Three-dimensional object printing apparatus and printing method

Abstract

This design suppresses head vibrations caused by robot movement while expanding the printable area of ​​the workpiece. [Solution] The three-dimensional object printing apparatus performs a printing operation in which a robot moves the head along the printing area of ​​the workpiece while discharging liquid from the head. In the printing operation, the position on the printing area where the head begins to discharge liquid is defined as the starting point, and the position on the printing area where the head finishes discharging liquid is defined as the ending point. In a side view of the robot viewed from the side at the timing when the head discharges liquid toward the starting point during the printing operation, the starting point is closer to the base than the ending point in a first direction parallel to the base mounting surface, and further from the mounting surface than the ending point in a second direction parallel to the normal of the mounting surface.

Description

Technical Field

[0001] The present disclosure relates to a three-dimensional object printing method and a data generation method.

Background Art

[0002] There is known a three-dimensional object printing apparatus that performs printing on the surface of a three-dimensional workpiece by an inkjet method. For example, Patent Document 1 discloses an apparatus that moves a head away from the base of a robot while ejecting ink from the head during the execution of a printing operation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the apparatus described in Patent Document 1, there is room for improvement in making the printing area of the workpiece as wide as possible while suppressing the vibration of the head caused by the operation of the robot.

Means for Solving the Problems

[0005] One embodiment of a three-dimensional object printing apparatus according to the present disclosure comprises a robot that changes the relative position between the workpiece and the head, including a head for discharging liquid toward a three-dimensional workpiece, an arm, and a base connected to one end of the arm, wherein the robot performs a printing operation in which it moves the head along a printing area of ​​the workpiece while discharging liquid from the head, and in the printing operation, the position on the printing area where the head begins to discharge liquid is defined as the starting point, and the position on the printing area where the head finishes discharging liquid is defined as the ending point, wherein in the printing operation, when the head discharges liquid toward the starting point, in a side view of the robot viewed from the side, the starting point is closer to the base than the ending point in a first direction parallel to the mounting surface of the base, and further from the mounting surface than the ending point in a second direction parallel to the normal of the mounting surface.

[0006] One embodiment of the printing method according to the present disclosure is a printing method using a three-dimensional object printing apparatus comprising a robot that changes the relative position between the workpiece and the head, the robot comprising a head for discharging liquid toward a three-dimensional workpiece, an arm, and a base connected to one end of the arm, the method comprising the steps of determining a starting point which is a position on the printing area toward which the head begins to discharge liquid toward the printing area of ​​the workpiece, and an ending point which is a position on the printing area toward which the head finishes discharging liquid toward the printing area, and performing a printing operation in which the robot moves the head along the printing area while discharging liquid from the head based on the starting point and the ending point, wherein in the printing operation, in a side view of the robot viewed from the side at the timing when the head discharges liquid toward the starting point, the starting point is closer to the base than the ending point in a first direction parallel to the mounting surface of the base, and further from the mounting surface than the ending point in a second direction parallel to the normal of the mounting surface. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram of a three-dimensional object printing apparatus according to an embodiment. [Figure 2]This is a block diagram showing the electrical configuration of a three-dimensional object printing apparatus according to an embodiment. [Figure 3] This is a perspective view of a robot. [Figure 4] This is a flowchart showing the printing method according to the embodiment. [Figure 5] This diagram shows the state of the robot at the moment the print head ejects liquid towards the starting point of the printing area during the printing process. [Figure 6] This diagram shows the state of the robot at the moment the print head ejects liquid towards the end of the printing area during the printing process. [Figure 7] This is a diagram illustrating the movement path of the print head during the printing process. [Modes for carrying out the invention]

[0008] Preferred embodiments of the present disclosure will be described below with reference to the attached drawings. Note that the dimensions and scale of parts in the drawings may differ from actual dimensions as appropriate, and some parts are shown schematically for ease of understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise stated in the following description.

[0009] For convenience, the following explanation will use the X, Y, and Z axes intersecting each other as appropriate. In the following, one direction along the X axis is the X1 direction, and the direction opposite to the X1 direction is the X2 direction. Similarly, opposite directions along the Y axis are the Y1 and Y2 directions. Also, opposite directions along the Z axis are the Z1 and Z2 directions.

[0010] Here, the X, Y, and Z axes are the coordinate axes of the world coordinate system set in the space where robot 2 and holding robot 4, described later, are installed. Typically, the Z axis is the vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. The base coordinate system, based on the bases 210 and 410 described later, is mapped to the world coordinate system through calibration. In the following examples, for convenience, the world coordinate system is used as the robot coordinate system to control the movements of robot 2 and holding robot 4.

[0011] Note that the Z-axis does not have to be a vertical axis. Also, while the X, Y, and Z axes are typically orthogonal to each other, they are not limited to this and may not be orthogonal. For example, the X, Y, and Z axes can intersect each other at angles between 80° and 100°.

[0012] 1. First Embodiment 1-1. Outline of a 3D object printing device Figure 1 is a schematic diagram of a three-dimensional object printing apparatus 1 according to an embodiment. The three-dimensional object printing apparatus 1 is a device that prints on the surface of a three-dimensional workpiece W using an inkjet method.

[0013] The workpiece W has a surface WF that includes the printing area RP, which is the area to be printed, as described later. In the example shown in Figure 1, the workpiece W is approximately a hemisphere, and the surface WF is approximately a convex sphere. Note that the size, shape, and installation orientation of the workpiece W are not limited to the example shown in Figure 1 and are arbitrary.

[0014] As shown in Figure 1, the 3D object printing apparatus 1 includes a robot 2, a head unit 3, and a holding robot 4. Below, we will first briefly describe each part of the 3D object printing apparatus 1 in order, based on Figure 1.

[0015] Robot 2 is a robot that supports the head unit 3 and changes the position and orientation of the head unit 3 in the world coordinate system. In the example shown in Figure 1, robot 2 is a so-called 6-axis vertical articulated robot.

[0016] The robot 2 has a base 210 and an arm 220. The base 210 is a platform that supports the arm 220 and is fixed to the installation surface FB by means such as screwing. The arm 220 is a robot arm, and at the tip of the arm 220, the head unit 3 is mounted as an end effector in a state fixed by means such as screwing. Thus, the robot 2 includes the arm 220 and the base 210 connected to one end of the arm 220, and changes the relative position between the work W and the head 3a. The details of the robot 2 will be described later based on FIG. 3.

[0017] The installation surface FB is a surface facing in the Z1 direction, and for example, it is the outer surface of an installation table or the floor surface of a building. Note that the installation surface FB is not limited to the outer surface of an installation table or the floor surface of a building, and may be, for example, the wall surface or ceiling surface of a building.

[0018] The head unit 3 is an assembly having a head 3a that discharges ink, which is an example of "liquid", toward the work W. The head 3a has a nozzle surface FN, and a plurality of nozzles N for discharging ink are opened on the nozzle surface FN. The plurality of nozzles N constitute one or more nozzle rows arranged linearly. In the present embodiment, the head unit 3 has, in addition to the head 3a, a curing light source 3c. The details of the head unit 3 will be described later based on FIG. 3.

[0019] The ink is not particularly limited. For example, it may be an aqueous ink in which a coloring material such as a dye or a pigment is dissolved in an aqueous solvent, a curable ink using a curable resin such as an ultraviolet curable type, or a solvent-based ink in which a coloring material such as a dye or a pigment is dissolved in an organic solvent. Among them, the curable ink is preferably used. The curable ink is not particularly limited. For example, it may be any of a thermosetting type, a photocuring type, a radiation curing type, and an electron beam curing type, etc., but a photocuring type such as an ultraviolet curable type is preferable. Note that 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. Further, the ink is not limited to an ink containing a coloring material. For example, it may be 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 work W.

