In-line screwing method and method for controlling screwing operations

Abstract

The present invention relates to a screwing method and a method for controlling the quality of screwing operations, on a production line comprising a series of workstations, the method comprising at least: - a step of performing at least one screwing operation on a structure to be assembled at at least some of the workstations, each screwing operation performed at a workstation being done so by means of a screwing device dedicated to the corresponding station and screwing operation; - a step of controlling the quality of the at least one screwing operation. According to the invention, the step of controlling the quality of a screwing operation is carried out at a workstation subsequent to the workstation where the screwing operation being controlled was performed, the quality control step being carried out by means of a screwing device dedicated to the subsequent station.

Description

[0001] DESCRIPTION

[0002] Screwdriving process and online control of screwdriving operations

[0003] 1. Field of the invention

[0004] The field of the invention is that of methods for carrying out screwing operations online and for controlling the quality of screwing operations.

[0005] 2. Prior art

[0006] In various industrial sectors, such as in particular that of automobile construction, it is known to implement assembly lines 1 along which several work stations Pl, P2, Px are installed. A structure to be assembled 10, such as for example an automobile, an engine, a gearbox or other, is moved along the assembly line 1 to undergo one or more screwing operations at the various stations. After the screwing operations have been carried out, the structure to be assembled is conveyed to a quality control station Pc where operators control, by means of torque wrenches specifically dedicated to quality control, all or part of the screwing operations carried out at the various stations to ensure that they satisfy one or more predetermined quality criteria.Alternatively, screwing operations can be controlled online directly at the workstations by operators also using torque wrenches specifically dedicated to quality control.

[0007] During the quality control of a screw, a torque wrench is used to apply a tightening torque to the screw whose tightening is being checked. When the torque reaches a value called slip torque, the screw begins to turn. This torque is representative of the quality of the screwing. The operator must then immediately stop driving the screw, otherwise overtightening may occur, which could affect the quality of the screwing and / or be damaging.

[0008] For productivity reasons, only a certain number of screw connections are checked. In practice, the most critical screw connections are checked, and their inspection provides a statistical picture of the quality of all the screw connections carried out.

[0009] Although such an approach can be used to control the quality of screw connections made during screwdriving operations quite effectively, it can still be optimized.

[0010] Indeed, such an approach consisting of controlling the quality of successive screwing operations after the last screwing operation has been carried out does not allow in particular to detect an anomaly on a screwing operation as soon as it occurs and to take the necessary corrective measures accordingly, such as for example: correcting the defective screwing operation on the line before continuing with the subsequent screwing operations or sending the assembly with a defective screwing operation to a rework station; replacing the defective tool on the line with a tool in working order and sending the defective tool for maintenance; This control method according to the prior art therefore does not allow to take into consideration in an anticipated manner the occurrence of a screwing anomaly quickly after it has occurred and to learn from it which will allow to restore the situation as quickly as possible in order to guarantee the quality of the screwing operations and the productivity at which they are carried out.

[0011] Furthermore, this control method requires the implementation, in addition to the workstations dedicated to carrying out screwing operations, of a workstation dedicated solely to quality control. This tends to complicate the structure of the assembly lines and harms productivity because it is necessary to wait until all the screwing operations have been carried out before starting their control.

[0012] Furthermore, whether quality control operations are carried out at a final control station or directly at the workstations, they are carried out using specific control tools, such as torque wrenches. These control tools are in addition to the screwdrivers used to carry out the screwing operations, so carrying out screwing operations and their control requires the use of a large number of tools to be acquired, handled and maintained in working order.

[0013] Furthermore, the technique of checking the quality of a screwing operation using a torque wrench requires the development of specific know-how by the operator who implements it. Indeed, the operator should develop a skill to immediately stop the driving of the screw whose tightening is being checked as soon as the wrench "disengages" so as not to cause over-tightening during the check.

[0014] There is therefore a need to improve quality control techniques for screwdriving operations.

[0015] 3. Objectives of the invention

[0016] The invention aims in particular to provide an effective solution to at least some of these different problems.

[0017] In particular, according to at least one embodiment, an objective of the invention is to provide a technique for carrying out successive screwing operations and for quality control of the screwing operations which is efficient and economical.

