Automobile special-shaped part adaptive electrostatic spraying process

Abstract

The application discloses a kind of automobile special-shaped parts adaptive electrostatic spraying process, belong to automobile accessory surface treatment technical field, comprising the following steps: one, to be electrostatically sprayed automobile special-shaped parts are pretreated;Two, after being electrostatically sprayed automobile special-shaped parts of pretreatment are hung in rotatable hanger;Three, according to the structure of being electrostatically sprayed automobile special-shaped parts hung in rotatable hanger and along preset spraying track spray gun, construct space charge cloud density prediction model;Four, according to the space charge cloud density prediction model of construction, predict the surface space charge cloud density of automobile special-shaped parts during spraying process;Five, according to the space charge cloud density of prediction, adaptive adjustment spraying scheme is carried out adaptive spraying;The application will be electrostatically sprayed automobile special-shaped parts space charge cloud density distribution from passive distribution into active regulation and control, can improve the uniform distribution of space charge cloud density, improve electrostatic spraying effect.

Description

Technical Field

[0001] This invention belongs to the field of automotive parts surface treatment technology, specifically relating to an adaptive electrostatic spraying process for irregularly shaped automotive parts. Background Technology

[0002] Electrostatic spraying refers to a coating process that utilizes a high-voltage electrostatic field to create a strong electrostatic field between the spray gun and the workpiece. After being atomized by the spray gun, the paint particles are charged with high-voltage electrostatic charges of the same polarity. Under the influence of Coulomb attraction and electric field force, they are directionally adsorbed onto the grounded or oppositely polarized workpiece surface. After leveling and curing, a uniform paint film is formed. This process is widely used in the surface treatment of irregularly shaped automotive parts.

[0003] In current electrostatic spraying processes for automotive irregular parts, the space charge cloud density is passively distributed and cannot be controlled during electrostatic spraying. This can easily lead to excessive accumulation of high density in the convex curved areas of automotive irregular parts, generating a strong electrostatic repulsion reaction, which prevents subsequent paint particles from reaching these areas. Conversely, in the recessed areas of automotive irregular parts, the accumulation density is low, and the electric field lines are shielded, making it difficult for subsequent paint to enter these areas, thus reducing the effectiveness of electrostatic spraying.

[0004] In view of this, an adaptive electrostatic spraying process for irregularly shaped automotive parts is designed to solve the above problems. Summary of the Invention

[0005] To address the problems mentioned in the background section, this invention provides an adaptive electrostatic spraying process for automotive irregularly shaped parts. This process transforms the passive distribution of the space charge cloud density of the automotive irregularly shaped parts into active control, thereby improving the uniformity of the space charge cloud density distribution and enhancing the electrostatic spraying effect.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an adaptive electrostatic spraying process for irregularly shaped automotive parts, comprising the following steps:

[0007] 1. Pre-treatment of irregularly shaped automotive parts to be electrostatically sprayed;

[0008] 2. The pre-treated automotive irregular parts to be electrostatically sprayed are mounted on a rotatable hanger.

[0009] 3. Based on the structure of the irregularly shaped automotive parts to be electrostatically sprayed on the rotatable hanger and the spray gun spraying along the preset spraying trajectory, a space charge cloud density prediction model is constructed.

[0010] IV. Predict the space charge cloud density on the surface of automotive irregular parts during the painting process based on the constructed space charge cloud density prediction model;

[0011] V. Adaptive spraying is performed by adjusting the spraying scheme based on the predicted space charge cloud density.

[0012] Furthermore, in step three, the steps for constructing the space charge cloud density prediction model include:

[0013] Mesh-slicing is performed on the surface of the factory design drawings for irregularly shaped automotive parts.

