A three-dimensional laser etching method based on tire cylindrical coordinates

Abstract

The application provides a three-dimensional laser etching method based on tire cylindrical coordinates, which establishes a plane design polar coordinate based on the shape characteristics of the tire in the design, gives a reference point coordinate and an etching coordinate polar radius and polar angle, obtains a polar radius deviation value and a polar angle deviation value through operation to determine the relative plane position of the etching point to the reference point; the polar coordinate is established on the tire conveying surface, the polar point is the center of the tire; the polar axis is established in the opposite direction by connecting the polar point and the projection point of the base coordinate origin of the robot in the polar coordinate; the Z axis passes through the polar point, is perpendicular to the polar coordinate plane and faces upward to establish a three-dimensional cylindrical coordinate; based on the three-dimensional coordinate, the robot performs 3D camera scanning and modeling; through calculation of the running coordinate of the sixth axis and the coordinate conversion with the base coordinate of the robot, after the sixth axis center of the robot runs to the second center, the sixth axis is rotated by an angle to perform laser etching.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of tire production and manufacturing, and particularly relates to a three-dimensional laser etching method based on tire cylindrical coordinates. BACKGROUND

[0002] Tire vulcanization molding technology is a traditional tire production technology, but the annual week number movable block on the mold needs to be replaced regularly every week, which has the following problems: 1. It is easy to cause damage to the mold, affecting the appearance quality of the tire; 2. The replacement of the movable block affects the machine efficiency and energy consumption loss; 3. It causes a large annual manual maintenance cost and mold replacement cost; 4. It cannot guarantee the timeliness of the annual week number replacement. Secondly, the production number of the all-steel radial tire is formed by placing a "small steel sheet" on the lower mold of the tire side, which requires manual intervention for each tire, and is not ideal in terms of precision, product appearance and material consumption. In addition, it is easy to cause appearance damage to the tire and tire information matching error. In addition, the commercial demand for some personalized custom identification is increasing, which also increases the frequency of mold replacement and production cost.

[0003] In recent years, with the rapid development of domestic laser technology and intelligent technology, tire surface laser etching technology has begun to develop in the industry and is rapidly spreading. At present, some domestic leading tire enterprises have adopted laser etching technology to etch production numbers, annual week numbers, custom identification and other information on the surface of the tire. Because this technology is highly flexible and advanced, it replaces part of the functions of tire molding technology, bringing new vitality and innovation value to the traditional tire production process.

[0004] However, due to the lack of deep understanding of the tire shape and tire surface pattern identification layout in technology, the traditional Cartesian coordinate system method is used in the description of tire scanning imaging and etching positioning, which causes the mixed automatic production site of large-scale specifications and varieties of tires to be unable to realize accurate positioning of tire identification, and also affects the beauty of the identification etching; or completely through manual adjustment to determine the positioning of the identification on site, which is low in efficiency, increases the etching period and labor cost, and cannot achieve rapid response to production. SUMMARY

[0005] The application provides a tire laser etching method based on a six-axis robot and a laser in a tire cylindrical coordinate system. The etching position of the workpiece-tire, the center coordinate and the rotation angle of the sixth axis of the robot are expressed by the cylindrical coordinate system, and the running track of the robot is finally realized. The process flow comprises the following steps: after the tire reaches the etching station, the tire is clamped and positioned by a centering mechanism, and a laser ranging sensor detects the height of the tire; the robot moves to a preset position, performs barcode identification and 3D modeling; a 3D camera scans the tire side, generates a three-dimensional model, and determines the identification position through image intelligent identification; and the laser performs etching according to the three-dimensional coordinates of the tire. Through the three-dimensional cylindrical coordinate system, the system converts the six-axis center of the etching robot into a rectangular coordinate system, and then runs at the joint coordinate angle to accurately control the laser etching positioning process. In this process, the six-axis robot not only carries the laser, but also is installed with a 3D camera for identifying the identification position, so that accurate laser etching is realized. This process can be self-adapted according to different shapes and sizes of the tire, and higher etching accuracy and flexibility are realized.

