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 performs a printing work for an object by discharging an ink from a nozzle while relatively moving the object and a print head along the printing path with use of a robot comprising the print head in which a plurality of nozzles are arranged. According to the method, timing for discharging the ink from the nozzle or a discharge speed of the ink is controlled on the basis of a clearance between the nozzle and the object.SELECTED DRAWING: Figure 7

Description

[Technical field]

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

[0002] The printing system described in Patent Document 1 prints on an object by ejecting ink from the print head toward the object while moving a robot equipped with a print head attached to its tip along a print track. The printing system also has a rotation angle sensor for detecting the actual position of the print head, and a piezo actuator that is disposed between the print head and corrects the position of the print head based on the actual position of the print head. By correcting the position of the print head based on the actual position of the print head, printing without strips (gaps) is achieved. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-202781 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the printing system of Cited Document 1, when printing on a non-flat printing surface such as a curved or bent surface, the ink ejection distance, i.e., the distance between the print head and the printing surface, varies from part to part of the printing surface, which leads to print misalignment, blurring, and other degradation in print quality. [Means for solving the problem]

[0005] A printing method of the present invention uses a robot equipped with a print head having a plurality of nozzles arranged therein, and performs a printing operation on an object by ejecting ink from the nozzles while moving an object and the print head relatively along a printing trajectory, The timing at which the ink is ejected from the nozzle or the ejection speed of the ink is controlled based on the distance between the nozzle and the target object.

[0006] The robot system of the present invention comprises: a robot having a print head in which a plurality of nozzles are arranged; A control device for controlling the driving of the robot, the control device performs a printing operation on the object by ejecting ink from the nozzles while moving the object and the print head relatively along a print trajectory; In the printing operation, the timing at which the ink is ejected from the nozzle or the ejection speed of the ink is controlled based on the distance between the nozzle and the target object. [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 tip surface of a print head provided in the robot shown in FIG. 1. [Diagram 3] 2 is a plan view showing a moving stage provided in the robot shown in FIG. 1. [Figure 4] 11 is a flowchart illustrating a printing method. [Diagram 5] FIG. [Figure 6] FIG. 13 is a diagram illustrating an example of a print image. [Figure 7] 4 is a time chart showing an example of ink ejection timing. [Figure 8] FIG. [Figure 9] 1A and 1B are diagrams for explaining problems with a conventional printing method. [Figure 10] 1A and 1B are diagrams for explaining problems with a conventional printing method. [Figure 11] 1A and 1B are diagrams for explaining problems with a conventional printing method. [Figure 12]1A and 1B are diagrams for explaining problems with a conventional printing method. [Figure 13] 1A and 1B are diagrams for explaining problems with a conventional printing method. [Figure 14] 1A and 1B are diagrams for explaining problems with a conventional printing method. [Figure 15] FIG. 13 illustrates an example of a GUI. [Figure 16] 11 is a graph showing the relationship between the shape of an object and the deviation of the ink landing position. [Figure 17] 17 is a time chart corrected based on the relationship shown in FIG. 16. [Figure 18] 11 is a graph showing the relationship between the shape of an object and the deviation of the ink landing position. [Figure 19] 19 is a time chart corrected based on the relationship shown in FIG. 18. [Figure 20] 10 is a time chart showing the ink ejection timing after correction. [Figure 21] FIG. 13 is a diagram showing a modified example of the object. [Figure 22] FIG. 13 is a diagram showing a modified example of the object. [Diagram 23] FIG. 13 is a diagram showing a modified example of the object. [Figure 24] 13 is a diagram showing a configuration of a tip portion of a robot included in a robot system according to a third embodiment. FIG. 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 tip surface of a print head provided in the robot shown in FIG. 1. FIG. 3 is a plan view showing a moving stage provided in the robot shown in FIG. 1. FIG. 4 is a flow chart for explaining a printing method. FIG. 5 is a diagram showing a state of a printing operation. FIG. 6 is a diagram showing an example of a printed image. FIG. 7 is a time chart showing an example of ink ejection timing. FIG. 8 is a diagram showing a state of a printing operation. FIGS. 9 to 14 are diagrams for explaining problems of a conventional printing method. FIG. 15 is a diagram showing an example of a GUI. FIG. 16 is a graph showing a relationship between the shape of an object and a deviation of an ink landing position. FIG. 17 is a time chart corrected based on the relationship shown in FIG. 16. FIG. 18 is a graph showing a relationship between the shape of an object and a deviation of an ink landing position. FIG. 19 is a time chart corrected based on the relationship shown in FIG. 18. FIG. 20 is a time chart showing the ink ejection timing after correction. FIGS. 21 to 23 are diagrams showing modified examples of an object, respectively.

