Abstract:
A blank positioning and guide construction which includes guide pin slotting that effects the accurate positioning of the sheet on the forming die and guide pin thereof and which provides for the enlargement of the guide pin slot by the predetermined deformation of portion of the sheet at a predetermined bend line adjacent to the guide pin slot to eliminate adherence of the part to the pin so that the part can be ejected from the die without detrimental part distortion of the part.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to the art of manufacturing parts using sheet metal blanks and forming dies and more particularly to new and improved constructions and techniques for the superplastic forming of metal parts with rapid and trouble free extraction of formed parts from forming dies.  
         BACKGROUND OF THE INVENTION  
         [0002]    Prior to the present invention, various types of forming equipment and processes have been developed for quantity production improvements to shape blanks of metallic materials into a wide range of items. Among such equipment and processes are super and quick plastic forming dies and processes in which a ductile sheet of superplastic metal alloy is heated and stretched onto the forming surfaces of heated dies to produce high- quality, light- weight parts such as panels for automotive vehicles. Often such sheets are quite large so that trunk lids, engine hoods or other large panels can be formed in one piece. Examples of such processes and equipment are found in U.S. Pat. No. 5,974,847 issued Nov. 2, 1999 to Sanders et al for Superplastic Forming Process and U.S. Pat. No. 5,819, 572 issued Oct. 13, 1998 to P. E Krajewski for Lubricating System For Hot Forming, both assigned to the assignee of this invention and both hereby incorporated by reference.  
           [0003]    In the patent to Sanders et al. a blank sheet of metal alloy is heated to a superplastic forming temperature and is pulled over and around a forming insert in a die set. Subsequently using differential gas pressure, the sheet is further stretched into conformity with a forming surface of the insert so that thinning of the formed part is minimized. In the patent to Krajewski, dry lubricant is applied to a metallic sheet which is subsequently heated to predetermined forming temperatures and formed into a part in superplastic forming die equipment. The lubricant initially provides improved forming of the part and subsequently improved release of the formed part from the forming die.  
           [0004]    Formed part removal is further addressed in copending patent application Ser. No. 09/837597 filed Apr. 19, 2001 by R. Kleeber et al for Panel Extraction Assist for Super and Quick Plastic Forming Equipment assigned to the assignee of this invention and hereby incorporated by reference. In the above-identified application, forming pressures used for making superplastic parts in hot forming dies are further employed for improved ejection of the part from the forming die.  
           [0005]    While the above identified patents and patent application constructions provide improvements in super and quick plastic forming they often do not attain new and higher standards for the production of such formed parts with minimized part rejection from part distortion resulting from part ejection forces. More particularly with some equipment, difficulties have been experienced in quantity production in accurately positioning the blanks or sheets onto the forming die and then subsequently removing the formed part or panel without distortion or other damage from release or ejection forces.  
           [0006]    The employment of guide pins and cooperating guide pin slots for the forming die and blank sheet respectively to precisely position the blank sheet on the forming die has only met with limited success in view of the fact that the material of the blank expands or otherwise distorts during the forming process and grips onto the guide and positioning pin. This gripping inhibits removal of the formed panel from the die. Often the formed panel is distorted to such an extent by the part ejection forces moving the part from the pin and the associated forming die that the panel has to scrapped and recycled. FIG. 4 of the accompanying drawings illustrates prior art panel distortions from the panel being held to the forming die by the guide pin and in response to ejection forces being applied to remove the panel.  
         SUMMARY OF THE INVENTION  
         [0007]    In contrast the prior art, the present invention is drawn to new and improved methods and constructions that provides improved blank positioning on the forming die and improved formed parts. This invention importantly meets higher standards for ejection and removal of high quality formed parts from hot super plastic and quick plastic forming dies particularly while in the press and operating at elevated temperatures. More particularly, the invention is directed to the quick and effective removal of super plastically formed parts from hot forming dies without part damage.  
