Three-dimensional object printer and printing method

Abstract

To perform printing to print areas having different flatness of a workpiece.SOLUTION: A three-dimensional object printer includes: a liquid discharge head which discharges a liquid; and a moving mechanism which moves the liquid discharge head relative to a three-dimensional workpiece while changing an attitude of the liquid discharge head. In a time period of a first operation of the moving mechanism, the liquid is discharged from the liquid discharge head to a first area of the workpiece and a second area which is located at the outer side of the first area of the workpiece in a main scanning direction and has flatness lower than that of the first area.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] Conventionally, a three-dimensional printing device is known that uses a robot to print on the surface of a three-dimensional workpiece by an inkjet method. For example, Patent Document 1 describes a three-dimensional printing device that prints on the entire area of ​​one flat surface of a rectangular parallelepiped workpiece. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-10639 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the three-dimensional object printing device described in Patent Document 1, if the flatness of the print area of ​​the workpiece is low, there is a risk of the print quality being reduced. [Means for solving the problem]

[0005] In order to solve the above problems, one aspect of a three-dimensional object printing device disclosed herein comprises a liquid ejection head that ejects liquid, and a moving mechanism that moves the liquid ejection head while changing the attitude of the liquid ejection head relative to a three-dimensional workpiece, and during a first operation of the moving mechanism, liquid is ejected from the liquid ejection head onto a first region of the workpiece and a second region that is located outside the first region of the workpiece in the main scanning direction and has a lower flatness than the first region.

[0006] One aspect of the printing method disclosed herein is a printing method using a three-dimensional printing device including a liquid ejection head that ejects liquid, and a moving mechanism that moves the liquid ejection head while changing the attitude of the liquid ejection head relative to a three-dimensional workpiece, and includes a step of ejecting liquid from the liquid ejection head during a first operation in which the moving mechanism moves the liquid ejection head onto a first region of the workpiece and a second region that is located outside the first region of the workpiece in the main scanning direction and has a lower flatness than the first region. [Brief description of the drawings]

[0007] [Figure 1] 1 is a perspective view showing an outline of a three-dimensional object printing device according to a first embodiment. FIG. [Diagram 2] FIG. 2 is a block diagram showing the electrical configuration of the three-dimensional object printing device according to the first embodiment. [Diagram 3] FIG. 4 is a diagram showing a flow of a printing method according to the first embodiment. [Figure 4] FIG. 11 is a diagram for explaining a print area in a first operation. [Diagram 5] FIG. 4 is a diagram for explaining a first region and a second region of a workpiece in a first operation. [Figure 6] FIG. 11 is a diagram showing the flow of a printing method according to a second embodiment. [Figure 7] FIG. 11 is a diagram for explaining a print area in a second operation. [Figure 8] 13 is a diagram for explaining a third area and a fourth area of ​​the workpiece in the second operation. FIG. [Figure 9] FIG. 11 is a diagram showing the flow of a printing method according to a third embodiment. [Figure 10] FIG. 11 is a diagram for explaining a print area in a third operation. [Figure 11] 13 is a diagram for explaining a sixth area and a seventh area of ​​the workpiece in the third operation. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions, and some parts are shown diagrammatically to facilitate understanding. In addition, the scope of the present disclosure is not limited to these forms unless otherwise specified in the following description to the effect that the present disclosure is limited.

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

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

[0011] The Z axis does not have to be a vertical axis. The X axis, the Y axis, and the Z axis are typically mutually orthogonal, but are not limited thereto, and may not be orthogonal. For example, the X axis, the Y axis, and the Z axis may intersect each other at an angle within a range of 80° to 100°.

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

[0013] In the example shown in FIG. 1, the workpiece W has faces Fx1, Fx2, Fy1, Fy2, Fz1, and Fz2. Face Fx1 is a plane facing the X1 direction. Face Fx2 is a plane facing the X2 direction. Face Fy1 is a plane facing the Y1 direction. Face Fy2 is a plane facing the Y2 direction. Face Fz1 includes face Fa, which is a plane facing the Z1 direction, and face Fb, which is a plane inclined with respect to face Fa. Face Fa is a plane perpendicular to the Z axis.

[0014] In FIG. 1, the workpiece W has the shape described above for convenience of explanation, but the shape of the workpiece W is not limited to the example shown in FIG. 1 and may be any shape. For example, each of the faces Fx1, Fx2, Fy1, Fy2, Fz1, and Fz2 may be a curved surface curved convexly or concavely, or may be a surface inclined around at least one axis of the X-axis, the Y-axis, and the Z-axis. In addition, for example, among the faces Fx1, Fx2, Fy1, Fy2, Fz1, and Fz2, two adjacent faces may be continuously connected so as not to form a corner, or the corner formed by the two adjacent faces may be rounded. In addition, in FIG. 1, the workpiece W is fixed and installed, but is not limited to this, and the workpiece W may be supported by a mechanism such as a six-axis vertical articulated robot other than the robot 2.

[0015] In this embodiment, the entire surface Fz1 is the surface that is the main printing target, as will be described later in detail with reference to FIG.

[0016] As shown in Fig. 1, the three-dimensional object printing apparatus 1 includes a robot 2, which is an example of a "movement mechanism", a head unit 3 including a liquid ejection head 3a, and a controller 5. First, these will be briefly described below in order based on Fig. 1.

[0017] The robot 2 is a robot that changes the position and posture of the head unit 3 in the world coordinate system. That is, the robot 2 moves the liquid ejection head 3a while changing the posture of the liquid ejection head 3a relative to the three-dimensional workpiece W. In the example shown in Fig. 1, the robot 2 is a so-called six-axis vertical articulated robot.

[0018] As shown in FIG. 1, the robot 2 has a base 210 and an arm 220 .

[0019] The base 210 is a platform that supports the arm 220. In the example shown in Fig. 1, the base 210 is fixed to an installation surface such as a floor surface or a base facing the Z1 direction by screwing or the like. The installation surface to which the 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 dolly, or the like.

[0020] The arm 220 is connected to the base 210 and changes the position and orientation of the liquid ejection head 3a relative to the workpiece W. More specifically, the arm 220 is a six-axis robot arm that three-dimensionally changes the position and orientation of the head unit 3 relative to the base 210. Specifically, the arm 220 has arms 221, 222, 223, 224, 225, and 226, which are connected in this order.

[0021] The arm 221 is connected to the base 210 via a joint J1 so as to be rotatable around a rotation axis O1. The arm 222 is connected to the arm 221 via a joint J2 so as to be rotatable around a rotation axis O2. The arm 223 is connected to the arm 222 via a joint J3 so as to be rotatable around a rotation axis O3. The arm 224 is connected to the arm 223 via a joint J4 so as to be rotatable around a rotation axis O4. The arm 225 is connected to the arm 224 via a joint J5 so as to be rotatable around a rotation axis O5. The arm 226 is connected to the arm 225 via a joint J6 so as to be rotatable around a rotation axis O6.

[0022] Each of the joints J1 to J6 is a mechanism that rotatably connects one of two adjacent members among the base 210 and the arms 221 to 226 to the other. Note that, hereinafter, each of the joints J1 to J6 may be referred to as a "joint J."

[0023] Although not shown in Fig. 1, each of the joints J1 to J6 is provided with a drive mechanism for rotating one of the two corresponding adjacent members relative to the other. The assembly of the drive mechanisms of the joints J1 to J6 corresponds to an arm drive mechanism 2a shown in Fig. 2, which will be described later.

[0024] 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.

[0025] With regard to 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 offset within a range of about ±5° from 90°. Similarly, "parallel" refers not only to the case where the two rotation axes are exactly parallel, but also to the case where one of the two rotation axes is inclined relative to the other axis within a range of about ±5°. Furthermore, the orientation of these rotation axes is not limited to the example shown in FIG. 1.

[0026] A head unit 3 is attached as an end effector to an arm 226 which is the tip of the arm 220 of the robot 2. In the example shown in Fig. 1, the head unit 3 is fixed to the arm 226 by screws or the like.

[0027] The head unit 3 is an assembly having a liquid ejection head 3a that ejects ink, which is an example of a "liquid," toward the workpiece W. The liquid ejection head 3a has a plurality of nozzles n that open to an ejection surface Fn, and although not shown, the liquid ejection head 3a is provided with a piezoelectric element, which is a driving element, and a cavity that contains ink for each nozzle n. Here, the piezoelectric element ejects ink from the nozzle corresponding to the cavity by changing the pressure of the cavity corresponding to the piezoelectric element. Such a liquid ejection head 3a is obtained, for example, by bonding a plurality of substrates, such as silicon substrates, that have been appropriately processed by etching or the like, with an adhesive or the like. Note that, instead of the piezoelectric element, a heater that heats the ink in the cavity may be used as a driving element for ejecting ink from the nozzle.

[0028] 1, the multiple nozzles n of the liquid ejection head 3a are divided into nozzle rows nL1 and nL2. Each of the nozzle rows nL1 and nL2 is a collection of multiple nozzles n aligned in the width direction of the liquid ejection head 3a. Here, the liquid ejection head 3a is configured so that the type of ink used in the nozzle row nL1 can be made different from the type of ink used in the nozzle row nL2. Note that the multiple nozzles n of the liquid ejection head 3a may be divided into three or more nozzle rows.

