Printing method and robotic system

Abstract

A printing method and a robot system are provided, which can suppress the occurrence of printing defects in which a blank is generated between lines and overlapping becomes obvious when performing multi-line printing on an object using a robot. The printing method is characterized by performing multi-line printing using an ink ejection head that ejects ink, a robot that relatively moves the ink ejection head with respect to the object along a printing direction, and a detection unit that detects a relative trajectory of the ink ejection head with respect to the object, and has: a line width setting step of acquiring a fluctuation amount of the trajectory in a direction orthogonal to the printing direction by the detection unit, and setting a line width of the trajectory when performing multi-line printing based on the acquired fluctuation amount; and a printing step of performing multi-line printing on the object while relatively moving the ink ejection head to generate overlapping corresponding to the line width in the multi-line printing.

Description

Technical Field

[0001] This invention relates to printing methods and robotic systems. Background Technology

[0002] There is a known stereolithography printing apparatus that combines the actions of multiple movable parts to move an inkjet head, thereby printing on the surface of a stereolithography object.

[0003] For example, Patent Document 1 discloses a system for printing on a three-dimensional object, the system comprising: an articulated robot, a print head, a piezoelectric actuator disposed therebetween, and a detector for determining the position of the print point. The robot is configured to move the print head along the surface of the object. Thus, printing can be performed in multiple paths, including print tracks that are adjacent to each other.

[0004] Furthermore, Patent Document 1 discloses a piezoelectric actuator that causes relative movement of the print head relative to a robot. Patent Document 1 also discloses the following operation: when using this system to print in multiple paths while moving the print head in two adjacent print tracks, the actual position of the printing point on the first print track is determined; the offset between the target position and the actual position is calculated; and a compensating movement is performed in the second print track to eliminate the offset. Thus, offset between print paths is suppressed, enabling the printing of error-free images.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-202781

[0006] However, in the system described in Patent Document 1, the offset between the target position and the actual position cannot be sufficiently eliminated due to factors such as vibrations generated by the robot. Insufficient elimination of the offset results in printing defects such as gaps between printing paths and noticeable overlap between printing paths. Summary of the Invention

[0007] The printing method described in the application example of the present invention uses an ink ejector head, a robot, and a detection unit to perform multi-line printing. The ink ejector head ejects ink, the robot moves the ink ejector head relative to the object along the printing direction, and the detection unit detects the relative trajectory of the ink ejector head relative to the object. The printing method includes: an overlap width setting step in which the detection unit acquires the fluctuation amount of the trajectory in a direction orthogonal to the printing direction and sets the overlap width of the trajectory during multi-line printing based on the acquired fluctuation amount; and a printing step in which the ink ejector head performs multi-line printing on the object while moving relative to it, so as to generate an overlap corresponding to the overlap width during multi-line printing.

[0008] The robot system involved in the application example of the present invention performs multi-line printing on an object. The robot system includes: an ink ejector head that ejects ink; a robot having a robotic arm that moves the ink ejector head relative to the object along a printing direction; a detection unit that detects the relative trajectory of the ink ejector head relative to the object; and a printing control unit that controls the movements of the ink ejector head and the robot. The printing control unit includes: a fluctuation amount acquisition unit that acquires the fluctuation amount of the trajectory in a direction orthogonal to the printing direction; and an overlap width setting unit that sets the overlap width between the trajectories during multi-line printing based on the acquired fluctuation amount. While the robot moves the ink ejector head relative to the object, the ink ejector head performs multi-line printing on the object to generate an overlap corresponding to the overlap width during multi-line printing. Attached Figure Description

[0009] Figure 1 This is a perspective view showing the overall structure of the robot system (printing apparatus) according to the first embodiment.

[0010] Figure 2 yes Figure 1 The diagram shows the functional block diagram of the printing apparatus.

[0011] Figure 3 It is shown Figure 1 The top view of the moving platform and the liquid nozzle shown.

[0012] Figure 4 This is a schematic diagram illustrating a general outline of the printing method according to the first embodiment.

[0013] Figure 5 This is a flowchart used to explain the printing method involved in the first embodiment.

[0014] Figure 6 It is used for explanation Figure 5 A schematic diagram of the printing method shown.

[0015] Figure 7 It is used for explanation Figure 5 A schematic diagram of the printing method shown.

[0016] Figure 8 It is used for explanation Figure 5 A schematic diagram of the printing method shown.

[0017] Figure 9 It is a graph showing the relationship between the residual error and the corresponding overlap width in two directions, D1 and D2.

[0018] Figure 10 This is a schematic diagram illustrating a method for sparsifying points within a range OL corresponding to the overlap width.

[0019] Figure 11 This is a schematic diagram illustrating a method for sparsifying points within a range OL corresponding to the overlap width.

[0020] Figure 12 This is a flowchart illustrating the printing method involved in the second embodiment.

[0021] Figure 13 This is a flowchart illustrating the printing method involved in the third embodiment.

[0022] Explanation of reference numerals in the attached figures

[0023] 100… Printing apparatus (robot system), 200… Robot, 210… Base, 220… Robotic arm, 221… Arm, 222… Arm, 223… Arm, 224… Arm, 225… Arm, 226… Arm, 230… Arm drive mechanism, 240… Robot controller, 242… Arm control unit, 244… Mobile stage controller, 246… Storage unit, 300… Mobile stage, 310… Base, 320… Stage, 320X…X Stage, 320Y…Y stage, 330…moving mechanism, 330X…X moving mechanism, 330Y…Y moving mechanism, 340…piezoelectric actuator, 400…liquid ejector (ink ejector), 411…ink ejector hole, 420…print controller, 700…fixed component, 800…camera, 900…control device, 910…print control unit, 912…print data generation unit, 914…fluctuation acquisition unit, 916…front and rear measurement acquisition unit 918…Calibration setting unit, 920…Overlap width setting unit, 930…Storage unit, D1…Orthogonal direction, D2…Printing direction, E…Encoder, J1…Joint, J2…Joint, J3…Joint, J4…Joint, J5…Joint, J6…Joint, L1…First line, L2…Second line, LA…Scan line, LB…Scan line, M…Motor, OL…Range, P1…First pattern, P2…Second pattern, Q…Object S100…Width setting process, S102…Step, S104…Step, S106…Step, S108…Step, S110…Step, S114…Step, S116…Step, S118…Step, S120…Step, S121…Step, S122…Step, S124…Step, S200…Printing process, T0…Scanning track, T1…Trajectory, T2…Trajectory, d…Point, da…Point, db…Point. Detailed Implementation

[0024] Hereinafter, preferred embodiments of the printing method and robot system of the present invention will be described in detail with reference to the accompanying drawings.