           [0008]    The present invention specifically alleviates blank guidance and formed part removal problems by providing a new and improved guide pin slot configurations that have adequate in-plane stiffness for blank locating purposes. The configurations further provides discrete offal or waste areas in the part responsive to removal forces particularly those angled to the plane of the part to allow limited and controlled bending of such predetermined and specific waste areas of the part to enhance part removal from the forming die.  
           [0009]    This invention provides a new and improved positioning and guide slot arrangement in a blank of formable sheet material such as aluminum alloy which is engineered to cooperate with an upstanding blank locating and positioning guide pin of a forming die that augments removal of a formed part from the die. When the formed part is being ejected a guide pin slot in a sacrificial or waste part of the formed member is frictionally engaged by the surface of the pin that effects the bending of the waste part that turns away from the guide pin and effects enlargement of the pin guide slot to enhance release of the formed part from the forming die and the guide pin thereof.  
           [0010]    It is a feature, object and advantage of this invention to provide a new and improved guide pin slot arrangement in a blank of sheet metal to be formed into a part of predetermined shape that allows the controlled deformation of specific waste areas of the part containing the slot arrangement on removal from the guide pin of the forming die. In this invention side walls in the waste area defining the guide pin slot can physically contact the guide pin as the formed part is being removed from the die to cause the waste portion to bend along a predetermined bend line so that the guide pin is clear of the part to thereby augment part removal without part distortion or other damage.  
           [0011]    Another feature object and advantage of this invention is to provide new and improved blank positioning and guide pin slot arrangement in a blank of sheet material used in superplastic forming that augments removal of a part formed from the blank on a forming die having a guide pin that cooperates with the guide pin slot to accurately position the blank on the forming die.  
           [0012]    Another feature object and advantage of the present invention is to provide a new and improved guide pin slot arrangement in a blank to be superplastically formed that prevents the gripping of the formed part onto a guide pin carried by the forming equipment to allow the formed part to be easily removed from the equipment by part extraction forces.  
           [0013]    In a preferred form of the invention a centralized guide pin receiving slot is bounded on either side by edge slots that extend from predetermined positions in the periphery of the blank to predetermined terminal points to thereby establish specific bend lines or hinges in the blank that easily bend under load when the part is removed from a forming die to enlarge the pin slot to augment removal of the part from the guide pin and the associated die. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    These and other objects, advantages and features of the invention will become more apparent from the following detailed description of one preferred embodiment of the invention and drawing in which:  
         [0015]    [0015]FIG. 1 is a pictorial view of a superplastic forming equipment forming sheet metal blanks into formed parts;  
         [0016]    [0016]FIG. 1 a  is a plan view of a portion to the sheet metal blank of FIG. 1 as positioned on a blank guide and positioning pin of a forming die  
         [0017]    [0017]FIG. 1 b  is a plan view similar to the view of FIG. 1 a  illustrating the removal of the blank from the pin;  
         [0018]    [0018]FIG. 2 is a pictorial view of a portion of the forming equipment of FIG. 1 illustrating the guidance and locating of the sheet blank onto the forming die;  
         [0019]    [0019]FIG. 3 is a pictorial view similar to FIG. 2 illustrating the formed part being removed from the forming die; and  
         [0020]    [0020]FIG. 4 is a pictorial view of a prior art construction showing a part being removed from a guide pin of the forming die. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]    Turning now in greater detail to the drawing, FIG. 1 illustrates a forming press  10  comprising a lower bolster plate  12  on which lower steel or forming die  14  is mounted. The press additionally has an upper reciprocating ram plate  16  that carries a chambered upper tool  18  that corresponds to the upper tool of the above referenced U.S. Pat. No. 5,819,572. Both plates  12  and  16  may be electrically heated to establish the required heat energy levels in the die and the sheet metal blanks  20  loaded therein for super and quick plastic forming as is known in this art. Forming die  14  can be mounted on the upper plate instead of the lower plate and the chambered upper tool  18  operatively supported on the lower plate if desired and depending on the characteristics of the part to be made.  
