Abstract:
For examining a metal sheet processing operation, a method includes scanning a detection beam along a processed metal sheet by causing a relative movement between the detection beam and the processed metal sheet, during the scanning, determining a position of an edge of the metal sheet hole by monitoring the detection beam, determining, from the determined hole edge position, a geometric configuration of the metal sheet hole, performing a comparison of the determined geometric configuration of the metal sheet hole with a corresponding desired hole configuration; and then sending a signal indicating information about the metal sheet processing operation, based upon the comparison.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §119(a) from EP Application No. 07 005 442.4, filed Mar. 16, 2007, the entire contents of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The invention relates to examining a metal sheet processing operation in respect of the presence of regular conditions during operation, such as by examining the quality of edges of a hole formed by the operation. 
     BACKGROUND 
     U.S. Pat. No. 5,721,587 discloses a revolver punching press having an upper tool revolver and having a lower tool revolver. When processing workpieces during regular operation, punching tools are used that are positioned in mutually opposite tool receiving members of the two tool revolvers and that cooperate with each other. Before the start of the regular workpiece processing operation, one performs a test processing operation. A video camera and a light source of an image capturing device are mounted in two cooperating tool receiving members for receiving punching tools. After the test processing operation, the workpiece with a punched-out portion is moved into the receiving region of the video camera. Subsequently, the video camera records the punched-out portion, which is back-lit by the light source. Finally, the quality of the punched-out portion is examined by computer-supported evaluation of the recording made of the punched-out portion. 
     The EP publication EP 0 536 685 A1 discloses examining a quality of a perforation of paper webs with a measurement device, which comprises a light source and a detector device spaced apart from each other. The paper web to be examined is moved through the intermediate space between the light source and the detector device. Light directed from the light source to the detector device passes through the perforations of the paper web and reaches the detector device. This produces, owing to the incidence of light, a detector signal that is supplied to an evaluation unit. If irregular conditions prevail when the perforations are produced, for instance, if the perforation blades used are worn, paper fibers remain in the perforations produced. The more paper fibers project into an illuminated perforation, the lower is the intensity of the light which reaches the detector device and the smaller is a signal stroke of the detector signal which is generated at the detector device owing to the incidence of light. Consequently, the signal stroke of the detector signal allows an observation to be made as to whether the perforation of the paper web has or has not been carried out under regular conditions. 
     SUMMARY 
     In one general aspect of the invention, a method of examining a metal sheet processing operation includes scanning a detection beam along a processed metal sheet by causing a relative movement between the detection beam and the processed metal sheet, during the scanning, determining a position of an edge of the metal sheet hole by monitoring the detection beam, determining, from the determined hole edge position, a geometric configuration of the metal sheet hole, performing a comparison of the determined geometric configuration of the metal sheet hole with a corresponding desired hole configuration, and then sending a signal indicating information about the metal sheet processing operation, based upon the comparison. 
     In another aspect, a method for processing a metal sheet includes processing the metal sheet with a process for generating a metal sheet hole, scanning a detection beam along a processed metal sheet by moving the detection beam and the processed metal sheet relative to each other, monitoring the detection beam having passed a metal sheet hole processed by the metal sheet processing operation, during the scanning, detecting an edge of the metal sheet hole based on detecting the detection beam at a defined position of the detection beam and of the metal sheet, determining a geometric actual state of the metal sheet hole on the basis of the position of the edge, and comparing the determined geometric actual configuration of the metal sheet hole with a corresponding desired configuration, thereby evaluating an operating condition during the previous metal sheet processing operation. 
     In another aspect, a method of forming desired holes in sheet metal includes forming a hole by a set of hole forming operation parameters, moving a detection beam across an edge of the formed hole to locate the edge based on detecting the detection beam at a defined position of the detection beam and of the metal sheet, determining, from the edge location, a characteristic of the formed hole, making a comparison of the determined characteristic to a desired characteristic, and based upon the comparison, modifying one or more of the hole forming operation parameters for forming a further hole. 
