Printing method and robot system

Abstract

The invention provides a printing method and a robot system capable of performing high-quality printing. The printing method uses a robot including a print head having a plurality of nozzles arranged side by side in a predetermined direction, performs a print job on a target object by moving the target object and the print head relative to each other and discharging ink from the nozzles, and includes: a virtual line setting step of setting a virtual line on the target object; setting, for the 3D model of the target object, a plurality of virtual lines parallel to the ejection direction of the ink and arranged in a direction orthogonal to the ejection direction and the movement direction; an intersection point detection step of obtaining an intersection point between each virtual line and the target object; a distance detection step of detecting the distance between the adjacent intersection points; and a non-ejection nozzle determination step of determining the nozzles that do not eject the ink on the basis of the distance.

Description

Technical Field

[0001] The invention relates to a printing method and a robot system. Background Art

[0002] The painting robot described in Patent Document 1 comprises: a robot body having an arm; and a nozzle head unit mounted on the front end of the arm. Ink is ejected from the nozzle head unit toward the target object while the nozzle head unit is moved relative to the target object using the robot body, thereby printing the target object. In addition, the nozzle head unit is provided with a plurality of nozzles arranged in a prescribed direction. Here, if the separation distance between the nozzle and the target object is large, the printed image may be offset, distorted, skewed, etc., which may result in reduced print quality. Therefore, in Patent Document 1, ink is set to non-ejection for nozzles whose separation distance from the target object is greater than a prescribed value, thereby controlling the print width of each scan to try to suppress the reduction in print quality.

[0003] Patent Document 1: International Publication No. 2021 / 255896

[0004] However, when the target object is tilted greatly relative to the ink ejection direction, even if the separation distance between the nozzle and the target object is small, the printed image may be offset, twisted, skewed, etc., resulting in reduced print quality. In the painting robot described in Patent Document 1, it is impossible to suppress the reduction in print quality in this case. Summary of the invention

[0005] The printing method of the present invention uses a robot equipped with a print head, which has a plurality of nozzles arranged in a specified direction. The printing method performs a printing operation on the target object by moving the target object relative to the print head and ejecting ink from the nozzles. The printing method includes: a virtual line setting step, setting a plurality of virtual lines parallel to the ejection direction of the ink and arranged in a direction orthogonal to the ejection direction and the moving direction for a 3D model of the target object; an intersection detection step, finding the intersection of each of the virtual lines and the target object; a distance detection step, detecting the distance between adjacent intersections; and a non-ejection nozzle determination step, determining the nozzle that does not eject the ink based on the distance.

[0006] The robot system of the present invention comprises: a robot having a print head, the print head having a plurality of nozzles arranged in a specified direction; and a control device, which controls the driving of the robot, and performs a printing operation on the target object by causing the target object and the print head to move relative to each other and ejecting ink from the nozzles. The control device sets a plurality of virtual lines parallel to the ejection direction of the ink and arranged in a direction orthogonal to the ejection direction and the movement direction for a 3D model of the target object, the control device calculates the intersection point of each of the virtual lines with the target object, the control device detects the distance between adjacent intersection points, and the control device determines the nozzle that does not eject the ink based on the distance. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is an overall diagram of the robot system according to the first embodiment.

[0008] Figure 2 It is shown Figure 1 A top view of the mobile stage of the robot shown.

[0009] Figure 3 is a flowchart for explaining the printing method.

[0010] Figure 4 It is a three-dimensional diagram showing the shape of the target object and the printing track.

[0011] Figure 5 It is a diagram for explaining the preparation steps.

[0012] Figure 6 It is a perspective view showing a target object according to the second embodiment.

[0013] Figure 7 It is a diagram for explaining the preparation steps.

[0014] Figure 8 It is a diagram for explaining the preparation steps.

[0015] Fig. 9 It is a table showing the relationship between time points and non-discharging nozzles.

[0016] Fig.10 This is a table showing the relationship between the position of the print head and the non-ejecting nozzles.

[0017] Fig.11 It is a perspective view showing a target object according to the third embodiment.

[0018] Fig.12 It is a diagram for explaining the preparation steps.

