Three-dimensional object printing device and control method

Abstract

To improve printing quality.SOLUTION: A three-dimensional object printing device acquires first scanning information related to a first actual printing trajectory being a trajectory actually scanned by a liquid discharge head when a multi-joint robot is operated on the basis of target path information related to a target printing trajectory, acquires a first movement amount in a sub-scanning direction intersecting with a main scanning direction of the liquid discharge head on the basis of the first scanning information, acquires a first error amount in the sub-scanning direction of the first actual printing trajectory with respect to the target printing trajectory on the basis of the target printing trajectory and the first movement amount, specifies a correction range being a range to be corrected with respect to the target printing trajectory, and corrects the target printing trajectory on the basis of the first error amount in the correction range.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] There are known three-dimensional printing devices that use an inkjet printing method to print on the surface of a three-dimensional workpiece. For example, the device described in Patent Document 1 has a robot arm and a print head fixed to the tip of the robot arm, and prints an image on the target object using ink from the print 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] The device described in Patent Document 1 has a problem in that a movement error of the robot arm causes a deviation in the sub-scanning direction that intersects with the main scanning direction of the print head, resulting in a deterioration in print quality. [Means for solving the problem]

[0005] One aspect of the three-dimensional object printing device disclosed herein comprises a liquid ejection head that ejects liquid toward a workpiece, a multi-joint robot having a tip that supports the liquid ejection head and scans the liquid ejection head relative to the workpiece, and a control unit that controls the operation of the liquid ejection head and the multi-joint robot, wherein the control unit acquires first scanning information regarding a first actual printing trajectory, which is the trajectory that the liquid ejection head actually scans when the multi-joint robot is operated based on target path information regarding the target printing trajectory, acquires a first movement amount in a sub-scanning direction that intersects the main scanning direction of the liquid ejection head based on the first scanning information, acquires a first error amount in the sub-scanning direction of the first actual printing trajectory relative to the target printing trajectory based on the target printing trajectory and the first movement amount, identifies a correction range that is the range that is subject to correction for the target printing trajectory, and corrects the target printing trajectory based on the first error amount in the correction range.

[0006] One aspect of the control method disclosed herein is a control method for a three-dimensional object printing device that includes a liquid ejection head that ejects liquid toward a workpiece, and a multi-joint robot that has a tip that supports the liquid ejection head and scans the liquid ejection head relative to the workpiece, and includes the steps of: acquiring first scanning information regarding a first actual printing trajectory, which is the trajectory that the liquid ejection head actually scans when the multi-joint robot is operated based on target path information regarding the target printing trajectory; acquiring a first movement amount in a sub-scanning direction that intersects the main scanning direction of the liquid ejection head based on the first scanning information; acquiring a first error amount in the sub-scanning direction of the first actual printing trajectory relative to the target printing trajectory based on the target printing trajectory and the first movement amount; identifying a correction range that is the range that is subject to correction for the target printing trajectory; and correcting the target printing trajectory based on the first error amount in the correction range. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a perspective view showing an outline of a three-dimensional object printing device according to a first embodiment. FIG. [Figure 2]FIG. 1 is a block diagram showing the electrical configuration of a three-dimensional object printing device according to a first embodiment. [Figure 3] FIG. 2 is a perspective view showing a schematic configuration of a head unit according to the first embodiment. [Figure 4] FIG. 10 is a diagram illustrating an example of the operation of the three-dimensional object printing device. [Figure 5] 4 is a flowchart showing a control method according to the first embodiment. [Figure 6] 5 is a flowchart showing the flow of correction processing in the first embodiment. [Figure 7] FIG. 4 is a diagram for explaining acquisition of first scanning information in the first embodiment. [Figure 8] FIG. 4 is a diagram illustrating an example of a first error amount. [Figure 9] 10A and 10B are diagrams illustrating an example of a correction amount for correcting meandering of a long-period component of a first actual printing trajectory. [Figure 10] FIG. 4 is a diagram illustrating an example of a first error amount. [Figure 11] FIG. 10 is a diagram for explaining actual measurement points and interpolation points of a first actual printing trajectory. [Figure 12] FIG. 12 is an enlarged view of a part of FIG. [Figure 13] 5A and 5B are diagrams for explaining a first error amount and a correction range in the first embodiment. [Figure 14] 14 is a diagram for explaining a correction amount based on a first error amount shown in FIG. 13. FIG. [Figure 15] 15 is a diagram for explaining a second error amount, which is an error amount after application of the correction amount shown in FIG. 14. FIG. [Figure 16] 16 is a diagram for explaining a correction amount based on a second error amount shown in FIG. 15. FIG. [Figure 17] 17 is a diagram for explaining a second error amount after the correction amount shown in FIG. 16 is applied. FIG. [Figure 18] 18 is a diagram for explaining a correction amount based on a second error amount shown in FIG. 17. FIG. [Figure 19] 19 is a diagram for explaining a second error amount after the correction amount shown in FIG. 18 is applied. FIG. [Figure 20]10 is a flowchart showing the flow of correction processing in the second embodiment. [Figure 21] 10 is a diagram for explaining a first error amount and a correction range in the second embodiment. FIG. [Figure 22] 22 is a diagram for explaining a correction amount based on a first error amount shown in FIG. 21. FIG. [Figure 23] 23 is a diagram for explaining a second error amount, which is an error amount after application of the correction amount shown in FIG. 22. FIG. [Figure 24] 24 is a diagram for explaining a correction amount based on a second error amount shown in FIG. 23. FIG. [Figure 25] 25 is a diagram for explaining a second error amount after the correction amount shown in FIG. 24 is applied. FIG. [Figure 26] 10 is a flowchart showing the flow of correction processing in the third embodiment. [Figure 27] FIG. 11 is a diagram for explaining a second error amount in the third embodiment. [Figure 28] 28 is a diagram for explaining a correction amount based on a second error amount shown in FIG. 27. FIG. [Figure 29] 29 is a diagram for explaining a second error amount after the correction amount shown in FIG. 28 is applied. FIG. [Figure 30] FIG. 10 is a block diagram showing the electrical configuration of a three-dimensional object printing device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present disclosure 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 are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0009] For ease of explanation, the following description will use the mutually intersecting X-axis, Y-axis, and Z-axis as appropriate. Also, hereinafter, one direction along the X-axis is the X1 direction, and the direction opposite the X1 direction is the X2 direction. Similarly, the opposite directions along the Y-axis are the Y1 direction and the Y2 direction. Also, the opposite directions along the Z-axis are the Z1 direction and the Z2 direction.

[0010] Here, the X-axis, Y-axis, and Z-axis correspond to the coordinate axes of a world coordinate system set in a space in which the robot 2 (described later) is installed. Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward vertical direction. A base coordinate system based on the position of a base 210 (described later) of the robot 2 is associated with the world coordinate system by calibration. For convenience, the following describes an example in which the operation of the robot 2 is controlled using the world coordinate system as the robot coordinate system.

[0011] The Z axis does not have to be a vertical axis. Furthermore, the X axis, Y axis, and Z axis are typically perpendicular to one another, but this is not a limitation and they 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°.

[0012] 1-1. Overview of the 3D printing device 1 is a perspective view showing an outline of a three-dimensional object printing apparatus 1 according to the first embodiment. The three-dimensional object printing apparatus 1 is an apparatus that performs printing on the surface of a three-dimensional workpiece W by an inkjet method.

[0013] The workpiece W has a surface WF to be printed. In the example shown in FIG. 1, the surface WF is a convex curved surface that protrudes in the Z1 direction so as to be parallel to the Y axis. The curvature of the surface WF may vary depending on the position along the X axis, or may be constant over the entire area along the X axis. The printing target may be a surface other than the surface WF among the multiple surfaces of the workpiece W. Furthermore, the size, shape, or installation orientation of the workpiece W is not limited to the example shown in FIG. 1 and may be arbitrary. For example, the surface WF may have a shape that follows a spherical surface.

[0014] As shown in Fig. 1, the three-dimensional object printing device 1 has a robot 2, which is an example of an "articulated robot," a head unit 3, a controller 5, and a camera 9. Below, these will first be briefly described in order based on Fig. 1.

[0015] The robot 2 is an articulated robot that moves the workpiece W relative to the head unit 3. In the example shown in Fig. 1, the robot 2 is a so-called six-axis vertical articulated robot.

[0016] The robot 2 has a tip E that supports a liquid ejection head 3a (described later), and causes the liquid ejection head 3a to scan the workpiece W. More specifically, as shown in FIG.

[0017] Base 210 is a platform that supports arm 220. In the example shown in Fig. 1, base 210 is fixed by screws or the like to an installation surface such as a floor surface or a base facing in the Z1 direction. The installation surface to which base 210 is fixed may be a surface facing 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.

[0018] Arm 220 is a six-axis robot arm having a base end attached to base 210 and a tip E that changes its position and posture three-dimensionally relative to the base end. Specifically, arm 220 has arms 221, 222, 223, 224, 225, and 226, which are also called links, and these are connected in this order.

[0019] Arm 221 is connected to base 210 via joint J1 so as to be rotatable around rotation axis O1. Arm 222 is connected to arm 221 via joint J2 so as to be rotatable around rotation axis O2. Arm 223 is connected to arm 222 via joint J3 so as to be rotatable around rotation axis O3. Arm 224 is connected to arm 223 via joint J4 so as to be rotatable around rotation axis O4. Arm 225 is connected to arm 224 via joint J5 so as to be rotatable around rotation axis O5. Arm 226 is connected to arm 225 via joint J6 so as to be rotatable around rotation axis O6.

[0020] Each of the joints J1 to J6 is a mechanism that rotatably connects one of two adjacent members among the base 210 and the arms 221 to 226 to the other. Note that, hereinafter, each of the joints J1 to J6 may be referred to as a "joint J."

[0021] Although not shown in Fig. 1, each of the joints J1 to J6 is provided with a drive mechanism that rotates one of the two corresponding adjacent members relative 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 for the joints J1 to J6 corresponds to an arm drive mechanism 2a shown in Fig. 2, which will be described later.