[0025] 1. First Implementation Method

[0026] First, the printing method and robot system involved in the first embodiment will be described.

[0027] 1.1. Printing apparatus

[0028] Figure 1 This is a perspective view showing the overall structure of the robot system (printing apparatus 100) according to the first embodiment. Figure 2 yes Figure 1 The diagram shows the functional block diagram of the printing apparatus 100. Figure 3 It is shown Figure 1 The top view of the moving stage 300 and the liquid ejector head (ink ejector head) 400 shown.

[0029] Figure 1 The printing apparatus 100 shown includes: a robot 200, a liquid ejector head 400, a fixing component 700 that supports and fixes the object Q, a camera 800, and a control device 900.

[0030] Robot 200 is a 6-axis vertical joint robot with 6 drive axes. Robot 200 includes: a base 210 fixed to the ground, a robotic arm 220 connected to the base 210, and a moving stage 300 mounted on the robotic arm 220. It should be noted that robot 200 can have fewer or more drive axes than 6. Furthermore, robot 200 can also be a horizontal joint robot or a multi-arm robot with multiple robotic arms.

[0031] The robotic arm 220 is a robot arm with multiple arms 221, 222, 223, 224, 225, and 226 connected in a freely rotatable manner, and has six joints J1 to J6. Among them, joints J2, J3, and J5 are bending joints, and joints J1, J4, and J6 are torsional joints. In addition, the robotic arm 220 is equipped with... Figure 2 The arm drive mechanism 230 is shown. The arm drive mechanism 230 consists of components respectively disposed at... Figure 1 The joints J1, J2, J3, J4, J5, and J6 shown are composed of motor M and encoder E. Motor M is the drive source that drives joints J1, J2, J3, J4, J5, and J6 respectively. Encoder E detects the rotation amount (rotation angle of the arm) of motor M.

[0032] At the anterior end of arm 226, such as Figure 3 As shown, a liquid nozzle 400 is installed via a movable platform 300. Figure 3The liquid ejector head 400 shown has an ink chamber (not shown), a vibrating plate disposed on the wall of the ink chamber, and an ink ejection hole 411 connected to the ink chamber, forming a structure in which the vibrating plate vibrates so that the ink in the ink chamber is ejected from the ink ejection hole 411. The structure of the liquid ejector head 400 is not particularly limited.

[0033] In addition, the printing apparatus 100 includes a print controller 420. For example... Figure 2 As shown, the liquid ejector head 400 is connected to the print controller 420. In Figure 1 In this example, the print controller 420 is mounted on the front end of the arm 226 via the stage 300, just like the liquid nozzle 400. The print controller 420 controls the movement of the liquid nozzle 400 based on control signals output from the control device 900.

[0034] For example, the print controller 420 includes one or more processors such as a CPU (Central Processing Unit), memory, external interfaces, etc. It should be noted that the print controller 420 can also replace the CPU or include programmable logic devices such as an FPGA (Field Programmable Gate Array) on top of the CPU. Alternatively, the print controller 420 can be assembled into the control device 900.

[0035] like Figure 3 As shown, the moving stage 300 includes: a base 310 connected to the arm 226, a stage 320 movable relative to the base 310, and a moving mechanism 330 for moving the stage 320 relative to the base 310. Figure 3 As shown, when the three orthogonal axes are designated as the X-axis, Y-axis, and Z-axis, the stage 320 has: a Y-stage 320Y that can move relative to the base 310 in the direction along the Y-axis, and an X-stage 320X that can move relative to the Y-stage 320Y in the direction along the X-axis. The X-stage 320X and Y-stage 320Y are linearly guided in the X-axis and Y-axis directions (not shown) and can move smoothly. Furthermore, a liquid nozzle 400 is mounted on the X-stage 320X.

[0036] The moving mechanism 330 includes a Y moving mechanism 330Y that moves the Y stage 320Y relative to the base 310 in the direction along the Y axis, and an X moving mechanism 330X that moves the X stage 320X relative to the Y stage 320Y in the direction along the X axis.

[0037] The Y-motion mechanism 330Y and the X-motion mechanism 330X each have a piezoelectric actuator 340 as a drive source. The piezoelectric actuator 340 vibrates by extending and contracting a piezoelectric element, and transmits this vibration to the X-stage 320X and Y-stage 320Y to move them. This allows for miniaturization and weight reduction of the moving stage 300. Furthermore, the driving accuracy of the moving stage 300 is improved. Moreover, the piezoelectric actuator 340 has a large holding torque when stopped, which is advantageous because it eliminates the need for a brake and provides high positional stability of the stage 320 when stopped. It should be noted that mechanisms other than the piezoelectric actuator 340 can also be used as drive sources; for example, mechanisms combining rack and pinion gears with a rotary motor, or mechanisms combining ball screws with a rotary motor, can also be used.

[0038] Additionally, the printing apparatus 100 includes a robot controller 240. A motor M and an encoder E are connected to the robot controller 240. The robot controller 240 controls the movement of the robot 200 based on control signals output from the control device 900.

[0039] The robot controller 240 has an arm control unit 242, a mobile stage controller 244, and a storage unit 246 as functional units.

[0040] The arm control unit 242 controls the robotic arm 220 to a desired posture by outputting control signals to control the movement of the arm drive mechanism 230.

[0041] The mobile stage controller 244 moves the liquid nozzle 400 relative to the robotic arm 220 to a designated position by outputting control signals to control the movement of the mobile stage 300. It should be noted that the mobile stage controller 244 can also operate independently of the robot controller 240.

[0042] The storage unit 246 stores the programs required for the operation of the robot controller 240, as well as the data required for the execution of the programs.

[0043] For example, the robot controller 240 includes one or more processors such as a CPU, memory, external interfaces, etc. It should be noted that the robot controller 240 may also replace the CPU or include programmable logic devices such as FPGAs based on the CPU.

[0044] The camera 800 is positioned on the arm 225 with its end facing the robotic arm 220. By positioning the camera 800 on the robotic arm 220 in this way, it is possible to capture images of the object Q from a relatively close distance, resulting in a sharper image.

[0045] It should be noted that there are no particular limitations on the configuration of camera 800. For example, it can be configured on arms 221-224, 226, or at a location far from robot 200. Examples of cameras 800 include monochrome cameras, color cameras, and spectrophotometers.

