Printing method and three dimensional object printing apparatus

Abstract

To improve printing quality.SOLUTION: The printing method includes a printing region determination step of determining, based on a shape of a three-dimensional workpiece, a printing region of the workpiece to which a liquid is applied from a head, the head including a nozzle that ejects the liquid toward the workpiece, a first movement mechanism that moves the head along a first axis, and a second movement mechanism that moves the head along a second axis intersecting the first axis, a printing trajectory creation step of creating a printing trajectory along which the head is scanned with respect to the printing region, and an orientation determination step of determining an orientation of the workpiece caused by an operation of the robot based on the printing trajectory.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Conventionally, there are known three-dimensional object printing devices that perform inkjet printing on the surface of a three-dimensional workpiece. For example, the device described in Patent Document 1 has multiple heads and a head lifting mechanism that moves the multiple heads up and down. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-035552 Summary of the Invention [Problem to be solved by the invention]

[0004] In the device described in Patent Document 1, the installation posture of the workpiece is determined depending on the shape of the workpiece, etc., so depending on the shape of the workpiece, the head cannot be properly positioned opposite the workpiece, resulting in a decrease in print quality. [Means for solving the problem]

[0005] In order to solve the above problems, one aspect of the printing method disclosed herein is a printing method that prints using a three-dimensional object printing device that includes a robot that supports a three-dimensional workpiece, a head having a nozzle that ejects liquid toward the workpiece, a first movement mechanism that moves the head along a first axis, and a second movement mechanism that moves the head along a second axis that intersects the first axis, and includes a printing area determination process that determines a printing area of ​​the workpiece that will receive liquid from the head based on the shape of the workpiece, a printing trajectory creation process that creates a printing trajectory that scans the head over the printing area, and an attitude determination process that determines the attitude of the workpiece due to the operation of the robot based on the printing trajectory.

[0006] One aspect of a three-dimensional object printing device disclosed herein includes a robot that supports a three-dimensional workpiece, a head having a nozzle that ejects liquid toward the workpiece, a first movement mechanism that moves the head along a first axis, and a second movement mechanism that moves the head along a second axis that intersects with the first axis, and the device creates a first print trajectory and a second print trajectory as print trajectories that cause the head to scan a print area of ​​the workpiece, determines the posture of the workpiece by operation of the robot based on the print trajectories, scans the head along the first print trajectory by operation of the first movement mechanism and the second movement mechanism, and executes a first printing operation that ejects liquid from the head toward a first area of ​​the workpiece, and and performing a second printing operation in which the head is scanned along the second printing trajectory by operation of the second moving mechanism and liquid is ejected from the head toward a second region of the workpiece, the first region and the second region overlap each other at least partially, and in the first printing operation, the robot supports the workpiece in a first posture of the workpiece at a first point on the first printing trajectory, where an angle between a normal to the position of the first region and the nozzle surface of the head is 90 degrees, and in the second printing operation, the robot supports the workpiece in a second posture of the workpiece at a second point on the second printing trajectory, where an angle between a normal to the position of the second region and the nozzle surface of the head is 90 degrees. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing an outline of a three-dimensional object printing device according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the three-dimensional object printing device according to the embodiment. [Figure 3] FIG. 3 is an explanatory diagram of data and programs stored in the computer shown in FIG. 2. [Figure 4] FIG. 2 is a perspective view showing an outline of a head unit. [Figure 5] 4 is a flowchart illustrating a printing method according to the embodiment. [Figure 6] FIG. 10 is a diagram for explaining the setting of a print area. [Figure 7] FIG. 10 is a diagram for explaining details of a sub-scanning reference line. [Figure 8] FIG. 10 is a diagram for explaining a plurality of reference points. [Figure 9] FIG. 10 is a diagram for explaining a printing trajectory. [Figure 10] FIG. 10 is a diagram for explaining a method for setting a print trajectory. [Figure 11] FIG. 10 is a diagram illustrating a plurality of points on a print trajectory. [Figure 12] FIG. 10 is a diagram for explaining another example of a plurality of points on a print trajectory. [Figure 13] FIG. 10 is a diagram for explaining normal vectors at multiple points on a print trajectory. [Figure 14] 10A and 10B are diagrams for explaining ejection directions at a plurality of points on a printing trajectory. [Figure 15] FIG. 10 is a diagram for explaining a printing trajectory. [Figure 16] FIG. 10 is a diagram for explaining how to determine the posture of a workpiece. [Figure 17] FIG. 10 is an explanatory diagram illustrating a case where the posture of the workpiece is determined based on the center point of a printing area having an asymmetric shape. [Figure 18] FIG. 10 is an explanatory diagram illustrating a case where the posture of the workpiece is determined based on a specific position in a printing area having an asymmetric shape. [Figure 19] 3A and 3B are diagrams for explaining generation of pixel data and print data; [Figure 20] 10 is a flowchart showing the flow of a printing process. [Figure 21] FIG. 2 is an explanatory diagram of a first print trajectory and a second print trajectory. [Figure 22] FIG. 10 is an explanatory diagram of a first printing operation. [Figure 23] FIG. 10 is an explanatory diagram of a first printing operation. [Figure 24] FIG. 10 is an explanatory diagram of a second printing operation. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0009] For convenience, the following description will use the mutually intersecting X-axis, Y-axis, and Z-axis as appropriate. The Z-axis is an example of a "first axis," the X-axis is an example of a "second axis," and the Y-axis is an example of a "third axis." In the following description, one direction along the X-axis is the X1 direction, and the direction opposite the X1 direction is the X2 direction. Similarly, the opposite directions along the Y-axis are the Y1 direction and the Y2 direction. In addition, the opposite directions along the Z-axis are the Z1 direction and the Z2 direction.

[0010] Here, the X-axis, Y-axis, and Z-axis correspond to the coordinate axes of a world coordinate system set in a space in which the moving mechanism 2 and support mechanism 4 (described later) are installed. Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. For convenience, the following describes an example in which the operation of the moving mechanism 2 is controlled using the world coordinate system.

[0011] The Z axis does not have to be a vertical axis. Furthermore, the X axis, Y axis, and Z axis are typically perpendicular to one another, but this is not a limitation and they may not be perpendicular. For example, the X axis, Y axis, and Z axis may intersect each other at an angle between 80° and 100°.

[0012] 1. Embodiment 1-1.Outline of the printing device Fig. 1 is a perspective view showing an outline of a three-dimensional object printing apparatus 1 according to an embodiment. The three-dimensional object printing apparatus 1 is an apparatus that performs printing by inkjet printing on the surface of a three-dimensional workpiece W. For ease of explanation, in Fig. 1, a base 10 and a case 11, which will be described later, are simply indicated by two-dot chain lines.

[0013] The workpiece W has a surface WF that includes an area to be printed. In the example shown in Fig. 1, the workpiece W is approximately hemispherical, and the surface WF is approximately a convex spherical surface. Note that the size, shape, and installation orientation of the workpiece W are not limited to the example shown in Fig. 1 and are arbitrary.

[0014] As shown in Fig. 1, the three-dimensional object printing apparatus 1 includes a base 10, a case 11, a movement mechanism 2, head units 3-1 to 3-6, sensor units 30-1 and 30-2, a support mechanism 4, and a maintenance mechanism 8. Each part of the three-dimensional object printing apparatus 1 will be briefly described below with reference to Fig. 1. Note that, below, each of the head units 3-1 to 3-6 may be referred to as a head unit 3. Each of the sensor units 30-1 and 30-2 may be referred to as a sensor unit 30.

[0015] The base 10 is a platform having a surface 10a that supports the movement mechanism 2. The surface 10a faces the Z1 direction. The movement mechanism 2 is fixed to the base 10 directly by screws or the like, or indirectly via another member.

[0016] In the example shown in FIG. 1, the base 10 is box-shaped, with a surface 10a facing the Z1 direction. An opening 10b is provided in the surface 10a. The opening 10b is used as a passage for the support mechanism 4 to access a position in the Z1 direction from the inside of the base 10 relative to the surface 10a. A placement portion 10c is also provided on the surface 10a. A workpiece W to be used for the next printing or the like is placed on the placement portion 10c so that it is accessible to the robot 4W. Note that the configuration and arrangement of the placement portion 10c are not limited to the example shown in FIG. 1.

[0017] A case 11 enclosing the moving mechanism 2 and other components is disposed at a position in the Z1 direction relative to the base 10. The case 11 is a box-shaped structure that forms a space between itself and the surface 10a to accommodate structures such as the moving mechanism 2 supported by the base 10. The case 11 has, for example, multiple pillars and multiple beams made of metal or the like, and multiple plate members such as a top plate and wall plates made of a transparent material such as acrylic resin. The case 11 also has a viewing section 11a. The viewing section 11a is a window through which a user can view the workpiece W held by the robot 4W in a direction along the Y axis. The case 11 may be provided with a door (not shown) for supplying and removing the workpiece W to and from the support mechanism 4. The door may also serve as the viewing section 11a.

[0018] The configuration of the base 10 is not limited to the example shown in Fig. 1 and is arbitrary. Furthermore, the base 10 and case 11 may be provided as needed or may be omitted. When the base 10 is omitted, the components of the three-dimensional object printing device 1 are installed, for example, on the floor, wall, or ceiling of a building.

[0019] The movement mechanism 2 is a mechanism that changes the relative positions of the head units 3-1 to 3-6 and the sensor units 30-1 and 30-2 with respect to the workpiece W in the direction along the X axis and the direction along the Z axis. As a result, the movement mechanism 2 moves the head 3a (described later) along both the Z axis and the X axis that intersects with the Z axis. The movement mechanism 2 includes an X movement mechanism 2X and Z movement mechanisms 2Z-0 to 2Z-7. The X movement mechanism 2X is an example of a "second movement mechanism." Each of the Z movement mechanisms 2Z-0 to 2Z-7 is an example of a "first movement mechanism." Note that, hereinafter, each of the Z movement mechanisms 2Z-0 to 2Z-7 may be referred to as a Z movement mechanism 2Z.

[0020] The X movement mechanism 2X is a linear motion mechanism that changes the relative positions of the head unit 3 and the sensor unit 30 with respect to the workpiece W along the X axis, which is perpendicular to the Z axis. By using this X movement mechanism 2X, the movement mechanism 2 moves the head 3a (described below) along the X axis. In the example shown in FIG. 1, the X movement mechanism 2X supports the head units 3-1 to 3-6 and the sensor units 30-1 and 30-2 via the Z movement mechanisms 2Z-0 to 2Z-7, and moves the Z movement mechanisms 2Z-0 to 2Z-7 collectively along the X axis. This causes the head units 3-1 to 3-6 and the sensor units 30-1 and 30-2 to move along the X axis with respect to the workpiece W.

[0021] X-movement mechanism 2X has a pair of pillars 2a, a beam 2b, a pair of rails 2c, and a movable body 2d, which are substantially rigid bodies made of metal such as iron, stainless steel, or aluminum alloy.

[0022] Each of the pair of pillars 2a is a member extending in the Z1 direction from the surface 10a of the base 10. In the example shown in FIG. 1, the pair of pillars 2a are aligned in a direction along the X-axis. A beam 2b is attached to the tips of the pair of pillars 2a. The beam 2b is a member supported by the pair of pillars 2a. In the example shown in FIG. 1, the beam 2b extends in a direction along the X-axis and is a plate-like member with its thickness direction along the Z-axis. A pair of rails 2c is disposed on the surface of the beam 2b facing the Z1 direction. Each of the pair of rails 2c is a linear rail that guides the movable body 2d to move relative to the pair of pillars 2a and beams 2b in a direction along the X-axis, and extends in a direction along the X-axis. The movable body 2d is attached to the pair of rails 2c via linear bearings (not shown). The movable body 2d is a member that moves relative to the pair of pillars 2a and beams 2b in the direction along the X-axis. In the example shown in FIG. 1, it is a plate-like member with its thickness direction along the Z-axis. Although not shown, the X-movement mechanism 2X has an actuator having an electric motor such as a servo motor that generates a driving force for the movement, and an encoder such as a linear encoder that detects the amount of movement. Note that the configuration of the X-movement mechanism 2X is not limited to the example shown in FIG. 1.

