WO2022223533A1

WO2022223533A1 - Method for monitoring a screwing or drilling process by clustering

Info

Publication number: WO2022223533A1
Application number: PCT/EP2022/060270
Authority: WO
Inventors: David Herault; David AICHELIN
Original assignee: Etablissements Georges Renault
Priority date: 2021-04-19
Filing date: 2022-04-19
Publication date: 2022-10-27
Also published as: FR3122014A1

Abstract

The invention relates to a method for monitoring a screwing or drilling process involving performing a plurality of consecutive screwing or drilling operations according to a predetermined strategy, said method comprising: - a step of collecting the results of a plurality of said screwing or drilling operations; - a step of clustering said results; - a step of counting the number of clusters identified in said clustering step; - a step of emitting a first type of alert when the number of clusters identified equals at least 2.

Description

DESCRIPTION

Title: Process for monitoring a screwing or drilling process by partitioning

1. Field of the invention

The field of the invention is that of monitoring the quality of operations carried out in industrial production, such as, for example, screwing or drilling operations.

2. Prior Art

In many industrial fields, assembly lines are implemented to produce products, particularly in medium and large series. This is for example the case of the field of automobile production, that of household appliances or other...

On assembly lines, servo-driven screwdrivers, fitted with sensors and connected to a controller, are mainly used to screw together assemblies of technical parts. These screwdrivers collect and transmit a very large amount of information related to the results of the tightenings carried out. These data can be used to statistically analyze the evolution and quality of tightenings. Several thousand tightenings can be carried out every day on one line.

The maintenance and quality departments of the companies analyze this data a posteriori to estimate a general level of quality of the assembly as well as to detect statistically trends in the evolution of the tightening process and possibly identify undetected quality problems on workstation, which could be related to the screwdriver, the assembly, the operator or the environment.

An automobile assembly line has dozens of assembly stations. One or more types of screwing are performed at each station, and each type of screwing has one or more occurrences per vehicle to be produced. One or more screwdrivers are used by an operator on each of the stations. The operator tightens all the nuts at his station, the screwdrivers collect the tightening results and these are recorded in a database.

According to a predetermined frequency, for example monthly, the quality or maintenance departments retrieve all the tightening results carried out over a period and analyze them to detect any problems.

There are several types of tightening strategies: so-called torque tightenings: a tightening operation of this type is carried out until a target tightening torque is reached; after tightening, the torque tightening must be within a tolerance interval predefined by minimum and maximum torque values, and the tightening angle reached must also be within an interval predefined by minimum and maximum angle values; so-called angle tightening: a tightening operation of this type is carried out until a target tightening angle is reached; at the end of the tightening, the tightening angle must be within a tolerance interval predefined by minimum and maximum angle values, and the tightening torque reached must be within an interval predefined by minimum and maximum values of torque.

The angle is counted from an angular counting threshold which is a level of torque reached during the rise in torque.

The interest of an angle screwing is to have a better regularity of the force installed in the screw body than the strategy consisting in applying a torque objective. Indeed, the fact of tightening at an angle makes it possible to directly control the elongation value of the screw and therefore the force installed in the screw. Conversely, the relationship between torque and force installed in the screw involves friction in the thread which can vary from one screw to the next and therefore introduce greater variability in the force installed.

Also referred to as tightening strategy is the set of parameters that the behavior of the tightening system must follow during tightening. This includes the rotation frequencies of pre-tightening (initial phase of a tightening carried out at high speed most often until the head of the screw approaches the assembly) and tightening (finalization of tightening until reaching the torque or the objective angle), the torque or objective angle values, the associated tolerances, the angular counting threshold, etc.

A result of a tightening operation is generally a data couplet including the maximum torque and angle values reached during the torque increase. These values are assumed to be within a tolerance interval. Their dispersion can be evaluated over several tightenings to determine the precision of the tightening means.

These values can be assimilated to a couplet by screwing. It is thus possible to make a graphic representation of these couplets by points on a graph whose axes represent the torque and the angle. Figure 1 illustrates such a representation.

