3D printing apparatus

Abstract

This design prevents the print head from colliding with the workpiece during both the first and second printing operations, while suppressing a decrease in print quality. [Solution] The three-dimensional object printing apparatus performs a first printing operation in which the head is moved along a first path by the operation of a Z-movement mechanism and an X-movement mechanism, and liquid is discharged from the head toward a three-dimensional workpiece; and a second printing operation in which the head is moved along a second path by the operation of a Z-movement mechanism and an X-movement mechanism, and liquid is discharged from the head toward a workpiece. The first path and the second path are aligned with each other in a sub-scanning direction that intersects with the direction in which the head is scanned. When the distance between the head and the workpiece in the first printing operation is called the first distance, and the distance between the head and the workpiece in the second printing operation is called the second distance, the first distance and the second distance are different from each other when the head is in a first position in the direction along the X axis.

Description

Technical Field

[0001] This disclosure relates to a three-dimensional object printing apparatus.

Background Art

[0002] Conventionally, a three-dimensional object printing apparatus that performs printing on the surface of a three-dimensional workpiece by an inkjet method is known. For example, the apparatus described in Patent Document 1 has a plurality of heads and a head vertical movement mechanism that moves the plurality of heads up and down. After measuring the distance between the head and the printing surface with a distance measuring device, the apparatus moves the head up and down based on the measurement result and performs printing while maintaining a constant interval between the workpiece and the printing surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, the workpieces to be printed have become diversified, and the demand for printing on workpieces having curved surfaces has been increasing.

[0005] However, in the apparatus described in Patent Document 1, since the interval between the workpiece and the printing surface is maintained at a constant value regardless of the shape of the workpiece, there is a possibility that the head may collide with the workpiece depending on the shape of the workpiece.

Means for Solving the Problems

[0006] To solve the above problems, one embodiment of the three-dimensional object printing apparatus of the present disclosure comprises a head for ejecting liquid, a Z-movement mechanism for moving the head along the Z-axis, and an X-movement mechanism for moving the head along the X-axis by moving the Z-movement mechanism along the X-axis intersecting the Z-axis, wherein the apparatus performs a first printing operation in which the head is moved along a first path by the operation of the Z-movement mechanism and the X-movement mechanism and liquid is ejected from the head toward a three-dimensional workpiece, and a second printing operation in which the head is moved along a second path by the operation of the Z-movement mechanism and the X-movement mechanism and liquid is ejected from the head toward the workpiece, wherein the first path and the second path are aligned with each other in a sub-scanning direction intersecting the direction in which the head is scanned, and when the distance between the head and the workpiece in the first printing operation is defined as the first distance and the distance between the head and the workpiece in the second printing operation is defined as the second distance, the first distance and the second distance are different from each other when the head is located at a first position in the direction toward the X-axis. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic perspective view showing the three-dimensional object printing apparatus according to the first embodiment. [Figure 2] This is a block diagram showing the electrical configuration of a three-dimensional object printing apparatus according to the first embodiment. [Figure 3] Figure 2 is an explanatory diagram of the data stored in a computer. [Figure 4] This is a perspective view showing the general layout of the head unit. [Figure 5] This is a flowchart for generating the print path in the first embodiment. [Figure 6] This is an explanatory diagram for obtaining the shape of a workpiece. [Figure 7] This is an explanatory diagram for creating a reference route. [Figure 8] This is a diagram illustrating the creation of a virtual print path. [Figure 9] This is an explanatory diagram illustrating the collision detection of the head with the workpiece and the calculation of the adjustment amount. [Figure 10] It is an explanatory diagram of creating a printing path. [Figure 11] It is an explanatory diagram of the first distance, the second distance, the third distance, and the fourth distance after adjustment. [Figure 12] It is an explanatory diagram of another example of creating a printing path. [Figure 13] It is a flowchart showing the flow of a printing operation. [Figure 14] It is an explanatory diagram of the first path and the second path. [Figure 15] It is an explanatory diagram of the first printing operation. [Figure 16] It is an explanatory diagram of the first printing operation. [Figure 17] It is an explanatory diagram of the second printing operation. [Figure 18] It is an explanatory diagram of the first distance, the second distance, the third distance, and the fourth distance in a printing operation. [Figure 19] It is an explanatory diagram of creating a reference path in the second embodiment. [Figure 20] It is an explanatory diagram of the first path and the second path in the second embodiment. [Figure 21] It is an explanatory diagram of the first printing operation in the second embodiment. [Figure 22] It is an explanatory diagram of the second printing operation in the second embodiment.

Mode for Carrying Out the Invention

[0008] Hereinafter, preferred embodiments according to the present disclosure will be described while referring to the accompanying drawings. Note that the dimensions and scales of each part in the drawings are appropriately different from the actual ones, and there are also some parts shown schematically for easy understanding. Further, the scope of the present disclosure is not limited to these embodiments unless there is a description specifically limiting the present disclosure in the following description.

[0009] In the following description, for convenience, the X-axis, Y-axis, and Z-axis that intersect each other are appropriately used. Also, in the following description, one direction along the X-axis is the X1 direction, and the direction opposite to the X1 direction is the X2 direction. Similarly, the directions opposite to each other along the Y-axis are the Y1 direction and the Y2 direction. Also, the directions opposite to each other 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 the world coordinate system set in the space where the later-described moving mechanism 2 and support mechanism 4 are installed. Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. In the following, for convenience, the case of controlling the operation of the moving mechanism 2 using the world coordinate system is exemplified.

[0011] Note that the Z-axis does not have to be a vertical axis. Also, the X-axis, Y-axis, and Z-axis typically intersect each other at right angles, but are not limited to this, and may not intersect at right angles. For example, the X-axis, Y-axis, and Z-axis may intersect each other at an angle within the range of 80° or more and 100° or less.

[0012] 1. First Embodiment 1-1. Outline of the Printing Apparatus FIG. 1 is a perspective view showing an outline of a three-dimensional object printing apparatus 1 according to the first embodiment. The three-dimensional object printing apparatus 1 is an apparatus that performs printing on the surface of a three-dimensional workpiece W by an inkjet method. In FIG. 1, for convenience of explanation, the later-described base 10 and case 11 are schematically shown by a two-dot chain line.

[0013] The workpiece W has a surface WF including a region to be printed. In the example shown in FIG. 1, the workpiece W is a substantially hemispherical body, and the surface WF is a substantially convex spherical surface. Note that the size, shape, or installation posture of the workpiece W is not limited to the example shown in FIG. 1 and is arbitrary.

[0014] As shown in Figure 1, the 3D object printing apparatus 1 comprises a base 10, a case 11, a moving 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. Below, each part of the 3D object printing apparatus 1 will be briefly described in order based on Figure 1. In the following, head units 3-1 to 3-6 may each be referred to as head unit 3, and sensor units 30-1 and 30-2 may each be referred to as sensor unit 30.

[0015] The base 10 is a platform having a surface 10a that supports the moving mechanism 2. Surface 10a faces in the Z1 direction. The moving mechanism 2 is fixed to the base 10 either directly or indirectly via screws or other components.

[0016] In the example shown in Figure 1, the base 10 is box-shaped, with surface 10a facing the Z1 direction. An opening 10b is provided on 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 surface 10a. A mounting section 10c is also provided on surface 10a. A workpiece W to be used for subsequent printing, etc., is placed on the mounting section 10c so that it can be accessed by the robot 4W. Note that the configuration and arrangement of the mounting section 10c are not limited to the example shown in Figure 1.

[0017] A case 11 enclosing the moving mechanism 2, etc., is positioned 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 for housing the moving mechanism 2 and other structures supported by the base 10. The case 11 has, for example, a plurality of columns and beams made of metal, and a plurality of plate materials such as a top plate and wall plates made of transparent material such as acrylic resin. The case 11 also has a viewing section 11a. The viewing section 11a is a window for the user to view the workpiece W held by the robot 4W in a direction along the Y axis. The case 11 may also be provided with a door (not shown) for supplying and retrieving the workpiece W to and from the support mechanism 4. This door may also serve as the viewing section 11a.

[0018] Note that the configuration of the base 10 is not limited to the example shown in Figure 1 and is arbitrary. Also, the base 10 and case 11 may be provided as needed and may be omitted. If the base 10 is omitted, each component of the 3D object printing device 1 will be 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 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 the Z-axis and the X-axis intersecting the Z-axis. The movement mechanism 2 comprises an X-movement mechanism 2X and Z-movement mechanisms 2Z-0 to 2Z-7. In the following, each of the Z-movement mechanisms 2Z-0 to 2Z-7 may be referred to as Z-movement mechanism 2Z.

[0020] The X-movement mechanism 2X is a linear motion mechanism that moves the Z-movement mechanism 2Z along the X-axis. In the example shown in Figure 1, the X-movement mechanism 2X supports the head units 3-1 to 3-6 and 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 together along the X-axis. As a result, the head units 3-1 to 3-6 and sensor units 30-1 and 30-2 move along the X-axis relative to the workpiece W. Consequently, the X-movement mechanism 2X moves the head 3a, described later, along the X-axis.

