Printing method and robot system

Abstract

The invention provides a printing method and a robot system capable of performing high-quality printing. A printing method for performing a printing job on an object by discharging ink from a plurality of nozzles while moving the object and the print head relative to each other along a printing track using a robot provided with a print head in which a plurality of nozzles are disposed, the timing at which the ink is ejected from the nozzle or the ejection speed of the ink is controlled on the basis of the separation distance between the nozzle and the object.

Description

Technical Field

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

[0002] The printing system described in Patent Document 1 prints on an object by causing a robot having a print head mounted on its front end to move along a printing track while ejecting ink from the print head toward the object. In addition, the printing system has a rotation angle sensor and a piezoelectric actuator, the rotation angle sensor is used to detect the actual position of the print head, and the piezoelectric actuator is arranged between the print head and corrects the position of the print head based on the actual position of the print head. Thus, by correcting the position of the print head based on the actual position of the print head, printing without stripes (gaps) is achieved.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2013-202781

[0004] However, in the printing system of Patent Document 1, when printing on a non-planar printing surface such as a curved surface or a bent surface, the ink ejection distance, that is, the separation distance between the print head and the printing surface, may vary in different parts of the printing surface, thereby reducing the printing quality due to printing deviation, blurring, etc. Summary of the invention

[0005] The printing method of the present invention uses a robot equipped with a printing head equipped with multiple nozzles, and prints the object by ejecting ink from the nozzles while moving the object and the printing head relative to each other along a printing track. In the printing method, the timing of ejecting the ink from the nozzles or the ejection speed of the ink is controlled based on the separation distance between the nozzles and the object.

[0006] The robot system of the present invention comprises: a robot having a printing head equipped with a plurality of nozzles; and a control device for controlling the driving of the robot, wherein the control device performs a printing operation on the object by causing the ink to be ejected from the nozzle while causing the object and the printing head to move relative to each other along a printing track, and during the printing operation, the control device controls the timing of ejecting the ink from the nozzle or the ejection speed of the ink based on the separation distance between the nozzle and the object. 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 Yes means Figure 1 A top view of the front end surface of a printing head included in the robot shown.

[0009] Figure 3 Yes means Figure 1 A top view of a mobile worktable provided with the robot is shown.

[0010] Figure 4 is a flowchart for explaining the printing method.

[0011] Figure 5 This is a diagram showing a printing job situation.

[0012] Figure 6 This is a diagram showing an example of a printed image.

[0013] Figure 7 This is a timing chart showing an example of ink ejection timing.

[0014] Figure 8 This is a diagram showing a printing job situation.

[0015] Fig. 9 This is a diagram for explaining problems of the conventional printing method.

[0016] Fig.10 This is a diagram for explaining problems of the conventional printing method.

[0017] Fig.11 This is a diagram for explaining problems of the conventional printing method.

[0018] Fig.12 This is a diagram for explaining problems of the conventional printing method.

[0019] Fig.13 This is a diagram for explaining problems of the conventional printing method.

[0020] Fig.14 This is a diagram for explaining problems of the conventional printing method.

[0021] Fig.15 This is a diagram showing an example of a GUI.

[0022] Fig.16 This is a graph showing the relationship between the shape of an object and the deviation of the landing position of ink.

[0023] Fig.17 is based on Fig.16 The relationships shown are corrected timing diagrams.

[0024] Fig.18 This is a graph showing the relationship between the shape of an object and the deviation of the landing position of ink.

[0025] Fig.19 is based on Fig.18 The relationships shown are corrected timing diagrams.

[0026] Fig. 20 This is a timing chart showing the corrected ink ejection timing.

[0027] Fig.21 It is a diagram showing a modified example of the object.

[0028] Fig. 22 It is a diagram showing a modified example of the object.

[0029] Fig.23 It is a diagram showing a modified example of the object.

[0030] Fig.24 It is a diagram showing the configuration of a front end portion of a robot included in a robot system according to a third embodiment.

[0031] Description of Reference Numerals

[0032] 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 table, 40: base, 400: piezoelectric actuator, 41: first table, 42: second table, 45: first table drive unit, 46: second table drive unit, 5: vibrator, 8: distance sensor, 9: control device, A: first direction, B: second direction, D: separation distance, D': separation distance, D0: separation distance, Db: separation distance, Dc: separation distance Distance, Dm: separation distance, Dy: separation distance, d: distance, G1: printing setting column, G2: shape reading column, G3: printing range designation column, I: ink, Ib: ink, Ic: ink, Im: ink, Iy: ink, J1: joint, J2: joint, J3: joint, J4: joint, J5: joint, J6: joint, P: quadrilateral, Pb: quadrilateral, Pc: quadrilateral, Pcb: quadrilateral, Pm: quadrilateral, Pmy: quadrilateral, Py: quadrilateral, Q: printing track, S1: driving condition determination step, S2: printing step, Tb: target landing position, Tc: target landing position, Tm: target landing position, Ty: target landing position, W: object, W0: object. DETAILED DESCRIPTION

[0033] 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.

