Abstract:
A tool for manufacturing a multi-colored plastic automotive part, such as a door panel, is manufactured using multiple molding shots without opening the mold between each shot. The door panel comes out finished with no scuffing, warping, or shrinkage. The process for manufacturing the panel includes selectively locating spacers within the tool to a first position and then injecting a first material. The parting line is held closed while the spacers are then advanced to a second position so as to set the inner insert to a desired second shot wall thickness position. A second shot of material is then introduced into the rear of the injection unit through an opening in the first shot part. The process can be repeated for additional colors and materials to create a multi-colored or even multi-material final assembly. Once the part is cured, it is ejected and the process is complete.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage of International Application No. PCT/IB2004/003067, filed Jun. 24, 2004 which claims priority to Patent application Ser. No. 60/480,966 filed on Jun. 24, 3003. 
     FIELD OF THE INVENTION 
     The present invention relates generally to a process of molding a plastic part comprised of more than one material, and to an injection molding tool for making a part such as but not limited to a door panel that is made with multi-colored or multi-material parts. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     It is well known to use the process of injection molding for creating plastic parts that are used in the automotive industry. Typical molding processes will use a single-colored plastic part that has consistent coloring throughout the entire part. Interior automotive components, such as door panels, traditionally use one color throughout the entire door panel. However, the appearance is not aesthetically appealing. Alternatively, door panel assemblies were created comprising separate inter-connectible parts having one or more colors that fit together to make a final door panel assembly. However, these conventional practices have problems such as the multiple door panel components not fitting together with a clean fit once the assembly is completed. Thus, it would be desirable to overcome these problems. 
     One of the previous methods of making a multi-colored part utilizing an injection molding machine required machine tooling that had numerous working parts that were necessary for each step of the color molding process. These machines were capable of injection molding parts that have different materials as well. Other methods of manufacturing multi-colored and multi-material plastic parts utilized large band areas, that is the area separating different portions of the plastic part from the rest of the colored plastic part. The band surrounds each object to be covered differently, but the problem with the band areas is that they inherently create dead spots from which non-reflective areas are created. If a reflective part is desired, it would be undesirable to have these dead spots since it is preferred to maximize reflective areas. 
     Another method of injection molding plastic parts includes the rotary method where the mold is rotated between the shot processer so as to create multiple colored parts. However, rotary machines require large tonnage and hence significant capitol investment. 
     Accordingly, it is desirable to provide a tool for manufacturing multi-colored plastic parts and multi-material plastic parts that reduce scuffing, warpage and shrinkage. It is also desirable to provide a tool for use in injection molding a multi-colored part through a one step process of not opening the mold during the creation of different colored sections of the final part. It is also desirable to provide a tool that is operable to injection mold a part made of multiple materials that can be injection molded in a single process without opening the mold when the different materials are being shot. Thus, it is preferred to maintain the parting line closed which will reduce scuffing, warpage and shrinkage. 
     One aspect of the invention includes an improved mold having a pair of clamping plates, a cavity block, a core block, an inner-insert mechanism assembly comprised of retainer pins, retainer slides and slide holders, a spacer mechanism, a moving mechanism retainer plate for holding the spacers in place, springs positioned between the core block and the retainer plate, a clamp plate, an ejector retainer plate, an ejector plate, a manifold retainer plate, a manifold plate, a first shot manifold assembly, a second shot manifold assembly, ejector cylinders, a set of full length parallels, and cylinders for advancing the spacers. 
     It is also desirable to provide a process of manufacturing a multi-colored part, such as a multi-colored door panel, that overcomes the previously mentioned disadvantages. It will be appreciated that said process can be used on a variety of interior and exterior automotive components, and is not limited to the door panel described herein, which is discussed for illustrative purposed only and is not intended to limit the present invention. It is also desirable to provide a process of manufacturing a multi-colored and multi-material part that decreases cycle time, yet increases part quality, and has improved gas removal during the molding process in order to minimize imperfections in the surface of the part. It would also be desirable to provide a process which results in reducing the amount of scrap material. It is also desirable to provide an improved process of manufacturing a multi-colored part that has improved tolerances with a cleaner fit between the various colored and materialed components within the final part. 