[0020] On the other hand, the holding robot 4 is a robot that holds the work W, and changes the position and posture of the work W in the world coordinate system. In the example shown in FIG. 1, the holding robot 4 is a six-axis vertical articulated robot.

[0021] The holding robot 4 has a base 410 and an arm 420. The base 410 is a stand that supports the arm 420, and is fixed to the installation surface FB by screwing or the like. The arm 420 is a robot arm, and a holding mechanism HJ is mounted at the tip of the arm 420 in a state of being fixed by screwing or the like as an end effector.

[0022] The holding robot 4 is configured similarly to robot 2, except for the end effector to which it is attached. However, robot 2 and holding robot 4 may have different configurations, and in this embodiment, the arm length or payload capacity may differ from each other as needed. Also, the number of joints of robot 2 and holding robot 4 may differ from each other. Furthermore, the base 410 may be fixed to a surface different from the mounting surface FB, or to a surface different from the base 210 of robot 2. For example, robot 2 may be installed on one of the floor, wall, and ceiling, and holding robot 4 may be installed on another, or robot 2 may be installed on one of several walls facing different directions, and holding robot 4 may be installed on another.

[0023] The holding mechanism HJ is a robot hand that detachably holds the workpiece W. Here, "holding" is a concept that includes both suction and gripping. For example, the holding mechanism HJ may include a mechanism that attracts the workpiece W using negative pressure, a magnetic attraction mechanism, or a gripping hand mechanism having multiple fingers or claws.

[0024] The robot 2, head unit 3, and holding robot 4 described above each operate under the control of the control unit 10, which will be described later. For example, under the control of the control unit 10, the holding robot 4 positions the workpiece W in the desired position, the head unit 3 ejects ink toward the surface WF of the workpiece W, and the robot 2 moves the head unit 3 along the surface WF of the workpiece W. As a result, the three-dimensional object printing apparatus 1 performs a printing operation in which the head 3a ejects ink and the robot 2 moves the head 3a along the printing area RP of the workpiece W, which will be described later.

[0025] Here, the holding robot 4 changes either or both the position and orientation of the workpiece W before the printing operation. This eliminates the need for manual changes to the orientation or position of the workpiece W.

[0026] The holding robot 4 may be omitted if necessary. In this case, the workpiece W is positioned in the desired position and orientation by a jig that holds the workpiece W. The workpiece W may also be positioned manually.

[0027] 1-2. Electrical configuration of a three-dimensional object printing device Figure 2 is a block diagram showing the electrical configuration of the three-dimensional object printing apparatus 1 according to this embodiment. In Figure 2, the electrical components of the three-dimensional object printing apparatus 1 are shown. As shown in Figure 2, the three-dimensional object printing apparatus 1 includes the aforementioned robot 2, head unit 3, and holding robot 4, as well as a control unit 10.

[0028] The control unit 10 controls the movements of the robot 2, the head unit 3, and the holding robot 4. In the example shown in Figure 2, the control unit 10 includes a controller 11, a control module 12, and a computer 13.

[0029] Furthermore, the electrical components shown in Figure 2 may be divided as appropriate, some of which may be included in other components, or may be integrated with other components. For example, some or all of the functions of the controller 11 or control module 12 may be implemented by the computer 13, or by other external devices such as a PC (personal computer) connected to the controller 11 via a network such as a LAN (Local Area Network) or the Internet.

[0030] Controller 11 is a robot controller that controls the drive of robot 2 and holding robot 4. Controller 11 has the function of controlling the drive of robot 2 and holding robot 4, and the function of generating a signal D3 to synchronize the ink ejection operation of head unit 3 with the operation of robot 2. Controller 11 has a memory circuit 11a and a processing circuit 11b.

[0031] The memory circuit 11a stores various programs executed by the processing circuit 11b and various data processed by the processing circuit 11b. The memory circuit 11a includes, for example, one or both of semiconductor memories: volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable ROM). Note that part or all of the memory circuit 11a may be included in the processing circuit 11b.

[0032] The memory circuit 11a stores the first path data Db1 and the second path data Db2.

[0033] The first path data Db1 is information about the movement path of the head unit 3 by the robot 2, and includes information indicating the position and orientation of the head 3a during the printing operation. Here, the movement path indicated by the first path data Db1 includes positions corresponding to the start point PS and end point PE described later. The second path data Db2 is information about the movement path of the workpiece W by the holding robot 4, and includes information indicating the position and orientation of the workpiece W during and before the printing operation. Here, the movement path indicated by the second path data Db2 includes the start point PS and end point PE described later. Both the first path data Db1 and the second path data Db2 are generated by the computer 13.

[0034] The processing circuit 11b controls the operation of the arm drive mechanism 2a of the robot 2 based on the first path data Db1 and generates the signal D3. The processing circuit 11b also controls the operation of the arm drive mechanism 4a of the holding robot 4 based on the second path data Db2. The processing circuit 11b includes, for example, one or more processors such as CPUs (Central Processing Units). The processing circuit 11b may also include a programmable logic device such as an FPGA (field-programmable gate array) instead of a CPU, or in addition to a CPU.

[0035] The arm drive mechanism 2a includes a motor for driving each joint of the robot 2 and an encoder for detecting the rotation angle of each joint of the robot 2. Similarly, the arm drive mechanism 4a includes a motor for driving each joint of the holding robot 4 and an encoder for detecting the rotation angle of each joint of the holding robot 4.

[0036] The processing circuit 11b performs inverse kinematics calculations, which convert the position and orientation indicated by the first path data Db1 into motion quantities such as the rotation angle and rotation speed of each joint of the robot 2. Then, the processing circuit 11b outputs a control signal Sk1 based on the output D1 from each encoder of the arm drive mechanism 2a so that the actual motion quantities such as the rotation angle and rotation speed of each joint match the calculation results. The control signal Sk1 controls the drive of the motors of the arm drive mechanism 2a.

[0037] Similarly, the processing circuit 11b performs inverse kinematics calculations, which are calculations that convert the position and orientation indicated by the second path data Db2 into motion quantities such as the rotation angle and rotation speed of each joint of the holding robot 4. Then, the processing circuit 11b outputs a control signal Sk2 based on the output D2 from each encoder of the arm drive mechanism 4a so that the actual motion quantities such as the rotation angle and rotation speed of each joint become the aforementioned calculation results. The control signal Sk2 controls the driving of the motors of the arm drive mechanism 4a.

[0038] Furthermore, the processing circuit 11b generates a signal D3 based on the output D1 from at least one of the multiple encoders of the arm drive mechanism 2a. For example, the processing circuit 11b generates a trigger signal D3 that includes a pulse at a timing when the output D1 from one of the multiple encoders reaches a predetermined value.

[0039] The control module 12 is a circuit module that is communicatively connected to the controller 11 and controls the head unit 3. The control module 12 is a circuit that controls the ink ejection operation of the head unit 3 based on the signal D3 output from the controller 11 and the print data Img from the computer 13. The control module 12 includes a timing signal generation circuit 12a, a power supply circuit 12b, a control circuit 12c, and a drive signal generation circuit 12d.

[0040] The timing signal generation circuit 12a generates a timing signal PTS based on signal D3. The timing signal generation circuit 12a is composed of a timer that, for example, starts generating the timing signal PTS when signal D3 is detected.

[0041] The power supply circuit 12b receives power from a commercial power source (not shown) and generates various predetermined potentials. The generated potentials are supplied as appropriate to the control module 12 and the head unit 3. For example, the power supply circuit 12b 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 supplied to the drive signal generation circuit 12d.

[0042] The control circuit 12c generates a control signal SI, a waveform specification 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 specification signal dCom is input to the drive signal generation circuit 12d, and the other signals are input to the switch circuit 3d of the head unit 3.

