Assembly system for monitoring proper fastening of an article of assembly at more than one location

Abstract

A more reliable and fool-proof method and apparatus for assembling an article of assembly (e.g. with predetermined screw torque requirements) in which the article of assembly has multiple fastening locations. The method comprises holding the article of assembly fixed while providing at least two different types of targets fixed relative to the article of assembly that correspond to the individual fastening locations. Fasteners are fastened into the article of assembly at the fastening locations. When fastening is occurring at one of the fastening locations, one of the targets is being sensed. Based on the target sensed, a target output is generated that differentiates between different types of targets thereby indicating fastening location of the fastening tool. The electronic target output is used for electronic control such as for stopping a conveyor to keep the article of assembly at an assembly station until the fastening operations have been completed.

What is claimed is: 
     
       1. An assembly system for assembling articles of assembly, each article of assembly having a plurality of fastening locations including at least first and second fastening locations in spaced apart relation, comprising:
 a fixture holding the article of assembly;   a plurality of targets including at least a first target fixed relative to the fixture, corresponding to the first fastening location, and a second target fixed relative to the fixture, the second target corresponding to the second fastening location, the second target having a different characteristic than the first target;   a fastening tool adapted to fasten fasteners into the article of assembly at the first and second fastening locations, the fastening tool having a first position relative to the fixture in which the fastening tool is in position to fasten a fastener at the first location, and a second position relative to the fixture in which the fastening tool is in position to fasten a fastener at the second location;   a target sensor fixed relative to the fastening tool along at least one axis, the target sensor sensing the first target when the fastening tool is in the first position, the target sensor sensing the second target when the fastening tool is in the second position, the target sensor providing a target output differentiating between the first and second targets and indicating when the fastening tool is in either of the first fastening location and the second fastening location; and   an electronic controller in communication with the target sensor utilizing said target output to check a quality characteristic of manual fastening operations facilitated by the fastening tool at the plurality of fastening locations, wherein the fastening tool moves independent of the electronic controller and is not controllably positioned thereby.   
     
     
       2. The assembly system of  claim 1  wherein the fixture is carried by a conveyor, the fastening tool being movable relative to the conveyor. 
     
     
       3. The assembly system of  claim 2  further comprising an assembly station along the conveyor, the fixture being conveyed on the conveyor to the assembly station where the fixture is intermittently stopped by a stop mechanism for fastening by the fastening tool, further comprising an electronic controller in communication with the target sensor, the electronic controller monitoring the location of the fastening tool to ensure proper fastening of fasteners at the fastening locations. 
     
     
       4. The assembly system of  claim 2  further comprising an assembly station along the conveyor, the conveyor transporting the fixtures through the assembly station substantially without stopping on a continuous basis. 
     
     
       5. The assembly system of  claim 4  comprising at least two types of the fixtures and at least two types of first and second targets for the at least two types of the fixtures, respectively, wherein the target sensor provides said target output that also differentiates between the at least two types of first and second targets, further comprising an electronic controller in communication with the target sensor, the electronic controller monitoring the location of the fastening tool and determining the fixture being serviced by the fastening tool to ensure proper fastening of fasteners at the fastening locations on articles of assembly held by each fixture. 
     
     
       6. The assembly system of  claim 2  wherein the sensor comprises a laser and laser sensing device, the fastening tool being movable in a plane spaced from the article of assembly held in the fixture to selectively position the fastening tool at the first and second fastening locations, the laser and laser so sensing device being movable with the fastening tool in said plane, the first and second targets comprising reflective material spaced at different distances perpendicular to said plane. 
     
     
       7. The assembly system of  claim 1  further comprising an electronic controller in electrical communication with the target sensor and the fastening tool, the electronic controller enabling the fastening tool when the target sensor is in sensory communication with one of the targets and disabling the fastening tool when target sensor is not in sensory communication with one of the targets. 
     
     
       8. The assembly system of  claim 1  wherein the target sensor comprises a machine vision camera and wherein the first and second targets have different visual characteristics, wherein electronic controller an is in communication with the machine vision camera differentiating between the different visual characteristic to determine the location of the fastening tool. 
     
     
       9. The assembly system of  claim 8  wherein the fasteners are spaced horizontally and vertically according to a predetermined spacing, the first and second targets being spaced horizontally and vertically according to the predetermined spacing, the fastening tool being movable along vertical and horizontal axes relative to the fixture. 
     