[0014] The surface of the meshed slice is divided into convex curved surface region, planar region, concave groove region and edge dead corner region;

[0015] Extract the surface curvature radius and surface normal vector of convex surface regions, planar regions, concave regions of grooves, and dead corner regions of folded edges;

[0016] A reference charge density value is assigned to the convex curved surface region, the planar region, the concave region of the groove, and the dead corner region of the folded edge;

[0017] Obtain the unit direction vector of the center axis of the spray gun in the spraying posture along the spraying trajectory;

[0018] Find the angle between the surface normal vector of the irregularly shaped automotive part and the axis vector under the spray gun's spraying posture;

[0019] Based on the reference charge density of the planar region, the reference surface curvature radius of the planar region, the surface curvature radius of the region, the angle between the normal vector of the curved surface of the automotive irregular part and the axis vector under the spray gun's spraying posture, the calibrated airflow loss coefficient, the spraying distance, the calibrated charge accumulation attenuation coefficient, and the spraying time, a spatial charge cloud density prediction model is constructed, and its expression is:

[0020]

[0021] In the formula: This represents the reference charge density in a planar region; The radius of curvature of a standard planar region; Represents the surface curvature radius of the mesh patch; This represents the angle between the surface normal vector of the automotive irregular part and the axis vector under the spray gun's spraying posture; Indicates the calibrated airflow loss coefficient; Indicates the spraying distance; Indicates the calibrated charge accumulation decay coefficient; Indicates the spraying time.

[0022] Furthermore, in step three, the meshed slice surface is divided according to the surface curvature radius and the surface opening angle.

[0023] Furthermore, in step three, the step of extracting the surface curvature radius includes:

[0024] Extract the coordinates of the four vertices of the mesh face after meshing and slicing;

[0025] Fit a local surface bivariate function using vertex coordinates;

[0026] Find the second-order partial derivative of the bivariate function on the local surface, and solve for the minimum and maximum curvature of the mesh patch.

[0027] The average of the minimum and maximum curvatures is taken as the surface curvature radius of the mesh element.

[0028] Furthermore, in step three, the step of extracting the surface normal vector includes:

[0029] Extract three adjacent points of the mesh patch to construct two planar tangent vectors. Solve the cross product of the two planar tangent vectors to obtain the initial normal vector. After normalization, the normal vector is uniformly oriented towards the outside of the automotive irregular part to generate the surface normal vector.

[0030] Furthermore, in step three, the step of assigning the reference charge density includes:

[0031] Planar region: Select multiple measured values ​​of the planar region under standard spraying conditions, and take the average value as the reference charge density of the planar region;

[0032] Convex surface region: The reference charge density of the convex surface region is assigned by the inverse curvature correction formula;

[0033] The concave region of the groove: The reference charge density of the concave region of the groove is assigned by the included angle correction formula;

[0034] Bending edge dead corner area: The base charge density of the bending edge dead corner area is assigned by a fixed attenuation coefficient formula.

[0035] Furthermore, in step three, the expression for the angle between the surface normal vector of the automotive irregular part and the axis vector under the spray gun's spraying posture is as follows:

[0036]

[0037] In the formula: Represents the surface normal vector of an irregularly shaped automotive part; This represents the axis vector under the spray gun's spraying posture.

[0038] Furthermore, in step four, the step of predicting the surface space charge cloud density during the painting process of the automotive irregularly shaped parts includes:

[0039] Determine the type of the sprayed mesh area: convex curved surface area, flat area, concave groove area, or folded edge dead corner area;

[0040] The reference charge density of the spraying mesh is adjusted based on the type of the spraying area of ​​the irregularly shaped automotive part.

[0041] The spraying time, angle between the surface normal vector of the automotive irregular part and the axis vector under the spray gun spraying posture, spraying distance and surface curvature radius of the mesh patch for spraying automotive irregular parts are obtained.

[0042] The space charge cloud density prediction model predicts the space charge cloud density of the mesh surface of the automotive irregular part based on the spraying time, the angle between the surface normal vector of the automotive irregular part and the axis vector under the spraying posture of the spray gun, the spraying distance, and the surface curvature radius.

[0043] Furthermore, in step five, the adaptive adjustment of the spraying scheme includes:

[0044] A preset space charge cloud density threshold is set, and the spraying scheme is adjusted based on the comparison between the predicted space charge cloud density value and the space charge cloud density threshold.