[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 print head 3 attached to the tip of the robot body 2, a moving stage 4 arranged between the robot body 2 and the print head 3, and a vibration meter 5 arranged on the print head 3.

[0011] <Robot body 2> The robot body 2 is a six-axis vertical articulated robot having six drive shafts, 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 these 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 as a drive source and an encoder for detecting 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 in a desired attitude.

[0012] 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.

[0013] <Print Head 3> The print head 3 is disposed at the tip of the robot arm 22, i.e., on the arm 226. The print head 3 is not particularly limited, but in this embodiment, a piezoelectric drive type inkjet head is used. A piezoelectric drive type inkjet head has an ink chamber, a diaphragm that constitutes part of the wall surface of the ink chamber, a piezoelectric element that vibrates the diaphragm, and a nozzle connected to the ink chamber. When a voltage is applied to the piezoelectric element to vibrate the piezoelectric element, the diaphragm vibrates and ink I in the ink chamber is ejected from the nozzle.

[0014] In particular, the print head 3 of this embodiment is capable of full-color printing of the CMYK color model. As shown in FIG. 2, the print head 3 has a nozzle 31c that ejects cyan ink Ic, a nozzle 31m that ejects magenta ink Im, a nozzle 31y that ejects yellow ink Iy, and a nozzle 31b that ejects black ink Ib. In this embodiment, the print head 3 is controlled to move relative to the target W along a print trajectory Q indicated by an arrow, and the nozzles 31c, 31m, 31y, and 31b are arranged side by side along the print trajectory Q. The nozzles 31c, 31m, 31y, and 31b are arranged side by side in a direction perpendicular to the print trajectory Q. Then, printing is performed by ejecting ink I from each nozzle 31 of the print head 3 at a predetermined timing and landing it on the target W while moving the print head 3 along the print trajectory Q.

[0015] However, the arrangement of the multiple nozzles 31 and the color of the ink I ejected from each nozzle 31 are not particularly limited. For example, the configuration may be such that black ink Ib is ejected from all of the nozzles 31. Furthermore, the configuration of the print head 3 is not limited to the inkjet head of the above-mentioned piezoelectric drive type. For example, it may be an inkjet head of a thermal type that utilizes the film boiling phenomenon of the ink I, a bubble ejection type that generates bubbles in the ink I by applying heat and ejects the ink I, or an electrostatic actuator type that ejects the ink I by displacing and vibrating a vibration plate by electrostatic force.

[0016] <Mobile Stage 4> As shown in Fig. 1, the moving stage 4 is disposed between the arm 226 and the print head 3. Such a moving stage 4 is used to correct the position of the print head 3. As shown in Fig. 3, 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.

[0017] 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 transmit the vibration of the piezoelectric actuator 400 to the first and second stages 41 and 42 to move 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. Therefore, the position correction of the print head 3 can be performed with high accuracy. In addition, the moving stage 4 can be made smaller and lighter. Therefore, the increase in the weight of the tip of the robot body 2 due to the placement of the moving stage 4 can be suppressed as much as possible, and the deterioration of the driving characteristics such as the responsiveness and vibration damping of the robot body 2 can be effectively suppressed.

[0018] However, the configuration of the moving stage 4 is not particularly limited. For example, the first and second stage drivers 45, 46 may be configured to use a drive source other than the piezoelectric actuator 400, such as a motor that rotates when energized. Also, the moving stage 4 may be omitted. In this case, the position of the print head 3 can be corrected by the robot arm 22.

[0019] ≪Vibration meter 5≫ 1, 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 displacements of the print head 3 other than the displacement along a print trajectory Q, which will be described later. The vibration meter 5 is, for example, a triaxial angular velocity sensor that detects angular velocities in three mutually perpendicular axial directions.

