Three-dimensional object printing method

Abstract

To provide a proper method of teaching of a robot according to the shape of a workpiece.SOLUTION: A surface of a workpiece includes a smooth region and a step region adjacent to the smooth region and including a step. A three-dimensional object printing method comprises: a first printing operation for executing discharge of liquid from a head to the smooth region during a period in which the relative positions and postures of a head and the workpiece change; and a second printing operation that is preceding or succeeding to the first printing operation in the same printing path as the first printing operation and that executes discharge of the liquid from the head to the step region during a period in which the relative positions and postures of the head and the workpiece change. When the normal line of the discharge surface is the first normal line, the normal line at an intersection point with the first normal line of the surface of the workpiece is the second normal line, and the angle formed between the first normal line and the second normal line is the discharge angle, a change amount of the discharge angle during execution of the second printing operation is larger than a change amount of the discharge angle during execution of the first printing operation.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] There is a known three-dimensional printing method that uses a robot to print on the surface of a three-dimensional workpiece by an inkjet method. For example, the system described in Patent Document 1 has a robot and a print head placed on the robot, and ejects ink droplets from the print head toward the curved surface of the object.

[0003] Patent document 1 discloses a method having the steps of measuring an area of ​​an object surface in three dimensions, creating a set of spatial points corresponding to the area, creating a three-dimensional net corresponding to the area, and creating a three-dimensional path for moving a robot. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2015-520011 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 does not disclose a specific method for the step of creating a three-dimensional path. In order to perform high-quality printing on the surface of a workpiece using a robot, it is desirable to realize an appropriate operation of the robot according to the shape of the workpiece. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of a three-dimensional object printing method according to the present disclosure is a three-dimensional object printing method using a head having an ejection surface provided with a plurality of nozzles that eject liquid, and a robot that changes the relative position and posture of the head with respect to a three-dimensional workpiece, wherein a surface of the workpiece has a smooth region and a step region that is adjacent to the smooth region and includes a step, and the method includes the steps of: a first printing operation that ejects liquid from the head onto the smooth region during a period in which the relative position and posture of the head and the workpiece is changed; and a second printing operation that precedes or follows the first printing operation in the same printing pass as the printing operation, and ejects liquid from the head into the step area during a period in which the relative position and attitude of the head and the workpiece are changed, wherein the normal to the ejection surface is defined as a first normal, the normal to the surface of the workpiece at its intersection with the first normal is defined as a second normal, and the angle between the first normal and the second normal is defined as an ejection angle, and the amount of change in the ejection angle during execution of the second printing operation is greater than the amount of change in the ejection angle during execution of the first printing operation.

[0007] One aspect of a robot teaching method according to the present disclosure is a robot teaching method that changes the relative position and posture between a head that ejects liquid and a three-dimensional workpiece based on printing path information, wherein the surface of the workpiece has a smooth region and a step region adjacent to the smooth region and including a step, and the method includes the following steps: a first step of acquiring three-dimensional data representing the shape of the workpiece using a plurality of polygons; a second step of specifying a plurality of passing polygons among the plurality of polygons that are polygons corresponding to an area to be scanned by the head; a third step of setting positions and postures indicated by a plurality of smooth teaching points that are teaching points on the smooth region based on a plurality of smooth passing polygons among the plurality of passing polygons that are polygons corresponding to the smooth region; a fourth step of setting one or both of positions and postures indicated by a plurality of step teaching points that are teaching points on the step region based on the plurality of smooth passing polygons or the plurality of smooth teaching points; and a fifth step of generating the printing path information based on the plurality of smooth teaching points and the plurality of step teaching points. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view showing an outline of a three-dimensional object printing device used in a three-dimensional object printing method according to a first embodiment. FIG. [Diagram 2] FIG. 2 is a block diagram showing the electrical configuration of a three-dimensional object printing device used in the three-dimensional object printing method according to the first embodiment. [Diagram 3] FIG. 2 is a perspective view showing a schematic configuration of a head unit. [Figure 4] FIG. 11 is a diagram for explaining an example of a printing operation of a robot. [Diagram 5] FIG. 2 is a diagram for explaining a smooth region and a step region of a workpiece. [Figure 6] FIG. 2 is a diagram for explaining a three-dimensional object printing method according to the first embodiment. [Figure 7] 11A and 11B are diagrams for explaining a moving path of a head in a reference example. [Figure 8] FIG. 2 is a diagram for explaining a movement path of a head in the first embodiment. [Figure 9] 4 is a flowchart showing a teaching method for a robot according to the first embodiment. [Figure 10] FIG. 2 is a diagram for explaining acquisition of three-dimensional data in a first step. [Figure 11] 13 is a diagram for explaining a virtual plane used to specify a passing polygon in the second step. FIG. [Figure 12] FIG. 11 is a diagram for explaining the specification of passing polygons in the second step. [Figure 13] 10A and 10B are diagrams for explaining setting of positions and orientations of a plurality of teaching points; [Figure 14] FIG. 11 is a diagram for explaining setting of a plurality of smooth teaching points in a third step. [Figure 15] FIG. 13 is a diagram for explaining setting of a plurality of step teaching points in a fourth step. [Figure 16] FIG. 11 is a diagram for explaining setting of a plurality of step teaching points in a fourth step in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 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.

[0010] For convenience, the following description will be made using the mutually intersecting X-axis, Y-axis, and Z-axis as appropriate. 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.

[0011] Here, the X-axis, Y-axis, and Z-axis correspond to the coordinate axes of a world coordinate system set in a space in which 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.

[0012] 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°.

[0013] 1. First embodiment 1-1. Overview of the 3D printing device 1 is a perspective view showing an outline of a three-dimensional object printing apparatus 1 used in a three-dimensional object printing method according to the first embodiment. The three-dimensional object printing apparatus 1 is an apparatus that performs printing on the surface of a three-dimensional workpiece W by an inkjet method.

[0014] The workpiece W has a surface WF to be printed. In the example shown in FIG. 1, the surface WF is a convex curved surface having a plurality of portions with different curvatures. Although not shown in FIG. 1, as will be described in detail later, the surface WF has an area including a step. During printing, the workpiece W is supported by a structure such as a predetermined installation table, a robot hand, or a conveyor as necessary. Note that the printing target may be a surface other than the surface WF among the plurality of surfaces of the workpiece W. In addition, the size, shape, or installation posture of the workpiece W is not limited to the example shown in FIG. 1 and is arbitrary.

[0015] 1, the three-dimensional object printing apparatus 1 has a robot 2, a head unit 3, a controller 5, a piping section 10, and a wiring section 11. First, each of these will be briefly described in order below.

[0016] The robot 2 is a robot that changes the position and orientation of the head unit 3 in the world coordinate system. In the example shown in Fig. 1, the robot 2 is a so-called six-axis vertical articulated robot.

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

[0018] The base 210 is a platform that supports the arm 220. In the example shown in Fig. 1, the base 210 is fixed by screws or the like to an installation surface such as a floor surface or a base facing the Z1 direction. 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.

