Three-dimensional object printing device and three-dimensional object printing method

Abstract

To suppress vibration of a robot generated caused by the movement of a head.SOLUTION: A three-dimensional object printer includes: a head which discharges liquid to a printing region on a three-dimensional workpiece; and a robot which supports the head and changes relative position between the workpiece and the head and posture of the head. The three-dimensional object printer executes a first speed adjusting operation in which moving speed of the head is adjusted while the robot moves the position of the head from a printing preparation position toward a printing start position closer to the printing region than the printing preparation position and a printing operation in which the head starts discharge of liquid to the printing region at the printing start position and the robot changes the position and posture of the head while the head discharges the liquid. Posture change amount of the head per unit period during the execution of the first speed adjusting operation is smaller than posture change amount of the head per unit period during the execution of the printing operation.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a three-dimensional object printing device and a three-dimensional object printing method. [Background technology]

[0002] Conventionally, there are known three-dimensional printing devices that use an inkjet method to print on the surface of a three-dimensional workpiece. For example, Patent Document 1 discloses a three-dimensional printing device that has a head that ejects a liquid such as ink onto a printing area on the workpiece, and a robot that supports the head and changes the relative position between the workpiece and the head. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-050832 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the above-described conventional technology, vibrations occur in the robot as the head moves during printing, and the vibrations generated in the robot are transmitted to the head, which may result in a deterioration in print quality. [Means for solving the problem]

[0005] In order to solve the above problems, one aspect of the three-dimensional object printing device of the present invention is a three-dimensional object printing device having a head that ejects liquid onto a printing area on a three-dimensional workpiece, and a robot that supports the head and changes the relative position and attitude of the workpiece and the head, wherein the robot performs a first speed adjustment operation in which the head moves from a print preparation position toward a print start position that is closer to the printing area than the print preparation position, while adjusting the movement speed of the head, and a printing operation in which the head begins ejecting liquid onto the printing area at the print start position, and the robot changes the position and attitude of the head while ejecting liquid from the head, and the amount of change in attitude of the head per unit period during the first speed adjustment operation is smaller than the amount of change in attitude of the head per unit period during the execution of the printing operation.

[0006] In order to solve the above problems, one aspect of the three-dimensional object printing method of the present invention is a three-dimensional object printing method that uses a head that ejects liquid onto a printing area on a three-dimensional workpiece, and a robot that supports the head and changes the relative position and attitude of the workpiece and the head, and performs a first speed adjustment operation in which the robot adjusts the movement speed of the head while moving the position of the head from a print preparation position toward a print start position that is closer to the printing area than the print preparation position, and a printing operation in which the head begins ejecting liquid onto the printing area at the print start position, and while ejecting liquid from the head, the robot moves the head and changes the attitude of the head, and the amount of change in attitude of the head per unit period during the first speed adjustment operation is smaller than the amount of change in attitude of the head per unit period during the execution of the printing operation. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a perspective view showing an outline of a three-dimensional object printing apparatus 100 according to a first embodiment. [Figure 2] FIG. 1 is a block diagram showing the electrical configuration of a three-dimensional object printing device 100 according to a first embodiment. [Figure 3] FIG. 1 is a perspective view showing a schematic configuration of a liquid ejection unit 300 according to a first embodiment. [Figure 4] FIG. 2 is a flowchart showing the flow of a three-dimensional object printing method according to the first embodiment. [Figure 5] 1A to 1C are explanatory diagrams illustrating a series of operations during execution of a three-dimensional object printing method. [Figure 6] FIG. 10 is an explanatory diagram for explaining a movement path RU of the head 310 from the first speed adjustment operation to the printing operation. [Figure 7] FIG. 10 is an explanatory diagram for explaining a movement route RUa in a reference example. [Figure 8] 10A and 10B are explanatory diagrams for explaining the attitude of the head 310 from the first speed adjustment operation to the printing operation. [Figure 9] FIG. 10 is a diagram showing an output signal D1_5 with respect to elapsed time. [Figure 10] FIG. 4 is a diagram for explaining the intensity of vibration of a joint 230_1 in the first embodiment. [Figure 11] FIG. 10 is a diagram for explaining the vibration intensity of a joint 230_1 in a reference example. [Figure 12] FIG. 10 is a flowchart showing the flow of a three-dimensional object printing method according to a second embodiment. [Figure 13] FIG. 10 is an explanatory diagram illustrating a series of operations during execution of a three-dimensional object printing method according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and some parts are shown schematically to facilitate understanding. Furthermore, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description to the effect that the present invention is limited thereto.

[0009] The following description will use the mutually intersecting X-axis, Y-axis, and Z-axis as appropriate. Furthermore, one direction along the X-axis will be referred to as the X1 direction, and the direction opposite the X1 direction will be referred to as the X2 direction. Similarly, opposite directions along the Y-axis will be referred to as the Y1 direction and the Y2 direction. Furthermore, opposite directions along the Z-axis will be referred to as the Z1 direction and the Z2 direction.

[0010] Here, the X-axis, Y-axis, and Z-axis are coordinate axes of a base coordinate system set in the space in which the workpiece W and base 210 (described later) are installed. Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. Note that the Z-axis does not have to be a vertical axis. Furthermore, the X-axis, Y-axis, and Z-axis are typically perpendicular to each other, but are not limited to this and may not be perpendicular. For example, the X-axis, Y-axis, and Z-axis may intersect each other at an angle between 80° and 100°.

[0011] 1. First embodiment 1-1. Overview of the 3D printing device Fig. 1 is a perspective view showing an outline of a three-dimensional object printing apparatus 100 according to the first embodiment. The three-dimensional object printing apparatus 100 is an apparatus that performs printing by inkjet printing on a printing area WF, which is a part of the surface of a three-dimensional workpiece W. In Fig. 1, the printing area WF is a part of the surface of the workpiece W, but it may be the entire surface.

[0012] In the example shown in FIG. 1, the workpiece W is a rugby ball having an elongated spheroid shape about the major axis AX, and the printing area WF is a curved surface with a substantially constant curvature. However, the printing area WF may also be a curved surface with an inconstant curvature. In this embodiment, the workpiece W is positioned so that the major axis AX is parallel to the X axis. Note that the workpiece W is not limited to a rugby ball. For example, the workpiece W may be an object that will become a product, and printing in the printing area WF is one of a series of processes for manufacturing this product. The shape and size of the workpiece W are not limited to the example shown in FIG. 1 and are arbitrary. For example, the surface of the workpiece W may have a flat surface, a stepped surface, an uneven surface, or the like. Furthermore, the installation posture of the workpiece W is not limited to the example shown in FIG. 1 and is arbitrary.

[0013] In the example shown in Fig. 1, the three-dimensional object printing apparatus 100 is an inkjet printer that uses a vertical articulated robot. Specifically, as shown in Fig. 1, the three-dimensional object printing apparatus 100 has a robot 200, a liquid ejection unit 300, a liquid supply unit 400, a controller 600, and a maintenance unit 800. Below, we will first briefly explain each part of the three-dimensional object printing apparatus 100 shown in Fig. 1.

[0014] The robot 200 is a moving mechanism that changes the position and posture of the liquid discharge unit 300 relative to the workpiece W. In the example shown in Fig. 1, the robot 200 is a so-called six-axis vertical articulated robot. Specifically, the robot 200 has a base 210 and an arm 220.

[0015] The base 210 is a platform that supports the arm 220. In the example shown in Fig. 1, the base 210 is fixed by screws or the like to an installation surface BN, such as a floor surface, that faces the Z1 direction. The installation surface BN to which the base 210 is fixed may be a surface that faces any direction and is not limited to the example shown in Fig. 1, and may be, for example, a wall, a ceiling, a surface of a movable cart, or the like.

[0016] Arm 220 is a six-axis robot arm having a base end attached to base 210 and a tip end that changes position and posture three-dimensionally relative to the base end. Specifically, arm 220 has arm part 221, arm part 222, arm part 223, arm part 224, arm part 225, and arm part 226, which are connected in this order.

[0017] The arm part 221 is connected to the base part 210 via a joint 230_1 so as to be rotatable around a rotation axis O1. The arm part 222 is connected to the arm part 221 via a joint 230_2 so as to be rotatable around a rotation axis O2. The arm part 223 is connected to the arm part 222 via a joint 230_3 so as to be rotatable around a rotation axis O3. The arm part 224 is connected to the arm part 223 via a joint 230_4 so as to be rotatable around a rotation axis O4. The arm part 225 is connected to the arm part 224 via a joint 230_5 so as to be rotatable around a rotation axis O5. The arm part 226 is connected to the arm part 225 via a joint 230_6 so as to be rotatable around a rotation axis O6. Note that hereinafter, each of the joints 230_1 to 230_6 may be referred to as a joint 230.

[0018] Each of the joints 230_1 to 230_6 is a mechanism that rotatably connects one of two adjacent arm components with respect to the other. Although not shown in FIG. 1, each of the joints 230_1 to 230_6 is provided with a drive mechanism that rotates one of the two adjacent arm components with respect to the other. The drive mechanism includes, for example, a motor that generates a drive force for the rotation, a reducer that reduces and outputs the drive force, and an encoder such as a rotary encoder that detects the amount of movement, such as the angle of the rotation. The assembly of the drive mechanisms corresponds to an arm drive mechanism 240 shown in FIG. 2, which will be described later. The encoder corresponds to an encoder 241 shown in FIG. 2, etc., which will be described later.

