Printing method and robot system

Abstract

To provide a printing method and a robot system that can perform printing with high quality.SOLUTION: A printing method uses a robot comprising a print head having a plurality of nozzles juxtaposed in a prescribed direction, and performs a printing work for an object by discharging the ink from the nozzle while relatively moving the object and the print head. The method includes: a virtual line setting step at which a plurality of virtual lines, which are juxtaposed in a direction parallel to a discharge direction of the ink and orthogonal to the discharge direction and the movement direction, are set to a 3D model of the object; an intersection point detection step at which an intersection point between the virtual line and the object is determined; a distance detection step at which a distance between adjacent intersection points is detected; and a non-discharge nozzle determination step at which the nozzle, which does not discharge the ink, is determined on the basis of the distance.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a printing method and a robotic system. [Background technology]

[0002] The painting robot described in Patent Document 1 has a robot body with an arm and a nozzle head unit attached to the tip of the arm. The robot body is used to move the nozzle head unit relative to the object while ejecting ink from the nozzle head unit toward the object, thereby printing on the object. The nozzle head unit is provided with a plurality of nozzles aligned in a predetermined direction. Here, if the distance between the nozzle and the object is large, the printed image may be misaligned, warped, distorted, etc., and the print quality may decrease. Therefore, Patent Document 1 attempts to suppress the deterioration of print quality by controlling the print width per scan by not ejecting ink from nozzles that are separated from the object by a predetermined value or more. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 255896 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even if the distance between the nozzle and the target is small, or the target is greatly tilted with respect to the ink ejection direction, the printed image may become misaligned, warped, distorted, etc., resulting in a deterioration in print quality. The painting robot described in Patent Document 1 cannot prevent the deterioration in print quality in such cases. [Means for solving the problem]

[0005] A printing method of the present invention is a printing method using a robot equipped with a print head having a plurality of nozzles arranged in a predetermined direction, and performing a printing operation on an object by ejecting ink from the nozzles while moving the object and the print head relatively, a virtual line setting step of setting a plurality of virtual lines arranged in a direction parallel to the ink ejection direction and perpendicular to the ink ejection direction and the movement direction with respect to the 3D model of the object; an intersection detection step of determining an intersection between each of the virtual lines and the object; a distance detection step of detecting a distance between adjacent intersections; and a non-ejecting nozzle determination step of determining the nozzles that do not eject the ink based on the distance.

[0006] The robot system of the present invention comprises: a robot having a print head with a plurality of nozzles arranged in a predetermined direction; A control device for controlling the driving of the robot, A robot system that performs a printing operation on an object by ejecting ink from the nozzles while moving the object and the print head relatively, The control device includes: setting a plurality of virtual lines arranged in a direction parallel to the ink ejection direction and perpendicular to the ink ejection direction and the movement direction with respect to the 3D model of the object; determining an intersection point between each of the virtual lines and the object; Detecting the distance between adjacent intersections; The nozzles that do not eject the ink are determined based on the distance. [Brief description of the drawings]

[0007] [Figure 1] 1 is an overall view of a robot system according to a first embodiment. [Diagram 2] 2 is a plan view showing a moving stage provided in the robot shown in FIG. 1. [Diagram 3] 11 is a flowchart illustrating a printing method. [Figure 4] FIG. 2 is a perspective view showing the shape of an object and a printing trajectory. [Diagram 5] FIG. 13 is a diagram for explaining a preparation step. [Figure 6] FIG. 11 is a perspective view showing an object according to the second embodiment. [Figure 7] FIG. 13 is a diagram for explaining a preparation step. [Figure 8] FIG. 13 is a diagram for explaining a preparation step. [Figure 9] 11 is a table showing the relationship between time and non-ejecting nozzles. [Figure 10] 11 is a table showing the relationship between the position of the print head and non-ejecting nozzles. [Figure 11] FIG. 11 is a perspective view showing an object according to a third embodiment. [Figure 12] FIG. 13 is a diagram for explaining a preparation step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a printing method and a robot system according to the present invention will be described in detail based on the embodiments shown in the accompanying drawings.

[0009] First Embodiment Fig. 1 is an overall view of a robot system according to a first embodiment. Fig. 2 is a plan view showing a moving stage provided in the robot shown in Fig. 1. Fig. 3 is a flow chart for explaining a printing method. Fig. 4 is a perspective view showing a shape of an object and a printing trajectory. Fig. 5 is a diagram for explaining a preparation step.