Since industrial assembly processes are inherently stable, the points representing a succession of tightenings of the same assembly station must be grouped into a two-dimensional normal law, such as that illustrated in figure 2, one of the dimensions being the maximum torque and the other being the maximum tightening angle .

The tighter the dispersion of these points, the more regular and controlled the manufacturing process. Conversely, if these points are divided into several groups, this may reflect an abnormal process, the cause of which may be a drift in the characteristics of the screws or the assembled parts or even a degradation of the screwing or drilling means.

This dispersion can be checked by the method technician on a case-by-case basis. For this, graphic representations are displayed, for each type of tightening, for the attention of the control technician. An example of representation is illustrated in figure 1 on which are represented the couplets of results of a plurality of tightening operations of the same type. By viewing such a representation, the technician can know if the tightening results, each represented by a point, are outside the torque and tightening angle tolerance ranges. It can also detect if the results are uniform or if they are dispersed in several groups. This allows him to have information on the quality of the tightening operations carried out.

However, there are a large number of different types of tightening operations, and each type of tightening operation is carried out on several workstations and on several lines. Consequently, the technician must analyze the results line by line, station by station, and type of tightening by type of tightening.

The analysis carried out by the quality or maintenance departments is long and tedious. This involves spending a significant amount of time analyzing the data, which is also costly.

In addition, the detection of the problem is visual (graphical) and subject to errors of appreciation by the technician working on their analysis.

It may also happen that the torque or angle tolerance ranges are programmed abnormally wide. If this is the case, the tool control means are no longer able to detect whether a result of the screwing or drilling operation complies with the quality requirements or not.

There is therefore a need to improve techniques for monitoring tightening processes.

3. Objects of the invention

The object of the invention is in particular to provide an effective solution to at least some of these various problems. In particular, according to at least one embodiment, an objective of the invention is to provide a technique for monitoring a screwing or drilling process, which facilitates the work of the technician in charge of checking the quality of the results of operation.

In particular, the invention aims, according to at least one embodiment, to provide such a technique which allows a technician to simply, efficiently and quickly check a large number of operation results.

Another object of the invention is, according to at least one embodiment, to provide such a technique which can automatically detect an anomaly in the results of operations.

Another objective of the invention is, according to at least one embodiment, to provide such a technique which is simple and/effective and/or reliable and or economical.

4. Presentation of the invention

For this, the invention proposes a method for monitoring a screwing or drilling process comprising the performance of several successive screwing or drilling operations according to a predetermined strategy, said method comprising: a step of collecting the results of a plurality of said screwing or drilling operations; a step of grouping said results into groups; a step of counting the number of groups identified in said grouping step; a step of issuing a first type of alert when the number of identified groups is equal to at least 2.

Thus, according to this aspect, the invention consists in recovering a plurality of results of a type of operation and then grouping them automatically (“clusterization” in English) so as to divide these results into groups. When the number of groups of results is divided into at least two groups, an alert is issued to the attention of the technician working in quality control.

Thus, the technician, rather than checking the results one by one, is automatically informed of a drift in the results of the operations he is checking.

The technician can thus carry out the check quickly, efficiently, safely and in a relatively short time.

According to one possible characteristic, said results comprise for each operation at least one datum. According to one possible characteristic, said operations are tightening operations, said at least one datum comprising a tightening torque value or a tightening angle value.

A tightening torque can for example be measured by means of a strain gauge bridge or by measuring the current consumed by the tool rotation drive motor. Thus, a torque value can for example be the intensity measured at the level of the strain gauge bridge or at the level of the motor. More generally, a torque value or an angle value can be any information representing a torque or an angle.

According to one possible characteristic, said operations are drilling operations, said at least one datum belonging to the group comprising: a torque value along the axis of the cutting tool used to perform the operation, a depth value drilling, an axial thrust value along the axis of the cutting tool used to perform the operation.