[0019] Arm 220 is a six-axis robot arm having a base end attached to base 210 and a tip end that changes its position and posture three-dimensionally relative to the base end. Specifically, arm 220 has arms 221, 222, 223, 224, 225, and 226, also called links, which are connected in this order.

[0020] The arm 221 is connected to the base 210 via a joint 230_1 so as to be rotatable around a rotation axis O1. The arm 222 is connected to the arm 221 via a joint 230_2 so as to be rotatable around a rotation axis O2. The arm 223 is connected to the arm 222 via a joint 230_3 so as to be rotatable around a rotation axis O3. The arm 224 is connected to the arm 223 via a joint 230_4 so as to be rotatable around a rotation axis O4. The arm 225 is connected to the arm 224 via a joint 230_5 so as to be rotatable around a rotation axis O5. The arm 226 is connected to the arm 225 via a joint 230_6 so as to be rotatable around a rotation axis O6.

[0021] Each of the joints 230_1 to 230_6 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 230_1 to 230_6 may be referred to as a "joint 230."

[0022] Although not shown in Fig. 1, each of the joints 230_1 to 230_6 is provided with a drive mechanism for rotating one of the two corresponding adjacent members relative to the other. The drive mechanism includes, for example, a motor that generates a drive force for the rotation, a reducer that reduces the speed of the drive force and outputs it, and an encoder such as a rotary encoder that detects an amount of movement such as an angle of the rotation. The assembly of the drive mechanisms of the joints 230_1 to 230_6 corresponds to an arm drive mechanism 2a shown in Fig. 2 described later.

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

[0024] 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°.

[0025] A head unit 3 is attached as an end effector to the arm 226 located at the very tip of the arm section 220 of the robot 2 as described above, in a state fixed thereto by screws or the like.

[0026] The head unit 3 is an assembly having a head 3a that ejects ink, which is an example of a "liquid," toward the workpiece W. In this embodiment, the head unit 3 has a pressure adjustment valve 3b and an energy emission unit 3c in addition to the head 3a. Details of the head unit 3 will be described later with reference to FIG.

[0027] The ink is not particularly limited, and examples thereof include water-based inks in which a coloring material such as a dye or pigment is dissolved in a water-based solvent, curable inks using a curable resin such as an ultraviolet curable type, and solvent-based inks in which a coloring material such as a dye or pigment is dissolved in an organic solvent. Among them, curable inks are 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. 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.

[0028] A piping section 10 and a wiring section 11 are connected to the head unit 3. The piping section 10 is a piping or a group of piping that supplies ink from an ink tank (not shown) to the head unit 3. The wiring section 11 is a wire or a group of wires that supplies an electrical signal that drives the head 3a.

[0029] 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.

[0030] 1-2. Electrical configuration of the 3D printing device Fig. 2 is a block diagram showing the electrical configuration of the three-dimensional object printing apparatus 1 used in the three-dimensional object printing method according to the first embodiment. Fig. 2 shows electrical components among the components of the three-dimensional object printing apparatus 1. As shown in Fig. 2, in addition to the components shown in Fig. 1 described above, the three-dimensional object printing apparatus 1 has 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.

[0031] 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.

[0032] 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.

[0033] The controller 5 includes a memory circuit 5a and a processing circuit 5b.

[0034] 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.

[0035] The memory circuit 5a stores the print path information Da. The print path information Da is used to control the operation of the robot 2, and is information indicating the position and posture of the head 3a on the path along which the head 3a should move. The print path information Da is expressed, for example, using coordinate values ​​in a base coordinate system or a world coordinate system. The print path information Da is generated by the computer 7 based on three-dimensional data Db indicating the shape of the workpiece W in a teaching method for the robot 2 described later. The print path information Da is input from the computer 7 to the memory circuit 5a. The print path information Da may be expressed using coordinate values ​​in a workpiece coordinate system. In this case, the print path information Da is used to control the operation of the robot 2 after being converted from the coordinate values ​​in the workpiece coordinate system to the coordinate values ​​in the base coordinate system or the world coordinate system.

[0036] The processing circuit 5b controls the operation of the arm driving mechanism 2a of the robot 2 based on the print path information Da, and generates a signal D3. The processing circuit 5b includes, for example, 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.

[0037] Here, the arm driving mechanism 2a is an assembly of driving mechanisms for the aforementioned joints 230_1 to 230_6, and each joint 230 has a motor for driving the joint of the robot 2 and an encoder for detecting the rotation angle of the joint of the robot 2.

[0038] The processing circuit 5b performs inverse kinematic calculations, which are calculations that convert the print path information Da into amounts of movement, such as the rotation angle and rotation speed, of each joint 230 of the robot 2. The processing circuit 5b then outputs a control signal Sk1 based on the output D1 from each encoder of the arm drive mechanism 2a so that the actual amounts of movement, such as the rotation angle and rotation speed, of each joint 230 become the above-mentioned calculation results based on the print path information Da. The control signal Sk1 is a signal for controlling the drive of the motor of the arm drive mechanism 2a. Here, the control signal Sk1 is corrected by the processing circuit 5b as necessary based on the output from a distance sensor (not shown).

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

[0040] 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.

[0041] 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.

[0042] 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.

[0043] The control circuit 6c generates a control signal SI, a waveform designation signal dCom, a latch signal LAT, a clock signal CLK, and a change signal CNG based on the timing signal PTS. These signals are synchronized with the timing signal PTS. Of these signals, the waveform designation signal dCom is input to the drive signal generation circuit 6d, and the other signals are input to the switch circuit 3e of the head unit 3.

[0044] The control signal SI is a digital signal for specifying the operating state of the driving element of the head 3a of the head unit 3. Specifically, the control signal SI is a signal for specifying whether or not to supply a driving signal Com, which will be described later, to the driving element based on the print data Img. This specification, for example, specifies whether or not to eject ink from the nozzle corresponding to the driving 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 driving 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 driving 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.

[0045] 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.

[0046] The drive signal generating circuit 6d is a circuit that generates a drive signal Com for driving each drive element of the 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 of 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 3e of the head unit 3.

[0047] Here, the switch circuit 3e is a circuit including a switching element that switches whether or not at least a part of the waveform included in the drive signal Com is supplied as the drive pulse PD based on a control signal SI.

[0048] The computer 7 is a desktop or notebook computer on which a program such as the program PG is installed. The computer 7 has a function of generating print path information Da, a function of supplying information such as the print path information Da to the controller 5, and a function of supplying information such as the print data Img to the control module 6. In addition to these functions, the computer 7 of this embodiment has a function of controlling the driving of the energy emission unit 3c.

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

[0050] 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.

