Abstract:
This invention includes a method of determining the correct timing of a material release mechanism (42) of a material feed mechanism (14) and includes the steps of: cycling a press mechanism (12) through a working portion of a tooling mechanism (17); monitoring the press mechanism (12) position; determining, by a location device (58), the desired timing for the material release mechanism (42) to release contact with material (18); and correlating the desired material release mechanism (42) timing to the press mechanism (12) position. The present invention also is a stamping system (10) for working the material (18). This stamping system (10) includes a press mechanism (12) having a tooling mechanism (17) configured to punch holes (66) in the material (18). The stamping system (10) also includes a material feed mechanism (14) to feed material (18) to the press mechanism (12), and this material feed mechanism (14) includes a material release mechanism (42). Finally, the stamping system (10) includes a location device (58) to monitor the press mechanism (12) position and determine desired material release mechanism (42) timing.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to stamping systems having material feed mechanisms and, in particular, to a method and apparatus for determining and setting a material release mechanism timing for a material feed mechanism.  
           [0003]    2. Description of the Prior Art  
           [0004]    Typically, parts made with an automated stamping press utilize a progressive die set. The progressive die set uses multiple stations, each station typically containing at least one piercing or forming punch and a mating die or dies. Continuous strip material, from which the part will be made, is incrementally fed through the die set, progressing from station to station with an automated feeding device. A material feed mechanism intermittently moves the strip material a distance, corresponding to the distance between each die station, while the die set is open. This mechanism then stops the material at each station when the die set closes. Examples of prior art material feed mechanisms may be found in U.S. Pat. Nos. 5,755,370; 5,868,296; 5,915,293; and 5,808,465.  
           [0005]    Alignment devices are commonly used in a progressive die set to position the strip in the die set for each subsequent operation more accurately than is possible with the material feed mechanism. The most commonly used and most easily understood alignment device is a tapered or beveled point pilot positioning pin or a plurality of such pins. The pilot positioning pin is mounted in the moving, usually the upper, die shoe. Typically, a hole of slightly larger diameter than the diameter of the pilot positioning pin is pierced in the continuous strip material in a first station during the first closure of the die. The automated material feed mechanism then moves the material a predetermined distance corresponding to the distance between subsequent die stations. Upon subsequent die closures, the pilot positioning pin, which is longer in length than the working punches, enters the hole created by the punch and locates the material accurately.  
           [0006]    Pilot positioning pins may be used at any number of subsequent die stations. In order for the pilot positioning pin, or other alignment device; to effectively position the material accurately, the material feed mechanism must relinquish its grip on the strip material. The timing of the release function of the material feed mechanism is critical, as premature release may allow the material to move out of position too far for the pilot positioning pin to be effective. Alternatively, if the material feed mechanism releases the strip material too late or not at all, tension will be developed in the strip material when the pilot positioning pin enters the hole. This may cause hole deformation with resulting improperly positioned material. This improperly positioned material will cause the manufacture of malformed parts and can damage the pilot positioning pin as well as the die set.  
           [0007]    Various methods of releasing the strip material from the material gripping mechanism are well known in the prior art. Typically, these methods utilize cams, air cylinders, or various other devices. Technology currently exists for both setting and maintaining precise material release mechanism timing between the material feed mechanism and the stamping press. For example, see U.S. Pat. No. 5,720,421. Further more, this technology provides for infinite variation in release timing, as well as a convenient means for adjusting this timing. However, no technology exists for determining the precise press slide or press mechanism position when the alignment device contacts the material and the material gripping mechanism release should occur.  
           [0008]    Determining the precise point in the press stroke when the material feed mechanism should release its grip on the strip material is difficult due to two primary problems. First, the alignment device is typically located in a position which makes it difficult or impossible to visually inspect. Second, the nature of a flywheel driven mechanical stamping press makes it difficult to precisely position the press slide in small increments. The process of moving the press slide in small incremental movements is called “inching” or “jogging” and is accomplished by repeated engagement of the press clutch for short periods of time. This causes a motion that is very erratic and makes it difficult to precisely position the press slide, in order to verify the correct position of the alignment device relative to the strip material. The difficult nature of the current methods is best illustrated by example.  
