Three-dimensional object printer and path generation method

Abstract

To improve printing quality while suppressing collision between a liquid discharge head and a workpiece even when a surface to be printed of the workpiece has unevenness.SOLUTION: A three-dimensional object printer includes: a liquid discharge head including a plurality of nozzles that discharge liquid toward a workpiece; a multi-joint robot that has a distal end portion supporting the liquid discharge head and causes the liquid discharge head to scan the workpiece; and a control part that controls operation of the liquid discharge head and the multi-joint robot. The control part generates smoothing data by performing smoothing processing on workpiece data indicating a shape of a printing surface being a surface to be printed of the workpiece, and creates a printing path on the basis of the smoothing data.SELECTED DRAWING: Figure 8

Description

[Technical Field]

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

[0002] Conventionally, a known three-dimensional printing device that uses an inkjet method is configured to use an articulated robot to scan a liquid ejection head over a workpiece while ejecting a liquid such as ink from the liquid ejection head toward the workpiece. In this configuration, it is necessary to generate a path for scanning the liquid ejection head over the workpiece in order to control the operation of the articulated robot.

[0003] For example, Patent Document 1 describes a method of generating a movement path of a head relative to a workpiece based on an intersection line between the surface of the workpiece and a virtual plane in a virtual space, using data indicating the shape of the workpiece. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-031611 Summary of the Invention [Problem to be solved by the invention]

[0005] To ensure print quality in a three-dimensional object printing device, it is preferable to shorten the distance between the head and the workpiece as much as possible. In this regard, as described in Patent Document 1, it is preferable to move the head so that it closely follows the shape of the workpiece's surface. However, in the method described in Patent Document 1, if the surface of the workpiece to be printed has an uneven surface, shortening the distance between the head and the workpiece may result in a collision between the head and the workpiece. Furthermore, in the method described in Patent Document 1, if the distance between the head and the workpiece is increased to avoid a collision between the head and the workpiece, the overall distance increases, resulting in a problem of reduced print quality. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the three-dimensional object printing device disclosed herein comprises a liquid ejection head having multiple nozzles that eject liquid toward a workpiece, an articulated robot having a tip that supports the liquid ejection head and scans the liquid ejection head over the workpiece, and a control unit that creates a printing path for scanning the liquid ejection head, wherein the control unit generates smoothed data by performing a smoothing process on workpiece data that indicates the shape of the printing surface, which is the surface of the workpiece that is to be printed, and creates the printing path based on the smoothed data.

[0007] One aspect of the path generation method disclosed herein is a path generation method for creating a printing path, which is the movement path of the liquid ejection head during printing using a three-dimensional printing device that includes a liquid ejection head having multiple nozzles that eject liquid toward a workpiece, and an articulated robot that has a tip that supports the liquid ejection head and scans the liquid ejection head against the workpiece, the method including: generating smoothed data by performing a smoothing process on work data that indicates the shape of the printing surface, which is the surface of the workpiece that is to be printed; and creating a printing path based on the smoothed data, wherein in the smoothing data generation process, the printing surface is divided into predetermined areas and the smoothing process is performed. [Brief explanation of the drawings]

[0008] [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. [Figure 4] FIG. 3 is a diagram showing the flow of a route generation method according to the first embodiment. [Figure 5] FIG. 10 is a diagram showing an example of a shape indicated by workpiece data. [Figure 6] FIG. 10 is a diagram for explaining generation of a tentative route. [Figure 7] FIG. 10 is a diagram for explaining the relationship between a tentative route and a workpiece. [Figure 8] FIG. 4 is a diagram showing a flow of generating a print path in the first embodiment. [Figure 9] FIG. 10 is a diagram for explaining points at which smoothing is performed. [Figure 10] FIG. 10 is a diagram for explaining the relationship between points where smoothing is performed and areas where smoothing is performed. [Figure 11] 10A and 10B are diagrams for explaining the relationship between a region to be smoothed and a head unit. [Figure 12] FIG. 10 is a diagram for explaining a region to be smoothed; [Figure 13] FIG. 10 is a diagram for explaining smoothing. [Figure 14] FIG. 10 is a diagram for explaining a route based on smoothed data. [Figure 15] FIG. 10 is a diagram showing the flow of generating a curing path. [Figure 16] FIG. 2 is a diagram illustrating a curing path. [Figure 17] FIG. 2 is a diagram illustrating a printing path. [Figure 18] FIG. 2 is a diagram for explaining a first distance, a second distance, a third distance, and a fourth distance. [Figure 19] FIG. 10 is a diagram showing a flow of collision determination. [Figure 20] FIG. 4 is a diagram showing a flow of generating print data. [Figure 21] 3A and 3B are diagrams for explaining the correspondence between image data and print data; [Figure 22] FIG. 10 is a diagram showing a flow of generating a print path in the second embodiment. [Figure 23] 10 is a diagram showing a flow of generating a curing path in Modification 1. FIG. [Figure 24] FIG. 10 is a diagram for explaining a printing path in Modification 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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°.

[0013] 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.

[0014] The workpiece W has a printing surface WF, which is the surface to be printed. In the example shown in FIG. 1, the workpiece W is a face mask in the shape of a human face, and the printing surface WF has irregularities that conform to the shape of the human face. During printing, the workpiece W is supported as needed by, for example, a predetermined installation table, the hand of a robot other than the robot 2 described below, or a structure such as a conveyor. The size, shape, or installation posture of the workpiece W is not limited to the example shown in FIG. 1 and is arbitrary. However, when the printing surface WF has irregularities, the effects of the present disclosure described below become more pronounced.

[0015] 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, and a controller 5. These will be briefly described below in order, first with reference to Fig. 1.

[0016] The robot 2 is an articulated robot that has a tip E that supports the head unit 3 and scans the liquid ejection head 3a relative to the workpiece W in the world coordinate system. In the example shown in Fig. 1, the robot 2 is a so-called six-axis vertical articulated robot.

[0017] As shown in FIG. 1, the robot 2 has a base 210 and an arm 220 .

[0018] 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.

[0019] 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, also called links, which are connected in this order.

[0020] 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, and has a tip E.

[0021] 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, the joints J1 to J6 may be referred to as "joint J" without distinction.

[0022] 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.

[0023] The rotation axis O1 is an axis perpendicular to an installation surface (not shown) to which the base 210 is fixed. The rotation axis O2 is an axis perpendicular to the rotation axis O1. The rotation axis O3 is an axis parallel to the rotation axis O2. The rotation axis O4 is an axis perpendicular to the rotation axis O3. The rotation axis O5 is an axis perpendicular to the rotation axis O4. The rotation axis O6 is an axis perpendicular to the rotation axis O5.

[0024] Regarding these rotation axes, "perpendicular" refers not only to the case where the angle between the two rotation axes is exactly 90°, but also to the case where the angle between the two rotation axes is deviated from 90° within a range of about ±5°. Similarly, "parallel" refers not only to the case where the two rotation axes are strictly parallel, but also to the case where one of the two rotation axes is inclined relative to the other within a range of about ±5°.

[0025] A head unit 3 is attached as an end effector to the tip E of the robot 2 in a state fixed by screws or the like.

[0026] The head unit 3 is an assembly having a liquid ejection head 3a with a plurality of nozzles N that eject ink, which is an example of a "liquid," toward the workpiece W. In this embodiment, the head unit 3 has a curing section 3c in addition to the liquid ejection head 3a. Details of the head unit 3 will be described later with reference to FIG. 3.

[0027] The ink is not particularly limited, and examples thereof include water-based inks in which a coloring material such as a dye or pigment is dissolved in an aqueous solvent, curable inks using curable resins such as UV-curable inks, and solvent-based inks in which a coloring material such as a dye or pigment is dissolved in an organic solvent. Among these, curable inks are preferred. The curable ink is not particularly limited, and may be, for example, a heat-curable ink, a photocurable ink, a radiation-curable ink, or an electron beam-curable ink. Photocurable inks such as UV-curable inks are preferred. The ink is not limited to a solution, but may also be an ink in which a coloring material or the like is dispersed as a dispersoid in a dispersion medium. The ink is also not limited to an ink containing a coloring material, and may also be, for example, an ink containing conductive particles such as metal particles as a dispersoid for forming wiring, a clear ink, or a treatment liquid for surface treatment of the workpiece W.

[0028] 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.

[0029] 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 includes a control unit 8 in addition to the components shown in FIG. 1. The control unit 8 controls the operation of the liquid ejection head 3a and the robot 2. The control unit 8 also has the function of generating printing path information Da (described below) and generates a printing path RU. In the example shown in FIG. 2, the control unit 8 includes a controller 5, a control module 6 communicatively connected to the controller 5, and a computer 7 communicatively connected to the controller 5 and the control module 6. Each component of the control unit 8 will be described below with reference to FIG. 2.

[0030] 2 may be appropriately divided, 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. Furthermore, the computer 7 may be a server or the like communicatively connected to the controller 5 and control module 6 via a network such as a LAN or the Internet.

[0031] 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.

[0032] The controller 5 includes a memory circuit 5a and a processing circuit 5b.

[0033] The storage circuit 5a stores various programs executed by the processing circuit 5b and various data processed by the processing circuit 5b. The storage circuit 5a includes, for example, one or both of semiconductor memories: a volatile memory such as a random access memory (RAM) and a nonvolatile memory such as a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), or a programmable read-only memory (PROM). Note that part or all of the storage circuit 5a may be included in the processing circuit 5b.

[0034] The memory circuit 5a stores print path information Da.

[0035] The printing path information Da is used to control the operation of the robot 2 and indicates the position and orientation of the liquid ejection head 3a along a printing path RU (described below), which is the path along which the liquid ejection head 3a should move during printing operations. The printing path information Da includes information indicating changes in the relative position of the liquid ejection head 3a with respect to the workpiece W during printing operations, and information indicating changes in the relative orientation of the liquid ejection head 3a with respect to the workpiece W during printing operations. The position and orientation of the liquid ejection head 3a are based on a tool center point TCP (described below). The tool center point TCP is a virtual point whose positional relationship with the liquid ejection head 3a is fixed. Therefore, the printing path information Da can be said to include position information indicating the position of the tool center point TCP and orientation information indicating the orientation of the tool center point TCP. In this embodiment, the tool center point TCP is located a predetermined distance from the liquid ejection head 3a. As will be described in detail later, in this embodiment, the liquid ejection head 3a passes through a path that is a predetermined distance away from the printing path RU indicated by the printing path information Da during actual printing operations. The printing path information Da is expressed using, for example, coordinate values ​​in a work coordinate system, a base coordinate system, or a world coordinate system based on the position of the workpiece W. The printing path information Da is generated by the processing circuit 7b and input from the processing circuit 7b to the memory circuit 5a. Note that when the printing path information Da is expressed using coordinate values ​​in the work coordinate system, it is used to control the operation of the robot 2 after being converted from the coordinate values ​​in the work coordinate system to coordinate values ​​in the base coordinate system or the world coordinate system.

[0036] The processing circuit 5b controls the operation of the arm drive mechanism 2a of the robot 2 based on the print path information Da and generates a signal D3. The processing circuit 5b includes, for example, one or more processors such as a CPU (Central Processing Unit). Note that the processing circuit 5b may include a programmable logic device such as an FPGA (Field-Programmable Gate Array) instead of or in addition to a CPU.

[0037] 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.

[0038] The processing circuit 5b performs inverse kinematics calculations, which are calculations that convert the print 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 drive 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 print path information Da. The control signal Sk1 is a signal for controlling the drive of the motor of the arm drive 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).

[0039] Furthermore, the processing circuit 5b generates a signal D3 based on an output D1 from at least one of the multiple encoders included in the arm driving 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.

[0040] 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 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.

[0041] The timing signal generating circuit 6a generates a timing signal PTS based on the signal D3. The timing signal generating circuit 6a is configured, for example, with a timer that starts generating the timing signal PTS when the signal D3 is detected.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] The control circuit 6c described above includes, for example, one or more processors such as CPUs, etc. Note that the control circuit 6c may include a programmable logic device such as an FPGA instead of or in addition to a CPU.

[0046] 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.

[0047] 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.

[0048] The computer 7 has a function to generate printing path information Da, a function to supply information such as the printing path information Da to the controller 5, and a function to supply information such as print data Img to the control module 6. In addition to these functions, the computer 7 of this embodiment also has a function to control the driving of the curing unit 3c.

[0049] The computer 7 has a memory circuit 7a and a processing circuit 7b. In addition, although not shown, the computer 7 has an input device such as a keyboard or mouse for accepting operations from a user. The computer 7 may also have a display device such as a liquid crystal panel for displaying information necessary for generating the print path information Da.

[0050] 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.

[0051] The storage circuit 7a stores print path information Da, tentative path information Db, work data Dc, image data Dd, smoothed data De, print data Img, and program PR.

[0052] The tentative path information Db is used to generate the print path information Da and indicates the position and orientation of the liquid ejection head 3a along multiple tentative paths used as a reference for creating a print path RU (described later) in a virtual space VS, which is a virtual space simulating real space. The tentative path information Db includes information indicating changes in the relative position of the liquid ejection head 3a with respect to the workpiece W and information indicating changes in the relative orientation of the liquid ejection head 3a with respect to the workpiece W. The tentative path information Db can also be said to include a position information component indicating the position of the tool center point TCP and an orientation information component indicating the orientation of the tool center point TCP. The tentative path information Db is expressed using coordinate values ​​in, for example, a workpiece coordinate system, a base coordinate system, or a world coordinate system. The tentative path information Db is generated by the processing circuitry 7b and input from the processing circuitry 7b to the memory circuitry 5a. At least one of the multiple tentative paths indicated by the tentative path information Db is selected as a reference for creating the print path RU indicated by the print path information Da.

[0053] The workpiece data Dc is data that represents the shape of at least a portion of the workpiece W. Specifically, the workpiece data Dc is, for example, three-dimensional data in a format such as STL (Standard Triangulated Language) that represents the shape of the workpiece W using multiple polygons, and 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 workpiece data Dc is obtained by converting CAD (computer-aided design) data that represents the three-dimensional shape of the workpiece W as needed. The workpiece data Dc may be represented using coordinate values ​​in a workpiece coordinate system, or may be represented by point cloud data that uses coordinate values ​​in a base coordinate system or a world coordinate system. The workpiece data Dc may also be represented by mathematical formulas, etc., and the format of the workpiece data Dc may be appropriately converted as needed.

[0054] The image data Dd is three-dimensional image information that represents an ideal print image to be printed on the printing surface WF of the workpiece W. The image data Dd represents an image of a three-dimensional shape that conforms to the printing surface WF, and includes, for example, color data or gradation data for each pixel at a position corresponding to the shape of the printing surface WF. The image data Dd is obtained by applying two-dimensional image data as a texture to the three-dimensional printing surface WF of the workpiece W. The image data Dd is expressed using coordinate values ​​in, for example, a work coordinate system, a base coordinate system, or a world coordinate system. Note that the image data Dd may be included in the workpiece data Dc.

[0055] The smoothed data De is data representing the shape of the workpiece W after smoothing, and is obtained by smoothing the workpiece data Dc. The smoothing process is a process for reducing the depth of recesses in the area to be processed. Specific smoothing processes are not particularly limited, but include, for example, convex hull processing, alpha shape processing, and alpha wrapping processing.

[0056] Among these, convex hull processing is preferred. Convex hull processing is a process using a mathematical convex hull. Specifically, convex hull processing uses points on polygon data as a point cloud to identify the smallest polyhedron that contains all points in the target area, and considers the faces of the identified polyhedron as the surface of the workpiece W. As a result, points located within the polyhedron and in the recesses of the target area are no longer considered, resulting in a shape with smoothed recesses. Convex hull processing is easy to use and has the advantage of excellent reproducibility of the shape represented by the workpiece data Dc, since the positions of the vertices of the convex parts of the target area do not change before and after the smoothing process. Furthermore, convex hull processing can simplify the shape of the workpiece W, thereby speeding up processing. The smoothed data De may be expressed using coordinate values ​​in the workpiece coordinate system, or may be expressed as point cloud data using coordinate values ​​in the base coordinate system or world coordinate system. The smoothed data De may also be expressed using mathematical formulas, and the format of the smoothed data De may be appropriately converted as needed.

[0057] The print data Img is information indicating an image to be printed on the workpiece W for each path (pass) of the print path indicated by the print path information Da. When an image indicated by the image data Dd is divided and printed over multiple passes, the print data Img indicates multiple images obtained by distributing the image indicated by the image data Dd to the multiple print paths indicated by the print path information Da.

[0058] The program PR is a program for generating the print path information Da.

[0059] The processing circuit 7b realizes the above-mentioned functions by executing a program such as the program PR. The processing circuit 7b includes, for example, one or more processors such as CPUs. Note that the processing circuit 7b may include a programmable logic device such as an FPGA instead of or in addition to a CPU.

[0060] By executing the program PR, the processing circuit 7b realizes various functions for a path generation method described below, including generating print path information Da, etc. Details of the path generation method will be described later with reference to Figures 4 to 20.

[0061] As described above, the driving of the robot 2 is controlled based on the print path information Da, and the driving of the liquid ejection head 3a is controlled based on the print data Img and signal D3, thereby performing a printing operation. During the printing operation, the robot 2 changes the position and posture of the liquid ejection head 3a based on the print path information Da, and causes the liquid ejection head 3a to eject ink from the liquid ejection head 3a toward the workpiece W at appropriate timing based on the print data Img and signal D3. This forms an image on the workpiece W based on the print data Img.

[0062] In this way, the control unit 8 controls the operations of the liquid ejection head 3a and the robot 2, thereby executing a printing operation for printing on the workpiece W.

[0063] 1-3.Head unit configuration FIG. 3 is a perspective view showing a schematic configuration of the head unit 3. 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.

[0064] 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.

[0065] 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 this embodiment, as shown in FIG. 3, the tool center point TCP is located in a space spaced a predetermined distance in the ink ejection direction DE from the center of the nozzle row NL in the b-axis direction of the liquid ejection head 3a. 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, the center CP of the nozzle surface FN.

[0066] As described above, the head unit 3 has a liquid ejection head 3a and a curing unit 3c. These are 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 that shown in FIG. 3 and may be two or more. In addition to the liquid ejection head 3a and the curing unit 3c, the head unit 3 may have, for example, a pressure adjustment valve that adjusts the pressure of the ink in the liquid ejection head 3a, or a sensor that measures physical quantities related to the head unit 3.

[0067] The support 3f is made of, for example, a metal material, etc., and is substantially rigid. Although the support 3f is shown in Fig. 3 as having a flat box shape, the shape of the support 3f is not particularly limited and may be any shape.

[0068] The support 3f is attached to the arm 226. Therefore, the liquid ejection head 3a and the curing portion 3c are collectively supported on the arm 226 by the support 3f. This fixes the relative positions of the liquid ejection head 3a and the curing portion 3c with respect to the arm 226. In the example shown in Fig. 3, the curing portion 3c is positioned in the a2 direction with respect to the liquid ejection head 3a.

[0069] The liquid ejection head 3a has a nozzle surface FN and multiple nozzles N opening on the nozzle surface FN. The nozzle surface FN is the surface where the nozzles N open, and is made of, for example, silicon (Si) or metal, or, if another component is arranged as a component of the head unit 3 on a plane extending from the nozzle surface, the surface is formed by the nozzle plate surface and the surface of the other component. Here, the nozzle plate is a plate-like component made of silicon, metal, or the like, on which multiple nozzles N are formed. Examples of such other components include a fixing plate and a cover head. The fixing plate is a component provided around the nozzle plate for purposes such as fixing or protecting the nozzle plate. The cover head is a component provided for purposes such as protecting the liquid ejection head 3a, and has a portion disposed around the nozzle plate. Note that the fixing plate and cover head may not be provided depending on the configuration of the liquid ejection head 3a. Furthermore, the surfaces of the fixing plate and cover head may differ from the surface of the nozzle plate by up to approximately 0.8 mm in position along the c-axis. 3, the nozzle surface FN is composed of only the plate surface of one nozzle plate, but it may also have multiple nozzle plates, in which case the nozzle surface FN is defined as a surface that encompasses the multiple nozzle plates. Also, in the example shown in Fig. 3, the normal direction of the nozzle surface FN, i.e., the ink ejection direction DE from the nozzles N, is direction c2. Strictly speaking, the ejection direction DE and direction c2 may not be parallel due to the influence of inertia or air currents caused by the operation of the robot 2, but this embodiment does not take such errors into account.

[0070] The plurality of nozzles N are divided into a first nozzle row NL1 and a second nozzle row NL2 that 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 that are linearly arranged in the nozzle row direction DN, which is the direction along the b-axis. Here, in the liquid ejection head 3a, 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 are configured to be approximately symmetrical to each other in the direction along the a-axis.

[0071] However, the positions of the multiple nozzles N in the first nozzle row NL1 and the multiple nozzles N in the second nozzle row NL2 in the direction along the b-axis may or may not match. Also, elements related to each nozzle N in one of the first nozzle row NL1 and the second nozzle row NL2 may be omitted. Below, a configuration in which the positions of the multiple nozzles N in the first nozzle row NL1 and the multiple nozzles N in the second nozzle row NL2 in the direction along the b-axis match will be exemplified.

[0072] In the following description, the first nozzle row NL1 and the second nozzle row NL2 may be collectively referred to as the nozzle row NL. The nozzle row NL includes the first nozzle row NL1 and the second nozzle row NL2.

[0073] 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 ejects ink in an ejection direction DE from the nozzle corresponding to the cavity by changing the pressure in the cavity corresponding to the piezoelectric element. 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.

[0074] The curing section 3c is disposed behind the liquid ejection head 3a in the scanning direction in which the liquid ejection head 3a scans the workpiece W, and cures the ink ejected onto the workpiece W from the liquid ejection head 3a.

[0075] The curing unit 3c emits energy such as light, heat, electron beams, or radiation to harden or solidify the ink on the workpiece W. For example, if the ink is ultraviolet-curable, the curing unit 3c is composed of a light-emitting element such as an LED (light emitting diode) that emits ultraviolet light. The curing unit 3c may also include optical components such as lenses for adjusting the energy emission direction or emission range, as appropriate.