[0034] First embodiment

[0035] Figure 1It is an overall diagram of the robot system according to the first embodiment. Figure 2 Yes means Figure 1 A top view of the front end surface of a printing head included in the robot shown. Figure 3 Yes means Figure 1 A top view of a mobile worktable provided with the robot is shown. Figure 4 is a flowchart for explaining the printing method. Figure 5 This is a diagram showing a printing job situation. Figure 6 This is a diagram showing an example of a printed image. Figure 7 This is a timing chart showing an example of ink ejection timing. Figure 8 This is a diagram showing a printing job situation. Figures 9 to 14 Each of these is a diagram for explaining a problem of a conventional printing method. Fig.15 This is a diagram showing an example of a GUI. Fig.16 This is a graph showing the relationship between the shape of an object and the deviation of the landing position of ink. Fig.17 is based on Fig.16 The relationships shown are corrected timing diagrams. Fig.18 This is a graph showing the relationship between the shape of an object and the deviation of the landing position of ink. Fig.19 is based on Fig.18 The relationships shown are corrected timing diagrams. Fig. 20 This is a timing chart showing the corrected ink ejection timing. Figure 21 to Figure 23 Each of them is a diagram showing a modified example of the object.

[0036] Figure 1 The robot system 1 shown is applied to a printing system that performs a printing operation on an object W. The robot system 1 includes a robot 10 and a control device 9 that controls the driving of the robot 10. In addition, the robot 10 includes a robot body 2, a printing head 3 mounted on the front end of the robot body 2, a movable table 4 disposed between the robot body 2 and the printing head 3, and a vibrator 5 disposed on the printing head 3.

[0037] Robot body 2

[0038] The robot body 2 is a six-axis vertical multi-joint robot with six drive axes, and has a base 21 fixed to a loading table, a floor, etc. and a robot arm 22 rotatably connected to the base 21. The robot arm 22 is a structure in which six arms 221, 222, 223, 224, 225, and 226 are rotatably connected in sequence from the side of the base 21, and has 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 driving mechanism is provided at each of the joints J1, J2, J3, J4, J5, and J6, and the driving mechanism has a motor as a driving source and an encoder for detecting the rotation amount of the joint. Then, by independently operating the joints J1 , J2 , J3 , J4 , J5 , and J6 , the print head 3 attached to the front end of the robot arm 22 can be moved in a desired direction with a desired posture.

[0039] 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 dual-arm robot, a horizontal multi-joint robot (SCARA robot), etc. In addition, the robot body 2 may not be fixed to a loading table, a floor, etc., but may be able to move on its own.

[0040] Printing head 3

[0041] The print head 3 is arranged at the front end of the mechanical arm 22, that is, the arm 226. There is no particular limitation on the print head 3, and in this embodiment, a piezoelectric drive inkjet head is used. The piezoelectric drive inkjet head has an ink chamber, a vibration plate constituting a part of the wall surface of the ink chamber, a piezoelectric element that vibrates the vibration plate, and a nozzle connected to the ink chamber. Then, 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.

[0042] In particular, the print head 3 of this embodiment can perform full-color printing in the CMYK color model. Figure 2As shown, there are nozzles 31c for ejecting cyan ink Ic, nozzles 31m for ejecting magenta ink Im, nozzles 31y for ejecting yellow ink Iy, and nozzles 31b for ejecting black ink Ib. It should be noted that in the present embodiment, the print head 3 is controlled to move relative to the object W along the printing track Q indicated by the arrow, and the nozzles 31c, 31m, 31y, and 31b are arranged along the printing track Q. In addition, a plurality of each nozzle 31c, 31m, 31y, and 31b are arranged in a direction orthogonal to the printing track Q. Thus, printing is performed by ejecting ink I from each nozzle 31 of the print head 3 at a predetermined timing so that the ink I lands on the object W while the print head 3 is moved along the printing track Q.

[0043] However, the arrangement of the plurality of nozzles 31, the color of the ink I ejected from each nozzle 31, etc. are not particularly limited. For example, a configuration in which black ink Ib is ejected from all the nozzles 31 is also possible. In addition, the configuration of the print head 3 is not limited to the above-mentioned piezoelectric drive type inkjet head. For example, an inkjet head of a thermal type utilizing the film boiling phenomenon of the ink I, a bubble ejection type in which the ink I is ejected by generating bubbles in the ink I by heating, an electrostatic actuator type in which the vibrating plate is displaced and vibrated by electrostatic force to eject the ink I, etc. may also be used.

[0044] Mobile workbench 4

[0045] like Figure 1 As shown in FIG. 2 , the movable workbench 4 is disposed between the arm 226 and the printing head 3. Such a movable workbench 4 is used to correct the position of the printing head 3. Figure 3 As shown, the movable stage 4 includes a base 40 supported by an 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 that is orthogonal to the first direction A relative to the first stage 41. In addition, the print head 3 is disposed on the second stage 42.

[0046] In addition, the movable table 4 has a first table driving unit 45 and a second table driving unit 46. The first table driving unit 45 moves the first table 41 relative to the base 40 in the first direction A, and the second table driving unit 46 moves the second table 42 relative to the first table 41 in the second direction B. The first table driving unit 45 and the second table driving unit 46 each have a piezoelectric actuator 400 driven by the expansion and contraction of the piezoelectric element caused by energization, and the vibration of the piezoelectric actuator 400 is transmitted to the first table 41 and the second table 42 to move them. In this way, by using the piezoelectric actuator 400, the movement amount and movement speed of the first table 41 and the second table 42 can be finely and accurately controlled, and the switching of the movement direction also becomes quick. Therefore, the position correction of the printing head 3 can be performed with good accuracy. In addition, the miniaturization and lightness of the movable table 4 can also be achieved. Therefore, it is possible to minimize the increase in the front end weight of the robot body 2 due to the configuration of the moving table 4, and effectively suppress the reduction in driving characteristics such as responsiveness and vibration damping of the robot body 2.

[0047] However, the structure of the movable table 4 is not particularly limited. For example, the first table drive unit 45 and the second table drive unit 46 may also be structures using a drive source other than the piezoelectric actuator 400, such as a motor that rotates by powering on. In addition, the movable table 4 may be omitted. In this case, the position correction of the print head 3 can be performed by the robot arm 22.

[0048] Vibrator 5

[0049] like Figure 1 As shown, the vibrator 5 is disposed on the print head 3 to detect vibration of the print head 3. It should be noted that the "vibration" refers to displacement of the print head 3 other than displacement along the printing track Q described later. The vibrator 5 is, for example, a three-axis angular velocity sensor that detects angular velocity in three mutually orthogonal axial directions.

[0050] Control device 9

[0051] like Figure 1 As shown, the control device 9 is electrically connected to the robot 10 to control the driving of the robot 10. Specifically, the control device 9 controls the driving of the robot body 2, the printing head 3, the moving workbench 4, and the vibrator 5 independently or in conjunction with each other. Such a control device 9 is composed of, for example, a computer, and has a processor (CPU) for processing information, a memory connected to the processor in a communicable manner, 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.

[0052] The configuration of the robot system 1 has been described above. Next, a printing method using the robot system 1 will be described. Figure 4 As shown, the printing method includes a driving condition determination step S1 and a printing step S2, wherein the driving condition determination step S1 is a step of determining the driving condition of the print head 3 in advance, and the printing step S2 is a step of driving the print head 3 to print the object W based on the driving condition determined in the driving condition determination step S1. It should be noted that the shape of the object W, more specifically, the shape of the printed surface of the object W, is not particularly limited, but is preferably a non-planar shape such as a curved surface, a bent surface, and a surface formed by combining them, that is, a three-dimensional shape other than a plane. As a result, the effect of the printing method of this embodiment is significant. Below, each of these steps S1 and S2 is described in detail, but before that, the characteristics of the printing method of this embodiment are briefly described.

[0053] Here, as an example, Figure 7 As shown in Figure 5 As shown in the figure, the printing head 3 is moved at a constant speed along a printing track Q with an ideal distance D0 maintained while ejecting ink I to print on a planar object W0. Figure 6 The ink ejection timing of the quadrilateral P shown. Figure 7 In the above, it means that the ink I is ejected from each nozzle 31c, 31m, 31y, and 31b at the timing of "1".