     In another aspect, a hole forming machine includes a tool operable to form a hole in sheet metal, a beam source operable to direct a hole detection beam across a hole formed by the tool, a beam detector responsive to the hole detection beam to generate a signal indicating beam detection, a hole edge evaluator that receives the signal from the beam detector, determines a position of an edge of the hole and a geometric configuration of the hole, based on the received signal, makes a comparison of the determined geometric hole configuration to a desired configuration, and sends a signal indicative of an undesired state of one or more hole forming operation parameters. 
     In another aspect, a device for examining an operating condition of a metal sheet processing operation by examining a quality of a metal sheet hole being a result of the metal sheet processing operation, includes a detection device comprising a transmitter and a receiver for transmitting and monitoring a detection beam, respectively, a movement unit for moving the detection beam and the processed metal sheet relative to each other, and an evaluation device connected to the detection device, wherein the detection device is configured to detect an edge of the metal sheet hole at a defined relative position of the detection beam and of the metal sheet, and the evaluation device is configured to determine a geometric actual state of the metal sheet hole and to compare the geometric actual state with a corresponding desired state, thereby evaluating the operation condition of the metal sheet processing operation. 
     In another aspect, a mechanical production arrangement includes a processing device for producing metal sheet holes in metal sheets, and a device for examining an operating condition of a metal sheet processing operation of the processing device as described above. 
     In another aspect, a method for examining a metal sheet processing operation includes scanning a detection beam over a processed metal sheet with a metal sheet hole, based on monitoring the detection beam, detecting an edge of the metal sheet hole and identifying a position on the metal sheet corresponding to the detected edge, based on the position of the edge, determining a geometric actual state of the hole, comparing the determined geometric actual state of the metal sheet hole with an desired state being associated with the metal sheet processing operation, and deriving information about the metal sheet processing operation. 
     Implementations may include one or more of the following features. In some embodiments, the signal can indicate the presence of regular or irregular conditions during the metal sheet processing operation. 
     In some embodiments, based on the comparison, the quality of the metal sheet hole processed by the metal sheet processing operation can be evaluated. 
     The detection beam can be a light beam, e.g. a laser beam. 
     In some embodiments, the detection beam and the processed metal sheet can be moved relative to each other such that a scanned path extends transversely through the metal sheet hole. Then, during scanning, the edge of the metal sheet hole can be detected at points of intersection of the edge of the metal sheet hole with the path. The points of intersection can then be, for example, at opposite sides of the hole. 
     In some embodiments, an actual extent between the detected points of intersection can be determined. Then, one can compare the determined actual extent of the metal sheet hole with a corresponding desired extent. 
     In some embodiments, the method can further include examining a quality of a circular metal sheet hole by scanning a path, which extends transversely through the circular metal sheet hole, and detecting points of intersection of the edge of the circular metal sheet hole and the path, wherein the determined geometric configuration of the circular metal sheet hole can be an actual diameter of the circular metal sheet hole given by the distance between the detected points of intersection and wherein the actual diameter of the circular metal sheet hole can be compared with a corresponding desired diameter as a corresponding desired configuration. 
     In some embodiments, the detection beam can be scanned relative to the processed metal sheet along a path that extends along the edge of the metal sheet hole. Then, at least a partial length of the edge of the metal sheet hole can be detected. 
     In some embodiments, the geometric actual configuration can be a determined actual configuration of at least a portion of the edge contour of the metal sheet hole. 
     In some embodiments, the determined geometric actual configuration can be at least one of an actual shape and an actual orientation of at least a portion of the edge contour of the metal sheet hole. For example, the actual shape of the edge contour of the metal sheet hole can be compared with a corresponding desired shape. In addition, or alternatively, an actual orientation can be compared with a corresponding desired orientation. 
     In some embodiments, making a comparison can include gaining information about the presence or absence of desired conditions during the metal sheet processing operation. 
     In some embodiments, the method can further include determining a deviation of the determined characteristic from the corresponding desired characteristic, the deviation being indicative for the absence of regular conditions and performing an intervention to correct for the deviation to provide regular conditions for a succeeding metal sheet processing operation. 
     In some embodiments, forming a hole can include applying a punching tool to the sheet metal for generating the hole and wherein modifying the hole forming operation parameter includes exchanging the punching tool. 
