Calibration method for coaxiality of powder feeding head and laser in laser cladding

Abstract

The invention relates to a method for calibrating the coaxiality of a powder feeding head and laser in laser cladding. The method comprises the following steps that S1, a laser system of a cladding head and the powder feeding head are kept coaxial; preparing a cladding substrate; s2, controlling the moving distance of the laser system in the direction of the direction vector, wherein the moving direction vector and the moving distance are moving data of the laser system; s3, printing on the cladding substrate to obtain a single-channel circular ring cladding layer; s4, measuring the contour of the single-channel circular ring cladding layer to obtain geometric data of the contour; s5, based on the geometric data of the contour, calculating to obtain the offset data of the offset angle and the offset direction of the contour; s6, obtaining a single data group of the mobile data and the corresponding offset data according to the steps, circularly repeating the steps S2 to S5 to obtain a data set formed by a plurality of data groups, and fitting to obtain a mapping relationship between the mobile data and the offset data based on the data set; and adjusting the laser system in a direction opposite to the offset direction based on the mapping relation.

Description

Technical Field

[0001] The present invention relates to the technical field of laser cladding, and particularly relates to a method for calibrating the coaxiality of a powder feeding head and a laser in laser cladding. Background Art

[0002] As an advanced surface modification and additive manufacturing technology, laser cladding has received extensive attention and application in industrial production in recent years. Laser cladding uses a high-energy laser beam as a heat source to rapidly melt the pre-placed or synchronously fed powder material and form a metallurgical bond with the surface of the substrate metal, thereby forming a cladding layer with specific properties on the substrate surface.

[0003] The powder feeding methods of laser cladding include coaxial powder feeding and off-axis powder feeding. Among them, coaxial powder feeding laser cladding means that the powder delivery channel is coaxial with the axis of the laser beam. The powder flow of the coaxial powder feeding laser cladding technology is isotropic, the powder transmission is uniform, and the stability is good. Coaxial powder feeding overcomes the limitation of the directionality of off-axis powder feeding and can achieve precision machining, and is widely used in the industrial field.

[0004] Since the accuracy of the coaxiality between the powder feeding head and the laser system plays a decisive role in the finished product quality of the cladding layer; if the accuracy of the light-powder coaxiality is not high, it will cause the powder to be unevenly distributed in the molten pool, and then the cladding layer will have defects such as inconsistent thickness, holes, and cracks, seriously affecting the performance and service life of the cladding layer. In the actual cladding processing process, as the powder feeding nozzle of the coaxial powder feeding laser cladding is disassembled, maintained, and the use time increases, the coaxiality between the powder feeding head and the laser system will gradually produce small deviations. To ensure the coaxiality of the light-powder coaxiality, the coaxiality needs to be adjusted. However, the existing accuracy adjustment of the light-powder coaxiality generally depends on the adjustment at the time of the cladding head leaving the factory and the use of a special calibration instrument matching the specification of the cladding head. Since there are many brands and specifications of cladding heads, it often requires using calibration instruments or methods of different specifications to calibrate cladding heads of different specifications. Frequent switching consumes a lot of time, resulting in reduced efficiency, and at the same time increases the equipment cost required for coaxiality calibration.

[0005] Currently, there is no simple and effective method for uniformly calibrating the coaxiality of different specifications of cladding heads. Summary of the Invention

[0006] Based on this, it is necessary to provide a method for calibrating the coaxiality of a powder feeding head and a laser in laser cladding.

[0007] The present invention provides a method for calibrating the coaxiality of a powder feeding head and a laser in laser cladding, including the following steps:

[0008] S1. Adjust the laser cladding equipment to make the laser system of the cladding head and the powder feeding head maintain light-powder coaxiality; prepare a cladding substrate and set the laser cladding parameters;

[0009] S2. Control the movement of the laser system so that the laser system moves a distance l in the direction of the direction vector φ l The moving direction vector φ l and the moving distance l are the moving data of the laser system;

[0010] S3. Start the laser cladding equipment and control the cladding head to print a single-pass circular cladding layer on the cladding substrate;

[0011] S4. Use a measuring device to measure the profile of the single-pass circular cladding layer to obtain the geometric data of the profile;