[0006] The application provides a three-dimensional laser etching method based on a tire cylindrical coordinate system. In the design, a planar design polar coordinate is established based on the shape characteristics of the tire, reference point coordinates and polar radius and polar angle of etching coordinates are given, polar radius deviation values and polar angle deviation values are obtained through operation to determine the relative planar position of the etching point to the reference point; a polar coordinate is established on a tire conveying surface, and the polar point is the center of the tire; the polar axis is established in the opposite direction by connecting the polar point and the projection point of the base coordinate origin of the robot in the polar coordinate; the Z-axis passes through the polar point and is perpendicular to the polar coordinate plane upward to establish a three-dimensional cylindrical coordinate; through installation adjustment and correction, the initial center (motion origin) of the sixth axis of the robot is on the Z-axis of the three-dimensional cylindrical coordinate, the 6-axis joint coordinate is parallel to the tire conveying polar coordinate, and the attitude of the fifth axis is kept parallel to or on the Z-axis. Based on the three-dimensional coordinate, the robot performs 3D camera scanning and modeling; through calculation of the running coordinates of the sixth axis and the coordinate conversion of the base coordinates of the robot, after the center of the sixth axis of the robot runs to a second center, the sixth axis rotates by an angle to perform laser etching. It can be understood that, although the method uses a robot laser etching, the method based on the tire cylindrical coordinate and the etching basic principle are also applicable to tire laser etching of other equipment types.

[0007] Specifically, the three-dimensional laser method provided by the application comprises the following steps: 1. A tire polar coordinate establishment method: 1.1. A tire design plane polar coordinate system is established as follows: according to a top view of a tire mold design, taking a tire center as a polar point O, taking a connecting ray from the polar point O to a tire mark position as a polar axis, and establishing a polar coordinate system in a counterclockwise direction; 1.2. A tire three-dimensional cylindrical coordinate system is established as follows: based on a tire conveying bottom surface for conveying a tire, taking a tire center as a polar point O, taking a tire conveying direction vertical ray as a polar axis, establishing a polar coordinate system in a counterclockwise direction, and taking a ray perpendicular to the polar coordinate system plane as a Z axis to establish a tire three-dimensional cylindrical coordinate system; when a tire enters equipment in actual automatic mass production, the polar angle direction of the polar coordinate is disordered, so the polar axis of the polar coordinate in the production site is referenced to the position of the combined equipment and is different from that in the design. The three-dimensional etching method comprises the following steps when the equipment is running:

[0008] Step 1) The tire reaches the etching work station conveying belt, the centering mechanism clamps and centers the tire, and the laser ranging sensor detects the tire height;

[0009] Step 2) The six-axis robot drives the 3D camera to descend to a preset shooting focal depth height from the tire surface;

[0010] Step 3) The robot 1-5 axes maintain the posture, the sixth axis drives the code reader and the 3D camera to rotate 365 degrees, and the image and the barcode are read;

[0011] Step 4) The code reader reads and identifies the tire barcode, the system and the MES management system interact, the system gives the etching content and etching positioning information;

[0012] Step 5) The 3D camera scans the tire side to establish a three-dimensional model, and the OCR identification or the template comparison searches for a reference mark in the model; according to the reference point coordinates and the relative polar coordinate position of the etching mark, the absolute position of the etching mark is obtained.

[0013] Step 6) The etching position is etched by laser galvanometer focusing, according to the tire three-dimensional cylindrical coordinate, the three-dimensional cylindrical coordinate of the etching center is converted into a three-dimensional rectangular coordinate by the system after the tire is scanned by the 3D camera, so that the laser moves to the etching center according to the rectangular coordinate and the joint coordinate angle.

[0014] In some embodiments, the robot is provided with a 3D camera and a laser emitter lens, O' is the initial position of the robot's sixth axis, O2 is the coordinate of the robot's sixth axis when the 3D camera scans, and O3 is the target position of the robot's sixth axis for laser etching. When the robot's sixth axis reaches the scanning target position O2, the robot rotates through the sixth axis, bringing the 3D lens and the code reader to the depth of field range for tire reading to scan, and after completion, the robot's sixth axis runs to the focal depth height above the laser etching center point, and the galvanometer performs laser etching. After completion, the axis and the rotation angle return to the original position. The angle of rotation and positioning are in cylindrical coordinates.

[0015] In some embodiments, in step 2), the laser running track is calculated as follows:

[0016] Step i) The robot's sixth axis runs from the initial coordinate O' (X0, Y0, Z0) to O2 (X22, Y22, Z22).

[0017] X0 = D1 (Formula 1)

[0018] Y0 = 0 (Formula 2)

[0019] Z0 = Zdmax + F1 + H1 + D2 + C (Formula 3)

[0020] D1: The distance between the robot's base coordinate and the tire's cylindrical coordinate on the X-axis, which is a constant;

[0021] D2: The distance between the robot's base coordinate and the tire's cylindrical coordinate on the Z-axis, which is a constant;

[0022] Zdmax: The highest tire section height;

[0023] F1: The scanning focal length of the 3D camera;

[0024] H1: The height distance of the 3D camera lens center to the motion axis center in the Z-axis direction;

[0025] C: A constant set.

