Quality inspection method for screw tightening device

Abstract

According to the quality inspection method for the screw tightening device, the defects in the prior art are overcome, comprehensive judgment is carried out according to various parameters, and whether a screw is tightened in place or not is accurately detected; the method is implemented according to the following steps: determining an initial detection distance L0; in the screw tightening process, L0 is equal to 2 * r0; the screw position or the screw displacement difference is detected, if the displacement difference is within the allowable tolerance, whether characteristics exist is detected, if the screw exceeds the set position or the displacement difference is equal to 0, an abnormal alarm is given, and characteristic detection continues after adjustment; the characteristics of the tightened screw comprise a down pressure parameter, and an offset drilling alarm parameter and a screw loose and interference alarm parameter are determined according to the torque curve characteristics; if all the parameters cannot be met, an abnormal alarm is given out; if the characteristic parameters after the screw is tightened are met, screw tightening is completed, and the next cycle is started; the device can be widely applied to the field of screw tightening detection.

Description

Technical Field

[0001] The invention relates to a quality inspection method for a screw tightening device, belonging to the technical field of screw tightening detection. Background Art

[0002] For the screw connection process, the state of the screw when it is finally tightened is very critical. The height of the screw head position, the torque when the screw is tightened, the speed during the tightening process, and the downward pressure of the cutter head may all affect the final connection quality. Therefore, judging the screw tightening process is particularly critical. However, current detection methods mostly only limit the maximum output torque. Summary of the invention

[0003] The present invention overcomes the shortcomings of the prior art and provides a quality inspection method for a screw tightening device, which makes a comprehensive judgment based on multiple parameters and accurately detects whether the screw is tightened in place.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a quality inspection method for a screw tightening device, which is implemented according to the following steps: The first step is to determine the starting detection distance L0; During the screw tightening process, L0=2*r0; where r0 is the screw pitch; The second step is feature detection; Detect the screw position or screw displacement difference. If the displacement difference is within the allowable tolerance, detect whether it has the feature. If the screw exceeds the set position or the displacement difference is equal to 0, an abnormal alarm is issued and the feature detection continues after waiting for adjustment; The third step is to determine whether it has the characteristics after the screw is tightened; The characteristics of the screw after tightening include the downward pressure parameter, the deviation drill alarm parameter and the slipping and interference alarm parameter determined according to the torque curve characteristics; if all the above parameters cannot be met, an abnormal alarm is issued; Step 4: If the characteristic parameters after the screw is tightened in step 3 are met, the screw tightening is completed and the next cycle is entered.

[0005] Furthermore, the method for determining the downforce parameter is as follows: If the bottom layer is aluminum: The downforce setting should satisfy: 4α≤F0≤6α+3α*(thk-0.6); If the bottom layer is a combination of steel; The downforce setting should satisfy: 3α≤F0≤7α+3α*(thk-0.6); Where: F0 is the downforce; thk is the thickness of the bottom layer; α is the downforce coefficient.

[0006] Furthermore, according to the torque curve characteristics, the method for determining the deviation drilling alarm parameters and the slipping and interference alarm parameters is as follows: Assume n is a variable between [0, N-1]; T theory =(rpm0 / 60)*η; T rate =(Tmax-Tmin) / N; T diff =Torque[n+1]-Torque[n]; If there is a deviation in the drilling, T will appear. diffmin <0.6*T rate , or T diffmax >1.3*T rate ; The data shows serious polarization, poor consistency, and non-equivalence increasing trend; In order to eliminate this defect, it is necessary to make a biased drilling judgment, that is, for each T diff Need to meet T diff ≥0.6*T rate ,T diffmax N-1 T diff The maximum value among them, and T diffmax ≤1.3*T rate ; When T rate >1.5*T theory When the lower end of the screw interferes with other parts, the screw becomes stuck. Similarly, when T rate <0.8*T theory When T rate ≥0.8, and T rate ≤1.5*T theory When the feature is met, it is determined that the feature search fails, otherwise it is determined that the feature search fails and an alarm is issued; Where: Torque[N] is the torque value sequence of the last N sampling cycles ending when the set tightening torque is reached; Tmax is the maximum torque value in N sampling cycles; Tmin is the minimum torque value in N sampling periods; T diff is the torque difference between every two sampling periods; T rate is the slope of the last N sampling periods; η is the torque rise coefficient during the torque tightening process; rpm0 is the set torque speed; T theory is the theoretical torque rise rate.

[0007] Compared with the prior art, the present invention has the following beneficial effects: the present invention sets a detection reference for the screw to be detected by setting a starting detection distance of the screw, and then determines the deviation drill alarm parameter and the slipping thread and interference alarm parameter according to the down force parameter and the torque curve characteristics, and makes a comprehensive judgment based on these parameters to accurately detect whether the screw is tightened in place. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention will be further described below in conjunction with the accompanying drawings.

