Patent Application
20240269992
The present application is based on, and claims priority from JP Application Serial Number 2023-020907, filed Feb. 14, 2023, the disclosure of which is hereby incorporated by reference herein in its entirety.
The present disclosure relates to a three-dimensional object printing apparatus and a three-dimensional object printing method.
In the related art, a three-dimensional object printing apparatus that has a head which ejects a liquid, and performs printing on a surface of a three-dimensional workpiece with an ink jet method by using a robot is known. For example, JP-A-2022-66696 discloses a three-dimensional object printing apparatus that performs printing on a workpiece having a curved surface.
In the technique in the related art described above, when a printing region on the workpiece is divided into a plurality of regions and printed, some of the plurality of divided regions may be overlapped with each other. Meanwhile, an image having a low quality may be formed in the overlapping region.
According to an aspect of the present disclosure, there is provided a three-dimensional object printing apparatus including: a head having a plurality of nozzles that eject a liquid to a printing region on a workpiece; a movement mechanism that changes a relative position and posture between the workpiece and the head; and a control portion that controls the head and the movement mechanism, in which the control portion executes a first printing operation of ejecting the liquid from the head to the workpiece while changing the relative position between the workpiece and the head through a first path, and a second printing operation of ejecting the liquid from the head to the workpiece while changing the relative position between the workpiece and the head through a second path, the printing region includes a first band region into which the liquid is ejected from the head in the first printing operation, and a second band region into which the liquid is ejected from the head in the second printing operation, and when a width of a region in which a region of the first band region into which the liquid is ejected from the head at a first position in the first path and a region of the second band region into which the liquid is ejected from the head at a second position in the second path overlap with each other is set as a first overlapping width, a width of a region in which a region of the first band region into which the liquid is ejected from the head at a third position in the first path and a region of the second band region into which the liquid is ejected from the head at a fourth position in the second path overlap with each other is set as a second overlapping width, an angle formed by a vector representing a relative movement between the workpiece and the head at the first position and a vector representing the relative movement between the workpiece and the head at the second position is set as a first angle, and an angle formed by a vector representing the relative movement between the workpiece and the head at the third position and a vector representing the relative movement between the workpiece and the head at the fourth position is set as a second angle, the first angle is more than the second angle, and the first overlapping width is less than the second overlapping width.
According to another aspect of the present disclosure, there is provided a three-dimensional object printing method for a three-dimensional object printing apparatus including a head having a plurality of nozzles that eject a liquid to a printing region on a workpiece, and a movement mechanism that changes a relative position and posture between the workpiece and the head, the method including: a first printing operation of ejecting the liquid from the head to the workpiece while changing the relative position between the workpiece and the head through a first path; and a second printing operation of ejecting the liquid from the head to the workpiece while changing the relative position between the workpiece and the head through a second path, in which the printing region includes a first band region into which the liquid is ejected from the head in the first printing operation, and a second band region into which the liquid is ejected from the head in the second printing operation, and when a width of a region in which a region of the first band region into which the liquid is ejected from the head at a first position in the first path and a region of the second band region into which the liquid is ejected from the head at a second position in the second path overlap with each other is set as a first overlapping width, a width of a region in which a region of the first band region into which the liquid is ejected from the head at a third position in the first path and a region of the second band region into which the liquid is ejected from the head at a fourth position in the second path overlap with each other is set as a second overlapping width, an angle formed by a vector representing a relative movement between the workpiece and the head at the first position and a vector representing the relative movement between the workpiece and the head at the second position is set as a first angle, and an angle formed by a vector representing the relative movement between the workpiece and the head at the third position and a vector representing the relative movement between the workpiece and the head at the fourth position is set as a second angle, the first angle is more than the second angle, and the first overlapping width is less than the second overlapping width.
Hereinafter, appropriate embodiments according to the present disclosure will be described with reference to the accompanying drawings. In the drawings, dimensions and scale of each portion are appropriately different from the actual ones, and some portions are schematically illustrated for easy understanding. In addition, the scope of the present disclosure is not limited to the forms unless the present disclosure is particularly limited in the following description.
In the following, for convenience of description, an X-axis, a Y-axis, and a Z-axis that intersect with each other are appropriately used. In the following, one direction along the X-axis is an X1 direction, and a direction opposite to the X1 direction is an X2 direction. In the same manner, directions opposite to each other along the Y-axis are a Y1 direction and a Y2 direction. Further, directions opposite to each other along the Z-axis are a Z1 direction and a Z2 direction.
Here, the X-axis, the Y-axis, and the Z-axis correspond to the coordinate axes of a world coordinate system set in a space in which a robot 2, which will be described below, is installed. Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to a downward direction in a vertical direction. A base coordinate system based on a position of a base portion 210, which will be described below, of the robot 2 is associated with the world coordinate system by calibration. In the following, for convenience, a case where an operation of the robot 2 is controlled by using the world coordinate system as a robot coordinate system will be illustrated.
The Z-axis may not be the vertical axis. Further, the X-axis, the Y-axis, and the Z-axis are typically orthogonal to each other, but the present disclosure is not limited to this, and the X-axis, the Y-axis, and the Z-axis may not be orthogonal to each other. For example, the X-axis, Y-axis, and Z-axis may intersect with each other at an angle within a range equal to or more than 80° and equal to or less than 100°.
The workpiece W has a surface including the printing region Wa, which is a range in which an image is formed. In the example illustrated in
As illustrated in
Hereinafter, first, the robot 2, the head unit 3, the controller 5, and the piping portion 10 will be briefly described in order.
The robot 2 is a movement mechanism that changes a position and a posture of the head unit 3 in the world coordinate system. In the example illustrated in
As illustrated in
The base portion 210 is a base that supports the arm portion 220. In the example illustrated in
The arm portion 220 is a 6-axis robot arm having a base end attached to the base portion 210 and a tip that changes a position and a posture three-dimensionally with respect to the base end. Specifically, the arm portion 220 has arms 221, 222, 223, 224, 225, and 226 also referred to as links, which are coupled in this order.
The arm 221 is rotatably coupled to the base portion 210 around a rotation axis O1 via a joint 230_1. The arm 222 is rotatably coupled to the arm 221 around a rotation axis O2 via a joint 230_2. The arm 223 is rotatably coupled to the arm 222 around a rotation axis O3 via a joint 230_3. The arm 224 is rotatably coupled to the arm 223 around a rotation axis O4 via a joint 230_4. The arm 225 is rotatably coupled to the arm 224 around a rotation axis O5 via a joint 230_5. The arm 226 is rotatably coupled to the arm 225 around a rotation axis O6 via a joint 230_6.
Each of the joints 230_1 to 230_6 is a mechanism for rotatably coupling one of two adjacent members of the base portion 210 and the arms 221 to 226 to the other. In the following, each of the joints 230_1 to 230_6 may be referred to as a “joint 230”.
Although not illustrated in
The rotation axis O1 is an axis perpendicular to the installation surface, which is not illustrated, to which the base portion 210 is fixed. The rotation axis O2 is an axis perpendicular to the rotation axis O1. The rotation axis O3 is an axis parallel with the rotation axis O2. The rotation axis O4 is an axis perpendicular to the rotation axis O3. The rotation axis O5 is an axis perpendicular to the rotation axis O4. The rotation axis O6 is an axis perpendicular to the rotation axis O5.
Regarding these rotation axes, “perpendicular” includes not only a case where an angle formed by the two rotation axes is strictly 90°, but also a case where the angle formed by the two rotation axes deviates within a range of approximately 90° to ±5°. In the same manner, “parallel” includes not only a case where the two rotation axes are strictly parallel with each other, but also a case where one of the two rotation axes is inclined within a range of approximately ±5° with respect to the other.
The head unit 3 is mounted on the arm 226 located at the most tip among the arms 221 to 226 of the above robot 2, in a state of being fixed by screwing or the like as an end effector.
The head unit 3 is an assembly having a head 3a that ejects an ink, which is an example of a “liquid”, toward the workpiece W. The surface of the workpiece W is made of, for example, a material that is non-absorbent to inks. The material non-absorbent with respect to inks is a material that does not absorb the inks. For example, the material which is non-absorbent to inks is plastic and inorganic compound such as metals or glass. Meanwhile, the surface of the workpiece W may not be made of a material that is non-absorbent to inks.
In the present embodiment, the head unit 3 also has a pressure regulating valve 3b and an energy emitting portion 3c. Details of the head unit 3 will be described below with reference to
The ink is not particularly limited, and includes, for example, an aqueous ink in which a coloring material such as a dye or a pigment is dissolved in an aqueous solvent, a curable ink using a curable resin such as an ultraviolet curable type, a solvent-based ink in which a coloring material such as a dye or a pigment is dissolved in an organic solvent, and the like. Among the inks, the curable ink is preferably used. The curable ink is not particularly limited, and may have, for example, any of a thermosetting type, a photocurable type, a radiation curable type, an electron beam curable type, and the like, and a photocurable type such as an ultraviolet curable type is preferable. The ink is not limited to the solution, and may be an ink in which a coloring material or the like is dispersed as a dispersant in a dispersion medium. Further, the ink is not limited to an ink containing a coloring material, and may be, for example, an ink containing conductive particles such as metal particles for forming wiring or the like as a dispersant, a clear ink, or a treatment liquid for surface treatment of the workpiece W.
Each of the piping portion 10 and a wiring portion, which is not illustrated, is coupled to the head unit 3. The piping portion 10 is a piping or a piping group that supplies the ink from an ink tank, which is not illustrated, to the head unit 3. The wiring portion is a wiring or a wiring group for supplying an electric signal for driving the head 3a. The routing of the wiring portion may have the same manner as or different from the routing of the piping portion 10.
The controller 5 is a robot controller that controls the drive of the robot 2. The computer 7 is a computer such as a desktop type or a notebook type in which a program is installed, and controls the drive of the head unit 3. Hereinafter, an electrical configuration of the three-dimensional object printing apparatus 1 will be described with reference to
Each electrical component illustrated in
The controller 5 has a function of controlling the drive of the robot 2 and a function of generating a signal D3 for synchronizing an ink ejection operation of the head unit 3 with the operation of the robot 2. The controller 5 has a storage circuit 5a and a processing circuit 5b.
The storage circuit 5a stores various programs to be executed by the processing circuit 5b and various types of data to be processed by the processing circuit 5b. The storage circuit 5a includes, for example, one or both semiconductor memories of a volatile memory such as a random-access memory (RAN) and a non-volatile memory such as a read only memory (ROM), an electrically erasable programmable read-only memory (EEPROM) or a programmable ROM (PROM). A part or all of the storage circuit 5a may be included in the processing circuit 5b.
Printing path information Da is recorded in the storage circuit 5a. The printing path information Da is information which is used for controlling the operation of the robot 2 and indicates a position and a posture of the head 3a in a path RT, which is a path to be described below, along which the head 3a is to be moved when a printing operation is executed. The printing path information Da includes information indicating a change in relative position of the head 3a with respect to the workpiece W when the printing operation is executed, and information indicating a change in relative posture of the head 3a with respect to the workpiece W when the printing operation is executed. The printing path information Da is represented by using, for example, the coordinate values of the workpiece coordinate system, the base coordinate system, or the world coordinate system. When the printing path information Da is represented by using a coordinate value of the workpiece coordinate system, the printing path information Da is used for controlling the operation of the robot 2 after conversion from the coordinate value of the workpiece coordinate system to a coordinate value of the base coordinate system or the world coordinate system.
The processing circuit 5b controls an operation of the arm drive mechanism 2a of the robot 2 based on the printing path information Da, and generates the signal D3. The processing circuit 5b includes, for example, one or more processors such as a central processing unit (CPU). The processing circuit 5b may include a programmable logic device such as a field-programmable gate array (FPGA), instead of the CPU or in addition to the CPU.
Here, the arm drive mechanism 2a is an aggregation of the drive mechanisms of the joints 230_1 to 230_6 described above, and includes a motor for driving the joint of the robot 2 and encoders 241_1 to 241_6 that measure a rotation angle of the joint of the robot 2, for each joint 230.