[0019] Description of Reference Numerals

[0020] 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: vibrometer; 9: control device; A: first direction; B: second direction; D: distance; D12: distance; D23: distance; D34: distance; D45: distance; D56: distance From; 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: print track; S1: preparation step; S10: print track setting step; S11: virtual line setting step; S12: intersection detection step; S13: distance detection step; S14: non-ejection nozzle determination step; S2: printing step; W: target object; W1: first cylindrical portion; W2: second cylindrical portion. DETAILED DESCRIPTION

[0021] Hereinafter, the printing method and the robot system of the present invention will be described in detail based on the embodiments shown in the drawings.

[0022] First embodiment

[0023] Figure 1 It is an overall diagram of the robot system according to the first embodiment. Figure 2 It is shown Figure 1 A top view of the mobile stage of the robot shown. Figure 3 is a flowchart for explaining the printing method. Figure 4 It is a three-dimensional diagram showing the shape of the target object and the printing track. Figure 5 It is a diagram for explaining the preparation steps.

[0024] Figure 1The robot system 1 shown is applied to a printing system for performing a printing operation on a target object W. The robot system 1 includes a robot 10 and a control device 9 for controlling the driving of the robot 10. In addition, the robot 10 includes: a robot body 2; a moving stage 4, which is arranged at the front end of the robot body 2; a print head 3, which is arranged on the moving stage 4; and a vibrometer 5, which is arranged on the print head 3. In such a robot system 1, the printing operation on the target object W is performed by moving the print head 3 relative to the target object W using the robot arm 22, and ejecting ink I from the print head 3 at a predetermined timing.

[0025] It should be noted that in this embodiment, the position of the target object W is fixed and only the print head 3 is moved, thereby causing the target object W and the print head 3 to move relative to each other. However, this is not limited to this, and the print head 3 and the target object W may also be moved together, thereby causing the target object W and the print head 3 to move relative to each other.

[0026] Robot body 2

[0027] The robot body 2 is a six-axis vertical multi-joint robot having six drive axes, and has: a base 21 fixed to a mounting table, a floor, etc.; and a robot arm 22 connected to the base 21 in a rotatable manner. The robot arm 22 is composed of six arm parts 221, 222, 223, 224, 225, and 226 connected in this order in a rotatable manner from the side of the base 21, and has six joints J1, J2, J3, J4, J5, and J6. Among the joints J1 to J6, the joints J2, J3, and J5 are bending joints, respectively, and the joints J1, J4, and J6 are torsion joints, respectively. In addition, a driving mechanism having a motor and an encoder that detects the rotation amount of the joint is provided in each joint J1, J2, J3, J4, J5, and J6. Furthermore, by independently moving the joints J1 , J2 , J3 , J4 , J5 , and J6 , the print head 3 mounted on the front end of the robot arm 22 can be moved in a desired direction at a desired posture and speed.

[0028] However, the structure of the robot body 2 is not particularly limited. For example, the number of arms provided by the robot arm 22 is not limited to six. In addition, the robot body 2 may also be a two-arm robot, a horizontal multi-joint robot (SCARA robot), etc. In addition, the robot body 2 may not be fixed to a mounting table, a floor, etc., but may be able to move autonomously.

[0029] Mobile stage 4

[0030] like Figure 1 As shown, the movable stage 4 is disposed at the front end of the mechanical arm 22, that is, the arm portion 226. The movable stage 4 is used for position correction of the print head 3. Figure 2As shown, the movable stage 4 includes: a base 40 supported by the arm 226; a first stage 41 linearly moving in a first direction A relative to the base 40; and a second stage 42 linearly moving in a second direction B orthogonal to the first direction A relative to the first stage 41. The print head 3 is arranged on the second stage 42.

[0031] In addition, the movable stage 4 has: a first stage driving unit 45, which moves the first stage 41 along the first direction A relative to the base 40; and a second stage driving unit 46, which moves the second stage 42 along the second direction B relative to the first stage 41. The first and second stage driving units 45 and 46 respectively have piezoelectric actuators 400 driven by the expansion and contraction of the piezoelectric element caused by energization, and transmit the vibration of the piezoelectric actuator 400 to the first and second stages 41 and 42, thereby moving 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 accurately controlled, and the switching of the movement direction is also flexible. In addition, the miniaturization and lightness of the movable stage 4 can also be achieved. Therefore, the position correction of the print head 3 can be performed with better accuracy.

[0032] However, the structure of the movable stage 4 is not particularly limited. For example, the first and second stage driving parts 45 and 46 may also be configured to use a driving source other than the piezoelectric actuator 400, such as a motor that rotates by energizing. In addition, further, the movable stage 4 may also have a third stage that moves linearly in a direction orthogonal to the first direction A and the second direction B, and a fourth stage that rotates around an axis orthogonal to the first direction A and the second direction B. In addition, the movable stage 4 may be omitted. In this case, the position correction of the print head 3 may be performed by the robot arm 22.

[0033] Print head 3

[0034] like Figure 2 As shown, the print head 3 is arranged on the second stage 42. The print head 3 is not particularly limited, but a piezoelectric driven inkjet head is used in this embodiment. The piezoelectric driven inkjet head has: an ink chamber; a vibration plate, which constitutes a part of the wall surface of the ink chamber; a piezoelectric element, which vibrates the vibration plate; and a nozzle 31 connected to the ink chamber. In such a structure, 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. In addition, as Figure 2As shown, seven nozzles 31 are formed at equal intervals along a direction perpendicular to the print track Q, that is, the moving direction of the print head 3 during printing. It should be noted that, hereinafter, when the seven nozzles 31 are distinguished, they are also referred to as nozzles 311, 312, 313, 314, 315, 316, and 317.

[0035] Ink I of the same color, for example, black ink I, is ejected from each nozzle 31. Then, while the print head 3 is moved along the print track Q, ink I is ejected from each nozzle 31 at a predetermined timing so that the ink I lands on the target object W, thereby printing a predetermined print image on the target object W. In this way, by having a plurality of nozzles 31 arranged in a direction orthogonal to the print track Q, that is, in a predetermined direction, the print range of each scan of the print head 3 is expanded, and the printing operation can be performed efficiently.

[0036] 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 described below may include: a nozzle 31 ejecting cyan ink I, a nozzle 31 ejecting magenta ink I, a nozzle 31 ejecting yellow ink I, and a nozzle 31 ejecting black ink I, and may be a print head 3 capable of full-color printing in a CMYK color model. In this case, the nozzles of each color may be arranged in a direction along the print track Q.

[0037] In addition, the configuration of the print head 3 is not limited to the above-mentioned piezoelectric drive type inkjet head. For example, it may be a thermal type inkjet head that utilizes the film boiling phenomenon of the ink I, a bubble ejection type inkjet head that generates bubbles in the ink I by heating and ejects the ink I, an electrostatic actuator type inkjet head that ejects the ink I by displacing / vibrating a vibration plate by electrostatic force, etc.

[0038] Vibration meter 5

[0039] like Figure 1 and Figure 2 As shown, the vibrometer 5 is disposed on the print head 3 to detect the vibration of the print head 3. It should be noted that the "vibration" refers to the unnecessary displacement other than the displacement along the print track Q of the print head 3. The vibrometer 5 is not particularly limited as long as it can detect vibration. For example, a three-axis acceleration sensor that detects angular velocity in three mutually orthogonal axial directions can be used.

[0040] Control device 9

[0041] like Figure 1As shown, 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 robot body 2, the print head 3, the moving stage 4 and the vibration meter 5 so that they are driven independently or in conjunction. Such a control device 9 is composed of, for example, a computer and has: a processor (CPU) for processing information, a memory that can be connected to the processor in communication, and an external interface for connecting to an external device. The memory stores various programs that can be executed by the processor, and the processor can read and execute the programs stored in the memory.

[0042] The configuration of the robot system 1 has been described above. Next, a printing method for printing a target object W using the robot system 1 will be described. Figure 3 As shown, the printing method includes: a preparation step S1, determining the nozzle 31 that does not eject the ink I based on the shape of the target object W; and a printing step S2, performing a printing operation on the target object W. It should be noted that the shape of the target object W, more specifically, the shape of the printing surface of the target object W is not particularly limited, and a non-plane such as a curved surface, a folded surface, and a surface composed of them, that is, a three-dimensional shape other than a plane, is preferably used. Therefore, the effect of the printing direction of this embodiment is significant. Below, each of these steps S1 and S2 is described in detail.

