunger 67 when discharge is stopped, as described below.

[0064] FIG. 16 is a graph showing the target value of the internal pressure according to the position of the plunger 67. The control unit 300 controls the rotation speed of the screw 40 so that the internal pressure during the discharge stop period becomes smaller as the position of the plunger 67 becomes farther from the flow path 65 when the discharge is stopped. In other words, the rotation speed of the screw 40 is controlled so that the internal pressure becomes larger as the position of the plunger 67 becomes closer to the flow path 65. In further other words, the rotation speed of the screw 40 is controlled so that the internal pressure at a first position of the plunger 67 becomes higher than the internal pressure at a second position that is farther from the flow path 65 than the first position. An example of the relationship between the rotation speed of the screw 40 and the internal pressure is shown in FIG. 10.

[0065] As described above, the position of the plunger 67 is dynamically changed by the control unit 300 in order to keep the discharge amount constant when or immediately after the discharge is resumed. Therefore, the position of the plunger 67 when the discharge is stopped is not fixed and can be in various positions. For example, when the plunger 67 is far from the flow path 65, it is difficult to pull the plunger 67 further, so that it is difficult to absorb the pressure when the internal pressure increases when the discharge is resumed. Conversely, when the plunger 67 is close to the flow path 65, it is difficult to push the plunger 67 further, so that it is difficult to compensate for the pressure when the internal pressure decreases when the discharge is resumed. In the third embodiment described above, the rotation speed of the screw 40 during the discharge stop period is controlled according to the position of the plunger 67. More specifically, the rotation speed of the screw 40 is controlled so that the internal pressure decreases as the position of the plunger 67 when the discharge is stopped is farther from the flow path 65. Therefore, according to the third embodiment, it is possible to prevent the internal pressure from becoming such that it hinders the operation of the plunger 67 when the discharge is resumed, and it is easy to keep the discharge amount constant when the discharge is resumed.

[0066] D. Fourth embodiment: The configuration of the three-dimensional printing system 10 in the fourth embodiment is the same as that in the first embodiment. In the fourth embodiment, a part of the printing process executed by the control unit 300 is different from that in the first embodiment.

[0067] 17 is a flowchart of the forming process executed by the control unit 300 in the fourth embodiment. In the fourth embodiment, the first control is not executed, and after the discharge is resumed in step S60, the second control is executed in step S70. Since the other process contents are the same as those in the first embodiment, the following description will be omitted except for the second control.

[0068] The second control is a control that changes the rotational speed of the screw 40 in multiple stages during the extrusion resumption period, which is the period from when the extrusion of the plasticizing material from the nozzle opening 62 resumes until the opening of the flow path 65 reaches the opening specified for the extrusion amount adjustment mechanism 70.

[0069] Fig. 18 is a timing chart showing the processing contents of the second control in the fourth embodiment. Fig. 18 shows a timing chart of a signal indicating the target rotation speed of the screw 40 output from the control unit 300 to the plasticizing unit 30, a signal indicating the target opening degree of the flow path 65 output from the control unit 300 to the discharge amount adjustment mechanism 70, and an actual opening degree of the flow path 65. In the fourth embodiment, in the second control, the control unit 300 lowers and then increases the rotation speed of the screw 40 during the discharge restart period. More specifically, the control unit 300 lowers and then increases the rotation speed of the screw 40 to a normal rotation speed during modeling during the discharge restart period.

[0070] According to the fourth embodiment described above, after the discharge of the plasticizing material from the nozzle opening 62 is resumed, during the discharge restart period, which is the period until the opening of the flow path 65 reaches the opening specified for the discharge amount adjustment mechanism 70, the rotation speed of the screw 40 is decreased and then increased. Therefore, even if the internal pressure becomes excessive during the discharge stop period, the rotation speed of the screw 40 is decreased during the discharge restart period, thereby preventing the discharge amount from increasing immediately after discharge is resumed. Therefore, the discharge amount immediately after discharge is resumed can be stabilized, making it easy to maintain a constant line width.

[0071] E. Other embodiments: (E1) In the above-described first to third embodiments, the control unit 300 executes the first control in the forming process, and in the fourth embodiment, the control unit 300 executes the second control. In contrast to this, the control unit 300 may execute both the first control and the second control.

[0072] (E2) In the first control in each of the above embodiments, the control unit 300 may repeat increasing and decreasing the rotation speed of the screw 40 multiple times. The control unit 300 may change the number of times that the rotation speed is repeatedly increased and decreased depending on the length of the discharge suspension period.

[0073] (E3) In each of the above embodiments, the plasticizing unit 30 may plasticize the material by rotating an in-line screw.

[0074] F. Other forms: The present disclosure is not limited to the above-mentioned embodiment, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features of the embodiments corresponding to the technical features in each form described below can be appropriately replaced or combined in order to solve some or all of the above-mentioned problems or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0075] (1) According to a first aspect of the present disclosure, there is provided a three-dimensional modeling apparatus comprising: a plasticizing unit having a screw and a motor for rotating the screw and for plasticizing a material to generate a plasticized material; a nozzle having a nozzle opening and for discharging the plasticized material; a discharge amount adjustment mechanism provided in a flow path through which the plasticized material flows and communicating with the nozzle opening and for controlling the amount of the plasticized material discharged from the nozzle opening by adjusting the opening of the flow path; and a control unit for controlling the plasticizing unit and the discharge amount adjustment mechanism, wherein the control unit is operable to stop discharging the plasticized material from the nozzle opening. and performing at least one of the following controls: a first control for changing the rotational speed of the screw in multiple stages during an extrusion stop period, which is a period before the extrusion of the plasticizing material from the nozzle opening is resumed after the extrusion of the plasticizing material from the nozzle opening is stopped; and a second control for changing the rotational speed of the screw in multiple stages during an extrusion restart period, which is a period until the opening of the flow path reaches the opening specified for the extrusion amount adjustment mechanism after the extrusion of the plasticizing material from the nozzle opening is resumed, and the control unit performs the second control by lowering and then increasing the rotational speed of the screw. According to this embodiment, by changing the rotation speed of the screw in multiple stages during the discharge stop period or the discharge restart period, the discharge amount of the plasticizing material can be stabilized at or immediately after discharge restart.

