KR20220032558A - Process monitoring method for monitoring the bonding of at least two workpieces by means of a self-piercing riveting device with bonding tongs, and a device having a control unit designed to carry out the method - Google Patents

Abstract

A process monitoring method for monitoring the engagement of at least two workpieces by a self-piercing riveting device having engagement tongs, wherein the at least two workpieces are disposed between a punch and a counter support, and between the punch and the workpiece facing the punch. The placed rivet is pressed against the at least two workpieces by applying a force F to the punch, which force acts in the direction of the counter holder. According to this method: a) the total sheet metal thickness, rivet length, and bending constant of the bonding tongs are detected for a plurality of bonding operations for each operation before bonding; b) the punch path for a specific force, the final force, the path final value for the final force, the set path of the rivet, and the rivet head final position are detected for a plurality of engaging operations for each operation during and/or after engagement become; c) according to the parameters detected in steps a) and b), absolute force/path windows and/or relative force/path final windows of the plurality of joining operations are determined; d) the determined absolute force/path window and/or the relative force/path final window of the at least one further joining operation is combined with the absolute force/path window and/or the relative force/path final window of the plurality of joining operations determined in step c) are compared, and at least one further bonding operation is monitored so that any bonding related defects are identified.

Description

Process monitoring method for monitoring the bonding of at least two workpieces by means of a self-piercing riveting device with bonding tongs, and a device having a control unit designed to carry out the method

The present invention relates to a process monitoring method for monitoring the bonding of at least two workpieces by means of a self-piercing riveting device with engaging forceps, and to a device having a control unit designed to carry out such a method.

The self-piercing riveting method serves to join at least two workpieces, wherein the rivet is pressed into the at least two workpieces by means of a punch or punching tool, and by means of a counter holder of a corresponding shape cooperating with the punching tool, the rivet Or it is ensured that the workpiece is deformed in a certain way to create friction and a positive connection between the workpieces.

A self-piercing riveting method is known from the prior art in which quality control is performed by an envelope of a force/displacement profile. When components of a brittle material are joined by a self-piercing riveting method, defects, such as cracks, may develop as a result of the application of force. The occurrence of these defects results in certain short-time fluctuations in the force applied to the punch and components. Thereby it is possible to check whether the force profile moves within certain limits of the envelope. Deviations from the envelope result in installation disruption, which makes it necessary to perform a manual check and release the affected component. Any deviation from the envelope does not mean that the quality of the resulting component is unsatisfactory; for this reason, inspect the component and determine which component is actually affected. In general, only a small fraction of the components are affected. Thus, the envelope is learned based on the defined production lot. However, this procedure is complicated because it has to be newly performed for each type of component and a large number of parameters must be set.

In a self-piercing riveting device, it is likewise known how the punching force with respect to the pressing displacement of the punch and its gradient are determined during the setting of the rivet. When a rivet joint fails, there is a variation in the draft profile. Thereby, the gradient of force is determined for a specific time and/or displacement range during pressing of the rivet. Because the fluctuations in the punching force gradient are generally relatively small, such fluctuations are not detected in the context of monitoring the force profile within certain limits.

German published application DE 10 2016 214 943 A1 discloses a method of joining at least two components by means of a self-piercing riveting device, the at least two components being arranged between the punch and the counter holder, the punch and at least A rivet arranged between one of the two components facing the punch is pressed into the at least two components in a state where a force is applied to the punch, and during pressing of the rivet, a gradient of the force is determined at least temporarily. A manufacturing device having such a self-piercing riveting device is further disclosed.

However, a disadvantage of the method known from the prior art is that when a limit is applied to the force or gradient of force required to press the rivet into the two components to be joined, a mating part completely free of any defects is rejected .

Accordingly, the object underlying the present invention is to provide a process monitoring method for monitoring the bonding of at least two workpieces by means of a self-piercing riveting device with engaging forceps, and a device having a control unit designed to carry out such a method As a result, the mentioned disadvantages do not occur and in particular more accurate quality control is possible.

The object is achieved in that the subject matter of the independent claims is provided. Advantageous embodiments follow from the dependent claims.