     In some embodiments, making the comparison can provide information about at least one of the punching tool being the correct punching tool, the punching toll being in an acceptable operating condition, the punching tool being worn, and the punching toll being broken. 
     In some embodiments, the hole forming machine can further include a control device, which is connected to hole edge evaluator and receives the signal and which is configured to control the tool based on the signal. 
     In some embodiments, the processing device can includes a punching tool for generating the metal sheet hole, and the device for examining the operating condition is configured to derive information about the operating condition of the punching tool. The information can include, for example, the punching tool being the correct punching tool, the punching tool being in an acceptable operating condition, the punching tool being worn, and the punching tool being broken. 
     Alternatively, or in addition, the processing device can further include a threading tool for generating a thread in the metal sheet hole, and the device for examining the operating condition can be configured to derive information about the operating condition of the threading tool. The information can include, for example, the threading tool being the correct threading tool, the threading tool being in an acceptable operating condition, the threading tool being worn, and the threading tool being broken. 
     In a further aspect of the invention, a detection beam allows highly precise detection of an edge of the metal sheet hole to be examined. On the basis of the highly precise detection result, it is possible to establish a geometric actual state of the metal sheet holes in a highly precise manner. By comparing the geometric actual state with a corresponding desired state of the metal sheet holes, the result of the preceding metal sheet processing operation can be examined. As the geometric actual state of the metal sheet holes has been established with a high degree of precision, the comparison with the corresponding desired state can also provide a highly precise result. If a deviation of the established geometric actual state from the corresponding desired state of a metal sheet hole is established based on the comparison, one can take steps within during the production process and/or at a production arrangement in order to make the relevant geometric actual state of the metal sheet hole correspond to the associated desired state. Preferably, the corresponding correction is carried out during ongoing operation and immediately after the detection of the deviation of the geometric actual state from the geometric desired state of the metal sheet hole. In that manner, it is possible to ensure maximum process or operational reliability of the production process and the production arrangement. The production of rejects can be minimized or decreased. 
     If a light beam is used as the detection beam, it is possible to make use of a large variety of technically developed and highly precisely functioning optical systems and evaluation devices. 
     In some embodiments, the path of the detected movement, with which the processed metal sheet and the detection beam are moved relative to each other, extends transversely through the metal sheet hole. The parts of the edge of the metal sheet hole that one detects are the intersection points of the edge with the path of the detection movement. The intersection points are mutually opposite along the path of the detection movement. 
     The intersection points of the edge of the metal sheet hole with the path of the detection movement are particularly apparent and can consequently be detected with great precision. The actual extent of the metal sheet hole between the detected intersection points that is determined can be meaningful in several regards. If an examined metal sheet hole is, for example, the result of a punching metal sheet processing operation, a deviation of the actual extent from the corresponding desired extent of the metal sheet hole can indicate a partial breakage of the punching stamp used. The deviation can also indicate an incorrect orientation of a punching tool used with respect to the axis of the punching stroke or it can indicate the use of a punching tool with the incorrect stamp and/or die cross-section or diameter. 
     If a thread is formed in a prefabricated metal sheet hole, the metal sheet hole provided with the thread has, owing to the processing operation, a smaller diameter than the prefabricated metal sheet hole. It is possible to determine whether a thread forming operation has produced the desired processing result. The desired result has not been achieved if the measured actual extent of the metal sheet hole is, for example, greater than the associated desired extent. The measurement result that the actual extent of the metal sheet hole corresponds to the actual extent of the prefabricated metal sheet hole to be provided with a thread may be an indication of a fracture of the thread forming tool. 
     In some embodiments, the metal sheet hole to be examined has a circular cross-section, in which case an incorrect orientation of punching tools with respect to the axis of the punching stroke may be considered irrelevant in punching tools having a circular cross-section. 
     In some embodiments, the edge contour of the metal sheet hole can be detected in addition or alternatively to the actual extent of the metal sheet hole to be examined along a path of the detection movement that traverses the metal sheet hole. For example, the shape and the orientation of the edge contour of the metal sheet hole can be meaningful. For instance, the measurement result that the actual shape of a metal sheet hole produced by a punching metal sheet processing operation deviates from the corresponding desired shape may indicate, for example, a partial breakage of the punching tool or the use of a punching tool with the incorrect tool cross-section. Determining that the measured actual orientation of the edge contour of the metal sheet hole does not correspond to the associated desired orientation can indicate incorrect orientation of the punching tool with respect to the axis of the punching stroke. 
