阅读说明：本技术 一种扭矩结合转角对拧紧质量监控的方法 (Method for monitoring tightening quality by combining torque with corner ) 是由 李�浩 朱青山 阳玉龙 卢磊 于 2021-07-09 设计创作，主要内容包括：本发明提供一种扭矩结合转角对拧紧质量监控的方法,依据紧固件的目标扭矩获得目标转角及其上下限；当实际扭矩值到达目标扭矩值的上限值,或者实际转角值到达目标转角的上限值时,判断转角-扭矩曲线是否有部分与预设范围重合,预设范围是指目标扭矩允许的上限值、下限值以及目标转角允许的上限值、下限值所限定的范围；当判断结果为转角-扭矩曲线上与预设范围存在重合时,则认定为合格曲线；当判断结果为转角-扭矩曲线与预设范围不重合时,则认为是不合格曲线。通过增加目标转角即拧紧角度参数,在采用扭矩控制的同时,用目标转角作为指标对拧紧状态进行监控的方法,实现对紧固件紧固效果全面/有效地进行监控,弥补单纯使用扭矩监控拧紧效果的缺陷。(The invention provides a method for monitoring tightening quality by combining torque with a corner, which is characterized in that a target corner and upper and lower limits thereof are obtained according to the target torque of a fastener; when the actual torque value reaches the upper limit value of the target torque value or the actual corner value reaches the upper limit value of the target corner, judging whether a part of a corner-torque curve is overlapped with a preset range, wherein the preset range is defined by the upper limit value and the lower limit value allowed by the target torque and the upper limit value and the lower limit value allowed by the target corner; when the judgment result is that the corner-torque curve is coincident with the preset range, the curve is determined to be a qualified curve; and when the judgment result is that the corner-torque curve is not coincident with the preset range, the curve is regarded as an unqualified curve. By increasing the target corner, namely the tightening angle parameter, and adopting the torque control, the tightening state is monitored by using the target corner as an index, the fastening effect of the fastening piece is comprehensively/effectively monitored, and the defect that the tightening effect is monitored by only using the torque is overcome.)

1. A method of monitoring tightening quality in combination with torque and corner, comprising the steps of:

step A1, processing according to a preset torque standard range and a preset corner standard range to obtain a tightening strategy of the fastener in a tightening process;

step A2, the tightening gun performs tightening operation on the fastener according to the tightening strategy, and outputs an actual torque value and an actual turning angle value obtained through collection in the tightening operation process;

step A3, drawing a corner-torque curve according to the actual corner value and the actual torque value;

step A4, judging whether a part of the corner-torque curve is overlapped with a preset range, wherein the preset range is defined by a preset torque standard range and a preset corner standard range;

when the corner-torque curve is coincident with the preset range, the corner-torque curve is used for representing a monitoring result that the tightening quality monitoring is qualified;

and when the corner-torque curve is not coincident with the preset range, the corner-torque curve is used for representing a monitoring result that the screwing quality monitoring is unqualified.

2. A method of monitoring the quality of tightening with torque in combination with rotational angle as set forth in claim 1, wherein in said step a1, said tightening strategy comprises: and stopping executing the tightening operation when the actual torque value reaches the upper limit value of the preset torque standard range or the actual rotation angle value reaches the upper limit value of the preset rotation angle standard range.

3. A method of torque-in-corner tightening quality monitoring according to claim 1, wherein the predetermined standard range of the corner is obtained by:

step B1, selecting a plurality of fasteners as test samples, setting a target torque, an upper torque limit value and a lower torque limit value in a tightening gun, and taking a range defined by the upper torque limit value and the lower torque limit value as the standard torque range;

step B2, the tightening gun respectively performs tightening operation on each test sample so as to obtain the current standard turning angle value of the tightening gun when the actual output torque of the tightening gun reaches the target torque, and thus the standard turning angle value corresponding to all the test samples is obtained;

step B3, randomly extracting a preset number of the standard rotation angle values as sampling data;

step B4, calculating and obtaining a target corner, a corner upper limit value and a corner lower limit value based on the sampling data; and the range limited by the corner upper limit value and the corner lower limit value is defined as the corner standard range.

4. A method for monitoring the quality of tightening with torque-in-rotation angle as set forth in claim 3, characterized in that in step B2, the starting point of the standard rotation angle value is recorded when the actual output torque of the tightening gun reaches 20% of the target torque, and

when the actual output torque of the tightening gun reaches the target torque, recording the end point of the standard turning angle value;

the standard angle value is calculated using the recorded start and end points.

5. A method for monitoring the quality of tightening with torque in combination with the turning angle as set forth in claim 3, wherein said step B3 specifically comprises:

step B30, randomly selecting a preset number from the standard rotation angle values as the sampling data;

step B31, judging whether the sampling data conforms to normal distribution:

if yes, go to step B4;

if not, go to step B32;

and step B32, removing part of the sampling data which do not conform to normal distribution, continuously and randomly extracting a plurality of supplementary sampling data from the rest standard corner values to ensure that the number of the sampling data is the preset number, and continuously performing the step B31.

6. A method of monitoring the quality of tightening of torque in combination with rotational angle as set forth in claim 5, wherein after said step B30, if the sampled data conforms to a normal distribution, before continuing to execute said step B4, the following steps are further executed:

step B33, averagely dividing the sampling data into a plurality of groups;

step B34, calculating the average value and the range of each group of the sampling data, and calculating the total average value and the average range of a preset number of the sampling data according to the average value and the range of each group of the sampling data;

step B35, drawing a mean value control chart by taking the total mean value as a central line, and drawing a range control chart by taking the mean range as a central line; respectively judging whether each group of the sampling data is qualified or not according to the mean control chart and the range control chart:

step B36, respectively judging whether each group of the sampling data is qualified according to the mean control chart and the range control chart:

if the average value is not in the range between the upper control limit and the lower control limit in the average value control map or the range between the upper control limit and the lower control limit in the range control map, indicating that the sampling data of the corresponding group is unqualified, and continuing to the step B37;

if the mean values of all the groups are within the range between the upper control limit and the lower control limit in the mean value control map and all the range between the upper control limit and the lower control limit in the range control map, the sampled data of all the groups are qualified, and the step B4 is continuously executed;

step B37, removing the sampling data of the unqualified group;

and step B38, continuing to randomly select a plurality of the added sample data from the remaining standard rotation angle values which are not decimated to ensure that the number of the sample data is the preset number, and then returning to the step B31.

7. A method for monitoring the quality of tightening with torque combining with a turning angle according to claim 6, wherein in step B4, the total average value is used as the target turning angle, and the upper and lower turning angle values are obtained by the following formulas:

wherein the content of the first and second substances,

CPU＝CPL＝Cpk；

cpk is a set index indicating process capability expectation;

the CPU represents the degree of the total mean value approaching the upper limit value of the standard range of the rotation angle;

CPL represents the degree of the total mean value approaching the lower limit value of the standard range of the rotation angle;

USL represents an upper limit value of the rotation angle standard range;

LSL represents a lower limit value of the rotation angle standard range;

represents the overall mean;

mean range is indicated;

d₂representing a predetermined constant.

8. A method for monitoring the quality of tightening with torque in combination with rotational angle according to claim 6, wherein in step B34, the mean and the range of each set of said sampled data are calculated, and the calculation formula for calculating said total mean and said average range is as follows:

R＝x_max-x_min；

wherein the content of the first and second substances,

represents the overall mean;

mean range is indicated;

n represents the number of sample data in each set of sample data;

x₁、x₂and x_nRepresenting a standard rotation angle value in each set of sampled data;

x_maxa maximum value representing a standard rotation angle value in each set of sample data;

x_mina minimum value representing a standard rotation angle value in each set of sample data;

r represents the range of each group of sampling data;

means representing the mean of each set of sampled data;

k denotes the number of groups into which a preset number of sample data are equally divided.

9. The method for monitoring the tightening quality through the combination of the torque and the rotation angle as claimed in claim 6, wherein in the step B35, the calculation formula of the upper control limit and the lower control limit in the mean control map is as follows:

wherein the content of the first and second substances,

representing the upper control limit in the mean control map;

representing a lower control limit in the mean control map;

mean range is indicated;

represents the overall mean;

A₂the calculation coefficients are used to represent the upper and lower control limits of the calculation in the mean value control map.

10. A method for monitoring the tightening quality by combining the torque and the rotational angle as set forth in claim 6, wherein in said step B35, the calculation formula of the upper control limit and the lower control limit in the worst control map is as follows:

wherein the content of the first and second substances,

UCL_Rrepresenting the upper control limit in the range control map;

LCL_Rrepresenting a lower control limit in the range control map;

mean range is indicated;

D₄calculating a calculation coefficient used by the upper control limit in the range control chart respectively;

D₃and calculating a calculation coefficient used for the lower control limit in the respective range control map.

