Abstract:
A method of dispensing a strip product using a strip fabrication assembly, by entering arm positions for guide arms of the assembly into a guide arm controller device, moving the corresponding guide arms of the strip fabrication assembly to the respective arm positions using the guide arm controller device, and feeding different strip materials through the assembly using the guide arms, after moving them to the entered arm positions. The guide arms are coupled to threaded rods, and are moved by actuating servo motors which are coupled to the threaded rods. The guide arm controller device may include a programmable logic controller, which has been programmed to control the servo motors in response to entry of guide arm positions. The controller may further provide for the listing and searching of different sets of previously entered arm positions on a display device of the guide arm controller device, and selection of one of the previously entered sets of arm positions as a current set of arm positions, using an input interface. Multiple sets of arm positions corresponding to different strip product orders can be stored for later use.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a divisional application of U.S. patent application Ser. No. 10/121,304, filed Apr. 12, 2002 now U.S. Pat. No. 6,705,500, which is a continuation-in-part of U.S. patent application Ser. No. 09/912,914, filed Jul. 25, 2001, now abandoned, which in turn claims the benefit of U.S. provisional application Ser. Nos. 60/285,442 filed Apr. 19, 2001 now abandoned, and 60/283,490 filed Apr. 12, 2001, all of which are incorporated herein. 
    
    
     BACKGROUND 
     The present invention generally relates to manufacturing processes and process control technology, and more particularly to a method and system for positioning guide members in a mechanical assembly that is used to dispense various strip materials, such as yarns, strings, tapes, webs, and ribbons, where the guide members are positioned by electromechanical servos (servomechanisms) that are managed by a microcontroller having a user interface. 
     There are many conventional machines and mechanisms for dispensing strip-or string-like materials such as tapes, webs, ribbons and yarns. These machines typically include a series of rollers and supports or plates that are used to bring different layers of the end product together along an assembly path, or to apply other materials, such as adhesives, to one or more surfaces of the substrate strip material. 
     In this type of machinery, it is usually important to have a relatively precise positioning of the strip materials that are to be integrated, and to properly align any applicators that coat the substrates with other materials. Guide arms or guide members of varying designs are often employed for this purpose. One laminating machine that changes the position of tape guide arms to vary the position of tape in relationship to the web is shown in U.S. Pat. No. 4,452,837 (Clausen et al.) wherein a plurality of ribbons are fed through a guide member onto a sheet-like web. The guide is a reciprocating bar having eyelets for receiving a plurality of ribbons, and the bar places the ribbons onto the web in a serpentine pattern to provide continuous reinforcement of the substrate in both the machine direction and the transverse direction. The machine uses a ribbon that is pre-coated with a substrate. 
     U.S. Pat. No. 5,759,339 (Hartman) discloses a machine for adjusting the position of tape dispensing arms between the webs of a laminating machine using a reciprocating belt to change the position of the dispensing arms and a transducer to identify the position of each dispensing arm. 
     In PCT Application No. WO 88/04272, (Persson) an arrangement is disclosed for applying longitudinally extending tapes to a moving web having a plurality of tape holders and a plurality of tape applicators for guiding the tape into contact with web. The tape applicators are carried by and are capable of being positioned along mutually separate beams of a beam structure that extends transversely to the direction of web travel. The applicators can be adjusted positionally in relation to an applicator-setting beam, which extends transversely to the direction of web movement, and can be locked to this beam in selected positions therealong. The applicator-setting beam is, in turn, carried for longitudinal movement by a stationary carrier beam, which extends parallel with the applicator-setting beam. The applicator-setting beam can also have graduations provided along the length thereof to show the position of the applicators. The applicator-setting beam is moved in relation to the fixed carrier beam by the tape applicators carried thereby, the carriages of the tape applicators being provided to this end with rotatably journalled wheels that support the applicator-setting beam. Longitudinal movement of the applicator-setting beam is effected by means of a threaded spindle that engages a screw-threaded bore in a nut rigidly connected to the applicator-setting beam. The spindle is journalled, but is locked against axial movement in a stationary frame part. The single treaded spindle moves the applicator-setting beam and the tape applicators. 