[0021] The X-movement mechanism 2X comprises a pair of columns 2a and beams 2b, a pair of rails 2c, and a movable body 2d. These are essentially rigid bodies and are made of metal such as iron, stainless steel, or aluminum alloy.

[0022] Each of the pair of columns 2a is a member that extends in the Z1 direction from the surface 10a of the base 10. In the example shown in Figure 1, the pair of columns 2a are aligned along the X axis. A beam 2b is spanned across the ends of the pair of columns 2a. The beam 2b is a member that is supported by the pair of columns 2a. In the example shown in Figure 1, the beam 2b extends along the X axis and has a plate-like shape with the Z axis as its thickness. A pair of rails 2c are arranged on the Z1-facing surface of the beam 2b. Each of the pair of rails 2c is a linear rail that guides the movable body 2d to move relative to the pair of columns 2a and beam 2b in the direction along the X axis, and extends 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 a pair of columns 2a and beams 2b in the direction along the X-axis. In the example shown in Figure 1, it is plate-shaped with the direction along the Z-axis as the thickness direction. Although not shown, the X-movement mechanism 2X includes an actuator having an electric motor such as a servo motor that generates the 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 Figure 1.

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

[0024] The support 2e may be attached to the movable body 2d via a manual or electric linear motion mechanism that moves the support 2e in the direction along the Z axis relative to the movable body 2d. In this case, the Z-movement mechanisms 2Z-0 to 2Z-7 can be moved together in the direction along the Z axis. Furthermore, the number of Z-movement mechanisms 2Z attached to the X-movement mechanism 2X is not limited to the example shown in Figure 1, and may be 7 or fewer, or 9 or more.

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

[0026] In contrast, the Z-movement mechanisms 2Z-0 and 2Z-7 are linear motion mechanisms that move the sensor unit 30 relative to the workpiece W along the Z-axis, and operate independently of the aforementioned 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, Z-movement mechanisms 2Z-0 and 2Z-7 each change the relative position of the sensor unit 30 relative to the workpiece W in the direction along the Z-axis, independently of the head units 3-1 to 3-6.

[0027] The Z-movement mechanisms 2Z-0 to 2Z-7 described above are configured similarly to each other, except that the objects being moved differ as described above. Although not shown in the figures, each of the Z-movement mechanisms 2Z-0 to 2Z-7 includes a rail, a movable body, an actuator, and an encoder. The rail is a linear rail fixed to the support 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 the 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 the Z-movement mechanisms 2Z-0 to 2Z-7 may differ from each other. However, from the viewpoint of cost reduction, it is preferable that the Z-movement mechanisms 2Z-0 to 2Z-7 have the same configuration. Also, the Z-movement mechanism 2Z-0 may be provided as needed or omitted.

[0028] Furthermore, each of the Z-movement mechanisms 2Z-0 to 2Z-7 may be fitted with either the head unit 3 or the sensor unit 30 via an adjustment mechanism for fine-tuning the posture of the head unit 3 or the sensor unit 30. Also, the number of Z-movement mechanisms 2Z to which the head unit 3 is fitted is not limited to the example shown in Figure 1, and may be five or fewer, or seven or more. Additionally, the number of Z-movement mechanisms 2Z to which the sensor unit 30 is fitted is not limited to the example shown in Figure 1, and may be one or three or more. Furthermore, both the head unit 3 and the sensor unit 30 may be fitted 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, such as a piezoelectric or thermal type, which ejects ink, an example of a "liquid," toward the workpiece W in the Z2 direction, which is 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 curing or solidifying the ink on the workpiece W, and a pressure regulating valve for maintaining the ink pressure in the head 3a at a negative pressure within a predetermined range.

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

[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 Figure 1, the sensor unit 30 has a sensor 32 and a light source 31.

[0032] The sensor 32 includes, for example, one or both of the following: a contact-type sensor that detects contact with the workpiece W, and an optical displacement sensor that detects the distance between the workpiece W and the sensor. The light source 31 emits energy such as light, heat, electron beams, or radiation to cure or solidify the ink on the workpiece W. The light source 31 is composed of, for example, a light-emitting element such as an LED (Light Emitting Diode) that emits ultraviolet light. In addition, one or both of the sensor 32 and the light source 31 may be provided as needed or omitted.

[0033] The support mechanism 4 is a mechanism that supports the workpiece W and can change the orientation of the workpiece W. In the example shown in Figure 1, the support mechanism 4 includes a Y-movement mechanism 4Y and a robot 4W.

[0034] The Y-movement mechanism 4Y is a linear motion mechanism that moves the robot 4W along the Y-axis. This movement makes it possible to change 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 Y-axis. In the example shown in Figure 1, the Y-movement mechanism 4Y is located within the base 10.

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

[0036] The support 4a is a base that is fixedly installed on the base 10. In the example shown in Figure 1, the support 4a extends in the direction along the Y axis and has a plate-like shape with the direction along the Z axis as the thickness direction. A pair of rails 4b are arranged on the surface of the support 4a facing the Z1 direction. The support 4a may be part of the base 10, or it may be formed integrally with the base 10. Furthermore, the shape of the support 4a is not limited to the example shown in Figure 1 and is arbitrary.

[0037] Each of the pair of rails 4b is a linear rail that guides the movable body 4c to move relative to the support 4a in a direction along the Y-axis, and extends in a 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 4a.

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

[0039] Stage 4d is a component that supports the robot 4W. In the example shown in Figure 1, stage 4d is plate-shaped. An electrically or manually operated adjustment mechanism may be interposed between stage 4d and the movable body 4c to adjust the position and orientation of stage 4d relative to the movable body 4c. Alternatively, stage 4d may be integrated 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. The operation of the Y-movement mechanism 4Y allows the workpiece W to be moved with high precision along the Y-axis without operating the robot 4W. The Y-movement mechanism 4Y may be provided as needed or omitted. In this case, the robot 4W is directly attached to the base 10 or the like.

[0041] Robot 4W supports the workpiece W. Robot 4W can change the position and orientation of the workpiece W and supports the workpiece W in a desired position and orientation that allows it to receive ink ejected from the heads 3a of head units 3-1 to 3-6 during the printing operation. In the example shown in Figure 1, robot 4W is a 6-axis articulated robot with an arm AR. Here, the base of robot 4W is fixed to the stage 4d. A hand mechanism for holding the workpiece W by electrostatic adsorption or other means, or by gripping, is attached as an end effector to the tip of arm AR of robot 4W. The workpiece W may also be fixed to the tip of 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 Figure 1, the maintenance mechanism 8 includes a cap mechanism 8F, a cap cover 8P, a cleaning device 8C, and a cleaning device moving mechanism 8M.

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

[0044] The cap cover 8P is movable along the Y-axis by a mechanism (not shown), and can switch between overlapping and not overlapping the cap mechanism 8F when viewed along the Z-axis. When the cap mechanism 8F is not used, the cap cover 8P overlaps the cap mechanism 8F when viewed along the Z-axis and functions as a cover over the cap mechanism 8F. In this state, the cap cover 8P can also be used as an inspection stand to support the medium for test printing. On the other hand, when the cap mechanism 8F is used, the cap cover 8P does not overlap the cap mechanism 8F when viewed along the Z-axis. The cap cover 8P may also overlap the cleaning device 8C when viewed along the Z-axis, but when the cleaning device 8C is used, it does not overlap the cleaning device 8C when viewed along the Z-axis.

[0045] The cleaning device 8C is a mechanism for wiping 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 Figure 1, the cleaning device 8C is positioned in the Y2 direction relative to the cap mechanism 8F.

[0046] The cleaning device moving mechanism 8M moves the cleaning device 8C in a direction along the Y-axis. This causes the cleaning device moving mechanism 8M to move the cleaning device 8C relative to the head 3a along the Y-axis. In the example shown in Figure 1, the cleaning device moving mechanism 8M moves the cap mechanism 8F in addition to the cleaning device 8C in a direction along the Y-axis. The cleaning device moving mechanism 8M, for example, similar to the Y-movement mechanism 4Y, includes a support fixed to the base 10, a pair of rails extending in a direction along the Y-axis, and a movable body that moves relative to the support in a direction along the Y-axis along the pair of rails. The cleaning device 8C and the cap mechanism 8F are fixed to the movable body by screws or the like.

[0047] The cleaning device moving mechanism 8M can switch between multiple states, including a state in which the cleaning device 8C can perform cleaning of the head 3a and a state in which the capping mechanism 8F can perform capping of the head 3a. Furthermore, when cleaning the head 3a with the cleaning device 8C, the cleaning device moving mechanism 8M moves the cleaning device 8C in a 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 Figure 1. For example, the cap mechanism 8F and the cap cover 8P may be provided or omitted as needed. Also, the maintenance mechanism 8 may be provided or omitted as needed.

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

[0050] The control unit 50 controls the operation 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 Figure 2, the control unit 50 includes a controller 5, a control module 6, and a computer 7. The controller 5, control module 6, and computer 7 will be described in order below.