[0043] Preparation step S1

[0044] like Figure 3 As shown, the preparation step S1 includes: a print track setting step S10, setting a print track Q based on the shape of the target object W; a virtual line setting step S11, setting multiple virtual lines L for the target object W; an intersection detection step S12, finding the intersection O of each virtual line L and the surface of the target object W; a distance detection step S13, detecting the distance D between adjacent intersections O; and a non-ejecting nozzle determination step S14, determining the nozzle 31 that does not eject ink I based on the distance D.

[0045] In the print track setting step S10, first, the control device 9 obtains 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, measurement data obtained by measuring the target object W using a measuring device such as a 3D scanner, etc. It should be noted that in this embodiment, CAD data is used as the 3D model. Therefore, in order to obtain shape data with good accuracy, this step can be performed with good accuracy.

[0046] Next, if Figure 4As shown, the control device 9 determines the print track Q of the print head 3 based on the 3D model of the target object W. That is, the moving direction of the print head 3 relative to the target object W for printing the print image on the target object W is determined. It should be noted that in this step, the print track Q is preferably determined on the premise of ejecting ink I from all nozzles 31. In this way, the print width of each scan is maximized, and the print track Q for effective printing can be determined. However, the method for setting the print track Q is not particularly limited as long as the print image can be printed on the target object W.

[0047] It should be noted that if Figure 4 As shown, in this embodiment, the target object W is cylindrical. That is, the cross-sectional shape of the target object W is constant along the printing track Q. In addition, the printing track 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 track Q are not particularly limited.

[0048] Next, if Figure 5 As shown, in the 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 for the 3D model of the target object W. In addition, the plurality of virtual lines L are arranged in a predetermined direction, specifically, in a direction orthogonal to the moving direction of the print head 3 and the virtual lines L along the print track Q.

[0049] In particular, in the present embodiment, more than three virtual lines L are set at equal intervals. In addition, the interval between adjacent virtual lines L, that is, the separation distance DL, is in an integer multiple ratio with the interval between adjacent nozzles 31. It should be noted that, in the present embodiment, the separation distance DL is 1 times the interval between adjacent nozzles 31. That is, the separation distance DL is equal to the interval between adjacent nozzles 31. In addition, seven virtual lines L are set corresponding to each nozzle 31, and each virtual line L is consistent with a vertical line passing through the center of the corresponding nozzle 31. It should be noted that the "parallel" means that in addition to the case where the virtual line L is parallel to the ejection direction of the ink I, it also includes the case where the virtual line L is inclined relative to the ejection direction of the ink I to a degree that can be regarded as parallel in technical common sense.

[0050] In addition, hereinafter, when the virtual lines L are distinguished, the virtual line L corresponding to the nozzle 311 is also referred to as a virtual line L1, the virtual line L corresponding to the nozzle 312 is also referred to as a virtual line L2, the virtual line L corresponding to the nozzle 313 is also referred to as a virtual line L3, the virtual line L corresponding to the nozzle 314 is also referred to as a virtual line L4, the virtual line L corresponding to the nozzle 315 is also referred to as a virtual line L5, the virtual line L corresponding to the nozzle 316 is also referred to as a virtual line L6, and the virtual line L corresponding to the nozzle 317 is also referred to as a virtual line L7. In the present embodiment, since the nozzles 311, 312, 313, 314, 315, 316, and 317 are arranged at equal intervals, the virtual lines L1, L2, L3, L4, L5, L6, and L7 are also set at equal intervals accordingly.

[0051] Next, if Figure 5 As shown, in the intersection detection step S12, the control device 9 detects the intersection points O of the 3D model of the target object W and each virtual line L and their positions. It should be noted that, hereinafter, when the intersection points O are distinguished, the intersection point O of the target object W and the virtual line L1 is also referred to as the intersection point O1, the intersection point O of the target object W and the virtual line L2 is also referred to as the intersection point O2, the intersection point O of the target object W and the virtual line L3 is also referred to as the intersection point O3, the intersection point O of the target object W and the virtual line L4 is also referred to as the intersection point O4, the intersection point O of the target object W and the virtual line L5 is also referred to as the intersection point O5, the intersection point O of the target object W and the virtual line L6 is also referred to as the intersection point O6, and the intersection point O of the target object W and the virtual line L7 is also referred to as the intersection point O7.

[0052] Next, if Figure 5 As shown, in the distance detection step S13, the control device 9 detects the distance D between the adjacent intersections O. 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 the straight line connecting the two intersections O1 and O2, or the distance between the two intersections O1 and O2 along the surface of the target object W. By defining the distance D12 in this way, the distance D12 can be simply calculated according to the positions of the intersections O1 and O2 and the shape of the target object W. It should be noted that in this embodiment, the distance D12 is set to the latter, that is, the distance between the two intersections O1 and O2 along the surface of the target object W. As a result, the state of the surface of the target object W can be determined with better accuracy. This also applies to other distances D23, D34, D45, D56, and D67.

[0053] In the non-ejection nozzle determination step S14, the nozzles 31 that do not eject the ink I in the next printing step S2 are determined based on the distance D. In other words, for each nozzle 31, whether to eject the ink I in the next printing step S2 is selected based on the distance D. It should be noted that the distance D12 is used as a representative in the following description.

[0054] For example, Figure 5 As shown, when the surface of the target object W is a plane F that is orthogonal to the virtual line L and the print track Q between the intersection points O1 and O2, the distance D12 is equal to the separation distance DL of the virtual lines L1 and L2. In contrast, as described in the present embodiment, when the surface of the target object W is inclined relative to the plane F between the intersection points O1 and O2, the distance D12 is greater than the separation distance DL. Furthermore, the greater the inclination of the surface of the target object W relative to the plane F, the greater the difference ΔD12 (= D12 - DL) between the distance D12 and the separation distance DL.

[0055] If the inclination of the surface of the target object W relative to the surface F increases, for example, the ink I that has landed may droop and expand on the surface of the target object W due to its own weight, or the distance between adjacent ink dots, that is, the landing positions of adjacent ink I, may increase. Therefore, the printed image may be blurred, distorted, skewed, etc., resulting in a decrease in print quality. Therefore, in order to suppress the decrease in print quality, the control device 9 does not eject the ink I from the nozzle 311 in the next printing step S2 when the difference ΔD12 exceeds a predetermined threshold value SH. It should be noted that the threshold value SH is not particularly limited, and for example, it can be set to be greater than 1.5 times and less than 2.0 times the separation distance DL.

[0056] In addition, the control device 9 similarly detects the differences ΔD23, ΔD34, ΔD45, ΔD56, and ΔD67 from the separation distance DL for other distances D23, D34, D45, D56, and D67, and compares the detected differences ΔD23, ΔD34, ΔD45, ΔD56, and ΔD67 with the threshold value SH. Then, when the difference ΔD23 exceeds the threshold value SH, the ink I is not ejected from the nozzle 312 in the printing step S2, when the difference ΔD34 exceeds the threshold value SH, the ink I is not ejected from the nozzle 313 in the printing step S2, when the difference ΔD45 exceeds the threshold value SH, the ink I is not ejected from the nozzle 315 in the printing step S2, when the difference ΔD56 exceeds the threshold value SH, the ink I is not ejected from the nozzle 316 in the printing step S2, and when the difference ΔD67 exceeds the threshold value SH, the ink I is not ejected from the nozzle 317 in the printing step S2. In this way, the expansion of the dripping of the ink I after landing and the increase in the distance between adjacent ink dots caused by the inclination of the surface of the target object W can be effectively suppressed, and high-quality printing with little blurring, distortion, and skewness can be performed.

[0057] As an example, in the present embodiment, the differences ΔD12 and ΔD67 exceed the threshold SH, and the other differences ΔD23, ΔD34, ΔD45, and ΔD56 are below the threshold SH. Therefore, the control device 9 does not eject ink I from the nozzles 311 and 317 in the next printing step S2, but ejects ink I from the remaining nozzles 312, 313, 314, 315, and 316.