     In many of these prior art machines, the position of one or more parts is sensed electronically, and (when the machinery is off-line) a positioning or guide member is moved and adjusted by actuating an electromechanical motor that is coupled to the guide member, i.e., a servo motor or servomechanism. Servomechanisms are used in a wide variety of applications. By using electronic sensors and servos, process controls for these fabrication systems may be automated, at least in part The sensors and servos may be managed by a microcontroller having a user interface. 
     Allen-Bradley Co. (Rockwell Automation) sells a line of microcontrollers and related products that may be used for industrial automation. To microcontrollers include the family of small programmable controllers available under the trade designation SLC500. These controllers are one of a type of integrated circuit known generally as a programmable logic controller (PLC). PLCs use a plurality of logic elements and associated interconnect resources that are easily programmed by the end-user to implement user-defined logic operations. They can be programmed using a personal computer (PC) or similar workstation, with appropriate software and a device programmer. Therefore, unlike fully-customized (application-specific) integrated circuits that require a protracted layout procedure and an expensive fabrication process to implement a user&#39;s logic operation, a PLC may be utilized to implement the logic operation in a relatively quick and inexpensive manner. Once programmed, these controllers can be operated in conjunction with a user interface (display and keyboard) to automate manufacturing processes in a customized manner. 
     Unfortunately, these automated process controls have proved inadequate for the manufacture of strip materials. Adjustments of positioning in the machinery, such as tape placement, often require stopping the machinery, i.e., interruption of the actual strip fabrication. There is also a great deal of manual involvement required, such as moving final guides for termination of the strip. It would, therefore, be desirable to devise an improved method of automating the positioning of guide arms for mechanical assemblies used to dispense strip materials. It would be further advantageous if the method could be implemented. 
     SUMMARY 
     The foregoing objects are achieved in a method of dispensing a strip product, generally comprising the steps of entering a plurality of arm positions for corresponding guide arms of a strip fabrication assembly into a guide arm controller device (wherein the guide arms align a plurality of moving strip materials), moving the corresponding guide arms of the strip fabrication assembly to the respective arm positions using the guide arm controller device, and feeding a plurality of strip materials through the strip fabrication assembly using the guide arms, after said moving step, to form an integrated strip product The guide arms may be coupled to a respective one of a plurality of threaded rods, such that the moving step includes the actuation of a plurality of motors, such as servo motors, which are respectively coupled to the threaded rods. The guide arm controller device may include a programmable logic controller, which has been programmed to control the servo motors in response to entry of guide arm positions. The controller may further provide for the listing of a plurality of sets of previously entered arm positions on a display device of the guide arm controller device, and selection of one of the previously entered sets of arm positions as a current set of arm positions, using an input interface of the guide arm controller device. The controller may also search for an order number associated with one of a plurality of sets of previously entered arm positions, and allow the user to select one of the previously entered sets of arm positions as a current set of arm positions. Multiple sets of arm positions corresponding to different strip product orders can be stored for later use. 
     In one embodiment, the plurality of arm positions is a first plurality of arm positions, and the integrated strip product is a first integrated strip product, and the method further includes the steps of entering a second plurality of arm positions into the guide arm controller device, moving the corresponding guide arms of the strip fabrication assembly to the respective ones of the second plurality of arm positions using the guide arm controller device, and feeding a plurality of strip materials through the strip fabrication assembly using the guide arms, after the moving step, to form a second integrated strip product. 
     In another embodiment, the guide arm controller device includes a programmable logic controller, and further including the step of programming the controller to allow for the entry and retention of multiple sets of arm positions corresponding to different strip product orders. 
     In another aspect, the invention features an apparatus for controlling a guide arm system of a strip fabrication assembly, the apparatus including a display device, a user input device, and a microcontroller connected to the display device and the user input device, the microcontroller having means for receiving a plurality of arm positions for corresponding guide arms which are entered into the user input device, and means for transmitting control signals to a plurality of servo motors which are coupled respectively to the guide arms, to thereby move the guide arms based on the plurality of arm positions. In some embodiments, the microcontroller is a programmable logic controller. In other embodiments, the display device and the user input device are a single device. 
     In one embodiment, the microcontroller further includes means for listing a plurality of sets of previously entered arm positions on the display device, and means for selecting one of the previously entered sets of arm positions as a current set of arm positions in response to the user input device. In other embodiments, the microcontroller further includes means for searching for an order number associated with one of a plurality of sets of previously entered arm positions, and means for selecting one of the previously entered sets of arm positions as a current set of arm positions, using the user input device. In some embodiments, the microcontroller further includes means for allowing the entry and retention of multiple sets of arm positions corresponding to different strip product orders. 