[0051] Furthermore, the electrical components shown in Figure 2 may be divided as appropriate, some of which may be included in other components, or may be integrated with other components. For example, some or all of the functions of the controller 5 or control module 6 may be implemented by the computer 7, or by other external devices 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 the function of controlling the drive of the moving mechanism 2 and the support mechanism 4, and the function of generating a signal D3 to synchronize the ink ejection operation of the head unit 3 with the operation of the moving mechanism 2.

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

[0054] The memory circuit 5a stores various programs executed by the processing circuit 5b and various data processed by the processing circuit 5b. The memory circuit 5a includes, for example, one or both of the following semiconductor memories: a volatile memory such as RAM (Random Access Memory) and a non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable ROM). Note that part or all of the memory circuit 5a may be included in the processing circuit 5b.

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

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

[0057] The processing circuit 5b controls the operation 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 CPUs (Central Processing Units). The processing circuit 5b may also include a programmable logic device such as an FPGA (Field-Programmable Gate Array) instead of a CPU, or in addition to a CPU.

[0058] Specifically, the processing circuit 5b performs calculations to convert the path information Da into operational quantities such as the amount of movement and speed of movement of the movement mechanism 2. Then, the processing circuit 5b outputs control signals Sx, Sz-0 to Sz-7 based on the output signals Dx, Dz-0 to Dz-7 from each encoder of the movement mechanism 2, so that the actual operational quantities of the movement mechanism 2 match the calculation results. Output signal Dx is the signal output from the encoder of the X movement mechanism 2X. Output signals Dz-0 to Dz-7 are the signals output from the encoders of the Z movement mechanism 2Z-0 to 2Z-7. Control signal Sx is a signal for controlling the drive of the actuator of the X movement mechanism 2X. Control signals Sz-0 to Sz-7 are signals for controlling the drive of the actuator of the Z movement mechanism 2Z-0 to 2Z-7. Here, the control signals Sx, Sz-0 to Sz-7 are corrected by the processing circuit 5b as needed based on the output signal D1 from the sensor 32 of the sensor unit 30.

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

[0060] Furthermore, the processing circuit 5b generates signal D3 based on output signals Dx and at least one of Dz-0 to Dz-7. For example, the processing circuit 5b may generate signal D3 that includes a pulse at a timing when the output signal Dx is a predetermined value, or it may output the output signal Dx as 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 the print data from the computer 7. The control module 6 includes 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 generation circuit 6a generates a timing signal PTS based on signal D3. The timing signal generation circuit 6a is configured, for example, as a timer that starts generating the timing signal PTS when signal D3 is detected, or, if signal D3 is output signal Dx, as a circuit that generates a signal as the timing signal PTS that includes pulses synchronized with the pulses of 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 supplied to the drive signal generation circuit 6d.

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

[0065] The control signal SI is a digital signal used to specify the operating state of the drive element of the head 3a of the head unit 3. Specifically, the control signal SI is a signal used to specify whether or not to supply the 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 used to define the waveform of the drive signal Com. The latch signal LAT and the change signal CNG are used in conjunction with the control signal SI to define the timing of ink ejection from the nozzle by defining the driving timing of the drive element. The clock signal CLK is a reference clock signal synchronized with the timing signal PTS.

[0066] The control circuit 6c described above includes, for example, one or more processors such as CPUs. The control circuit 6c may also include a programmable logic device such as an FPGA instead of a CPU, 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 amplification circuit. In the drive signal generation circuit 6d, the DA conversion circuit converts the waveform specification signal dCom from the control circuit 6c from a digital signal to an analog signal, and the amplification circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 6b to generate the drive signal Com. Here, among the waveforms included in the drive signal Com, the signal of the waveform that is 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 that includes a switching element that, based on the control signal SI, switches whether or not to supply at least a portion of the waveform included in the drive signal Com as a drive pulse PD.

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

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

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

[0072] As shown in Figure 3, the memory circuit 7a stores path information Da, orientation information Db, work information Dc, print area information Dd, image data De, pixel data Df, head information Dg, and print data Img.

[0073] Work information Dc is data representing the shape of at least a part of the workpiece W. Specifically, work information Dc is 3D data such as in STL (Standard Triangulated Language) format, representing the shape of the workpiece W with multiple polygons. 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 the normal vectors indicating the front and back of the polygon faces. Work information Dc can be obtained, for example, by converting CAD (computer-aided design) data showing the 3D shape of the workpiece W as needed, or by measuring the shape of the workpiece W using a sensor 32 or the like. Work information Dc may be represented using coordinate values ​​of the work coordinate system, or it may be represented by point cloud data using coordinate values ​​of the base coordinate system or the world coordinate system. Furthermore, work information Dc may be represented by mathematical formulas, and the format of work information Dc can be converted as appropriate as needed.

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

[0075] Image data De is information that represents the image to be printed in two dimensions, and is, for example, image data created by image editing software. Specifically, image data De may be file format using page description languages ​​such as PostScript, PDF (Portable Document Format), XPS (XML Paper Specification), or various vector formats, or raster format.

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

[0077] Head information Dg is information about head 3a. Specifically, head information Dg is information for representing head 3a as a virtual object in the virtual space SV, and includes information such as the number, spacing, and discharge direction of the multiple nozzles, and the position of the tool center point TCP described later.

[0078] The print data Img is information indicating the image to be printed on the workpiece W for each path of the print path indicated by the path information Da, and for each pixel of the image indicated by the pixel data Df, it indicates the amount of ink ejected from the head 3a.

[0079] The processing circuit 7b implements various functions by reading and executing a program from the memory circuit 7a. The processing circuit 7b includes, for example, one or more processors such as CPUs. The processing circuit 7b may also include a programmable logic device such as an FPGA instead of a CPU, or in addition to a CPU.

[0080] 1-3. Head Unit Figure 4 is a schematic perspective view of the head unit 3. As shown in Figure 4, the head unit 3 has a head 3a and a support 3g. In the example shown in Figure 4, the head unit 3 has one head 3a, but this number is not limited to the example shown in Figure 4 and may be two or more.

[0081] The support 3g is a structure that supports the head 3a and is attached to the Z-movement mechanism 2Z. Therefore, the head 3a is supported by the Z-movement mechanism 2Z via the support 3g.

[0082] The support 3g is essentially a rigid body and is made of, for example, a metal material. In Figure 4, the support 3g is plate-shaped, but the shape of the support 3g is not particularly limited and can be arbitrary. The support 3g may also be composed 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 of the workpiece W, or a pressure regulating valve for maintaining the ink pressure in the head 3a at a negative pressure within a predetermined range.

[0083] A head 3a is positioned in the X1 direction relative to the aforementioned support 3g, and the head 3a is fixed to the support 3g by screws or the like.

[0084] The print head 3a has an ejection surface FN and a plurality of nozzles N that open into the ejection surface FN. In the example shown in Figure 4, the normal direction of the ejection surface FN is the Z2 direction, and the plurality of nozzles N are divided into nozzle rows NLa and nozzle rows NLb, which are spaced apart from each other in the direction along the X axis. Each of the nozzle rows NLa and NLb is a set of a plurality of nozzles N arranged linearly in the nozzle row direction DN, which is the direction along the Y axis. Here, the elements associated with each nozzle N in nozzle row NLa and the elements associated with each nozzle N in nozzle row NLb in print head 3a are substantially symmetrical with respect to the direction along the X axis. Hereinafter, the set of nozzle rows NLa and NLb may be referred to as nozzle row NL. Each nozzle N ejects ink along the parallel ejection direction DE. Under ideal conditions, the ejection direction DE is the Z2 direction, which is the normal direction of the ejection surface FN.

[0085] Although not shown in the diagram, the print head 3a has, for each nozzle N, a piezoelectric element which is a driving element and a cavity that contains ink. Here, the piezoelectric element causes ink to be ejected from the nozzle corresponding to the cavity by changing the pressure in the cavity corresponding to the piezoelectric element. Such a print head 3a can be obtained, for example, by bonding together multiple substrates such as silicon substrates that have been appropriately processed by etching or the like using an adhesive. In addition, instead of the piezoelectric element, a heater that heats the ink in the cavity may be used as the driving element for ejecting ink from the nozzle.

[0086] The position of the head 3a is defined with respect to the tool center point TCP. In this embodiment, as shown in Figure 4, the tool center point TCP is set at the center of the ejection surface FN. Note that the position of the tool center point TCP is not limited to the example shown in Figure 4, and may be, for example, a position in the space at a predetermined distance from the center of the nozzle row NL in the ink ejection direction DE.

[0087] The head 3a described above is connected to a supply pipe and a discharge pipe (not shown). The supply pipe is a flexible tube that supplies ink from an ink tank (not shown) to the head unit 3. The discharge pipe is a flexible tube that transfers ink to a circulation mechanism or discharge mechanism (not shown).

[0088] 1-4. Generating a print path Figure 5 is a flowchart of the generation of print paths RU in the first embodiment. The 3D object printing apparatus 1 executes steps S10 to S110 as shown in Figure 5. As a result, the control unit 50 generates print paths RU-1 to RU-5 as multiple print paths RU. The outline of each step is described below.

