Abstract:
A method of manufacturing an article includes the steps of: establishing a defined location for a tool activity to occur; determining an actual location of the tool; comparing the actual location of the tool with the defined location; ascertaining an occurrence of the tool activity at the actual location; and verifying whether the tool activity occurred at the defined location.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method and system for manufacturing an article, and, more particularly, to a method and system for avoiding mistakes using portable hand-tools during manufacture an article. 
       BACKGROUND OF THE INVENTION 
       [0002]    During the manufacture of an article, it is often necessary for a worker to use a hand-held tool to carry out various manufacturing steps, such as assembling, welding, painting, etc. The article may be in the form of an assembly or sub-assembly such as a transmission, machine frame, operator&#39;s cab, electronic packaging, etc. 
         [0003]    In the manufacturing environment, a worker using a hand-held tool cannot consistently duplicate exact work from one assembly to another assembly. For example, assembly lines often require many threaded fasteners to be assembled using a torque gun at a single workstation. Known control systems can count the number of times the torque gun reaches the required torque value, but cannot determine if all the fasteners were tightened, or if some were tightened twice, or if the fasteners were tightened in a specific sequence. 
         [0004]    What is needed in the art is a method and system which not only can determine whether a particular manufacturing task is carried out, but also determine whether the manufacturing task was carried out at the correct location and/or in the correct sequence. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention in one form is directed to a method of manufacturing an article, including the steps of: establishing a defined location for a tool activity to occur; determining an actual location of the tool; comparing the actual location of the tool with the defined location; ascertaining an occurrence of the tool activity at the actual location; and verifying whether the tool activity occurred at the defined location. 
         [0006]    The invention in another form is directed to a system for manufacturing an article, including a tool for carrying out a tool activity on the article, a memory storing a defined location for the tool activity to occur, a location detector for detecting an actual location of the tool, and an electrical processor in communication with the memory and the location detector. The electrical processor is configured for comparing the actual location of the tool with the defined location, ascertaining an occurrence of the tool activity at the actual location; and verifying whether the tool activity occurred at the defined location. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic illustration of an embodiment of a system of the present invention for manufacturing an article; and 
           [0008]      FIG. 2  is a flowchart of an embodiment of the method of the present invention for manufacturing an article, which may be carried out using the system shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0009]    Referring now to the drawings, and more particularly to  FIG. 1 , there is shown an embodiment of a system  10  for manufacturing an article  12 . Article  12  may be any type of manufactured article which is assembled, welded, painted, etc. For example, article  12  could be a transmission, machine frame, etc. For ease of illustration, article  12  is simply shown as a three-dimensional block with dimensions in the X, Y and Z directions. It will be appreciated that the exact size and shape of article  12  may vary. 
         [0010]    For a given manufacturing process, article  12  is assumed to have a number of defined locations  14  corresponding to tool activities to be carried out using tool  16 . In the embodiment shown in  FIG. 1 , tool  16  is assumed to be a torque gun, and defined locations  14  are assumed to be the locations of threaded openings in article  12  for receiving threaded fasteners, such as bolts. In the case of a spot welding operation, defined locations  14  could correspond to the spot weld locations. Likewise, in the case of a welding or painting operation requiring movement of a gun, the defined locations  14  could be used to represent the start and/or termination points for a predefined movement of the gun. 
         [0011]    As indicated above, tool  16  is assumed to be a torque gun in the embodiment shown in  FIG. 1 . To that end, although tool  16  is shown in simplified block form, it will be appreciated that the exterior shape would more closely approximate a typical torque gun. Torque gun  16  includes a rotatably driven socket  18 , which in turn is engaged with and drives the head of a threaded bolt (not shown) placed in a respective threaded hole at a corresponding defined location  14 . Torque gun  16  is coupled with a suitable source of power, such as through an air hose  20  connected to a remote air supply (not shown). It will be appreciated that torque gun  16  could be electrically driven, in which case reference number  20  would correspond to an electrical cable coupled with an electrical power supply. 
         [0012]    Tool  16  could also take the form of other types of portable hand-held tools, such as a torque wrench, weld gun, paint gun, pulse gun, air tool or banding tool. 
         [0013]    Tool  16  also includes one or more optical targets  22  which are placed at corresponding exterior locations. In the embodiment shown, tool  16  includes a single optical target in the form of an active target which emanates a particular type of light. Rather than being an active target requiring a source of electrical power (e.g., battery power), it is also possible that target  22  could be a passive target such as a number of reflective balls, a reflective strip, a projection with a predefined shape, etc. 
         [0014]    An electrical circuit  24  includes an electrical processor  26 , memory  28 , one or more cameras  30 , and feedback  31 . Electrical processor  26  preferably is a microprocessor which is coupled with each of memory  28  and camera(s)  30 . Electrical processor  26  is hardwired with each of memory  28  and camera  30  in the illustrated embodiment, but could also be coupled via wireless connections, etc. 
         [0015]    Memory  28  is any suitable type of memory capable of long term storage of data which is provided to electrical processor  26 . For example, memory  28  can be used to store the coordinates of defined locations  14  on article  12 . 