[0043] The control signal SI is a digital signal used to specify the operating state of the drive element of the head 3a of the head unit 3. Specifically, the control signal SI specifies whether or not to supply the drive signal Com, described below, to the drive element. 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 used to define the waveform of the drive signal Com. The latch signal LAT and the change signal CNG are used in conjunction with the control signal SI to define the timing of ink ejection from the nozzle by defining the driving timing of the drive element. The clock signal CLK is a reference clock signal synchronized with the timing signal PTS.

[0044] The control circuit 12c described above includes, for example, one or more processors such as CPUs (Central Processing Units). The control circuit 12c may also include a programmable logic device such as an FPGA (field-programmable gate array) instead of a CPU, or in addition to a CPU.

[0045] The drive signal generation circuit 12d 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 generation circuit 12d includes, for example, a DA conversion circuit and an amplification circuit. In the drive signal generation circuit 12d, the DA conversion circuit converts the waveform specification signal dCom from the control circuit 12c from a digital signal to an analog signal, and the amplification circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 12b to generate the drive signal Com. The drive signal Com is supplied from the drive signal generation circuit 12d to the drive element via the switch circuit 3d of the head unit 3. Here, the signal that is actually supplied to the drive element from among the waveforms included in the drive signal Com is the drive pulse PD. Based on the control signal SI, the switch circuit 3d switches whether or not to supply at least a part of the waveforms included in the drive signal Com as the drive pulse PD.

[0046] Computer 13 is a desktop, laptop, or tablet computer that is communicatively connected to the controller 11 and the control module 12. Computer 13 has the function of generating first route data Db1 and second route data Db2, the function of supplying information such as first route data Db1 and second route data Db2 to the controller 11, and the function of supplying information such as print data Img to the control module 12.

[0047] Computer 13 has a memory circuit 13a and a processing circuit 13b. The memory circuit 13a stores various programs executed by the processing circuit 13b and various data processed by the processing circuit 13b. These various programs include, for example, a program for determining a start point PS and an end point PE, which will be described later. The memory circuit 13a includes, for example, one or both of semiconductor memories, such as volatile memory like RAM and non-volatile memory like ROM, EEPROM, or PROM. Note that part or all of the memory circuit 13a may be included in the processing circuit 13b.

[0048] The processing circuit 13b implements the various functions described above by reading and executing a program from the memory circuit 13a. The processing circuit 13b includes, for example, one or more processors such as CPUs. The processing circuit 13b may also include a programmable logic device such as an FPGA instead of a CPU, or in addition to a CPU.

[0049] 1-3. Example of robot configuration Figure 3 is a perspective view of robot 2. The following describes an example configuration of robot 2. Note that the configuration of holding robot 4 is the same as robot 2, except for the attached end effector, so its description is omitted. However, as mentioned above, the configurations of robot 2 and holding robot 4 may differ from each other.

[0050] In the example shown in Figure 3, the arm 220 of robot 2 is a 6-axis robot arm having a base end attached to the base 210 and an end that changes position and orientation 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. Arm 226 is an example of an "end."

[0051] Arm 221 is connected to the base 210 via a joint J1 that rotates around a rotation axis O1. Rotation axis O1 is an example of a "first rotation axis," and joint J1 is an example of a "first joint." Arm 222 is connected to arm 221 via a joint J2 that rotates around a rotation axis O2. Rotation axis O2 is an example of a "second rotation axis," and joint J2 is an example of a "second joint." Arm 223 is connected to arm 222 via a joint J3 that rotates around a rotation axis O3. Rotation axis O3 is an example of a "third rotation axis," and joint J3 is an example of a "third joint." Arm 224 is connected to arm 223 via a joint J4 that rotates around a rotation axis O4. Rotation axis O4 is an example of a "fourth rotation axis," and joint J4 is an example of a "fourth joint." Arm 225 is connected to arm 224 via joint J5 which rotates around rotation axis O5. Rotation axis O5 is an example of a "fifth rotation axis," and joint J5 is an example of a "fifth joint." Arm 226 is connected to arm 225 via joint J6 which rotates around rotation axis O6. Rotation axis O6 is an example of a "sixth rotation axis," and joint J6 is an example of a "sixth joint." As described above, arm 220 has joints J1 to J6. Joints J2, J3, J4, and J6 are provided in this order from the base 210 toward arm 226 of arm 220.

[0052] Each of the joints J1 to J6 is a mechanism that rotatably connects one of two adjacent members from the base 210 and arms 221 to 226 to the other. Although not shown in Figure 3, each of the joints J1 to J6 is provided with a drive mechanism that rotates one of the two adjacent members relative to the other. This drive mechanism includes, for example, a motor that generates the driving force for the rotation, a reduction gear that reduces and outputs the driving force, and an encoder such as a rotary encoder that detects the amount of movement, such as the angle of rotation. The assembly of these drive mechanisms for joints J1 to J6 corresponds to the arm drive mechanism 2a shown in Figure 2 above.

[0053] The rotation axis O1 is an axis perpendicular to the mounting surface FB 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.

[0054] Regarding these axes of rotation, "perpendicular" includes not only cases where the angle between the two axes of rotation is exactly 90°, but also cases where the angle between the two axes of rotation intersects within a range of approximately ±5° from 90°. Similarly, "parallel" includes not only cases where the two axes of rotation are exactly parallel, but also cases where one of the two axes of rotation is tilted relative to the other within a range of approximately ±5°.

[0055] A head unit 3 is mounted as an end effector on arm 226, which is the tip of arm 220. The head unit 3 is mounted on arm 226 such that, for example, the normal of the nozzle surface FN is parallel to the rotation axis O6, that is, the direction of ink ejection from nozzle N is parallel to the rotation axis O6. The normal of the nozzle surface FN or the direction of ink ejection from nozzle N may be inclined with respect to the rotation axis O6.

[0056] Here, the head unit 3 is configured with a tool coordinate system. The relative position and orientation of the coordinate axes of this tool coordinate system change with respect to the X, Y, and Z axes as described above, due to the movement of the robot 2. However, the tool coordinate system and the base coordinate system are associated through calibration. Furthermore, the tool coordinate system is configured such that, for example, the center of the nozzle surface FN becomes the reference point (tool center point).

[0057] As described above, the head unit 3 has a head 3a and a curing light source 3c, which are supported by the arm 226 via a support (not shown) in a fixed relative position.

[0058] Although not shown in the diagram, the print head 3a has, for each nozzle N, a piezoelectric element which is a driving element and a cavity that contains ink. Here, the piezoelectric element causes ink to be ejected from the nozzle corresponding to the cavity by changing the pressure in the cavity corresponding to the piezoelectric element. Such a print head 3a can be obtained, for example, by bonding together multiple substrates such as silicon substrates that have been appropriately processed by etching or the like using an adhesive. In addition, instead of the piezoelectric element, a heater that heats the ink in the cavity may be used as the driving element for ejecting ink from the nozzle.

[0059] The curing light source 3c emits energy such as light, heat, electron beams, or radiation to cure or solidify the ink on the workpiece W. The curing light source 3c is composed of a light-emitting element such as an LED (light-emitting diode) that emits ultraviolet light. The curing light source 3c may also have optical components such as lenses to adjust the direction or range of energy emission. The curing light source 3c may be provided as needed and may be omitted. Furthermore, the curing light source 3c may partially solidify or partially cure the ink on the workpiece W without completely curing it. In this case, for example, the ink on the workpiece W is completely cured by a separately installed curing light source.

[0060] The curing light source 3c may be provided as needed, or it may be omitted. In addition to the head 3a and the curing light source 3c, the head unit 3 may also have, for example, a pressure regulating valve for adjusting the pressure of the ink in the head 3a.

[0061] 1-4.Printing method Figure 4 is a flowchart showing a printing method according to an embodiment. The printing method shown in Figure 4 is performed using the three-dimensional object printing apparatus 1 described above, and includes steps S10 and S20 in this order.