[0023] Z movement mechanisms 2Z-0 to 2Z-7 are attached to movable body 2d of X movement mechanism 2X via support body 2e. As a result, Z movement mechanisms 2Z-0 to 2Z-7 move in the direction along the X axis as movable body 2d moves. In the example shown in Figure 1, Z movement mechanisms 2Z-0 to 2Z-7 are lined up in this order in the X1 direction.

[0024] Support body 2e may be attached to movable body 2d via a manual or electric linear motion mechanism that moves support body 2e relative to movable body 2d in the direction along the Z axis. In this case, Z movement mechanisms 2Z-0 to 2Z-7 can be moved collectively in the direction along the Z axis. Furthermore, the number of Z movement mechanisms 2Z attached to X movement mechanism 2X is not limited to the example shown in FIG. 1, and may be seven or less or nine or more.

[0025] Each of Z movement mechanisms 2Z-1 to 2Z-6 is a linear motion mechanism that moves head unit 3 relative to workpiece W along the Z axis. Head units 3-1 to 3-6 correspond one-to-one to Z movement mechanisms 2Z-1 to 2Z-6, respectively. A corresponding head unit 3 is attached to each of Z movement mechanisms 2Z-1 to 2Z-6. Therefore, Z movement mechanism 2Z-1 changes the relative position of head unit 3-1 with respect to workpiece W in the direction along the Z axis. Similarly, Z movement mechanisms 2Z-2 to 2Z-6 change the relative positions of head units 3-2 to 3-6 with respect to workpiece W in the direction along the Z axis. In this way, Z movement mechanisms 2Z-1 to 2Z-6 change the relative positions of head units 3-1 to 3-6 with respect to workpiece W in the direction along the Z axis, independently of each other.

[0026] In contrast, each of Z movement mechanisms 2Z-0 and 2Z-7 is a linear motion mechanism that moves sensor unit 30 relative to workpiece W along the Z axis, and operates independently of each of the previously described Z movement mechanisms 2Z-1 to 2Z-6. Sensor unit 30-1 is attached to Z movement mechanism 2Z-0, and Z movement mechanism 2Z-0 moves sensor unit 30-1 in the direction along the Z axis. Sensor unit 30-2 is attached to Z movement mechanism 2Z-7, and Z movement mechanism 2Z-7 moves sensor unit 30-2 in the direction along the Z axis. In this way, each of Z movement mechanisms 2Z-0 and 2Z-7 changes the position of sensor unit 30 relative to workpiece W in the direction along the Z axis, independently of each of head units 3-1 to 3-6.

[0027] The above Z movement mechanisms 2Z-0 to 2Z-7 are configured similarly to one another, except for the fact that they move different objects, as described above. Although not shown, each of Z movement mechanisms 2Z-0 to 2Z-7 has a rail, a movable body, an actuator, and an encoder. The rail is a linear rail fixed to support body 2e and extending in the direction along the Z axis. The movable body is attached to the rail via a linear bearing and moves in the direction along the Z axis. The actuator has an electric motor such as a servo motor that generates a driving force for the movement. The encoder is a linear encoder or the like that detects the amount of movement. Note that the configurations of Z movement mechanisms 2Z-0 to 2Z-7 may be different from one another. However, from the perspective of cost reduction, etc., it is preferable that Z movement mechanisms 2Z-0 to 2Z-7 have the same configuration. Furthermore, Z movement mechanism 2Z-0 may be provided as needed and may be omitted.

[0028] Note that the head unit 3 or the sensor unit 30 may be attached to each of the Z movement mechanisms 2Z-0 to 2Z-7 via an adjustment mechanism for finely adjusting the attitude of the head unit 3 or the sensor unit 30. Furthermore, the number of Z movement mechanisms 2Z to which the head units 3 are attached is not limited to the example shown in FIG. 1 and may be five or less or seven or more. Furthermore, the number of Z movement mechanisms 2Z to which the sensor units 30 are attached is not limited to the example shown in FIG. 1 and may be one or three or more. Furthermore, both the head unit 3 and the sensor unit 30 may be attached to the Z movement mechanism 2Z.

[0029] Each of the head units 3-1 to 3-6 is an assembly having a head 3a. The head 3a is an inkjet head of a piezoelectric drive type or a thermal type, and ejects ink, which is an example of a "liquid," toward the workpiece W in the Z2 direction, which is a direction along the Z axis. In addition to the head 3a, the components of the head unit 3 may include, for example, a heater and a temperature sensor, a light source for hardening or solidifying the ink on the workpiece W, and a pressure adjustment valve for maintaining the pressure of the ink in the head 3a at a negative pressure within a predetermined range.

[0030] The ink ejected from the head 3a is not particularly limited, but in this embodiment, a curable ink using a curable resin such as a heat-curable, photo-curable, radiation-curable, or electron beam-curable type is used. The ink is not limited to ink containing a colorant, and may be, for example, an ink containing conductive particles such as metal particles as dispersoids for forming wiring, or a clear ink, or a treatment liquid for surface treatment of the workpiece W. The types of ink used in the head units 3-1 to 3-6 may be the same or different from each other.

[0031] The sensor unit 30 is an assembly having a sensor 32 that detects the positional relationship with the workpiece W. In the example shown in FIG.

[0032] The sensor 32 has, for example, one or both of a contact sensor that detects contact with the workpiece W and an optical displacement sensor that detects the distance from the workpiece W. The light source 31 emits energy such as light, heat, an electron beam, or radiation to harden or solidify the ink on the workpiece W. The light source 31 is formed of, for example, a light-emitting element such as an LED (Light Emitting Diode) that emits ultraviolet light. Furthermore, one or both of the sensor 32 and the light source 31 may be provided as needed or may be omitted.

[0033] The support mechanism 4 is a mechanism that supports the workpiece W. In the example shown in Fig. 1, the support mechanism 4 has a Y-movement mechanism 4Y and a robot 4W.

[0034] Y-movement mechanism 4Y is a linear motion mechanism that moves robot 4W along the Y-axis. This movement makes it possible to change the relative positions of head units 3-1 to 3-6 and sensor units 30-1 and 30-2 with respect to workpiece W in the direction along the Y-axis. In the example shown in FIG. 1, Y-movement mechanism 4Y is disposed inside base 10.

[0035] The Y-movement mechanism 4Y includes a support 4a, a pair of rails 4b, a movable body 4c, and a stage 4d, which are substantially rigid bodies made of metal such as iron, stainless steel, or aluminum alloy.

[0036] The support 4a is a platform that is fixed to the base 10. In the example shown in FIG. 1, the support 4a extends in the direction along the Y axis and is plate-shaped with its thickness direction along the Z axis. A pair of rails 4b is arranged on the surface of the support 4a facing the Z1 direction. The support 4a may be a part of the base 10 described above, or may be configured integrally with the base 10. The shape of the support 4a is not limited to the example shown in FIG. 1 and may be any shape.

[0037] Each of the pair of rails 4b is a linear rail that guides the movable body 4c so that it moves relative to the support body 4a in a direction along the Y axis, and extends in the direction along the Y axis. The movable body 4c is attached to the pair of rails 4b via linear bearings (not shown). The pair of rails 4b may be formed integrally with the support body 4a.

[0038] The movable body 4c is a member that moves relative to the support body 4a in the direction along the Y-axis. In the example shown in FIG. 1, it is a plate-like member with its thickness direction along the Z-axis. Although not shown, the Y-movement mechanism 4Y includes an actuator having an electric motor such as a servo motor that generates a driving force for the movement, and an encoder such as a linear encoder that detects the amount of movement. A stage 4d is attached to the movable body 4c by screws or the like.

[0039] The stage 4d is a member that supports the robot 4W. In the example shown in FIG. 1, the stage 4d is plate-shaped. An electric or manual adjustment mechanism for adjusting the position and orientation of the stage 4d relative to the movable body 4c may be interposed between the stage 4d and the movable body 4c. The stage 4d may also be configured integrally with the movable body 4c.

[0040] The robot 4W is attached to the stage 4d of the Y-movement mechanism 4Y by screws or the like. By the operation of the Y-movement mechanism 4Y, the workpiece W can be moved with high precision along the Y-axis without operating the robot 4W. The Y-movement mechanism 4Y is provided as needed and may be omitted. In this case, the robot 4W is attached directly to the base 10 or the like.

[0041] The robot 4W supports the workpiece W. The robot 4W can change the position and posture of the workpiece W, and supports the workpiece W at a desired position and posture that allows it to receive ink ejected from the heads 3a of the head units 3-1 to 3-6 during printing operations. In the example shown in FIG. 1, the robot 4W is a six-axis articulated robot having an arm AR. Here, the base of the robot 4W is fixed to the stage 4d. In addition, a hand mechanism that holds the workpiece W by adsorption such as electrostatic adsorption or by gripping is attached to the tip of the arm AR of the robot 4W as an end effector. The workpiece W may be fixed to the tip of the arm AR with a jig or the like.

[0042] The maintenance mechanism 8 is a mechanism for maintaining the head 3a of the head unit 3. In the example shown in Fig. 1, the maintenance mechanism 8 has a capping mechanism 8F, a cap cover 8P, a cleaning device 8C, and a cleaning device moving mechanism 8M.

[0043] The cap mechanism 8F covers the nozzle surface (not shown) of the head 3a to prevent the ink near the nozzles on the nozzle surface from drying, hardening, or solidifying, and prevents nozzle clogging by suction while covering the nozzle surface.

[0044] The cap cover 8P can be moved along the Y-axis by a mechanism (not shown) and can be switched between overlapping and not overlapping with the capping mechanism 8F along the Z-axis. When the capping mechanism 8F is not in use, the cap cover 8P overlaps the capping mechanism 8F along the Z-axis and functions as a cover for the capping mechanism 8F. In this state, the cap cover 8P can also be used as an inspection table that supports media for test printing. When the capping mechanism 8F is in use, the cap cover 8P does not overlap the capping mechanism 8F along the Z-axis. The cap cover 8P may be able to overlap the cleaning device 8C along the Z-axis, but when the cleaning device 8C is in use, it does not overlap the cleaning device 8C along the Z-axis.

[0045] The cleaning device 8C is a mechanism that wipes the nozzle surface (not shown) of the head 3a, and is provided in the three-dimensional object printing apparatus 1. In the example shown in Fig. 1, the cleaning device 8C is disposed at a position in the Y2 direction relative to the capping mechanism 8F.

[0046] The cleaning device moving mechanism 8M moves the cleaning device 8C in the direction along the Y axis. As a result, the cleaning device moving mechanism 8M moves the cleaning device 8C along the Y axis relative to the head 3a. In the example shown in FIG. 1, the cleaning device moving mechanism 8M moves not only the cleaning device 8C but also the capping mechanism 8F in the direction along the Y axis. Like the Y movement mechanism 4Y, the cleaning device moving mechanism 8M has, for example, a support fixed to the base 10, a pair of rails extending in the direction along the Y axis, and a movable body that moves along the pair of rails relative to the support in the direction along the Y axis. The cleaning device 8C and the capping mechanism 8F are fixed to the movable body by screws or the like.

[0047] The cleaning device moving mechanism 8M can switch between a number of states, including a state in which cleaning of the head 3a can be performed by the cleaning device 8C and a state in which capping of the head 3a can be performed by the capping mechanism 8F. When cleaning of the head 3a by the cleaning device 8C is performed, the cleaning device moving mechanism 8M moves the cleaning device 8C in the direction along the Y axis while a wiping member (not shown) of the cleaning device 8C is in contact with the head 3a.

[0048] The configuration of the maintenance mechanism 8 is not limited to the example shown in Fig. 1. For example, the cap mechanism 8F and the cap cover 8P may be provided or omitted as needed. Furthermore, the maintenance mechanism 8 may be provided or omitted as needed.

[0049] 1-2. Electrical configuration of the printing device Fig. 2 is a block diagram showing the electrical configuration of the three-dimensional object printing device 1 according to the embodiment. Fig. 3 is an explanatory diagram of data and programs stored in the computer 7 shown in Fig. 2. As shown in Fig. 2, the three-dimensional object printing device 1 includes a control unit 50 in addition to the components shown in Fig. 1. Note that Fig. 2 shows only the electrical components of the three-dimensional object printing device 1.

