Patent Publication Number: US-6212924-B1

Title: Process and apparatus for determination of the quality of a crimped connection

Description:
This application is a Divisional of U.S. patent application Ser. No. 09/152,039, filed Sep. 11, 1998 now U.S. Pat. No. 6,161,407. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a process and an apparatus for determination of the quality of a crimped connection between a conductor and a contact. The crimping equipment produces a crimping force, by which the contact is connectable with the conductor so as to be electrically and mechanically non-detachable. 
     2. Description of the Related Art 
     The tern “crimping” is internationally established and standardized in terms of technique. In practice, however, expressions such as pressing, squeezing, fixing or attaching are also used. Under crimping, there is understood the production of a non-detachable electrical and mechanical connection between a conductor and a contact. During the crimping operation, the material to be connected is permanently plastically deformed. Poorly conducting surface layers, if present, are broken up, which promotes the electrical conductivity. A correct crimping, however, also prevents the ingress of corrosive media even under more difficult operational conditions such as temperature change or vibration. 
     The object of the crimping is the production of a good mechanical and electrical connection which remains unchanged qualitatively over a long period of time. 
     For crimping, contact-specific crimping tools are used with a stationary crimping anvil below and vertically displaceable crimping dies above (see FIGS. 1 to  3 ). A wire crimper and an insulation crimper are mounted in the crimping tool and can mostly be set to the wire diameter or the insulation diameter independently of each other in a vertical direction by way of raster discs with different height cams. These settings directly influence the quality of the crimped connection. 
     In the case of open crimped contacts (FIGS. 4 and 5) the conductive feed takes place above the contact. The conductor, previously stripped of insulation, is usually positioned correctly for the crimping operation relative to the contact, simultaneously in a radial and an axial direction, by automatic devices. Due to a downward movement of the crimping die, the conductor is first lowered by means of a mechanical system into the upwardly open wire and insulation crimping claws. The actual crimping operation begins thereafter with reshaping of the straps according to the crimping die shapes. After the stroke of the crimping dye, the crimp has the intended pressed shape (FIG.  5 ), which is in turn dependent on the contact sheet metal used, the wire cross-section, the copper of the wire and the insulation stripping. When the contacts are closed, the crimping region, shaped as a tube, must be entered axially in a radial orientation. 
     A sectional diagram of a faultlessly executed crimped connection shows the originally individual round flexible wires of the conductor pressed compactly one against the other into polygons. An internal surface in the crimped region of the contact shows deformations of the contact points of the individual flexible wires. In the wire crimping, all individual wires must be encompassed. The individual wires must, according to respective cross-section, project by about 0.5 millimeters out at a front end of the wire crimp and may not disappear in the crimp. The conductor and the conductor insulation must be visible in a window lying between the wire crimp and the insulation crimp. The insulation crimp must encompass the insulation without penetrating thereinto. 
     Important criteria for judgement of a crimped connection are the shape of the crimp, the height of the crimp and the resistance to tearing-out of wires. These kind of criteria are suitable however only during the setting-up of a crimping machine and in the case of random samples during production. In order to meet present-day quality requirements for all crimped connections, means must be available, which can receive, evaluate and store crimping data about each crimped connection during the crimping process so as to influence machine data in dependence on the result. For the judgement of the crimped connection (without mechanical destruction of the crimped connection), the crimping force is related to crimping travel or to crimping time. By appropriate evaluation of the crimp data, the quality of a crimped connection can be reliably judged. 
     The process or the apparatus for the judgement of the quality of a crimped connection must recognize crimping faults, such as, incorrect insulation crimp height, incorrect wire crimp height, not encompassed flexible wires, wrong or no stripped insulation length, wrong laying-in depth, and flexible wires cut off during the insulation stripping. Corresponding fault reports must then be provided. 