According to one possible characteristic, said results comprise for each operation at least one couplet of data.

According to one possible characteristic, said operations are tightening operations, said at least one couplet comprising a tightening torque value and a tightening angle value.

According to one possible characteristic, said operations are drilling operations, said at least one couplet comprising: a torque value along the axis of the cutting tool used to perform the operation, and a drilling depth value , or an axial thrust value along the axis of the cutting tool used to perform the operation, and a drilling depth value.

According to one possible characteristic, each of said operation results or each of said couplets are associated with information representative of the instant at which the data of said couplet are recorded. According to one possible characteristic, a method according to the invention comprising a step of generating a second type of alert when at least one of said at least 2 groups comprises verses concentrated over a period less than a predetermined percentage of the total duration recording of the results taken into consideration to carry out said grouping step.

According to one possible characteristic, a method according to the invention comprises: a step of determining the time elapsed between the first result and the last result taken into consideration to carry out said grouping step; a step of determining the time elapsed between the first result and the last result of each of said identified groups; a step of determining the ratio between the time elapsed between the first result and the last result of each of said identified groups and the time elapsed between the first result and the last result taken into consideration to carry out said grouping step; a step of issuing said second type of alert when said ratio of one of said groups is below a predetermined threshold.

According to one possible characteristic, a method according to the invention comprises a step of displaying a chronological timeline illustrating the appearance over time of each of said results taken into consideration to carry out said grouping step, the results belonging to different groups being represented differently.

According to one possible characteristic, a method according to the invention comprises several collection and grouping steps, said collection and grouping steps being implemented successively according to a predetermined frequency.

According to a possible characteristic, each grouping step is carried out taking into account all of the operation results.

According to one possible characteristic, each grouping step is carried out taking into account the results of operations recorded since the previous grouping. The invention also relates to a device for monitoring a screwing or drilling process comprising the performance of several successive screwing or drilling operations according to a predetermined strategy, said device comprising: means for collecting the results of a plurality of said screwing or drilling operations; means for grouping said results into groups; means for counting the number of groups identified in said grouping step; means for transmitting a first type of alert when the number of identified groups is equal to at least 2.

According to one possible characteristic, said results comprise for each operation at least one datum.

According to one possible characteristic, said operations are tightening operations, said at least one datum comprising a tightening torque value or a tightening angle value.

According to one possible characteristic, said operations are drilling operations, said at least one couplet comprising: a torque value along the axis of the cutting tool used to perform the operation, and a drilling depth value , Where an axial thrust value along the axis of the cutting tool used to perform the operation, and a drilling depth value.

According to one possible characteristic, each of said operation results or each of said couplets are associated with information representative of the instant at which the data of said couplet are recorded.

According to a possible characteristic, a device according to the invention comprises means for generating a second type of alert when at least one of said at least 2 groups comprises verses concentrated over a period less than a predetermined percentage of the total duration recording of the results taken into consideration by said grouping means.

According to one possible characteristic, a device according to the invention comprises: means for determining the time elapsed between the first result and the last result taken into consideration to carry out said grouping step; means for determining the time elapsed between the first result and the last result of each of said identified groups; means for determining the ratio between the time elapsed between the first result and the last result of each of said identified groups and the time elapsed between the first result and the last result taken into consideration to carry out said grouping step; means for transmitting said second type of alert when said ratio of one of said groups is below a predetermined threshold.

According to one possible characteristic, a device according to the invention comprises means for displaying a timeline illustrating the appearance over time of each of said results taken into consideration by said grouping means, the results belonging to different groups being represented differently.

According to one possible characteristic, said collection and regrouping means are able to implement collection and regrouping steps successively according to a predetermined frequency. According to one possible characteristic, said grouping means take into account all of the results of operations to carry out each grouping.

According to one possible characteristic, each grouping is carried out by said grouping means taking into account the results of operations recorded since the previous grouping.

The invention also relates to a computer program product, comprising program code instructions for implementing a method according to any one of the above variants, when said program is executed on a computer.