The processing circuit 5b performs an inverse kinematics calculation, which is an arithmetic operation for converting the printing path information Da into the operation amount such as a rotation angle and a rotation speed of each joint 230 of the robot 2. The processing circuit 5b outputs control signals Sk_1 to Sk_6 based on output signals D1_1 to D1_6 from each of the encoders 241_1 to 241_6 of the arm drive mechanism 2a such that the operation amount such as the actual rotation angle and the rotation speed of each joint 230 becomes the arithmetic operation result described above based on the printing path information Da. Each of the control signal Sk_1 to the control signal Sk_6 corresponds to each of the joint 230_1 to the joint 230_6, and controls the drive of the motor provided in the corresponding joint 230. Each of the output signal D1_1 to the output signal D1_6 corresponds to each of the encoder 241_1 to the encoder 241_6. Hereinafter, each of the output signal D1_1 to the output signal D1_6 may be collectively referred to as an output signal D1. The control signals Sk_1 to Sk_6 are signals for controlling the drive of the motor of the arm drive mechanism 2a. Here, the control signals Sk_1 to Sk_6 are corrected by the processing circuit 5b based on an output from a distance sensor (not illustrated), as needed.
Further, the processing circuit 5b generates the signal D3, based on the output signal D1 from at least one of the encoders 241_1 to 241_6 included in the arm drive mechanism 2a. For example, the processing circuit 5b generates a trigger signal including a pulse at a timing at which the output signal D1 from one of the plurality of encoders becomes a predetermined value as the signal D3.
The control module 6 is a circuit that controls an ink ejection operation in the head unit 3 based on the signal D3 output from the controller 5 and print data Img from the computer 7. The print data Img is information indicating an image to be printed on the workpiece W along each of a plurality of paths indicated by the printing path information Da. 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.
The timing signal generation circuit 6a generates a timing signal PTS based on the signal D3. The timing signal generation circuit 6a is configured with, for example, a timer that starts generation of the timing signal PTS by using detection of the signal D3 as a trigger.
The power supply circuit 6b receives power from a commercial power supply (not illustrated) to generate various predetermined potentials. The various generated potentials are appropriately supplied to each portion of the control module 6 and the head unit 3. For example, the power supply circuit 6b generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the head unit 3. Further, the power supply potential VHV is supplied to the drive signal generation circuit 6d.
The control circuit 6c generates a control signal SI, a waveform designation signal dCom, a latch signal LAT, a clock signal CLK, and a change signal CNG, based on the timing signal PTS. These signals are synchronized with the timing signal PTS. Among these signals, the waveform designation signal dCom is input to the drive signal generation circuit 6d, and the other signals are input to the switch circuit 3e of the head unit 3.
The control signal SI is a digital signal for designating an operation state of a piezoelectric element 311 included in the head 3a of the head unit 3. Specifically, the control signal SI is a signal for designating whether or not to supply a drive signal Com, which will be described below, to the piezoelectric element 311 based on the print data Img. With this designation, for example, whether or not to eject inks from a nozzle N corresponding to the piezoelectric element 311 is designated, and the amount of ink ejected from the nozzle N is designated. The waveform designation signal dCom is a digital signal for defining a waveform of the drive signal Com. The latch signal LAT and the change signal CNG are signals for defining an ejection timing of the ink from the nozzle N, in combination with the control signal SI, by defining a drive timing of the piezoelectric element 311. The clock signal CLK is a reference clock signal synchronized with the timing signal PTS.
The above control circuit 6c includes, for example, one or more processors such as a CPU. The control circuit 6c may include a programmable logic device such as an FPGA instead of the CPU or in addition to the CPU.
The drive signal generation circuit 6d is a circuit that generates the drive signal Com for driving each drive element included in the head 3a of the head unit 3. Specifically, the drive signal generation circuit 6d includes, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generation circuit 6d, the DA conversion circuit converts the waveform designation signal dCom from the control circuit 6c from a digital signal to an analog signal, and the amplifier circuit uses the power supply potential VHV from the power supply circuit 6b to amplify the analog signal and generate the drive signal Com. Here, among waveforms included in the drive signal Com, a signal of a waveform actually supplied to the piezoelectric element 311 is a drive pulse PD. The drive pulse PD is supplied from the drive signal generation circuit 6d to the piezoelectric element 311, via the switch circuit 3e of the head unit 3.
Here, the switch circuit 3e is a circuit including a switching element that switches whether or not to supply at least a part of the waveform included in the drive signal Com as the drive pulse PD based on the control signal SI.
The computer 7 has a function of generating the printing path information Da, a function of supplying information such as the printing path information Da to the controller 5, and a function of supplying information such as the print data Img to the control module 6. For example, the computer 7 generates the printing path information Da based on workpiece information indicating a position and a shape of the workpiece W, and provides the generated printing path information Da to the controller 5. The computer 7 is, for example, a PC. The computer 7 functions as a user interface of the three-dimensional object printing apparatus 1, and a user of the three-dimensional object printing apparatus 1 causes the robot 2 and the head unit 3 to execute a plurality of printing operations including a first printing operation and a second printing operation, which will be described below, via the controller 5 and the control module 6. The computer 7 further has a function of controlling a drive of the energy emitting portion 3c.
As described above, by controlling the drive of the robot 2 based on the printing path information Da and controlling the drive of the head 3a based on the print data Img and the signal D3, the plurality of printing operations are performed. In each printing operation of the plurality of printing operations, while the robot 2 changes the position and the posture of the head 3a based on the printing path information Da, the head 3a ejects inks from the head 3a toward the workpiece W at an appropriate timing based on the print data Img and the signal D3. Thus, an image based on the print data Img is formed at the workpiece W.