Technical Field

The invention relates to the technical field of fastener tightening control, in particular to a method for monitoring tightening quality by combining torque with a corner.

Background

In order to realize the detection and control of the tightening effect of the workpiece, a tightening system of a matched controller is adopted to tighten the fastener under the common condition, and a torque monitoring method is adopted to control the torque of the fastener, namely, the torque result value is in the range of the design requirement as the only judgment standard for the qualified tightening of the fastener. When the quality of a fastener is poor or the quality of a nut/thread sleeve and the like matched with the fastener is not good (such as welding slag/uneven coating of anti-loose glue and the like in burrs/holes), the fastening resistance of the fastener is high in the fastening process, the qualified false image of fastening torque can be shown, the fastener is not contacted or pressed with a workpiece at all in practice, and therefore the torque result is not strict as the only judgment standard alone.

Disclosure of Invention

Based on the problems, the invention provides a method for monitoring the tightening quality by combining torque with a corner, and aims to solve the technical problems that the tightening effect is not accurate only by using torque judgment in the prior art and the like.

A method of torque-in-corner tightening quality monitoring comprising the steps of:

step A1, processing according to a preset torque standard range and a preset corner standard range to obtain a tightening strategy of the fastener in a tightening process;

step A2, the tightening gun performs tightening operation on the fastener according to a tightening strategy, and outputs an actual torque value and an actual turning angle value which are acquired in the tightening operation process;

step A3, drawing a corner-torque curve according to the actual corner value and the actual torque value;

step A4, judging whether a part of the corner-torque curve is overlapped with a preset range, wherein the preset range is defined by a preset torque standard range and a preset corner standard range;

when the corner-torque curve is coincident with the preset range, the monitoring result is used for representing that the tightening quality is qualified;

and when the corner-torque curve is not coincident with the preset range, the monitoring result is used for indicating that the screwing quality monitoring is unqualified.

Further, in step a1, the tightening strategy includes: and stopping executing the tightening operation when the actual torque value reaches the upper limit value of the preset torque standard range or the actual rotation angle value reaches the upper limit value of the preset rotation angle standard range.

Further, the preset standard range of the rotation angle is obtained through the following steps:

b1, selecting a plurality of fasteners as test samples, setting a target torque, an upper torque limit value and a lower torque limit value in a tightening gun, and using a range limited by the upper torque limit value and the lower torque limit value as a standard torque range;

step B2, the tightening gun respectively performs tightening operation on each test sample so as to obtain the current standard turning angle value of the tightening gun when the actual output torque of the tightening gun reaches the target torque, and thus the standard turning angle values corresponding to all the test samples are obtained;

step B3, randomly extracting a preset number of standard rotation angle values as sampling data;

step B4, calculating and obtaining a target corner, a corner upper limit value and a corner lower limit value based on the sampling data; the range defined by the rotation angle upper limit value and the rotation angle lower limit value is a rotation angle standard range.

Further, in step B2, when the actual output torque of the tightening gun reaches 20% of the target torque, the start point of the standard turning angle value is recorded, and

when the actual output torque of the tightening gun reaches the target torque, recording the end point of the standard turning angle value;

the standard angle value is calculated using the recorded start and end points.

Further, step B3 specifically includes:

step B30, randomly selecting a preset number from the standard rotation angle values as sampling data;

step B31, judging whether the sampling data conforms to normal distribution:

if yes, go to step B4;

if not, go to step B32;

and step B32, removing partial sampling data which do not conform to normal distribution, continuously and randomly extracting a plurality of complementary sampling data from the rest standard corner values to ensure that the number of the sampling data is a preset number, and continuing the step B31.

Further, after the step B30, if the sampled data conforms to the normal distribution, before continuing to perform the step B4, the following steps are performed:

step B33, averagely dividing the sampling data into a plurality of groups;

step B34, calculating the average value and the range of each group of sampling data, and calculating the total average value and the average range of the sampling data with the preset number according to the average value and the range of each group of sampling data;

step B35, drawing a mean value control chart by taking the total mean value as a center line, and drawing a range control chart by taking the mean range as a center line; and respectively judging whether each group of sampling data is qualified or not according to the mean control chart and the range control chart:

and step B36, respectively judging whether each group of sampling data is qualified according to the mean control chart and the range control chart:

if the average value is not in the range between the upper control limit and the lower control limit in the average value control map or the extreme difference is not in the range between the upper control limit and the lower control limit in the extreme difference control map, indicating that the sampling data of the corresponding group is unqualified, and continuing to the step B37;

if the mean values of all the groups are in the range between the upper control limit and the lower control limit in the mean value control map and all the range between the upper control limit and the lower control limit in the range difference control map, the sampled data of all the groups are qualified, and the step B4 is continuously executed;

step B37, removing unqualified group of sampling data;

and step B38, randomly selecting a plurality of added sample data from the remaining standard rotation angle values which are not selected to ensure that the number of the sample data is a preset number, and then returning to step B31.