The invention also relates to a computer-readable and non-transitory storage medium storing a computer program product according to the invention.

5. Description of figures

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

[Fig 1] Figure 1 illustrates an example of a visual representation of the distribution of results of operations into groups;

[Fig 2] Figure 2 illustrates an example of representation according to a two-dimensional normal law of tightening results;

[Fig 3] Figure 3 illustrates a timeline for displaying operation results;

[Fig 4] Figure 4 illustrates an example of a method according to the invention;

[Fig 5] Figure 5 illustrates an example of a device according to the invention

[FIG 6] FIG. 6 illustrates the grouping of results of operations carried out with a programming fault where the minimum tolerance of the torque has been set by mistake at 0; [Fig 7] figure 7 illustrates the grouping of results of operations carried out with a programming defect where the tolerance on the angle is too wide and therefore indiscriminate, and where the angular counting threshold is probably too low;

[Fig 8] Figure 8 illustrates curves recorded during the tightening operation as well as an angle counting threshold terminal;

[Fig 9] Figure 9 illustrates the grouping of results of operations carried out with a programming defect where the tolerance on the angle is too wide and indiscriminate.

6. Description of particular embodiments 6.1. Monitoring process

The invention relates to a method for monitoring a screwing or drilling process. A screwing or drilling process conventionally comprises the performance of a plurality of successive screwing or drilling operations according to a predetermined strategy.

A policy includes the parameters for performing a given operation and controlling its outcome.

For a tightening operation, the strategy includes, for example: movement parameters: pretightening rotation frequency tightening rotation frequency intermediate thresholds: end of pretightening torque angular counting threshold (value of the tightening torque from which one begins to measuring the tightening angle) of the end of tightening objectives: reaching a torque with angle control or reaching an angle with torque control as well as, where applicable, the tolerance intervals of these parameters, in particular those taken taken into account to assess the quality of the tightening, such as the tightening torque and/or tightening angle.

For a drilling operation, the strategy includes, for example: motion parameter: drill rotation frequency for each material traversed advance per revolution of the drill for each material traversed intermediate thresholds: torque or thrust threshold corresponding to: the entry or material exit of the drill the change of material objective of the end of the drilling: crossing of the wall by: reaching a depth value detection of a material exit. as well as, where applicable, the tolerance intervals of these parameters, in particular those taken into consideration to assess the quality of a hole, such as for example the torque and the axial thrust, where applicable layer by layer of materials.

These operations carried out according to a predetermined strategy are repeated on one or more production lines comprising one or more workstations each equipped with a screwing or drilling device comprising a screwdriver or a drill and a controller, to produce a plurality of products , such as automobiles, airplanes, household appliances or the like.

It is generally appropriate to monitor the quality of the operations carried out tool by tool, station by station, line by line.

For this, a process according to the invention can be implemented, such as that illustrated in Figure 3.

To carry out the monitoring of a screwing or drilling process comprising a plurality of screwing or drilling operations carried out according to a predetermined strategy by means of a given screwing or drilling tool on a given workstation located on a given production line, the method firstly comprises a step 10 of collecting the results of a plurality of screwing or drilling operations. A tightening result can for example comprise: a tightening torque, or a tightening angle, or one or more couplets of data comprising a tightening angle and a tightening torque.

Several couplets can be collected for a complex tightening operation comprising several successive phases such as for example a pre-tightening followed by a tightening or other.

A drilling result can for example comprise one or more couplets each comprising: a torque value along the axis of the cutting tool used to perform the operation, and a drilling depth value, or a axial thrust along the axis of the cutting tool used to perform the operation, and a drilling depth value.

Each operation result or each couplet can be associated with information representative of the instant at which the data it includes are recorded.

In the case of an operation result comprising several couplets, each couplet corresponds to a particular part of the screwing or drilling operation. Each verse must therefore be monitored.

The method therefore comprises a step 11 of grouping into group(s) the results of the screwing or drilling operation. If the operation result includes several couplets, the grouping step is performed from each couplet.