Here, the a-axis, the b-axis, and the c-axis correspond to coordinate axes of a tool coordinate system set in the head unit 3, and relative positions and relationships of postures with the world coordinate system or the robot coordinate system described above are changed by the operation of the robot 2 described above. In the example illustrated in
As described above, the head unit 3 has the head 3a, the pressure regulating valve 3b, and the energy emitting portion 3c. The head 3a, the pressure regulating valve 3b, and the energy emitting portion 3c are supported by a support body 3f illustrated by a two-dot chain line in
The support body 3f is made of, for example, a metal material or the like, and is a substantially rigid body. In
The above support body 3f is mounted to the arm 226 described above. Therefore, the head 3a, the pressure regulating valve 3b, and the energy emitting portion 3c are collectively supported on the arm 226 by the support body 3f. Therefore, each relative position of the head 3a, the pressure regulating valve 3b, and the energy emitting portion 3c with respect to the arm 226 is fixed. In the example illustrated in
The head 3a has the nozzle surface FN and a plurality of nozzles N that are opened on the nozzle surface FN. The plurality of nozzles N are divided into a first nozzle array NL1 and a second nozzle array NL2 aligned apart from each other in a direction along the a-axis. Each of the first nozzle array NL1 and the second nozzle array NL2 is a set of the plurality of nozzles N linearly arrayed in a nozzle array direction DN which is a direction along the b-axis. Here, elements related to each of the nozzles N of the first nozzle array NL1 and elements related to each of the nozzles N of the second nozzle array NL2 in the head 3a are configured to be substantially symmetrical with each other in a direction along the a-axis.
Meanwhile, positions of the plurality of nozzles N in the first nozzle array NL1 and the plurality of nozzles N in the second nozzle array NL2 in the direction along the b-axis may or may not coincide with each other. The elements related to each nozzle N of one of the first nozzle array NL1 and the second nozzle array NL2 may be omitted. In the following, a configuration in which the positions of the plurality of nozzles N in the first nozzle array NL1 and the plurality of nozzles N in the second nozzle array NL2 in the direction along the b-axis coincide with each other will be described.
Although not illustrated, the head 3a has the piezoelectric element 311 and a cavity for accommodating inks, for each nozzle N. Here, the piezoelectric element 311 ejects the ink from the nozzle N corresponding to the cavity in an ejection direction DE by changing a pressure of the cavity corresponding to the piezoelectric element 311, and a liquid droplet, which is a droplet of the ink, is landed on the surface of the workpiece W. Such a head 3a can be obtained, for example, by bonding a plurality of substrates such as a silicon substrate appropriately processed by etching or the like with an adhesive or the like. As a drive element for ejecting the ink from the nozzle N, a heater that heats the ink in the cavity may be used, instead of the piezoelectric element 311.
Ink is supplied to the above head 3a from an ink tank, which is not illustrated, via the piping portion 10. Here, the piping portion 10 is coupled to the head 3a via the pressure regulating valve 3b.
The pressure regulating valve 3b is a valve mechanism that is opened and closed according to a pressure of the ink in the head 3a. By this opening and closing, the pressure of the ink in the head 3a is maintained at a negative pressure within a predetermined range even when a positional relationship between the head 3a and the ink tank described above is changed. Therefore, a meniscus of the ink formed at the nozzle N of the head 3a is stabilized. As a result, it is possible to prevent air bubbles from entering the nozzle N, and the ink from overflowing from the nozzle N. Further, the ink from the pressure regulating valve 3b is appropriately distributed to a plurality of locations of the head 3a via a branch flow path, which is not illustrated. Here, the ink from the ink tank is supplied to the pressure regulating valve 3b at a predetermined pressure by a pump or the like.
The energy emitting portion 3c emits energy such as light, heat, an electron beam, or radiation for curing or solidifying the ink on the workpiece W. For example, when the ink has ultraviolet curability, the energy emitting portion 3c is configured with a light emitting element such as a light emitting diode (LED) that emits ultraviolet rays. Further, the energy emitting portion 3c may appropriately have an optical component such as a lens for adjusting an emitting direction or an emitting range of the energy.
As illustrated in
When an image is formed in the printing region Wa, which includes a curved surface, the three-dimensional object printing apparatus 1 divides the printing region Wa into a plurality of band regions BR, and forms a partial image in each of the band regions BR to form the image on the printing region Wa. The band region BR is a strip-shaped region. A longitudinal direction of the band region BR is substantially a main scanning direction, and a lateral direction of the band region BR is substantially a sub-scanning direction. Hereinafter, a width of the band region BR in the lateral direction may be referred to as a width of the band region BR. When printing on the printing region Wa, which includes a curved surface, it is necessary to change the width of the band region BR according to the longitudinal direction of the band region BR. In other words, a shape of the band region BR is not a rectangular shape. The shape that is not the rectangular shape is, for example, a substantially elliptical shape, a rhomboidal shape, a trapezoidal shape, or the like. The reason for changing the width of the band region BR is that a distance between the nozzle N of the head 3a and the printing region Wa is to be kept within a predetermined range since an air flow is generated by changing the relative position and posture between the workpiece W and the head 3a and landing accuracy of liquid droplets is decreased due to an influence of the air flow described above as the distance between the nozzle N of the head 3a and the printing region Wa is larger.
Meanwhile, when the band region BR does not overlap with the adjacent band region BR, a so-called white spot, which is a region in which no image is partially formed, occurs when a positional deviation occurs in at least one band region BR in the longitudinal direction and the lateral direction. In particular, when the head 3a is scanned by using a 6-axis vertical articulated robot as in the present embodiment, a fluctuation of a speed in the main scanning direction and meandering in the sub-scanning direction are large, and it is difficult to eliminate the white spot without overlapping with the band region BR. Therefore, since the band region BR has an overlapping region DR in which the band region BR overlaps with the adjacent band region BR, the occurrence of the white spot can be reduced. Meanwhile, experiments by the inventors clarify that a low quality image may be formed in the overlapping region DR. More specifically, when a direction in which an ink flies to one band region BR among the adjacent band regions BR is significantly different from a direction in which an ink flies to the other band region BR, it is understood that one or both of a low local density and a high local density of the liquid droplets occur. Hereinafter, one or both of the low local density and the high local density of the liquid droplets may be collectively referred to as “uneven liquid droplets”. The uneven liquid droplets will be described with reference to
In the state in
As understood from
As illustrated in
The third position P3 is located at a center of the band region BR_1 on the X-axis. The fifth position P5 is located at an end portion of the band region BR_1 in the X1 direction. The first position P1 is located between the third position P3 and the fifth position P5 in the path RT_1. The fourth position P4 is located at a center of the band region BR_2 on the X-axis. The sixth position P6 is located at an end portion of the band region BR_2 in the X1 direction. The second position P2 is located between the fourth position P4 and the sixth position P6 in the path RT_2.