[0022] A head unit 3 is attached as an end effector to the arm 226, which is the tip E of the robot 2. Here, the head unit 3 is fixed to the arm 226 by screws or the like.

[0023] The head unit 3 is an assembly having a liquid ejection head 3a that ejects ink, which is an example of a "liquid," toward the workpiece W, and has a first nozzle row NL1 and a second nozzle row NL2.

[0024] The ink is not particularly limited, but may be, for example, an ultraviolet curable ink. Note that the ink is not limited to ink containing a coloring material, and may be, for example, ink containing conductive particles such as metal particles as dispersoids for forming wiring, or may be clear ink, or may be a treatment liquid for surface treatment of the workpiece W.

[0025] The camera 9 is a sensor that measures the coordinate system of the ink ejected onto the surface WF of the workpiece W. For example, the camera 9 measures the coordinates of the ink on the printing surface, with the surface WF of the workpiece W being a two-dimensional plane. The camera 9 is supported by a support (not shown) and captures an image of the workpiece W. The camera 9 is, for example, a vision sensor.

[0026] The camera 9 may be a three-dimensional camera that measures the three-dimensional shape of a target three-dimensional object.

[0027] Here, the camera 9 may be a sensor such as a passive sensor or an active sensor based on the principle of triangulation, or may be a sensor such as a focus-based sensor or a time-of-flight (TOF) sensor based on the principle of coaxial surveying.

[0028] Here, a three-axis image capture coordinate system is set for the camera 9. This image capture coordinate system is associated with a world coordinate system by calibration. Then, the camera 9 generates shape data that indicates the three-dimensional shape of the target object in this image capture coordinate system.

[0029] The camera 9 may be installed in any manner as long as it can capture an image of the workpiece W, and may be supported by, for example, the robot 2, or by a moving mechanism such as an articulated robot or a conveyor that is different from the robot 2. Furthermore, the image capturing by the camera 9 may be performed manually.

[0030] The controller 5 is a robot controller that controls the driving of the robot 2. Below, the electrical configuration of the three-dimensional object printing apparatus 1 will be described with reference to FIG. 2, including a detailed description of the controller 5.

[0031] 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 apparatus 1 according to the first embodiment. FIG. 2 shows the electrical components of the three-dimensional object printing apparatus 1. As shown in FIG. 2, the three-dimensional object printing apparatus 1 has a control unit 8 in addition to the components shown in FIG. 1 described above. The control unit 8 controls the operation of the liquid ejection head 3a and the robot 2. In the example shown in FIG. 2, the control unit 8 has a control module 6 communicatively connected to the controller 5, and a computer 7 communicatively connected to the camera 9, the controller 5, and the control module 6. Each part of the control unit 8 will be described below in order with reference to FIG. 2.

[0032] 2 may be divided appropriately, some may be included in other components, or may be integrated with other components. For example, some or all of the functions of the controller 5 or control module 6 may be implemented by a computer 7, or may be implemented by another external device such as a PC (personal computer) connected to the controller 5 via a network such as a LAN (Local Area Network) or the Internet.

[0033] The controller 5 has a function of controlling the driving of the robot 2 and a function of generating a signal D3 for synchronizing the ink ejection operation of the head unit 3 with the operation of the robot 2.

[0034] The controller 5 includes a memory circuit 5a and a processing circuit 5b.

[0035] The storage circuitry 5a stores various programs executed by the processing circuitry 5b and various data processed by the processing circuitry 5b. Note that part or all of the storage circuitry 5a may be included in the processing circuitry 5b.

[0036] Although not shown, the storage circuit 5a appropriately stores the target route information Da0, tentative route information Da1, and corrected route information Da2 supplied from the computer 7.

[0037] The target path information Da0, tentative path information Da1, and corrected path information Da2 are each used to control the operation of the robot 2 and indicate the target position and target posture of the liquid ejection head 3a or head unit 3 along the path along which the liquid ejection head 3a or head unit 3 should move. The target path information Da0 is information relating to a target print trajectory RU-0 (described below), which is an ideal print path in the robot coordinate system. The tentative path information Da1 is information relating to a tentative print path for generating the corrected path information Da2, and indicates a path obtained by correcting the target print trajectory RU-0 (described below) indicated by the target path information Da0. The corrected path information Da2 is information relating to the print path used when performing a printing operation, and is generated using the tentative path information Da1. Below, the target path information Da0, tentative path information Da1, and corrected path information Da2 may be referred to as path information Da without distinction.

[0038] Here, the position and orientation of the liquid ejection head 3a are defined by the position and orientation of the tool center point TCP (described later) of the robot 2. Therefore, the path information Da includes position information indicating the target position of the tool center point TCP and orientation information indicating the target orientation of the tool center point TCP. For example, the position information is expressed by multiple coordinate values ​​indicating the target position in the robot coordinate system, and the orientation information is expressed by multiple vectors indicating the target orientation corresponding to the target position. Note that the tool center point TCP is a virtual point whose positional relationship with the liquid ejection head 3a is fixed, and it may be located at a distance from the liquid ejection head 3a. The path information Da may also be expressed using a workpiece coordinate system. In this case, the path information Da is used to control the operation of the robot 2 after converting the coordinate values ​​of the workpiece coordinate system into coordinate values ​​of the base coordinate system or the world coordinate system.

[0039] The processing circuit 5b controls the operation of the arm driving mechanism 2a of the robot 2 based on the path information Da, and generates a signal D3.

[0040] Here, the arm drive mechanism 2a is an assembly of drive mechanisms for the aforementioned joints J1 to J6, and for each joint J, it has a motor for driving the joint of the robot 2 and an encoder for detecting the rotation angle of the joint of the robot 2.

[0041] The processing circuit 5b performs inverse kinematics calculations, which are calculations that convert the path information Da into movement quantities such as the rotation angle and rotation speed of each joint J of the robot 2. The processing circuit 5b then outputs a control signal Sk1 based on the output D1 from each encoder of the arm driving mechanism 2a so that the movement quantities such as the actual rotation angle and rotation speed of each joint J match the aforementioned calculation results based on the path information Da. The control signal Sk1 is a signal for controlling the driving of the motor of the arm driving mechanism 2a. Here, the control signal Sk1 may be corrected by the processing circuit 5b, as necessary, based on the output from a distance sensor (not shown).

[0042] Furthermore, the processing circuit 5b generates a signal D3 based on an output D1 from at least one of the multiple encoders of the arm drive mechanism 2a. For example, the processing circuit 5b generates, as the signal D3, a trigger signal including a pulse at the timing when the output D1 from one of the multiple encoders reaches a predetermined value.

[0043] The control module 6 is a circuit that controls the ink ejection operation of the head unit 3 based on the signal D3 output from the controller 5, and the print data Img and timing information Dt from the computer 7. The control module 6 has a timing signal generation circuit 6a, a power supply circuit 6b, a control circuit 6c, and a drive signal generation circuit 6d.

[0044] The timing signal generating circuit 6a generates a timing signal PTS based on the signal D3 and the timing information Dt. The timing signal generating circuit 6a is a circuit that generates the timing signal PTS at the timing indicated by the timing information Dt, and starts generating the timing signal PTS when the signal D3 is detected.

[0045] The power supply circuit 6b receives power from a commercial power supply (not shown) and generates various predetermined potentials. The generated potentials are supplied appropriately to the control module 6 and each component of the head unit 3. For example, the power supply circuit 6b generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the head unit 3. The power supply potential VHV is also supplied to the drive signal generation circuit 6d.

[0046] The control circuit 6c 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 the drive signal generation circuit 6d, and the other signals are input to the switch circuit 3e of the head unit 3.

[0047] The control signal SI is a digital signal that specifies the operating state of the drive elements of the liquid ejection head 3a of the head unit 3. Specifically, the control signal SI is a signal that specifies whether or not to supply a drive signal Com (described below) to the drive element based on the print data Img. This specification, for example, specifies whether or not to eject ink from the nozzle corresponding to the drive element, or specifies the amount of ink ejected from the nozzle. The waveform specification signal dCom is a digital signal that defines 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 drive element, thereby specifying the timing of ink ejection from the nozzle. The clock signal CLK is a reference clock signal synchronized with the timing signal PTS.

[0048] The drive signal generation circuit 6d is a circuit that generates a drive signal Com for driving each drive element of the liquid ejection head 3a of the head unit 3. Specifically, the drive signal generation circuit 6d includes, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generation circuit 6d, the DA conversion circuit converts the waveform designation signal dCom from the control circuit 6c 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 6b to generate the drive signal Com. Here, of the waveforms included in the drive signal Com, the signal with the waveform actually supplied to the drive element is the drive pulse PD. The drive pulse PD is supplied from the drive signal generation circuit 6d to the drive element via the switch circuit 3e of the head unit 3.

[0049] Here, the switch circuit 3e is a circuit including a switching element that switches whether or not at least a part of the waveform included in the drive signal Com is to be supplied as the drive pulse PD based on the control signal SI.

[0050] The computer 7 has a function of generating path information Da, a function of supplying information such as the path information Da to the controller 5, and a function of supplying information such as print data Img to the control module 6.

[0051] The computer 7 includes a memory circuit 7a and a processing circuit 7b. Although not shown, the computer 7 also includes an input device such as a keyboard or a mouse for accepting user operations. The computer 7 may also include a display device such as a liquid crystal panel for displaying information necessary for generating the path information Da.

[0052] The storage circuitry 7a stores various programs executed by the processing circuitry 7b and various data processed by the processing circuitry 7b. The storage circuitry 7a includes, for example, one or both of semiconductor memories, such as a volatile memory such as RAM and a nonvolatile memory such as a ROM, EEPROM, or PROM. Note that part or all of the storage circuitry 7a may be included in the processing circuitry 7b.

[0053] The memory circuit 7a stores target path information Da0, tentative path information Da1, corrected path information Da2, workpiece information Dc, print data Img, first scanning information Db1, second scanning information Db2, and a program PR1.