[0062] In step S10, the control unit 10 determines the start point PS and the end point PE, which will be explained later with reference to Figures 5 to 7. The start point PS is the position on the printing area RP, which will be explained later, where the head 3a begins to eject ink during the printing operation. The end point PE is the position on the printing area RP, which will be explained later, where the head 3a finishes ejecting ink during the printing operation.

[0063] In the example shown in Figure 4, step S10 includes step S11, which generates the aforementioned first route data Db1, and step S12, which generates the aforementioned second route data Db2.

[0064] In step S11, the computer 13 generates first path data Db1 by calculating the position and orientation of the head 3a in the work coordinate system so that the head 3a moves along the print area RP described later during the printing operation, based on information indicating the shape of the workpiece W and information indicating the print area RP described later, and then converting this to the robot coordinate system. At this time, the first path data Db1 is determined so that the start point PS and end point PE described later have the positional relationship described later. The generated first path data Db1 is transmitted from the computer 13 to the controller 11 and stored in the memory circuit 11a. Although not shown in the figures, in step S10, print data Img is generated based on information indicating the image to be printed and the first path data Db1.

[0065] In step S12, the computer 13 generates second path data Db2 by first calculating the position and orientation of the workpiece W in the workpiece coordinate system so that the workpiece W corresponds to the movement path indicated by the first path data Db1 in the printing operation, based on information indicating the shape of the workpiece W and the first path data Db1, and then converting this to the robot coordinate system. At this time, the second path data Db2 is determined so that the start point PS and end point PE, described later, have the positional relationship described later. The generated second path data Db2 is transmitted from the computer 13 to the controller 11 and stored in the memory circuit 11a.

[0066] In step S20, the control unit 10 executes a printing operation based on the start point PS and the end point PE. Specifically, in step S20, with the processing circuit 11b controlling the movement of the holding robot 4 based on the second path data Db2, the processing circuit 11b controls the movement of the robot 2 based on the first path data Db1, while the control module 12 controls the ink ejection operation of the head 3a based on the signal D3 and the print data Img.

[0067] Figure 5 shows the state of robot 2 at the timing when the head 3a ejects ink toward the starting point PS of the printing area RP during the printing operation in step S20. Figure 6 shows the state of robot 2 at the timing when the head 3a ejects ink toward the ending point PE of the printing area RP during the printing operation in step S20. Figure 7 is an explanatory diagram of the movement path of head 3a during the printing operation in step S20.

[0068] During the printing operation, as shown in Figures 5 and 6, the holding robot 4 supports the workpiece W, while the robot 2 moves the head 3a, and the head 3a ejects ink toward the printing area RP on the workpiece W.

[0069] Here, robot 2 moves the head 3a along the movement path RU based on the first path data Db1. The movement path RU is a path along the printing area RP on the workpiece W. Also, before robot 2's operation based on the first path data Db1, holding robot 4 positions the workpiece W based on the second path data Db2.

[0070] In this embodiment, during the printing operation, the holding robot 4 does not move, and the robot 2 moves instead. This prevents vibration of the workpiece W. Here, from the viewpoint of reducing meandering of the movement path RU of the head 3a, it is preferable to minimize the number of joints that the robot 2 moves during the printing operation. For this reason, Figures 5 and 6 illustrate an embodiment in which the head 3a is moved by the movement of joints J2, J3, and J5 of three parallel rotation axes O2, O3, and O5. In this embodiment, from the viewpoint of reducing meandering of the movement path RU of the head 3a, it is preferable that joints other than joints J2, J3, and J5 are not moved. As a result, the movement path RU is straight when viewed in the direction along the Z axis. Note that during the printing operation, rotation axis O5 may be non-parallel to rotation axes O2 and O3, and joints other than joints J2, J3, and J5 may move. Also, the movement path RU may be curved or bent when viewed in the direction along the Z axis.

[0071] In the example shown in Figures 5 and 6, during the printing operation, the robot 2 changes from a retracted state to an extended state of the arm 220. This reduces vibration of the head 3a caused by the movement of the robot 2 compared to the mode in which the arm 220 changes from an extended state to a retracted state.

[0072] In a side view of the robot 2 at the moment the print head 3a ejects ink toward the starting point PS during the printing operation, the starting point PS, which is the position on the printing area RP where the print head 3a begins ejecting ink, is closer to the base 210 than the ending point PE in a first direction DR1 parallel to the mounting surface FB of the base 210. Furthermore, in a plan view, the starting point PS is further from the mounting surface FB than the ending point PE, which is the position on the printing area RP where the print head 3a finishes ejecting ink, in a second direction DR2 parallel to the normal of the mounting surface FB.

[0073] In other words, in the side view, as shown in Figure 7, the distance LS1 between the starting point PS and the base 210 in the first direction DR1 is shorter than the distance LE1 between the ending point PE and the base 210 in the first direction DR1, and the distance LS2 between the starting point PS and the installation surface FB in the second direction DR2 is longer than the distance LE2 between the ending point PE and the installation surface FB in the second direction DR2. The position of the base 210 in the first direction DR1 is relative to the rotation axis O1. Therefore, distance LS1 can be said to be the distance between the starting point PS and the rotation axis O1 in the first direction DR1, and distance LE1 can be said to be the distance between the ending point PE and the rotation axis O1 in the first direction DR1.

[0074] With the starting point PS and ending point PE positioned in this manner, the robot 2 can be operated in such a way that it swings the head 3a downwards during the printing operation, that is, as the head 3a moves away from the base 210, it moves toward the mounting surface FB. As a result, it is possible to secure a wide printing area RP while suppressing vibrations of the head 3a caused by the movement of the robot 2.

[0075] Furthermore, "the side of robot 2" refers to the surface facing in the direction along the rotation axis O2 or rotation axis O3 of robot 2. Therefore, "a side view of robot 2" means viewing the robot 2 in the direction along the rotation axis O2 or rotation axis O3.

[0076] The imaginary line segment LSE connecting the starting point PS and the ending point PE is closer to the base 210 than the movement path RU6 of joint J6 during the printing operation. As a result, the head 3a moves in a way that it is wrapped around the robot 2 as it moves from the starting point PS to the ending point PE. Therefore, the extension amount of the arm 220 can be suppressed compared to a configuration in which the head 3a moves linearly from the starting point PS to the ending point PE. As a result, a wide printing area RP can be secured while suppressing vibrations of the head 3a caused by the movement of the robot 2.

[0077] Joint J6, an example of a "sixth joint," is the joint closest to head 3a, that is, the furthest joint among the multiple joints J1 to J6 that robot 2 has.

[0078] If the robot 2 is a 6-axis robot as in this embodiment, the head 3a needs to rotate around the rotation axis O5 of the robot 2. Here, in the first direction DR1, when the arm 220 is fully extended as shown by the dashed line in Figure 6, the distance between the arm 226 and the base 210 of the arm 220 is defined as the first distance LMX. Preferably, the distance LS1 between the starting point PS and the base 210, and the distance LE1 between the ending point PE and the base 210 are both at least half of the first distance LMX and less than the first distance LMX. This effectively suppresses vibrations of the head 3a caused by the movement of the robot 2, and as a result, improves print quality.

[0079] In contrast, if the distance LS1 between the starting point PS and the base 210 is less than half of the first distance LMX, the amount of rotation of the robot 2's joint J5 increases, and as a result, vibrations of the head 3a caused by the robot 2's movement during printing tend to increase. Also, if the distance LS1 between the starting point PS and the base 210 is less than half of the first distance LMX, there are many points on the front side of the robot 2 that act as the limit of its movement, making the generation of the printing path complicated. On the other hand, if the distance LS1 between the starting point PS and the base 210 is greater than or equal to the first distance LMX, the arm 220 is fully extended, so vibrations of the head 3a caused by the robot 2's movement tend to increase.

[0080] Furthermore, "when robot 2 is fully extended" means when the furthest joint of robot 2 is furthest from the base 210.