[0026] X22 = X0 = D1 (Formula 4)

[0027] Y22 = Y0 = 0 (Formula 5)

[0028] Z22 = Zd + F1 + H1 + D2 (Formula 6)

[0029] Zd: The tire height detected by the laser ranging sensor;

[0030] After the sixth axis is positioned, the sixth axis rotates 365 degrees for scanning and code scanning.

[0031] According to the tire laser etching method of claim 2, the laser trajectory is calculated as follows in steps 5) to 6):

[0032] Step ii) Calculate the three-dimensional Cartesian coordinates O3(X3,Y3,Z3) of the robot's sixth axis center when it moves to the etching task;

[0033] Step 2a) Let M0(ρ0, θ0, Z0) be the reference position point identified in the 3D camera scan image, and let M0'(ρ0, θ0) be the polar coordinates projected onto the bottom surface of the tire conveyor.

[0034] Step 2b) Calculate the three-dimensional coordinates of the etching: M2(ρ2, θ2, Z2) is the center point of the laser etching on the tire, P2(ρ2, θ2, Z12) is the center coordinate of the laser etching lens, and the projection onto the polar coordinate point is M2'(ρ2, θ2).

[0035] ρ2=ρ0+▽ρ; (Equation 7)

[0036] θ2 = θ0 + ▽θ; (Equation 8)

[0037] In the formula, ▽ρ represents the polar diameter deviation between the etching position and the reference point position;

[0038] In the formula, ▽θ: the polar angle deviation between the etching position and the reference point position;

[0039] The Z2 value is retrieved based on ρ2, θ2, and the 3D cylindrical coordinates of the tire.

[0040] Step 2c) Calculate the lens coordinates of the scanning point: When scanning to the etching center point M2, the lens center point of the 3D camera is at P1(ρ1, θ1, Z11), the vertical scanning point on the tire is M1(ρ1, θ1, Z1), and the coordinates projected onto the bottom surface of the tire are M1'(ρ1, θ1).

[0041] θ1=θ2 (Equation 9)

[0042] ρ1=R1 (Equation 10)

[0043] R1: Length of the 3D camera scanning robotic arm, the extreme radius distance from the center of the scanning lens to the center of the sixth axis, which is a constant;

[0044] Z11 = Z2 - H2 + H1 (Equation 11)

[0045] H1: The height distance from the center of the 3D camera lens to the center of the sixth axis of motion.

[0046] H2: The height distance from the laser etching center to the center of the sixth axis of motion;

[0047] Step 2d) Calculate the etching polar coordinates: Calculate the polar coordinates O3(ρ3, θ3) of the sixth axis center when the tire is etched according to the results of steps 2b and 2c;

[0048] Y12 = ρ2 - ρ1 = ρ0 +▽ρ - R1 (Formula 12)

[0049] ρ3 = R2 - R1 + Y12 = R2 + ρ0 +▽ρ - 2R1 (Formula 13)

[0050] θ3 = θ2 + 180 = θ0 +▽θ + 180 (Formula 14)

[0051] R2: Laser etching arm length, polar distance from etching lens center to sixth axis center;

[0052] R1: 3D camera scanning arm length, polar distance from scanning lens center to sixth axis center;

[0053] Y12: Distance from etching center to 3D camera scanning lens center in steps 2b and 2c;

[0054] Step 2e) Coordinate conversion: The rectangular coordinates of O3 in the three-dimensional rectangular coordinate system of the robot are (X33, Y33, Z33), which are obtained according to Formula (13) and Formula (14) and the coordinate conversion formula:

[0055] X33 = ρ3COSθ3 + D1 = (R2 + ρ0 +▽ρ - 2R1)COS(θ0 +▽θ + 180) + D1 (Formula 15)

[0056] Y33 = ρ3SINθ3 = (R2 + ρ0 +▽ρ - 2R1)SIN(θ0 +▽θ + 180) (Formula 16)

[0057] Z33 = Z2 + F2 + H2 + D2 (Formula 17)

[0058] F2: Laser etching focal length

[0059] H2: Height distance from laser etching center to motion axis center in Z-axis direction;

[0060] D1: Distance between robot base coordinates and tire cylindrical coordinates in X-axis, which is a constant;

[0061] D2: Distance between robot base coordinates and tire cylindrical coordinates in Z-axis, which is a constant;

[0062] Step 6) The sixth axis arm rotates in joint coordinates, and the running angle is equal to θ3:

[0063] θ3 = θ2 + 180 = θ0 +▽θ + 180 (Formula 18)

[0064] Step ) Calculate the sixth axis center coordinates and the rotation angle of the sixth axis of the following multiple tasks according to the above principle.