[0058] According to the above, the preparation step S1 is completed. In particular, in the present embodiment, three or more virtual lines L are set at equal intervals along a specified direction in the virtual line setting step S11. Therefore, the surface of the target object W can be evenly and well divided into narrower areas, and it is determined for each divided area whether the difference between the distance D and the separation distance DL exceeds the threshold SH. Therefore, the inclination of the surface of the target object W can be more locally determined. As a result, in the non-ejecting nozzle determination step S14, the nozzle 31 that does not eject the ink I can be determined with better accuracy.

[0059] In addition, in the present embodiment, the interval between adjacent virtual lines L is equal to the interval between adjacent nozzles 31. Therefore, the surface of the target object W can be divided into a plurality of regions at the same interval as the interval between the nozzles 31. Therefore, the surface of the target object W can be divided into sufficiently narrow regions, and the inclination of the surface of the target object W can be better determined locally. As a result, in the non-ejecting nozzle determination step S14, the nozzle 31 that does not eject the ink I can be determined with better accuracy.

[0060] Furthermore, the virtual line L is set in a manner corresponding to the nozzles 31. Therefore, the area divided by the virtual line L coincides with the interval between the adjacent nozzles 31, and the surface of the object W is divided into a plurality of areas at the optimal positions relative to the nozzles 31. Therefore, in the non-ejecting nozzle determination step S14, the nozzles 31 that do not eject the ink I can be determined with greater accuracy.

[0061] Printing step S2

[0062] In the printing step S2, the control device 9 drives the robot arm 22 to move the print head 3 along the printing track Q, and at a predetermined timing, the ink I is ejected from the nozzles 312, 313, 314, 315, and 316, so that the ejected ink I lands on the surface of the target object W, and the printing operation on the target object W is performed. According to such a method, it is possible to effectively suppress the ink I from falling and expanding after landing due to the inclination of the surface of the target object W, and the increase in the distance between adjacent ink dots, and it is possible to perform high-quality printing with little blur, distortion, skew, etc. In addition, during the printing operation, the control device 9 detects the vibration of the print head 3 based on the output of the vibration meter 5, and controls the driving of the movable stage 4 in a manner to eliminate the detected vibration. Specifically, the driving of the movable stage 4 is controlled in a manner to apply a vibration in the opposite phase to the detected vibration to the print head 3. As a result, the vibration of the print head 3 during the printing operation is suppressed, and higher-quality printing can be performed.

[0063] In the above, the printing method using the robot system 1 has been described. As described above, such a printing method is a printing method for performing a printing operation on a target object W by using a robot 10 having a print head 3, the print head 3 having a plurality of nozzles 31 arranged in a predetermined direction, and ejecting ink I from the nozzles 31 while moving the target object W relative to the print head 3, and the printing method includes: a virtual line setting step S11, setting a plurality of virtual lines L arranged in a direction parallel to the ejection direction of the ink I and orthogonal to the ejection direction of the ink I and the moving direction of the print head 3 for a 3D model of the target object W; an intersection point detection step S12, finding the intersection point O of the virtual line L and the target object W; a distance detection step S13, detecting the distance D between adjacent intersection points O; and a non-ejection nozzle determination step S14, determining the nozzle 31 that does not eject the ink I based on the distance D. According to such a method, it is possible to effectively suppress the ink I from dripping and expanding after landing due to the inclination of the surface of the target object W, and to increase the distance between adjacent ink dots, and to perform high-quality printing.

[0064] In addition, 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. Therefore, the surface of the target object W can be divided into narrow areas in a well-balanced manner, and the inclination of the surface of the target object W can be determined more locally. Therefore, in the non-ejecting nozzle determination step S14, the nozzles 31 that do not eject the ink I can be determined with more accuracy.

[0065] In addition, as described above, the interval between adjacent virtual lines L is proportional to the interval between adjacent nozzles 31 in an integral multiple. Therefore, the width of each area divided by the virtual lines is equal to or smaller than the interval between the nozzles 31. Therefore, the surface of the target object W can be divided into sufficiently narrow areas, and the inclination of the surface of the target object W can be determined more locally. As a result, in the non-ejecting nozzle determination step S14, the nozzle 31 that does not eject the ink I can be determined with better accuracy.