     A method for the detection of missing flexible wires, or of crimped-in conductor insulation in a crimped connection, by reference a graph of the crimping force, is known from the reference EP 0 460 441. Value pairs, consisting of crimping force and the position of the crimping die are measured during a crimping operation and stored. The value pairs are plotted on a graph to show the crimping force of the crimping operation in dependence on the position of the crimping die. A curve section of the graph, with a strong rise in force, is linearized and a point is determined from the mean of the minimum and the maximum crimping force. The point is compared with a reference value. If the point lies within a predetermined deviation from the reference value, the crimped connection is judged to be of acceptable quality. During the evaluation of the graph of the crimping force of the crimping operation, the maximum crimping force is also taken into consideration. If the maximum crimping force deviates excessively from a second reference value, the crimped connection is rejected as unusable. The point in the curved section with a strong rise in force and the maximum crimping force yield information related to missing flexible wires or crimped-in conductor insulation in the crimped connection. 
     In a crimping press common in the market, a force sensor detects the force, which is stored in digital form as a force-dependent curve course, during the crimping operation. This course is compared with a reference curve. The type of crimping fault is deduced in accordance with the magnitude of the deviation from the reference curve. 
     It is a disadvantage of this known process and apparatus that no differentiated statement about the quality of the crimped connection is possible in spite of great expenditure for the computer, memory and computing. 
     SUMMARY OF THE PRESENT INVENTION 
     It is an object of the present invention to overcome the disadvantages of the prior art. It is a further object to provide a process and apparatus having improved fault sensitivity. 
     The present invention advantageously provides a method for ascertaining the quality of a crimp connection between a conductor and a contact and, in particular, wherein crimping equipment produces a crimping force by which the contact is made connectable with the conductor so as to be electrically and mechanically nondetachable. The advantageous method of the present invention determines a reference crimping force curve which is divided into several zones. A curve of the crimping force for each zone is then evaluated with reference to the curve of the reference crimping force thereby enabling the production of fault reports and statements about the quality of the crimp connection. A typical crimping press includes a tool holder which actuates a tool that together with an anvil produces a crimp connection. Advantageously the present invention provides for the substitution of a crimping simulator in place of the tool. The crimping simulator allows a force sensor of the crimping press to be calibrated. During production of the crimp connections therefore the quality of the crimp connections is checked by reference to a curve of the crimping force. 
     The advantages achieved by the invention are to be seen substantially in that an increase in quality is possible by the better resolution of the faults, that fewer rejects arise with the more sensible fault diagnosis and that consequential faults, for example a breakdown of a passenger vehicle because of intermittent contacts in a plug connection, are avoided. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, wherein like reference numerals denote similar elements throughout the several views: 
     FIGS. 1 to  3  show a schematic illustration of a crimping operation; 
     FIG. 4 shows a crimped connection between a conductor and a contact; 
     FIG. 5 shows details of a wire crimp; 
     FIG. 6 shows a crimping press with a crimping simulator for calibration of a force sensor; 
     FIG. 7 shows the crimping simulator with a die in the lower dead center position; 
     FIG. 8 shows the crimping simulator with the die in the upper dead center position; 
     FIG. 9 shows details of the crimping insulator; 
     FIG. 9 a  shows a voltage-crimping force graph of the force sensor; 
     FIGS. 10 and 11 show details of the force sensor; 
     FIG. 12 shows details of a press control; 
     FIGS. 13 to  15  show graphs of the crimping force for different crimping faults; 
     FIG. 16 shows a graph of the crimping force with a zone division; 
     FIG. 17 shows a table of zone-dependent measured and computed values; and 
     FIGS. 18 a  to  18   c  show tables of limit values for fault types. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 to  3  show a crimping operation in which an end of an insulated conductor  1  is connected to a contact  2 . The contact  2  has an open crimp zone  3 . Proximal the crimp zone  3  is a first double strap  4  for forming an insulation crimp  5  and a second double strap  6  for forming a wire crimp  7 . FIG. 1 shows crimping dies  8 ,  9  in an upper dead center position above the conductor  1 . The end of the conductor insulation rests in the first double strap  4  and a conductor portion stripped of insulation rests in the second double strap  6 . Wedge-shaped recesses  10  are configured in the crimp dies  8 ,  9 . As shown in FIG. 2, the double straps  4 ,  6  are pressed one against the other by the wedge-shaped recesses  10  of the crimping dies  8 ,  9  during lowering of the crimping dies  8 ,  9 . An anvil  9 . 1  is placed below the conductor  1  to serve as a support. The recess  10  has a dome-shaped upper end which imparts a final shape to the double straps  4 ,  6  together with the conductor insulation or the conductor wire. FIG. 3 shows the finished crimped connection with the dies  8 , 9  and the anvil  9 . 1  removed from the connection. The first double strap  4  is pressed around the conductor insulation  11  so as form the insulation crimp  5 . The second double strap  6  is pressed around a conductor wire  12  so as to form the wire crimp  7 . 