[0010] The robot system 1 shown in Fig. 1 is applied to a printing system that performs a printing operation on an object W. The robot system 1 has a robot 10 and a control device 9 that controls the driving of the robot 10. The robot 10 also has a robot body 2, a moving stage 4 arranged at the tip of the robot body 2, a print head 3 arranged on the moving stage 4, and a vibration meter 5 arranged on the print head 3. In this robot system 1, a printing operation is performed on the object W by ejecting ink I from the print head 3 at a predetermined timing while moving the print head 3 relative to the object W using a robot arm 22.

[0011] In this embodiment, the position of the object W is fixed, and the object W and the print head 3 are moved relatively by moving only the print head 3, but this is not limited to this, and the object W and the print head 3 may be moved relatively by moving both the print head 3 and the object W.

[0012] <Robot body 2> The robot body 2 is a six-axis vertical articulated robot having six drive axes, and includes a base 21 fixed to a mounting table, a floor, or the like, and a robot arm 22 rotatably connected to the base 21. The robot arm 22 is configured with six arms 221, 222, 223, 224, 225, and 226 rotatably connected in this order from the base 21 side, and includes six joints J1, J2, J3, J4, J5, and J6. Among the joints J1 to J6, the joints J2, J3, and J5 are bending joints, and the joints J1, J4, and J6 are torsion joints. In addition, a drive mechanism including a motor and an encoder that detects the amount of rotation of the joint is installed in each of the joints J1, J2, J3, J4, J5, and J6. By independently moving each of the joints J1, J2, J3, J4, J5, and J6, the print head 3 attached to the tip of the robot arm 22 can be moved in a desired direction, at a desired attitude, and at a desired speed.

[0013] However, the configuration of the robot body 2 is not particularly limited. For example, the number of arms provided on the robot arm 22 is not limited to six. The robot body 2 may be a dual-arm robot, a horizontally articulated robot (SCARA robot), or the like. The robot body 2 may be self-propelled without being fixed to a stand, floor, or the like.

[0014] <Mobile Stage 4> As shown in Fig. 1, the moving stage 4 is disposed at the tip of the robot arm 22, i.e., on the arm 226. The moving stage 4 is used to correct the position of the print head 3. As shown in Fig. 2, the moving stage 4 has a base 40 supported by the arm 226, a first stage 41 that moves linearly in a first direction A relative to the base 40, and a second stage 42 that moves linearly in a second direction B perpendicular to the first direction A relative to the first stage 41. The print head 3 is disposed on the second stage 42.

[0015] The moving stage 4 also has a first stage driving unit 45 that moves the first stage 41 relative to the base 40 along the first direction A, and a second stage driving unit 46 that moves the second stage 42 relative to the first stage 41 along the second direction B. The first and second stage driving units 45 and 46 each have a piezoelectric actuator 400 that is driven by utilizing the expansion and contraction of a piezoelectric element caused by energization, and move the first and second stages 41 and 42 by transmitting the vibration of the piezoelectric actuator 400 to them. In this way, by using the piezoelectric actuator 400, the movement amount and movement speed of the first and second stages 41 and 42 can be finely and highly accurately controlled, and the movement direction can be quickly switched. In addition, the moving stage 4 can be made smaller and lighter. Therefore, the position correction of the print head 3 can be performed with higher accuracy.

[0016] However, the configuration of the moving stage 4 is not particularly limited. For example, the first and second stage driving units 45, 46 may be configured to use a driving source other than the piezoelectric actuator 400, such as a motor that rotates when energized. Furthermore, the moving stage 4 may further include a third stage that moves linearly in a direction perpendicular to the first direction A and the second direction B, and a fourth stage that moves rotationally around an axis perpendicular to the first direction A and the second direction B. The moving stage 4 may also be omitted. In this case, the position of the print head 3 may be corrected by the robot arm 22.

