Screwing and online control method for screwing operations

Abstract

The present invention relates to a method for screwing and quality control of screwing operations on a production line comprising a succession of workstations. The method comprises at least: - a step of performing at least one screwing operation on a structure to be assembled at at least some of said workstations, each screwing operation performed at a workstation being carried out using a screwing device dedicated to the corresponding workstation and screwing operation; - a quality control step of said at least one screwing operation. According to the invention, the quality control step of a screwing operation is carried out at a workstation subsequent to the workstation where said screwing operation was performed, said quality control step being carried out using a screwing device dedicated to said subsequent workstation. Fig. 3

Description

Title of the invention: Method for screwing and online control of screwing operations

[0001] 1. Scope of the invention

[0002] The field of the invention is that of methods for carrying out screwing operations online and for quality control operations of screwing operations.

[0003] 2. Prior art

[0004] In various industrial sectors, such as the automotive industry, it is common practice to implement assembly lines 1 along which several workstations PI, P2, Px are located. A structure to be assembled 10, such as an automobile, an engine, a gearbox, or other component, is moved along the assembly line 1 to undergo one or more tightening operations at the various workstations. After the tightening operations have been completed, the structure to be assembled is transported to a quality control workstation Pc where operators, using torque wrenches specifically designed for quality control, check all or part of the tightening operations performed at the various workstations to ensure that they meet one or more predetermined quality criteria.Alternatively, screwing operations can be controlled online directly at workstations by operators using torque wrenches specifically dedicated to quality control.

[0005] During quality control of a screw tightening operation, a torque wrench is used to apply a tightening torque to the screw being checked. When the torque reaches a value known as the slip torque, the screw begins to rotate. This torque is indicative of the quality of the screw tightening. The operator must then immediately stop turning the screw to avoid overtightening it, which could compromise the quality of the screw tightening and / or cause damage.

[0006] For productivity reasons, only a certain number of screw fastenings are checked. In practice, the most critical screw fastenings are checked, and their inspection provides a statistical picture of the quality of all the screw fastenings performed.

[0007] Although such an approach can allow fairly effective control of the quality of screwing carried out during screwing operations, it can still be optimized.

[0008] Indeed, such an approach, consisting of checking the quality of successive screwings after the last screwing has been carried out, does not allow, in particular, the detection of an anomaly in a screwing as soon as it occurs and the taking of the necessary corrective measures accordingly, such as:

[0009] - correct the defective screwing on the line before proceeding with the realization the following screws or send the assembly with a defective screw to a rework station;

[0010] - replace the defective tool on the line with a working tool and send the defective tool for maintenance;

[0011]

[0012] This prior art control method therefore does not allow for the early consideration of the occurrence of a screwing anomaly quickly after it has occurred and for drawing lessons from it which will allow the situation to be restored as quickly as possible in order to guarantee the quality of the screwing and the productivity according to which it is carried out.

[0013] Furthermore, this control method requires the implementation, in addition to the workstations dedicated to screwing operations, of a workstation dedicated solely to quality control. This tends to complicate the structure of the assembly lines and hinders productivity because it is necessary to wait until all the screwing operations are completed before starting their inspection.

[0014] Furthermore, whether quality control operations are carried out at a final inspection station or directly at the workstations, they are performed using specific inspection tools, such as torque wrenches. These inspection tools are in addition to the screwdrivers used for the screwing operations, so carrying out and inspecting these operations requires a significant number of tools to be acquired, handled, and maintained in working order.

[0015] Furthermore, the technique of verifying the quality of a screw tightening operation using a torque wrench requires the operator to develop specific skills. Indeed, the operator must develop a dexterity that allows them to immediately stop the screw being tightened as soon as the wrench "disengages" in order to avoid over-tightening during the check.

[0016] There is therefore a need to improve the quality control techniques of screwing operations.

[0017] 3. Objectives of the invention

[0018] The invention aims in particular to provide an effective solution to at least some of these different problems.

[0019] In particular, according to at least one embodiment, an objective of the invention is to provide a technique for carrying out successive screwing and quality control of screwing that is efficient and economical.

[0020] In particular, an objective of the invention is, according to at least one embodiment, to avoid the occurrence of over-tightening during a quality control operation due to misuse by an operator of the torque wrench implemented for this purpose.