[0054] In contrast, Figure 8 1 shows a case where the printing head 3 is moved at a constant speed along a printing track Q with an ideal distance D0 while ejecting ink I to print on an object W having an arc-shaped curved surface. Figure 6 In the case of the same quadrilateral, such as Fig. 9 As shown in FIG. 1 , the planar quadrilateral P must be printed in a curved form along the object W. However, when Figure 7 When the ink ejection timing shown is used to print the object W, Fig.10 As shown, the printed shape is a shape obtained by plane-projecting the quadrilateral P onto the object W, and the quadrilateral P is deformed.

[0055] Specifically, if Fig.11 As shown, the landing position of ink Im is offset to the front side of the printing track Q relative to the target landing position Tm, the landing position of ink Ic is offset to the front side of the printing track Q relative to the target landing position Tc, the landing position of ink Iy is offset to the rear side of the printing track Q relative to the target landing position Ty, and the landing position of ink Ib is offset to the rear side of the printing track Q relative to the target landing position Tb. Fig.12As shown, quadrilaterals Pc, Pm, Py, and Pb formed by inks Ic, Im, Iy, and Ib are formed along the printing track Q in a mutually offset manner. Therefore, quadrilateral P is offset, blurred, deformed, and the printing quality is reduced. It should be noted that the smaller the radius of curvature of the object W is, and the larger the distance d between the nozzle 31 and the center of the printing head 3 is, the larger the offset is. Hereinafter, such a factor that leads to reduced printing quality is also referred to as the "first factor."

[0056] In addition, if Fig.13 As shown, when the moving distance between the nozzle 31 and the object W is set to D, specifically, the moving distance between the nozzle 31c and the object W is set to Dc, the moving distance between the nozzle 31m and the object W is set to Dm, the moving distance between the nozzle 31y and the object W is set to Dy, and the moving distance between the nozzle 31b and the object W is set to Db, the separation distances Dc and Db of the nozzles 31c and 31b located in the front and rear rows of the printing track Q are larger than the separation distances Dm and Dy of the nozzles 31m and 31y located in the center row of the printing track Q. In other words, the relationship Dc=Db>Dm=Dy is achieved. In addition, the nozzles 31c, 31m, 31y, and 31b are respectively arranged to be offset from the center of the print head 3 to the front side or the rear side of the printing track Q, so the separation distances Dc, Dm, Dy, and Db are respectively larger than the ideal distance D0.

[0057] The larger the separation distance D is, the longer the time from when the ink Ic, Im, Iy, Ib is ejected to when it lands on the object W (hereinafter also referred to as "flight time"). Fig.13 As shown in FIG. 1 , the inks Ic, Im, Iy, and Ib fly with a velocity component in the moving direction of the print head 3. Therefore, the longer the flight time, the more the actual landing point of the inks Ic, Im, Iy, and Ib deviates toward the front side of the printing track Q relative to the target landing position Tc, Tm, Ty, and Tb. Figure 7 When printing is performed at the ink ejection timing shown, Fig.14 As shown, the quadrilateral Pcb formed by inks Ic and Ib is offset to the front side of the printing track Q relative to the quadrilateral Pmy formed by inks Im and Iy. Therefore, the printing is offset, blurred, deformed, etc., and the printing quality is reduced. Hereinafter, such a factor that leads to reduced printing quality is also referred to as the "second factor".

[0058] The purpose of the printing method of this embodiment is to eliminate the reduction of printing quality caused by the first factor and the second factor and improve the printing quality. The printing method of this 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, so that each ink Ic, Im, Iy, and Ib can land on the target landing position with good accuracy without being affected by the first factor and the second factor. Specifically, in the printing method of this embodiment, the larger the separation distances Dc, Dm, Dy, and Db, the earlier the ejection timing of the inks Ic, Im, Iy, and Ib, so that each ink Ic, Im, Iy, and Ib can land on the target landing position with good accuracy without being affected by the first factor and the second factor. In other words, the deviation of the actual landing position relative to the target landing position can be suppressed to be smaller. Therefore, the printing is not prone to deviation, blur, deformation, etc., and the printing quality can be improved.

[0059] Hereinafter, the driving condition determination step S1 and the printing step S2 of the printing method according to the present embodiment will be described in detail.

[0060] Driving condition determination step S1

[0061] In the driving condition determination step S1, first, the control device 9 acquires various information required for determining the driving conditions of the print head 3. It should be noted that in this embodiment, the information of the print head 3 is set in advance in the control device 9, specifically, the position of each nozzle 31 and the ejection speed of the ink I are set. Fig.15 The GUI (Graphical User Interface) shown receives various other necessary information from the user. The GUI includes a print setting field G1 , a shape reading field G2 , and a print range designation field G3 .