     FIG. 4 shows a faultless crimped connection, having a window  13  through which the insulation  11  of the conductor end  1  and the individual flexible strands of the conductor wire  12  are visible. The individual flexible strands are also visible at the contact side end of the wire crimp  7 . 
     FIG. 5 shows the second double straps  6  squeezed together with the individual flexible strands of conductor wire  12 , in the case of a faultless wire crimp  7 . 
     A crimping press with a crimping simulator for calibration of a force sensor  23 . 1  is illustrated in FIGS. 6 to  12 . The crimping press has a frame  14  without a right-hand side wall. A motor  15  and a gear  16  are mounted to the frame  14 , the motor  15  being drivingly connected to the gear  16 . First guides  17 , at which a crimp ram  18  is guided, are arranged at the frame  14 . A shaft  19  which is driven by the gear  16  has an eccentric spigot  20  arranged at one end and a resolver  21  for the detection of a rotary angle coupled on at the other end. The crimping ram  18  consists of a slide member  22  which is guided in the first guides  17  and of a tool holder  23  which has the fore sensor  23 . 1  and a retaining fork  24 . The slide member  22  stands in loose connection with the eccentric spigot  20 , so that rotational movement of the eccentric spigot  20  is converted into a linear movement of the slide member  22 . A maximum stroke of the slide member  22  is determined by an upper dead center and a lower dead center of the eccentric spigot  20 . The tool holder  23 , in a conventional manner, actuates a tool including the anvil  9 . 1  to produce the crimped connection. For calibration of the force sensor  23 . 1 , a crimping simulator  25  is used in place of the tool. An adjusting screw  26  is provided for precise adjustment of the stroke. An operating terminal  27  is provided so as to act as an interface between an operator and the crimping press. The operating terminal  27  comprises a rotary knob  29  and a keyboard  30  for the input of operational data and commands to a control  28 . A display  31  is provided for visualization of data. 
     FIGS. 7,  8  and  9  show details of the crimping simulator  25  for the calibration of the force sensor  23 . 1 . A die  33  is slidably guided in a tool housing  32 . A carrier head  34  is arranged at one end of the die  33  so as to be in loose connection with the retaining fork  24  of the tool holder  23 . A base plate  37 , which carries a force pick-up  38 , is fastened, for example by means of a screw  36 , at one foot  35  of the tool housing  32 . An intermediate member  39  transmits the force of the die  33  to the force pick-up  38 . The intermediate member  39  is elastic so that an increase in force is extended over time during the calibration. The force pick-up  38 , for example a quartz force pick-up, is expensive, calibratable and has a very linear characteristic. The force sensor  23 . 1  built into the tool holder  23  on the other hand is cheaper and has a greater linearity error. For calibration of the force sensor  23 . 1 , the die  33  is moved from the upper dead center position into the lower dead center position and then back to the upper dead center position. A force is produced in the course thereof being in the order of magnitude of a genuine crimping operation. The course of the force is detected simultaneously and exclusively by each of the force sensor  23 . 1  and by the force pick-up  38  and stored, wherein the force pick-up  38  detects a calibratable course of force. Thereby, a force calibration is possible at the force sensor  23 . 1 . The course of the force, and force deviations from the measured course of the force, which are due to the non-linearity of the force sensor  23 . 1 , are detected by the force pick-up  38  and filed in a correction table. After the calibration process, the crimping simulator  25  is taken out and the crimping tool is inserted. In the case that the force sensor  23 . 1  is replaced, the calibration process must be repeated. The force sensor  23 . 1  suffices for measuring the crimping force during the production of crimped connections because the force sensor  23 . 1  is calibrated and the measurement deviations caused by the non-linearity of the force sensor  23 . 1  are corrected by means of the correction table. In this manner, a course of the crimping force can be ascertained accurately and absolutely with an inexpensive force sensor  23 . 1  which in itself is inaccurate. It is furthermore advantageous that a maker of crimped connections needs only one expensive crimping simulator for the calibration of all crimping presses for his machine inventory, usually consisting of several like similar crimping presses. 
