Patent Publication Number: US-2016243739-A1

Title: Injection-Molding Tool with Integrated Air Jets

Description:
TECHNICAL FIELD 
     The present disclosure relates to injection-molding tools. 
     BACKGROUND 
     Automotive components may be produced by injection-molding processes. In conventional injection molding, a resin material is injected into a part cavity defined by a plurality of dies. After molding, the part typically under goes secondary processing, such as painting, film, or plating. 
     In mold-in-color plastic-injection molding a class “A” finished surface is created during the injection-molding process and secondary processing is not preformed. Because there is no secondary processing, any defects formed during molding of the component cannot be fixed and the component must be scrapped. 
     SUMMARY 
     According to one aspect of this disclosure, an injection-molding tool includes a first die having a first surface, and a second die having a second surface. The first and second surfaces cooperate to define a part cavity when the tool is closed. The tool also includes at least one jet disposed on the first surface for blowing gas toward the second surface to remove debris from the second surface. The injection-molding tool may include ejector pins extendable out of the first surface for ejecting and trimming an injection-molded part. The at least one jet may be activated subsequent to the actuation of the ejector pins to remove any debris created during trimming of the part. 
     According to another aspect of this disclosure, a method is disclosed for operating an injection-molding tool. The tool includes first and second dies that each have a tool face. At least one jet is disposed on one of the first and second dies. The method includes the steps of closing the dies to form a part cavity defined by the tool faces, and injecting resin into the cavity. The method further includes cooling the part, opening the cavity allowing removal of the part, and blowing compressed gas through the jets to remove debris from the tool faces. The method may also include the steps of ejecting the part and trimming excess material from the part with one or more ejector pins. The blowing step may be performed after the trimming step. 
     According to yet another aspect of this disclosure, an injection-molding tool includes a mold cavity having a first tool surface, and a mold core having a second tool surface. The first and second tool surfaces cooperate to at least partially define a part cavity when the tool is closed. A cooling plate is disposed adjacent to the mold cavity on a side opposite the mold core. The cooling plate includes coolant channels. At least one jet is disposed on the second tool surface for blowing gas toward the first tool surface to remove debris from the second surface. The mold core may include ejector pins extendable out of the second tool surface for ejecting a part and trimming runners from the part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of an injection-molding tool with first and second dies closed and with a cooling plate in a disengaged position. 
         FIG. 2  is a schematic cross-sectional view of the injection-molding tool with the first and second dies closed and with the cooling plate in an engaged position. 
         FIG. 3  is a schematic cross-sectional view of the injection-molding tool with the first and second dies open. 
         FIG. 4  is a flow chart illustrating steps for molding a part using the injection-molding tool from  FIGS. 1 to 3 . 
         FIG. 5  is a zoomed-in perspective view of the injection-molding tool illustrating an ejector pin and a runner of the part. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     Referring to  FIGS. 1, 2, and 3 , an injection-molding tool  20  is illustrated. The injection-molding tool  20  may be configured to create a part having a finished surface that does not require secondary operations, such as painting. The tool  20  is schematically illustrated and some ancillary equipment that may be required to completely form a part through an injection-molding process are omitted. 
     The tool  20  includes a first die (or mold core)  22  and a second die (or mold cavity)  24 . The first die  22  includes a tool surface  26  and the second die  24  includes a tool surface  28 . The first and second dies  22 ,  24  are movable relative to each other between an open position (illustrated in  FIG. 3 ) and a closed position (illustrated in  FIGS. 1 and 2 ). When in the closed position, the tool surfaces  26  and  28  cooperate to at least partially define a part cavity  30 . The first die  22  may define an injector port  32  providing access into the part cavity  30 . An injector  34  injects a resin material into the injector port  32  and subsequently into the part cavity  30  via subgates. The resin material is heated to a predefined temperature by a heater (not shown) prior to injection. The injected resin material is then allowed cool into a hardened part  36 . The tool  20  may include cooling devices to speed up the hardening time of the resin. For example, the tool  20  includes a cooling plate  27  disposed against the second die  24 . The cooling plate  27  defines coolant channels  38  configured to circulate coolant through the plate  27 . The first die  22  may also include cooling channels  40 . In some embodiments, the second die  24  and the cooling plate  27  are combined into a single part. After the part has hardened, the first and second dies open and the part  36  is ejected via one or more ejector pins  42 . 
     The tool  20  may be configured to produce mold-in-color parts. Mold-in-color parts exit the injection-molding tool with a finished surface and do not require any secondary operations—such as painting or plating. Because mold-in-color parts do not undergo secondary operations, any defects created on the class-A surface during injection molding cannot be fixed and the defective part must be scrapped. To reduce part defects, the tool  20  may include heating elements  44 . The heating elements  44  may be disposed in the second die  24  adjacent to tool surface  26 , which is the tool surface that forms the class-A surface of the part. The heating elements  44  maintain the tool surface  26  at a temperature near or above the glass transition temperature of the injected resin to prevent premature cooling of the resin as it enters the part cavity  30 . This helps to reduce defects formed during injection molding of the part  36 . The heating elements  44  may be electric heating elements, or may be heated by other methods, such as steam or gas. 
     Referring to  FIG. 4 , a flow chart illustrating one example of an injection-molding process is shown with reference to  FIGS. 1 through 3 . At step  100  the first and second dies  22 ,  24  are in the open position and the heating elements  44  are activated to heat tool surface  26 . The second die  24  is heated in isolation to reduce the size of the heat sink and shorten heating times and reduce the energy required. After the second die  24  is heated to a desired temperature, the dies  22 ,  24  are closed forming the part cavity  30  at step  102 . At step  104  resin is injected into the part cavity  30 . At step  106  the cooling plate  27  is closed around the second die  24  to cool the resin into a hardened part  36 . At the same time, coolant may be circulated through coolant channels  40  of the first die  22  to further facilitate hardening of the resin. The cooling plate  27  is retracted from the second die  24 , and the first and second dies  22 ,  24  are opened at step  108  after the resin has hardened forming a part  36 . 
     At step  110  the part  36  is ejected from the tool  20  by one or more ejector pins  42 . As best seen in  FIG. 5 , at least one of the ejector pins  42  is arranged to eject the part  36  and simultaneously sheer the runner  46  from the part  36  during ejection. Each of the ejector pins  42  may include a cutting surface  48  engageable with one of the runners  46  to sheer the runner  46  from the part  36 . Sheering the runner can create debris that settle onto the tool surfaces  26 ,  28 . If any of the debris remain on the tool surface  28  during subsequent injection molding, the class-A surface of the part  36  can be blemished. If the part  36  is a mold-in-color part, the blemish cannot be fixed, and the part must be scrapped. 
     The tool  20  includes gas jets  48  for blowing the debris off of one or more of the tool surfaces  26 ,  28  at step  112 . The gas jets  48  are configured to blow compressed gas, such as air, nitrogen, oxygen or any other type of gas. The gas jets  48  may be disposed on the tool surface  26  of the first die  22 . The gas jets  48  may be aimed to blow gas at tool surface  28 . Each of the gas jets  48  includes a supply line  50  for receiving compressed gas. The supply lines  50  link the jets  48  in fluid flow communication with a compressor  52 . The compressor  52  may include a gas storage tank for holding compressed gas. The compressor  52  may be disposed on the first die  22  or may be separate from the tool  20 . 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.