[0019] The rotation axis O1 is an axis perpendicular to the installation surface BN to which the base 210 is fixed. The rotation axis O2 is an axis perpendicular to the rotation axis O1. The rotation axis O3 is an axis parallel to the rotation axis O2. The rotation axis O4 is an axis perpendicular to the rotation axis O3. The rotation axis O5 is an axis perpendicular to the rotation axis O4. The rotation axis O6 is an axis perpendicular to the rotation axis O5.

[0020] Regarding these rotation axes, "perpendicular" refers not only to the case where the angle between the two rotation axes is exactly 90 degrees, but also to the case where the angle between the two rotation axes is deviated from 90 degrees within a range of about ±5 degrees. Similarly, "parallel" refers not only to the case where the two rotation axes are strictly parallel, but also to the case where one of the two rotation axes is inclined relative to the other within a range of about ±5 degrees.

[0021] A liquid discharge unit 300 is attached as an end effector to the tip of the arm 220, that is, to the arm part 226, in a state fixed by screws or the like.

[0022] The liquid ejection unit 300 is a device having a head 310 that ejects ink, which is an example of a liquid, toward the workpiece W. In this embodiment, in addition to the head 310, the liquid ejection unit 300 also has a pressure adjustment valve 320 that adjusts the pressure of the ink supplied to the head 310, and a sensor 330 that measures the distance to the workpiece W. These are all fixed to the arm part 226, so the relative positions and orientations of these are fixed.

[0023] The ink is not particularly limited, and examples thereof include water-based inks in which a coloring material such as a dye or pigment is dissolved in a water-based solvent, curable inks using curable resins such as ultraviolet curable inks, and solvent-based inks in which a coloring material such as a dye or pigment is dissolved in an organic solvent. The ink is not limited to a solution, but may be an ink in which a coloring material or the like is dispersed as a dispersoid in a dispersion medium. The ink is also not limited to an ink containing a coloring material, but may be an ink containing conductive particles such as metal particles for forming wiring or the like as a dispersoid.

[0024] Although not shown in FIG. 1, the head 310 has a piezoelectric element, a cavity that contains ink, and a nozzle that communicates with the cavity. Here, a piezoelectric element is provided for each cavity, and ink is ejected from the nozzle corresponding to the cavity by changing the pressure in the cavity. Such a head 310 can be obtained, for example, by bonding together, with an adhesive, a plurality of substrates, such as silicon substrates, that have been appropriately processed by etching or the like. The piezoelectric element corresponds to the piezoelectric element 311 shown in FIG. 2, which will be described later. Instead of the piezoelectric element, a heater that heats the ink in the cavity may be used as a driving element for ejecting ink from the nozzle.

[0025] The pressure adjustment valve 320 is a valve mechanism that opens and closes in response to the pressure of the ink inside the head 310. This opening and closing maintains the ink pressure inside the head 310 at a negative pressure within a predetermined range. This stabilizes the ink meniscus formed in the nozzle N of the head 310. As a result, it is possible to prevent air bubbles from entering the nozzle N and ink from overflowing from the nozzle N.

[0026] The sensor 330 is an optical displacement sensor that measures the distance between the head 310 and the workpiece W. The sensor 330 may be provided as needed, or may be omitted. In the example shown in FIG. 1, the liquid discharge unit 300 has one head 310 and one pressure adjustment valve 320, but the numbers are not limited to those shown in FIG. 1 and may be two or more. In addition, the installation position of the pressure adjustment valve 320 is not limited to the arm part 226 and may be, for example, on another arm or the like, or may be in a fixed position relative to the base part 210.

[0027] The liquid supply unit 400 is a mechanism for supplying ink to the head 310. The liquid supply unit 400 has a liquid storage section 410 and a supply flow path 420.

[0028] Liquid storage section 410 is a container that stores ink. Liquid storage section 410 is, for example, a bag-shaped ink pack made of a flexible film.

[0029] 1, the liquid storage unit 410 is fixed to a wall, ceiling, pillar, or the like so that it is always located further in the Z1 direction than the head 310. In other words, the liquid storage unit 410 is located vertically above the movement area of the head 310. Therefore, ink can be supplied from the liquid storage unit 410 to the head 310 with a predetermined pressure without using a mechanism such as a pump.

[0030] The liquid storage unit 410 may be located vertically below the head 310 as long as it can supply ink from the liquid storage unit 410 to the head 310 at a predetermined pressure. In this case, for example, a pump may be used to supply ink from the liquid storage unit 410 to the head 310 at a predetermined pressure.

[0031] The supply flow path 420 is a flow path that supplies ink from the liquid storage section 410 to the head 310. A pressure adjustment valve 320 is provided midway along the supply flow path 420. Therefore, even if the positional relationship between the head 310 and the liquid storage section 410 changes, fluctuations in the ink pressure inside the head 310 can be reduced.

[0032] The supply flow path 420 is formed, for example, by the internal space of a tube. Here, the tube used for the supply flow path 420 is made of an elastic material such as a rubber material or an elastomer material, and is flexible. By forming the supply flow path 420 using a flexible tube in this way, changes in the relative positional relationship between the liquid storage section 410 and the pressure adjustment valve 320 are permitted. Therefore, even if the position or attitude of the head 310 changes while the position and attitude of the liquid storage section 410 remain fixed, ink can be supplied from the liquid storage section 410 to the pressure adjustment valve 320.

[0033] Note that a portion of the supply flow path 420 may be made of a non-flexible material. Also, a portion of the supply flow path 420 may have a distribution flow path that distributes ink to multiple locations, or may be formed integrally with the head 310 or the pressure adjustment valve 320.

[0034] The controller 600 is a robot controller that controls the driving of the robot 200. Although not shown in FIG. 1, the controller 600 is electrically connected to a control module that controls the discharge operation of the liquid discharge unit 300. A computer is communicably connected to the controller 600 and the control module. The control module corresponds to the control module 500 shown in FIG. 2, which will be described later. The computer corresponds to the computer 700 shown in FIG. 2, which will be described later.

[0035] The maintenance unit 800 is a mechanism for performing maintenance on the head 310 of the liquid ejection unit 300. In the example shown in FIG. 1, the maintenance unit 800 has a case 810, a cap unit 820, a support base 830, a suction mechanism 840, and a wiper unit 850. As shown in FIG. 1, the case 810 is fixed to the installation surface BN by screws or the like, similar to the base unit 210 of the robot 200. However, the case 810 may be fixed to a surface different from the installation surface BN to which the base unit 210 is fixed. Furthermore, maintenance is a concept that includes covering the nozzle surface F of the head 310 with the cap unit 820, suction by the suction mechanism 840, wiping by the wiper unit 850, and the like.

[0036] 1-2. Electrical configuration of the 3D printing device FIG. 2 is a block diagram showing the electrical configuration of the three-dimensional object printing device 100 according to the first embodiment. FIG. 2 shows electrical components among the components of the three-dimensional object printing device 100. FIG. 2 also shows an arm drive mechanism 240 including encoders 241_1 to 241_6. The arm drive mechanism 240 is an assembly of the drive mechanisms described above that operate the joints 230_1 to 230_6. Each of the encoders 241_1 to 241_6 is provided corresponding to each of the joints 230_1 to 230_6, and measures the movement amounts, such as the rotation angles, of the encoders 241_1 to 241_6. Note that hereinafter, each of the encoders 241_1 to 241_6 may be referred to as the encoder 241.

[0037] As shown in Figure 2, the three-dimensional object printing apparatus 100 includes the robot 200, liquid ejection unit 300, controller 600, and maintenance unit 800 described above, as well as a control module 500 and a computer 700. Note that each of the electrical components described below may be appropriately divided, some of which may be included in other components, or may be integrated with other components. For example, some or all of the functions of the control module 500 or controller 600 may be implemented by a computer 700 connected to the controller 600, or may be implemented by another external device such as a PC (personal computer) connected to the controller 600 via a network such as a LAN (local area network) or the Internet.

[0038] The controller 600 has a function to control the driving of the robot 200 and a function to generate a signal D3 for synchronizing the discharge operation of the head 310 with the operation of the robot 200. Note that the controller 600 of this embodiment also has a function to control the driving of the maintenance unit 800, but this function may be realized by another device such as a computer 700.

[0039] The controller 600 includes a memory circuit 610 and a processing circuit 620 .

[0040] The storage circuitry 610 stores various programs executed by the processing circuitry 620 and various data processed by the processing circuitry 620. The storage circuitry 610 includes, for example, one or both of semiconductor memories: a volatile memory such as a random access memory (RAM) and a non-volatile memory such as a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), or a programmable read-only memory (PROM). Note that part or all of the storage circuitry 610 may be included in the processing circuitry 620.