     FIG. 9 a  shows a graph of voltage U in relation to crimping force CK of the force sensor  23 . 1 . The voltage U, for example in volts, is entered on the vertical axis of the diagram and the crimping force CK, for example in kilonewtons, is entered on the horizontal axis of the diagram. A non-linear voltage of the force sensor  23 . 1  is illustrated by a solid line. The broken line shows a linear voltage curve of the crimping simulator  25 . In the calibration process, respectively associated voltage differences between the non-linear and the linear curves are retained for, for example, 100 force values and filed in the aforementioned correction table as force/voltage value pairs. During the production of crimped connections, the corresponding force values are read from the correction table and the respectively associated voltage differences are added to corresponding actually measured voltages. 
     FIG. 10 shows the force sensor  23 . 1  as installed in the tool holder  23 . FIG. 11 shows the individual parts of the force sensor  23 . 1 . The force sensor  23 . 1  consists of a sensor housing  40  with a lid  42  and a base  41  configured, for example, of synthetic material. The inward sides of the base  41  and the lid  42  are laminated with an electrically conductive layer, for example a copper layer  43 . The layer  43  of the base  41  is connected by means of a connecting wire  44  with an inner conductor of a connecting bush  45 , a housing of the connecting bush  45  being connected directly with the coating of the lid  42 . The sensor housing  40  includes a shelf  46  having recesses  47  arranged, for the retention of sensors  48 , for example piezo-ceramic discs. The shelf  46  is configured of synthetic material of smaller thickness than the thickness of the sensors  48 . 
     The force exerted on the lid  42  during the calibration process or the crimping operation is transmitted exclusively to the sensors  48  and from these to the base  41 . The pressure exerted on the sensors  48  produces an electrical charge which is measurable at the connecting bush  45 . 
     FIG. 12 shows details of the control  28  for the crimping press. A converter  50  equipped with a mains or power filter  49  at a main input L 1 , L 2 , L 3  converts mains voltage into a direct current voltage which is fed to an inverter  51 . The inverter  51  has controlled semiconductor switches Gu to Gz which chop the direct-current voltage by a pulse width modulation process into three pulsed alternating current voltages which produce sinusoidal currents of variable frequency in a motor  15 , for example an asynchronous motor ASM. Rotational movement is transmitted from the motor  15  to the gear  16  and then to the shaft  19 , at the one end of which the eccentric spigot  20  and at the other end of which the resolver  21  are arranged. Rotation of the eccentric spigot  20  produces a linear movement of the crimping ram  18 . A pulse generator  52 , in the function of a target speed course, generates a pulse pattern which is necessary for drive control of the semiconductor switches Gu to Gz. The pulse pattern is fed into a driver stage  53 , having an output connected with control lines of the semiconductor switches Gu to Gz. A computer  54  controls all functions of the crimping press. A bus system  55  is provided for data exchange between the computer  54  and peripheral components. A mains unit  56 , automatically adaptable to different mains situations, produces auxiliary voltages necessary for the operation of the control  28 . 