[0017] <Print Head 3> As shown in FIG. 2, the print head 3 is disposed on the second stage 42. The print head 3 is not particularly limited, but in this embodiment, a piezoelectric drive type inkjet head is used. The piezoelectric drive type inkjet has an ink chamber, a vibration plate constituting a part of the wall surface of the ink chamber, a piezoelectric element for vibrating the vibration plate, and a nozzle 31 connected to the ink chamber. In this configuration, when a voltage is applied to the piezoelectric element to vibrate the piezoelectric element, the vibration plate vibrates and the ink I in the ink chamber is ejected from the nozzle 31. Also, as shown in FIG. 2, the tip surface of the print head 3 has seven nozzles 31 arranged at equal intervals along the print track Q, that is, the direction perpendicular to the movement direction of the print head 3 during printing work. In the following, when distinguishing between the seven nozzles 31, they are also called nozzles 311, 312, 313, 314, 315, 316, and 317.

[0018] Furthermore, ink I of the same color, for example black ink I, is ejected from each nozzle 31. Then, while moving the print head 3 along the print trajectory Q, the ink I is ejected from each nozzle 31 at a predetermined timing and caused to land on the target object W, thereby printing a predetermined print image on the target object W. In this way, by having multiple nozzles 31 aligned in a direction perpendicular to the print trajectory Q, i.e., in a predetermined direction, the printing range per scan of the print head 3 is expanded, and printing work can be performed efficiently.

[0019] However, the configuration of the print head 3 is not particularly limited. For example, the number and arrangement of the nozzles 31, the color of the ink I ejected from the nozzles 31, etc. are not particularly limited. For example, the print head 3 may have nozzles 31 that eject cyan ink I, nozzles 31 that eject magenta ink I, nozzles 31 that eject yellow ink I, and nozzles 31 that eject black ink I, and is capable of full-color printing of the CMYK color model. In this case, the nozzles of each color may be arranged side by side in a direction along the print trajectory Q.

[0020] Furthermore, the configuration of the print head 3 is not limited to the above-mentioned piezo-driven inkjet head, but may be, for example, an inkjet head of a thermal type that utilizes the film boiling phenomenon of the ink I, a bubble ejection type that ejects the ink I by generating bubbles in the ink I by applying heat, or an electrostatic actuator type that ejects the ink I by displacing and vibrating a vibration plate by electrostatic force.

[0021] ≪Vibration meter 5≫ 1 and 2, the vibration meter 5 is disposed on the print head 3 and detects vibrations of the print head 3. Note that the "vibration" refers to unnecessary displacements other than the displacement of the print head 3 along the print trajectory Q. The vibration meter 5 is not particularly limited as long as it can detect vibrations, and for example, a three-axis acceleration sensor that detects angular velocity in three mutually perpendicular axial directions can be used.

[0022] <Control device 9> As shown in Fig. 1, the control device 9 is electrically connected to the robot 10 and controls the driving of the robot 10. Specifically, the control device 9 controls the driving of the robot body 2, the print head 3, the moving stage 4, and the vibration meter 5, either independently or in conjunction with each other. Such a control device 9 is, for example, composed of a computer, and has a processor (CPU) for processing information, a memory communicatively connected to the processor, and an external interface for connecting to an external device. Various programs executable by the processor are stored in the memory, and the processor can read and execute the programs stored in the memory.

[0023] The configuration of the robot system 1 has been described above. Next, a method for printing on an object W using the robot system 1 will be described. As shown in FIG. 3, the printing method includes a preparation step S1 for determining the nozzles 31 that do not eject the ink I based on the shape of the object W, and a printing step S2 for performing a printing operation on the object W. The shape of the object W, more specifically, the shape of the printing surface of the object W is not particularly limited, but is preferably a non-flat surface such as a curved surface, a bent surface, or a surface that combines these, that is, a three-dimensional shape other than a flat surface. This makes the effect of the printing direction of this embodiment more pronounced. Below, these steps S1 and S2 will be described in detail.

[0024] <Preparation step S1> As shown in FIG. 3, the preparation step S1 includes a print trajectory setting step S10 in which a print trajectory Q is set based on the shape of the target object W, a virtual line setting step S11 in which multiple virtual lines L are set on the target object W, an intersection detection step S12 in which an intersection O between each virtual line L and the surface of the target object W is determined, a distance detection step S13 in which the distance D between adjacent intersection points O is detected, and a non-ejecting nozzle determination step S14 in which nozzles 31 that do not eject ink I are determined based on the distance D.