[0021] An objective of the invention is, according to at least one embodiment, to provide such a technique which can allow the earliest possible detection of an anomaly on a screw.

[0022] In particular, the invention aims, according to at least one embodiment, to provide such a technique which can enable preventive maintenance actions to be launched on the tools used to perform screwing quickly after an anomaly is detected on a screwing.

[0023] Another objective of the invention is, according to at least one embodiment, to provide such a technique which can increase the number of quality checks carried out on assemblies without however inducing a decrease in productivity.

[0024] Another objective of the invention, in at least one embodiment, is to provide such a technique which is simple to implement and / or reliable and / or economical.

[0025] 4. Presentation of the invention

[0026] To this end, the invention proposes a method for screwing and quality control of screwing operations, on a production line comprising a succession of workstations, said method comprising at least:

[0027] - a step of carrying out at least one screwing operation on a structure to assemble at least some of said workstations, each screwing operation carried out at a workstation being done by means of a screwing device dedicated to the corresponding workstation and screwing operation;

[0028] - a quality control step of said at least one screwing operation.

[0029] According to the invention, the quality control step of a screwing operation is carried out at a workstation subsequent to the workstation where said controlled screwing operation was carried out, said quality control step being carried out by means of the screwing device dedicated to said subsequent workstation.

[0030] Thus, according to this aspect, the invention consists of:

[0031] - rather than using a specific tool such as a torque wrench to work for control operations, to use screwing tools for this purpose, and

[0032] - rather than waiting for the structure to be assembled to pass through all the stations of Work is carried out to ensure that all screwing operations are completed before performing quality control on at least some of the screwing operations, and to perform quality control on at least some of the screwing operations at one or more workstations subsequent to the one(s) where they were performed. Furthermore, the control operations performed at a workstation are carried out using the screwing tool dedicated to that workstation.

[0033] This approach allows:

[0034] - to reduce the number of tools used to perform the screwing and checks because the checks are carried out with screwing tools, at least some of which are likely to be used to perform screwing operations as well;

[0035] - to carry out quality checks earlier and thus detect any potential issues earlier anomaly and draw the consequences compared to prior art cases in which control operations are carried out at a final control station;

[0036] - to reduce the risk of overtightening during quality control or at the very least to reduce its level.

[0037] In the prior art, the number of quality control checks performed after all the screwing operations are completed is relatively small so as not to reduce productivity. By implementing the invention, it is possible to perform inspection operations at workstations where operators have some downtime after completing the required screwing operations at those stations, in order to also perform one or more inspection checks. Utilizing this downtime at certain workstations to perform inspection checks in advance thus makes it possible to increase the number of checks performed without harming productivity.

[0038] According to one possible feature, said screwing operations are carried out at predetermined screwing points of said structure to be assembled, and said control operations are carried out at predetermined control points of said structure to be assembled, a control point of a quality control operation corresponding to a screwing point at which a screwing operation has been previously carried out.

[0039] According to one possible feature, each screwing device dedicated to a workstation is programmed to perform at that workstation at least one screwing operation and / or at least one control operation at the corresponding screwing or control points.

[0040] According to one possible characteristic, the order of execution of the operations to be carried out at a workstation is predetermined.

[0041] According to one possible feature, said method includes, prior to the execution of each of said steps of carrying out a screwing operation and the steps of carrying out a control operation, a step of geolocating said corresponding screwing device, in relation to said screwing points and / or said control points of said structure to be assembled, a screwing operation adapted to the corresponding screwing point and / or a control operation adapted to the corresponding control point being activated when said screwing device is located at said screwing point and / or said corresponding control point.

[0042] According to one possible feature, a method according to the invention comprises:

[0043] - a step of masking said screwing points and / or said control points, and

[0044] - in an essentially synchronous manner with the activation in said screwing device of a screwing operation or a control operation, a step of releasing access by said screwing device to the screwing point or control point corresponding to said screwing or control operation activated, all other screwing points and control points other than the one at which the activated screwing or control operation is to be carried out being masked to remain inaccessible by said screwing device.

[0045] According to one possible feature, a method according to the invention comprises, essentially synchronously with the activation in said screwing device of a screwing operation or a control operation, a step, an illumination step of the screwing point or the corresponding control point where said activated operation is to be carried out.