     If a deviation of the geometric actual state of the examined metal sheet hole from a corresponding geometric desired state is determined, tone can initiate various steps. For example, tone can produce a signal that causes a machine operator to intervene. One can further initiate an automatic interruption of the production process or automatic stoppage of the production arrangement. In the interests of large automation of the production process and the production arrangement, tone can automatically correct the cause of the determined deviation of the geometric actual state from the geometric desired state of the metal sheet hole examined. For instance, if a partial breakage of the punching tool used is indicated, a tool changing operation can automatically be introduced by the control unit of the production arrangement. With the tool changing operation, the possibly defective punching tool can be exchanged for an operational punching tool. By subsequently examining metal sheet holes, which have been processed with the exchanged punching tool, one can determine whether by changing the tool, the geometric actual state of the examined metal sheet hole has been made to correspond to the relevant desired state. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of a mechanical arrangement for producing metal sheets with a processing device and with a device for examining the processing result. 
         FIG. 2  is an illustration for explaining the operation of the device of  FIG. 1  for examining the processing result in a first application. 
         FIG. 3  is an illustration of the operation of the device of  FIG. 1  for examining the processing result in a second application. 
         FIG. 4  is an illustration of the operation of the device of  FIG. 1  for examining the processing result in a third application and 
         FIGS. 5   a,    5   b,  and  5   c  are illustrations of the operation of the device of  FIG. 1  for examining the processing result in a fourth application. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     In  FIG. 1 , a mechanical arrangement  1  for producing metal sheets comprises a C-shaped machine frame  2 , having an upper frame member  3  and a lower frame member  4 . A movement unit in the form of a conventional coordinate guide unit  6  is received in a jaw space  5  of the machine frame  2 . A carriage  7  of the coordinate guide unit  6  can be moved along a guide rail  8  perpendicularly to the plane of the drawing of  FIG. 1 . Together with the guide rail  8 , the carriage  7  can be moved on the lower frame member  4  of the machine frame  2  in the directions indicated by a double-headed arrow  9 . 
     At the front side of the carriage  7  of the coordinate guide unit  6  a plurality of clamping claws  10  are provided, one of which is shown in  FIG. 1 . The clamping claws I 0  conventionally clamp the edge of a workpiece, which is to be processed by means of the mechanical arrangement  1 . The workpiece can be a metal sheet  1 . The metal sheet  11  is further supported on a metal sheet support  12 , which is attached to the lower frame member  4  of the machine frame  2 . The metal sheet  11  can be moved in a horizontal plane owing to the described mobility of the carriage  7  of the coordinate guide unit  6 . 
     The mobility of the metal sheet  11  can be used in particular for processing metal sheets. In the embodiment illustrated in  FIG. 1 , for processing the metal sheets, a press device  13  is provided at the free end of the upper frame member  3  of the machine frame  2 . The press device  13  has an upper tool receiving member  14  that receives a schematically indicated punching stamp  15 . An also schematically indicated punching die  16  is associated with the punching stamp  15  and provided in a lower tool receiving member  17  of the lower frame member  4  of the machine frame  2 . Together with the punching stamp  15 , the punching die  16  represents a processing device in the form of a punching tool  18 . Instead of the punching tool  18 , a thread forming tool  19  can be provided as the processing device. The respective tool members are mounted in the upper tool receiving member  14  and the lower tool receiving member  17 . 
     A press drive (not illustrated in detail) of the press device  13  raises and lowers the upper tool receiving member  14  with the tool member mounted thereon in a lifting direction  20  along a double-headed arrow. A housing  21  of the press device  13  remains stationary during the lifting movement of the upper tool receiving member  14 . 