[0009] Figure 1 It is a schematic diagram of the process framework of the present invention.

[0010] Figure 2 It is a schematic diagram of the state when the screw is drilled off-center in the present invention.

[0011] Figure 3 It is a schematic diagram of the state when the screws are interfered and stuck in the present invention.

[0012] Figure 4 This is the first experimental data of the lower pressure test in the present invention.

[0013] Figure 5 This is the second experimental data of the lower pressure test in the present invention.

[0014] Figure 6 This is the third pressure test experimental data of the present invention.

[0015] Figure 7 This is the fourth experimental data of the lower pressure test in the present invention.

[0016] Figure 8 This is the fifth experimental data of the lower pressure test in the present invention.

[0017] Fig. 9 This is the sixth experimental data of the lower pressure test in the present invention.

[0018] Fig.10 This is the lower pressure test experimental data seven of the present invention.

[0019] Fig.11 This is the lower pressure test experimental data eight of the present invention.

[0020] Fig.12 This is the lower pressure test experimental data nine of the present invention.

[0021] Fig.13 This is the lower pressure test experimental data ten of the present invention.

[0022] Fig.14This is the lower pressure test experimental data eleven in the present invention.

[0023] Fig.15 This is the lower pressure test experimental data twelve of the present invention.

[0024] Fig.16 This is a test data diagram of the eccentric drilling alarm in the present invention.

[0025] Fig.17 This is the test data of the slipping & interference alarm in the present invention Figure 1 .

[0026] Fig.18 This is the test data of the slipping & interference alarm in the present invention Figure 2 .

[0027] Fig.19 This is the test data of the slipping & interference alarm in the present invention Figure 3 . DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments.

[0029] like Figure 1 As shown, the quality inspection method for a screw tightening device of the present invention is implemented according to the following steps: The first step is to determine the starting detection distance L0; During the screw tightening process, L0=2*r0; where r0 is the screw pitch; The second step is feature detection; Detect the screw position or screw displacement difference. If the displacement difference is within the allowable tolerance, detect whether it has the feature. If the screw exceeds the set position or the displacement difference is equal to 0, an abnormal alarm is issued and the feature detection continues after waiting for adjustment; The third step is to determine whether it has the characteristics after the screw is tightened; The characteristics of the screw after tightening include the downward pressure parameter, the deviation drill alarm parameter and the slipping and interference alarm parameter determined according to the torque curve characteristics; if all the above parameters cannot be met, an abnormal alarm is issued; Step 4: If the characteristic parameters after the screw is tightened in step 3 are met, the screw tightening is completed and the next cycle is entered.

[0030] The implementation process is as follows: 1. Downforce setting Different downward pressures may affect the connection quality and process time. Too little downward pressure may cause the screw to rotate in place after tapping during the tightening process, directly damaging the thread. Too much downward pressure may cause the screw to not be screwed in along the thread, but to be directly rushed out from the thread position under the downward pressure, thereby damaging the thread and causing thread slippage. Therefore, too little or too much downward pressure may cause material slippage during the tightening process, and the setting of downward pressure is also a relatively important parameter.

[0031] Figures 4 to 15 This is the process data of the test of the present invention, where × represents yes and ○ represents no.

[0032] For common application materials, the present invention selects 3 types of aluminum and 3 types of steel respectively, and obtains the following from the above data: If the bottom layer is aluminum: The downforce setting should satisfy: 4α≤F0≤6α+3α*(thk-0.6); If the bottom layer is a combination of steel; The downforce setting should satisfy: 3α≤F0≤7α+3α*(thk-0.6); Where: F0 is the downforce; thk is the thickness of the bottom layer; α is the downforce coefficient.

[0033] 2. Determine the characteristics Through a lot of experimental analysis, if a screw is tightened normally and has no tilt connection, its torque curve has the following characteristics: Assumptions Torque[N] is the torque value sequence of the last N sampling cycles ending when the set tightening torque is reached; Tmax is the maximum torque value in N sampling cycles; Tmin is the minimum torque value in N sampling periods; T diff is the torque difference between every two sampling periods; T rate is the slope of the last N sampling periods; η is the torque rise coefficient during the torque tightening process; rpm0 is the set torque speed; T theory is the theoretical torque rising rate; Where: n is a variable between [0, N-1], T theory =(rpm0 / 60)*η; T rate =(Tmax-Tmin) / N.

[0034] 2.1、Drilling deviation alarm Test data chart such as Fig.16 shown.