[0045] When the predicted value of the space charge cloud density in the convex curved surface area is greater than the maximum value of the space charge cloud density threshold, the spray gun is moved to that position to spray the same polarity charged coating particles.

[0046] When the predicted value of the space charge cloud density in the concave area of ​​the groove is less than the minimum threshold value of the space charge cloud density, the spray gun is moved to that position to spray charged particles.

[0047] Compared with the prior art, the beneficial effects of the present invention are:

[0048] This invention constructs a space charge cloud density prediction model. During the electrostatic spraying process of automotive irregular parts, the space charge cloud density prediction model predicts the space charge cloud density on the surface of the automotive irregular parts in real time. When the predicted space charge cloud density value in the convex curved area is greater than the maximum value of the space charge cloud density threshold, the spray gun is adaptively moved to that position to spray the same polarity charged coating particles. Similarly, when the predicted space charge cloud density value in the concave area of ​​the groove is less than the minimum value of the space charge cloud density threshold, the spray gun is adaptively moved to that position to spray charged particles. Compared with the prior art, this transforms the space charge cloud density distribution of automotive irregular parts from passive distribution to active control, which can improve the uniform distribution of space charge cloud density and improve the electrostatic spraying effect. Attached Figure Description

[0049] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] I. Pre-processing of irregularly shaped automotive parts

[0052] (a) Dust removal from the surface of irregularly shaped automotive parts

[0053] High-pressure air guns are used to blow away dust and debris from the surface of the irregularly shaped automotive parts to be electrostatically sprayed.

[0054] (ii) Degreasing of the surface of irregularly shaped automotive parts

[0055] First, wipe the surface of the automotive irregular part to be electrostatically sprayed with a degreasing solvent to remove the release agent and oil stains. Then, clean the automotive irregular part to be electrostatically sprayed with deionized water. Finally, dry the automotive irregular part to be electrostatically sprayed in a hot air drying oven to remove the moisture from the surface of the automotive irregular part to be electrostatically sprayed.

[0056] II. Car Parts Hangers

[0057] The irregularly shaped automotive parts to be electrostatically sprayed are vertically suspended on a rotatable hanger made of insulating and antistatic material.

[0058] III. Constructing a space charge cloud density prediction model

[0059] (a) Mesh-based slicing of irregularly shaped automotive parts

[0060] The surface of the factory design drawings for electrostatically sprayed irregularly shaped automotive parts is sliced ​​into a grid.

[0061] (II) Division of Automotive Irregular Parts Areas

[0062] Based on the surface curvature radius and surface opening angle, the surface of the meshed slice is divided into convex curved surface region, planar region, concave groove region and edge dead corner region;

[0063] Convex surface region: If the radius of curvature of the surface is 10mm≤R≤500mm, it is determined to be a convex surface region;

[0064] Planar region: If the radius of curvature R of the surface is greater than 500 mm, it is determined to be a planar region;

[0065] Concave area within a groove: If the opening angle of the curved surface is 30° to 150°, it is determined to be a concave area within a groove;

[0066] Bending edge dead corner area: If the opening angle of the curved surface is <30°, it is determined to be a bending edge dead corner area.

[0067] (III) Structural Parameter Extraction

[0068] Extract structural parameters from convex surface regions, planar regions, concave groove regions, and edge dead corner regions, including surface curvature radius and surface normal vector;

[0069] Surface radius of curvature:

[0070] Extract the coordinates of the four vertices of the mesh face after meshing and slicing;

[0071] Fit a local surface bivariate function using vertex coordinates;

[0072] Find the second-order partial derivative of the bivariate function on the local surface, and solve for the minimum and maximum curvature of the mesh patch.