     At the side facing away from the coordinate guide unit  6 , the housing  21  of the press device  13  is provided with a transmission and reception unit  22 . A reflector  23 , is mounted to the lower frame member  4  of the machine frame  2  and forms a detection device together with the transmission and reception unit  22 . The reflector is located opposite the transmission and reception unit  22 . The coordinate guide unit  6 , the press device  13 , and the transmission and reception unit  22  are connected to a control computer  24  of a numerical control unit for the mechanical arrangement  1 . The transmission and reception unit  22  is connected to an evaluation device  25  of the control computer  24 . The evaluation device  25  is connected to a movement control unit  26  and a press control unit  27 . The drive motors of the coordinate guide unit  6  are controlled by the movement control unit  26  and the press drive of the press device  13  is controlled by the press control unit  27 . In this respect, the press control unit  27  is a control device for the punching tool  18  and/or the thread forming tool  19 . 
     In order to process the metal sheet  11  in a punching manner, the punching tool  18  provided for the relevant processing operation is fitted in the upper tool receiving member  14  and the lower tool receiving member  17 . Subsequently, the coordinate guide unit  6  positions the metal sheet  11  held by the clamping claws  10 , relative to the punching tool  18 . If punched-out portions (e.g. metal sheet holes) are intended to be formed in the metal sheet  11 , a plurality of operating strokes of the punching tool  18  or different punching tools can be required and the metal sheet  11  is moved by the coordinate guide unit  6  after each individual operating stroke of the punching tool  18 . 
     The sheet metal processing operation can be based on processing parameters e.g. hole forming operation parameters. Those parameters can include, for example, the type of tool, the size and shape of the punched out area, the position and orientation (in 3D) with which a tool is applied. Moreover, the parameters can define a sequence of tool operations and the geometrical change between succeeding applications of the same or of different processing tools. 
     After the punching processing operation has been finished, the coordinate guide unit  6  moves the processed metal sheet  11  with the punched-out portion produced out of the immediate vicinity of the punching tool  18  into a region in which the punched-out portion is accessible to the transmission and reception unit  22 . The examination of the quality of the result of the metal sheet processing operation, e.g. of the quality of the punched-out portion produced, is then carried out. 
     In  FIG. 1 , the metal sheet  11  with a previously produced metal sheet hole or punched-out portion  28  is positioned below the transmission and reception unit  22 . A transmitter of the transmission and reception unit  22  directs a detection beam, e.g. a laser beam  29 , towards the metal sheet  11 . The position of the axis of the laser beam  29  is defined in an x-y-z coordinate system, which is used for the numerical control of the mechanical arrangement  1 . The current position of the metal sheet  11  and consequently also the current position of the punched-out portion  28  are also defined in an x-y-z coordinate system. In place of the laser beam  29 , other types of detection beams, e.g. a red light beam, can also be employed. 
     To examine the result of the preceding metal sheet processing operation, the coordinate guide unit  6  moves the metal sheet  11  with a detection movement in a transverse direction relative to the laser beam  29 . In  FIG. 2 , a path  30  is indicated by dot-dash lines. Along this path  30 , the laser beam  29  scans transversely through the punched-out portion  28  during the detection movement on the metal sheet  11 . 
     At the beginning of the detection movement, the laser beam  29  strikes the non-perforated metal sheet  11 . In the course of the detection movement, the laser beam  29  reaches the edge  31  of the punched-out portion  28  at a first point of intersection P 1  of the edge  31  with the path  30 . For the numerical control of the mechanical arrangement  1  or the evaluation device  25  of the control computer  24  connected to the transmission and reception unit  22 , the first intersection point P 1  is marked in that the laser beam  29  strikes the reflector  23  through the punched-out portion  28  practically when the first intersection point P 1  is reached. The reflector  23  is arranged below the metal sheet  11  and reflects the laser beam back to the receiver of the transmission and reception unit  22 . At that time at which the laser beam  29  is first reflected back by the reflector  23  and strikes the receiver of the transmission and reception unit  22 , the position of the metal sheet  11  is established in the x-y-z coordinate system of the mechanical arrangement  1 . 