As illustrated in
As illustrated in
The path RT_1 and the path RT_2 are paths from a start position PS to an end position PE along the surface of the workpiece W. Here, a main scanning direction DΦ_1 is a direction defined by the path RT_1. The main scanning direction DΦ_1 is a longitudinal direction of the band region BR_1 and is a direction along the path RT_1, and the direction is constantly changed. The main scanning direction DΦ_1 can be said to be a direction in which a relative movement distance of the head 3a is largest in a printing operation on the band region BR_1. In the same manner, a main scanning direction DΦ_2 is a direction defined by the path RT_2. The main scanning direction DΦ_2 is a direction along the path RT_2, and the direction is constantly changed. The main scanning direction DΦ_2 can be said to be a direction in which the relative movement distance of the head 3a is largest in the printing operation on the band region BR_2. The arrangement of the start position PS and the end position PE in the present embodiment is an example, and the arrangement of the start position PS and the end position PE of one or both paths RT may be reversed in a direction along the X-axis.
In the following description, each of the path RT_1 and the path RT_2 may be collectively referred to as a path RT without distinguishing the path RT_1 and the path RT_2. In the same manner, without distinguishing each of the main scanning direction DΦ_1 and the main scanning direction DΦ_2, the main scanning direction DΦ_1 and the main scanning direction DΦ_2 may be collectively referred to as a main scanning direction DΦ. The main scanning direction DΦdefines a vector by a start point and an end point of the relative movement of the head 3a for each printing operation on each band region BR, and can be said to be a direction parallel to a vector obtained by combining these vectors. Therefore, the main scanning direction DΦ is a concept indicating a direction substantially equal to the main scanning direction DΦ_1 and the main scanning direction DΦ_2. As can be understood from
In the following description, a direction orthogonal to the main scanning direction DΦ is referred to as a sub-scanning direction DΦ. More strictly, the sub-scanning direction DΦ is a direction that is orthogonal to the main scanning direction DΦ, and is along the printing region Wa. In the present embodiment, the sub-scanning direction Dθ is a direction rotating around the X-axis, and is a direction along the Y-axis as illustrated in
Here, the first position P1 and the second position P2 have the same positions in the main scanning direction DΦ, the third position P3 and the fourth position P4 have the same positions in the main scanning direction DΦ, and the fifth position P5 and the sixth position P6 have the same positions in the main scanning direction DΦ.
As illustrated in
A flight direction of an ink at a certain position in the path RT when the workpiece W is viewed from the head 3a along the ejection direction DE approximately coincides with a vector at the position in the path RT. The vector of the certain position in the path RT is a vector representing a relative movement between the workpiece W and the head 3a at this position, and is a tangent line vector of the path RT at this position. Further, it can be said that the vector at the certain position in the path RT is a vector representing a relative movement between the workpiece W and the head 3a in a predetermined section of the path RT in the forward-rearward direction, which is represented by this position. In
As illustrated in
As illustrated in
The band region BR_1 is an example of a “first band region”, the path RT_1 is an example of a “first path”, and a printing operation of ejecting inks from the head 3a onto the workpiece W while being changed by the path RT_1 along the main scanning direction DΦ_1 is an example of a “first printing operation”. Further, the band region BR_2 is an example of a “second band region”, the path RT_2 is an example of a “second path”, and a printing operation of ejecting the inks from the head 3a to the workpiece W while being changed by the path RT_2 along the main scanning direction DΦ_2 is an example of a “second printing operation”.
A magnitude of an angle formed by vectors in the two adjacent paths RT is small at a center of the band region BR, and becomes large at an end portion of the band region BR. A specific example of a deviation in a direction in which the ink lands will be described with reference to
In the vicinity of the first virtual line segment L1 in the region PA, among flight directions of the liquid droplets DP_1, a component parallel to the surface of the workpiece W is a direction indicated by the vector V1, and among flight directions of the liquid droplet DP_2, a component parallel to the surface of the workpiece W is a direction indicated by the vector V2. An angle formed by the vector V1 and the vector V2 is a first angle θ12. In addition, in the vicinity of the second virtual line segment L2 in the region PA, among flight directions of the liquid droplets DP_1, a component parallel to the surface of the workpiece W is a direction indicated by the vector V3, and among flight directions of the liquid droplet DP_2, a component parallel to the surface of the workpiece W is a direction indicated by the vector V4. An angle formed by the vector V3 and the vector V4 is a second angle θ34. As illustrated in
As can be understood from
As illustrated in
The description will be continued with reference to
For example, in
As a method of determining the overlapping width DW, the computer 7 may calculate an inner product of a unit tangent line vector at a position Pa in one of the two adjacent paths RT and a unit tangent line vector at a position Pb in the other path RT to calculate an angle formed by the vector of the position Pa and the vector of the position Pb. Here, the position Pa and the position Pb are examples of two positions that are the same position in the main scanning direction DΦ, and a part of the region in which the head 3a at the position Pa can eject inks and a part of the region in which the head 3a at the position Pb can eject the inks overlap with each other. The computer 7 or the user determines the overlapping region DR such that the overlapping width DW becomes more as the calculated angle becomes less. In this determination, the user may input any value, a default value stored in advance in the computer 7 may be used, or an appropriate value calculated by the computer 7 according to a shape of the workpiece W may be used such that the overlapping width DW becomes more as the calculated angle becomes less. It is possible to construct an algorithm in which the overlapping width DW is increased in accordance with the decrease in the calculated angle, and such a relationship is represented by any function such as a linear function, for example. Since an appropriate length of the overlapping width DW may be changed depending on the shape of the workpiece W or performance of the head 3a, characteristics of the ink, a speed or a weight of a liquid droplet ejected by the head 3a, and the like, it is preferable to adjust the length appropriately according to these conditions such that the overlapping width DW becomes more as the calculated angle becomes less.