[0081] Joint J2 rotates about the rotation axis O2. The rotation axis O2 is aligned in a direction that intersects both the first direction DR1 and the second direction DR2. Here, in the second direction DR2, it is preferable that the start point PS and the end point PE are located in a direction toward the mounting surface FB (Z2 direction) rather than the rotation axis O2. That is, the distance between the start point PS and the mounting surface FB in the second direction DR2, and the distance between the end point PE and the mounting surface FB in the second direction DR2, are both shorter than the distance between the rotation axis O2 and the mounting surface FB in the second direction DR2. This makes it possible to suppress collisions between the robot 2 and the workpiece W even when a wide printing area RP is secured. Note that in the second direction DR2, the start point PS and the end point PE may coincide with the rotation axis O2, or they may be located in the Z1 direction relative to the rotation axis O2.

[0082] The distance LSE1 between the starting point PS and the ending point PE in the first direction DR1 may be equal to or different from the distance LSE2 between the starting point PS and the ending point PE in the second direction DR2.

[0083] If the distance LSE1 between the starting point PS and the ending point PE in the first direction DR1 is shorter than the distance LSE2 between the starting point PS and the ending point PE in the second direction DR2, vibrations associated with the extension of the robot 2 can be suppressed by suppressing the robot 2's extension in the first direction DR1.

[0084] On the other hand, if the distance LSE2 between the starting point PS and the ending point PE in the second direction DR2 is shorter than the distance LSE1 between the starting point PS and the ending point PE in the first direction DR1, and if the second direction DR2 is aligned with the vertical axis, the deterioration of discharge characteristics due to fluctuations in negative pressure within the head 3a can be suppressed by reducing the vertical displacement of the head 3a.

[0085] During printing, the print head 3a rotates around a rotation axis O5 that is aligned with the direction intersecting the first direction DR1. The rotation range of the print head 3a around the rotation axis O5 is preferably between +90 degrees and -90 degrees, and more preferably between +45 degrees and -45 degrees. This has the advantage of easily widening the printing area RP. Furthermore, if the second direction DR2 is aligned with the vertical axis, the nozzle surface of the print head 3a does not face vertically upward, thus suppressing the risk of weakening of the negative pressure within the print head 3a during printing. As a result, print quality can be improved. In particular, when the rotation range is between +45 degrees and -45 degrees, the fluctuation of the negative pressure within the print head 3a can be suitably suppressed, thereby suitably improving print quality.

[0086] Here, the container for holding the liquid supplied to the head 3a is, for example, attached to the arm 226 of the robot 2 together with the head 3a. The container may also be located outside the robot 2. In this case, the container is connected to the head 3a, for example, via a tube for transferring the liquid to the head 3a. The aforementioned "rotation range of the head 3a rotating around the rotation axis O5" is the range of rotation angles with the state where the nozzle surface of the head 3a faces the opposite direction to the second direction DR2 (the direction facing the ground surface FB) as the reference (0 degrees).

[0087] When viewed along the axis of rotation O2, if we define the first virtual line segment L1 as the virtual line segment connecting joint J2 and joint J3, and the second virtual line segment L2 as the virtual line segment connecting joint J3 and joint J5, and define the first angle θ1 as the angle between the first virtual line segment L1 and the second virtual line segment L2, then in the printing operation, it is preferable that the first angle θ1 at the timing when the head 3a ejects ink toward the starting point PS is 30 degrees or more, and the first angle θ1 at the timing when the head 3a ejects ink toward the ending point PE is 170 degrees or less.

[0088] Furthermore, the first virtual line segment L1 can be said to be a virtual line segment connecting the center of joint J2 and the center of joint J3 when viewed along the axis of rotation O2 or along the axis of rotation O2, or it can be said to be a virtual line segment connecting the axis of rotation O2 and the axis of rotation O3. The second virtual line segment L2 can be said to be a virtual line segment connecting the center of joint J3 and the center of joint J5 when viewed along the axis of rotation O2 or the axis of rotation O3, or it can be said to be a virtual line segment connecting the axis of rotation O3 and the axis of rotation O5 when the axes of rotation O3 and the axis of rotation O5 are parallel to each other.

[0089] When the first angle θ1 is within this angular range, the deterioration of print quality due to vibrations of the head 3a caused by the movement of the robot 2 during printing can be effectively suppressed. In contrast, if the first angle θ1 at the timing when the head 3a ejects ink toward the starting point PS is less than 30 degrees, the dependence of the rotation of joint J5 on the change in the posture of the head 3a increases. As a result, the amount of rotation of joint J5 becomes large in order to secure the necessary displacement of the head 3a, so vibrations of the head 3a caused by the movement of the robot 2 during printing tend to increase, which may result in a deterioration of print quality. Also, if the first angle θ1 at the timing when the head 3a ejects ink toward the ending point PE is greater than 170 degrees, the amount of change in the extension of the robot 2 becomes larger than the amount of displacement of the head 3a, so the timing of liquid ejection by the head 3a tends to be off.

[0090] When viewed along the rotation axis O2, if the angle between the rotation axis O4 and the rotation axis O6 is defined as the second angle θ2, then in the printing operation, if the amount of variation of the second angle θ2 is smaller than the amount of variation of the first angle θ1, the amount of rotation of joint J5 can be made smaller than the amount of rotation of joint J3. As a result, the displacement of the head 3a can be reduced, and consequently, vibrations of the head 3a caused by the movement of the robot 2 can be suppressed.

[0091] On the other hand, in the printing operation, if the amount of variation of the second angle θ2 is greater than the amount of variation of the first angle θ1, the amount of rotation of joint J5 can be made greater than the amount of rotation of joint J3. Therefore, the degree of freedom in setting the positions of the start point PS and the end point PE can be increased, and as a result, the printing area RP can be expanded.

[0092] The angle variation during printing refers to the difference between the maximum and minimum values ​​of the angle variation from the time the print head 3a ejects ink towards the starting point PS until it finishes ejecting ink towards the ending point PE.

[0093] In the printing operation, when the position of the head 3a in the pre-ejection run-up section SE1, where the head 3a moves to the position where it ejects ink toward the starting point PS, is defined as the first point PH1, it is preferable that, when viewed from the side, the angle α between the virtual line segment LH1 connecting the first point PH1 and the starting point PS and the first direction DR1 is smaller than the angle β between the virtual line segment LSE connecting the starting point PS and the ending point PE and the first direction DR1. This suppresses vibration of the head 3a at the timing when ink is ejected toward the starting point PS. As a result, print quality can be improved.

[0094] In the illustration, the first point PH1 is located at the starting position of the pre-discharge run-up section SE1, but it may also be located at an intermediate position in the pre-discharge run-up section SE1. In this case as well, it is preferable that angle α is smaller than angle β.

[0095] From the viewpoint of suppressing vibration of the head 3a at the start of the printing operation, the pre-ejection run-up section SE1 is preferably along the tangent to a virtual circle centered on the rotation axis O2 and passing through the starting point PS.

[0096] In the printing operation, when the position of the head 3a in the post-ejection run-up section SE2, where the head 3a moves after ejecting ink toward the end point PE, is defined as the second point PH2, it is preferable that the distance DD1 between the second point PH2 and the workpiece W, when viewed from the side, is greater than the distance DD2 between the head 3a and the workpiece W at the time the head 3a ejects ink toward the end point PE. This ensures that even if the arm 220 vibrates after passing the end point PE, the head 3a is moved away from the workpiece W, thereby suppressing collision between the head 3a and the workpiece W.

[0097] Note that, although the second point PH2 is shown as being located at the end of the post-discharge run-up section SE2 in the figure, it may also be located at an intermediate position in the post-discharge run-up section SE2. In this case as well, it is preferable that distance DD1 is farther than distance DD2.

[0098] Near the end point PE, the inclination of the printing area RP with respect to the mounting surface FB increases, so if the second direction DR2 is aligned with the vertical axis, there is a risk that the ejected ink may drip. In this case, the curing light source 3c, which emits light to cure or solidify the ink, may be moved closer to the end point PE.

