Three-dimensional object printing apparatus and three-dimensional object printing method

A three-dimensional object printing apparatus includes: a head having a nozzle surface; a robot that has a base portion that supports the head, and changes a position of the head with respect to the base portion; and a cap portion having a fixed position to the base portion to cover the nozzle surface, in which the three-dimensional object printing apparatus is configured to execute: a capping operation of causing the robot to locate the head at a position at which the nozzle surface is covered with the cap portion, and a printing operation of causing the head to eject the liquid to a work with respect to the work, and a yaw angle of the head during the execution of the capping operation and a yaw angle of the head during the execution of the printing operation are different from each other.

The present application is based on, and claims priority from JP Application Serial Number 2021-037082, filed Mar. 9, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a three-dimensional object printing apparatus and a three-dimensional object printing method.

2. Related Art

A three-dimensional object printing apparatus that performs printing on a surface of a three-dimensional work by an ink jet method is known. For example, an apparatus described in JP-A-2014-050832 includes a robot arm and a print head fixed to a tip of the robot arm.

The printing apparatus described in JP-A-2014-050832 has a problem that an ink in the vicinity of a nozzle of the print head becomes thickened or solidified due to an influence of external light or drying by the outside air, so that the nozzle is clogged, and as a result, an ejection failure occurs.

SUMMARY

According to an aspect of the present disclosure, there is provided a three-dimensional object printing apparatus including: a head having a nozzle surface provided with a plurality of nozzles for ejecting a liquid; a robot that has a base portion and an arm portion that supports the head, is provided with a plurality of rotating portions from the base portion to the arm portion, and changes a position of the head with respect to the base portion by rotating the rotating portion; and a cap portion that covers the nozzle surface, in which the three-dimensional object printing apparatus is configured to execute: a capping operation of causing the robot to locate the head at a position at which the nozzle surface is covered with the cap portion, and a printing operation of causing the head to eject the liquid to a work while causing the robot to change a position of the head with respect to the work to a position different from a position during the execution of the capping operation, and a yaw angle of the head during the execution of the capping operation and a yaw angle of the head during the execution of the printing operation are different from each other.

According to another aspect of the present disclosure, there is provided a three-dimensional object printing method using a head having a nozzle surface provided with a plurality of nozzles for ejecting a liquid, a robot that has a base portion and an arm portion that supports the head, is provided with a plurality of rotating portions from the base portion to the arm portion, and changes a position of the head with respect to the base portion by rotating the rotating portion, and a cap portion that covers the nozzle surface, the method including: performing a capping operation of causing the robot to locate the head at a position at which the nozzle surface is covered with the cap portion; and performing a printing operation of causing the head to eject the liquid to a work while causing the robot to change a position of the head with respect to the work to a position different from a position during the execution of the capping operation, and a yaw angle of the head during the execution of the capping operation and a yaw angle of the head during the execution of the printing operation are different from each other.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, appropriate embodiments of the present disclosure will be described with reference to the accompanying drawings. In the drawings, dimensions and scale of each portion are appropriately different from the actual ones, and some portions are schematically illustrated for easy understanding. In addition, the scope of the present disclosure is not limited thereto unless otherwise stated to limit the present disclosure in the following description.

In the following description, for convenience, an X-axis, a Y-axis, and a Z-axis that intersect each other will be appropriately used. Further, in the following description, one direction along the X-axis is an X1 direction, and a direction opposite to the X1 direction is an X2 direction. In the same manner, directions opposite to each other along the Y-axis are a Y1 direction and a Y2 direction. Further, directions opposite to each other along the Z-axis are a Z1 direction and a Z2 direction.

Here, the X-axis, the Y-axis, and the Z-axis correspond to the coordinate axes of the world coordinate system set in a space in which a robot2, which will be described below, is installed. Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to a downward direction in the vertical direction. A base coordinate system using a base portion of the robot2as a reference is associated with the world coordinate system by calibration. In the following, for convenience, a case where an operation of the robot2is controlled by using the world coordinate system as a robot coordinate system will be illustrated.

The Z-axis may not be the vertical axis. Further, the X-axis, the Y-axis, and the Z-axis are typically orthogonal to each other, but the present disclosure is not limited to this, and the X-axis, the Y-axis, and the Z-axis may not be orthogonal to each other. For example, the X-axis, Y-axis, and Z-axis may intersect each other at an angle within a range equal to or more than 80° and equal to or less than 100°.

1. First Embodiment

1-1. Outline of Three-dimensional Object Printing Apparatus

FIG.1is a perspective view illustrating an outline of a three-dimensional object printing apparatus1according to an embodiment. The three-dimensional object printing apparatus1is an apparatus that performs printing on a surface of a three-dimensional work W by an ink jet method.

The work W has a surface WF as a printing target. In the example illustrated inFIG.1, the work W is a rugby ball having a long spherical shape, and the surface WF is a curved surface. For example, the work W at a time of printing is supported by a structure such as a predetermined setting table, a robot hand, or a conveyor, as needed. An aspect such as a shape or a size of the work W or the surface WF is not limited to the example illustrated inFIG.1, and is freely determined. Further, a position or a posture of the work W or the surface WF at the time of printing may be set so that printing is possible, and is freely determined without being limited to the example illustrated inFIG.1.

As illustrated inFIG.1, the three-dimensional object printing apparatus1includes the robot2, a head unit3, a maintenance unit4, a controller5, a piping portion10, and a wiring portion11. Hereinafter, first, the robot2, the head unit3, the maintenance unit4, the controller5, the piping portion10, and the wiring portion11will be briefly described in order.

The robot2is a robot that changes a position and a posture of the head unit3in the world coordinate system. In the example illustrated inFIG.1, the robot2is a so-called 6-axis vertical articulated robot.

As illustrated inFIG.1, the robot2has a base portion210and an arm portion220.

The base portion210is a base that supports the arm portion220. In the example illustrated inFIG.1, the base portion210is fixed to a floor surface or the like facing the Z1 direction or an installation surface such as a base plate by screwing or the like. The installation surface to which the base portion210is fixed may be a surface facing in any direction, is not limited to the example illustrated inFIG.1, and may be, for example, a surface provided by a wall, a ceiling, a movable trolley, or the like. Further, in the following, when viewed in a direction perpendicular to the installation surface of the base portion210, that is, viewed in the Z1 direction or the Z2 direction in the present embodiment is referred to as a “plan view of the base portion210” or simply a “plan view”, in some cases.