In step S110, the three-dimensional object printing apparatus 1 executes a pre-printing operation. The pre-printing operation in step S110 is an operation in which the robot 2 changes a relative position of the head 3a with respect to the workpiece W before a printing operation. In the pre-printing operation, the head 3a does not eject inks. The pre-printing operation includes, for example, a preparation operation such as an operation in which the robot 2 moves the head 3a from a position at which a cap (not illustrated) for covering the nozzle surface FN is provided to the start position PS of any one band region BR among the plurality of band regions BR, an operation in which the rotation axis O2, the rotation axis O3, and the rotation axis O5 are in a state to be parallel to each other, and the like. The fact that the rotation axis O2, the rotation axis O3, and the rotation axis O5 are parallel to each other means that the rotation axis O2 and the rotation axis O3 are parallel to each other, the rotation axis O3 and the rotation axis O5 are parallel to each other, and the rotation axis O2 and the rotation axis O5 are parallel to each other. In the pre-printing operation, all of the six joints 230 of the robot 2 can be operated.
After step S110 is ended, the three-dimensional object printing apparatus 1 executes the printing operation in step S120. The printing operation is an operation in which the head 3a ejects inks while the robot 2 changes the relative position of the head 3a with respect to the workpiece W in the main scanning direction DΦ. Although the number of joints 230 that operate in the printing operation among the plurality of joints 230 is not particularly limited, in the printing operation, the head 3a may be moved by operations of a smaller number of joints 230 than in the pre-printing operation. As compared with the pre-printing operation, a deviation of an actual movement path from an ideal movement path of the head 3a is reduced by operating the smaller number of joints 230.
In addition, in order to form a partial image to be formed in each band region BR of the plurality of band regions BR in the printing operation, the computer 7 generates the print data Img indicating the partial image corresponding to each band region BR of the plurality of band regions BR, prior to the printing operation.
After step S120 is ended, the three-dimensional object printing apparatus 1 determines whether or not to execute the next printing operation in step S130. In other words, the three-dimensional object printing apparatus 1 determines whether or not there is a band region BR in which the printing operation is not executed among the plurality of band regions BR.
When the determination result in step S130 is positive, the three-dimensional object printing apparatus 1 executes a movement operation in step S140. The positive determination result in step S130 is a case where the next printing operation is to be executed, and can be said that there is a band region BR in which the printing operation is not executed among the plurality of band regions BR. The movement operation is an operation of moving the head 3a to the start position PS of the band region BR corresponding to the next printing operation. In the movement operation, the head 3a does not eject the inks. In the movement operation, the robot 2 changes a posture of the head 3a while fixing a posture of the workpiece W. After step S140 is ended, the three-dimensional object printing apparatus 1 executes the printing operation in step S120.
When the determination result in step S130 is negative, the three-dimensional object printing apparatus 1 executes a post-printing operation in step S150. The fact that the determination result in step S130 is negative is a case where the next printing operation is not to be executed, and can be said to be a case where the printing operation is executed for the plurality of band regions BR. The post-printing operation includes, for example, an operation in which the robot 2 moves the head 3a from the end position PE of any one of the plurality of band regions BR to another position. The other position is, for example, the position at which the cap described above is provided. In the post-printing operation, all of the six joints 230 of the robot 2 can be operated, and the head 3a is moved by operations of a larger number of joints 230 than in the printing operation. After step S150 is ended, the three-dimensional object printing apparatus 1 ends the series of operations illustrated in
Hereinafter, a summary of the first embodiment will be described by using an example in which in step S120 for the first time, a printing operation on the band region BR_1 is executed, and in the second step S120, the printing operation on the band region BR_2 is executed. In the summary of the first embodiment, the printing operation in step S120 for the first time is an example of the “first printing operation”, and the printing operation in step S120 for the second time is an example of the “second printing operation”. The printing operation for the first time in step S120 is described as a first-time printing operation, and the printing operation in step S120 for the second time is described as a second-time printing operation.
As described above, the three-dimensional object printing apparatus 1 according to the first embodiment includes the head 3a having the plurality of nozzles N that eject inks to the printing region Wa on the workpiece W, and a movement mechanism that changes a relative position and posture between the workpiece W and the head 3a. The three-dimensional object printing apparatus 1 executes the first-time printing operation of ejecting the inks from the head 3a to the workpiece W while changing the relative position between the workpiece W and the head 3a with the path RT_1 along the main scanning direction DΦ_1, and a second-time printing operation of ejecting the inks from the head 3a to the workpiece W while changing the relative position between the workpiece W and the head 3a by a path RT_2 along the main scanning direction DΦ_2.
Further, in the three-dimensional object printing method according to the first embodiment, step S120 of executing the first-time printing operation of ejecting the inks from the head 3a to the workpiece W while changing the relative position between the workpiece W and the head 3a with the path RT_1 along the main scanning direction DΦ_1, and step S120 of executing the second-time printing operation of ejecting the inks from the head 3a to the workpiece W while changing the relative position between the workpiece W and the head 3a with path RT_2 along the main scanning direction DΦ_2 are executed.
The printing region Wa includes the band region BR_1 in which the ink is ejected from the head 3a in the printing operation for the first time and the band region BR_2 in which the ink is ejected from the head 3a in the printing operation for the second time. When an angle formed by the vector V1 at the first position P1 in the path RT_1 and the vector V2 at the second position P2 in the path RT_2 is set as the first angle θ12, an angle formed by the vector V3 at the third position P3 in the path RT_1 and the vector V4 at the fourth position P4 in the path RT_2 is set as the second angle θ34, a width with which the band region BR_1 overlaps with the band region BR_2 at the first position P1 is set as the overlapping width DW1, and a width with which the region BR_1 overlaps with the band region BR_2 at the third position P3 is set as the overlapping width DW3, the first virtual line segment L1 coupling the first position P1 and the second position P2 along the surface of the workpiece W and second virtual line segment L2 coupling the third position P3 and the fourth position P4 along the surface of the workpiece W do not intersect each other, the first angle θ12 is more than the second angle θ34, and the overlapping width DW1 is less than the overlapping width DW3.