[0076] (2) In the above embodiment, the control unit may, in the first control, increase the rotation speed of the screw to a second rotation speed that is higher than the first rotation speed in the period before the discharge stop period, and then decrease the rotation speed to a third rotation speed that is lower than the first rotation speed. According to this embodiment, the discharge amount of the plasticizing material can be stabilized when discharge is resumed.

[0077] (3) In the above embodiment, the control unit may gradually decrease the rotation speed of the screw when decreasing the rotation speed of the screw from the second rotation speed to the third rotation speed in the first control. According to this embodiment, it is possible to shorten the time until the pressure in the flow passage upstream of the discharge amount adjustment mechanism becomes stable during the discharge stop period.

[0078] (4) In the above embodiment, the control unit may increase the rotation speed of the screw to a second rotation speed that is higher than the first rotation speed in the period before the discharge stop period, and then return the rotation speed to the first rotation speed in the first control. According to this embodiment, even if the discharge stop period is short, the pressure in the flow passage upstream of the discharge amount adjustment mechanism can be quickly increased to an appropriate pressure.

[0079] (5) In the above embodiment, a suction mechanism may be provided that has a branch flow path connected to the flow path and a plunger disposed in the branch flow path, and that can suck the plasticized material in the flow path into the branch flow path by changing the position of the plunger, and the control unit may control the rotation speed of the screw according to the position of the plunger in the branch flow path in the first control. With this embodiment, it is possible to prevent the pressure in the flow path upstream of the discharge amount adjustment mechanism from becoming a pressure that inhibits the operation of the plunger when discharge is resumed.

[0080] The present disclosure can be realized in various forms, including but not limited to the above-mentioned three-dimensional printing device, a three-dimensional printing system, a method for manufacturing a three-dimensional object, a computer program, and a non-transitory tangible recording medium on which a computer program is recorded in a computer-readable manner. [Explanation of symbols]

[0081] 10...3D modeling system, 20...material supply section, 22...connecting passage, 30...plasticizing section, 31...screw case, 32...driving motor, 40...screw, 42...groove section, 43...ridge section, 44...material inlet, 46...center section, 47...upper surface, 48...lower surface, 50...barrel, 52...upper surface, 54...guide groove, 56...connecting hole, 58...barrel heater, 60...discharge section, 61...nozzle, 62...nozzle opening, 65...flow path, 66...branching flow path, 67...plunger, 70...discharge amount adjustment mechanism, 74...first drive section, 7 5...suction mechanism, 76...second drive unit, 77...discharge control unit, 100...three-dimensional modeling apparatus, 110...head unit, 210...stage, 211...modeling surface, 212...stage heater, 230...movement mechanism, 300...control unit, 310...processor, 320...storage device, 400...information processing device, 410...CPU, 411...data generation unit, 420...memory, 430...storage device, 440...communication interface, 450...input / output interface, 460...bus, 470...input device, 480...display unit

Claims

1. a plasticizing section having a screw and a motor for rotating the screw, and for plasticizing a material to generate a plasticized material; a nozzle having a nozzle opening for discharging the plasticizing material; a discharge amount adjustment mechanism that is provided in a flow path through which the plasticizing material flows and that is in communication with the nozzle opening, and that controls the amount of the plasticizing material discharged from the nozzle opening by adjusting the opening of the flow path; A control unit that controls the plasticizing unit and the discharge amount adjusting mechanism, The control unit is A first control for changing the rotation speed of the screw in multiple stages during a discharge stop period, which is a period from when the discharge of the plasticizing material from the nozzle opening is stopped until when the discharge of the plasticizing material from the nozzle opening is resumed; and a second control for changing the rotation speed of the screw in multiple steps during a discharge restart period, which is a period until the opening of the flow path reaches an opening designated for the discharge amount adjustment mechanism after the discharge of the plasticizing material from the nozzle opening is restarted; Control at least one of the following: The control unit, in the second control, reduces and then increases the rotation speed of the screw. Three-dimensional printing equipment.

2. The three-dimensional modeling apparatus according to claim 1 , The control unit, in the first control, increases the rotational speed of the screw to a second rotational speed that is higher than a first rotational speed in a period before the discharge stop period, and then decreases the rotational speed to a third rotational speed that is lower than the first rotational speed.

3. The three-dimensional modeling apparatus according to claim 2, The control unit, in the first control, gradually decreases the rotation speed of the screw when decreasing the rotation speed of the screw from the second rotation speed to the third rotation speed.

4. The three-dimensional modeling apparatus according to claim 1 , The control unit, in the first control, increases the rotation speed of the screw to a second rotation speed that is higher than the first rotation speed in the period before the discharge stop period, and then returns the rotation speed to the first rotation speed.

5. The three-dimensional modeling apparatus according to claim 1 , a suction mechanism including a branch flow path connected to the flow path and a plunger disposed in the branch flow path, the suction mechanism being capable of sucking the plasticized material in the flow path into the branch flow path by changing the position of the plunger; The control unit, in the first control, controls a rotation speed of the screw depending on a position of the plunger in the branch flow channel.

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