[0076] 1-4. Route generation method FIG. 4 is a diagram showing the flow of the path generation method according to the first embodiment. As shown in FIG. 4, the path generation method includes steps S100, S200, S300, S400, and S500, in this order, and creates a printing path RU, which is the path along which the liquid ejection head 3a moves during printing using the three-dimensional object printing apparatus 1. In this embodiment, these steps are executed by the control unit 8, or more specifically, the processing circuit 7b of the computer 7. An outline of each step will be described below.

[0077] In step S100, workpiece data Dc and image data Dd are acquired. The acquisition of the workpiece data Dc is not particularly limited, but may be performed, for example, by appropriately converting CAD data of the workpiece W, by reading existing shape data from another device, or by measuring the shape of the workpiece W using a camera or the like capable of measuring three-dimensional shapes. The acquisition of the image data Dd is not particularly limited, but may be performed, for example, by reading existing image data from another device, or by applying two-dimensional image data as a texture to the three-dimensional shape indicated by the workpiece data Dc. Specific examples of the workpiece data Dc will be described later with reference to FIG. 5.

[0078] In step S200, a plurality of tentative routes LM, which will be described later, are created. The plurality of tentative routes LM are created, for example, using a printing route creation method described in Japanese Patent Application Laid-Open No. 2023-31611. This creates tentative route information Db indicating the plurality of tentative routes LM, which will be described later. Specific examples of the plurality of tentative routes LM indicated by the tentative route information Db will be described later with reference to FIGS. 6 and 7.

[0079] Step S300 creates a print route RU, which will be described later. Details of creating a print route RU will be explained later with reference to FIGS.

[0080] In step S400, print data Img is created. Details of how print data Img is created will be explained later with reference to FIGS.

[0081] In step S500, the print route RU is stored as print route information Da.

[0082] Each step of the route generation method of this embodiment will be described in detail below.

[0083] Fig. 5 is a diagram showing an example of a shape indicated by the workpiece data Dc. Fig. 5 illustrates an example in which the shape indicated by the workpiece data Dc is a human face shape, and the workpiece data Dc is polygon data.

[0084] FIG. 5 shows a workpiece W in a virtual space VS. A coordinate system is established in the virtual space VS, with mutually intersecting x-, y-, and z-axes as its coordinate axes. Here, the x-, y-, and z-axes correspond to the coordinate axes of the workpiece coordinate system and are appropriately associated with the world coordinate system or the robot coordinate system by calibration or the like. Specifically, the x-axis corresponds to the X-axis, one direction along the x-axis is the x1 direction, and the direction opposite to the x1 direction is the x2 direction. The y-axis corresponds to the Y-axis, and the opposite directions along the y-axis are the y1 and y2 directions. The z-axis corresponds to the Z-axis, and the opposite directions along the z-axis are the z1 and z2 directions. The x-, y-, and z-axes are typically perpendicular to each other, but are not limited thereto and may intersect at an angle between 80° and 100°.

[0085] The workpiece data Dc acquired in step S100 is represented by a plurality of polygons, as shown in Fig. 5, for example. In the example shown in Fig. 5, the shape indicated by the workpiece data Dc is a human face shape, and therefore the printing surface WF has a concave-convex shape corresponding to the human face shape. The concave-convex shape includes convex portions C1 and concave portions C2 and C3, which will be described later. Here, the front direction of the human face indicated by the workpiece data Dc is the z1 direction, the left-right direction of the human face is the direction along the x-axis, and the up-down direction of the human face is the direction along the y-axis.

[0086] Fig. 6 is a diagram for explaining the generation of the tentative route LM. Fig. 7 is a diagram for explaining the relationship between the tentative route LM and the workpiece W. Note that Figs. 6 and 7 show the workpiece W and the tentative route LM in the virtual space VS.

[0087] In step S200, as shown by the two-dot chain line in FIG. 6, multiple tentative routes LM are created in the virtual space VS, indicating changes in the relative positions of the workpiece W and the liquid ejection head 3a. In the example shown in FIG. 6, when viewed in the direction along the z-axis, multiple tentative routes LM along the x-axis are arranged in the direction along the y-axis. Here, each tentative route LM extends in the left-right direction of the face represented by the workpiece data Dc. Note that the extension direction of the tentative routes LM is not limited to the example shown in FIG. 6 and may, for example, be the up-down direction of the face represented by the workpiece data Dc, or may be inclined relative to the left-right or up-down direction of the face represented by the workpiece data Dc. Furthermore, the number of tentative routes LM and the size of the intervals between the multiple tentative routes LM are not limited to the example shown in FIG. 6 and are arbitrary.

[0088] Each tentative path LM is located on the same virtual plane throughout the entire area. In the example shown in FIG. 6, each tentative path LM is located on a virtual plane perpendicular to the y-axis throughout the entire area. Also, as shown in FIG. 7, each tentative path LM is located on the printing surface WF. In FIG. 7, of the multiple tentative paths LM shown in FIG. 6, a tentative path LM that passes near the tip of the nose of the human face shape on the printing surface WF is shown together with a cross section of the workpiece W. In this cross section, the printing surface WF has a convex portion C1 due to the nose and concave portions C2 and C3 provided on both sides of the convex portion C1.

[0089] Furthermore, in step S200, a printing area RP, which is the area of ​​the printing surface WF to be printed, is set, as shown by the dashed line in Figure 6. After creating the multiple tentative paths LM as described above, the multiple tentative paths LM may be selected so that, when printing on the printing area RP, the amount of change in the attitude of the liquid ejection head 3a or the number of printing passes is optimized. In this case, for example, a tentative path LM is selected that minimizes the amount of change in the attitude of the liquid ejection head 3a, the amount of change in the ink landing angle on the printing surface WF, and the distance between the liquid ejection head 3a and the workpiece W. In this case, multiple tentative paths LM with a combination that minimizes the number of printing passes are selected.

[0090] The following describes, as a representative example, the tentative route LM that passes near the tip of the nose of the human face shape on the printing surface WF, among the multiple tentative routes LM shown in Fig. 6. When printing is performed using multiple passes, the following process is also performed for each of the multiple tentative routes LM corresponding to the multiple passes.

[0091] Fig. 8 is a diagram showing the flow of generating a print path RU in the first embodiment. Fig. 8 shows the flow of processing in step S300 shown in Fig. 4. As shown in Fig. 8, step S300 includes steps S301 to S310.

[0092] More specifically, in step S300, first, in step S301, the control unit 8 acquires a point Pa, which will be described later and at which the smoothing process is performed on the printing surface WF. Details of this acquisition will be described later with reference to FIG.

[0093] After step S301, in step S302, the control unit 8 sets a region RL (to be described later) for performing smoothing processing on the printing surface WF. Details of this setting will be explained later with reference to Figs. 10 to 12.

[0094] After step S302, in step S303, the control unit 8 performs a smoothing process on the printing surface WF for each point Pa and each area RL, which will be described later, to generate smoothed data De. Details of this generation will be described later with reference to FIG. 13.

[0095] After step S303, in step S304, the control unit 8 generates a route RUa, which will be described later, based on the smoothed data De. Details of this generation will be described later with reference to FIG.

[0096] After step S304, in step S305, the control unit 8 stores a route RUa (to be described later) obtained in step S304.

[0097] After step S305, in step S306, the control unit 8 determines whether there are other points Pa (described below) that have not been subjected to the smoothing process. If there are other points Pa (step S306: YES), the control unit 8 returns to the above-mentioned step S303. As a result, the smoothing process is performed on all points Pa.

[0098] If there is no other point Pa (step S306: NO), in step S307, the control unit 8 creates a curing path RUC, which will be described later. In this embodiment, in step S307, in addition to the curing path RUC, which will be described later, a run-up path RUB, which will be described later, is created. Details of step S307 will be described later with reference to FIGS. 15 and 16.

[0099] After step S307, in step S308, the control unit 8 creates a print route RU, which will be described later. Details of this creation will be explained later with reference to FIG.

[0100] After step S308, in step S309, the control unit 8 performs a collision determination to determine whether or not the head unit 3 will collide with the workpiece W when using the printing path RU created in step S308. Details of this collision determination will be described later with reference to FIG.

[0101] After step S309, in step S310, the control unit 8 confirms the printing route RU, for which it has been determined in step S309 that the head unit 3 will not collide with the workpiece W, as the route indicated by the printing route information Da. Note that in step S310, the printing route RU created in step S308 may be confirmed as is as the route indicated by the printing route information Da, but if necessary, a route obtained by performing correction such as polynomial approximation or spline interpolation on the printing route RU created in step S308 may be confirmed as the route indicated by the printing route information Da.

[0102] 9 is a diagram illustrating the first point Pa-1, the second point Pa-2, the third point aM-3, and the fourth point Pa-4 that are to be smoothed. The first point Pa-1, the second point Pa-2, the third point aM-3, and the fourth point Pa-4 may be referred to as point Pa without distinction.

[0103] The first point Pa-1 is the intersection of the tentative path LM and the edge of the printing area RP on the x1 direction side. The second point Pa-2 is a point on the tentative path LM near the bottom of the recess C2. The third point Pa-3 is a point on the tentative path LM near the bottom of the recess C3. The fourth point Pa-4 is the intersection of the tentative path LM and the edge of the printing area RP on the x2 direction side.

[0104] 9, four points Pa are shown as a representative example, but the number of points Pa is not limited to the example shown in FIG. 9. The points Pa may be a plurality of points that define the tentative route LM, or a point that interpolates the plurality of points. Each of the plurality of points is, for example, an intersection point between a side of a polygon indicated by the work data Dc and a virtual plane that includes the tentative route LM.

[0105] The position of each point Pa is not limited to the example shown in Figure 9, and may be arranged such that a portion of the tentative path LM is not smoothed. For example, the smoothing process may not be performed on flat portions of the printing surface WF because the shape of the flat portions does not change before and after the process. In this case, the smoothing process may be performed only on uneven portions of the printing surface WF.

[0106] FIG. 10 is a diagram illustrating the relationship between the point Pa where smoothing is performed and the region RL where smoothing is performed. FIG. 10 illustrates the region RL when smoothing is performed at the fourth point Pa-4. As shown in FIG. 10, the region RL is an area extending in the main scanning direction, which is the direction in which the tentative path LM extends, and the sub-scanning direction, which is the direction perpendicular to the main scanning direction, and is based on the center CP of the nozzle surface FN. In the example shown in FIG. 10, the region RL is a rectangle having a pair of sides extending in the main scanning direction and a pair of sides extending in the sub-scanning direction. The shape of the region RL is not limited to the example shown in FIG. 10 and can be any shape. However, as will be described later, it is preferable that the shape of the region RL corresponds to the shape of the head unit 3.

[0107] Fig. 11 is a diagram for explaining the relationship between the region RL where smoothing is performed and the head unit 3. Fig. 11 shows the relationship between the region RL and the head unit 3 based on the a-axis, b-axis, and c-axis, which correspond to the coordinate axes of the tool coordinate system. Note that the size of the head unit 3 shown in Fig. 11 corresponds to the size of the end face of the head unit 3 in the c1 direction, that is, the size of the surface consisting of the nozzle surface FN and the irradiation surface FL.

[0108] As shown in FIG. 11, when viewed with the a-axis, b-axis, and c-axis as references, the region RL forms a quadrangle having a pair of sides along the a-axis and a pair of sides along the b-axis.

[0109] The length La of the region RL in the direction along the a-axis is longer than the length of the head unit 3 in the direction along the a-axis. In addition, the length Lb of the region RL in the direction along the b-axis is longer than the length of the head unit 3 in the direction along the b-axis.