[0041] The memory circuit 610 stores path information Da. The path information Da is information indicating the path along which the head 310 should move. Specifically, the path information Da includes information indicating the path along which the tool center point, which indicates the origin of the aforementioned tool coordinate system, should move. The path information Da is expressed, for example, using coordinate values of a base coordinate system. The path information Da is determined based on work information indicating the position and shape of the workpiece W and information indicating the position and shape of the maintenance unit 800. The workpiece information is obtained by associating information such as CAD (computer-aided design) data indicating the three-dimensional shape of the workpiece W with the aforementioned base coordinate system. The above path information Da is input from the computer 700 to the memory circuit 610.

[0042] The processing circuit 620 controls the movements of the joints 230_1 to 230_6 based on the path information Da and generates a signal D3. Specifically, the processing circuit 620 performs inverse kinematics calculation, which is a calculation to convert the path information Da into movement quantities such as the rotation angle and rotation speed of each of the joints 230_1 to 230_6. The processing circuit 620 then outputs control signals Sk_1 to Sk_6 based on output signals D1_1 to D1_6 from encoders 241_1 to 241_6 included in the arm drive mechanism 240 of the robot 200, respectively, so that the movement quantities such as the actual rotation angle and rotation speed of each of the joints 230_1 to 230_6 become the calculation results described above. The control signals Sk_1 to Sk_6 correspond to the joints 230_1 to 230_6, respectively, and control the driving of the motors provided in the corresponding joints 230. The output signals D1_1 to D1_6 correspond to the encoders 241_1 to 241_6, respectively. Hereinafter, the output signals D1_1 to D1_6 may each be referred to as the output signal D1.

[0043] Furthermore, the processing circuit 620 generates a signal D3 based on an output signal D1 from at least one of the encoders 241_1 to 241_6. For example, the processing circuit 620 generates, as the signal D3, a trigger signal including a pulse at a timing when the output signal D1 from one of the encoders 241_1 to 241_6 reaches a predetermined value.

[0044] The processing circuit 620 includes, for example, one or more processors such as a CPU (Central Processing Unit). Note that the processing circuit 620 may include a programmable logic device such as an FPGA (Field-Programmable Gate Array) instead of or in addition to a CPU.

[0045] The control module 500 is a circuit that controls the ejection operation of the head 310 based on a signal D3 output from the controller 600 and print data Img from the computer 700. The control module 500 has a timing signal generation circuit 510, a power supply circuit 520, a control circuit 530, and a drive signal generation circuit 540.

[0046] The timing signal generating circuit 510 generates a timing signal PTS based on the signal D3. The timing signal generating circuit 510 is configured, for example, with a timer that starts generating the timing signal PTS when the signal D3 is detected.

[0047] The power supply circuit 520 receives power from a commercial power supply (not shown) and generates various predetermined potentials. The generated potentials are supplied appropriately to each section of the three-dimensional object printing device 100. For example, the power supply circuit 520 generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the liquid ejection unit 300. The power supply potential VHV is also supplied to the drive signal generation circuit 540.

[0048] The control circuit 530 generates a control signal SI, a waveform designation signal dCom, a latch signal LAT, a clock signal CLK, and a change signal CNG based on the timing signal PTS. These signals are synchronized with the timing signal PTS. Of these signals, the waveform designation signal dCom is input to a drive signal generation circuit 540, and the other signals are input to a switch circuit 340 of the liquid ejection unit 300.

[0049] The control signal SI is a digital signal for specifying the operating state of the piezoelectric element 311 of the head 310. Specifically, the control signal SI specifies whether or not to supply a drive signal Com, described below, to the piezoelectric element 311. This specification, for example, specifies whether or not to eject ink from the nozzle corresponding to the piezoelectric element 311, and specifies the amount of ink ejected from that nozzle. The waveform specification signal dCom is a digital signal for defining the waveform of the drive signal Com. The latch signal LAT and change signal CNG are used in conjunction with the control signal SI to specify the drive timing of the piezoelectric element 311, and thereby specify the timing of ink ejection from the nozzle. The clock signal CLK is a reference clock signal synchronized with the timing signal PTS. Of the above signals, the signals input to the switch circuit 340 of the liquid ejection unit 300 will be described in detail later.

[0050] The control circuit 530 includes, for example, one or more processors such as a CPU (Central Processing Unit). Note that the control circuit 530 may include a programmable logic device such as an FPGA (Field-Programmable Gate Array) instead of or in addition to a CPU.

[0051] The drive signal generation circuit 540 is a circuit that generates a drive signal Com for driving each piezoelectric element 311 of the head 310. Specifically, the drive signal generation circuit 540 includes, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generation circuit 540, the DA conversion circuit converts the waveform designation signal dCom from the control circuit 530 from a digital signal to an analog signal, and the amplifier circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 520 to generate the drive signal Com. Here, of the waveforms included in the drive signal Com, a signal with a waveform that is actually supplied to the piezoelectric element 311 is a drive pulse PD. The drive pulse PD is supplied from the drive signal generation circuit 540 to the piezoelectric element 311 via a switch circuit 340. The switch circuit 340 switches whether or not to supply at least a portion of the waveform included in the drive signal Com as the drive pulse PD based on a control signal SI.

[0052] The computer 700 has a function to supply information such as path information Da to the controller 600 and a function to supply information such as print data Img to the control module 500. The computer 700 of this embodiment is also electrically connected to the aforementioned sensor 330, and supplies information for correcting the path information Da to the controller 600 based on the signal D2 from the sensor 330. The computer 700 functions as a control unit for the three-dimensional object printing apparatus 100, and causes the robot 200 and liquid ejection unit 300 to execute the printing operation, which will be described later, and a series of operations that occur before and after the printing operation, via the controller 600 and the control module 500.

[0053] 1-3. Liquid Discharge Unit FIG. 3 is a perspective view showing a schematic configuration of a liquid ejection unit 300 in the first embodiment.

[0054] In the following explanation, the mutually intersecting a-axis, b-axis, and c-axis will be used as appropriate. Furthermore, one direction along the a-axis will be referred to as the a1 direction, and the direction opposite the a1 direction will be referred to as the a2 direction. Similarly, the opposite directions along the b-axis will be referred to as the b1 direction and the b2 direction. Furthermore, the opposite directions along the c-axis will be referred to as the c1 direction and the c2 direction.

[0055] Here, the a-axis, b-axis, and c-axis are coordinate axes of a tool coordinate system set in the liquid discharging unit 300, and the relative position and posture relationships with the X-axis, Y-axis, and Z-axis change depending on the operation of the robot 200. In the example shown in Fig. 3, the c-axis is an axis parallel to the rotation axis O6. Note that the a-axis, b-axis, and c-axis are typically perpendicular to each other, but are not limited to this, and may intersect at an angle within a range of 80° to 100°, for example.

[0056] As described above, the liquid ejection unit 300 has the head 310, the pressure adjustment valve 320, and the sensor 330. These are supported by a support 350 indicated by the two-dot chain line in FIG.

[0057] The support 350 is made of, for example, a metal material, and is substantially rigid. Although the support 350 is shown in Fig. 3 as having a flat box shape, the shape of the support 350 is not particularly limited and may be any shape.

[0058] The support 350 is attached to the tip of the arm 220, that is, to the arm part 226. Therefore, the head 310, the pressure regulation valve 320, and the sensor 330 are each fixed to the arm part 226.

[0059] 3, the pressure regulating valve 320 is positioned in the c1 direction relative to the head 310. The sensor 330 is positioned in the a2 direction relative to the head 310.

[0060] The supply flow path 420 is divided into an upstream flow path 421 and a downstream flow path 422 by the pressure adjustment valve 320. That is, the supply flow path 420 has an upstream flow path 421 that connects the liquid storage section 410 and the pressure adjustment valve 320, and a downstream flow path 422 that connects the pressure adjustment valve 320 and the head 310. In the example shown in FIG. 3, a part of the downstream flow path 422 of the supply flow path 420 is configured with a flow path member 422a. The flow path member 422a has a flow path that distributes ink from the pressure adjustment valve 320 to multiple locations in the head 310. The flow path member 422a is, for example, a laminate of multiple substrates made of a resin material, and each substrate is appropriately provided with grooves or holes for ink flow paths.

[0061] The head 310 has a nozzle surface F and a plurality of nozzles N opening in the nozzle surface F. In the example shown in FIG. 3, the normal direction of the nozzle surface F is the c2 direction, and the plurality of nozzles N are divided into a first nozzle row La and a second nozzle row Lb that are arranged at intervals in the direction along the a-axis. Each of the first nozzle row La and the second nozzle row Lb is a collection of a plurality of nozzles N that are linearly arranged in the direction along the b-axis. Here, the elements associated with each nozzle N of the first nozzle row La in the head 310 and the elements associated with each nozzle N of the second nozzle row Lb are configured to be approximately symmetrical to each other in the direction along the a-axis.

[0062] However, the positions of the multiple nozzles N in the first nozzle row La and the multiple nozzles N in the second nozzle row Lb in the direction along the b-axis may be the same or different. Also, elements related to each nozzle N in one of the first nozzle row La and the second nozzle row Lb may be omitted. Below, a configuration in which the positions of the multiple nozzles N in the first nozzle row La and the multiple nozzles N in the second nozzle row Lb in the direction along the b-axis are the same will be exemplified.

[0063] 1-4. Operation of the three-dimensional object printing device and three-dimensional object printing method Fig. 4 is a flowchart showing the flow of the three-dimensional object printing method according to the first embodiment. Fig. 5 is an explanatory diagram illustrating a series of operations performed during execution of the three-dimensional object printing method. The three-dimensional object printing method is performed using the three-dimensional object printing device 100 described above. Fig. 5 shows a graph gv1 showing the relationship between the time at which each operation in the series of operations performed during execution of the three-dimensional object printing method and the movement speed of the head 310, and a graph gd1 showing the relationship between the time at which each operation in the series of operations was performed and the movement distance of the head 310.

[0064] 4 and 5, the three-dimensional object printing apparatus 100 executes the three-dimensional object printing method in the following order as a series of operations during the three-dimensional object printing method: step S110 for performing a standby operation, step S120 for performing a first movement operation, step S130 for performing a print preparation operation, step S140 for performing a first speed adjustment operation, step S150 for performing a speed maintenance operation, step S160 for performing a printing operation, step S170 for performing a second speed adjustment operation, and step S180 for performing a second movement operation. The operations shown in FIGS. 4 and 5 are executed by the computer 700 controlling the robot 200 and the liquid discharge unit 300 via the controller 600 and the control module 500. The first movement operation is an example of "a movement operation in which the robot moves the head from the standby position toward the print preparation position."

[0065] The standby operation of step S110 is an operation of standby of the head 310. The standby position of the head 310 is typically a position where the nozzle surface F is covered by the cap portion 820. Hereinafter, the standby position of the head 310 is referred to as the "standby position," and the position where the nozzle surface F is covered by the cap portion 820 is referred to as the "cap position." By having the head 310 in the cap position, thickening or solidification of ink on the nozzle surface F can be reduced even if printing operations are not performed for an extended period of time. However, the standby position is not limited to the cap position and may be any position within the space in which the robot 200 is installed. As shown in graph gv1, the head 310 does not move from time t10 to time t11, and as shown in graph gd1, the head 310 is standby at the standby position.

[0066] The first movement operation in step S120 is an operation in which the robot 200 moves the head 310 from the standby position to the print preparation position PP, which is near the workpiece W, while changing the position of the head 310 relative to the workpiece W. Although not shown, the standby position is located farther from the print area WF than the print preparation position PP. However, the standby position may also be located closer to the print area WF than the print preparation position PP.

[0067] The three-dimensional object printing apparatus 100 executes the first movement operation, for example, when the control module 500 receives the signal D3 and the print data Img. In the first movement operation, the head 310 may be moved at any speed. To shorten the time required for the first movement operation, it is preferable to move the head 310 at its maximum speed Vmax. As shown in graph gv1, between time t11 and time t12, the robot 200 accelerates the head 310 to the maximum speed Vmax. When the movement speed of the head 310 reaches the maximum speed Vmax, the robot 200 maintains the movement speed of the head 310 at the maximum speed Vmax. When the head 310 approaches the print preparation position PP, the robot 200 decelerates the movement speed of the head 310 until it reaches speed V0. Speed V0 is the movement speed of the head 310 at the print preparation position PP, and is 0 meters per second.

[0068] The print preparation operation of step S130 is an operation that stops the relative movement of the head 310 with respect to the workpiece W for a certain period of time. The print preparation operation is performed to dampen the vibration of the head 310 generated by the first movement operation so that this vibration does not remain during the printing operation. The certain period is, for example, 0.5 seconds. However, the three-dimensional object printing apparatus 100 does not necessarily perform the print preparation operation. As shown in graph gv1, the head 310 does not move from time t12 to time t13, which is the execution period of the print preparation operation. As shown in graph gd1, the head 310 is stopped at the print preparation position PP. Note that in this embodiment, stopping refers not only to the head 310 being completely still, but also to the head 310 vibrating slightly with an amplitude of 500 micrometers or less. Such minute vibrations include residual vibrations generated by inertia associated with the movement operation as described above, as well as vibrations associated with control errors and mechanical errors.

[0069] The first speed adjustment operation in step S140 is an operation in which the robot 200 adjusts the movement speed of the head 310 while changing the position of the head 310 relative to the workpiece W. More specifically, the first speed adjustment operation adjusts the movement speed of the head 310 from speed V0 to printing speed VP. While it is preferable to also change the orientation of the head 310 in the first speed adjustment operation, the orientation of the head 310 does not necessarily have to be changed. The printing speed VP is the movement speed of the head 310 at the print start position PS and is a speed greater than speed V0. As shown in graph gv1, between time t13 and time t14, the robot 200 adjusts the movement speed of the head 310 from speed V0 to printing speed VP, and moves from the print preparation position PP to the speed maintenance start position PJ as shown in graph gd1. The robot 200 monotonically increases the movement speed of the head 310 from speed V0 to approach printing speed VP. In this specification, monotonous increase refers to monotonous increase in a broad sense. In the first embodiment, the speed V0 is an example of a "first speed," and the printing speed VP is an example of a "second speed."

[0070] The speed maintenance operation in step S150 is an operation in which the robot 200 changes the position of the head 310 relative to the workpiece W while maintaining the movement speed of the head 310 at the printing speed VP, thereby reducing vibrations caused by the acceleration of the head 310 during the first speed adjustment operation. However, the three-dimensional object printing apparatus 100 does not necessarily have to perform the speed maintenance operation. The orientation of the head 310 may not change during the speed maintenance operation, or the orientation of the head may change within a range equal to or less than that of the printing operation. As shown in graph gv1, the movement speed of the head 310 is maintained at the printing speed VP from time t14 to time t15, and as shown in graph gd1, the head 310 moves from the speed maintenance start position PJ to the printing start position PS.

[0071] The printing operation of step S160 is an operation in which the head 310 ejects ink while the robot 200 changes the position and posture of the head 310 relative to the workpiece W. The start of the printing operation refers to the head 310 starting to eject ink onto the workpiece W. The end of the printing operation refers to the head 310 stopping to eject ink onto the workpiece W. It is preferable that the head 310 does not eject ink during the execution of the first movement operation of step S120, the print preparation operation of step S130, the first speed adjustment operation of step S140, the speed maintenance operation of step S150, the second speed adjustment operation of step S170, and the second movement operation of step S180.

[0072] Of the multiple joints 230, the number of joints 230 that operate during the printing operation is not particularly limited. However, it is preferable that the head 310 be moved by operating a fewer number of joints 230 during the printing operation compared to other operations. Operating a fewer number of joints 230 than during other operations reduces deviation of the actual movement path of the head 310 from the ideal movement path. During the printing operation in this embodiment, the head 310 is moved by operating three of the six joints 230 of the robot 200. More specifically, in the first embodiment, during the printing operation, the robot 200 operates these joints 230 with the rotation axes of the joints 230_2, 230_3, and 230_5 parallel to the Y axis. In this manner, the rotation axes O2, O3, and O5 are set parallel to each other. However, this is not a limitation. For example, the rotation axes O2, O3, and O6 may be set parallel to each other.

[0073] As shown in graph gv1, from time t15 to time t16, the movement speed of head 310 is maintained at print speed VP, and as shown in graph gd1, head 310 moves from print start position PS to print end position PE. The movement path RU of head 310 from the first speed adjustment operation to the printing operation will be described using FIG. 6.

[0074] FIG. 6 is an explanatory diagram illustrating the movement path RU of the head 310 from the first speed adjustment operation to the printing operation. In FIG. 6, the liquid ejection unit 300 positioned at the print preparation position PP is indicated by a two-dot chain line, and the liquid ejection unit 300 positioned at the print start position PS and the print end position PE are indicated by solid lines. Furthermore, to avoid cluttering the drawing, the liquid ejection unit 300 positioned at the speed maintenance start position PJ is omitted, and only the rotation axis O6 when the liquid ejection unit 300 is positioned at the speed maintenance start position PJ is shown. The movement path RU includes a path RP from the print preparation position PP to the speed maintenance start position PJ, a path RJ from the speed maintenance start position PJ to the print start position PS, and a path RS from the print start position PS to the print end position PE. As shown in FIG. 6, the print start position PS is located at the edge of the print region WF and is therefore closer to the print region WF than the print preparation position PP.

[0075] During the printing operation, the robot 200 operates the joints 230_2, 230_3, and 230_5 so that the b-axis of the tool coordinate system set in the liquid ejection unit 300 and the Y-axis of the base coordinate system are kept parallel to each other. In other words, during the printing operation, the robot 200 keeps the first nozzle row La and the second nozzle row Lb parallel to the joints 230_2, 230_3, and 230_5. In other words, during the printing operation, the robot 200 does not operate the joints 230 whose rotation axes are not parallel to the Y-axis, that is, the joints 230_1, 230_4, and 230_6.

[0076] During the printing operation, the shortest distance WG between the head 310 and the workpiece W is maintained within a predetermined distance. The shortest distance WG between the head 310 and the workpiece W is also referred to as the "work gap." In this embodiment, the print area WF has a substantially constant curvature, and therefore the curvature of the path RS is also substantially constant. On the other hand, the paths RP and RJ are paths that do not follow the shape of the workpiece W and curve more gently than the path RS. The curvature of each of the paths RP and RJ is smaller than the curvature of the path RS. Note that the curvature is the reciprocal of the radius of a circle that approximates the degree of curvature at a certain point. The amount of change in posture of the head 310 per unit period during the first speed adjustment operation is smaller than the amount of change in posture of the head 310 per unit period during the printing operation. The orientation of the head 310 refers to the orientation of the head 310 around the b-axis when viewed along the b-axis. The orientation of the head 310 can also be expressed as the angle that the rotation axis O6 forms with respect to an imaginary line LV that is normal to the installation surface BN when viewed along the rotation axis O5. In FIG. 6, the orientation of the head 310 when the liquid ejection unit 300 is located at the print preparation position PP is shown as an angle θ. The orientation of the head 310 when the liquid ejection unit 300 is at the print start position PS is assumed to be 0 degrees, and the counterclockwise rotation direction of the rotation axis O6 with respect to the imaginary line LV is defined as the positive direction, and the clockwise rotation direction is defined as the negative direction. Regarding the amount of change in attitude of the head 310 per unit period, the unit period may be any length. The amount of change in attitude of the head 310 per unit period is the absolute value of the angle indicating the attitude of the head 310 at the start of the unit period minus the angle indicating the attitude of the head 310 at the end of the unit period, divided by the length of the unit period. In this division, the dividend is a value greater than or equal to 0, and the divisor is a positive value. Therefore, the amount of change in attitude of the head 310 is a value greater than or equal to 0. If the execution period of the first speed adjustment operation or the printing operation spans multiple unit periods, the amount of change in attitude of the head 310 per unit period is a representative value of the amount of change in attitude of the head 310 for each of the multiple unit periods. The representative value may be, for example, the average, maximum, or median. When the representative value is an average value, the amount of change in attitude of the head 310 per unit period is the average value of the amounts of change in attitude of the head 310 over multiple unit periods. For example, if the execution period of a printing operation spans two unit periods and the amount of change in attitude of the head 310 over the first unit period is 10 degrees / second and the amount of change in attitude of the head 310 over the second unit period is 20 degrees / second, then the amount of change in attitude of the head 310 over the unit period is (10+20) / 2=15 degrees / second. Furthermore, if the representative value is the maximum value, the amount of change in attitude of the head 310 per unit period is the maximum value of the amounts of change in attitude of the head 310 over multiple unit periods. For example, if the execution period of a printing operation spans two unit periods and the amount of change in attitude of the head 310 over the first unit period is 10 degrees / second and the amount of change in attitude of the head 310 over the second unit period is 20 degrees / second, then the amount of change in attitude of the head 310 over the unit period is Max(10,20)=20 degrees / second. Here, Max() is a function that outputs the value of the maximum argument among one or more arguments.

[0077] 6, the amount of change in attitude of the head 310 per unit period during the first speed adjustment operation is 5 degrees / second, and the amount of change in attitude of the head 310 per unit period during the printing operation is 10 degrees / second. Therefore, the amount of change in attitude of the head 310 per unit period during the first speed adjustment operation is smaller than the amount of change in attitude of the head 310 per unit period during the printing operation. Note that in the drawings, the unit of angle is expressed as "deg," and the unit of second is expressed as "sec."

[0078] Furthermore, in the first embodiment, the condition that the amount of change in attitude of the head 310 around the b-axis per unit movement amount in the first speed adjustment operation is smaller than the amount of change in attitude of the head 310 around the b-axis per unit movement amount in the printing operation is satisfied. The unit movement amount may be any length. The amount of change in attitude of the head 310 around the b-axis per unit movement amount is the absolute value of the angle indicating the attitude of the head 310 around the b-axis before the head 310 moved the unit movement amount, minus the angle indicating the attitude of the head 310 around the b-axis after the head 310 moved the unit movement amount, divided by the length of the unit movement amount. The b-axis is an example of the "arrangement direction of a plurality of nozzles."

[0079] 4 and 5. The second speed adjustment operation in step S170 is an operation in which, after the printing operation, the robot 200 decelerates the head 310 from the print end position PE while changing the position of the head 310 relative to the workpiece W. As shown in graph gv1, from time t16 to time t17, the movement speed of the head 310 is decelerated from the printing speed VP to a speed V0, which is 0 meters / second.

[0080] Furthermore, since the printing operation has already ended during the second speed adjustment operation, there is no problem even if the head 310 vibrates significantly after the second speed adjustment operation has ended. Therefore, the absolute value of the acceleration of the head 310 during the second speed adjustment operation may be greater than the absolute value of the acceleration of the head 310 during the first speed adjustment operation. In the example of Figure 6, the absolute value of the speed change ΔV2 during the minute period Δt2 during the second speed adjustment operation is greater than the absolute value of the speed change ΔV1 during the minute period Δt1 during the first speed adjustment operation. The minute periods Δt1 and Δt2 have approximately the same duration. The speed change ΔV1 for the minute period Δt1 is an example of "head acceleration in the first speed adjustment operation," and the speed change ΔV2 for the minute period Δt2 is an example of "head acceleration in the second speed adjustment operation."

[0081] The second movement operation in step S180 is an operation in which the robot 200 moves the head 310 to a standby position while changing the position of the head 310 relative to the workpiece W. In the second movement operation, the head 310 may be moved at any speed. To shorten the time required for the second movement operation, it is preferable to move the head 310 at its maximum speed Vmax. As shown in graph gv1, between time t17 and time t18, the robot 200 accelerates the head 310 to the maximum speed Vmax. When the movement speed of the head 310 reaches the maximum speed Vmax, the robot 200 maintains the movement speed of the head 310 at the maximum speed Vmax. When the head 310 approaches the standby position, the robot 200 decelerates the head 310 until the movement speed becomes zero. Furthermore, as shown in graph gd1, the head 310 reaches the standby position at time t18.

[0082] After the process of step S180 is completed, the head 310 moves to the standby position. For example, when the control module 500 receives the signal D3 and the print data Img, the three-dimensional object printing apparatus 100 executes the first movement operation again.

[0083] 1.5. Summary of the First Embodiment The three-dimensional object printing apparatus 100 includes a head 310 that ejects ink onto a printing area WF on a three-dimensional workpiece W, and a robot 200 that supports the head 310 and changes the relative position and orientation of the workpiece W and the head 310. The three-dimensional object printing apparatus 100 executes a first speed adjustment operation and a printing operation. The first speed adjustment operation adjusts the movement speed of the head 310 while moving the position of the head 310 from a print preparation position PP toward a print start position PS that is closer to the printing area WF than the print preparation position PP. The printing operation begins when the head 310 starts ejecting ink onto the printing area WF at the print start position PS, and the robot changes the position and orientation of the head 310 while ejecting ink from the head 310. The amount of change in orientation of the head 310 per unit period during the first speed adjustment operation is smaller than the amount of change in orientation of the head 310 per unit period during the printing operation. Changing the posture of the head 310 causes a large rotation in the joint 230, and the vibration generated in the joint 230 is propagated to the head 310 via the arm 220, causing the head 310 to vibrate. When the head 310 vibrates, a difference occurs between the ideal path of the head 310 and the actual path of the head 310, resulting in a deterioration in print quality. In particular, vibrations generated before the printing operation remain even during the printing operation, degrading print quality. Here, because the head 310 does not eject ink before the printing operation, changing the posture of the head 310 according to the shape of the workpiece W is not essential. In the first embodiment, the amount of posture change of the head 310 per unit period during the first speed adjustment operation is smaller than the amount of posture change of the head 310 per unit period during the printing operation. In other words, in the first speed adjustment operation performed before the printing operation, the head 310 moves along a path that is less curved than the path along the workpiece W. In the first speed adjustment operation, the head 310 moves along a path that is less curved than the path along the workpiece W, thereby reducing the amount of posture change of the head 310 per unit period, and therefore vibrations occurring in the joint 230 can be suppressed compared to the reference example. To explain in more detail how vibrations can be suppressed, the movement path RUa in the reference example will be described with reference to FIG. 7, the amount of posture change of the head 310 in the first embodiment and the first reference example will be described with reference to FIG. 8, and vibrations occurring in the joint 230_1 will be described with reference to FIGS. 9 and 10.

[0084] FIG. 7 is an explanatory diagram for explaining the movement path RUa in the reference example. The entire movement path RUa follows the shape of the workpiece W, which differs from the movement path RU, which is a path that partially follows the shape of the workpiece W. More specifically, the movement path RUa differs from the movement path RU in that it has a path RPa instead of the path RP and a path RJa instead of the path RJ. The path RPa is the path from the print preparation position PPa to the speed maintenance start position PJa. The path RJa is the path from the speed maintenance start position PJa to the print start position PS. Because the entire movement path RUa follows the shape of the workpiece W, the shortest distance WG between the print preparation position PPa and the workpiece W and the shortest distance WG between the speed maintenance start position PJa and the workpiece W are within a predetermined distance.

[0085] 7, as in Fig. 6, the liquid ejection unit 300 positioned at the print preparation position PPa is indicated by a two-dot chain line, and the liquid ejection unit 300 positioned at the print start position PS and the liquid ejection unit 300 positioned at the print end position PE are indicated by solid lines. Furthermore, to avoid complicating the drawing, the liquid ejection unit 300 positioned at the speed maintenance start position PJa is not shown, and only the rotation axis O6 when the liquid ejection unit 300 is positioned at the speed maintenance start position PJ is shown.

[0086] 7, in the reference example, the amount of change in attitude of the head 310 per unit period during the first speed adjustment operation is 10 degrees / second, and the amount of change in attitude of the head 310 per unit period during the printing operation is also 10 degrees / second. Therefore, in the reference example, the amount of change in attitude of the head 310 per unit period during the first speed adjustment operation is approximately the same as the amount of change in attitude of the head 310 per unit period during the printing operation.

[0087] FIG. 8 is an explanatory diagram illustrating the posture of the head 310 from the first speed adjustment operation to the printing operation. In the graph gk shown in FIG. 8, the horizontal axis represents the movement distance of the head 310 from the first speed adjustment operation to the printing operation, and the vertical axis represents the posture of the head 310. The graph gk illustrates a posture characteristic K1 that represents the posture characteristic of the head 310 in the first embodiment and a posture characteristic K2 that represents the posture characteristic of the head 310 in the reference example. In the first embodiment and the reference example, the posture of the head 310 at the print start position PS is 0 degrees. As shown by the posture characteristic K2, in the reference example, the slope of the posture characteristic K2 is constant from the first speed adjustment operation to the printing operation. On the other hand, as shown by the posture characteristic K1, the slope of the posture characteristic K1 is gentle during the first speed adjustment operation in which the head 310 accelerates. However, after the print start position PS, the posture of the head 310 follows the shape of the workpiece W, so the slope of the posture characteristic K1 is constant.

[0088] FIG. 9 illustrates the output signal D1_5 versus elapsed time. The output signal D1_5 represents the amount of rotation of the rotation axis O5. Graph gm in FIG. 9 illustrates pulse values of the output signal D1_5 at each time during a period including the time when the head 310 is positioned at the print start position PS. In graph gm, the time when the head 310 is positioned at the print start position PS is set to 0, and the unit of time, seconds, is expressed as [sec]. Graph gm illustrates a rotation amount characteristic M1 that represents the characteristics of the rotation amount of the rotation axis O5 in the first embodiment and a rotation amount characteristic M2 that represents the characteristics of the rotation amount of the rotation axis O5 in the reference example. In the reference example, as indicated by the rotation amount characteristic M2, the absolute value of the rotation amount of the rotation axis O5 over time is large before the printing operation, causing vibrations in the joint 230_5. In contrast, in the first embodiment, as indicated by the rotation amount characteristic M1, the change in the rotation amount of the rotation axis O5 over time is suppressed compared to the reference example. Since the change in the amount of rotation of the rotation axis O5 is suppressed, the vibration generated in the joint 230_5 is suppressed, and the vibration of the head 310 can be suppressed.

[0089] 9 shows the amount of rotation of the rotation axis O5, but the same applies to the rotation axis O2 and the rotation axis O3. That is, in the reference example, the absolute values of the amount of rotation of the rotation axis O2 and the rotation axis O3 over time are large, and therefore vibrations occur in the joints 230_2 and 230_3. On the other hand, in the first embodiment, changes in the amount of rotation of the rotation axis O2 and the rotation axis O3 over time are suppressed compared to the reference example.

[0090] FIG. 10 is a diagram illustrating the vibration intensity of the joint 230_1 in the first embodiment. FIG. 11 is a diagram illustrating the vibration intensity of the joint 230_1 in a reference example. FIG. 10 shows the output signal D1_1 of the encoder 241_1 during the printing operation in the first embodiment, and FIG. 11 shows the output signal D1_1 of the encoder 241_1 in the reference example. During the printing operation in the first embodiment and the printing operation in the reference example, the motor of the joint 230_1 does not operate and does not generate a driving force for rotating the arm part 221. However, vibrations generated in the joint 230 cause the arm part 221 to rotate very slightly around the rotation axis O1.

[0091] Graph ge1 shown in FIG. 10 shows the output signal D1_1 during execution of a printing operation. The horizontal axis of graph ge1 indicates the elapsed time from the start of the printing operation, and the vertical axis of graph ge1 indicates the pulse value indicated by encoder 241_1. Similarly, graph ge2 shown in FIG. 11 shows the output signal D1_1 during execution of a printing operation of the reference example. The horizontal axis of graph ge2 indicates the elapsed time from the start of the printing operation, and the vertical axis of graph ge2 indicates the pulse value indicated by output signal D1_1.

[0092] As shown in graphs ge1 and ge2, the vibrations occurring in the joint 230 cause the arm part 221 to rotate very slightly around the rotation axis O1, and the pulse value also fluctuates. A pulse value of 0 indicates that the arm part 221 is not rotating, and a large absolute value of the pulse value indicates that the arm part 221 has rotated relatively greatly. Therefore, it can be said that the amplitude of the vibration of the pulse value indicates the strength of the vibration occurring in the joint 230_1.

[0093] The maximum amplitude of the vibration of the pulse value in the graph ge1 is width w1, and the maximum amplitude of the vibration of the pulse value in the graph ge2 is width w2. Width w1 is narrower than width w2. Therefore, the first embodiment can suppress the vibration generated in the joint 230 more effectively than the reference example.

[0094] The first speed adjustment operation is an operation that adjusts the movement speed of head 310 from speed V0 at print preparation position PP to print speed VP at print start position PS while moving the position of head 310 from print preparation position PP toward print start position PS. During the period from time t13 to time t14 while the first speed adjustment operation is being performed, the movement speed of head 310 monotonically increases from speed V0 to approach print speed VP. The movement speed of the head 310 increases monotonically, so there is no repeated acceleration and deceleration. By not repeating acceleration and deceleration, vibration of the head 310 is suppressed, and print quality can be improved.

[0095] Furthermore, during the period between the first speed adjustment operation and the printing operation, the three-dimensional object printing device 100 executes a speed maintenance operation that moves the head 310 toward the print start position PS while maintaining the movement speed of the head 310 at the printing speed VP. By performing the speed maintenance operation, speed fluctuations immediately before ink is ejected can be suppressed, and the three-dimensional object printing apparatus 100 can improve print quality. In addition, from the viewpoint of suppressing deterioration of print quality due to vibration of the head 310, it is preferable that the amount of change in attitude of the head 310 per unit period during the speed maintenance operation is equal to or smaller than the amount of change in attitude of the head 310 per unit period during the printing operation.

[0096] The three-dimensional object printing device 100 executes, before the first speed adjustment operation, a standby operation in which the robot 200 positions the head 310 at a standby position farther from the printing area than the print standby position PP, and a movement operation in which the robot 200 moves the head 310 from the standby position toward the print standby position PP. When the workpiece W is set in a position where the three-dimensional object printing apparatus 100 can print, the head 310 is usually kept waiting in a standby position. By keeping the head 310 waiting in a standby position away from the workpiece W, it is possible to prevent the head 310 from interfering when the workpiece W is placed. Furthermore, since the standby position is the cap position, it is possible to prevent the nozzle N from drying out and solidifying.

[0097] Furthermore, the three-dimensional object printing apparatus 100 executes a print preparation operation in which the relative movement of the head 310 with respect to the workpiece W is stopped for a certain period at the print preparation position PP before the first speed adjustment operation. By stopping the movement of the head 310 for a certain period of time, it is possible to attenuate the vibrations caused by the first movement operation.

[0098] As described above, in the first speed adjustment operation, the movement speed of the head 310 monotonically increases from speed V0 to approach the printing speed VP. Because of the monotonous increase, the printing speed VP is greater than speed V0. In this way, in the first speed adjustment operation, the speed is accelerated from 0 meters / second, which is speed V0, so the printing operation can be started in a state where the vibrations that occurred before the first speed adjustment operation have been damped, thereby improving the print quality.

[0099] Furthermore, following the printing operation, the three-dimensional object printing device 100 executes a second speed adjustment operation in which the head 310 stops ejecting ink and changes the moving speed of the head 310. The absolute value of the acceleration of the head 310 in the second speed adjustment operation is greater than the absolute value of the acceleration of the head 310 in the first speed adjustment operation. In the first speed adjustment operation, the absolute value of the acceleration of the head 310 is reduced compared to the absolute value of the acceleration of the head 310 in the second speed adjustment operation, thereby suppressing vibration of the head 310 and improving print quality. On the other hand, in the second speed adjustment operation, the absolute value of the acceleration of the head 310 is increased compared to the absolute value of the acceleration of the head 310 in the first speed adjustment operation, thereby shortening the takt time required to manufacture products and improving product productivity.

[0100] Furthermore, the amount of change in attitude of the head 310 around the b axis per unit movement amount in the first speed adjustment operation is smaller than the amount of change in attitude of the head 310 around the b axis per unit movement amount in the printing operation. According to the first embodiment, the vibrations occurring in the joint 230 can be suppressed compared to a configuration in which the amount of change in posture of the head 310 around the b-axis per unit movement amount in the first speed adjustment operation is larger than the amount of change in posture of the head 310 around the b-axis per unit movement amount in the printing operation.