[0065] Step v) After the etching task is completed, the sixth axis center returns to the O' coordinate, and the rotation angle of the axis arm returns to 0 degrees.

[0066] Through the present application, the precise control of the etching position is carried out through the three-dimensional cylindrical coordinate system of the tire, which takes the tire center as the pole point, and the etching position is calculated in combination with the tire height and the scanning distance. In addition, the coordinate change of the robot axis is described in detail in the application, and the motion trajectory from the scanning position O2 of the center of the sixth axis of the robot to the target position O3 of the laser etching is calculated through a series of formulas, and the rotation angle of the joint arm of the sixth axis, which ensures the precision of the laser etching.

[0067] The laser etching technology provided by the present application is based on the tire polar coordinates and cylindrical coordinates, and through the combination of robot technology and 3D camera scanning, the efficient, precise and beautiful etching of the tire surface mark is realized. This not only greatly improves the automation level of tire production, but also reduces the production cost and mold loss, so that the production efficiency and mark precision are greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0068] Figure 1 is a schematic diagram of a tire polar coordinate system;

[0069] Figure 2 is a schematic diagram of a tire three-dimensional cylindrical coordinate system;

[0070] Figure 3 is a relationship diagram of tire and robot three-dimensional coordinate system;

[0071] Figure 4 is a planar top view of the tire laser etching coordinate system;

[0072] Figure 5 is a planar side view of the tire laser etching coordinate system;

[0073] Figure 6 is a reference photo of laser etching of a passenger car tire;

[0074] Figure 7 is a reference photo of laser etching of a heavy-duty tire. DETAILED DESCRIPTION

[0075] 1. The equipment adopts a laser light source of carbon dioxide laser parameter, and the wavelength is 10.6 μm;

[0076] 2. The device uses a six-axis robot to move the tool, the sixth axis has a double rotating arm, one arm has a core tool; the 3D camera scans and the code reader are on one rotating arm, the laser etching lens is on the other rotating arm, the two arms are 180 degrees apart.

[0077] 3. The tire is transported by a conveying line and centered by a clamping arm. The line connecting the centering center and the robot origin is perpendicular to the conveying direction of the tire, and the tire is within the working range of the robot.

[0078] 4. The positioning accuracy requirements and explanations are shown in the following table.

[0079] Table 1 Positioning accuracy reference requirements

[0080] Item (Units) Parameter 1 Identification position circumferential error (mm) ±2.00 2 Identification position radial error (mm) ±2.00 3 Identification position rotational error (mm) ±3.00 4 Repeatability deviation (mm) ±2.0

[0081] Note:

[0082] 1. Radial error The laser etching positioning center is marked as M2(ρ,θ,z), which refers to the difference between the actual value ρ' and the set value ρ of the polar radius, and the coordinate reference is attached Figure 2 .

[0083] 2. Circumferential error

[0084] The laser etching positioning center is marked as M2(ρ,θ,z), which refers to the difference between the actual value θ' and the set value θ of the polar angle. The corresponding arc length with ρ as the radius is marked as L, and the coordinate reference is attached Figure 2 .

[0085] 3. Rotation error

[0086] The laser etching positioning center is marked as M(ρ,θ,z), which refers to the difference between the vertical distance of the two ends of the etching mark length to the circle with ρ as the radius. The distance in the circle is negative, and the distance outside the circle is positive. The coordinate reference is attached Figure 2 .

[0087] 5. Establish the tire coordinate system

[0088] 5.1.1 Establish the tire plane design coordinate system

[0089] Please refer to the attached Figure 1 , according to the top view of the tire mold design, taking the mold center as the polar point and the connecting ray from the polar point to the tire mark position as the polar axis, establish the polar coordinate system in the counterclockwise direction; determine the reference point coordinates and etching point coordinates, and calculate their relative positions.

[0090] 5.1.2 Establish the tire three-dimensional coordinate system

[0091] Please refer to the attached Figure 2, the polar coordinate system is established based on the tire conveying bottom surface, with the tire center as the polar point, the tire conveying center line as the polar axis, and the counterclockwise direction as positive; the Z-axis is established as a ray perpendicular to the plane of the polar coordinate system to establish a three-dimensional cylindrical coordinate system.