[0012] S5. Based on the geometric data of the profile, calculate the offset angle θ and the offset direction φ p of the profile. The offset angle θ and the offset direction φ p are the offset data of the profile;

[0013] S6. Complete a single experiment according to the above steps to obtain a single data set of the moving data and the corresponding offset data. Repeat the above steps S2 to S5 in a loop to obtain a data set formed by multiple data sets. Based on the data set, fit the mapping relationship between the moving data and the offset data; Based on the mapping relationship, adjust the laser system in the opposite direction of the offset direction φ p so that the laser system of the cladding head and the powder feeding head maintain coaxiality of the light and powder.

[0014] Preferably, in step S1, the laser cladding parameters include laser power, scanning speed, powder feeding amount, spot diameter, protective gas flow rate, and powder feeding gas flow rate.

[0015] Preferably, in step S1, establish a three-dimensional rectangular coordinate system O-XYZ, take the plane where the surface of the cladding substrate is located as the two-dimensional plane composed of the X-axis and the Y-axis, take the initial position of the laser system as the coordinate origin O, and take the central axis of the laser system as the Z-axis.

[0016] Preferably, in step S2, by adjusting the adjusting thread, the laser system is moved in the plane direction composed of the X-axis and the Y-axis.

[0017] Preferably, the mapping relationship between the moving data and the offset data obtained by fitting has the following expression:

[0018] θ = f(l)

[0019] φ p = f(φ l )

[0020] Wherein,

[0021] θ is the offset angle of the contour of the single-pass circular cladding layer;

[0022] φ p is the direction of the contour of the single-pass circular cladding layer;

[0023] l is the moving distance of the laser system;

[0024] φ l is the moving direction vector of the laser system.

[0025] Preferably, the offset distance l is the offset distance Δx in the X-axis direction and the offset distance Δy in the Y-axis direction of the laser system, and has the following expression:

[0026]

[0027] Preferably, based on the data set, multiple linear regression is performed on the data set to fit the mapping relationship between the moving data and the offset data.

[0028] Preferably, after starting the laser cladding equipment, control the cladding head to scan on the flat plate in a circular trajectory with a fixed radius, so that a single-pass circular cladding layer is printed on the cladding substrate.

[0029] Preferably, the measuring device is a laser profiler.

[0030] Preferably, the laser profiler measures the contour of the printed single-pass circular cladding layer. The specific steps are as follows: M measurement points are uniformly selected on the single-pass circular cladding layer for measurement, and the position data of the measurement points of the contour of the single-pass circular cladding layer are respectively recorded. Based on the position data of the measurement points, the geometric data of the contour of the single-pass circular cladding layer are obtained; the M measurement points are spaced at the same distance from each other.

[0031] The present invention provides a calibration method for the powder-laser coaxiality in laser cladding, which can quickly and accurately calibrate the deviation when the powder-laser coaxiality is inconsistent, and calibrate the powder-laser coaxiality applicable to different specifications of cladding heads by adjusting the position of the laser beam. Description of the Drawings

[0032] Specifically illustrated by the preferred embodiments of the present invention shown in the drawings, the above and other objects, features and advantages of the present invention will become clearer. The same reference numerals indicate the same parts in all the drawings, and the drawings are not deliberately drawn to scale in actual size, and the focus is on showing the gist of the present invention.

[0033] Figure 1 is the main step flow chart of the calibration method for the powder feeding head and laser coaxiality in the laser cladding of the embodiment of the present invention;

[0034] Figure 2 Schematic diagram of printing a single - pass ring using a cladding head and a powder feeding head according to a preferred embodiment of the present invention;

[0035] Figure 3 Schematic diagram of the offset angle and direction of printing a single - pass ring by the method according to an embodiment of the present invention;

[0036] Figure 4 Schematic diagram of the offset distance and direction of the laser system of the method according to a preferred embodiment of the present invention;

[0037] Figure 5 Schematic diagram of the offset distance and direction of the laser system of the method according to a preferred embodiment of the present invention;

[0038] Laser system 11; powder feeding head 12; distance - adjusting thread 13; single - pass ring cladding layer 14; cladding substrate 15. Detailed implementation manners

[0039] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments given are not intended to limit the present invention.