In this embodiment, the grouping step by implementing a data grouping method called DEÎSCAN.

The DBSCAN grouping process consists in evaluating the proximities between results and in considering as distinct groups areas of high density and separated.

More precisely, DBSCAN calculates for each given result how many results are at a Euclidean distance lower than a predetermined Epsilon value of this given result. If this number is greater than a predetermined value minPts then the method concludes that said given result belongs to a zone of high density.

The grouping process repeats this neighbor result evaluation to neighbor result. As long as the density remains high, the grouping process considers that the results examined and their neighboring results belong to the same zone of high density or to the same group.

When the number of neighboring results becomes less than minPts and the considered result is not close to a previously identified group, then the grouping process considers it to be an isolated result.

When the number of neighboring results is greater than minPts but the considered result is not close to a previously identified group, then the clustering process considers it to be a new cluster.

The grouping process therefore requires that the values of the two predetermined parameters Epsilon and minPts be entered, these values are subject to experimental evaluation.

The steps of collecting the results of operations and then of grouping are for example implemented according to a predetermined frequency. This frequency can for example be temporal and be performed after a predetermined production period has elapsed. This frequency can for example be based on the achievement by the number of operation results of a predetermined threshold. In a variant, each grouping step is carried out taking into account all of the results of operations collected.

In another variant, each grouping step is carried out taking into account the results of operations recorded since the previous grouping.

Alternatively, the clustering step could be performed by implementing another data clustering method, such as K-mean, for example.

At the end of the grouping stage, the results of operations taken into consideration are divided into one or more groups of results (clusters).

The method includes a step 12 of counting the number of groups identified in the grouping step.

The method also comprises a step 13 of issuing a first type of alert when the number of identified groups is equal to at least 2.

Alternatively, the method may include a step 14 of generating a second type of alert when at least one of said at least 2 groups comprises verses concentrated over a period less than a predetermined percentage of the total recording time of the results taken into consideration to carry out the grouping step. This makes it possible to indicate to the technician that a rapid drift in the process is taking place, or that a particular event may have affected the production process and that, if necessary, the cause should be determined and corrected.

The grouping by chronological group makes it possible to highlight trends: if a tightening is carried out with a torque objective and the coefficient of friction of the screw has become stronger then, the angle reached by the screw at the end of the tightening will be weaker; if tightening is carried out with an angle objective and the coefficient of friction of the screw has become higher, then the torque reached at the end of tightening will be greater.

In this case, the method comprises: a step of determining the time elapsed between the first result and the last result taken into consideration to carry out the grouping step; a step of determining the time elapsed between the first result and the last result of each of the identified groups; a step of determining the ratio between the time elapsed between the first result and the last result of each of the identified groups and the time elapsed between the first result and the last result taken into consideration to carry out the grouping step; a step of sending the second type of alert when the ratio of one of the groups is below a predetermined threshold.

The alert(s) may be visual and/or audible and can indicate to the technician carrying out the check that the results of the operations monitored are experiencing a drift.

In the case of the monitoring of tightening operations, the results of which each include a tightening angle/tightening torque couplet, the display can be a representation of the couplets in an orthonormal frame of reference whose abscissa axis is the angle of tightening and the ordinate axis is the tightening torque such as that shown in Figure 1. On this marker, the different groups of results highlighted by the grouping step will be visible by being dissociated from each other, the appearance of at least two groups indicating a drift in the tightening process. The torque and angle tolerance intervals can also be represented to allow the technician to know whether the results, independently of any drift, are compliant or not.

The alert may also correspond to the display of a timeline illustrating the appearance over time of each of said results taken into consideration to carry out the grouping step, the results belonging to different groups being represented differently. Figure 4 illustrates such a timeline.

When the method technician is required to carry out a modification of the strategy of the operation under supervision, he can choose to apply the monitoring process only to the results obtained after modification of the said strategy.

This can make it easier to compare the groups before and after changing the strategy.

