Method for monitoring a crimping device, monitoring unit and crimping device

Abstract

The invention relates to a method for monitoring a crimping device, a monitoring unit, and a crimping device. Such a crimping device is used to connect contact parts and electrical conductors. For example, a contact part and a conductor are connected to each other by plastic deformation of the contact part.

Description

Technical area

[0001] The invention relates to a method for monitoring a crimping device and to a crimping device. Such a crimping device is used to connect contact parts and electrical conductors. For example, a contact part and a conductor are connected to each other in a force-locking manner by plastic deformation of the contact part. State of the art

[0002] It is already known to determine a so-called crimp force curve during a crimping process. Using the crimp force curve, it can be determined, for example, whether a crimping process was successful, or whether a crimp contact was not inserted into the crimping press during the crimping process, or whether a wire strand was missing.

[0003] For example, DE 101 44 322 A1 describes a method for producing an electrical insulation displacement connection. In this process, a corresponding force and / or displacement sensor is preferably introduced into the press-in or joining process in order to record the forces or displacements resulting during the press-in or joining process. The measured values ​​supplied by the sensors are fed to an evaluation unit in order to determine the actual process curve. According to one embodiment, a process-specific tolerance range is assigned to each actual process curve, and a bad or error message is only output if the determined actual process curve lies at least substantially outside this tolerance range. When dimensioning the tolerance range, the permissible process fluctuations in particular can be taken into account. On the basis of the process curve comparison carried out, errors in the press-in or joining process, for example, can be identified.Joining process, material defects, tool breakage or corresponding defects in the press-in or joining device, contact errors and all other significant manufacturing or production errors are recorded.

[0004] While such an approach has generally proven effective in quality assurance, if a deviation outside the tolerance range is detected, action can only be taken after the error has already occurred. If it is determined that the material feed is failing, for example, because the corresponding workpiece storage unit has been emptied, the crimping device is stopped. This leads to undesirable downtime of the system.

[0005] US Patent No. 6,418,769 B1 describes a method for quality assurance of crimped connections produced with a crimping device. An electronic data storage device stores tool-specific data derived from a force-stroke characteristic curve of a crimping process of the tool.

[0006] US 2010 / 0139351 A1 also discloses a method for determining the quality of a crimp connection between a conductor and a contact, in the course of which a crimping device is operated to exert a crimping force on a conductor and a contact.

[0007] EP 1 071 174 A1 describes a terminal crimp quality decision method by which the crimp quality of the terminal crimped to the conductor is determined. Subject of the invention

[0008] The invention aims to ensure the availability of a crimping device while maintaining a high level of quality and to avoid or reduce downtimes.

[0009] The subject matter of claim 1 provides a corresponding method. Preferred embodiments are listed in the dependent claims. Furthermore, the invention relates to a crimping device according to claim 12.

[0010] According to the invention, the production of defective parts (faulty crimp connections) can be prevented at an early stage. Furthermore, predictive maintenance for the elements of a crimping device, in particular the crimping die and anvil, can be implemented on this basis. The wear status and thus upcoming replacements can be predicted based on models. This allows the production process to prepare for an upcoming replacement situation in advance, significantly reducing setup and / or downtimes.

[0011] The crimping force curve mentioned below can also be referred to as the crimping process curve.

[0012] The invention provides a method for monitoring a crimping device, which comprises the following steps: recording a crimping force curve (or also called crimping process curve), determining at least one characteristic value of the crimping force curve, comparing the determined characteristic value with at least one threshold value that defines a (wear) state of one or more tools, in particular the crimping die or the anvil, of the crimping device.

[0013] Several thresholds should be provided. If a first threshold is exceeded, a user is notified (for example, by a message on the machine's display or by sending an electronic message). If a second threshold is exceeded, an order is requested. If a third threshold is exceeded, a machine shutdown is triggered. The third threshold is the one closest to the time of reaching the maximum wear level or corresponds to the value of the maximum wear level. This allows the user to be informed in a timely manner about the necessary steps.