[0062] The control device 9 receives the print image to be printed on the object W and the moving speed (print scanning speed) of the print head 3 from the user in the print setting field G1. The user presses the "Select" button to select the desired image stored in the computer. The control device 9 receives the image selected by the user as the print image. Note that, assuming that Figure 6 The quadrilateral P shown. In addition, the user can specify a desired numerical value as the print scan speed by inputting the desired numerical value in the print scan speed column.

[0063] The control device 9 receives the shape data of the object W from the user at the shape reading column G2. The user presses the "Select" button to select the desired shape data stored in a computer, server, etc. The control device 9 receives 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, measurement data obtained by measuring the object W using a measuring instrument such as a 3D scanner, and the like. In addition, for example, in the case where the object W is a simple shape such as a plane or an arc with a constant curvature, the control device 9 can also receive the shape data of the object W through numerical input from the user. It should be noted that in the present embodiment, CAD data is used as the shape data of the object W. Thus, since shape data with good accuracy can be obtained, the printing track Q and the separation distance D can be calculated with good accuracy and simplicity.

[0064] The control device 9 displays the shape of the object W in the print range designation column G3 and receives the print start point from the user. The user can designate the print start point by inputting a desired value in the start position column. In addition, the user can designate the print start point by dragging the dotted line indicating the print start position.

[0065] As described above, the control device 9 acquires various information required to determine the driving conditions of the print head 3. However, the method of acquiring these various information is not particularly limited. In addition, the configuration of the GUI and the type of information received by the GUI are not particularly limited.

[0066] Next, the control device 9 determines the printing track Q for printing the quadrilateral P at the designated position of the object W based on various information received from the user. The printing track Q is automatically generated by the control device 9 without receiving instructions from the user. The printing track Q includes information required for the printing operation, such as the position and posture of the print head 3 relative to the object W, the moving direction, and the moving speed in each control cycle. Furthermore, the control device 9 calculates the separation distance D between each nozzle 31 and the object W based on the shape data of the object W, the printing track Q, and the information of the print head 3. The separation distance D includes the separation distance Dc between each nozzle 31c and the object W, the separation distance Dm between each nozzle 31m and the object W, the separation distance Dy between each nozzle 31y and the object W, and the separation distance Db between each nozzle 31b and the object W. It should be noted that in the case of the present embodiment, the separation distances Dc of each nozzle 31c are equal to each other, the separation distances Dm of each nozzle 31m are equal to each other, the separation distances Dy of each nozzle 31y are equal to each other, and the separation distances Db of each nozzle 31b are equal to each other.

[0067] Next, the ink ejection timing of each nozzle 31 is determined. Figure 7 The ink ejection timing shown in FIG. 1 is corrected to determine the ink ejection timing of each nozzle 31. At this time, for example, by using Fig.16 and Fig.18 The relationship shown above allows the ink ejection timing to be easily corrected with high accuracy.

[0068] Fig.16 This is a graph showing the relationship between the curvature radius R of the object W and the offset of the actual landing position of the ink I relative to the target landing position, and is suitable for eliminating the influence of the first factor. This relationship can be calculated based on the position of each nozzle 31, the shape of the object W, the moving speed of the print head 3, the ejection speed of the ink I, etc.

[0069] As can be seen from the graph, for example, when the curvature radius of the object W is 50 mm, Figure 7 When printing is performed at the ink ejection timing shown, due to the influence of the first factor, the actual landing position of the ink Ic ejected from each nozzle 31c is offset 120 μm forward from the target landing position, the actual landing position of the ink Im ejected from each nozzle 31m is offset 5 μm forward from the target landing position, the actual landing position of the ink Iy ejected from each nozzle 31y is offset 5 μm backward from the target landing position, and the actual landing position of the ink Ib ejected from each nozzle 31b is offset 120 μm backward from the target landing position.

[0070] Furthermore, when the moving speed of the printing head 3 is 127 mm / s, in order to eliminate the above-mentioned deviation and make each ink Ic, Im, Iy, Ib land on the target landing position, as shown in FIG. Fig.17 As shown, as long as relative to Figure 7 The ink ejection timing shown in the figure can be adjusted to make the ejection timing of each ink Ic earlier by (120μm) / (127mm / s)=0.94ms, the ejection timing of each ink Im earlier by (5μm) / (127mm / s)=0.04ms, the ejection timing of each ink Iy later by (5μm) / (127mm / s)=0.04ms, and the ejection timing of each ink Ib later by (120μm) / (127mm / s)=0.94ms. Thus, the influence of the first factor is eliminated, and high-quality printing with less displacement, blurring, deformation, etc. can be performed.