     In other aspects, the invention features a strip fabrication assembly including a plurality of feed rollers, positioned to integrate strip materials into a strip product, a plurality of guide members located proximate the rollers, the guide members aligning a plurality of the strip materials, and means for controlling the positions of the guide members. In one embodiment, the guide members are tape dispensing arms. In some embodiments, the controlling means includes a programmable logic controller. In other embodiments, the controlling means includes a plurality of motors coupled respectively to the guide members. 
     In another embodiment, the controlling means receives a plurality of arm positions for corresponding guide arms, and transmits control signals to the motors to thereby move the guide arms based on the plurality of arm positions. In some embodiments, the controlling means lists a plurality of sets of previously entered arm positions on a display device, and selects one of the previously entered sets of arm positions as a current set of arm positions in response to a user input device. In other embodiments, the controlling means searches for an order number associated with one of a plurality of sets of previously entered arm positions, and selects one of the previously entered sets of arm positions as a current set of arm positions in response to a user input device. In one embodiment, the controlling means allows the entry and retention of multiple sets of arm positions corresponding to different strip product orders. 
     In another aspect, the invention features a computer program product including a computer-readable storage medium, and program instructions stored on the storage medium for controlling a guide arm system of a strip fabrication assembly, including program instructions for receiving a plurality of arm positions for corresponding guide arms, and program instructions for transmitting control signals to a plurality of motors which are coupled respectively to the guide arms, to thereby move the guide arms based on the plurality of arm positions. In some embodiments, the program instructions further provide a listing of a plurality of sets of previously entered arm positions, and allow a user to select one of the previously entered sets of arm positions as a current set of arm positions. 
     In one embodiment, the program instructions further search for an order number associated with one of a plurality of sets of previously entered arm positions, and allow a user to select one of the previously entered sets of arm positions as a current set of arm positions. In some embodiments, the program instructions further allow the entry and retention of multiple sets of arm positions corresponding to different strip product orders. 
     In other aspects, the invention features a method of positioning multiple operating units relative to a moving web, the method including: entering a plurality of positions into a controller device, the positions corresponding to a plurality of operating units, moving the operating units to the positions, sensing the position of an edge of a moving web, and, when the position of the edge of the web changes, changing the position of the operating units. In one embodiment, a web tracking unit senses the position of the edge of the moving web, the web tracking unit including a pair of spaced optical sensors for directing light toward a web and receiving reflected light from the web, the sensors being capable of signaling a motor to move the sensors until a desired signal is received from the sensors. In other embodiments, the desired signal from the pair of sensors is a “1” and a “0”, the “1” being a reflection from a web, the “0” being no reflection, wherein the motor moves the sensors when the signal from the sensors is the same. In some embodiments, the operating units comprise guide arms. 
     In another aspect, the invention features an apparatus for controlling a number of operating units, the apparatus including: a user interface, a control system connected to the user interface, the control system including a receiver for receiving a plurality of positions corresponding to a plurality of operating units, the plurality of positions being entered into the control system through the user interface, and a transmitter for transmitting control signals to a plurality of servo motors, which are coupled to the operating units, to thereby move the operating units based on the plurality of positions, and a web tracking unit connected to the control system, the web tracking unit being capable of sensing the position of an edge of a moving web. In one embodiment, the web tracking unit senses a change in the position of the edge of a moving web, the web tracking unit sends a signal to the control system to change the position of the operating units relative to the change in position of the edge of the moving web. In some embodiments, the operating units include guide arms. 
     The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention may be better understood, and its numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings. 
         FIG. 1  is a block diagram of an automated system for positioning guide members. 