     A battery-supported read-write memory  57  serves as working memory for the computer  54 . The program for the control of the crimping press is filed in a read-only memory  58 . Other machines participating in the crimping operation, such as for example conductor feed or contact feed, control equipment, safety loops and so forth are denoted by the reference symbol  70  and communicate, for example for synchronization, by way of the bus system  55  with the control  28 . The operating terminal  27  is connected with the computer  54  by means of a serial interface  60 . In case the crimping press belongs to a superordinate cable-finishing unit  63 , the communication of the control  28  with the finishing unit  63  also takes place by way of the serial interface  60 . An evaluating unit  61  detects the measurement values of the force sensor  23 . 1  and of the force pick-up  38  and processes the measurement data as explained above. 
     User-specific data such as password, speech, units and so forth, and operation-specific data such as acceleration, retardation, frequency of the motor, position points along the stroke for synchronization of the peripheral machines and equipment participating in the crimping operation, are entered, as for example by menu-guided means, at the operating terminal  27 . Furthermore, system information data, service-relevant data, statistical evaluations, protocol data of the communication, drive data and so forth can be accessed by way of the operating terminal  27 . Modes of operation such as calibration of the initial position of the crimping ram  18 , calibration of the force sensor  23 . 1 , setting-up operation for the presetting of the stroke necessary for the respective tool, initiation of a single crimping operation for the checking of the cumping connection, crimping operation with intermediate stop for positioning of the contact and subsequent compressing of the contact, crimping operation with preselected stroke and so forth can also be preset as for example by menu-guided means by way of the operating terminal  27  of the control  28 , wherein the crimping ram  18  and thus the crimping tool are positionable by means of the rotary knob  29 . 
     The resolver  21  is used in the crimping press for measurement of angular positions. The resolver  21  supplies an absolute signal for each revolution and is insensitive to vibration loadings and temperature. By reason of its mechanical build-up, its angle information is maintained even in the case of a voltage failure. The resolver  21  has a stator and a rotor driven by the shaft  19 . A first stator winding and a second stator winding are arranged at the stator and a rotor winding is arranged at the rotor. The rotor winding is excited by an alternating current voltage U 1  of constant amplitude and frequency, for example 5000 hertz. The second stator winding is arranged displaced through 90° relative to the first stator winding. By electromagnetic coupling, the alternating voltage U 1  produces two voltages Usin and Ucos at terminals of the stator windings. The two voltages Usin, Ucos have the same frequency as U 1 . The amplitude is, however, proportional to the sine or cosine of mechanical deflection angle θ. A current feed of the rotor winding takes place by way of an oscillator. In the case of a resolver with one pole pair, the amplitude of the two voltages Usin, Ucos runs through a respective sinusoidal wave for each mechanical revolution. A resolver interface  62  evaluates the sine signal and the cosine signal of the resolver  21  with, for example, a resolution of 0.35°, and converts the angle θ into a digital value. 
     FIGS. 13 to  15  show graphs of the crimping force CK of a typical contact family for different crimping faults. The crimping force CK is entered on the vertical axis of the diagram and time, the deflection angle or crimping travel CW is entered on the horizontal axis of the diagram. The crimping travel CW is derived from the deflection angle θ of the resolver  21 . The curve with a solid line is a reference curve ascertained, for example, from ten faultless crimpings and represents the mean value of these crimping forces. The curve of the force of a faulty crimping is illustrated by a broken line. 
     FIG. 13 shows the graph of the force of a crimping in which three of nineteen individual flexible wires of the conductor wire  12  are absent in the wire crimp  7 . The three individual flexible wires have either been pushed back during the positioning of the conductor or were cut off during the insulation stripping. The reference curve and the curve of the faulty crimping lie one on the other, which is represented by the sign +−, in a first zone Z 1  of the force curve, which approximately represents the closing operation of the double straps  4 ,  6 . In a second zone Z 2  of the force curve, which approximately represents the pressing of the first double strap  4  into the conductor insulation  11  and the pressing of the second double strap  6  into the conductor wire  12 , the values of the faulty crimping lie significantly below the reference values, which is represented by the sign —. In a third zone Z 3  of the force curve, which approximately reproduces the final plastic deformation of the double straps  4 ,  6 , the values of the faulty crimping still lie somewhat below the reference values, which is represented by the sign —. The region to the right of the third zone Z 3  reproduces the course of the force during the opening operation of the tool. In this region, the curves are congruent to a large extent independently of the fault of the crimping. 