[0018] 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 incorrect use by an operator of the torque wrench used for this purpose.

[0019] An objective of the invention is, according to at least one embodiment, to provide such a technique which can allow the earliest detection of an anomaly in a screwing.

[0020] In particular, the invention aims, according to at least one embodiment, to provide such a technique which can make it possible to launch preventive maintenance actions on the tools used to carry out screwing operations quickly after an anomaly is detected on a screwing operation.

[0021] Another objective of the invention is, according to at least one embodiment, to provide such a technique which can make it possible to increase the number of quality controls carried out on assemblies without however inducing a drop in productivity.

[0022] 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.

[0023] 4. Presentation of the invention

[0024] For this, the invention proposes a method of screwing and controlling the quality of screwing operations, on a production line comprising a succession of work stations, said method comprising at least:

[0025] - a step of carrying out at least one screwing operation on a structure to be assembled at at least some of said work stations, each screwing operation carried out at a work station being carried out by means of a screwing device dedicated to the corresponding station and screwing operation;

[0026] - a quality control step of said at least one screwing operation.

[0027] According to the invention, the step of controlling the quality 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.

[0028] Thus, according to this aspect, the invention consists of:

[0029] - rather than using a specific tool such as a torque wrench to carry out control operations, to use screwing tools for this purpose, and

[0030] - rather than waiting for the structure to be assembled to pass through all the workstations so that all the screwing operations are carried out before carrying out the quality control of at least some screwing operations, to carry out the quality control of at least some screwing operations on one or more workstations subsequent to the one or those on which they were carried out. In addition, the control operations carried out on a workstation are carried out using the screwing tool dedicated to this workstation.

[0031] This approach allows:

[0032] - to reduce the number of tools used to carry out screwing operations and checks because the checks are carried out with screwing tools, at least some of which are likely to be used to carry out screwing operations as well;

[0033] - to carry out quality checks earlier and thus to detect any anomaly earlier and draw conclusions from it compared to the cases of the prior art in which the control operations are carried out at a final control station;

[0034] - to reduce the risk of overtightening during quality control or at least to reduce its level. In the prior art, the number of quality controls carried out after all the screwing operations have been completed is relatively small so as not to reduce productivity. By implementing the invention, it is possible to carry out control operations at workstations where the operators have a little downtime once they have carried out the screwing operations to be carried out at these stations, to further carry out one or more control operations. Exploiting this downtime at certain workstations to carry out control operations in advance thus makes it possible to increase the number of controls carried out without harming productivity.

[0035] According to a possible characteristic, 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 previously been carried out.

[0036] According to a possible characteristic, each screwing device dedicated to a workstation is programmed to carry out at this workstation at least one screwing operation and / or at least one control operation at the corresponding screwing or control points.

[0037] According to one possible characteristic, the order of carrying out the operations to be carried out at a workstation is predetermined.

[0038] According to a possible characteristic, said method comprises, prior to carrying out each of said steps of carrying out a screwing operation and steps of carrying out a control operation, a step of geolocating said corresponding screwing device, relative to said screwing points and / or to 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.

[0039] According to a possible characteristic, a method according to the invention comprises:

[0040] - a step of masking said screwing points and / or said control points, and

[0041] - 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 to the control point corresponding to said activated screwing or control operation, all the other screwing points and control points other than that at which the activated screwing or control operation must be carried out being masked to remain inaccessible by said screwing device.

[0042] According to a possible characteristic, 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, a step of illuminating the screwing point or the corresponding control point where said activated operation must be carried out.

[0043] According to a possible characteristic, a method according to the invention comprises, during the performance of each step of carrying out a screwing operation, a possible step of detecting over-tightening illustrating that the screwing operation is carried out on a tightening previously carried out rather than on a tightening to be carried out.

[0044] According to a possible characteristic, a method according to the invention comprises, at the end of 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 interval, then a step of generating a first screwing report.