[0046] According to one possible feature, a method according to the invention includes, during the execution of each step of carrying out a screwing operation, an optional step of detecting over-tightening illustrating that the screwing operation is carried out on a previously performed tightening rather than on a tightening to be carried out.

[0047] According to one possible feature, a method according to the invention comprises, after a screwing operation, a step of measuring at least one parameter representative of the quality of the screwing carried out, a step of verifying the presence of the value of said at least one parameter in a first predetermined tolerance range, and then a step of generating a first screwing report.

[0048] According to one possible characteristic, each quality control operation includes:

[0049] - a training step in the direction of screwing the screwed element during the screwing operation to be checked;

[0050] - a detection step, during the previous step, of the slippage of said element screwed in relation to said structure to be assembled;

[0051] - a stopping step of said drive step after detection of said slip;

[0052] - a step of measuring the value of the sliding tightening torque reached during the cessation of said training stage;

[0053] - a first step of verifying the presence, in a second interval of predetermined tolerance, of said sliding tightening torque, said first verification step being followed by a step of generating a second report;

[0054] - a second step of verifying the presence, in a third interval of predetermined tolerance, of said sliding tightening torque reached when stopping said drive step, said second verification step being followed by a third report generation step.

[0055] According to one possible feature, a method according to the invention comprises the emission of a consolidated report taking one or more of the first, second and third reports.

[0056] According to one possible feature, each of said quality control operations is recorded with an identifier associated with the identifier of the corresponding controlled screwing operation.

[0057] The invention also covers a computer program product downloadable from a communication network and / or stored on a computer-readable medium and / or executable by a microprocessor, said computer program product comprising program code instructions for the execution of a process according to any of the above variants, when executed by a computer.

[0058] 5. Description of the figures

[0059] Other features and advantages of the invention will become apparent from the following description of particular embodiments, given by way of simple illustrative and non-limiting example, and the accompanying drawings, among which:

[0060] [Fig-1] [Fig.1] illustrates an assembly line according to the prior art;

[0061] [Fig.2] [Fig.2] illustrates an example of an assembly line according to the invention;

[0062] [Fig.3] [Fig.3] illustrates a general example of a method according to the invention;

[0063] [Fig.4] [Fig.4] illustrates a detailed example of a method according to the invention

[0064] [Fig.5], [Fig.6], [Fig.7]: Figures 5, 6, 7 illustrate optional blocks of a method according to the invention.

[0065] 6. Description of particular embodiments

[0066] 6.1. General structure of an assembly line

[0067] In relation to [Fig.2], an example of an assembly line 2 is presented along which a structure to be assembled 21 is likely to be moved to undergo a plurality of screwing operations and quality control operations.

[0068] Such an assembly line 2 classically comprises a plurality of workstations. In the illustrated example, the assembly line comprises three workstations 22, 23, 24. In variants, it may comprise at least two workstations.

[0069] Each workstation is dedicated to performing at least one screwing operation on the structure being worked on. Each screwing operation is performed on a screwing point of the structure being worked on. The structure being worked on therefore has as many screwing points as there are screwing operations to be performed on it.

[0070] At least some workstations are dedicated to performing, on the structure being worked on, at least one quality control operation of at least one screwing operation carried out at a previous workstation. Each quality control operation is carried out at a control point on the structure being worked on. A control point at a later workstation corresponds to a screwing point at a previous workstation.

[0071] Although not optimal, some workstations could be dedicated to the performance of one or more quality control operations only and not the additional performance of one or more screwing operations.

[0072] Each workstation is equipped with at least one screw-driving device D1, D2, D3, D4. A screw-driving device is pre-programmed to perform at least one screw-driving operation on the workstation to which it is dedicated. It may also be pre-programmed to perform one or more screw-driving quality control operations carried out during screw-driving operations on one or more preceding workstations.

[0073] The screwing operations are carried out at predetermined screwing points on the structure to be assembled. The inspection operations are carried out at predetermined inspection points on the structure to be assembled. An inspection point for a quality control operation corresponds to a screwing point at which a screwing operation has previously been carried out.

[0074] 6.2. Example of a method according to the invention

[0075] 6.2.1. Organization of screwing and quality control operations at the workstations work

[0076] An example of an embodiment of a method according to the invention for screwing and quality control of screwing operations, on a production line comprising a succession of workstations, will now be described.