[0054] The work information Dc is data that represents the shape of at least a portion of the workpiece W. Specifically, the work information Dc is, for example, three-dimensional data in an STL (Standard Triangulated Language) format or the like that represents the shape of the workpiece W using multiple polygons. The work information Dc includes coordinate information, which is information about the coordinates of each vertex of the polygon, and vector information, which is information about normal vectors that indicate the front and back of the polygon faces. The work information Dc is obtained by converting CAD (computer-aided design) data that represents the three-dimensional shape of the workpiece W as needed. The work information Dc may be created based on the imaging results obtained by the camera 9. The work information Dc may be expressed using coordinate values ​​in a work coordinate system, or may be expressed as point cloud data using coordinate values ​​in a base coordinate system or a world coordinate system. The work information Dc may also be expressed using mathematical formulas, etc., and the format of the work information Dc may be appropriately converted as needed.

[0055] The print data Img is information that indicates an image to be printed on the workpiece W for each path (pass) of the printing path indicated by the path information Da. Here, the image to be ultimately printed on the workpiece W is represented by a collection of dots, which are tiny dots, and printing is performed by applying ink droplets corresponding to these dots onto the workpiece W. The image to be printed is composed of an image formed by ink droplets ejected from a first nozzle row NL1 (described below) and an image formed by ink droplets ejected from a second nozzle row NL2 (described below) superimposed on each other.

[0056] The first scanning information Db1 is information relating to a first actual printing trajectory RU-1 (described later), which is a trajectory that the liquid ejection head 3a actually scans when the robot 2 is operated based on the target path information Da0. In this embodiment, the first scanning information Db1 is information indicating the results of capturing an image of dots M (described later) formed on the workpiece W by ejecting ink from the liquid ejection head 3a toward the workpiece W when the robot 2 is operated based on the target path information Da0, using the camera 9.

[0057] The second scanning information Db2 is information about a second actual printing trajectory RU-2 (described later), which is the trajectory that the liquid ejection head 3a actually scans when the robot 2 is operated based on the tentative path information Da1. In this embodiment, the second scanning information Db2 is information that indicates the results of imaging, by the camera 9, dots M (described later) that are formed on the workpiece W by ejecting ink from the liquid ejection head 3a toward the workpiece W when the robot 2 is operated based on the tentative path information Da1. The results of imaging by the camera 9 are input to the computer 7 as a signal D2.

[0058] The program PR1 is a program for executing various processes for generating the corrected path information Da2.

[0059] The processing circuit 7b realizes the above-mentioned functions by executing programs such as the program PR1, etc. The processing circuit 7b includes, for example, one or more processors such as CPUs.

[0060] The processing circuit 7b executes the program PR1 to perform various processes required for the control method described below, and the control unit 8 thereby executes various processes required for the control method described below.

[0061] 1-3.Head unit configuration FIG. 3 is a perspective view showing a schematic configuration of the head unit 3 of the first embodiment. For convenience, the following description will be made using the mutually intersecting a-axis, b-axis, and c-axis as appropriate. In the following description, one direction along the a-axis is the a1 direction, and the direction opposite the a1 direction is the a2 direction. Similarly, the opposite directions along the b-axis are the b1 direction and the b2 direction. Furthermore, the opposite directions along the c-axis are the c1 direction and the c2 direction.

[0062] Here, the a-axis, b-axis, and c-axis correspond to the coordinate axes of the tool coordinate system set in the head unit 3, and the relative position and orientation relationship with the world coordinate system or the robot coordinate system changes depending on the operation of the robot 2. In the example shown in FIG. 3, the c-axis is an axis parallel to the rotation axis O6. The a-axis, b-axis, and c-axis are typically perpendicular to each other, but are not limited to this. For example, they may intersect at an angle between 80° and 100°. The tool coordinate system and the base coordinate system or the robot coordinate system are associated with each other by calibration.

[0063] The tool coordinate system is set with the tool center point TCP as its reference. Therefore, the position and orientation of the liquid ejection head 3a are determined with the tool center point TCP as its reference. In the example shown in FIG. 3, the tool center point TCP is located at the center of the nozzle surface FN. Note that the position of the tool center point TCP is not limited to the example shown in FIG. 3, and may be, for example, a position spaced apart from the liquid ejection head 3a in the ink ejection direction DE. In this case, a printing path RU, which will be described later, is set on the surface of the workpiece W.

[0064] As described above, the head unit 3 has a liquid ejection head 3a. The liquid ejection head 3a is supported by a support 3f indicated by a two-dot chain line in FIG. 3. In the example shown in FIG. 3, the head unit 3 has one liquid ejection head 3a, but the number is not limited to the example shown in FIG. 3 and may be two or more. The head unit 3 may also have elements other than the liquid ejection head 3a, such as a pressure adjustment valve that adjusts the pressure of the ink in the liquid ejection head 3a, and a light source that emits energy such as light, heat, an electron beam, or radiation to harden or solidify the ink on the workpiece W.

[0065] The support 3f is attached to the arm 226. Therefore, the liquid ejection heads 3a are collectively supported by the support 3f on the arm 226. Therefore, the relative positions of the liquid ejection heads 3a with respect to the arm 226 are fixed.

[0066] The liquid ejection head 3a has a nozzle surface FN and a plurality of nozzles N opening in the nozzle surface FN. The nozzle surface FN is the nozzle surface on which the nozzles N open, and is made of, for example, a material such as silicon (Si) or metal. Alternatively, if another member is arranged as a component of the head unit 3 on a plane extending from the nozzle surface, the nozzle surface FN is a surface formed by the plate surface of the nozzle plate and the surface of the other member. The plurality of nozzles N are divided into a first nozzle row NL1 and a second nozzle row NL2, which are arranged at intervals along the a-axis. Each of the first nozzle row NL1 and the second nozzle row NL2 is a collection of a plurality of nozzles N linearly arranged in the nozzle row direction DN, which is the direction along the b-axis. Here, elements associated with each nozzle N of the first nozzle row NL1 and elements associated with each nozzle N of the second nozzle row NL2 in the liquid ejection head 3a are configured to be approximately symmetrical to each other in the direction along the a-axis.

[0067] The first nozzle row NL1 and the second nozzle row NL2 are aligned along the a-axis, which is parallel to the main scanning direction DM, which is the direction in which the liquid ejection head 3a moves during the preparatory operation and the printing operation. The first nozzle row NL1 and the second nozzle row NL2 constitute the nozzle row NL.

[0068] Although not shown, the liquid ejection head 3a has a piezoelectric element, which is a drive element, and a cavity that contains ink for each nozzle N. Here, the piezoelectric element changes the pressure in the cavity corresponding to the piezoelectric element, thereby ejecting ink from the nozzle corresponding to the cavity in the ejection direction DE, which is the direction c2. Such a liquid ejection head 3a can be obtained, for example, by bonding together, with an adhesive, multiple substrates, such as silicon substrates, that have been appropriately processed by etching or the like. Note that instead of the piezoelectric element, a heater that heats the ink in the cavity may be used as the drive element for ejecting ink from the nozzle.

[0069] 1-4.Control method Figure 4 is a diagram showing an example of the operation of the three-dimensional object printing apparatus 1. Figure 4 illustrates an example of printing on the surface WF of the workpiece W placed at a position further in the X2 direction than the robot 2.

[0070] The three-dimensional object printing device 1 performs a printing operation to print an image in ink on the surface WF of the workpiece W by changing the position and posture of the liquid ejection head 3a relative to the workpiece W through the operation of the robot 2 and ejecting ink appropriately from the nozzle N of the liquid ejection head 3a toward the workpiece W.

[0071] During printing, the robot 2 moves the liquid ejection head 3a along a printing path RU from position PS to position PE while maintaining a predetermined orientation relative to the surface WF. At this time, the movement of the liquid ejection head 3a is controlled based on the print data Img. Here, while the position of the liquid ejection head 3a should change along the target printing path RU-0 indicated by the target path information Da0, when the movement of the robot 2 is controlled based on the target path information Da0, the actual printing path RU deviates from the target printing path RU-0. This is due to movement errors caused by a combination of factors, such as length errors in the arm 220 of the robot 2, eccentricity of the motor or reducer of the joint J, and vibration of the arm 220.

[0072] Therefore, the three-dimensional object printing apparatus 1 corrects the target path information Da0 based on the actual printing path RU when the drive of the robot 2 is controlled based on the target path information Da0. This correction generates corrected path information Da2 to be used for drive control of the robot 2 during printing operations.

[0073] In this embodiment, tentative route information Da1 is generated by correcting the target route information Da0 based on the actual printing route RU when the drive of the robot 2 is controlled based on the target route information Da0, and then corrected route information Da2 is generated by correcting the target route information Da0 an appropriate number of times based on the actual printing route RU when the drive of the robot 2 is controlled based on the tentative route information Da1.

[0074] 4, the printing path RU extends along the X-axis when viewed in the Z2 direction. That is, the main scanning direction DM is parallel to the X-axis when viewed in the direction along the Z-axis. During printing operations, the robot 2 mainly operates three of the six joints J: joints J2, J3, and J5. By aligning the rotation axes of the three joints J parallel to the Y-axis and operating only these three joints J, the liquid ejection head 3a can be moved in the main scanning direction DM while reducing meandering in the sub-scanning direction DS, which intersects with the main scanning direction DM, compared to an embodiment in which four or more joints J are operated.

[0075] However, even if only three joints J are operated in this manner, it is difficult to sufficiently reduce meandering in the sub-scanning direction DS of the liquid ejection head 3a. This is because, although meandering caused by operation errors of the joints J can be reduced by reducing the number of joints J to be operated and aligning the rotation axes, it is difficult to completely eliminate meandering caused by vibration of the arm 220 because the arm 220 of the robot 2 is long. Here, when the arm 220 is extended, such that the distance between the tip and base end of the arm 220 is large, meandering caused by vibration of the arm 220 is more likely to occur than when the arm 220 is retracted. Therefore, the likelihood of meandering caused by vibration of the arm 220 changes depending on the extension / contraction state of the arm 220.

[0076] The robot 2 may perform a printing operation by operating four or more of the six joints J. In this case, the installation position and installation posture of the workpiece W are not limited to the example shown in FIG. 4 and are arbitrary. The printing path RU is determined according to the shape, printing range, installation position, installation posture, etc. of the workpiece W, and is not limited to the example shown in FIG. 4 and is arbitrary. The positions and number of joints J to be operated in a printing operation are determined according to the printing path RU and the posture of the head unit 3 relative to the workpiece W during the printing operation.