[0046] The control device 900 controls the actions of the robot controller 240, the print controller 420, and the camera 800, causing them to perform printing on the object Q. The control device 900 has a print control unit 910 and a storage unit 930 as functional units. The print control unit 910 includes a print data generation unit 912, a fluctuation acquisition unit 914, a front / back measurement acquisition unit 916, a correction amount setting unit 918, and an overlap width setting unit 920.

[0047] The printing data generation unit 912 generates printing data and outputs it to the robot controller 240 and the printing controller 420.

[0048] The fluctuation measurement acquisition unit 914 and the front-to-back measurement acquisition unit 916 acquire the "fluctuation measurement" and "front-to-back measurement" as described below. The fluctuation measurement and the front-to-back measurement are the offsets from the scanning trajectory acquired for the trajectory of the liquid ejector head 400.

[0049] The calibration setting unit 918 sets the amount (calibration amount) by which the liquid ejector head 400 moves relative to the scanning track based on the fluctuation amount and the forward and backward amount. Then, it outputs the set calibration amount to the robot controller 240.

[0050] The overlap width setting unit 920 sets the overlap width between the tracks of the liquid ejector head 400 during multi-line printing based on the fluctuation amount and the front-to-back amount. Then, it outputs the set overlap width to the robot controller 240.

[0051] The storage unit 930 stores the programs required for the operation of the control device 900, as well as the data required for the execution of the programs.

[0052] For example, the control device 900 is composed of a computer, having a processor (CPU) for processing information, a memory connected to the processor in a communicative manner, and an external interface. Furthermore, the memory stores various programs that can be executed by the processor, and the processor reads and executes these programs stored in the memory to achieve the functions described above.

[0053] The structure of the robot system (printing apparatus 100) according to the first embodiment has been described above. However, it is also possible that the movable stage 300 is not part of the robot 200, but is configured to support the object Q at a position away from the robot 200. In this case, by moving the movable stage 300 supporting the object Q, the liquid nozzle 400 can be moved relative to the object Q.

[0054] 1.2. Printing Method

[0055] Next, the printing method according to the first embodiment will be described. It should be noted that, in the following description, the method using the printing apparatus 100 described above will be described as an example.

[0056] The printing method described in the first embodiment is a printing method for printing multiple lines of an object Q.

[0057] Figure 4 This is a schematic diagram illustrating a general outline of the printing method according to the first embodiment. Figure 5 This is a flowchart used to explain the printing method involved in the first embodiment. Figures 6 to 8 It is used for explanation Figure 5 A schematic diagram of the printing method shown.

[0058] like Figure 4 As shown, in the printing method according to the first embodiment, multiple rows, including a first row L1 and a second row L2, are printed. A row refers to the path (scanning row) traversed by the liquid ejector head 400. That is, while ink is ejected from the liquid ejector head 400, the robot 200 moves the liquid ejector head 400 to scan along the printing direction D2, thereby enabling the printing of the first row L1. Furthermore, the robotic arm 220 moves the liquid ejector head 400 in an orthogonal direction D1, which is orthogonal to the printing direction D2. Then, the second row L2 is printed again by scanning the liquid ejector head 400 along the printing direction D2.

[0059] In this method, as mentioned earlier, vibrations from the robotic arm 220 can cause a deviation in the trajectory of the liquid ejector head 400. As a result, printing defects occur, such as gaps between lines or noticeable overlap between lines.

[0060] Therefore, in the printing method according to the first embodiment, the deviation of the trajectory of the liquid ejector head 400 is detected, and the overlap width between lines is set based on the detection result. The overlap width refers to the width of the overlap between the first line L1 and the second line L2 in the orthogonal direction D1. This allows for optimization of the overlap width, making it less noticeable even when blank spaces occur between lines or when changes in density occur due to line overlap. As a result, high-quality printing of the object Q is possible.

[0061] like Figure 5 As shown, the printing method according to the first embodiment includes an overlap width setting step S100 and a printing step S200. Hereinafter, each step will be described.

[0062] 1.2.1. Overlap Width Setting Procedure

[0063] The overlap width setting process S100 includes each action from step S102 to step S118.

[0064] In step S102, an object different from the object to be printed is prepared as object Q; that is, a temporary object is prepared as object Q. Figure 6 As shown, this is to avoid the printing object being smudged due to printing the first pattern P1 used as the test pattern. The temporary object can be a different object with the same shape as the printing object, or it can be obtained by forming a film of the coating layer on the surface of the printing object. Examples of structural materials for the coating layer include paper and resin. The coating layer can be removed after the overlap width setting process S100 is completed.

[0065] Furthermore, in step S102, the printing data generation unit 912 of the control device 900 generates printing data corresponding to the first pattern P1. The robot controller 240 then creates a scanning track T0 for the liquid nozzle 400 corresponding to the printing data. Based on the created scanning track T0, the liquid nozzle 400 prints the first pattern P1 onto the object Q within a range corresponding to the first row L1. It should be noted that in this application, the printing in step S102 is also referred to as the "first printing." The first pattern P1 is a pattern in which points d are arranged at equal intervals in the printing direction D2. Additionally, in step S102, the robotic arm 220 moves to move the liquid nozzle 400 along the printing direction D2. Further, in step S102, the moving stage 300 is not moved. That is, the scanning track T0 is the track of the liquid nozzle 400 scanned only by the robotic arm 220. Then, while the liquid nozzle 400 is moved along the printing direction D2 by the robotic arm 220, the liquid nozzle 400 prints on the object Q. This movement of the robot 200 and the liquid nozzle 400 is also referred to as the first pattern printing action.

[0066] In step S104, the camera 800 detects the first pattern P1 obtained through the first pattern printing operation. Specifically, the camera 800 acquires an image of the first pattern P1. Furthermore, the fluctuation acquisition unit 914 of the control device 900 calculates the position of point d based on the image acquired by the camera 800. Thus, the relative trajectory T1 of the liquid nozzle 400 relative to the object Q is detected. That is, the position of point d is considered as the trajectory T of the liquid nozzle 400. In this specification, the concept of the path of the liquid nozzle 400 created by the robot controller 240 and scanned by the robot 200, including the speed along that path, is referred to as a "scanning track." Additionally, the concept of the actual path of movement of the liquid nozzle 400, including the speed along that path, is referred to as a "trajectory."