[0077] In general, such a process comprises at least (see [Fig. 3]):

[0078] - a step 30 of carrying out at least one screwing operation on a structure to assemble at least some of the workstations;

[0079] - a quality control step 31 of at least some of said operations screwing.

[0080] At least some of the quality control steps are performed at a workstation subsequent to the workstation where the controlled screwing operation was carried out, each quality control step being performed using a screwing device dedicated to the subsequent workstation where it was performed. At least one screwing operation is carried out at the subsequent workstation where at least one quality control operation is carried out. However, it is possible that at one or more workstations, the screwing tool(s) dedicated to it or them are used only for carrying out control operations.

[0081] In the example described, with reference to [Fig.4]:

[0082] - at the first workstation 22, a first screwing operation V1 is to be carried out and a second screwing operation V2 using a first D1 screwing device dedicated to the first station and a third V3 screwing operation using a second D2 screwing device dedicated to the first station;

[0083] - at the second workstation 23, a fourth V4 operation is to be performed screwing using a third D3 screwing device dedicated to the second station as well as a first C1 control operation of the first screwing and a second C2 control operation of the second screwing using the third D3 screwing device dedicated to the second workstation;

[0084] - at the third workstation 24 are to perform a fifth V5 operation of screwing using a fourth D4 screwing device dedicated to the third station and a third C3 control operation of the fourth screwing using the fourth D4 screwing device dedicated to the third station.

[0085] This represents only one possible example and all variations are conceivable. In particular, there could be one or more workstations dedicated solely to control, even if this is not optimal.

[0086] Each screwing device dedicated to a workstation is programmed to perform at that workstation at least one screwing operation and / or at least one control operation at the corresponding screwing or control points.

[0087] 6.2.2. Implementation of a sequence of operations

[0088] A method according to the invention can implement a sequence of operations.

[0089] In this case, each screwing device dedicated to a workstation is programmed to perform screwing and / or control operations at that workstation at the corresponding screwing or control points, the screwing and / or control operations being programmed in the screwing device according to a predetermined order.

[0090] In other words, a screwing device at a workstation will be programmed to successively perform, for example, a first screwing operation, a second screwing operation, a first control operation and then a third screwing operation.

[0091] After each face and control operation is completed, a screwing or control report is issued.

[0092] An assembly line is equipped with control means, such as a line PLC, a controller, or other devices, which, when the structure to be assembled arrives at a workstation, activates the first screwing or inspection operation in the screwing device. The operator then performs the first screwing or inspection operation, and after the report for the first operation has been generated, the control means activates the second screwing or inspection operation in the screwing device. The operator performs this second operation, after which a report is generated. The operations continue in this way until all the operations to be performed at the workstation have been completed. The control means then command the movement of the structure to be assembled to the next workstation, where the operations to be performed there are carried out in turn.The process is repeated until the structure to be assembled reaches the end of the assembly line.

[0093] In the example described here, at the first workstation 22:

[0094] - the first screwing device DI is programmed to perform, in a sequenced, the first screwing operation VI on a first screwing point of the structure to be assembled, then the second screwing operation V2 on a second screwing point of the structure to be assembled, and

[0095] - the second screwing device D2 is programmed to perform the third V3 screwing operation on a third screwing point of the structure to be assembled.

[0096] At the second workstation 23, the third screwing device D3 is programmed to perform, in a sequence, the fourth screwing operation V4 on a fourth screwing point of the structure to be assembled, then the first quality control operation Cl on a first control point of the structure to be assembled corresponding to the first screwing point, then the second quality control operation C2 on a second control point of the structure to be assembled corresponding to the second screwing point.

[0097] At the third workstation 24, the fourth screwing device D4 is programmed to perform, in a sequential manner, the fifth screwing operation V5 on a fifth screwing point of the structure to be assembled, then the third quality control operation C3 on a third control point of the structure to be assembled corresponding to the fourth screwing point.

[0098] Upon arrival of the structure to be assembled at the first station 22:

[0099] - the control means activate in the first screwing device DI the first screwing operation VI, which the operator performs on a first screwing point of the structure to be assembled, then, after the report of the first operation has been issued,

[0100] - the control means activate in the first screwing device DI the second screwing operation V2 which the operator performs on a second screwing point of the structure to be assembled, after which a report of the second operation is issued, and

[0101] - the active control means then in the second screwing device D2 the third screwing operation V3 which the operator performs on a third screwing point of the structure to be assembled after which a report of the third operation is issued.