[0077] Figure 5 is a flowchart showing a control method according to the first embodiment. As shown in Figure 5, the control method for the three-dimensional object printing apparatus 1 includes steps S100, S200, and S300, in this order. Here, the control unit 8 executes steps S100, S200, and S300 in this order.

[0078] In step S100, the control unit 8 executes a preparatory operation. The preparatory operation in this embodiment is an operation in which the robot 2 is operated based on the target path information Da0 to cause the liquid ejection head 3 a to scan the workpiece W, and ink is ejected from the liquid ejection head 3 a toward the workpiece W to form dots M on the workpiece W.

[0079] In step S200, the control unit 8 performs a correction process. In the correction process of this embodiment, the target path information Da0 is corrected based on the trajectory that the liquid ejection head 3a actually scans during the preliminary operation, thereby generating tentative path information Da1 and corrected path information Da2.

[0080] In step S300, the control unit 8 executes a printing operation in which the liquid ejection head 3a is caused to scan the workpiece W and eject ink from the liquid ejection head 3a toward the workpiece W. At this time, the control unit 8 controls the operation of the robot 2 based on the corrected path information Da2, thereby changing the position and posture of the liquid ejection head 3a with respect to the workpiece W. This effectively reduces meandering of the liquid ejection head 3a in the sub-scanning direction DS.

[0081] 6 is a flowchart showing the flow of the correction process in the first embodiment. The correction process in step S200 includes steps S201 to S213, as shown in FIG.

[0082] Specifically, first, in step S201, the control unit 8 acquires first scanning information Db1. In this embodiment, in step S201, the control unit 8 acquires the first scanning information Db1 by measuring the dots M formed by executing the preliminary operation in step S100. Details of the first scanning information Db1 will be described later with reference to FIG. 7.

[0083] After step S201, in step S202, the control unit 8 acquires a first movement amount, which is the movement amount of the liquid ejection head 3a in the sub-scanning direction DS that intersects with the main scanning direction DM, based on the first scanning information Db1. Details of acquiring the first movement amount will be described later with reference to FIG.

[0084] After step S202, in step S203, the control unit 8 acquires a first error amount in the sub-scanning direction of a first actual printing trajectory RU-1 (described below) relative to the target printing trajectory RU-0, based on the target printing trajectory RU-0 indicated by the target path information Da0 and the first movement amount acquired in step S202. Details of the first error amount will be described later with reference to FIGS.

[0085] After step S203, in step S204, the control unit 8 identifies a correction range, which is a range that is subject to correction for the target print trajectory RU-0. In this embodiment, in step S204, the control unit 8 identifies a correction period, which is a period during which the first movement amount exceeds a predetermined threshold, as the correction range. Details of the correction range will be described later with reference to FIG. 13.

[0086] After step S204, in step S205, the control unit 8 corrects the target print trajectory RU-0 based on the first error amount within the correction range for which the correction amount is calculated. This generates tentative path information Da1. In this embodiment, in step S205, the control unit 8 corrects the target print trajectory RU-0 indicated by the target path information Da0 for the correction period identified in step S204. Details of this correction will be described later with reference to FIG. 14.

[0087] After step S205, in step S206, the control unit 8 acquires second scan information Db2. In this embodiment, in step S206, the control unit 8 acquires second scan information Db2 by forming dots M and then measuring the dots, similar to step S100, except that tentative route information Da1 is used instead of target route information Da0.

[0088] After step S206, in step S207, the control unit 8 acquires a second movement amount, which is the movement amount of the liquid ejection head 3a in the sub-scanning direction DS, based on the second scanning information Db2. Note that the acquisition of the second movement amount is performed in the same manner as the acquisition of the first movement amount.

[0089] After step S207, in step S208, the control unit 8 obtains a second error amount in the sub-scanning direction of a second actual print trajectory RU-2 (described below) relative to the target print trajectory RU-0 based on the target print trajectory RU-0 and the second movement amount. Details of the second error amount will be described later with reference to Figures 15, 17, and 19.

[0090] After step S208, in step S209, the control unit 8 determines whether the second error amount in the correction period is equal to or greater than a threshold value by comparing the second error amount with the threshold value.

[0091] If the second error amount is equal to or greater than the threshold value (step S209: YES), the control unit 8 again corrects the target print trajectory RU-0 for the correction period in step S211, and then returns to step S206. In step S211, the correction amount is adjusted, and the target print trajectory RU-0 for the correction period is corrected.

[0092] In this way, if the second error amount is equal to or greater than the threshold value (step S209: YES), step S211 adjusts the correction amount to correct the target print trajectory RU-0 during the correction period, thereby improving the effect of correcting the target print trajectory RU-0.

[0093] Furthermore, if the second error amount during the correction period is equal to or greater than the threshold value (step S209: YES), step S211 preferably advances the timing of the correction during the correction period. This prevents delays in the correction during the correction period due to acceleration during movement of the liquid ejection head 3a. As a result, the effectiveness of the correction of the target print trajectory RU-0 can be improved. This timing is determined based on the natural frequency of the arm 220. For example, the timing of the correction can be advanced within a range shorter than the natural vibration period of the arm 220.

[0094] On the other hand, if the second error amount in the correction period is less than the threshold value (step S209: NO), in step S212, the control unit 8 generates corrected route information Da2. This generation is performed based on the tentative route information Da1. For example, the tentative route information Da1 is adopted as the corrected route information Da2.

[0095] After step S212, in step S213, the control unit 8 determines whether there is another correction range. For example, if the second error amount is less than the threshold value over the entire range after the correction period, it is determined that there is no other correction range; otherwise, it is determined that there is another correction range.

[0096] If there are other correction ranges (step S213: YES), the control unit 8 returns to step S204. As a result, after another correction range is identified in step S204, the target print trajectory RU-0 is corrected for that correction range in step S205.

[0097] On the other hand, if there is no other correction range (step S213: NO), the control unit 8 ends the process.

[0098] 7 is a diagram for explaining the acquisition of the first scanning information Db1 in the first embodiment. Fig. 7 schematically shows the relationship between the detection pattern PT formed on the workpiece W by the liquid ejection head 3a during the preliminary operation of step S100, the target printing trajectory RU-0, and the first actual printing trajectory RU-1, which is the actual printing path RU.

[0099] In the preliminary operation of step S100, as shown in Fig. 7, a detection pattern PT for detecting the first actual printing trajectory RU-1 is printed on a workpiece W. At this time, the workpiece W may be the workpiece W used in the printing operation of step S300, or it may be another workpiece W having the same shape as the workpiece W used in the printing operation of step S300, or an object for inspection. If the workpiece W used in the preliminary operation is the workpiece W used in the printing operation of step S300, an inspection sheet such as paper is attached to the workpiece W used in the preliminary operation, and the detection pattern PT is formed on the inspection sheet.

[0100] In the example shown in FIG. 7, the detection pattern PT is made up of a plurality of dots M. The plurality of dots M are formed, for example, by ejecting ink from each nozzle N at regular time intervals. If there is no operational error in the robot 2, the first actual print trajectory RU-1 coincides with the target print trajectory RU-0. FIG. 7 shows a state in which the first actual print trajectory RU-1 deviates from the target print trajectory RU-0 in the X-axis direction and meanders, resulting in the arrangement of the plurality of dots M in the detection pattern PT being distorted in the X-axis direction. Note that the number and arrangement of dots M in the detection pattern PT are not limited to the example shown in FIG. 7 and are arbitrary.

[0101] In step S201, the detection pattern PT is imaged by the camera 9, and the imaged result is acquired as first scan information Db1. This image capturing may be performed, for example, during the execution of step S100.

[0102] As described above, in step S201, the control unit 8 acquires first scanning information Db1 by measuring the dots M formed by executing the preliminary operation in step S100. This has the advantage that, in step S205, the target print trajectory RU-0 is corrected based on the results of actual printing using the target path information Da0, making it easier to improve the correction accuracy of the target print trajectory RU-0. Furthermore, not only can errors resulting from operational errors of the robot 2 be corrected, but also errors in ink landing on the workpiece W resulting from operational errors of the liquid ejection head 3a can be corrected. As a result, print quality can be favorably improved.

[0103] In step S202, for example, the positions of the dots M in the captured image indicated by the first scanning information Db1 are detected using a known image recognition technique, and a first movement amount, which is the movement direction of the liquid ejection head 3a in the sub-scanning direction DS, is obtained based on the detection result. This makes it possible to obtain a first actual printing trajectory RU-1, which is the trajectory of the liquid ejection head 3a based on the first scanning information Db1.

[0104] Step S203, for example, obtains the first error amount in the sub-scanning direction of the first actual printing trajectory RU-1 relative to the target printing trajectory RU-0 by converting the first movement amount for each position in the main scanning direction DM into an amount based on the target printing trajectory RU-0.

[0105] FIG. 8 is a diagram showing an example of the first error amount. In FIG. 8, the vertical axis represents the first error amount, which is the error amount of the first actual print trajectory RU-1 in the sub-scanning direction DS relative to the target print trajectory RU-0, and the horizontal axis represents the position of the liquid ejection head 3a in the main scanning direction DM. FIG. 9 is a diagram showing an example of the correction amount for correcting the meandering of the long-period component of the first actual print trajectory RU-1. In FIG. 9, the vertical axis represents the correction amount of the long-period component described below, and the horizontal axis represents the position of the liquid ejection head 3a in the main scanning direction as point data for controlling the operation of the robot 2. FIG. 10 is a diagram showing an example of the first error amount. In FIG. 10, the vertical axis represents the first error amount after correction of the long-period component, and the horizontal axis represents time. Note that in this embodiment, the left side of the horizontal axis in FIGS. 8 to 10 corresponds to the X1 direction, and the right side corresponds to the X2 direction. 8 to 10, the left end of the horizontal axis is the start side of the scan of the liquid ejection head 3a, and the right end of the horizontal axis is the end side of the scan of the liquid ejection head 3a.