     According to another aspect of the present invention, a process of making a multi-colored injection molded part includes the steps of providing a mold, closing the mold, injecting plastic of a first color into the mold to create a first part, releasing the machine clamp pressure, adjusting a spacer mechanism to offset an inner-insert from the cavity of the first shot, applying tonnage and then injecting plastic of a second color to another part of the mold to create a second part, and opening the mold and ejecting the completed part. The entire process is performed while maintaining the parting line closed. 
     Another aspect of the present invention includes a multi-colored part, for example a door panel assembly, with a first portion made of a first type of material, for example, of one color, or of one type of material, and a second portion made of a different material or of a different color. The assembly is made through an injection molding process where the parting line of the mold stays closed during the creation of both parts in order to create the final assembly. Thus, shrinkage and warpage issues are minimized, enhancing fit and quality of the final assembly. 
     For the following specification taken in conjunction with the accompanying drawings, independent claims, other objects, features, and advantages, the present invention will become apparent to those skilled in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side sectional view of a mold for making a door panel, illustrating the present invention with the spacer and inner-insert assembly, when located in the first shot position. 
         FIG. 2  is a front view section of the figure one mold, illustrating the four spacers and inner-insert assembly, when in the first shot position. 
         FIG. 3  is an enlarged side view of the spacer mechanism shown in figure one, while in the first shot position. 
         FIG. 3A  is an enlarged view taken from the circle  3 A of  FIG. 3 , showing the first shot part relative to the core block, inner insert and cavity block. 
         FIG. 4  is an enlarged side view of the spacer mechanism advanced to the right which is the second shot position. 
         FIG. 4A  is an enlarged view taken from the circle  4 A of  FIG. 4 , showing the second shot part relative to the first shot part. 
         FIG. 4B  is an enlarged view taken from circle  4 B of  FIG. 4  (shown out of position), showing the second shot gate. 
         FIG. 5  is a top view of the mold of the present invention showing the spacer mechanisms relative to the hydraulic cylinders, retractor pins and inner insert. 
         FIG. 6  is a completed two-colored molded door panel utilizing the process of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates an injection molding tool  10  for making a multi-colored or multi-materialed part  12 . For illustration purposes only, the following discussion is of a mold  10  for making an automotive door panel  12  which is illustrated in  FIG. 6 . It will be appreciated that the present invention can be utilized for making a wide variety of components where it is desireable to have a single part comprised of more than one material. It will be appreciated that the materials can be made of polypropylene, polycarbonate, TPO, and others. Moreover, the present invention is operable to make finished parts having multi-colors and/or multiple textures. Further, the present tool allows an operator to run two or more shots without opening the mold during the molding process. 
     With continued reference to  FIG. 1 , the injection tool  10  includes a lower clamp plate  14  and an upper clamp plate  16 . Affixed to the lower clamp plate  14  is a mechanism retainer plate  18  with a spacer gap  20 . A mounting pad  22  is affixed to the lower clamp plate  14  and supports a means for activating a spacer. For example, hydraulic cylinders  24  are secured to the mounting pad  22  and as illustrated in  FIG. 5 , three separate hydraulic servers  24  are provided for imparting uniform pressure on a spacer mechanism assembly  26 . Rod extensions  28  interconnect each hydraulic cylinder  24  to the spacer mechanism assembly  26 . 
     As illustrated in  FIGS. 1 ,  2  and  5 , the spacer mechanism assembly  26  includes a driver  30  that is connected to the rod extensions  28  on one side, and to a set of four spacers  32  that traverse within four separate gib assemblies  34  within the mechanism retainer plate  18 . Each spacer  32  has a T-shaped portion for sliding within the gib assemblies  34  when the hydraulic cylinders  24  impart motion thereto. A stationery spacer  36  is in each of the locating gib assemblies  34  and stationery spacer  36  is housed within a lower recess  38  of the core  40 . The stationery spacer  36  has corners  42  and together the spacers  32  and  36  make metal to metal contact when the spacers  32  advance to the right (second shot position) after the clamp tonnage has been re-applied. Spacer  32  is shown in the first shot position in  FIGS. 1 and 3 . 