The arm portion220is a 6-axis robot arm having a base end attached to the base portion210and a tip that changes a position and a posture three-dimensionally with respect to the base end. Specifically, the arm portion220has arms221,222,223,224,225, and226, which are coupled in this order.

The arm221is rotatably coupled to the base portion210around a rotation axis O1via a joint portion230_1. The arm222is rotatably coupled to the arm221around a rotation axis O2via a joint portion230_2. The arm223is rotatably coupled to the arm222around a rotation axis O3via a joint portion230_3. The arm224is rotatably coupled to the arm223around a rotation axis O4via a joint portion230_4. The arm225is rotatably coupled to the arm224around a rotation axis O5via a joint portion230_5. The arm226is rotatably coupled to the arm225around a rotation axis O6via a joint portion230_6.

Each of the joint portions230_1to230_6is an example of a “rotating portion”, and is a mechanism for rotatably coupling one of two adjacent members of the base portion210and the arms221to226to the other. Here, among the joint portions230_1to230_6, the joint portion230_1which is closest to the base portion210is an example of a “first rotating portion”. Further, the joint portion230_6which is farthest from the base portion210among the joint portions230_1to230_6is an example of a “second rotating portion”. In the following, each of the joint portions230_1to230_6may be referred to as a “joint portion230”.

Although not illustrated inFIG.1, each of the joint portions230_1to230_6is provided with a drive mechanism for rotating one of the two adjacent members corresponding to each other to the other. The drive mechanism includes, for example, a motor that generates a drive force for the rotation, a speed reducer that decelerates and outputs the drive force, an encoder such as a rotary encoder that detects a movement amount such as an angle of the rotation, and the like. An aggregation of the drive mechanisms of the joint portions230_1to230_6corresponds to an arm drive mechanism2aillustrated inFIG.2, which will be described below.

The rotation axis O1is an axis perpendicular to the installation surface (not illustrated) to which the base portion210is fixed. The rotation axis O2is an axis perpendicular to the rotation axis O1. The rotation axis O3is an axis parallel with the rotation axis O2. The rotation axis O4is an axis perpendicular to the rotation axis O3. The rotation axis O5is an axis perpendicular to the rotation axis O4. The rotation axis O6is an axis perpendicular to the rotation axis O5.

Regarding these rotation axes, “perpendicular” includes that an angle formed by the two rotation axes is strictly 90°, and the angle formed by the two rotation axes deviates within a range of approximately 90° to ±5°. In the same manner, “parallel” includes not only a case where the two rotation axes are strictly parallel with each other, but also a case where one of the two rotation axes is tilted within a range of approximately ±5° with respect to the other.

The head unit3is attached to the arm226located at the most tip of the arm portion220of the above robot2in a state of being fixed by screwing or the like, as an end effector.

The head unit3is an assembly having a head3athat ejects an ink, which is an example of a “liquid”, toward the work W. In the present embodiment, the head unit3includes a pressure regulating valve3b, a curing light source3c, and a distance sensor3d, in addition to the head3a. Details of the head unit3will be described with reference toFIG.3, which will be described below.

The ink is not particularly limited, and includes, for example, 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, a solvent-based ink in which a coloring material such as a dye or a pigment is dissolved in an organic solvent, and the like. Among the inks, the curable ink is preferably used. The curable ink is not particularly limited, and may be, for example, any of a thermosetting type, a photocurable type, a radiation curable type, an electron beam curable type, or the like, and a photocurable type such as an ultraviolet curable type is preferable. The ink is not limited to the solution, and may be an ink in which a coloring material or the like is dispersed as a dispersant in a dispersion medium. Further, 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 dispersant, a clear ink, or a treatment liquid for surface treatment of the work W.

Each of the piping portion10and the wiring portion11is coupled to the head unit3. The piping portion10is a pipe or a pipe group including a supply pipe10athat supplies an ink from an ink tank (not illustrated) to the head unit3. The supply pipe10ais a flexible pipe body made of, for example, a rubber material or an elastomer material. The wiring portion11is a wiring or a wiring group including a drive wiring11afor supplying an electrical signal for driving the head3a. The drive wiring11ais configured with, for example, various flexible electrical wirings. In addition to the supply pipe10a, the piping portion10may include other pipes such as a pipe for transferring the ink ejected from the head unit3, for example. Further, in addition to the drive wiring11a, the wiring portion11appropriately includes various wirings for transmitting other electronic signals such as a control signal SI, which will be described below, which are necessary for driving the head3a, for example.

Each of the piping portion10and the wiring portion11is fixed to the head unit3at a fixed position FX1by being coupled to the head unit3. The fixed position FX1is a position in the end effector, specifically, a position of a connector (not illustrated) for coupling the piping portion10and the wiring portion11to the head unit3. Further, each of the piping portion10and the wiring portion11is fixed to the arm portion220of the robot2described above by a binding band or the like at fixed positions FX2, FX3, and FX4. The fixed position FX2is a position on the arm224described above. The fixed position FX3is a position on the arm223described above. The fixed position FX4is a position on the arm222described above. By partially fixing the piping portion10and the wiring portion11to a plurality of positions of the arm portion220in this manner, a positional relationship between the arm portion220, the piping portion10, and the wiring portion11can be maintained within a predetermined range while sufficiently allowing a movement of the arm portion220. The example inFIG.1includes a configuration in which routing routes of the piping portion10and the wiring portion11are identical to each other, and the routing routes of the piping portion10and the wiring portion11may have portions different from each other.

The maintenance unit4is a mechanism for performing maintenance on the head3aof the head unit3. In the example illustrated inFIG.1, the maintenance unit4has a case4a, a cap portion4b, a support table4c, a suction mechanism4d, and a wiper portion4e. In the same manner as the base portion210of the robot2, the case4ais fixed to a floor surface or the like facing the Z1 direction or an installation surface such as a base plate by screwing or the like. Details of the maintenance unit4will be described with reference toFIG.3, which will be described below. Further, the maintenance is a concept including covering the nozzle surface F of the head3awith the cap portion4b, performing suction by the suction mechanism4d, wiping with the wiper portion4e, and the like.

The controller5is a robot controller that controls a drive of the robot2. Hereinafter, an electrical configuration of the three-dimensional object printing apparatus1will be described with reference toFIG.2, including a detailed description of the controller5.