[0106] As shown in Figure 8, the first error amount appears as a deviation from the target printing trajectory RU-0, which is a long-period meandering that forms an arcuate trajectory from the start point to the end point, and a short-period meandering that occurs within the arcuate trajectory.

[0107] The long-period meandering is corrected by calculating the amount of meandering of the long-period meandering by polynomial approximation of the first error amount from the start point to the end point, and using a correction amount that causes the robot 2 to perform an operation in the opposite phase to the long-period meandering, as shown in Fig. 9. The opposite phase operation here is an operation that cancels out or reduces the long-period meandering, and is an operation in the opposite direction (opposite phase) to the long-period meandering. This correction results in a first error amount in which the long-period meandering has been reduced, as shown in Fig. 10.

[0108] Note that the anti-phase operation is an operation that cancels out or reduces a specific meandering by operating in the opposite direction (anti-phase) to the specific meandering. The control unit 8 cancels out or reduces the specific meandering by operating the robot 2 in the anti-phase. For example, the control unit 8 reduces the amount of error by moving the robot 2 in the opposite phase to the frequency of the error amount with respect to the target printing trajectory RU-0 and with the same amplitude as the amplitude, thereby canceling out or reducing the meandering.

[0109] 10, as the position of the liquid ejection head 3a moves in the X2 direction, the amount of short-period meandering increases. This is because as the extension amount of the arm portion 220 increases, meandering due to vibration of the arm portion 220 becomes more likely to occur.

[0110] On the other hand, the correction of the long-period meandering is performed by using a correction amount that causes the robot 2 to move in the opposite phase to the short-period meandering at a limited point or range within the period from the start point to the end point of the first error amount.

[0111] Figure 11 is a diagram for explaining the actual measurement points and interpolation points of the first actual printing trajectory RU-1. Figure 12 is an enlarged view of a portion of Figure 11. In Figures 11 and 12, the vertical axis represents the first error amount, and the horizontal axis represents the position of the liquid ejection head 3a in the main scanning direction DM. However, the horizontal axis uses the starting point of the first actual printing trajectory RU-1 as the position reference.

[0112] 11 and 12, in step S203, the first error amount is obtained by finding an approximate line by linearly interpolating the period T and the interpolated points of the period t of the actual measurement points measured during the period T. This makes it possible to find the correction amount for the period T.

[0113] The period T corresponds to the period of point data for controlling the position of the liquid ejection head 3a in the main scanning direction of the robot 2, and is shorter than the period of the short-period meandering described above, preferably 1 mm or less. This makes it possible to apply a path that follows the short-period meandering described above.

[0114] However, if a correction amount is applied that causes the robot 2 to move in the opposite phase to the short-period meandering over the entire range from the start point to the end point of the first error amount, the short-period meandering will be amplified. This is presumably because the application of the correction amount changes the subsequent meandering, causing the phase of the prepared correction amount to not match the actual meandering.

[0115] Therefore, in step S204, the range and period for correcting short-period meandering are limited.

[0116] Fig. 13 is a diagram illustrating the first error amount and correction range in the first embodiment. In Fig. 13, the vertical axis represents the first error amount after correcting the long-period meandering, and the horizontal axis represents the position of the liquid ejection head 3a in the main scanning direction DM. Fig. 14 is a diagram illustrating the correction amount based on the first error amount shown in Fig. 13. In Fig. 14, the vertical axis represents the correction amount obtained by combining the correction amount for the long-period component and the correction amount for the short-period component based on the first error amount within the correction range, and the horizontal axis represents the position of the liquid ejection head 3a in the main scanning direction as point data for controlling the operation of the robot 2.

[0117] In step S204, as shown in FIG. 13, a predetermined range of the first error amount on the end side of the scan of the liquid ejection head 3a is identified as the correction range. This makes it possible to appropriately correct the short-period meandering described above. In the example shown in FIG. 13, a period of six periods of the meandering is identified as the correction range. Note that the period of the correction range is not limited to the example shown in FIG. 13, and may be five periods or less, or seven periods or more. In step S204 after execution of step S213, a range of the second error amount that is different from the previous correction range is identified.

[0118] Step S205 calculates a correction amount for the correction range such that the robot 2 moves in the opposite phase to the short-period meandering, as shown in Fig. 14. Then, step S205 uses this correction value to correct the target printing trajectory RU-0, thereby generating tentative path information Da1.

[0119] In this way, since the target print trajectory RU-0 is corrected based on the first error amount in step S205, deviation in the sub-scanning direction of the trajectory actually scanned by the liquid ejection head 3a can be reduced. As a result, print quality can be favorably improved. Furthermore, by narrowing the correction range in step S204, the time required to correct the target print trajectory RU-0 can be shortened.

[0120] In this embodiment, as described above, step S205 corrects the target print trajectory RU-0 during the correction period. By specifying the correction period in step S204, the increase in error associated with the correction can be suppressed. As a result, the correction accuracy of the target print trajectory RU-0 can be improved. Furthermore, by correcting the specified period rather than the entire period from the start point to the end point of the correction range, the correction processing time can be shortened.

[0121] Step S206 is similar to step S100, except that tentative path information Da1 is used instead of target path information Da0. After forming dots M, second scanning information Db2 is obtained by measuring the dots. Then, like step S202 described above, step S207 detects the positions of multiple dots M in the captured image represented by the second scanning information Db2 using a known image recognition technique, and obtains a second movement amount, which is the movement direction of the liquid ejection head 3a in the sub-scanning direction DS, based on the detection results. This makes it possible to determine a second actual printing trajectory RU-2, which is the trajectory of the liquid ejection head 3a based on the second scanning information Db2.

[0122] Step S208, for example, obtains a second error amount in the sub-scanning direction of the second actual printing trajectory RU-2 relative to the target printing trajectory RU-0 by converting the second movement amount for each position in the main scanning direction DM into an amount based on the target printing trajectory RU-0.

[0123] Fig. 15 is a diagram for explaining the second error amount, which is the error amount after application of the correction amount shown in Fig. 14. In Fig. 15, the vertical axis indicates the second error amount, which is the error amount after application of the correction amount shown in Fig. 14, and the horizontal axis indicates the position of the liquid ejection head 3a in the main scanning direction DM. Fig. 16 is a diagram for explaining the correction amount based on the second error amount shown in Fig. 15. In Fig. 16, the vertical axis indicates the correction amount based on the second error amount shown in Fig. 15, and the horizontal axis indicates the position of the liquid ejection head 3a in the main scanning direction as point data for controlling the operation of the robot 2.

[0124] As shown in Fig. 15, the second error amount reduces short-period meandering compared to the first error amount shown in Fig. 13. Here, the second error amount shown in Fig. 15 includes a range where the correction in step S205 is effective and a range where it is not effective. In the example shown in Fig. 15, in the range where the correction in step S205 is not effective, short-period meandering is amplified due to changes in the meandering state before that range.

[0125] In step S209, it is determined whether the second error amount in the correction period is equal to or greater than a threshold value. The range in which the second error amount is less than the threshold value is the range in which the correction in step S205 is effective. In the example shown in FIG. 15, the correction period includes a range in which the correction in step S205 is not effective, so step S211 is executed.

[0126] 16, step S211 calculates a correction amount that causes the robot 2 to move in the opposite phase to the short-period meandering within a range where the second error amount is less than the threshold value. Then, step S211 uses this correction value to correct the target printing trajectory RU-0, thereby generating new tentative path information Da1.

[0127] Fig. 17 is a diagram for explaining the second error amount after application of the correction amount shown in Fig. 16. In Fig. 17, the vertical axis indicates the second error amount, which is the error amount after application of the correction amount shown in Fig. 16, and the horizontal axis indicates the position of the liquid ejection head 3a in the main scanning direction DM. Fig. 18 is a diagram for explaining the correction amount based on the second error amount shown in Fig. 17. In Fig. 18, the vertical axis indicates the correction amount based on the second error amount shown in Fig. 17, and the horizontal axis indicates the position of the liquid ejection head 3a in the main scanning direction as point data for controlling the operation of the robot 2.

[0128] As shown in Fig. 17, the second error amount after application of the correction amount shown in Fig. 16 is reduced in the range indicated by the dashed line in the figure. However, in the range after this range, the second error amount exceeds the threshold.

[0129] Therefore, after step S212 is executed, in step S213, it is determined that there is another correction range (step S213: YES), and step S204 is executed. At this time, as shown in Fig. 18, the range after the range indicated by the dashed line in Fig. 17 is identified as the correction range. Thereafter, in step S205, the correction amount shown in Fig. 16 is also applied to the range after the range indicated by the dashed line in Fig. 17, and a correction amount is applied to the range after that range so that the robot 2 moves in an opposite phase to the short-period meandering, based on the second error amount shown in Fig. 17.

[0130] Fig. 19 is a diagram for explaining the second error amount after application of the correction amount shown in Fig. 18. In Fig. 19, the vertical axis represents the second error amount, which is the error amount after application of the correction amount shown in Fig. 18, and the horizontal axis represents the position of the liquid ejection head 3a in the main scanning direction DM.

[0131] As shown in Fig. 19, by applying the correction amounts shown in Fig. 18, the second error amount is also reduced in the range after the range indicated by the dashed line in Fig. 17. Therefore, the control unit 8 ends the process after executing steps S212 and S213.

[0132] As described above, in this embodiment, by suppressing meandering of the liquid ejection head 3a in the sub-scanning direction DS, it is possible to improve print quality.

[0133] 2. Second embodiment A second embodiment of the present disclosure will be described below. In the following exemplary embodiment, for elements whose actions and functions are similar to those of the first embodiment, the reference numerals used in the description of the first embodiment will be used, and detailed descriptions of each element will be omitted as appropriate.

[0134] 20 is a flowchart showing the flow of correction processing in the second embodiment. The correction processing in this embodiment is the same as the correction processing in the first embodiment, except that steps S204A, S205A, S211A, and S213A are included instead of steps S204, S205, S211, S212, and S213 in the first embodiment.