[0045] According to a possible characteristic, each quality control operation includes:

[0046] - a training step in the direction of screwing the screwed element during the screwing operation to be controlled;

[0047] - a step of detecting, during the previous step, the sliding of said screwed element relative to said structure to be assembled;

[0048] - a step of stopping said training step after detecting said slippage;

[0049] - a step of measuring the value of the sliding tightening torque reached when stopping said driving step;

[0050] - 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;

[0051] - a second step of verifying the presence, within a third predetermined tolerance interval, of said sliding tightening torque reached when said driving step is stopped, said second verification step being followed by a step of generating a third report.

[0052] According to one possible feature, a method according to the invention comprises issuing a consolidated report taking one or more of the first, second and third reports.

[0053] According to a possible characteristic, each of said quality control operations is recorded with an identifier associated with the identifier of the corresponding controlled screwing operation.

[0054] The invention also covers a computer program product downloadable from a communications network and / or stored on a computer-readable medium and / or executable by a microprocessor, said computer program product comprising program code instructions for executing a method according to any one of the above variants, when executed by a computer.

[0055] 5. Description of figures

[0056] Other characteristics and advantages of the invention will appear on reading the following description of particular embodiments, given as a simple illustrative and non-limiting example, and the appended drawings among which:

[0057] [Fig 1] Figure 1 illustrates an assembly line according to the prior art;

[0058] [Fig 2] Figure 2 illustrates an example of an assembly line according to the invention;

[0059] [Fig 3] Figure 3 illustrates a general example of a method according to the invention; [Fig 4] Figure 4 illustrates a detailed example of a method according to the invention

[0060] [Fig 5], [Fig 6], [Fig 7]: Figures 5, 6, 7 illustrate optional blocks of a method according to the invention.

[0061] 6. Description of particular embodiments

[0062] 6.1. General structure of an assembly line

[0063] 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.

[0064] Such an assembly line 2 conventionally comprises a plurality of workstations. In the example illustrated, the assembly line comprises three workstations 22, 23, 24. In variants, it may comprise at least two workstations.

[0065] Each workstation is dedicated to carrying out at least one screwing operation on the structure to be worked. Each screwing operation is carried out on a screwing point of the structure to be worked. The structure to be worked therefore has as many screwing points as there are screwing operations to be carried out on it.

[0066] At least some workstations are dedicated to carrying out, on the structure to be worked, 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 on a control point of the structure to be worked. A control point at a later workstation corresponds to a screwing point at a previous workstation.

[0067] Although this is not optimal, some workstations could be dedicated to carrying out one or more quality control operations only and not to carrying out one or more screwing operations in addition.

[0068] Each workstation is equipped with at least one screwing device D1, D2, D3, D4. A screwing device is preprogrammed to carry out, on the workstation to which it is dedicated, at least one screwing operation. It may also be preprogrammed to carry out one or more screwing quality control operations carried out during the performance of screwing operations on one or more previous workstations.

[0069] Screwing operations are carried out at predetermined screwing points of the structure to be assembled. Control operations are carried out at predetermined control points of the structure to be assembled. A control point of a quality control operation corresponds to a screwing point at which a screwing operation has previously been carried out.

[0070] 6.2. Example of a method according to the invention

[0071] 6.2.1. Organization of screwing operations and quality control at work stations 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 work stations, will now be described.

[0072] Generally speaking, such a process comprises at least (see figure 3):

[0073] - a step 30 of carrying out at least one screwing operation on a structure to be assembled at at least some of the work stations;

[0074] - a step 31 of quality control of at least some of said screwing operations.

[0075] At least some of the quality control steps are carried out at a workstation subsequent to the workstation where the controlled screwing operation in question was carried out, each quality control step being carried out by means of a screwing device dedicated to the subsequent workstation where it was carried out. At least one screwing operation is carried out at the subsequent workstation where at least one quality control operation is carried out. It is however possible that at one or more workstations, the screwing tool(s) dedicated to it or them are used only to carry out control operations.

[0076] In the example described, with reference to Figure 4:

[0077] - at the first work station 22, a first screwing operation VI and a second screwing operation V2 are to be carried out by means of a first screwing device DI dedicated to the first station and a third screwing operation V3 by means of a second screwing device D2 dedicated to the first station;

[0078] - at the second work station 23 a fourth V4 screwing operation is to be carried out by means of a third D3 screwing device dedicated to the second station as well as a first Cl operation for checking the first screwing and a second C2 operation for checking the second screwing by means of the third D3 screwing device dedicated to the second work station;

[0079] - at the third workstation 24 a fifth V5 screwing operation is to be carried out by means of a fourth D4 screwing device dedicated to the third station and a third C3 operation of controlling the fourth screwing by means of the fourth D4 screwing device dedicated to the third station.