[0101] 2. Second embodiment The three-dimensional object printing method in the second embodiment differs from the first embodiment in that the print preparation operation and the second speed adjustment operation are not executed. The second embodiment will be described below.

[0102] FIG. 12 is a flowchart showing the flow of the three-dimensional object printing method according to the second embodiment. FIG. 13 is an explanatory diagram illustrating a series of operations performed during execution of the three-dimensional object printing method according to the second embodiment. FIG. 13 shows a graph gv2 showing the relationship between the time at which each operation in the series of operations performed during execution of the three-dimensional object printing method according to the second embodiment and the movement speed of the head 310, and a graph gd2 showing the relationship between the time at which each operation in the series of operations was performed and the movement distance of the head 310. The movement distance of the head 310 refers to the distance traveled by the head 310 from the time execution of the three-dimensional object printing method began.

[0103] As shown in Figures 12 and 13, the three-dimensional object printing device 100 according to the second embodiment performs, in the following order, a series of operations during execution of the three-dimensional object printing method according to the second embodiment: step S210 for performing a standby operation, step S220 for performing a first movement operation, step S230 for performing a first speed adjustment operation, step S240 for performing a speed maintenance operation, step S250 for performing a printing operation, and step S260 for performing a second movement operation.

[0104] The standby operation in step S210 is an operation for waiting the head 310 before the printing operation. The standby operation in step S210 is the same as the standby operation in step S110 in the first embodiment, and therefore a description thereof will be omitted. As shown by the graph gv2, the head 310 does not move from time t20 to time t21, and as shown by the graph gd2, the head 310 is kept waiting at the waiting position.

[0105] The first movement operation in step S220 is an operation in which, prior to the printing operation, the robot 200 moves the head 310 from the standby position to the print preparation position PP while changing the position of the head 310 relative to the workpiece W. However, the second embodiment differs from the first embodiment in that the head 310 passes through the print preparation position PP without stopping. In the second embodiment, the movement speed of the head 310 at the end of the first movement operation is faster than the print speed VP. While any speed faster than the print speed VP may be used at the end of the first movement operation, it is preferable that the movement speed of the head 310 at the end of the first movement operation be the maximum speed Vmax of the head 310 in order to shorten the period required for the first movement operation. As shown in graph gv2, the robot 200 accelerates the head 310 to the maximum speed Vmax between time t21 and time t22. Then, when the movement speed of the head 310 reaches the maximum speed Vmax, the robot 200 maintains the movement speed of the head 310 at the maximum speed Vmax until the head 310 passes the print preparation position PP.

[0106] The first speed adjustment operation in step S230 is an operation in which the robot 200 adjusts the movement speed of the head 310 while changing the relative position of the head 310 with respect to the workpiece W before the printing operation. More specifically, the first speed adjustment operation in step S230 adjusts the movement speed of the head 310 from the maximum speed Vmax to the printing speed VP. The printing speed VP is a speed lower than the maximum speed Vmax. As shown in graph gv2, between time t22 and time t23, the robot 200 adjusts the movement speed of the head 310 from the maximum speed Vmax to the printing speed VP, and moves from the print preparation position PP to the speed maintenance start position PJ as shown in graph gd2. The robot 200 monotonically decreases the movement speed of the head 310 from the maximum speed Vmax to approach the printing speed VP. In this specification, "monotonically decreasing" refers to a monotonically decreasing movement speed in a broad sense. In the second embodiment, the maximum speed Vmax is an example of a "first speed," and the printing speed VP is an example of a "second speed."

[0107] The speed maintenance operation of step S240 is an operation in which, before the printing operation, the robot 200 changes the position of the head 310 relative to the workpiece W while maintaining the movement speed of the head 310 at the printing speed VP, thereby reducing vibrations that occur when the head 310 decelerates in the first speed adjustment operation. As shown in graph gv2, from time t23 to time t24, the movement speed of the head 310 is maintained at the printing speed VP, and as shown in graph gd2, the head 310 moves from the speed maintenance start position PJ to the print start position PS.

[0108] The printing operation in step S250 is an operation in which the head 310 ejects ink while the robot 200 changes the position of the head 310 relative to the workpiece W. As shown in graph gv2, from time t24 to time t25, the movement speed of the head 310 is maintained at the printing speed VP, and as shown in graph gd2, the head 310 moves from the printing start position PS to the printing end position PE.

[0109] The second movement operation in step S260 is an operation in which the robot 200 moves the head 310 to a standby position while changing the position of the head 310 relative to the workpiece W. In the second movement operation, the head 310 may be moved at any speed. To shorten the period required for the second movement operation, it is preferable to move the head 310 at its maximum speed Vmax. As shown in graph gv2, between time t25 and time t26, the robot 200 accelerates the head 310 to the maximum speed Vmax. Then, when the movement speed of the head 310 reaches the maximum speed Vmax, the robot 200 maintains the movement speed of the head 310 at the maximum speed Vmax. When the head 310 approaches the standby position, the robot 200 decelerates the movement speed of the head 310 until the movement speed of the head 310 reaches speed V0.

[0110] After the process of step S260 is completed, the head 310 moves to the standby position. In the three-dimensional object-printing apparatus 100 of the second embodiment, for example, when the control module 500 receives the signal D3 and the print data Img, the three-dimensional object-printing apparatus 100 executes the first movement operation of step S220 again.

[0111] Here, the amount of change in posture of the head 310 per unit period during the first speed adjustment operation in step S230 is smaller than the amount of change in posture of the head 310 per unit period during the printing operation in step S250. Therefore, as in the first embodiment, vibrations occurring in the joint 230 can be suppressed, improving print quality.

[0112] 2.1. Summary of the Second Embodiment As described above, during the first speed adjustment operation in the second embodiment, from time t22 to time t23, the movement speed of the head 310 monotonically decreases from the maximum speed Vmax to approach the printing speed VP. The moving speed of the head 310 decreases monotonically, so there is no repeated acceleration and deceleration. By not repeating acceleration and deceleration, vibration of the head 310 can be suppressed, and print quality can be improved.

[0113] As described above, during the first speed adjustment operation in the second embodiment, the movement speed of the head 310 monotonically decreases from the maximum speed Vmax to approach the printing speed VP. Because of the monotonous decrease, the printing speed VP is lower than the maximum speed Vmax. In the first speed adjustment operation in the second embodiment, the average movement speed of the head 310 in the first speed adjustment operation is higher than in the first speed adjustment operation in the first embodiment. The reason for this is that in the second embodiment, the movement speed of the head 310 is decelerated from a speed higher than the printing speed VP, whereas in the first embodiment, the movement speed of the head 310 in the first speed adjustment operation is accelerated from a speed V0 lower than the printing speed VP. Therefore, in the second embodiment, the average movement speed of the head 310 in the first speed adjustment operation is higher than in the first embodiment, and therefore the three-dimensional object printing apparatus 100 in the second embodiment can shorten the period required for the first speed adjustment operation. Furthermore, in the first movement operation in the second embodiment, the average movement speed of the head 310 in the first movement operation is higher than in the first movement operation in the first embodiment. The reason for this is that in the second embodiment, the movement speed of the head 310 at the end of the first movement operation is maximum speed Vmax, while the movement speed of the head 310 at the end of the first movement operation is speed V0. Therefore, in the second embodiment, the average movement speed of the head 310 in the first movement operation is higher than in the first embodiment, and therefore the three-dimensional object printing apparatus 100 in the second embodiment can shorten the period required for the first movement operation. As a result, in the second embodiment, the period required for the first movement operation and the first speed adjustment operation is shortened compared to the first embodiment, thereby reducing the takt time required for manufacturing products and improving product productivity. On the other hand, in the first embodiment, the first speed adjustment operation accelerates from a speed V0 of 0 meters / second, so the printing operation can be started in a state where the vibrations that occurred before the first speed adjustment operation have been damped, thereby improving the printing quality compared to the second embodiment.

[0114] 3. Variations The above-described embodiments can be modified in various ways. Specific modifications are exemplified below. Two or more embodiments selected from the following examples can be combined as long as they are not mutually contradictory.

[0115] 3-1. First modified example In the first speed adjustment operation of the first embodiment, the movement speed of the head 310 is described as monotonically increasing from speed V0 to print speed VP, but it may not monotonically increase, but may alternately increase and decrease as it approaches print speed VP from speed V0. Similarly, in the first speed adjustment operation of the second embodiment, the movement speed of the head 310 is described as monotonically decreasing from maximum speed Vmax to print speed VP, but it may not monotonically decrease, but may alternately increase and decrease as it approaches print speed VP from maximum speed Vmax.

[0116] 3-2. Second modified example In the first and second embodiments, if the standby position and the print start position PS are close to each other, the three-dimensional object printing apparatus 100 does not need to perform the first movement operation. If the first movement operation is not performed, the three-dimensional object printing apparatus 100 considers the standby position to be the print preparation position PP, and adjusts the movement speed of the head 310 while moving the position of the head 310 from the standby position toward the print start position PS.