[0110] As described above, the region RL is based on the center CP of the nozzle surface FN. Here, the length L1 between the center CP and the edge of the region RL in the a2 direction is greater than the length Ld between the center CP and the edge of the head unit 3 in the a2 direction. The length L2 between the center CP and the edge of the region RL in the a1 direction is greater than the length Lc between the center CP and the edge of the head unit 3 in the a1 direction. The length L3 between the center CP and the edge of the region RL in the b1 or b2 direction is greater than the length Le between the center CP and the edge of the head unit 3 in the b1 or b2 direction. In other words, the region RL is set so as to include the bottom surface of the head unit 3 in the c1 direction.

[0111] The lengths L1, L2, and L3 are each set appropriately. For example, the lengths L1, L2, and L3 are determined according to the setting of the distance PG, which will be described later, and are set to become smaller as the distance PG increases.

[0112] Fig. 12 is a diagram for explaining the region RL where smoothing is performed. For convenience of explanation, Fig. 12 shows the region RL where smoothing is performed at the third point Pa-3.

[0113] As shown in Fig. 12, the region RL is the region obtained by projecting the region of the size shown in Fig. 11 onto the printing surface WF in the normal direction of the printing surface WF at the target point Pa. Note that the size of the region RL shown in Fig. 11 is the size of the region RL as seen in the normal direction of the printing surface WF at the target point Pa when the reference center CP is positioned at the target point Pa.

[0114] FIG. 13 is a diagram for explaining smoothing. When there are multiple points Pa, step S303 is repeatedly executed, and the printing surface WF is smoothed in the region RL for each of the above-mentioned points Pa in the virtual space VS. As a result, a workpiece Ws having a shape in which the depth of the recesses C2 and C3 is reduced is obtained, as shown in FIG. 13. As a result, data indicating the shape of the workpiece Ws is generated as smoothed data De.

[0115] Although FIG. 13 shows the workpiece Ws after the smoothing process has been performed on all points Pa, the shape of the workpiece Ws gradually changes each time step S303 is executed.

[0116] In this way, the control unit 8 sets the predetermined regions RL in step S302, and then divides the printing surface WF into each of the predetermined regions RL and performs the smoothing process on each region in step S303. This allows for improved reproducibility of the shape of the printing surface WF in the smoothing data De compared to a mode in which the entire printing surface WF is smoothed collectively. As a result, the distance PG between the liquid ejection head 3a and the printing surface WF can be reduced. In contrast, in a mode in which the entire printing surface WF is smoothed collectively, the reproducibility of the shape of the printing surface WF in the smoothing data De may be reduced depending on the shape of the printing surface WF, and the distance PG at recesses may become large.

[0117] Furthermore, in step S200, the control unit 8 creates a tentative path LM based on the workpiece data Dc, and then in step S303, performs a smoothing process based on the tentative path LM, thereby enabling the smoothing process to be suitably performed along the scanning direction of the liquid ejection head 3a relative to the printing surface WF.

[0118] Fig. 14 is a diagram for explaining a route RUa based on the smoothed data De. Fig. 14 shows the route RUa generated by executing step S304 after performing the smoothing process on all points Pa.

[0119] The generation of the route RUa is performed in the same manner as the generation of the tentative route LM, except that it is based on the shape of the workpiece Ws instead of the shape of the workpiece W. However, the generation of the route RUa is performed only for the printing area RP. As a result, as shown in FIG. 14, a route RUa based on the workpiece Ws indicated by the smoothed data De is generated for the printing area RP. The data of the generated route RUa is stored in the memory circuit 7a in step S305.

[0120] 14 shows the path RUa based on the workpiece Ws after smoothing processing has been performed on all points Pa, but the path RUa gradually changes each time step S304 is performed. The data for the path RUa stored in step S305 is updated each time step S305 is performed. The path RUa finally obtained is a path that spans the entire printing area RP from point PS to point PE, as shown in FIG.

[0121] The data for the path RUa includes the position and orientation of the liquid ejection head 3a. The orientation of the liquid ejection head 3a is determined, for example, so that the normal to the nozzle surface FN passing through the center CP is perpendicular to the surface of the workpiece Ws at the intersection with the surface. Similarly to the tentative path LM, the path RUa is located on the same virtual plane throughout its entire area, and its normal is also located on the same virtual plane. The orientation of the liquid ejection head 3a may be determined so as to minimize the variation in the angle between the surface of the workpiece Ws and not only the normal passing through the center CP but also multiple normals to the nozzle surface FN passing through multiple points on the nozzle surface FN. In other words, the orientation of the liquid ejection head 3a may be determined so as to minimize the variation in the landing angle of ink from the multiple nozzles N onto the printing region RP. In this case, the normal to the nozzle surface FN passing through the center CP does not have to be located on the virtual plane on which the path RUa is located throughout its entire area.

[0122] Fig. 15 is a diagram showing the flow of generating the curing path RUC. Fig. 15 shows the flow of the process in step S307 shown in Fig. 8. As shown in Fig. 15, step S307 includes step S307a and step S307b in this order.

[0123] In this embodiment, the head unit 3 has a curing portion 3c, and an extension path is created to scan the curing portion 3c to cure the ink ejected by the liquid ejection head 3a at point PE, the end of the aforementioned path RUa, and to prevent the head unit 3 from colliding with the surface of the workpiece W ahead of point PE. Also, at point PS, the start of path RUa, the extension path is created so that the moving speed of the liquid ejection head 3a on path RUa is constant while preventing the curing portion 3c from colliding with the workpiece W when the liquid ejection head 3a is located at point PS, the start of path RUa.

[0124] Specifically, in step S307a, the control unit 8 identifies the point PE at the end of the route RUa. In this embodiment, in step S307a, the control unit 8 identifies the point PS at the start of the route RUa in addition to the point PE.

[0125] After step S307a, in step S307b, the control unit 8 creates a curing route RUC (described later) as an extension route. In this embodiment, in step S307b, the control unit 8 creates an approach route RUb as an extension route in addition to the curing route RUC.

[0126] Fig. 16 is a diagram for explaining the curing path RUc. In Fig. 16, in addition to the curing path RUc, the approach path RUb is also shown.

[0127] In step S307a, as shown in Fig. 16, a terminal point PE and a starting point PS of the path RUa are identified. Point PE is, for example, the point located furthest forward in the scanning direction of the liquid ejection head 3a among the multiple points defining the path RUa. Point PS is, for example, the point located furthest rearward in the scanning direction of the liquid ejection head 3a among the multiple points defining the path RUa.

[0128] In step S307b, the path RUa is extended from point PE to create a curing path RUc. The extension direction is set appropriately. For example, the extension direction may be the same direction as the direction near the end of the path RUa, or may be a direction away from the workpiece W to avoid collision between the head unit 3 and the workpiece W. If the extension direction is the same direction as the direction near the end of the path RUa, the extension direction may be a direction along a straight line connecting multiple points located near the end of the path RUa.

[0129] The length L5 of the curing path RUc is preferably longer than the aforementioned length L1, so that the curing by the curing unit 3c can be suitably performed over the entire printing region RP.

[0130] Furthermore, in step S307b, a run-up path RUb is created by extending the path RUa from point PS. The extension direction is set appropriately. For example, the extension direction may be the same direction as the direction near the start of the path RUa, or may be a direction away from the workpiece W so as to avoid collision between the head unit 3 and the workpiece W. If the extension direction is the same direction as the direction near the start of the path RUa, the extension direction may be a direction along a straight line connecting multiple points located near the start of the path RUa.

[0131] The length L4 of the approach path RUb is preferably longer than the distance over which the movement speed of the liquid ejection head 3a reaches a predetermined speed when the robot 2 starts to move from a stationary state, thereby allowing the liquid ejection head 3a to scan the entire printing area RP at the predetermined printing speed.

[0132] The process of creating the extension path in step S307 is provided as needed and may be omitted as in the second embodiment described below. The curing path RUc and the run-up path RUb may be created at the same time as the path RUa. In this case, for example, the creation range of the path RUa can be set to be wider than the printing area RP, thereby creating the curing path RUc and the run-up path RUb. Furthermore, if the head unit 3 has a sensor that measures a physical quantity related to the head unit 3, the shape of the workpiece W, or the distance between the head unit 3 and the workpiece W, an extension path for the sensor may be created.

[0133] FIG. 17 is a diagram illustrating the printing path RU. FIG. 17 shows the printing path RU created in step S308. FIG. 18 is a diagram illustrating the first distance PG-1, the second distance PG-2, the third distance LG-1, and the fourth distance LG-2. Note that in FIG. 17, the liquid ejection head 3a and the cured portion 3c in the printed state for the upward gradient created by the convex portion C1 during the printing operation are shown as liquid ejection head 3a-1 and cured portion 3c-1, and the liquid ejection head 3a and the cured portion 3c in the printed state for the downward gradient created by the convex portion C1 are shown as liquid ejection head 3a-2 and cured portion 3c-2. Also, for ease of explanation, FIG. 18 shows the convex portion C1 (described later) of the workpiece W enlarged and schematically illustrated.

[0134] When the liquid ejection head 3a is scanned along the printing path RU, the arm 220 extends to increase the distance from the base 210, but the direction in which the arm 220 scans the liquid ejection head 3a is arbitrary. For example, the arm 220 may operate to scan the liquid ejection head 3a while contracting to decrease the distance from the base 210, or may operate to scan the liquid ejection head 3a along the Y axis so that the distance from the base 210 remains approximately constant.

[0135] In step S308, the path RUa finally created in step S304 is combined with the curing path RUc and the run-up path RUb created in step S307 to create a printing path RU, which is the path along which the liquid ejection head 3a moves when the printing operation is performed, as shown in Fig. 17. However, in step S308, one or both of the position and attitude of the liquid ejection head 3a on the printing path RU may be corrected as necessary.

[0136] In this way, in step S302, the control unit 8 generates smoothed data De by performing a smoothing process on the work data Dc that indicates the shape of the printing surface WF, which is the surface to be printed on the work W, and in step S308, creates a printing path RU based on the smoothed data De.

[0137] By creating the printing path RU based on the smoothing data De, even if the printing surface WF has an uneven shape, it is possible to reduce the distance PG between the liquid ejection head 3a and the workpiece W while preventing the liquid ejection head 3a from colliding with the workpiece W. It is also possible to create a printing path RU in which the amount of change in the position and attitude of the liquid ejection head 3a is gradual.

[0138] In step S301, the control unit 8 acquires points Pa on the tentative path LM, and in step S303, performs smoothing processing for each point Pa on the tentative path LM. This allows the printing surface WF to be divided into predetermined regions RL along the scanning direction of the liquid ejection head 3a relative to the printing surface WF and smoothing processing to be performed thereon. This improves the reproducibility of the shape of the printing surface WF in the smoothed data De compared to a mode in which smoothing processing is performed collectively on the entire printing surface WF. As a result, the distance PG between the liquid ejection head 3a and the printing surface WF can be reduced. Furthermore, fluctuations in the distance PG can be reduced. Note that the point Pa on the tentative path LM refers to a point indicating a polygon when the workpiece data Dc is polygon data, or the position of the liquid ejection head 3a on the tentative path LM.