Three examples of results of operations combining two clusters are presented below, in relation to FIGS. 6, 7, 8 and 9. Figure 6 illustrates the grouping of results of operations carried out with a programming fault where the minimum torque tolerance has been set by mistake at 0. Such a programming error would prevent the usual control means of the tool from detecting a drift of the process. However, the detection of several clusters makes it possible to alert the user as to a process anomaly.

More specifically, Figure 6 corresponds to the results obtained for the implementation of a torque tightening strategy with control of the tightening angle. In other words, it is desired to achieve at the end of a tightening operation an objective torque situated within a tolerance interval, and the tightening angle must be within a tolerance interval. In this example, the objective tightening torque is set at 50 N.m. with minimum and maximum torque values respectively set at 0 N.m. and 60 N.m. The limits of the tolerance interval of the tightening angle are equal to 0° and 720°. The tolerance on the angle is abnormally wide, the user was content to cap the angle at a maximum value of 720°. Likewise for the torque, the user has programmed a maximum of 60 N.m for an objective torque of 50 N.m., but he has left the minimum tolerance at 0.

We observe that the results of operations are grouped into two clusters, with some results not belonging to either of the two clusters. Note that: the most populous cluster (21019 operation results) with an average tightening torque level of 2 N.m and an average tightening angle of around 200 the least populous cluster (52 operation results ) with an average tightening torque level of 25 N.m and an average tightening angle of around 100°. The tightening torque level reached for these two clusters is very far from the objective torque for a reason that is not identified here.

The operator can deduce the existence of a programming fault and resolve it after checking the tightening parameters.

The presence of two clusters can here make it possible to obtain an alert on the programming fault. Figure 7 corresponds to the results obtained for the implementation of a torque tightening strategy with control of the tightening angle. In other words, it is desired to achieve, at the end of a tightening operation, an objective torque situated within a tolerance interval, and the tightening angle must be within a tolerance interval. In this example, the target tightening torque is set at 2 Nm with minimum and maximum torque values respectively set at 1.5 Nm and 2.5 Nm The limits for the tightening angle tolerance interval are equal to 10° and 9999°. The angle tolerance is abnormally large (in fact the user left the default value on the maximum angle tolerance).

FIG. 8 illustrates two tightening curves recorded during the performance of two tightening operations. These curves express the variation in tightening torque as a function of the tightening angle. The angle counting threshold is shown on this graph. The angle count threshold is the torque level at which the angle begins to be measured. Conventionally, an initial torque plateau corresponding to the pre-tightening torque is observed on each curve until the head of the screw approaches the element to be tightened, then a rise in torque until the final tightening torque is reached. Note that for one of the curves, the tightening torque during the pre-tightening phase is lower than the angle counting threshold, while for the other curve, this torque is higher than the angle counting threshold.

It is observed that the results of operations are grouped into two clusters, some results not belonging to either of the two clusters. Note that: the most populous cluster (1373 operation results) with an average angle of around 200°: for these results, the angle counting threshold had to be reached at the foot of the torque climb , as shown in one of the curves in figure 8. the least populous cluster (14 operation results) with an average angle of 800°: for these results, the pre-tightening torque must be greater than the counting threshold d angle for example due to a self-tapping screw and the counting threshold had to be reached from the start of pre-screwing, as illustrated on one of the curves in figure 8. The operator can deduce therefrom, after analysis of the parameters of the tightening strategy, the existence of a programming defect which is twofold: a tolerance on the tightening angle that is too wide and therefore indiscriminate; the probable programming of an angular counting threshold that is too low with a screw whose pre-tightening torque can vary from one screw to another and sometimes exceed the counting threshold, this leading to the measured angle no longer characterizing only the increase in torque but also takes into account the pre-screwing angle which is not necessarily sought.