Further, in step B4, the total average value is used as the target rotation angle, and the rotation angle upper limit value and the rotation angle lower limit value are obtained by using the following formulas:

wherein the content of the first and second substances,

CPU＝CPL＝Cpk；

cpk is a set index indicating process capability expectation;

the CPU represents the degree of the total mean value approaching the upper limit value of the standard range of the rotation angle;

CPL represents the degree of the total mean value approaching the lower limit value of the standard range of the rotation angle;

USL represents the upper limit value of the corner standard range;

LSL represents the lower limit of the standard range of the turning angle;

represents the overall mean;

mean range is indicated;

d₂representing a predetermined constant.

Further, in step B34, the calculation formula for calculating the mean and the range of each group of sample data, and calculating the total mean and the average range is as follows:

R＝x_max-x_min；

wherein the content of the first and second substances,

represents the overall mean;

mean range is indicated;

n represents the number of sample data in each set of sample data;

x₁、x₂and x_nRepresenting a standard rotation angle value in each set of sampled data;

x_maxa maximum value representing a standard rotation angle value in each set of sample data;

x_mina minimum value representing a standard rotation angle value in each set of sample data;

r represents the range of each group of sampling data;

means representing the mean of each set of sampled data;

k denotes the number of groups into which a preset number of sample data are equally divided.

Further, in step B35, the calculation formulas of the upper control limit and the lower control limit in the mean value control map are as follows:

wherein the content of the first and second substances,

representing the upper control limit in the mean control map;

representing a lower control limit in the mean control map;

mean range is indicated;

represents the overall mean;

A₂the calculation coefficients are used to represent the upper and lower control limits of the calculation in the mean value control map.

Further, in step B35, the calculation formulas of the upper control limit and the lower control limit in the range control map are as follows:

wherein the content of the first and second substances,

UCL_Rrepresenting the upper control limit in the range control map;

LCL_Rrepresenting a lower control limit in the range control map;

mean range is indicated;

D₄on the calculation control in the differential range control chartLimiting the used calculation coefficients;

D₃and calculating a calculation coefficient used for the lower control limit in the respective range control map.

The beneficial technical effects of the invention are as follows: by increasing the target corner, namely the tightening angle parameter, and adopting the torque control, the tightening state is monitored by using the target corner as an index, the fastening effect of the fastening piece is comprehensively/effectively monitored, and the defect that the tightening effect is monitored by only using the torque is overcome.

Drawings

FIG. 1 shows constants used for control of a map;

FIG. 2 is a schematic representation of a pass curve and a fail curve;

FIG. 3 shows preset ranges defined by upper and lower limits of target torque and upper and lower limits of target steering angle;

FIG. 4 shows a rating criterion for an expected value Cpk;

FIG. 5 is a flow chart illustrating the steps of a method of torque-in-corner tightening quality monitoring according to the present invention;

6-8 are flowcharts illustrating steps of a target torque acquisition method of the present invention;

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.

Referring to fig. 1-7, the present invention provides a method for monitoring tightening quality in combination with torque and turning angle, comprising the steps of:

step A1, processing according to a preset torque standard range and a preset corner standard range to obtain a tightening strategy of the fastener in a tightening process;

step A2, the tightening gun performs tightening operation on the fastener according to a tightening strategy, and outputs an actual torque value and an actual turning angle value which are acquired in the tightening operation process;

step A3, drawing a corner-torque curve according to the actual corner value and the actual torque value;

step A4, judging whether a part of the corner-torque curve is overlapped with a preset range, wherein the preset range is defined by a preset torque standard range and a preset corner standard range;

and when the corner-torque curve is coincident with the preset range, determining the curve as a qualified curve, and using the qualified curve to represent a monitoring result of the screwing quality monitoring.

When the corner-torque curve is not coincident with the preset range, determining that the curve is an unqualified curve; and the monitoring result is used for indicating that the tightening quality monitoring is unqualified.

Further, in step a1, the tightening strategy includes: and stopping executing the tightening operation when the actual torque value reaches the upper limit value of the preset torque standard range or the actual rotation angle value reaches the upper limit value of the preset rotation angle standard range.

