Methods and systems for assessing whether paint exhibits pinhole defects.
By comparing the deviation of the paint surface tension curve, the bubble pressure method was used to detect whether the paint has crater defects, which solved the problem of dents in the painted car body, improved the detection efficiency and accuracy, and reduced the cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-12-15
- Publication Date
- 2026-03-10
AI Technical Summary
Existing technologies cannot quickly and accurately detect whether paint materials will produce pinhole defects, which can lead to dents on the painted car body, affecting the quality and efficiency of the coating process. Furthermore, the detection methods are time-consuming and labor-intensive.
By comparing the surface tension curve of the paint under test with that of the standard paint, the surface tension characteristic value is determined using the bubble pressure method to determine whether the paint will produce pinhole defects.
It enables rapid and accurate prevention of paint pinhole defects, improves detection efficiency and accuracy, reduces labor and material costs, and enhances the quality and production efficiency of painted car bodies.
Smart Images
Figure CN116263394B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of vehicle coating quality control technology, specifically relating to a method and system for assessing whether paint has pinhole defects. Background Technology
[0002] In the automotive painting process, paint materials are easily contaminated, leading to dents or depressions on the painted car body, a defect known as pinholes. Pinholes are often called the "cancer" of automotive painting quality. Once pinholes appear on the car body, rework or repair is necessary, severely impacting the first-time inspection pass rate and resulting in a huge waste of manpower and resources. Furthermore, rework or repair affects the decorative properties of the paint film, reduces its corrosion resistance, and can easily cause color differences and uneven thickness on the car body. To reduce and avoid the harm caused by pinholes, the best approach is to prevent pinholes caused by paint material contamination. However, currently, there is no method in the painting industry that can quickly and accurately detect pinholes in paint materials, thus preventing this defect from appearing on the car body.
[0003] Currently, the most common method used in the painting industry is the laboratory spray test. This involves simulating the application of paint materials suspected of having pinholes onto a steel plate (the same plate as the car body) in a laboratory setting. If pinholes appear on the steel plate, the paint material is considered unsuitable for producing pinholes; otherwise, if no pinholes appear, the paint material is considered acceptable and can be applied to the production vehicle. The typical painting area for a car body is 30-60 square meters. 2 The size of the steel plates to be sprayed in the laboratory is generally 0.2-0.4m × 0.1-0.4m (length × width), and the spraying area calculated based on the maximum size is 0.16m². 2 / sheet. If each painted car body has one shrinkage cavity, resulting in a 100% defect rate, and six steel plates are sprayed in the laboratory, the actual detection probability is only 3% (0.16*6 / 30) because the substances causing shrinkage cavity defects in painted car bodies are random. If steel plates of the same area as the car body are sprayed in the laboratory, at least 188 plates would need to be sprayed, leading to significant consumption of laboratory personnel and materials. In laboratory simulations of spraying, the steel plates used for the car body can be replaced with photocopying film, which is more sensitive to shrinkage cavities. However, this still suffers from the problem of insufficient laboratory spraying area, limiting the improvement in the accuracy and efficiency of shrinkage cavity detection.
[0004] Invention Patent Content
[0005] To address the aforementioned problems, this invention aims to provide a method and system for evaluating whether paint will develop pinhole defects, thereby enabling convenient and quick determination before coating to determine whether the paint will develop pinhole defects after coating, improving production efficiency, and reducing labor and material costs. This objective is achieved through the following technical solution:
[0006] This invention first provides a method for assessing whether paint will develop pinhole defects. It evaluates the likelihood of pinhole defects by comparing the deviation between the surface tension curve of the tested paint and that of a standard paint. The principle of this invention is that pinholes on the surface of a painted vehicle body are caused by low-surface-tension contaminants in the paint material. If the surface tension is high, it is impossible for the paint to spread and form pinholes; however, when the surface tension is low, low-surface-tension areas are created during paint film formation, resulting in uneven surface tension. Under the influence of this surface tension difference, the paint material flows from areas of low surface tension to areas of high surface tension, forming recessed cavities in between—the pinholes. This invention measures the change in the characteristic value of the surface tension of the paint material after contamination to determine whether pinholes will form during paint film formation, thereby preventing pinholes in advance and avoiding their impact on coating yield and quality.
[0007] Furthermore, the surface tension curve of the standard paint is defined as the standard curve; the surface tension curve of the paint to be tested is defined as the measured curve. The method includes the following steps:
[0008] Step S10: Store multiple standard curves corresponding to standard paints with various different compositions;
[0009] Step S20: Obtain the measured curve, randomly or according to the instruction select multiple feature points and compare the measured feature values of the measured curve at the selected multiple feature point positions;
[0010] Step S30: Read the standard eigenvalues of the multiple feature points selected in step S20 on the standard curve;
[0011] Step S40: Determine whether the paint will produce pinhole defects based on the deviation of the measured characteristic value from the standard characteristic value.