[0050] The control unit 50 controls the operations of the moving mechanism 2, head units 3-1 to 3-6, support mechanism 4, sensor units 30-1 and 30-2, and maintenance mechanism 8. In the example shown in Fig. 2, the control unit 50 has a controller 5, a control module 6, and a computer 7. Below, the controller 5, the control module 6, and the computer 7 will be described in order.

[0051] 2 may be divided appropriately, some may be included in other components, or may be integrated with other components. For example, some or all of the functions of the controller 5 or control module 6 may be implemented by a computer 7, or may be implemented by another external device such as a PC (Personal Computer) connected to the controller 5 via a network such as a LAN (Local Area Network) or the Internet.

[0052] The controller 5 has a function to control the driving of the movement mechanism 2 and the support mechanism 4, and a function to generate a signal D3 for synchronizing the ink ejection operation of the head unit 3 with the operation of the movement mechanism 2.

[0053] The controller 5 includes a memory circuit 5a and a processing circuit 5b.

[0054] The storage circuit 5a stores various programs executed by the processing circuit 5b and various data processed by the processing circuit 5b. The storage circuit 5a includes, for example, one or both of semiconductor memories: a volatile memory such as a random access memory (RAM) and a nonvolatile memory such as a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), or a programmable read-only memory (PROM). Note that part or all of the storage circuit 5a may be included in the processing circuit 5b.

[0055] The storage circuit 5a stores path information Da and attitude information Db.

[0056] The path information Da is used to control the operation of the moving mechanism 2, and is information that indicates the position of the head 3a on the path along which the head 3a should move as a target position. The attitude information Db is used to control the operation of the support mechanism 4, and is information that indicates the position and attitude of the workpiece W on the path along which the workpiece W should move as a target position and target attitude. The path information Da and attitude information Db are input from the computer 7 to the memory circuit 5a.

[0057] The processing circuit 5b controls the operations of the moving mechanism 2 and the support mechanism 4 and generates the signal D3. The processing circuit 5b includes, for example, one or more processors such as a CPU (Central Processing Unit). Note that the processing circuit 5b may include a programmable logic device such as an FPGA (Field-Programmable Gate Array) instead of or in addition to a CPU.

[0058] Specifically, processing circuit 5b performs a calculation to convert path information Da into movement amounts, such as the movement amount and movement speed, of movement mechanism 2. Processing circuit 5b then outputs control signals Sx, Sz-0 to Sz-7 based on output signals Dx, Dz-0 to Dz7 from each encoder of movement mechanism 2 so that the actual movement amount of movement mechanism 2 matches the calculation results. Output signal Dx is a signal output from the encoder of X movement mechanism 2X. Output signals Dz-0 to Dz-7 are signals output from the encoders of Z movement mechanisms 2Z-0 to 2Z-7. Control signal Sx is a signal for controlling the driving of the actuators of X movement mechanism 2X. Control signals Sz-0 to Sz-7 are signals for controlling the driving of the actuators of Z movement mechanisms 2Z-0 to 2Z-7. Control signals Sx, Sz-0 to Sz-7 are corrected by processing circuit 5b as necessary based on output signal D1 from sensor 32 of sensor unit 30.

[0059] Furthermore, the processing circuit 5b performs inverse kinematics calculations, which are calculations that convert the posture information Db into movement quantities such as the rotation angle and rotation speed of each joint of the robot 4W. The processing circuit 5b then outputs a control signal Sw based on the output Dw from the encoder provided in each joint of the robot 4W so that the movement quantities such as the actual rotation angle and rotation speed of each joint match the calculation results described above. The control signal Sw is a signal that controls the drive of the motor provided in each joint of the robot 4W.

[0060] Furthermore, the processing circuit 5b generates the signal D3 based on at least one of the output signals Dx and Dz-0 to Dz-7. For example, the processing circuit 5b may generate the signal D3 including a pulse at the timing when the output signal Dx reaches a predetermined value, or may output the output signal Dx as is as the signal D3.

[0061] The control module 6 is a circuit that controls the ink ejection operation of the head unit 3 based on the signal D3 output from the controller 5 and print data from the computer 7. The control module 6 has a timing signal generation circuit 6a, a power supply circuit 6b, a control circuit 6c, and a drive signal generation circuit 6d.

[0062] The timing signal generating circuit 6a generates a timing signal PTS based on the signal D3. The timing signal generating circuit 6a may be configured, for example, as a timer that starts generating the timing signal PTS upon detection of the signal D3, or as a circuit that generates, when the signal D3 is the output signal Dx, the timing signal PTS as a signal including a pulse whose timing is synchronized with the pulse of the output signal Dx.

[0063] The power supply circuit 6b receives power from a commercial power supply (not shown) and generates various predetermined potentials. For example, the power supply circuit 6b generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the head unit 3. The power supply potential VHV is also supplied to the drive signal generation circuit 6d.

[0064] The control circuit 6c generates control signals SI-1 to SI-6, a waveform designation signal dCom, a latch signal LAT, a clock signal CLK, and a change signal CNG based on the timing signal PTS. These signals are synchronized with the timing signal PTS. Of these signals, the waveform designation signal dCom is input to the drive signal generation circuit 6d, and the other signals are input to the switch circuit 3e of the head unit 3. The control signals SI-1 to SI-6 correspond one-to-one to the head units 3-1 to 3-6, respectively. Note that, hereinafter, each of the control signals SI-1 to SI-6 may also be referred to as a control signal SI.

[0065] The control signal SI is a digital signal that specifies the operating state of the drive elements of the head 3a of the head unit 3. Specifically, the control signal SI is a signal that specifies whether or not to supply a drive signal Com (described below) to the drive element based on the print data. This specification, for example, specifies whether or not to eject ink from the nozzle corresponding to the drive element, or specifies the amount of ink ejected from the nozzle. The waveform specification signal dCom is a digital signal that defines the waveform of the drive signal Com. The latch signal LAT and change signal CNG are used in conjunction with the control signal SI to specify the drive timing of the drive element, thereby specifying the timing of ink ejection from the nozzle. The clock signal CLK is a reference clock signal synchronized with the timing signal PTS.

[0066] The control circuit 6c described above includes, for example, one or more processors such as CPUs, etc. Note that the control circuit 6c may include a programmable logic device such as an FPGA instead of or in addition to a CPU.

[0067] The drive signal generation circuit 6d is a circuit that generates a drive signal Com for driving each drive element of the head 3a of the head unit 3. Specifically, the drive signal generation circuit 6d includes, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generation circuit 6d, the DA conversion circuit converts the waveform designation signal dCom from the control circuit 6c from a digital signal to an analog signal, and the amplifier circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 6b to generate the drive signal Com. Here, of the waveforms included in the drive signal Com, the signal with the waveform actually supplied to the drive element is the drive pulse PD. The drive pulse PD is supplied from the drive signal generation circuit 6d to the drive element via the switch circuit 3e of the head unit 3.

[0068] Here, the switch circuit 3e is a circuit including a switching element that switches whether or not at least a part of the waveform included in the drive signal Com is to be supplied as the drive pulse PD based on the control signal SI.

[0069] The computer 7 is, for example, a computer on which a program is installed. The computer 7 has the functions of generating path information Da and attitude information Db, supplying information such as the path information Da and attitude information Db to the controller 5, supplying information such as print data to the control module 6, and controlling the operation of the maintenance mechanism 8. In addition to these functions, the computer 7 of this embodiment also has the function of controlling the driving of the light source 31 of the sensor unit 30.

[0070] The computer 7 has a memory circuit 7a and a processing circuit 7b.

[0071] The memory circuitry 7a stores various programs executed by the processing circuitry 7b and various data such as route information Da processed by the processing circuitry 7b. The memory circuitry 7a includes, for example, one or both of semiconductor memories, such as a volatile memory such as RAM and a nonvolatile memory such as a ROM, EEPROM, or PROM. Note that part or all of the memory circuitry 7a may be included in the processing circuitry 7b.

[0072] As shown in FIG. 3, the storage circuit 7a stores path information Da, attitude information Db, workpiece information Dc, print area information Dd, image data De, pixel data Df, and print data Img.

[0073] The work information Dc is data that represents the shape of at least a portion of the workpiece W. Specifically, the work information Dc is three-dimensional data in a format such as STL (Standard Triangulated Language) that represents the shape of the workpiece W using multiple polygons. The work information Dc includes coordinate information, which is information about the coordinates of each vertex of the polygon, and vector information, which is information about normal vectors that indicate the front and back of the polygon faces. The work information Dc is obtained by converting CAD (computer-aided design) data that represents the three-dimensional shape of the workpiece W as needed. The work information Dc may be expressed using coordinate values ​​in a work coordinate system, or may be expressed as point cloud data using coordinate values ​​in a base coordinate system or a world coordinate system. The work information Dc may also be expressed using mathematical formulas, etc., and the format of the work information Dc may be appropriately converted as needed.

[0074] The print area information Dd is information that indicates the print area RP, which will be described later and is the area to be printed on the surface WF of the workpiece W, and includes information that indicates the shape and size of the print area RP. The print area information Dd is expressed using coordinate values ​​in, for example, the work coordinate system, the base coordinate system, or the world coordinate system.

[0075] The image data De is information that two-dimensionally represents an image to be printed, and is, for example, image data created by image editing software. Specifically, the image data De is, for example, image data in a file format based on a page description language such as PostScript, PDF (Portable Document Format), or XPS (XML Paper Specification), or image data in various vector formats, or image data in raster format.

[0076] The pixel data Df is information that represents an ideal three-dimensional image to be printed in the print area RP (described below), and includes, for example, color data or gradation data for each pixel. The pixel data Df is obtained by pasting an image represented by the image data De onto the print area RP. The pixel data Df is expressed using coordinate values ​​in, for example, the work coordinate system, the base coordinate system, or the world coordinate system. The pixel data Df may be included in the print area information Dd or in the work information Dc.

[0077] The print data Img is information indicating the image to be printed on the workpiece W for each path (pass) of the printing trajectory indicated by the path information Da, and indicates the amount of ink to be ejected from the head 3a for each pixel of the image indicated by the pixel data Df.

[0078] The processing circuitry 7b implements various functions by reading and executing programs from the storage circuitry 7a. The processing circuitry 7b includes, for example, one or more processors such as CPUs. Note that the processing circuitry 7b may include a programmable logic device such as an FPGA instead of or in addition to a CPU.

[0079] 1-3.Head unit Fig. 4 is a perspective view showing an outline of the head unit 3. As shown in Fig. 4, the head unit 3 has a support 3g in addition to the head 3a. In the example shown in Fig. 4, the head unit 3 has one head 3a, but the number is not limited to the example shown in Fig. 4 and may be two or more.

[0080] Support body 3g is a structure that supports head 3a, and is attached to Z movement mechanism 2Z. Therefore, head 3a is supported by Z movement mechanism 2Z via support body 3g.

[0081] The support 3g is a substantially rigid body and is made of, for example, a metal material. Although the support 3g is shown as a plate in FIG. 4, the shape of the support 3g is not particularly limited and is arbitrary. The support 3g may also be made of multiple members. Furthermore, in addition to the head 3a, the support 3g may support, for example, a heater and a temperature sensor, a light source for curing or solidifying the ink on the workpiece W, or a pressure adjustment valve for maintaining the pressure of the ink in the head 3a at a negative pressure within a predetermined range.

[0082] The head 3a is disposed at a position in the X1 direction relative to the support 3g, and the head 3a is fixed to the support 3g by means of screws or the like.

[0083] The head 3a has a nozzle surface FN and multiple nozzles N opening in the nozzle surface FN. In the example shown in FIG. 4, the normal direction of the nozzle surface FN is the Z2 direction, and the multiple nozzles N are divided into nozzle arrays NLa and NLb, which are spaced apart along the X-axis. Each of the nozzle arrays NLa and NLb is a collection of multiple nozzles N linearly arranged in the nozzle array direction DN, which is along the Y-axis. Herein, the elements associated with each nozzle N in the nozzle array NLa and the elements associated with each nozzle N in the nozzle array NLb in the head 3a are configured substantially symmetrically with each other along the X-axis. Hereinafter, the collection of the nozzle arrays NLa and NLb may be referred to as the nozzle array NL. Each nozzle N ejects ink along a parallel ejection direction DE. Under ideal conditions, the ejection direction DE is the Z2 direction, which is normal to the nozzle surface FN.