[0014] In particular, such a crimping device can comprise a crimping die and an anvil, which, through relative movement, attach a contact element to a conductor. The crimping force curve or crimping process curve is the force curve during a working cycle or a portion thereof. To determine the force curve, a force or pressure sensor can be provided in the area of ​​the crimping die, anvil, or eccentric press.

[0015] According to a preferred embodiment, the integral of the crimping force curve is determined as the characteristic value. The integral corresponds to the work performed by the crimping device, which is converted during a specific forming process. As wear progresses, the work / energy required for the crimping process increases, so that a wear condition can be derived accordingly.

[0016] According to a further embodiment, a local maximum can be determined as the characteristic value, which can be precisely read from the determined or documented crimping force curve / crimping process curve.

[0017] In particular, a (first) local maximum (k1; K2) in the crimping force curve can describe the point in time at which tabs of the crimp contact start to roll in the vertices of the radii of the crimping die.

[0018] It has been shown that the (first) local maximum changes in force level and / or travel position as the radii of the crimping tool undergo wear. Thus, for example, the force level and / or travel or angular position of the first local maximum k1 or its distance from the point of maximum compressive force (bottom dead center of the crimping die) can be used as a parameter for crimping die wear.

[0019] The force level can be an absolute force level or a relative force level, for example, relative to the maximum compressive force. The displacement or angular position can be an absolute displacement or angular position or a relative displacement or angular position, for example, relative to the maximum compressive force.

[0020] Preferably, a (second) local maximum (k2) in the crimp force curve can describe the point in time at which the tabs of the crimp contact touch. If the crimping process is symmetrical, there is a kind of "collision" of the crimp tabs.

[0021] This leads to a corresponding increase in force and thus to the (second) local maximum (k2). A second local maximum is thus formed in tools in such a way that it is clear that the crimping die is not yet worn. If, however, wear is present, the crimping occurs asymmetrically, so that the second local maximum (k2) is no longer pronounced.

[0022] The second local maximum (k2) can therefore also be an indication of a corresponding wear condition of the tool. The second local maximum (k2) can also change the force level and / or the travel or angular position as the radii of the crimping tool wear. The change can be recorded accordingly and used to determine the corresponding degree of wear.

[0023] As already mentioned, the force level can be an absolute force level or a relative force level, for example, relative to the maximum compressive force. The displacement or angular position can be an absolute displacement or angular position, or a relative displacement or angular position, for example, relative to the maximum compressive force.

[0024] Furthermore, a local minimum k3 is formed in the crimping force curve, which describes the beginning of the so-called compression phase. With a worn tool, the distance between the local minimum k3 and the point of maximum compressive force shortens. The distance between the local minimum k3 and the point of maximum compressive force (dead center of the press) can also be used to assess the wear status of the tool.

[0025] As already mentioned, the force level can be an absolute force level or a relative force level, for example, relative to the maximum compressive force. The displacement or angular position can be an absolute displacement or angular position, or a relative displacement or angular position, for example, relative to the maximum compressive force.

[0026] It is preferred that the characteristic value(s) (k1, k2, k3) be taken from a region of the crimp force curve before the start of a compression phase of the crimp force curve. During the compression phase, compression of the crimp contact with the strands occurs.

[0027] The previously described points in the crimp force curve (k1, k2, k3) are thus taken from the so-called preparation phase, in which the crimping die comes into contact with the crimp contact and bends the tabs of the crimp contact. It has been shown that points in the so-called preparation phase (the area of ​​the crimp force curve before compression of the crimp contact with the strands occurs) are well suited for making such an assessment.

[0028] Furthermore, a point k4 at the end of the compression phase has proven to be a suitable and advantageous parameter. It has been shown that a worn tool can cause the crimp contact to jam in the crimping die, which would be indicated by another local minimum k4 in the crimp force curve.