[0089] In step S10, the processing circuit 7b acquires the shape of the workpiece W. This acquisition is performed, for example, by converting CAD data showing the three-dimensional shape of the workpiece W as needed, or by measuring the shape of the workpiece W using a sensor 32 or the like. In this way, the control unit 50 acquires workpiece information Dc regarding the shape of the workpiece W in step S10. The acquired shape information is stored in the storage circuit 7a as workpiece information Dc.

[0090] After step S10, in step S20, the processing circuit 7b creates a reference path LM in the virtual space VS described later, based on the work information Dc.

[0091] After step S20, in step S30, the processing circuit 7b creates a virtual printing path LM-V in the virtual space VS described later, to which the head 3a moves relative to the workpiece W. This creation is performed, for example, by shifting the reference path LM based on the workpiece information Dc by a distance MD0 described later for each reference path LM. In this way, the control unit 50 generates the virtual printing path LM-V in step S30 based on the workpiece information Dc.

[0092] After step S30, in step S40, the processing circuit 7b determines the orientation of the workpiece W in the virtual space VS described later. This determination is made, for example, based on the virtual plane described later when creating the reference path LM in step S20 and the normal direction of the surface of the workpiece W at the reference point Pt described later. In this way, the control unit 50 obtains the orientation of the workpiece W in the virtual space VS. The information indicating the determined orientation is stored in the storage circuit 7a as part of the orientation information Db.

[0093] After step S40, in step S50, the processing circuit 7b determines whether the head 3a located on the virtual printing path LM-V in the virtual space VS described later will collide with the workpiece W. Here, the control unit 50 calculates the minimum distance between the head 3a and the workpiece W in the virtual space VS based on the virtual printing path LM-V, and determines whether a collision has occurred based on the calculation result. This minimum distance is an example of a "virtual distance".

[0094] In this embodiment, the control unit 50 calculates a virtual distance based on the virtual printing path LM-V and the orientation of the workpiece W in the virtual space VS.

[0095] After step S50, in step S60, the processing circuit 7b determines whether or not a collision has occurred based on the determination result of step S50.

[0096] If a collision is determined based on the result of step S50 (step S60: YES), in step S70, the processing circuit 7b calculates the adjustment amount for the virtual print path LM-V at the target point Pt, which will be described later. For points Pt that are not subject to step S70, the adjustment amount is treated as zero.

[0097] If, based on the result of step S50, it is determined that there is no collision (step S60: NO), or after step S70, in step S80, the processing circuit 7b determines whether there is a next point Pt to be targeted. This determination is carried out until the adjustment amount is calculated for all of the multiple points Pt set in the reference path LM described later.

[0098] If there is a next point Pt (step S80: YES), the processing circuit 7b returns to step S50. On the other hand, if there is no next point Pt (step S80: NO), the processing circuit 7b calculates the maximum adjustment amount of the virtual printing path LM-V in step S90. This calculation is performed, for example, by selecting the largest adjustment amount among the adjustment amounts for each point Pt of the reference path LM.

[0099] After step S90, in step S100, the processing circuit 7b creates the print path RU described later. This creation is performed, for example, by shifting the virtual print path LM-V by the maximum value calculated in step S90 so that the distance PG between the head 3a and the workpiece W increases for each reference path LM.

[0100] After step S100, in step S110, the processing circuit 7b determines whether there is a next path that will be the target reference path LM. This determination is performed for all of the multiple reference path LMs required for the printing operation until a printing path RU is created.

[0101] If there is a next path (step S110: YES), the processing circuit 7b returns to step S30. On the other hand, if there is no next path (step S110: NO), the processing circuit 7b terminates the process.

[0102] Figure 6 is an explanatory diagram for obtaining the shape of the workpiece W. In the following explanation, we will use the x, y, and z axes, which intersect each other, as coordinate axes of the 3D coordinate system that defines the virtual space VS, a virtual space that mimics real space. In the following, one direction along the x axis is the x1 direction, and the direction opposite to the x1 direction is the x2 direction. Opposite directions along the y axis are the y1 and y2 directions. Opposite directions along the z axis are the z1 and z2 directions. Note that the relationship between the x, y, and z axes and the X, Y, and Z axes is not particularly limited and can be arbitrary. Also, the x, y, and z axes are typically orthogonal to each other, but are not limited to this, and can intersect each other at an angle within the range of 80° to 100°.

[0103] In step S10, the shape of the workpiece W is acquired, and as shown in Figure 6, the workpiece W with the shape based on the workpiece information Dc is placed in the virtual space VS, and the print area RP based on the print area information Dd is set. The print area RP is the area on the surface of the workpiece W that is to be printed.

[0104] Then, in step S20, a sub-scanning reference line LS is first set in the virtual space VS along the surface of the workpiece W. Hereafter, 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 parallel to the sub-scanning virtual plane VPS described later, and is also parallel to the tangent line between the workpiece W and the surface at any point on the sub-scanning reference line LS. In the example shown in Figure 6, when viewed along the z-axis, the sub-scanning direction DS is the direction along the y-axis.

[0105] The sub-scanning reference line LS is set in the virtual space VS based on the intersection of the sub-scanning virtual plane VPS and the surface of the workpiece W, after setting the sub-scanning virtual plane VPS to intersect 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 of the sub-scanning virtual plane VPS and the surface of the workpiece W, or a line segment along that intersection line, and is represented using coordinate values ​​of the coordinate system set in the virtual space VS.

[0106] The sub-scanning reference line LS passes through the print area RP. In the example shown in Figure 6, the center of the sub-scanning reference line LS within the print area RP is closer to the center of the print area RP than to the edge of the print area RP. That is, the sub-scanning reference line LS is set to pass through the print area RP at a position closer to the center of the print area RP than to the edge of the print area RP in the main scanning direction DM, which intersects the sub-scanning direction DS (described later). The main scanning direction DM is the direction along the reference path LM or the print path RU (described later).

[0107] Figure 7 is an explanatory diagram for the creation of the reference path LM. In step S20, after setting the sub-scan reference line LS as described above, multiple reference paths LM-1 to LM-5 that intersect the sub-scan reference line LS are set in the virtual space VS as shown in Figure 7. Hereafter, each of the reference paths LM-1 to LM-5 may be referred to simply as the reference path LM without distinction.

[0108] The distance between two adjacent reference path LMs of a plurality of reference path LMs is less than or equal to the width of the nozzle row NL along the Y axis, and more preferably less than or equal to half the width of the nozzle row NL. In the example shown in Figure 7, the plurality of reference path LMs are arranged at equal intervals on the sub-scanning reference line LS so as to be parallel to each other. Here, reference path LM-1 is set to align with one end of the printing area RP in the sub-scanning direction DS, and the plurality of reference path LMs are set based on reference path LM-1. This minimizes the number of reference path LMs, and as a result, the printing path RU can be generated efficiently. Note that the distance between the plurality of reference path LMs does not have to be equal. Also, the number of reference path LMs can be two or more, and is not limited to the example shown in Figure 7, but is arbitrary. Furthermore, reference path LM-1 may be set to have a portion that is slightly offset and does not coincide with the end of the printing area RP in the sub-scanning direction DS, or there may be no reference path LM that coincides with the end of the printing area RP in the sub-scanning direction DS. Furthermore, the method for setting multiple reference path LMs is not limited to a method that uses reference path LM-1 as the reference; for example, it may also be a method that sets multiple reference path LMs using the center of the print area RP as the reference.

[0109] The reference path LM is set in the virtual space VS based on the intersection line between a virtual plane that intersects the sub-scan reference line LS and the surface of the workpiece W. This virtual plane is orthogonal to the aforementioned sub-scan virtual plane VPS and serves as a reference plane for defining the relative position and orientation of the head 3a with respect to the workpiece W during printing. In this embodiment, this virtual plane is orthogonal to the y-axis.

[0110] Figure 8 is an explanatory diagram for the creation of the virtual print path LM-V. In step S30, as shown in Figure 8, the virtual print path LM-V is set in the virtual space VS. The virtual print path LM-V is a path obtained by offsetting the reference path LM by a distance MD0 away from the workpiece W along the z-axis. The virtual print path LM-V includes multiple points Pt-V, each point Pt being offset by a distance MD0 away from the workpiece W along the z-axis.

[0111] Distance MD0 is the reference distance for distance PG between head 3a and workpiece W, and is the minimum distance that can prevent collision between head 3a and workpiece W. This minimum distance is determined considering mounting errors of head 3a, operational errors of the moving mechanism 2, shape errors of workpiece W, etc., and is not particularly limited, but is, for example, about 2 mm. Distance MD0 may be set to 2 mm or less if the possibility of head 3a colliding with workpiece W is low.

[0112] To explain step S30 in more detail, first, multiple points Pt are set on the reference path LM in the virtual space VS. These multiple points Pt are set within the print area RP. In the example shown in Figure 8, these multiple points P are arranged at equal intervals when viewed along the z-axis. Note that the number of points P is not limited to the example shown and can be arbitrary. Also, the spacing between these multiple points pt is not limited to the example shown in Figure 8, and for example, they may be arranged at equal intervals along the print area RP.

