Abstract:
A system and method for detecting a defective part and the type of defect formed during stamping operations. The system and method will not only detect the defect but also the nature of the defect and the time at which the defect occurred during stamping operations. Such information is useful not only in quality control but also in isolating a problem which may exist in stamping operations and thus eliminating time for isolating such problems and correcting them. The system and method uses a profile of a properly stamped part to detect a defect, and the root cause of the defect.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 13/041,857 filed on Mar. 7, 2011, which is incorporated in its entirety herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a system for stamping a part from a blank of material. More particularly, the invention relates to a system and method for detecting abnormalities in the part stamped by a die using forces measured during stamping operations and comparing them with a profile of forces for a properly stamped part. 
       BACKGROUND OF THE INVENTION 
       [0003]    Stamping operations are done using a die. The die includes an upper die and a lower die, also referenced herein as a slide press and a die cushion respectively. A sheet of material, also referenced in the art as a blank, is placed between the slide and die cushion and the slide and die cushion are pressed against each other so as to form the blank into a desired part. 
         [0004]    The part may then be visually inspected to ensure that no abnormalities existed during stamping operations. As visual inspection may be time consuming and subject to human error, systems have been put in place to make the inspection automated. 
         [0005]    For instance, it is known to use the displacement of the press with respect to stamping operations to determine whether or not any flaws occurred during stamping operations. Other methods include measuring compressive and tensile forces on the production part. However, these methods do not take into account the work and force peaks which are transmitted during the stamping operation and thus will not determine the type of the flaw that has occurred. Further, such methods and systems do not provide the type of defect present in the stamped part. 
         [0006]    Accordingly, it remains desirable to have a system which not only detects whether or not the part is defective but will also provide the type of flaw that occurred thus allowing for operators and management to reconfigure stamping operations to eliminate the flaw. For example, if it is detected that the machine has produced parts which have wrinkles, then the forming characteristics of the forces with respect to time may direct the user as to where in the forming process the wrinkles have been formed. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a system and method for detecting a defective part and the type of defect formed during stamping operations. The system and method will not only detect the defect but also the nature of the defect and the time at which the defect occurred during stamping operations. Such information is useful not only in quality control but also in isolating a problem which may exist in stamping operations and thus eliminating time for isolating such problems and correcting them. 
         [0008]    The method includes the step of establishing a profile. The profile includes characteristics of forces of a properly stamped part. Such characteristics include peak forces applied by the die with respect to a particular point in time during stamping operations. Stamping operations as used herein refers to the process by which die parts are moved together to press a blank and are released from each other so as to free the blank for use in manufacturing. 
         [0009]    The method further includes the step of measuring the forces of the stamped blank of material and comparing the force characteristics of each of the stamped blanks of material with the profile of the properly stamped part. The profile may further include defective profiles, the defective profile being a profile of an improperly formed part having a particular defect. The defective profiles may include force characteristics for a part formed with a wrinkle, or a split. The existence of the wrinkle or split may be analyzed to determine the root cause of the defect. This root cause may be recorded as part of the defective profile. For instance, a wrinkle may be formed for numerous reasons; however, a particular reason may have a unique force characteristic. Once the root cause is determined, the identified root cause is then associated with that particular wrinkle. 
         [0010]    The force characteristics of various defects, to include the location of the defect within the part may be recorded and used to for a respective defective profile. Thus, operators overseeing stamping operations may be able to not only identify that the part is defective but the location and nature of the defect. Further, the die operators may be able to easily recognize the root cause of the defect and take corrective measures to minimize manufacturing loss. 
         [0011]    A system for controlling the quality of a stamped part from a blank of material is also provided. The system includes a die having a slide press and a cushion press. A sensor is mounted to the die and is operable to detect the forces applied to the blank of material. A database having a profile including characteristics of forces of a properly stamped part is used to compare the forces measured during stamping operations. 
         [0012]    The profile may further include defective profiles. Each of the defective profiles having characteristics of forces which identify the nature of the defect. A processor is in communication with the sensor. The processor compares the forces detected during the stamping of a part and labels the part defective when the detected forces deviate from the profile of the properly stamped part. The processor may further search the database for a defective profile which matches the detected profile so as to identify the nature of the defect. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a cross-sectional view of a die and a blank; 
           [0014]      FIG. 2  is a cross-sectional view of  FIG. 1  showing the blank being formed; 
           [0015]      FIG. 3A  is an overhead view of the upper die showing sensors formed at each corner; 
           [0016]      FIG. 3B  is a view taken from the bottom of the cushion press showing sensors mounted at each corner of the die cushion; 
           [0017]      FIG. 4  shows a profile of the forces of a properly formed part for the slide press; 
           [0018]      FIG. 5  shows a profile of a properly formed part with respect to the die cushion; 
           [0019]      FIG. 6  is a chart showing the characteristics of forces with respect to the strokes of the die; 
           [0020]      FIG. 7  is a chart showing forces outside of the force parameters indicating a defect; 
           [0021]      FIG. 8  is a perspective view of a manufacturing line showing the stamping operations of a part; and 
           [0022]      FIG. 9  is a diagram showing the steps of a method for detecting a defective part. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Referring to  FIGS. 1-8 , a system  10  for controlling the quality of a part  12  stamped from a blank of material  14  is provided. The system  10  includes at least one die  16  operable to stamp the blank of material  14  into a desired part  12 . A sensor  18  monitors the forces exerted by the die  16 . The forces are compared to a profile  20 . The profile  20  includes the forces generated during a stamping operation of a properly formed part  12 . The profile  20  shows the proper distribution of forces with respect to time. The system  10  labels a part  12  defective when the forces measured differ a predetermined amount from the profile  20 . 
         [0024]    With reference first to  FIGS. 1 and 2 , an operation of the die  16  is provided. The die  16  has an upper die  22  and a lower die  24 , referenced herein as a slide press  22  and a die cushion  24  respectively. The slide press  22  includes tabs  26 . The tabs  26  are shown on opposing sides of the slide press  22 . The die  16  further includes a pair of binders  28  each having a catch  30 . The die cushion  24  is disposed between respective binders  28 . The tabs  26  and binders  28  are respectively aligned with each other. 
         [0025]    The surfaces of the slide press  22  and cushion press  24  are configured to form a predetermined part  12  from a blank. With reference first to  FIG. 1 , the blank is shown disposed between the slide press  22  and the cushion press  24 . The slide press  22  and cushion press  24  are pressed towards each other. The tabs  26  are seated within the catches  30  of the binder  28  and the blank is held in place. The slide press  22  and cushion press  24  are then displaced towards each other so as to stamp the blank of material  14  into a desired part  12 . With reference now to  FIG. 2 , the slide press  22  and cushion press  24  are moved away from each other and the part  12  may then be taken from the die  16 . 
         [0026]    With reference now to  FIGS. 3A and 3B , the sensors  18  are shown mounted to respective slide and cushion presses. The sensors  18  are in communication with the processor  32 . Preferably the sensors  18  are mounted to the corners of the presses. Such sensors  18  are currently known and used and illustratively include a connection screw. Force is transmitted through the connection screw to the processor  32 . 
         [0027]    A database  34  having a profile  20  of characteristic forces of a properly stamped part  12  may be used to compare forces detected during the stamping of a part  12  to determine the existence of a defect. The profile  20  may be formed through the manufacture of a desired part  12 . Specifically, the force characteristics of the part  12  may be collected and compared so as to create the profile  20 . Thus the profile  20  may be a historical record of stamped parts  12  which were formed properly. The profile  20  may include force characteristics for both the slide press  22  and the cushion press  24 . 
         [0028]    As used herein, force characteristics relates to the amount of force measured with respect to time, displacement of respective slide and cushion presses with respect to time, and the amount of work done with respect to time. Thus, not only does the profile  20  include the amount of force, but a point along time in which the force was experienced, how much work was done to stamp the part  12 , and the whether the slide and cushion presses were in proper position throughout the stamping operation. 
         [0029]    The profile  20  may further include defective profiles  36 . The defective profiles  36  are force characteristics or force characteristics of a particular defect. Thus as parts  12  are stamped, particular defects are recorded. The force characteristics of those defects may be stored in the database  34  as a defective profile  36 . For instance, if a part  12  is stamped with a wrinkle or a tear, the force characteristics of the defective part  12  is recorded and stored as a defective profile  36 . 
         [0030]    The processor  32  is in communication with the sensors  18 . The processor  32  compares the forces detected during the stamping of the part  12  and compares those forces with the profile  20  of a properly stamped part  12 . If the profile  20  matches the detected forces, then the part  12  is identified as being properly formed. If the detected forces do not match the profile  20 , then the part  12  is labeled as defective. In cases where a part  12  is labeled defective, the processor  32  further searches the database  34  to determine if the detected forces match any one of the defective profiles  36 . Detected forces corresponding to a defective profile  36  is then used to identify the nature of the defect. The processor  32  may further compare other aspects of the stamping operation to the profile  20 , to include the work done on the part  12  and the position of the slide and cushion presses with respect to time. 
         [0031]    The system  10  further includes an encoder  38 . The encoder  38  may be disposed on either the slide press  22  or the die cushion  24 . The encoder  38  is operable to detect the position of the respective slide or cushion press  22 ,  24  during stamping operations. [there seems to be more to the use of the encoder  38 , in the slides you mentioned how the encoder  38  was necessary, please explain why] 
         [0032]    With reference now to  FIGS. 4 and 5 , the profile  20  of a properly stamped part  12  with respect to the slide press  22  and cushion press  24  are provided. The forces are measured with respect to position. 
         [0033]    As shown, there are peak forces which occur during stamping operations respectively labeled A, B and C. Peak forces indicated by references A and B show the peak forces applied by the slide press  22 , whereas peak force labeled C is the peak force applied by the cushion press  24 . These force characteristics indicate characteristics which are acceptable for a properly formed part  12 . 
         [0034]    The profiles  20  further include the work done by the respective slide and cushion presses as indicated in the lined portion shown in  FIGS. 4 and 5 . Thus the profile  20  not only includes identifying when these peak forces are formed with respect to the stamping operations but also how much work each press has done on the part. These five characteristics (the three peak forces and work done by each press) are used to indicate that the part  12  was properly formed. It should be appreciated that these characteristics exemplify a proper forming condition. However, as will be discussed later, other forces and inputs may be used to further narrow what is acceptable as a properly formed part  12 . 
         [0035]    With reference now to  FIGS. 6 ,  7  and  8 , a chart showing the forces with respect to the strokes performed by dies  16  placed in succession is provided.  FIG. 6  shows a proper profile  20  for the operation of a plurality of dies  16  with respect to the force characteristics and the strokes or presses of the die  16  function. Strokes as used herein refers to the displacement of a slide and cushion press  22 ,  24  to and from each other. 
         [0036]    With reference to  FIG. 6 , a force parameter is provided. The force parameter is indicated by the dashed lines found above and beneath the profile  20 . The force parameter is a threshold of acceptable forces during stamping operations. With reference now to  FIG. 7 , the forces measured during the stamping process of a part  12  is shown. The profile  20  is created by the forces detected by the sensor  18  and transmitted to the processor  32  and processed. In this case it may be seen that there are three instances in which the forces exceed or are outside of the force parameters as defined by the dashed lines. In such a case the system  10  may be shut down. 
         [0037]    The profile  20  includes peak forces of the slide and cushion presses with respect to time and as stated below, the work performed by both the slide and the cushion presses. However, the profile  20  may also take into account various inputs such as the position of the slide and cushion presses during the stamping operations with respect to time and whether or not oil was placed on the presses or the blank. Other inputs may further include the temperature of the die  16  or the slide and cushion presses or the temperature of the blank for that matter. Thus, a profile  20  of force characteristics for a properly stamped part  12  having a thin film of oil, or without oil may be recorded and used to detect defective parts  12 . 
         [0038]    Thus the profile  20  may be one of many that the user may select based upon the part  12  being stamped, the material used in the blank, and the temperature of the die  16 , or whether or not a film of oil was used. The measured forces are compared to the selected profile  20  to determine whether the stamping process produced an abnormal or defective part  12 . 
         [0039]    With reference now to  FIG. 8 , an operation of the system  10  is provided. The system  10  includes a plurality of dies  16  disposed downstream a steel blank feeder. The steel blank feeder collects blanks and positions them in between the press and cushion slides. Once the blank of material  14  is fed, the slide and cushion presses are displaced towards one another and the tabs  26  of the slide press  22  engage the binders  28  so as to hold the blank in position during forming operations. 