[0051] The memory circuit 7a stores print path information Da, three-dimensional data Db, and a program PG. The program PG is a program for generating print path information Da based on the three-dimensional data Db. The three-dimensional data Db is data in a format such as STL (Standard Triangulated Language) that represents the shape of the workpiece W by a plurality of polygons. The three-dimensional data Db includes coordinate information Db1, which is information about the coordinates of each vertex of the polygon, and vector information Db2, which is information about normal vectors indicating the front and back of the polygon surface. The three-dimensional data Db is obtained by converting CAD (computer-aided design) data indicating the three-dimensional shape of the workpiece W as necessary. The three-dimensional data Db may be expressed using coordinate values ​​of a workpiece coordinate system, or may be expressed using coordinate values ​​of a base coordinate system or a world coordinate system.

[0052] The processing circuit 7b realizes each of the above-mentioned functions by executing a program such as the program PG. 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 the CPU.

[0053] Processing circuit 7b executes program PG to function as generator 7b1. Generator 7b1 generates print path information Da based on three-dimensional data Db. The generation of print path information Da by generator 7b1 will be described in detail later with reference to FIGS. 5 to 15.

[0054] 1-3.Head unit configuration 3 is a perspective view showing a schematic configuration of the head unit 3. In the following description, for convenience, the mutually intersecting a-axis, b-axis, and c-axis are appropriately used. In the following description, one direction along the a-axis is the a1 direction, and the direction opposite to the a1 direction is the a2 direction. Similarly, the opposite directions along the b-axis are the b1 direction and the b2 direction. In addition, the opposite directions along the c-axis are the c1 direction and the c2 direction.

[0055] Here, the a-axis, the b-axis, and the c-axis correspond to the coordinate axes of the tool coordinate system set in the head unit 3, and the relative position and posture relationship with the world coordinate system or the robot coordinate system changes due to the operation of the robot 2. In the example shown in FIG. 3, the c-axis is an axis parallel to the rotation axis O6. The a-axis, the b-axis, and the c-axis typically intersect at right angles to each other, but are not limited to this, and may intersect at an angle within a range of 80° to 100°. The tool coordinate system and the base coordinate system or the robot coordinate system are associated with each other by calibration.

[0056] The tool coordinate system is set with the tool center point TCP as a reference. Therefore, the position and orientation of the head 3a are defined with the tool center point TCP as a reference. For example, the tool center point TCP may be located at the center of the ejection surface FN, or may be located in a space spaced apart from the head 3a in the ink ejection direction DE.

[0057] As described above, the head unit 3 has the head 3a, the pressure regulating valve 3b, and the energy emission unit 3c. These are supported by a support 3f indicated by a two-dot chain line in FIG. 3. In the example shown in FIG. 3, the head unit 3 has one head 3a and one pressure regulating valve 3b, but the number is not limited to the example shown in FIG. 3 and may be two or more. In addition, the installation position of the pressure regulating valve 3b is not limited to the arm 226 and may be, for example, another arm or the like, or may be a fixed position relative to the base 210.

[0058] The support 3f is made of, for example, a metal material, and is substantially rigid. Although the support 3f has a flat box shape in Fig. 3, the shape of the support 3f is not particularly limited and may be any shape.

[0059] The support 3f is attached to the arm 226 described above. Therefore, the head 3a, the pressure regulating valve 3b, and the energy emitter 3c are collectively supported on the arm 226 by the support 3f. Therefore, the relative positions of the head 3a, the pressure regulating valve 3b, and the energy emitter 3c with respect to the arm 226 are fixed. In the example shown in Fig. 3, the pressure regulating valve 3b is disposed at a position in the c1 direction with respect to the head 3a. The energy emitter 3c is disposed at a position in the a2 direction with respect to the head 3a.

[0060] The head 3a has an ejection surface FN and a plurality of nozzles N opening on the ejection surface FN. The ejection surface FN is a nozzle surface on which the nozzles N open, and is formed, for example, by the surface of a nozzle plate in which the nozzles N are provided as through holes in a plate-like member formed of a material such as silicon (Si) or metal. In the example shown in FIG. 3, the direction along the first normal line LDE, which is the normal line of the ejection surface FN, that is, the ejection direction DE of the ink from the nozzles N is the c2 direction, and the plurality of nozzles N are divided into nozzle rows L1 and L2 arranged at intervals from each other in the direction along the a-axis. Each of the nozzle rows L1 and L2 is a collection of a plurality of nozzles N linearly arranged in the direction along the b-axis. Here, the elements related to each nozzle N of the nozzle row L1 in the head 3a and the elements related to each nozzle N of the nozzle row L2 are configured to be approximately symmetrical to each other in the direction along the a-axis. In addition, the arrangement direction DN, which will be described later, is parallel to the b-axis.

[0061] However, the positions of the multiple nozzles N in the nozzle row L1 and the multiple nozzles N in the nozzle row L2 in the direction along the b-axis may be the same or different. Also, elements related to each nozzle N of one of the nozzle row L1 and the nozzle row L2 may be omitted. In the following, a configuration in which the positions of the multiple nozzles N in the nozzle row L1 and the multiple nozzles N in the nozzle row L2 in the direction along the b-axis are the same will be exemplified.

[0062] Although not shown, the head 3a has a piezoelectric element as a drive element and a cavity that contains ink for each nozzle N. Here, the piezoelectric element changes the pressure in the cavity corresponding to the piezoelectric element, thereby discharging ink from the nozzle corresponding to the cavity in a discharge direction DE. Such a head 3a can be obtained, for example, by bonding together 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 drive element for discharging ink from the nozzle.

[0063] To the head 3a, ink is supplied from an ink tank (not shown) via a supply pipe 10a of the piping unit 10. Here, a pressure adjustment valve 3b is interposed between the supply pipe 10a and the head 3a.

[0064] The pressure regulating valve 3b is a valve mechanism that opens and closes according to the pressure of the ink in the head 3a. This opening and closing maintains the pressure of the ink in the head 3a at a negative pressure within a predetermined range even if the positional relationship between the head 3a and the ink tank (not shown) changes. This stabilizes the meniscus of the ink formed in the nozzle N of the head 3a. As a result, air bubbles are prevented from entering the nozzle N and ink is prevented from overflowing from the nozzle N. In addition, the ink from the pressure regulating valve 3b is appropriately distributed to multiple locations in the head 3a via branch channels (not shown). Here, the ink from the ink tank (not shown) is transferred into the supply pipe 10a at a predetermined pressure by a pump or the like.

[0065] The energy emission unit 3c emits energy such as light, heat, electron beams, or radiation to harden or solidify the ink on the workpiece W. For example, if the ink is ultraviolet-curable, the energy emission unit 3c is configured with a light-emitting element such as an LED (light emitting diode) that emits ultraviolet light. The energy emission unit 3c may also include optical components such as lenses for adjusting the energy emission direction or emission range, as appropriate.

[0066] It should be noted that the energy emission unit 3c does not have to completely cure or completely solidify the ink on the workpiece W. In this case, for example, the ink after being irradiated with energy from the energy emission unit 3c may be completely cured or completely solidified by energy from a curing light source separately installed on the installation surface of the base 210 of the robot 2.