[0113] In step S30, after setting multiple points Pt, a virtual print path LM-V is generated based on point Pt-V, which is obtained by moving each point Pt by a distance MD0 in the direction away from the workpiece W along the z axis. This generation may be performed by linear interpolation between the multiple points Pt-V, or by fitting the multiple points Pt-V with an arbitrary function.

[0114] Figure 9 is an explanatory diagram illustrating the collision detection and adjustment amount calculation of the head 3a with respect to the workpiece W. In Figure 9, head 3a-1, which is a head 3a moving along a virtual printing path LM-V corresponding to the reference path LM-1, and head 3a-2, which is a head 3a moving along a virtual printing path LM-V corresponding to the reference path LM-2, are typically shown. Here, head 3a is in a state where it is located at a first position P1 in the direction along the X axis.

[0115] Prior to collision detection in step S50, in step S40, the orientation of the workpiece W is set in the virtual space VS based on the virtual plane described later, which is used when creating the reference path LM in step S20, and the normal direction of the surface of the workpiece W at the reference point Pt described later. This orientation is such that the y-axis is perpendicular to the plane and the z-axis is parallel to the normal direction.

[0116] In step S50, a head 3a moving along the virtual printing path LM-V is set in the virtual space VS for the target point Pt, and it is determined whether or not the head 3a collides with the workpiece W.

[0117] Here, the size of the head 3a in the virtual space VS is set based on the head information Dg so that the ratio of the size of the head 3a to the workpiece W in the virtual space VS is equal to the ratio of the size of the head 3a to the workpiece W in the real space. Also, the position of the head 3a relative to the workpiece W in the virtual space VS is set based on the target virtual printing path LM-V so that the head 3a is located on the virtual printing path LM-V in the virtual space VS. Furthermore, the orientation of the head 3a relative to the workpiece W in the virtual space VS is set based on the orientation of the workpiece W determined in step S40 so that the nozzle row direction DN is parallel to the y-axis and the ejection direction DE is parallel to the z-axis.

[0118] Furthermore, whether or not the head 3a collides with the workpiece W is determined by calculating the minimum distance between the discharge surface FN and the workpiece W as a virtual distance, and checking whether the calculated minimum distance is greater than or equal to a predetermined distance. If the discharge surface FN does not have a portion where the minimum distance from the workpiece W is less than the predetermined distance, it is determined that the head 3a does not collide with the workpiece W. On the other hand, if the discharge surface FN has a portion where the minimum distance from the workpiece W is less than the predetermined distance, it is determined that the head 3a collides with the workpiece W. This predetermined distance is, for example, distance MD0.

[0119] The head 3a-1 shown in Figure 9 is the head 3a that simulated the first printing operation described later in the virtual space VS in step S50. In step S50, the first distance PG-1 between the head 3a-1 and the workpiece W in the virtual space VS is the distance MD0 set in step S30. The surface of the workpiece W facing the ejection surface FN of the head 3a-1 is inclined with respect to the ejection surface FN. The normal of the ejection surface FN of the head 3a-1 intersects the surface of the workpiece W at a first angle θ-1. Therefore, in step S50, the minimum distance between the head 3a-1 and the workpiece W is the third distance MD-1, which is shorter than the distance MD0. Thus, in step S50, it is determined that the head 3a-1 collides with the workpiece W. In step S70, for example, the difference ΔL-1 between the third distance MD-1 and the distance MD0 is calculated as an adjustment amount so that the third distance MD-1 becomes the distance MD0.

[0120] The head 3a-2 shown in Figure 9 is the head 3a that simulated the second printing operation described later in the virtual space VS in step S50. In step S50, the second distance PG-2 between the head 3a-2 and the workpiece W in the virtual space VS is the distance MD0 set in step S30. The surface of the workpiece W facing the ejection surface FN of the head 3a-2 is inclined with respect to the ejection surface FN. The normal of the ejection surface FN of the head 3a-2 intersects the surface of the workpiece W at a second angle θ-2. Therefore, in step S50, the minimum distance between the head 3a-2 and the workpiece W is the fourth distance MD-2, which is shorter than the distance MD0. Thus, in step S50, it is determined that the head 3a-2 collides with the workpiece W. In step S70, for example, the difference ΔL-2 between the fourth distance MD-2 and the distance MD0 is calculated as an adjustment amount so that the fourth distance MD-2 becomes the distance MD0.

[0121] In the example shown in Figure 9, the second angle θ-2 is greater than the first angle θ-1. Therefore, the second distance PG-2 is smaller than the first distance PG-1. Also, the difference ΔL-2 is smaller than the difference ΔL-1.

[0122] In the example shown in Figure 9, the distance PG-3 between the head 3a moving along the virtual printing path LM-V corresponding to the reference path LM-3 and the workpiece W is the distance MD0 set in step S30, and is also the minimum distance between the head 3a and the workpiece W. Therefore, in step S50, it is determined that the head 3a will not collide with the workpiece W.

[0123] As described above, in step S70, the adjustment amount is calculated for each point Pt. Then, in this embodiment, in step S90, the maximum value among the multiple adjustment amounts for each point Pt is calculated.

[0124] Figure 10 is an explanatory diagram for the creation of the print path RU. In step S100, the print path RU is created by shifting the virtual print path LM-V by the maximum value ΔL calculated in step S90 so that the distance PG is large. For example, in step S100 of this embodiment, after all points Pt-V of the virtual print path LM-V are shifted by the maximum value ΔL, the print path RU is generated by interpolating or fitting multiple points Pt-V with an arbitrary function.

[0125] In the print path RU shown in Figure 10, the distance PG is constant throughout the entire print path RU. Therefore, in the first print operation MP1 and the second print operation MP2 described later, the distance PG between the head 3a and the workpiece W is constant in the scanning direction that scans the head 3a. This reduces variations in print quality in the main scanning direction. Note that "constant" includes not only strictly constant values ​​but also cases where there are slight differences such as errors.

[0126] Figure 11 is an explanatory diagram of the adjusted first distance PG-1, second distance PG-2, third distance MD-1, and fourth distance MD-2. In Figure 11, the printing paths RU-1 to RU-5, which correspond to the reference paths LM-1 to LM-5, are shown, and head 3a-1, which moves along printing path RU-1, and head 3a-2, which moves along printing path RU-2, are shown as representative examples. Printing path RU-1 is an example of the "first path," and printing path RU-2 is an example of the "second path." Here, head 3a is in a state where it is in a first position P1 in the direction along the X axis.

[0127] The adjusted third distance MD-1 and fourth distance MD-2 are each equal to distance MD0. Therefore, the adjusted third distance MD-1 and fourth distance MD-2 are equal to each other.

[0128] As described above, the print path RU is generated. In step S100, the print path RU may also be created by shifting only a portion of point Pt-V of the virtual print path LM-V by the maximum value ΔL. This point will be explained below with reference to Figure 12.

[0129] In this way, the control unit 50 determines the first distance PG-1 and the second distance PG-2 based on the virtual distance calculated in step S50. As a result, the movement path of the head 3a, the first distance PG-1 and the second distance PG-2 are determined in the simulation, making it possible to execute the printing operation more easily compared to the method using direct teaching. In addition, since collision detection of the head 3a with the workpiece W can be performed in the simulation, actual collisions of the head 3a with the workpiece W can be effectively prevented.

[0130] In this embodiment, the control unit 50 determines the first distance PG-1 and the second distance PG-2 based on the virtual distance calculated in step S50, as well as the orientation of the workpiece W in the virtual space VS. As a result, the orientation of the head 3a is taken into consideration in the simulation, enabling highly accurate collision detection of the head 3a with the workpiece W. Consequently, actual collisions of the head 3a with the workpiece W can be more effectively prevented.

[0131] Figure 12 is an explanatory diagram of another example of the creation of a print path RU. In the example shown in Figure 12, in step S100, some points Pt-V of the virtual print path LM-V are shifted by a maximum value ΔL, and then the print path RU is generated by interpolating or fitting multiple points Pt-V with an arbitrary function. This partial set of points Pt-V includes the point Pt-V whose adjustment amount calculated in step S70 is the maximum value ΔL. In the example shown in Figure 12, this partial set of points Pt-V includes not only the point Pt-V whose adjustment amount calculated in step S70 is the maximum value ΔL, but also the points Pt-V adjacent to it. Note that the number of such partial set of points Pt-V is not limited to the example shown in Figure 12 and can be arbitrary.

[0132] In the print path RU shown in Figure 12, the distance PG decreases as you move from the center to the edge of the print path RU. Therefore, the distance PG-E at the edge of the print path RU is greater than the distance PG-C at the center of the print path RU. Consequently, in the first print operation MP1 and the second print operation MP2 described later, the distance PG between the head 3a and the workpiece W varies in the scanning direction in which the head 3a is scanned. This prevents the head 3a from colliding with the workpiece W, even if the workpiece W has a curved or uneven shape in the main scanning direction.

[0133] After the creation of the print path RU described above, the print data Img is generated.

[0134] To explain in more detail, although not shown in the diagram, in the virtual space VS, the image represented by image data De is pasted onto the print area RP. This creates pixel data Df. Then, for each print path RU, based on the intersection of the print area RP and the virtual lines extending from each nozzle N of the head 3a in the ejection direction DE, color data or gradation data corresponding to the intersection is extracted from the pixel data Df for each print path RU. The pixel data Df is then divided for each printing operation, and the divided pixel data Df is converted into ink ejection amounts to generate print data Img.