[0020] <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.

[0021] The configuration of the robot system 1 has been described above. Next, a printing method using the robot system 1 will be described. As shown in FIG. 4, the printing method includes a drive condition determination step S1 in which the drive conditions of the print head 3 are determined in advance, and a printing step S2 in which the print head 3 is driven based on the drive conditions determined in the drive condition determination step S1 to print on the object W. The shape of the object W, more specifically, the shape of the surface to be printed on 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 method of this embodiment more pronounced. Below, these steps S1 and S2 will be described in detail, but before that, the features of the printing method of this embodiment will be briefly described.

[0022] As an example, Fig. 7 shows the ink ejection timing for printing a rectangle P shown in Fig. 6 by ejecting ink I while moving the print head 3 at a constant speed along a print trajectory Q that maintains an ideal distance D0 from a planar target W0 as shown in Fig. 5. In Fig. 7, the timing "1" means that ink I is ejected from each of the nozzles 31c, 31m, 31y, and 31b.

[0023] In contrast, Fig. 8 shows printing performed by discharging ink I while moving print head 3 at a constant speed along a print trajectory Q that maintains an ideal distance D0 from target object W, which has an arc-shaped curved surface. When printing the same rectangle as in Fig. 6 on curved target object W, a flat rectangle P must be printed in a curved shape along target object W, as shown in Fig. 9. However, when printing is performed on target object W with the ink discharge timing shown in Fig. 7, the rectangle P is printed in a shape that is a planar projection onto target object W, and the rectangle P is distorted, as shown in Fig. 10.

[0024] Specifically, as shown in FIG. 11, the landing position of ink Im is shifted forward of the print trajectory Q from the target landing position Tm, the landing position of ink Ic is shifted more forward of the print trajectory Q from the target landing position Tc, the landing position of ink Iy is shifted rearward of the print trajectory Q from the target landing position Ty, and the landing position of ink Ib is shifted more rearward of the print trajectory Q from the target landing position Tb. Therefore, as shown in FIG. 12, the rectangles Pc, Pm, Py, and Pb formed by inks Ic, Im, Iy, and Ib are shifted from each other along the print trajectory Q. As a result, the rectangle P is shifted, blurred, distorted, and the like, and the print quality is reduced. Note that this shift is larger as the radius of curvature of the target object W is smaller and as the distance d of the nozzle 31 from the center of the print head 3 is larger. Such a factor that causes a decrease in print quality is also referred to as the "first factor" below.

[0025] 13, the distance traveled between the nozzle 31 and the object W is D, specifically, the distance traveled between the nozzle 31c and the object W is Dc, the distance traveled between the nozzle 31m and the object W is Dm, the distance traveled between the nozzle 31y and the object W is Dy, and the distance traveled between the nozzle 31b and the object W is Db. The distances Dc and Db between the nozzles 31c and 31b located in the front and rear rows of the print trajectory Q are greater than the distances Dm and Dy between the nozzles 31m and 31y located in the center row of the print trajectory Q. In other words, the relationship is Dc=Db>Dm=Dy. The nozzles 31c, 31m, 31y, and 31b are each shifted from the center of the print head 3 to the front or rear side of the print trajectory Q, so the distances Dc, Dm, Dy, and Db are each greater than the ideal distance D0.

[0026] The larger the separation distance D, the longer the time (hereinafter also referred to as "flight time") from when the inks Ic, Im, Iy, and Ib are discharged to when they land on the target object W. As shown in FIG. 13, the inks Ic, Im, Iy, and Ib fly with a velocity component in the moving direction of the print head 3, so the longer the flight time, the more the actual landing points of the inks Ic, Im, Iy, and Ib are shifted forward of the print trajectory Q with respect to the target landing positions Tc, Tm, Ty, and Tb. Therefore, when printing is performed with the ink discharge timing shown in FIG. 7, as shown in FIG. 14, the rectangle Pcb formed by the inks Ic and Ib is shifted forward of the print trajectory Q with respect to the rectangle Pmy formed by the inks Im and Iy. As a result, the printing is shifted, blurred, distorted, and the like, resulting in a decrease in print quality. Such factors that cause a decrease in print quality are also referred to as "second factors" below.