[0092] 5.1.3 According to the positional relationship between the tire three-dimensional cylindrical coordinate system and the robot three-dimensional base coordinate system, the operating parameters and attitude of the robot are set and corrected, and the original position O' of the sixth axis of the six-axis robot is set. Rectangular base coordinates (X0, Y0, Z0) are calculated as follows:

[0093] X0=D1 (Formula 1)

[0094] Y0=0 (Formula 2)

[0095] Z0=Zdmax+F1+H1+D2+C (Formula 3)

[0096] D1: the distance between the robot base coordinate and the tire cylindrical coordinate on the X-axis, which is a constant;

[0097] D2: the distance between the robot base coordinate and the tire cylindrical coordinate on the Z-axis, which is a constant;

[0098] Zdmax: the highest tire section height;

[0099] F1: the scanning focal length of the 3D camera;

[0100] H1: the height distance of the 3D camera lens center to the motion axis center in the Z-axis direction;

[0101] C: a constant set.

[0102] 6 Tire laser etching process, comprising the following steps

[0103] Step 1) The sixth axis of the six-axis robot is at the original position O' (X0, Y0, Z0), the tire is conveyed to the lettering work station conveying belt, the centering mechanism clamps and centers the tire, and the laser ranging sensor detects the tire section height Zd;

[0104] Step 2) The sixth axis of the six-axis robot is lowered from the original position O' to the preset focus depth shooting height, reaching O2 (X22, Y22, Z22); the coordinates are calculated as follows:

[0105] X22=X0=D1 (Formula 4)

[0106] Y22=Y0=0 (Formula 5)

[0107] Z22=Zd+F1+H1+D2 (Formula 6)

[0108] Zd: the tire height detected by the laser ranging sensor;

[0109] Step 3) The robot sixth axis drives the code reader, 3D camera and laser to rotate 365° to ensure panoramic scanning;

[0110] Step 4) The code reader reads the tire barcode, and the system and process management system interact; the factory management system sends the etching information to the laser control system;

[0111] And the 3D camera scans the tire sidewall to build a three-dimensional model, and searches for the reference point mark in the model through image intelligent recognition;

[0112] Step 5) Laser galvanometer focusing etching: according to the three-dimensional cylindrical coordinates and reference point mark coordinates processed by the tire 3D camera scanning, and according to the coordinate deviation value of the reference mark and the etching mark, the actual three-dimensional coordinates of the etching mark are calculated. According to the coordinates of the etching mark, the center operating cylindrical coordinates O3(ρ3, θ3, z3) of the robot sixth axis are calculated, and through coordinate conversion, the robot base coordinates O3(X33, Y33, Z33) of the robot operation are calculated.

[0113] The robot sixth axis center moves to the etching center O3 according to the rectangular coordinates; according to the polar angle deviation of the reference mark and the etching mark, the robot sixth axis mechanical arm rotates θ3 angle to drive the laser lens to run above the etching center; the laser etches according to the content and parameters of etching.

[0114] Step 6) The system continues to drive the laser lens to run to the second, third... position according to multiple etching tasks to etch in turn.

[0115] Step 7) After completing the laser etching task, the robot returns to the origin O'.

[0116] In this embodiment, please refer to Figures 2-5 In steps 5) ~ 6), the robot drives the tool, and the trajectory is calculated as follows:

[0117] Step ii) Calculate the robot sixth axis center from the three-dimensional rectangular base coordinates O2(X22, Y22, Z22) to the three-dimensional rectangular base coordinates O3(X3, Y3, Z3) of the etching task;

[0118] Step 2a) M0(ρ0, θ0, Z0) is the reference position point identified in the 3D camera scanning image, projected to the tire conveying bottom surface polar coordinates as M0'(ρ0, θ0);

[0119] Step 2b) Refer to Figure 2, calculate the etching three-dimensional coordinates: M2(ρ2, θ2, Z2) is the etching center point etched on the tire, P2(ρ2, θ2, Z12) is the laser etching lens center coordinate, projected to the polar coordinate point is M2'(ρ2, θ2);

[0120] ρ2=ρ0+▽ρ; (Formula 7)

[0121] θ2=θ0+▽θ; (Formula 8)

[0122] In the formula, △ρ: the polar radius deviation value of the etching position and the reference point position, given by the MES system;

[0123] In the formula, △θ: the polar angle deviation value of the etching position and the reference point position, given by the MES system;

[0124] According to ρ2, θ2, 3D tire three-dimensional cylindrical coordinate to retrieve Z2 value;

[0125] Step 2c) Calculate the scanning point lens coordinate: when scanning the etching center point M2 point, the lens center point of the 3D camera is P1(ρ1, θ1, Z11), and the vertical scanning point on the tire is M1(ρ1, θ1, Z1), projected on the tire bottom coordinate is M1'(ρ1, θ1)

[0126] θ1=θ2 (Formula 9)

[0127] ρ1=R1 (Formula 10)

[0128] R1: the length of the 3D camera scanning mechanical arm, the polar radius distance from the scanning lens center to the sixth axis shaft center, which is a constant;

[0129] Z11=Z2-H2+H1 (Formula 11)

[0130] H1: the height distance from the 3D camera scanning lens center to the sixth axis motion shaft center.