[0135] Here, for example, based on the aforementioned intersection corresponding to the ink's landing position, the print area RP is divided into multiple areas, each containing a voxel, into which ink can be applied during each printing operation. Then, exclusive processing is performed so that each voxel is assigned one dot of ink from one nozzle N.

[0136] 1-5. Printing Operation Figure 13 is a flowchart showing the flow of the printing operation. As shown in Figure 13, the 3D object printing device 1 performs the transport operation MC, the first printing operation MP1, the head retraction operation ME, the feed operation MF, and the second printing operation MP2 in this order. Below, we will first explain the outline of these operations. For the sake of explanation, Figure 13 illustrates the printing operation using printing paths RU-1 and RU-2 of the aforementioned printing paths RU-1 to RU-5. Printing using other adjacent printing paths RU is similar.

[0137] The transport operation MC transports the workpiece W to a printable position and orientation relative to the first region RP1 by the operation of either or both of the robot 4W and the Y-movement mechanism 4Y.

[0138] The first printing operation MP1 moves the head 3a along the printing path RU-1 by the operation of the Z-movement mechanism 2Z and the X-movement mechanism 2X, while discharging liquid from the head 3a towards the three-dimensional workpiece W. This prints in the first region RP1. At this point, the robot 4W and the Y-movement mechanism 4Y do not operate. This stabilizes the posture of the workpiece W, preventing image quality degradation caused by the operation of the robot 4W and the Y-movement mechanism 4Y.

[0139] 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 by the Z-movement mechanism 2Z that is forward in the direction of movement by the X-movement mechanism 2X, and the ink on the workpiece W is cured by the light source 31 of the sensor unit 30 supported by the Z-movement mechanism 2Z that is backward in the direction of movement by the X-movement mechanism 2X.

[0140] The head retraction operation ME involves the movement of Z-movement mechanisms 2Z-1 to 2Z-6, causing each head 3a to move away from the workpiece W. This prevents contact between each head 3a and the workpiece W during the feed operation MF.

[0141] The feed operation MF transports the workpiece W to a printable position and orientation relative to the second region RP2 by the operation of either or both of the robot 4W and the Y-movement mechanism 4Y.

[0142] The second printing operation MP2 moves the head 3a along the printing path RU-2 by the operation of the Z-movement mechanism 2Z and the X-movement mechanism 2X, while discharging liquid from the head 3a toward the workpiece W. This causes printing to occur in the second area RP2. At this point, the robot 4W and the Y-movement mechanism 4Y do not operate. This stabilizes the posture of the workpiece W, thus preventing image quality degradation caused by the operation of the robot 4W and the Y-movement mechanism 4Y.

[0143] 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 by the Z-movement mechanism 2Z that is forward in the direction of movement by the X-movement mechanism 2X, and the ink on the workpiece W is cured by the light source 31 of the sensor unit 30 supported by the Z-movement mechanism 2Z that is backward in the direction of movement by the X-movement mechanism 2X.

[0144] Figure 14 is an explanatory diagram of print paths RU-1 and RU-2. Print path RU-1 is an example of the "first path," and print path RU-2 is an example of the "second path." Print paths RU-1 and RU-2 are aligned with each other in the sub-scanning direction that intersects with the scanning direction of the head 3a.

[0145] During the execution of the first printing operation MP1, printing is performed on the first area RP1 on the workpiece W, as shown in Figure 14. Here, ink ejected from the head 3a moves along the printing path RU-1 from the starting point PS1 to the ending point PE1, and this ink is applied to the first area RP1. The printing path RU-1 is a path that extends parallel to the X-axis when viewed along the Z-axis. In the example shown in Figure 14, the direction of the printing path RU-1 when viewed along the Z-axis is the X1 direction.

[0146] On the other hand, when the second printing operation MP2 is executed, printing is performed on a second area RP2 on the workpiece W that is different from the first area RP1. Here, ink ejected from the head 3a, which moves from the starting point PS2 to the ending point PE2 along the printing path RU-2, is applied to the second area RP2. The printing path RU-2 is a path that extends parallel to the X-axis when viewed along the Z-axis. In the example shown in Figure 14, the direction of the printing path RU-2 when viewed along the Z-axis is the X2 direction. Note that the direction of the printing path RU-2 may also be the X1 direction when viewed along the Z-axis.

[0147] Parts of the first region RP1 and the second region RP2 overlap with each other in the overlapping region OV. That is, each of the first region RP1 and the second region RP2 shares the overlapping region OV. Also, the parts of the first region RP1 other than the overlapping region OV do not overlap with the second region RP2. Similarly, the parts of the second region RP2 other than the overlapping region OV do not overlap with the first region RP1.

[0148] In this embodiment, the first printing operation MP1 is a printing operation on the first region RP1 located at the edge of the printing area RP in the workpiece W. In contrast, the second printing operation MP2 is a printing operation on the second region RP2 located inside the first region RP1 of the printing area RP.

[0149] Figures 15 and 16 are explanatory diagrams of the first printing operation MP1. Figure 15 shows the state of the first printing operation MP1 as viewed in the X1 direction. Figure 16 shows the state of the first printing operation MP1 as viewed in the Y1 direction.

[0150] As shown in Figure 15, during the execution of the first printing operation MP1, the robot 4W supports the workpiece W such that the first region RP1 is positioned directly below the head 3a.

[0151] As shown in Figure 16, in the first printing operation MP1, the X-movement mechanism 2X moves each head 3a and sensor unit 30 in the X1 direction, while 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, and each head 3a ejects ink toward the first area RP1 based on the print data Img.

[0152] Thus, the first printing operation MP1 scans the head 3a along the printing path RU-1 by the operation of the Z-movement mechanism 2Z and the X-movement mechanism 2X, and ejects ink from the head 3a toward the first area RP1 of the workpiece W.

[0153] Here, each head 3a moves along the print path RU-1. The movement path of the sensor unit 30 is not particularly limited, but for example, it is a path that is moved back in the Z1 direction from the print path RU-1. Also, during the execution of the first print operation MP1, the sensor unit 30 may be operated as needed.

[0154] Figure 17 is an explanatory diagram of the second printing operation MP2. Figure 17 shows the state of the second printing operation MP2 as viewed in the X1 direction. As shown in Figure 17, during the execution of the second printing operation MP2, the robot 4W supports the workpiece W such that the second region RP2 is located directly below the head 3a.

[0155] Although not shown in the diagram, in the second printing operation MP2, similar to the first printing operation MP1, the X-movement mechanism 2X moves each head 3a and sensor unit 30 along the X-axis, while 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, and each head 3a ejects ink toward the second area RP2 based on the print data Img.

[0156] In this manner, the second printing operation MP2 causes the head 3a to scan along the printing path RU-2 through the operation of the Z-movement mechanism 2Z and the X-movement mechanism 2X, and ejects ink from the head 3a toward the second area RP2 of the workpiece W.

[0157] The operation of the three-dimensional object printing device 1 described above enables printing on the first region RP1 and the second region RP2 of the workpiece W.

[0158] Figure 18 is an explanatory diagram of the first distance PG-1, second distance PG-2, third distance MD-1, and fourth distance MD-2 in the printing operation. Here, the head 3a is in the first position P1 in the direction along the X axis.

[0159] When the head 3a is positioned at a first position P1 along the X-axis, the first distance PG-1 and the second distance PG-2 are different from each other, as shown in Figure 18. Here, the first distance PG-1 is the distance PG between the center of the head 3a and the workpiece W during the first printing operation MP1. The second distance PG-2 is the distance PG between the center of the head 3a and the workpiece W during the second printing operation MP2.

[0160] Thus, when the head 3a is positioned at the first position P1 along the X-axis, the first distance PG-1 and the second distance PG-2 are different from each other, which prevents the head 3a from colliding with the workpiece W during both the first printing operation MP1 and the second printing operation MP2, while suppressing a decrease in print quality.

[0161] In contrast, when the head 3a is located at a first position P1 in the direction along the X-axis, and the first distance PG-1 and the second distance PG-2 are equal to each other, depending on the shape of the workpiece W in the sub-scanning direction, shortening the distance PG between the head 3a and the workpiece W may cause the head 3a to collide with the workpiece W in the other of the first printing operation MP1 and the second printing operation MP2, even if the head 3a does not collide with the workpiece W in one of the first printing operation MP1 and the second printing operation MP2.

[0162] When the head 3a is positioned at a first position P1 along the X-axis, the liquid discharge amounts for the overlapping region OV in the first printing operation MP1 and the second printing operation MP2 may differ from each other. For example, if the first distance PG-1 is greater than the second distance PG-2, it is preferable that the liquid discharge amount for the overlapping region OV in the second printing operation MP2 is greater than the liquid discharge amount for the overlapping region OV in the first printing operation MP1. This improves the print quality in the overlapping region OV.