[0012] Furthermore, the standard curve and the measured curve were determined by the bubble pressure method.
[0013] Furthermore, in step S20, at least 5 feature points are selected, and preferably more than 8 feature points are selected.
[0014] Furthermore, step S20 includes the following steps:
[0015] Step S21: Input the bubble lifetime value set to be detected into the detection instrument. The bubble lifetime value set contains multiple bubble lifetime values between 50ms and 13000ms.
[0016] Step S22: Start the detection program and allow it to complete the measurement of the actual curve within a temperature range of 21 to 25°C;
[0017] Step S23: Read the measured curve;
[0018] Step S24: Randomly or according to instructions select multiple feature points located in the range of 100ms to 10000ms bubble lifetime, and read the measured feature values at the corresponding feature point locations.
[0019] Furthermore, in step S21, the bubble life value group contains at least 10 bubble life values; preferably, it contains at least 20 bubble life values.
[0020] Furthermore, step S10 also stores a preset threshold for measured values defined by the minimum detection value allowed for different feature point positions of different curves and / or a preset threshold for deviation values defined by the maximum detection deviation value allowed for different feature point positions of different curves.
[0021] Furthermore, step S40 includes the following steps:
[0022] Step S41: Determine whether the measured feature value at each feature point location is less than the preset threshold for measured value, or calculate whether the detection deviation between the measured feature value at each selected feature point location and the standard feature value is greater than the preset threshold for deviation value;
[0023] Step S42: Count the feature points whose measured feature values are less than a preset threshold or whose detection deviation values are greater than a preset threshold.
[0024] Step S43: When the count reaches the preset value, it is determined that the paint to be inspected will produce pinhole defects during use. In production practice, the preset value is usually set to a value of 2 to 5 according to the number of feature points selected. In most cases, setting it to 3 can meet a pinhole detection rate of close to 100%.
[0025] The present invention further provides a system for evaluating whether paint has pinhole defects, comprising:
[0026] - Storage module, used to store multiple standard curves corresponding to standard paints with different components and preset thresholds defined according to the minimum detection value allowed at different feature point positions of the corresponding different curves and / or the maximum detection deviation value allowed at each feature point position;
[0027] - The interaction module is used to receive the first and second instructions input by the user, and control the testing instrument to complete the surface tension curve measurement of the paint to be tested according to the first instruction, and read the measured curve obtained by the testing instrument after the test instrument has completed the measurement.
[0028] - Comparison and calculation module, used to compare whether the measured feature value or its detection deviation value of each selected feature point exceeds the preset threshold according to the second instruction;
[0029] - The counting module is used to measure the number of feature points whose measured feature values exceed a preset threshold.
[0030] - The result judgment module determines whether the paint to be inspected will produce pinhole defects based on the number of feature points measured by the counting module.
[0031] Furthermore, the first instruction includes specifying a group of bubble lifetime values for generating the measured curve, and the second instruction includes specifying multiple feature points for comparison with the standard curve, wherein the number of bubble lifetime values contained in the bubble lifetime value group in the first instruction is greater than the number of feature points in the second instruction, and the feature points specified in the second instruction correspond to the corresponding multiple bubble lifetime values in the bubble lifetime value group in the first instruction.
[0032] The beneficial effects of this invention are as follows:
[0033] (1) The present invention can pre-evaluate whether the paint to be tested will produce pinhole defects by means of surface tension curve. The operation is simple and convenient, and the testing time is reduced by about 40% compared with the original method of spray plate method for detecting pinholes.
[0034] (2) The evaluation method of the present invention has a high detection rate. If the paint material is suspected of causing pinholes, the detection rate can be close to or even reach 100%, thereby preventing the occurrence of batch pinhole defects and improving the quality of painted car bodies and production efficiency. Attached Figure Description
[0035] Figure 1 The figure shown is a comparison between the measured curve and the standard curve in Embodiment 2 of the present invention;
[0036] Figure 2 The figure shows the comparison results between the measured feature values and the standard feature values in Embodiment 2 of the present invention;
[0037] Figure 3 The diagram shown is a schematic diagram of Embodiment 3 of the present invention. Detailed Implementation
[0038] The preferred embodiments of the method and system for evaluating whether paint has pinhole defects will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0039] It should be noted that in the following description, the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, in the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0040] Example 1:
[0041] This invention first provides a method for evaluating whether paint produces pinhole defects. The method assesses the potential for pinhole defects by comparing the surface tension curve of the paint under test with that of a standard paint. Specifically, the surface tension curve of the standard paint is defined as the standard curve; the surface tension curve of the paint under test is defined as the measured curve. The method includes the following steps:
[0042] Step S10: Store multiple standard curves corresponding to standard paints with different components, and preset threshold values for measured values defined according to the minimum measured values allowed by the different feature point positions of the corresponding curves;
[0043] Step S21: Input the bubble lifetime value set to be detected into the detection instrument. The bubble lifetime value set contains more than 10 bubble lifetime values between 50ms and 13000ms.
[0044] Step S22: Start the detection program and complete the measurement of the actual curve in the temperature range of 21-25℃ using the SITA differential bubble pressure method;
[0045] Step S23: Read the measured curve;
[0046] Step S24: Randomly or according to instructions select 5 or more feature points located in the range of 100ms to 10000ms bubble lifetime, and read the measured feature values at the corresponding feature point locations.
[0047] Step S30: Read the standard eigenvalues of the multiple feature points selected in step S20 on the standard curve;
[0048] Step S41: Determine whether the measured feature value at each selected feature point is lower than a preset threshold value.
[0049] Step S42: Count the feature points whose measured values are lower than a preset threshold;
[0050] Step S43: When the count reaches 3, it is determined that the paint to be inspected will produce pinhole defects during use.
[0051] In a preferred embodiment, in step S21, the bubble lifetime value group includes more than 20 bubble lifetime values.
[0052] In another preferred embodiment, step S10 stores multiple standard curves corresponding to standard paints with different compositions, and a preset threshold for deviation value defined according to the maximum allowable detection deviation value of different feature point positions corresponding to different curves; and in step S41, the detection deviation value between the measured feature value and the standard feature value at each selected feature point position is calculated, and it is determined whether the detection deviation value exceeds the preset threshold for deviation value. Then, in step S42, feature points whose detection deviation values exceed their preset threshold are counted.
[0053] In other embodiments, the count value for triggering the determination of pinhole defects in step S43 can also be set to 2 or 4 or other values based on the specific paint composition category, the actual number of selected feature points, and actual production experience.
[0054] In a preferred embodiment, when measuring the surface tension curve of the paint to be tested, a cylindrical capillary tube with a diameter of 0.2 mm to 0.5 mm is used. Before the test, the paint to be tested needs to be stirred thoroughly for 2 to 6 hours to ensure the uniformity of the paint.
[0055] Example 2:
[0056] This embodiment provides an example of the process for evaluating whether paint has pinhole defects using the above method, and the verification results, such as... Figure 1 The figure shows a comparison between the measured curve and the standard curve obtained using the method of Example 1, and a display of the measured characteristic values and standard characteristic values at selected characteristic points. In this example, the preset threshold for the measured characteristic value and the standard characteristic value is -1.5 mN / m. That is, when the measured characteristic value is within a deviation of 1.5 mN / m from the standard characteristic value, it is not considered to be out of limit, and this point is not used for counting. As shown in the figure, 22 bubble lifetime values between 50 ms and 13000 ms are set as detection points to generate the measured curve. Then, bubble lifetime values of 100 ms, 500 ms, 2000 ms, 5000 ms, and 10000 ms are selected as 5 characteristic points. The measured characteristic values and standard characteristic values corresponding to the measured curve and the standard curve at these 5 characteristic points are compared. Figure 2 As shown, it can be seen that the measured deviation values of 4 out of the 5 selected feature points exceed the preset threshold of -1.5mN / m, meaning that the measured deviation values of more than 3 feature points exceed the limit. Counting more than 3 instances indicates that the paint will produce pinhole defects in actual application. Actual verification showed that after applying the tested paint B to the painting workshop, the pinhole rate on the painted car body reached 20%, consistent with the evaluation results.
[0057] Example 3:
[0058] This embodiment provides a system for evaluating whether paint has pinhole defects, comprising:
[0059] - Storage module, used to store multiple standard curves corresponding to standard paints with different components and preset thresholds defined according to the minimum detection value allowed at different feature point positions of the corresponding different curves and / or the maximum detection deviation value allowed at each feature point position;
[0060] - The interaction module is used to receive the first and second instructions input by the user, and control the testing instrument to complete the surface tension curve measurement of the paint to be tested according to the first instruction, and read the measured curve obtained by the testing instrument after the test instrument has completed the measurement.
[0061] - Comparison and calculation module, used to compare whether the measured feature value or its detection deviation value of each selected feature point exceeds the preset threshold according to the second instruction;
[0062] - The counting module is used to measure the number of feature points whose measured feature values exceed a preset threshold.
[0063] - The result judgment module determines whether the paint to be inspected will produce pinhole defects based on the number of feature points measured by the counting module.
[0064] - Output module, used to output the judgment result.
