Patent Publication Number: US-2011061406-A1

Title: Method of cooling stretch-formed-part

Description:
TECHNICAL FIELD 
     The technical field generally relates to stretch forming processes and ways to cool parts made by stretch forming processes. 
     BACKGROUND 
     Stretch forming processes, such as quick plastic forming and super plastic forming, often include heating metal sheets and stretching the metal sheets by gas pressure into desired shapes. The automotive industry uses these processes to form parts such as body panels. After heating and stretching, the shaped metal sheets are commonly placed and rest on fixtures to cool. Some shaped metal sheets, such as those eventually forming relatively large automotive hood outer panels, might sag due to gravity or otherwise distort as they are resting and cooling from a high temperature malleable state to a lower temperature less malleable state. 
     SUMMARY OF EXEMPLARY EMBODIMENTS OF THE INVENTION 
     One exemplary embodiment includes a method which may include removing an automotive part from a stretch forming machine. The method may also include spraying a coolant over at least a portion of an exterior surface of the automotive part to cool the automotive part to a lower temperature nonmalleable state. 
     One exemplary embodiment includes a method which may include lifting an automotive part out of a first forming tool half of a stretch forming machine. The method may also include carrying the automotive part from the stretch forming machine to a conveyer. The method may further include placing the automotive part on the conveyer. And the method may include spraying a coolant over at least a portion of an exterior surface of the automotive part as the automotive part is being carried from the stretch forming machine to the conveyer and before the automotive part is placed on the conveyer. 
     One exemplary embodiment includes a method which may include stretch forming an automotive part using a stretch forming machine. The method may also include removing the automotive part from the stretch forming machine. The method may further include carrying the automotive part away from the stretch forming machine. The method may include spraying a coolant over at least a portion of an exterior surface of the automotive part as the automotive part is being carried away from the stretch forming machine. 
     Other exemplary embodiments of the invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while disclosing exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a schematic view of an exemplary embodiment of a stretch forming process with an automotive part located in a stretch forming machine. 
         FIG. 2  is a schematic view of the stretch forming process of  FIG. 1  with the automotive part being carried away from the stretch forming machine. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The following description of the embodiment(s) is merely exemplary (illustrative) in nature and is in no way intended to limit the invention, its application, or uses. 
     The figures illustrate an exemplary embodiment of a stretch forming process such as a quick plastic forming (QPF) process or a super plastic forming (SPF) process. In the automotive industry, for example, this process may be used to form an automotive part  10  such as a relatively large body panel like a hood outer panel. In the stretch forming process, a cooling process may be used that may prevent the automotive part  10  from sagging due to gravity or otherwise distorting. 
     In one exemplary stretch forming process, a sheet metal substrate or blank may be placed in a stretch forming machine  12  (e.g., quick plastic forming machine or super plastic forming machine) at a workstation or forming cell, and placed between an upper or first forming tool half  14  and a lower or second forming tool half  16 . In select embodiments, this sheet metal blank may include magnesium alloys, aluminum alloys, a low carbon steel, or another suitable material. An exterior surface of the sheet metal blank, or a part thereof, may be coated with a dry lubricant. An upper or first forming press  18  and a lower or second forming press  20  may be brought together under force and may clamp and seal a periphery of the sheet metal blank via the first and second forming tool halves  14 ,  16 . The first and second forming tool halves  14 ,  16  may then be heated and may in turn heat the sheet metal blank to a suitable forming temperature (e.g., in the case of magnesium-containing aluminum the temperature may range between 400° C.-510° C.). A continually increasing gas pressure may then be applied to one side of the sheet metal blank (e.g., 0 p.s.i. gauge to 250-500 p.s.i. or higher) and the sheet metal blank may be forced against and may take on the shape of the forming tool half located opposite the gas pressure application. Exemplary gases may include air, nitrogen, argon, and others. In the example of  FIG. 1 , the sheet metal blank may take on the female or somewhat concaved-shaped second forming tool half  16 . In other embodiments the stretch forming process may have more, less, and/or different steps than shown and described. For example, pre-forming processes such as heating and bending may be performed to the sheet metal blank before the sheet metal blank is placed in the stretch forming machine  12 . Illustrative examples of stretch forming processes may be found in U.S. Pat. Nos. 6,253,588 and 5,974,847. 