[0067] 1-4. Printing operation of robot 2 Fig. 4 is a diagram for explaining an example of the printing operation of the robot 2. Fig. 4 illustrates an example in which printing is performed on a surface WF of a workpiece W placed at a position further away from the robot 2 in the X2 direction.

[0068] In the printing operation, the head 3a ejects ink while the robot 2 changes the position and posture of the head 3a. The position and posture of the head 3a are changed based on the print path information Da. As a result, the head 3a moves along the movement path RU while maintaining a predetermined posture with respect to the surface WF. The movement path RU is the path from position PS to position PE.

[0069] In the example shown in FIG. 4, the movement path RU is a straight line extending along the X-axis when viewed in the Z2 direction. In this embodiment, the robot 2 performs a printing operation by operating three of the six joints 230. More specifically, during the execution of the printing operation, the robot 2 operates these joints 230 while setting the rotation axes of the joints 230_2, 230_3, and 230_5 in a state parallel to the Y-axis. The operation of the three joints 230 in this manner allows the head 3a to move stably along the movement path RU. The robot 2 may perform a printing operation by operating four or more of the six joints 230. In this case, the installation position and installation posture of the workpiece W are not limited to the example shown in FIG. 4 and are arbitrary.

[0070] Fig. 5 is a diagram for explaining the smooth regions RP1, RP3 and the step region RP2 of the workpiece W. Although not shown in Fig. 4, as shown in Fig. 5, the surface WF of the workpiece W has the smooth regions RP1, RP3 and the step region RP2. These regions are arranged in the order of the smooth region RP1, the step region RP2, and the smooth region RP3 along the relative movement direction of the workpiece W and the head 3a during the printing operation.

[0071] In the example shown in Figure 5, positions P_1 to P_5 are arranged in order in the X2 direction, the region from position P_1 to position P_2 is smooth region RP1, the region from position P_2 to position P_4 is step region RP2, and the region from position P_4 to position P_5 is smooth region RP3.

[0072] Each of the smooth regions RP1 and RP3 is a smooth surface with substantially no steps. A substantially smooth surface is, for example, a surface without steps of 300 μm or more. In other words, a surface with minute steps of less than 300 μm can be considered to be a substantially smooth surface. The step region RP2 is a region adjacent to the smooth regions RP1 and RP3, and is a surface of a predetermined width including the steps SP.

[0073] The step SP is composed of two faces with different heights, a step surface connecting the two faces, and two corners between the two faces and the step surface. In the example shown in FIG. 5, position P_3 is on the step surface. Here, the inclination angle of the step surface with respect to each of the two faces is 40° or more. In addition, the width of the step surface along the direction from one of the two faces to the other through the step surface is not more than twice the width in the direction along the a-axis of the ejection surface FN. The predetermined width is not less than twice and not more than five times the width in the direction along the a-axis of the ejection surface FN. Note that the step in the present disclosure is not limited to this, and the step surface of the step SP may be a convex or concave curved surface, or one or both of the two corners of the step SP may be rounded. In addition, the step SP may be a concave portion having a cross-sectional shape such as a local V-shape or U-shape, or a convex portion that is an inverted version of the concave portion. In other words, the step SP may have a groove-like shape or a bump-like shape.

[0074] Here, it can be said that the step region RP2 includes a portion having a larger curvature than the smooth regions RP1 and RP3. This is because, for example, when the above-mentioned two corners located in the step region RP2 are microscopically observed, the curvature of the cross section of the corners is larger than the curvature of the cross section of the surfaces constituting the smooth regions RP1 and RP3. More specifically, when each part of the cross section is approximated by a circle, the step region RP2, particularly the corners, are represented by a circle with a smaller radius than the smooth regions RP1 and RP3, and the smooth regions RP1 and RP3 are represented by a circle with a larger radius than the step region RP2.

[0075] 5 shows normal lines LN_1 to LN_5 and normal vectors V_1 to V_5 at positions P_1 to P_5, respectively. Note that, hereinafter, each of positions P_1 to P_5 may be referred to as position P. Similarly, each of normal lines LN_1 to LN_5 may be referred to as second normal line LN. Each of normal vectors V_1 to V_5 may be referred to as normal vector V.

[0076] Fig. 6 is a diagram for explaining the three-dimensional object printing method according to the first embodiment. Fig. 6 shows the position and posture of the head unit 3 at each of positions P_1 to P_5 in the printing operation. The three-dimensional object printing method includes a first printing operation MP1a that prints on a smooth region RP1 of the workpiece W, a second printing operation MP2 that prints on a step region RP2 of the workpiece W, and a first printing operation MP1b that prints on a smooth region RP3 of the workpiece W.

[0077] In this embodiment, the first printing operation MP1a, the second printing operation MP2, and the first printing operation MP1b are performed in the same printing pass in this order. Therefore, the second printing operation MP2 is performed following the first printing operation MP1a in the same printing pass as the first printing operations MP1a and MP1b. Also, the second printing operation MP2 is performed prior to the first printing operation MP1b in the same printing pass as the first printing operations MP1a and MP1b.

[0078] The first printing operation MP1a ejects ink from the head 3a to the smooth region RP1 during a period in which the relative position and posture of the head 3a and the workpiece W is changed. Similarly, the first printing operation MP1b ejects ink from the head 3a to the smooth region RP3 during a period in which the relative position and posture of the head 3a and the workpiece W is changed.

[0079] Here, from the viewpoint of improving image quality, it is preferable that the change amount of the discharge angle θ during the execution of the first printing operations MP1a and MP1b is as small as possible. The discharge angle θ is the angle between the first normal line LDE, which is the normal line of the discharge surface FN, and the second normal line LN, which is the normal line at the intersection point of the first normal line LDE and the surface of the workpiece W. In other words, when the change amount of the discharge angle θ is small, it can be said that the head 3a scans relatively faithfully to the shape of the surface of the workpiece W. Conversely, when the change amount of the discharge angle θ is large, it can be said that the head 3a scans relatively unfaithfully to the shape of the surface of the workpiece W. For this reason, it can be said that the scanning of the head 3a during the execution of the first printing operations MP1a and MP1b is relatively faithful to the shape of the surface of the workpiece W.

[0080] In the second printing operation MP2, while the relative position and attitude of the head 3a and the workpiece W is being changed, ink is ejected from the head 3a to the step region RP2.

[0081] Here, the change in the discharge angle θ during the second printing operation MP2 is larger than the change in the discharge angle θ during the first printing operations MP1a and MP1b. Therefore, it is possible to reduce abrupt changes in the posture of the head 3a caused by the operation of the robot 2 between the first printing operation MP1a and the first printing operation MP1b. In other words, during the second printing operation MP2, the head 3a does not scan the shape of the surface of the workpiece W as faithfully as during the first printing operations MP1a and MP1b. As a result, it is possible to prevent a collision between the head 3a and the workpiece W. In addition, by reducing the vibration of the robot 2, it is possible to improve the overall image quality.