     
       10. The assembly system of  claim 8  wherein the characteristics of the first and second targets are selected from the group consisting of geometric shapes, colors and alphanumeric characters. 
     
     
       11. The assembly system of  claim 1  wherein the articles of assembly comprise an automotive seat comprised of at least two parts, the fasteners comprising threaded fasteners for fastening the at least two parts together. 
     
     
       12. The assembly system of  claim 1 , wherein the first and second targets are separate from and not part of the article of assembly. 
     
     
       13. An assembly system for assembling articles of assembly, each article of assembly having a plurality of fastening locations including at least first and second fastening locations in spaced apart relation, comprising:
 a fixture holding the article of assembly;   a plurality of targets including at least a first target fixed relative to the fixture, corresponding to the first fastening location, and a second target fixed relative to the fixture, the second target corresponding to the second fastening location, the second target having a different characteristic than the first target;   a fastening tool adapted to fasten fasteners into the article of assembly at the first and second fastening locations, the fastening tool having a first position relative to the fixture in which the fastening tool is in position to fasten a fastener at the first location, and a second position relative to the fixture in which the fastening tool is in position to fasten a fastener at the second location;   a target sensor fixed relative to the fastening tool along at least one axis, the target sensor sensing the first target when the fastening tool is in the first position, the target sensor sensing the second target when the fastening tool is in the second position, the target sensor providing a target output differentiating between the first and second targets and indicating when the fastening tool is in either of the first fastening location and the second fastening location;   wherein the fixture is carried by a conveyor, the fastening tool being movable relative to the conveyor, further comprising an assembly station along the conveyor, the fixture being conveyed on the conveyor to the assembly station where the fixture is intermittently stopped by a stop mechanism for fastening by the fastening tool, further comprising an electronic controller in communication with the target sensor, the electronic controller monitoring the location of the fastening tool to ensure proper fastening of fasteners at the fastening locations; and   wherein the electronic controller controls the stop mechanism, the electronic controller maintaining the fixture at the assembly station and not releasing the fixture for movement on the conveyor out of the assembly station until the fastening tool has properly fastened fasteners into the article of assembly at the fastening locations.   
     
     
       14. An assembly system for assembling articles of assembly, each article of assembly having a plurality of fastening locations including at least first and second fastening locations in spaced apart relation, comprising:
 a fixture holding the article of assembly;   a plurality of targets including at least a first target fixed relative to the fixture, corresponding to the first fastening location, and a second target fixed relative to the fixture, the second target corresponding to the second fastening location, the second target having a different characteristic than the first target;   a fastening tool adapted to fasten fasteners into the article of assembly at the first and second fastening locations, the fastening tool having a first position relative to the fixture in which the fastening tool is in position to fasten a fastener at the first location, and a second position relative to the fixture in which the fastening tool is in position to fasten a fastener at the second location;   a target sensor fixed relative to the fastening tool along at least one axis, the target sensor sensing the first target when the fastening tool is in the first position, the target sensor sensing the second target when the fastening tool is in the second position, the target sensor providing a target output differentiating between the first and second targets and indicating when the fastening tool is in either of the first fastening location and the second fastening location;   an electronic controller in communication with the target sensor, the electronic controller monitoring the location of the fastening tool to ensure proper fastening of fasteners at the fastening locations;   wherein the fixture is carried by a conveyor, the fastening tool being movable relative to the conveyor, further comprising an assembly station along the conveyor, the fixture being conveyed on the conveyor to the assembly station where the fixture is intermittently stopped by a stop mechanism for fastening by the fastening tool; and   wherein the fasteners are threaded fasteners, the fastening tool having a torque monitor, the torque monitor providing an indication to the electronic controller of torque applied to the fasteners, the electronic controller having predetermined torque values for at least one of the fastening locations, the electronic controller determining the location of the fastening tool that corresponds to the indication of torque and providing an output indicating whether the predetermined torque values for at least one of the fastening locations have been reached.   
     
     
       15. The assembly system of  claim 14  wherein the electronic controller releases the stop mechanism when the predetermined torque values have been reached thereby allowing the fixture to be conveyed on the conveyor. 
     