[0027] The printing method of the present embodiment aims to eliminate the deterioration of print quality caused by the first and second factors and improve print quality. The printing method of the present embodiment controls the ejection timing of the inks Ic, Im, Iy, and Ib from the nozzles 31c, 31m, 31y, and 31b based on the separation distances Dc, Dm, Dy, and Db, thereby allowing the inks Ic, Im, Iy, and Ib to land at the target landing positions with high accuracy without being affected by the first and second factors. Specifically, the printing method of the present embodiment allows the inks Ic, Im, Iy, and Ib to land at the target landing positions with high accuracy without being affected by the first and second factors by accelerating the ejection timing of the inks Ic, Im, Iy, and Ib as the separation distances Dc, Dm, Dy, and Db are larger. In other words, the deviation of the actual landing positions from the target landing positions can be suppressed to a smaller extent. Therefore, deviation, blurring, distortion, and the like are less likely to occur in the print, and print quality can be improved.

[0028] The driving condition determination step S1 and the printing step S2 of the printing method of this embodiment will be described in detail below.

[0029] <<Drive condition determination step S1>> In the drive condition determination step S1, first, the control device 9 acquires various pieces of information necessary to determine the drive conditions of the print head 3. In this embodiment, information about the print head 3, specifically, the position of each nozzle 31 and the ejection speed of the ink I, is set in advance in the control device 9. The control device 9 then receives various other pieces of necessary information from the user, for example, via a GUI (graphical user interface) shown in Fig. 15. This GUI has a print setting field G1, a shape reading field G2, and a print range designation field G3.

[0030] The control device 9 receives from the user in the print setting field G1 the print image to be printed on the target object W and the movement speed of the print head 3 (print scan speed). The user presses the "Select" button to select the desired image stored in the computer. The control device 9 then receives the image selected by the user as the print image. It is assumed here that the rectangle P shown in FIG. 6 is selected. The user can also input a desired value in the print scan speed field to specify that value as the print scan speed.

[0031] The control device 9 accepts the shape data of the object W from the user in the shape reading field G2. The user presses the "Select" button to select the desired shape data stored in a computer, a server, or the like. The control device 9 accepts the shape data specified by the user as the shape data of the object W. The shape data is not particularly limited, and examples thereof include CAD (computer aided design) data of the object W, and measurement data obtained by measuring the object W using a measuring device such as a 3D scanner. In addition, when the object W has a simple shape, such as a flat shape or an arc shape with a constant curvature, the control device 9 can also accept the shape data of the object W by numerical input from the user. In this embodiment, CAD data is used as the shape data of the object W. As a result, accurate shape data can be obtained, and the printing trajectory Q and the separation distance D can be calculated accurately and easily.

[0032] The control device 9 displays the shape of the target object W in the print range designation field G3 and accepts the print start point from the user. The user can designate the print start point by inputting a desired value in the start position field. The user can also designate the print start position by dragging and moving the dashed line indicating the print start position.

[0033] In this way, the control device 9 acquires various pieces of information necessary to determine the drive conditions of the print head 3. However, there are no particular limitations on the method of acquiring this information. Furthermore, there are no particular limitations on the configuration of the GUI, the type of information received by the GUI, etc.

[0034] Next, the control device 9 determines a print trajectory Q for printing a rectangle P at a specified position on the object W based on various information received from the user. The print trajectory Q is automatically generated by the control device 9 without receiving instructions from the user. The print trajectory Q includes information necessary for printing work, such as the position and attitude of the print head 3 relative to the object W for each control cycle, the moving direction and moving speed, etc. Furthermore, the control device 9 calculates a separation distance D between each nozzle 31 and the object W based on the shape data of the object W, the print trajectory Q, and the information on the print head 3. The separation distance D includes a separation distance Dc between each nozzle 31c and the object W, a separation distance Dm between each nozzle 31m and the object W, a separation distance Dy between each nozzle 31y and the object W, and a separation distance Db between each nozzle 31b and the object W. In this embodiment, the nozzles 31c have equal separation distances Dc, the nozzles 31m have equal separation distances Dm, the nozzles 31y have equal separation distances Dy, and the nozzles 31b have equal separation distances Db.