[0082] FIG. 7 is a diagram for explaining the movement path RU of the head 3a in the reference example. In this reference example, the tool center point TCP is disposed at the center of the discharge surface FN, and the print path information Da is set so that the movement path RU is disposed in a space separated by a distance from the surface WF. FIG. 7 shows a vector Vr indicating the posture of the head 3a at a position Pr on the movement path RU when the discharge angle θ is constant. That is, in FIG. 7, the posture of the head 3a is approximately consistent with the normal vector V of the workpiece W over the smooth region RP1, the step region RP2, and the smooth region RP3. Therefore, the head 3a scans the surface shape of the workpiece W relatively faithfully in any region. In this case, a sudden change in posture of the head 3a occurs during the execution of the second printing operation MP2. As a result, there is a risk of the head 3a colliding with the workpiece W. In addition, the image quality may be deteriorated due to the vibration of the robot 2 caused by the sudden change in posture.

[0083] FIG. 8 is a diagram for explaining the movement path RU of the head 3a in the first embodiment. In this embodiment, the tool center point TCP is disposed at the center of the discharge surface FN, and the print path information Da is set so that the movement path RU is disposed in a space separated by a distance from the surface WF. FIG. 8 shows a vector Vr indicating the posture of the head 3a at a position Pr on the movement path RU when the change amount of the discharge angle θ during the execution of the second printing operation MP2 is larger than the change amount of the discharge angle θ during the execution of the first printing operations MP1a and MP1b. In this case, the position Pr and the vector Vr during the execution of the second printing operation MP2 change more gently than in the case shown in FIG. 7. In other words, a sudden change in posture of the head 3a is unlikely to occur.

[0084] Therefore, as described above, the amount of change in the discharge angle θ during the second printing operation MP2 is greater than the amount of change in the discharge angle θ during the first printing operations MP1a and MP1b. Also, the amount of change in the discharge distance LD during the second printing operation MP2 is greater than the amount of change in the discharge distance LD during the first printing operations MP1a and MP1b. Note that the discharge distance LD is the distance between the discharge surface FN and the workpiece W in the direction along the first normal line LDE.

[0085] The length L2 of the trajectory of the head 3a during the second printing operation MP2 is shorter than the length of the step region RP2 along that trajectory, i.e., the length L1 of the area printed on the surface of the workpiece W during the second printing operation MP2.

[0086] It is preferable that the relative movement speed between the ejection surface FN and the surface of the workpiece W be as constant as possible from the viewpoint of reducing vibration of the robot 2, but from the viewpoint of improving image quality in the step region RP2 while shortening the time required for printing, it is preferable that the relative movement speed between the ejection surface FN and the surface of the workpiece W during execution of the second printing operation MP2 be lower than the relative movement speed between the ejection surface FN and the surface of the workpiece W during execution of the first printing operations MP1a, MP1b.

[0087] 1-5. Robot teaching method 9 is a flowchart showing a teaching method for the robot 2 according to the first embodiment. The teaching method will be described below using the above-mentioned three-dimensional object printing apparatus 1 as an example. The teaching method is performed using a computer 7. The computer 7, more specifically, the generation unit 7b1, generates printing path information Da using the teaching method.

[0088] As shown in FIG. 9, the teaching method includes a first step S10, a second step S20, a third step S30, a fourth step S40, and a fifth step S50, and these steps are executed in this order.

[0089] The first step S10 acquires three-dimensional data Db. The second step S20 identifies a plurality of passing polygons POL_1 from a plurality of polygons POL represented by the three-dimensional data Db. The third step S30 sets a plurality of smooth teaching points Pa1 using the plurality of passing polygons POL_1. The fourth step S40 sets a plurality of step teaching points Pa2 using a plurality of smooth passing polygons POL_1a or a plurality of smooth teaching points Pa1. The fifth step S50 generates print path information Da based on the plurality of smooth teaching points Pa1 and the plurality of step teaching points Pa2. Here, the step S3 consisting of the third step S30 and the fourth step S40 sets a plurality of smooth teaching points Pa1 and a plurality of step teaching points Pa2 as a plurality of teaching points Pa on the surface WF of the workpiece W. Each step will be described in detail below.

[0090] FIG. 10 is a diagram for explaining acquisition of three-dimensional data Db in a first step S10. In the first step S10, the three-dimensional data Db is acquired. In FIG. 10, a part of a surface WDb represented by the three-dimensional data Db is representatively shown. The surface WDb corresponds to the surface WF of the workpiece W. In the example shown in FIG. 10, for ease of understanding and convenience of explanation, the surface WDb is shown in the base coordinate system or the robot coordinate system. Note that the surface WDb may be expressed in the workpiece coordinate system.

[0091] The surface WDb is composed of a plurality of polygons POL. In the example shown in FIG. 10, each polygon POL forms a triangle having three sides LE and three vertices PV. Here, each side LE is shared by two polygons POL. Two polygons POL sharing one side LE are adjacent to each other with the side LE as a boundary. Also, each vertex PV is shared by three or more polygons POL. Three or more polygons POL sharing one vertex PV are in contact with each other with the vertex PV as a contact point. In FIG. 10, for convenience of explanation, a normal vector Vp of each polygon POL is illustrated. The normal vector Vp is represented by vector information Db2. Note that the shape of each polygon POL is not limited to a triangle, and may be another polygon such as a quadrangle.

[0092] 11 is a diagram for explaining the virtual plane FV used to identify the passing polygon POL_1 in the second step S20. The method for identifying the passing polygon POL_1 is not particularly limited as long as it is possible to identify the polygon POL corresponding to the area to be scanned by the head 3a as the passing polygon POL_1, but in this embodiment, the passing polygon POL_1 is identified using the virtual plane FV.

[0093] Specifically, in the second step S20, a virtual plane FV expressed in the same coordinate system as the three-dimensional data Db is specified. The virtual plane FV crosses the surface WDb. The virtual plane FV and the surface WDb intersect with each other at a line of intersection LC.

[0094] The virtual plane FV is specified by the computer 7 based on the printing position information set by the user. The printing position information is information about one or both of the position and the posture on the surface of the work W at the time of printing desired by the user, and is set by the user's input to the computer 7. For example, the user inputs the printing position information using the input device of the computer 7 to set or appropriately adjust one or both of the position and the posture on the surface of the work W of the image printed by the three-dimensional printing device 1. More specifically, on the image corresponding to the work W displayed based on the three-dimensional data Db, the user can input the printing position information by setting the position according to the movement of the cursor by mouse operation, or adjusting the posture by mouse operation such as so-called drag and drop.

[0095] The computer 7 specifies the virtual plane FV according to the printing position information. Here, it is preferable that the virtual plane FV is specified so as to be as parallel as possible to the normal of the intersecting polygon POL (a passing polygon POL_1 described later). For example, as shown in Fig. 9, when there are five intersecting polygons POL, the virtual plane FV is specified so as to minimize the sum or average value of the difference between the angle between each polygon POL and the virtual plane FV and 90°.