     
       16. An assembly system for assembling articles of assembly, each article of assembly having a plurality of fastening locations including at least first and second fastening locations in spaced apart relation, comprising:
 a fixture holding the article of assembly;   a plurality of targets including at least a first target fixed relative to the fixture, corresponding to the first fastening location, and a second target fixed relative to the fixture, the second target corresponding to the second fastening location, the second target having a different characteristic than the first target;   a fastening tool adapted to fasten fasteners into the article of assembly at the first and second fastening locations, the fastening tool having a first position relative to the fixture in which the fastening tool is in position to fasten a fastener at the first location, and a second position relative to the fixture in which the fastening tool is in position to fasten a fastener at the second location;   a target sensor fixed relative to the fastening tool along at least one axis, the target sensor sensing the first target when the fastening tool is in the first position, the target sensor sensing the second target when the fastening tool is in the second position, the target sensor providing a target output differentiating between the first and second targets and indicating when the fastening tool is in either of the first fastening location and the second fastening location;   an electronic controller in communication with the target sensor, the electronic controller monitoring the location of the fastening tool to ensure proper fastening of fasteners at the fastening locations; and   wherein the fastening tool comprises a fastening monitor indicating a fastening operation, wherein the electronic controller has a predetermined sequence program requiring a predetermined sequence of fastening among the fastening locations, the electronic controller-monitoring the sequence of fastening based upon the target output, the electronic controller providing an output indicating whether the predetermined sequence has been achieved.   
     
     
       17. The assembly system of  claim 16 , wherein the fixture is carried by a conveyor, the fastening tool being movable relative to the conveyor, further comprising an assembly station along the conveyor, the fixture being conveyed on the conveyor to the assembly station where the fixture is intermittently stopped by a stop mechanism for fastening by the fastening tool, wherein the electronic controller releases the stop mechanism when the predetermined sequence has been achieved thereby allowing the fixture to be conveyed on the conveyor. 
     
     
       18. An assembly system for assembling articles of assembly, each article of assembly having a plurality of fastening locations including at least first and second fastening locations in spaced apart relation, comprising:
 a fixture holding the article of assembly;   a plurality of targets including at least a first target fixed relative to the fixture, corresponding to the first fastening location, and a second target fixed relative to the fixture, the second target corresponding to the second fastening location, the second target having a different characteristic than the first target;   a fastening tool adapted to fasten fasteners into the article of assembly at the first and second fastening locations, the fastening tool having a first position relative to the fixture in which the fastening tool is in position to fasten a fastener at the first location, and a second position relative to the fixture in which the fastening tool is in position to fasten a fastener at the second location;   a target sensor fixed relative to the fastening tool along at least one axis, the target sensor sensing the first target when the fastening tool is in the first position, the target sensor sensing the second target when the fastening tool is in the second position, the target sensor providing a target output differentiating between the first and second targets and indicating when the fastening tool is in either of the first fastening location and the second fastening location;   where in the fixture is carried by a conveyor, the fastening tool being movable relative to the conveyor, and further comprising an assembly station along the conveyor, the conveyor transporting the fixtures through the assembly station substantially without stopping on a continuous basis; and   wherein the assembly station has an input location receiving fixtures from an upstream station and an output location delivering fixtures to a downstream station, the fastening tool being movable horizontally along the conveyor between the input location and the output location, further comprising a fixture sensor in communication with fixtures passing through the assembly station, the fixture sensor having a fixture position output indicating when fixtures have exited the assembly station through the output location, an electronic controller in communication with the fixture sensor, the electronic controller outputting an alarm signal when one of the fixtures has exited the assembly station without proper fastening of fasteners at the fastening locations.   
     
     
       19. The assembly system of  claim 18 , wherein the fasteners are threaded fasteners, the fastening tool having a torque monitor, the torque monitor providing an indication to the electronic controller of torque applied to the fasteners, the electronic controller having predetermined torque values for at least one of the fastening locations, the electronic controller determining the location of the fastening tool that corresponds to the indication of torque and providing an output indicating whether the predetermined torque values for at least one of the fastening locations have been reached. 
     
     
       20. The assembly system of  claim 19  wherein the fastening tool comprises a fastening monitor indicating a fastening operation, wherein the electronic controller has a predetermined sequence program requiring a predetermined sequence of fastening among the fastening locations, the electronic controller controlling the sequence of fastening based upon the target output, the electronic controller providing an output indicating whether the predetermined sequence has been achieved. 
     