[0025] In the print trajectory setting step S10, first, the control device 9 acquires a 3D model representing the shape of the target object W. The 3D model is not particularly limited, and examples thereof include CAD (computer aided design) data of the target object W and measurement data obtained by measuring the target object W using a measuring device such as a 3D scanner. In this embodiment, CAD data is used as the 3D model. This makes it possible to obtain accurate shape data, and therefore this step can be performed with high accuracy.

[0026] Next, as shown in FIG. 4, the control device 9 determines the print trajectory Q of the print head 3 based on the 3D model of the object W. In other words, it determines the movement direction of the print head 3 relative to the object W in order to print the print image on the object W. Note that in this step, it is preferable to determine the print trajectory Q on the premise that ink I is ejected from all nozzles 31. This maximizes the printing width per scan, making it possible to determine the print trajectory Q that enables efficient printing. However, the method of setting the print trajectory Q is not particularly limited as long as it is possible to print the print image on the object W.

[0027] In this embodiment, the target object W is cylindrical as shown in Fig. 4. That is, the cross-sectional shape of the target object W is constant along the printing trajectory Q. The printing trajectory Q is a straight line along the axial direction above the target object W. However, the shape of the target object W and the printing trajectory Q are not particularly limited.

[0028] 5, in a virtual line setting step S11, the control device 9 sets a plurality of virtual lines L parallel to the ejection direction of the ink I on the 3D model of the target object W. The multiple virtual lines L are arranged side by side in a predetermined direction, specifically, in a direction perpendicular to the print trajectory Q, that is, the movement direction of the print head 3 and the virtual lines L.

[0029] In particular, in this embodiment, three or more virtual lines L are set at equal intervals. Furthermore, the separation distance DL between adjacent virtual lines L is proportional to an integer multiple of the separation distance between adjacent nozzles 31. Note that in this embodiment, the separation distance DL is 1x the separation distance between adjacent nozzles 31. In other words, the separation distance DL is equal to the separation distance between adjacent nozzles 31. Seven virtual lines L are set corresponding to each nozzle 31, and each virtual line L coincides with a perpendicular line passing through the center of the corresponding nozzle 31. Note that the above-mentioned "parallel" includes a case where the virtual line L is parallel to the ejection direction of the ink I, as well as a case where the virtual line L is inclined to an extent that can be regarded as being parallel to the ejection direction of the ink I in terms of technical common sense.

[0030] Furthermore, hereinafter, when distinguishing between the virtual lines L, the virtual line L corresponding to nozzle 311 will be referred to as virtual line L1, the virtual line L corresponding to nozzle 312 as virtual line L2, the virtual line L corresponding to nozzle 313 as virtual line L3, the virtual line L corresponding to nozzle 314 as virtual line L4, the virtual line L corresponding to nozzle 315 as virtual line L5, the virtual line L corresponding to nozzle 316 as virtual line L6, and the virtual line L corresponding to nozzle 317 as virtual line L7. In this embodiment, since the nozzles 311, 312, 313, 314, 315, 316, and 317 are arranged side by side at equal intervals, the virtual lines L1, L2, L3, L4, L5, L6, and L7 are correspondingly set at equal intervals.

[0031] Next, in an intersection detection step S12, the control device 9 detects intersections O between the 3D model of the object W and each virtual line L and their positions, as shown in Fig. 5. In the following, when distinguishing between the intersections O, the intersection O between the object W and virtual line L1 will be referred to as intersection O1, the intersection O between the object W and virtual line L2 as intersection O2, the intersection O between the object W and virtual line L3 as intersection O3, the intersection O between the object W and virtual line L4 as intersection O4, the intersection O between the object W and virtual line L5 as intersection O5, the intersection O between the object W and virtual line L6 as intersection O6, and the intersection O between the object W and virtual line L7 as intersection O7.