[0084] Although not shown, the head 3a has a piezoelectric element serving as a drive element and a cavity for storing ink for each nozzle N. Here, the piezoelectric element changes the pressure in the cavity corresponding to the piezoelectric element, thereby ejecting ink from the nozzle corresponding to the cavity. Such a head 3a can be obtained, for example, by bonding together, with an adhesive, multiple substrates such as silicon substrates that have been appropriately processed by etching or the like. Note that instead of the piezoelectric element, a heater that heats the ink in the cavity may be used as the drive element for ejecting ink from the nozzle.

[0085] The position of the head 3a is determined based on the tool center point TCP. In this embodiment, the tool center point TCP is set at the center of the nozzle face FN, as shown in Fig. 4. The position of the tool center point TCP is not limited to the example shown in Fig. 4, and may be, for example, a position in space spaced a predetermined distance from the center of the nozzle row NL in the ink ejection direction DE.

[0086] A supply pipe and a discharge pipe (not shown) are connected to the head 3a. The supply pipe is a flexible pipe that supplies ink from an ink tank (not shown) to the head unit 3. The discharge pipe is a flexible pipe that transports ink to a circulation mechanism or discharge mechanism (not shown).

[0087] 1-4.Printing method FIG. 5 is a flowchart showing a printing method according to an embodiment. This printing method is a method of printing using the three-dimensional object printing apparatus 1 described above, and as shown in FIG. 5, includes steps S10 to S100, in this order. These steps are executed by the processing circuit 7b of the computer 7. Here, step S10 is an example of a "printing area determination step." Step S30 is an example of a "printing trajectory creation step." Step S60 is an example of a "posture determination step." Step S100 is an example of a "printing step." An outline of each step will be described below.

[0088] In step S10, the processing circuitry 7b determines a printing area RP (described below) of the workpiece W to which ink is applied from the head 3a, based on the shape of the workpiece W. Information about the determined printing area RP is stored in the memory circuitry 7a as printing area information Dd. This determination may be made, for example, based on instructions from a user, or may be set automatically based on preset conditions. In addition to determining the printing area RP, in step S10 the processing circuitry 7b also sets a sub-scanning reference line LS (described below) in accordance with the printing area RP.

[0089] After step S10, in step S20, the processing circuitry 7b sets a plurality of reference points PM, which will be described later. The reference points PM are an example of "specific positions."

[0090] After step S20, in step S30, the processing circuit 7b generates a print trajectory LM, described below, for each reference point PM. The print trajectory LM is a path on the print area RP, described below, and serves as a reference for generating a print trajectory RU, described below, that scans the head 3a across the print area RP. Here, the print trajectory RU is located a distance PG, described below, away from the print trajectory LM. Therefore, both the print trajectory RU and the print trajectory LM are paths that follow the movement trajectory of the tool center point TCP.

[0091] After step S30, in step S40, the processing circuitry 7b sets a plurality of points P, which will be described later, for each print trajectory LM.

[0092] After step S40, if necessary, in step S50, the processing circuitry 7b resets the reference point PM.

[0093] After step S50, or after step S40 if step S50 is not performed, in step S60, the processing circuit 7b determines the posture of the workpiece W due to the operation of the robot 4W based on the printing trajectory LM or a printing trajectory RU described below. Information indicating the posture of the workpiece W determined thereby is stored in the memory circuit 7a as posture information Db. Also, in step S60, the processing circuit 7b determines the posture of the workpiece W, sets a discharge distance PG described below, and creates a printing trajectory RU based on the discharge distance PG and the printing trajectory LM. In other words, in step S60, the processing circuit 7b determines the posture of the workpiece W, sets a discharge distance PG described below, and creates a printing trajectory RU by correcting the printing trajectory LM based on the discharge distance PG. After step S60, in step S70, the processing circuit 7b generates pixel data Df.

[0094] Here, the three-dimensional object printing apparatus 1 creates a first printing trajectory RU1 and a second printing trajectory RU2, which will be described later, as printing trajectories RU along which the head 3a scans the printing area RP of the workpiece W.

[0095] After step S60, in step S70, the processing circuit 7b creates pixel data Df on the printing area RP based on the image data De representing the image to be printed.

[0096] After step S70, in step S80, the processing circuit 7b determines the amount of ink to be ejected from the head 3a based on the pixel data Df in the printing area RP that intersects with the normal to the nozzle face FN of the head 3a passing through the printing trajectory RU. This generates print data Img. Using this print data Img, the image represented by the image data De can be printed in the printing area RP.

[0097] After step S80, in step S90, the processing circuit 7b stores the print data Img in the storage circuit 7a.

[0098] After step S90, in step S100, the processing circuit 7b executes a printing process, in which printing is performed on the print area RP of the workpiece W using the print data Img.

[0099] 1-5. Generation of printing trajectory and determination of workpiece posture FIG. 6 is a diagram for explaining the setting of the print area RP. In the following description, the x-axis, y-axis, and z-axis, which intersect with each other, are used as appropriate coordinate axes of a three-dimensional coordinate system that defines a virtual space VS, a virtual space that mimics real space. In the following description, one direction along the x-axis is the x1 direction, and the direction opposite the x1 direction is the x2 direction. The y1 and y2 directions are opposite directions along the y-axis. The z1 and z2 directions are opposite directions along the z-axis. The relationship between the x-axis, y-axis, and z-axis and the X-axis, Y-axis, and Z-axis is not particularly limited and can be arbitrary. The x-axis, y-axis, and z-axis are typically perpendicular to each other, but this is not a limitation and they may intersect at an angle between 80° and 100°.

[0100] In step S10, the workpiece W is placed in the virtual space VS based on the workpiece information Dc, and a printing area RP is set based on the printing area information Dd, as shown in Figure 6. The printing area RP is the area on the surface of the workpiece W that is to be printed.

[0101] Then, in step S20, a sub-scanning reference line LS is set in the virtual space VS along the surface of the workpiece W. Hereinafter, the direction along the sub-scanning reference line LS may be referred to as the sub-scanning direction DS. More specifically, the sub-scanning direction DS is a direction parallel to a sub-scanning virtual plane VPS (described later) and is also parallel to a tangent to the surface of the workpiece W at any point on the sub-scanning reference line LS. In the example shown in FIG. 6, the sub-scanning direction DS is a direction along the y-axis when viewed in a direction along the z-axis.

[0102] The sub-scanning reference line LS is set based on the intersection of the sub-scanning virtual plane VPS and the surface of the workpiece W after the sub-scanning virtual plane VPS is set in the virtual space VS so that it intersects with the printing area RP. Here, the sub-scanning virtual plane VPS is a virtual plane in the virtual space VS. The sub-scanning reference line LS is the intersection line between the sub-scanning virtual plane VPS and the surface of the workpiece W or a line segment along the intersection line, and is expressed using coordinate values ​​of a coordinate system set in the virtual space VS.

[0103] The sub-scanning reference line LS passes through the printing area RP. In the example shown in FIG. 6, the center of the sub-scanning reference line LS within the printing area RP is closer to the center of the printing area RP than to the edges of the printing area RP. In other words, the sub-scanning reference line LS is set to pass through the printing area RP at a position closer to the center of the printing area RP than to the edges of the printing area RP in the main scanning direction DM, which will be described later and which intersects with the sub-scanning direction DS. The main scanning direction DM is a direction along the printing trajectory LM or printing trajectory RU, which will be described later. More specifically, the main scanning direction DM is a direction parallel to the main scanning virtual plane VPM, which will be described later, and a direction parallel to a tangent to the surface of the workpiece W at any point on the printing trajectory LM or printing trajectory RU.

[0104] Here, the length of the edges of the print area RP in the main scanning direction DM along the sub-scanning direction DS may be shorter than the length of the center of the print area RP in the sub-scanning direction DS along the main scanning direction DM. Even in such cases, the center of the sub-scanning reference line LS within the print area RP is located closer to the center of the print area RP than the edges of the print area RP, making it easier to appropriately set the print trajectories LM and RU, described below. From this perspective, in this case, it is preferable that the sub-scanning reference line LS pass through the widest part of the print area RP along the sub-scanning direction DS.

[0105] 7 is a diagram for explaining the details of the sub-scanning reference line LS, and representatively shows a portion of the surface WF of the workpiece W represented by the workpiece information Dc.

[0106] In the virtual space VS, a surface WF is composed of multiple polygons POL. In the example shown in FIG. 7, each polygon POL forms a triangle having three sides LE and three vertices PV. Here, each side LE is shared by two polygons POL. Two polygons POL that share one side LE are adjacent to each other with that side LE as their boundary. Furthermore, each vertex PV is shared by three or more polygons POL. Three or more polygons POL that share one vertex PV are in contact with each other at that vertex PV. The normal vector Vp of each polygon POL is obtained from vector information included in the work information Dc. Note that the shape of each polygon POL is not limited to a triangle and may be another polygon such as a quadrangle.

[0107] The sub-scanning virtual plane VPS intersects with the surface WF. The sub-scanning virtual plane VPS and the surface WF intersect with each other at a sub-scanning reference line LS as their intersection line.

[0108] The sub-scanning virtual plane VPS is specified by the processing circuitry 7b based on a user specification. The specification is made, for example, by a user input to the computer 7. For example, one or both of the position and orientation of the sub-scanning virtual plane VPS in the virtual space VS is set by input using an input device of the computer 7. Note that the specification may also be made automatically in accordance with preset criteria based on the shape of the printing area RP, etc.

[0109] The sub-scanning virtual plane VPS is preferably specified so as to be as parallel as possible to the normal of the intersecting polygon POL (intersecting polygon POL_1, described later). For example, as shown in Fig. 7, if there are five intersecting polygons POL, the sub-scanning virtual plane VPS is specified so as to minimize the sum or average value of the differences between the angles formed by each polygon POL and the sub-scanning virtual plane VPS and 90°.

[0110] In step S20, after the sub-scanning virtual plane VPS is specified as described above, among the multiple polygons POL, multiple intersecting polygons POL_1 that intersect with the sub-scanning virtual plane VPS are identified in the virtual space VS. Because the sub-scanning virtual plane VPS crosses the surface WF as described above, the multiple polygons POL that make up the surface WF are divided into multiple intersecting polygons POL_1 that intersect with the sub-scanning virtual plane VPS and multiple polygons POL_2 that do not intersect with the sub-scanning virtual plane VPS. In Figure 7, for ease of explanation, the intersecting polygon POL_1 is shown shaded.

[0111] The position of the sub-scanning reference line LS is set in the virtual space VS based on a plurality of intersection polygons POL_1. Specifically, the position of the sub-scanning reference line LS is set based on a plurality of intersection points Pa between the sides LE of the plurality of intersection polygons POL_1 and the sub-scanning virtual plane VPS.

[0112] In the example shown in FIG. 7, the spaces between the multiple intersection points Pa are interpolated with interpolation points Pb. The multiple points consisting of the multiple intersection points Pa and the multiple interpolation points Pb are set as the position of the sub-scanning reference line LS. In this way, the position of the sub-scanning reference line LS is set based on the multiple intersection points Pa and the multiple interpolation points Pb. Note that in the example shown in FIG. 7, there is one interpolation point Pb placed between two adjacent intersection points Pa, but the number may be two or more. The multiple points consisting of the multiple intersection points Pa and the multiple interpolation points Pb do not have to be equally spaced.

[0113] The position of the sub-scanning reference line LS may be based on at least one of the multiple intersection points Pa and the multiple interpolation points Pb, and does not have to coincide with the positions of the multiple intersection points Pa and the multiple interpolation points Pb. For example, the position of the sub-scanning reference line LS may be a position obtained by moving the multiple intersection points Pa and the multiple interpolation points Pb in a direction that uniformly moves them away from the intersection polygon POL_1.