[0131] H2: the height distance from the laser etching center to the sixth axis motion shaft center;

[0132] Step 2d) refer to the attached Figure 4 , calculate the etching polar coordinates: according to the results of steps 2b and 2c, calculate the polar coordinates O3(ρ3, θ3) of the sixth axis center when etching the tire;

[0133] Y12=ρ2-ρ1=ρ0+▽ρ-R1 (Formula 12)

[0134] ρ3 =R2-R1+Y12= R2+ρ0+▽ρ-2R1 (Formula 13)

[0135] θ3=θ2+180= θ0+▽θ+180 (Formula 14)

[0136] R2: the polar distance from the etching lens center to the sixth axis center;

[0137] R1: the polar distance from the scanning lens center to the sixth axis center;

[0138] Y12: the distance from the etching center to the scanning lens center in steps 2b and 2c;

[0139] Step 2e) Refer to the attached Figure 3 and the attached Figure 5 , the coordinate conversion and calculation are performed: the coordinates of O3 in the three-dimensional rectangular coordinate system of the robot are (X33, Y33, Z33), according to formula (13) and formula (14) and the coordinate conversion formula, we get:

[0140] X33=ρ3COSθ3+D1=(R2+ρ0+▽ρ-2R1)COS(θ0+▽θ+180)+D1 (Formula 15)

[0141] Y33=ρ3SINθ3=(R2+ρ0+▽ρ-2R1)SIN(θ0+▽θ+180) (Formula 16)

[0142] Z33=Z2+F2+H2 +D2 (Formula 17)

[0143] F2: the focal length of the laser etching

[0144] H2: the height distance of the laser etching center to the Z-axis direction of the motion axis;

[0145] D1: the distance between the robot base coordinate and the tire cylindrical coordinate in the X-axis, which is a constant;

[0146] D2: the distance between the robot base coordinate and the tire cylindrical coordinate in the Z-axis, which is a constant;

[0147] Step ) The sixth axis arm operates in joint coordinates, and the operating angle is equal to θ3, referring to formula 14:

[0148] Step ) According to the above principle, the coordinates of the sixth axis center and the rotation angle of the sixth axis arm of the subsequent multiple tasks are calculated.

[0149] 6. Quality detection method

[0150] a) Apply vernier caliper or laser equipment, etc. to perform 5*5 repetitive measurement, select 5 tires of the same specification and 5 tires of different specifications for measurement, detect each etching parameter of each tire for 5 times, and calculate the deviation value, error value and standard deviation value of the planar size, positioning, etc. of the etching mark.

[0151] The standard deviation of each parameter {i=1,2,...,M} for each tire is calculated using formula (1). ), and calculated according to formula (2) The average standard deviation of each tire ( The calculated etching accuracy should meet the requirements of 4.2.3 to 4.2.5, with a standard deviation of (). It should not exceed 1 / 2 of the repeatability deviation requirement.

[0152] (Equation 18)

[0153] In the formula:

[0154] N—Number of measurements = 5

[0155] X j —Measured value

[0156] —Standard deviation of a single tire

[0157] Reproducibility mean standard deviation ( ) is defined as:

[0158] (Equation 19)

[0159] In the formula:

[0160] M—Number of tires = 5

[0161] —The average standard deviation of 5 tires

[0162] b) Visually inspect the clarity and integrity of the etched markings.

[0163] Test Example 1: Car Tire Markings

[0164] The etched content on car tires includes the year and week number, as well as a QR code, arranged circumferentially with the production code. Circumferential distance is measured by measuring the character edge distance, while radial distance is measured by measuring the center distance between the character heights. See details... Figure 6 And Table 2.

[0165] Table 2 Repeatability and Accuracy Inspection of 5x5 Laser Etching on Passenger Tires

[0166]

[0167] Test Example 2: Truck Tires

[0168] The content of the heavy-duty tire etching is tire production code, annual week number and two-dimensional code, the annual week number and the production code are arranged in the circumferential direction, and the two-dimensional code and the annual week number are arranged in the radial direction. The circumferential distance between the annual week number and the tire code is measured by measuring the character margin, and the radial distance is measured by the character height center distance. The radial distance from the production code to the tire code and the two-dimensional code to the annual week number is measured by the character radial margin; the circumferential distance of the production code is measured by the circumferential margin of the starting character, and the circumferential distance of the two-dimensional code is measured by the circumferential center distance of the mark. For details, see Figure 7 and Table 3.

[0169] Table 3 5*5 repeatability accuracy check of heavy-duty tire laser etching

[0170]

[0171] Through the 5*5 repeatability accuracy check of the tire laser etching of the equipment, the etching accuracy is confirmed, and the accuracy of the etching method is proved.

Claims

1. A three-dimensional laser etching method based on tire cylindrical coordinates, characterized in that:

1. Establish tire polar coordinates 1.1 The planar polar coordinate system for tire design is established as follows: Based on the top view of the tire mold design, a polar coordinate system is established with the tire center as the pole O, the ray connecting the pole O to the tire marking position as the polar axis, and the counterclockwise direction as positive. 1.2 The three-dimensional cylindrical coordinate system of the tire is established as follows: Based on the tire conveying bottom surface used to transport the tire, a polar coordinate system is established with the tire center as the pole O, the ray perpendicular to the tire conveying direction as the polar axis, and the counterclockwise direction as positive. The ray perpendicular to the plane of the polar coordinate system is the Z-axis, and the three-dimensional cylindrical coordinate system of the tire is established.

2. The three-dimensional laser etching method further includes the following steps: Step 1) When the tire arrives at the lettering station conveyor belt, the centering mechanism clamps and centers the tire, and the laser rangefinder detects the tire height. Step 2) The six-axis robot lowers the 3D camera to the preset depth-of-focus height above the tire surface; Step 3) The six-axis robot maintains its posture on axes 1-5, while the sixth axis drives the barcode reader and 3D camera to rotate 365° to read the image and barcode; Step 4) The barcode reader reads and identifies the tire barcode, and the system interacts with the MES management system. The system provides the etched content and etched positioning information. Step 5) The 3D camera scans the tire sidewall to create a 3D model. The reference mark is retrieved in the model by OCR recognition or template comparison. Based on the coordinates of the reference point and the relative polar coordinates of the etched mark, the absolute position of the polar coordinates of the etched mark is obtained. Step 6) The etching position is etched by focusing the laser galvanometer. Based on the three-dimensional cylindrical coordinates of the tire, the 3D camera scans the tire to confirm the three-dimensional cylindrical coordinates that need to be etched. The system converts the three-dimensional cylindrical coordinates of the etching center into three-dimensional rectangular coordinates so that the robot can drive the laser lens to move to the etching center according to the rectangular coordinates and joint coordinates. Then, the marking is engraved on the tire surface by the laser galvanometer. The equipment operates based on a cylindrical three-dimensional coordinate system of the tire, combined with the robot's three-dimensional Cartesian coordinate system and joint coordinate system, to perform coordinate transformation. In step 6), the robot drives the laser lens to move to the etching center according to the Cartesian and joint coordinate angles, and then uses a laser galvanometer to engrave the mark on the tire surface. The robot's trajectory includes: Step i) The robot's sixth axis center moves from the initial coordinates O'(X0,Y0,Z0) to O2(X22,Y22,Z22); X0=D1 (Equation 1) Y0=0 (Equation 2) Z0 = Zdmax + F1 + H1 + D2 + C (Equation 3) O' is the initial position of the robot's sixth axis center, and O2 is the coordinate position of the robot's sixth axis center when the 3D camera scans. D1: The distance between the robot's base coordinates and the tire's cylindrical coordinates on the X-axis, which is a constant; D2: The distance between the robot's base coordinates and the tire's cylindrical coordinates on the Z-axis, which is a constant; Zdmax: Maximum tire height; F1: The scanning focal length of the 3D camera; H1: The height distance from the center of the 3D camera lens to the center of motion axis in the Z-axis direction; C: The set constant; X22=X0=D1 (Equation 4) Y22=Y0=0 (Formula 5) Z22=Zd+F1+H1+D2 (Equation 6) Zd: Laser rangefinder sensor for detecting tire height; Once the sixth axis is in position, it rotates 365 degrees to perform scanning and barcode scanning.