[0096] Here, the virtual plane FV is a plane that represents the ideal ink ejection direction by the head 3a and the ideal movement direction of the head 3a. In other words, during printing, the head 3a ejects ink parallel to the virtual plane FV, and the head 3a moves in a direction parallel to the virtual plane FV. In this way, the virtual plane FV is a reference plane for defining the position and posture of the head 3a during printing.

[0097] In this embodiment, as described above, during the execution of the printing operation, the robot 2 operates the joints 230_2, 230_3, and 230_5 with their respective rotation axes parallel to the Y axis. For this reason, the virtual plane FV is specified so as to be perpendicular to all of the rotation axes O2, O3, and O5.

[0098] Fig. 12 is a diagram for explaining the specification of the passing polygon POL_1 in the second step S20. In the second step S20, after the virtual plane FV is specified, a plurality of passing polygons POL_1 that are polygons POL intersecting with the virtual plane FV are specified among the plurality of polygons POL. As described above, since the virtual plane FV crosses the face WDb, the plurality of polygons POL constituting the face WDb are divided into a plurality of passing polygons POL_1 that intersect with the virtual plane FV and a plurality of polygons POL_2 that do not intersect with the virtual plane FV. In Fig. 12, for convenience of explanation, the passing polygon POL_1 is displayed with a cross-hatched pattern.

[0099] 13 is a diagram for explaining the setting of the positions and orientations of the multiple teaching points Pa. Step S3 sets the multiple teaching points Pa based on the multiple passing polygons POL_1. Specifically, step S3 uses each of the multiple intersections between the sides LE of the multiple passing polygons POL_1 and the virtual plane FV as the teaching points Pa. Each teaching point Pa indicates the position and orientation of the head 3a.

[0100] In FIG. 13, the attitude indicated by the teaching point Pa is represented by a vector Va. The vector Va is a normal vector at the teaching point Pa, and is specified based on the vector information Db2. For example, the vector Va indicating the direction along the normal corresponding to the above-mentioned intersection is defined based on the first vertex vector Vc_1 and the second vertex vector Vc_2. Here, if the side LE including the intersection among the sides LE of the multiple passing polygons POL_1 is the first side LE_1, one end of the first side LE_1 is the first vertex PV_1, and the other end of the first side LE_1 is the second vertex PV_2, the first vertex vector Vc_1 is the normal vector corresponding to the first vertex PV_1, and the second vertex vector Vc_2 is the normal vector corresponding to the second vertex PV_2. It is preferable that these vertex vectors are obtained in advance based on the vector information Db2 included in the three-dimensional data Db.

[0101] In the example shown in FIG. 13, in addition to the plurality of intersections, an interpolation point, which is a point obtained by interpolating between the plurality of intersections, is used as the teaching point Pa. Therefore, even if the number of polygons POL representing the shape of the workpiece W is small, the density of the teaching points Pa can be increased. In the example shown in FIG. 13, the number of interpolation points arranged between two adjacent intersections is one, but the number may be two or more. In addition, in the present embodiment, the case where the interpolation is performed by adding an interpolation point is exemplified, but the interpolation is not limited to this, and may be performed by adding a curve or line segment for interpolation. In addition, depending on the number of polygons POL representing the shape of the workpiece W, the interpolation may be omitted. In addition, when the interpolation is performed, the interpolation may be performed after thinning out a part of the plurality of intersections as necessary.

[0102] Here, the interpolation points are preferably arranged on a smooth curve passing through the multiple intersection points. Such a curve is expressed by, for example, a spline function. That is, the interpolation points are preferably arranged based on spline interpolation. In this case, the interpolation points may deviate from the intersection line LC, but are preferably located on the virtual plane FV. The interpolation points can also be arranged based on linear interpolation. However, from the viewpoint of smoothing the movement path of the head 3a by the robot 2 and suppressing vibrations accompanying the operation of the robot 2, it is preferable to arrange the interpolation points by a curved interpolation method such as spline interpolation.

[0103] As described above, the surface WF of the workpiece W has the smooth regions RP1, RP3 and the step region RP2. Therefore, the surface WDb has regions corresponding to the smooth regions RP1, RP3 and the step region RP2. In the regions of the surface WDb corresponding to the smooth regions RP1, RP3, a plurality of teaching points Pa are set using a plurality of intersections and a plurality of interpolation points as described above. In contrast, in the region of the surface WDb corresponding to the step region RP2, a plurality of teaching points Pa are set so that the moving path RU as shown in FIG. 8 described above can be obtained. This point will be described in detail below.

[0104] FIG. 14 is a diagram for explaining the setting of a plurality of smooth teaching points Pa1 in the third step S30. The surface WDb has a step SPd corresponding to the step SP. The above-mentioned plurality of passing polygons POL_1 are divided into a plurality of smooth passing polygons POL_1a which are polygons POL corresponding to the smooth regions RP1 and RP3, and a plurality of step passing polygons POL_1b which are polygons POL corresponding to the step region PR2. The division can be performed numerically based on the vector information Db2 included in the three-dimensional data Db. The division may also be performed by judging whether or not a collision occurs during scanning of the head 3a on the surface WF by simulation. The third step S30 includes a step of identifying a plurality of smooth passing polygons POL_1a from among the plurality of passing polygons POL_1.

[0105] In the third step S30, the positions and orientations of the smooth teaching points Pa1 are set based on the smooth passing polygons POL_1a. Each of the smooth teaching points Pa1 is a teaching point Pa on the smooth region RP1 or the smooth region RP3. In FIG. 14, the orientation of the smooth teaching point Pa1 is represented by a vector Va1.

[0106] The position and orientation of the smooth teaching point Pa1 are set in the same manner as the position and orientation of the teaching point Pa using a plurality of intersections and a plurality of interpolation points as described above. In this embodiment, since the tool center point TCP is located at the center of the discharge surface FN as described above, each smooth teaching point Pa1 is placed at a position away from the surface WDb in the Z1 direction as shown in FIG. 14. Here, the plurality of smooth teaching points Pa1 are placed so that the distance between the smooth teaching points Pa1 and the surface WDb is as constant as possible. In addition, the vector Va1 at each smooth teaching point Pa1 is set so as to follow the normal line of the surface WDb at the corresponding position. Here, the setting of the vector Va1 at each smooth teaching point Pa1 may be based on the vector Va.

[0107] FIG. 15 is a diagram for explaining the setting of a plurality of step teaching points Pa2 in the fourth step S40. In the fourth step S40, the positions and orientations of a plurality of step teaching points Pa2 are set based on a plurality of smooth passing polygons POL_1a or a plurality of smooth teaching points Pa1. Each step teaching point Pa2 is a teaching point Pa on a step region RP2. In FIG. 15, the orientation indicated by the step teaching point Pa2 is represented by a vector Va2.

