Patent Publication Number: US-2005133959-A1

Title: System and method for producing multi-color polymeric components

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a system and method for producing multi-color polymeric components.  
      2. Background Art  
      Aromatic spray polyurethane in-mold coating (IMC) has recently emerged as a cost effective method of producing a variety of different polymeric components. In some cases, spray polyurethane IMC has been able to replace reaction injection molding (RIM) in the production of rugged structural components. The spray polyurethane IMC process takes advantage of cross-link bonding between a coating, usually of a color desired for the finished component, and a polyurethane substrate. The part produced by the spray polyurethane IMC process can then be used in the manufacture of a component, such as an instrument panel for a vehicle, that does not need to be post painted. Indeed, the coating used in the spray polyurethane IMC process can be specifically chosen to match the vehicle interior.  
      In addition to facilitating production of monochrome parts, the spray polyurethane IMC process can also be used to produce parts having two or more colors. Of course, this adds complexity to the process. One method of producing a multi-color component using the spray polyurethane IMC process, involves masking a portion of a mold as the mold is sprayed with a coating having one color. The mask is then removed and a second color is sprayed on the mold. In this type of process, the masking material must be constantly cleaned or discarded, and must be applied and removed for each component produced. This adds time and cost to the operation, and requires messy cleanup even when the masking material is discarded.  
      Therefore a need exists for a method of producing a multi-color component using a process that eliminates the need to mask portions of the mold to produce a component having more than one color.  
     SUMMARY OF THE INVENTION  
      Accordingly, the invention provides a method for producing a multi-color polymeric component using a mold having at least two pieces. The method includes applying a polymeric coating having a first color to a first piece of the mold. A polymeric coating having a second color is applied to a second piece of the mold. At least one of the coatings is applied when the first and second mold pieces are separated from each other. The two mold pieces are disposed in close proximity to each other, and a polymeric bonding material is applied to at least a portion of each coating, thereby integrating the coatings and the bonding material.  
      The invention also provides a method for producing a multi-color polymeric component using a mold having at least two pieces. The method includes spraying a first piece of the mold with a polymeric coating having a first color. A second piece of the mold is sprayed with a polymeric coating having a second color. At least one of the coatings is sprayed when the first and second mold pieces are separated from each other. The two mold pieces are disposed in close proximity to each other, and a polymeric bonding material is sprayed on at least a portion of each coating, thereby forming a unitary structure.  
      The invention further provides a system for producing a multi-color polymeric component. The system includes a mold having at least two pieces separable from each other and configured to cooperate with each other to facilitate production of an integrated component. At least one robotic spray arm is configured to spray polymeric coatings on the at least two mold pieces, and further configured to spray a polymeric bonding material on at least a portion of each coating, thereby forming an integrated component. A controller is provided for controlling operation of the at least one robotic spray arm such that a first piece of the mold is sprayed with a coating having a first color, and a second piece of the mold is sprayed with a coating having a second color. At least one of the coatings are sprayed when the first and second mold pieces are separated from each other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of a split mold for use in accordance with the present invention;  
       FIG. 2  is a flowchart illustrating a method of the present invention;  
       FIGS. 3A and 3B  show a cross-sectional view of a two-piece mold used in accordance with the present invention;  
       FIG. 4  shows a two-color polymeric skin produced using the present invention;  
       FIG. 5  shows a cross-sectional view of a three-piece mold for use in accordance with the present invention;  
       FIG. 6  shows a three-color polymeric skin produced in accordance with the present invention; and  
       FIG. 7  shows a simplified schematic of a system used in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)  
       FIG. 1  shows a mold  10  that can be used in accordance with a system and method of the present invention. The mold  10  includes a first piece  12  and a second piece  14 . As indicated by the directional arrow, the second mold piece  14  is movable along slides  16 ,  18 . In this way, the two mold pieces  12 ,  14  can be separated or abutted against one another. As described below, the use of a split mold, such as the mold  10 , facilitates the production of a two-color component.  