           [0009]    Current methods exist for determining and setting the correct material release mechanism timing, but these methods typically require the press operator to locate the material in the die in a position which will allow the piercing of the initial locating hole. The operator must then effect movement of the press rain, to close the die, piercing the locating hole in the material. The material is then progressed a single progression, thereby positioning the material correctly to allow the alignment device to contact the material on a subsequent closure of the die. The operator then “inches” or “bars” the press to the point at which the material alignment device begins to contact the material. The point at which the material alignment device begins contact with the material is determined visually or, alternatively, by grasping the material in hand, moving or trying to move the material, and feeling for resistance to movement of the material provided by the alignment device. Having determined the press position where the material alignment device begins to contact the material, the operator then adjusts the material feed mechanism to release the hold on the material at this point or slightly before this point in the press stroke. This process is then repeated and adjustments are made until proper timing of the material release mechanism is verified.  
         SUMMARY OF THE INVENTION  
         [0010]    It is, therefore, an object of the present invention to provide a method for determining the correct timing of the material release mechanism. It is another object of the present invention to provide a method for setting the correct timing of the material release mechanism. It is a further object of the present invention to provide an automated system for accurately determining release mechanism timing. It is a still further object of the present invention to provide a method and apparatus that is capable of disengaging contact with a material immediately prior to engagement by an alignment device.  
           [0011]    The present invention includes a method for determining the correct timing of a material release mechanism of a material feed mechanism, including the steps of. (1) cycling a press mechanism through a working portion of a tooling mechanism; (2) monitoring the press mechanism position; (3) determining, by a location device, the desired timing for the material release mechanism to release contact with the material; and (4) correlating the desired material release mechanism timing to the press mechanism position. In another embodiment, the method also includes the step of adjusting the timing of the material release mechanism to the determined desired material release mechanism timing.  
           [0012]    The present invention is also directed to a stamping system for working a material. This stamping system includes a press mechanism configured to punch holes in the material. The stamping system also includes a material feed mechanism having a material release mechanism for feeding material to the punching mechanism, and a location device for monitoring the press mechanism position in determining a desired material release mechanism timing.  
           [0013]    The present invention, both as to its construction and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a side schematic view of a stamping system according to the present invention;  
         [0015]    [0015]FIG. 2 is a front view of a material feed mechanism of the stamping system in FIG. 1;  
         [0016]    [0016]FIG. 3 is an edge view of the material feed mechanism in FIG. 2;  
         [0017]    [0017]FIG. 4 is a side schematic view of a tooling mechanism according to the present invention;  
         [0018]    [0018]FIG. 5 is a flow diagram of a method according to the present invention; and  
         [0019]    [0019]FIG. 6 is a graph of press mechanism position versus material position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    As illustrated in FIGS.  1 - 3 , the present invention is directed to a stamping system  10 , which includes a press mechanism  12 , a material feed mechanism  14  and a material dispenser  16 . The material feed mechanism  14  is used to feed an elongated strip of material  18  from the material dispenser  16  through the material feed mechanism  14  and into the press mechanism  12 . This press mechanism  12  typically includes a tooling mechanism  17  having an upper die shoe  20  and lower die shoe  22 . The upper die shoe  20  is mounted to a press slide  24  in the press mechanism  12 . The upper die shoe  20  of the tooling mechanism  17  has a punching device  26  and an alignment device  28  mounted on its underside. The punching device  26  is constructed so that it is capable of piercing or punching the material  18 . In the preferred embodiment, the alignment device  28  is a pilot positioning pin  30 . As discussed above, this upper die shoe  20  is mounted to the press slide  24  which, in turn, moves up and down in relation to the lower die shoe  22 . The lower die shoe  22  of the tooling mechanism  17  is mounted to a bolster plate  32  rigidly mounted to a fixed press bed  34 .  
         [0021]    The material  18 , typically, but not exclusively, in the form of a continuous strip, is fed to and moves between the upper die shoe  20  and the lower die shoe  22 . Further, the press mechanism  12  also includes a driver having a crankshaft  36  to drive or move the press slide  24  towards and away from the lower die shoe  22 , as represented by arrow A. As detailed in FIGS.  1 - 3 , the material feed mechanism  14  includes a feed drive roll motor  38 , typically a servo motor, to power and drive the feed drive roll  40 , which advances the material  18  through the material feed mechanism  14 .  
         [0022]    A material release mechanism  42  includes a material gripping mechanism  44 , which works along with the feed drive roll  40  to grip the material  18 . Typically, this material gripping mechanism  44  is a secondary drive roll. The material gripping mechanism  44  is mounted in a pivot frame  46 , which is pivotably mounted to a material feed mechanism frame  48 . The material release mechanism  42  also includes an actuator  50 , typically pneumatic, capable of applying downward pressure on the pivot frame  46 , thereby allowing the material gripping mechanism  44  to grip the material  18  between the material gripping mechanism  44  and the feed drive roll  40 .  