With the first embodiment, it is possible to reduce a region in which an image having a low quality such as uneven liquid droplets occurs, as compared with an aspect in which the overlapping width DW1 is more than the overlapping width DW3.
The width W1 of the band region BR_1 at the first position P1 is less than the width W3 of the band region BR_1 at the third position P3, and the width W2 of the band region BR_2 at the second position P2 is less than the width W2 of the band region BR_2 at the fourth position P4.
As described above, since printing is performed on the printing region Wa, which is a curved surface, a shape of the band region BR is not a rectangular shape. With the first embodiment, a region in which an image having a low quality such as uneven liquid droplets that may occur when printing is performed on the printing region Wa, which is a curved surface, can be reduced.
The first position P1 is closer to an end of the band region BR_1 than the third position P3, and the overlapping width DW1 is more than 0.
As described above, when the head 3a is scanned by using a 6-axis vertical articulated robot, the fluctuation of the speed in the main scanning direction DΦ and the meandering in the sub-scanning direction Dθ are large. Therefore, with the first embodiment, since the overlapping width DW1 is more than 0, the overlapping region DR can be provided at the first position P1, and occurrence of white spots can be prevented.
In addition, when among the plurality of nozzles N, the nozzle N that ejects inks to the overlapping region DR_1 in which the band region BR_1 overlaps with the band region BR_2 is set as the nozzle N1 and among the plurality of nozzles N, the nozzle N that ejects the inks to the non-overlapping region SR_1 in which the band region BR_1 does not overlap with the band region BR_2 is set as the nozzle N2, the distance PG1 between the position PD1 at which the ink ejected from the nozzle N1 lands in the band region BR_1 and the nozzle N1 is less than the distance PG2 between a position at which the ink ejected from the nozzle N2 lands in the band region BR_1 and the nozzle N2.
The reason why the distance between the nozzle N of the head 3a and the printing region Wa is within a predetermined range is that an air flow occurs since the relative position and posture between the workpiece W and the head 3a are changed, and the longer the distance between the nozzle N of the head 3a and the print region Wa is, the more the print region is affected by the air flow described above. Therefore, as the distance between the nozzle N and the printing region Wa is increased, the ink ejected from the nozzle N is likely to deviate from the position at which the ink is to land due to the influence of the air flow. As illustrated in
In addition, the third position P3 is a position having the largest width in the band region BR_1.
At the position at which the width is the largest, an angle formed by the vectors of the two adjacent paths RT can be substantially 0 degrees, that is, directions of the respective vectors can be made substantially parallel. By setting the directions of the respective vectors to be substantially parallel to each other, it is possible to prevent occurrence of uneven liquid droplets applied onto the workpiece W.
Further, a surface forming the printing region Wa is made of a material that does not absorb the inks ejected from each of the plurality of nozzles N.
When the nozzle surface FN and the surface forming the printing region Wa are not parallel and have an inclination, the landing position may deviate from the original landing position due to the deviation in a direction in which the ink lands on the printing region Wa, and the quality of the image may deteriorate. In particular, when the printing region Wa is configured with a material that does not absorb inks, a part of the liquid droplet moves due to the deviation in the direction in which the ink lands, and the quality of the image significantly deteriorates. Therefore, the three-dimensional object printing apparatus 1 according to the present embodiment can reduce the occurrence of the deviation in the landing direction by making the overlapping width DW1 less than the overlapping width DW3, and thus the quality of the image formed in the printing region Wa can be maintained even when the printing region Wa is made of a material that does not absorb inks.
In addition, the ink ejected from each of the plurality of nozzles N is an ultraviolet curable ink.
The ultraviolet curable ink is not absorbed by the workpiece W. In particular, in a case of low-density printing, the ink ejected from one nozzle N among the plurality of nozzles N adheres in the printing region Wa in a state of an isolated dot without being combined with an ink ejected from other nozzles. Therefore, in the aspect in which the ultraviolet curable ink is used, the deviation in the direction in which the ink lands is more likely to affect the image quality, as compared with an aspect in which the ink absorbed inside the workpiece W is used. Since the three-dimensional object printing apparatus 1 according to the present embodiment can reduce the occurrence of the deviation in the direction in which the ink lands by making the overlapping width DW1 less than the overlapping width DW3, the quality of the image formed in the printing region Wa can be maintained even when the ultraviolet curable ink is used.
In the first embodiment, the overlapping region DR exists from one end to the multiple ends of the X-axis of the band region BR. Meanwhile, the overlapping region DR may not exist at an end portion of the band region BR in the X1 direction and an end portion of the band region BR in the X2 direction. A second embodiment will be described below.
In the second embodiment, the printing region Wa includes a band region BR-A_1 and a band region BR-A_2.
The band region BR-A_1 has a non-overlapping region SR-A_1 and an overlapping region DR-A_1 that overlaps with the band region BR-A_2. The band region BR-A_2 has a non-overlapping region SR-A_2 and an overlapping region DR-A_2 that overlaps with the band region BR-A_1. In the following description, each of the non-overlapping region SR-A_1 and the non-overlapping region SR-A_2 may be described as a non-overlapping region SR-A without distinguishing the non-overlapping region SR-A_1 and the non-overlapping region SR-A_2. In addition, without distinguishing each of the overlapping region DR-A_1 and the overlapping region DR-A_2, the overlapping region DR-A_1 and the overlapping region DR-A_2 may be described as an overlapping region DR-A.