[0032] Next, in the distance detection step S13, the control device 9 detects the distance D between adjacent intersections O as shown in FIG. 5. That is, the control device 9 detects the distance D12 between the intersections O1 and O2, the distance D23 between the intersections O2 and O3, the distance D34 between the intersections O3 and O4, the distance D45 between the intersections O4 and O5, the distance D56 between the intersections O5 and O6, and the distance D67 between the intersections O6 and O7. Here, the distance D12 may be the length of a straight line connecting the two intersections O1 and O2, or may be the distance along the surface of the object W between the two intersections O1 and O2. By defining the distance D12 in this way, the distance D12 can be easily calculated from the positions of the intersections O1 and O2 and the shape of the object W. In this embodiment, the distance D12 is the latter, that is, the distance along the surface of the object W between the two intersections O1 and O2. This makes it possible to more accurately determine the condition of the surface of the object W. The same is true for the other distances D23, D34, D45, D56, and D67.

[0033] In non-ejecting nozzle determination step S14, nozzles 31 that will not eject ink I in the next printing step S2 are determined based on the distance D. In other words, for each nozzle 31, whether or not to eject ink I in the next printing step S2 is selected based on the distance D. Note that the following description will be given representatively of the distance D12.

[0034] 5, when the surface of the object W between the intersections O1 and O2 is a plane F that is perpendicular to the virtual line L and the print trajectory Q, the distance D12 is equal to the separation distance DL between the virtual lines L1 and L2. In contrast, when the surface of the object W between the intersections O1 and O2 is inclined with respect to the plane F as in this embodiment, the distance D12 is greater than the separation distance DL. The difference ΔD12 (=D12-DL) between the distance D12 and the separation distance DL increases as the inclination of the surface of the object W with respect to the plane F increases.

[0035] When the inclination of the surface of the object W with respect to the plane F becomes large, for example, the ink I after landing may spread over the surface of the object W due to its own weight, or the distance between adjacent dots, i.e., the landing positions of adjacent ink I, may widen. This may result in blurring, bleeding, distortion, etc. in the printed image, leading to a deterioration in print quality. Therefore, in order to suppress the deterioration in print quality, the control device 9 does not eject ink I from the nozzle 311 in the next printing step S2 when the difference ΔD12 exceeds a preset threshold value SH. The threshold value SH is not particularly limited, but may be, for example, about 1.5 times or more and 2.0 times or less the separation distance DL.

[0036] Similarly, the control device 9 detects the differences ΔD23, ΔD34, ΔD45, ΔD56, ΔD67 from the separation distance DL for the other distances D23, D34, D45, D56, D67, and compares the detected differences ΔD23, ΔD34, ΔD45, ΔD56, ΔD67 with a threshold value SH. If the difference ΔD23 exceeds the threshold value SH, the ink I is not discharged from the nozzle 312 in the printing step S2, if the difference ΔD34 exceeds the threshold value SH, the ink I is not discharged from the nozzle 313 in the printing step S2, if the difference ΔD45 exceeds the threshold value SH, the ink I is not discharged from the nozzle 315 in the printing step S2, if the difference ΔD56 exceeds the threshold value SH, the ink I is not discharged from the nozzle 316 in the printing step S2, and if the difference ΔD67 exceeds the threshold value SH, the ink I is not discharged from the nozzle 317 in the printing step S2. This effectively prevents the ink I from spreading after landing and the increase in the distance between adjacent dots caused by the inclination of the surface of the target object W, enabling high-quality printing with little blurring, bleeding, distortion, etc.

[0037] As an example, in this embodiment, the differences ΔD12 and ΔD67 exceed the threshold SH, while the other differences ΔD23, ΔD34, ΔD45, and ΔD56 are equal to or smaller than the threshold SH. Therefore, in the next printing step S2, the control device 9 does not eject ink I from the nozzles 311 and 317, but ejects ink I from the remaining nozzles 312, 313, 314, 315, and 316.

[0038] With the above, the preparation step S1 is completed. Particularly in this embodiment, three or more virtual lines L are set at equal intervals along a predetermined direction in the virtual line setting step S11. Therefore, the surface of the object W can be divided into smaller regions in a balanced manner, and it can be determined whether or not the difference between the distance D and the separation distance DL exceeds the threshold value SH for each divided region. Therefore, the inclination of the surface of the object W can be determined more locally. As a result, in the non-ejecting nozzle determination step S14, the nozzles 31 that do not eject ink I can be determined with greater accuracy.

[0039] Furthermore, in this embodiment, the interval between adjacent virtual lines L is equal to the interval between adjacent nozzles 31. Therefore, the surface of the object W can be divided into a plurality of regions at intervals equal to the pitch of the nozzles 31. Therefore, the surface of the object W can be divided into sufficiently narrow regions, and the inclination of the surface of the object W can be determined more locally. As a result, in the non-ejecting nozzle determination step S14, the nozzles 31 that do not eject ink I can be determined with greater accuracy.