         [0023]    As seen in FIG. 3, it is also envisioned that the material feed mechanism  14  includes a motor  52  to drive a release screw  54 , which mates with a nut  56 , for effecting the movement of the pivot frame  46  against the force of actuator  50 . It is this release screw  54  and nut  56  arrangement which allows the material gripping mechanism  44  to move away from the feed drive roll  40 , thereby releasing the grip pressure on the strip material  18 .  
         [0024]    In order to determine a desired material release mechanism timing, the stamping system  10  also includes a location device  58 . In the preferred embodiment, this location device  58  includes a controller  60  that monitors the press mechanism  12  position and determines the desired timing for the material release mechanism  42  to release contact with the material  18 . Further, this controller  60  can perform the correlation between the desired material release mechanism  42  timing to the press mechanism  12  position. It is also envisioned that the location device  58  include a first feedback device  62  to monitor, collect and transmit information regarding the press mechanism  12 , as well as its parts, to the controller  60 . Similarly, a second feedback device  64  may be used to monitor, collect and transmit information regarding the material feed mechanism  14 , and its parts, to the controller  60 .  
         [0025]    In a preferred embodiment, the location device  58  uses the first feedback device  62  to monitor the crankshaft  36  of the press mechanism  12 . Next, this first feedback device  62  communicates the angular position information of the crankshaft  36  to the controller  60 . The second feedback device  64  is mounted to the feed drive roll motor  38  and is used to monitor and communicate the angular position of the feed drive roll motor  38  to the controller  60 . Finally, the controller  60  computes position error information based on the required motion of the feed drive roll motor  38 , and the measured actual motor angular position. Controller  60  may also compute the required torque command for the feed drive roll motor  38 , based on the position error information computed above. This torque command is sent to the motor  38 . Also, the required torque commands, by definition, may be used and/or referred to as the measured torque of the motor  38 . Although the location device  58  has been described as monitoring the specific equipment discussed above, it is envisioned and discussed in greater detail hereinafter, that this location device  58  may be used to monitor and determine the desired material release mechanism  14  timing and press mechanism  12  position based upon any of the physical characteristics of the stamping system  10  parts and equipment, including the feed mechanism and the press itself.  
         [0026]    As illustrated in FIG. 5, the present invention also includes a method for determining the correct timing of the material release mechanism  14 . In order to determine this timing, the press mechanism  12  is cycled through the working portion of the alignment device  28  of the tooling mechanism  17 . The press mechanism  12  position is monitored. The above-described location device  58  may be used to determine the desired timing for the material release mechanism.  42  to release contact with the material  18 . Typically, the desired timing for release is immediately prior to contact with the material  18  by the alignment device  28 , or in this embodiment, the pilot positioning pin  30 . Next, the determined desired material release mechanism  14  timing is correlated to the press mechanism  12  position. Overall, this will allow the material release mechanism  42  to disengage the material  18 , allow the pilot positioning pin  30  to contact the material  18  and align it, before the material gripping mechanism  44  again contacts the material  18  and the material feed mechanism  14  continues the feed. After the desired timing has been determined, the actual material release mechanism  42  timing may be adjusted to the determined desired material release mechanism  42  timing.  
         [0027]    In the preferred embodiment, the strip material.  18  is positioned with the leading edge through the first die station, containing the punching device  26 . The press mechanism  12  is then cycled through one complete press stroke, with the punching device  26  piercing or punching a hole  66  into the strip material  18 . The material  18  is then advanced by the material feed mechanism  14  a predetermined distance, short of the die progression. This will position the material  18 , such that the pilot positioning pin  30  is located substantially above the previously punched hole  66 , but slightly misaligned. This condition is illustrated in FIG. 4, with the misalignment greatly exaggerated. In practice, this misalignment is small, typically only 0.003 inches to 0.008 inches.  
         [0028]    The next step is to cycle the press mechanism  12  through the working portion of the alignment device  28 , and typically through a complete press stroke, while the controller  60  simultaneously monitors the position of the feed drive roll motor  38 . When the upper die shoe  20  closes, the pilot positioning pin  30  enters the prepunched hole  66 , and the material  18  is forced into a final aligned position. This causes movement of the material gripping mechanism  44  and the feed drive roll motor  38 , which are gripping the material  18 . When the press cycle is complete, the controller  60  analyzes the information gathered and correlates the movement of the material release mechanism  42  (including the material gripping mechanism  44 ) and the feed drive roll motor  38  to the position of the press mechanism  12 , thereby determining the press mechanism  12  position where the pilot positioning pin  30  entered the strip  18 . An example of this correlated data is shown in FIG. 6. Finally, the material feed mechanism  14 , specifically the material release mechanism  42 , is programmed to release the material  18  at the calculated press mechanism  12  position for subsequent press cycles. In this preferred embodiment, the controller  60  automatically sets the correct release point and stores the information for future use.  