[0040] As Figures 1 - 5 shown, the present invention provides a method for calibrating the coaxiality of a powder feeding head 12 and a laser in laser cladding, including the following steps:

[0041] S1. Adjust the laser cladding equipment, adjust the coaxial powder feeding laser cladding equipment to the working state during actual cladding, use a coaxiality calibration tool or an optical - powder coaxiality test system to adjust the coaxiality of the laser system 11 and the powder feeding head 12, so that the laser system 11 of the cladding head and the powder feeding head 12 maintain optical - powder coaxiality; prepare the cladding substrate 15 and set the laser cladding parameters; establish an O - XYZ three - dimensional rectangular coordinate system, use the plane where the surface of the cladding substrate is located as the two - dimensional plane composed of the X - axis and the Y - axis, use the initial position of the laser system as the coordinate origin O, and use the central axis of the laser system as the Z - axis.

[0042] S2. Control the laser system 11 to move, so that the laser system 11 moves a distance l in the direction of the direction vector φ l The direction vector φ l and the moving distance l are the moving data of the laser system 11;

[0043] S3. Start the laser cladding equipment, and control the cladding head to print a single - pass ring cladding layer 14 on the cladding substrate 15;

[0044] S4. Use a measuring device to measure the contour of the single - pass ring cladding layer 14 to obtain the geometric data of the contour of the single - pass ring.

[0045] S5. Calculate the offset angle θ and offset direction φ of the contour based on the geometric data of the contour of the single-pass ring. p , the offset angle θ and offset direction φ p are the offset data of the contour; as Figure 4 shown, a single-pass ring cladding layer 14 is printed on the cladding substrate 15 to form a ring tube body with a thickness. The outer contour of the single-pass ring cladding layer 14 is inclined, and the inclination angle of the outer contour is the offset angle θ of the contour of the single-pass ring cladding layer 14, and the direction of the inclined offset of the outer contour is the offset direction φ. p .

[0046] S6. Complete a single experiment according to the above steps to obtain a single data set of movement data and corresponding offset data. Loop and repeat the above steps S2 to S5 to obtain a data set formed by multiple data sets. Based on the data set, fit the mapping relationship between the movement data and the offset data; based on the mapping relationship, adjust the laser system 11 in the opposite direction of the offset direction φ p so that the laser system 11 of the cladding head and the powder feeding head 12 maintain optical powder coaxiality. Using the established mapping relationship, according to the offset angle θ and direction φ of the printed ring contour p , the offset distance l and direction φ of the laser system 11 can be obtained l , and then reverse-adjust the distance-adjusting thread 13 of the laser system 11 to compensate for the coaxiality deviation.

[0047] In a preferred embodiment, in step S1, the laser cladding parameters include laser power, scanning speed, powder feeding amount, spot diameter, protective gas flow rate, and powder feeding gas flow rate.

[0048] In a preferred embodiment, in step S1, establish a three-dimensional rectangular coordinate system O-XYZ, use the plane where the surface of the cladding substrate 15 is located as the two-dimensional plane composed of the X-axis and the Y-axis, use the initial position of the laser system 11 as the coordinate origin O, and use the central axis of the laser system 11 as the Z-axis.

[0049] In a preferred embodiment, in step S2, by adjusting the distance-adjusting thread 13, the laser system 11 is moved in the plane direction of the plane composed of the X-axis and the Y-axis.

[0050] In a preferred embodiment, in different experiments, continuously change the moving distance and direction of the laser system 11 along the x and y axes, and then collect the offset angle and direction of the printed ring contour in different situations. Use the least squares method to perform multiple linear regression on the data set to establish the offset angle θ and direction φ of the printed ring contour p and the offset distance l and direction φ of the laser system 11 lThe mapping relationship between the two, that is, the mapping relationship between the moving data and the offset data obtained by fitting, has the following expression:

[0051] θ = f(l)

[0052] φ p = f(φ l )

[0053] Wherein,

[0054] θ is the offset angle of the contour of the single-pass circular cladding layer 14;

[0055] φ p is the direction of the contour of the single-pass circular cladding layer 14;

[0056] l is the moving distance of the laser system 11;

[0057] φ l is the moving direction vector of the laser system 11.

[0058] In a preferred embodiment, the laser system 11 moves a distance l in the direction of the direction vector φ l . The initial position coordinates of the cladding point represented by the laser system 11 are P(x0, y0), and the position coordinates after movement are P'(x1, y1). Then, the length of the line connecting PP' is the moving distance l. Then, Δx = x1 - x0, and Δy = y1 - y0.

[0059] The offset distance l of the laser system 11 is represented by the offset distance Δx in the X-axis direction and the offset distance Δy in the Y-axis direction of the laser system 11, and has the following expression:

[0060]

[0061] Wherein, the inference calculation of the mapping relationship obtained by performing multiple linear regression on the data set by the least squares method is as follows:

[0062] Assume that the linear relationship between the offset angle θ and the direction φ p of the circular ring contour and the offset distance Δx in the x-axis direction, the offset distance Δy in the y-axis direction of the laser system 11, and the direction φ l is:

[0063] θ = β0 + β1l + ε1

[0064] φ p = γ0 + γ1φ l + ε2

[0065] Wherein,

[0066] β0, β1 are the regression coefficients of θ, and γ0, γ1 are φ pThe regression coefficients, ε1 and ε2 are error terms.

[0067] Write the model in matrix form:

[0068] θ = Xβ + ε1

[0069] φ p = Xγ + ε2

[0070] Where,

[0071] X is the design matrix, θ and φ p are the target variable vectors, and β and γ are the regression coefficient vectors. The goal of the least squares method is to find the regression coefficients β and γ to minimize the sum of squared errors,

[0072] That is:

[0073] S(β) = ‖θ - Xβ‖ 2

[0074] S(γ) = ‖φ p - Xγ‖ 2

[0075] The solutions for β and γ are

[0076] β = (X T X) -1 X T θ

[0077] γ = (X T X) -1 X T φ p

[0078] Through the above calculations, after obtaining the regression coefficients, the following mapping relationship can be obtained

[0079] θ = β0 + β1l + ε1

[0080] φ p = γ0 + γ1φ l + ε2

[0081] So after the offset angle θ and direction φ of the printed circular ring contour of the already printed circular ring p are obtained, the offset distance l and direction φ of the laser system 11 can be solved using the mapping relationship l to adjust the coaxiality of the laser system.

[0082] In the preferred embodiment, based on the dataset, multiple linear regression is performed on the dataset to fit the mapping relationship between the movement data and the offset data.

[0083] In a preferred embodiment, after starting the laser cladding equipment, the cladding head is controlled to scan on a flat plate along a circular trajectory with a fixed radius, so that a single-pass circular cladding layer 14 is printed on the cladding substrate 15 by the cladding head.

[0084] In a preferred embodiment, the measuring device is a laser profiler.

[0085] In a preferred embodiment, the laser profiler measures the profile of the printed single-pass circular cladding layer 14. The specific steps are as follows: M measuring points are uniformly selected on the single-pass circular cladding layer 14 for measurement, and the position data of the measuring points of the profile of the single-pass circular cladding layer 14 are respectively recorded. Based on the position data of the measuring points, the geometric data of the profile of the single-pass circular cladding layer 14 are obtained; the M measuring points are spaced at the same distance from each other.

[0086] The calibration method of the present invention has a simple and clear operation process. Only by adjusting the laser position, printing a circle, measuring the circle profile and analyzing data and other steps, the calibration of the optical powder coaxiality can be completed. There is no need for complex equipment and cumbersome operation processes, which greatly saves time and labor costs.

[0087] During the calibration process of the calibration method of the present invention, it can simulate the real working conditions. By strictly simulating the process parameters and operation environment of actual laser cladding, the calibration result can truly reflect the optical powder coaxiality situation in actual production, effectively improving the reliability and practicality of the calibration result.

[0088] The calibration method of the present invention has good repeatability. By strictly controlling the experimental conditions and operation processes, this calibration method has good repeatability. When different operators perform calibration under the same conditions, relatively consistent results can be obtained, which is beneficial to ensuring the stability of the production process and the consistency of product quality.