     FIG. 14 shows the graph of the force of a crimping, in which the conductor insulation  11  reaches into the wire crimp  7 . In the first zone Z 1  and at the beginning of the second zone Z 2 , the course of the force of the faulty crimping displays a significant heightening relative to the reference curve, which is represented by the sign ++++. The closing of the second double strap  6  requires more force because of the conductor insulation  11 . 
     FIG. 15 shows the graph of the force of a crimping, in which the conductor wire  12  reaches only partially into the wire crimp  7 . In the second zone Z 2  and in the third zone Z 3 , the course of the force of the faulty crimping lies significantly below the reference curve, which is represented by the sign — or by the sign —. The deformation of the double straps  4 ,  6  in the case of incompletely filled insulation crimp  4  and wire crimp  6  needs less force. 
     FIG. 16 shows the graph of the crimping force CK with a zone division for evaluation of the deviations of the crimping force curve K 2  of a crimping from a reference curve K 1 . The zone formation takes place, for example, on the basis of the peak width of the reference curve K 1  and on the basis of the force decline between 90% and 10%. Other criteria for zone formation are impossible, such as for example a first zone Z 1  at 20% of the maximum force with the disadvantage that the increase in force is very dependent on the contact and significant intermediate minima can be contained in the graph of the force. The zone division having fewer or more than four zones is also possible. 
     The zone widths of the zones Z 1 , Z 2  and Z 3  already mentioned in FIGS. 13 to  15  are denoted by W 1 , W 2  and W 3 . The maximum crimping force during the crimping operation is denoted by Fp. The third zone Z 3  reaches from the 90% point of the force increase up to the 90% point of the force decline. The area below the reference curve K 1  of the width W 3  is standardized to 1000 parts per thousand. The width belonging to the fourth zone Z 4  from the 90% point to the 10% point of the force decline is denoted by W 4 . In this region, no significant deviations arise between the curves K 1  and K 2 , because the curve of the force in the zone Z 4  is determined substantially by the resilience of the contact and/or the crimping press. W 4  can therefore be used as reference width for ascertaining the first width W 1  and of the second width W 2 . 
     For evaluation, the area of the width W 3  below the reference curve K 1  and the area of the difference between the curves K 1  and K 2  are used theoretically. In practice, individual crimping forces D are measured at very small angular spacings preset, for example, by the resolver  21  and added up into areas. 
     FIG. 17 shows the relationships between factors, measurement values and computed values for the individual zones as well as also for all the zones together. It is possible on the basis of the measurement values and the computed values to make statements about the quality of a crimped connection and to generate fault reports. 
     For determination of the width of the first zone Z 1  and of the second zone Z 2 , the fourth zone width W 4  is multiplied by a factor in the order of magnitude of, for example, 0 to 2. The third zone width W 3  is determined by the 90% points of the reference crimping force course K 1 . The averaged reference curve K 1  is decisive for the zone width. 
     The different properties of the kinds of contacts to be processed are taken into consideration for each zone by means of a sensitivity factor S 1 , S 2  and S 3  in the order of magnitude of, for example, 0.5 to 1. 
     The respective area (surface) of a zone is denoted by F 1 , F 2  and F 3 . The averaged reference curve K 1  is decisive for the area. 
     A first measurement value (Result Signed) is the sum of the positive and the negative difference areas between the reference curve K 1  and the crimping force curve K 2 . If the majority of the crimping force curve K 2  lies above the reference curve K 1 , a positive area results. If the majority of the crimping force K 2  lies below the reference curve K 1 , a negative area results. The first measurement value RS 1  to RS 3  is set up for the zones Z 1  to Z 3  and is represented in parts per thousand relative to the standardized area of the zone Z 3 . 