         [0029]    The pilot positioning pin  30  has a guide end  68 , which is typically beveled. When the press mechanism  12  enters the working portion of the tooling mechanism  17 , the guide end  68  of the pilot positioning pin  30  is partially engaged with the hole  66 . Due to the misalignment, a side wall of the guide cud  68  contacts an inner edge of the hole  66 , such that the material  18  is moved along a first axis (arrow B) as the side wall of the guide end  68  continues through the hole  66 . The desired material release mechanism  42  timing is based upon the linear movement of the material  18  along this first axis B. Further, the linear movement of the material  18  along this first axis B after the guide end  68  has filly engaged the hole  66  may be measured. The linear movement of the material  18  may then be correlated to the position of the press mechanism  12 , to determine the desired material release mechanism  42  timing. It is also envisioned that the angular rotation of the feed drive roll  40  caused by the linear movement of the material  18  may be correlated to the position of the press mechanism  12 , to determine the desired material release mechanism  42  timing. If the press mechanism  12  includes a press ram, the linear movement of the press ram position may be measured and correlated to the movement of the material  18 , to determine the desired material release mechanism  42  timing.  
         [0030]    It is also envisioned that the disturbance force produced upon contact of the pilot positioning pin  30  with the material  18  may be measured. As above, this measurement may be used to determine the desired material release mechanism  42  timing. The torque exerted upon the feed drive roll  40  after the guide end  68  of the pilot positioning pin  30  has fully engaged the hole  66  may also be measured. Similarly, the force exerted upon the material gripping mechanism  44  may be measured. These measurements may then be used to determine the desired material release mechanism  42  timing. Material  18  movement at the material dispenser  16  may also be measured and used to determine the desired material release mechanism  42  timing. The torque exerted upon the feed drive roll  40 , the force exerted upon the material gripping mechanism  44 , as well as the feed drive roll motor  38  position error may all be used to determine the desired material release mechanism  42  timing. It is envisioned that the controller  60 , together with appropriate feedback devices ( 62 ,  64 ) may be used to monitor, transmit, and calculate the desired release mechanism  42  timing based upon any of these measurements.  
         [0031]    Overall, the present invention is a stamping system  10  and method for determining and adjusting the desired timing of a material release mechanism  42 . When using the controller  60 , the present invention is an automated system, which eliminates the prior art guesswork previously used by operators to set the material release mechanism  42  timing. This, in turn drastically increases productivity and reduces both operator error and possible operator safety concerns.  
         [0032]    The present invention determines the precise press mechanism  12  (typically the press slide  24 ) position when the alignment device  28  is about to contact the material  18  and the material release should occur. It is this precise point in the press stroke when the material feed mechanism  14  should release its grip on the strip material  18 . This precise point, as described in detail above, is determined by the controller  60  based upon the linear or angular movements of certain components and subcomponents of the stamping system  10 . However, it is also envisioned that one or more sensors can be used and positioned adjacent or in the vicinity of the punching device  26  or the alignment device  28 . Such sensors could sense contact or exact positioning of the alignment device  28  and/or the punching device  26 , and this information could be used to determine the material release mechanism  42  timing. For example, the contact of either the punching device  26  or the alignment device  28  could be sensed when an electrical circuit is complete, thereby determining the timing for material  18  release. Also, sensors could be used to directly measure the movement of material  18  to determine the timing of material  18  release. Alternatively, the material  18  could be mechanically dithered (or moved back and forth) as the alignment device  28  is entering the hole  66 . Using the forward and backward contact of sidewalls of the guide end  68  of the pilot positioning pin  30 , the controller  60  could determine the material release mechanism  42  timing.  
         [0033]    Furthermore, although the aforementioned preferred embodiments reference feed drive roll  38  and/or drive rolls in the material feed mechanism  14  and the material gripping mechanism  44 , it is envisioned that the material feed mechanism  14  could utilize sliding gripper(s) for advancing the strip material  18  and/or sliding or stationary gripper(s), as a part of the material feed mechanism  14  and/or the material gripping mechanism  44  and/or as a part of the material release mechanism  42 .  
         [0034]    This invention has been described with reference to the preferred embodiments. Obvious modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations.