A method for obtaining metal burr height

Abstract

The present invention belongs to the field of production and manufacturing technology, and proposes a method for obtaining the height of metal burrs. This method addresses the problems that existing methods cannot directly obtain the burr height of the entire circumference, and must manually select measurement points and then repeat multiple measurements to calculate the average, which is time-consuming, obviously subjective, has large errors, and low precision. The proposed method for obtaining the height of metal burrs obtains metal burr point cloud data through image processing, and then performs fitting and index evaluation through mathematical methods to obtain a quantitative evaluation method for the burr height of the entire hole. The present invention significantly improves the efficiency of metal burr height measurement, avoids the problems of high subjectivity and low reliability of metal burr height measurement results, and can be applied to the optimization of process parameters in working conditions such as metal drilling, composite material / metal laminate drilling, etc. It can help related companies research new technologies for aluminum alloy deburring, reduce hole making costs, and has good engineering prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of production and manufacturing, and in particular to a method for obtaining the height of metal burrs. Background Art

[0002] Drilling is one of the most important machining methods, widely used in all aspects of high-end equipment manufacturing. Due to the high ductility of metal, burrs are easily formed at the exit or entrance of the drilling process. These burrs can cause dimensional deviations at the part edge, increase assembly complexity, and even cause stress concentration at the assembly point, leading to failure. Therefore, metal burrs have become a significant factor affecting workpiece precision and joint strength. Research on this issue has been a hot topic and is of great significance for improving equipment safety.

[0003] Accurately measuring burr height is fundamental to burr reduction research. Ping Wanpeng et al. from Huizhou Yiwei Lithium Energy Co., Ltd. disclosed a "Method for Measuring Burrs in Metal Strips," patent number ZL 201910506925. This method uses a coagulant to solidify a metal strip sample into a solid sample, which is then cut and polished. A measuring instrument is then used to measure and record the burr length on the cross-section of the cut and polished solid sample. This method avoids measurement errors caused by burr compression during measurement. Liang et al. from Zhengzhou University, in their paper "Hole Burr Measurement and Evaluation Based on Linear Laser Displacement Sensors," published in the Journal of Harbin Institute of Technology, describe the effects of stray light caused by multiple reflections and the tilt of the laser imaging surface and the surface of the hole being measured on measurement accuracy. They also propose methods for eliminating stray light and calibrating for tilt. They then develop an algorithm for calculating burr height using sensor measurement data, visualizing burr height and describing the hole burr height. The above research provides some insights for measuring metal burr height. However, existing measurement methods cannot directly obtain the burr height of the entire circumference. It requires manually selecting measurement points and then repeating the measurement multiple times to calculate the average. This is not only time-consuming, but also subjectivity in the selection of measurement points leads to large errors and low accuracy. Therefore, existing measurement methods still cannot meet the needs, and an efficient and high-precision method for obtaining metal burr height is urgently needed. Summary of the Invention

[0004] Based on the above problems, the present invention proposes a method for obtaining metal burr height. This method obtains metal burr point cloud data through image processing, and then performs fitting and index evaluation through mathematical methods to obtain an efficient and high-precision quantitative evaluation method for the burr height of the entire hole.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for obtaining metal burr height, which obtains metal burr point cloud data through image processing, and then performs fitting and index evaluation through mathematical methods to obtain a quantitative evaluation method for the burr height of the entire hole. The specific steps are as follows:

[0007] Step 1: Obtain 3D point cloud data of drilling exit

[0008] According to the metal burr image acquired by the camera, the corresponding three-dimensional point cloud data set is obtained by the following formula:

[0009] V k (u)=R k K -1 u (1)

[0010] Among them, V k Represents a 3D point cloud data set, R k Represents the image depth, K represents the intrinsic matrix parameters of the camera, and u represents the homogeneous coordinates corresponding to the pixel point.

[0011] Step 2: Fitting the drilling exit plane

[0012] According to the acquired 3D point cloud data set, V k The set without burrs is determined based on the mode of the drilled surface, and the point cloud data set V of the drilled surface is obtained. k1 ;

[0013] For the acquired point cloud data set V k1 Linear regression is used to perform plane fitting to obtain the drilling exit plane surface M:

[0014] z=a0x+a1y+a2 (2)

[0015] Among them, x, y, z represent the three-dimensional point cloud data set V k The coordinate values corresponding to each point in the , a0, a1 and a2 are constants; calculate the three-dimensional point cloud data set V k The sum of the residuals from each point in to the fitted plane:

[0016]

[0017] Where n represents V k The number of points in .

[0018] Finally, the plane fitting results are optimized with the goal of minimizing the residual to obtain the final fitting plane Q.

[0019] Step 3: Obtain metal burr point cloud data

[0020] Calculate the three-dimensional point cloud data set V k The distance from each point to the final fitting plane Q;

[0021]

[0022] The threshold μ is preset, and each point with a distance greater than μ from the plane is set as a valid point, and each point with a distance less than μ is set as an invalid point, and the point cloud set V of the metal burr is obtained. k2 :

[0023]

[0024] Step 4: Get the drilling diameter and center

[0025] The point cloud set V of the metal burr will be obtained k2 , project onto the final fitting plane Q obtained in step 2, and calculate the projection points (x i ,y i ) is fitted using the following matrix form:

[0026]

[0027] Where A, B, C, and D are constants, and the vector P is defined as (A, B, C, D) T , and satisfy:

[0028] P T NP=1 (7)

[0029] The vector N is the constraint matrix, which is:

[0030]

[0031] in, Represents the point cloud set V k2 The average value of the coordinates in the x, y, and z axes.

[0032] According to formulas 7 and 8, constants A, B, C, and D can be solved. And the results are substituted into:

[0033]

[0034] The center coordinates D(c1, d1) of the circle corresponding to the metal processing outlet hole and the radius R1 of the circle can be obtained.

[0035] Step 5: Get the burr height

[0036] Divide the circle corresponding to the processing outlet hole into m equal parts, and the coordinates of the points on the line connecting each dividing point and the center of the circle are (x mi ,y mj ) represents that i and j are used to obtain the coordinates of the points and calculate the corresponding points (x mi ,y mi ,zmk ) to the final fitting plane Q, with the maximum value representing the burr height at this equally divided point:

[0037]

[0038] Step 6: Calculate the average burr height

[0039] The burr height data of each equally divided point in step 5 are averaged, and the burr height on the entire circumference is averaged to obtain the burr height at the metal outlet, H:

[0040]

[0041] The beneficial effects of the present invention are as follows: the present invention specifically quantifies metal burrs through image processing, significantly improves the efficiency of metal burr height measurement, proposes a quality measurement index suitable for the metal drilling process, avoids the problems of high subjectivity and low reliability of metal burr height measurement results, and can be applied to the process parameter optimization of working conditions such as metal drilling and composite material / metal laminate drilling, which can help related companies reduce hole making costs and has good engineering prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The figure is a flow chart of a method for obtaining the height of metal burrs. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to the accompanying drawings and examples. This example uses a laminated structure of 8mm thick T800 grade carbon fiber reinforced resin composite material and 4mm thick 7050 aluminum alloy as the object for drilling experiments. Full factorial experiments were conducted at 1500rpm and 3000rpm with feed rates of 50mm / min, 100mm / min, 150mm / min and 200mm / min to verify this method. The treatment form for the height of aluminum alloy burrs is as follows: Figure 1 The specific steps are as follows:

[0044] Step 1: Obtain export 3D point cloud data

[0045] Based on the image of the aluminum alloy burr acquired by the camera, the corresponding three-dimensional point cloud set is obtained using the following formula:

[0046] V k (u)=R k K -1 u (12)

[0047] Where V k represents a point cloud set, R kRepresents the image depth, K represents the intrinsic matrix parameters of the camera, and u represents the homogeneous coordinates corresponding to a pixel point.

[0048] Step 2: Drilling exit plane fitting

[0049] According to the acquired point cloud set, since the drilling exit surface has the most data points, V k Based on the mode in , we get the point cloud set V that does not produce burr surface k1 .

[0050] For the obtained point cloud set V k1 The linear regression method is used to perform plane fitting, and the equation of the plane drilling outlet surface M is obtained as follows:

[0051] z=a0x+a1y+a2 (13)

[0052] Where a0, a1 and a2 are constants. Calculate the residual from each point to the plane drilling exit surface:

[0053]

[0054] The plane fitting results are optimized with the goal of minimizing the residual to obtain the final fitting plane Q;

[0055] Step 3: Obtain aluminum alloy burr point cloud data

[0056] Calculate point cloud set V k The distance from each point to the final fitting plane Q:

[0057]

[0058] The threshold μ is preset, and the points with a distance greater than μ from the plane are set as valid points, and those with a distance less than μ are set as invalid points, and the point cloud set V of the aluminum alloy burr is obtained. k2 :

[0059]

[0060] Step 4: Obtaining the drilling diameter and center point

[0061] The point cloud set V of the aluminum alloy burr will be obtained k2 Project on the final fitting plane Q and use the following matrix form for fitting:

[0062]

[0063] Where A, B, C, and D are constants, and the vector P is defined as (A, B, C, D) T , and satisfy:

[0064] P TNP=1 (18)

[0065] The vector N is the constraint matrix, which can be expressed as:

[0066]

[0067] The center coordinates D(a1, b1) of the circle corresponding to the aluminum alloy processing hole and the radius R1 of the circle are obtained.