The overlapping region DR-A is narrower than the overlapping region DR in the first embodiment. Since the overlapping region DR-A has a shape different from the shape of the overlapping region DR, the band region BR-A also has a shape different from the shape of the band region BR. In the second embodiment, among a width W3-A of the band region BR-A_1 at the third position P3, a width W1-A of the band region BR-A_1 at the first position P1, and a width W5-A of the band region BR-A_1 at the fifth position P5, the width W3-A is the largest, the width W1-A is the next largest, and the width W5-A is the smallest. In addition, among a width W4-A of the band region BR-A_2 at the fourth position P4, a width W2-A of the band region BR-A_2 at the second position P2, and a width W6-A of the band region BR-A_2 at the sixth position P6, the width W4-A is the largest, the width W2-A is the next largest, and the width W6-A is the smallest. In
As illustrated in
Ejection directions of the liquid droplets DP-A in the vicinity of the first virtual line segment L1 and in the vicinity of the second virtual line segment L2 in the region PA are the same as in
As described above, in the second embodiment, when the angle formed by the vector V5 at the fifth position P5 in the path RT_1 and the vector V6 at the sixth position P6 in the path RT_2 is set as the third angle θ56, the third virtual line segment L3 coupling the fifth position P5 and the sixth position P6 along a surface of the workpiece W does not intersect with the first virtual line segment L1 and the second virtual line segment L2, the third angle θ56 is more than the first angle θ12, and the band region BR-A_1 and the band region BR-A_2 do not overlap with each other at the fifth position P5. The first virtual line segment L1 is located between the second virtual line segment L2 and the third virtual line segment L3.
A magnitude of the angle formed by the vectors in the two adjacent paths RT is large at the end portion of the band region BR-A. Therefore, in the second embodiment, the overlapping region DR-A is not provided at the fifth position P5, which is the end portion of the band region BR-A, so that an image having a low quality such as uneven liquid droplets can be prevented from being formed.
In addition, as illustrated in
Each form exemplified above can be variously modified. A specific aspect of the modification is illustrated below. Any two or more aspects selected from the following examples can be combined as appropriate as long as there is no contradiction.
In the printing operation in step S130 in each of the aspects described above, the position of the head 3a is moved once from the start position PS to the end position PE with respect to one band region BR. Meanwhile, the present disclosure is not limited thereto. For example, the position of the head 3a may be moved a plurality of times along the path RT with respect to one band region BR, and the head 3a may eject inks in each of the plurality of movements. In each of the plurality of movements, the computer 7 generates the print data Img indicating a partial image corresponding to each of the plurality of movements. For example, when n times of movement are executed with respect to one band region BR, the computer 7 generates the print data Img such that the recording ratio is 1/n in one movement.
The printing region Wa of the workpiece W in each of the aspects described above is a projecting curved surface. Meanwhile, the present disclosure is not limited thereto. Another example of the surface of the workpiece W will be described as a second modification example.
The printing region Wa-E includes a band region BR-E_1 and a band region BR-E_2. Hereinafter, each of the band region BR-E_1 and the band region BR-E_2 may be collectively referred to as a band region BR without distinguishing the band region BR-E_1 and the band region BR-E_2.
As illustrated in
The path RT-E_1 is a path from a start position PS-E_1 to an end position PE-E_1 along the surface of the workpiece W-E. The path RT-E_2 is a path from a start position PS-E_2 to the end position PE-E_2 along the surface of the workpiece W-E. A main scanning direction DΦ-E_1 is a longitudinal direction of the band region BR-E_1 and is a direction along the path RT-E_1, and the direction is constantly changed. A main scanning direction DΦ-E_2 is the longitudinal direction of the band region BR-E_2 and is a direction along the path RT-E_2, and the direction is constantly changed.
Regarding the specific shape of the band region BR-E, a width at a center of the band region BR-E on the X-axis is the smallest, and the width of the band region BR-E becomes larger toward the X2 direction or the X1 direction. Specifically, a width WC-E_1 at a position PC-E_1 which is a center of the band region BR-E_1 on the X-axis is less than a width WS-E_1 of the band region BR-E_1 at the start position PS-E_1. In the same manner, a width WC-E_2 at a position PC-E_2 which is a center of the band region BR-E_2 on the X-axis is less than a width WS-E_2 of the band region BR-E_2 at the start position PS-E_2.
In the example in
In the second modification example, the start position PS-E_1 is an example of the “first position”, the start position PS-E_2 is an example of the “second position”, the position PC-E_1 is an example of the “third position”, and the position PC-E_2 is an example of the “fourth position”. The width DS-E is an example of the “first overlapping width”, and the width DC-E is an example of the “second overlapping width”.
In each of the aspects described above, the surface forming the printing region Wa is configured with a material that does not absorb the ink ejected from each of the plurality of nozzles N. Meanwhile, the present disclosure is not limited thereto. For example, the surface forming the printing region Wa may be made of a material that is less likely to absorb the ink, as compared with a printing paper such as paper.
In each of the embodiments described above, the configuration using the 6-axis vertical multi-axis robot as the robot is described. Meanwhile, the configuration is not limited to this configuration. The robot 2 may be, for example, a vertical multi-axis robot other than the 6-axis robot, or a horizontal multi-axis robot. Further, the arm portion 220 of the robot 2 may have a telescopic mechanism, a linear motion mechanism, or the like in addition to the joint configured with the rotation mechanism. Meanwhile, from the viewpoint of the balance between the print quality in the printing operation and the degree of freedom of the robot 2 operation in the non-printing operation such as the pre-printing operation, the movement operation, and the post-printing operation, the robot 2 may be a multi-axis robot having 6 axes or more.
In each of the embodiments described above, the configuration using screwing or the like as a method of fixing the head 3a to the robot 2 is described, and the configuration is not limited to this configuration. For example, the head 3a may be fixed to the robot 2 by gripping the head 3a with a gripping mechanism such as a hand mounted as an end effector of the robot 2.
In each of the embodiments described above, the configuration in which printing is performed by using one type of ink is described. Meanwhile, the configuration is not limited to this configuration, and the present disclosure can be applied to a configuration in which printing is performed by using two or more types of ink.
The use of the three-dimensional object printing apparatus of the present disclosure is not limited to image printing. For example, a three-dimensional object printing apparatus that ejects a solution of a conductive material is used as a manufacturing apparatus of forming wirings or electrodes on a wiring substrate. In addition, the three-dimensional object printing apparatus can also be used as a jet dispenser of applying a liquid such as an adhesive to a medium.
In each of the embodiments described above, the configuration in which the head 3a is supported by the robot 2 and moved is described. Meanwhile, the configuration is not limited to this configuration. For example, the head 3a may be fixed to a base or the like, and the workpiece W may be supported by the robot 2 and moved.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-020907 | Feb 2023 | JP | national |