[0108] The position and orientation of the step teaching point Pa2 are set based on the multiple smooth passing polygons POL_1a or the multiple smooth teaching points Pa1 so that the change in the position and orientation of the step teaching point Pa2 is as small as possible. More specifically, the positions and orientations of the multiple step teaching points Pa2 are set by interpolating between the smooth teaching point Pa1 corresponding to the smooth region RP1 and the smooth teaching point Pa1 corresponding to the smooth region RP3. For example, the position and orientation indicated by the step teaching point Pa2 are set using a weighted average of the position and orientation indicated by the smooth teaching point Pa1.

[0109] As described above, a plurality of smooth teaching points Pa1 and a plurality of step teaching points Pa2 are set. In a fifth step S50, after step S3, print path information Da is generated based on the plurality of smooth teaching points Pa1 and the plurality of step teaching points Pa2. For example, the plurality of smooth teaching points Pa1 and the plurality of step teaching points Pa2 are set as positions Pr shown in FIG. 8 described above. In addition, as necessary, a relative movement direction between the head 3a and the workpiece W along the position indicated by the print path information Da is specified. In this embodiment, of one direction along the intersection line LC and the opposite direction, the direction away from the robot 2 is set as the movement direction.

[0110] As described above, the teaching method for the robot 2 includes the first step S10, the second step S20, the third step S30, and the fifth step S50. Here, the robot 2 changes the relative position and posture between the head 3a that ejects ink, which is an example of a "liquid," and the three-dimensional workpiece W, based on the print path information Da. The surface of the workpiece W has smooth regions RP1, RP3, and a step region RP2 that is adjacent to the smooth regions RP1, RP3 and includes a step SP.

[0111] The first step S10 acquires three-dimensional data that represents the shape of the workpiece W by a plurality of polygons POL. The second step S20 specifies a plurality of passing polygons POL_1, which are polygons POL corresponding to the area to be scanned by the head 3a, among the plurality of polygons POL. The third step S30 sets the positions and orientations of a plurality of smooth teaching points Pa1, which are teaching points Pa on the smooth areas RP1 and RP3, based on a plurality of smooth passing polygons POL_1a, which are polygons POL corresponding to the smooth areas RP1 and RP3, among the plurality of passing polygons POL_1. The fourth step S40 sets the positions and orientations of a plurality of step teaching points Pa2, which are teaching points Pa on the step area RP2, based on the plurality of smooth passing polygons POL_1a or the plurality of smooth teaching points Pa1. The fifth step S50 generates print path information Da based on the plurality of smooth teaching points Pa1 and the plurality of step teaching points Pa2.

[0112] The above teaching method for the robot 2 makes it possible to generate print path information Da that reduces sudden changes in the position and posture of the head 3a during printing operation, even if a stepped region RP2 exists on the surface of the workpiece W. In this way, it is possible to realize appropriate operation of the robot 2 according to the shape of the workpiece W.

[0113] In particular, the fourth step S40 sets the position and attitude indicated by the multiple step teaching points Pa2 without using the polygon corresponding to the step region RP2 among the multiple passing polygons POL_1. This makes it possible to suitably reduce abrupt changes in the position and attitude of the head 3a during the execution of the printing operation using the printing path information Da. Note that the fourth step S40 may set one of the positions and attitudes indicated by the multiple step teaching points based on the multiple smooth passing polygons POL_1a or the multiple smooth teaching points Pa1. This point will be described in detail later in the second embodiment.

[0114] As described above, the method for printing a three-dimensional object uses the head 3a and the robot 2. Here, the method for printing a three-dimensional object includes first printing operations MP1a and MP1b and a second printing operation MP2.

[0115] The first printing operations MP1a, MP1b execute the ejection of ink from the head 3a to the smooth regions RP1, RP3 during a period in which the relative position and posture between the head 3a and the workpiece W is changed. The second printing operation MP2 executes the ejection of ink from the head 3a to the step region RP2 during a period in which the relative position and posture between the head 3a and the workpiece W is changed, preceding or following the first printing operations MP1a, MP1b in the same printing pass as the first printing operations MP1a, MP1b.

[0116] In addition, the amount of change in the discharge angle θ during the second printing operation MP2 is larger than the amount of change in the discharge angle θ during the first printing operations MP1a and MP1b. Here, when the normal to the discharge surface FN is the first normal LDE and the normal at the intersection with the first normal LDE to the surface of the workpiece W is the second normal LN, the angle between the first normal LDE and the second normal LN is the discharge angle θ.

[0117] In the above three-dimensional object printing method, it is possible to reduce abrupt changes in the posture of the head 3a relative to the workpiece W during the second printing operation MP2, compared to when the amount of change in the discharge angle θ during execution of the second printing operation MP2 is equal to or less than the amount of change in the discharge angle θ during execution of the first printing operations MP1a and MP1b. As a result, it is possible to prevent collisions between the head 3a and the workpiece W and reduce vibrations of the robot 2. In this way, it is possible to realize appropriate operation of the robot 2 according to the shape of the workpiece W.

[0118] As described above, the change in the discharge distance LD during the second printing operation MP2 is greater than the change in the discharge distance LD during the first printing operations MP1a and MP1b. This has the advantage that it is easier to reduce abrupt changes in the positions of the head 3a and the workpiece W during the second printing operation MP2, compared to when the change in the discharge distance LD during the second printing operation MP2 is equal to or less than the change in the discharge distance LD during the first printing operations MP1a and MP1b. The distance between the discharge surface FN and the workpiece W in the direction along the first normal line LDE is the discharge distance LD.

[0119] Furthermore, as described above, the length of the trajectory of the head 3a during the second printing operation MP2 is shorter than the length of the area printed on the surface of the workpiece W during the second printing operation MP2. Therefore, the printing speed can be increased compared to the case where the length of the trajectory of the head 3a during the second printing operation MP2 is equal to the length of the area printed on the surface of the workpiece W during the second printing operation MP2.

[0120] As described above, the relative movement speed between the discharge surface FN and the surface of the workpiece W during the second printing operation MP2 is preferably equal to or lower than the relative movement speed between the discharge surface FN and the surface of the workpiece W during the first printing operations MP1a and MP1b. In this case, the deterioration of print quality can be suppressed compared to when the relative movement speed between the discharge surface FN and the surface of the workpiece W during the second printing operation MP2 is higher than the relative movement speed between the discharge surface FN and the surface of the workpiece W during the first printing operations MP1a and MP1b. Note that the relative movement speed between the discharge surface FN and the surface of the workpiece W during the second printing operation MP2 may be higher than the relative movement speed between the discharge surface FN and the surface of the workpiece W during the first printing operations MP1a and MP1b.

[0121] 2. Second embodiment A second embodiment of the present invention will be described below. In the following example, for elements having the same actions and functions as those in 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.

[0122] 16 is a diagram for explaining the setting of the plurality of step teaching points Pa2 in the fourth step S40 in the second embodiment. This embodiment is similar to the first embodiment described above, except that the positions of the plurality of step teaching points Pa2 are set differently in the fourth step S40.