[0029] The ink is not particularly limited, and examples thereof include water-based ink in which a coloring material such as a dye or pigment is dissolved in a water-based solvent, curable ink using a curable resin such as an ultraviolet curable type, and solvent-based ink in which a coloring material such as a dye or pigment is dissolved in an organic solvent. Among them, curable ink is preferably used. The curable ink is not particularly limited, and may be, for example, any of a heat curable type, a photocurable type, a radiation curable type, and an electron beam curable type, but a photocurable type such as an ultraviolet curable type is preferable. The ink is not limited to a solution, and may be an ink in which a coloring material or the like is dispersed as a dispersoid in a dispersion medium. In addition, the ink is not limited to an ink containing a coloring material, and may be, for example, an ink containing conductive particles such as metal particles for forming wiring or the like as a dispersoid, a clear ink, or a treatment liquid for surface treatment of the workpiece W.

[0030] In addition to the liquid ejection head 3a, the head unit 3 may have, for example, a valve mechanism that opens and closes depending on the pressure of the ink in the liquid ejection head 3a, or may have a light source that emits energy such as light, heat, electron beams or radiation to harden or solidify the ink on the workpiece W.

[0031] 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.

[0032] 1-2. Electrical configuration of the 3D printing device FIG. 2 is a block diagram showing the electrical configuration of the three-dimensional object printing device 1 according to the first embodiment. FIG. 2 shows electrical components among the components of the three-dimensional object printing device 1. As shown in FIG. 2, the three-dimensional object printing device 1 has, in addition to the components shown in FIG. 1 described above, 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. Here, the controller 5, the control module 6, and the computer 7 constitute a control unit 8. The control unit 8 controls the operations of the robot 2 and the head unit 3. Each part of the control unit 8 will be described below in order based on FIG. 2.

[0033] 2 may be appropriately divided, some of the components may be included in other components, or the components may be integrated with other components. For example, some or all of the functions of the controller 5 or the control module 6 may be implemented by a computer 7, or may be implemented by another external device such as a personal computer (PC) connected to the controller 5 via a network such as a local area network (LAN) or the Internet.

[0034] 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.

[0035] The controller 5 includes a memory circuit 5a and a processing circuit 5b.

[0036] 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 one or both of semiconductor memories, for example, a volatile memory such as a random access memory (RAM) and a non-volatile memory such as a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM) or a programmable ROM (PROM). Note that a part or the whole of the storage circuit 5a may be included in the processing circuit 5b.

[0037] The storage circuit 5a stores route information Da.

[0038] The path information Da is used to control the operation of the robot 2, and is information indicating the position and posture of the liquid ejection head 3a on the path along which the liquid ejection head 3a should move when performing a printing operation. The position and posture of the liquid ejection head 3a are defined based on the tool center point of the robot 2. The tool center point may be located, for example, at the center of the nozzle surface, which is the tip surface of the liquid ejection head 3a, or may be a position spaced apart from the liquid ejection head 3a in the ink ejection direction. The path information Da is expressed, for example, by coordinate values ​​in a coordinate system such as a work coordinate system, a base coordinate system, or a world coordinate system. The path information Da is generated by the processing circuit 7b, and input from the processing circuit 7b to the storage circuit 5a. When the 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 the coordinate values ​​in the base coordinate system or the world coordinate system.

[0039] The processing circuit 5b controls the operation of the arm driving mechanism 2a of the robot 2 based on the path information Da, and generates a signal D3. The processing circuit 5b includes, for example, a processor such as one or more CPUs (Central Processing Units). 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.

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

[0041] The processing circuit 5b performs inverse kinematic calculation, which is a calculation for converting the path information Da into movement amounts such as the rotation angle and rotation speed of each joint J of the robot 2. Then, the processing circuit 5b outputs a control signal Sk1 based on the output D1 from each encoder of the arm driving mechanism 2a so that the movement amounts such as the actual rotation angle and rotation speed of each joint J become the above-mentioned calculation results based on the path information Da. The control signal Sk1 is a signal for controlling the driving of the motor of the arm driving mechanism 2a. Here, the control signal Sk1 is corrected by the processing circuit 5b based on the output from a distance sensor (not shown) as necessary.

[0042] 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 a timing when the output D1 from one of the multiple encoders becomes a predetermined value.

[0043] The control module 6 is a circuit that controls the ink ejection operation of the head unit 3 based on a signal D3 output from the controller 5 and 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.

[0044] The timing signal generating circuit 6a generates a timing signal PTS based on the signal D3. The timing signal generating circuit 6a is formed of, for example, a timer that starts generating the timing signal PTS in response to detection of the signal D3.

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

[0046] The control circuit 6c generates a control signal SI, a waveform designation signal dCom, a latch signal LAT, a clock signal CLK, and a change signal CNG based on the timing signal PTS. These signals are synchronized with the timing signal PTS. Of these signals, the waveform designation signal dCom is input to the drive signal generation circuit 6d, and the other signals are input to the switch circuit 3b of the head unit 3.

[0047] The control signal SI is a digital signal for specifying the operating state of the drive element of the liquid ejection head 3a of the head unit 3. Specifically, the control signal SI is a signal for specifying whether or not to supply a drive signal Com, which will be described later, 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 for defining the waveform of the drive signal Com. The latch signal LAT and the change signal CNG are signals used in conjunction with the control signal SI to specify the drive timing of the drive element, thereby specifying the ejection timing of ink from the nozzle. The clock signal CLK is a reference clock signal synchronized with the timing signal PTS.

[0048] The control circuit 6c described above includes, for example, one or more processors such as a CPU, 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.

[0049] The drive signal generating 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 generating circuit 6d has, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generating 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, among the waveforms included in the drive signal Com, a signal having a waveform that is actually supplied to the drive element is a drive pulse PD. The drive pulse PD is supplied from the drive signal generating circuit 6d to the drive element via the switch circuit 3b of the head unit 3.

[0050] Here, the switch circuit 3b 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 supplied as the drive pulse PD based on a control signal SI.

[0051] The computer 7 has a function of generating path information Da, a function of supplying information such as the path information Da to the controller 5, and a function of supplying information such as the print data Img to the control module 6.

[0052] The computer 7 includes a storage circuit 7a and a processing circuit 7b. The computer 7 may also include an input device such as a keyboard or a mouse for receiving operations from a user, and may also include a display device such as a liquid crystal panel for displaying information required for generating the path information Da.

[0053] The storage circuit 7a stores various programs executed by the processing circuit 7b and various data processed by the processing circuit 7b. The storage circuit 7a includes, for example, one or both of semiconductor memories, a volatile memory such as a RAM, and a non-volatile memory such as a ROM, an EEPROM, or a PROM. Note that a part or the whole of the storage circuit 7a may be included in the processing circuit 7b.

[0054] The memory circuit 7a stores path information Da, work information Dc, print data Img, and a program PR.

[0055] The work information Dc is data representing at least a part of the shape of the work W. Specifically, the work information Dc is, for example, three-dimensional data in a format such as STL (Standard Triangulated Language) that represents the shape of the work W by a plurality of polygons. The work information Dc includes coordinate information, which is information about the coordinates of each vertex of the polygon, and vector information, which is information about normal vectors indicating the front and back of the polygon surface. The work information Dc may be data generated by measuring the shape of the work W, or may be data obtained by converting CAD (computer-aided design) data indicating the three-dimensional shape of the work W as necessary. The work information Dc may be represented using coordinate values ​​of a work coordinate system, or may be represented by point cloud data using coordinate values ​​of a base coordinate system or a world coordinate system. The work information Dc may also be represented by a formula or the like, and the format of the work information Dc may be appropriately converted as necessary.

[0056] The print data Img is information that indicates an image to be printed on the workpiece W for each path (pass) of the print path indicated by the path information Da.

[0057] The program PR is a program for generating path information Da and for printing based on the path information Da.

[0058] The processing circuit 7b realizes each of 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 a CPU. Note that the processing circuit 7b may include a programmable logic device such as an FPGA instead of or in addition to a CPU.

[0059] The processing circuit 7b executes the program PR to realize various functions for a printing method described below, including generation of path information Da and print data Img, etc. The printing method will be described in detail later with reference to Figs. 3 to 5.

[0060] As described above, the driving of the robot 2 is controlled based on the path information Da, and the driving of the liquid ejection head 3a is controlled based on the print data Img and the signal D3, thereby performing a printing operation. In the printing operation, the robot 2 changes the position and posture of the liquid ejection head 3a based on the path information Da, while the liquid ejection head 3a ejects ink from the liquid ejection head 3a toward the workpiece W at appropriate timing based on the print data Img and the signal D3. As a result, an image based on the print data Img is formed on the workpiece W.

[0061] 1-3.Printing method Fig. 3 is a diagram showing the flow of the printing method according to the first embodiment. The printing method is executed using the above-mentioned three-dimensional object printing device 1, and as shown in Fig. 3, includes, in this order, a step S10 of acquiring work information Dc, a step S20 of setting a printing area which is an area to be printed on the work W, a step S30 of generating path information Da, a step S40 of generating print data Img, and a step S50 of performing a printing operation.