[0073] Minimum curvature:

[0074]

[0075] Maximum curvature:

[0076]

[0077] In the formula: Indicates the average curvature of the surface; Indicates Gaussian curvature;

[0078] Mean curvature of the surface:

[0079]

[0080] Gaussian curvature:

[0081]

[0082] In the formula: and These represent the first-order partial derivatives of the surface in the x and y directions, respectively, and characterize the tangential slope; , and and represent the second-order partial derivatives, characterizing the degree of local curvature;

[0083] Second-order partial derivative:

[0084]

[0085]

[0086]

[0087] In the formula: a, b, and c represent the fitting coefficients of the local surface bivariate function;

[0088] The average of the minimum and maximum curvatures is taken as the surface curvature radius of the mesh element;

[0089] Surface radius of curvature:

[0090]

[0091] In the formula: This represents the maximum radius of curvature corresponding to the minimum principal curvature. This represents the minimum radius of curvature corresponding to the maximum principal curvature.

[0092] The minimum principal curvature corresponds to the maximum radius of curvature:

[0093]

[0094] The maximum principal curvature corresponds to the minimum radius of curvature:

[0095]

[0096] In the formula: Indicates minimum curvature; Indicates the maximum curvature;

[0097] Surface normal vector: Extract three adjacent points of the mesh patch to construct two planar tangent vectors, solve the cross product of the two planar tangent vectors to obtain the initial normal vector, and after normalization, uniformly face the outside of the automotive irregular part to generate the surface normal vector.

[0098] (iv) Assignment of reference charge density in the region of irregularly shaped automotive parts

[0099] A reference charge density value is assigned to the convex curved surface region, the planar region, the concave region of the groove, and the dead corner region of the folded edge;

[0100] Planar region: Select multiple measured values ​​of the planar region under standard spraying conditions, and take the average value as the reference charge density of the planar region;

[0101] Convex surface region: The reference charge density of the convex surface region is assigned by the inverse curvature correction formula;

[0102] Inverse curvature correction formula:

[0103]

[0104] In the formula: This represents the reference charge density in a planar region; The radius of curvature of a standard planar region; Represents the surface curvature radius of the mesh patch;

[0105] The concave region of the groove: The reference charge density of the concave region of the groove is assigned by the included angle correction formula;

[0106] Angle correction formula:

[0107]

[0108] In the formula: This represents the reference charge density in a planar region; Indicates the included angle of the groove opening;

[0109] Edge dead corner region: The base charge density of the edge dead corner region is assigned by a fixed attenuation coefficient formula;

[0110] Formula for fixed attenuation coefficient:

[0111]

[0112] In the formula: This represents the reference charge density in a planar region.

[0113] (V) Extraction of axis vector under spray gun spraying posture

[0114] Obtain the unit direction vector of the center axis of the spray gun in the spraying posture along the spraying trajectory.

[0115] (vi) Solve for the angle between the normal vector of the curved surface of the vehicle part to be electrostatically sprayed and the axis vector under the spray gun's spraying posture.

[0116] included angle:

[0117]

[0118] In the formula: This represents the normal vector of the curved surface of the automotive irregular part to be electrostatically sprayed; This represents the axis vector under the spray gun's spraying posture;

[0119] (vii) Establishing a space charge cloud density prediction model

[0120] Space charge cloud density prediction model:

[0121]

[0122] In the formula: This represents the reference charge density in a planar region; The radius of curvature of a standard planar region; Represents the surface curvature radius of the mesh patch; This represents the angle between the normal vector of the curved surface of the automotive irregular part to be electrostatically sprayed and the axis vector under the spray gun's spraying posture. Indicates the calibrated airflow loss coefficient; Indicates the spraying distance; Indicates the calibrated charge accumulation decay coefficient; Indicates the spraying time.

[0123] IV. Spray Painting of Irregularly Shaped Automotive Parts

[0124] Electrostatic spraying is performed on irregularly shaped automotive parts that require electrostatic spraying.

[0125] V. Adaptive Adjustment of Painting for Irregularly Shaped Automotive Parts

[0126] (a) Determining the type of paint area on irregularly shaped automotive parts

[0127] The type of sprayed mesh can be determined by the radius of curvature and the opening angle of the surface: convex curved surface area, flat area, concave groove area, or edge dead corner area.