1-2. Electrical Configuration of Three-dimensional Object Printing Apparatus

FIG.2is a block diagram illustrating an electrical configuration of the three-dimensional object printing apparatus1according to the embodiment. InFIG.2, among components of the three-dimensional object printing apparatus1, electrical components are illustrated. As illustrated inFIG.2, in addition to the components illustrated inFIG.1described above, the three-dimensional object printing apparatus1includes a control module6that is communicably connected to the controller5and a computer7that is communicably connected to the controller5and the control module6Hereinafter, before the detailed description of the controller5, the control module6and the computer7will be described in this order.

Each electrical component illustrated inFIG.2may be appropriately divided, a part thereof may be included in another component, or may be integrally formed with the other component. For example, a part or all of functions of the controller5or the control module6may be realized by the computer7, or may be realized by another external device such as a personal computer (PC) connected to the controller5via a network such as a local area network (LAN) or the Internet.

The controller5has a function of controlling the drive of the robot2and a function of generating a signal D3for synchronizing an ink ejection operation of the head unit3with the operation of the robot2. The controller5according to the present embodiment also has a function of controlling a drive of the maintenance unit4, and the function may be realized by another apparatus such as the computer7.

The controller5has a storage circuit5aand a processing circuit5b.

The storage circuit5astores various programs to be executed by the processing circuit5band various types of data to be processed by the processing circuit5b. The storage circuit5aincludes, for example, one or both semiconductor memories of 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). A part or all of the storage circuit5amay be included in the processing circuit5b.

Route information Da is stored in the storage circuit5a. The route information Da is information indicating a route in which the head unit3is to be moved and a posture of the head unit3in the route. Here, as the information indicating the route and the posture, the route information Da includes information indicating a movement route and a posture of the head unit3when printing on the work W, and information indicating a movement route and a posture between a position of the head unit3during the printing and a position during maintenance by the maintenance unit4. The route information Da is determined based on, for example, a shape of the work W, and is expressed by using coordinate values of the base coordinate system or the world coordinate system. The shape of the work W is determined by, for example, computer-aided design (CAD) data illustrating a three-dimensional shape of the work W. The above route information Da is input from the computer7to the storage circuit5a.

The processing circuit5bcontrols an operation of the arm drive mechanism2aof the robot2based on the route information Da, and generates the signal D3. The processing circuit5bincludes, for example, one or more processors such as a central processing unit (CPU). The processing circuit5bmay include a programmable logic device such as a field-programmable gate array (FPGA), instead of the CPU or in addition to the CPU.

Here, the arm drive mechanism2ais an aggregation of the drive mechanisms of the joint portions230_1to230_6described above, and includes a motor for driving the joint portion of the robot2and an encoder that measures a rotation angle of the joint portion of the robot2, for each joint portion.

The processing circuit5bperforms inverse kinematics calculation, which is a calculation for converting the route information Da into a movement amount such as a rotation angle and a rotation speed of each joint of the robot2. The processing circuit5boutputs a control signal Sk1based on an output D1from each encoder of the arm drive mechanism2aso that the movement amount such as the actual rotation angle and rotation speed of each of the joints becomes the above-described calculation result based on the route information Da. The control signal Sk1controls a drive of the motor of the arm drive mechanism2a. Here, the control signal Sk1is corrected by the processing circuit5bbased on an output from the distance sensor3d, as needed.

Further, the processing circuit5bgenerates the signal D3, based on the output D1from at least one of a plurality of encoders of the arm drive mechanism2a. For example, the processing circuit5bgenerates a trigger signal including a pulse at a timing at which the output D1from one of the plurality of encoders becomes a predetermined value as the signal D3.

The control module6is a circuit that controls the ink ejection operation of the head unit3, based on the signal D3output from the controller5and print data from the computer7. The control module6includes a timing signal generation circuit6a, a power supply circuit6b, a control circuit6c, and a drive signal generation circuit6d.

The timing signal generation circuit6agenerates a timing signal PTS based on the signal D3. The timing signal generation circuit6ais configured with, for example, a timer that starts generation of the timing signal PTS by using detection of the signal D3as a trigger.

The power supply circuit6breceives power from a commercial power source (not illustrated) to generate various predetermined potentials. The various generated potentials are appropriately supplied to each portion of the control module6and the head unit3. For example, the power supply circuit6bgenerates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the head unit3. Further, the power supply potential VHV is supplied to the drive signal generation circuit6d.

The control circuit6cgenerates 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. Among these signals, the waveform designation signal dCom is input to the drive signal generation circuit6d, and the other signals are input to the switch circuit3eof the head unit3.

The control signal SI is a digital signal for designating an operation state of a drive element included in the head3aof the head unit3. Specifically, the control signal SI designates whether or not to supply a drive signal Com, which will be described below, to the drive element. With this designation, for example, whether or not to eject inks from a nozzle corresponding to the drive element is designated, and the amount of ink ejected from the nozzle is designated. The waveform designation signal dCom is a digital signal for defining a waveform of the drive signal Com. The latch signal LAT and the change signal CNG are used in combination with the control signal SI, and by defining a drive timing of the drive element, an ejection timing of the ink from the nozzle is defined. The clock signal CLK is a reference clock signal synchronized with the timing signal PTS.

The above control circuit6cincludes, for example, one or more processors such as a central processing unit (CPU). The control circuit6cmay include a programmable logic device such as a field-programmable gate array (FPGA), instead of the CPU or in addition to the CPU.

The drive signal generation circuit6dis a circuit that generates the drive signal Com for driving each drive element included in the head3aof the head unit3. Specifically, the drive signal generation circuit6dincludes, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generation circuit6d, the DA conversion circuit converts the waveform designation signal dCom from the control circuit6cfrom a digital signal to an analog signal, and the amplifier circuit uses the power supply potential VHV from the power supply circuit6bto amplify the analog signal and generate the drive signal Com. Here, among waveforms included in the drive signal Com, a signal of a waveform actually supplied to the drive element is a drive pulse PD. The drive pulse PD is supplied to the drive element from the drive signal generation circuit6dvia the switch circuit3eof the head unit3.

Here, the switch circuit3eis a circuit that switches whether or not to supply at least a part of the waveform included in the drive signal Com as the drive pulse PD, based on the control signal SI.

The computer7has a function of supplying information such as the route information Da to the controller5, and a function of supplying information such as the print data to the control module6. The computer7is, for example, a desktop computer or a notebook computer in which a program that realizes these functions is installed.