      The first mold piece  12  includes a first cavity  20 , and the second mold piece  14  includes a second cavity  22 . As shown in  FIG. 1 , the mold cavities  20 ,  22  do not include component details; however, a mold cavity can be produced with many details, having a net shape, or near net shape, of a finished component. The mold  10  can be manufactured from any material, or materials, which facilitate the molding of a finished component. Because of their durability, nickel alloys have been found to be particularly well suited for use in molds, such as the mold  10 . In addition, a nickel alloy mold can be produced with a surface texture that provides a finished appearance for the molded component. For example, surfaces  24 ,  26  of mold cavities  20 ,  22  can be produced with a textured finish that will be molded into the finished component. Thus, if a particular texture is desired on the finished component, surfaces  24 ,  26  can be produced with a negative of that surface, so that the molded component has the desired texture without additional processing.  
       FIG. 2  shows a flowchart  28  illustrating a method in accordance with the present invention. With reference to the mold shown in  FIG. 1 , the first step  30  of the method includes spraying a release agent in each of the cavities  20 ,  22  of the mold pieces  12 ,  14 . The release agent may be any material, including those currently used in the art, which facilitates easy removal of the molded component after the molding process is complete. For example, a silicone based material can be used to facilitate removal of the molded component, while not interfering with a chemical bonding of the polymeric components used in the molding process. At step  32 , the first mold piece  12  has applied to it a coating having a first color. Various different types of coatings may be used in an IMC process, for example, a polymeric material having aliphate triiscocynate and polyols has been found to be effective.  
      When the coating is sprayed onto the first mold piece  12 , the two mold pieces  12 ,  14  are separated from each other, as shown in  FIG. 1 . The illustration in  FIG. 1  is greatly exaggerated, however, in that the two mold pieces  12 ,  14  can be separated by as little as one inch or smaller when the coating is applied to the first mold piece  12 . Some care must be taken to avoid overspray, so that the coating is not inadvertently applied to the second mold piece  14 . Controlling the application of the coating to the first mold piece  12 , thereby allowing the mold pieces  12 ,  14  to be separated by a very small gap, facilitates rapid closing of the mold pieces  12 ,  14  in the next step.  
      At step  34 , the mold pieces  12 ,  14  are brought in close proximity to each other, in fact, abutting one another. Movement of the second mold piece  14  along the slides  16 ,  18  can be effected with an actuator, which is particularly beneficial for large molds. As shown in  FIG. 1 , the smaller of the two mold pieces—i.e., the second mold piece  14 —is moved toward the large mold piece  12 . Of course, a mold, such as the mold  10 , can be configured such that both mold pieces move toward each other simultaneously. After the two mold pieces  12 ,  14  are brought together, the second mold piece  14  has a coating applied to it that has a second color—i.e., a color different from the color of the coating applied to the first mold piece  12 .  
      When the coating is applied to the first mold piece  12 , care is taken to ensure that overspray does not contact the second mold piece  14 . When the coating having the second color is applied to the second mold piece  14 , no such precautionary measures are required. This is because the appearance surface of the finished component is at the interface of the mold  12  and the coating. Thus, if a second coating is sprayed into the cavity  24  of the first mold piece  12 , it will merely coat the back side of the first coating, and will not be visible when the finished component is used in its final application. Of course, a coating may be applied to the second mold piece  14  prior to the two mold pieces  12 ,  14  being brought together, if desired. After the second mold piece  14  is coated, a bonding material, or substrate, is sprayed into the mold  10  to cover both of the coatings. As with the coatings, different materials may be used for the substrate; however, polymeric materials including polyurethanes have been found to be effective. Such a material can cross-link with the coatings, thereby integrating the coatings and the substrate into a unitary structure.  
      When the coatings and the substrate have cured, a skin is formed which can be removed from the mold  10 —see step  40 . At this point, the desired two-color component is complete; however, for many uses, it will be desirable to further process the skin. For example, at step  42 , a substrate may be sprayed on the bonding material to facilitate application of a structural foam at step  44 . This additional processing provides a relatively stiff component having desired structural characteristics, with a two-color surface finish having the texture of the mold cavity surfaces, such as the surfaces  24 ,  26 .  