         FIG. 2  is a simplified elevational view of an assembly for fabricating strip materials, particularly corrugated sheeting, in accordance with one implementation of the present invention; 
         FIG. 3  is a perspective view with a cutout of the corrugated sheeting fabricated by the assembly of  FIG. 2 ; 
         FIG. 4  is a perspective view of a part of the apparatus frame, with the top plate removed to show the interior parts in greater detail; 
         FIG. 5  is a detailed cross-sectional view of the apparatus showing the beam on the support beam of the web handling machine and of the apparatus with a tape dispensing guide arm; 
         FIG. 6  is a detailed longitudinal sectional view of the tape dispensing apparatus; and 
         FIG. 7  is a further longitudinal sectional view showing the drive connection of the apparatus; 
         FIG. 8  is a plan view of one embodiment of a user interface screen used in conjunction with the strip fabrication assembly of  FIG. 2 , for entering or recalling customer orders (e.g., guide arm specifications); 
         FIG. 9  is a plan view of one embodiment of another user interface screen used in conjunction with the strip fabrication assembly of  FIG. 2 , for carrying out orders that have been previously entered via the order listing screen of  FIG. 8 ; 
         FIG. 10  is a flow diagram illustrating the logical flow for carrying out an illustrative embodiment of the present invention. 
         FIG. 11  is a side view of the web traveling through a machine and past a web tracking system and toward the tape dispensing unit, 
         FIG. 12A  is a detail view of the sensor and support structure of the web tracking system of  FIG. 11 , and  FIG. 12B  is an enlarged view of the sensor; 
         FIGS. 13A–C  are diagrammatic views of the sensors tracking the edge of a web; and 
         FIG. 14  is a flow diagram illustrating the logical flow for carrying out a second illustrative embodiment of the invention. 
     
    
    
     The use of the same reference symbols in different drawings indicates similar or identical items. 
     DETAILED DESCRIPTION 
     The present invention is directed to a method and system for positioning guide members in a mechanical assembly that is used to dispense a lineal or strip material including, e.g., tape, ribbon, web, string, yarn and combinations thereof. The system includes a control system  2 , a user interface  4 , an operating unit positioning apparatus  6 , and, optionally, a web tracking unit  8 , an example of which is illustrated in  FIG. 1 . 
     The invention may be understood, for example, with reference to an illustrative implementation in the manufacture of corrugated sheeting. With reference now to the figures, and in particular with reference to  FIG. 2 , there is depicted a simplified elevational view of one embodiment  10  of a tape fabrication assembly constructed in accordance with the present invention Tape fabrication assembly  10  includes a pair of rollers  12 ,  14 , a series of hot plates  16 . An inside liner or substrate layer  18  moves along roller  12 , to the right in  FIG. 2 , and roller  12  applies a reinforcement tape  20  to one side of the inside liner  18  as it moves along. Another reinforcement tape  22  moves along roller  14 , also to the right in  FIG. 2 , and roller  14  applies an outer liner or substrate layer  24  against reinforcement tape  22  as it moves along. These two rollers also capture a corrugated medium  26  between the combined inside layer/tape  18 / 20  and combined outside layer/tape  24 / 22 . This multi-layer sheeting is then drawn across the hot plates  16  which activate, e.g., a hot-melt adhesive imbedded in the corrugated medium. Examples of hot melt adhesives include an ethylene-vinyl acetate copolymer (EVA-based) hot melt adhesive, EMA-based hot melt adhesive (ethylene methylacrylate), EnBA-based hot melt adhesive (ethylene n-butyl acrylate), hot melt adhesives based on polyamide, polyethylene and polypropylene homopolymers, copolymers and interpolymers, rubbery block copolymer hot melt adhesives, and remoistentable hot-melt adhesive including, e.g., polyamide-based and copolyester-based adhesives. 
     The result of the process is a strip of corrugated sheeting  28 , as illustrated in  FIG. 3 . This sheeting can be used for many applications, particularly to form boxes used for packaging. Additional details of the corrugating machine may be found in U.S. Pat. No. 5,759,339 and incorporated herein. 
     The tape fabrication assembly  10  utilizes several tape dispensing guide arms to apply the tapes to the webs. These tape dispensing guide arms are described in detail in U.S. provisional patent application Ser. No. 60/283,490 and incorporated herein. 
       FIG. 4  illustrates an apparatus  108  (with the top cover plate removed) for remotely positioning spaced operating units (e.g., guide arms). The apparatus  108  includes a main beam  110 , which supports six of the tape dispensing guide arms  111  (any number of guide arms could be used). The main beam  110  of the apparatus  108  is an extruded part, which can be metal or a composite, preferably made of aluminum. Extending parallel or substantially parallel to the main beam  110  is a bearing rail  112  to support the guide arms  111 , as will be further described. There is an end plate  114 , and a bearing plate  115  that supports the ends of a plurality of threaded lead rods  116  (which could be threaded lead screws), and at the other end of the main beam  110  is a bearing mount plate  118  and a motor mount plate  119 . 