[0114] In the example shown in FIG. 7, the interpolation points Pb are arranged on the intersection line between the sub-scanning virtual plane VPS and the surface WF. The multiple points consisting of the multiple intersection points Pa and the multiple interpolation points Pb are typically arranged as evenly spaced as possible. Here, it is preferable that the interpolation points Pb are arranged on a smooth curve that passes through the multiple intersection points Pa. Such a curve is represented, for example, by a spline function. Note that the multiple intersection points Pa may be sorted into multiple valid intersection points and at least one invalid intersection point, and the position of the sub-scanning reference line LS may then be set by interpolating between the multiple valid intersection points.

[0115] FIG. 8 is a diagram illustrating a plurality of reference points PM. In step S20, after the sub-scanning reference line LS is set as described above, a plurality of reference points PM are set on the sub-scanning reference line LS in the virtual space VS, as shown in FIG. 8. This setting is performed, for example, by selecting the intersection points Pa or interpolation points Pb described above as the reference points PM, or by using a function such as a spline function representing the sub-scanning reference line LS based on the intersection points Pa or interpolation points Pb to determine a plurality of appropriate points on the sub-scanning reference line LS as the reference points PM. The number of reference points PM may be two or more, and is not limited to the example shown in FIG. 8, and may be any number.

[0116] The distance Dm between two adjacent reference points PM along the sub-scanning reference line LS is equal to or less than the width of the nozzle row NL in the direction along the Y axis over the entire area of ​​the sub-scanning reference line LS, and more preferably equal to or less than half the width of the nozzle row NL. In the example shown in Figure 7, the multiple reference points PM are arranged at equal intervals on the sub-scanning reference line LS. Note that the intervals between the multiple reference points PM along the sub-scanning reference line LS do not have to be equal.

[0117] 9 is a diagram illustrating the print trajectory LM. In step S30, multiple print trajectories LM are set in the virtual space VS for each reference point PM, as shown in FIG. 9. Each of the multiple print trajectories LM passes through the corresponding reference point PM and intersects with the sub-scanning reference line LS.

[0118] Here, of the two adjacent print trajectories LM, one print trajectory LM is an example of a "first print trajectory," and the other print trajectory LM is an example of a "second print trajectory."

[0119] Fig. 10 is a diagram for explaining a method for setting a print trajectory LM. For ease of explanation, Fig. 10 representatively shows three of the multiple reference points PM, that is, reference points PM_1, PM_2, and PM_3, and three print trajectories LM corresponding to the reference points PM_1, PM_2, and PM_3, that is, print trajectories LM_1, LM_2, and LM_3.

[0120] The printing trajectory LM_1 is set in the virtual space VS based on the intersection between a first main scanning virtual plane VPM_1, which is a virtual plane passing through the reference point PM_1, and the surface of the workpiece W. Similarly, the printing trajectory LM_2 is set in the virtual space VS based on the intersection between a second main scanning virtual plane VPM_2, which is a virtual fixed plane passing through the reference point PM_2, and the surface of the workpiece W. Furthermore, the printing trajectory LM_3 is set in the virtual space VS based on the intersection between a third main scanning virtual plane VPM_3, which is a virtual fixed plane passing through the reference point PM_3, and the surface of the workpiece W. Note that hereinafter, the first main scanning virtual plane VPM_1, the second main scanning virtual plane VPM_2, and the third main scanning virtual plane VPM_3 may each be referred to as the main scanning virtual plane VPM.

[0121] In this way, the printing trajectory LM is set in the virtual space VS based on the intersection between the main scanning virtual plane VPM, which is a virtual plane passing through the reference point PM, and the surface of the workpiece W. The intersection between the main scanning virtual plane VPM and the surface of the workpiece W is set in the same manner as the intersection Pa between the sub-scanning virtual plane VPS and the surface WF and the interpolation point Pb shown in Figure 7. However, the main scanning virtual plane VPM is perpendicular to the sub-scanning virtual plane VPS.

[0122] Such a main scanning virtual plane VPM roughly represents the ideal ink ejection direction by the head 3a and the ideal movement direction of the head 3a. In other words, during a printing operation when the print trajectory LM is used as the print trajectory RU described below, the head 3a ejects ink generally parallel to the main scanning virtual plane VPM, and the head 3a moves in a direction generally parallel to the main scanning virtual plane VPM. In this way, the main scanning virtual plane VPM is a reference plane for defining the relative position and orientation of the head 3a with respect to the workpiece W during printing.

[0123] In this embodiment, the main scanning virtual plane VPM is parallel to the normal to the surface WF at the reference point PM. In this embodiment, the position of the tool center point TCP in the nozzle array direction DN is set to the center of the nozzle array NL, so by making the main scanning virtual plane VPM parallel to the normal to the surface WF at the reference point PM, it is possible to easily set a print trajectory RU with a narrow ejection distance PG, described below, for a relatively large number of nozzles N.

[0124] Here, for example, when the reference point PM is set by selecting the intersection point Pa or the interpolation point Pb as the reference point PM, the normal to the surface WF at the reference point PM is parallel to the vector Va or vector Vb shown in Fig. 7. That is, in this case, the normal vectors Vpm_1 to Vpm_3 of the surface WF at the reference points PM_1 to PM_3 are the vector Va or vector Vb shown in Fig. 7. Hereinafter, each of the normal vectors Vpm_1 to Vpm_3 may be referred to as the normal vector Vpm.

[0125] The vector Va is a normal vector of the face WF at the intersection Pa, and is preferably defined based on the normal vectors Vp of the multiple polygons POL that share both ends of the edge LE including the corresponding intersection Pa. Specifically, with reference to FIG. 7 , if one of the multiple intersections Pa is defined as the first intersection, the vector Va indicating the direction along the normal corresponding to the first intersection is preferably defined based on the first vertex vector Vc_1 and the second vertex vector Vc_2. Here, if the edge LE including the first intersection among the edges LE of the multiple intersection polygons POL_1 is defined as the first edge LE_1, one end of the first edge LE_1 is defined as the first vertex PV_1, and the other end of the first edge LE_1 is defined as the second vertex PV_2, the first vertex vector Vc_1 is the normal vector corresponding to the first vertex PV_1, and the second vertex vector Vc_2 is the normal vector corresponding to the second vertex PV_2. These vertex vectors are preferably calculated in advance based on vector information included in the work information Dc.

[0126] The vector Vb is a normal vector of the surface WF at the interpolation point Pb, and is preferably defined to be the average of two adjacent vectors Va.

[0127] In this embodiment, the position of the printing trajectory LM is made up of multiple points where the main scanning virtual plane VPM intersects with the surface of the workpiece W, and is located on the plane WF. Note that the position indicated by the printing trajectory LM may be based on multiple intersections between the main scanning virtual plane VPM and the surface of the workpiece W, and does not have to coincide with the positions of the intersections between the main scanning virtual plane VPM and the surface of the workpiece W. For example, the position of the printing trajectory LM may be a position obtained by moving the multiple intersections between the main scanning virtual plane VPM and the surface of the workpiece W in a direction that uniformly moves them away from the surface of the workpiece W.

[0128] As described above, the print trajectory LM is set for each reference point PM.

[0129] FIG. 11 is a diagram illustrating multiple points P on the print trajectory LM. In step S40, as shown in FIG. 11, multiple points P are set on the print trajectory LM in the virtual space VS. The multiple points P are set within the print area RP. In the example shown in FIG. 11, the multiple points P include a reference point PM as the point P, a point PE1 that is a point P located at one end of the print area RP, and a point PE2 that is a point P located at the other end of the print area RP.

[0130] The spacing between the multiple points P corresponds to the resolution of the image represented by the print data Img. In the example shown in Fig. 11, the multiple points P are arranged at equal intervals pi when viewed in the normal direction (the direction of the normal vector Vpm) at the reference point PM of the print area RP. Note that the number of points P is not limited to the example shown in the figure and can be any number.

[0131] 12 is a diagram illustrating another example of multiple points P on the print trajectory LM. In the example shown in FIG. 12, the intervals pi between the multiple points P are equal on the print trajectory LM. Note that the number of points P is not limited to the example shown in the figure and can be any number.

[0132] 13 is a diagram for explaining the normal vector V at multiple points P on the printing trajectory LM. In step S40, after multiple points P are set as described above, the normal vector V of the printing area RP at each point P is set in the virtual space VS, as shown in FIG.

[0133] One normal vector V among the normal vectors V of multiple points P is set as a reference for the posture of the workpiece W. The point P corresponding to the one normal vector V corresponds to a "specific position." In the example shown in FIG. 13, the normal vector Vpm is set as a reference for the posture of the workpiece W. Note that if the normal vector Vpm is not appropriate as a reference for the posture of the workpiece W, step S50 is executed. Step S50 will be described later with reference to FIGS. 17 and 18.

[0134] 14 is a diagram for explaining the ejection direction DE at multiple points P on the printing trajectory LM. In step S60, as shown in FIG. 14, the ejection direction DE at multiple points P is set in the virtual space VS. This setting is performed so that the ejection direction DE at each point P is parallel to the normal vector Vpm. Therefore, the ejection directions DE at multiple points P are parallel to each other.

[0135] FIG. 15 is a diagram illustrating the print trajectory RU. In step S60, after setting the ejection direction DE at multiple points P as described above, the print trajectory RU is set in the virtual space VS as shown in FIG. 15. This setting is performed by moving the print trajectory LM to a position away from the print area RP by the ejection distance PG for each point P, and defining the path obtained as the print trajectory RU. Therefore, the print trajectory RU is defined by the points obtained by moving multiple points P on the print trajectory LM by the ejection distance PG. The ejection distance PG at each point P is set according to the shape of the print area RP, the dimensions of the head 3a, and the like. Note that setting the ejection distance PG, in other words, generating the print trajectory RU, may be performed in a step prior to step S60. In this case, fine adjustment of the ejection distance PG may be performed in step S60.

[0136] FIG. 16 is a diagram for explaining the determination of the posture of the workpiece W. In step S60, the posture of the workpiece W is determined as shown in FIG. 16. This determination is performed by making the discharge direction DE parallel to the Z axis and positioning the reference point PM at the printing center set in the world coordinate system. This establishes correspondence between the coordinate system that defines the virtual space VS and the world coordinate system that is set in the installation space of the movement mechanism 2 and the support mechanism 4. The printing center is an arbitrary position within the movement area of ​​the head 3a moved by the movement mechanism 2.

[0137] As described above, in step S60, the posture of the workpiece W is determined so that the angle between the normal to the nozzle surface FN of the head 3a and the surface of the printing area RP at the reference point PM, which is a specific position in the printing area RP along the printing trajectory RU, is 90 degrees. That is, the posture of the workpiece W is determined so that the normal to the nozzle surface FN is perpendicular to the surface of the workpiece W at the specific position. In other words, the posture of the workpiece W is determined so that the normal from the specific position on the surface of the workpiece W is perpendicular to the nozzle surface FN. In other words, the posture of the workpiece W is determined so that the normal from the specific position on the surface of the workpiece W and the normal to the nozzle surface FN are parallel to each other. By determining the posture of the workpiece W in this manner, the impact position of the ink from the head 3a on the surface of the workpiece W is less likely to deviate than in a mode in which the angle deviates from 90 degrees, thereby improving printing quality.

[0138] Fig. 17 is an explanatory diagram of a case where the posture of the workpiece W is determined based on the center point of the asymmetrically shaped printing area RP. Fig. 18 is an explanatory diagram of a case where the posture of the workpiece W is determined based on a specific position of the asymmetrically shaped printing area RP. Figs. 17 and 18 show the relationship between points A and B on the printing area RP as viewed in the direction along the Y axis, head 3a-A which is the head 3a that ejects ink to point A, and head 3a-B which is the head 3a that ejects ink to point B.

[0139] When the shape of the printing area RP is asymmetric, as shown in FIG. 17, if the orientation of the workpiece W is determined based on point P-1, which is the point P corresponding to the center point of the printing area RP, one of the ejection distances PG-A and PG-B of the heads 3a-A and 3a-B becomes extremely large, or one of the angles θ-A and θ-B between the ejection direction DE of the heads 3a-A and the printing area RP becomes extremely small. As a result, the deviation of the ink landing position at either point A or point B becomes noticeable, which may degrade print quality. Note that angle θ-A corresponds to the landing angle of ink from head 3a-A to the printing area RP. Angle θ-B corresponds to the landing angle of ink from head 3a-B to the printing area RP.