[0066] In addition, as described above, the virtual line L is set in a manner corresponding to the nozzles 31. Therefore, the area divided by the virtual line L coincides with the interval between the adjacent nozzles 31, and the surface of the object W is divided into a plurality of areas at the optimal position relative to the nozzles 31. Therefore, the nozzles 31 that do not eject the ink I can be more accurately identified in the non-ejecting nozzle identification step S14.

[0067] As described above, the distance D is the length of a straight line connecting two adjacent intersection points O. Therefore, the distance D can be easily calculated based on the positions of the intersection points O1 and O2.

[0068] As described above, the distance D is the distance between two adjacent intersection points O along the surface of the object W. Thus, the distance D can be easily calculated based on the positions of the intersection points O1 and O2 and the 3D model of the object W. In addition, the state of the surface of the object W can be detected with higher accuracy.

[0069] In addition, as described above, the robot system 1 is a robot system 1 that includes: a robot 10 having a print head 3, the print head 3 having a plurality of nozzles 31 arranged in a predetermined direction; and a control device 9 that controls the driving of the robot 10, and performs a printing operation on the target object W by ejecting ink I from the nozzles 31 while moving the target object W and the print head 3 relative to each other. In addition, the control device 9 sets a plurality of virtual lines L that are parallel to the ejection direction of the ink I and are arranged in a direction orthogonal to the ejection direction of the ink I and the moving direction of the print head 3 for the 3D model of the target object W, obtains the intersection point O of each virtual line L with the target object W, detects the distance D between adjacent intersection points O, and determines the nozzle 31 that does not eject the ink I based on the distance D.

[0070] Second embodiment

[0071] Figure 6 It is a perspective view showing a target object according to the second embodiment. Figure 7 and Figure 8 Each of the figures is for explaining the preparation steps. Fig. 9 It is a table showing the relationship between time points and non-discharging nozzles. Fig.10 This is a table showing the relationship between the position of the print head and the non-ejecting nozzles.

[0072] This embodiment is the same as the first embodiment described above except that the shape of the target object W is different. It should be noted that in the following description, the present embodiment is described mainly with respect to the differences from the first embodiment described above, and the description of the same matters is omitted. In addition, in each of the drawings of this embodiment, the same symbols are marked for the same components as those in the above embodiment.

[0073] like Figure 6 As shown, in this embodiment, the shape of the target object W changes in the middle of the printing track Q. Specifically, the target object W has a cylindrical first cylindrical portion W1 and a cylindrical second cylindrical portion W2 having a diameter larger than the first cylindrical portion W1, and the first and second cylindrical portions W1 and W2 are coaxially connected along the printing track Q. Thus, the control device 9 determines the nozzles 31 that set the ink I to non-ejection for the first cylindrical portion W1 and the second cylindrical portion W2, respectively.

[0074] As an example, in Figure 7 The intersection O of the virtual lines L1, L7 and the first cylindrical portion W1 does not exist at the first cylindrical portion W1 shown. Therefore, ΔD12 and ΔD67 do not exist and are set to exceed the threshold value SH. In addition, ΔD23 and ΔD56 exceed the threshold value SH. Therefore, the control device 9 does not eject ink I from the nozzles 311, 312, 316, and 317 when printing the first cylindrical portion W1 in the printing step S2, but ejects ink I from the remaining nozzles 313, 314, and 315. In addition, Figure 8 In the second cylindrical portion W2 shown, the differences ΔD12 and ΔD67 exceed the threshold SH. Therefore, the control device 9 ejects ink I from the remaining nozzles 312, 313, 314, 315, and 316 while printing the second cylindrical portion W2 in the printing step S2.

[0075] In this case, for example Fig. 9 As shown in FIG. 1 , table data for specifying the nozzles 31 from which ink is not ejected at each time point is generated, and the ejection of ink I can be controlled based on the table data. Fig.10 As shown in FIG. 1 , table data for specifying the nozzles 31 for non-ejection of ink at each position of the print head 3 during the printing operation is generated, and the ejection of ink I can be controlled based on the table data. In addition, table data obtained by combining them is generated, and the ejection of ink I can be controlled based on the table data. It should be noted that in Fig. 9 and Fig.10 In the figure, “1” indicates a nozzle that can eject ink I, and “0” indicates a non-ejecting nozzle that does not eject ink I.