[0035] T diff =Torque[n+1]-Torque[n], according to the test data, when the deviation of drilling occurs, Figure 2 When some data will appear T diffmin <0.6*T rate or T diffmax Will be greater than 1.3*T rate The data shows serious polarization, poor consistency, and non-equivalent increasing trend. Therefore, in order to eliminate this defect, it is necessary to make a biased drilling judgment, that is, for each T diff Need to meet T diff ≥0.6*T rate ,T diffmax N-1 T diff The maximum value among them, and T diffmax ≤1.3*T rate ; 2.2. Slippage & Interference Alarm T rate Test data chart such as Figure 17 to Figure 19 .

[0036] According to the test data, when T rate >1.5*T theory When the screw is in the wrong position, there is an 85% probability that the lower end of the screw interferes with other parts, such as Figure 3 As shown, the screw is stuck and the screw is stuck. rate <0.8*T theory When T is 0, there is an 80% probability that the screw has slipped. Therefore, in order to eliminate the connection defects caused by screw interference and slipping, it is necessary to determine the torque rise rate. rate ≥0.8, and T rate ≤1.5*T theory In other cases, it is judged that the feature search fails.

[0037] The present invention sets a detection reference for the detected screw by setting a starting detection distance of the screw, and then determines the deviation drill alarm parameter and the slipping thread and interference alarm parameter according to the downward force parameter and the torque curve characteristics, and makes a comprehensive judgment based on these parameters to accurately detect whether the screw is tightened in place.

[0038] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A quality inspection method for a screw tightening device, characterized in that: Follow these steps to implement: The first step is to determine the starting detection distance L0; During the screw tightening process, L0=2*r0; where r0 is the screw pitch; The second step is feature detection; Detect the screw position or screw displacement difference. If the displacement difference is within the allowable tolerance, detect whether it has the feature. If the screw exceeds the set position or the displacement difference is equal to 0, an abnormal alarm is issued and the feature detection continues after waiting for adjustment; The third step is to determine whether it has the characteristics after the screw is tightened; The characteristics of the screw after tightening include the downward pressure parameter, the deviation drill alarm parameter and the slipping and interference alarm parameter determined according to the torque curve characteristics; if all the above parameters cannot be met, an abnormal alarm is issued; Step 4: If the characteristic parameters after the screw is tightened in step 3 are met, the screw tightening is completed and the next cycle is entered.

2. A quality inspection method for a screw tightening device according to claim 1, characterized in that: The method for determining the downforce parameter is as follows: If the bottom layer is aluminum: The downforce setting should satisfy: 4α≤F0≤6α+3α*(thk-0.6); If the bottom layer is a combination of steel; The downforce setting should satisfy: 3α≤F0≤7α+3α*(thk-0.6); Where: F0 is the downforce; thk is the thickness of the bottom layer; α is the downforce coefficient.

3. A quality inspection method for a screw tightening device according to claim 1, characterized in that: According to the torque curve characteristics, the method for determining the deviation drilling alarm parameters and the slipping and interference alarm parameters is as follows: Assume n is a variable between [0, N-1]; T theory =(rpm0 / 60)*η; <h2 style=";text-align:left;direction:ltr">T<h2 style=";text-align:left;direction:ltr"> rate <h2 style=";text-align:left;direction:ltr"> =(Tmax-Tmin) / N; T diff =Torque[n+1]-Torque[n]; If there is a deviation in the drilling, T will appear. diffmin <0.6*T rate , or T diffmax >1.3*T rate ; The data shows serious polarization, poor consistency, and non-equivalence increasing trend; In order to eliminate this defect, it is necessary to make a biased drilling judgment, that is, for each T diff Need to meet T diff ≥0.6*T rate ,T diffmax N-1 T diff The maximum value among them, and T diffmax ≤1.3*T rate ; When T rate >1.5*T theory When the lower end of the screw interferes with other parts, the screw becomes stuck. Similarly, when T rate <0.8*T theory When the screw has slipped, in order to eliminate the connection defects caused by screw interference and slipping, it is necessary to determine the torque rise rate. rate ≥0.8, and T rate ≤1.5*T theory When the feature is met, it is determined that the feature search fails, otherwise it is determined that the feature search fails and an alarm is issued; Where: Torque[N] is the torque value sequence of the last N sampling cycles ending when the set tightening torque is reached; Tmax is the maximum torque value in N sampling cycles; Tmin is the minimum torque value in N sampling periods; T diff is the torque difference between every two sampling periods; T rate is the slope of the last N sampling periods; η is the torque rise coefficient during the torque tightening process; rpm0 is the set torque speed; T theory is the theoretical torque rise rate.

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