[0140] 17, the tilt angle of the printing area RP at point B is larger than the tilt angle at point A. Therefore, angle θ-B is smaller than angle θ-A. Furthermore, if the tilt angle of the printing area RP at point B is larger than the tilt angle at point A, then in order to prevent the head 3a from colliding with the workpiece W, the discharge distance PG-B will be larger than the discharge distance PG-A.

[0141] 18, by determining the posture of the workpiece W based on point P-2, which is point P (reference point PM) corresponding to a specific position, it is possible to reduce the difference between the discharge distance PG-A of head 3a-A and the discharge distance PG-B of head 3a-B, and to reduce the difference between the angle θ-A between the discharge direction DE of head 3a-A and the printing area RP and the angle θ-B between the discharge direction DE of head 3a-B and the printing area RP. As a result, it is possible to improve print quality.

[0142] In the example shown in Figure 18, point P-2 is positioned between point P-1 and point A so as to reduce the difference between the ejection distance PG-A and the ejection distance PG-B and also reduce the difference between the angle θ-A and the angle θ-B.

[0143] In this way, the reference points PM are set so that the variations in the ejection distance PG and landing angle are small across the entire print area RP. Such reference points PM are set for each print trajectory LM.

[0144] As a result, in step S60, a specific reference point PM is determined based on the angle θ between the normal to the nozzle surface FN and the printing area RP along the printing trajectory RU. This makes it possible to determine the posture of the workpiece W so that the deviation of the ink landing position from the head 3a onto the surface of the workpiece W is minimized, even if the printing area RP has an uneven shape. As a result, printing quality can be improved.

[0145] In step S60, the angle θ between the normal to the printing area RP at multiple points P in the printing area RP along the printing trajectory RU is obtained, and a specific reference point PM is determined so that the amount of change or variation in the angle θ is minimized. This reduces variation in the ink landing position at multiple points P in the printing area RP. As a result, print quality can be improved.

[0146] Furthermore, in step S60, as described above, the multiple points P include point PE1 at one end of the printing area RP and point PE2 at the other end. This reduces deviations in the ink landing position at the ends of the printing area RP, thereby improving print quality.

[0147] Furthermore, in step S60, the ejection distance PG, which is the distance between the nozzle surface FN of the head 3a and the surface of the printing area RP, is acquired at multiple points P on the printing trajectory RU, and the posture of the workpiece W due to the operation of the robot 4W is determined based on the ejection distance PG. This makes it possible to reduce variations in the ink ejection distance at multiple points P on the printing area RP. As a result, print quality can be improved.

[0148] In step S50, if the reference point PM is not appropriate, the reference point PM is reset so that the variation in the ejection distance PG and the landing angle is reduced across the entire print area RP. This resetting is performed for each print trajectory LM as necessary.

[0149] 1-6.Generating print data Fig. 19 is a diagram for explaining the generation of pixel data Df and print data Img. For ease of explanation, Fig. 19 shows heads 3a_1 to 3a_3, which are heads 3a corresponding to print trajectories RU_1 to RU_3, which are three print trajectories RU, with dashed two-dot lines, and also shows the relationship between the multiple nozzles N of each of heads 3a_1 to 3a_3 and the ink landing positions on the workpiece W. Note that head 3a_1 is the head 3a when performing the first print operation, head 3a_2 is the head 3a when performing the second print operation, and head 3a_3 is the head 3a when performing the third print operation.

[0150] In step S70, the image represented by the image data De is pasted onto the print area RP in the virtual space VS, thereby creating pixel data Df.

[0151] Here, the print area RP is quantized into multiple voxels BX in the virtual space VS as shown in Figure 19. Each voxel BX is a cube, and all voxels have the same side length, and are arranged three-dimensionally in a continuous manner along the print area RP in the virtual space VS. Note that the side lengths of the voxels BX are preferably adjusted appropriately according to the printing resolution.

[0152] After step S70, in step S80, print data Img is generated for each print trajectory RU based on the intersection of the print region RP and an imaginary line extending in the ejection direction DE from each nozzle N of the heads 3a_1 to 3a_3.

[0153] The intersections correspond to the landing positions of ink from head 3a. Step S80 extracts color data or gradation data corresponding to the intersections for each print trajectory RU from pixel data Df, divides pixel data Df for each print operation (first print operation, second print operation, and third print operation), and converts the divided pixel data Df into ink ejection amounts, thereby generating print data Img.

[0154] In step S80, the print area RP is divided into a first area RP1 to which ink can be applied during the first printing operation, a second area RP2 to which ink can be applied during the second printing operation, and a third area RP3 to which ink can be applied during the third printing operation, in units of voxels BX, based on the aforementioned intersections corresponding to the ink landing positions. Next, in step S80, exclusion processing is performed so that each voxel BX corresponds to one dot of ink from one nozzle N. In this manner, exclusion processing between dots is performed in units of voxels BX. Through exclusion processing between dots, the pixel data Df is divided into the first, second, and third printing operations. In other words, print data Img is generated for each printing operation. In step S90, the generated print data Img is stored in the memory circuit 7a.

[0155] In the example shown in Figure 19, the three-dimensional image information indicated by the pixel data Df is divided into three-dimensional image information corresponding to the multiple voxels BX to which the dot Dt1 formed by the ink from head 3a_1 belongs, three-dimensional image information corresponding to the multiple voxels BX to which the dot Dt2 formed by the ink from head 3a_2 belongs, and three-dimensional image information corresponding to the multiple voxels BX to which the dot Dt3 formed by the ink from head 3a_3 belongs.

[0156] The 3D image information corresponding to the plurality of voxels BX to which the ink dots Dt1 from the head 3a_1 belong is used in the first printing operation. The 3D image information corresponding to the plurality of voxels BX to which the ink dots Dt2 from the head 3a_2 belong is used in the second printing operation. The 3D image information corresponding to the plurality of voxels BX to which the ink dots Dt3 from the head 3a_3 belong is used in the third printing operation.

[0157] Step S80 also checks whether there are any voxels BX in the printing area RP that do not have any dots. This checks whether defects such as chipping will occur in the actual printed image. If there are any voxels BX in the printing area RP that do not have any dots, the printing trajectory RU is added or changed as appropriate, and step S80 is executed again.

[0158] In step S70, pixels in the two-dimensional image represented by the image data De may be used instead of the voxels BX. In this case, the pixel data Df is divided for each printing operation by performing exclusive processing so that one dot of ink from one nozzle N belongs to one of the two-dimensionally arranged pixels. In this case, the pixels of the three-dimensional image represented by the pixel data Df and the pixels of the two-dimensional image represented by the image data De must correspond to each other.

[0159] As another example of a unit for exclusive processing between dots, particles may be used instead of voxels BX. In this case, the print area RP is represented by multiple particles in the virtual space VS. Preferably, each particle is spherical, with the same radius, and is arranged three-dimensionally along the print area RP. It is further preferable that the particle radius be adjusted appropriately depending on the printing resolution. The center of each particle indicates the position where the dot is to be arranged. The center of each particle is located in the virtual space VS by determining the intersection between the print area RP and a virtual line extending from each nozzle N of the head 3a in the ejection direction DE. Furthermore, while other particles are permitted to be arranged outside the radius of a certain particle, they are not permitted to partially invade inside the radius of the certain particle, and other particles are excluded. In other words, the surface of the print area RP is filled with multiple particles, and the position of each particle changes dynamically depending on the shape of the print area RP and the individual arrangement order. Particles defined in this way can more smoothly represent the curved surface of the printing area RP than the voxels BX described above, and can suppress the occurrence of moire in the printed image formed by the three-dimensional object printing apparatus 1.

[0160] In addition to the aforementioned example in which the mutual exclusion between particles is defined by a binary condition, such as whether the particle is inside or outside the radius, it may also be defined by a continuous condition depending on the distance from the center of the particles. More specifically, a continuous repulsive potential, expressed by a Gaussian function or the like, is set at the center of each particle so that the repulsive force that excludes other particles is maximized. The sum of the repulsive potentials between the particle to be newly placed and the surrounding particles already placed is then calculated. If this sum is lower than a certain threshold, the new particle is placed. On the other hand, if this sum is higher than a certain threshold, the placement of the new particle is suspended. By defining the mutual exclusion between particles using conditions that incorporate the concept of repulsive potential in this way, the curved surface of the printing area RP can be expressed more smoothly than when the mutual exclusion is defined by the aforementioned binary condition, and moiré patterns can be suppressed in the printed image formed by the three-dimensional object printing device 1.

[0161] 1-7.Printing process FIG. 20 is a flowchart showing the flow of the printing process executed in step S100. In this printing process, the three-dimensional object printing apparatus 1 executes a transport operation MC, a first printing operation MP1, a head retraction operation ME, a feed operation MF, and a second printing operation MP2 in this order, as shown in FIG. 20. First, an outline of these operations will be explained. For ease of explanation, FIG. 21 illustrates an example of printing using two adjacent printing trajectories RU out of the above-mentioned printing trajectories RU_1 to RU_3. Below, printing using these two printing trajectories RU will be explained as a representative example, but printing using other adjacent printing trajectories RU is similar.

[0162] The transport operation MC transports the workpiece W to a position and orientation that allows printing in the first area RP1 by the operation of one or both of the robot 4W and the Y-movement mechanism 4Y. The position and orientation are determined in step S60 described above.

[0163] In the first printing operation MP1, the Z movement mechanisms 2Z-1 to 2Z-6 and the X movement mechanism 2X are operated, while ink is ejected from each head 3a toward a first region RP1 (described below) on the workpiece W. This causes printing to be performed on the first region RP1. Here, the robot 4W does not operate. This stabilizes the posture of the workpiece W, preventing degradation of image quality due to the operation of the robot 4W.

[0164] Here, the timing of ink ejection from the head 3a to the workpiece W corresponds to the interval pi between the multiple points P described above. Therefore, if the interval pi between the multiple points P is set as shown in FIG. 11 in step S40, the timing of ink ejection from the head 3a to the workpiece W in step S100 corresponds to equal intervals along the X-axis as viewed along the Z-axis. This has the advantage of simplifying ejection timing control, since the ejection timing can be set at equal time intervals when the movement speed of the head 3a along the X-axis is constant. Furthermore, when ejecting UV ink, the ink landing density on the surface of the workpiece W that is inclined with respect to the X-axis is sparse, which has the advantage of making the UV ink less likely to drip and easier to harden. Furthermore, the ejection timing can be set based on equal time interval pulses from an encoder that detects the position of the head 3a along the X-axis, simplifying the device configuration.

[0165] Furthermore, in step S40 described above, when the intervals pi between the multiple points P are set as shown in Fig. 12 described above, in step S100, the timing of ejecting ink from the head 3a onto the workpiece W corresponds to each equidistant interval on the printing trajectory RU. As a result, when printing is performed using multiple printing trajectories RU, even if there is a difference in the shape of the printing areas RP due to adjacent printing trajectories RU, differences in print image quality are unlikely to occur between these printing areas RP, and degradation of print quality can be suppressed.

[0166] In the first printing operation MP1, if necessary, contact with the workpiece W is detected by the sensor 32 of the sensor unit 30 supported on the front Z movement mechanism 2Z in the movement direction of the X movement mechanism 2X, out of the Z movement mechanisms 2Z-0 and 2Z-7, and the ink on the workpiece W is cured, etc., by the light source 31 of the sensor unit 30 supported on the rear Z movement mechanism 2Z in the movement direction of the X movement mechanism 2X.

[0167] In the head retraction operation ME, the Z movement mechanisms 2Z-1 to 2Z-6 operate to move each head 3a in a direction away from the workpiece W. This prevents contact between each head 3a and the workpiece W when the feed operation MF is performed.

[0168] The feed operation MF transports the workpiece W to a position and orientation that allows printing in the second area RP2 by the operation of one or both of the robot 4W and the Y-movement mechanism 4Y. The position and orientation are determined in step S60 described above.

[0169] In the second printing operation MP2, the Z movement mechanisms 2Z-1 to 2Z-6 and the X movement mechanism 2X are operated, and ink is ejected from each head 3a toward the second region RP2 adjacent to the first region RP1 on the workpiece W. This causes printing to be performed on the second region RP2. Here, the robot 4W does not operate. This stabilizes the posture of the workpiece W, preventing a deterioration in image quality due to the operation of the robot 4W.