[0099] 2. Variations Each of the above examples can be modified in various ways. Specific examples of modifications that can be applied to each of the aforementioned examples are given below. Note that two or more of the following examples can be arbitrarily selected and combined as appropriate, provided they do not contradict each other.

[0100] 2-1. Variation 1 In the aforementioned configuration, a 6-axis vertical multi-axis robot is used as the moving mechanism, but the system is not limited to this configuration. The moving mechanism only needs to be capable of three-dimensionally changing the relative position and orientation of the liquid discharge head with respect to the workpiece. Therefore, the moving mechanism may be a vertical multi-axis robot other than a 6-axis robot, or a horizontal multi-axis robot. In addition, the robot arm may have an extension mechanism or the like in addition to the joints composed of a rotation mechanism. However, from the viewpoint of balancing the print quality in printing operations and the degree of freedom of the movement mechanism in non-printing operations, it is preferable that the moving mechanism be a multi-axis robot with 6 or more axes. A dual-arm robot may also be used, in which case one arm can be used as the first robot and the other arm as the second robot.

[0101] For example, in the case of a 7-axis robot, the 7th joint from the base to the tip is the furthest joint, and this 7th joint corresponds to the "6th joint." Similarly, the multiple joints of a multi-axis robot correspond to the "1st joint," "2nd joint," "3rd joint," "4th joint," and "5th joint," in order from the base to the tip.

[0102] 2-2. Variation 2 In the aforementioned configuration, an example is given of a method for fixing the head to the robot using screws, but the configuration is not limited to this. For example, the head may be fixed to the robot by gripping it with a gripping mechanism such as a hand attached as an end effector to the robot.

[0103] 2-3. Variation 3 While the above-described embodiment exemplifies a configuration in which printing is performed using one type of ink, the disclosure is not limited to this configuration and can also be applied to configurations in which printing is performed using two or more types of ink.

[0104] 2-4. Variation 4 The applications of the three-dimensional object printing apparatus described herein are not limited to printing. For example, a three-dimensional object printing apparatus that dispenses a colorant solution can be used as a manufacturing apparatus for forming color filters for liquid crystal display devices. A three-dimensional object printing apparatus that dispenses a conductive material solution can be used as a manufacturing apparatus for forming wiring and electrodes on a wiring board. Furthermore, a three-dimensional object printing apparatus can also be used as a jet dispenser for applying liquids such as adhesives to a workpiece.

[0105] 3. Addendum A summary of this disclosure is provided below.

[0106] (Note 1) A first embodiment of a three-dimensional object printing apparatus of the present disclosure includes a head for discharging liquid toward a three-dimensional workpiece, an arm, and a base connected to one end of the arm, and a robot for changing the relative position between the workpiece and the head, wherein the robot performs a printing operation in which it moves the head along a printing area of ​​the workpiece while discharging liquid from the head, and in the printing operation, the position on the printing area where the head begins to discharge liquid is defined as the starting point, and the position on the printing area where the head finishes discharging liquid is defined as the ending point, wherein in the printing operation, when the robot is viewed from the side at the timing when the head discharges liquid toward the starting point, the starting point is closer to the base than the ending point in a first direction parallel to the mounting surface of the base, and further from the mounting surface than the ending point in a second direction parallel to the normal of the mounting surface.

[0107] In the above embodiment, the robot can be operated in such a way that it swings the head downwards during the printing operation, that is, as the head moves away from the base, it moves toward the mounting surface. As a result, it is possible to secure a wide printing area while suppressing head vibrations caused by the robot's movement.

[0108] (Note 2) In the second embodiment, which is a preferred example of the first embodiment, the arm has a sixth joint closest to the head, and the imaginary line segment connecting the start point and the end point is closer to the base than the movement path of the sixth joint in the printing operation. In the above embodiment, the head moves so as to be wrapped around the robot from the start point to the end point. Therefore, the amount of extension of the arm can be suppressed compared to the embodiment in which the head moves linearly from the start point to the end point. As a result, a wide printing area can be secured while suppressing vibrations of the head caused by the movement of the robot.

[0109] (Note 3) In a third embodiment, which is a preferred example of the first or second embodiment, when the distance between the tip of the arm and the base of the arm when the arm is fully extended in the first direction is defined as the first distance, the distance between the starting point and the base, and the distance between the ending point and the base are each at least half of the first distance and less than the first distance. In the above embodiment, head vibrations caused by the robot's movement can be suitably suppressed, and as a result, print quality can be improved. On the other hand, if the robot is, for example, a 6-axis robot, the head needs to rotate around the fifth rotation axis of the robot, but if the distance between the starting point and the base is less than half of the first distance, the amount of rotation of the fifth joint of the robot becomes large, and as a result, head vibrations caused by the robot's movement during printing tend to be large. Also, if the distance between the starting point and the base is less than half of the first distance, there are many points on the front side of the robot that are the limits of the robot's movement, so the generation of the printing path becomes complicated. On the other hand, if the distance between the starting point and the base is the first distance, the arm will be fully extended, which tends to increase head vibrations caused by the robot's movement.

[0110] (Note 4) In a fourth embodiment, which is a preferred example of any of the first to third embodiments, the arm has a second joint that rotates about a second axis of rotation that intersects both the first and second directions, and in the second direction, the start point and the end point are located closer to the mounting surface than the second axis of rotation. In this embodiment, even if a wide printing area is secured, collisions between the robot and the workpiece can be suppressed.

[0111] (Note 5) In the fifth embodiment, which is a preferred example of any of the first to fourth embodiments, the distance between the start point and the end point in the first direction is shorter than the distance between the start point and the end point in the second direction. In the above embodiments, vibrations associated with the extension of the robot can be suppressed by suppressing the extension of the robot.

[0112] (Note 6) In the sixth embodiment, which is a preferred example of any of the first to fourth embodiments, the distance between the start point and the end point in the second direction is shorter than the distance between the start point and the end point in the first direction. In the above embodiments, when the second direction is along the vertical axis, the deterioration of discharge characteristics due to fluctuations in negative pressure inside the head can be suppressed by reducing the vertical displacement of the head.

[0113] (Note 7) In the seventh embodiment, which is a preferred example of any of the first to sixth embodiments, in the printing operation, the head rotates about a fifth rotation axis along a direction intersecting the first direction, and the rotation range of the head rotating about the fifth rotation axis is between +90 degrees and -90 degrees. The above embodiments have the advantage of making it easier to widen the printing area. In addition, when the second direction is along the vertical axis, the nozzle surface of the head does not face vertically upward, so the risk of the negative pressure inside the head during the printing operation weakening can be suppressed. As a result, the print quality can be improved.

[0114] The container for holding the liquid supplied to the head is, for example, attached to the tip of the robot together with the head. Alternatively, the container may be located outside the robot. In this case, the container is connected to the head, for example, via a tube for transferring the liquid to the head. Furthermore, the "rotation range of the head" refers to the angular range around the fifth rotation axis, with the state where the nozzle surface of the head faces the mounting surface of the base being the reference point (0 degrees).

[0115] (Note 8) In the eighth embodiment, which is a preferred example of the seventh embodiment, the rotation range of the head is between +45 degrees and -45 degrees. In the above embodiments, the print quality can be suitably improved by suitably suppressing fluctuations in negative pressure within the head.

[0116] (Note 9) In the ninth embodiment, which is a preferred example of any of the first to eighth embodiments, the arm has a second joint that rotates about a second axis of rotation along a direction intersecting the first direction, a third joint that rotates about a third axis of rotation parallel to the second axis of rotation, a fourth joint that rotates about a fourth axis of rotation intersecting the third axis of rotation, and a fifth joint that rotates about a fifth axis of rotation intersecting the fourth axis of rotation, and the second joint, the third joint, the fourth joint and the fifth joint are in this order from the base to the arm Provided toward the tip of the head, and when viewed along the second rotation axis, if the imaginary line segment connecting the second joint and the third joint is defined as the first imaginary line segment, and the imaginary line segment connecting the third joint and the fifth joint is defined as the second imaginary line segment, and the angle between the first imaginary line segment and the second imaginary line segment is defined as the first angle, then in the printing operation, the first angle at the timing when the head ejects liquid toward the starting point is 30 degrees or more, and the first angle at the timing when the head ejects liquid toward the ending point is 170 degrees or less.