[0139] In step S303, when the control unit 8 performs the smoothing process at each point Pa on the tentative path LM, the control unit 8 performs the smoothing process on a region RL that includes a range up to a predetermined length L2 forward from each point Pa in the scanning direction, which is the direction in which the liquid ejection head 3a scans the workpiece W along the tentative path LM. In other words, the control unit 8 performs the smoothing process including the region located forward of the position of the liquid ejection head 3a. As a result, it is possible to suppress sudden changes in the position and attitude of the liquid ejection head 3a, and it is possible to suppress the amount of change in the position and attitude of the liquid ejection head 3a.

[0140] As described above, the predetermined length L2 in the scanning direction is longer than the length Lc from the center CP to the edge of the nozzle surface FN of the liquid ejection head 3a. In other words, the smoothing process is performed including the area located forward of the length of the liquid ejection head 3a. As a result, it is possible to suppress sudden changes in the position and attitude of the liquid ejection head 3a, and it is also possible to suppress the amount of change in the position and attitude of the liquid ejection head 3a.

[0141] Furthermore, as described above, when the control unit 8 performs the smoothing process at each point Pa on the tentative path LM, the control unit 8 performs the smoothing process on the region RL including the range from each point Pa backward in the scanning direction to a length L1 corresponding to the length Ld of the hardened portion 3c. This makes it possible to suppress collision between the hardened portion 3c and the workpiece W.

[0142] Furthermore, as described above, in step S303, the control unit 8 performs the smoothing process including the area ahead of the front end of the printing region RP in the scanning direction, which is the direction in which the liquid ejection head 3a scans along the tentative path LM relative to the workpiece W. This makes it possible to suppress collisions between the liquid ejection head 3a and irregularities ahead of the printing surface WF of the workpiece W.

[0143] Furthermore, it is preferable that the control unit 8 is capable of adjusting the size of the region RL where the smoothing process is performed. This allows the size of the region RL where the smoothing process is performed to be adjustable, making it easy to use. For example, when a structure supported by the tip E of the robot 2 is replaced, even if the dimensions of the structure before and after the replacement differ or deviations occur due to tolerances of the structure, the smoothing process can be performed appropriately by adjusting the size of the region RL where the smoothing process is performed.

[0144] Furthermore, when the control unit 8 has performed the smoothing process at each point Pa on the tentative path LM in step S303, in step S308, when creating the printing path RU, the control unit 8 corrects the attitude of the liquid ejection head 3a so that the normal to the nozzle surface FN of the liquid ejection head 3a located at each point Pa is perpendicular to the plane indicated by the smoothing data De. This corrects the attitude of the liquid ejection head 3a so that the nozzle surface FN is horizontal to the plane indicated by the smoothing data De, making it possible to suitably suppress collisions between the liquid ejection head 3a and the workpiece W.

[0145] Furthermore, when the liquid ejection head 3a scans the printing surface WF along the printing path RU, the distance PG between the printing surface WF and the liquid ejection head 3a is preferably 1 mm or more and 15 mm or less, and more preferably 1 mm or more and 10 mm or less. This prevents the liquid from landing misaligned on the printing surface WF from the liquid ejection head 3a. On the other hand, if the distance PG is less than 1 mm, the liquid ejection head 3a is more likely to collide with the workpiece W due to tolerances or misalignment of the arm 220 or the head unit 3. Furthermore, if the distance PG is greater than 15 mm, print quality tends to deteriorate. Therefore, it is preferable to set the parameters of the smoothing process described above so that the distance PG is 1 mm or more and 15 mm or less. Furthermore, if the distance PG is 10 mm or less, the influence of airflow between the liquid ejection head 3a and the workpiece W is suppressed, so the distance PG is more preferably 10 mm or less. The distance PG is not limited to this range and can be changed as appropriate taking into consideration the type of ink, the ejection speed, the degree of airflow generation, etc., but it is preferable that it is as small as possible.

[0146] The entire printing path RU is located on the same imaginary plane, similar to the temporary path LM, which makes it possible to prevent the liquid ejection head 3a from meandering in the sub-scanning direction that intersects with the scanning direction.

[0147] 18 is the liquid ejection head 3a at a first position P1 where the liquid ejection head 3a faces upward in the scanning direction so as to approach the top of the convex portion C1 during a printing operation. The liquid ejection head 3a-2 is the liquid ejection head 3a at a second position P2 where the liquid ejection head 3a faces downward in the scanning direction so as to move away from the top of the convex portion C1 during a printing operation. The first distance PG-1, which is the distance PG between the liquid ejection head 3a-1 and the workpiece W, is greater than the second distance PG-2, which is the distance PG between the liquid ejection head 3a-2 and the workpiece W.

[0148] Thus, in the printing method using the three-dimensional object printing apparatus 1, the first distance PG-1 is greater than the second distance PG-2 during printing. This makes it possible to prevent collisions between the head unit 3 and the surface of the workpiece W. Furthermore, by reducing the second distance PG-2, it is possible to improve print quality when the liquid ejection head 3a is scanned over the workpiece W so as to move away from the tops of the protrusions C1.

[0149] Here, when the liquid ejection head 3a is scanned relative to the workpiece W so as to move away from the apex of the convex portion C1, the rear end of the head unit 3 in the scanning direction moves away from the surface of the workpiece W, making it less likely that the head unit 3 will come into contact with the surface of the workpiece W. Therefore, even if the second distance PG-2 is smaller than the first distance PG-1, collision between the head unit 3 and the surface of the workpiece W can be suppressed. On the other hand, when the liquid ejection head 3a is scanned relative to the workpiece W so as to approach the apex of the convex portion C1, the rear end of the head unit 3 in the scanning direction moves closer to the surface of the workpiece W. Therefore, in an embodiment in which the first distance PG-1 and the second distance PG-2 are equal, contact between the head unit 3 and the surface of the workpiece W is more likely to occur. In contrast, by making the first distance PG-1 greater than the second distance PG-2, collision between the head unit 3 and the surface of the workpiece W is suppressed. Note that the distance PG between the liquid ejection head 3a and the workpiece W refers to the distance between the center CP of the nozzle surface FN and the workpiece W in the normal direction of the nozzle surface FN.

[0150] The first angle θ1, which is the absolute value of the tilt angle of the liquid ejection head 3a-1 with respect to the workpiece W, is equal to the second angle θ2, which is the absolute value of the tilt angle of the liquid ejection head 3a-2 with respect to the workpiece W. When viewed in a plane including the printing path RU, the first angle θ1 is the angle between the vertical axis or z-axis and a normal to the nozzle surface FN of the liquid ejection head 3a-1 that passes through the center CP of the nozzle surface FN. When viewed in a plane including the printing path RU, the second angle θ2 is the angle between the vertical axis or z-axis and a normal to the nozzle surface FN of the liquid ejection head 3a-2 that passes through the center CP of the nozzle surface FN.

[0151] For example, when the first angle θ1 and the second angle θ2 are each 30°, the first distance PG-1 is approximately 9 mm, and the second distance PG-2 is approximately 4 mm.

[0152] As described above, the head unit 3 has a curing section 3c. Here, the curing section 3c is provided at a position where the irradiation surface FL is farther from the workpiece W than the nozzle surface FN. This makes it possible to reduce the distance PG between the liquid ejection head 3a and the workpiece W while suppressing collisions between the curing section 3c and the surface of the workpiece W. Note that the curing section 3c may be provided so that the distance between the irradiation surface FL and the workpiece W is the same as the distance between the nozzle surface FN and the workpiece.

[0153] The third distance LG-1, which is the distance LG between the hardened portion 3c and the workpiece W at the first position P1, is shorter than the fourth distance LG-2, which is the distance LG between the hardened portion 3c and the workpiece W at the second position P2. This prevents a decrease in print quality. In contrast, in an embodiment in which the third distance LG-1 is equal to or greater than the fourth distance LG-2, the first distance PG-1 becomes too large, which may result in a decrease in print quality. Note that the distance LG between the hardened portion 3c and the workpiece W refers to the distance between the center CPa of the irradiation surface FL of the hardened portion 3c in the irradiation direction and the workpiece W.

[0154] The difference between the first distance PG-1 and the second distance PG-2 is preferably smaller than the difference between the third distance LG-1 and the fourth distance LG-2. In other words, it is preferable that the amount of change in the distance PG during printing is smaller than the amount of change in the distance LG. This makes it possible to suppress deviations in landing positions due to shaking of the liquid ejection head 3a.

[0155] In creating the printing path RU, the control unit 8 sets the posture of the head unit 3 so that the angle between the perpendicular to the nozzle surface FN of the liquid ejection head 3a and the plane indicated by the smoothing data De is closer to 90 degrees than the angle between the perpendicular to the irradiation surface FL of the cured portion 3c and the plane indicated by the smoothing data De. This makes it possible to more reliably suppress collisions between the liquid ejection head 3a and the workpiece W.

[0156] 19 is a diagram showing the flow of collision determination in step S309. In step S309, first, as shown in Fig. 19, in step S309a, the control unit 8 determines whether or not there is a collision point between the workpiece W and the head unit 3 when the head unit 3 is moved using the printing path RU. This determination is made, for example, by simulating the movement of the head unit 3 relative to the workpiece W when using the printing path RU in the virtual space VS, and determining whether or not there is an intersection point between the workpiece W and the head unit 3.

[0157] If there is a collision point between the workpiece W and the head unit 3 (step S309a: YES), in step S309b, the control unit 8 identifies the collision point. This identification is performed, for example, by finding the intersection point between the workpiece W and the head unit 3 in the virtual space VS using the above-mentioned simulation.

[0158] After step S309b, in step S309c, the control unit 8 recreates the smoothed data De. This recreation is performed by changing the correction value of the smoothing process for the identified collision locations and performing the same process as in step S303 described above again. That is, this recreation is performed on the work data Dc by performing the same process as in step S303, except that the correction value of the smoothing process for the identified collision locations is different. Note that in step S309c, the smoothing process may be performed on the smoothed data De.

[0159] The correction value for the smoothing process is a value that defines the size of the aforementioned region RL. Note that other correction values ​​in the smoothing process may also be adjusted.

[0160] After step S309c, in step S309d, the control unit 8 recreates the print path RU based on the smoothed data De recreated in step S309c. This recreate is performed by again executing the same processes as in steps S304 and S307 described above, except that the smoothed data De recreated in step S309c is used.

[0161] After step S309d, the control unit 8 returns to step S309a. Therefore, steps S309a to S309d are repeated until there are no more collision points between the workpiece W and the head unit 3 (step S309a: YES).

[0162] If there is no collision point between the workpiece W and the head unit 3 (step S309a: NO), in step S309e, the control unit 8 stores the printing path RU in which there is no collision point between the workpiece W and the head unit 3 in the memory circuit 7a, and ends step S309.

[0163] In the example shown in FIG. 19, the printing path RU is recreated until there are no more collision points between the workpiece W and the head unit 3, as described above. However, this is not limited to this. If there is a collision point between the workpiece W and the head unit 3 (step S309a: YES), the control unit 8 may display an error and prompt the user to change the settings of the tentative path LM, etc. In this case, the printing path RU can be recreated after changing the orientation of the workpiece W, the printing direction, the number of printing passes, etc. Also, step S309b may be provided as necessary and may be omitted. In this case, step S309c may perform smoothing processing on the entire area.