[0080] This is just one possible example and any variation is possible. In particular, there could be one or more workstations dedicated to monitoring only, even if this is not optimal.

[0081] Each screwing device dedicated to a workstation is programmed to carry out at least one screwing operation and / or at least one control operation at the corresponding screwing or control points at this workstation.

[0082] 6.2.2. Implementation of a sequencing of operations

[0083] A method according to the invention can implement an operation sequencing.

[0084] In this case, each screwing device dedicated to a workstation is programmed to carry out screwing and / or control operations at this 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. In other words, a screwing device at a workstation will be programmed to carry out successively, for example, a first screwing operation, a second screwing operation, a first control operation and then a third screwing operation.

[0085] After each face and control operation has been completed, a screwing or control report is issued.

[0086] An assembly line is equipped with control means, such as a line automaton, a controller or others, which allows, when the structure to be assembled arrives at a workstation, to activate the first screwing or control operation in the screwing device. The operator then carries out the first screwing or control operation and then, after the report of the first operation has been issued, the control means activate the second screwing or control operation in the screwing device. The operator carries out this second operation at the end of which a report is issued. The operations continue in this way until all the operations to be carried out on the station have been completed. The control means then command the movement of the structure to be assembled to the subsequent station where the operations to be carried out there are carried out in turn.The process is repeated until the structure to be assembled reaches the end of the assembly line.

[0087] In the example described here, at the first workstation 22:

[0088] - the first screwing device DI is programmed to carry out, in a sequential manner, 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

[0089] - the second screwing device D2 is programmed to carry out the third screwing operation V3 on a third screwing point of the structure to be assembled.

[0090] At the second workstation 23, the third screwing device D3 is programmed to carry out, in a sequential manner, the fourth screwing operation V4 on a fourth screwing point of the structure to be assembled, then the first quality control operation C1 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.

[0091] At the third workstation 24, the fourth screwing device D4 is programmed to carry out, 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.

[0092] Upon arrival of the structure to be assembled at the first station 22:

[0093] - the control means activate in the first screwing device DI the first screwing operation VI that the operator carries out on a first screwing point of the structure to be assembled then, after the issue of the report of the first operation,

[0094] - the control means activate in the first screwing device DI the second screwing operation V2 which the operator carries out on a second screwing point of the structure to be assembled at the end of which a report of the second operation is issued, and

[0095] - the control means then activate in the second screwing device D2 the third screwing operation V3 which the operator carries out on a third screwing point of the structure to be assembled at the end of which a report of the third operation is issued.

[0096] After the report of the third operation has been issued, the control means control 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 that the operator performs on a fourth screwing point of the structure to be assembled, then after the report of the fourth screwing operation has been issued, the control means activate the first quality control operation C1 that the operator performs on a first control point of the structure to be assembled corresponding to the first screwing point. At the end of the report of the first control operation has been issued, the control means activate in the third screwing device D3 the second quality control operation C2 that the operator performs on a second control point of the structure to be assembled corresponding to the second screwing point.

[0097] After the report of the second control operation has been issued, the control means control the movement of the structure to be assembled to the third work station 24. The control means then activate in the fourth screwing device D4 the fifth screwing operation V5 that the operator carries out on a fifth screwing point of the structure to be assembled, then after the report of the fifth screwing operation has been issued, the control means activate in the fourth screwing device D4 the third quality control operation C3 that the operator carries out on a third control point of the structure to be assembled corresponding to the fourth screwing point. The assembly is completed after the report of the third control operation has been issued.

[0098] When operations must be carried out according to a predetermined sequence, the operator in charge of carrying them out is preferably previously trained to know the order in which the operations are to be carried out.

[0099] 6.2.3. Implementation of geolocation

[0100] A method according to the invention can implement geolocation of the screwing devices relative to the structure to be assembled.