[0135] FIG. 21 is a diagram illustrating the first error amount and correction range in the second embodiment. In FIG. 21, the vertical axis represents the first error amount after correcting the long-period meandering, and the horizontal axis represents the position of the liquid ejection head 3a in the main scanning direction DM. FIG. 22 is a diagram illustrating the correction amount based on the first error amount shown in FIG. 21. In FIG. 22, the vertical axis represents the correction amount obtained by combining the correction amount for the long-period component and the correction amount for the short-period component based on the first error amount within the correction range, and the horizontal axis represents the position of the liquid ejection head 3a in the main scanning direction as point data for controlling the operation of the robot 2.

[0136] Step S204A is the same as step S204 in the first embodiment, except that a point surrounded by a solid circle in Fig. 21 is specified as the correction range. This point is a point where the first error amount is equal to or greater than a predetermined threshold, and corresponds to one peak of the first error amount.

[0137] Step S205A calculates a correction amount for the point identified in step S204A so that the robot 2 moves in the opposite phase to the short-period meandering. Then, step S205A uses this correction value to correct the target printing trajectory RU-0, thereby generating tentative path information Da1.

[0138] In this way, the control unit 8 identifies points in the target print trajectory RU-0 where the first error amount is equal to or greater than a predetermined threshold as the correction range, and corrects the target print trajectory RU-0 at those points. This prevents the increase in error amount associated with the correction. As a result, the correction accuracy of the target print trajectory RU-0 can be improved. Furthermore, since performing correction at a point that indicates a specific peak may result in the error amount at subsequent points falling within the acceptable range, the correction process can be simplified by performing correction at specific points rather than for the entire period from the start point to the end point of the correction range.

[0139] After step S205A, in this embodiment, as in the first embodiment, the control unit 8 acquires second scanning information Db2 in step S206, acquires a second movement amount in step S207, and acquires a second error amount in step S208.

[0140] Fig. 23 is a diagram for explaining the second error amount, which is the error amount after application of the correction amount shown in Fig. 22. In Fig. 23, the vertical axis indicates the second error amount, which is the error amount after application of the correction amount shown in Fig. 22, and the horizontal axis indicates the position of the liquid ejection head 3a in the main scanning direction DM. Fig. 24 is a diagram for explaining the correction amount based on the second error amount shown in Fig. 23. In Fig. 24, the vertical axis indicates the correction amount based on the second error amount shown in Fig. 23, and the horizontal axis indicates the position of the liquid ejection head 3a in the main scanning direction as point data for controlling the operation of the robot 2.

[0141] As shown in Fig. 23, the second error amount reduces short-period meandering for the point identified in step S204A compared to the first error amount shown in Fig. 21. In the example shown in Fig. 23, the second error amount for the point is less than the threshold value (step S209: NO). Therefore, after executing step S212, the control unit 8 executes step S213A.

[0142] In step S213A, the control unit 8 determines whether there are any other points that need to be corrected. For example, if all of the peaks of the second error amount throughout the entire correction range are less than the threshold, it is determined that there are no other correction ranges. On the other hand, if there are one or more peaks that are equal to or greater than the threshold, it is determined that there are other correction ranges. If there are other correction ranges (step S213A: YES), the control unit 8 returns to step S204A. This causes correction of the target print trajectory RU-0 for the other points.

[0143] In the example shown in FIG. 23, the second error amount is equal to or greater than the threshold value in the range after this point (step S213A: YES). Therefore, the control unit 8 returns to step S204A and calculates a correction amount for the point surrounded by the dashed circle in FIG. 23, which will cause the robot 2 to move in the opposite phase to the short-period meandering. This point is a point after the point identified in the first step S204A. Then, in step S205A, this correction amount is used to correct the target printing trajectory RU-0, thereby generating new tentative path information Da1. Note that the point identified in the second step S204A is not limited to the example shown in FIG. 23, and may be, for example, a point after the point surrounded by the dashed circle in FIG. 23.

[0144] If the second error amount for the point identified in step S204A is equal to or greater than the threshold value (step S209: YES), in step S211A, the control unit 8 adjusts the correction amount and then corrects the target print trajectory RU-0 at the point. This improves the effect of correcting the target print trajectory RU-0. After step S211A, step S206 is executed.

[0145] Fig. 25 is a diagram for explaining the second error amount after application of the correction amount shown in Fig. 24. In Fig. 25, the vertical axis represents the second error amount, which is the error amount after application of the correction amount shown in Fig. 24, and the horizontal axis represents the position of the liquid ejection head 3a in the main scanning direction DM.

[0146] As shown in FIG. 25, by applying the correction amounts shown in FIG. 24, the second error amount is also reduced for the points identified in step S204A for the second time.

[0147] In the example shown in FIG. 25, all of the peaks of the second error amount are less than the threshold value over the entire correction range, so after step S212 is executed, it is determined in step S213A that there are no other correction ranges (step S213A: NO), and the processing ends.

[0148] According to the second embodiment described above, it is also possible to improve print quality by suppressing meandering of the liquid ejection head 3a in the sub-scanning direction DS.

[0149] 3. Third embodiment A third embodiment of the present disclosure will be described below. In the following exemplary embodiments, elements that have the same actions and functions as those in the first embodiment will be designated by the same reference numerals as those in the first embodiment, and detailed descriptions of each element will be omitted where appropriate.

[0150] 26 is a flowchart showing the flow of correction processing in the third embodiment. The correction processing in this embodiment is the same as the correction processing in the first embodiment except that steps S204B, S205B, S211B, and S213A are included instead of steps S204, S205, S211, S212, and S213 in the first embodiment. Note that step S213B in this embodiment is the same as step S213A in the second embodiment described above.

[0151] Although not shown, step S204B, when executed for the first time, identifies a point corresponding to one peak of the first error amount as the correction range, similar to step S204A in the second embodiment described above. Also, step S205B, when executed for the first time, calculates the correction amount and corrects the target print trajectory RU-0, similar to step S205A in the second embodiment described above.

[0152] Fig. 27 is a diagram for explaining the second error amount in the third embodiment. In Fig. 27, the vertical axis represents the second error amount, which is the error amount after application of the correction amount shown in Fig. 22, and the horizontal axis represents the position of the liquid ejection head 3a in the main scanning direction DM. Fig. 28 is a diagram for explaining the correction amount based on the second error amount shown in Fig. 27. In Fig. 28, the vertical axis represents the correction amount based on the second error amount shown in Fig. 23, and the horizontal axis represents the position of the liquid ejection head 3a in the main scanning direction as point data for controlling the operation of the robot 2.

[0153] As shown in Fig. 27, with the second error amount, the short-period meandering is reduced for the points identified in step S204B (points circled by solid lines in the figure) compared to the first error amount shown in Fig. 21. In the example shown in Fig. 27, the second error amount for the points is less than the threshold value (step S209: NO). Therefore, after executing step S212, the control unit 8 executes step S213B.

[0154] In the example shown in FIG. 27, the second error amount is equal to or greater than the threshold value in the range after that point (step S213B: YES). Therefore, the control unit 8 returns to step S204B and calculates correction amounts for the multiple points surrounded by the dashed circle in FIG. 27, so that the robot 2 moves in the opposite phase to the short-period meandering. These multiple points are points after the points identified in the first step S204B. Then, in step S205B, this correction amount is used to correct the target printing trajectory RU-0, thereby generating new tentative path information Da1. Note that the points identified in the second step S204B are not limited to the example shown in FIG. 27, and may be, for example, points after the points surrounded by the dashed circle in FIG. 27.

[0155] If the second error amount for the point identified in step S204B is equal to or greater than the threshold value (step S209: YES), in step S211B, the control unit 8 adjusts the correction amount and then corrects the target print trajectory RU-0 at the point. This improves the effect of correcting the target print trajectory RU-0. After step S211B, step S206 is executed.

[0156] Fig. 29 is a diagram for explaining the second error amount after application of the correction amount shown in Fig. 28. In Fig. 29, the vertical axis represents the second error amount, which is the error amount after application of the correction amount shown in Fig. 28, and the horizontal axis represents the position of the liquid ejection head 3a in the main scanning direction DM.

[0157] As shown in FIG. 29, by applying the correction amounts shown in FIG. 28, the second error amounts are also reduced for the multiple points identified in step S204B for the second time.

[0158] In the example shown in FIG. 29, all of the peaks of the second error amount are less than the threshold value over the entire correction range, so after step S212 is executed, it is determined in step S213A that there are no other correction ranges (step S213A: NO), and the processing ends.

[0159] According to the third embodiment described above, it is also possible to improve print quality by suppressing meandering of the liquid ejection head 3a in the sub-scanning direction DS.

[0160] 4. Fourth embodiment A fourth embodiment of the present disclosure will be described below. In the following exemplary embodiments, elements whose actions and functions are similar to those of the first embodiment will be designated by the same reference numerals as those used in the description of the first embodiment, and detailed descriptions of each element will be omitted where appropriate.

[0161] 30 is a block diagram showing the electrical configuration of a three-dimensional object printing device 1A according to the fourth embodiment. The three-dimensional object printing device 1A is configured similarly to the three-dimensional object printing device 1 of the first embodiment, except that the camera 9 is omitted, a head unit 3A is provided instead of the head unit 3 of the first embodiment, and a program PR2 is used instead of the program PR1 of the first embodiment. The three-dimensional object printing device 1A may also be provided with a camera 9.

[0162] The head unit 3A is configured in the same manner as the head unit 3 of the first embodiment, except that a detection unit 3c is added.

[0163] The detection unit 3c is a sensor that detects the movement of the liquid ejection head 3a, and is, for example, an inertial sensor that detects one or both of the acceleration and angular velocity applied to the liquid ejection head 3a. Note that the detection unit 3c is not limited to a mode that detects acceleration and angular velocity, as long as it can detect a physical quantity corresponding to the meandering of the liquid ejection head 3a in the sub-scanning direction DS, and may be, for example, a tracking sensor, motion capture sensor, or other sensor that detects the velocity or position of the liquid ejection head 3a in the scanning direction.

[0164] The program PR2 is a program for executing various processes for generating the corrected path information Da2. The processing circuit 7b executes the program PR2 to execute various processes required for the control method described below. As a result, the control unit 8 executes various processes required for the control method described below.