[0123] In the fourth step S40 of this embodiment, similarly to the first embodiment described above, the attitudes of the plurality of step teaching points Pa2 are set based on the plurality of smooth passing polygons POL_1a or the plurality of smooth teaching points Pa1.

[0124] In addition, in a fourth step S40, the positions of the step teaching points Pa2 are set based on the step passing polygons POL_1b. This setting is performed in the same manner as the setting of the position of the smooth teaching point Pa1, except that the step passing polygon POL_1b is used instead of the smooth passing polygon POL_1a. Therefore, the step teaching points Pa2 are arranged so that the distance between the step teaching points Pa2 and the surface WDb is as constant as possible.

[0125] The second embodiment described above also allows the robot 2 to operate appropriately in accordance with the shape of the workpiece W. In this embodiment, as described above, the fourth step S40 sets the posture indicated by the multiple step teaching points Pa2 based on the multiple smooth passing polygons POL_1a or the multiple smooth teaching points Pa1, and sets the position indicated by the multiple step teaching points Pa2 based on the polygon POL corresponding to the step region RP2 among the multiple passing polygons POL_1. Therefore, compared to the first embodiment, the amount of calculation for setting the position and posture of the step teaching point P2a can be reduced. In addition, the distance between the face WF and the head 3a can be maintained while preventing a sudden change in posture of the head 3a, thereby improving the image quality in the step region RP2.

[0126] 3. Variations Each of the above-mentioned exemplary embodiments can be modified in various ways. Specific modified embodiments that can be applied to each of the above-mentioned embodiments are 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.

[0127] 3-1. Variation 1 In the above-mentioned embodiment, a configuration in which a six-axis vertical multi-axis robot is used as the robot is exemplified, but the configuration is not limited to this. The robot 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 portion 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.

[0128] 3-2. Variation 2 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.

[0129] 3-3. Variation 3 In the above-mentioned embodiment, the robot is exemplified as a robot that moves the head, but the present invention is not limited to this configuration, and may be configured such that, for example, the position of the liquid ejection head is fixed, and the robot moves the workpiece, thereby changing the position and posture of the workpiece three-dimensionally relative to the head. In this case, for example, the workpiece is gripped by a gripping mechanism such as a hand attached to the tip of the robot arm.

[0130] 3-4. Variation 4 In the above-described embodiment, a configuration in which printing is performed using one type of ink is exemplified, but this is not limited to this configuration, and the present disclosure can also be applied to a configuration in which printing is performed using two or more types of ink.

[0131] 3-5. Variation 5 The use of the three-dimensional printing device of the present disclosure is not limited to printing. 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 of 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. [Explanation of symbols]

[0132] 1 ... Three-dimensional object printing device, 2 ... Robot, 2a ... Arm drive mechanism, 3 ... Head unit, 3a ... Head, 3b ... Pressure regulating valve, 3c ... Energy output unit, 3e ... Switch circuit, 3f ... Support, 5 ... Controller, 5a ... Memory circuit, 5b ... Processing circuit, 6 ... Control module, 6a ... Timing signal generation circuit, 6b ... Power supply circuit, 6c ... Control circuit, 6d ... Drive signal generation circuit, 7 ... Computer, 7a ... Memory circuit, 7b ... Processing circuit, 7b1 ... Generation unit, 10 ... Piping unit, 10a ... Supply pipe, 11 ... Wiring unit, 210 ... Base, 220 ... Arm unit, 221 ... Arm, 222 ... Arm, 223...arm, 224...arm, 225...arm, 226...arm, 230...joint, 230_1...joint, 230_2...joint, 230_3...joint, 230_4...joint, 230_5...joint, 230_6...joint, CLK...clock signal, CNG...change signal, Com...drive signal, D1...output, D3...signal, DE...ejection direction, DN...arrangement direction, Da...print path information, Db...three-dimensional data, Db1...coordinate information, Db2...vector information, FN...ejection surface, FV...virtual plane, Img...print data, L1...nozzle row, L2...nozzle row, LAT...latch signal , LC...intersection line, LD...discharge distance, LDE...first normal line, LE...side, LE_1...first side, LN...second normal line, LN_1...normal line, MP1a...first printing operation, MP1b...first printing operation, MP2...second printing operation, N...nozzle, O1...rotation axis, O2...rotation axis, O3...rotation axis, O4...rotation axis, O5...rotation axis, O6...rotation axis, P2a...step teaching point, PD...driving pulse, PG...program, POL...polygon, POL_1...passing polygon, POL_1a...smooth passing polygon, POL_1b...step passing polygon, POL_2...polygon, PR2...step area, PTS...timing Signal, PV...vertex, PV_1...first vertex, PV_2...second vertex, Pa...teaching point, Pa1...smooth teaching point, Pa2...step teaching point, RP1...smooth area, RP2...step area, RP3...smooth area, RU...movement path, S10...first step, S20...second step, S3...step, S30...third step, S40...fourth step, S50...fifth step, SI...control signal, SP...step, SPd...step, Sk1...control signal, TCP...tool center point, V...normal vector, VBS...offset potential, VHV...power supply potential, V_1...normal vector, Va...vector,Va1...vector, Va2...vector, Vc_1...first vertex vector, Vc_2...second vertex vector, Vp...normal vector, Vr...vector, W...work, WDb...surface, WF...surface, dCom...waveform designation signal, θ...discharge angle.

Claims

1. a head having an ejection surface provided with a plurality of nozzles for ejecting liquid; A three-dimensional object printing method using a robot that changes the relative position and posture of the head with respect to a three-dimensional workpiece, The surface of the workpiece has a smooth region and a step region adjacent to the smooth region and including a step, a first printing operation for ejecting liquid from the head onto the smooth area during a period in which the relative position and attitude of the head and the workpiece are changed; a second printing operation that precedes or follows the first printing operation in the same printing pass as the first printing operation, and ejects liquid from the head to the step region during a period in which the relative position and attitude of the head and the workpiece are changed; A normal line to the ejection surface is defined as a first normal line, A normal line at an intersection point of the surface of the workpiece with the first normal line is defined as a second normal line; If the angle between the first normal line and the second normal line is defined as a discharge angle, a change amount of the ejection angle during the second printing operation is greater than a change amount of the ejection angle during the first printing operation, A relative movement speed between the ejection surface and the surface of the workpiece during the second printing operation is equal to or lower than a relative movement speed between the ejection surface and the surface of the workpiece during the first printing operation. A three-dimensional object printing method.

2. If the distance between the discharge surface and the workpiece in the direction along the first normal line is defined as a discharge distance, a change amount of the ejection distance during the second printing operation is greater than a change amount of the ejection distance during the first printing operation; The three-dimensional object printing method according to claim 1 .

3. The length of the trajectory of the head during the execution of the second printing operation is shorter than the length of the area printed on the surface of the workpiece during the execution of the second printing operation. The three-dimensional object printing method according to claim 1 or 2.

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