     Referring to  FIGS. 4–7 , secured to the top plate  121  is the bearing rail  112 . The main beam  110  supports track roller brackets  124 , which support the apparatus  108  on a track  125 , which is supported by the frame of the web handling machine. The guide arm  111  includes an exterior final guide plate  128  connected to a bearing mount plate  129  by a mounting plate structure  130 . A bearing mounting assembly  131 , supported by the bearing mount plate  129 , supports a given guide arm  111  from the bearing rail  112 . Supported by the bearing mount plate  129 , opposite the bearing mounting assembly  131 , is the support plate  134  through which extend the threaded rods  116 . The support plate  134  includes a series of holes having support bushings  136 . The multiple threaded rods  116  pass through the holes and are supported by the bushings  136 . In one of the holes in the support plate  134  is a threaded nut  138  mounted on the support plate  134  by a mounting flange  139  such that rotation of the threaded rod  116  engaging the threaded nut  138  will move the threaded rod support plate  134 . This movement moves the support plate  134  along the rail  112  and the guide arm  111  along the main beam  110 . It is this movement that controls the position of a given tape dispensing guide arm. 
     The guide arm  111  includes the series of rollers for directing the tape  140 , including the entry pulley assembly  142  and an exit pulley assembly  143 , the latter including a spacer plate  144 , and pulleys  145  and  146  directing the tape  140  toward the web path. 
     The threaded rods  116  have ACME threads and are rotatable in opposite directions to move the tape dispensing units to the desired positions. The ends of the rods  116  terminate in self-aligning bearing blocks  148  and bearings  149 . The plate  115  supports the thrust bearing  150 . The rods  116  have a castellated nut  151 , a washer  152 , which is preferably a rubber washer, and a washer  153  on the reduced end of the rods  116 , as shown, secured by a cotter pin  154 . The threaded rods  116  are journalled in the plate  118  by a single ball bearing  158  mounted in a bearing block  159 , which also supports a double row ball bearing assembly  160 . Connected at the drive end of the rods  116  is a shaft end stop  161  and a flexible coupling  162 . 
     A flexible coupling  162  connects a given threaded rod  116  to a corresponding servo motor  165  with an attached gear head (not shown) having a drive shaft  167  joined to the flexible couplings  162 . There is one servo motor  165  for each threaded rod  116 , e.g., in the illustrated apparatus there would be six motors  165 . Each servo motor  165  is connected to an operating computer  170  and an external power source  171 . The apparatus  108  could have any number of rods and/or motors, depending on the number of operating units used. All rods are positioned in a parallel or substantially parallel relationship. More motors than rods could be present for backup purposes. 
     In the illustrative embodiment, the control system  2  includes a controller, e.g., a microcontroller, e.g., a programmable logic controller (PLC), particularly the Allen-Bradley model SLC 5/04 PLC with power supply, Allen Bradley 1746-BAS basic module, and Allen Bradley PanelView 600 Color/Touchscreen operator interface, all available from Rockwell Automation, 1 Allen-Bradley Drive, Mayfield Heights, Ohio 44124-6118, U.S.A. Suitable servos are available from Quicksilver Controls, Inc. 712 Arrow Grand Circle, Covina, Calif. 91722, U.S.A., such as their Quicksilver Control QCI-23H-5 servos. Other control systems could include a computer other than a PLC including, e.g., an industrial computer system. 
     The control system  2  transmits information to the servo motors, resulting in the movement of the tape dispensing guide arms. The operator determines a desired tape position on the web, and then inputs these values into the operator interface, which can be in the form of an interactive screen on a display. Once all of the guide arm positions have been entered, the controller calculates the move distance for each guide arm, and transmits these values to the servo motors. The threaded rods start spinning as the servo motors are actuated, causing the tape guide arms to move. When a given guide arm reaches the predetermined location, the servo motor stops. In some instances, the computer may transmit a zero-move distance to one or more of the servo motors while transmitting non-zero move distances to other servo motors. In these instances, the servo motor or servo motors receiving a “no move” or “zero distance” signal will not move at all. 