[0102] After the report of the third operation is issued, the control means command the movement of the structure to be assembled to the second workstation 23. They then activate, in the third screwing device D3, the fourth screwing operation V4, which the operator performs on a fourth screwing point of the structure to be assembled. Then, after the report of the fourth screwing operation is issued, the control means activate the first quality control operation C1, which the operator performs on a first control point of the structure to be assembled. corresponding to the first screwing point. Following the issuance of the report of the first control operation, the control means activate in the third screwing device D3 the second quality control operation C2 which the operator performs on a second control point of the structure to be assembled corresponding to the second screwing point.

[0103] After the second inspection report is issued, the control means command the movement of the structure to be assembled to the third workstation 24. The control means then activate the fifth screwing operation V5 in the fourth screwing device D4, which the operator performs on a fifth screwing point of the structure to be assembled. After the fifth screwing operation report is issued, the control means activate the third quality control operation C3 in the fourth screwing device D4, which the operator performs on a third inspection point of the structure to be assembled, corresponding to the fourth screwing point. The assembly is completed after the third inspection operation report is issued.

[0104] When operations are to be carried out according to a predetermined sequence, the operator in charge of carrying them out is preferably trained beforehand to know the order of operations.

[0105] 6.2.3. Implementation of geolocation

[0106] A method according to the invention can implement geolocation of the screwing devices in relation to the structure to be assembled.

[0107] Means for geolocating screwing devices relative to the screwing points and control points of the structure to be assembled at the various workstations are then implemented. These geolocation means can be of different types; for example, they can use one or more infrared cameras fixed above the workstation and a first tag equipped with infrared LEDs fixed to the tool and a second tag of the same type fixed to the structure to be assembled. The camera control means are also capable of calculating, from the image of the tags captured by the camera, the position of the screwing device and the structure to be assembled in the camera's frame of reference, and then of calculating the relative position of the screwing device with respect to the structure to be assembled. It is then possible to deduce at which screwing or control point the tool is located.Such a technique is described, for example, in patent document WO2021259523.

[0108] In this case, the method comprises (see [Fig. 5]), prior to the execution of each of the steps for carrying out a screwing operation and the steps for carrying out a control operation, a step 50 of geolocating the corresponding screwing device, relative to the screwing points and / or the control points of the structure to be assembled, a screwing operation adapted to the screwing point. responding and / or a control operation adapted to the corresponding control point being activated in an activation step 51 when the screwing device is located at the screwing point and / or the corresponding control point.

[0109] The geolocation means installed at a station on a screwing device will preferably be connected to the assembly line control means to provide them with information on the screwing or control point where the screwing device is located and consequently allow the control means to activate the screwing or control strategy adapted to said screwing or control point where the screwing device is located.

[0110] In the embodiment described here, this principle could be implemented for example in the following way.

[0111] Although in variants not all screw-driving devices at all workstations are necessarily equipped with such a device, in the example described here, all screw-driving devices will be equipped with geolocation means.

[0112] In addition:

[0113] - when the control means detect the presence of the structure to be assembled at First workstation 22, the control systems are activated:

[0114] - in the first screwing device DI:

[0115] - a first screwing strategy when the geolocation means detect that its screw head is located at the first screwing point, and

[0116] - a second screwing strategy when the geolocation means detect that its screw tip is located at the second screwing point;

[0117] - in the second screwing device D2 a third screwing strategy when the geolocation means detect that its screw bit is located at the third screwing point;

[0118] - when the control means detect the presence of the structure to be assembled at second workstation 23, the control means are activated in the third screwing device D3:

[0119] - a fourth screwing strategy when the geolocation means detect that its screw tip is located at the fourth screwing point,

[0120] - a first control strategy when geolocation means detect that its screwdriver bit is located at the first checkpoint, and

[0121] - a second control strategy when the geolocation means detect that its screw tip is located at the second checkpoint;

[0122] - when the control means detect the presence of the structure to be assembled at third workstation 24, the control means are activated in the fourth screwing device D4:

[0123] - a fifth screwing strategy when the geolocation means detect that its screw head is located at the fifth screwing point, and

[0124] - a third control strategy when the geolocation means detect that its screw tip is located at the third checkpoint.

[0125] In one variant, the control means may impose on the operator a specific order for performing the various operations to be carried out at a workstation, with the control means blocking the screwing device if the operator does not follow the order of operations. The operator will have been trained beforehand on the order to be followed.

[0126] 6.2.4. Implementation of a masking

[0127] A method according to the invention can implement masking of screwing points and / or control points.

[0128] In this case, a masking device is implemented at the workstation(s) concerned. Such a masking device may consist of a physical screen placed between the operator and the structure to be assembled. This screen is equipped with hatches that can be operated by the assembly line control means to provide access to the screwing or inspection point according to the desired sequence.

[0129] In this case, the method comprises (see [Fig.6]), at at least some of the workstations essentially synchronously with the activation in the screwing device of a screwing operation or a control operation during an activation step 61, a step 60 of releasing access by the screwing device to the screwing point or the control point corresponding to the activated screwing or control operation, all other screwing points and control points other than the one at which the activated screwing or control operation is to be carried out being masked to remain inaccessible by the screwing device.

[0130] In the embodiment described here, this principle could be implemented, for example, at the second station 23 only, in the following manner:

[0131] - the assembly line control means control the masking device (not shown) to release access to the third screw point only, then to the first control point only, then to the second control point only;

[0132] - the assembly line control means activate in the third D3 screw device: the fourth screw strategy when only the fourth screw point is not masked, the first control strategy when only the first control point is unmasked, and the second control strategy when only the second control point is not masked.

[0133] 6.2.5. Implementation of an illumination

[0134] A method according to the invention can implement illumination of screwing points and / or control points.

[0135] In this case, illumination means are implemented. Such illumination means may consist of a laser spot whose beam orientation is controllable by the assembly line control means to illuminate screwing or inspection points according to the desired sequence of operations. The beam orientation is synchronized with the activation of screwing or inspection strategies in the screwing devices by the control means.

[0136] In this case, the method comprises (cf. [Fig.7]), at at least some of the workstations in an essentially synchronous manner with the activation in the screwing device of a screwing operation or a control operation during an activation step 71, a step 70 of illumination of the screwing point or the corresponding control point where the activated operation is to be carried out.

[0137] In the embodiment described here, this principle could be implemented, for example, at the third station 24 only, in the following manner:

[0138] - the assembly line control means operate a lighting device (not shown) to illuminate the fifth screw point only, then to illuminate the third control point only;

[0139] - the assembly line control means activate in the fourth D4 screw-in device:

[0140] - the fifth screwing strategy when they control the illumination of the fifth screw point,

[0141] - the third control strategy when they command the illumination of the third checkpoint.

[0142] 6.2.6. Implementation of an overtightening detection

[0143] A method according to the invention can implement a detection of possible overtightening of certain screwing points.

[0144] In this case, the method includes, during the execution of each step 30 of carrying out a screwing operation, an optional step 300 of detecting overtightening illustrating that the screwing operation is carried out on a previously performed tightening rather than on a tightening to be carried out.

[0145] By way of example, if the third tightening operation V3 is mistakenly performed at the first station 22 on the second previously tightened screw point, rather than on the third screw point, the second screw point will be overtightened. Such overtightening can be detected, for example, in a manner known in the prior art, by monitoring the angle of rotation of the screw whose tightening is being checked until the target tightening torque is reached. In the case of tightening, the angle of rotation will be several tens of degrees, whereas in the case of overtightening, the angle will be a few degrees.

[0146] 6.2.7. First screwing report

[0147] A method according to the invention may include steps for generating, at the end of each of the screwing steps, a first screwing report.

[0148] A first screwing report may include the recording result of at least one parameter illustrating the quality of a screwing, such as tightening torque and / or tightening angle.

[0149] The strategy for each screwing operation includes a range of tolerances for each parameter illustrating the quality of the corresponding screwing.

[0150] A first screwing report includes, in addition to the value of the parameter(s) illustrating the quality of the screwing, an indication of the type "ok / not ok" indicating for each interval whether the corresponding parameter is properly located there.

[0151] 6.2.8. Second and third screw reports

[0152] It is known to implement quality control operations for screwing, known as sliding control operations.