[0040] Furthermore, the virtual line L is set corresponding to the nozzle 31. Therefore, the area divided by the virtual line L overlaps with the area between adjacent nozzles 31, and the surface of the target object W is divided into a plurality of areas at optimal positions for the nozzles 31. Therefore, in the non-ejecting nozzle determination step S14, the nozzles 31 that do not eject ink I can be determined with greater accuracy.

[0041] <Printing step S2> In the printing step S2, the control device 9 drives the robot arm 22 to move the print head 3 along the print trajectory Q, while discharging ink I from the nozzles 312, 313, 314, 315, and 316 at a predetermined timing, thereby causing the discharged ink I to land on the surface of the object W, and performing a printing operation on the object W. According to this method, the ink I after landing, which is caused by the inclination of the surface of the object W, spreads, and an increase in the distance between adjacent dots can be effectively suppressed, and high-quality printing with little blurring, bleeding, distortion, etc. can be performed. In addition, the control device 9 detects vibration of the print head 3 based on the output of the vibration meter 5 during the printing operation, and controls the driving of the moving stage 4 so that the detected vibration is canceled. Specifically, the control device 9 controls the driving of the moving stage 4 so that vibration of the opposite phase to the detected vibration is applied to the print head 3. This suppresses vibration of the print head 3 during the printing operation, enabling higher quality printing.

[0042] The printing method using the robot system 1 has been described above. As described above, this printing method uses the robot 10 equipped with the print head 3 having a plurality of nozzles 31 arranged in a predetermined direction, and performs printing on the object W by ejecting ink I from the nozzles 31 while moving the object W and the print head 3 relatively. The printing method includes a virtual line setting step S11 for setting a plurality of virtual lines L arranged in a direction parallel to the ejection direction of the ink I and perpendicular to the ejection direction of the ink I and the moving direction of the print head 3 with respect to a 3D model of the object W, an intersection detection step S12 for determining an intersection O between the virtual line L and the object W, a distance detection step S13 for detecting the distance D between adjacent intersections O, and a non-ejecting nozzle determination step S14 for determining a nozzle 31 that does not eject ink I based on the distance D. According to this method, the ink I after landing spreads due to the inclination of the surface of the object W, and an increase in the distance between adjacent dots can be effectively suppressed, and high-quality printing can be performed.

[0043] As described above, in the virtual line setting step S11, three or more virtual lines L are set at equal intervals along a predetermined direction. This allows the surface of the object W to be divided into smaller regions in a well-balanced manner, and the inclination of the surface of the object W can be determined more locally. This allows the nozzles 31 that do not eject ink I to be determined more accurately in the non-ejecting nozzle determination step S14.

[0044] Furthermore, as described above, the interval between adjacent virtual lines L is proportional to an integer multiple of the interval between adjacent nozzles 31. Therefore, the width of each region divided by the virtual lines is equal to or smaller than the pitch of the nozzles 31. Therefore, the surface of the object W can be divided into sufficiently narrow regions, and the inclination of the surface of the object W can be determined more locally. As a result, in the non-ejecting nozzle determination step S14, the nozzles 31 that do not eject ink I can be determined with greater accuracy.

[0045] As described above, the virtual line L is set in correspondence with the nozzle 31. Therefore, the area divided by the virtual line L overlaps with the area between adjacent nozzles 31, and the surface of the target object W is divided into a plurality of areas at optimal positions for the nozzles 31. Therefore, in the non-ejecting nozzle determination step S14, the nozzles 31 that do not eject ink I can be determined with greater accuracy.

[0046] As described above, the distance D is the length of the straight line connecting two adjacent intersections O. This makes it possible to easily calculate the distance D from the positions of the intersections O1 and O2.

[0047] As described above, the distance D is the distance along the surface of the object W between two adjacent intersections O. This makes it possible to easily calculate the distance D from the positions of the intersections O1 and O2 and the 3D model of the object W. In addition, the surface condition of the object W can be detected with higher accuracy.