[0029] Furthermore, it is preferred that a time-based or path-based distance from the local maximum is determined as the characteristic value.

[0030] It is preferred that several characteristic values ​​be determined, and each of the determined characteristic values ​​is compared with an associated first threshold value. This further increases precision.

[0031] In a further embodiment, the crimping force curve is plotted against the rotation angle of a press moving the crimping die. These values ​​can be determined without additional effort, thus providing a cost-effective solution.

[0032] The first threshold can be a percentage of a maximum wear value. The percentage value can be determined empirically, numerically, or analytically, for example.

[0033] In one embodiment, the first threshold value is stored in a manufacturer's database or a cloud-based database. During operation of the crimping device, a threshold value can be loaded into a local memory of the crimping device. Storing it in a manufacturer's database enables particularly fast access. A cloud-based database, on the other hand, has the advantage of allowing universal access from different production locations.

[0034] The invention further provides a monitoring unit for monitoring a crimping device. The monitoring unit is configured to determine a characteristic value of the crimping force curve based on a crimping force curve. The monitoring unit is further configured to compare the determined characteristic value with at least one first threshold value that defines a state of one or more tools, in particular the crimping die or the anvil, of the crimping device. The monitoring unit can be configured to execute a method according to one of the aforementioned aspects.

[0035] According to a further aspect, the invention relates to a crimping device. The crimping device comprises a crimping die and an anvil, a sensor configured to determine a crimping force, and a monitoring unit, in particular the aforementioned monitoring unit, wherein the monitoring unit is configured to determine a characteristic value of the crimping force curve based on a crimping force curve. The monitoring unit is further configured to compare the determined characteristic value with at least one first threshold value that defines a state of one or more tools, in particular of the crimping die or the anvil, of the crimping device. Short description of the drawings

[0036] Fig. 1 shows a crimping force curve plotted against the angle of rotation of an eccentric press or the (process) time, resulting from the crimping die stroke, which illustrates various parameters. Fig. 2 shows a crimping force curve plotted against the travel path of the crimping die, comparing a crimping device in its initial state with a crimping device with a worn tool. Fig. 3 shows another example of a crimping force curve plotted against the travel path of the crimping die. Fig. 4 illustrates the interaction of a device with databases. Detailed description of the preferred embodiments

[0037] The invention is described in more detail below using an illustrative example. Although the following explanation is intended to be exemplary and not restrictive, features of the following description can also be used individually to specify the invention.

[0038] As explained in the introduction, it is generally known to determine a crimp force curve during a crimping process in which a contact part is connected to an electrical conductor. Based on the recorded results, this can be used to perform basic monitoring of the crimping device and detect potential processing errors. However, this does not allow any conclusions to be drawn as to whether an unacceptable deterioration in processing quality or even a tool failure is indicated.

[0039] The crimping device monitoring system can be integrated into a monitoring unit already provided on the crimping device to determine the crimping force curve, or the monitoring unit can be designed as a separate unit. In this context, it is also possible to provide the monitoring unit as a retrofit solution. This allows existing crimping devices to be expanded.

[0040] First, when commissioning the crimping device or changing tools, a reference crimping force curve is determined. This curve defines a target value for the crimping device without further wear. The target crimping force curve is stored in a memory device of the crimping device or the monitoring unit, or alternatively in an external storage device, such as a cloud, and serves as a reference for further quality monitoring.

[0041] During operation, a crimping force curve is subsequently determined during each crimping process, which is shown in the Figures 1-2 shown, can be plotted against the angle of rotation (the (process) time) of the eccentric press or the distance traveled by the crimping die. The actual crimping force curve thus determined is saved for further evaluation.

[0042] It has been shown that one of the following parameters can be used to assess the wear condition of the crimping device, in particular the crimping tool.

[0043] In particular, the Fig. 1 The area under the curve, or the integral of the crimping force curve plotted by the eccentric press, is evaluated based on the angle of rotation (parameter K1). This area under the crimping force curve corresponds to the work performed by the crimping device, which is required and converted during a specific forming process. With progressive wear, the work / energy required for the crimping process increases, so this can be derived accordingly from the determined area.

[0044] Another possible parameter is a local maximum. This is described in Fig. 1marked with the characteristic value K2, which indicates the deviation of the force at the local maximum from the maximum compressive force (bottom dead center of the crimping die). Alternatively or additionally, an absolute force can also be used as a characteristic value.

[0045] Furthermore, it has been shown that a characteristic value can be determined based on a time- or path-based distance from the local maximum (characteristic value K3), which can also be used to evaluate tool wear.

[0046] For each of the previously mentioned characteristic values ​​K1-K3, one or more threshold values ​​can be defined, based on which it is determined that the tools of the crimping device, in particular the crimping die and the anvil, should be replaced.

[0047] The threshold(s) can be stored as fixed values, for example, in the crimping device's control system, a crimping device user database, or a cloud server. The parameters can be determined empirically or numerically, or based on an analytical basis.

[0048] Over the lifetime of a crimping device, a threshold may need to be updated based on specific findings. To facilitate this, one option is to store the updated threshold in a user database or on a cloud server so that the threshold can be queried. Alternatively, it is also possible to update the crimping device's control unit to update the threshold.

[0049] Thus, the present embodiment makes it possible to identify defective parts and to recognize at an early stage whether production with reduced quality is foreseeable.

[0050] Furthermore, based on the determined values, it is possible to plan predictive maintenance for wear parts of the crimping device, allowing, in particular, the crimping die and anvil to be replaced. The current wear status and the corresponding, potential tool replacement can be predicted using a model, allowing the necessary tool changes to be planned and carried out within a specific time frame. This avoids unexpected setup and downtime.

[0051] To integrate a model-based wear condition prediction into a crimp force monitoring / crimping process monitoring system, a characteristic value Ki C1 of the new parts can be documented at the beginning of production. This value serves as a reference for a characteristic value Ki Ci at any time i before reaching the point of maximum or critical wear condition (Ki C2 ). To record the wear progression, a relative difference can be calculated, for example: Δ Ki = Ki Ci − Ki C 1 Ki C 1

[0052] For this relative difference, threshold values ​​can also be defined at which a critical wear condition of the wear parts is reached (e.g., Ki C2 ). The Ki C2 value can be determined, for example, on an empirical or numerical basis or based on analytical calculations.

[0053] A threshold value can be set for ΔKi to detect wear progression. If exceeded, a wear part replacement is required. To enable earlier response and thus avoid defective parts, a notification could be issued, for example, when 70% is reached (first threshold for informing the user). Assuming approximately linear wear over time, the wear progression can be approximated, for example, by interpolation. Alternatively, nonlinear wear can be assumed and modeled accordingly.

[0054] In particular, if a first threshold for informing the user is exceeded, a service message may appear on the machine's display or such a message may be transmitted to the machine manufacturer.

[0055] In addition to the aforementioned threshold for user information, which may be shown, for example, on a machine display or sent to the user via an electronic message, it is possible to define a further (second) threshold that prompts the user to order a specific spare part. The threshold level for prompting an order lies between the Ki C2 value (critical wear condition) and the threshold for user information.

[0056] In this way, an order process can be initiated or prepared, for example, to reorder the crimping die or anvil. This ensures that the reordered tool reaches the manufacturer in time before a replacement of the corresponding tool becomes absolutely necessary. The manufacturer can integrate the time for replacing the tool into their daily workflow, for example, if a machine downtime is planned for other reasons anyway.

[0057] Furthermore, a third threshold can be defined, which lies between the value Ki C2 (critical wear condition) and the second threshold. If the third threshold is exceeded, the machine will shut down.

[0058] Fig. 2shows a crimping force curve plotted against the travel of the crimping die. Crimping force curve C1 illustrates the course of a crimping process with crimping tools (crimping die and anvil) that are considered new. Crimping force curve C2 represents a crimping process in which the crimping tools (crimping die and anvil) are already worn and will need to be replaced in the foreseeable future.

[0059] In Fig. 3 A crimp force curve C3 is shown, which, similar to the crimp force curves in Fig. 2 , plotted against the path of the crimping die. Differences in the crimp force curve arise due to a specific crimp contact type being processed.

[0060] The crimp force curve shows several characteristic values ​​k1, k2, k3, and k4. The corresponding positions of a crimping die 100 are shown for these characteristic values, into which a crimp contact with crimp tabs 200 and strands located between the crimp tabs 200 are inserted. An evaluation can be performed as explained above.

[0061] The characteristic value k1 is a first local maximum of the crimping force curve C3. The first local maximum k1 describes the point in time in the crimping force curve C3 at which tabs 200 of the crimp contact begin to roll at the apex of the crimping die's radii. It has been shown that the first local maximum changes in the (force level and / or travel position) when the radii of the crimping tool are subject to wear. Thus, the position (force level) of the first local maximum k1 or its distance from the point of maximum compressive force (bottom dead center of the crimping die 100) can be used as a parameter for crimping die wear.

[0062] A second local maximum k2 describes the point in time in the crimp force curve C3 at which the tabs 200 of the crimp contact touch. If the crimping process proceeds symmetrically, there is a kind of "collision" of the crimp tabs. This leads to a corresponding increase in force and thus to the second local maximum k2. A second local maximum is thus formed in tools in such a way that it is recognizable that the crimping die is not yet worn. If, however, wear is present, the crimping takes place asymmetrically, so that the second local maximum k2 is no longer pronounced. The second local maximum k2 is therefore also an indication of a corresponding wear condition of the tool. The second local maximum k2 can also change in position (force level and / or travel position) as the radii of the crimping tool wear.The change can be recorded accordingly and used to determine the corresponding degree of wear.

[0063] Furthermore, the crimp force curve according to Fig. 3 A local minimum k3 is drawn, which describes the beginning of the so-called compression phase. With a worn tool, the distance between the local minimum k3 and the point of maximum compressive force shortens. The distance between the local minimum k3 and the point of maximum compressive force (dead center of the press) can also be used to assess the wear status of the tool.

[0064] The previously described points in the crimp force curve (k1, k2, k3) are taken during the so-called preparation phase, in which the crimping die comes into contact with the terminal and bends the tabs of the crimp contact. It has been shown that points in the so-called preparation phase (the area of ​​the crimp force curve before compression of the crimp contact with the strands occurs) are well suited for this assessment.

[0065] Furthermore, Fig. 3 a point k4 is plotted at the end of the compression phase. It has been shown that a worn tool can cause jamming of the crimp contact in the crimping die, which would be indicated by another local minimum k4 in the crimp force curve. Fig. 4 such a further local minimum does not exist in the area of ​​the point k4.

[0066] To evaluate the wear condition of the crimping tool, in particular the crimping die, one of the previously mentioned points k1-k4 can be used individually or in combination with other points.

[0067] In Fig. 4 The communication of a crimping device X1 operated by a user is clearly illustrated. In particular, the crimping device X1 can communicate via a local network with a user-side database X2, in which device-specific information is stored. Furthermore, a communication interface is available that allows the crimping device X1 to communicate with a cloud-based database C. In the cloud-based database C, for example, characteristic values ​​and threshold values ​​can be documented and managed.

[0068] The manufacturer maintains a communication interface and a manufacturer-side database Y, which enables internet-based communication with the cloud-based database C. In this way, for example, data collected by the manufacturer can be incorporated into a re-evaluation of threshold values ​​or similar stored in the cloud-based database C.