[0117] 3-3.Third Modification As described in the first embodiment, the print preparation operation does not have to be performed. Furthermore, if the print preparation operation is not performed, the movement speed of the head 310 at the end of the first movement operation and the start of the first speed adjustment operation is not limited to speed V0, but may be a speed greater than speed V0 and equal to or less than printing speed VP. In the second modified example, a speed greater than speed V0 and equal to or less than printing speed VP is an example of the "first speed."

[0118] 3-4.Fourth variant In the second embodiment, the maximum speed Vmax is described as an example of the "first speed," but this is not limiting. For example, the "first speed" may be a speed that is greater than the printing speed VP but less than the maximum speed Vmax.

[0119] 3-5. Fifth Modification In the second embodiment, the three-dimensional object printing apparatus 100 does not execute the second speed adjustment operation, but the second speed adjustment operation may be executed between the printing operation and the second movement operation. In the fifth modification, too, it is preferable that the absolute value of the acceleration of the head 310 during the second speed adjustment operation is larger than the absolute value of the acceleration of the head 310 during the first speed adjustment operation.

[0120] 3-6. Sixth Modification In the above-described embodiment, a configuration in which screws or the like are used as a method for fixing head 310 to the tip of arm 220 is exemplified, but the present invention is not limited to this configuration. For example, head 310 may be fixed to the tip of arm 220 by gripping head 310 with a gripping mechanism such as a hand attached to the tip of arm 220.

[0121] 3-7. Seventh Variation In the above-described embodiment, a configuration in which printing is performed using one type of ink is exemplified, but the present invention is not limited to this configuration and can also be applied to a configuration in which printing is performed using two or more types of ink.

[0122] 3-8. Eighth Variation The uses of the three-dimensional printing device of the present invention are not limited to printing. For example, a three-dimensional printing device that ejects a solution of color material is used as a manufacturing device for forming color filters for liquid crystal display devices. Also, a three-dimensional printing device that ejects a solution of conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board. Furthermore, a three-dimensional printing device can also be used as a jet dispenser that applies liquid such as adhesive to a workpiece. [Explanation of symbols]

[0123] 100... Three-dimensional object printing device, 200... Robot, 210... Base, 220... Arm, 221, 222, 223, 224, 225, 226... Arm parts, 230, 230_1, 230_2, 230_3, 230_4, 230_5, 230_6... Joints, 240... Arm drive mechanism, 241, 241_1... Encoder, 300... Liquid ejection unit, 310... Head, 311... Piezoelectric element, 320... Pressure adjustment valve, 330... Sensor, 340... Switch circuit, 350... Support, 400... Liquid supply unit , 410...liquid storage portion, 420...supply flow path, 421...upstream flow path, 422...downstream flow path, 422a...flow path member, 500...control module, 510...timing signal generation circuit, 520...power supply circuit, 530...control circuit, 540...drive signal generation circuit, 600...controller, 610...memory circuit, 620...processing circuit, 700...computer, 800...maintenance unit, 810...case, 820...cap portion, 830...support base, 840...suction mechanism, 850...wiper portion, AX...long axis, BN... Installation surface, CLK...clock signal, CNG...change signal, Com...drive signal, D1, D1_1, D1_5...output signal, D2, D3...signal, Da...path information, F...nozzle surface, Img...print data, K1, K2...posture characteristics, LAT...latch signal, La...first nozzle row, Lb...second nozzle row, M1, M2...rotation amount characteristics, N...nozzle, O1, O2, O3, O4, O5, O6...rotation axis, PA...print area, PD...drive pulse, PE...print end position, PJ, PJa...speed maintenance start position, PP, PPa... Print preparation position, PS...print start position, PTS...timing signal, RD, RDa, RP, RPa, RS...path, RU, RUa...movement path, SI, Sk_1...control signal, V0...speed, VBS...offset potential, VHV...power supply potential, VP...print speed, Vmax...maximum speed, W...work, WF...print area, WG...shortest distance, dCom...waveform specification signal, gd1, gd2, ge1, ge2, gk, gm1, gv1, gv2...graph, ΔV1, ΔV2...speed change, Δt1, Δt2...short period, θ...angle.

Claims

1. A head that ejects liquid onto a printing area on a three-dimensional workpiece, the head having a plurality of nozzles; The head is supported, and the relative position and posture of the workpiece and the head are changed. a robot having a plurality of joints; A three-dimensional object printing device having: The robot moves the head from the print ready position to the print ready position. a first step of adjusting the moving speed of the head while moving the head toward a print start position close to the area; Speed adjustment operation, At the print start position, the head starts discharging liquid to the print area, While discharging the liquid from the head, the robot changes the position and posture of the head. Printing operation and Run an amount of change in the attitude of the head per unit period during the execution of the first speed adjustment operation, The amount of change in the attitude of the head per unit period during the execution of the printing operation is smaller than the amount of change in the attitude of the head per unit period. Ku, The first speed adjustment operation is performed when the head does not eject liquid and the nozzle surface of the head is While facing the workpiece, the head and the front The robot moves the head so that the distance between the head and the workpiece becomes small, The distance between the head and the printing area in the printing operation is adjusted by the first speed adjusting movement. When the head is positioned at the print preparation position, shorter than the distance between A three-dimensional object printing device characterized by the above.

2. The first speed adjusting operation is While moving the position of the head from the print preparation position toward the print start position, The moving speed of the head is changed from a first speed, which is the speed at the print preparation position, to a second speed, which is the speed at the print start position. the second speed, which is the speed at the position, During the period in which the first speed adjustment operation is being performed, the moving speed of the head is monotonically increasing or decreasing from the first speed to the second speed; The three-dimensional object printing device according to claim 1 .

3. During the period between the first speed adjustment operation and the printing operation, the moving speed of the head is While maintaining the second speed, the head is moved toward the print start position. Performing a holding action, 3. The three-dimensional object printing device according to claim 2.

4. The robot sets the position of the head to a waiting position farther from the printing area than the print preparation position. a standby operation of waiting at the machine position; The robot moves the head from the standby position toward the print preparation position. Movement and is performed before the first speed adjustment operation. The three-dimensional object printing device according to any one of claims 1 to 3.

5. The robot sets the position of the head to a waiting position farther from the printing area than the print preparation position. a standby operation of waiting at the machine position; The robot moves the head from the standby position toward the print preparation position. Movement and The moving operation is performed between the moving operation and the first speed adjusting operation, and the moving operation is performed before the printing preparation position. a print preparation operation for stopping the relative movement of the head with respect to the work for a certain period of time; death, During the period in which the first speed adjustment operation is being performed, the moving speed of the head is monotonically increasing from the first speed to the second speed; 4. The three-dimensional object printing device according to claim 2 or 3.

6. At the print preparation position, the head is moved relative to the workpiece for a certain period of time. a print preparation operation to stop the printing is performed before the first speed adjustment operation; The three-dimensional object printing device according to any one of claims 1 to 4.

7. The first speed adjusting operation is While moving the position of the head from the print preparation position toward the print start position, The moving speed of the head is changed from a first speed, which is the speed at the print preparation position, to a second speed, which is the speed at the print start position. the second speed, which is the speed at the position, The second speed is greater than the first speed. The three-dimensional object printing device according to any one of claims 1 to 6.

8. The first speed adjusting operation is While moving the position of the head from the print preparation position toward the print start position, The moving speed of the head is changed from a first speed, which is the speed at the print preparation position, to a second speed, which is the speed at the print start position. the second speed, which is the speed at the position, The second speed is less than the first speed.

5. The three-dimensional object printing device according to claim 1, wherein the printing head is a laser beam.

9. The head stops discharging the liquid, and a second speed adjusting operation is performed to change the moving speed of the head. the operation is performed following the printing operation, The absolute value of the acceleration of the head in the second speed adjustment operation is is greater than the absolute value of the acceleration of the head at The three-dimensional object printing device according to any one of claims 1 to 8.

10. a unit movement amount around the arrangement direction of the plurality of nozzles in the first speed adjustment operation; The amount of change in the posture of the head is the amount of change in the arrangement direction per unit movement amount in the printing operation. is smaller than the amount of change in the posture of the head in the forward direction, The three-dimensional object printing device according to any one of claims 1 to 9.

11. A head that ejects liquid onto a printing area on a three-dimensional workpiece, the head having a plurality of nozzles; The head is supported, and the relative position and posture of the workpiece and the head are changed. a robot having a plurality of joints; A three-dimensional object printing method using The robot moves the head from the print ready position to the print ready position. a first step of adjusting the moving speed of the head while moving the head toward a print start position close to the area; Speed adjustment operation, At the print start position, the head starts discharging liquid to the print area, The robot moves the head while discharging the liquid from the head, and A printing operation that changes the position of the paper. Run an amount of change in the attitude of the head per unit period during the execution of the first speed adjustment operation, The amount of change in the attitude of the head per unit period during the execution of the printing operation is smaller than the amount of change in the attitude of the head per unit period. Ku, The first speed adjustment operation is performed when the head does not eject liquid and the nozzle surface of the head is While facing the workpiece, the head and the front The robot moves the head so that the distance between the head and the workpiece becomes small, The distance between the head and the printing area in the printing operation is adjusted by the first speed adjusting movement. When the head is positioned at the print preparation position, shorter than the distance between A three-dimensional object printing method.

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