[0068] Step 5: Get the burr height

[0069] Divide the points on the circumference of the metal processing outlet hole into n equal parts, and each divided point is (x ni ,y nj ) means that the points (x ni ,y ni ,z nj ) to the final fitting plane Q, with the maximum value representing the burr height at this equally divided point:

[0070]

[0071] Step 6: Calculate the average burr height

[0072] The data from step 5 is averaged and the burr height over the entire circumference is averaged to obtain the burr height at the aluminum alloy outlet, H:

[0073]

[0074] The burr height of aluminum alloy outlet is shown in Table 1;

[0075] Table 1 Burr height of aluminum alloy outlet at different rotation speeds and feed speeds

[0076]

[0077] A method for quantifying metal burrs is proposed based on image processing, which significantly improves the measurement efficiency and accuracy of metal burrs. It can help measure the processing quality and optimize process parameters in metal drilling, composite material / metal stack drilling, etc., reduce the production costs of related companies, and has broad engineering prospects.

Claims

1. A method for obtaining the height of metal burrs, characterized in that: The metal burr height acquisition method obtains metal burr point cloud data through image processing, and then performs fitting and index evaluation through mathematical methods to obtain a quantitative evaluation method for the burr height of the entire hole. The specific steps are as follows: Step 1: Obtain 3D point cloud data of drilling exit According to the metal burr image acquired by the camera, the corresponding three-dimensional point cloud data set is obtained by the following formula: V k (u)=R k K -1 u (1) Among them, V k Represents a 3D point cloud data set, R k Represents the image depth, K represents the intrinsic matrix parameter of the camera, and u represents the homogeneous coordinates corresponding to the pixel point; Step 2: Fitting the drilling exit plane According to the acquired 3D point cloud data set, V k The set without burrs is determined based on the mode of the drilled surface, and the point cloud data set V of the drilled surface is obtained. k1 ; For the acquired point cloud data set V k1 Linear regression is used to perform plane fitting to obtain the drilling exit plane surface M: z=a0x+a1y+a2 (2) Among them, x, y, z represent the three-dimensional point cloud data set V k The coordinate values corresponding to each point in the , a0, a1 and a2 are constants; calculate the three-dimensional point cloud data set V k The sum of the residuals from each point in to the fitted plane: Where n represents the three-dimensional point cloud data set V k The number of points in ; Finally, the plane fitting results are optimized with the goal of minimizing the residual error to obtain the final fitting plane Q; Step 3: Obtain metal burr point cloud data Calculate the three-dimensional point cloud data set V k The distance from each point to the final fitting plane Q; The threshold μ is preset, and each point with a distance greater than μ from the plane is set as a valid point, and each point with a distance less than μ is set as an invalid point, and the point cloud set V of the metal burr is obtained. k2 : Step 4: Get the drilling diameter and center The point cloud set V of the metal burr will be obtained k2 , project onto the final fitting plane Q obtained in step 2, and calculate the projection points (x i ,y i ) is fitted using the following matrix form: Where A, B, C, and D are constants, and the vector P is defined as (A, B, C, D) T , and satisfy: P T NP=1 (7) The vector N is the constraint matrix, which is: in, Represents the point cloud set V of metal burrs k2 The average value of the coordinates in the directions of the three coordinate axes x, y, and z; According to formulas (7) and (8), the constants A, B, C, and D are solved and the results are substituted into: That is, the center coordinates D(c1, d1) of the circle corresponding to the metal processing outlet hole and the radius R1 of the circle are obtained; Step 5: Get the burr height The circle corresponding to the metal processing outlet hole is divided into m equal parts, and the coordinates of the points on the line connecting each equal point and the center of the circle are (x mi ,y mj ) represents that i and j are used to obtain the coordinates of the points and calculate the corresponding points (x mi ,y mi ,z mk ) to the final fitting plane Q, with the maximum value representing the burr height at this equally divided point: Step 6: Calculate the average burr height The burr height data of each equally divided point in step 5 are averaged, and the burr height on the entire circumference is averaged to obtain the burr height at the metal outlet, H:

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