[0165] In this embodiment, ink is not ejected from the liquid ejection head 3a during the preparatory operation in step S100. That is, the control unit 8 of this embodiment performs the preparatory operation of scanning the liquid ejection head 3a over the workpiece W by operating the robot 2 based on the target path information Da0 without ejecting ink from the liquid ejection head 3a. The control unit 8 then acquires the first scanning information Db1 based on the detection results of the detection unit 3c during the execution of the preparatory operation. This has the advantage of easily improving the correction accuracy of the target printing trajectory RU-0, since the target printing trajectory RU-0 is corrected based on the results of actual printing using the target path information Da0. Furthermore, because ink is not ejected from the liquid ejection head 3a during the preparatory operation, neither the workpiece W nor ink is wasted.

[0166] In this way, the first scanning information Db1 in this embodiment is information that indicates the detection result of the detection unit 3c when the robot 2 is operated based on the target path information Da0. Therefore, in step S202, the control unit 8 acquires the first movement amount, which is the movement amount of the liquid ejection head 3a in the sub-scanning direction DS, based on the detection result.

[0167] The second scanning information Db2 in this embodiment is information indicating the detection result of the detection unit 3c when the robot 2 is operated based on the tentative path information Da1. Therefore, in step S207, the control unit 8 acquires the second movement amount, which is the movement amount of the liquid ejection head 3a in the sub-scanning direction DS, based on the detection result.

[0168] According to the fourth embodiment described above, it is also possible to improve print quality by suppressing meandering of the liquid ejection head 3a in the sub-scanning direction DS.

[0169] 3. Variations Each of the above-mentioned exemplary embodiments can be modified in various ways. Specific modified embodiments that can be applied to each of the above-mentioned embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be appropriately combined within the scope of not contradicting each other.

[0170] 3-1. Variation 1 In the above-described embodiment, an example is given of a mode in which the correction path information Da2 is generated taking into consideration only the amount of movement of the liquid ejection head 3a in the sub-scanning direction DS, but this mode is not limited to this, and for example, the correction path information Da2 may be generated taking into consideration the posture of the liquid ejection head 3a in addition to the amount of movement.

[0171] In this case, the three-dimensional object printing apparatus includes a posture detection unit that detects changes in the posture of the liquid ejection head 3a. For example, an angular velocity sensor like the detector 3c in the fourth embodiment can be used as the posture detection unit. In this case, the control unit 8 adjusts the correction amount of the target printing trajectory RU-0 based on the detection results of the posture detection unit when the robot 2 is operated based on the target path information Da0. This allows the correction amount to be adjusted in response to changes in the posture of the liquid ejection head 3a around the roll axis due to factors such as the shape of the workpiece W. As a result, the liquid ejection head 3a can be moved more stably. However, if the correction amount of the target printing trajectory RU-0 is not adjusted when the posture of the liquid ejection head 3a around the roll axis changes, the path after correction is likely to become unstable.

[0172] 3-2. Variation 2 In the third embodiment, the control unit 8 may identify, as the correction range, multiple points on the target print trajectory RU-0 where the first error amount is equal to or greater than a predetermined threshold in step S204B for the first time. In this case, the control unit 8 also corrects the target print trajectory RU-0 at those multiple points in step S205B for the first time. This allows the correction processing time to be shortened by correcting multiple points in the correction range all at once, rather than correcting each point one by one.

[0173] 3-3. Variation 3 In the above-described embodiment, the movement direction of the liquid ejection head 3a when performing a printing operation is the X1 direction when viewed along the Z axis, but this is not limiting. For example, when viewed along the Z axis, the movement direction of the liquid ejection head 3a when performing a printing operation may be the X2 direction, when viewed along the Z axis, the movement direction of the liquid ejection head 3a when performing a printing operation may be a direction perpendicular to the X axis when viewed along the Z axis, or when viewed along the Z axis, the movement direction of the liquid ejection head 3a when performing a printing operation may be a direction inclined to both the X axis and the Y axis when viewed along the Z axis.

[0174] 3-4. Variation 4 In the above-described embodiment, a configuration using a six-axis vertical multi-axis robot is exemplified as the robot, but the configuration is not limited to this. The robot may be, for example, a multi-joint robot other than a six-axis robot. Furthermore, the arm of the robot may have an extension mechanism or a linear motion mechanism in addition to a joint formed by a rotation mechanism. However, from the viewpoint of balancing the print quality during printing operations and the degree of freedom of the robot's operation during non-printing operations, it is preferable that the robot be a multi-axis robot with six or more axes.

[0175] 3-5. Variation 5 In the above-described embodiment, the head is fixed to the robot using screws or the like, but is not limited to this. For example, the head may be fixed to the robot by gripping it with a gripping mechanism such as a hand attached as an end effector of the robot.

[0176] 3-6. Variation 6 In the above-described embodiment, a configuration in which printing is performed using one type of ink is exemplified, but this is not limited to this configuration, and the present disclosure can also be applied to a configuration in which printing is performed using two or more types of ink. Furthermore, the number of nozzle rows is not limited to two, and may be three or more.

[0177] 3-7. Variation 7 In the above-described embodiment, a configuration is exemplified in which the long-period meandering is corrected for the first error amount and then the short-period meandering is corrected, but the present invention is not limited to this configuration. For example, only the short-period meandering may be corrected without correcting the long-period meandering, or the long-period meandering may be corrected after correcting the short-period meandering.

[0178] For example, in the first embodiment, steps S204 to S213 may be performed to correct short-period meandering without correcting long-period meandering for the first error amount acquired in step S203.

[0179] 4. Notes A summary of this disclosure is provided below.

[0180] (Appendix 1) A first aspect, which is a preferred example of a three-dimensional object printing device of the present disclosure, comprises a liquid ejection head that ejects liquid toward a workpiece, an articulated robot having a tip that supports the liquid ejection head and scans the liquid ejection head relative to the workpiece, and a control unit that controls the operation of the liquid ejection head and the articulated robot, wherein the control unit acquires first scanning information regarding a first actual printing trajectory, which is a trajectory that the liquid ejection head will actually scan when the articulated robot is operated based on target path information regarding the target printing trajectory, acquires a first movement amount in a sub-scanning direction that intersects with the scanning direction of the liquid ejection head based on the first scanning information, acquires a first error amount in the sub-scanning direction of the first actual printing trajectory relative to the target printing trajectory based on the target printing trajectory and the first movement amount, identifies a correction range that is a range that is subject to correction for the target printing trajectory, and corrects the target printing trajectory based on the first error amount in the correction range.

[0181] In the above-described aspect, the target print trajectory is corrected based on the first error amount, thereby reducing deviation in the sub-scanning direction of the trajectory actually scanned by the liquid ejection head. As a result, print quality can be favorably improved. Furthermore, by narrowing the correction range, the time required to correct the target print trajectory can be shortened.

[0182] (Supplementary Note 2) In a second aspect, which is a preferred example of the first aspect, the control unit operates the articulated robot based on the target path information to cause the liquid ejection head to scan the workpiece, while ejecting liquid from the liquid ejection head toward the workpiece to form dots on the workpiece, and acquires the first scanning information by measuring the dots. This aspect has the advantage of easily improving the correction accuracy of the target print trajectory because the target print trajectory is corrected based on the results of actual printing using the target path information. Furthermore, it is possible to correct not only errors caused by operational errors of the articulated robot, but also errors in the impact of the liquid on the workpiece caused by operational errors of the liquid ejection head. As a result, print quality can be favorably improved.

[0183] (Supplementary Note 3) In a third aspect, which is a preferred example of the first or second aspect, a detection unit is further provided for detecting movement of the liquid ejection head, and the control unit performs a preparatory operation in which the liquid ejection head scans the workpiece by operating the articulated robot based on the target path information without ejecting liquid from the liquid ejection head, and acquires the first scanning information based on the detection results of the detection unit during the preparatory operation. In the above aspect, the target printing trajectory is corrected based on the results of actual printing using the target path information, which has the advantage of making it easier to improve the accuracy of correction of the target printing trajectory. Furthermore, because liquid is not ejected from the liquid ejection head during the preparatory operation, neither the workpiece nor the liquid is wasted.

[0184] (Supplementary Note 4) In a fourth aspect, which is a preferred example of any of the first to third aspects, the control unit further includes an attitude detection unit that detects changes in the attitude of the liquid ejection head, and the control unit adjusts the correction amount of the target printing trajectory based on the detection result of the attitude detection unit when the articulated robot is operated based on the target path information. In the above aspect, even if the attitude of the liquid ejection head around the roll axis changes due to the shape of the workpiece, etc., the correction amount can be adjusted in response to the change. As a result, the liquid ejection head can be moved more stably. However, if the correction amount of the target printing trajectory is not adjusted when the attitude of the liquid ejection head around the roll axis changes, the path after correction is likely to become unstable.

[0185] (Supplementary Note 5) In a fifth aspect, which is a preferred example of any of the first to fourth aspects, the control unit identifies a correction period as the correction range, which is a period during which the first movement amount exceeds a predetermined threshold, and corrects the target print trajectory during the correction period. In the above aspect, by identifying the correction period, it is possible to suppress an increase in the amount of error associated with correction. As a result, it is possible to improve the correction accuracy of the target print trajectory. Furthermore, by correcting the identified period rather than the entire period from the start point to the end point of the correction range, it is possible to shorten the correction processing time.

[0186] (Supplementary Note 6) In the sixth aspect, which is a preferred example of the fifth aspect, the control unit acquires second scanning information regarding a second actual printing trajectory, which is a trajectory actually scanned by the liquid ejection head when the articulated robot is operated based on tentative path information regarding a trajectory obtained by correcting the target printing trajectory, acquires a second movement amount of the liquid ejection head in the sub-scanning direction based on the second scanning information, acquires a second error amount of the second actual printing trajectory in the sub-scanning direction relative to the target printing trajectory based on the target printing trajectory and the second movement amount, and if the second error amount is equal to or greater than a threshold, adjusts the correction amount to correct the target printing trajectory during the correction period. This aspect can improve the effectiveness of the correction of the target printing trajectory.