     
       21. An assembly system for assembling articles of assembly, each article of assembly having a plurality of fastening locations including at least first and second fastening locations in spaced apart relation, comprising:
 a fixture holding the article of assembly;   a plurality of targets including at least a first target fixed relative to the fixture, corresponding to the first fastening location, and a second target fixed relative to the fixture, the second target corresponding to the second fastening location, the second target having a different characteristic than the first target;   a fastening tool adapted to fasten fasteners into the article of assembly at the first and second fastening locations, the fastening tool having a first position relative to the fixture in which the fastening tool is in position to fasten a fastener at the first location, and a second position relative to the fixture in which the fastening tool is in position to fasten a fastener at the second location;   a target sensor fixed relative to the fastening tool along at least one axis, the target sensor sensing the first target when the fastening tool is in the first position, the target sensor sensing the second target when the fastening tool is in the second position, the target sensor providing a target output differentiating between the first and second targets and indicating when the fastening tool is in either of the first fastening location and the second fastening location; and   wherein the fasteners are threaded fasteners, the fastening tool having a torque monitor, the torque monitor providing an indication to an electronic controller of torque applied to the fasteners, the electronic controller having predetermined torque values for at least one of the fastening locations, the electronic controller determining the location of the fastening tool that corresponds to the indication of torque and providing an output indicating whether the predetermined torque values for at least one of the fastening locations have been reached.   
     
     
       22. An assembly system for assembling articles of assembly, each article of assembly having a plurality of fastening locations including at least first and second fastening locations in spaced apart relation, comprising:
 a fixture holding the article of assembly;   a plurality of targets including at least a first target fixed relative to the fixture, corresponding to the first fastening location, and a second target fixed relative to the fixture, the second target corresponding to the second fastening location, the second target having a different characteristics than the first target;   a fastening tool adapted to fasten fasteners into the article of assembly at the first and second fastening locations, the fastening tool having a first position relative to the fixture in which the fastening tool is in position to fasten a fastener at the first location, and a second position relative to the fixture in which the fastening tool is in position to fasten a fastener at the second location;   a target sensor fixed relative to the fastening tool along at least one axis, the target sensor sensing the first target when the fastening tool is in the first position, the target sensor sensing the second target when the fastening tool is in the second position, the target sensor providing a target output differentiating between the first and second targets and indicating when the fastening tool is in either of the first fastening location and the second fastening location; and   wherein the fastening tool plunges along a fastening axis perpendicular to said plane, the laser and laser sensing device remaining stationary during plunging of the fastening tool.   
     
     
       23. The assembly system of  claim 22  wherein the fixture is carried by a conveyor, the fastening tool being movable horizontally relative to the conveyor, the laser and laser sensing device being restricted to horizontal movement along a horizontal axis along with the fastening tool, further comprising a reflective panel extending in the horizontal axis in reflective communication with the laser and laser sensing device with a reflective surface aligned at an oblique angle relative to said plane. 
     
     
       24. An assembly system for assembling articles of assembly, each article of assembly having a plurality of fastening locations including at least first and second fastening locations in spaced apart relation, comprising:
 a fixture holding the article of assembly;   a fastening tool adapted to fasten fasteners into the article of assembly at the first and second fastening locations, the fastening tool having a first position relative to the fixture in which the fastening tool is in position to fasten a fastener at the first location, and a second position relative to the fixture in which the fastening tool is in position to fasten a fastener at the second location;   at least one sensor providing a sensor output indicating when the fastening tool is the first and second fastening locations;   an electronic controller in communication with the at least one sensor, the electronic controller monitoring the location of the fastening tool to ensure proper fastening of fasteners at the fastening locations; and   wherein the fastening tool comprises a fastening monitor indicating a fastening operation, wherein the electronic controller has a predetermined sequence program requiring a predetermined sequence of fastening among the fastening locations, the electronic controller monitoring the sequence of fastening based upon the sensor output, the electronic controller providing an output indicating whether the predetermined sequence has been achieved.   
     
     
       25. The assembly system of  claim 1  wherein the fixture is carried by a conveyor, the fastening tool being movable relative to the conveyor, further comprising an assembly station along the conveyor, the fixture being conveyed on the conveyor to the assembly station where the fixture is intermittently stopped by a stop mechanism for fastening by the fastening tool, wherein the electronic controller releases the stop mechanism when the predetermined sequence has been achieved thereby allowing the fixture to be conveyed on the conveyor. 
     