[0089] The calibration method of the present invention is a method for adjusting the inconsistency in coaxiality between the laser system 11 and the powder feeding system by establishing a mapping relationship between the offset angle and direction of the circle profile and the offset distance and direction of the laser system 11. The adjustment of traditional optical powder coaxiality requires developing corresponding optical powder coaxiality test systems for different specifications of cladding heads. This method realizes the rapid and accurate calibration of optical powder coaxiality through rigorous data analysis and modeling, is applicable to cladding heads of different specifications and manufacturers, has a wider applicability. After clarifying the mapping relationship, there is no need for an additional dedicated optical powder coaxiality test system, solving the pain points of the prior art relying on special tools and poor adaptability.

[0090] In order to better illustrate the technical solution of the present invention, the following embodiments are further described below.

[0091] Embodiment 1

[0092] 1) Use the coaxial powder feeding cladding head of a five-axis additive and subtractive machine tool. Prepare a 304 stainless steel flat plate with dimensions of 100mm×100mm×10mm as the cladding substrate 15. Use sandpaper to polish the surface of the flat plate to remove the surface oxide layer and impurities, then clean it with alcohol and dry it. Set the laser power to 800W, the scanning speed to 10mm / s, the powder feeding rate to 0.5r / min, the spot diameter to 2mm, the protective gas flow rate to 20L / min, and the powder feeding gas flow rate to 5L / min.

[0093] 2) By adjusting the distance adjusting screw 13 of the laser system 11 in the x-axis and y-axis directions, move the laser system 11 along the positive x-axis direction by a distance l of 0.5mm.

[0094] 3) Start the laser cladding equipment and control the cladding head to scan on the flat plate in a circular trajectory with a radius of 20mm to print a single-pass ring.

[0095] 4) Use a laser profiler to measure the profile of the printed ring. Uniformly select measurement points on the ring and record the profile data of the printed ring in detail.

[0096] 5) Analyze the measured ring profile data and calculate the ring profile offset angle θ and direction φ p .

[0097] 6) As Figure 4 shown, adjust the moving distance l of the laser system 11 in the positive x-axis direction in step 3 to 1mm, 1.5mm, 2mm, repeat steps 4 to 6, and record the ring profile offset angle θ and direction φ p . Perform multiple linear regression on the data set to establish the mapping relationship between the printed ring profile offset angle θ and direction φ p and the offset distance l and direction φ of the laser system 11 l between the two.

[0098] Reverse-adjust the position of the XY plane of the laser system 11 through the obtained corresponding relationship to keep the optical powder coaxiality consistent.

[0099] Example Two

[0100] 1) Use the coaxial powder feeding cladding head of a three-axis cladding machine tool. Prepare a 40Cr steel flat plate with dimensions of 100mm×100mm×8mm as the cladding substrate 15. Use sandpaper to polish the surface of the flat plate to remove the surface oxide layer and impurities, then clean it with alcohol and dry it. Through the optical powder coaxiality test system, ensure that the initial coaxiality of the laser and the powder feeding head 12 is consistent.

[0101] 2) Set the laser power to 700 W, the scanning speed to 8 mm / s, the powder feeding rate to 0.5 r / min, the spot diameter to 2 mm, the protective gas flow rate to 20 L / min, and the powder feeding gas flow rate to 5 L / min.

[0102] 3) By adjusting the distance-adjusting threads 13 of the laser system 11 in the x and y directions, move the laser system 11 along the positive y-axis by a distance l of 0.5 mm.

[0103] 4) Start the laser cladding equipment, and control the cladding head to scan on the flat plate in a circular trajectory with a radius of 20 mm to print a single-pass ring.

[0104] 5) Use a laser profiler to measure the profile of the printed ring, uniformly select measurement points on the ring, and record in detail the profile data of the printed ring.

[0105] 6) Analyze the measured ring profile data and calculate the ring profile offset angle θ and direction φ p 。

[0106] 7) As Figure 4 shown, adjust the moving distance l of the laser system 11 in the positive x-axis direction in step 3 to 1 mm, 1.5 mm, and 2 mm, and repeat steps 4 to 6, respectively record the ring profile offset angle θ and direction φ p 。Perform multiple linear regression on the data set to establish the mapping relationship between the printed ring profile offset angle θ and direction φ p and the offset distance l and direction φ of the laser system 11 l between the two.