     The tool  10  further includes a core  40  which is one half of the mold and it receives a retractor or a inner insert  44  with a finished surface  46 . The inner insert  44  is positioned at an angle to cause both a vertical and horizontal displacement in order to allow for the space required for the second injection shot. The inner insert mechanism assembly  44  is the part of the mold that the plastic is injected against in order to create a part, and in this instance, the part is an automotive interior door panel. The inner insert mechanism assembly  44  includes four retainer pins  50 , four retainer slides  52  and four slide holders  54 . The insert assembly  44  is secured to the moving mechanism retainer plate  18  while the core  40  moves relative thereto. This arrangement allows the spacer mechanisms  32  to slide relative to the moving mechanism retainer plate  18 . 
     With reference to  FIG. 2 , the tool  10  further includes a set of parallels  56  positioned above the cavity block  48 , an ejector retainer plate  58 , an ejector plate  59 , a set of ejector cylinders  60 , a manifold plate  62  and a clamp plate  64 . The ejector plate  59  and ejector retainer plate  58  are connected through tee slots to the manifold retainer plate  61 . The hydraulic ejector cylinders  60  are attached to the ejector plate  58  and they help eject the part  12  when the process is finished (during the ejection stage). The parallels  56  are located on each side of the ejector plate and ejector retainer plate. On one side one parallel is attached to the manifold retainer plate and the opposite parallel is only attached to the manifold retainer plate. The parallel height minus the ejector plate thickness determines the ejector stroke. The empty space within the mold provides the ejection stoke. Within the manifold plate  62  are standard heaters and flow channels that make up a manifold assembly  66  which includes first shot injector nozzle assembly  68  and a second shot injector assembly  70 . The material flows from the machine nozzle through the manifold, down the nozzle drops, through the runners and in to the part. The material injected first could be polypropylene and the second could be thermo plastic elastomer (TPE). Heaters surround the outside diameter of the nozzles to keep the plastic in a liquid state until it reaches the runners. 
     A set of coil springs  72  are positioned within the moving mechanism retainer plate  18  as shown in  FIGS. 2 and 5 . The springs  72  maintain an upper biasing force against the core block  40  to maintain the parting line  74  closed during the molding process. Maintaining the parting line  74  closed during the first shot and second shot processes is critical to the present invention. It will be appreciated that other means for biasing the core  40  upward, can be contemplated. For example, hydraulic mechanisms can be applied in order to maintain the upper biasing pressure so as to maintain the parting line closed during the molding process. Shifting the mechanical components within the mold while maintaining the parting line closed during the entire injection process, allows for reduced shrinkage, flashing and warpage of the final part  12 . 
       FIG. 2  is a front sectional view of the tool  10  illustrating the various components of the present invention. Each spacer mechanism  32  is shown juxtaposed to gib  34  which in turn is secured to the spacer cavity  34  by fasteners  78 . 
     The tool  10  has three separate nozzles, nozzles  68  for the first shot and nozzle  70  for the second shot. It will be appreciated that the present invention contemplates being operable in environments where more than two colors or more than two different materialed parts can be made, and therefore, additional ejector nozzles are contemplated. 
       FIG. 3  illustrates the  FIG. 1  embodiment in greater detail where the inner insert assembly  44  has a set of four retainer pins  50 , (only two shown in the  FIG. 3  side section), wherein at that the distal end  80  of each retainer pin, a bolt  82  is threaded thereto for securing the inner insert  44  to the retainer slide  52 .  FIG. 3  further illustrates the first shot part  84  after it has been injection molded, with the parting line  74  maintained in the closed position. 
       FIG. 3A  further illustrates the first shot part  84  after the first injection step. A recess  86  provides a void or cavity for the second shot material to be inserted during the second shot process. The outer surface  88  of the first shot part  84  has a butting edge  90  that will mate with a corresponding butting edge of the second shot material. It will be appreciated that overlapping edge designs could be employed as well. 