     
       26. An assembly system for assembling components of an article of assembly, comprising:
 first and second physically separate components that, when assembled together, form at least a portion of the article of assembly, wherein
 (a) a single set of discrete portions of the first and second components, when placed together, form at least a single process site consisting of a plurality of fastening locations within the single process site including at least first and second fastening locations, 
 (b) each of the first and second fastening locations consists of a single opening for receiving a single fastener that, when fastened in the single opening, partially assembles the first and second components together, and 
 (c) wherein the article of assembly is structurally designed so that the first and second fastening locations are positioned within the single process site is spaced apart relation to each other such that a fastener must be inserted in the first fastening location before a fastener is inserted in the second fastening location to reduce the risk of structural failure of the assembled combination of the first and second components that would arise if a fastener were inserted in the second fastening location before a fastener were inserted in the first fastening location; 
   a fixture holding the first and second components of the article of assembly in a predetermined position in which the first and second components are placed together to form the single process site;   a fastening tool adapted to fasten fasteners into the single process site formed by the first and second components of the article of assembly, the fastening tool having a first position relative to the fixture in which the fastening tool is in position to fasten a fastener at the first fastening location, and a second position relative to the fixture in which the fastening tool is in position to fasten a fastener at the second fastening location;   at least one sensor providing a sensor output indicating when the fastening tool is at the first and second fastening locations;   an electronic controller in communication with the at least one sensor, the electronic controller monitoring the location of the fastening tool to ensure proper fastening of fasteners at the fastening locations and having stored in a memory thereof before an operator has commenced manual fastening using the fastening tool
 (a) data representative of the location of the first fastening location within the single process site together with first order data indicating that a fastener must be inserted in the first fastening location at a point in time before a fastener is inserted in the second fastening location, and 
 (b) data representative of the location of the second fastening location within the single process site together with second order data indicating that a fastener must be inserted in the second fastening location at a point in time after a fastener has been inserted in the first fastening location, 
 wherein the location data and the first and second order data for the first and second fastening locations form a predetermined fastening sequence for the single process site that must be followed in order for the first and second components to be assembled together in a manner that reduces the risk of structural failure of the assembled combination that would arise if a fastener were inserted in the second fastening location before a fastener were inserted in the first fastening location; 
   wherein the fastening tool comprises a fastening monitor indicating a fastening operation,   wherein the electronic controller has a predetermined sequence program that, when executed, requires the operator's use of the fastening tool to conform to the predetermined sequence of fastening among the first and second fastening locations by the electronic controller
 (a) monitoring the sequence of fastening based upon the sensor output, 
 (b) electronically comparing the sensed position of the fastening tool with the data representative of the location of the first and second fastening locations within the single process site to determine if the fastening tool is located in operative relation to one of the first and second fastening locations and then 
 (c) using the order data associated with the one of the first and second fastening locations to
 (i) enable the fastening tool, when it is positioned in operative relation to the first fastening location, to insert a fastener in the first fastening location only if the operator has not inserted a fastener in the second fastening location, and 
 (ii) enable the fastening tool, when it is positioned in operative relation to the second fastening location, only if the operator already has inserted a fastener in the first fastening location, 
 
 wherein requiring that the operator's use of the fastening tool conform to the predetermined sequence of fastening in the single process site reduces the risk of structural failure of the assembled combination that would arise if a fastener were inserted in the second fastening location before a fastener were inserted in the first fastening location; 
   the electronic controller providing a sequence output indicating whether the predetermined fastening sequence has been achieved each time that the operator attempts to fasten a fastener in one of the first and second fastening locations;   wherein the electronic controller also has stored in its memory first and second predetermined torque values that represent torque values that the operator is supposed to apply to fasteners inserted in the first and second fastening locations only when the operator's use of the fastening tool conforms to the predetermined sequence of fastening; and   wherein the execution of the predetermined sequence program by the electronic controller requires the predetermined sequence of fastening to be followed in the single process site and also
 (a) uses the fastening monitor to measure torque applied to a fastener as it is being inserted in the first fastening location and then compares the measured torque to the first predetermined torque value, 
 (b) requires that the torque applied to the fastener located in the first fastening location equal the first predetermined torque value before the operator is allowed to insert a fastener in the second fastening location, which reduces the risk of structural failure of the assembled combination that would result if the operator were allowed to insert a fastener in the second fastening location when the torque applied to the first fastener does not equal the first predetermined torque value; 
 (c) uses the fastening monitor to measure torque applied to a fastener as it is being inserted in the second fastening location and then compares the measured torque to the second predetermined torque value, and 
 (d) requires that the torque applied to the fastener located in the second fastening location equal the second predetermined torque value after the first fastener has been inserted in the first fastening location at the first predetermined torque value, which reduces the risk of structural failure of the assembled combination that would result if the operator were allowed to complete assembly of the first and second components when the torque applied to the fastener inserted in the second fastening location did not equal the second predetermined torque value. 
   