         [0040]    As the presses are pressed towards one another, the forces exerted by the presses are measured by the sensors  18 . The forces are measured throughout the stamping operation of a respective die  16 , which is until the presses are displaced from each other. The blank of material  14  is fed downstream the line through each of the dies  16 . In the instant case three other die  16  presses are shown downstream the initial die  16 . Each die  16  press will have a profile  20  that is characteristic for the work that the die  16  is to do on the blank of material  14 . Thus the system  10  may be operable to detect a defective part  12  in any of the die  16  forming processes. 
         [0041]    Not only is the system  10  capable of detecting a defect, the system  10  may be operable to detect the nature of the defect if a defective profile  36  matches a force characteristic of a formed part  12 . The system  10  may further include an automatic shut-off  40  operable to cease operations of the die  16 . The automatic shut-off may be actuated when the detected forces deviate from the profile  20  of the properly stamped part  12 . With reference to  FIG. 8 , the automatic shut-off is a button in electrical communication with the system  10 . The automatic shut-off  40  may be manually actuated by a press of a button, or may be actuated by the processor depending upon the type or number of defects occurring along the line. 
         [0042]    An indication as to the nature of the defect may be provided wherein the detected forces match one of the defective profiles  36  stored in the database  34 . The existence of the wrinkle or tear may be analyzed to determine the root cause of the defect. This root cause may be recorded as part  12  of the defective profile  36 . For instance, a wrinkle may be formed for numerous reasons; however, a particular reason may have a unique force characteristic. Once the root cause is determined, the identified root cause is then associated with that particular wrinkle. Identification of the root cause may reduce manufacturing loss by allowing the operator to go right to the source of the error as opposed to trouble shooting the entire system  10 . 
         [0043]    With reference now to  FIG. 9 , a method  100  for controlling the quality of a part  12  stamped from the blank of material  14  formed by the operation of a die  16  is provided. The method  100  includes the step of establishing a profile  20  at  102 . The profile  20  has characteristics of forces of a properly stamped part  12 . The profile  20  may be established by stamping a part  12  and determining if the part  12  meets design specifications and does not include any faults. The characteristic of forces of such a part  12  may be used as the profile  20 . 
         [0044]    The method  100  further includes the step of measuring the forces of a stamped blank of material  14  and comparing the stress characteristics of each of the stamped blank of material  14  with the profile  20  of the properly stamped part  12  at  108 . The method  100  proceeds to step  110  where any of the stamped blank material is labeled as being a defective part  12  where the forces deviate from the profile  20  of the properly stamped part  12 . The profile  20  may take into consideration the force of the slide and cushion presses and may include establishing a force parameter wherein stamped materials having slide and cushion press  22 ,  24  forces outside of the side force parameter are labeled as defective. 
         [0045]    The method  100  may include using other inputs to further define a profile  20 . For instance, the method  100  may include the use of the speed of the die  16  operation, the temperature of the die  16 , or the existence of a film of oil on the blank of the material to establish the profile  20 . Thus, a profile  20  for a properly formed part  12  at 100° Fahrenheit may have different force characteristics than that same part  12  properly formed at 80° Fahrenheit. Likewise, a profile  20  may have different force and force characteristics for the same part  12  where one part  12  is made with a film of oil and the other is not. 
         [0046]    The method  100  may further include the step of establishing a defective profile  36  at. The defective profile  36  may be established by recording the forces exerted by the slide and cushion press  22 ,  24  in the formation of a defect in a particular part  12 . For instance, the formation of a wrinkle in a part  12  may leave a unique force characteristic. The force characteristics of each of the stamped part  12  may be compared with the defective profiles  36 , and the nature of the defect may be provided as shown at step  112 . 
         [0047]    The method  100  may further include the step of recording the root cause and associating the root cause with the defective profile  36  at  106 . The root cause of the defect may be analyzed by die  16  operators. Thus the method  100  not only identifies a defect, but also provides the nature of the defect and the root cause. 
         [0048]    In view of the teaching presented herein, it is to be understood that numerous modifications and variations of the present invention will be readily apparent to those of skill in the art. Likewise, the foregoing is illustrative of specific embodiments of the invention but is not meant to be a limitation upon the practice thereof. It is the following claims, including all equivalents, which define the scope of the invention.