[0035] Next, the ink ejection timing is determined for each nozzle 31. In this embodiment, the ink ejection timing is determined for each nozzle 31 by correcting the ink ejection timing shown in Fig. 7. At this time, the ink ejection timing can be corrected accurately and easily by using the relationships shown in Figs. 16 and 18, for example.

[0036] 16 is a graph showing the relationship between the radius of curvature R of the target object W and the amount of deviation of the actual landing position of the ink I from the target landing position, and is preferably used to cancel the influence of the first factor. This relationship can be calculated from the positions of the nozzles 31, the shape of the target object W, the moving speed of the print head 3, the ejection speed of the ink I, etc.

[0037] From this graph, it can be seen that, for example, when the radius of curvature of the target object W is 50 mm, if printing is performed with the ink ejection timing shown in Figure 7, due to the influence of the first factor, the actual landing position of ink Ic ejected from each nozzle 31c will be shifted 120 μm forward from the target landing position, the actual landing position of ink Im ejected from each nozzle 31m will be shifted 5 μm forward from the target landing position, the actual landing position of ink Iy ejected from each nozzle 31y will be shifted 5 μm backward from the target landing position, and the actual landing position of ink Ib ejected from each nozzle 31b will be shifted 120 μm backward from the target landing position.

[0038] Furthermore, when the moving speed of the print head 3 is 127 mm / s, in order to cancel the above-mentioned deviation and cause each of the inks Ic, Im, Iy, and Ib to land on the target landing positions, the ejection timing of each ink Ic should be advanced by (120 μm) / (127 mm / s)=0.94 ms, the ejection timing of each ink Im should be advanced by (5 μm) / (127 mm / s)=0.04 ms, the ejection timing of each ink Iy should be delayed by (5 μm) / (127 mm / s)=0.04 ms, and the ejection timing of each ink Ib should be delayed by (120 μm) / (127 mm / s)=0.94 ms, relative to the ink ejection timing shown in Fig. 7, as shown in Fig. 17. This cancels the influence of the first factor, and high-quality printing with little deviation, blurring, distortion, etc. can be performed.

[0039] 18 is a graph showing the relationship between the radius of curvature R of the target W and the amount of deviation in the landing positions between the nozzles 31c, 31m, 31y, and 31b, and is used to cancel the influence of the second factor. This relationship can be calculated from the position of each nozzle 31, the shape of the target W, the moving speed of the print head 3, the ejection speed of the ink I, etc.

[0040] For example, when the radius of curvature of the target object W is 50 mm and the moving speed of the print head 3 is 127 mm / s, it can be seen that the inks Ic and Ib land 85 μm ahead of the inks Im and Iy. Therefore, to cancel this deviation, as shown in FIG. 19, the ejection timing of the inks Ic and Ib should be further advanced by (85 μm) / (127 mm / s) = 0.67 ms with respect to the ejection timing of the inks Im and Iy after the correction shown in FIG. 17. This cancels the effect of the second factor, enabling high-quality printing with less deviation, blurring, distortion, etc. to be performed.

[0041] In this manner, the driving conditions of the print head 3 shown in FIG. 20 are determined. In this manner, by correcting the ink ejection timing shown in FIG. 7 using the relationships shown in FIG. 16 and FIG. 18, the deviation of the landing position due to the first factor and the second factor can be effectively canceled, and each ink I can be landed at the target landing position. In this embodiment, the ink ejection timing shown in FIG. 7 is set as the initial setting, and this setting is corrected using the relationships shown in FIG. 16 and FIG. 18 to determine the driving conditions of the print head 3, but the method of determining the driving conditions is not particularly limited. For example, the driving conditions of the print head 3 shown in FIG. 20 may be determined using the relationships shown in FIG. 16 and FIG. 18 without using the initial setting shown in FIG. 7.