[0153] A slip test consists, after a screwing operation, of applying a tightening torque to the screw. When this torque is close to the final tightening torque, the screw begins to rotate, i.e., to slip. The torque measured at the moment the screw slips is the slip torque, the value of which is representative of the final tightening torque.

[0154] A method according to the invention may include a generation step 310, at the end of each of the control steps 31, of a second and a third screw report.

[0155] In this case, each quality control operation includes:

[0156] - a drive step 310 in the direction of screwing the screwed element during the screwing operation to be checked;

[0157] - a detection step 311, during the preceding step 310, of the slippage of the screwed element in relation to the structure to be assembled, i.e. separation of the screwed element in relation to the structure to be assembled; the slippage occurs when the torque applied, during the check, on the already tightened screw, reaches the torque at which the screw was previously tightened;

[0158] - a step 312 of stopping the drive step 311 after detection of slippage; This training is somewhat abrupt since its sole purpose is to enable the detection of slippage. This training must be as short as possible to limit over-tightening, and using a screw-driving device for this purpose rather than a torque wrench offers an advantage since the amplitude of this over-tightening is managed by the control means of the screw-driving device, which are by nature more responsive than the user of the torque wrench who manually controls the amplitude of this over-tightening;

[0159] - a step 313 of measuring the value of the sliding tightening torque reached during from the stoppage of training stage 310;

[0160] - a first step 314 of verifying the presence, in a first interval of predetermined tolerance, of the sliding tightening torque, the first verification step 314 being followed by a step 315 of generating a second report;

[0161] - a second step 316 of checking for presence, in a second interval of predetermined tolerance, of the sliding tightening torque reached when stopping the drive step 310, the second verification step 316 being followed by a step 317 of generating a third report.

[0162] A report may be the torque or angle value reached and an OK or NOK meaning that this value is in the corresponding range or not.

[0163] 6.2.9. Consolidated reports

[0164] A method according to the invention may include a step 32 of issuing a consolidated report taking one or more of the first, second and third reports.

[0165] Such a consolidated report could be a synthesis of the three reports grouping the different parameters measured and the indication whether or not they are within the corresponding tolerance ranges.

[0166] 6.2.10. Other aspects and advantages

[0167] According to one possible variant, each quality control operation is recorded with an identifier associated with an identifier of the corresponding controlled screwing operation. This ensures traceability.

[0168] A screw tightening operation may, over a period of time after its completion, undergo a relaxation phenomenon, causing the final tightening torque to reach a lower, subsequently stabilized value. Therefore, if a screw tightening operation undergoing relaxation is checked before the relaxation occurs, its quality may be considered acceptable, whereas it might not be after relaxation. Thus, postponing the quality control of a screw tightening operation performed at an earlier station to a later workstation can avoid this drawback.

[0169] On an assembly line, it sometimes happens that the number of operations to be performed at certain workstations is less and / or that the time required to perform these operations is less. Thus, the operator in charge of these workstations has some "free" time. This "free" time can be used, according to the invention, to perform quality control operations in-line rather than at a final inspection station as provided for in the prior art. In this way, the invention makes it possible to increase productivity. It can also make it possible to increase the number of quality checks performed, which allows for a statistical picture of the quality of the operations that is more faithful to reality. Thus, if only 5% of the products are inspected according to the prior art, the quality costs are reduced, but doubt remains for 95% of the products.Increasing the frequency / population of products controlled according to the invention helps to reduce the risk of not achieving zero-defect delivery. mainly using downtime (free time).

[0170] The invention makes it possible to avoid the need for a station dedicated exclusively to quality control, which helps to simplify assembly lines.

[0171] Carrying out quality controls upstream and not at a final station can make it possible to detect upstream any deviation highlighting a defect in one or more screwing devices which have been implemented to carry out screwing operations which do not meet the required level of quality.

[0172] The quality of a previous screwing operation may be influenced by a subsequent screwing operation carried out nearby. In this case, it is preferable to check the quality of the previous screwing operation after the subsequent screwing operation has been carried out, which is permitted by the invention.

[0173] The technique according to the invention makes it possible to avoid the use of prior art screwdrivers comprising two torque sensors, one allowing the detection of the attainment of the final tightening torque and triggering the stopping of the screwing and the other allowing a quality control of the screwing to be carried out, such an approach having the disadvantages of not allowing the influence of a possible relaxation of the screwing or of a similar tightening to be taken into account.

