Apparatus and methods for die casting

Abstract

An apparatus and method for die casting includes a multi-part, reusable die having at least two die sections defining a die cavity for receiving molten material to be cast. The die sections are moveable relative to one another. Each die section defines a portion of the die cavity and the die sections define the die cavity when positioned in engagement with one another. A melting unit of the apparatus melts the material, and a shot sleeve receives molten material from the melting unit and is in fluid communication with the die. A plunger unit urges material from the sleeve into the die. The apparatus further includes a reduced pressure means, e.g., a vacuum unit, coupled to at least the die for providing a reduced pressure to at least the die cavity. A sealing mechanism of the apparatus is coupled to the die. The sealing mechanism engages the die sections to define an evacuation cavity, including at least the die cavity, when the die sections are brought into close proximity with one another, thereby enabling evacuation of the die while the die sections are in spaced relation and more thoroughly and completely evacuating the die cavity.

What is claimed is:  
     
         1 . An apparatus for die casting in which molten material is injected under pressure into a multi-part, reusable die, comprising: 
 a die including at least two die sections defining a die cavity for receiving molten material to be cast, the die sections being supportably moveable relative to one another, each die section defines a portion of the die cavity and the die sections define the mold cavity when positioned in engagement with one another;    a melting unit for melting the material;    a shot sleeve in fluid communication with the die for receiving molten material from the melting unit;    a plunger unit in sealing and moveable engagement with the shot sleeve for urging material from the sleeve into the die;    a reduced pressure means coupled to at least the die for providing a reduced pressure to at least the die cavity; and    a sealing mechanism coupled to the die, the sealing mechanism engaging the die sections to define an evacuation cavity including at least the die cavity when the die sections are brought into close proximity with one another, thereby enabling evacuation of at least the die cavity while the die sections are in spaced relation.    
     
     
         2 . The apparatus of    claim 1   , further comprising: 
 means for controllably supporting and moving the mold sections toward and away from one another; and    a controller for controlling movement of the supporting and moving means and the operation of the reduced pressure means, so that the die sections are moved into and supported in the spaced apart relationship while the reduced pressure means is operated to reduce the pressure within the die cavity prior to moving the die sections into engagement.    
     
     
         3 . The apparatus of    claim 1   , wherein at least one of the die sections defines a sealing channel, the sealing mechanism including a tubular sealing member coupled to the channel, whereby the sealing member engages the channel and the other die section when the die sections are positioned in the spaced apart relationship.  
     
     
         4 . The apparatus of    claim 3   , wherein the other die section includes a sealing shroud, the shroud engaging the sealing member.  
     
     
         5 . The apparatus of    claim 3   , wherein the tubular sealing member is hollow and resilient, and further comprising a source of compressed gas for selectively inflating the sealing member.  
     
     
         6 . The apparatus of    claim 3   , wherein the sealing member is composed of a fluoroelastomer.  
     
     
         7 . The apparatus of    claim 1   , further comprising a source of compressed gas coupled to the sealing mechanism, wherein the sealing mechanism includes an inflatable, resilient sealing member.  
     
     
         8 . The apparatus of    claim 7   , wherein the sealing member is inflatable up to a thickness of about 1 inch.  
     
     
         9 . The apparatus of    claim 1   , wherein the sealing mechanism enables evacuation of the die cavity when the die sections are separated by less than about 1 inch.  
     
     
         10 . A method of die casting in an apparatus having a die composed of at least two cooperating die sections defining a die cavity and being moveable relative to one another, each die section having a mating surface positioned in opposing relationship to one another, a melting unit for melting the material, a shot sleeve for receiving molten material from the melting unit and in fluid communication with the die, a plunger unit urging material from the sleeve into the die, and vacuum unit coupled to at least the die for providing a reduced pressure to at least the die cavity, comprising the steps of: 
 providing a sealing member on a mating surface, the sealing member extending around at least the die cavity;    moving the die sections into close proximity such that the sealing member engages the other mating surface and the mating surfaces are in close proximity but spaced relation;    evacuating the die cavity while the die sections are in close proximity but spaced relationship;    moving the die sections such that the mating surfaces engage one another to define the die cavity; and    injecting molten material into the die cavity.    
     
     
         11 . The method of    claim 10   , further comprising the step of: 
 controlling movement of the supporting and moving means and the operation of the reduced pressure means, so that the die sections are moved into and supported in the spaced apart relationship while the reduced pressure means is operated to reduce the pressure within the die cavity prior to moving the die sections into engagement.    
     
     
         12 . The method of    claim 10   , wherein the tubular sealing member is hollow and resilient, and further comprising the step of selectively inflating the sealing member.  
     
     
         13 . The method of    claim 10   , wherein during the step of evacuating the sealing mechanism enables evacuation of the die cavity when the die sections are separated by less than about one inch.  
     
     
         14 . The method of    claim 10   , further comprising the step of: 
 ejecting the part from the die cavity.    
     
     
         15 . A method of die casting with a reduced cycle time in an apparatus having a die composed of at least two cooperating die sections defining a die cavity and being moveable relative to one another, each die section having a mating surface positioned in opposing relationship to one another, a melting unit for melting the material, a shot sleeve for receiving molten material from the melting unit and in fluid communication with the die, a plunger unit urging material from the sleeve into the die, and vacuum unit coupled to at least the die for providing a reduced pressure to at least the die cavity, comprising the steps of: 
 providing a sealing member on a mating surface, the sealing member extending around at least the die cavity;    moving the die sections into close proximity such that the sealing member engages the other mating surface and the mating surfaces are in close proximity but spaced relation;    evacuating the die cavity while the die sections are in close proximity but spaced relationship; and    moving the die sections such that the mating surfaces engage one another.    
     
     
         16 . The method of    claim 15   , further comprising the step of: 
 injecting molten material from the sleeve into the die cavity.    
     
     
         17 . The method of    claim 10   , wherein the sealing member is hollow and resilient; and further comprising the step of inflating the sealing member prior to the step of moving the die sections into close proximity.