         [0022]    The ram plate  16  is cycled by hydraulic cylinders  22  from the illustrated open position shown in FIG. 1 for blank loading to the closed position for blank forming and then back to the open position for removal of the formed part from the hot forming die. A second blank can then be loaded onto the forming die for another part forming cycle. The blanks utilized with one preferred embodiment of this invention are flattened rectilinear sheets  24  of aluminum alloy coated with a dry lubricant such boron nitride to function as an agent to enhance the stretching and forming of the part during super plastic forming operation and as a release agent to prevent the formed panel  28  from sticking to the die thereby enhancing part release.  
         [0023]    As best shown in FIG. 1 the upper tool  18  is operatively connected to the ram plate and projects downwardly therefrom. This tool has a downwardly extending and rectilinear peripheral wall whose free end provides a continuous face seal that sealingly engages the upper surface of the metal sheet  24  along a continuous sealing line  32  that extends adjacent to the peripheral edge  34  of the sheet. This contact establishes an air chamber when the upper tool is brought into engagement therewith during part forming operation. The air chamber is supplied with a suitable inert gas such as pressurized air from a compressor or other source via airlines that connect to an orifice in one of the walls thereof leading to the chamber. Moreover, the forming equipment may be provided with conventional air control valves therein to control the feed and exhaust of air with respect to the air chamber for metal forming operations as disclosed in the referenced patent application Ser. No. 09/837597.  
         [0024]    The lower tool or forming die  14  extends upwardly from support by the face of the bolster plate  12  and has a rectilinear peripheral wall terminating in a flattened end face  36  for support of the alloy sheet  24  when loaded thereon. The lower tool further comprises a thick main forming body profiled to form the desired configuration of the part being produced. As best shown in FIGS. 1 and 2 the lower forming die  14  has an upwardly extending blank guide pin  40  comprising a cylindrical steel member anchored at a predetermined station in the blank supporting end face thereof. The pin has an outwardly bent end portion so that it can readily be received by the inclined or slanted clearance recess  42  in an the wall of the upper tool  18  to allow sealing closure of the upper tool onto the blank loaded on the forming die for part forming operation. Various part ejection devices can be employed with this invention such as ejection pins, air assisted ejection as disclosed in the above referenced co-pending patent application Ser. No. 09/837,597 or removed by an operating arm of an associated robot.  
         [0025]    The guide pin  40  is further designed to be operatively received in a guide and positioning slot arrangement  46  formed in the sheet  24  in an area which is to be subsequently removed or concealed in the final use of the formed part. More particularly the guide and positioning slot arrangement has a main channel  48  which is generally rectilinear and is in part defined by opposing straight sides  50  spaced at a width which is slightly greater than the diameter of the cylindrical guide pin  40 . The main channel of the guide pin slot arrangement extends through the peripheral edge  34  of the blank and defines an open gate  52  for receiving the guide pin so that the sides can contact and guide the sheet onto the forming die. The main channel further extends to a terminal inboard edge or end  56  that may be horizontal or curved to fit the periphery of the pin to make an effective stop for the upstanding pin  46  so that the blank being guided by the slot is positioned at a predetermined location on the forming die with precision to augment the forming of an acceptable formed part.  
         [0026]    The inboard end of the slot communicates with left and right side branches  58  and  60  that extend at predetermined angles from direct communication with the end of the guide pin channel. The overall shape of the main channel and the mirror-imaged side branches may define an Y shaped configuration although other configurations, such as a T- shape could be used. These branches cooperate with left and right side boundary slots  62 ,  64  generally parallel to and offset to either side of the main channel  48 . The boundary slots, the pin channel, and its branches cooperate to define left and right side offal or waste parts  66 , 68  of the blank. More particularly these portions are further defined by left and right side live hinges or bend lines  70 , 72 . The hinges  70 , 72  are generally linear, intentionally weakened bend lines which extend from respective ends of the side branches to the associated ends or terminal points of the left and right side boundary slots  62  and  64  to allow controlled bending of the waste parts or offal  66 , 68  away from the guide pin and thereby augment removal of the formed panel or part from the forming die without bending of the formed areas of the parts or other damage.  