[0117] In the above embodiment, the deterioration of print quality due to head vibration caused by the robot's movement during printing can be effectively suppressed. In contrast, if the first angle at the timing when the head ejects liquid toward the starting point is less than 30 degrees, the degree of dependence of the rotation of the fifth joint on the change in the head's posture increases. As a result, the amount of rotation of the fifth joint becomes large in order to secure the necessary displacement of the head, which tends to increase head vibration caused by the robot's movement during printing, and this may result in a deterioration of print quality. Also, if the first angle at the timing when the head ejects liquid toward the ending point is greater than 170 degrees, the amount of change in the robot's extension becomes larger than the amount of head displacement, so the timing of liquid ejection by the head tends to be off.

[0118] (Note 10) In the tenth embodiment, which is a preferred example of any of the first to ninth embodiments, the arm has a second joint that rotates about a second axis of rotation along a direction intersecting the first direction, a third joint that rotates about a third axis of rotation parallel to the second axis of rotation, a fourth joint that rotates about a fourth axis of rotation intersecting the third axis of rotation, a fifth joint that rotates about a fifth axis of rotation intersecting the fourth axis of rotation, and a sixth joint that rotates about a sixth axis of rotation intersecting the fifth axis of rotation, and the second joint, the third joint, the The fourth, fifth, and sixth joints are provided in this order from the base toward the tip of the arm. When viewed along the second rotation axis, the imaginary line segment connecting the second and third joints is defined as the first imaginary line segment, the imaginary line segment connecting the third and fifth joints is defined as the second imaginary line segment, the angle between the first and second imaginary line segments is defined as the first angle, and the angle between the fourth and sixth rotation axes is defined as the second angle. In the printing operation, the amount of variation of the second angle is smaller than the amount of variation of the first angle. In the above embodiment, the amount of rotation of the fifth joint can be made smaller than the amount of rotation of the third joint. As a result, the amount of displacement of the head can be reduced, and as a result, vibrations of the head caused by the movement of the robot can be suppressed.

[0119] (Note 11) In the 11th embodiment, which is a preferred example of any of the 1st to 9th embodiments, the arm has a second joint that rotates about a second axis of rotation along a direction intersecting the first direction, a third joint that rotates about a third axis of rotation parallel to the second axis of rotation, a fourth joint that rotates about a fourth axis of rotation intersecting the third axis of rotation, a fifth joint that rotates about a fifth axis of rotation intersecting the fourth axis of rotation, and a sixth joint that rotates about a sixth axis of rotation intersecting the fifth axis of rotation, and the second joint, the third joint, the The fourth, fifth, and sixth joints are provided in this order from the base toward the tip of the arm. When viewed along the second rotation axis, the imaginary line segment connecting the second and third joints is defined as the first imaginary line segment, the imaginary line segment connecting the third and fifth joints is defined as the second imaginary line segment, the angle between the first and second imaginary line segments is defined as the first angle, and the angle between the fourth and sixth rotation axes is defined as the second angle. In the printing operation, the amount of variation of the second angle is greater than the amount of variation of the first angle. In the above embodiment, the amount of rotation of the fifth joint can be made greater than the amount of rotation of the third joint. Therefore, the degree of freedom in setting the positions of the start and end points can be increased, and as a result, the printing area can be expanded.

[0120] (Note 12) In the 12th embodiment, which is a preferred example of any of the 1st to 11th embodiments, in the printing operation, when the position of the head in the pre-discharge run-up section, where the head moves to the position where it discharges liquid toward the starting point, is defined as the first point, when viewed from the side, the angle between the imaginary line segment connecting the first point and the starting point and the first direction is smaller than the angle between the imaginary line segment connecting the starting point and the ending point and the first direction. In the above embodiment, vibration of the head at the timing of discharging liquid toward the starting point can be suppressed. As a result, print quality can be improved.

[0121] (Note 13) In the 13th embodiment, which is a preferred example of any of the 1st to 12th embodiments, when the position of the head in the post-ejection run-up section, where the head moves after ejecting liquid toward the end point, is defined as the second point, the distance between the second point and the workpiece in a side view is greater than the distance between the head and the workpiece at the time the head ejects liquid toward the end point. In the above embodiment, even if the arm vibrates after passing the end point, the head is moved away from the workpiece, so that the head does not collide with the workpiece.

[0122] (Note 14) In a 14th embodiment, which is a preferred example of any of the 1st to 13th embodiments, a holding robot is further provided to hold the workpiece, and the holding robot changes either or both of the position and orientation of the workpiece before the printing operation. In the above embodiments, manual changes to the orientation or position adjustment of the workpiece can be omitted.

[0123] (Note 15) A 15th aspect of the printing method of the present disclosure is a printing method using a three-dimensional object printing apparatus comprising: a head for discharging liquid toward a three-dimensional workpiece; an arm; and a base connected to one end of the arm; and a robot for changing the relative position between the workpiece and the head, comprising the steps of: determining a starting point which is a position on the printing area toward which the head begins to discharge liquid toward the printing area of ​​the workpiece; and an ending point which is a position on the printing area toward which the head finishes discharging liquid toward the printing area; and performing a printing operation in which the robot moves the head along the printing area while discharging liquid from the head based on the starting point and the ending point, wherein in the printing operation, in a side view of the robot viewed from the side at the timing when the head discharges liquid toward the starting point, the starting point is closer to the base than the ending point in a first direction parallel to the mounting surface of the base, and further from the mounting surface than the ending point in a second direction parallel to the normal of the mounting surface.

[0124] In the above embodiment, the robot can be operated in such a way that it swings the head downwards during the printing operation, that is, so that the head moves vertically downwards as it moves away from the base. As a result, it is possible to ensure a wide printing area while suppressing head vibrations caused by the robot's movement. [Explanation of symbols]

[0125] 1...3D object printing device, 2...Robot, 2a...Arm drive mechanism, 3...Head unit, 3a...Head, 3c...Curing light source, 3d...Switch circuit, 4...Holding robot, 4a...Arm drive mechanism, 10...Control unit, 11...Controller, 11a...Memory circuit, 11b...Processing circuit, 12...Control module, 12a...Timing signal generation circuit, 12b...Power supply circuit, 12c...Control circuit, 12d...Drive signal generation circuit, 13...Computer, 210...Base, 220...Arm, 221...Arm, 222...Arm, 223...A Arm, 224...arm, 225...arm, 226...arm, 410...base, 420...arm, CLK...clock signal, CNG...change signal, Com...drive signal, D1...output, D2...output, D3...signal, DD1...distance, DD2...distance, DR1...first direction, DR2...second direction, Db1...first path data, Db2...second path data, FB...mounting surface, FN...nozzle surface, HJ...holding mechanism, Img...print data, J1...joint (first joint), J2...joint (second joint), J3...joint (third joint), J4...joint (fourth joint) J5...Joint (5th joint), J6...Joint (6th joint), L1...First virtual line segment, L2...Second virtual line segment, LAT...Latch signal, LE1...Distance, LE2...Distance, LH1...Virtual line segment, LMX...First distance, LS1...Distance, LS2...Distance, LSE...Virtual line segment, LSE1...Distance, LSE2...Distance, N...Nozzle, O1...Rotation axis (1st rotation axis), O2...Rotation axis (2nd rotation axis), O3...Rotation axis (3rd rotation axis), O4...Rotation axis (4th rotation axis), O5...Rotation axis (5th rotation axis), O6...Rotation axis (6th rotation axis), PD...Drive pulse S, PE...end point, PH1...first point, PH2...second point, PS...start point, PTS...timing signal, RP...printing area, RU...movement path, RU6...movement path, S10...step, S11...step, S12...step, S20...step, SE1...pre-ejection run-up section, SE2...post-ejection run-up section, SI...control signal, Sk1...control signal, Sk2...control signal, VBS...offset potential, VHV...power supply potential, W...workpiece, WF...surface, dCom...waveform specification signal, α...angle, β...angle, θ1...first angle, θ2...second angle.