     
     
       27. The assembly system of claim 26, wherein the fastening tool forms a part of an assembly station, the electronic controller requiring the first and second components to remain in the assembly station until after it is verified that (a) the operator's use of the fastening tool conformed to the predetermined sequence of fastening for the single process site, and (b) torque values equal to the first and second predetermined torque values were applied to fasteners located in the first and second fastening locations when the operator's use of the fastening tool conformed to the predetermined sequence of fastening for the single process site. 
     
     
       28. The assembly system of claim 27, wherein the electronic controller produces an alarm simultaneously with when an attempt is made to remove the first and second components from the assembly station before it is verified that (a) the operator's use of the fastening tool conforms to the predetermined sequence of fastening for the single process site, and (b) torque values equal to the first and second predetermined torque values were applied to fasteners located in the first and second fastening locations when the operator's use of the fastening tool conformed to the predetermined sequence of fastening for the single process site. 
     
     
       29. The assembly system of claim 28 wherein the assembly system further comprises a stop mechanism that requires the first and second components to remain in the assembly station. 
     
     
       30. The assembly system of claim 29, wherein the stop mechanism prevents removal of the first and second components from the assembly station. 
     
     
       31. The assembly system of claim 30, wherein the fixture is carried by a conveyor into and out of the assembly station the movement of which is stopped by the stop mechanism. 
     
     
       32. The assembly system of claim 31, wherein the conveyor comprises an intermittent conveyor. 
     
     
       33. The assembly system of claim 31, wherein the conveyor comprises a continuous conveyor. 
     
     
       34. The assembly system of claim 26, wherein the first and second components comprise components of a vehicle seat. 
     
     
       35. The assembly system of claim 26, wherein the article of assembly comprises a vehicle seat. 
     
     
       36. The assembly system of claim 26, wherein the assembly station forms a part of a conveyor line. 
     
     
       37. The assembly system of claim 36, wherein the conveyor comprises an intermittent conveyor. 
     
     
       38. The assembly system of claim 36, wherein the conveyor comprises a continuous conveyor. 
     
     
       39. The assembly system of claim 26, wherein the electronic controller, when executing the predetermined sequence program, disables the fastening tool when it is not in either the first or second positions. 
     
     
       40. The assembly system of claim 26, wherein the at least one sensor comprises first and second targets arranged in relation to the first and second fastening locations, the first and second targets being sensed when said fastening is occurring at the first and second fastening locations, respectively, and wherein the electronic controller is adapted to generate an electronic target output based upon said sensing that differentiates between the first and second targets thereby indicating when the fastening tool is in either of the first and second fastening locations. 
     
     
       41. The assembly system of claim 26, wherein each fastener consists of a threaded fastener. 
     
     
       42. The assembly system of claim 26, wherein the article of assembly includes an unassembled base frame. 
     
     
       43. The assembly system of claim 42, wherein the unassembled based frame is clamped into the fixture. 
     
     
       44. The assembly system of claim 43, wherein the fixture and unasssembled based frame are provided by means of a continuous moving line conveyor. 
     
     
       45. The assembly system of claim 43, wherein the fixture and unassembled base frame are provided by means of an intermittent conveyor line. 
     
     
       46. The assembly system of claim 26, wherein the single process site includes a third fastening location that consists of a single opening for receiving a single fastener. 
     
     
       47. The assembly system of claim 46, wherein the predetermined sequence of fastening is of all of the first, second, and third fastening locations such that a fastener must be inserted in the first fastening location before a fastener is inserted in the second or third fastening locations. 
     
     
       48. The assembly system of claim 26, wherein the electronic controller, when executing the predetermined sequence program, requires that the operator's use of the fastening tool conforms to the predetermined sequence of fastening of the first and second fastening locations and disables the fastening tool from performing a fastening operation when it is located at the first fastening location if the operator already has applied a first fastener in the first fastening location with a torque that equals the first predetermined torque. 
     
     
       49. The assembly system of claim 28, wherein the alarm is sounded as a result of the attempt to remove the first and second components from the assembly station.