The object is achieved in particular in that there is provided a process monitoring method for monitoring the engagement of at least two workpieces by means of a self-piercing riveting device with engagement tongs, the at least two workpieces being arranged between the punch and the counter holder, A rivet arranged between the punch and the workpiece facing the punch is pressed against the at least two workpieces by the punch with a force F in the direction towards the counter holder applied to the punch. The method is as follows: a) the total thickness of the bonding tongs, the rivet length, and the bending constant are recorded for a plurality of bonding operations prior to bonding, and b) the punch displacement at a specified force, the final force, the displacement final value at the final force, the rivet the set displacement of, and the rivet head final position are recorded for a plurality of joining operations during and/or after mating, c) absolute force/ a displacement window and/or a relative force/displacement final window is determined, d) the determined absolute force/displacement window and/or the relative force/displacement final window of the at least one further coupling operation is determined in step c) of the plurality of coupling operations characterized in that the absolute force/displacement window and/or the relative force/displacement final window are compared and at least one further joining operation is monitored such that defects in the joining are identified.

Preferably, the at least two workpieces have a total thickness, in particular a total sheet thickness.

Preferably, by applying a process monitoring method, the quality determining area is deterministically determined.

A defect is understood to be in particular a crack.

A quality determining area is understood to be in particular the area of the absolute force/displacement window and/or the area of the relative force/displacement final window which is important for the quality of the joining operation and/or the joined at least two workpieces in which defects can be identified.

Preferably, the workpiece is formed of a metal or metal alloy.

Preferably, the joining of at least two workpieces yields a component.

A component is understood to be in particular a part of a vehicle, in particular a bodywork component, preferably a passenger car, truck, bus, camper, construction vehicle, commercial vehicle or rail vehicle, boat, ship or aircraft.

Preferably, the component is a coated component, in particular a painted or galvanized component.

Preferably, process monitoring is performed automatically.

The process monitoring method according to the invention for monitoring the bonding of at least two workpieces by means of a self-piercing riveting device with engaging forceps has advantages compared to the prior art. Advantageously, improved quality control is ensured. Advantageously, the number of components that are erroneously identified as defective is reduced. Advantageously, the availability of the components is increased and in particular installation interruptions are reduced. Advantageously, costs are reduced and faster production is possible. Advantageously, monitoring of the entire bonding operation is not required. Advantageously, training costs for commissioning and serial operation of the plant are reduced. Advantageously, no specially trained staff is required.

According to a further development of the invention, it is provided that the relevant quality determining area of the combining operation is determined, and process monitoring is reduced to the relevant quality determining area.

Preferably, a quality determining area of the envelope is defined and process monitoring is reduced to the quality determining area of the envelope.

According to a further development of the invention, it is provided that the relevant quality determining region is determined time-dependently and/or displacement-dependently.

Preferably, in step c) a gradient of the force/displacement profile and/or the force/time profile, in particular the force/displacement profile and/or the force/time profile, is recorded. Preferably, the gradient is determined from the force/displacement profile and/or the force/time profile. Thus, it is ensured that an erroneous pressing of the rivet with the two workpieces to be joined is identified, since this erroneous engagement is in most cases associated with a sharp pressing movement. Such an abrupt pressing motion can be viewed as a sharp rise or fall in the force/displacement profile.

According to a further development of the present invention, in step d), the defect in the bonding is determined by the determined absolute force/displacement window and the relative force/displacement final window of the further bonding operation and the determined absolute force/displacement window of the plurality of bonding operations and/ or to be identified above a certain threshold of the difference between the relative force/displacement final windows.

A threshold is in particular understood to be a specific difference between the determined absolute force/displacement window and the relative force/displacement final window of a further coupling operation and the determined absolute force/displacement window and/or the relative force/displacement final window of a plurality of coupling operations. . Above the threshold, defects in binding are identified and below the threshold, defects in binding are not identified. The threshold may be determined or specified according to requirements.

According to a further development of the invention, it is provided that the threshold is determined by comparison with at least one standard component and/or by learning based on a plurality of combining tasks.