1-3. Head Unit Configuration

FIG.3is a perspective view illustrating a schematic configuration of the head unit3including the head3a. In the following description, for convenience, an a-axis, a b-axis, and a c-axis that intersect with each other will be appropriately used. Further, in the following description, one direction along the a-axis is an a1 direction, and a direction opposite to the a1 direction is an a2 direction. In the same manner, directions opposite to each other along the b-axis are a b1 direction and a b2 direction. Further, directions opposite to each other along the c-axis are a c1 direction and a c2 direction.

Here, the a-axis, the b-axis, and the c-axis correspond to the coordinate axes of a tool coordinate system set in the head unit3, and relative positions and relationships of postures with the above-described world coordinate system or robot coordinate system are changed by the operation of the above-described robot2. In the example illustrated inFIG.3, the c-axis is an axis parallel with the above-described rotation axis O6. The a-axis, the b-axis, and the c-axis are typically orthogonal to each other without being limited thereto, and may intersect at an angle within a range of 80° or more and 100° or less, for example. The tool coordinate system and the base coordinate system or the robot coordinate system are associated with each other by calibration. Further, the tool coordinate system is set so that, for example, a center of the nozzle surface F, which will be described below, serves as a reference (tool center point).

As described above, the head unit3includes the head3a, the pressure regulating valve3b, the curing light source3c, and the distance sensor3d. The head3a, the pressure regulating valve3b, the curing light source3c, and the distance sensor3dare supported by a support body3fillustrated by an alternate long and short dash line inFIG.3. In the example illustrated inFIG.3, the number of each of the head3aand the pressure regulating valve3bincluded in the head unit3is one without being limited to the example illustrated inFIG.3, and the number may be equal to or more than 2. Further, an installation position of the pressure regulating valve3bis not limited to the arm226, and may be, for example, another arm or the like, or may be a fixed position with respect to the base portion210.

The support body3fis made of, for example, a metal material or the like, and is a substantially rigid body. InFIG.3, the support body3fhas a planar box shape, and a shape of the support body3fis not particularly limited and is freely determined.

The above support body3fis attached to the above-described arm226. Therefore, the head3a, the pressure regulating valve3b, the curing light source3c, and the distance sensor3dare collectively supported by the arm226with the support body3f. Therefore, a relative position of each of the head3a, the pressure regulating valve3b, the curing light source3c, and the distance sensor3dwith respect to the arm226is fixed. In the example illustrated inFIG.3, the pressure regulating valve3bis disposed at a position from the head3ain the c1 direction. The curing light source3cis disposed at a position from the head3ain the a2 direction. The distance sensor3dis disposed at a position from the head3ain the a1 direction.

The head3ahas the nozzle surface F and a plurality of nozzles N that are opened on the nozzle surface F. In the example illustrated inFIG.3, a normal direction of the nozzle surface F is the c2 direction, and the plurality of nozzles N are divided into nozzle rows La and nozzle rows Lb which are arranged at intervals along the a-axis. Each of the nozzle row La and the nozzle row Lb is a set of the plurality of nozzles N linearly arranged in a direction along the b-axis. Here, the element related to each nozzle N of the nozzle row La and the element related to each nozzle N of the nozzle row Lb in the head3aare configured to be substantially symmetrical with each other in a direction along the a-axis. Further, a nozzle row direction DN, which will be described below, is parallel with the b-axis.

The nozzle surface F in the present embodiment has a concept including both a surface formed by a nozzle plate and a surface formed by a fixing plate or a cover head. The nozzle plate is a member in which the nozzle N is opened in a plate-shaped member made of silicon (Si), metal, or the like, and the fixing plate and the cover head are members provided around the nozzle plate for the purpose of fixing or protecting the nozzle plate. The fixing plate and the cover head may not be provided depending on the configuration of the head3a, and the nozzle surface F illustrated inFIG.3is formed only by the nozzle plate.

Meanwhile, positions of the plurality of nozzles N in the nozzle row La and the plurality of nozzles N in the nozzle row Lb in the direction along the b-axis may be the same or different from each other. Further, the element related to each nozzle N of one of the nozzle row La and the nozzle row Lb may be omitted. In the following, a configuration in which the positions of the plurality of nozzles N in the nozzle row La and the plurality of nozzles N in the nozzle row Lb in the direction along the b-axis coincide with each other is exemplified.

Although not illustrated, the head3ahas a piezoelectric element which is a drive element and a cavity for accommodating inks, for each nozzle N. Here, the piezoelectric element ejects an ink from a nozzle corresponding to the cavity by changing a pressure of the cavity corresponding to the piezoelectric element. Such a head3acan be obtained, for example, by bonding a plurality of substrates such as a silicon substrate appropriately processed by etching or the like with an adhesive or the like. As the drive element for ejecting the ink from the nozzle, a heater that heats the ink in the cavity may be used instead of the piezoelectric element.

As described above, the ink is supplied to the head3afrom an ink tank (not illustrated) via the supply pipe10a. Here, the pressure regulating valve3bis interposed between the supply pipe10aand the head3a.

The pressure regulating valve3bis a valve mechanism that is opened and closed according to a pressure of the ink in the head3a. By this opening and closing, the pressure of the ink in the head3ais maintained at a negative pressure within a predetermined range even when a positional relationship between the head3aand the ink tank (not illustrated) described above changes. Therefore, a meniscus of the ink formed at the nozzle N of the head3ais stabilized. As a result, it is possible to prevent air bubbles from entering the nozzle N, and the ink from overflowing from the nozzle N. Further, the ink from the pressure regulating valve3bis appropriately distributed to a plurality of locations of the head3avia a branch flow path (not illustrated). Here, the ink from the ink tank (not illustrated) is transferred into the supply pipe10aat a predetermined pressure by a pump or the like.

The curing light source3cemits energy such as light, heat, electron beam, or radiation for curing or solidifying the ink on the work W. For example, when the ink has ultraviolet curability, the curing light source3cis configured with a light emitting element such as a light emitting diode (LED) that emits ultraviolet rays. Further, the curing light source3cmay appropriately have an optical component such as a lens for adjusting an emission direction or an emission range of energy.

The curing light source3cmay not completely cure or completely solidify the ink on the work W. In this case, for example, the ink after the energy irradiation from the curing light source3cmay be completely cured or completely solidified by the energy from the curing light source separately installed on the installation surface of the base portion210of the robot2. Further, the curing light source3cmay be provided as needed, or may be omitted.