[0048] As described above, the robot system 1 includes a robot 10 equipped with a print head 3 having multiple nozzles 31 arranged in a predetermined direction, and a control device 9 that controls the driving of the robot 10, and is the robot system 1 that performs a printing operation on an object W by ejecting ink I from the nozzles 31 while moving the object W and the print head 3 relatively. The control device 9 also sets multiple virtual lines L aligned in a direction parallel to the ejection direction of the ink I and perpendicular to the ejection direction of the ink I and the moving direction of the print head 3 with respect to a 3D model of the object W, finds intersections O between each virtual line L and the object W, detects distances D between adjacent intersections O, and determines nozzles 31 that do not eject ink I based on the distance D.

[0049] <Second embodiment> Fig. 6 is a perspective view showing an object according to the second embodiment. Fig. 7 and Fig. 8 are diagrams for explaining the preparation step. Fig. 9 is a table showing the relationship between time and non-ejecting nozzles. Fig. 10 is a table showing the relationship between the position of the print head and non-ejecting nozzles.

[0050] This embodiment is similar to the first embodiment described above, except that the shape of the target object W is different. In the following description, the present embodiment will be described focusing on the differences from the first embodiment described above, and the description of the similarities will be omitted. In each drawing of this embodiment, the same reference numerals are used for the same configurations as the above-mentioned embodiment.

[0051] 6, in this embodiment, the shape of the target object W changes midway along the printing trajectory Q. Specifically, the target object W has a first cylindrical portion W1 and a second cylindrical portion W2 having a larger diameter than the first cylindrical portion W1, and the first and second cylindrical portions W1, W2 are coaxially connected along the printing trajectory Q. Therefore, the control device 9 determines the nozzles 31 that do not eject ink I separately for the first cylindrical portion W1 and the second cylindrical portion W2.

[0052] As an example, in the first cylindrical portion W1 shown in FIG. 7, there is no intersection O between the virtual lines L1 and L7 and the first cylindrical portion W1. Therefore, ΔD12 and ΔD67 do not exist and exceed the threshold value SH. In addition, ΔD23 and ΔD56 exceed the threshold value SH. Therefore, when printing on the first cylindrical portion W1 in the printing step S2, the control device 9 does not eject ink I from the nozzles 311, 312, 316, and 317, but ejects ink I from the remaining nozzles 313, 314, and 315. In addition, in the second cylindrical portion W2 shown in FIG. 8, the differences ΔD12 and ΔD67 exceed the threshold value SH. Therefore, when printing on the second cylindrical portion W2 in the printing step S2, the control device 9 does not eject ink I from the nozzles 311 and 317, but ejects ink I from the remaining nozzles 312, 313, 314, 315, and 316.

[0053] In this case, for example, as shown in Fig. 9, table data that defines the non-ink-ejecting nozzles 31 for each time period can be generated, and the ejection of ink I can be controlled based on this table data. Also, as shown in Fig. 10, table data that defines the non-ink-ejecting nozzles 31 for each position of the print head 3 during printing can be generated, and the ejection of ink I can be controlled based on this table data. Also, table data that combines these can be generated, and the ejection of ink I can be controlled based on this table data. Note that in Figs. 9 and 10, "1" indicates a nozzle that can eject ink I, and "0" indicates a non-ejecting nozzle that does not eject ink I.

[0054] Thus, in this embodiment, when the shape of the target object W changes along the print trajectory Q, the nozzles 31 that do not eject ink I are changed every time the shape changes. In other words, the nozzles 31 that do not eject ink I change while the print head 3 is moving along the print trajectory Q. This makes it possible to perform high-quality printing on targets W of various shapes.

[0055] In the second embodiment described above, as described above, the nozzles 31 that do not eject ink I change while the print head 3 is moving. Therefore, high-quality printing can be performed on targets W of various shapes.

[0056] The second embodiment as described above can also achieve the same effects as the first embodiment described above.

[0057] <Third embodiment> Fig. 11 is a perspective view showing an object according to the third embodiment, and Fig. 12 is a diagram for explaining a preparation step.

[0058] This embodiment is similar to the first embodiment described above, except that the shape of the target object W is different. In the following description, the present embodiment will be described focusing on the differences from the first embodiment described above, and the description of the similarities will be omitted. In addition, in the drawings of this embodiment, the same reference numerals are used for the same configurations as the above-mentioned embodiment.