[0071] in addition, Fig.18 This is a graph showing the relationship between the curvature radius R of the object W and the offset amount of the landing position between the nozzles 31c, 31m, 31y, and 31b, and is used to eliminate the influence of the second factor. This relationship can be calculated based on the position of each nozzle 31, the shape of the object W, the moving speed of the print head 3, the ejection speed of the ink I, etc.

[0072] For example, it can be seen that when the curvature radius of the object W is 50 mm and the moving speed of the printing head 3 is 127 mm / s, the inks Ic and Ib land 85 μm ahead of the inks Im and Iy. Fig.19 As shown, as long as relative to Fig.17 The corrected ink ejection timing shown is to make the ejection timing of inks Ic and Ib earlier than that of inks Im and Iy by (85 μm) / (127 mm / s)=0.67 ms. This eliminates the influence of the second factor and enables high-quality printing with less offset, blurring, and deformation.

[0073] As mentioned above, determine Fig. 20 The driving conditions of the print head 3 are shown. Fig.16 and Fig.18 The relationship shown is Figure 7 By correcting the ink ejection timing shown in FIG. 1 , the deviation of the landing position caused by the first factor and the second factor can be effectively eliminated, and each ink I can be landed at the target landing position. Figure 7 The ink ejection timing shown is used as the initial setting and Fig.16 and Fig.18 The relationship shown in FIG. 1 is used to correct the setting and determine the driving condition of the print head 3, but the method for determining the driving condition is not particularly limited. Figure 7 The initial settings shown are Fig.16 and Fig.18 The relationship shown determines Fig. 20 The driving conditions of the printing head 3 are shown.

[0074] Printing step S2

[0075] 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 determines the printing direction determined in step S1 based on the driving conditions. Fig. 20 The driving condition (ink ejection timing) of the print head 3 shown in FIG. 1 is used to control the driving of the print head 3 to perform the printing operation. As a result, a high-quality quadrilateral P with less deviation, blur, deformation, etc. is printed on the object W. In addition, in the printing step S2, the vibration of the print head 3 is detected based on the output of the vibrometer 5 during the printing operation, and the driving of the movable table 4 is controlled to eliminate the detected vibration. Specifically, the driving of the movable table 4 is controlled in a manner that a vibration with a phase opposite to the detected vibration is applied to the print head 3. As a result, the vibration of the print head 3 in the printing step S2 is suppressed, and higher-quality printing can be performed.

[0076] The robot system 1 has been described above. As described above, the printing method using such a robot system 1 is a printing method as follows: the robot 10 having a print head 3 provided with a plurality of nozzles 31 is used to relatively move the object W and the print head 3 along the printing track Q while ejecting ink I from the nozzles 31, thereby performing a printing operation on the object W. In this printing method, the timing of ejecting the ink I from the nozzles 31 is controlled based on the separation distance D between the nozzles 31 and the object W. According to such a method, even if the shape of the object W is a curved surface or a curved surface other than a plane, it is possible to perform high-quality printing on the object W with little deviation, blurring, deformation, etc.

[0077] As described above, in the printing method using the robot system 1, the above control is performed for each nozzle 31. That is, the timing of ejecting the ink I is controlled for each nozzle 31. Thus, high-quality printing with little deviation, blurring, deformation, etc. can be performed on the object W.

[0078] In addition, as described above, in the printing method using the robot system 1, the larger the separation distance D is, the earlier the timing of ejecting the ink I is. As a result, it is 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 object W with less deviation, blurring, deformation, etc.

[0079] Furthermore, as described above, in the printing method using the robot system 1 , the separation distance D is calculated using the CAD data of the object W. Thus, the separation distance D can be calculated with high accuracy and in a simple manner.

[0080] In addition, as described above, the plurality of nozzles 31 are arranged along the printing track Q. Specifically, the nozzles 31c, 31m, 31y, and 31b are arranged along the printing track Q. Therefore, when printing on a non-planar object W, the separation distance D varies between the nozzles 31c, 31m, 31y, and 31b. Therefore, the effect of the above control can be more significantly exerted.

[0081] In addition, as described above, inks Ic, Im, Iy, and Ib of different colors are ejected from the plurality of nozzles 31c, 31m, 31y, and 31b, respectively, thereby enabling multi-color printing, particularly full-color printing.