The distance sensor3dis an optical displacement sensor that measures a distance between the head3aand the work W. The distance sensor3daccording to the present embodiment outputs a signal according to the distance between the head3aand the work W in a direction along the c-axis. The distance sensor3dmay be provided as needed or may be omitted.

1-4. Maintenance Unit Configuration

FIG.4is a perspective view illustrating a schematic configuration of the maintenance unit4including the cap portion4b. As described above, the maintenance unit4illustrated inFIG.4includes the case4a, the cap portion4b, the support table4c, the suction mechanism4d, and the wiper portion4e.

The case4ais a box-shaped structure that supports the cap portion4b, the support table4c, the suction mechanism4d, and the wiper portion4e. The shape of the case4ais not limited to the example illustrated inFIG.4, and is freely determined.

The cap portion4bis a structure having a cap4b1that covers the nozzle surface F of the head3a, a guide portion4b2, and a biasing mechanism. In the example illustrated inFIG.4, the cap portion4bhas a longitudinal shape. The cap4b1is an elastic lid made of a rubber material, an elastomer material, or the like, and covers the nozzle surface F of the head3ato prevent inks in the vicinity of the nozzle N of the head3afrom drying. The cap4b1is provided with an outer frame portion that abuts on the nozzle surface F of the head3a, a bottom surface that is recessed with respect to the outer frame portion in the Z2 direction, and a hole that penetrates the cap4b1. In a capping operation of covering the nozzle surface F of the head3awith the cap portion4b, which will be described below, the outer frame portion abuts on the nozzle surface F of the head3aso as to surround the nozzle N provided on the nozzle surface F in the horizontal state. At this time, the bottom surface faces the nozzle surface F. The hole has one end open that is opened to the bottom surface of the recess portion and the other end open that is coupled to the suction mechanism4d.

The biasing mechanism is a mechanism that supports the cap4b1and is biased in the Z1 direction, and is configured with an elastic body such as a spring or rubber. The guide portion4b2is a member that regulates movement of the cap4b1in a direction different from the Z direction. When the nozzle surface F of the head3aand the above-described outer frame portion come into contact with each other, the elastic body of the biasing mechanism is elastically deformed so as to contract in the Z direction. The biasing mechanism may be a mechanism such as a gas stay.

The above cap portion4bis supported by the support table4c. The support table4cis configured with a top surface portion4c1to which the cap portion4bis fixed, and a plurality of leg portions4c2that support the top surface portion4c1. The top surface portion4c1is a plate-shaped member made of a metal material or the like, and the cap portion4band the wiper portion4eare fixed to the top surface portion4c1by screwing or the like.

The suction mechanism4dis a mechanism for reducing a pressure in a space formed between the cap portion4band the nozzle surface F. Due to the reduced pressure, an ink is sucked from the nozzle N of the head3ain a state in which the cap portion4bcovers the nozzle surface F, so that the ink in the nozzle N is refreshed. The suction mechanism4dhas a decompression tank and a decompression pump4d2(not illustrated). The decompression tank is, for example, a metal chamber having an internal space for decompression, and is disposed in the case4adescribed above. The decompression tank communicates with the hole of the cap portion4bdescribed above, and also communicates with the decompression pump. The decompression pump is a mechanism for decompressing the inside of the decompression tank by discharging air from the decompression tank. Valves and the like for pressure adjustment or opening and closing are respectively provided between the decompression tank and the cap portion4b, and between the decompression tank and the decompression pump.

The wiper portion4eis a structure that is disposed at a position adjacent to the cap portion4b, and has a wiper4e1that wipes the nozzle surface F. In the example illustrated inFIG.4, the wiper portion4ehas a longitudinal shape, and is disposed to be parallel with the cap portion4b. The wiper4e1is an elastic blade-shaped member made of a rubber material, an elastomer material, or the like, and cleans the nozzle surface F by wiping the nozzle surface F of the head3a. The wiper4e1is fixed to the top surface portion4c1of the support table4cvia the support body4e2by screwing or the like.

1-5. Operation of Three-dimensional Object Printing Apparatus

FIG.5is a flowchart illustrating an operation of the three-dimensional object printing apparatus1according to the embodiment. First, as illustrated inFIG.5, the three-dimensional object printing apparatus1determines whether or not there is a printing instruction, in step S1. For example, for this determination, the processing circuit5bdetermines whether or not the computer7instructs printing execution.

When the printing instruction is given, the three-dimensional object printing apparatus1performs a first movement operation in step S2. This first movement operation is an operation of moving the head3ato an execution start position of the printing operation, which will be described below, and is performed by the processing circuit5bcontrolling the drive of the robot2based on the route information Da.

After step S2, the three-dimensional object printing apparatus1performs the printing operation in step S3. This printing operation is an operation of printing on the work W with inks from the head3a, and is performed by the processing circuit5bcontrolling the drive of the robot2based on the route information Da, and the control module6controlling the drive of the head3a.

After step S3, or when there is no printing instruction, the three-dimensional object printing apparatus1determines whether or not there is a cap instruction, in step S4. For example, for this determination, the processing circuit5bdetermines whether or not there is the cap instruction from the computer7. When the printing instruction and the cap instruction are not given from the computer7for a predetermined time or more, the processing circuit5bmay determine that the cap instruction is given.

When there is no cap instruction, the three-dimensional object printing apparatus1returns to step S1described above. On the other hand, when there is the cap instruction, the three-dimensional object printing apparatus1performs a second movement operation in step S5. This second movement operation is an operation of moving the head3ato an execution start position of a capping operation, which will be described below, and is performed by the processing circuit5bcontrolling the drive of the robot2based on the route information Da.

After step S5, the three-dimensional object printing apparatus1performs the capping operation in step S6. This capping operation is, for example, an operation in which the nozzle surface F of the head3aand the cap portion4bcome into contact with each other to cover the nozzle surface F with the cap portion, and is performed by the processing circuit5bcontrolling the drive of the robot2based on the route information Da. The capping operation may include an operation in which the nozzle surface F and the cap portion4bdo not strictly contact each other. For example, this case corresponds to a case where the nozzle surface F and the cap portion4bare separated by several millimeters, or a case where an ink or the like is interposed between the nozzle surface F and the cap portion4b.

After step S6, the three-dimensional object printing apparatus1determines whether or not there is an end instruction, in step S7. For example, for this determination, the processing circuit5bdetermines whether or not there is an end instruction from the computer7.

When there is no end instruction, the three-dimensional object printing apparatus1returns to step S1described above, and on the other hand, when there is the end instruction, the three-dimensional object printing apparatus1ends the operation.