[0069] In Fig. 4Furthermore, a communication option is provided between the manufacturer's database Y and the crimping device X1, which is designed, for example, as a teleservice connection. Furthermore, the user can, if necessary, enable a data exchange between the user's database X2 and the manufacturer's database Y. Such communication can also be enabled only one-way, in particular from the manufacturer's database Y to the user's database X2, in order to provide the user with specific data for the operation of the crimping device X1.

Claims

1. Method for monitoring a crimping device, comprising the steps of: recording a crimping force curve using a sensor that is configured to determine a crimping force, determining at least one characteristic value (K1; K2; K3; k1, k2, k3, k4) of the crimping force curve (C1, C2, C3), using a monitoring unit to compare the determined characteristic value with a threshold value that defines a state of one or more tools, in particular of the crimping die or anvil, of the crimping device, characterised in that the monitoring unit is further configured to compare the characteristic value with a plurality of threshold values, wherein an item of information is provided to a user when a first threshold value is exceeded, the user is prompted to order a particular spare part when a second threshold value is exceeded and a downtime of the machine is triggered at a third threshold value.

2. Method according to claim 1, characterised in that the integral of the crimping force curve is determined as the characteristic value (K1).

3. Method according to claim 1, characterised in that a local maximum (K2; k1, k2) is determined as the characteristic value, wherein it is preferred that the local maximum (k1) of the crimping force curve describes a point in time on the crimping force curve at which tabs (200) of a crimp contact at the vertex points of the radii of the tool, in particular of the crimping die, start to roll, and / or the local maximum (k2) describes the point in time on the crimping force curve at which tabs (200) of a crimp contact touch one another.

4. Method according to claim 1, characterised in that a local minimum (k3) is determined as the characteristic value, wherein the local minimum (k3) describes the start of a compression phase.

5. Method according to claim 3 or 4, characterised in that a temporal or distance-based interval from the local maximum or local minimum is determined as the characteristic value (K3).

6. Method according to claim 1, characterised in that a value of the crimping force curve that describes an end of a compression phase is determined as the characteristic value (k4).

7. Method according to any of the preceding claims, characterised in that a plurality of characteristic values (K1; K2; K3; k1, k2, k3, k4) are determined, and the determined characteristic value is compared in each case with an assigned threshold value.

8. Method according to any of the preceding claims, characterised in that the crimping force curve is plotted over an angle of rotation of a press moving the crimping die or a process time.

9. Method according to any of the preceding claims, characterised in that the threshold value is a percentage value of a maximum wear value.

10. Method according to any of the preceding claims, characterised in that the threshold value is stored in a manufacturer-side database (Y) or cloud-based database (C).

11. Method according to any of the preceding claims, characterised in that a relative difference is determined in order to record the progress of wear using the following formula: Δ Ki = Ki Ci − Ki C 1 Ki C 1 wherein KiC1 is a characteristic value for a new part and KiCi is a characteristic value at a point in time i before the threshold value is reached, in particular the point in time of the maximum state of wear (KiC2).

12. Crimping device, comprising: a crimping die or an anvil, a sensor that is configured to determine a crimping force, a monitoring unit, wherein the monitoring unit is configured to determine a characteristic value (K1, K2, K3; k1, k2, k3, k4) of a crimping force curve based on the crimping force curve, wherein the monitoring unit is further configured to compare the determined characteristic value (K1, K2, K3; k1, k2, k3, k4) with a threshold value that defines a state of one or more tools, in particular of the crimping die or anvil, of the crimping device, characterised in that the monitoring unit is further configured to compare the characteristic value with a plurality of threshold values, wherein an item of information is provided to a user when a first threshold value is exceeded, the user is prompted to order a particular spare part when a second threshold value is exceeded and a downtime of the machine is triggered at a third threshold value.

13. System, comprising a crimping device according to claim 12 and the database, in particular a user-side database (X2) and / or a cloud-based database (C), wherein the threshold value is stored in the database.

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