[0042] <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 controlling the driving of the print head 3 based on the driving conditions (ink ejection timing) of the print head 3 shown in FIG. 20 determined in the driving condition determination step S1, thereby performing a printing operation. As a result, a high-quality rectangle P with little misalignment, blurring, distortion, etc. is printed on the object W. Also, in the printing step S2, during the printing operation, the vibration of the print head 3 is detected based on the output of the vibration meter 5, and the driving of the moving stage 4 is controlled so that the detected vibration is canceled. Specifically, the driving of the moving stage 4 is controlled so that vibration of the opposite phase to the detected vibration is applied to the print head 3. As a result, the vibration of the print head 3 during the printing step S2 is suppressed, enabling higher quality printing.

[0043] The above describes the robot system 1. As described above, the printing method using such a robot system 1 is a printing method that uses a robot 10 equipped with a print head 3 in which a plurality of nozzles 31 are arranged, and performs printing on an object W by ejecting ink I from the nozzles 31 while moving the object W and the print head 3 relatively along a print trajectory Q, and controls the timing of ejecting the ink I from the nozzles 31 based on the separation distance D between the nozzles 31 and the object W. According to this method, even if the shape of the object W is a curved or bent surface other than a flat surface, high-quality printing with little shifting, blurring, distortion, etc. can be performed on the object W.

[0044] As described above, in the printing method using the robot system 1, the above-mentioned control is performed for each nozzle 31. That is, the timing of ejecting the ink I is controlled for each nozzle 31. This makes it possible to perform high-quality printing on the target object W with little misalignment, blurring, distortion, etc.

[0045] Furthermore, as described above, in the printing method using the robot system 1, the greater the separation distance D, the earlier the ejection timing of the ink I. This makes it possible to reduce the deviation of the actual landing position of the ink I from the target landing position. Therefore, it is possible to perform high-quality printing on the target object W with little deviation, blurring, distortion, etc.

[0046] Furthermore, as described above, in the printing method using the robot system 1, the separation distance D is calculated using CAD data of the target object W. This makes it possible to calculate the separation distance D accurately and easily.

[0047] As described above, the multiple nozzles 31 are arranged along the printing trajectory Q. Specifically, the nozzles 31c, 31m, 31y, and 31b are arranged along the printing trajectory Q. Therefore, when printing on a non-planar target W, the separation distance D varies between the nozzles 31c, 31m, 31y, and 31b. Therefore, the effect of the above-mentioned control can be more significantly exhibited.

[0048] As described above, different color inks Ic, Im, Iy, and Ib are ejected from the nozzles 31c, 31m, 31y, and 31b, respectively, making it possible to perform multi-color printing, in particular full-color printing.

[0049] As described above, the robot system 1 includes a robot 10 equipped with a print head 3 having a plurality of nozzles 31 arranged thereon, and a control device 9 that controls the driving of the robot 10. The control device 9 performs a printing operation on the object W by ejecting ink I from the nozzle 31 while moving the object W and the print head 3 relatively along a print trajectory Q, and in the printing operation, controls the timing of ejecting the ink I from the nozzle 31 based on the separation distance D between the nozzle 31 and the object W. With this configuration, even if the shape of the object W is a curved or bent surface other than a flat surface, high-quality printing with little misalignment, blurring, distortion, etc. can be performed on the object W.

[0050] The printing method of this embodiment has been described above. However, the printing method is not particularly limited. For example, the shape of the target object W is not particularly limited, and may be a wavy uneven shape as shown in FIG. 21 or FIG. 22. In this case, the separation distances Dc, Dm, Dy, and Db repeatedly increase and decrease during the printing step S2, so the ink ejection timing may be corrected accordingly. Also, as shown in FIG. 23, the shape may be curved when viewed from the direction along the printing trajectory Q. In this case, since the separation distances Dc are different for each nozzle 31c, the ink ejection timing may be corrected for each nozzle 31c. The same applies to the other nozzles 31m, 31y, and 31b.

[0051] <Second embodiment> This embodiment is similar to the first embodiment described above, except that the driving condition determination step S1 of the printing method 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.