FIG.6is a side view of the robot2during execution of a printing operation in step S3.FIG.6illustrates a case where printing is performed on the surface WF of the work W disposed so that a long axis AX of the work W having a long spherical shape is parallel with the X-axis. Here, the work W is placed at a position from the robot2in the X2 direction. At a posture of the head3aillustrated by the solid line inFIG.6, the a-axis and the X-axis are parallel, the b-axis and the Y-axis are parallel, and the c-axis and the Z-axis are parallel.

In the printing operation, as illustrated inFIG.6, the robot2moves the head3aalong a movement route RU. The movement route RU is a route from a position PS to a position PE along the surface WF. The movement route RU has a linear shape extending along the X-axis when viewed in the Z2 direction.

In the printing operation, the robot2operates the three joint portions230among the six joint portions230. In the example illustrated inFIG.6, the robot2sets a rotation axis of each of the joint portion230_2, the joint portion230_3, and the joint portion230_5to a state of being parallel with the Y-axis during the execution of the printing operation, and operates these joint portions. In this manner, the head3acan be stably moved along the movement route RU by the operation of the three joint portions230.

Here, it is preferable that the robot2controls the posture of the head3aaccording to a curved surface of the surface WF so that a landing direction of the ink from the head3aon the surface WF is constant. Therefore, it is preferable that a yaw angle and a roll angle of the head3ain the movement route RU are constant. On the other hand, a pitch angle of the head3ain the movement route RU is preferably changed. That is, it is preferable that the pitch angles of the heads3aat the first position P1and the second position P2, which are any two points in the movement route RU, are different from each other. In the present embodiment, the movement route RU is set so that an ejection direction vector of the ink droplets ejected by the head3aalways includes a vertically downward component. In other words, a vector in the c2 direction includes a component in the Z2 direction. According to the setting of the movement route RU, the head3adoes not eject the ink droplets in a direction against gravity, so that the ink droplets fly stably.

The printing is performed on the work W by the above printing operation.

Here, the yaw angle, the roll angle, and the pitch angle of the head3awill be described. The yaw angle, the roll angle, and the pitch angle of the head3aare expressed as the amount of rotation around the c-axis, the a-axis, and the b-axis based on a reference posture of the head3aset in any manner. At the reference posture of the head3a, relationships between the a-axis, b-axis, and c-axis and the X-axis, Y-axis, and Z-axis are uniquely fixed.

The yaw angle of the head3aat a first posture of the head3ais expressed as the amount of rotation around the c-axis required for a posture change from the reference posture to the first posture. The amount of rotation around the c-axis is an absolute value of an angle formed by the a-axis at the reference posture and the a-axis at the first posture when viewed in a direction along the c-axis at the reference posture. Alternatively, the amount of rotation around the c-axis is an absolute value of an angle formed by the b-axis at the reference posture and the b-axis at the first posture when viewed in the direction along the c-axis at the reference posture.

In the same manner, the roll angle of the head3aat the first posture of the head3ais expressed as the amount of rotation around the a-axis required for the posture change from the reference posture to the first posture. The amount of rotation around the a-axis is an absolute value of an angle formed by the b-axis at the reference posture and the b-axis at the first posture when viewed in a direction along the a-axis at the reference posture. Alternatively, the amount of rotation around the a-axis is an absolute value of an angle formed by the c-axis at the reference posture and the c-axis at the first posture when viewed in the direction along the a-axis at the reference posture.

In the same manner, the pitch angle of the head3aat the first posture of the head3ais expressed as the amount of rotation around the b-axis required for the posture change from the reference posture to the first posture. The amount of rotation around the b-axis is an absolute value of an angle formed by the a-axis at the reference posture and the a-axis at the first posture when viewed in a direction along the b-axis at the reference posture. Alternatively, the amount of rotation around the b-axis is an absolute value of an angle formed by the c-axis at the reference posture and the c-axis at the first posture when viewed in the direction along the b-axis at the reference posture.

The yaw angle, the roll angle, and the pitch angle of the head3awill be further described with reference toFIG.6. For example, the reference posture of the head3ais set as a posture at which the a-axis and the X-axis are parallel, the b-axis and the Y-axis are parallel, and the c-axis and the Z-axis are parallel. At this time, all the yaw angle, the roll angle, and the pitch angle of the head3aillustrated by a solid line inFIG.6are 0°. On the other hand, the pitch angle of the head3aillustrated by a broken line inFIG.6is approximately 45°, and the yaw angle and the roll angle are 0°. That is, the head3aillustrated by the solid line and the head3aillustrated by the broken line inFIG.6have different pitch angles.

FIG.7is a plan view of the three-dimensional object printing apparatus1during execution of the printing operation. In a posture of the head3aillustrated by the solid line inFIG.7, the a-axis and the X-axis are parallel, the b-axis and the Y-axis are parallel, and the c-axis and the Z-axis are parallel. During the execution of the printing operation, as illustrated inFIG.7, in the plan view of the base portion210, the nozzle row direction DN which is an arrangement direction of the plurality of nozzles N of the head3ais orthogonal to a scanning direction DS of the head3ain the above-described movement route RU. Here, when the virtual line segment coupling the head3aand the base portion210during the execution of the printing operation in the plan view of the base portion210is defined as a first line segment L1, an angle θ1formed by the nozzle row direction DN and a first line segment L1is 90°. Meanwhile, the angle θ1is not limited to 90°, and may be, for example, in a range equal to or more than 70° and equal to or less than 110°. The first line segment L1can be more strictly defined as a virtual line segment coupling a center point of the nozzle surface F and the rotation axis O1during execution of a printing operation in the plan view of the base portion210.

After executing the printing operation, the head3amoves onto the cap portion4bby the second movement operation described above, as illustrated by an alternate long and short dash line inFIG.7. At the posture of the head3aillustrated by the alternate long and short dash line inFIG.7, the c-axis and the Z-axis are parallel, and an angle formed by the a-axis and the X-axis is 45° and an angle formed by the b-axis and the Y-axis is 45°.