According to a further development of the invention, the parameters of steps a) and b) are at least one specific time and/or range of displacement during pressing of the punch, preferably at least one time and/or that a defect is expected on the basis of experience. Alternatively, it is provided that is determined in a displacement range.

According to a further development of the invention, it is provided that no gradients are used for process monitoring, in particular for identifying defects in the joining, and in particular no gradients of force used during pressing of the rivets.

According to a further development of the invention, it is provided that the parameters recorded in steps a) and b) are weighted differently to determine the absolute force/displacement window and/or the relative force/displacement final window.

According to a further development of the invention, it is provided that at least one further parameter, in particular a force/displacement profile and/or a force/time profile of the joining operation, is used for process monitoring.

The object is also achieved in that there is provided a device having a control unit designed to carry out the method according to the invention, in particular according to one of the previously described exemplary embodiments, the device comprising: a self-serve with engaging forceps, a punch and a counter holder It further has a piercing riveting device, wherein a force F in a direction towards the counter holder can be applied to the punch so that the rivet can be pressed into at least two workpieces arranged between the punch and the counter holder, the device setting the parameters a sensor for recording, and determining an absolute force/displacement window and a relative force/displacement final window of a plurality of coupling operations and combining this with the determined absolute force/displacement window and/or a relative force/displacement final window of at least one further coupling operation; It has at least one evaluation unit for comparison. The advantages already described above with respect to the process monitoring method for monitoring the bonding of at least two workpieces, in particular by means of a self-piercing riveting device with engaging forceps, are thereby obtained for the device.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail below with reference to the drawings. One figure shows, as a flow chart, a schematic diagram of an exemplary embodiment of a process monitoring method for monitoring the joining of at least two workpieces by means of a self-piercing riveting device having joining forceps.

The figure shows in a flow chart a schematic diagram of an exemplary embodiment of a process monitoring method for monitoring the bonding of at least two workpieces by means of a self-piercing riveting device having engagement tongs. In a process monitoring method for monitoring the bonding of at least two workpieces by a self-piercing riveting device having engagement tongs, the at least two workpieces are arranged between a punch and a counter holder, and between the punch and the punch-facing workpiece. The arranged rivets are pressed against the at least two workpieces by the punch with a force F in the direction towards the counter holder being applied to the punch. In step a), the total thickness of the bonding tongs, the rivet length, and the bending constant are recorded for a plurality of bonding operations prior to bonding. In step b), the punch displacement at a specified force, the final force, the final displacement value at the final force, the set displacement of the rivet, and the rivet head final position are recorded for a plurality of engagement operations during and/or after engagement. In step c), according to the parameters recorded in steps a) and b), an absolute force/displacement window and/or a relative force/displacement final window of a plurality of joining operations is determined. In step d), the determined absolute force/displacement window and/or the relative force/displacement final window of the at least one further coupling operation is the absolute force/displacement window and/or the relative force/displacement window determined in step c) of the plurality of coupling operations The final window is compared, and at least one further joining operation is monitored so that defects in the join are identified.

Thereby, improved quality control is ensured. The number of components erroneously identified as defects is reduced. Advantageously, costs are reduced and faster production is possible.

In an embodiment of the present invention, the relevant quality determining area of the combining operation is determined, and process monitoring is reduced to the relevant quality determining area.

In another embodiment of the invention, the relevant quality determining region is determined time-dependently and/or displacement-dependently.

In another embodiment of the present invention, in step d), the defect in the engagement comprises: a determined absolute force/displacement window and a relative force/displacement final window of a further bonding operation and a determined absolute force/displacement window of a plurality of bonding operations and/ or above a certain threshold of difference between relative force/displacement final windows.

In another embodiment of the invention, the threshold is determined by comparison with at least one standard component and/or by learning based on a plurality of combining tasks.

In another embodiment of the invention, the parameters of steps a) and b) are at least one specific time and/or displacement range during pressing of the punch, preferably at least one time and/or at least one time and/or a defect is expected based on experience. or in the displacement range.