[0170] In the second printing operation MP2, if necessary, contact with the workpiece W is detected by the sensor 32 of the sensor unit 30 supported on the front Z movement mechanism 2Z in the movement direction of the X movement mechanism 2X, out of the Z movement mechanisms 2Z-0 and 2Z-7, and the ink on the workpiece W is cured, etc., by the light source 31 of the sensor unit 30 supported on the rear Z movement mechanism 2Z in the movement direction of the X movement mechanism 2X.

[0171] 21 is an explanatory diagram of the first print trajectory RU1 and the second print trajectory RU2. The first print trajectory RU1 and the second print trajectory RU2 correspond to two print trajectories RU adjacent to each other among the print trajectories RU_1 to RU_3.

[0172] When the first printing operation MP1 is performed, printing is performed on a first region RP1 on the workpiece W, as shown in FIG. 21. Here, ink is applied to the first region RP1 from the head 3a, which moves along the first printing trajectory RU1 from a starting point PS1 to an ending point PE1. The first printing trajectory RU1 is a path that extends parallel to the X-axis when viewed along the Z-axis. In the example shown in FIG. 21, the direction of the first printing trajectory RU1 when viewed along the Z-axis is the X1 direction.

[0173] On the other hand, when the second printing operation MP2 is performed, printing is performed on a second region RP2 on the workpiece W, which is different from the first region RP1. Here, ink is applied to the second region RP2 ejected from the head 3a, which moves along the second printing trajectory RU2 from the starting point PS2 to the ending point PE2. The second printing trajectory RU2 is a path that extends parallel to the X axis when viewed in the direction along the Z axis. In the example shown in FIG. 21, the direction of the second printing trajectory RU2 when viewed in the direction along the Z axis is the X2 direction. Note that the direction of the second printing trajectory RU2 may also be the X1 direction when viewed in the direction along the Z axis.

[0174] A portion of the first region RP1 and a portion of the second region RP2 overlap each other in an overlap region OV. That is, the first region RP1 and the second region RP2 share the overlap region OV. Furthermore, a portion of the first region RP1 other than the overlap region OV does not overlap the second region RP2. Similarly, a portion of the second region RP2 other than the overlap region OV does not overlap the first region RP1.

[0175] Figure 22 is an explanatory diagram of the first printing operation MP1. Figure 22 shows the state of the first printing operation MP1 as viewed in the X1 direction. As shown in Figure 22, during the execution of the first printing operation MP1, the robot 4W supports the workpiece W so that the first region RP1 is located directly below the head 3a.

[0176] During the first printing operation MP1, the robot 4W supports the workpiece W in a first posture where the angle between the normal to the first region RP1 and the nozzle surface FN of the head 3a at a first point on the first printing trajectory RU1 is 90 degrees. This improves the printing quality in the first region RP1. The first point is any point on the first printing trajectory RU1.

[0177] Figure 23 is an explanatory diagram of the printing operation. Figure 23 shows the state of the first printing operation MP1 as viewed in the Y1 direction. As shown in Figure 23, in the first printing operation MP1, the X movement mechanism 2X moves each head 3a and the sensor unit 30 in the X1 direction, and the Z movement mechanisms 2Z-1 to 2Z-6 move each head 3a along the Z axis so as to follow the surface WF of the workpiece W, while each head 3a ejects ink toward the first region RP1 based on the print data Img.

[0178] In this way, the first printing operation MP1 scans the head 3a along the first printing trajectory RU1 by operating the Z movement mechanism 2Z and the X movement mechanism 2X, and ejects ink from the head 3a toward the first region RP1 of the workpiece W.

[0179] Here, each head 3a moves along the first print trajectory RU1. The movement path of the sensor unit 30 is not particularly limited, but may be, for example, a path retreated in the Z1 direction from the first print trajectory RU1. Furthermore, during execution of the first print operation MP1, the sensor unit 30 may be operated as needed.

[0180] Figure 24 is an explanatory diagram of the second printing operation MP2. Figure 24 shows the state of the second printing operation MP2 as viewed in the X1 direction. As shown in Figure 24, during the execution of the second printing operation MP2, the robot 4W supports the workpiece W so that the second region RP2 is located directly below the head 3a.

[0181] During the second printing operation MP2, the robot 4W supports the workpiece W in a second posture where the angle between the normal at the position of the second region RP2 and the nozzle surface FN of the head 3a at a second point on the second print trajectory RU2 is 90 degrees. This improves the printing quality in the second region RP2. The second point is any point on the second print trajectory RU2, preferably a point corresponding to the reference point PM. In particular, the first and second points are at different positions when viewed in a direction intersecting the print trajectory RU. This improves the printing quality using multiple print trajectories RU.

[0182] Although not shown, in the second printing operation MP2, similar to the first printing operation MP1, the X movement mechanism 2X moves each head 3a and the sensor unit 30 along the X axis, and the Z movement mechanisms 2Z-1 to 2Z-6 move each head 3a along the Z axis so as to follow the surface WF of the workpiece W, while each head 3a ejects ink toward the second region RP2 based on the printing data Img.

[0183] In this way, the second printing operation MP2 scans the head 3a along the second printing trajectory RU2 by operating the Z movement mechanism 2Z and the X movement mechanism 2X, and ejects ink from the head 3a toward the second region RP2 of the workpiece W.

[0184] By the above-described operation of the three-dimensional object printing apparatus 1, that is, the printing method using the three-dimensional object printing apparatus 1, printing can be performed on the first area RP1 and the second area RP2 of the workpiece W.

[0185] As described above, in step S100, the Z movement mechanism 2Z and the X movement mechanism 2X are operated to scan the head 3a along the printing trajectory RU, and ink is ejected from the head 3a toward the workpiece W. Also, in step S100, the posture of the workpiece W is fixed by the operation of the robot 4W over the period during which ink is being ejected from the head 3a. This makes it possible to prevent printing misalignment due to vibrations caused by the operation of the robot 4W. Note that the posture of the workpiece W may be changed during step S100 depending on the shape of the workpiece W or the range of the printing area RP, etc.

[0186] In the printing method described above, the posture of the workpiece W due to the operation of the robot 4W is determined based on the printing trajectory LM or RU, thereby improving print quality. Furthermore, because the printing trajectory LM or RU is determined in advance based on the shape of the workpiece W, user convenience is improved and the time required to determine the printing trajectory RU can be shortened compared to modes in which the printing trajectory LM or RU is determined using direct teaching.

[0187] In this embodiment, as described above, the area printed by scanning the head 3a along the second print trajectory RU2 overlaps at least a portion of the area printed by scanning the head 3a along the first print trajectory RU1. This prevents white streaks from appearing between the first area RP1, which is the area printed by the first print trajectory RU1, and the second area RP2, which is the area printed by the second print trajectory RU2. As a result, print quality can be improved.

[0188] Here, in step S60, the posture of the workpiece W is determined so that the angle between the normal to the printing area RP at the position corresponding to the first point, which is the reference point PM on the first printing trajectory RU1, and the nozzle surface FN of the head 3a is 90 degrees, and the posture of the workpiece W is determined so that the angle between the normal to the printing area RP at the position corresponding to the second point, which is the reference point PM on the second printing trajectory RU2, and the nozzle surface FN of the head 3a is 90 degrees. In this way, because the posture of the workpiece W is determined for each printing trajectory RU, it is possible to reduce differences in printing quality between printing trajectories RU. As a result, it is possible to improve the printing quality using multiple printing trajectories RU.

[0189] 2. Variations Each of the above-mentioned exemplary embodiments can be modified in various ways. Specific modified embodiments that can be applied to each of the above-mentioned embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be appropriately combined within the scope of not contradicting each other.

[0190] 2-1. Variation 1 In the above-described embodiment, an example is given in which the number of Z movement mechanisms 2Z that move the heads 3a along the Z axis is six, but this is not limited to this embodiment, and the number or the number of heads 3a may be five or less or seven or more.

[0191] 2-2. Variation 2 In the above-described embodiment, the robot 4W is exemplified as a six-axis articulated robot, but the number of joints possessed by the robot 4W is not limited to six, and may be two to five or seven or more.

[0192] 3. Notes A summary of this disclosure is provided below.

[0193] (Appendix 1) A first aspect, which is a preferred example of the printing method of the present disclosure, is a printing method for printing using a three-dimensional object printing device that includes a robot that supports a three-dimensional workpiece, a head having a nozzle that ejects liquid toward the workpiece, a first movement mechanism that moves the head along a first axis, and a second movement mechanism that moves the head along a second axis that intersects with the first axis, and includes a printing area determination step that determines a printing area of ​​the workpiece that will receive liquid from the head based on the shape of the workpiece, a printing trajectory creation step that creates a printing trajectory that scans the head over the printing area, and an attitude determination step that determines the attitude of the workpiece due to the operation of the robot based on the printing trajectory.

[0194] In the above-described embodiment, the posture of the workpiece caused by the robot's operation is determined based on the printing trajectory, thereby improving print quality. Furthermore, since the printing trajectory is determined in advance based on the shape of the workpiece, it is more convenient for the user and reduces the time required to determine the printing trajectory compared to embodiments in which the printing trajectory is determined using direct teaching.

[0195] (Note 2) In a second aspect, which is a preferred example of the first aspect, the method further includes a printing step of scanning the head along the printing trajectory by operation of the first movement mechanism and the second movement mechanism and discharging liquid from the head toward the workpiece, and the posture of the workpiece is fixed by operation of the robot during the period when liquid is being discharged from the head in the printing step. In the above aspect, it is possible to suppress printing misalignment caused by vibrations accompanying robot operation.

[0196] (Note 3) In a third aspect, which is a preferred example of the second aspect, the attitude of the workpiece is determined in the attitude determination step so that the angle between the normal to the nozzle face of the head and the surface of the printing area at a specific position in the printing area along the printing trajectory is 90 degrees. In this aspect, the landing position of the liquid from the head onto the surface of the workpiece is less likely to deviate than in an aspect in which the angle deviates from 90 degrees, thereby improving print quality.

[0197] (Appendix 4) In a fourth aspect, which is a preferred example of the third aspect, the specific point is determined in the attitude determination step based on the angle between the normal to the nozzle face and the printing area along the printing trajectory. In this aspect, even if the printing area has an uneven shape, the attitude of the workpiece can be determined so as to minimize the deviation of the landing position of the liquid from the head onto the surface of the workpiece. As a result, printing quality can be improved.

[0198] (Supplementary Note 5) In the fifth aspect, which is a preferred example of the fourth aspect, the orientation determination step obtains the angle between the normal and the printing area at multiple points in the printing area along the printing trajectory, and determines the specific points so as to minimize the amount of change or variation in the angle. In this aspect, it is possible to reduce variation in the landing position of liquid at multiple points in the printing area. As a result, it is possible to improve print quality.

[0199] (Supplementary Note 6) In a sixth aspect, which is a preferred example of the fifth aspect, in the attitude determination step, the plurality of points include a point at one end of the print area and a point at the other end. In this aspect, it is possible to reduce deviations in the landing position of liquid at the ends of the print area. As a result, it is possible to improve print quality.

[0200] (Appendix 7) In the seventh aspect, which is a preferred example of any of the first to sixth aspects, the attitude determination step acquires the distance between the nozzle surface of the head and the surface of the printing area at multiple points on the printing trajectory, and determines the attitude of the workpiece due to the operation of the robot based on the distance. In the above aspect, it is possible to reduce variation in the liquid ejection distance at multiple points in the printing area. As a result, it is possible to improve print quality.

[0201] (Appendix 8) In an eighth aspect, which is a preferred example of any of the first to sixth aspects, in the print trajectory creation step, a first print trajectory and a second print trajectory adjacent to the first print trajectory are created as the print trajectories, and the area printed by scanning the head along the second print trajectory overlaps at least a portion of the area printed by scanning the head along the first print trajectory. In this aspect, it is possible to prevent white streaks from occurring between the area printed by the first print trajectory and the area printed by the second print trajectory. As a result, print quality can be improved.