     After the sheet metal blank takes the general shape of the automotive part  10 , the first and second forming tool halves  14 ,  16  may be brought apart (i.e., opened) and the automotive part may be removed out of the stretch forming machine  12 . A part removal process and system may be used to take the automotive part  10  out of the stretch forming machine  12 . The part removal system may have many forms and arrangements. In the example of  FIGS. 1 and 2 , a robotic gantry system  22  may be used and may include one or more rails  24 , multiple wheels  26 , a frame  28 , and multiple clamps  30 . In use, the frame  28  may move horizontally between the opened first and second forming tool halves  14 ,  16  via the wheels  26  rolling against the rails  24 . The clamps  30  may then be lowered vertically to grip a periphery of the automotive part  10 . Once gripped, the clamps  30  may be raised to lift the automotive part  10  out of the second forming tool half  16 , and the frame  28  may then carry the automotive part to a conveyer  32  and may place the automotive part on the conveyer. In other embodiments, the part removal process and system may have more, less, and/or different steps than shown and described. For example, the conveyer  32  need not necessarily be provided whereby the gantry system  22  would set the automotive part  10  down at another location, the transit between the stretch forming machine  12  and the conveyer need not necessarily be a straight line, and other robotic automation equipment may be used in addition to or instead of the gantry system. 
     Before the automotive part  10  is placed on the conveyer  32 , the cooling process may be performed to the automotive part via a cooling system  34 . The cooling process may help prevent sagging and other distortion caused by gravity and other effects to the automotive part  10  when the automotive part is in a high temperature and malleable state upon exiting the stretch forming machine  12 . The cooling process may begin cooling the automotive part  10  as soon as possible in order to bring the part to a lower temperature nonmalleable state. In one example, the lower temperature nonmalleable state may be a rigid state where the part is not susceptible to and resists deformation due to the forces of gravity. One example lower temperature nonmalleable state is room temperature; of course, other lower temperature nonmalleable states other than room temperature may exist. The exact lower temperature nonmalleable state may depend on, among other things, the material used for the sheet metal blank and the thickness and size of the sheet metal blank. 
     The cooling system  34  may have many forms and arrangements. In the example of  FIGS. 1 and 2 , the cooling system  34  may include a first hose  36  that communicates with a coolant supply tank (not shown) and with a first manifold  38 . A coolant, such as CO 2 , may be stored in the coolant supply tank. The cooling system  34  may also include a first and second nozzle  40 ,  42  communicating with the first manifold  38 . In use, coolant flows from the coolant supply tank, through the first hose  36 , through the first manifold  38 , and out the first and second nozzles  40 ,  42 . The cooling system  34  may be retrofitted to the part removal system. For example, the first manifold  38  and the first and second nozzles  40 ,  42  may be connected to the frame  28  of the gantry system  22 , and may move with the frame. The first and second nozzles  40 ,  42  may be located horizontally between the clamps  30  and may be directed at the exterior of the automotive part  10 . The first and second nozzles  40 ,  42  may constitute an initial and primary set of nozzles of the cooling system  34 . 
     The cooling system  34  may also include a second hose  44  that may communicate with the same supply tank as the first hose  36 , or may communicate with another coolant supply tank. The second hose  44  may also communicate with a second manifold  46  which itself may communicate with a third and fourth nozzle  48 ,  50 . In use, coolant flows from the coolant supply tank through the second hose  44 , through the second manifold  46 , and out the third and fourth nozzles  48 ,  50 . The second manifold  46  and the third and fourth nozzles  48 ,  50  may be connected to a stationary support  52 . The stationary support  52  may be located away from the stretch forming machine  12  as shown in  FIGS. 1 and 2 , or may be located near and may even extend from the stretch forming machine. The third and fourth nozzles  48 ,  50  may be positioned and directed to spray coolant to the exterior of the automotive part  10  as the automotive part is in transit from the stretch forming machine  12  to the conveyer  32 . The third and fourth nozzles  48 ,  50  may constitute a final or secondary set of nozzles. 
     In other embodiments, the cooling system  34  may have more, less, and/or different components than shown and described. For example, more nozzles may be provided for the cooling system  34  and at different locations such as on the stretch forming machine  12 , the cooling system need not have the third and fourth nozzles  48 ,  50  whereby only the first and second nozzles  40 ,  42  would be provided, and mechanical devices and ways other than nozzles may be used to spray coolant to the automotive part  10 . 