[0062] In step S10, work information Dc is acquired by measuring the shape of the work W or converting, as necessary, CAD (computer-aided design) data showing the three-dimensional shape of the work W. The acquisition is performed by the processing circuit 7b of the computer 7.

[0063] In step S20, a printing area on the workpiece W is set based on the workpiece information Dc and a designation of a printing area on the workpiece W. The setting is performed by the processing circuit 7b of the computer 7. The designation may be based on preset designation information, or may be based on an input by the user.

[0064] In this embodiment, the entire surface Fz1 of the workpiece W is designated as the printing area. In the three-dimensional object printing device 1, a printing area that includes the designated printing area is set. In other words, an area larger than the designated printing area is set as the printing area. Details of the printing area will be described later with reference to FIG. 4.

[0065] In step S30, path information Da is generated based on the printing area set in step S20. The generation is performed by the processing circuit 7b of the computer 7. Here, for example, in step S30, the number of printing passes is determined based on the size of the printing area and the printing width of the liquid ejection head 3a so that the entire printing area can be printed. The printing width is the effective width of the nozzle rows nL1 and nL2 described above, that is, the width of the nozzle group consisting of a plurality of nozzles n capable of ejecting. In addition, in step S30, the attitude and movement path of the liquid ejection head 3a in each printing pass are determined based on the shape of the printing area and the number of printing passes. As a result, path information Da is generated. Details of the attitude and movement path of the liquid ejection head 3a will be described later with reference to FIG. 4 and FIG. 5.

[0066] In step S40, print data Img is generated based on image information (not shown), the print area set in step S20, and path information Da. The generation is performed by the processing circuit 7b of the computer 7. Here, for example, in step S40, the print data Img is generated by image processing the image information (not shown) based on the print area and path information Da. The image processing includes, for example, color conversion processing, quantization processing, and rasterization processing in this order.

[0067] The color conversion process converts the color values indicated by the image information from the coordinate values in a color space such as the RGB color space in the image information to the coordinate values in a color space such as the CMY color space for the liquid ejection head 3a for each pixel. For this color conversion process, a color conversion table showing the correspondence between the luminance value indicated by the coordinate values in a color space such as the RGB color space used to represent the color indicated by the image information and the density value indicated by the coordinate values in a color space such as the CMY color space used to represent the color indicated by the print data Img is used. Therefore, in this color conversion table, by using the luminance value as the input value and the density value as the output value, the image information is converted into ink color data indicated by the density value for each ink color. In step S40, before the color conversion process, a process of converting the resolution of the image information to the resolution of the print data Img is performed as necessary.

[0068] The quantization process converts the gradation value for each pixel group composed of a plurality of pixels indicated by the ink color data based on the print area and the path information Da into the gradation values of each of the plurality of pixels. More specifically, this quantization process, based on the print area and the path information Da, as shown in FIG. 4 described later, divides the print area RP1 to be printed on the workpiece W into a normal density area RPa and a low density area RPb, and then performs quantization of the normal density area RPa and the low density area RPb so that the print density of the low density area RPb is lower than the print density of the normal density area RPa. Different dither patterns are used for this quantization process in the normal density area RPa and the low density area RPb. The dither pattern defines a threshold value for each of the plurality of pixels for converting the gradation value of a pixel group composed of a plurality of pixels into the gradation values of each of the plurality of pixels. Here, the ink color data is N (N is a natural number) - value data indicating the gradation value of a pixel group composed of the plurality of pixels. The quantization data is M (M is a natural number satisfying 2 ≦ M < N) - value data indicating the gradation value of each of the plurality of pixels.

[0069] Here, from the viewpoint of improving print quality, it is preferable that the print density of the low density area RPb is set to decrease as the position away from the normal density area RPa increases.

[0070] In the rasterization process, when an image is recorded by distributing the quantized data to multiple scans in a printing area to be printed on the workpiece W, print data Img is generated by distributing the quantized data to the multiple scans. Although not shown, a mask pattern is used in this rasterization process. This mask pattern specifies whether or not the quantized data is to be distributed to each of the multiple scans.

[0071] In step S50, printing is performed on the workpiece W using the path information Da from step S30 and the print data Img from step S40. Here, in step S50, the operation of the robot 2 is controlled based on the path information Da, and the operation of the liquid ejection head 3a is controlled based on the print data Img, thereby printing is performed on a print area RP1 described below. Therefore, step S50 includes step S51, which performs a first operation, which is the operation of the robot 2 based on the path information Da.

[0072] Fig. 4 is a diagram for explaining the printing area RP1 in the first operation of step S51. Fig. 4 shows the printing area RP1 on the workpiece W. For ease of explanation, Fig. 4 shows faces Fx1, Fx2, Fy1, Fy2, and Fz1 of the workpiece W, excluding face Fz2, developed into a plane.

[0073] In this embodiment, in the above-mentioned step S20, the entire surface Fz1 of the workpiece W is designated as the printing area, and as shown in FIG. 4, a printing region RP1 that includes the entire surface Fz1 is set.

[0074] In the above-mentioned step S30, the number of printing passes is determined based on the size of the printing area RP1 and the printing width of the liquid ejection head 3a so that the entire printing area RP1 can be printed, and then the posture of the liquid ejection head 3a and the movement paths RU1-1 to RU1-4 in each printing pass are determined based on the shape of the printing area RP1 and the number of printing passes. Hereinafter, the movement paths RU1-1 to RU1-4 may be referred to as the movement path RU1 without distinction.

[0075] In the example shown in Fig. 4, the number of printing passes for printing area RP1 is four. For ease of explanation, the boundaries between the areas of each printing pass in printing area RP1 are shown with dashed lines in Fig. 4. Note that, although illustration is omitted in Fig. 4 for ease of viewing, in reality, areas of adjacent printing passes in printing area RP1 partially overlap by a certain width.

[0076] Each of the four movement paths RU1-1 to RU1-4 is a trajectory of the position of the liquid ejection head 3a for each printing pass during printing on the printing area RP1. Here, during printing on the printing area RP1, the direction indicated by the movement path RU1 is the main scanning direction, and the direction intersecting the main scanning direction is the sub-scanning direction. In the example shown in FIG. 4, the direction indicated by the movement path RU1 is the direction from the second area R2 described later to the first area R1 described later. In addition, at each position on each movement path RU1, the posture of the liquid ejection head 3a is determined so that the width direction of the liquid ejection head 3a intersects with the main scanning direction, and the ejection surface Fn of the liquid ejection head 3a faces the surface of the workpiece W within a predetermined angle range. Note that the main scanning direction during printing on the printing area RP1 is not limited to the example shown in FIG. 4, and may be the opposite direction to the direction shown in FIG. 4.

[0077] In the above-mentioned step S40, the print data Img is generated by image processing the image information (not shown) based on the print area RP1 and the path information Da. As described above, the image processing includes, for example, color conversion processing, quantization processing, and rasterization processing in this order.

[0078] In this quantization process, the print area RP1 is divided into a normal density area RPa and a low density area RPb. The normal density area RPa is an area inside the outer edge of the surface Fz1 designated as the print area, and is set to a normal print density. The low density area RPb is an area outside the normal density area RPa that overlaps with the outer edge of the surface Fz1, and is set to a print density lower than the normal print density. Therefore, the amount of ink ejected per unit area from the liquid ejection head 3a to the low density area RPb is less than the amount of ink ejected per unit area from the liquid ejection head 3a to the normal density area RPa. Note that the comparison of these ejection amounts is a comparison when the density indicated by the input data is the same.

[0079] The outer edge of such a printing area RP1 is located outside the outer edge of the surface Fz1. Therefore, even if an error occurs in the landing of ink from the liquid ejection head 3a onto the workpiece W, printing can be performed reliably over the entire surface Fz1. Here, since the print density of the low-density area RPb is lower than the normal print density, even if the outer edge of the low-density area RPb is located outside the outer edge of the surface Fz1, it is possible to reduce the adverse effects of ink adhesion to surfaces of the workpiece W other than the surface Fz1.

[0080] Here, the low-concentration region RPb includes corners C1, C2, C3, and C4. Corner C1 is a corner formed by surface Fx1 and surface Fz1. Corner C2 is a corner formed by surface Fx2 and surface Fz1. Corner C3 is a corner formed by surface Fy1 and surface Fz1. Corner C4 is a corner formed by surface Fy2 and surface Fz1.

[0081] 4, the number of printing passes for the printing area RP1 is four, as described above, so printing is performed in four separate printing operations for the printing area RP1. The operation of the robot 2 in each of the four printing operations is the first operation of step S51 described above.

[0082] Here, the normal density region RPa in each printing operation for the printing region RP1 is the first region R1. Also, among the low density regions RPb in each printing operation for the printing region RP1, one or both of a pair of regions located outside the first region R1 in the scanning direction is the second region R2, and the region located outside the first region R1 in the sub-scanning direction is the fifth region R5.