Here, the reference posture of the head3ais set as a posture at which the a-axis and the X-axis are parallel, the b-axis and the Y-axis are parallel, and the c-axis and the Z-axis are parallel. At this time, the yaw angle, the roll angle, and the pitch angle of the head3aillustrated by a solid line inFIG.7are all 0°. On the other hand, the yaw angle of the head3aillustrated by the alternate long and short dash line inFIG.7is 45°, and the roll angle and pitch angle are 0°. That is, the yaw angle of the head3aillustrated by the solid line and the head3aillustrated by the alternate long and short dash line inFIG.7is different from each other. In other words, the nozzle row direction DN of the nozzles N when viewed from any coordinate in the world coordinate system in the Z1 direction differs during the execution of the printing operation and after the execution of the movement operation or during the execution of the capping operation. More specifically, an angle formed by the nozzle row direction DN during the printing operation and the nozzle row direction DN after the movement operation or the capping operation is executed is 45°.

The second movement operation is mainly performed by operating the joint portion230_1. Here, the joint portion230_2, the joint portion230_3, and the joint portion230_5used in the above-described printing operation may be operated, and it is preferable not to operate the joint portion230_4and the joint portion230_6. In this case, when the printing operation is performed again, reproducibility of the operation of the robot2in the printing operation can be improved.

FIG.8is a plan view of the three-dimensional object printing apparatus1during execution of a capping operation. As illustrated inFIG.8, when a virtual line segment coupling the head3aand the base portion210during the execution of the capping operation in the plan view of the base portion210is defined as a second line segment L2, an angle θ2formed by the nozzle row direction DN and the second line segment L2is 90°. Meanwhile, the angle θ2is not limited to 90°, and may be, for example, in a range equal to or more than 70° and equal to or less than 110°. The second line segment L2can be more strictly defined as a virtual line segment coupling the center point of the nozzle surface F during execution of the capping operation and the rotation axis O1in the plan view of the base portion210.

Here, when an angle formed by the first line segment L1and the second line segment L2in the plan view of the base portion210is θ3, the angles θ1, θ2, and θ3 satisfy a relationship of |θ1−θ2|<θ3. Further, from the viewpoint of reducing twisting of the piping portion10and the wiring portion11, |θ1−θ2| is preferably as small as possible.

After executing the capping operation, the head3amoves to the above-described printing position by the above-described first movement operation as illustrated by an alternate long and short dash line inFIG.8. The first movement operation is mainly performed by operating the joint portion230_1, in the same manner as the second movement operation.

As described above, the three-dimensional object printing apparatus1has the head3a, the robot2, and the cap portion4b. The head3ahas the nozzle surface F at which the plurality of nozzles N for ejecting an ink, which is an example of a “liquid” are provided. The robot2includes the base portion210, and the arm portion220that supports the head3a, and the joint portions230_2to230_6, which are examples of a “plurality of rotating portions”, are provided from the base portion210to the arm portion220to change a position of the head3awith respect to the base portion210by rotation of the joint portions230_2to230_6. The cap portion4bcovers the nozzle surface F.

As described above, the three-dimensional object printing apparatus1executes the capping operation in step S6and the printing operation in step S3as described above. In the capping operation in step S6, the robot2locates the head3aat a position at which the nozzle surface F is covered with the cap portion4b. In the printing operation in step S3, the head3aejects inks to the work W while the robot2changes the position of the head3awith respect to the work W at a position different from the position during the execution of the capping operation in step S6. Here, the yaw angle of the head3aduring the execution of the capping operation in step S6and the yaw angle of the head3aduring the execution of the printing operation in step S3are different from each other.

In the above three-dimensional object printing apparatus1, since the nozzle surface F is covered with the cap portion4bduring the execution of the capping operation in step S6, it is possible to reduce thickening or solidification of the ink on the nozzle surface F even when the printing operation in step S3is not executed for a long period of time. As a result, clogging of each nozzle N due to the ink can be reduced. Further, by making the yaw angles of the head3adifferent from each other between the execution of the capping operation in step S6and the execution of the printing operation in step S3, the amount of rotation of the joint portion230_6closest to the head3aamong a plurality of joint portions230of the robot2can be reduced when the head3ais moved between the execution positions of these operations. As a result, damage due to twisting of the wiring or the like related to the head3acan be reduced.

Here, the three-dimensional object printing apparatus1further includes the supply pipe10afor supplying inks to the head3a, and the drive wiring11afor supplying an electrical signal for driving the head3ato the head3a. Each of the supply pipe10aand the drive wiring11ais provided outside the arm portion220. When the printing operation in step S3and the capping operation in step S6are repeatedly executed while maintaining the yaw angle of the head3aconstant, each of the supply pipe10aand the drive wiring11amay be damaged by twisting. Therefore, when such a supply pipe10aor a drive wiring11ais used, the above-described effect by making the yaw angle of the head3adifferent from each other between the printing operation in step S3and the capping operation in step S6becomes remarkable.

Further, from the viewpoint of reducing damage due to twisting of the wiring, as described above, in the plan view of the base portion210, when an angle formed by the first line segment L1and the nozzle row direction DN during the execution of the printing operation in step S3is defined as θ1, an angle formed by the second line segment L2and the nozzle row direction DN during the execution of the capping operation in step S6is defined as θ2, and an angle formed by the first line segment L1and the second line segment L2is defined as θ3, it is preferable to satisfy a relationship of |θ1−θ2|<θ3. Here, the nozzle row direction DN is an arrangement direction of the plurality of nozzles N, in the plan view of the base portion210. The first line segment L1is a virtual line segment coupling the head3aand the base portion210during execution of the printing operation in step S3, in the plan view of the base portion210. The second line segment L2is a virtual line segment coupling the head3aand the base portion210during execution of the capping operation in step S6, in the plan view of the base portion210.

When the angles θ1, θ2, and θ3 satisfy the above-described relationship, as compared with a case where the yaw angles of the head3aare equal to each other during the execution of the capping operation in step S6and the execution of the printing operation in step S3, the amount of rotation of the joint portion230_6can be reduced when the head3ais moved between execution positions of the capping operation in step S6and the printing operation in step S3.

In the three-dimensional object printing apparatus1, when the two positions through which the head3apasses during the execution of the printing operation in step S3are set as the first position P1and the second position P2, it is preferable that the pitch angle at the first position P1and the pitch angle at the second position P2of the head3aare different from each other. In this case, even when the printing surface of the work W is a curved surface or the like, the posture of the head3awith respect to the target portion of the printing surface can be kept constant. Therefore, there is an advantage that the image quality can be easily improved regardless of the shape of the printing surface of the work W.

Here, the printing operation in step S3preferably includes an operation of changing the position of the head3awith respect to the work W while maintaining the yaw angle and the roll angle of the head3ato be constant. In this case, it is possible to reduce unevenness of a density of the ink ejected from the head3ato the work W during the execution of the printing operation in step S3. As a result, there is an advantage that the image quality can be easily improved.