     As the detection movement continues, the laser beam  29  scans across the punched-out portion  28  until it reaches a second point of intersection P 2  of the edge  31  of the punched-out portion  28  with the path  30 . During its movement transversely through the punched-out portion  28 , the laser beam  29  is continuously reflected by the reflector  23  to the receiver of the transmission and reception unit  22 . The associated light incidence at the receiver of the transmission and reception unit  22  ends as soon as the laser beam  29  reaches the edge  31  of the punched-out portion  28  at the second intersection point P 2 . The end of the light incidence at the transmission and reception unit  22  marks for the numerical control unit of the mechanical arrangement  1  an operating state at which the position of the metal sheet  11  is again established in the x-y-z coordinate system of the mechanical arrangement  1 . Based on the positional change of the metal sheet  11  between the first determination of the position (laser beam  29  at P 1 ) and the second determination of the position (laser beam  29  at P 2 ), the evaluation device  25  derives the actual extent of the punched-out portion  28  between the first intersection point P 1  and the second intersection point P 2 . In  FIG. 2 , the actual extent corresponds to the diameter of the circular punched-out portion  28 . The determined actual extent of the punched-out portion  28  is compared in the evaluation device  25  with a desired extent of the punched-out portion  28  stored in the numerical control unit of the mechanical arrangement  1 . That desired extent is defined by the dimensions of the punching tool  18 , which was used for producing the punched-out portion  28 . 
     The fact that light emitted from the transmitter has reached the reflector  23  and then the receiver during the detection movement between the metal sheet  11  and the laser beam  29 , demonstrates that the preceding processing operation on the metal sheet  11  has produced a workpiece hole. Details of the workpiece hole, e.g. characteristics of the specific geometric configuration, can be obtained by evaluating the changes of the detected detection beam during the detection movement. 
     The determination of a significant deviation of the actual extent from the desired extent of the punched-out portion  28  by the comparison indicates irregular conditions during the preceding metal sheet punching processing operation. Accordingly, for example, the evaluation device  25  can generate a signal indicating information about the metal sheet processing operation that has taken place. Based on the signal, the processing operation can be modified by, for example, adjusting the processing parameters. Exemplary irregular conditions include the use of an incorrect punching tool  18  during the punching processing of the metal sheet  11 , for example, a punching stamp  15  and a punching die  16  with an excessively large diameter. Exemplary irregular conditions include further a partial stamp breakage of the punching tool  18  so that the punched-out portion  28  has been cut only partially. The processing result in the case of a partial stamp breakage can result, for example, in a faulty punched-out portion  28 . 1  as illustrated in  FIG. 2 . 
     If a significant deviation of the actual extent of the punched-out portion  28  from the desired extent is determined, irrespective of the cause, the drive motors of the coordinate guide unit  6  are stopped by the movement control unit  26  and the press drive of the press device  13  is stopped by the press control unit  27 . Furthermore, the numerical control unit of the mechanical arrangement  1  generates an error message, which informs the operator about the malfunction which has occurred. Alternatively, or in addition, a message suggesting modifications through the operator or a message showing the performed modifications can be generated. 
     As an alternative to the path  30 , a path  32  of the detection movement of the laser beam  29  along the metal sheet  11  is indicated in  FIG. 2 . 
     For clarification, the path  32  is illustrated to be displaced within to the circular edge  31  of the punched-out portion. Actually, the path  32  follows the desired contour of the edge  31  of the punched-out portion  28 . During the detection movement, the laser beam  29  scans along the path  32  with its beam axis. Accordingly, a portion of the cross-section of the laser beam  29  passes through the punched-out portion  28  and the other portion of the laser beam cross-section falls on the upper side of the metal sheet  11 . 
     In general, and specifically in this case, one can replace the above-described transmission and reception unit  22  and the associated reflector  23  by a transmission device  33  above the metal sheet  11  and a reception device  34  below the metal sheet  11 . The portion of the cross-section of the laser beam  29  that passes through the punched-out portion  28  reaches the reception device  34 . The transmission device  33  and reception device  34  form a detection device and are connected to the evaluation device  25  of the control computer  24 . 
     During the detection movement, the path  32  and therefore the desired contour of the edge  31  of the punched-out portion  28  are scanned with the laser beam  29 . If the correct portion of the cross-section of the laser beam  29  strikes the reception device  34  during the entire detection movement, then the actual contour of the edge  31  of the punched-out portion  28  seems to be in agreement with the desired contour. Instead, the fact that the laser beam  29  strikes the reception device  34  during the detection movement with one or more interruptions, can indicate a partial stamp breakage and accordingly the presence of a punched-out portion in the manner of the punched-out portion  28 . 1  as shown, for example, in  FIG. 2 . Moreover, the fact that no light at all falls on the reception device  34  during the detection movement along the path  32 , can indicate an excessively small diameter of the punched-out portion produced or a complete stamp breakage, because of which no workpiece hole has been produced in the region of the metal sheet  11 , which should have been processed. 
     In the event of punched-out portion having a cross-section which deviates from the circular shape, it can additionally be possible to examine whether the punched-out portion is arranged on the metal sheet  11  with its desired orientation. For this purpose, the movement path of the detection movement to be carried out can also extend either transversely through the relevant punched-out portion ( FIG. 3 ) or along the edge of the relevant punched-out portion ( FIG. 4 ). 
     In the first case illustrated in  FIG. 3 , the actual extent of a metal sheet hole or punched-out portion  35  between intersection points P 1 , P 2  and/or between intersection points P 3 , P 4  between an edge  31  of the punched-out portion  35  and a movement path  30  or  36  is compared with a corresponding desired extent. As shown in  FIG. 3 , an incorrect punched-out portion  35 . 1  can cause a deviation of the established actual extent of the punched-out portion  35  from the desired extent. Such a deviation can indicate incorrect orientation of the punched-out portion  35  with respect to the metal sheet  11 . An incorrect orientation of the punching tool  18  can be, for example, the reason for the incorrect orientation of the punched-out portion  35 . 1 . 
     Accordingly, as shown in  FIG. 4 , a path  38  of a detection movement can follow the desired contour of the edge  31  of a metal sheet hole or a punched-out portion  37 , to determine whether the punched-out portion  37  is orientated correctly or incorrectly with respect to the metal sheet  11 . 
     In  FIGS. 5   a,    5   b,  and  5   c,  a metal sheet hole in the form of a punched-out portion  39  is produced first by a punching tool  18  of the mechanical arrangement  1 . In  FIG. 5   a,  the circular punched-out portion  39  in the embodiment has a diameter dl. After the punching processing of the metal sheet  11 , a thread forming tool  19  is mounted at the upper tool receiving member  14  and the lower tool receiving member  17  in place of the punching tool  18 . A thread  40  is then formed in the wall of the punched-out portion  39  by the thread forming tool  19 . In  FIG. 5   b,  a metal sheet hole or threaded hole  41  provided with the thread  40  has a core diameter d 2 . 
     The core diameter d 2  is a few tenths of a millimeter smaller than the diameter dl for processing reasons. The punched-out portion  39  can also be produced in a completely separate operation, for example, on a processing device, which is different from the mechanical arrangement  1 . 
     To examine the processing result, the metal sheet  11  with the region of the threaded hole  41  is moved relative to the laser beam  29  which is emitted from the transmission and reception unit  22  of the mechanical arrangement  1 . A path  42  of the detection movement is indicated as a dot-dash line in  FIG. 5   c.  As discussed in connection with  FIG. 2 , the actual extent, e.g. the actual diameter of the threaded hole  41 , is determined between intersection points P 1 ′ and P 2 ′. Subsequently, the determined actual extent is compared with the corresponding desired extent. If that comparison yields that the actual extent of the threaded hole  41  does not have the desired dimension, but instead the dimension dl, this indicates a malfunction of the thread forming operation. A damaged thread forming tool  19  can be the reason for that malfunction. As discussed above, signals can be generated that indicate information about the processing operation based on the comparison between actual and desired configurations. Moreover, the treading process can be modified based on the comparison. 
     In the applications shown in  FIGS. 3 ,  4 , and  5   a  to  5   c,  an intervention can be also carried out in the production process of the mechanical arrangement  1  in case an irregular processing result is determined. For example, the drive motors of the coordinate guide unit  6  and the press drive of the press device  13  can be stopped and an error message for the machine operator can be generated. 
     A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.