[0083] Therefore, in the above-mentioned step S50, the three-dimensional object printing apparatus 1 ejects ink from the liquid ejection head 3a onto the first region R1 and the second region R2 of the workpiece W during the first operation of the robot 2. Here, the second region R2 is located outside the first region R1 of the workpiece W in the main scanning direction and has a lower flatness than the first region R1. Therefore, in the first operation, ink is ejected from the liquid ejection head 3a onto the first region R1 and the second region R2 of the workpiece W, which have different flatnesses, while the robot 2 moves the liquid ejection head 3a in the main scanning direction. This allows printing to be performed on printing regions of the workpiece W that have different flatnesses. Note that "flatness" refers to the radius of curvature when the target surface is approximated by a spherical surface.

[0084] Here, the width W2 of the second region R2 in the main scanning direction is determined according to at least one of the angle of the corner C2, the degree of the angle α shown in Fig. 5 described later, and the attitude of the liquid ejection head 3a during printing with respect to the second region R2, and is preferably smaller than a distance PG described later which is the opposing distance between the liquid ejection head 3a and the workpiece W during the first operation period, and more preferably is larger than 1 / 10 of the distance PG and smaller than the distance PG. This prevents the ink ejected from the liquid ejection head 3a from landing outside the printing region RP1 of the workpiece W, so that deterioration of print quality can be suitably suppressed.

[0085] Also, the width W5 of the fifth region R5 in the sub-scanning direction is smaller than the width W2 of the second region R2 in the main scanning direction. This improves the print quality compared to the embodiment in which the width W5 is equal to or larger than the width W2. This is because the landing error of the liquid from the liquid ejection head 3a to the workpiece W is more likely to occur in the main scanning direction than in the sub-scanning direction. In the main scanning direction, in addition to the motion error of the robot 2, the error in the timing of ink ejection from the liquid ejection head 3a appears as an error in ink landing from the liquid ejection head 3a to the workpiece W. In contrast, in the sub-scanning direction, the motion error of the robot 2 appears as an error in ink landing from the liquid ejection head 3a to the workpiece W, but the motion error of the robot 2 is less likely to appear as an error in ink landing from the liquid ejection head 3a to the workpiece W.

[0086] FIG. 5 is a diagram for explaining the first region R1 and the second region R2 of the workpiece W in the first operation of step S51. As shown in FIG. 5, in the above-mentioned step S51, the robot 2 moves the liquid ejection head 3a along the movement path RU1. In the example shown in FIG. 5, the position of the liquid ejection head 3a on the movement path RU1 is set so that the distance PG between the liquid ejection head 3a and the workpiece W is constant. In addition, the posture of the liquid ejection head 3a on the movement path RU1 is set so that the normal direction of the ejection surface Fn of the liquid ejection head 3a is perpendicular to the surface Fz1 of the workpiece W at each position on the movement path RU1. Here, the distance PG is not particularly limited, but is, for example, 1 mm or more and 5 mm or less.

[0087] The distance PG between the liquid ejection head 3a and the workpiece W during the first operation does not have to be constant, and for example, the distance PG when printing on the surface Fa and the distance PG when printing on the surface Fb may be different from each other. Furthermore, the normal direction of the ejection surface Fn of the liquid ejection head 3a at each position on the movement path RU1 does not have to be perpendicular to the surface Fz1 of the workpiece W, and for example, the posture of the liquid ejection head 3a when printing on the surface Fa and the posture of the liquid ejection head 3a when printing on the surface Fb may be the same.

[0088] As described above, of the corners C1, C2, C3, and C4 included in the low-density region RPb, the corner C2 is included in the second region R2, which is a part of the low-density region RPb. In this way, by including the corner C2 of the workpiece W in the second region R2, it is possible to perform borderless printing on the workpiece W having the corner C2.

[0089] As described above, the first region R1 is the normal density region RPa, whereas the second region R2 is a part of the low density region RPb. Therefore, during the first operation, the amount of ink discharged per unit area from the liquid discharge head 3a to the second region R2 is less than the amount of ink discharged per unit area from the liquid discharge head 3a to the first region R1. In this way, by printing the second region R2 including the corner C2 at a lower density than the first region R1, it is possible to suppress the adhesion of liquid and mist to the outside of the printing region RP1 of the workpiece W. As a result, it is possible to suppress the deterioration of the print quality.

[0090] Here, during the first operation, the amount of ink discharged per unit area from the liquid discharge head 3a to the second region R2 is preferably 20% to 80% of the amount of ink discharged per unit area from the liquid discharge head 3a to the first region R1, more preferably 40% to 60%, and even more preferably 45% to 55%. By keeping the amount of ink discharged per unit area from the liquid discharge head 3a to the second region R2 within such a range, deterioration in print quality can be suitably suppressed.

[0091] In contrast, if the amount of ink ejected per unit area from the liquid ejection head 3a to the second region R2 is too small, the difference in print quality between the first region R1 and the second region R2 becomes noticeable depending on the color of the ink, etc. On the other hand, if the amount of ink ejected per unit area from the liquid ejection head 3a to the second region R2 is too large, there is a tendency for ink mist to increase outside the printing region RP1.

[0092] 5, the position of the liquid ejection head 3a when printing on the second region R2 is on an extension of the movement path of the liquid ejection head 3a when printing on the first region R1. Also, the posture of the liquid ejection head 3a when printing on the second region R2 is the same as the posture of the liquid ejection head 3a when printing on the first region R1.

[0093] Therefore, the closer the angle of corner C2, i.e., the angle between surface Fx2 and surface Fb of surface Fz1, is to 90°, the more likely it is that the ink ejected from the liquid ejection head 3a when printing on the second region R2 will become ink mist and float, or land on the workpiece W in an area outside the printing region RP1.

[0094] Therefore, it is preferable to reduce the width W2 of the second region R2 shown in Fig. 4 as the angle of the corner C2 approaches 90°, thereby making it possible to suppress deterioration in print quality.

[0095] From the same viewpoint, since the smaller the angle α between the first region R1 and the second region R2, the more likely the above-mentioned problems such as ink mist occur, it is preferable to reduce the width W2 of the second region R2 shown in Fig. 4. That is, the width W2 when the angle α is a first angle is longer than the width W2 when the angle α is a second angle smaller than the first angle. The angle α is the angle between a first plane that approximates the first region R1 to a plane and a second plane that approximates the second region R2 to a plane.

[0096] Here, when the angle α is the first angle, the operation of the robot 2 when ejecting ink from the liquid ejection head 3a onto the first region R1 and the second region R2 of the workpiece W corresponds to the first operation, and when the angle α is the second angle, the operation of the robot 2 when ejecting ink from the liquid ejection head 3a onto the first region R1 and the second region R2 of the workpiece W corresponds to the fourth operation. Moreover, during the fourth operation, the first region R1 corresponds to the "eighth region" and the second region R2 corresponds to the "ninth region." In this way, the print quality can be improved by adjusting the width W2 in the main scanning direction of the second region R2, which is a region with low flatness in the print region RP1 of the workpiece W, according to the flatness or the angle of the corner of the print region RP1 of the workpiece W.

[0097] Further, from the same viewpoint, when printing on the second region R2, the larger the angle θa between the discharge surface Fn of the liquid discharge head 3a and the second region R2, the more likely the above-mentioned problems such as ink mist occur, so it is preferable to reduce the width W2 of the second region R2 shown in Fig. 4 described above. In other words, when printing on the second region R2, the smaller the attitude angle θb, which is the angle between the normal direction of the installation surface on which the work W is placed and the discharge surface Fn of the liquid discharge head 3a, the more preferable it is ... the width W2 when the attitude angle θb is the third angle is longer than the width W2 when the attitude angle θb is the fourth angle smaller than the third angle.

[0098] Here, when the attitude angle θb is the third angle, the operation of the robot 2 when ejecting ink from the liquid ejection head 3a onto the first region R1 and the second region R2 of the workpiece W corresponds to the first operation, and when the attitude angle θb is the fourth angle, the operation of the robot 2 when ejecting ink from the liquid ejection head 3a onto the first region R1 and the second region R2 of the workpiece W corresponds to the fourth operation. Moreover, during the fourth operation, the first region R1 corresponds to the "eighth region" and the second region R2 corresponds to the "ninth region". In this way, the print quality can be improved by adjusting the width W2 in the main scanning direction of the second region R2, which is a region with low flatness in the print region RP1 of the workpiece W, according to the attitude angle θb. This is because the larger the attitude angle θb, the more likely it is that the liquid will land on the workpiece W.

[0099] In addition, since the type of ink used in the nozzle row nL1 and the type of ink used in the nozzle row nL2 can be different as described above, the liquid ejection head 3a can eject a first color liquid and a second color liquid having a higher brightness than the first color. When two types of liquid with different brightness are used in this way, the three-dimensional object printing device 1 ejects the first color liquid and the second color liquid from the liquid ejection head 3a to the first region R1 during the first operation. In contrast, the three-dimensional object printing device 1 ejects the second color liquid but not the first color liquid from the liquid ejection head 3a to the second region R2 during the first operation. This makes it possible to improve printing quality by not using a liquid that stands out in the second region R2 for printing.

[0100] Such a distinction between the first color liquid and the second color liquid is realized, for example, by setting the dither pattern used in the quantization process in step S40 described above.

[0101] 2. Second embodiment A second embodiment of the present disclosure will be described below. In the following example, 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 will be omitted as appropriate.