[0128] (ii) Correction of reference charge density

[0129] The reference charge density of the spraying mesh is adjusted based on the type of the spraying area of ​​the irregularly shaped automotive part.

[0130] (iii) Obtaining spraying parameters during the painting process of irregularly shaped automotive parts

[0131] The spraying time, angle between the surface normal vector of the automotive irregular part and the axis vector under the spray gun spraying posture, spraying distance and surface curvature radius of the mesh surface of the automotive irregular part are obtained.

[0132] (iv) Prediction of space charge cloud density

[0133] The space charge cloud density prediction model predicts the space charge cloud density of the mesh surface of the automotive irregular part based on the spraying time, the angle between the surface normal vector of the automotive irregular part and the axis vector under the spraying posture of the spray gun, the spraying distance, and the surface curvature radius.

[0134] (v) Electrostatic spraying adaptive adjustment

[0135] A preset space charge cloud density threshold is set, and the spraying scheme is adjusted based on the comparison between the predicted space charge cloud density value and the space charge cloud density threshold.

[0136] When the predicted value of the space charge cloud density in the convex curved surface area is greater than the maximum value of the space charge cloud density threshold, the spray gun is moved to this position to spray the same polarity charged paint particles, superimpose the space negative charge, strengthen the electrostatic repulsion effect between particles, and cause the paint particles to shift to the surrounding sparsely charged planar area, thus eliminating the charge accumulation phenomenon in the convex curved surface area.

[0137] When the predicted value of the space charge cloud density in the concave area of ​​the groove is less than the minimum threshold value of the space charge cloud density, the spray gun is moved to this position to spray charged particles, forming a closed charge guiding wall at the groove port. Using the repulsive force of like charges, the free paint particles are precisely guided into the groove, making up for the deficiency of insufficient electrostatic adsorption in the groove area.

[0138] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An adaptive electrostatic spraying process for irregularly shaped automotive parts, characterized in that, Includes the following steps:

1. Pre-treatment of irregularly shaped automotive parts to be electrostatically sprayed; 2. The pre-treated automotive irregular parts to be electrostatically sprayed are mounted on a rotatable hanger.

3. Based on the structure of the irregularly shaped automotive parts to be electrostatically sprayed on the rotatable hanger and the spray gun spraying along the preset spraying trajectory, a space charge cloud density prediction model is constructed. IV. Predict the space charge cloud density on the surface of automotive irregular parts during the painting process based on the constructed space charge cloud density prediction model; V. Adaptive spraying is performed by adjusting the spraying scheme based on the predicted space charge cloud density.

2. The adaptive electrostatic spraying process for automotive irregularly shaped parts according to claim 1, characterized in that: Step three, the steps for constructing the space charge cloud density prediction model include: Mesh-slicing is performed on the surface of the factory design drawings for irregularly shaped automotive parts. The surface of the meshed slice is divided into convex curved surface region, planar region, concave groove region and edge dead corner region; Extract the surface curvature radius and surface normal vector of convex surface regions, planar regions, concave regions of grooves, and dead corner regions of folded edges; A reference charge density value is assigned to the convex curved surface region, the planar region, the concave region of the groove, and the dead corner region of the folded edge; Obtain the unit direction vector of the center axis of the spray gun in the spraying posture along the spraying trajectory; Find the angle between the surface normal vector of the irregularly shaped automotive part and the axis vector under the spray gun's spraying posture; Based on the reference charge density of the planar region, the reference surface curvature radius of the planar region, the surface curvature radius of the region, the angle between the normal vector of the curved surface of the automotive irregular part and the axis vector under the spray gun's spraying posture, the calibrated airflow loss coefficient, the spraying distance, the calibrated charge accumulation attenuation coefficient, and the spraying time, a spatial charge cloud density prediction model is constructed, and its expression is: In the formula: This represents the reference charge density in a planar region; The radius of curvature of a standard planar region; Represents the surface curvature radius of the mesh patch; This represents the angle between the surface normal vector of the automotive irregular part and the axis vector under the spray gun's spraying posture; Indicates the calibrated airflow loss coefficient; Indicates the spraying distance; Indicates the calibrated charge accumulation decay coefficient; Indicates the spraying time.