         [0027]    In operation of a preferred embodiment, a robot  80  or other suitable loading unit turns and lowers an operating arm  82  thereof to pick up a top sheet or blank  24  from a stacked supply  84  of blanks. The arm  82  of the robot moves forwardly from the elevated position illustrated in FIG. 1 in the direction of the arrow “A” and into the press to load the blank on top of the hot forming die  14 . As the blank  24  is being displaced as shown in FIGS. 1, 1 a  and  2  the guide pin  40  of the forming die clears the open gate  52  and enters the main pin channel  48  which cooperates therewith and effectively guides the moving blank into predetermined position on the forming die. The final position of the blank on the forming die is established by contact of pin  40  with the end  56  of the guide pin channel. With the blank loaded and released, the robot moves to an out of way position.  
         [0028]    The ram plate then moves downwardly so that the upper tool establishes operative sealing engagement with the heated blank seated on the die. Appropriate forming pressure is then fed into the forming chamber of the upper tool for part forming. The part is superplastically formed as is known in this art and the upper tool is subsequently raised to expose the formed part on the die. The arm  88  of a second robot  90  or other suitable unloading tool is moved into the opened forming equipment to pick up the hot formed part  28  that has a facsimile of the profile of the forming tool  14 .  
         [0029]    As the part is picked up by the robot arm  88  or otherwise ejected from the forming either die either or both sacrificial parts or offal  66 , 68  of the formed part may be bent downwardly. This may occur because of frictional contact of the pin  40  with either or both sides  50 , 50  of the guide pin channel as the formed part is moved off of the forming die. Part flow arrow B diagrammatically illustrates the unencumbered removal of a finished part from the forming die. For example, the waste part or offal  68  shown in FIG. 1 b  and FIG. 3 is bent downwardly, turning a limited amount along live hinge line  72 .  
         [0030]    The waste part  68  is accordingly displaced by direct contact with the guide and positioning pin as the formed part  28  is moved off of the forming die by part ejection forces. This turning movement of the waste part significantly enlarges the guide pin —main slot clearance such as diagrammatically illustrated at  94  in FIG. 1 b  and ensures that the part being removed from the forming die does not hang up on the pin and be deformed by part removal forces. The parts so removed are acceptable and are accumulated in a stack  98  by the robot arm  88  moving the part as illustrated by part flow arrows C and D.  
         [0031]    In contrast, FIG. 4 shows a prior art slot configuration S and illustrates part deformation D resulting when a formed part F being removed from the forming die is hung up on guide pin P of a forming die fitted into the slot S provided in the blank.  
         [0032]    In any event, such deformation is substantially obviated with the new guide pin slot arrangement of this invention so that large numbers of identically formed parts can be successfully made with no adverse part deformation or bending and with minimized part rejection.  
         [0033]    While the bend lines  72  are shown as being angled from the horizontal in FIG. 1 a  and  1   b  for example so that the waste areas bend away from the pin on part ejection, the bend lines could be horizontal or have other orientations to enhance formed part removal. As indicated above, both sacrificial areas can bend during part removal as the part may have some lateral movement as it is being moved off the pin. In all of these designs, the slotted areas of the blank that is subsequently removed or otherwise altered such as for fitting with an adjacent part or to accommodate tubing or wiring.  
         [0034]    While some preferred methods and mechanisms have been disclosed to illustrate this invention, other methods and mechanisms embracing this invention will now be apparent to those skilled in the art. Accordingly, the scope of the invention is to be considered limited only by the following claims.