[0102] 6 is a diagram showing the flow of a printing method according to the second embodiment. This printing method is similar to the printing method of the first embodiment, except that it includes steps S20A to S50A instead of steps S20 to S50 of the first embodiment.

[0103] Step S20A is the same as step S20 in the first embodiment, except that a print area RP2 is set in step S20A, which will be described later. The print area RP2 is set in the same manner as the print area RP1 in the first embodiment.

[0104] Step S30A is the same as step S30 in the first embodiment, except that a step for determining the position and attitude of the liquid ejection head 3a when printing on a printing area RP2 (described later) is added. The position and attitude of the liquid ejection head 3a when printing on a printing area RP2 (described later) is determined by a method similar to that for determining the position and attitude of the liquid ejection head 3a when printing on a printing area RP1 in the first embodiment.

[0105] Step S40A is the same as step S40 in the first embodiment, except that processing of image information used when printing on print area RP2, which will be described later, is added. The processing of image information used when printing on print area RP2, which will be described later, is performed in the same manner as the processing of image information used when printing on print area RP1.

[0106] Step S50A is the same as step S50 in the first embodiment, except for adding step S52 for printing on the printing area RP2 described later. In step S50A, the operation of the robot 2 is controlled based on the path information Da, and the operation of the liquid ejection head 3a is controlled based on the print data Img, so that printing is performed on the printing area RP1 as well as the printing area RP2 described later. Therefore, in addition to step S51, step S52 includes a second operation, which is an operation of the robot 2 during a period different from the first operation and based on the path information Da. The order of execution of steps S51 and S52 is not particularly limited and is arbitrary, and may be step S51 followed by step S52, or step S52 followed by step S51.

[0107] Fig. 7 is a diagram for explaining the printing area RP2 in the second operation. Fig. 7 shows the relationship between the printing area RP1 and the printing area RP2 on the workpiece W. Note that, in Fig. 7, similar to Fig. 4 described above, for convenience of explanation, faces Fx1, Fx2, Fy1, Fy2, and Fz1 of the workpiece W, excluding face Fz2, are shown in a state developed on a plane.

[0108] In this embodiment, in the aforementioned step S20A, in addition to the processing of step S20 in the first embodiment, a portion of the surface Fx2 of the workpiece W is designated as a printing area, and in addition to the printing area RP1, a printing area RP2 that encompasses the designated area is set, as shown in FIG. 7.

[0109] In the aforementioned step S30A, in addition to the processing of step S30 in the first embodiment, the number of printing passes is determined based on the size of the printing area RP2 and the printing width of the liquid ejection head 3a so as to print the entire area of ​​the printing area RP2, and then the attitude and movement path RU2 of the liquid ejection head 3a in each printing pass are determined based on the shape of the printing area RP2 and the number of printing passes.

[0110] In the example shown in FIG. 7, the number of printing passes for the print area RP2 is one.

[0111] The movement path RU2 is a trajectory of the position of the liquid ejection head 3a when printing the printing area RP2. Here, when printing the printing area RP2, the direction indicated by the movement path RU2 is the main scanning direction, and the direction intersecting the main scanning direction is the sub-scanning direction. In the example shown in FIG. 7, the direction indicated by the movement path RU2 is the direction from the third area R3 to the fourth area R4 described later. In addition, at each position on the movement path RU2, the attitude of the liquid ejection head 3a is determined so that the width direction of the liquid ejection head 3a intersects with the main scanning direction, and the ejection surface Fn of the liquid ejection head 3a faces the surface of the workpiece W within a predetermined angle range. The main scanning direction when printing the printing area RP2 is not limited to the example shown in FIG. 7, and may be the opposite direction to the direction shown in FIG. 7.

[0112] In the above-mentioned step S40A, in addition to the process of step S40 in the first embodiment, the print data Img is generated by image processing the image information (not shown) based on the print area RP2 and the path information Da. The image processing includes, for example, color conversion processing, quantization processing, and rasterization processing in this order, similar to the processing in the print area RP1.

[0113] In the quantization process of step S40A, the printing area RP2 is divided into a third area R3 and a fourth area R4. The third area R3 is an area inside the outer edge of the surface Fx2 designated as the printing area, and is set to a normal printing density. The fourth area R4 is an area outside the third area R3 and overlaps with a part of the outer edge of the surface Fx2, and is set to a printing density lower than the normal printing density. Therefore, the amount of ink discharged per unit area from the liquid discharge head 3a to the fourth area R4 is less than the amount of ink discharged per unit area from the liquid discharge head 3a to the third area R3. Here, the fourth area R4 includes the corner C2. In contrast, the third area R3 is a flat surface that does not include the corners of the workpiece W. Therefore, the flatness of the fourth area R4 is lower than the flatness of the third area R3.

[0114] Here, at least a portion of the fourth region R4 overlaps at least a portion of the second region R2. In the example shown in FIG. 7, a mode in which the fourth region R4 coincides with the second region R2 in the main scanning direction is illustrated. Therefore, in the example shown in FIG. 7, the width W4 of the fourth region R4 in the main scanning direction is equal to the width W2 of the second region R2 in the main scanning direction. Note that, in the main scanning direction, a portion of the fourth region R4 does not have to overlap the second region R2, and a portion of the second region R2 does not have to overlap the fourth region R4. Also, the width W2 and the width W4 may be different from each other.

[0115] Since the fourth region R4 has an overlapping portion with the second region R2 in this manner, if the image to be printed in the printing region RP2 is an integrated image with the image to be printed in the printing region RP1, in the rasterization process for printing by the first operation and the second operation, exclusive processing may be performed to each pixel in the overlapping area between the second region R2 and the fourth region R4, either by applying ink in the first operation or by applying ink in the second operation.

[0116] 8 is a diagram for explaining the third region R3 and the fourth region R4 of the workpiece W in the second operation of step S52. As shown in FIG. 8, in the above-mentioned step S52, the robot 2 moves the liquid ejection head 3a along the movement path RU2. In the example shown in FIG. 8, the position of the liquid ejection head 3a on the movement path RU2 is set so that the distance PG between the liquid ejection head 3a and the workpiece W is constant. In addition, the attitude of the liquid ejection head 3a on the movement path RU2 is set so that the normal direction of the ejection surface Fn of the liquid ejection head 3a is perpendicular to the surface Fx2 of the workpiece W at each position on the movement path RU2.

[0117] Note that the distance PG between the liquid ejection head 3a and the workpiece W during the second operation does not have to be constant. Furthermore, the normal direction of the ejection surface Fn of the liquid ejection head 3a does not have to be perpendicular to the surface Fx2 of the workpiece W at each position on the movement path RU2.

[0118] Here, the posture of the workpiece W during the second operation may be different from the posture of the workpiece W during the first operation. For example, the posture of the workpiece W during the second operation may be a posture obtained by rotating the posture of the workpiece W during the first operation by 90° around an axis parallel to the Y axis. Such a change in the posture of the workpiece W is performed by, for example, a mechanism such as a six-axis articulated robot that supports the workpiece W.

[0119] In this way, the three-dimensional object printing apparatus 1 ejects ink from the liquid ejection head 3a to the third region R3 and the fourth region R4 of the workpiece W during the second operation in which the robot 2 moves the liquid ejection head 3a in a period different from the first operation. Here, as described above, the fourth region R4 is adjacent to the third region R3 of the workpiece W in the main scanning direction and has a lower flatness than the third region R3. The second region R2 and the fourth region R4 overlap each other. In this way, since the second region R2 and the fourth region R4 overlap each other, it is possible to suppress the occurrence of printing defects such as blank spaces at the boundary between the printing region RP1 by the first operation and the printing region RP2 by the second operation.

[0120] Here, the second region R2 is provided between the first region R1 and the third region R3, and includes the corner C2 of the workpiece W. This makes it possible to perform borderless printing on the two faces Fx2 and Fz1 that sandwich the corner C2 of the workpiece W.

[0121] When the second region R2 and the fourth region R4 overlap each other as described above, the overlapping region is supplied with ink ejected from the liquid ejection head 3a toward the second region R2 during the first operation period, and ink ejected from the liquid ejection head 3a toward the fourth region R4 during the second operation period.

[0122] Here, from the viewpoint of preventing deterioration in print quality, it is preferable that the amount of ink applied to the overlapping areas of the second region R2 and the fourth region R4 is not excessively large compared to the first region R1 and the third region R3.

[0123] Specifically, when the amount of ink ejected per unit area from the liquid ejection head 3a to the first region R1 during the first operation period is IW1, the amount of liquid ejected per unit area from the liquid ejection head 3a to the second region R2 during the first operation period is IW2, the amount of liquid ejected per unit area from the liquid ejection head 3a to the third region R3 during the second operation period is IW3, and the amount of ink ejected per unit area from the liquid ejection head 3a to the fourth region R4 during the second operation period is IW4, it is preferable that the sum of IW2 / IW1 and IW4 / IW3 is as close to 100% as possible, and specifically, it is preferable that it is 80% or more and 120% or less, more preferably 90% or more and 110% or more, and even more preferably 95% or more and 105% or less.