[0163] When the head 3a is in a first position P1 along the X-axis, if the second angle θ-2 is greater than the first angle θ-1, then the second distance PG-2 is shorter than the first distance PG-1. This improves the print quality in the second printing operation MP2. The first angle θ-1 is the acute angle formed when the normal of the ejection surface FN of the head 3a intersects with the surface of the workpiece W when viewed along the X-axis in the first printing operation MP1. The second angle θ-2 is the acute angle formed when the normal of the ejection surface FN of the head 3a intersects with the surface of the workpiece W when viewed along the X-axis in the second printing operation MP2.

[0164] In this embodiment, the printing area RP has a shape such as a convex curved surface, and the acute angle between the normal of the ejection surface FN and the second area RP2 is larger than the acute angle between the normal of the ejection surface FN and the first area RP1. Therefore, by making the second distance PG-2 shorter than the first distance PG-1, the printing quality of the second area RP2 can be improved. In addition, white streaks or ink defects inside the image tend to be noticeable, but by improving the printing quality of the second area RP2, the overall printing quality of the image can be improved.

[0165] Furthermore, when the head 3a is positioned at the first position P1 along the X-axis, the difference between the third distance MD-1 and the fourth distance MD-2 is 10% or less. This allows for improved print quality by reducing the distance PG between the head 3a and the surface of the workpiece W during the first printing operation MP1. The third distance MD-1 is the minimum distance between the head 3a and the workpiece W during the first printing operation MP1. The fourth distance MD-2 is the minimum distance between the head 3a and the workpiece W during the second printing operation MP2.

[0166] The distance MD0 to be maintained between the head 3a and the workpiece W is, for example, 2 mm or more. The difference between the third distance MD-1 and the fourth distance MD-2 is preferably small, and more preferably zero.

[0167] 2. Second Embodiment The following describes a second embodiment of this disclosure. The following description will focus on the differences from the first embodiment, and will omit explanations of matters similar to those in the first embodiment.

[0168] This embodiment is the same as the first embodiment, except that it creates different print paths RU for the orientation of the workpiece W in the first print operation MP1 and the second print operation MP2.

[0169] Figure 19 is an explanatory diagram of the creation of the reference path LM in the second embodiment. In step S20 of this embodiment, as shown in Figure 19, reference paths LM-1 and LM-2 are set in the virtual space VS. Reference path LM-1 passes through the corresponding reference point PM-1 and intersects the sub-scan reference line LS. Reference path LM-2 passes through the corresponding reference point PM-2 and intersects the sub-scan reference line LS. Reference points PM-1 and PM-2 are points on the sub-scan reference line LS. Hereinafter, reference points PM-1 and PM-2 may be referred to as reference point PM.

[0170] The reference path LM-1 is set based on the intersection of the first main scan virtual plane VPM-1, which is a virtual plane passing through the reference point PM-1 in the virtual space VS, and the surface of the workpiece W. Similarly, the reference path LM-2 is set based on the intersection of the second main scan virtual plane VPM-2, which is a virtual plane passing through the reference point PM-2 in the virtual space VS, and the surface of the workpiece W. In the following, the first main scan virtual plane VPM-1 and the second main scan virtual plane VPM-2 may each be referred to as the main scan virtual plane VPM.

[0171] The primary scanning virtual plane VPM is parallel to the normal of the plane WF at the reference point PM. Furthermore, the first primary scanning virtual plane VPM-1 and the second primary scanning virtual plane VPM-2 are non-parallel to each other.

[0172] Figure 20 is an explanatory diagram of printing paths RU-1 and RU-2 in the second embodiment. Printing path RU-1 is an example of the "first path," and printing path RU-2 is an example of the "second path."

[0173] The printing path RU-1 in this embodiment is a path that extends in a straight line when viewed in a direction parallel to the normal of the surface WF at the aforementioned reference point PM-1, but has a curved shape when viewed in a direction parallel to the normal of the surface WF at the aforementioned reference point PM-2.

[0174] On the other hand, the printing path RU-2 in this embodiment is a path that extends in a straight line when viewed in a direction parallel to the normal of the surface WF at the aforementioned reference point PM-2, but has a curved shape when viewed in a direction parallel to the normal of the surface WF at the aforementioned reference point PM-1.

[0175] Figure 21 is an explanatory diagram of the first printing operation MP1 in the second embodiment. Figure 21 shows the state of the first printing operation MP1 as viewed in the X1 direction.

[0176] As shown in Figure 21, in this embodiment as well, the robot 4W during the execution of the first printing operation MP1 supports the workpiece W such that the first region RP1 is located directly below the head 3a. At this time, the workpiece W is positioned such that the printing path RU-1 extends parallel to the X-axis when viewed in the direction along the Z-axis.

[0177] Then, similar to the first embodiment, the first printing operation MP1 causes the head 3a to scan along the printing path RU-1 by the operation of the Z-movement mechanism 2Z and the X-movement mechanism 2X, and ejects ink from the head 3a toward the first area RP1 of the workpiece W.

[0178] Following the first printing operation MP1 described above, in the feed operation MF, the robot 4W changes the orientation of the workpiece W to a different orientation than that of the first printing operation MP1.

[0179] Figure 22 is an explanatory diagram of the second printing operation MP2 in the second embodiment. Figure 22 shows the state of the second printing operation MP2 as viewed in the X1 direction. As shown in Figure 22, the robot 4W during the execution of the second printing operation MP2 supports the workpiece W such that the second region RP2 is located directly below the head 3a. At this time, the workpiece W is positioned such that the printing path RU-2 extends parallel to the X axis when viewed along the Z axis.

[0180] In this embodiment, the orientation of the workpiece W during the execution of the second printing operation MP2 is different from the orientation of the workpiece W during the execution of the first printing operation MP1. In the example shown in Figure 22, the position of the workpiece W during the execution of the second printing operation MP2 in this embodiment is the same as the position of the workpiece W during the execution of the first printing operation MP1. Note that the position of the workpiece W during the execution of the second printing operation MP2 in this embodiment is determined according to the shape of the workpiece W or the printing path RU-1, etc., and may be different from the position of the workpiece W during the execution of the first printing operation MP1.

[0181] Then, similar to the first embodiment, the second printing operation MP2 causes the head 3a to scan along the printing path RU-2 by the operation of the Z-movement mechanism 2Z and the X-movement mechanism 2X, and ejects ink from the head 3a toward the second area RP2 of the workpiece W.

[0182] The second embodiment described above also makes it possible to prevent the head 3a from colliding with the workpiece W in both the first printing operation MP1 and the second printing operation MP2, while suppressing a decrease in print quality.

[0183] 2. Variations Each of the above examples can be modified in various ways. Specific examples of modifications that can be applied to each of the aforementioned examples are given below. Two or more of the following examples can be arbitrarily selected and combined as appropriate, provided they do not contradict each other.

[0184] 2-1. Variation 1 In the above-described embodiment, an example is given in which PG-2 is determined from the first distance PG-1 and the second distance PG-2 based on the results of collision detection of the head 3a with the workpiece W by simulation. However, the embodiment is not limited to this, and for example, the determination of the first distance PG-1 and the second distance PG-2 may be performed based on the results of direct teaching.

[0185] 2-2. Variation 2 In the above-described embodiment, an example is given in which there are 6 Z-movement mechanisms 2Z that move the head 3a along the Z-axis. However, the embodiment is not limited to this, and the number of such mechanisms or the number of heads 3a may be 5 or less, or 7 or more.

[0186] 2-3. Variation 3 In the above-described embodiment, an example is given in which robot 4W is a 6-axis articulated robot. However, the number of joints that robot 4W has is not limited to 6, but may be 2 to 5 or 7 or more.

[0187] 3. Addendum A summary of this disclosure is provided below.

[0188] (Note 1) A first embodiment of a three-dimensional object printing apparatus of the present disclosure comprises a head for ejecting liquid, a Z-movement mechanism for moving the head along the Z-axis, and an X-movement mechanism for moving the head along the X-axis by moving the Z-movement mechanism along the X-axis intersecting the Z-axis. The apparatus performs a first printing operation in which the head is moved along a first path by the operation of the Z-movement mechanism and the X-movement mechanism, and liquid is ejected from the head toward a three-dimensional workpiece; and a second printing operation in which the head is moved along a second path by the operation of the Z-movement mechanism and the X-movement mechanism, and liquid is ejected from the head toward the workpiece. The first path and the second path are aligned with each other in a sub-scanning direction intersecting the direction in which the head is scanned. When the distance between the head and the workpiece in the first printing operation is defined as the first distance, and the distance between the head and the workpiece in the second printing operation is defined as the second distance, the first distance and the second distance are different from each other when the head is in a first position in the direction toward the X-axis.

[0189] In the above embodiment, since the first distance and the second distance are different when the head is positioned at the first position along the X-axis, it is possible to prevent the head from colliding with the workpiece in both the first and second printing operations while suppressing a decrease in print quality. Furthermore, since the head has a width in the sub-scanning direction, the workpiece and the head are prone to colliding in the sub-scanning direction. According to this embodiment, it is possible to prevent the head from colliding with the workpiece in the sub-scanning direction.