[0082] In addition, as described above, the robot system 1 includes the robot 10 and the control device 9, the robot 10 includes the print head 3 provided with a plurality of nozzles 31, and the control device 9 controls the driving of the robot 10. Then, the control device 9 performs a printing operation on the object W by ejecting the ink I from the nozzles 31 while moving the object W and the print head 3 relatively along the printing track Q, and during the printing operation, the timing of ejecting the ink I from the nozzles 31 is controlled based on the separation distance D between the nozzles 31 and the object W. According to such a configuration, even if the shape of the object W is a curved surface or a curved surface other than a flat surface, it is possible to perform high-quality printing on the object W with little deviation, blurring, deformation, etc.

[0083] The printing method of this embodiment has been described above. However, there is no particular limitation on the printing method. For example, there is no particular limitation on the shape of the object W. Fig.21 , Fig. 22 As shown in FIG. 1 , it may also be a wavy concave-convex shape. In this case, since the separation distances Dc, Dm, Dy, and Db are repeatedly increased and decreased in the printing step S2, it is sufficient to correct the ink ejection timing accordingly. Fig.23 As shown, the shape may be curved when viewed from the direction along the printing track Q. In this case, the separation distance Dc between the nozzles 31c is different, so it is sufficient to correct the ink ejection timing for each nozzle 31c. The same applies to the other nozzles 31m, 31y, and 31b.

[0084] Second embodiment

[0085] This embodiment is the same as the first embodiment described above, except that the driving condition determination step S1 of the printing method is different. It should be noted that in the following description, this embodiment is described around 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 figure marks are marked for the same components as those in the above embodiment.

[0086] In the first embodiment described above, in order to eliminate the influence of the second factor, as Fig.19 Shown Fig.17 The ejection timing of the ink I shown in FIG. 1 is corrected. In contrast, in this embodiment, in order to eliminate the influence of the second factor, Fig.17The ink ejection timing shown is used to correct the ejection speed of ink I. Specifically, the larger the separation distances Dc, Dm, Dy, and Db, the faster the ejection speed of inks Ic, Im, Iy, and Ib, so that each ink Ic, Im, Iy, and Ib can land on the target landing position with good accuracy without being affected by the second factor. In other words, the deviation of the actual landing position relative to the target landing position can be suppressed to be smaller. Therefore, printing is not prone to deviation, blurring, deformation, etc., and the printing quality can be improved. In the present embodiment, the ejection speed of inks Ic and Ib is increased in a manner that the flight time of inks Ic and Ib is shortened by 0.67ms relative to the flight time of inks Im and Iy. As a result, the influence of the second factor is eliminated, and high-quality printing with less deviation, blurring, deformation, etc. can be performed.

[0087] It should be noted that there is no particular limitation on the method of changing the ejection speed of the ink I. For example, the print head 3 is a piezoelectric driven inkjet head, and the piezoelectric element is vibrated by applying a voltage to the piezoelectric element, thereby vibrating the vibration plate and ejecting the ink I in the ink chamber from the nozzle 31. At this time, the greater the voltage applied to the piezoelectric element, the greater the vibration plate vibrates, and the ink I is ejected at a higher speed. Therefore, by making full use of such characteristics, in this embodiment, the ejection speed of the inks Ic and Ib is increased by increasing the voltage applied to the piezoelectric element for vibrating the vibration plate of the ink chamber configured in the inks Ic and Ib relative to the initial condition. According to such a method, the influence of the second factor can be eliminated by simple control.

[0088] As described above, the printing method of the present embodiment is a printing method as follows: the robot 10 having the print head 3 provided with a plurality of nozzles 31 is used to relatively move the object W and the print head 3 along the printing track Q while ejecting the ink I from the nozzles 31, thereby printing the object W. In this printing method, the ejection speed of the ink I is controlled based on the separation distance D between the nozzles 31 and the object W. According to such a method, the influence of the second factor can be eliminated, and even if the shape of the object W is a curved surface other than a flat surface or a curved surface, the object W can be printed with high quality with little deviation, blurring, deformation, etc.

[0089] In addition, as described above, in the printing method using the robot system 1, the larger the separation distance D is, the faster the ejection speed is. As a result, the deviation of the actual landing position of the ink I from the target landing position can be reduced. Therefore, the object W can be printed with high quality with less deviation, blur, deformation, etc.

[0090] In addition, as described above, the robot system 1 includes the robot 10 and the control device 9, the robot 10 includes the print head 3 provided with a plurality of nozzles 31, and the control device 9 controls the driving of the robot 10. Then, the control device 9 performs a printing operation on the object W by ejecting the ink I from the nozzles 31 while moving the object W and the print head 3 relatively along the printing track Q, and during the printing operation, the ejection speed of the ink I is controlled based on the separation distance D between the nozzles 31 and the object W. According to such a configuration, the influence of the second factor can be eliminated, and even if the shape of the object W is a curved surface other than a flat surface or a curved surface, the object W can be printed with high quality with little deviation, blurring, deformation, etc.