[0052] In the first embodiment described above, the ejection timing of the ink I shown in FIG. 17 is corrected as shown in FIG. 19 in order to cancel the influence of the second factor. In contrast, in the present embodiment, the ejection speed of the ink I is corrected with respect to the ink ejection timing shown in FIG. 17 in order to cancel the influence of the second factor. Specifically, the larger the separation distances Dc, Dm, Dy, and Db are, the faster the ejection speed of the inks Ic, Im, Iy, and Ib are, so that the inks Ic, Im, Iy, and Ib can be accurately landed at the target landing positions without being affected by the second factor. In other words, the deviation of the actual landing positions from the target landing positions can be suppressed to be smaller. Therefore, the printing is less likely to be shifted, blurred, distorted, and the like, and the printing quality can be improved. In the present embodiment, the ejection speed of the inks Ic and Ib is increased so that the flight time of the inks Ic and Ib is shorter by 0.67 ms than the flight time of the inks Im and Iy. This cancels the influence of the second factor, and high-quality printing with less shift, blur, distortion, and the like can be performed.

[0053] The method for changing the ejection speed of the ink I is not particularly limited. For example, the print head 3 is a piezoelectric drive type inkjet head, and the ink I in the ink chamber is ejected from the nozzle 31 by applying a voltage to a piezoelectric element to vibrate the piezoelectric element and vibrating the vibration plate. At this time, the larger the voltage applied to the piezoelectric element, the larger the vibration plate vibrates, and the ink I is ejected at a higher speed. Therefore, by utilizing such characteristics, in this embodiment, the ejection speed of the ink Ic and Ib is increased by increasing the voltage applied to the piezoelectric element for vibrating the vibration plate arranged in the ink chamber of the ink Ic and Ib relative to the initial condition. According to such a method, the influence of the second factor can be canceled by simple control.

[0054] As described above, the printing method of the present embodiment is a printing method that uses a robot 10 equipped with a print head 3 in which a plurality of nozzles 31 are arranged, and performs printing on an object W by ejecting ink I from the nozzles 31 while moving the object W and the print head 3 relatively along a print trajectory Q, and controls the ejection speed of the ink I based on the separation distance D between the nozzles 31 and the object W. According to this method, it is possible to cancel the influence of the second factor, and it is possible to perform high-quality printing on the object W with little misalignment, blurring, distortion, etc., even if the shape of the object W is a curved or bent surface other than a flat surface.

[0055] Furthermore, as described above, in the printing method using the robot system 1, the greater the separation distance D, the faster the ejection speed is set. This makes it possible to reduce deviation of the actual landing position of the ink I from the target landing position. As a result, high-quality printing can be performed on the target object W with little deviation, blurring, distortion, etc.

[0056] As described above, the robot system 1 includes a robot 10 equipped with a print head 3 having a plurality of nozzles 31 arranged thereon, and a control device 9 that controls the driving of the robot 10. The control device 9 performs a printing operation on the object W by ejecting ink I from the nozzles 31 while moving the object W and the print head 3 relatively along a print trajectory Q, and controls the ejection speed of the ink I based on the separation distance D between the nozzles 31 and the object W during the printing operation. With this configuration, the influence of the second factor can be canceled, and high-quality printing with little misalignment, blurring, distortion, etc. can be performed on the object W even if the shape of the object W is a curved or bent surface other than a flat surface.

[0057] The second embodiment as described above can also achieve the same effects as the first embodiment described above.

[0058] In this embodiment, the first factor is cancelled by correcting the ink ejection timing, and the second factor is cancelled by correcting the ink ejection speed, but the present invention is not limited to this. For example, the first factor may be cancelled by correcting the ink ejection speed, and the second factor may be cancelled by correcting the ink ejection timing. In addition, the ink ejection speed may be corrected to cancel both the first factor and the second factor. Similar effects can be achieved by such methods.

[0059] <Third embodiment> FIG. 24 is a diagram showing the configuration of the tip portion of the robot included in the robot system according to the third embodiment.

[0060] This embodiment is similar to the first embodiment described above, except for the printing method. In the following description, the differences between this embodiment and the first embodiment will be mainly described, and the description of the similarities will be omitted. In the drawings of this embodiment, the same reference numerals are used for the same configurations as the above-mentioned embodiment.

[0061] In the first embodiment described above, the driving condition determination step S1 for determining the driving conditions of the print head 3 was performed prior to the printing step S2, but in this embodiment, the driving conditions of the print head 3 are corrected during the printing step S2. According to this method, the time required for the driving condition determination step S1 can be omitted, and the efficiency of the printing work can be improved.