[0067] Furthermore, in step S104, the fluctuation acquisition unit 914 of the control device 900 acquires at least the offset in a direction orthogonal to the printing direction D2 (orthogonal direction D1). The offset in the orthogonal direction D1 is, for example... Figure 6 The figure shows the distance between the scanning trajectory T0 on the orthogonal direction D1 obtained for each point d and point d (trajectory T1). It should be noted that in this application... Figure 6 In the other figures, for ease of explanation, a positive offset is defined as an offset that is higher than the scan track T0, and a negative offset is defined as an offset that is lower than the scan track T0. The operation of this control device 900 is referred to as the first offset acquisition operation. Furthermore, the offset acquired from the first pattern P1 is also called the "initial offset".

[0068] It should be noted that, Figure 6 The first pattern P1 shown includes a total of 8 points d, but the initial offset in the orthogonal direction D1 and the initial offset in the printing direction D2 are both 0 mm. That is to say, Figure 6 The first pattern P1 shown indicates that the trajectory T1 of the liquid ejector head 400 is consistent with the scanning track T0, which is an ideal state.

[0069] on the other hand, Figure 7 The first pattern P1 shown illustrates a non-ideal state.

[0070] exist Figure 7 In the example shown, three points d are offset in the orthogonal direction D1, and five points d are offset in the printing direction D2. Such offsets in the self-scanning track T0 occur for a variety of reasons. For example, vibrations generated by the robot 200 can be cited as a cause.

[0071] Furthermore, in this embodiment, the front-to-back measurement unit 916 of the control device 900 also acquires the initial offset in the printing direction D2. The initial offset in the printing direction D2, for example... Figure 7 As shown, for example, this refers to the distance between the ideal state and the printing result in the printing direction D2 for each point d when the pattern with printed dots d spaced at 1mm intervals is considered ideal. It should be noted that, for ease of explanation, in the figures of this application, for the sake of clarity, the offset to a position further forward than the ideal state in the printing direction D2 is defined as a positive offset, and the offset to a position further backward is defined as a negative offset. Furthermore, the so-called... Figures 6 to 8 The ideal state of point d in the printing direction D2 refers to the state where point d is located at the intersection of the scanning track T0 and a line orthogonal to the scanning track T0.

[0072] In step S106, the correction setting unit 918 of the control device 900 calculates, based on the initial offset obtained through the first offset acquisition action, the amount by which the liquid nozzle 400 moves in the direction that reduces the offset (correction amount). The correction amount is calculated based on the initial offset. The calculation method can be based on experimental or simulation methods and is not particularly limited. For example, Figure 7 As shown, methods can be listed to move in the opposite direction by the same amount as the initial offset obtained. That is, Figure 7 The correction values ​​shown are all obtained by multiplying the acquired initial offset by -1. The storage unit 930 of the control device 900 stores the correction value in a state where the correction value is synchronized with the scanning of the liquid nozzle 400 for each scan line; that is, the correction value is tied to the position of the liquid nozzle 400. Such operation of the control device 900 is also called correction value calculation operation.

[0073] It should be noted that this correction amount can be reflected in the scanning track T0 in the printing process S200 described later, but preferably in the movement of the moving stage 300 in the printing process S200. That is, this correction amount can be a control value used to correct the trajectory T1 by reflecting the movement of the robotic arm 220, but it is preferred to use it as a control value used to correct the trajectory T1 by reflecting the movement of the moving stage 300. This allows for more accurate correction of the trajectory T1, ultimately resulting in better printing results. Furthermore, ultimately, there are many situations in the robotic arm 220 where the effects of vibration are difficult to suppress through scanning speed, so using the moving stage 300 for correction is useful.

[0074] In step S108, a temporary object other than the one prepared in step S102 is prepared as object Q. Furthermore, in step S108, using the robotic arm 220 and the moving stage 300, a second pattern P2 is printed on the area corresponding to the first row L1 of object Q. It should be noted that in this application, the printing in step S108 is also referred to as the "second printing." The second pattern P2 is a pattern where dots d are evenly spaced along the printing direction D2, and is the same pattern as the first pattern P1. Additionally, in step S108, the robot 200 moves to cause the liquid nozzle 400 to move along the printing direction D2. It should be noted that, preferably, the scanning track T0 created by the robot controller 240 in the second printing is the same as that in the first printing. Further, in step S108, the moving stage 300 moves to cause the liquid nozzle 400 to move along the orthogonal direction D1 and the printing direction D2.

[0075] In this embodiment, in step S108, the correction amount calculated from the action is reflected in the movement of the moving table 300. This correction amount, as described above, is set for the purpose of correcting deviations from the ideal state caused by factors such as vibrations generated by the robot 200. In the second printing, the same scanning track T0 created by the robot controller 240 as in the first printing is preferably used. Therefore, the probability that the deviation from the ideal state caused by the aforementioned factors will be the same in the second printing as in the first printing increases. As a result, if the correction amount calculated from the action is used, the possibility of accurately correcting the deviation increases. This movement of the liquid ejector head 400 is referred to as the second pattern printing movement.

[0076] In step S110, the camera 800 detects the second pattern P2 obtained through the second pattern printing operation. Specifically, the camera 800 acquires an image of the second pattern P2. Furthermore, the control device 900 calculates the position of point d based on the image acquired by the camera 800. Thus, the relative trajectory T2 of the liquid nozzle 400 relative to the object Q is detected.

[0077] Furthermore, in step S110, the fluctuation acquisition unit 914 of the control device 900 acquires at least the offset in the orthogonal direction D1. In this embodiment, the offset is acquired in both the orthogonal direction D1 and the printing direction D2. This operation of the control device 900 is referred to as the second offset acquisition operation. It should be noted that the offset acquired from the second pattern P2 is also called the "corrected offset". In addition, in this embodiment, the corrected offset in the orthogonal direction D1 is defined as the "fluctuation amount", and the corrected offset in the printing direction D2 is defined as the "front and back amount".

[0078] In step S114, the absolute value of the fluctuation amount (corrected offset in the orthogonal direction D1) is calculated for each point d of the second pattern P2. Furthermore, as... Figure 8 As shown, the absolute values ​​obtained are summed over the entire second pattern P2. The sum of the obtained absolute values ​​is called the residual error in the orthogonal direction D1. Furthermore, in step S114, the absolute value of the front-to-back amount (corrected offset in the printing direction D2) is calculated for each point d of the second pattern P2. And, as... Figure 8 As shown, the absolute values ​​obtained are summed over the entire second pattern P2. The sum of the obtained absolute values ​​is called the residual error in the printing direction D2.