[0101] Means for geolocating screwing devices relative to the screwing points and the 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 on the tool and a second tag of the same type fixed on 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 calculating the relative position of the screwing device relative to the structure to be assembled. It is then possible to deduce on which screwing or control point the tool is located.Such a technique is for example described in patent document WO2021259523.

[0102] In this case, the method comprises (see figure 5), prior to carrying out each of the steps of carrying out a screwing operation and the steps of carrying out a control operation, a step 50 of geolocation of 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 corresponding screwing point 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.

[0103] The geolocation means installed at a workstation 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.

[0104] In the embodiment described here, this principle could be implemented for example in the following manner.

[0105] Although in variants not all screwdriving devices at all workstations are necessarily equipped with such a device, in the example described here, all screwdriving devices will be equipped with geolocation means.

[0106] Furthermore :

[0107] - when the control means detect the presence of the structure to be assembled at the first workstation 22, the control means activate:

[0108] - in the first screwing device DI:

[0109] - a first screwing strategy when the geolocation means detect that its screwing tip is at the first screwing point, and

[0110] - a second screwing strategy when the geolocation means detect that its screwing tip is at the second screwing point;

[0111] - in the second screwing device D2 a third screwing strategy when the geolocation means detect that its screwing tip is at the third screwing point;

[0112] - when the control means detect the presence of the structure to be assembled at the second work station 23, the control means activate in the third screwing device D3:

[0113] - a fourth screwing strategy when the geolocation means detect that its screwing tip is at the fourth screwing point,

[0114] - a first control strategy when the geolocation means detect that its screw tip is at the first control point, and

[0115] - a second control strategy when the geolocation means detect that its screwing tip is at the second control point; - when the control means detect the presence of the structure to be assembled at the third workstation 24, the control means activate in the fourth screwing device D4:

[0116] - a fifth screwing strategy when the geolocation means detect that its screwing tip is at the fifth screwing point, and

[0117] - a third control strategy when the geolocation means detect that its screw tip is at the third control point.

[0118] In a variant, the control means may impose on the operator an order of carrying out the various operations to be carried out at a station, the control means blocking the screwing device if the operator does not respect an order of carrying out the operations. The operator will have been trained beforehand when the order to be respected.

[0119] 6.2.4. Implementing masking

[0120] A method according to the invention can implement masking of screwing points and / or control points.

[0121] 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 control point depending on the desired order.

[0122] In this case, the method comprises (see figure 6), at at least some of the work stations 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 to the control point corresponding to the activated screwing or control operation, all of the other screwing points and control points other than that at which the activated screwing or control operation must be carried out being masked to remain inaccessible by the screwing device.

[0123] In the embodiment described here, this principle could be implemented for example at the second station 23 only in the following manner:

[0124] - the assembly line control means control the masking device (not shown) to free access to the third screwing point only, then to the first control point only and then to the second control point only;

[0125] - the assembly line control means activate in the third screwing device D3 the fourth screwing strategy when only the fourth screwing 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.

[0126] 6.2.5. Implementation of illumination A method according to the invention can implement illumination of screwing points and / or control points.

[0127] In this case, illumination means are implemented. Such illumination means may consist of a laser spot whose beam orientation can be controlled by the assembly line control means to illuminate the screwing or control points according to the desired production order. The beam orientation is synchronized with the activation of the screwing or control strategies in the screwing devices by the control means.

[0128] In this case, the method comprises (see figure 7), at at least some of the work stations essentially synchronously with the activation in the screwing device of a screwing operation or a control operation during an activation step 71, a step 70 of illuminating the screwing point or the corresponding control point where the activated operation must be carried out.

[0129] In the embodiment described here, this principle could be implemented for example at the third station 24 only in the following manner:

[0130] - the assembly line control means control a lighting device (not shown) to illuminate the fifth screwing point only, then to illuminate the third control point only;

[0131] - the assembly line control means activate in the fourth screwing device D4:

[0132] - the fifth screwing strategy when they control the illumination of the fifth screwing point,

[0133] - the third control strategy when they control the illumination of the third control point.

[0134] 6.2.6. Implementation of overtightening detection

[0135] A method according to the invention can implement detection of possible over-tightening of certain screwing points.