     The control system  2  may be programmed using a ladder-logic programming language, particularly the RSLogix 500 software of Allen-Bradley. Once the program is created, it is downloaded into the PLC. Details of appropriate program code may vary based upon the application, and will become apparent to one skilled in the art upon reference to this specification. The steps involved with the novel processes of the present invention may alternatively be embodied in software that is executed by a general-purpose computer or other logic device. For such software implementations, the reader will understand that the invention can thus take the form of a computer program product that may be embodied in a computer-readable medium, including storage media, or transmission media. 
       FIG. 8  illustrates an operator interface  4  in the form of an order listing screen  30  that is constructed in accordance with the present invention. This interface is used for customer recipe/order management, by allowing the operator to enter predetermined tape setups (e.g., guide arm positions), and save those setups for later use. After the tape setups have been saved to the PLC memory they will be listed on the order listing screen. The orders will be displayed in the first open memory position. To select an order number the operator pushes the corresponding function key next to the order number to be recalled. If there are more than 10 order numbers in memory, the operator will push the next page button and be taken to the next 10 order numbers in memory. The page number will be displayed on the bottom of the screen. 
       FIG. 9  illustrates a main operator screen  50  that is further used in accordance with the present invention to carry out previous orders that have been entered via order listing screen  30 . After the operator selects an order, the previously entered arm positions will be displayed in the appropriate locations. The position that was previously entered will be shown in the box that has the TARG label next to it. The actual position of the guide arm will be shown in a field directly above the TARG box. The current active filename will be listed in the upper right hand corner of the screen. When the operator wants to move the arms into position, the operator will push the F6 button and the arms will start moving. The GANG OFFSET button will automatically move all of the guide arms by an entered value. If the operator wants to change the arm position for one guide arm, the operator will touch the box of the appropriate arm number. The operator will be prompted to enter a new number, using the keypad on the right of the operator interface, and then the new value will be displayed in the appropriate box. The operator will then push the F6 button to get the arm to move. 
     The invention may be further understood with reference to the flow chart of  FIG. 10 . The process begins with the controller determining whether all of the servo motors are homed ( 70 ), i.e., determining whether the servo motors are properly positioned to ensure proper calibration, and then homing any servo motors as required ( 72 ). The controller then displays the main operator screen  30  on the display device of the system ( 74 ). If the operator selects the Fl button on the touch-sensitive display screen, all orders in memory are listed ( 76 ). When one of the orders is selected, the corresponding arm positions are recalled from the PLC memory ( 78 ). If the operator instead desires to enter the order number manually ( 80 ), then the order is recalled and the arm positions are loaded from memory ( 82 ). Alternatively, the operator may search for an order number ( 84 ), and retrieve the order number. The act of retrieving the corresponding order will cause the arm positions to be recalled from the PLC memory ( 86 ). 
     The system preferably displays the arm positions, which allows the operator to determine if they appear correct for the selected order number ( 88 ). The operator then decides whether to move the arms into position ( 90 ). Alternately, the operator could be queried as to whether to move the arms into position ( 90 ). If the operator decides to move the guide arms into position, the relative move of the servo motors is calculated and the guide arms are moved ( 92 ). Current guide arm positions are displayed during operation of the strip fabrication assembly ( 94 ). The process may then continue in an iterative fashion, returning to step  74 , to allow the operator to enter or select a different order. In this manner, when the latter order is effectuated by moving the guide arms to different positions (in step  92 ), this switchover to a different order may be completed on-the-fly, that is, without interruption of the actual fabrication process. 
     Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. For example, while the invention has been described in the context of an assembly for dispensing corrugated sheeting, it is applicable to other web-type handling machinery such as web-slitting knives, strip-coating units, or tape applicators. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined in the appended claims. 
     In one embodiment, for example, the system for positioning guide members is used in conjunction with a web tracking unit. Referring to  FIGS. 11 ,  12 A and  12 B, a web tracking unit  175  is used to track the position of a web  113  as it moves right or left from the normal web path or position. The web tracking unit  175  is also used to maintain the position of the guide arms  111  in relation to the web  113 . The web tracking unit  175  is placed up stream from the positioning apparatus  108  on a beam  176  of the frame of the web handling machine. The web handling machine supports spaced web guiding rollers  178 ,  179  and  180 . As the web  113  passes the roller  179 , the tracking unit  175  looks at the position of the web  113 . The web tracking unit  175  includes a linear slide  182 , supporting an arm  184  that supports a pair of sensors  185  and  186  that are spaced transversely or substantially transversely of the normal web path and that are spaced in the direction of movement of the web  113 . The arm  184  is moved along the linear slide  182  by a servo motor  188 . The linear slide  182  is supported from the beam  176 , which also supports a cable track  189 , which supports electrical cables (not shown). The servo motor  188  is coupled to a threaded rod  187  in the linear slide  182  and the threaded rod is connected to the arm  184 . As formed, one spin of the threaded rod clockwise or counterclockwise moves the arm  184  10 millimeters and the encoder of the servo motor takes 4000 counts per revolution to precisely tell the position of the arm  184 . 