[0079] Additionally, in step S114, as Figure 8 As shown, the residual error in the orthogonal direction D1 and the residual error in the printing direction D2 are summed. This yields the residual error in both directions D1 and D2. This residual error is the residual error present in the first row L1.

[0080] The action of such a control device 900 is called the residual error calculation action. It should be noted that the calculation of residual error can be performed as needed or omitted. In this case, the overlap width described below can be set directly based on the fluctuation amount and the preceding and following amounts, or the fluctuation amount and the preceding and following amounts can be calculated differently than described above, and the overlap width can be set based on the obtained calculation results.

[0081] In step S116, the overlap width setting unit 920 of the control device 900 sets the overlap width based on the residual errors in two directions D1 and D2. This overlap width is the overlap width that should be set when the second row L2 overlaps with the first row L1 based on the residual errors of the first row L1. Then, the storage unit 930 of the control device 900 saves this overlap width in a state bound to the first row L1. This operation of the control device 900 is called the overlap width setting operation.

[0082] The method for determining the overlap width based on the residual errors in two directions, D1 and D2, is not particularly limited. As an example, the following are listed: Figure 9 The method shown uses the correlation between residual error and overlap width in two directions, D1 and D2. Figure 9 This is a graph showing the relationship between the residual errors and the corresponding overlap widths in two directions, D1 and D2. (Using...) Figure 9 The relationship shown allows us to derive the overlap width that matches the residual errors in the two directions, D1 and D2. Figure 9 In the example, it was found that when the residual error in the two directions D1 and D2 is 5mm, the overlap width can be set to 6mm.

[0083] Figure 9 The relationship shown is one of increasing overlap width as the residual error in both directions D1 and D2 increases. This is based on the phenomenon that by setting a wider overlap width according to the residual error, printing defects become less noticeable even if residual errors exist. In other words, if residual errors are present, the printing density can easily fluctuate drastically. However, by setting a wider overlap width, the fluctuations in printing density can be mitigated, making them less noticeable.

[0084] In step S118, the robotic arm 220 re-rows the scan lines of the liquid nozzle 400. That is, the liquid nozzle 400 is moved along the orthogonal direction D1 from position L1 in the first row to position L2 in the second row. The re-row width is typically set to be equal to the length of the liquid nozzle 400 in the orthogonal direction D1. However, if the overlap width set by the overlap width setting operation exceeds zero, the width obtained by subtracting the overlap width from the normal re-row width is set as the appropriate re-row width. For example, if the length of the liquid nozzle 400 in the orthogonal direction D1 is 24 mm and the overlap width is 6 mm, the re-row width to be set in step S118 is 18 mm. This operation of the robotic arm 220 is called a re-rowing operation.

[0085] It should be noted that when only the initial offset in the orthogonal direction D1 is obtained, step S114 is omitted, and in step S116, the overlap width is calculated only based on the residual error in the orthogonal direction D1. In this case, based on... Figure 9 The horizontal axis of the chart shown can be set to the residual error in the orthogonal direction D1. For new charts, the overlap width can be set accordingly.

[0086] In step S120, it is determined whether an overlap width needs to be set for the new scan line. That is, in multi-line printing, it is determined whether the overlap width setting has ended up to the final scan line. If the setting has not ended, the process returns to step S102. If the setting has ended, the process transitions to the printing process S200.

[0087] If the process returns to step S102, in the second steps S102 to S118, the residual error of the second row L2 is calculated, and the overlap width is set based on the residual error of the second row L2. By repeating this action until the final scan line, the overlap width can be set for all scan lines. Based on the overlap width set in the above manner, printing can be performed with an appropriate overlap width in the printing process S200 described later.

[0088] 1.2.2. Printing Process

[0089] In printing process S200, while the robotic arm 220 and the moving table 300 move the liquid nozzle 400 relative to each other, the liquid nozzle 400 prints multiple lines onto the object Q to produce an overlap corresponding to the overlap width set in the overlap width setting process S100. That is, the control device 900 controls the movement of the robot 200 based on the overlap width stored in the state bound to each scan line, so that the scan lines overlap each other. Furthermore, in each scan line, the control device 900 controls the movement of the moving table 300 based on the correction amount stored in the state bound to the position of the liquid nozzle 400, to correct the position of the liquid nozzle 400. Thus, the scan lines can overlap each other with an appropriate overlap width corresponding to the residual error. Therefore, there are no gaps between lines or significant variations in print density, and high-quality printing is achieved. In particular, this printing method can be used even when the object Q is a three-dimensional object. When printing on a three-dimensional object, the posture of the robotic arm 220 varies considerably depending on the position of the scanned lines, and the vibration of the robotic arm 220 also changes. Therefore, as in this embodiment, by experimentally determining an appropriate overlap width for each scanned line and performing multi-line printing based on this, the impact of changes in the vibration of the robotic arm 220 on the printing result can be suppressed.

[0090] Furthermore, in this embodiment, the residual error is reduced by the moving stage 300, resulting in a smaller overlap width. Moreover, the moving stage 300 can correct the position of the liquid ejector head 400 with higher precision and higher speed than the robotic arm 220. As a result, higher quality printing can be performed at higher speeds.

[0091] It should be noted that during printing in printing process S200, the overlap width setting unit 920 can also change the printing data for the range corresponding to the overlap width. For example, this function changes the printing data by thinning out the dots in the range corresponding to the overlap width. This helps to suppress excessive increases in printing density in the range corresponding to the overlap width.

[0092] Figure 10 as well as Figure 11 This is a schematic diagram illustrating a method for sparsifying points within a range OL corresponding to the overlap width. Figure 10 as well as Figure 11 The figure shows an example where, within the range OL where adjacent scan lines LA and LB overlap, the points da constituting scan line LA and db constituting scan line LB are sparsified.

[0093] Furthermore, in Figure 10 In the diagram, points da and db are sparsified in a comb-like pattern within the range OL corresponding to the overlap width. That is, in... Figure 10 In the range OL shown, the set of comb-shaped dots da and the set of comb-shaped dots db interlock with each other. This suppresses excessive increases in print density within the range OL.

[0094] In addition, Figure 11 In the diagram, points da and db are sparsified within the range OL corresponding to the overlap width based on density dispersion. Density dispersion refers to the process of dispersing points in a way that does not constitute a specific visual frequency. In other words, in... Figure 11 Within the range OL shown, the set of points da, which are thinned based on density dispersion, interlocks with the set of points db, which are thinned based on density dispersion. This suppresses excessive increases in print density within the range OL. Furthermore, in density dispersion, printing defects based on residual errors are less noticeable compared to other thinning methods. Therefore, even when residual errors cannot be sufficiently suppressed, printing defects can be minimized without ensuring an overlap width greater than necessary. As a result, high-quality printing can be achieved without significantly reducing printing speed.

[0095] 2. Second Implementation Method

[0096] Next, the printing method according to the second embodiment will be described.

[0097] Figure 12 This is a flowchart illustrating the printing method involved in the second embodiment.

[0098] The second embodiment will be described below; however, the description will focus on the differences from the first embodiment, and similar details will be omitted. It should be noted that... Figure 12 In this document, the same reference numerals are used for structures that are the same as those in the first embodiment.

[0099] The printing method described in the second embodiment is the same as that described in the first embodiment, except that the calculation methods for the "fluctuation amount" and "front and back amount" used to set the overlap width are different.

[0100] In the first embodiment described above, in the overlap width setting step S100, after sequentially calculating the initial offset and the corrected offset, the corrected offset is regarded as "fluctuation amount" and "front and back amount". Furthermore, the overlap width is set based on the residual error calculated according to the fluctuation amount and the front and back amount.

[0101] In this embodiment, the initial offset is considered as both "fluctuation" and "previous / nearer offset".

[0102] Specifically, in Figure 12 In the printing method shown, the following is omitted Figure 5 Steps S108 and S110 are involved in printing the second pattern P2 shown.

[0103] On the other hand, in step S104, the initial offset in the orthogonal direction D1 is set as "fluctuation amount", and the initial offset in the printing direction D2 is set as "front and back amount". Furthermore, in step S114, the absolute values ​​of the fluctuation amount and the front and back amount are calculated, and then summed to calculate the residual error in the orthogonal direction D1 and the residual error in the printing direction D2.

[0104] In this second embodiment, the same effect as in the first embodiment is obtained.

[0105] Furthermore, in the second embodiment, the printing and inspection of the second pattern P2 can be omitted, thus reducing the time required to set the overlap width. As a result, the overlap width can be set in a shorter time.

[0106] 3. Third Implementation Method

[0107] Next, the printing method according to the third embodiment will be described.

[0108] Figure 13 This is a flowchart illustrating the printing method involved in the third embodiment.

[0109] The third embodiment will be described below; however, the description will focus on the differences from the first embodiment, and similar details will be omitted. It should be noted that... Figure 13 In this document, the same reference numerals are used for structures that are the same as those in the first embodiment.

[0110] The printing method described in the third embodiment is the same as that described in the first and second embodiments, except that the calculation methods for the "fluctuation amount" and "front and back amount" used to set the overlap width are different.

[0111] In the first and second embodiments described above, the points d included in the first pattern P1 and the second pattern P2 printed by the liquid ejector head 400 are detected, and the fluctuation amount and the front and back amount are calculated based on their positions.

[0112] In this embodiment, a camera 800 is used to detect the liquid ejector head 400 itself, and the amount of fluctuation and the amount of forward and backward movement are calculated based on its position.

[0113] Specifically, in Figure 13 In the printing method shown, the following is omitted Figure 5 The steps S102, S104, S106, S108, and S110 are shown. On the other hand, Figure 13 The printing method shown has steps S121, S122, and S124.

[0114] Figure 13 Step S121 shown is the same as step S102 of the first embodiment in terms of printing the pattern, but it differs from the first embodiment in that the pattern can be arbitrary. It should be noted that in step S121, there is an advantage that ink may not be ejected from the liquid ejection head 400. That is to say, in Figure 13 In step S121 shown, the robotic arm 220 scans the liquid nozzle 400 along the scanning track T0 created by the robot controller 240. This movement of the robot 200 and the liquid nozzle 400 is referred to as a head movement.

[0115] In step S122, the camera 800 detects the liquid nozzle 400 itself, which is performing a head-moving motion. Therefore, it is preferable to position the camera 800 away from the robot 200. Furthermore, the fluctuation acquisition unit 914 of the control device 900 detects the relative trajectory T1 of the liquid nozzle 400 relative to the object Q.

[0116] Furthermore, in step S122, the fluctuation acquisition unit 914 of the control device 900 acquires the distance between the scanning track T0 and the trajectory T1 in the orthogonal direction D1 as the initial offset in the orthogonal direction D1. In this embodiment, the distance between the scanning track T0 and the trajectory T1 in the orthogonal direction D1, detected at a fixed time period, is used as the initial offset in the orthogonal direction D1. A fixed time period, for example, is a time interval of approximately 1 mm for acquiring the initial offset.

[0117] Furthermore, the forward and backward measurement unit 916 of the control device 900 also acquires the initial offset in the printing direction D2. In this embodiment, the initial offset in the printing direction D2 is the distance between the ideal state and the actual position in the printing direction D2, which is detected at a fixed time period.

[0118] The action of such a control device 900 is called the offset acquisition action.

[0119] In step S124, the correction amount setting unit 918 of the control device 900 calculates the correction amount based on the initial offset obtained through the offset acquisition operation. Furthermore, in step S124, the calculated correction amount is reflected in the movement of the moving stage 300 in real time. As a result, the moving stage 300 can move the liquid nozzle 400 in real time in the direction that reduces the initial offset. Consequently, the trajectory T1 is corrected in real time. This operation of the control device 900 is called the correction amount calculation operation.

[0120] In step S114 of this embodiment, the camera 800 detects the corrected trajectory T1. Furthermore, the control device 900 acquires the offset between the scanning track T0 and the corrected trajectory T1. In this embodiment, the offset in the orthogonal direction D1 is designated as the "fluctuation amount," and the offset in the printing direction D2 is designated as the "front-to-back amount." Otherwise, it is the same as step S114 of the first embodiment. Additionally, steps S116 and thereafter are also the same as in the first embodiment.

[0121] In this third embodiment, the same effect as in the first embodiment is obtained.

[0122] Furthermore, in the third embodiment, the overlap width can be set even without actual printing in the overlap width setting process S100. Therefore, it is not necessary to prepare a temporary object as the object, and the overlap width can be set using an object that is actually being printed.