The presence of 2 clusters makes it possible to obtain an alert on the programming fault. FIG. 9 corresponds to the results obtained for the implementation of a torque tightening strategy with control of the tightening angle. In other words, it is desired to achieve, at the end of a tightening operation, an objective torque situated within a tolerance interval, and the tightening angle must be within a tolerance interval. In this example, the target tightening torque is set at 4 Nm with minimum and maximum torque values respectively set at 3.6 Nm and 4.4 Nm The limits for the tightening angle tolerance interval are equal to 0° and 9999°. The tolerance on the angle is abnormally large (in fact the user left default values). It is observed that the results of operations are grouped into two clusters, some results not belonging to either of the two clusters. Note that: the most populous cluster (172 operation results) with an average tightening angle of around 25°: for these results, the angle counting threshold had to be reached at the foot of the climb in torque of the corresponding tightening curves and the measured tightening angle undoubtedly reflects the angle of increase in torque measured from the start of the increase in torque of the tightening phase. the least populous cluster (26 operation results) with an average screwing angle of 11°: for these results, it is possible that this low angle is explained by poor engagement of the screw in the thread, leading to seizing of the screw before tightening it, the tightening torque having increased very quickly with a low tightening angle. The operator can deduce the existence of a programming fault relating to a tolerance on the angle that is too wide and therefore non-discriminating.

The presence of 2 clusters thus makes it possible to obtain an alert on the programming fault.

6.2. Monitoring device

A screwing or drilling device for which it is desired to monitor the results of operations conventionally comprises a tool (a screwdriver or a drill) connected to a controller.

The tool includes all the sensors used to measure the data composing the results of the operation.

The tool and/or its controller can be connected to a server and/or a human-machine interface, such as a PC.

A monitoring device according to the invention comprises all the hardware and software components making it possible to implement the different steps of the method. These components are known per se and include in particular the sensors necessary for measuring the parameters making up the results of operations, a microprocessor, one or more memories containing a computer program comprising program code instructions for the execution of a method according to the invention the execution of a monitoring method according to the invention. Such components are known and not described in further detail. Their respective functionalities are described in relation to the description of the monitoring method according to the invention.

A monitoring device according to the invention comprises in particular with reference to FIG. 5: functional means 20 for collecting the results of operations; functional means 21 for grouping operation results into groups; functional means 22 for counting the groups of results of operations; functional means 23 for transmitting a first type of alert when the number of groups is at least equal to 2. Such a device can also comprise functional means 24 for generating a second type of alert when at least one of said at least 2 groups comprises couplets concentrated over a period less than a predetermined percentage of the total recording time of the results taken into consideration to perform the grouping step. This lets the technician know that rapid process drift is occurring.

Claims

1. Method for monitoring a screwing or drilling process comprising the performance of several successive screwing or drilling operations according to a predetermined strategy, said method comprising: a step of collecting the results of a plurality of said screwing or drilling; a step of grouping said results into groups; a step of counting the number of groups identified in said grouping step; a step of issuing a first type of alert when the number of identified groups is equal to at least 2.

2. Method according to claim 1 wherein said results comprise for each operation at least one datum.

3. Method according to claim 2, in which said operations are tightening operations, said at least one datum comprising a tightening torque value or a tightening angle value.

4. Method according to claim 2, in which said operations are drilling operations, said at least one datum belonging to the group comprising: a torque value along the axis of the cutting tool used to perform the operation, a drilling depth value, an axial thrust value along the axis of the cutting tool used to perform the operation.

5. Method according to claim 1, in which the said results comprise, for each operation, at least one couplet of data.

6. Method according to claim 5 wherein said operations are screwing operations, said at least one couplet comprising a screwing torque value and a screwing angle value.

7. Method according to claim 5, in which said operations are drilling operations, said at least one couplet comprising: a torque value along the axis of the cutting tool used to perform the operation, and a value drilling depth, or an axial thrust value along the axis of the cutting tool used to perform the operation, and a drilling depth value.

8. Method according to any one of claims 2 to 7 wherein each of said operation results or each of said couplets are associated with information representative of the time at which the data of said couplet are recorded.