[0187] (Supplementary Note 7) In the seventh aspect, which is a preferred example of the sixth aspect, the control unit advances the timing of the correction during the correction period when the second error amount is equal to or greater than the threshold value. This aspect prevents delays in the correction during the correction period due to acceleration during movement of the liquid ejection head. As a result, the effectiveness of the correction of the target print trajectory can be improved.

[0188] (Appendix 8) In the eighth aspect, which is a preferred example of any of the first to fourth aspects, the control unit identifies, as the correction range, a point on the target print trajectory where the first error amount is equal to or greater than a predetermined threshold, and corrects the target print trajectory at that point. In the above aspect, an increase in the amount of error due to correction can be suppressed. As a result, the correction accuracy of the target print trajectory can be improved. Furthermore, since performing correction at a point showing a specific peak may result in the amount of error at a subsequent point becoming within the acceptable range, the correction process can be simplified by performing correction at a specific point rather than for the entire period from the start point to the end point of the correction range.

[0189] (Supplementary Note 9) In the ninth aspect, which is a preferred example of the eighth aspect, the control unit acquires second scanning information regarding a second actual printing trajectory, which is a trajectory actually scanned by the liquid ejection head when the articulated robot is operated based on tentative path information regarding a trajectory obtained by correcting the target printing trajectory, acquires a second movement amount of the liquid ejection head in the sub-scanning direction based on the second scanning information, acquires a second error amount of the second actual printing trajectory in the sub-scanning direction relative to the target printing trajectory based on the target printing trajectory and the second movement amount, and if the second error amount is equal to or greater than a threshold, adjusts the correction amount and then corrects the target printing trajectory at the point. This aspect can improve the effectiveness of correcting the target printing trajectory.

[0190] (Supplementary Note 10) In a tenth aspect, which is a preferred example of any of the first to fourth aspects, the control unit identifies, as the correction range, multiple points on the target print trajectory where the first error amount is equal to or greater than a predetermined threshold, and corrects the target print trajectory at the multiple points. In the above aspect, by correcting multiple points in the correction range collectively rather than correcting each point in the correction range one by one, the correction processing time can be shortened.

[0191] (Appendix 11) An eleventh aspect, which is a preferred example of the control method of the present disclosure, is a control method for a three-dimensional object printing device including a liquid ejection head that ejects liquid toward a workpiece, and an articulated robot having a tip that supports the liquid ejection head and scans the liquid ejection head relative to the workpiece, the control method including the steps of: acquiring first scanning information regarding a first actual printing trajectory, which is a trajectory that the liquid ejection head will actually scan when the articulated robot is operated based on target path information regarding a target printing trajectory; acquiring a first movement amount in a sub-scanning direction that intersects with the scanning direction of the liquid ejection head based on the first scanning information; acquiring a first error amount in the sub-scanning direction of the first actual printing trajectory relative to the target printing trajectory based on the target printing trajectory and the first movement amount; identifying a correction range that is a range that is subject to correction for the target printing trajectory; and correcting the target printing trajectory based on the first error amount in the correction range.

[0192] In the above-described aspect, the target print trajectory is corrected based on the first error amount, thereby reducing deviation in the sub-scanning direction of the trajectory actually scanned by the liquid ejection head. As a result, print quality can be favorably improved. Furthermore, by narrowing the correction range, the time required to correct the target print trajectory can be shortened. [Explanation of symbols]

[0193] 1...three-dimensional object printing device, 1A...three-dimensional object printing device, 2...robot, 2a...arm drive mechanism, 3...head unit, 3A...head unit, 3a...liquid ejection head, 3c...detection unit, 3e...switch circuit, 3f...support, 5...controller, 5a...memory circuit, 5b...processing circuit, 6...control module, 6a...timing signal generation circuit, 6b...power supply circuit, 6c...control circuit, 6d...drive signal generation circuit, 7...computer, 7a...memory circuit, 7b...processing circuit, 8...control unit, 9...camera, 210...base, 220...arm, 221...arm, 222...arm, 223...arm, 224...arm, 225...arm, 226...arm, CLK...clock signal, CNG...change signal, Com...drive signal, D1...output, D2...signal, D3...signal, DE...ejection direction, DM...main scanning direction, DN...nozzle row direction, DS...sub-scanning direction, Da...path information, Da0...target path information, Da1...tentative path information, Da2...corrected path information, Db1...first scanning information, Db2...second scanning information, Dc...work information, Dt...timing information, E...tip, FN...nozzle surface, Img...printing data, J...joint, J1...joint, J2...joint, J3...joint, J4...joint, J5...joint, J6...joint, LAT...latch signal, M...dot, N...nozzle, NL...nozzle row, NL1...first nozzle row, NL2...second nozzle row, O1...rotation axis, O2...rotation axis, O3...rotation axis, O4...rotation axis, O5...rotation axis, O6...rotation axis, PD...drive pulse, PE...position, PR1...program, PR2...program, PS...position, PT...detected pattern, PTS...timing signal, RU...print path, RU-0...target print trajectory, RU-1...first actual print trajectory, RU-2...second actual print trajectory, S100...step, S200...step, S201...step, S202...step, S 203...step, S204...step, S204A...step, S204B...step, S205...step, S205A...step, S205B...step, S206...step, S207...step, S208...step, S209...step, S211...step, S211A...step, S211B...step, S212...step, S213...step, S213A...step, S300...step, SI...control signal, Sk1...control signal, T...period, TCP...tool center point, VBS...offset potential, VHV...power supply potential, W...workpiece,WF…surface, dCom…waveform specified signal, t…period.

Claims

1. a liquid ejection head that ejects liquid toward the workpiece; an articulated robot having a tip portion that supports the liquid ejection head and that scans the liquid ejection head over the workpiece; a control unit that controls the operation of the liquid ejection head and the articulated robot, The control unit acquiring first scanning information relating to a first actual printing trajectory, which is a trajectory along which the liquid ejection head is actually scanned when the articulated robot is operated based on target path information relating to the target printing trajectory; acquiring a first movement amount in a sub-scanning direction intersecting with a main scanning direction of the liquid ejection head based on the first scanning information; obtaining a first error amount in the sub-scanning direction of the first actual print trajectory relative to the target print trajectory based on the target print trajectory and the first movement amount; Identifying a correction range that is a range to be corrected for the target print trajectory; correcting the target print trajectory based on the first error amount within the correction range; A three-dimensional object printing device characterized by the above.

2. The control unit an operation of forming dots on the workpiece by discharging liquid from the liquid discharge head toward the workpiece while scanning the workpiece with the liquid discharge head by operating the articulated robot based on the target path information; obtaining the first scan information by measuring the dots; The three-dimensional object printing device according to claim 1 .

3. a detection unit that detects movement of the liquid ejection head; The control unit performing a preliminary operation of scanning the liquid ejection head over the workpiece by operating the articulated robot based on the target path information without ejecting liquid from the liquid ejection head; acquiring the first scanning information based on a detection result of the detection unit during execution of the preparatory movement; The three-dimensional object printing device according to claim 1 .

4. a posture detection unit that detects a change in posture of the liquid ejection head; The control unit adjusting a correction amount of the target printing trajectory based on a detection result of the posture detection unit when the articulated robot is operated based on the target path information; The three-dimensional object printing device according to claim 1 .

5. The control unit specifying a correction period as the correction range, the period during which the first movement amount exceeds a predetermined threshold; correcting the target print trajectory during the correction period; The three-dimensional object printing device according to claim 1 .

6. The control unit acquiring second scanning information relating to a second actual printing trajectory, which is a trajectory along which the liquid ejection head is actually scanned when the articulated robot is operated based on tentative path information relating to a trajectory obtained by correcting the target printing trajectory; acquiring a second movement amount of the liquid ejection head in the sub-scanning direction based on the second scanning information; obtaining a second error amount in the sub-scanning direction of the second actual print trajectory relative to the target print trajectory based on the target print trajectory and the second movement amount; If the second error amount is equal to or greater than a threshold value, the correction amount is adjusted to correct the target print trajectory during the correction period. The three-dimensional object printing device according to claim 5 .

7. The control unit When the second error amount is equal to or greater than the threshold value, the timing of performing the correction during the correction period is advanced. The three-dimensional object printing device according to claim 6.

8. The control unit a point on the target print trajectory where the first error amount is equal to or greater than a predetermined threshold is identified as the correction range; correcting the target print trajectory at the point; The three-dimensional object printing device according to claim 1 .

9. The control unit acquiring second scanning information relating to a second actual printing trajectory, which is a trajectory along which the liquid ejection head is actually scanned when the articulated robot is operated based on tentative path information relating to a trajectory obtained by correcting the target printing trajectory; acquiring a second movement amount of the liquid ejection head in the sub-scanning direction based on the second scanning information; obtaining a second error amount in the sub-scanning direction of the second actual print trajectory relative to the target print trajectory based on the target print trajectory and the second movement amount; If the second error amount is equal to or greater than a threshold value, the target print trajectory at the point is corrected after adjusting the correction amount. The three-dimensional object printing device according to claim 8.

10. The control unit Identifying a plurality of points on the target print trajectory where the first error amount is equal to or greater than a predetermined threshold as the correction range; correcting the target print trajectory at the plurality of points; The three-dimensional object printing device according to claim 1 .

11. a liquid ejection head that ejects liquid toward the workpiece; a multi-joint robot having a tip portion that supports the liquid ejection head and that scans the liquid ejection head over the workpiece, acquiring first scanning information relating to a first actual printing trajectory, which is a trajectory along which the liquid ejection head is actually scanned when the articulated robot is operated based on target path information relating to a target printing trajectory; acquiring a first movement amount in a sub-scanning direction intersecting with a main scanning direction of the liquid ejection head based on the first scanning information; acquiring a first error amount in the sub-scanning direction of the first actual print trajectory relative to the target print trajectory based on the target print trajectory and the first movement amount; a step of identifying a correction range that is a range to be corrected with respect to the target print trajectory; correcting the target print trajectory based on the first error amount within the correction range; A control method comprising:

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