In another embodiment of the present invention, no gradient is used for process monitoring, particularly to identify defects in bonding.

In another embodiment of the invention, the parameters recorded in steps a) and b) are weighted differently to determine the absolute force/displacement window and/or the relative force/displacement final window.

In another embodiment of the invention, at least one further parameter is used for process monitoring, in particular the force/displacement profile and/or the force/time profile of the joining operation.

The method is carried out in particular in a device having a control unit designed to carry out said method. The device has a self-piercing riveting device with engaging forceps, a punch and a counter holder, wherein a force F in a direction towards the counter holder can be applied to the punch so that the rivet is arranged between the punch and the counter holder for at least two operations can be pressed sideways, the device includes a sensor for recording the parameters, and an absolute force/displacement window and a relative force/displacement final window of a plurality of mating operations, which determine the determined absolute force/displacement window of the at least one further mating operation at least one evaluation unit for comparison with a window and/or a relative force/displacement final window.

Claims (10)

A process monitoring method for monitoring the engagement of at least two workpieces by a self-piercing riveting device having engagement tongs, wherein the at least two workpieces are arranged between a punch and a counter holder, and between the punch and the punch-facing workpiece. A method in which the arranged rivets are pressed against the at least two workpieces by the punch with a force F in the direction towards the counter holder being applied to the punch,
a) the total thickness of the bonding tongs, the rivet length, and the bending constant are recorded for a plurality of bonding operations prior to bonding;
b) the punch displacement at a specified force, the final force, the final displacement value at the final force, the set displacement of the rivet, and the rivet head final position are recorded for a plurality of engagement operations during and/or after engagement;
c) determining, according to the parameters recorded in steps a) and b), absolute force/displacement windows and/or relative force/displacement final windows of a plurality of joining operations, and
d) the determined absolute force/displacement window and/or the relative force/displacement final window of the at least one further coupling operation is combined with the absolute force/displacement window and/or the relative force/displacement final window determined in step c) of the plurality of coupling operations A method comprising the step of being compared, wherein at least one further bonding operation is monitored such that defects in bonding are identified. Method according to claim 1, characterized in that a relevant quality-determining area of the combining operation is determined, and process monitoring is reduced to the relevant quality-determining area. Method according to claim 2, characterized in that the relevant quality determining region is determined in a time-dependent manner and/or in a displacement-dependent manner. 4. The method according to any one of claims 1 to 3, wherein, in step d), the defects in the joining are: a determined absolute force/displacement window of a further joining operation and a determined absolute force/displacement window of a further joining operation and a determined absolute of a plurality of joining operations with a relative force/displacement final window. and/or is identified above a certain threshold of difference between the force/displacement window and/or the relative force/displacement final window. Method according to one of the preceding claims, characterized in that the threshold value is determined by comparison with at least one standard component and/or by learning based on a plurality of combining tasks. 6. The method according to any one of the preceding claims, wherein the parameters of steps a) and b) are at least one specific time and/or displacement range during the pressing of the punch at which a defect is predicted, preferably on the basis of experience. Method, characterized in that determined in at least one time and/or displacement range. Method according to one of the preceding claims, characterized in that no gradients are used for process monitoring, in particular for identifying defects in bonding. 8. The method according to any one of the preceding claims, characterized in that the parameters recorded in steps a) and b) are weighted differently to determine the absolute force/displacement window and/or the relative force/displacement final window. How to. 9 . The method according to claim 1 , characterized in that at least one further parameter, in particular a force/displacement profile and/or a force/time profile of the joining operation, is used for process monitoring. A device having a control unit designed to carry out a method according to any one of claims 1 to 9, the device further having a self-piercing riveting device with engaging forceps, a punch and a counter holder, facing the counter holder A force F of can be applied to the punch so that the rivet can be pressed into at least two workpieces arranged between the punch and the counter holder, the device comprising a sensor for recording the parameters, and the absolute force of a plurality of joining operations /device having at least one evaluation unit for determining the displacement window and the relative force/displacement final window and comparing it with the determined absolute force/displacement window and/or the relative force/displacement final window of the at least one further coupling operation.

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