3. The adaptive electrostatic spraying process for automotive irregularly shaped parts according to claim 2, characterized in that: In step three, the meshed slice surface is divided according to the surface curvature radius and the surface opening angle.

4. The adaptive electrostatic spraying process for irregularly shaped automotive parts according to claim 3, characterized in that: Step three, the step of extracting the surface curvature radius, includes: Extract the coordinates of the four vertices of the mesh face after meshing and slicing; Fit a local surface bivariate function using vertex coordinates; Find the second-order partial derivative of the bivariate function on the local surface, and solve for the minimum and maximum curvature of the mesh patch. The average of the minimum and maximum curvatures is taken as the surface curvature radius of the mesh element.

5. The adaptive electrostatic spraying process for automotive irregularly shaped parts according to claim 4, characterized in that: Step three, the step of extracting the surface normal vector, includes: Extract three adjacent points of the mesh patch to construct two planar tangent vectors. Solve the cross product of the two planar tangent vectors to obtain the initial normal vector. After normalization, the normal vector is uniformly oriented towards the outside of the automotive irregular part to generate the surface normal vector.

6. The adaptive electrostatic spraying process for irregularly shaped automotive parts according to claim 5, characterized in that: Step three, the step of assigning the reference charge density, includes: Planar region: Select multiple measured values ​​of the planar region under standard spraying conditions, and take the average value as the reference charge density of the planar region; Convex surface region: The reference charge density of the convex surface region is assigned by the inverse curvature correction formula; The concave region of the groove: The reference charge density of the concave region of the groove is assigned by the included angle correction formula; Bending edge dead corner area: The base charge density of the bending edge dead corner area is assigned by a fixed attenuation coefficient formula.

7. The adaptive electrostatic spraying process for irregularly shaped automotive parts according to claim 6, characterized in that: In step three, the expression for solving the angle between the normal vector of the curved surface of the automotive irregular part and the axis vector under the spray gun's spraying posture is as follows: In the formula: Represents the surface normal vector of an irregularly shaped automotive part; This represents the axis vector under the spray gun's spraying posture.

8. The adaptive electrostatic spraying process for automotive irregularly shaped parts according to claim 7, characterized in that: Step four, the step of predicting the surface space charge cloud density during the painting process of the automotive irregularly shaped parts, includes: Determine the type of the sprayed mesh area: convex curved surface area, flat area, concave groove area, or folded edge dead corner area; The reference charge density of the spraying mesh is adjusted based on the type of the spraying area of ​​the irregularly shaped automotive part. The spraying time, angle between the surface normal vector of the automotive irregular part and the axis vector under the spray gun spraying posture, spraying distance and surface curvature radius of the mesh patch for spraying automotive irregular parts are obtained. The space charge cloud density prediction model predicts the space charge cloud density of the mesh surface of the automotive irregular part based on the spraying time, the angle between the surface normal vector of the automotive irregular part and the axis vector under the spraying posture of the spray gun, the spraying distance, and the surface curvature radius.

9. The adaptive electrostatic spraying process for automotive irregularly shaped parts according to claim 8, characterized in that: Step five, the adaptive adjustment of the spraying scheme, includes: A preset space charge cloud density threshold is set, and the spraying scheme is adjusted based on the comparison between the predicted space charge cloud density value and the space charge cloud density threshold. When the predicted value of the space charge cloud density in the convex curved surface area is greater than the maximum value of the space charge cloud density threshold, the spray gun is moved to that position to spray the same polarity charged coating particles. When the predicted value of the space charge cloud density in the concave area of ​​the groove is less than the minimum threshold value of the space charge cloud density, the spray gun is moved to that position to spray charged particles.

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