[0123] 4. Effects achieved by each implementation method

[0124] As described above, the printing method of the embodiment uses the following components for multi-line printing: a liquid ejector head 400 that ejects ink, a robot 200 that moves the liquid ejector head 400 relative to the object Q along the printing direction, and a camera 800 (detection unit) that detects the relative trajectory of the liquid ejector head 400 relative to the object Q. The printing method includes an overlap width setting step S100 and a printing step S200. In the overlap width setting step S100, the camera 800 (detection unit) acquires the fluctuation amount of the trajectory in the orthogonal direction D1 (the direction orthogonal to the printing direction D2), and sets the overlap width of the trajectory for multi-line printing based on the acquired fluctuation amount. In the printing step S200, while the liquid ejector head 400 moves relative to the object Q, multi-line printing is performed to generate an overlap corresponding to the overlap width during multi-line printing.

[0125] Based on this structure, the overlap width of the trajectory during multi-line printing is set according to the fluctuation of the trajectory of the liquid ejector head 400. Therefore, even if the robot 200 vibrates, it is possible to suppress the generation of blank spaces between lines or printing defects where the overlap becomes obvious.

[0126] Alternatively, the overlap width setting process S100 can be a process in which the camera 800 (detection unit) acquires the front and back amounts of the trajectory on the printing direction D2, and sets the overlap width of the trajectory when printing multiple lines based on the acquired fluctuation amount and front and back amounts.

[0127] Based on this structure, in addition to the fluctuation amount, the overlap width of the trajectory when printing multiple lines is set on the basis of the front and back amounts, so that the occurrence of printing defects can be suppressed less.

[0128] Furthermore, it is preferable that the object Q during the overlap width setting process S100 and the object Q during the printing process S200 are different objects. This prevents the objects to be printed from being smudged during the overlap width setting process S100.

[0129] Furthermore, the overlap width setting step S100 of the printing method according to the first embodiment includes: a first pattern printing action (step S102), a first offset acquisition action (step S104), a correction amount calculation action (step S106), a second pattern printing action (step S108), a second offset acquisition action (step S110), and an overlap width setting action (step S116). In the first pattern printing action, while the robot 200 moves the liquid nozzle 400 relative to the object Q along the printing direction D2, the liquid nozzle 400 prints the first pattern P1 onto the object Q. In the first offset acquisition action, the camera 800 (detection unit) detects the first pattern P1 and acquires the offset of the first pattern P1 in the orthogonal direction D1 (the direction orthogonal to the printing direction D2) based on the detection result. In the correction amount calculation action, based on the offset acquired from the first pattern P1, the amount by which the liquid nozzle 400 moves relative to the object Q in the direction that reduces the offset is calculated as a correction amount. In the second pattern printing action, while the robot 200 moves the liquid nozzle 400 relative to the object Q along the printing direction D2 and, based on a correction amount, moves the liquid nozzle 400 relative to the object Q in the orthogonal direction D1, the liquid nozzle 400 prints the second pattern P2 onto the object Q. In the second offset acquisition action, the camera 800 detects the second pattern P2 and acquires the offset of the second pattern P2 in the orthogonal direction D1 based on the detection result. In the overlap width setting action, the offset acquired based on the second pattern P2 is set as the fluctuation amount, and the overlap width is set based on the fluctuation amount.

[0130] Based on this structure, an appropriate overlap width can be experimentally determined for each scan line, and multi-line printing can be performed using that overlap width. Therefore, even if the vibration of the robot 200 varies for each scan line, its impact on the printing result can be suppressed. Furthermore, in the first embodiment, the overlap width is set based on the position of point d included in the second pattern P2 after reflecting the correction amount. That is, the overlap width is set based on the corrected trajectory T2, thus suppressing excessive widening of the overlap width and enabling higher-quality printing at higher speeds.

[0131] Furthermore, the overlap width setting step S100 of the printing method according to the second embodiment includes: a first pattern printing action (step S102), a first offset acquisition action (step S104), and an overlap width setting action (step S116). In the first pattern printing action, while the robot 200 moves the liquid nozzle 400 relative to the object Q along the printing direction D2, the liquid nozzle 400 prints the first pattern P1 onto the object Q. In the first offset acquisition action, the camera 800 (detection unit) detects the first pattern P1 and acquires the offset of the first pattern P1 in the orthogonal direction D1 (the direction orthogonal to the printing direction D2) based on the detection result. In the overlap width setting action, the offset acquired based on the first pattern P1 is set as the fluctuation amount, and the overlap width is set based on the fluctuation amount.

[0132] Based on this structure, an appropriate overlap width can be experimentally determined for each scan line, and multi-line printing can be performed accordingly. Therefore, even if the vibration of the robot 200 varies for each scan line, its impact on the printing result can be suppressed. Furthermore, in the second embodiment, compared to the first embodiment, the printing and inspection of the second pattern P2 can be omitted, thus reducing the time required to set the overlap width and allowing for setting the overlap width in a shorter time.

[0133] Furthermore, the overlap width setting step S100 of the printing method according to the third embodiment includes: a head movement action (step S121), an offset acquisition action (step S122), and an overlap width setting action (step S116). In the head movement action, the robot 200 moves the liquid ejection head 400 along the printing direction D2. In the offset acquisition action, the camera 800 (detection unit) detects the trajectory T1 of the liquid ejection head 400 and acquires the offset in the orthogonal direction D1 (orthogonal to the printing direction D2) of the trajectory T1 based on the detection result. In the overlap width setting action, the offset acquired based on the trajectory T1 is set as the fluctuation amount, and the overlap width is set based on this fluctuation amount.

[0134] Based on this structure, an appropriate overlap width can be experimentally determined for each scan line, and multi-line printing can be performed using that overlap width. Therefore, even if the vibration of the robot 200 varies for each scan line, its impact on the printing result can be suppressed. Furthermore, in the third embodiment, the overlap width can be set based on the image from the liquid ejector head 400 even without actual printing. Therefore, it is not necessary to prepare a temporary object as the object Q, allowing the overlap width to be set using the object actually being printed.

[0135] Furthermore, in the printing process S200, the liquid ejector head 400 preferably performs multi-line printing by thinning the dots in the range OL corresponding to the overlap width. This helps to suppress excessive increases in print density within the range OL.

[0136] Furthermore, the robot system (printing apparatus 100) according to the above embodiment is an apparatus for multi-line printing on an object Q, and includes a liquid ejector head 400, a robot 200, a camera 800 (detection unit), and a printing control unit 910. The liquid ejector head 400 ejects ink (liquid) onto the object Q. The robot 200 has a robotic arm 220 that moves the liquid ejector head 400 relative to the object Q along the printing direction D2. The camera 800 detects the relative trajectory of the liquid ejector head 400 relative to the object Q. The printing control unit 910 controls the movements of the liquid ejector head 400 and the robot 200. Additionally, the printing control unit 910 includes a fluctuation amount acquisition unit 914 and an overlap width setting unit 920. The fluctuation amount acquisition unit 914 acquires the fluctuation amount of the trajectory in the orthogonal direction D1 (the direction orthogonal to the printing direction D2). The overlap width setting unit 920 sets the overlap width between the trajectories during multi-line printing based on the acquired fluctuation amount.