       FIG. 4  illustrates the tool  10  in the second shot position  92 . This is accomplished by first dumping the clamp tonnage and opening the press to the desired distance which separate spacers  32  and  36 . Hydraulic cylinders  24  can now impart motion in the direction of arrow  94  by advancing the spacer mechanism assembly  26 . The advancement of the spacer  32  now occurs which allows it to be repositioned under the stationery spacer  36 . The press is then closed and the tonnage is then reapplied thus separating core  40  from the mechanism retainer plate  18 . This causes a gap split  98  between the core block  40  and the mechanism retainer plate  18 . This gap does not occur in the first shot position, as seen at closed split  100  of  FIG. 3 . Because the inner insert remains stationery, the core block  40  around it shifts the face  102  of the inner insert  44  in an amount equal to the recess which equals the second shot wall thickness as shown in  FIG. 3A . This defines the cavity for the second shot material to be injected into during the second shot phase. The clamp tonnage can now be re-applied at approximately 1500 tons. 
       FIG. 4A  illustrates the second shot part  104  after having been injected. It has an exterior finished surface  106  with a well bonded joint  108  or interface that butts up against the corresponding edge  90  of the first shot part  84 . The sections essentially fuse together during the molding cycle. 
       FIG. 4B  illustrates in detail the second shot gate configuration. Here the second shot injector  70  injects hot plastic through the runner  110  and then into the gate  112  for dispersion within the cavity  114 . Once injected, second shot part  104  is created adjacent to the first shot part  84 . The insert assembly  44  is shown relative thereto. 
       FIG. 5  illustrates a top view of the lower clamp plate  14 , the spacer mechanism assembly  26 , the moving mechanism retainer plate  18 , the four guides  71  and the inner insert assembly  34 . The moving mechanism retainer plate  18  is on the moving side of the press and thus shifts when the press is open. A split line  35  opens when the tonnage is dumped and press is opened to a desired height distance. Ten springs  72  extend above a surface of the mechanism retainer plate  18  and (in the uncompressed state) aid in maintaining pressure against the core block  40  so as to maintain the parting line  74  closed relative to the cavity block  48 . To return the tool  10  to the first shot position, the tonnage is dumped, the press is opened to the desired distance and then spacer mechanism  32  is shifted in a direction opposite arrow  94  so as to allow the core block  40  to shift in a downward direction to the position illustrated in  FIG. 3 . This device does not utilize any wedges. 
       FIG. 6  illustrates a completed part  12  comprised of at least two distinct materials. The first material  84  was injected during the first shot process, and the second material  104  was injected during the second shot process. The completed part  12  has not yet been trimmed or finished and the runners are still showing. It will be appreciated that the door panel  12  could be manufactured utilizing the present process to have more than two different materials or colors by employing the unique closed parting line process. 
     A description of the process of manufacturing a multi-colored or multi-materialed part utilizing the present invention will now be presented. With reference to  FIG. 3 , the spacer mechanism  32  is located in the first shot position after the tool  10  has closed. The parting line  74  maintains closure throughout the injection process. The first shot injector nozzle assembly  68  delivers a first material through the cavity block  48  to create a first shot part. The part starts to cool at this step of the process. The stationery cavity block  48  remains closed during this period. Next, the clamp tonnage is dumped and the press is opened to the desired distance. All movement is done by the moving side of the injection machine which is on the lower clamp  14  side of the tool  10 . Thus, clamp  14  and mechanism retainer  18  advance downwardly in the direction of arrow  96  ( FIG. 4 ) with the ram when tonnage is dumped. Next, spacer  32  is shifted in place by moving in the direction of arrow  94  ( FIG. 4 ). The press then closes and tonnage is reapplied. A separation or gap  98  then occurs between the mechanism retainer plate  18  and the core block  40  which results in the inner insert  44  to become off-set from the first shot part  84 . This off-set clearance  86  ( FIG. 3 ) in part defines the new cavity area for the material of the second shot part  104  to be molded into during the second shot process. 
     When the core  40  shifts, each biasing spring  72  continues to apply pressure against the core block  40  so as to maintain the parting line  74  closed continuously during the process. The clamp tonnage is now applied to the mold whereby a second set of materials can now be injected through second injector assembly  70  to create a second shot part  104 . A well bonded joint  108  is thereby created having a tight fit configuration. Because of the molding process, the two parts are essentially fused thus enhancing the appearance and fit. Once the part  12  cools, the mold is opened and the cylinder ejectors  60  cause the part  12  to be ejected. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the closed parting line invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with a particular example of a door panel, the true scope of the invention should not be so limited, since other modifications will become apparent to the skilled partitioner upon a study of the drawings, specification and following claims.