       FIGS. 3A-3C  schematically illustrate some of the method described in the flow chart  28  in  FIG. 2 . Shown in cross section is a mold  45 , having first and second mold pieces  46 ,  48 , which are initially separated from each other. The two mold pieces  46 ,  48  are then brought together as shown in  FIG. 3B . A second coating  52  is applied to the second mold piece  48 . Although the second coating  52  is applied after the mold pieces  46 ,  48  are brought together, it may, alternatively, be applied while the mold pieces  46 ,  48  are still separated. Moreover, although the coating of the two mold pieces  46 ,  48  is described sequentially, the process may be configured such that both coatings are simultaneously applied. After the coatings are applied, a bonding material, or substrate,  54  is applied to both coatings  50 ,  52 —see  FIG. 3C . Once the substrate  54  and the coatings  50 ,  52  are cured, an integrated, unitary structure, or skin  56 , is the result—see  FIG. 4 .  
      As shown in  FIG. 4 , the skin  56  has a finished appearance surface  58  which comprises two differently colored surfaces  60 ,  62 . Because the skin  56  is made from polyurethane materials, it will have a certain amount of flexibility and/or elasticity. Thus, the skin  56  may be deformed somewhat prior to the application of an additional substrate and foam structural material for the forming of a component, such as a vehicle instrument panel. In such an application, the surfaces  60 ,  62  would be outwardly facing the interior of the vehicle, thereby providing an aesthetically pleasing, multi-color interior component.  
      It is worth noting that the method described above it not limited to components having two colors; rather, components having any number of different colors can be produced with the present invention. For example,  FIG. 5  shows a mold  64  having three mold pieces  66 ,  68 ,  70 . With this configuration, a three-color component can be produced using steps similar to those described above. In such a method, coatings having three different colors would be applied to the respective mold pieces. At least two of the coatings would be applied when at least some of the mold pieces are separated from each other, for example, as shown in  FIG. 5 . The mold pieces  66 ,  68 ,  70  could then be brought together, and the third coating and/or a bonding material would be applied to each of the coatings to form a unitary structure.  
      As shown in  FIG. 6 , the skin  72  created using the mold  64 , shown in  FIG. 5 , includes an appearance surface  74  comprising surfaces  76 ,  78 ,  80 , each of which has a different color. As shown in  FIG. 6 , the skin  72  has a shallower profile than the skin  56  shown in  FIG. 4 , and therefore may be suitable for the production of an automotive door panel. In such an application, the surfaces  76 ,  78 ,  80  would each face the interior of the vehicle, thereby presenting an integrated multi-color door panel to the vehicle occupants.  
       FIG. 7  shows a system  76  for utilizing the methods described above. The system  76  includes first and second work stations  78 ,  80 . Although the methods described above are conveniently performed with a system having two workstations, all of the processes can be integrated into a single workstation, or more than two workstations, as desired. The first workstation  78  includes three robotic spray arms  82 ,  84 ,  86 , all of which are controlled by a single controller, or control unit  88 . Alternatively, each robotic spray arm  82 ,  84 ,  86  may have a separate control unit. Because each of the spray arms  82 ,  84 ,  86  apply a different material, it is convenient to use three separate spray arms; however, a single robotic spray arm may be configured to perform all three functions.  
      The first spray arm  82  is configured to spray first and second pieces  90 ,  92  of a mold  94  with a release agent, as described above. The second spray arm  84  is configured to spray the first mold piece  90  with a coating having a first color. The first and second mold pieces  90 ,  92  are then brought together by a an actuator, such as the pneumatic cylinder  96 . Of course, other types of actuators can be used, such as hydraulic cylinders or electric motors. A coating having a second color is then sprayed by the third spray arm  86  on the second mold piece  92 . After the coatings are applied to the first and second mold pieces  90 ,  92 , they are moved to the second workstation  80  via an overhead conveyor  98 .  
      Once the mold  94  is at the second workstation  80 , a fourth robotic spray arm  100  is used to apply a bonding material to the coatings, thereby forming an integrated component, or skin. As shown in  FIG. 7 , the fourth robotic spray arm has its own control unit  102 , for controlling application of the bonding material. The foregoing method may also be carried out by a system that includes a single control unit configured to control a single robotic arm that is used to apply each of the various materials to a mold, such as the mold  94 . Moreover, such a robotic spray arm may be configured to apply more than two different colored coatings to a multi-piece mold, such as the three-piece mold  64 , shown in  FIG. 5 . As described above, a skin produced by a system, such as the system  76  shown in  FIG. 7 , can then be further processed by applying additional materials, such as a structural foam, to create an automotive component.  
      While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.