[0137] Furthermore, in the printing apparatus 100, while the robot 200 moves the liquid nozzle 400 relative to the object Q, the liquid nozzle 400 performs multi-line printing on the object Q to generate an overlap corresponding to the overlap width in the multi-line printing.

[0138] Based on this structure, the overlap width of the trajectory during multi-line printing is set according to the fluctuation amount of the trajectory of the liquid ejector head 400. Therefore, even if the robot 200 vibrates, it is possible to suppress the generation of printing defects such as blank spaces between lines and obvious overlap.

[0139] Additionally, the preferred robot 200 has a moving stage 300. The moving stage 300 is positioned between the robotic arm 220 and the liquid nozzle 400, allowing the liquid nozzle 400 to move relative to the robotic arm 220 in an orthogonal direction D1 (orthogonal to the printing direction D2).

[0140] With this structure, the moving stage 300 can correct the position of the liquid ejector head 400 with higher precision and higher speed than the robotic arm 220. As a result, higher quality printing can be performed at higher speeds.

[0141] In addition, the printing control unit 910 preferably has a front-back amount acquisition unit 916 for acquiring the front-back amount of the trajectory on the printing direction D2.

[0142] Based on this structure, the printing control unit 910 can set the overlap width based on both the fluctuation amount and the front-to-back amount. Therefore, it can suppress the occurrence of printing defects even more.

[0143] In addition, the printing control unit 910 preferably controls the operation of the liquid ejector head 400 by sparsifying the dots in the range OL corresponding to the overlap width.

[0144] Based on this structure, it is possible to suppress excessive increases in printing density within the range of OL.

[0145] The printing method and robot system of the present invention have been described above based on the illustrated embodiments; however, the printing method and robot system of the present invention are not limited to the embodiments described. For example, the printing method of the present invention may also be a printing method obtained by adding arbitrary processes or actions to the embodiments. In addition, the robot system of the present invention may be a robot system with any structure in which the parts of the embodiments are replaced with those having the same function, or it may be a robot system in which arbitrary structures are added to the embodiments.

Claims

1. A printing method, characterized in that, Multi-line printing is performed using an ink ejector head, a robot, and a detection unit. The ink ejector head ejects ink, the robot moves the ink ejector head relative to the object along the printing direction, and the detection unit detects the relative trajectory of the ink ejector head relative to the object. The printing method has the following characteristics: In the overlap width setting process, the detection unit acquires the fluctuation amount of the trajectory in a direction orthogonal to the printing direction, and sets the overlap width of the trajectory when printing multiple lines based on the acquired fluctuation amount. as well as In the printing process, the ink ejector head performs multi-line printing on the object while moving relative to it, so as to produce an overlap corresponding to the overlap width in the multi-line printing. In the overlap width setting process, it is set that the larger the fluctuation amount, the wider the overlap width.

2. The printing method according to claim 1, characterized in that, The overlap width setting process is a process in which the detection unit acquires the front and back amount of the trajectory in the printing direction, and sets the overlap width of the trajectory when printing multiple lines based on the acquired fluctuation amount and the front and back amount.

3. The printing method according to claim 1 or 2, characterized in that, The object being performed during the overlap width setting process and the object being performed during the printing process are different objects from each other.

4. The printing method according to claim 1, characterized in that, The overlap width setting process includes: In the first pattern printing action, while the robot moves the ink ejector head relative to the printing direction, the ink ejector head prints the first pattern onto the object. In the first offset acquisition action, the detection unit detects the first pattern and acquires the offset of the first pattern in a direction orthogonal to the printing direction based on the detection result; The correction amount is calculated based on the offset obtained from the first pattern, and the amount by which the ink ejector head moves relative to the offset in the direction that reduces the offset is calculated as the correction amount. The second pattern printing action occurs when the robot moves the ink ejector head relative to the object along the printing direction and moves the ink ejector head relative to the object in a direction orthogonal to the printing direction based on the correction amount; The second offset acquisition action involves the detection unit detecting the second pattern and, based on the detection result, acquiring the offset of the second pattern in a direction orthogonal to the printing direction; and The overlap width setting action sets the offset obtained from the second pattern as the fluctuation amount, and sets the overlap width based on the fluctuation amount.

5. The printing method according to claim 1, characterized in that, The overlap width setting process includes: The first pattern printing action occurs when the robot moves the ink ejector head relative to the object along the printing direction, and the ink ejector head prints the first pattern onto the object. In the first offset acquisition action, the detection unit detects the first pattern and, based on the detection result, acquires the offset of the first pattern in a direction orthogonal to the printing direction; and The overlap width setting action sets the offset obtained from the first pattern as the fluctuation amount, and sets the overlap width based on the fluctuation amount.

6. The printing method according to claim 1, characterized in that, The overlap width setting process includes: The robot moves the ink ejection head relative to the printing direction during the head movement action. The offset acquisition action involves the detection unit detecting the trajectory of the ink ejector head and, based on the detection result, acquiring the offset of the trajectory in a direction orthogonal to the printing direction; and The overlap width setting action sets the offset obtained from the trajectory as the fluctuation amount, and sets the overlap width based on the fluctuation amount.

7. The printing method according to claim 1 or 2, characterized in that, The printing process is a process in which the ink ejector head thins out the dots within the range corresponding to the overlap width to print multiple lines.

8. A robot system, characterized in that, Print multiple lines of text on the object. The robot system has the following features: The ink ejector head ejects ink. A robot having a robotic arm that moves the ink ejector head relative to the object along the printing direction; The detection unit detects the relative trajectory of the ink ejector head with respect to the object. as well as The printing control unit controls the movements of the ink ejector head and the robot. The printing control unit has: The fluctuation acquisition unit acquires the fluctuation amount of the trajectory in a direction orthogonal to the printing direction; and The overlap width setting unit sets the overlap width between the tracks during multi-line printing based on the acquired fluctuation amount. While the robot moves the ink ejector head relative to the object, the ink ejector head performs multi-line printing to create an overlap corresponding to the overlap width during multi-line printing. The overlap width setting unit is configured such that the larger the fluctuation amount, the wider the overlap width.

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