[0091] According to the second embodiment, it is possible to achieve the same effects as those of the first embodiment described above.

[0092] It should be noted that in this embodiment, the correction of the ink ejection timing is used to eliminate the first factor, and the correction of the ink ejection speed is used to eliminate the second factor, but it is not limited to this. For example, the correction of the ink ejection speed can also be used to eliminate the first factor, and the correction of the ink ejection timing can be used to eliminate the second factor. In addition, the correction of the ink ejection speed can also be used to eliminate both the first factor and the second factor. By such a method, the same effect can be achieved.

[0093] Third embodiment

[0094] Fig.24 It is a diagram showing the configuration of a front end portion of a robot included in a robot system according to a third embodiment.

[0095] This embodiment is the same as the first embodiment except that the printing method is different. It should be noted that in the following description, this embodiment is described around 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 figure marks are marked for the same structures as the above-mentioned embodiment.

[0096] In the first embodiment described above, the driving condition determination step S1 for determining the driving condition of the print head 3 is performed before the printing step S2, but in the present embodiment, the driving condition of the print head 3 is corrected in the printing step S2. According to such a method, the time required for the driving condition determination step S1 can be omitted, and the printing operation can be made more efficient.

[0097] like Fig.24As shown, the robot 10 of the present embodiment has a distance sensor 8, which is arranged on the printing head 3 and measures the separation distance D' from the object W. The distance sensor 8 is located on the front side of the printing track Q relative to the printing head 3 in the printing step S2. In the printing step S2, the control device 9 uses the distance sensor 8 to measure the separation distance D' from the part at a part in front of the printing head 3 during the movement of the printing head 3. Furthermore, the control device 9 calculates the separation distances Dc, Dm, Dy, and Db when each nozzle 31c, 31m, 31y, and 31b is facing the part based on the separation distance D'. Then, the control device 9 corrects the ejection timing or ejection speed of the ink I that lands on the part based on the calculated separation distances Dc, Dm, Dy, and Db, and controls the drive of the printing head 3 with the corrected drive conditions. By repeatedly performing such correction operations at a prescribed period during the movement of the printing head 3, it is possible to generate the following image while printing. Fig. 20 Therefore, even without determining the driving conditions of the print head 3 in advance, it is possible to perform high-quality printing on the object W with little deviation, blur, deformation, etc.

[0098] In the above-described printing method, the distance sensor 8 for measuring the separation distance D' is used to calculate the separation distance D' while the printing operation is being performed. According to such a method, the efficiency of the printing operation can be improved.

[0099] According to the third embodiment, the same effects as those of the first embodiment can be achieved.

[0100] The printing method and robot system of the present invention are described above with respect to the illustrated embodiments, but the present invention is not limited thereto, and the configuration or process of each part can be replaced with any configuration or process having the same function. In addition, any other configuration or process may be added to the present invention. In addition, the various embodiments may be appropriately combined.

Claims

1. A printing method, characterized in that: A robot including a print head provided with a plurality of nozzles is used to perform printing on the object by ejecting ink from the nozzles while moving the object and the print head relatively along a printing track. In the printing method, the timing of ejecting the ink from the nozzle or the ejection speed of the ink is controlled based on the separation distance between the nozzle and the object.

2. The printing method according to claim 1, characterized in that: The control is performed for each of the nozzles.

3. The printing method according to claim 1, characterized in that: The greater the separation distance, the earlier the timing.

4. The printing method according to claim 1, characterized in that: The larger the separation distance, the faster the ejection speed.

5. The printing method according to claim 1, characterized in that: The separation distance is calculated using CAD data of the object.

6. The printing method according to claim 1, characterized in that: The separation distance is calculated while the printing operation is being performed using a distance sensor that measures the separation distance.

7. The printing method according to claim 1, characterized in that: The plurality of nozzles are arranged along the printing track.

8. The printing method according to claim 7, characterized in that: The inks of different colors are ejected from the plurality of nozzles, respectively.

9. A robot system, characterized in that: have: A robot having a printing head configured with a plurality of nozzles; and A control device controls the driving of the robot, The control device performs a printing operation on the object by ejecting ink from the nozzle while moving the object and the print head relatively along a printing track. In the printing operation, the control device controls a timing of ejecting the ink from the nozzle or an ejection speed of the ink based on a separation distance between the nozzle and the object.

Images