[0164] As described above, in step S309, the control unit 8 performs a collision determination to determine whether or not there will be a collision between the liquid ejection head 3a and the workpiece W when the liquid ejection head 3a is scanned along the printing path RU over the printing surface WF. As a result, if it is determined that there will be a collision between the liquid ejection head 3a and the workpiece W, the creation of the printing path RU can be redone. As a result, a collision between the liquid ejection head 3a and the workpiece W can be avoided.

[0165] Furthermore, if the control unit 8 determines in the collision determination that the liquid ejection head 3a will collide with the workpiece W (step S309a: YES), in step S309c, it adjusts the correction value in the smoothing process and then performs the smoothing process again. This makes it possible to create a printing path RU that can avoid collision between the liquid ejection head 3a and the workpiece W.

[0166] Furthermore, in step S309c, the control unit 8 may adjust the correction value in the smoothing process and perform the smoothing process again in accordance with the first change amount, which is the change amount in the distance PG between the liquid ejection head 3a and the workpiece W, or the second change amount, which is the change amount in the attitude of the liquid ejection head 3a with respect to the workpiece W. The control unit 8 acquires the first change amount and the second change amount when the liquid ejection head 3a is caused to scan the printing surface WF along the printing path RU, and if one or both of the first change amount and the second change amount are greater than a predetermined value, in step S309c, the control unit 8 adjusts the correction value in the smoothing process and performs the smoothing process again.

[0167] If the first change amount is greater than a predetermined value, the control unit 8 may adjust the correction value in the smoothing process by reducing the size of the region RL where the smoothing process is performed. In this case, the reproducibility of the printing surface WF in the region RL is improved, allowing the distance PG to be adjusted appropriately. Furthermore, if the second change amount is greater than a predetermined value, the control unit 8 may adjust the correction value in the smoothing process by increasing the size of the region RL where the smoothing process is performed. In this case, a gentler printing path can be created, and the second change amount can be reduced. This adjustment may be performed by the user inputting a correction value, or may be performed automatically by a program.

[0168] Furthermore, when the second change amount is equal to or greater than a predetermined value, the control unit 8 may divide the pass in the main scanning direction or change the orientation of the workpiece W to be printed for each pass. For example, when the second change amount is equal to or greater than 65°, processing may be performed to divide the pass in the main scanning direction.

[0169] 20 is a diagram showing the flow of generating print data Img in step S400. As shown in FIG. 20, step S400 includes steps S401 to S404 in this order.

[0170] More specifically, first, in step S401, the control unit 8 acquires the attitude of the liquid ejection head 3a for each position on the printing path RU based on the printing path information Da.

[0171] After step S401, in step S402, the control unit 8 calculates the landing position of each nozzle N of the liquid ejection head 3a onto the workpiece W for each position on the printing path RU based on the posture of the liquid ejection head 3a for each position on the printing path RU.

[0172] After step S402, in step S403, the control unit 8 acquires the image coordinates of the pixel in the image data Dd that corresponds to the impact position calculated in step S402.

[0173] After step S403, in step S404, the control unit 8 creates print data Img based on the image coordinates acquired in step S403.

[0174] Fig. 21 is a diagram for explaining the correspondence between image data Dd and print data Img. Fig. 21 shows the relationship between the multiple nozzles N of each of the liquid ejection heads 3a_1 to 3a_3 in different passes and the ink landing positions on the workpiece W when an image indicated by image data Dd is printed on the printing surface WF in multiple passes. For ease of explanation, Fig. 21 shows only a schematic shape of the printing surface WF.

[0175] 21, step S400 determines, in the virtual space VS, for each printing path RU indicated by the printing path information Da, the intersection of the printing area RP with a virtual line extending in the ejection direction DE from each nozzle N of the liquid ejection head 3a as the landing position. Based on this intersection, print data Img is generated for each printing path RU indicated by the printing path information Da. In this manner, the print data Img is generated by associating the nozzle N at each position on the printing path RU with the pixel of the image indicated by the image data Dd. Note that in this embodiment, the calculation is based on the assumption that the ink flies in a straight line, so the ejection direction DE is the normal direction of the nozzle face FN. However, the intersection may be calculated by correcting for landing deviations due to factors such as the attitude of the liquid ejection head 3a and the ink mass.

[0176] The intersection corresponds to the landing position of ink from the liquid ejection head 3a, and is determined in step S402. In step S403, color data or gradation data corresponding to the intersection is extracted as image coordinates for each printing path RU from the 3D image information of the image data Dd. In step S404, the 3D image information is divided into printing operations for each pass, and the divided 3D image information is color converted and binarized as necessary to generate print data Img.

[0177] Here, the printing area RP is quantized into multiple voxels BX in the virtual space VS as shown in FIG. 21. Each voxel BX is a cube, with all voxels having the same side length, and is arranged three-dimensionally in the virtual space VS along the printing area RP. The side lengths of the voxels BX are preferably adjusted appropriately according to the printing resolution. Based on the quantization into voxels BX and the aforementioned intersections corresponding to the ink landing positions, the printing area RP is divided into areas for each printing pass, with voxels BX as units. Here, exclusive processing is performed so that each voxel BX corresponds to one dot of ink from one nozzle N.

[0178] The unit of exclusive processing between dots is not limited to voxels BX. Instead of voxels BX, for example, pixels in the two-dimensional image, which is planar image data, may be used. In this case, the three-dimensional image information included in the image data Dd is divided for each printing operation by performing exclusive processing so that one dot of ink from one nozzle N belongs to a two-dimensionally arranged pixel. In this case, the pixels of the three-dimensional image and the pixels of the two-dimensional image mentioned above must correspond to each other.

[0179] Particles may be used instead of voxels BX as units of exclusion between dots. In this case, the print area RP is represented by multiple particles in the virtual space VS. Preferably, each particle is spherical, with the same radius, and arranged three-dimensionally along the print area RP. It is further preferable that the particle radius be adjusted appropriately depending on the printing resolution. The center of each particle indicates the position where the dot is to be arranged. The particle center is located in the virtual space VS by determining the intersection between the print area RP and a virtual line extending from each nozzle N of the liquid ejection head 3a in the ejection direction DE. Furthermore, while other particles are permitted to be arranged outside the radius of a certain particle, they are not permitted to partially invade inside the radius of the certain particle, and other particles are excluded. In other words, the surface of the print area RP is filled with multiple particles, and the position of each particle dynamically changes depending on the shape of the print area RP and the individual particle arrangement order. Particles defined in this way can more smoothly represent the curved surface of the printing area RP than the voxels BX described above, and can suppress the occurrence of moire in the printed image formed by the three-dimensional object printing apparatus 1.

[0180] In the example shown in Figure 21, the three-dimensional image information of the image data Dd is divided into three-dimensional image information corresponding to the multiple voxels BX to which the dots Dt1 made of ink from the liquid ejection head 3a_1 belong, three-dimensional image information corresponding to the multiple voxels BX to which the dots Dt2 made of ink from the liquid ejection head 3a_2 belong, and three-dimensional image information corresponding to the multiple voxels BX to which the dots Dt3 made of ink from the liquid ejection head 3a_3 belong.

[0181] The 3D image information corresponding to the plurality of voxels BX to which the ink dots Dt1 from the liquid ejection head 3a_1 belong is used in the printing operation of the first pass. The 3D image information corresponding to the plurality of voxels BX to which the ink dots Dt2 from the liquid ejection head 3a_2 belong is used in the printing operation of the second pass adjacent to the first pass. The 3D image information corresponding to the plurality of voxels BX to which the ink dots Dt3 from the liquid ejection head 3a_3 belong is used in the printing operation of the third pass adjacent to the second pass.

[0182] In this way, the printing path RU is created using the smoothed data De as the reference three-dimensional data, while the printing data Img is created using the work data Dc as the reference three-dimensional data. Here, the printing data Img indicates the ejection operation of each nozzle N of the liquid ejection head 3a along the printing path RU.

[0183] As described above, in step S100, the control unit 8 acquires image data Dd representing the image to be printed on the printing surface WF. After performing the smoothing process in step S303, in step S400, the control unit 8 adjusts the ejection operation of each nozzle N of the liquid ejection head 3a along the printing path RU based on the printing path RU and the image data Dd. This makes it possible to suitably adjust the landing position of the liquid ejected from the liquid ejection head 3a onto the printing surface WF. As a result, print quality can be improved.

[0184] 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.

[0185] 22 is a diagram showing the flow of generating a print path in the second embodiment. The path generation method of this embodiment is the same as step S300 of the first embodiment, except that step S307 is omitted and step S308A is included instead of step S308. In this embodiment, the curing unit 3c may be omitted. In this case, omitting the curing unit 3c makes it unnecessary to create a curing path in step S307 of the first embodiment. In addition, the collision determination in step S309 may be omitted.

[0186] In this embodiment, if there is no other point Pa (step S306: NO), in step S308A, the control unit 8 creates the route RUa finally created in step S304 as the print route RU.

[0187] According to the second embodiment described above, even if the surface of the workpiece W to be printed has irregularities, it is possible to improve the printing quality while suppressing collision between the liquid ejection head 3a and the workpiece W.

[0188] 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.

[0189] 3-1. Variation 1 Fig. 23 is a diagram showing the flow of generating a curing path RUC in Modification 1. The generation of a curing path RUC shown in Fig. 23 is similar to step S307 in the first embodiment, except that step S307c and step S307d are included instead of step S307b in step S307 in the first embodiment.

[0190] In Modification 1, after step S307a, in step S307c, the control unit 8 adds a point Pa to be smoothed on the printing surface WF outside the printing area RP. For example, when creating a curing path RUc, point Pa is added at a position ahead of the printing area RP in the scanning direction of the liquid ejection head 3a. Also, when creating an approach path RUb, point Pa is added at a position behind the printing area RP in the scanning direction of the liquid ejection head 3a.

[0191] After step S307c, in step S307d, the control unit 8 performs a smoothing process on the printing surface WF at the added point Pa, and then creates an extension path according to the printing surface WF after the smoothing process using a method similar to that of step S304.

[0192] The smoothing process may be performed based on the center CPa of the irradiated surface FL of the hardened portion 3c. In this case, the posture of the head unit 3 is set so that the angle between the perpendicular to the irradiated surface FL of the hardened portion 3c and the surface indicated by the smoothing data De is close to 90 degrees. In this case, collision of the hardened portion 3c with the workpiece W can be further prevented.

[0193] 3-2. Variation 2 24 is a diagram illustrating a printing path RU in Modification 2. Modification 2 is similar to the first embodiment except that the workpiece W has a recess C4. Note that in FIG. 24, during execution of the printing operation, the liquid ejection head 3a and the cured portion 3c in a printed state relative to the upward gradient caused by the recess C4 are shown as liquid ejection head 3a-1 and cured portion 3c-1, and the liquid ejection head 3a and the cured portion 3c in a printed state relative to the downward gradient caused by the recess C4 are shown as liquid ejection head 3a-2 and cured portion 3c-2.

[0194] In FIG. 24, liquid ejection head 3a-1 is the liquid ejection head 3a at a first position P1 where, during a printing operation, liquid ejection head 3a faces upward in the scanning direction so as to move away from the bottom of recessed portion C4. Liquid ejection head 3a-2 is the liquid ejection head 3a at a second position P2 where liquid ejection head 3a faces downward in the scanning direction so as to move closer to the bottom of recessed portion C4. When a first angle θ1, which is the absolute value of the tilt angle of liquid ejection head 3a-1 with respect to the workpiece W, is equal to a second angle θ2, which is the absolute value of the tilt angle of liquid ejection head 3a-2 with respect to the workpiece W, a first distance PG-1, which is the distance PG between liquid ejection head 3a-1 and the workpiece W, is greater than a second distance PG-2, which is the distance PG between liquid ejection head 3a-2 and the workpiece W. Furthermore, a third distance LG-1, which is the distance LG between hardened portion 3c-1 and the workpiece W, is smaller than a fourth distance LG-2, which is the distance LG between hardened portion 3c-2 and the workpiece W.

[0195] In this way, when performing a printing operation, the control unit 8 moves the liquid ejection head 3a so that the first distance PG-1 is greater than the second distance PG-2 and the third distance LG-1 is smaller than the fourth distance LG-2.

[0196] In this way, even if the workpiece W has a recess C4, the first distance PG-1 is greater than the second distance PG-2, so it is possible to prevent collision between the head unit 3 and the surface of the workpiece W. Furthermore, by reducing the second distance PG-2, it is possible to improve the printing quality when the liquid ejection head 3a scans the workpiece W so as to approach the bottom of the recess C4.

[0197] Here, when the liquid ejection head 3a is scanned relative to the workpiece W so as to approach the bottom of the recessed portion C4, the rear end of the head unit 3 in the scanning direction moves away from the surface of the workpiece W, making it less likely that the head unit 3 will come into contact with the surface of the workpiece W. Therefore, even if the second distance PG-2 is smaller than the first distance PG-1, it is possible to prevent collision between the head unit 3 and the surface of the workpiece W. On the other hand, when the liquid ejection head 3a is scanned relative to the workpiece W so as to move away from the bottom of the recessed portion C4, the rear end of the head unit 3 in the scanning direction moves closer to the surface of the workpiece W. Therefore, in an embodiment in which the first distance PG-1 and the second distance PG-2 are equal, contact between the head unit 3 and the surface of the workpiece W is more likely to occur. Therefore, by making the first distance PG-1 greater than the second distance PG-2, collision between the head unit 3 and the surface of the workpiece W is prevented.

[0198] 3-3. Variation 3 The above-described embodiment illustrates an example in which the printing path RU is created from the work data Dc of polygon data, but is not limited to this. The printing path RU may be created using the work data Dc of point cloud data other than polygon data, or may be created based on points on a curve extracted as a point cloud from the work data Dc of curve data.

[0199] 3-4. Variation 4 In the above embodiment, the smoothing process for the workpiece data Dc is performed for each region RL, but the present invention is not limited to this, and the smoothing process for the workpiece data Dc may be performed all at once on the entire printing surface WF.

[0200] For example, if the depth of the recesses on the printing surface WF that are recessed relative to the flat surface of the printing surface WF is smaller than a predetermined value, or if the difference between the height of the protrusions that protrude relative to the flat surface of the printing surface WF and the depth of the recesses that are recessed relative to the flat surface is smaller than a predetermined value, the entire printing surface WF may be polished in one go.If the printing surface WF is highly flat, the distance PG between the liquid ejection head 3a and the workpiece W can be maintained within an appropriate range even if the entire printing surface WF is polished in one go.

[0201] 3-5. Variation 5 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. Robot 2 may be, for example, a vertical multi-axis robot other than a six-axis robot, or a horizontal multi-axis robot. Furthermore, the arm of robot 2 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 robot 2 be a multi-axis robot with six or more axes.

[0202] 3-6. Variation 6 In the above-described embodiment, a configuration in which screws or the like are used as a method for fixing the liquid ejection head 3 a to the robot 2 is exemplified, but the present invention is not limited to this configuration. For example, the liquid ejection head 3 a may be fixed to the robot 2 by gripping the liquid ejection head 3 a with a gripping mechanism such as a hand attached as an end effector of the robot 2.

[0203] 3-7. Variation 7 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.

[0204] 3-8. Variation 8 The use of the three-dimensional printing apparatus 1 of the present disclosure is not limited to printing images. For example, a three-dimensional printing apparatus 1 that ejects a solution of color material is used as a manufacturing device for forming color filters for liquid crystal display devices. Also, a three-dimensional printing apparatus 1 that ejects a solution of conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board. The three-dimensional printing apparatus 1 can also be used as a jet dispenser that applies a liquid such as an adhesive to a medium.

[0205] 3-9. Variation 9 In the above-described embodiment, the smoothing process is a process for reducing the depth of the recesses in the area to be processed. However, for example, it is preferable that the smoothing process is performed so as to reduce only the depth of the recesses without changing the height of the protrusions in the area to be processed.

[0206] When the smoothing process is performed to reduce the height of the convex portions, the distance between the liquid ejection head 3a and the convex portions during printing becomes smaller, increasing the possibility of collision between the liquid ejection head 3a and the convex portions. On the other hand, when the smoothing process is performed to reduce the depth of the concave portions, a predetermined distance can be secured between the liquid ejection head 3a and the concave portions during printing, resulting in a lower possibility of collision between the liquid ejection head 3a and the concave portions.

[0207] 3-10. Variation 10 In the above-described embodiment, the print data Img is generated in such a manner that, in step S403, color data or gradation data corresponding to the intersection point is extracted as image coordinates for each print path RU from the 3D image information of the image data Dd, and then, in step S404, the 3D image information is divided into printing operations for each pass, and the divided 3D image information is color converted and binarized as necessary. However, this is not limiting. For example, the image data Dd may be color converted and binarized to generate dot arrangement data converted into On / Off data for each color dot, and then the On / Off data corresponding to the intersection point is extracted to generate the print data Img.

[0208] 4. Notes A summary of this disclosure is provided below.

[0209] (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 having a plurality of nozzles that eject liquid toward a workpiece, an articulated robot having a tip that supports the liquid ejection head and scans the liquid ejection head over the workpiece, and a control unit that creates a printing path along which the liquid ejection head will scan, wherein the control unit generates smoothed data by performing a smoothing process on workpiece data that indicates the shape of the printing surface, which is the surface of the workpiece that is to be printed, and creates the printing path based on the smoothed data.

[0210] In the above-described aspect, since the printing path is created based on the smoothed data, even if the printing surface has an uneven shape, it is possible to reduce the distance between the liquid ejection head and the printing surface while suppressing collisions between the liquid ejection head and the printing surface. As a result, it is possible to suppress deterioration in print quality. Furthermore, it is possible to create a printing path with gradual changes in the position and attitude of the liquid ejection head.

[0211] (Supplementary Note 2) In a second aspect, which is a preferred example of the first aspect, the control unit divides the printing surface into predetermined regions and performs the smoothing process. In this aspect, the reproducibility of the shape of the printing surface in the smoothed data can be improved compared to an aspect in which the entire printing surface is subjected to the smoothing process all at once. As a result, the distance between the liquid ejection head and the printing surface can be reduced, and the fluctuations in the distance can be reduced. In contrast, in an aspect in which the smoothing process is performed all at once on the entire printing surface, the reproducibility of the shape of the printing surface in the smoothed data may be reduced depending on the shape of the printing surface, etc. As a result, there is a risk that the distance between the liquid ejection head and the printing surface will increase, or the fluctuations in the distance will increase.

[0212] (Supplementary Note 3) In a third aspect, which is a preferred example of the second aspect, the control unit creates a tentative path based on the workpiece data, and performs the smoothing process based on the tentative path. In the above aspect, the smoothing process can be preferably performed along the scanning direction of the liquid ejection head relative to the printing surface.

[0213] (Supplementary Note 4) In a fourth aspect, which is a preferred example of the third aspect, the control unit performs the smoothing process for each point on the tentative path. In the above aspect, the printing surface can be divided into predetermined regions along the scanning direction of the liquid ejection head relative to the printing surface and smoothed. This improves the reproducibility of the shape of the printing surface in the smoothed data compared to an aspect in which smoothing is performed collectively on the entire printing surface. As a result, the distance between the liquid ejection head and the printing surface can be reduced, and fluctuations in the distance between the liquid ejection head and the printing surface can be reduced. Note that a point on the tentative path refers to a point that indicates a polygon when the work data is polygon data, or the position of the liquid ejection head on the tentative path.

[0214] (Supplementary Note 5) In the fifth aspect, which is a preferred example of the fourth aspect, when the control unit performs the smoothing process at a first point on the tentative path, the control unit performs the smoothing process on an area including a range of a predetermined length forward from the first point in the scanning direction, which is the direction in which the liquid ejection head scans the workpiece along the tentative path. In the above aspect, the smoothing process can be performed including an area located forward of the position of the liquid ejection head. As a result, sudden changes in the position and orientation of the liquid ejection head can be suppressed. In other words, fluctuations in the position and orientation of the liquid ejection head can be suppressed.

[0215] (Supplementary Note 6) In the sixth aspect, which is a preferred example of the fifth aspect, the predetermined length in the scanning direction is longer than the length from the center to the edge of the nozzle surface of the liquid ejection head. In this aspect, the smoothing process can be performed including an area located forward of the length of the liquid ejection head. As a result, sudden changes in the position and orientation of the liquid ejection head can be suppressed. In other words, fluctuations in the position and orientation of the liquid ejection head can be suppressed.

[0216] (Supplementary Note 7) In the seventh aspect, which is a preferred example of any of the fourth to sixth aspects, the apparatus further includes a curing unit that is supported by the tip portion and is arranged behind the liquid ejection head in a scanning direction in which the liquid ejection head scans the workpiece, and that hardens the liquid ejected from the liquid ejection head onto the printing surface, and when the control unit performs the smoothing process at a first point on the tentative path, the control unit performs the smoothing process on an area that includes a range from the first point backward in the scanning direction to a length equivalent to the length of the cured unit. In the above aspect, it is possible to prevent collision between the hardened unit and the workpiece.

[0217] (Supplementary Note 8) In an eighth aspect, which is a preferred example of any of the fourth to seventh aspects, the control unit performs the smoothing process including a region ahead of the front end of the printing region in a scanning direction, which is a direction in which the liquid ejection head scans the workpiece along the tentative path. In the above aspect, it is possible to suppress collision between the surface of the workpiece ahead of the printing surface of the workpiece and the liquid ejection head.

[0218] (Supplementary Note 9) In a ninth aspect, which is a preferred example of any of the fourth to eighth aspects, the control unit is capable of adjusting the size of the area in which the smoothing process is performed. In the above aspects, the control unit is easy to use because the size of the area in which the smoothing process is performed is adjustable. For example, when a structure supported at the tip of an articulated robot is replaced, even if the dimensions of the structure before and after the replacement differ or deviations occur due to tolerances of the structure, the smoothing process can be performed appropriately by adjusting the size of the area in which the smoothing process is performed.

[0219] (Supplementary Note 10) In the tenth aspect, which is a preferred example of the ninth aspect, the control unit reduces the size of the area where the smoothing process is performed when the distance between the printing surface and the liquid ejection head in the printing path is greater than a predetermined value. In this aspect, the distance between the printing surface and the liquid ejection head can be appropriately adjusted. As a result, print quality can be improved.

[0220] (Supplementary Note 11) In an eleventh aspect, which is a preferred example of any of the fourth to tenth aspects, when the control unit performs the smoothing process at a first point on the tentative path, during creation of the printing path, the control unit corrects the attitude of the liquid ejection head so that a normal to the nozzle face of the liquid ejection head located at the first point is perpendicular to the plane indicated by the smoothing data. In the above aspect, the attitude of the liquid ejection head is corrected so that the nozzle face is horizontal to the plane indicated by the smoothing data, thereby making it possible to suitably suppress collisions between the liquid ejection head and the workpiece.

[0221] (Appendix 12) In a twelfth aspect, which is a preferred example of any of the first to eleventh aspects, when the liquid ejection head is caused to scan the printing surface along the printing path, the distance between the printing surface and the liquid ejection head is 1 mm or more and 10 mm or less. In this aspect, it is possible to suppress collision between the liquid ejection head and the workpiece while suppressing deviation in the landing position of the liquid ejected from the liquid ejection head onto the printing surface.

[0222] (Supplementary Note 13) In a thirteenth aspect, which is a preferred example of any of the second to eleventh aspects, the control unit performs a collision determination to determine whether or not a collision occurs between the liquid ejection head and the workpiece when the liquid ejection head is scanned along the printing path relative to the printing surface. In the above aspect, if a collision between the liquid ejection head and the workpiece is determined, the creation of the printing path can be redone. As a result, a collision between the liquid ejection head and the workpiece can be avoided.

[0223] (Supplementary Note 14) In a fourteenth aspect, which is a preferred example of the thirteenth aspect, if the control unit determines in the collision determination that the liquid ejection head will collide with the workpiece, it adjusts a correction value in the smoothing process and then performs the smoothing process again. In the above aspect, it is possible to create a printing path that can avoid collision between the liquid ejection head and the workpiece.

[0224] (Supplementary Note 15) In the fifteenth aspect, which is a preferred example of any of the second to eleventh aspects, the control unit acquires a first change amount, which is the amount of change in the distance between the liquid ejection head and the workpiece when the liquid ejection head is scanned over the printing surface along the printing path, and a second change amount, which is the amount of change in the attitude of the liquid ejection head relative to the workpiece, and if one or both of the first change amount and the second change amount are greater than a predetermined value, adjusts a correction value in the smoothing process and performs the smoothing process again. In the above aspect, it is possible to create a printing path in which the amount of change in the distance between the liquid ejection head and the workpiece and the amount of change in the attitude of the liquid ejection head relative to the workpiece are each appropriately set.

[0225] (Supplementary Note 16) In a sixteenth aspect, which is a preferred example of any one of the first to fifteenth aspects, the control unit acquires image data representing an image to be printed on the printing surface, and after the smoothing process, adjusts the ejection operation of each nozzle of the liquid ejection head in the printing path based on the printing path and the image data. In the above aspect, it is possible to suitably adjust the landing position of liquid from the liquid ejection head on the printing surface. As a result, print quality can be improved.

[0226] (Appendix 17) A 17th aspect, which is a preferred example of the path generation method of the present disclosure, is a path generation method for creating a printing path, which is the movement path of the liquid ejection head during printing using a three-dimensional printing device comprising: a liquid ejection head having a plurality of nozzles that eject liquid toward a workpiece; and an articulated robot having a tip that supports the liquid ejection head and scans the liquid ejection head against the workpiece, the method including: generating smoothed data by performing a smoothing process on work data that indicates the shape of the printing surface, which is the surface of the workpiece that is to be printed; and creating a printing path based on the smoothed data, wherein in the smoothing data generating process, the printing surface is divided into predetermined areas and the smoothing process is performed.

[0227] (Appendix 18) In the 18th aspect, which is a preferred example of the 17th aspect, the method includes a step of creating a tentative path based on work data indicating the shape of the printing surface, which is the surface to be printed on the work, and in the step of generating the smoothing data, the smoothing process is performed based on the tentative path.

[0228] In the above-described embodiment, a printing path is created based on the smoothing data, so even if the printing surface has an uneven shape, a printing path can be created that exhibits gentle changes in the position and orientation of the liquid ejection head. As a result, it is possible to reduce fluctuations in the distance between the liquid ejection head and the printing surface while suppressing collisions between the liquid ejection head and the workpiece. Furthermore, because the printing surface is divided into predetermined regions and smoothed, the smoothing process can be performed on the entire printing surface at once, thereby improving the reproducibility of the shape of the printing surface in the smoothing data. As a result, it is possible to reduce fluctuations in the distance between the liquid ejection head and the printing surface. [Explanation of symbols]

[0229] 1...three-dimensional object printing device, 2...robot (articulated robot), 2a...arm drive mechanism, 3...head unit, 3a...liquid ejection head, 3a...liquid ejection head, 3a-1...liquid ejection head, 3a-2...liquid ejection head, 3a_1...liquid ejection head, 3a_2...liquid ejection head, 3a_3...liquid ejection head, 3c...curing unit, 3c-1...curing unit, 3c-2...curing 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 generating circuit, 7...computer, 7a...storage circuit, 7b...processing circuit, 8...control unit, 210...base, 220...arm, 221...arm, 222...arm, 223...arm, 224...arm, 225...arm, 226...arm, BX...voxel, C1...convex portion, C2...concave portion, C3...concave portion, C4...concave portion, CLK...clock signal, CNG...change signal, CP...center, CPa...center, Com...drive signal, D1...output, D3...signal, DE...ejection direction, DN...nozzle array direction, Da...printing path information, Db...temporary path information, Dc...work data, Dd...image data, De...flat Smoothing data, Dt1...dot, Dt2...dot, Dt3...dot, E...tip, FL...irradiation surface, FN...nozzle surface, Img...print data, J...joint, J1...joint, J2...joint, J3...joint, J4...joint, J5...joint, J6...joint, LAT...latch signal, LG...distance, LG-1...third distance, LG-2...fourth distance, LM...temporary path, 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, P1...first position, P2...second position, PD...drive pulse, PE...point, PG...distance, PG-1...first distance, PG-2...second distance, PR...program, PS...point, PTS...timing signal, Pa...point, Pa-1...first point, Pa-2...second point, Pa-3...third point, Pa-4...fourth point, Pa-4...fourth point, RL...area, RP...printing area, RU...printing path, RUa...path, RUb...run-up path, RUc...curing path, S100...step, S200...step, S300...step, S301...step, S302...step, S303...step, S304...step,S305...step, S306...step, S307...step, S307a...step, S307b...step, S307c...step, S307d...step, S308...step, S308A...step, S309...step, S309a...step, S309b...step, S309c...step, S309d...step, S309e...step, S310...step, S400...step, S401...step, S402...step, S403...step, S404...step, S500...step, SI...control signal, Sk1...control signal, TCP...tool center point, VBS...offset potential, VHV...power supply potential, VS...virtual space, W...work, WF...printing surface, Ws...work, aM-3...third point, dCom...waveform designation signal, θ1...first angle, θ2...second angle.

Claims

1. a liquid ejection head having a plurality of nozzles for ejecting 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 creates a printing path for scanning the liquid ejection head, The control unit Generate smoothed data by performing a smoothing process on work data that indicates the shape of a printing surface that is a surface to be printed on the work; creating the printing path based on the smoothed data; A three-dimensional object printing device characterized by the above.

2. The control unit The printing surface is divided into predetermined regions and the smoothing process is performed. The three-dimensional object printing device according to claim 1 .

3. The control unit creating a tentative route based on the work data; performing the smoothing process based on the tentative route; 3. The three-dimensional object printing device according to claim 2.

4. The control unit performing the smoothing process for each point on the tentative route; 4. The three-dimensional object printing device according to claim 3.

5. The control unit When performing the smoothing process at a first point on the tentative path, the smoothing process is performed on an area including a range from the first point to a predetermined length forward in a scanning direction, which is a direction in which the liquid ejection head is scanned over the workpiece along the tentative path.

5. The three-dimensional object printing device according to claim 4.

6. In the scanning direction, the predetermined length is longer than the length from the center to the edge of the nozzle surface of the liquid ejection head.

6. The three-dimensional object printing device according to claim 5.

7. a curing unit that is supported by the tip portion and is disposed behind the liquid ejection head in a scanning direction in which the liquid ejection head scans the workpiece, and that cures the liquid ejected from the liquid ejection head onto the printing surface; The control unit when performing the smoothing process at a first point on the tentative path, the smoothing process is performed on an area including a range from the first point to a length corresponding to a length of the hardened portion behind the first point in the scanning direction.

5. The three-dimensional object printing device according to claim 4.

8. The control unit performing the smoothing process on an area including a front end of a printing area in a scanning direction, which is a direction in which the liquid ejection head is scanned relative to the workpiece along the tentative path; 5. The three-dimensional object printing device according to claim 4.

9. The control unit The size of the area where the smoothing process is performed is adjustable.

5. The three-dimensional object printing device according to claim 4.

10. The control unit If the distance between the printing surface and the liquid ejection head in the printing path is greater than a predetermined value, the size of the area to be subjected to the smoothing process is reduced. The three-dimensional object printing device according to claim 9 .

11. The control unit when the smoothing process is performed at a first point on the tentative path, correcting the attitude of the liquid ejection head so that a normal to a nozzle face of the liquid ejection head located at the first point becomes perpendicular to a plane indicated by the smoothing data when creating the printing path; 5. The three-dimensional object printing device according to claim 4.

12. when the liquid ejection head is caused to scan the printing surface along the printing path, the distance between the printing surface and the liquid ejection head is 1 mm or more and 10 mm or less; The three-dimensional object printing device according to any one of claims 1 to 11.

13. The control unit performing a collision determination to determine whether or not there is a collision between the liquid ejection head and the workpiece when the liquid ejection head is scanned along the printing path relative to the printing surface; The three-dimensional object printing device according to any one of claims 2 to 11.

14. The control unit When it is determined in the collision determination that the liquid ejection head and the workpiece will collide, the correction value in the smoothing process is adjusted and then the smoothing process is performed again. The three-dimensional object printing device according to claim 13 .

15. The control unit a first change amount, which is a change amount of the distance between the liquid ejection head and the workpiece when the liquid ejection head is scanned over the printing surface along the printing path, and a second change amount, which is a change amount of the attitude of the liquid ejection head with respect to the workpiece; If one or both of the first change amount and the second change amount are greater than a predetermined value, a correction value in the smoothing process is adjusted and the smoothing process is performed again. The three-dimensional object printing device according to any one of claims 2 to 11.

16. The control unit acquiring image data representing an image to be printed on the printing surface; After the smoothing process, adjusting the ejection operation of each nozzle of the liquid ejection head in the printing path based on the printing path and the image data. The three-dimensional object printing device according to any one of claims 1 to 11.

17. a liquid ejection head having a plurality of nozzles for ejecting 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 relative to the workpiece, the multi-joint robot having a tip portion that supports ... A step of generating smoothed data by performing a smoothing process on work data that indicates the shape of a printing surface that is a surface to be printed on the work; generating a print path based on the smoothed data; In the step of generating the smoothed data, The printing surface is divided into predetermined regions and the smoothing process is performed. A route generation method comprising:

18. and creating a tentative path based on work data indicating the shape of a printing surface, which is a surface to be printed on the work, In the step of generating the smoothed data, performing the smoothing process based on the tentative route; 18. The route generation method according to claim 17.

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