     A second measurement value (Result Unsigned) is the sum of the difference areas between the reference curve K 1  and the crimping force curve K 2  independently of whether the crimping force curve K 2  lies above or below the reference curve K 1 . The second measurement value RU 1  to RU 2  is set up for the zones Z 1  to Z 3  and is represented in parts per thousand relative to the standardized area of the zone Z 3 . The total value RUO is the sum of the zone values RU 1 , RU 2  and RU 3 . 
     The first measurement value RS 1 , RS 2  and RS 3  is compared with limit values (Limits) of the zones Z 1 , Z 2  and Z 3 . In case at least one of the first measurement values exceeds the limit values, a corresponding fault report is produced. An averaged drift-compensated reference curve is decisive for the bad threshold (Bad Limit—BL), a first reference curve is decisive for the learning threshold (Teach Limit—TL) and the averaged drift-compensated reference curve is decisive for the stop threshold (Stop Limit—SL). For a drift threshold (Drift Limit—DL), the original reference curve is compared with the drift-compensated averaged reference curve. The computation of the respective limit values is evident from FIG.  17 . 
     The first reference curve is the crimping force curve of the first crimping. The averaged reference curve is the mean of the crimping force curves of, for example, the first five crimpings and is filed as an original reference curve. The drift-compensated averaged reference curve is the averaged reference curve after the drift has been tracked. The drift is ascertainable by reference to deviations from crimping force courses evaluated as good. The tracking takes place with only a small portion of the ascertained deviations. 
     According to FIG. 17, the total value RUO is compared with total limit values which are factors or values computed from factors. The respective decisive curves are the same as described in the preceding paragraph. 
     Of the factors mentioned in FIG. 17, merely the factor BLO need be determined by the user, the remaining ones being preset by the manufacturer. The user has, however, the possibility of adapting all factors to the user&#39;s requirements at any time. 
     With the zone evaluation, faults in individual zones can be detected substantially more sensibly than with an overall evaluation. The overall evaluation is rather to be preferred in the case of unclear, blurred fault causes. 
     The first measurement values RS 1  to RS 3  are used not only for the initiation of fault reports, but also for statements about the fault and the probability that a specific fault is concerned. In case the limit values of type 1 occur as shown in FIG. 18 a , it is fairly certain that, for example, more than 10% individual flexible wires are absent in the wire crimp  7 . In case the limit values of type 2 occur, it is certain that, for example, more than 10% of the individual flexible wires are absent in th wire crimp  7 . In case the limit values of type 3 occur, it is quite certain that, for example, more than 10% of the individual flexible wires are missing in the wire crimp  7 . FIG. 18 b  shows the limit values for crimpings with conductor  1  laid in too deeply. FIG. 18 c  shows the limit values for crimpings with a conductor  1  laid in not deeply enough. In the case of the boldly printed limit values, corresponding fault reports are initiated. 
     A further possibility for improvement in the fault sensitivity exists in that the averaged increase of the crimping force curve is detected at the zone transitions. Thereby, for example, the fault type of the zone  2  of FIG. 18 a  can be distinguished more precisely from the fault type of the zone  2  of FIG. 18 c.    
     As mentioned above, the crimping force CK is measured by means of a force sensor  23 . 1 . The crimping force CK is distributed among the crimping dyes  8 ,  9 . The aforementioned crimping force evaluation can also be applied to a crimping press, in which the crimping force is measured for each crimping dye. Thereby, precise statements about the crimping force course in the crimping dye  8  for the insulation crimp  5  and about the crimping force course in the crimping dye  9  for the wire crimp  7  and thus about the quality of the insulation crimp  5  and the wire crimp  7  are possible. 
     The invention is not limited by the embodiments described above which are presented as examples only but can be modified in various ways within the scope of protection defined by the appended patent claims.