[0174] Real-time evaluation of screw quality, particularly through a technique for measuring residual breakaway torques, allows for continuous production monitoring, in anticipation of quality measurements. The implementation of automated statistical process control (SPC) enables preventive maintenance actions (tool readjustments / repairs) and the identification of root causes. The implementation of proactive quality alerts can facilitate root cause analysis, the adoption of a backup process, or the replacement of a qualified machine.

Claims

Demands

1. A method for screwing and quality control of screwing operations, on a production line comprising a succession of workstations, said method comprising at least: - a step of carrying out at least one screwing operation on a structure to be assembled at at least some of said workstations, each screwing operation carried out at a workstation being carried out by means of a screwing device dedicated to the corresponding workstation and screwing operation; - a quality control step of said at least one screwing operation; characterized in that the quality control step of a screwing operation is carried out at a workstation subsequent to the workstation where said screwing operation was carried out, said quality control step being carried out by means of a screwing device dedicated to said subsequent workstation.

2. A method according to claim 1 wherein said screwing operations are carried out at predetermined screwing points of said structure to be assembled, and said control operations are carried out at predetermined control points of said structure to be assembled, a control point of a quality control operation corresponding to a screwing point at which a screwing operation has been previously carried out.

3. A method according to claim 2 wherein each screwing device dedicated to a workstation is programmed to perform at that workstation at least one screwing operation and / or at least one control operation at the corresponding screwing or control points.

4. A method according to claim 3 wherein the order of execution of the operations to be carried out at a workstation is predetermined.

5. The method according to claim 3 or 4 comprises, prior to each of the steps for carrying out a screwing operation and the steps for carrying out a control operation, a step of geolocating said corresponding screwing device, relative to said screwing points and / or said control points of said structure to be assembled, a screwing operation adapted to the corresponding screwing point and / or an operation of control adapted to the corresponding control point being activated when said screwing device is located at said screwing point and / or said corresponding control point.

6. A method according to claim 3 or 4 comprising: - a step of masking said screwing points and / or said control points, and - essentially synchronously with the activation in said screwing device of a screwing operation or a control operation, a step of releasing access by said screwing device to the screwing point or control point corresponding to said screwing or control operation activated, all other screwing points and control points other than the one at which the activated screwing or control operation is to be carried out being masked so as to remain inaccessible by said screwing device.

7. Method according to claim 3 or 4 comprising, essentially synchronously with the activation in said screwing device of a screwing operation or a control operation, a step, an illumination step of the screwing point or the corresponding control point where said activated operation is to be carried out.

8. A method according to any one of claims 1 to 7 comprising, during the execution of each step of carrying out a screwing operation, an optional step of detecting overtightening illustrating that the screwing operation is carried out on a previously performed tightening rather than on a tightening to be carried out.

9. A method according to any one of claims 1 to 8 comprising, after a screwing operation, a step of measuring at least one parameter representative of the quality of the screwing carried out, a step of verifying the presence of the value of said at least one parameter in a first predetermined tolerance range, and then a step of generating a first screwing report.

10. A method according to any one of claims 1 to 9 in which each quality control operation comprises: - a drive step in the direction of screwing of the screwed element during the screwing operation to be controlled; - a detection step, during the preceding step, of the slippage of said screwed element relative to said structure to be assembled; - a stop step of said drive step after detection of said slippage; - a step of measuring the value of the sliding tightening torque reached when the said drive step was stopped; - a first step of verifying the presence, in a second predetermined tolerance interval, of said sliding tightening torque, said first verification step being followed by a step of generating a second report; - a second step of verifying the presence, in a third predetermined tolerance interval, of said sliding tightening torque reached when the said drive step was stopped, said second verification step being followed by a step of generating a third report.

11. A method according to claims 9 and 10 comprising the issuance of a consolidated report taking one or more of the first, second and third reports.

12. A method according to any one of claims 1 to 11 wherein each of said quality control operations is recorded with an identifier associated with the identifier of the corresponding controlled screwing operation.

13. Product computer program downloadable from a communication network and / or stored on a computer-readable medium and / or executable by a microprocessor, said product computer program comprising program code instructions for the execution of a process according to any one of claims 1 to 12, when executed by a computer.

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