     Referring now to  FIGS. 12A ,  12 B and  13 , the sensors  185  and  186  are formed of optical fibers. A laser light travels through each fiber and exits toward the web  113  on one side thereof. Light is reflected from the web  113  back to the fiber and is received by light receivers and sensor amplifiers  190  and  191 , respectively. The sensors  185  and  186  have a built in alternating light source to avoid interference, or avoid one fiber from receiving reflected light from the other fiber. Again, each fiber is an emitter and receiver. The amplifiers  190  and  191  generate signals to the PLC of the positioning apparatus  108 , which sends signals to the servo motor  188  to move the sensors, and then move the guide arms  111 . 
     Referring now to  FIGS. 13A–C , which diagrammatically illustrate the operation of the sensors, the illustration  13 A indicates the sensors  185  and  186  tracking the web  113  in the “normal position.” Sensor  186  will receive a reflection and output a “1” and sensor  185  will no reflection and output a “0.” This “1” and “0” will provide an indication that the web is in the normal position or deadband range (i.e., the area between the two sensors within which a movement of the web is not detected). If the web  113  moves to the position illustrated at  13 B, the sensor  186  will output a “1” and the sensor  185  will output a “1” as well. In this position, the web tracking device will sense the web  113  has moved to the left. Under this condition the arm  184  will be moved to the left to re-center the sensors to achieve the position shown in  13 A above. If the web  113  moves to the right, the condition shown in illustration  13 C may exist. In this position, the sensor  186  will output a “0” and the sensor  185  will output a “0”. Under this condition, the PLC will know the web has moved to the right and it will start a move to re-center the sensors by moving the sensors to the right to achieve the condition illustrated in  13 A. Movement of the sensor arm  184  will be measured to also cause the PLC to signal the servo motors  165  to move all the guide arms  111  to the left or to the right simultaneously, an equivalent amount to maintain the position of the tapes on the web  113  in the desired position. The linear slide  182  was obtained from NSK Corporation, of Cerritos, Calif., U.S.A. as part number MCM08070H10-000A and the fiber optic sensors and amplifiers were acquired from SICK, Inc., of Minneapolis, Minn. The part number for the fiber optic cable is LL3-DB01 and the amplifier is part No. WLL170T-F420 and with the alternate frequency light model, WLL170T-F430. 
     The signals from the receivers and amplifiers indicate movement of the web from the normal position, and the sensors are then moved to obtain the deadband position for the sensors, i.e., a sensor positioned on each side of the web edge. 
     Referring to  FIGS. 1 ,  8 ,  9  and  14 , the operator interface  4  can include an additional button to enable or disable the web tracking unit  175 . When the web tracking unit  175  is enabled ( 95 ), the web tracking unit  175  goes out across the web  113  to find the edge of the web  113  ( 96 ). When the edge of the web  113  is found, the servo motor  188  registers the distance the web tracking unit  175  has moved and  110  relays the information back to the control system  2  ( 92 ). The control system  2  then conducts a series of calculations ( 92 ) and sends a signal ( 92 ) that causes the guide arms  111  ( 92 ) to move a distance that reflects the change in the web position. The guide arms  111  maintain a predetermined distance from the edge of the web  113 , the distance having been predetermined according to an operator input. When the web tracking unit  175  is in the enabled mode, the web tracking unit  175  constantly monitors the position of the edge of the web  113  ( 96 ). If the position of the edge of the web  113  changes, the web tracking unit  175  conveys this information to the control system  2 , which then moves the guide arms  111  ( 92 ) to a new position according to the change in the position of the web edge. The current guide arm positions are then displayed on the monitor ( 94 ). 
     Other embodiments are within the claims.