2. The three-dimensional laser etching method based on tire cylindrical coordinates according to claim 1, characterized in that, The robot is equipped with a 3D camera and a laser emitting lens. O3 is the laser etching coordinate position of the robot's sixth axis. When the robot's sixth axis reaches the scanning target point O2, the robot rotates through the sixth axis, driving the 3D lens and barcode reader to reach the depth of field range of tire reading and 3D camera scanning for scanning. After completion, the robot's sixth axis moves to the focal depth height above the laser etching center point, and laser etching is performed through the galvanometer. After completion, the sixth axis drives the axis arm to rotate back to the original position angle; the sixth axis rises back to the initial point O'.

3. The three-dimensional laser etching method based on tire cylindrical coordinates according to claim 2, characterized in that, The robot's trajectory also includes: Step ii) The robot's sixth axis axis moves from O2(X22,Y22,Z22) to the three-dimensional Cartesian coordinates O3(X33,Y33,Z33) of the etching task; Step 2a) Let M0(ρ0, θ0, Z0) be the reference position point identified in the 3D camera scan image, and let M0'(ρ0, θ0) be the polar coordinates projected onto the bottom surface of the tire conveyor. Step 2b) Calculate the three-dimensional coordinates of the etching: M2(ρ2, θ2, Z2) is the center point of the laser etching on the tire, P2(ρ2, θ2, Z12) is the center coordinate of the laser etching lens, and the projection onto the polar coordinate point is M2'(ρ2, θ2). ρ2=ρ0+▽ρ; (Equation 7) θ2 = θ0 + ▽θ; (Equation 8) In the formula, ▽ρ represents the polar diameter deviation between the etching position and the reference point position; In the formula, ▽θ: the polar angle deviation between the etching position and the reference point position; The Z2 value is retrieved based on ρ2, θ2, and the 3D cylindrical coordinates of the tire. Step 2c) Calculate the lens coordinates of the scanning point: When scanning to the etching center point M2, the lens center point of the 3D camera is at P1(ρ1, θ1, Z11), the vertical scanning point on the tire is M1(ρ1, θ1, Z1), and the coordinates projected onto the bottom surface of the tire are M1'(ρ1, θ1). θ1=θ2 (Equation 9) ρ1=R1 (Equation 10) R1: Length of the 3D camera scanning robotic arm, the extreme radius distance from the center of the scanning lens to the center of the sixth axis, which is a constant; Z11 = Z2 - H2 + H1 (Equation 11) H1: The height distance from the center of the 3D camera lens to the center of the sixth axis of motion; H2: The height distance from the laser etching center to the center of the sixth axis of motion; Step 2d) Calculate the etching polar coordinates: Calculate the polar coordinates O3(ρ3, θ3) of the sixth axis center during tire etching based on the results of steps 2b and 2c; Y12=ρ2-ρ1=ρ0+▽ρ-R1 (Equation 12) ρ3 =R2-R1+Y12= R2+ρ0+▽ρ-2R1 (Equation 13) θ3=θ2+180= θ0+▽θ+180 (Equation 14) R2: Length of the laser etching robotic arm, the extreme radius distance from the center of the etching lens to the center of the sixth axis; R1: Length of the 3D camera scanning robotic arm, the extreme radius distance from the center of the scanning lens to the center of the sixth axis; Y12: Distance from the etching center to the center of the 3D camera scanning lens in steps 2b and 2c; Step 2e) Coordinate transformation: The rectangular coordinates of O3 in the robot's three-dimensional rectangular coordinate system are (X33, Y33, Z33). According to equations (13) and (14) and the coordinate transformation formula, we can obtain: X33=ρ3COSθ3+D1=(R2+ρ0+▽ρ-2R1)COS(θ0+▽θ+180)+D1 (Equation 15) Y33=ρ3SINθ3=(R2+ρ0+▽ρ-2R1)SIN(θ0+▽θ+180) (Equation 16) Z33 = Z2 + F2 + H2 + D2 (Equation 17) F2: Laser etching focal length; H2: The height distance in the Z-axis direction from the center of laser etching to the center of motion; D1: The distance between the robot's base coordinates and the tire's cylindrical coordinates on the X-axis, which is a constant; D2: The distance between the robot's base coordinates and the tire's cylindrical coordinates on the Z-axis, which is a constant; Step iii) The sixth axis arm moves in joint coordinates, with a movement angle equal to θ3: θ3=θ2+180= θ0+▽θ+180 (Equation 18) step Based on the above principles, calculate the sixth axis center coordinates and the sixth axis rotation angle for multiple subsequent tasks; Step v) After the etching task is completed, the sixth axis axis returns to the O' coordinate, and the rotation angle of the axis arm returns to 0 degrees.

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