A method for selective coating of a curved surface groove

Abstract

The application discloses a kind of selective coating methods of curved surface type groove, comprising the following steps: constructing groove spraying track;Laser ranging positioning is constructed;The workpiece position of laser ranging positioning is associated with groove spraying track.The application solves the positioning problem of groove by the method for measuring the height difference of workpiece surface during workpiece movement.In the process of height difference measurement, the measurement error of laser ranging sensor, workpiece movement and workpiece surface defect factors bring, all will lead to ranging result sudden jitter, leading to false detection;The application adopts the method for calculating moving average, avoids the above false detection problem.

Description

Technical Field

[0001] This invention relates to the field of surface coating technology, and more specifically to a selective coating method for curved grooves. Background Technology

[0002] During the painting process, it is often necessary to selectively paint local features such as grooves on curved surfaces. A common method is to mask the areas of the workpiece that are not to be painted, exposing only the parts that need painting, and then paint them. Finally, the masking material is removed, achieving the purpose of localized painting.

[0003] In automated coating processes on production lines, the aforementioned methods are inefficient. Furthermore, the positions of a series of workpieces on the production line often deviate, and curved grooves, being three-dimensional features, are difficult to locate, making selective spraying challenging. Commonly used visual positioning techniques struggle to reliably and accurately locate groove features due to their low contrast within the camera's field of view. This is especially true for grooves with a depth of less than 1mm, which are almost impossible to visually identify. Summary of the Invention

[0004] The purpose of this invention is to provide a selective coating method for curved grooves, in order to solve the technical problems in the background art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A selective coating method for curved grooves includes the following steps:

[0007] Construct the groove spraying trajectory;

[0008] Constructing laser ranging and positioning;

[0009] The position of the workpiece located by laser ranging is associated with the groove spraying trajectory.

[0010] In some embodiments, constructing the groove spraying trajectory includes:

[0011] The workpiece is fixed on the turntable, and the workpiece is rotated so that the central axis of the groove is in a direction that is convenient for the spraying robot to spray.

[0012] Based on the workpiece drawing and the current workpiece coordinate system, obtain the x, y, and z coordinates of the groove's central axis; ultimately, obtain a series of target points on the curved surface corresponding to the groove's central axis: (x 1,0 ,y 1,0 ,z 1,0 ), (x 2,0 ,y 2,0 ,z 2,0 ), (x 3,0 ,y 3,0 ,z3,0 )……(x i,0 ,y i,0 ,z i,0 );

[0013] Let variables a and b correspond to points (x, y) respectively. a,0 ,y a,0 ,z a,0 ) and point (x) b,0 ,y b,0 ,z b,0 The y-axis offset value at point (x); at point (x i,0 ,y i,0 ,z i,0 At position ), the corresponding y-axis offset should be:

[0014]

[0015] The centerline of the groove is offset and corrected. The target point of the corrected centerline of the groove is (x 1,0 ,y 1,0 +p,z 1,0 ), (x 2,0 ,y 2,0 +p,z 2,0 ), (x 3,0 ,y 3,0 +p,z 3,0 )……(x i,0 ,y i,0 +p,z i,0 );

[0016] Using a loop instruction, a series of parallel lines to the central axis of the groove after offset correction are calculated, which serve as the robot's walking trajectory.

[0017] During spraying, the robot can selectively spray the grooves by moving along the walking trajectory.

[0018] In some embodiments, the series of parallel lines includes:

[0019] Parallel line L1: (x 1,1 ,y 1,1 ,z 1,1 ), (x 2,1 ,y 2,1 ,z 2,1 ), (x 3,1 ,y 3,1 ,z 3,1 )……(x i,1 ,y i,1 ,z i,1 Parallel line L2: (x 1,2 ,y 1,2 ,z 1,2 ), (x2,2 ,y 2,2 ,z 2,2 ), (x 3,2 ,y 3,2 ,z 3,2 )……(x i,2 ,y i,2 ,z i,2 );

[0020] Parallel line Ln: (x 1,n ,y 1,n ,z 1,n ), (x 2,n ,y 2,n ,z 2,n ), (x 3,n ,y 3,n ,z 3,n )……(x i,n ,y i,n ,z i,n );

[0021] x i,n =x i,0 ,z i,n =z i,0

[0022] y i,n =y i,0 -L / 2+K / 2+(LK) / (N-1)

[0023] N is the number of spraying passes determined based on the coating thickness requirements of the groove, K is the spray width of the spray gun, and L is the width of the groove.

[0024] In some embodiments, the construction of laser ranging and positioning includes:

[0025] Both the laser rangefinder and the spray gun are fixed on the sixth axis of the robot. The laser rangefinder is used to locate the grooves on the surface of the workpiece, and the spray gun sprays them. The measurement value of the laser rangefinder is fed back to the robot in real time.

[0026] After the spraying program is completed, the workpiece remains stationary; control the robot to move so that the spot of the laser rangefinder is aligned with point 1 on the edge of the groove on the workpiece, and this point is recorded as point P1.

[0027] The robot remains stationary at point P1 and controls the turntable to make the workpiece rotate at a constant speed. During this process, the laser sensor continuously reads the distance from the laser rangefinder to the workpiece surface at set time intervals to obtain a series of distance values, d1, d2, d3, ..., dn.

[0028] Calculate the moving average values ​​of d1, d2, d3, ..., dn over a specific period, Md1, Md2, Md3, ..., Mdn, with the period of the moving average value being m. The value of m is related to the measurement accuracy of the laser sensor, and m should be taken as the minimum value that ensures Mdn is relatively smooth.

[0029] The height difference D is calculated by subtracting the moving average of period z (Mdz) from the current moving average (Mdn); z cannot be less than m.

[0030] In some embodiments, associating the workpiece position located by laser ranging with the groove spraying trajectory includes:

[0031] When assembling the workpiece, ensure that the groove is on the clockwise side of P1.

[0032] Rotate the workpiece slowly and uniformly at a certain speed to perform groove positioning;

[0033] When the height difference D exceeds a certain value, the workpiece stops rotating;

[0034] Perform one spraying procedure and measure the number of points (x). a,0 ,y a,0 ,z a,0 ) and point (x) b,0 ,y b,0 ,z b,0 The deviations between the actual spraying position and the groove position at point ) are calculated as a and b, respectively, and then input into the system.

[0035] The spraying procedure was executed again, and the spray gun offset was corrected. The workpiece position located by laser ranging was now associated with the spraying position, and the positioning and spraying procedures were directly executed on the workpiece during subsequent production.

[0036] The beneficial effects of this invention compared to the prior art are:

[0037] The method provided by this invention solves the problem of groove positioning by measuring the height difference on the workpiece surface during workpiece movement, using a robot in conjunction with a ranging sensor. During height difference measurement, factors such as measurement errors of the laser ranging sensor, workpiece movement, and workpiece surface defects can cause sudden fluctuations in the ranging results, leading to false detections. This invention avoids these false detection problems by employing a moving average calculation method. The above technical solution can achieve precise positioning of grooves with a depth of 0.2 mm or more. Detailed Implementation

[0038] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0039] The following will provide a detailed description of a selective coating method for curved grooves according to embodiments of this application. It is worth noting that the following embodiments are merely illustrative of this application and do not constitute a limitation thereof.

[0040] Example 1:

[0041] A selective coating method for curved grooves, comprising:

[0042] Construct the groove spraying trajectory;

[0043] The following system is used: a laser displacement sensor (Keyence IL-300), a robot (ABB IRB52), and a rotary table (custom-made, servo motor driven). The laser displacement sensor's detection data is fed back to the robot in real time. The robot can control the rotary table's start / stop, speed, and rotation angle.

[0044] Let variables a and b correspond to points (x, y) respectively. a,0 ,y a,0 ,z a,0 ) and point (x) b,0 ,y b,0 ,z b,0 The y-axis offset value at point (x). i,0 ,y i,0 ,z i,0 At position ), the corresponding y-axis offset should be:

[0045]

[0046] The centerline of the groove is offset and corrected. The target point of the corrected centerline of the groove is (x 1,0 ,y 1,0 +p,z 1,0 ), (x 2,0 ,y 2,0 +p,z 2,0 ), (x 3,0 ,y 3,0 +p,z 3,0 )……(x i,0 ,y i,0 +p,z i,0 );

[0047] Using a loop instruction, a series of parallel lines to the central axis of the groove after offset correction are calculated, which serve as the robot's walking trajectory.

[0048] Parallel line L1: (x 1,1 ,y 1,1 ,z 1,1 ), (x 2,1 ,y 2,1 ,z 2,1 ), (x 3,1 ,y 3,1 ,z 3,1 )……(x i,1 ,y i,1 ,z i,1 Parallel line L2: (x 1,2 ,y 1,2 ,z 1,2 ), (x 2,2 ,y 2,2 ,z 2,2 ), (x 3,2 ,y 3,2 ,z 3,2 )……(x i,2 ,y i,2 ,z i,2 );

[0049] Parallel line Ln: (x 1,n ,y 1,n ,z 1,n ), (x 2,n ,y 2,n ,z 2,n ), (x 3,n ,y 3,n ,z 3,n )……(x i,n ,y i,n ,z i,n );

[0050] x i,n =x i,0 ,z i,n =z i,0

[0051] y i,n =y i,0 -L / 2+K / 2+(LK) / (N-1)

[0052] N is the number of spraying times determined based on the coating thickness requirement of the groove (3), K is the spray width of the spray gun (2mm), and L is the width of the groove (10mm).

[0053] During spraying, the robot can selectively spray the grooves by moving along L1, L2, L3...Ln.

[0054] Constructing laser ranging and positioning;

[0055] After the spraying program is completed, the workpiece remains stationary. Control the robot to move so that the spot (distance measurement position) of the laser rangefinder is aligned with point 1 on the edge of the groove on the workpiece, and this point is recorded as point P1.

[0056] After the robot moves to point P1, it sends a speed command to the rotary table, causing the table to rotate counterclockwise at a speed of 0.02 revolutions per minute.

[0057] During the workpiece rotation, the laser rangefinder continuously monitors the distances d1, d2, d3, ..., dn between the workpiece surface and the rangefinder. The moving average values ​​Md1, Md2, Md3, ..., Mdn of d1, d2, d3, ..., dn are calculated, with a period m of 10.

[0058] The height difference D is calculated by subtracting the moving average of period z (Mdz) from the current moving average (Mdn). The value of z is 20.

[0059] When D exceeds 0.4mm, it indicates that the edge of the groove has been detected. The robot sends a command to stop the workpiece from rotating.

[0060] The position of the workpiece located by laser ranging is associated with the groove spraying trajectory.

[0061] When assembling the workpiece, ensure that the groove is on the clockwise side of P1.

[0062] The workpiece is rotated slowly and uniformly at a certain speed to perform groove positioning.

[0063] When the height difference D exceeds 0.4mm, the workpiece stops rotating.

[0064] Perform one spraying procedure and measure the number of points (x). a,0 ,y a,0 ,z a,0 ) and point (x) b,0 ,y b,0 ,z b,0 The deviation between the actual spraying position and the groove position at point ) is calculated to obtain a and b respectively, and then input into the system.

[0065] The spraying procedure was executed again, and the spray gun offset was corrected. The workpiece position, located by laser ranging, was now linked to the spraying position, allowing subsequent production to directly execute the positioning and spraying procedures on the workpiece.

[0066] During the groove spraying process, by defining boundaries and the number of passes, the spraying trajectory and step are automatically calculated, enabling selective coating of the grooves without exceeding the specified boundaries. In actual spraying, errors in spray gun manufacturing and assembly can cause the actual spraying position to deviate from the groove. This invention solves this problem by employing a method to correct the groove's central axis. This method enables selective coating of grooves at any initial position on a curved surface.

[0067] The above description is merely a preferred embodiment of the present invention and is intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A selective coating method for curved grooves, characterized in that, Includes the following steps: Construct the groove spraying trajectory; Constructing laser ranging and positioning; The position of the workpiece located by laser ranging is associated with the groove spraying trajectory; The construction of the groove spraying trajectory includes: The workpiece is fixed on the turntable, and the workpiece is rotated so that the central axis of the groove is in a direction that is convenient for the spraying robot to spray. Based on the workpiece drawing and the current workpiece coordinate system, obtain the x, y, and z coordinate values ​​of the groove's central axis; ultimately, obtain a series of target points on the curved surface corresponding to the groove's central axis: (x 1,0 ,y 1,0 ,z 1,0 ), (x 2,0 ,y 2,0 ,z 2,0 ), (x 3,0 ,y 3,0 ,z 3,0 )……(x) i,0 ,y i,0 ,z i,0 ); Let variables a and b correspond to points (x, y) respectively. a,0 ,y a,0 ,z a,0 ) and point (x) b,0 ,y b,0 ,z b,0 The y-axis offset value at point (x); at point (x i,0 ,y i,0 ,z i,0 At position ), the corresponding y-axis offset should be: ； The centerline of the groove is offset and corrected. The target point of the corrected centerline of the groove is (x 1,0 ,y 1,0 +p,z 1,0 ), (x 2,0 ,y 2,0 +p,z 2,0 ), (x 3,0 ,y 3,0 +p,z 3,0 )……(x) i,0 ,y i,0 +p,z i,0 ); Using a loop instruction, a series of parallel lines to the central axis of the groove after offset correction are calculated, which serve as the robot's walking trajectory. During spraying, the robot can selectively spray the grooves by moving along the walking trajectory; The construction of laser ranging and positioning includes: Both the laser rangefinder and the spray gun are fixed on the sixth axis of the robot. The laser rangefinder is used to locate the grooves on the surface of the workpiece, and the spray gun sprays them. The measurement value of the laser rangefinder is fed back to the robot in real time. After the spraying program is completed, the workpiece remains stationary; control the robot to move so that the spot of the laser rangefinder is aligned with point 1 on the edge of the groove on the workpiece, and this point is recorded as point P1. The robot remains stationary at point P1 and controls the turntable to make the workpiece rotate at a constant speed. During this process, the laser sensor continuously reads the distance from the laser rangefinder to the workpiece surface at set time intervals to obtain a series of distance values, d1, d2, d3, ..., dn. Calculate the moving average values ​​of d1, d2, d3, ..., dn over a specific period, Md1, Md2, Md3, ..., Mdn, with the period of the moving average value being m. The value of m is related to the measurement accuracy of the laser sensor, and m should be taken as the minimum value that ensures Mdn is relatively smooth. The height difference D is calculated by subtracting the moving average of period z (Mdz) from the current moving average (Mdn); z cannot be less than m.

2. The selective coating method for curved grooves according to claim 1, characterized in that, The series of parallel lines includes: Parallel line L1: (x 1,1 , y 1,1 , z 1,1 ), (x 2,1 , y 2,1 , z 2,1 ), (x 3,1 , y 3,1 , z 3,1 ) ... (x i,1 , y i,1 , z i,1 ); Parallel line L2: (x 1,2 , y 1,2 , z 1,2 ), (x 2,2 , y 2,2 , z 2,2 ), (x 3,2 , y 3,2 , z 3,2 ) ... (x i,2 , y i,2 , z i,2 ); Parallel line Ln: (x 1,n , y 1,n , z 1,n ), (x 2,n , y 2,n , z 2,n ), (x 3,n , y 3,n , z 3,n )... (x i,n , y i,n , z i,n ); x i,n = x i,0 , z i,n = z i,0 y i,n = y i,0 -L / 2+K / 2+(L- K) / (N-1) N is the number of spraying passes determined based on the coating thickness requirements of the groove, K is the spray width of the spray gun, and L is the width of the groove.

3. The selective coating method for curved grooves according to claim 1, characterized in that, The association between the workpiece position located by laser ranging and the groove spraying trajectory includes: When assembling the workpiece, ensure that the groove is on the clockwise side of P1. Rotate the workpiece slowly and uniformly at a certain speed to perform groove positioning; When the height difference D exceeds a certain value, the workpiece stops rotating; Perform one spraying procedure and measure the number of points (x). a,0 ,y a,0 ,z a,0 ) and point (x) b,0 ,y b,0 ,z b,0 The deviations between the actual spraying position and the groove position at point ) are calculated to obtain a and b respectively, and then input into the system; The spraying procedure was executed again, and the spray gun offset was corrected. The workpiece position located by laser ranging was now associated with the spraying position, and the positioning and spraying procedures were directly executed on the workpiece during subsequent production.

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