[0202] (Appendix 9) In the ninth aspect, which is a preferred example of the eighth aspect, in the attitude determination step, the attitude of the work is determined so that the angle between the normal to the position of the printing area corresponding to a first point on the first printing trajectory and the nozzle surface of the head is 90 degrees, and the attitude of the work is determined so that the angle between the normal to the position of the printing area corresponding to a second point on the second printing trajectory and the nozzle surface of the head is 90 degrees. In the above aspect, since the attitude of the work is determined for each printing trajectory, the difference in printing quality between printing trajectories can be reduced. As a result, the printing quality of multiple printing trajectories can be improved.

[0203] (Appendix 10) In the tenth aspect, which is a preferred example of the second aspect, in the printing process, the timing of ejecting liquid from the head onto the workpiece corresponds to equal intervals in the direction along the second axis as viewed in the direction along the first axis. This aspect has the advantage of simplifying ejection timing control, since the ejection timing can be set at equal time intervals when the head's movement speed along the second axis is constant. Furthermore, when ejecting UV ink, the landing density of the liquid on the surface of the workpiece that is inclined with respect to the second axis is sparse, which makes the UV ink less likely to drip and easier to harden. Furthermore, the ejection timing can be set based on equal time interval pulses from an encoder that detects the position of the head in the direction along the second axis, simplifying the device configuration.

[0204] (Appendix 11) In the eleventh aspect, which is a preferred example of the second aspect, in the printing process, the timing of ejecting liquid from the head onto the workpiece corresponds to each equidistant interval on the printing trajectory. In the above aspect, when printing is performed using multiple printing trajectories, even if there is a difference in the shape of the printing area between adjacent printing trajectories, there is unlikely to be a difference in print image quality between these printing areas, so a decrease in print quality can be suppressed.

[0205] (Supplementary Note 12) In a twelfth aspect, which is a preferred example of any of the first to eleventh aspects, the method further includes the steps of creating pixel data on the printing area based on image data representing an image to be printed, and determining the amount of liquid to be ejected from the head based on the pixel data on the printing area that intersects with a normal to the nozzle face of the head that passes through the printing trajectory. In the above aspects, an image represented by the image data can be printed in the printing area.

[0206] (Appendix 13) A thirteenth aspect, which is a suitable example of a three-dimensional object printing device of the present disclosure, comprises a robot that supports a three-dimensional workpiece, a head having a nozzle that ejects liquid toward the workpiece, a first movement mechanism that moves the head along a first axis, and a second movement mechanism that moves the head along a second axis that intersects with the first axis, and the device creates a first printing trajectory and a second printing trajectory as printing trajectories that cause the head to scan over a printing area of ​​the workpiece, determines the posture of the workpiece by operation of the robot based on the printing trajectories, scans the head along the first printing trajectory by operation of the first movement mechanism and the second movement mechanism, and executes a first printing operation that ejects liquid from the head toward the first area of ​​the workpiece, A second printing operation is performed in which the head is scanned along the second printing trajectory by the operation of the first moving mechanism and the second moving mechanism, and liquid is ejected from the head toward a second region of the workpiece, the first region and the second region overlap each other at least partially, and in the first printing operation, the workpiece is supported by the robot in a first posture of the workpiece at a first point on the first printing trajectory, where the angle between the normal at the position of the first region and the nozzle surface of the head is 90 degrees, and in the second printing operation, the workpiece is supported by the robot in a second posture of the workpiece at a second point on the second printing trajectory, where the angle between the normal at the position of the second region and the nozzle surface of the head is 90 degrees.

[0207] In the above aspect, print quality can be improved.

[0208] (Supplementary Note 14) In a fourteenth aspect, which is a preferred example of the thirteenth aspect, the first point and the second point are at different positions in a direction intersecting the print trajectory. In the above aspect, it is possible to improve the print quality using a plurality of print trajectories. [Explanation of symbols]

[0209] 1...3D object printing device, 2...movement mechanism, 2X...X-movement mechanism (second movement mechanism), 2Z...Z-movement mechanism, 2Z-0 to 2Z-7...Z-movement mechanism (first movement mechanism), 2a...column, 2b...beam, 2c...rail, 2d...movable body, 2e...support, 3...head unit, 3-1 to 3-6...head unit, 3a...head, 3a-A...head, 3a-B...head, 3a_1...head, 3a_2...head, 3a_3...head, 3e...switch circuit, 3g...support, 4...support mechanism, 4W...robot, 4Y...Y-movement mechanism, 4a...support, 4b...rail, 4c...movable body, 4d...stage, 5... Controller, 5a...memory circuit, 5b...processing circuit, 6...control module, 6a...timing signal generation circuit, 6b...power supply circuit, 6c...control circuit, 6d...drive signal generation circuit, 7...computer, 7a...memory circuit, 7b...processing circuit, 8...maintenance mechanism, 8C...cleaning device, 8F...cap mechanism, 8M...cleaning device moving mechanism, 8P...cap cover, 10...base, 10a...surface, 10b...opening, 10c...mounting portion, 11...case, 11a...visual recognition portion, 30...sensor unit, 30-1...sensor unit, 30-2...sensor unit, 31... Light source, 32...sensor, 50...control unit, A...point, AR...arm, B...point, BX...voxel, CLK...clock signal, CNG...change signal, Com...drive signal, D1...output signal, D3...signal, DE...ejection direction, DM...main scanning direction, DN...nozzle row direction, DS...sub-scanning direction, Da...path information, Db...posture information, Dc...workpiece information, Dd...printing area information, De...image data, Df...pixel data, Dm...distance, Dt1...dot, Dt2...dot, Dt3...dot, Dw...output, Dx...output signal, Dz-0...output signal, FN...nozzle surface, Img...printing data , LAT... latch signal, LE... edge, LE_1... first edge, LM... printing trajectory, LM_1... printing trajectory, LM_2... printing trajectory, LM_3... printing trajectory, LS... sub-scanning reference line, MC... transport operation, ME... head retraction operation, MF... feed operation, MP1... first printing operation, MP2... second printing operation, N... nozzle, NL... nozzle row, NLa... nozzle row, NLb... nozzle row, OV... overlapping area, PD... drive pulse, PE1... end point, PE2... end point, PG... ejection distance, PG-A... ejection distance, PG-B... ejection distance, PM... reference point, PM_1... reference point, PM_2... reference point, PM_3... reference point,POL...Polygon, POL_1...Intersection polygon, POL_2...Polygon, PS1...Start point, PS2...Start point, PTS...Timing signal, PV...Vertex, PV_1...First vertex, PV_2...Second vertex, Pa...Intersection point, Pb...Interpolation point, RP...Print area, RP1...First area, RP2...Second area, RP3...Third area, RU...Print trajectory, RU1...First print trajectory, RU2...Second print trajectory, RU_1~RU_3...Print trajectory, S10...Step (Print area determination process), S20...Step, S30...Step (Print trajectory creation process), S40...Step, S50...Step, S60...Step (Posture determination process), S70...Step, S80...Step, S90...Step, S100...Step (Printing process) process), SI...control signal, SI-1 to SI-6...control signal, Sw...control signal, Sx...control signal, Sz-0 to Sz-7...control signal, TCP...tool center point, V...normal vector, VBS...offset potential, VHV...power supply potential, VPM...main scanning virtual plane, VPM_1...first main scanning virtual plane, VPM_2...second main scanning virtual plane, VPM_3...third main scanning virtual plane, VPS...sub-scanning virtual plane, VS...virtual space, Va...vector, Vb...vector, Vc_1...first vertex vector, Vc_2...second vertex vector, Vp...normal vector, Vpm...normal vector, Vpm_1 to Vpm_3...normal vector, W...work, WF...surface, dCom...waveform specification signal, pi...interval, θ...angle.

Claims

1. A robot that supports three-dimensional workpieces, a head having a nozzle for discharging a liquid toward the workpiece; a first moving mechanism that moves the head along a first axis; a second movement mechanism that moves the head along a second axis that intersects with the first axis, a printing area determination step of determining a printing area of ​​the workpiece to be applied with liquid from the head based on the shape of the workpiece; a print trajectory creation step of creating a print trajectory for scanning the head over the print area; and a posture determination step of determining a posture of the workpiece due to the operation of the robot based on the printing trajectory. A printing method characterized by:

2. The method further includes a printing step of scanning the head along the printing track by operating the first movement mechanism and the second movement mechanism, and ejecting liquid from the head toward the workpiece, In the printing process, the posture of the workpiece is fixed by the operation of the robot throughout the period during which the liquid is being ejected from the head.

2. The printing method according to claim 1.

3. In the attitude determination step, The posture of the workpiece is determined so that the angle formed between the normal to the nozzle surface of the head and the surface of the printing area at a specific position of the printing area along the printing trajectory is 90 degrees.

3. The printing method according to claim 2.

4. In the attitude determination step, determining the specific point based on an angle between a normal to the nozzle face and the print area along the print trajectory; 4. The printing method according to claim 3.

5. In the attitude determination step, obtaining angles between the normal and the printing area at a plurality of points along the printing trajectory; determining the specific point so that the amount of change or variation in the angle is small; 5. The printing method according to claim 4.

6. In the attitude determination step, The plurality of points include points at one end and points at the other end of the printing area.

6. The printing method according to claim 5.

7. In the attitude determination step, obtaining the distance between the nozzle face of the head and the surface of the printing area at a plurality of points on the printing trajectory; determining a posture of the workpiece due to the operation of the robot based on the distance; 7. The printing method according to claim 1, wherein the printing method is a printing method for printing a plurality of images.

8. In the printing track creation step, As the printing trajectory, a first printing trajectory and a second printing trajectory adjacent to the first printing trajectory are created; an area printed by scanning the head along the second print trajectory overlaps with at least a portion of an area printed by scanning the head along the first print trajectory; 7. The printing method according to claim 1, wherein the printing method is a printing method for printing a plurality of images.

9. In the attitude determination step, determining the posture of the workpiece so that an angle formed between a normal to the printing area corresponding to a first point on the first printing trajectory and a nozzle surface of the head is 90 degrees; determining the posture of the workpiece so that the angle between the normal to the printing area at a position corresponding to a second point on the second printing trajectory and the nozzle surface of the head is 90 degrees; 9. The printing method according to claim 8.

10. In the printing process, the timing of ejecting the liquid from the head to the workpiece is a timing corresponding to each equidistant interval in a direction along the second axis as viewed in a direction along the first axis.

3. The printing method according to claim 2.

11. In the printing process, the timing of ejecting the liquid from the head to the workpiece corresponds to each equidistant interval on the printing trajectory.

3. The printing method according to claim 2.

12. creating pixel data on the printing area based on image data representing an image to be printed; determining an ejection amount of liquid to be ejected from the head based on pixel data on the printing area that intersects with a normal to the nozzle face of the head that passes through the printing trajectory, 7. The printing method according to claim 1, wherein the printing method is a printing method for printing a plurality of images.

13. A robot that supports three-dimensional workpieces, a head having a nozzle for discharging a liquid toward the workpiece; a first moving mechanism that moves the head along a first axis; a second movement mechanism that moves the head along a second axis that intersects with the first axis, creating a first printing trajectory and a second printing trajectory as printing trajectories for scanning the head over the printing area of ​​the workpiece; Based on the printing trajectory, a posture of the workpiece due to the operation of the robot is determined; a first printing operation is performed in which the head is scanned along the first printing track by the operation of the first movement mechanism and the second movement mechanism, and liquid is ejected from the head toward a first region of the workpiece; a second printing operation is performed in which the head is caused to scan along the second printing track by the operation of the first movement mechanism and the second movement mechanism, and liquid is ejected from the head toward a second region of the workpiece; the first region and the second region at least partially overlap each other, In the first printing operation, the workpiece is supported by the robot in a first posture of the workpiece such that an angle formed between a normal at a position of the first region and a nozzle surface of the head at a first point on the first printing trajectory is 90 degrees; In the second printing operation, the workpiece is supported by the robot in a second posture of the workpiece such that an angle formed between a normal at a position of the second region and a nozzle surface of the head at a second point on the second printing trajectory is 90 degrees. A three-dimensional object printing device characterized by the above.

14. the first point and the second point are at different positions in a direction intersecting the printing trajectory; The three-dimensional object printing device according to claim 13 .

Images