Claims

1. A head that dispenses liquid towards a three-dimensional workpiece, A robot comprising an arm and a base connected to one end of the arm, which changes the relative position between the workpiece and the head, While discharging liquid from the head, the robot performs a printing operation in which the head moves along the printing area of ​​the workpiece. In the aforementioned printing operation, The position on the printing area where the head begins to eject the liquid is taken as the starting point. When the position on the printing area where the head finishes ejecting the liquid is defined as the termination point, In the printing operation described above, at the timing when the head ejects liquid toward the starting point, the robot is viewed from the side in a side view, The aforementioned starting point is, In a first direction parallel to the mounting surface of the base, closer to the base than the termination point, In a second direction parallel to the normal of the installation surface, further from the installation surface than the termination point, A three-dimensional object printing apparatus characterized by the following features.

2. The arm has a sixth joint closest to the head, The imaginary line segment connecting the start point and the end point is closer to the base than the movement path of the sixth joint in the printing operation. The three-dimensional object printing apparatus according to feature 1.

3. In the first direction, When the distance between the tip and base of the arm when the arm is fully extended is defined as the first distance, The distance between the starting point and the base, and the distance between the ending point and the base, are each at least half of the first distance and less than the first distance. A three-dimensional object printing apparatus according to claim 1 or 2.

4. The arm has a second joint that rotates about a second axis of rotation that is in a direction intersecting both the first and second directions, In the second direction, The start point and the end point are each located closer to the installation surface than the second rotation axis. A three-dimensional object printing apparatus according to claim 1 or 2.

5. The distance between the start point and the end point in the first direction is shorter than the distance between the start point and the end point in the second direction. A three-dimensional object printing apparatus according to claim 1 or 2.

6. The distance between the start point and the end point in the second direction is shorter than the distance between the start point and the end point in the first direction. A three-dimensional object printing apparatus according to claim 1 or 2.

7. In the aforementioned printing operation, The head rotates about a fifth axis of rotation that is aligned with a direction intersecting the first direction. The rotation range of the head, which rotates around the fifth rotation axis, is between +90 degrees and -90 degrees. A three-dimensional object printing apparatus according to claim 1 or 2.

8. The rotation range of the head is between +45 degrees and -45 degrees. The three-dimensional object printing apparatus according to feature 7.

9. The aforementioned arm is A second joint that rotates about a second axis of rotation along a direction intersecting the first direction, A third joint that rotates about a third axis of rotation parallel to the second axis of rotation, A fourth joint that rotates around a fourth axis of rotation that intersects the third axis of rotation, It has a fifth joint that rotates about a fifth axis of rotation that intersects the fourth axis of rotation, The second joint, the third joint, the fourth joint, and the fifth joint are provided in this order from the base towards the tip of the arm, When viewed along the second axis of rotation, Let the imaginary line segment connecting the second joint and the third joint be the first imaginary line segment. Let the imaginary line segment connecting the third joint and the fifth joint be the second imaginary line segment. If the angle between the first virtual line segment and the second virtual line segment is called the first angle, In the aforementioned printing operation, The first angle at the timing when the head discharges the liquid toward the starting point is 30 degrees or more. The first angle at the timing when the head discharges the liquid toward the endpoint is 170 degrees or less. A three-dimensional object printing apparatus according to claim 1 or 2.

10. The aforementioned arm is A second joint that rotates about a second axis of rotation along a direction intersecting the first direction, A third joint that rotates about a third axis of rotation parallel to the second axis of rotation, A fourth joint that rotates around a fourth axis of rotation that intersects the third axis of rotation, A fifth joint that rotates around a fifth axis of rotation that intersects with the fourth axis of rotation, It has a sixth joint that rotates about a sixth axis of rotation that intersects the fifth axis of rotation, The second joint, the third joint, the fourth joint, the fifth joint, and the sixth joint are provided in this order from the base towards the tip of the arm, When viewed along the second axis of rotation, Let the imaginary line segment connecting the second joint and the third joint be the first imaginary line segment. Let the imaginary line segment connecting the third joint and the fifth joint be the second imaginary line segment. Let the angle between the first virtual line segment and the second virtual line segment be the first angle. When the angle between the fourth axis of rotation and the sixth axis of rotation is defined as the second angle, In the aforementioned printing operation, The amount of variation of the second angle is smaller than the amount of variation of the first angle. A three-dimensional object printing apparatus according to claim 1 or 2.

11. The aforementioned arm is A second joint that rotates about a second axis of rotation along a direction intersecting the first direction, A third joint that rotates about a third axis of rotation parallel to the second axis of rotation, A fourth joint that rotates around a fourth axis of rotation that intersects the third axis of rotation, A fifth joint that rotates around a fifth axis of rotation that intersects with the fourth axis of rotation, It has a sixth joint that rotates about a sixth axis of rotation that intersects the fifth axis of rotation, The second joint, the third joint, the fourth joint, the fifth joint, and the sixth joint are provided in this order from the base towards the tip of the arm, When viewed along the second axis of rotation, Let the imaginary line segment connecting the second joint and the third joint be the first imaginary line segment. Let the imaginary line segment connecting the third joint and the fifth joint be the second imaginary line segment. Let the angle between the first virtual line segment and the second virtual line segment be the first angle. When the angle between the fourth axis of rotation and the sixth axis of rotation is defined as the second angle, In the aforementioned printing operation, The amount of variation of the second angle is greater than the amount of variation of the first angle. A three-dimensional object printing apparatus according to claim 1 or 2.

12. In the printing operation described above, when the position of the head during the pre-discharge run-up section, where the head moves to the position where it discharges liquid toward the starting point, is defined as the first point, When viewed from the side, The angle between the imaginary line segment connecting the first point and the starting point and the first direction is smaller than the angle between the imaginary line segment connecting the starting point and the ending point and the first direction. A three-dimensional object printing apparatus according to claim 1 or 2.

13. In the aforementioned printing operation, when the position of the head in the post-ejection run-up section, where the head moves after ejecting liquid toward the endpoint, is defined as the second point, When viewed from the side, The distance between the second point and the workpiece is greater than the distance between the head and the workpiece at the time the head discharges the liquid toward the end point. A three-dimensional object printing apparatus according to claim 1 or 2.

14. The system further includes a holding robot for holding the workpiece, The holding robot changes either or both of the position and orientation of the workpiece before the printing operation. A three-dimensional object printing apparatus according to claim 1 or 2.

15. A head that dispenses liquid towards a three-dimensional workpiece, A printing method using a three-dimensional object printing apparatus comprising a robot that includes an arm and a base connected to one end of the arm, and which changes the relative position between the workpiece and the head, The steps include determining a starting point, which is the position on the printing area where the head begins to discharge liquid toward the printing area of ​​the workpiece, and an ending point, which is the position on the printing area where the head finishes discharging liquid toward the printing area. The step includes performing a printing operation in which the robot moves the head along the printing area while discharging liquid from the head based on the start point and the end point, In the printing operation described above, at the timing when the head ejects liquid toward the starting point, the robot is viewed from the side in a side view, The aforementioned starting point is, In a first direction parallel to the mounting surface of the base, closer to the base than the termination point, In a second direction parallel to the normal of the installation surface, further from the installation surface than the termination point, A printing method characterized by the following features.

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