     In the cooling process, the cooling system  34  may cool the automotive part  10  as the part is exiting the stretch forming machine  12  and before the part is placed on the conveyer  32 . The first and second nozzles  40 ,  42  may begin spraying a first or upper exterior surface  54 , or a portion thereof, of the automotive part  10  before the third and fourth nozzles  48 ,  50  begin spraying a second or lower exterior surface  56  of the part, or a portion thereof. In the female-shaped second forming tool half  16  of  FIGS. 1 and 2 , the first and second nozzles  40 ,  42  may begin spraying the automotive part  10  as soon as the clamps  30  grip the automotive part and while the automotive part is still seated in the second forming tool half. In some cases, depending on the exact shape of the automotive part  10 , spraying the automotive part while it is still in the second forming tool half  16  may facilitate lifting and removal of the automotive part out of the second forming tool half because of the resulting slight reduction in size of the automotive part as the part cools. In a male-shaped forming tool half (not shown), the first and second nozzles  40 ,  42  may begin spraying the automotive part  10  after the automotive part has been lifted out of the forming tool half. Of course, in a female-shaped forming tool half, the spraying may begin after the automotive part is lifted out of the forming tool half; and likewise, in a male-shaped forming tool half, the spraying may begin once the part is gripped and while it is still seated in the forming tool half. 
     After the automotive part  10  is lifted out of the second forming tool half  16 , the gantry system  22  may move the part toward the conveyer  32  and toward the third and fourth nozzles  48 ,  50 . Referring to  FIG. 2 , once the automotive part  10  is located in the vicinity of the third and fourth nozzles  48 ,  50 , the third and fourth nozzles may begin spraying the part. In one embodiment, the fourth nozzle  50  may begin spraying before the third nozzle  48  because the automotive part  10  may be located in the vicinity of the fourth nozzle before the third nozzle. The first and second nozzles  40 ,  42  may stop spraying the automotive part  10  once the automotive part is located or placed on the conveyer  32 , and the third and fourth nozzles  48 ,  50  may stop spraying the automotive part after it is carried out of the vicinity the third and fourth nozzles. 
     While in transit between the stretch forming machine  12  and the conveyer  32  (or another location), the first and second nozzles  40 ,  42  may continuously spray coolant to the automotive part, may intermittingly spray coolant, or may spray coolant another way. Likewise, while the automotive part  10  is in transit and within the vicinity of the third and fourth nozzles  48 ,  50 , the third and fourth nozzles may continuously spray coolant to the automotive part, may intermittingly spray coolant, or may do so another way. In one embodiment, the gantry system  22  may continuously carry the automotive part  10  from the stretch forming machine  12  to the conveyer  32  (or another location) without the cooling system  34  causing delay or a stop in the movement of the gantry system. In another embodiment, the gantry system  22  may carry the automotive part  10  in the vicinity of the third and fourth nozzles  48 ,  50  and may pause over the third and fourth nozzles temporarily while the third and fourth nozzles spray coolant to the automotive part. Or the gantry system  22  may carry the automotive part  10  from the stretch forming machine  12  to the conveyer  32  (or another location) more slowly than it otherwise would so that the duration of spraying coolant may be prolonged. The exact coolant spraying process (e.g., beginning of spraying, continuous or intermittent spraying, continuous or pause in transit, and speed of transit) may depend on, among other things, the thickness of the automotive part  10 , the material of the automotive part, the amount of coolant flowing out of the various nozzles, and the like. Once the automotive part  10  is sufficiently cooled, (i.e., lower temperature nonmalleable state), the gantry system  22  releases and places the automotive part onto the conveyer  32  (or another location) and the automotive part is taken away for further processing. 
     The cooling system  34  may provide a streamlined cooling process. The cooling system  34  may be integrated in the removal and transit process so that the automotive part  10  can be brought directly to the conveyer  32  (or another location) from the stretch forming machine  12 . By cooling the automotive part  10  in concert with removal and transit, the structural integrity of the automotive part  10  may be unaffected by the forces of gravity or other effects. The cooling system  34  may reduce the amount of time that the forces of gravity can act on the automotive part  10  while the automotive part is in the higher temperature malleable state. The cooling system  34  may also expedite the overall stretch forming process. 
     The above description of embodiments of the invention is merely exemplary in nature and, thus, variations thereof are not to be regarded as a departure from the spirit and scope of the invention.