[0124] As described above in the first embodiment, during the first operation period, the amount of liquid ejected per unit area from the liquid ejection head 3a to the second region R2 is preferably 20% or more and 80% or less, more preferably 40% or more and 60% or less, and even more preferably 45% or more and 55% or less, of the amount of ink ejected per unit area from the liquid ejection head 3a to the first region R1.

[0125] From the viewpoint of making the sum of IW2 / IW1 and IW4 / IW3 as close as possible to 100%, the amount of ink discharged per unit area from the liquid discharge head 3a to the fourth region R4 during the second operation is preferably 20% to 80%, more preferably 40% to 60%, and even more preferably 45% to 55% of the amount of liquid discharged per unit area from the liquid discharge head 3a to the third region R3. By keeping the amount of ink discharged per unit area from the liquid discharge head 3a to the printing regions RP1 and RP2 within such a range, it is possible to suitably suppress deterioration in print quality at the boundary between the printing region RP1 by the first operation and the printing region RP2 by the second operation and in the vicinity thereof.

[0126] According to the second embodiment described above, printing can also be performed appropriately on the printing areas RP1 and RP2 of the workpiece W having different flatnesses.

[0127] 3. Third embodiment The third embodiment of the present disclosure will be described below. In the following exemplary embodiment, the elements having the same actions and functions as those in the first embodiment will be referred to by the same reference numerals used in the description of the first embodiment, and detailed descriptions thereof will be omitted as appropriate.

[0128] 9 is a diagram showing the flow of a printing method according to the third embodiment. This printing method is similar to the printing method of the first embodiment, except that it includes steps S20B to S50B instead of steps S20 to S50 of the first embodiment.

[0129] Step S20B is the same as step S20 in the first embodiment, except that the setting of the print area RP2 in the second embodiment and the print area RP3 described below are added. That is, step S20B is the same as step S20A in the second embodiment, except that the setting of the print area RP3 described below is added. The setting of the print area RP3 described below is performed in the same manner as the setting of the print area RP1 in the first embodiment. Note that in this embodiment, matters related to the print area RP2 may be used as necessary and may be omitted.

[0130] Step S30B is the same as step S30 in the first embodiment, except that a step of determining the position and attitude of the liquid ejection head 3a when printing on the printing area RP2 in the second embodiment and a printing area RP3 described later is added. That is, step S30B is the same as step S30A in the second embodiment, except that a step of determining the position and attitude of the liquid ejection head 3a when printing on the printing area RP3 described later is added. The position and attitude of the liquid ejection head 3a when printing on the printing area RP3 described later is determined by the same method as the position and attitude of the liquid ejection head 3a when printing on the printing area RP1 in the first embodiment.

[0131] Step S40B is the same as step S40 in the first embodiment, except that it adds processing of image information used when printing on the print area RP2 of the second embodiment and the print area RP3 described below. That is, step S40B is the same as step S40A in the second embodiment, except that it adds processing of image information used when printing on the print area RP3 described below. The processing of image information used when printing on the print area RP3 described below is performed by the same method as the processing of image information used when printing on the print area RP1.

[0132] Process S50B is the same as process S50 in the first embodiment, except that process S52 in the second embodiment and process S53 for printing on the printing area RP3 described later are added. That is, process S50B is the same as process S50A in the second embodiment, except that process S53 for printing on the printing area RP3 described later is added. In process S50B, the operation of the robot 2 is controlled based on the path information Da, and the operation of the liquid ejection head 3a is controlled based on the print data Img, so that printing is performed on the printing areas RP1 and RP2 as well as the printing area RP3 described later. Therefore, process S50B includes, in addition to processes S51 and S52, process S53 for performing a third operation, which is an operation of the robot 2 during a period different from the first operation and the second operation and based on the path information Da. The order of execution of processes S51, S52, and S53 is not particularly limited and is arbitrary.

[0133] Fig. 10 is a diagram for explaining the printing area RP3 in the third operation. Fig. 10 shows the relationship between the printing areas RP1, RP2, and RP3 on the workpiece W. Note that, in Fig. 10, similar to Fig. 4 described above, for convenience of explanation, faces Fx1, Fx2, Fy1, Fy2, and Fz1 of the workpiece W, excluding face Fz2, are shown developed on a plane.

[0134] In this embodiment, in the aforementioned step S20B, in addition to the processing of step S20A in the second embodiment, a portion of the surface Fy2 of the workpiece W is designated as a printing area, and in addition to printing areas RP1 and RP2, a printing area RP3 that encompasses the designated area is set, as shown in FIG. 10.

[0135] In the aforementioned step S30B, in addition to the processing of step S30A of the second embodiment, the number of printing passes is determined based on the size of the printing area RP3 and the printing width of the liquid ejection head 3a so as to print the entire area of ​​the printing area RP3, and then the attitude and movement path RU3 of the liquid ejection head 3a in each printing pass are determined based on the shape of the printing area RP3 and the number of printing passes.

[0136] In the example shown in FIG. 10, the number of printing passes for the print area RP3 is one.

[0137] The movement path RU3 is a trajectory of the position of the liquid ejection head 3a when printing on the printing area RP3. Here, when printing on the printing area RP3, the direction indicated by the movement path RU3 is the main scanning direction, and the direction intersecting the main scanning direction is the sub-scanning direction. In the example shown in FIG. 10, the direction indicated by the movement path RU3 is the direction in which the corner C3 extends. In addition, at each position on the movement path RU3, the attitude of the liquid ejection head 3a is determined so that the width direction of the liquid ejection head 3a intersects with the main scanning direction, and the ejection surface Fn of the liquid ejection head 3a faces the surface of the workpiece W within a predetermined angle range. Note that the main scanning direction when printing on the printing area RP3 is not limited to the example shown in FIG. 10, and may be the opposite direction to the direction shown in FIG. 10.

[0138] In step S40B described above, in addition to the process of step S40A in the second embodiment, print data Img is generated by image processing image information (not shown) based on the print area RP3 and path information Da. The image processing includes, for example, color conversion processing, quantization processing, and rasterization processing in this order, similar to the processing in the print areas RP1 and RP2.

[0139] In the quantization process of step S40B, the printing area RP3 is divided into a sixth area R6 and a seventh area R7. The seventh area R7 is an area inside the outer edge of the surface Fy2 designated as the printing area, and is set to a normal printing density. The sixth area R6 is an area outside the seventh area R7 that overlaps with a part of the outer edge of the surface Fy2, and is set to a printing density lower than the normal printing density. Therefore, the amount of ink discharged per unit area from the liquid discharge head 3a to the sixth area R6 is less than the amount of ink discharged per unit area from the liquid discharge head 3a to the seventh area R7. Here, the sixth area R6 includes the corner C3.

[0140] As described in the first embodiment, during the first operation, the three-dimensional object printing device 1 of this embodiment ejects ink from the liquid ejection head 3a also onto a fifth region R5 adjacent to the first region R1 of the work W in the sub-scanning direction.

[0141] Here, at least a portion of the sixth region R6 overlaps at least a portion of the fifth region R5 of the print region RP1. In the example shown in FIG. 10, a mode in which the sixth region R6 coincides with the fifth region R5 in the sub-scanning direction is illustrated. Therefore, in the example shown in FIG. 10, the width W6 of the sixth region R6 in the sub-scanning direction is equal to the width W5 of the fifth region R5 in the sub-scanning direction. Note that, in the sub-scanning direction, a portion of the sixth region R6 does not have to overlap the fifth region R5, and a portion of the fifth region R5 does not have to overlap the sixth region R6. Furthermore, the width W5 and the width W6 may be different from each other.

[0142] Since the sixth region R6 has an overlapping portion with the fifth region R5 in this manner, if the image to be printed in the printing region RP3 is an integrated image with the image to be printed in the printing region RP1, in the rasterization process for printing by the first operation and the third operation, exclusive processing may be performed to apply ink to each pixel in the overlapping area between the fifth region R5 and the sixth region R6, either in the first operation or in the third operation.

[0143] 11 is a diagram for explaining the sixth region R6 and the seventh region R7 of the workpiece W in the third operation. As shown in FIG. 11, in the above-mentioned step S53, the robot 2 moves the liquid ejection head 3a along the movement path RU3. In the example shown in FIG. 11, the position of the liquid ejection head 3a on the movement path RU3 is set so that the distance PG between the liquid ejection head 3a and the workpiece W is constant. In addition, the posture of the liquid ejection head 3a on the movement path RU3 is set so that the normal direction of the ejection surface Fn of the liquid ejection head 3a is perpendicular to the surface Fy2 of the workpiece W at each position on the movement path RU3.

[0144] Note that the distance PG between the liquid ejection head 3a and the workpiece W during the third operation does not have to be constant. Furthermore, the normal direction of the ejection surface Fn of the liquid ejection head 3a does not have to be perpendicular to the surface Fy2 of the workpiece W at each position on the movement path RU3.

[0145] Here, the posture of the workpiece W during the third operation may be different from the posture of the workpiece W during the first operation. For example, the posture of the workpiece W during the third operation may be a posture obtained by rotating the posture of the workpiece W during the first operation by 90° around an axis parallel to the X-axis. Such a change in the posture of the workpiece W is performed by, for example, a mechanism such as a six-axis articulated robot that supports the workpiece W.

[0146] In this way, the three-dimensional object printing apparatus 1 of this embodiment ejects ink from the liquid ejection head 3a onto the sixth region R6 and the seventh region R7 of the workpiece W during the third operation in which the robot 2 moves the liquid ejection head 3a in a period different from the first and second operations. As described above, the seventh region R7 is adjacent to the sixth region R6 of the workpiece W in the sub-scanning direction and has a higher flatness than the sixth region R6. The fifth region R5 and the sixth region R6 overlap each other.

[0147] Here, the width in the sub-scanning direction of the area where the fifth region R5 and the sixth region R6 overlap each other is smaller than the width in the main scanning direction of the area where the second region R2 and the fourth region R4 overlap each other. This improves the print quality compared to an embodiment in which the width of the overlapping area in the sub-scanning direction is equal to or larger than the width of the overlapping area in the main scanning direction. This is because, as described above, landing errors of the liquid from the liquid ejection head 3a onto the workpiece W are more likely to occur in the main scanning direction than in the sub-scanning direction.

[0148] According to the third embodiment described above, printing can also be performed appropriately on the printing areas RP1, RP2, and RP3 of the workpiece W that have different flatnesses.

[0149] 4. 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 illustrated below. Note that two or more embodiments selected from the following exemplary embodiments can be appropriately combined as long as they are not contradictory to each other.

[0150] 4-1. Variation 1 In each of the above-described embodiments, an example is given in which an area including a corner on the workpiece W is used as the printing area, but the invention is not limited to this example, and the printing area may be an area that does not include the corners on the workpiece W. In other words, in each of the above-described embodiments, an example is given in which borderless printing is performed, but the invention is not limited to this example, and the printing start position and printing end position may be positions away from the corners of the workpiece W.

[0151] 4-2. Variation 2 In each of the above-described embodiments, an example is given in which the amount of ink ejected per unit area for the second region R2, the fourth region R4 or the sixth region R6 is adjusted to a low concentration by quantization processing, but this is not limited to this example, and the adjustment method may be, for example, a method of thinning out the print data itself, a method of lowering the ejection frequency, or a method of increasing the main scanning speed.

[0152] 4-3. Variation 3 In the above-mentioned embodiment, a configuration in which a six-axis vertical multi-axis robot is used as the moving mechanism is exemplified, but is not limited to this configuration. The moving mechanism may be, for example, a vertical multi-axis robot other than six axes, or a horizontal multi-axis robot. Furthermore, the arm of the robot may have an extension mechanism or a linear motion mechanism in addition to a joint formed by a rotation mechanism. However, from the viewpoint of the balance between the print quality in the printing operation and the degree of freedom of the robot's operation in the non-printing operation, it is preferable that the robot is a multi-axis robot with six or more axes.

[0153] 4-4. Variation 4 In the above embodiment, the head may be fixed to the robot by gripping the head with a gripping mechanism such as a hand attached as an end effector of the robot, but the present invention is not limited to this configuration.

[0154] 4-5. Variation 5 The use of the three-dimensional printing device of the present disclosure is not limited to printing images. For example, a three-dimensional printing device that ejects a solution of a color material is used as a manufacturing device that forms a color filter for a liquid crystal display device. Also, a three-dimensional printing device that ejects a solution of a conductive material is used as a manufacturing device that forms wiring and electrodes for a wiring board. Also, a three-dimensional printing device can be used as a jet dispenser that applies a liquid such as an adhesive to a medium.

[0155] 4. Notes The following is a summary of this disclosure.

[0156] (Additional Note 1) A three-dimensional object printing device of a first aspect, which is a preferred example of the present disclosure, comprises a liquid ejection head that ejects liquid, and a moving mechanism that moves the liquid ejection head while changing the attitude of the liquid ejection head relative to a three-dimensional workpiece, and during a first operation of the moving mechanism, ejects liquid from the liquid ejection head onto a first region of the workpiece and a second region that is located outside the first region of the workpiece in the main scanning direction and has a lower flatness than the first region.

[0157] In the above aspect, in the first operation, the liquid ejection head is moved in the main scanning direction by the moving mechanism to eject liquid from the liquid ejection head onto the first and second regions of the workpiece, the regions having different flatnesses from each other. This makes it possible to perform printing on the print regions of the workpiece having different flatnesses.

[0158] (Additional Note 2) In a second aspect which is a preferred example of the first aspect, the second region includes a corner of the workpiece. In the above aspect, borderless printing can be performed on a workpiece having corners.

[0159] (Note 3) In the third aspect, which is a preferred example of the first or second aspect, during the first operation, the amount of liquid discharged per unit area from the liquid discharge head to the second region is less than the amount of liquid discharged per unit area from the liquid discharge head to the first region. In the above aspect, by printing the second region, including the corners, at a lower density than the first region, it is possible to prevent the liquid and mist from adhering to the outside of the print region of the workpiece. As a result, it is possible to prevent a decrease in print quality.

[0160] (Note 4) In a fourth aspect, which is a preferred example of any of the first to third aspects, during the first operation, the amount of liquid discharged per unit area from the liquid discharge head to the second region is 20% to 80% of the amount of liquid discharged per unit area from the liquid discharge head to the first region. In the above aspect, deterioration of print quality can be preferably suppressed.

[0161] (Note 5) In a fifth embodiment, which is a preferred example of any of the first to fourth embodiments, during a second operation in which the moving mechanism moves the liquid ejection head in a period different from the first operation, liquid is ejected from the liquid ejection head onto a third region of the workpiece and a fourth region of the workpiece adjacent to the third region in the main scanning direction and having a lower flatness than the third region, and the second region and the fourth region overlap each other. In the above embodiment, since the second region and the fourth region overlap each other, it is possible to suppress printing defects such as blank areas at the boundary between the print region by the first operation and the print region by the second operation.

[0162] (Note 6) In the sixth aspect, which is a preferred example of the fifth aspect, during the first operation, the amount of liquid ejected per unit area from the liquid ejection head to the second region is 20% to 80% of the amount of liquid ejected per unit area from the liquid ejection head to the first region, and during the second operation, the amount of liquid ejected per unit area from the liquid ejection head to the fourth region is 20% to 80% of the amount of liquid ejected per unit area from the liquid ejection head to the third region. In the above aspect, deterioration of print quality in and near the boundary between the print area by the first operation and the print area by the second operation can be suitably suppressed.

[0163] (Appendix 7) In the seventh aspect, which is a preferred example of the fifth or sixth aspect, the second area is provided between the first area and the third area and includes a corner of the workpiece. In the above aspect, borderless printing can be performed on two surfaces that sandwich the corner of the workpiece.

[0164] (Note 8) In the eighth aspect, which is a preferred example of any one of the fifth to seventh aspects, during the first operation, the liquid ejection head ejects liquid onto a fifth area adjacent to the first area of ​​the workpiece in the sub-scanning direction, and during a third operation in which the moving mechanism moves the liquid ejection head in a period different from the first and second operations, the liquid ejection head ejects liquid onto a sixth area of ​​the workpiece and a seventh area adjacent to the sixth area of ​​the workpiece in the sub-scanning direction and having a higher flatness than the sixth area, the fifth area and the sixth area overlap each other, and the width of the area where the fifth area and the sixth area overlap each other in the sub-scanning direction is smaller than the width of the area where the second area and the fourth area overlap each other in the main scanning direction. In the above aspect, the print quality can be improved compared to the aspect in which the width of the area where the overlapping areas in the sub-scanning direction is equal to or larger than the width of the area where the overlapping areas in the main scanning direction is equal to or larger than the width of the area where the overlapping areas in the main scanning direction are overlapped. This is because landing errors of liquid from the liquid ejection head to the workpiece are more likely to occur in the main scanning direction than in the sub-scanning direction. In the main scanning direction, errors in the timing of ejection of liquid from the liquid ejection head, in addition to operational errors of the moving mechanism, appear as landing errors of liquid from the liquid ejection head to the workpiece. In contrast, in the sub-scanning direction, operational errors of the moving mechanism appear as landing errors of liquid from the liquid ejection head to the workpiece, but operational errors of the moving mechanism are less likely to appear as landing errors of liquid from the liquid ejection head to the workpiece.

[0165] (Note 9) In a ninth aspect, which is a preferred example of any one of the first to eighth aspects, the width of the second region in the main scanning direction is smaller than the opposing distance between the liquid ejection head and the workpiece during the first operation. In the above aspect, deterioration of print quality can be preferably suppressed.

[0166] (Note 10) In the tenth aspect, which is a preferred example of any one of the first to ninth aspects, during a fourth operation in which the moving mechanism moves the liquid ejection head, liquid is ejected from the liquid ejection head onto an eighth area of ​​the workpiece and a ninth area of ​​the workpiece that is located outside the eighth area of ​​the workpiece in the main scanning direction and has a lower flatness than the eighth area, and when the angle between the first area and the second area is greater than the angle between the eighth area and the ninth area, the width of the second area in the main scanning direction is longer than the width of the ninth area in the main scanning direction. In the above aspects, the print quality can be improved by adjusting the width in the main scanning direction of the area with low flatness in the print area of ​​the workpiece according to the flatness or angle of the corner of the print area of ​​the workpiece.

[0167] (Note 11) In the eleventh aspect, which is a preferred example of any one of the first to tenth aspects, during a fourth operation in which the moving mechanism moves the liquid ejection head, liquid is ejected from the liquid ejection head onto an eighth area of ​​the workpiece and a ninth area of ​​the workpiece that is located outside the eighth area of ​​the workpiece in the main scanning direction and has a lower flatness than the eighth area, and when the angle between the normal direction of the installation surface on which the workpiece is installed and the ejection surface of the liquid ejection head is taken as an attitude angle, if the attitude angle when printing on the second area is larger than the attitude angle when printing on the ninth area, the width of the second area in the main scanning direction is longer than the width of the ninth area in the main scanning direction. In the above aspect, the print quality can be improved by adjusting the width of the area with low flatness in the print area of ​​the workpiece in the main scanning direction according to the attitude angle. This is because the larger the attitude angle, the more likely it is that the liquid will land on the workpiece.

[0168] (Appendix 12) In the twelfth aspect, which is a preferred example of any of the first to eleventh aspects, the liquid ejection head is capable of ejecting a first color liquid and a second color liquid having a higher brightness than the first color, and during the first operation, the first color liquid and the second color liquid are ejected from the liquid ejection head to the first region, and the first color liquid is not ejected from the liquid ejection head to the second region but the second color liquid is ejected. In the above aspect, by not using a liquid that stands out in the second region for printing, it is possible to improve print quality.

[0169] (Appendix 13) A printing method of a thirteenth aspect, which is a preferred example of the present disclosure, is a printing method using a three-dimensional printing device including a liquid ejection head that ejects liquid, and a moving mechanism that moves the liquid ejection head while changing the attitude of the liquid ejection head relative to a three-dimensional workpiece, and includes a step of ejecting liquid from the liquid ejection head during a first operation in which the moving mechanism moves the liquid ejection head onto a first region of the workpiece and a second region that is located outside the first region of the workpiece in the main scanning direction and has a lower flatness than the first region.

[0170] In the above aspect, in the first operation, the liquid ejection head is moved in the main scanning direction by the moving mechanism to eject liquid from the liquid ejection head onto the first and second regions of the workpiece, the regions having different flatnesses from each other. This makes it possible to perform printing on the print regions of the workpiece having different flatnesses. [Explanation of symbols]

[0171] 1...3D object printing device, 2...robot (movement mechanism), 2a...arm drive mechanism, 3...head unit, 3a...liquid ejection head, 3b...switch circuit, 5...controller, 5a...memory circuit, 5b...processing circuit, 6...control module, 6a...timing signal generation circuit, 6b...power supply circuit, 6c...control circuit, 6d...drive signal generation circuit, 7...computer, 7a...memory circuit, 7b...processing circuit, 8...control unit, 210...base, 220...arm, 221...arm, 222...arm, 223...arm, 224...arm, 22 5...arm, 226...arm, C1...corner, C2...corner, C3...corner, C4...corner, CLK...clock signal, CNG...change signal, Com...drive signal, D1...output, D3...signal, Da...path information, Dc...work information, Fa...face, Fb...face, Fn...ejection face, Fx1...face, Fx2...face, Fy1...face, Fy2...face, Fz1...face, Fz2...face, Img...print data, J...joint, J1...joint, J2...joint, J3...joint, J4...joint, J5...joint, J6...joint, LAT...latch signal, O1...rotation axis, O2...rotation axis, O3...rotation axis, O4...rotation axis, O5...rotation axis, O6...rotation axis, PD...drive pulse, PG...distance, PR...program, PTS...timing signal, R1...first area, R2...second area, R3...third area, R4...fourth area, R5...fifth area, R6...sixth area, R7...seventh area, RP1...print area, RP2...print area, RP3...print area, RPa...normal density area, RPb...low density area, RU1...movement path, RU1-1~RU1-4...movement path, RU2...movement path, RU3...movement path, S10...process, S20...process , S20A...process, S20B...process, S30...process, S30A...process, S30B...process, S40...process, S40A...process, S40B...process, S50...process, S50A...process, S50B...process, S51...process, S52...process, S53...process, SI...control signal, Sk1...control signal, VBS...offset potential, VHV...power supply potential, W...work, W2...width, W4...width, W5...width, W6...width, dCom...waveform designation signal, n...nozzle, nL1...nozzle row, nL2...nozzle row, α...angle, θa...angle, θb...attitude angle.

Claims

1. A liquid ejection head that ejects liquid; a moving mechanism that moves the liquid ejection head while changing the attitude of the liquid ejection head relative to a three-dimensional workpiece, During a first operation period of the moving mechanism, liquid is ejected from the liquid ejection head onto a first region of the workpiece and a second region of the workpiece that is positioned outside the first region of the workpiece in a main scanning direction and has a lower flatness than the first region. A three-dimensional object printing device.

2. The second region includes a corner of the workpiece.

2. The three-dimensional object printing apparatus according to claim 1 .

3. during the first operation, a discharge amount of liquid discharged per unit area from the liquid discharge head to the second region is smaller than a discharge amount of liquid discharged per unit area from the liquid discharge head to the first region; 2. The three-dimensional object printing apparatus according to claim 1 .

4. during the first operation, a discharge amount of liquid discharged from the liquid discharge head to the second region per unit area is 20% or more and 80% or less of a discharge amount of liquid discharged from the liquid discharge head to the first region per unit area; 4. The three-dimensional object printing apparatus according to claim 3.

5. During a second operation in which the moving mechanism moves the liquid ejection head in a period different from the first operation, liquid is ejected from the liquid ejection head onto a third region of the workpiece and a fourth region adjacent to the third region of the workpiece in a main scanning direction and having a lower flatness than the third region; The second region and the fourth region overlap each other.

2. The three-dimensional object printing apparatus according to claim 1 .

6. during the first operation, a discharge amount of liquid discharged from the liquid discharge head to the second region per unit area is 20% or more and 80% or less of a discharge amount of liquid discharged from the liquid discharge head to the first region per unit area; during the second operation, a discharge amount of liquid discharged from the liquid discharge head to the fourth region per unit area is 20% or more and 80% or less of a discharge amount of liquid discharged from the liquid discharge head to the third region per unit area; 6. The three-dimensional object printing apparatus according to claim 5,

7. The second region is provided between the first region and the third region and includes a corner of the workpiece.

7. The three-dimensional object printing apparatus according to claim 6.

8. During the first operation, liquid is ejected from the liquid ejection head onto a fifth region adjacent to the first region of the workpiece in a sub-scanning direction; During a third operation in which the moving mechanism moves the liquid ejection head in a period different from that of the first operation and the second operation, liquid is ejected from the liquid ejection head onto a sixth region of the workpiece and a seventh region of the workpiece adjacent to the sixth region of the workpiece in a sub-scanning direction and having a flatness higher than that of the sixth region; the fifth region and the sixth region overlap each other, a width in a sub-scanning direction of an area where the fifth area and the sixth area overlap each other is smaller than a width in a main-scanning direction of an area where the second area and the fourth area overlap each other; 6. The three-dimensional object printing apparatus according to claim 5,

9. a width of the second region in the main scanning direction is smaller than a facing distance between the liquid ejection head and the workpiece during the first operation; The three-dimensional object printing device according to any one of claims 1 to 8.

10. During a fourth operation period in which the moving mechanism moves the liquid ejection head, liquid is ejected from the liquid ejection head onto an eighth region of the workpiece and a ninth region of the workpiece that is located outside the eighth region of the workpiece in a main scanning direction and has a lower flatness than the eighth region; When an angle between the first region and the second region is larger than an angle between the eighth region and the ninth region, a width of the second region in the main scanning direction is larger than a width of the ninth region in the main scanning direction. The three-dimensional object printing device according to any one of claims 1 to 8.

11. During a fourth operation period in which the moving mechanism moves the liquid ejection head, liquid is ejected from the liquid ejection head onto an eighth region of the workpiece and a ninth region of the workpiece that is located outside the eighth region of the workpiece in a main scanning direction and has a lower flatness than the eighth region; When the angle between the normal direction of the installation surface on which the workpiece is installed and the ejection surface of the liquid ejection head is defined as an attitude angle, When a posture angle when printing on the second region is larger than a posture angle when printing on the ninth region, a width of the second region in the main scanning direction is longer than a width of the ninth region in the main scanning direction. The three-dimensional object printing device according to any one of claims 1 to 8.

12. the liquid ejection head is capable of ejecting a first color liquid and a second color liquid having a lightness higher than that of the first color; During the first operation, the first color liquid and the second color liquid are ejected from the liquid ejection head to the first region, and the first color liquid is not ejected from the liquid ejection head to the second region but the second color liquid is ejected. The three-dimensional object printing device according to any one of claims 1 to 8.

13. A liquid ejection head that ejects liquid; a moving mechanism that moves the liquid ejection head while changing a posture of the liquid ejection head relative to a three-dimensional workpiece, During a first operation period in which the moving mechanism moves the liquid ejection head, liquid is ejected from the liquid ejection head onto a first region of the workpiece and a second region of the workpiece that is positioned outside the first region of the workpiece in a main scanning direction and has a lower flatness than the first region. A printing method comprising:

Images