[0190] (Note 2) In a second embodiment, which is a preferred example of the first embodiment, the acute angle formed when the normal of the ejection surface of the head intersects with the surface of the workpiece in the direction along the X-axis during the first printing operation is defined as the first angle, and the acute angle formed when the normal of the ejection surface of the head intersects with the surface of the workpiece in the direction along the X-axis during the second printing operation is defined as the second angle. When the head is in a first position in the direction along the X-axis, if the second angle is greater than the first angle, the second distance is shorter than the first distance. In the above embodiment, the print quality in the second printing operation can be improved.

[0191] (Note 3) In a third embodiment which is a preferred example of the first or second embodiment, the first printing operation is a printing operation on a first region located at the edge of the printing area in the workpiece, and the second printing operation is a printing operation on a second region located inside the first region of the printing area. In the above embodiments, when the printing area has a shape such as a convex curved surface, the acute angle between the normal of the ejection surface and the second region becomes larger than the acute angle between the normal of the ejection surface and the first region. Therefore, by making the second distance shorter than the first distance, the printing quality of the second region can be improved.

[0192] (Note 4) In a fourth embodiment, which is a preferred example of any of the first to third embodiments, when the minimum distance between the head and the workpiece in the first printing operation is defined as the third distance, and the minimum distance between the head and the workpiece in the second printing operation is defined as the fourth distance, the difference between the third distance and the fourth distance is 10% or less when the head is positioned at a first position in the direction along the X-axis. In the above embodiments, the print quality can be improved by reducing the distance between the head and the surface of the workpiece in the first printing operation.

[0193] (Note 5) In a fifth embodiment, which is a preferred example of any of the first to fourth embodiments, the distance between the head and the workpiece varies in the scanning direction in which the head is scanned during the first printing operation. In the above embodiments, even if the workpiece has a curved or uneven shape in the main scanning direction, collision of the head with the workpiece can be prevented.

[0194] (Note 6) In a fifth embodiment, which is a preferred example of any of the first to fourth embodiments, the distance between the head and the workpiece is constant in the scanning direction in which the head is scanned during the first printing operation. In this embodiment, variations in print quality in the main scanning direction can be reduced.

[0195] (Note 7) In a seventh embodiment, which is a preferred example of any of the first to sixth embodiments, a control unit is provided to generate the first path and the second path, wherein the control unit acquires work information relating to the shape of the work, generates a virtual printing path for the movement of the head relative to the work in a virtual space based on the work information, calculates a virtual distance which is the minimum distance between the head and the work in the virtual space based on the virtual printing path, and determines the first distance and the second distance based on the virtual distance. In the above embodiments, the movement path of the head, the first distance and the second distance are determined in the simulation, so the printing operation can be executed more easily than in embodiments using direct teaching. Furthermore, since collision detection of the head with the work can be performed in the simulation, actual collisions of the head with the work can be suitably prevented.

[0196] (Note 8) In the eighth embodiment, which is a preferred example of the seventh embodiment, a support mechanism is provided to support the workpiece and change the orientation of the workpiece, and the control unit acquires the orientation of the workpiece in the virtual space, calculates the virtual distance based on the virtual printing path and the orientation of the workpiece in the virtual space, and determines the first distance and the second distance based on the virtual distance and the orientation of the workpiece in the virtual space. In the above embodiment, since the orientation of the head is taken into consideration in the simulation, collision detection of the head with the workpiece can be performed with high accuracy. As a result, actual collisions of the head with the workpiece can be prevented more effectively. [Explanation of Symbols]

[0197] 1...3D object printing device, 2...movement mechanism, 2X...X movement mechanism, 2Z...Z movement mechanism, 2Z-0~2Z-7...Z movement mechanism, 2a...column, 2b...beam, 2c...rail, 2d...movable body, 2e...support, 3...head unit, 3-1~3-6...head unit, 3a...head, 3a-1...head, 3a-2...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 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 movement mechanism, 8P…Cap cover, 10…Base, 10a…Surface, 10b…Opening, 10c…Mounting section, 11…Case, 11a…Visibility section, 30…Sensor unit, 30-1…Sensor unit, 30-2…Sensor unit, 31…Light source, 32…Sensor, 50…Control unit, AR…Arm, 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...Position information, Dc...Work information, Dd...Print area information, De...Image data, Df...Pixel data, Dg...Head information, Dw...Output, Dx...Output signal, Dz-0~Dz-7...Output signal, FN...Ejection surface, Img...Print data, LAT...Latch signal, LM...Reference path, LM-1...Reference path, LM-2...Reference path, LM-3...Reference path, LM-V...Virtual print path, LS...Sub-scanning reference line, MC...Transport operation, M D-1...3rd distance, MD-2...4th distance, MD0...distance, ME...head retraction operation, MF...feed operation, MP1...1st printing operation, MP2...2nd printing operation, N...nozzle, NL...nozzle row, NLa...nozzle row, NLb...nozzle row, OV...overlap area, P1...1st position, PD...drive pulse, PE1...endpoint, PE2...endpoint, PG...distance, PG-1...1st distance, PG-2...2nd distance, PG-3...distance, PG-C...distance, PG-E...distance, PM...reference point, PM-1...reference point, PM-2...reference point, PS1...start point, PS2...start point, PTS...timing signal, RP...printing areaRP1...First area, RP2...Second area, RU...Print path, RU-1...Print path, RU-2...Print path, S10...Step, S13...Third step, S20...Step, S30...Step, S40...Step, S50...Step, S60...Step, S70...Step, S80...Step, S90...Step, S100...Step, S110...Step, SI...Control signal, SI-1~SI-6...Control signal, SV... Virtual space, Sw...control signal, Sx...control signal, Sz-0~Sz-7...control signals, TCP...tool center point, VBS...offset potential, VHV...power potential, VPM...main scan virtual plane, VPM-1...first main scan virtual plane, VPM-2...second main scan virtual plane, VPS...sub-scan virtual plane, VS...virtual space, W...workpiece, WF...plane, dCom...waveform specification signal, ΔL...maximum value, θ-1...first angle, θ-2...second angle.

Claims

1. A head that dispenses liquid, A Z-axis movement mechanism for moving the head along the Z-axis, The system includes an X-movement mechanism that moves the head along the X-axis by moving the Z-movement mechanism along the X-axis intersecting the Z-axis, A first printing operation in which the head is moved along a first path by the operation of the Z-movement mechanism and the X-movement mechanism, and liquid is ejected from the head toward a three-dimensional workpiece, A second printing operation is performed, in which the head is moved along a second path by the operation of the Z-movement mechanism and the X-movement mechanism, and liquid is ejected from the head toward the workpiece. The first path and the second path are aligned with each other in a sub-scanning direction that intersects with the direction in which the head is scanned. The distance between the head and the workpiece in the first printing operation is defined as the first distance. When the distance between the head and the workpiece in the second printing operation is defined as the second distance, When the head is positioned at a first position in the direction along the X-axis, the first distance and the second distance are different from each other. A three-dimensional object printing apparatus characterized by the following features.

2. In the first printing operation, the acute angle formed when the normal of the ejection surface of the head intersects with the surface of the workpiece, viewed in the direction along the X-axis, is defined as the first angle. In the second printing operation, when the acute angle formed when the normal of the ejection surface of the head intersects with the surface of the workpiece, viewed in the direction along the X-axis, is defined as the second angle. When the head is positioned at a first position in the direction along the X-axis, if the second angle is greater than the first angle, then the second distance is shorter than the first distance. The three-dimensional object printing apparatus according to feature 1.

3. The first printing operation is a printing operation on a first region located at the edge of the printing area in the workpiece, The second printing operation is a printing operation on a second region located inside the first region of the printing area. The three-dimensional object printing apparatus according to feature 2.

4. The minimum distance between the head and the workpiece in the first printing operation is defined as the third distance. When the minimum distance between the head and the workpiece in the second printing operation is defined as the fourth distance, When the head is positioned at a first position along the X-axis, the difference between the third distance and the fourth distance is 10% or less. The three-dimensional object printing apparatus according to feature 1.

5. In the first printing operation, the distance between the head and the workpiece varies in the scanning direction in which the head is scanned. A three-dimensional object printing apparatus according to any one of claims 1 to 4.

6. In the first printing operation, the distance between the head and the workpiece is constant in the scanning direction in which the head is scanned. A three-dimensional object printing apparatus according to any one of claims 1 to 4.

7. The system includes a control unit that generates the first and second paths, The control unit, Obtain workpiece information relating to the shape of the workpiece, Based on the work information, a virtual print path is generated in the virtual space for the movement of the head relative to the work. Based on the virtual printing path, the virtual distance, which is the minimum distance between the head and the workpiece in the virtual space, is calculated. Based on the virtual distance, the first distance and the second distance are determined. A three-dimensional object printing apparatus according to any one of claims 1 to 4.

8. The workpiece is supported and the workpiece's orientation can be changed, The control unit, The orientation of the workpiece in the virtual space is acquired, Based on the virtual printing path and the orientation of the workpiece in the virtual space, the virtual distance is calculated. Based on the virtual distance and the orientation of the workpiece in the virtual space, the first distance and the second distance are determined. The three-dimensional object printing apparatus according to feature 7.

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