         [0016]    Camera  30  is used to detect the actual location of optical target  22  on tool  16 , and provides corresponding output signals to electrical processor  26 . In the embodiment shown, camera  30  is assumed to be an infrared (IR) camera which detects light which is transmitted from optical target  22 . Preferably multiple cameras are used at different locations associate with the work station at which article  12  is located so that optical target  22  may be more accurately located relative to a known coordinate. 
         [0017]    Feedback  31  is a schematic representation of some type of feedback which is provided to an operator or assembler during the manufacturing process, discussed in more detail below. 
         [0018]    Referring now to  FIG. 2 , an embodiment of the method of the present invention for manufacturing an article will be described in greater detail. Initially, the one or more defined locations for carrying out a tool activity are established using data stored in memory  28  (block  40 ). If article  12  is accurately placed at a known position and orientation within the work station, then it is possible that the defined locations could simply be three-dimensional, absolute coordinates relative to a known coordinate. Alternatively, it is possible to establish the defined locations  14  relative to a three-dimensional model of article  12  within the work station. This approach may allow a more dynamic referencing of the defined locations  14  for a given tool activity relative to the size, shape, exact position and orientation of article  12  within the work station. (i.e., more of a relative rather than absolute determination of defined locations  14  on article  12 ). 
         [0019]    In the embodiment shown, a three-dimensional representation of article  12  is generated and stored within a computer aided drafting (CAD) library within memory  28 . Each defined location  14  is correlated to a corresponding point on the three-dimensional representation of article  12 . The three-dimensional coordinate of each correlated point is likewise stored in memory  28 . Additionally, a defined tool activity is assigned for each correlated point on the three-dimensional representation of article  12 . The assigned tool activities for each correlated point are likewise stored in memory  28 . Thus, the defined locations  14  in essence overlie the three-dimensional representation of article  12 , and each defined location has a corresponding defined tool activity. 
         [0020]    Rather than using a CAD library or numerical analysis technique to establish the defined locations  14  for a tool activity, it is also possible to empirically establish the defined locations  14 . In particular, the position(s) of tool  16  may be tracked during an initial data gathering stage and correlated with the occurrence of tool activities to establish the defined locations  14  which are stored within memory  28 . In the case of a moving tool activity such as welding or painting, a set of detected defined locations  14  can be used to define the tool activity. 
         [0021]    Electrical processor  26  uses the output signals from camera  30  to determine the actual location of tool  16  (block  42 ). The actual location is compared with a corresponding defined location for a given tool activity (block  44 ). Electrical processor  26  then ascertains whether the prescribed tool activity occurred at the actual location (block  46 ). For example, in the case of a torque gun, it is possible to sense whether the torque which is applied to the head of the bolt reaches a predefined torque value. This information can be sent via a wired or wireless connection to electrical processor  26 . The prescribed tool activity must occur, and the actual location must match with the defined location, in order for the tool activity to be verified (block  48 ). 
         [0022]    At decision block  50 , a determination is made as to whether an operator is to be provided with feedback in the event that the manufacturing process is not proceeding as expected. More particularly, if the tool activity does not correspond to the prescribed tool activity, and the actual location does not match with the defined location, then an operator is provided with feedback (block  52 ). For example, electrical processor  26  can control the manufacturing process to shut off tool  16 , not allow article  12  to advance to a next workstation, trigger a warning light observable by the operator and/or generate a written report. The feedback can be positive or negative. For instance, a monitor can be placed in front of an operator with a model of the assembly that has components turning a different color when the activity is completed on that component. This gives the operator visual feedback on what is left to complete, or shows what is next in the sequence if a sequence is required. Other types of feedback are of course also possible. 
         [0023]    On the other hand, if the tool activity does correspond to the expected tool activity, and the actual location matches with the defined location, then there is no need to provide feedback to an operator (line  54 ). 
         [0024]    At decision block  56 , a determination is made as to whether tool  16  should be moved to additional defined locations  14  for further tool activities. If so, then control loops to block  42  and the control logic repeats. On the other hand, if there is only a single defined location for a tool activity, or tool  16  is at the defined location corresponding to a last tool activity, then the control logic simply ends. 
         [0025]    For an article having multiple defined locations with corresponding tool activities at each defined location, it is possible to track the actual locations and/or tool activities at each actual location for various purposes. For example, one purpose for tracking the actual locations and tool activities at each actual location is to identify the particular article  12  which is being manufactured. This allows electrical processor  26  to know the sequence of the remaining defined locations and corresponding tool activities which are to occur after the article  12  is identified. If an operator does not perform a next expected tool activity for a given article  12 , then feedback may be provided to the operator at block  52 . 
         [0026]    From the foregoing description, it is apparent that the method and system of the present invention dynamically avoids mistakes during the manufacturing process by tracking the position and operation of tool  16  relative to a predetermined or dynamically identified article  12 . 
         [0027]    In the system  10  for manufacturing an article described above, a location detector detects the position of tool  16  using camera  30  and optical target  22 . Optical target  22  thus in essence is a passive component, the position of which is sensed using one or more cameras  30 . Cameras  30  are therefore the active components providing output signals to electrical processor  26 . It is also possible to configure system  10  with a location detector having an active component on tool  16  which provides an output signal to electrical processor  26  to determine the actual location of tool  16 . For example, tool  16  may include a location detector in the form of an active sensor which senses its position relative to a fixed coordinate and transmits a wireless signal to electrical processor  26 .