Further, the three-dimensional object printing apparatus1further executes the first movement operation in step S2, as described above. In the first movement operation in step S2, the robot2moves the head3awithin a period from an execution end of the capping operation in step S6to an execution start of the printing operation in step S3. Therefore, with the first movement operation in step S2, the capping operation in step S6can be shifted to the printing operation in step S3.

In addition, the amount of rotation of the joint portion230_6over an execution period of the first movement operation in step S2is smaller than the amount of rotation of the joint portion230_1over the execution period of the first movement operation in step S2. Here, the joint portion230_1is an example of a “first joint portion”, and is the joint portion230closest to the base portion210among the plurality of joint portions230. The joint portion230_6is an example of a “second joint portion”, and is the joint portion230farthest from the base portion210among the plurality of joint portions230. When the joint portion230_6rotates, the wiring or the like such as the supply pipe10aand the drive wiring11arelated to the head3ais more likely to be twisted than when the joint portion230_1rotates. Therefore, by making the amount of rotation of the joint portion230_6over the execution period of the first movement operation in step S2smaller than that of the joint portion230_1over the execution period of the first movement operation in step S2, it is possible to reduce twisting of the wiring or the like in the first movement operation in step S2.

Further, the three-dimensional object printing apparatus1further executes the second movement operation in step S5, as described above. In the second movement operation in step S5, the robot2moves the head3awithin a period from an execution end of the printing operation in step S3to an execution start of the capping operation in step S6. Therefore, with the second movement operation in step S5, the printing operation in step S3is shifted to the capping operation in step S6.

In addition, the amount of rotation of the joint portion230_6over an execution period of the second movement operation in step S5is smaller than the amount of rotation of the joint portion230_1over the execution period of the second movement operation in step S5. Therefore, it is possible to reduce twisting of the wiring or the like in the second movement operation in step S5, in the same manner as the first movement operation in step S2described above.

A change in yaw angle of the head3aover the execution period of the first movement operation in step S2or the second movement operation in step S5is equal to or more than preferably 45°, and more preferably equal to or more than 90°. As the change in yaw angle increases, a position of the head unit3during the execution of the capping operation in step S6and a position of the work W during the execution of the printing operation in step S3are separated from each other. Therefore, when performing an operation such as placing or removing the work W, or adjusting the position of the work W during the execution of the capping operation, it is possible to prevent the head unit3from interfering with this operation.

Further, as described above, at the execution end of the capping operation in step S6, the head3ais separated from the cap portion4balong a normal direction of the nozzle surface F. Therefore, at the execution end of the capping operation in step S6, the nozzle surface F is less likely to move while being in contact with the cap portion4b, so that dirt on the nozzle surface F due to the ink adhering to the cap portion4bis prevented.

From the same viewpoint, as described above, at the execution start of the capping operation in step S6, the head3aapproaches the cap portion4balong the normal direction of the nozzle surface F. Therefore, at the execution start of the capping operation in step S6, the nozzle surface F is less likely to move while being in contact with the cap portion4b, so that dirt on the nozzle surface F due to the ink adhering to the cap portion4bis prevented.

Further, as described above, it is preferable that the nozzle surface F during the execution of the capping operation in step S6is horizontal. In this case, since a meniscus of the ink in each nozzle N is stabilized during the execution of the capping operation in step S6, the ink in the vicinity of each nozzle N is unlikely to thicken, as compared with a case where the nozzle surface F is inclined to the horizontal plane.

As described above, the three-dimensional object printing apparatus1according to the present embodiment further includes the biasing mechanism. The biasing mechanism biases the cap portion4btoward the nozzle surface F during the execution of the capping operation in step S6. Therefore, the cap portion4band the nozzle surface F during the execution of the capping operation in step S6can be stably brought into close contact with each other.

Further, the three-dimensional object printing apparatus1according to the present embodiment further has the suction mechanism4d, as described above. The suction mechanism4ddepressurizes the space formed between the cap portion4band the nozzle surface F during the execution of the capping operation in step S6. Therefore, thickened or solidified inks in the vicinity of the nozzle N can be removed by the action of the suction mechanism4d.

Further, the three-dimensional object printing apparatus1according to the present embodiment further includes the wiper portion4e, as described above. The wiper portion4eis disposed at a position adjacent to the cap portion4b, and wipes the nozzle surface F. Therefore, inks adhering to the nozzle surface F can be removed by the action of the wiper portion4e. In particular, since the wiper portion4eis disposed at a position adjacent to the cap portion4b, it is possible to effectively perform maintenance using both the cap portion4band the wiper portion4e.

2. Modification Example

Each form in the above examples can be variously modified. Specific modification aspects that can be applied to each of the above-described forms are illustrated below. The two or more aspects freely selected from the following examples can be appropriately merged within a range not mutually contradictory.

In the above-described embodiment, a configuration using a 6-axis vertical multi-axis robot as a robot is exemplified, and the configuration is not limited to this configuration. The robot may be, for example, a vertical multi-axis robot other than the 6-axis robot, or a horizontal multi-axis robot. Further, the arm portion of the robot may have a telescopic mechanism or the like, in addition to the rotating portion configured with the rotating mechanism. Meanwhile, from the viewpoint of the balance between the print quality in the printing operation and the degree of freedom of the robot operation in the non-printing operation, the robot is preferably a multi-axis robot having 6 axes or more.

In the above-described embodiment, a configuration using screwing or the like as a method of fixing the head to the robot is exemplified, and the configuration is not limited to this configuration. For example, the head may be fixed to the robot by gripping the head with a gripping mechanism such as a hand mounted as an end effector of the robot.

In the above-described embodiment, a configuration in which printing is performed by using one type of ink is exemplified. Meanwhile, the configuration is not limited to this configuration, and the present disclosure can be applied to a configuration in which printing is performed by using two or more types of ink.

The application of the three-dimensional object printing apparatus of the present disclosure is not limited to printing. For example, a three-dimensional object printing apparatus that ejects a solution of a coloring material is used as a manufacturing apparatus of forming a color filter of a liquid crystal display apparatus. Further, a three-dimensional object printing apparatus that ejects a solution of a conductive material is used as a manufacturing apparatus of forming wirings or electrodes on a wiring substrate. In addition, the three-dimensional object printing apparatus can also be used as a jet dispenser of applying a liquid such as an adhesive to a work.