[0076] Thus, in the present embodiment, when the shape of the object W changes along the printing track Q, the nozzle 31 that does not eject the ink I is changed every time the shape changes. That is, the nozzle 31 that does not eject the ink I changes during the movement of the print head 3 along the printing track Q. Thus, high-quality printing can be performed on objects W of various shapes.

[0077] As described above, in the second embodiment, the nozzles 31 that do not eject the ink I are changed during the movement of the print head 3. Therefore, high-quality printing can be performed on objects W of various shapes.

[0078] According to such a second embodiment, it is also possible to produce the same effects as those of the above-described first embodiment.

[0079] Third embodiment

[0080] Fig.11 It is a perspective view showing a target object according to the third embodiment. Fig.12 It is a diagram for explaining the preparation steps.

[0081] This embodiment is the same as the first embodiment except that the shape of the target object W is different. It should be noted that in the following description, the present embodiment is described mainly with respect to the differences from the first embodiment, and the description of the same matters is omitted. In addition, in the drawings of this embodiment, the same symbols are used for the same components as those in the above embodiment.

[0082] like Fig.11 and Fig.12 As shown, in the target object W of the present embodiment, the surface thereof is irregularly bent along the arrangement direction of the nozzles 31. And, as an example, only the difference ΔD67 exceeds the threshold value SH. In this case, the control device 9 causes the ink I to be ejected from the remaining nozzles 311, 312, 313, 314, 315, and 316 in the printing step S2 without ejecting the ink I from the nozzle 317.

[0083] According to such a third embodiment as well, the same effects as those of the above-mentioned first embodiment can be achieved.

[0084] The printing method and robot system of the present invention are described above with the illustrated embodiments, but the present invention is not limited thereto, and the configuration and process of each part can be replaced with any configuration and process having the same function. In addition, any other configuration and process may be added to the present invention. In addition, the various embodiments may be appropriately combined. It should be noted that the direction in which the plurality of nozzles 31 are arranged is described as being orthogonal to the printing track Q, that is, the moving direction of the print head 3, but it may also be a direction that is not orthogonal but intersecting.

Claims

1. A printing method, characterized in that: Using a robot equipped with a print head, the print head having a plurality of nozzles arranged in a predetermined direction, a target object and the print head are moved relative to each other, and ink is ejected from the nozzles, thereby performing a printing operation on the target object, the printing method comprising: a virtual line setting step of setting, for the 3D model of the target object, a plurality of virtual lines that are parallel to the ejection direction of the ink and arranged in a direction orthogonal to the ejection direction and the moving direction; An intersection detection step, finding the intersection of each of the virtual lines and the target object; a distance detection step, detecting the distance between adjacent intersection points; and The non-ejection nozzle determination step determines the nozzle that does not eject the ink based on the distance.

2. The printing method according to claim 1, characterized in that: 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, characterized in that: 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, characterized in that: The virtual line is set in a manner corresponding to the nozzle.

5. The printing method according to claim 1, characterized in that: The distance is the length of a straight line connecting two adjacent intersection points.

6. The printing method according to claim 1, characterized in that: The distance is the distance between two adjacent intersection points along the surface of the target object.

7. The printing method according to claim 1, characterized in that: During the movement of the print head, the nozzles that do not eject the ink change.

8. A robot system, characterized in that: have: A robot including a print head having a plurality of nozzles arranged in a predetermined direction; and A control device controls the driving of the robot, The robot system performs a printing operation on the target object by moving the target object and the print head relative to each other and ejecting ink from the nozzle. The control device sets, for the 3D model of the target object, a plurality of virtual lines that are parallel to the ejection direction of the ink and arranged in a direction orthogonal to the ejection direction and the moving direction. The control device obtains the intersection point between each of the virtual lines and the target object. The control device detects the distance between adjacent intersection points. The control device determines the nozzle that does not eject the ink based on the distance.

Images