9. Method according to claim 8 comprising a step of generating a second type of alert when at least one of said at least 2 groups comprises verses concentrated over a period less than a predetermined percentage of the total recording time of the results taken into consideration to carry out said grouping step.

10. Method according to claim 9 comprising: a step of determining the time elapsed between the first result and the last result taken into consideration to carry out said grouping step; a step of determining the time elapsed between the first result and the last result of each of said identified groups; a step of determining the ratio between the time elapsed between the first result and the last result of each of said identified groups and the time elapsed between the first result and the last result taken into consideration to carry out said grouping step; a step of transmitting said second type of alert when said ratio of one of said groups is below a predetermined threshold.

11. Method according to any one of claims 1 to 10 comprising a step of displaying a timeline illustrating the appearance over time of each of said results taken into consideration to carry out said grouping step, the results belonging to different groups being represented differently.

12. Method according to any one of claims 1 to 11 comprising several collection and grouping steps, said collection and grouping steps being implemented successively according to a predetermined frequency.

13. Method according to claim 12, in which each grouping step is carried out taking into account all of the operation results.

14. Method according to claim 12, in which each grouping step is carried out taking into account the results of operations recorded since the previous grouping.

15. Device for monitoring a screwing or drilling process comprising the performance of several successive screwing or drilling operations according to a predetermined strategy, said device comprising: means for collecting the results of a plurality of said screwing or drilling; means for grouping said results into groups; means for counting the number of groups identified in said grouping step; means for transmitting a first type of alert when the number of identified groups is equal to at least 2.

16. Device according to claim 15 wherein said results comprise for each operation at least one datum.

17. Device according to claim 16, in which said operations are screwing operations, said at least one datum comprising a screwing torque value or a screwing angle value.

18. Device according to claim 16, in which said operations are drilling operations, said at least one datum belonging to the group comprising: a torque value along the axis of the cutting tool used to perform the operation, a drilling depth value, an axial thrust value along the axis of the cutting tool used to perform the operation.

19. Device according to claim 15, in which the said results comprise, for each operation, at least one couplet of data.

20. Device according to claim 19, in which said operations are screwing operations, said at least one couplet comprising a screwing torque value and a screwing angle value.

21. Device according to claim 19, in which said operations are drilling operations, said at least one couplet comprising: a torque value along the axis of the cutting tool used to perform the operation, and a value drilling depth, or an axial thrust value along the axis of the cutting tool used to perform the operation, and a drilling depth value.

22. Device according to any one of claims 16 to 21 wherein each of said operation results or each of said couplets are associated with information representative of the time at which the data of said couplet are recorded.

23. Device according to claim 22 comprising means for generating a second type of alert when at least one of said at least 2 groups comprises verses concentrated over a period less than a predetermined percentage of the total recording time of the results taken into consideration by said grouping means.

24. Device according to claim 23 comprising: means for determining the time elapsed between the first result and the last result taken into consideration to carry out said grouping step; means for determining the time elapsed between the first result and the last result of each of said identified groups; means for determining the ratio between the time elapsed between the first result and the last result of each of said identified groups and the time elapsed between the first result and the last result taken into consideration to carry out said grouping step; means for transmitting said second type of alert when said ratio of one of said groups is below a predetermined threshold.

25. Device according to any one of claims 15 to 24 comprising means for displaying a timeline illustrating the appearance over time of each of said results taken into consideration by said grouping means, the results belonging to different groups being represented differently.

26. Device according to any one of claims 15 to 25, in which said collection and grouping means are able to implement collection and grouping steps successively according to a predetermined frequency.

27. Device according to claim 26, in which the said grouping means take account of all the results of operations to carry out each grouping.

28. Device according to claim 26, in which each grouping is carried out by said grouping means taking into account the results of operations recorded since the previous grouping.

29. Computer program product, comprising program code instructions for implementing a method according to any one of claims 1 to 14, when said program is executed on a computer.

30. A computer-readable, non-transitory storage medium storing a computer program product according to claim 29.