[0065] The first instruction includes specifying a group of bubble lifetime values for generating the measured curve, and the second instruction includes specifying multiple feature points for comparison with the standard curve. The number of bubble lifetime values contained in the bubble lifetime value group in the first instruction is greater than the number of feature points in the second instruction, and the feature points specified in the second instruction correspond to the corresponding multiple bubble lifetime values in the bubble lifetime value group in the first instruction.
[0066] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention; the dimensions described in the drawings and embodiments are not related to the specific physical object and are not used to limit the protection scope of the present invention. The physical dimensions can be selected and changed according to actual needs.
Claims
1. A method for assessing whether a paint produces shrinkage defects, characterized in that, The method comprises the following steps: Step S10: storing a plurality of standard curves corresponding to standard paints of different compositions, wherein the standard curves are surface tension curves of the standard paints measured by the bubble pressure method; Step S20: obtaining a measured curve, randomly or according to an instruction, selecting a plurality of feature points, and comparing measured feature values of the measured curve at the selected plurality of feature points, wherein the measured curve is a surface tension curve of the paint to be detected measured by the bubble pressure method; Step S30: reading standard feature values corresponding to the plurality of feature points selected in step S20 on the standard curve; Step S40: determining whether the paint to be detected will produce shrinkage defects according to the deviation of the measured feature values from the standard feature values.
2. The method for assessing whether a paint produces a sink defect according to claim 1, characterized in that, In the step S20, at least 5 feature points are selected.
3. The method for assessing whether a paint produces a sink defect according to claim 2, characterized in that, The step S20 comprises the following steps: Step S21: inputting a bubble lifetime value group to be detected into the detection instrument, wherein the bubble lifetime value group contains a plurality of bubble lifetime values between 50 ms and 13000 ms; Step S22: starting the detection program to complete the measurement of the measured curve at a temperature range of 21-25℃; Step S23: reading the measured curve; Step S24: randomly or according to an instruction, selecting a plurality of feature points located in the interval of 100 ms-10000 ms of the bubble lifetime value, and reading the measured feature values at the positions of the corresponding feature points.
4. The method for assessing whether a paint produces a sink defect according to claim 3, characterized in that, In the step S21, the bubble lifetime value group contains at least 10 bubble lifetime values.
5. The method for assessing whether a paint produces a sink defect according to claim 4, characterized in that, In the step S21, the bubble lifetime value group contains at least 20 bubble lifetime values.
6. The method for assessing whether a paint produces a sink defect according to claim 3, wherein In step S10, the measured value preset threshold value defined according to the minimum detection value allowed at different feature point positions of different curves and / or the deviation value preset threshold value defined according to the maximum detection deviation value allowed at different feature point positions of different curves are also stored.
7. The method for assessing whether a paint produces a sink defect according to claim 6, characterized in that, The step S40 comprises the following steps: Step S41: determining whether the measured feature value at each feature point position is less than the measured value preset threshold value, or calculating whether the detection deviation value between the measured feature value at each selected feature point position and the standard feature value is greater than the deviation value preset threshold value; Step S42: counting the feature points whose measured feature values are less than the measured value preset threshold value or whose detection deviation values are greater than the deviation value preset threshold value; Step S43: determining that the paint to be detected will produce shrinkage defects when used when the count reaches a preset value.
8. A system for evaluating whether a paint produces a sink defect, for implementing the method for evaluating whether a paint produces a sink defect according to any one of claims 1 to 7, characterized in that, The method comprises the following steps: - a storage module for storing a plurality of standard curves corresponding to standard paints of different compositions measured by the bubble pressure method, and preset threshold values defined according to the minimum detection value allowed at different feature point positions of different curves and / or the maximum detection deviation value allowed at each feature point position; - an interactive module for receiving a first instruction and a second instruction input by a user, and controlling the detection instrument to complete the measurement of the surface tension curve of the paint to be detected by the bubble pressure method according to the first instruction, and reading the measured curve detected by the test instrument after the detection of the detection instrument is completed; - a comparison calculating module configured to compare whether the measured characteristic value or the detection deviation value of each selected characteristic point exceeds a preset threshold according to the second instruction; - a counting module configured to count the number of characteristic points whose measured characteristic value exceeds the preset threshold; - a result judging module configured to judge whether the paint to be inspected will produce shrinkage cavity defects according to the number of characteristic points counted by the counting module.
9. The system for assessing whether a paint produces a sink defect according to claim 8, wherein, The first instruction includes a bubble lifetime value group designated for generating a measured curve, and the second instruction includes a plurality of characteristic points designated for comparison with a standard curve, wherein the number of bubble lifetime values contained in the bubble lifetime value group in the first instruction is greater than the number of characteristic points in the second instruction, and the characteristic points designated in the second instruction correspond to a corresponding plurality of bubble lifetime values in the bubble lifetime value group in the first instruction.