[0107] Reverse-adjust the position of the XY plane of the laser system 11 through the obtained corresponding relationship to keep the powder-laser coaxiality consistent. By using a coaxiality calibration tool or a powder-laser coaxiality test system in advance to ensure the powder-laser coaxiality at the beginning of testing on the printer bed, after obtaining the mapping relationship through the method of the present invention, the mapping relationship can be applied to adjust the powder-laser coaxiality on the machine tool without using a coaxiality calibration tool or a powder-laser coaxiality test system.

[0108] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. A method for calibrating the coaxiality of a powder feeding head and a laser in laser cladding, characterized in that: The steps include: S1. Adjust the laser cladding equipment so that the laser system of the cladding head and the powder feeding head keep the laser and powder coaxial; prepare the cladding substrate and set the laser cladding parameters; S2, control the laser system to move so that the laser system moves in the direction vector φ l The moving direction vector φ l and the moving distance l are the moving data of the laser system; S3, starting the laser cladding equipment, controlling the cladding head to print on the cladding substrate to obtain a single circular cladding layer; S4, using a measuring device to measure the profile of the single-track circular cladding layer to obtain geometric data of the profile; S5. Based on the geometric data of the contour, calculate the offset angle θ and the offset direction φ of the contour p , offset angle θ and offset direction φ p is the offset data of the contour; S6, completing a single experiment according to the above steps to obtain a single data set of movement data and corresponding bias data, cyclically repeating the above steps S2 to S5 to obtain a data set formed by multiple data sets, and fitting the mapping relationship between the movement data and the bias data based on the data set; Based on the mapping relationship, towards the bias direction φ p The laser system is adjusted in the opposite direction of the offset so that the laser system of the cladding head and the powder feeding head keep the laser and powder coaxial.

2. The coaxiality calibration method according to claim 1, characterized in that: In step S1, the laser cladding parameters include laser power, scanning speed, powder feeding amount, spot diameter, shielding gas flow rate and powder feeding gas flow rate.

3. The coaxiality calibration method according to claim 1, characterized in that: In step S1, an O-XYZ three-dimensional rectangular coordinate system is established, with the surface plane of the cladding substrate as the two-dimensional plane composed of the X-axis and the Y-axis, the initial position of the laser system as the coordinate origin O, and the central axis of the laser system as the Z-axis.

4. The coaxiality calibration method according to claim 3, characterized in that: In step S2, the pitch adjusting thread is adjusted so that the laser system moves in the plane formed by the X-axis and the Y-axis.

5. The coaxiality calibration method according to claim 4, characterized in that: The mapping relationship between the mobile data and the bias data obtained by fitting is expressed as follows: θ=f(l) f p =f(φ l ) in, θ is the offset angle of the profile of the single-track circular cladding layer; φ p is the direction of the profile of the single-track circular cladding layer; l is the moving distance of the laser system; φ l is the moving direction vector of the laser system.

6. The coaxiality calibration method according to claim 5, characterized in that: The offset distance l is the offset distance Δx in the X-axis direction and the offset distance Δy in the Y-axis direction of the laser system, and has the following expression:

7. The coaxiality calibration method according to claim 1, characterized in that: Based on the data set, a multivariate linear regression is performed on the data set to fit the mapping relationship between the movement data and the bias data.

8. The coaxiality calibration method according to claim 1, characterized in that: After starting the laser cladding equipment, the cladding head is controlled to scan on the flat plate in a circular trajectory with a fixed radius, so that the cladding head prints a single circular cladding layer on the cladding substrate.

9. The coaxiality calibration method according to claim 1, characterized in that: The measuring device is a laser profiler.

10. The coaxiality calibration method according to claim 1, characterized in that: The laser profiler measures the profile of the printed single-track circular cladding layer, and the specific steps are as follows: M measuring points are evenly selected on the single-track circular cladding layer for measurement, and the position data of the measuring points of the profile of the single-track circular cladding layer are respectively recorded; based on the position data of the measuring points, the geometric data of the profile of the single-track circular cladding layer is obtained; the M measuring points are spaced the same distance from each other.

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