[0136] In this case, the method comprises, during the performance of each step 30 of carrying out a screwing operation, a possible step 300 of detecting over-tightening illustrating that the screwing operation is carried out on a tightening previously carried out rather than on a tightening to be carried out.

[0137] For example, if the third screwing operation V3 is carried out at the first station 22 by mistake at the second previously tightened screwing point, rather than at the third screwing point, the second screwing point will be overtightened. Such overtightening can be detected, for example in the following manner in a manner known in the state of the art consisting of controlling the angle of rotation of the screw, the screwing of which is to be controlled, until the objective tightening torque is reached. In the case of screwing, the angle of rotation will be several tens of degrees whereas in the case of overtightening, the angle will be a few degrees.

[0138] 6.2.7. First screwing report A method according to the invention may comprise steps of generating, at the end of each of the screwing steps, a first screwing report.

[0139] A first screwing report may include the result of recording at least one parameter illustrating the quality of a screwing, such as for example the tightening torque and / or the tightening angle.

[0140] The strategy for each screwing operation includes a tolerance interval for each parameter illustrating the quality of the corresponding screwing.

[0141] A first screwing report includes, in addition to the value of the parameter(s) illustrating the quality of the screwing, an indication of the “ok / not ok” type indicating for each interval whether the corresponding parameter is suitably located there.

[0142] 6.2.8. Second and third screwing reports

[0143] It is known to implement quality control operations for screwing called sliding control operations.

[0144] A slip test consists of applying a tightening torque to the screw after a screwing operation. When this torque is close to the final tightening torque, the screw begins to turn, 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.

[0145] A method according to the invention may comprise a generation step 310, at the end of each of the control steps 31, of a second and a third screwing report.

[0146] In this case, each quality control operation includes:

[0147] - a step 310 of driving in the direction of screwing the screwed element during the screwing operation to be controlled;

[0148] - a step 311 of detecting, during the previous step 310, the slipping of the screwed element relative to the structure to be assembled, i.e. detachment of the screwed element relative to the structure to be assembled; the slipping occurs when the torque applied, during the check, to the already tightened screw, reaches the torque to which the screw was previously tightened;

[0149] - a step 312 of stopping the training step 311 after detection of the slippage; this training is a little sudden since its sole objective is to allow the detection of the slippage. This training must be as short as possible to limit overtightening and the use of a screwing device for this purpose rather than a torque wrench offers an advantage since the amplitude of this overtightening is managed by the control means of the screwing device which are by nature more reactive than the user of the torque wrench who himself manually controls the amplitude of this overtightening

[0150] - a step 313 of measuring the value of the sliding tightening torque reached when the driving step 310 is stopped; - a first step 314 of verifying the presence, within a first predetermined tolerance interval, of the sliding tightening torque, the first verification step 314 being followed by a step 315 of generating a second report;

[0151] - a second step 316 of verifying the presence, in a second predetermined tolerance interval, of the sliding tightening torque reached when the driving step 310 is stopped, the second verification step 316 being followed by a step 317 of generating a third report.

[0152] A report can be the torque or angle value reached and an OK or NOK meaning that this value is within the corresponding range or not.

[0153] 6.2.9. Consolidated reports

[0154] A method according to the invention may comprise a step 32 of issuing a consolidated report taking one or more of the first, second and third reports.

[0155] Such a consolidated report could be a synthesis of the three reports grouping together the different parameters measured and the indication of whether or not they are within the corresponding tolerance intervals.

[0156] 6.2.10. Other aspects and advantages

[0157] According to a possible variant, each of the quality control operations is recorded with an identifier associated with an identifier of the corresponding controlled screwing operation. This ensures traceability.

[0158] A screwing operation may undergo, over a certain period of time after its completion, a relaxation phenomenon inducing that the final tightening torque at which it was carried out may reach a subsequently lower stabilized final value. Thus, if a screwing operation which undergoes relaxation is checked before the relaxation takes place, its quality may be considered acceptable whereas it might not be after relaxation. Thus, the fact of shifting to a later station the quality control of a screwing operation carried out at an earlier station can make it possible to avoid this disadvantage.

[0159] On an assembly line, it happens that the number of operations to be carried out at certain workstations is less important and / or that the time necessary to carry out these operations is less important. Thus, the operator in charge of these stations has a little “free” time. This “free” time can be used according to the invention to carry out quality control operations in line rather than at a final control station as provided for in the prior art. Thus, the invention makes it possible to increase productivity. It can also make it possible to increase the number of quality controls carried out, which makes it possible to have a statistical image of the quality of the operations that is more faithful to reality. Thus, if only 5% of the products are controlled according to the prior art, the quality costs are reduced, but doubt remains on 95% of the products.Increasing the frequency / population of products checked according to the invention reduces the risk of not achieving zero-defect delivery by using mainly idle time (free time). The invention makes it possible to avoid the need for a workstation dedicated exclusively to quality control, which helps to simplify assembly lines.

[0160] Carrying out quality checks upstream and not at a final workstation can make it possible to detect upstream any possible deviation highlighting a defect in one or more screwing devices that have been used to carry out screwing operations that do not meet the required quality level.

[0161] It is possible that the quality of a previous screwing operation is influenced by a subsequent, neighboring screwing operation carried out nearby. In this case, it is preferable to check the quality of the previous screwing operation after the subsequent, neighboring screwing operation has been carried out, which is enabled by the invention.

[0162] The technique according to the invention makes it possible to avoid the use of prior art screwdrivers comprising two torque sensors, one making it possible to detect the reaching of the final tightening torque and to trigger the stopping of the screwing and the other making it possible to carry out a quality control of the screwing, such an approach having the disadvantages of not making it possible to take into account the influence of a possible relaxation of the screwing or of a neighboring tightening.

[0163] Real-time assessment of screw quality, particularly through a technique for measuring residual detachment torques, allows for constant monitoring of production, in anticipation of quality measurements. The implementation of automatic statistical process control (SPC) allows for Preventive Maintenance actions (tool readjustments / repairs), and the identification of root causes. The implementation of Quality Alerts in anticipation can allow for an analysis of root causes / the adoption of a backup process or replacement of qualified machines.

Claims

CLAIMS 1. Method for screwing and controlling the quality of screwing operations, on a production line comprising a succession of work stations, 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 work stations, each screwing operation carried out at a work station being carried out by means of a screwing device dedicated to the corresponding station and screwing operation; - a step of quality control of said at least one screwing operation; characterized in that the step of quality control of a screwing operation is carried out at a work station subsequent to the work station where said controlled screwing operation was carried out, said quality control step being carried out by means of a screwing device dedicated to said subsequent station.

2. 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 previously been carried out.

3. Method according to claim 2 in which each screwing device dedicated to a workstation is programmed to carry out at this workstation at least one screwing operation and / or at least one control operation at the corresponding screwing or control points.

4. Method according to claim 3 in which the order of carrying out the operations to be carried out at a workstation is predetermined.

5. Method according to claim 3 or 4, said method comprises, prior to carrying out each of said steps of carrying out a screwing operation and steps of carrying out a control operation, a step of geolocating said corresponding screwing device, relative to said screwing points and / or to 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.

6. 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 to the control point corresponding to said activated screwing or control operation, all the other screwing points and control points other than that at which the activated screwing or control operation must be carried out being masked 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, a step of illuminating the screwing point or the corresponding control point where said activated operation is to be carried out.

8. Method according to any one of claims 1 to 7 comprising, during the performance of each step of carrying out a screwing operation, a possible step of detecting over-tightening illustrating that the screwing operation is carried out on a tightening previously carried out rather than on a tightening to be carried out.

9. Method according to any one of claims 1 to 8 comprising, at the end of 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 interval, then a step of generating a first screwing report.

10. Method according to any one of claims 1 to 9 in which each quality control operation comprises: - a training step in the direction of screwing the screwed element during the screwing operation to be controlled; - a step of detecting, during the previous step, the sliding of said screwed element relative to said structure to be assembled; - a step of stopping said training step after detecting said slippage; - a step of measuring the value of the sliding tightening torque reached when stopping said driving step; - 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, within a third predetermined tolerance interval, of said sliding tightening torque reached when said driving step is 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 issuing a consolidated report taking one or more of the first, second and third reports.

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

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

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