Specifically, the target rotation angle is also called a fastening rotation angle, which indicates an angle through which the fastening member rotates from a set torque point until the target torque, and is generally represented by θ.

Specifically, the set torque point generally refers to a torque value at 20% of the target torque.

Specifically, the curve passing represents that the fastening torque passes, and the curve failing represents that the fastening torque fails. For example, if the actual tightening resistance is large and the target torque is reached but the target turning angle is not reached, the tightening is not qualified. The fastening effect of the fastening piece is comprehensively/effectively monitored by combining the torque and the corner, and the defect of a torque method is overcome. As shown in fig. 2, the target torque is up, but the turning angle is not up, so that it is a fail curve.

Specifically, the preset range is a range defined by an upper limit value and a lower limit value of the target torque allowance and an upper limit value and a lower limit value of the target steering angle allowance, as shown in fig. 3.

Further, the preset standard range of the rotation angle is obtained through the following steps:

b1, selecting a plurality of fasteners as test samples, setting a target torque, an upper torque limit value and a lower torque limit value in a tightening gun, and using a range limited by the upper torque limit value and the lower torque limit value as a standard torque range;

step B2, the tightening gun respectively performs tightening operation on each test sample so as to obtain the current standard turning angle value of the tightening gun when the actual output torque of the tightening gun reaches the target torque, and thus the standard turning angle values corresponding to all the test samples are obtained;

step B3, randomly extracting a preset number of standard rotation angle values as sampling data;

step B4, calculating and obtaining a target corner, a corner upper limit value and a corner lower limit value based on the sampling data; the range defined by the rotation angle upper limit value and the rotation angle lower limit value is a rotation angle standard range.

Specifically, in step B3, sampling is performed by a scientific sampling method in SPC. In particular, a systematic random sampling method, i.e. a sampling in which samples are taken from the population at regular intervals as samples, may be used.

Specifically, for each test sample tested, a torque-rotation angle curve was obtained. Then, sampling is performed on the same point on the torque-rotation angle curve, and preferably, sampling is performed on a rotation angle value corresponding to the set target torque.

Further, step B2 includes: the tightening gun is performing the tightening process, as a starting point for recording the turning angle value when the actual torque value of the tightening gun reaches 20% of the target torque, and

when the actual output torque of the tightening gun reaches the target torque, recording the end point of the standard turning angle value;

the standard angle value is calculated using the recorded start and end points.

Specifically, the turning angle θ at 20% of the target torque is set to 0, i.e., the turning angle starting point, and the tightening is continued by applying the torque, and the calculation of the turning angle of the fastener is started.

Further, the step B3 specifically includes the following steps:

step B30, randomly extracting a preset number from the standard rotation angle value to obtain sampling data;

step B31, judging whether the sampled data extracted randomly conforms to normal distribution:

if yes, go to step B4;

if not, go to step B32;

and step B32, removing partial sampling data which do not conform to normal distribution, continuously randomly extracting a plurality of added sampling data from the rest standard corner values, ensuring the number of the sampling data to be a preset number, and continuing the step B31.

Specifically, whether the sampling data comply with the standard of normal distribution or not is checked through the p value of the normal distribution. p-values are statistical significance.

Specifically, if the sampled data does not conform to the normal distribution, the reasons for the non-conformity can be found, and the steps B31-B32 are repeated after the reasons for the non-conformity are eliminated and re-sampling is carried out.

Further, after the step B30, if the sampled data conforms to the normal distribution, before continuing to perform the step B4, the following steps are performed:

step B33, averagely dividing a preset number of sampling data into a plurality of groups;

step B34, calculating the average value and the range of each group of sampling data, and calculating the total average value and the average range of the sampling data with the preset number according to the average value and the range of each group of sampling data;

step B35, drawing a mean value control chart by taking the total mean value as a center line, and drawing a range control chart by taking the mean range as a center line;

and step B36, respectively judging whether each group of sampling data is qualified according to the mean control chart and the range control chart: judging whether the average value of each group is in the range between the upper control limit and the lower control limit in the average value control chart, and simultaneously judging whether the range of each group is in the range between the upper control limit and the lower control limit of the range control chart;

when the average value is not in the range between the upper control limit and the lower control limit in the average value control map or the extreme difference is not in the range between the upper control limit and the lower control limit in the extreme difference control map, the sampling data of the corresponding group is unqualified, and the step B37 is continued;

if the mean values of all the groups are in the range between the upper control limit and the lower control limit in the mean value control map and all the range between the upper control limit and the lower control limit in the range difference control map, the sampled data of all the groups are qualified, and the step B4 is continuously executed;

step B37, rejecting unqualified group sample data, namely rejecting group sample data with a mean value not within the range between the upper control limit and the lower control limit in the mean value control chart, and rejecting group sample data with a range not within the range between the upper control limit and the lower control limit in the range control chart;

and B38, randomly selecting a plurality of added sample data from the remaining decimated standard rotation angle values to ensure that the number of sample data is a preset number, and then returning to B31.

Specifically, the number of sample data is 30, and 30 sample data are divided into 10 groups on average, each group including 3 rotation angle values.

Specifically, 30 sampling data are averagely divided into 10 groups according to the sequence of sampling time, and each group comprises 3 rotation angle values.

Specifically, a minitab tool is adopted to draw a mean range extreme control chart so as to judge the stability of the process, the instability of the process, search the cause of the non-conformity, and re-sample and repeat the steps B31-B32 and B33-B38 after the cause of the non-conformity is eliminated.

Further, in step B4, the total average value is used as the target rotation angle, and the rotation angle upper limit value and the rotation angle lower limit value are obtained by using the following formulas:

wherein the content of the first and second substances,

CPU＝CPL＝Cpk；

cpk is a set index indicating process capability expectation;

the CPU represents the degree of the total mean value approaching the upper limit value of the standard range of the rotation angle;

CPL represents the degree of the total mean value approaching the lower limit value of the standard range of the rotation angle;

USL represents the upper limit value of the corner standard range;

LSL represents the lower limit of the standard range of the turning angle;

represents the overall mean;

mean range is indicated;

d₂representing a predetermined constant.

In particular, d₂A divisor for estimating the standard deviation in the range control chart is shown.

Further, in step B34, the calculation formula for calculating the mean and the range of each group of sample data, and calculating the total mean and the average range is as follows:

R＝x_max-x_min；

wherein the content of the first and second substances,

represents the overall mean;

mean range is indicated;

n represents the number of sample data in each set of sample data;

x₁、x₂and x_nRepresenting a specific value, namely a standard rotation angle value, in each set of sampling data;

x_maxa maximum value representing a standard rotation angle value in each set of sample data;

x_mina minimum value representing a standard rotation angle value in each set of sample data;

r represents the range of each group of sampling data;

means representing the mean of each set of sampled data;

k denotes the number of groups into which a preset number of sample data are equally divided.

Wherein, the standard deviation calculation formula of X is as follows:

is x standard deviation, d₂Representing estimated standard deviations in range control chartsThe divisor used.

The standard deviation of (a) is calculated as follows:

wherein the content of the first and second substances,is composed ofStandard deviation of (2).

Further, in step B35, the calculation formulas of the upper control limit and the lower control limit in the mean value control map are as follows:

wherein the content of the first and second substances,

representing the upper control limit in the mean control map;

representing a lower control limit in the mean control map;

mean range is indicated;

represents the overall mean;

A₂the calculation coefficients are used to represent the upper and lower control limits of the calculation in the mean value control map.

Further, in step B35, the calculation formulas of the upper control limit and the lower control limit in the range control map are as follows:

wherein the content of the first and second substances,

UCL_Rrepresenting the upper control limit in the range control map;

LCL_Rrepresenting a lower control limit in the range control map;

mean range is indicated;

D₄calculating a calculation coefficient used by the upper control limit in the range control chart respectively;

D₃and calculating a calculation coefficient used for the lower control limit in the respective range control map.

Specifically, the correlation constants of the control map are shown in fig. 1.

Specifically, the Cpk rating scale is shown in fig. 4.

Further, step a2, the tightening gun is performing the tightening process, and when the actual torque value of the tightening gun reaches 20% of the target torque, it is used as the starting point for recording the actual turning angle value.

Specifically, the fastening rotation angle theta, namely the range of the target rotation angle, is reasonably set, the theta is set to enter a tightening system, the target rotation angle and the upper limit value and the lower limit value of the target rotation angle are redeveloped according to the requirements of fasteners of different batches, and the torque rotation angle control is optimized. The torque angle monitoring method is started. The position of unqualified point of fastener quality can be effectively identified, the problems of repeated screwing and the like can be identified, various risks caused by the quality problem of the fastener are further eliminated, the application range is wide, the flexibility is high, and the development of work such as process optimization/part quality optimization/process management and control is facilitated.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.