[0062] As shown in FIG. 24, the robot 10 of this embodiment has a distance sensor 8 that is disposed on the print head 3 and measures the separation distance D' from the target object W. The distance sensor 8 is located on the front side of the print trajectory Q relative to the print head 3 during the print step S2. During the print step S2, the control device 9 uses the distance sensor 8 to measure the separation distance D' from a location forward of the print head 3 while the print head 3 is moving. Furthermore, the control device 9 calculates the separation distances Dc, Dm, Dy, and Db when each of the nozzles 31c, 31m, 31y, and 31b faces the location based on the separation distance D'. Then, the control device 9 corrects the ejection timing or ejection speed of the ink I to be landed on the location based on the calculated separation distances Dc, Dm, Dy, and Db, and controls the drive of the print head 3 under the corrected drive conditions. By repeating such a correction operation at a predetermined cycle while the print head 3 is moving, it is possible to generate the drive conditions shown in FIG. 20 while printing is being performed. Therefore, even if the drive conditions of the print head 3 are not determined in advance, high-quality printing can be performed on the target object W with little misalignment, blurring, distortion, etc.

[0063] In the printing method as described above, the distance sensor 8 that measures the separation distance D' is used to calculate the separation distance D' while the printing work is being performed. According to such a method, the efficiency of the printing work can be improved.

[0064] The third embodiment as described above can also achieve the same effects as the first embodiment described above.

[0065] Although the printing method and robot system of the present invention have been described above with reference to the illustrated embodiment, the present invention is not limited to this, and the configuration and steps of each part can be replaced with any configuration or step having a similar function. In addition, any other configuration or step may be added to the present invention. In addition, each embodiment may be appropriately combined. [Explanation of symbols]

[0066] 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, 31b...nozzle, 31c...nozzle, 31m...nozzle, 31y...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, 8...distance sensor, 9...control device, A...first direction, B...second direction, D...separation distance, D'...separation distance, D0...reason distance, Db...separation distance, Dc...separation distance, Dm...separation distance, Dy...separation distance, d...distance, G1...print setting field, G2...shape reading field, G3...print range specification field, I...ink, Ib...ink, Ic...ink, Im...ink, Iy...ink, J1...joint, J2...joint, J3...joint, J4...joint, J5...joint, J6...joint, P...rectangle, Pb...rectangle, Pc...rectangle, Pcb...rectangle, Pm...rectangle, Pmy...rectangle, Py...rectangle, Q...print trajectory, S1...drive condition determination step, S2...printing step, Tb...target impact position, Tc...target impact position, Tm...target impact position, Ty...target impact position, W...object, W0...object

Claims

1. A printing method using a robot equipped with a print head having a plurality of nozzles, performing a printing operation on an object by ejecting ink from the nozzles while moving the object and the print head relatively along a printing trajectory, comprising: A printing method comprising controlling a timing at which the ink is ejected from the nozzle or a speed at which the ink is ejected, based on a distance between the nozzle and the target object.

2. The printing method according to claim 1 , wherein the control is performed for each of the nozzles.

3. The printing method according to claim 1 , wherein the timing is made earlier as the distance between the ink droplets increases.

4. The printing method according to claim 1 , wherein the ejection speed is increased as the distance between the ink droplets increases.

5. The printing method of claim 1 , further comprising calculating the separation distance using CAD data of the object.

6. The printing method according to claim 1 , further comprising the step of calculating the separation distance while performing the printing operation, using a distance sensor that measures the separation distance.

7. The method of printing according to claim 1 , wherein the plurality of nozzles are arranged along the print trajectory.

8. The printing method according to claim 7 , wherein the inks ejected from the plurality of nozzles are of different colors.

9. A robot having a print head with a plurality of nozzles arranged thereon; A control device for controlling the driving of the robot, the control device performs a printing operation on the object by ejecting ink from the nozzles while moving the object and the print head relatively along a print trajectory; The robot system is characterized in that, during the printing operation, the timing at which the ink is ejected from the nozzle or the ejection speed of the ink is controlled based on the distance between the nozzle and the target object.

Images