[0059] 10 and 11, the surface of the target object W in this embodiment is irregularly curved along the arrangement direction of the nozzles 31. Then, as an example, only the difference ΔD67 exceeds the threshold SH. In this case, the control device 9 does not eject ink I from nozzle 317 in the printing step S2, but ejects ink I from the remaining nozzles 311, 312, 313, 314, 315, and 316.

[0060] The third embodiment as described above can also achieve the same effects as the first embodiment described above.

[0061] The printing method and robot system of the present invention have been described above in terms of the illustrated embodiment, but the present invention is not limited thereto, and the configuration and steps of each part can be replaced with any configuration or step having a similar function. Any other configuration or step may be added to the present invention. The embodiments may also be appropriately combined. The direction in which the multiple nozzles 31 are arranged side by side has been described as being perpendicular to the printing trajectory Q, i.e., the moving direction of the print head 3, but it may not be perpendicular and may be intersecting. [Explanation of symbols]

[0062] 1...robot system, 10...robot, 2...robot body, 21...base, 22...robot arm, 221...arm, 222...arm, 223...arm, 224...arm, 225...arm, 226...arm, 3...print head, 31...nozzle, 311...nozzle, 312...nozzle, 313...nozzle, 314...nozzle, 315...nozzle, 316...nozzle, 317...nozzle, 4...moving stage, 40...base, 400...piezoelectric actuator, 41...first stage, 42...second stage, 45...first stage drive unit, 46...second stage drive unit, 5...vibration meter, 9...control device, A...first direction, B...second direction, D...distance, D12...distance, D23...distance, D34...distance, D4 5...distance, D56...distance, D67...distance, DL...separation distance, F...surface, I...ink, J1...joint, J2...joint, J3...joint, J4...joint, J5...joint, J6...joint, L...virtual line, L1...virtual line, L2...virtual line, L3...virtual line, L4...virtual line, L5...virtual line, L6...virtual line, L7...virtual line, O...intersection, O1...intersection, O2...intersection, O3...intersection, O4...intersection, O5...intersection, O6...intersection, O7...intersection, Q...printing trajectory, S1...preparation step, S10...printing trajectory setting step, S11...virtual line setting step, S12...intersection detection step, S13...distance detection step, S14...non-ejecting nozzle determination step, S2...printing step, W...object, W1...first cylindrical portion, W2...second cylindrical portion

Claims

1. A printing method using a robot equipped with a print head having a plurality of nozzles arranged in a predetermined direction, performing a printing operation on an object by ejecting ink from the nozzles while moving the object and the print head relatively, comprising: a virtual line setting step of setting a plurality of virtual lines arranged in a direction parallel to the ink ejection direction and perpendicular to the ink ejection direction and the movement direction with respect to the 3D model of the object; an intersection detection step of determining an intersection between each of the virtual lines and the object; a distance detection step of detecting a distance between adjacent intersections; a non-ejecting nozzle determination step of determining the nozzles that do not eject the ink based on the distance.

2. The printing method according to claim 1 , wherein in the virtual line setting step, three or more virtual lines are set at equal intervals along the predetermined direction.

3. The printing method according to claim 1 , wherein the interval between adjacent virtual lines is proportional to an integral multiple of the interval between adjacent nozzles.

4. The printing method according to claim 3 , wherein the virtual lines are set corresponding to the nozzles.

5. The printing method according to claim 1 , wherein the distance is a length of a straight line connecting two adjacent intersections.

6. The printing method according to claim 1 , wherein the distance is a distance along the surface of the object between two adjacent intersections.

7. The printing method according to claim 1 , wherein the nozzles that do not eject the ink are changed while the print head is moving.

8. A robot having a print head having a plurality of nozzles arranged in a predetermined direction; A control device for controlling the driving of the robot, A robot system that performs a printing operation on an object by ejecting ink from the nozzles while moving the object and the print head relatively, The control device includes: setting a plurality of virtual lines arranged in a direction parallel to the ink ejection direction and perpendicular to the ink ejection direction and the movement direction with respect to the 3D model of the object; determining an intersection point between each of the virtual lines and the object; Detecting the distance between adjacent intersections; A robot system comprising: a nozzle that does not eject the ink, the nozzle being determined based on the distance.

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