Method and apparatus for molding parts

Abstract

A method and apparatus for injection molding plastic parts is described. In one embodiment, at least two materials are simultaneously injected into a mold. The resulting molded part can include at least two different regions. Each region can have distinct physical properties. Positions of the regions within the molded part can be at least partially controlled by controlling flow fronts of the at least two materials within the mold.

What is claimed is: 
     
         1 . A method for molding a uniform part with non-uniform physical properties, the method comprising:
 selecting a first material;   selecting a second material, wherein the second material has at least one different physical property than the first material;   simultaneously injecting the first and second materials into a mold; and   controlling flow fronts of the first and second materials in the mold.   
     
     
         2 . The method of  claim 1 , further comprising:
 producing a uniform molded part with a first region having a first physical property and a second region having a second physical property different from the first physical property.   
     
     
         3 . The method of  claim 1 , wherein the first material is injected through a first gate and the second material is injected through a second gate. 
     
     
         4 . The method of  claim 1 , wherein the first and second materials are plastic resins. 
     
     
         5 . The method of  claim 4 , wherein the first material includes a glass filler. 
     
     
         6 . The method of  claim 1 , wherein the flow fronts determine positions of the physical properties on the part 
     
     
         7 . The method of  claim 1 , the controlling flow fronts comprising:
 controlling positions of the first gate and the second gate on the mold;   controlling injection pressure of the first and second materials; and   controlling temperatures of the first and second materials.   
     
     
         8 . The method of  claim 2 , wherein the first region has a different stiffness from the second region. 
     
     
         9 . The method of  claim 2 , wherein the first region has a different hardness from the second region. 
     
     
         10 . The method of  claim 2 , wherein the first region has a different flexural strength from the second region. 
     
     
         11 . An apparatus for injection molding a part with non-uniform material properties, the apparatus comprising:
 a first hopper configured to hold a first material;   a second hopper configured to hold a second material;   a mold including a first gate and a second gate;   a first barrel, coupled to the first hopper and coupled to the first gate, the first barrel disposed between the first hopper and the first gate, the first barrel melting the first material;   a second barrel, coupled to the second hopper and coupled to the second gate, the second barrel disposed between the second hopper and the second gate, the second barrel melting the second material; and,   an injector controller coupled to the first and the second barrels, configured to coordinate the injection of the melted first and the second materials simultaneously into the mold.   
     
     
         12 . The apparatus of  claim 11 , wherein the first material has a different physical property than the second material. 
     
     
         13 . The apparatus of  claim 11 , wherein the first and second materials are plastic resins and the first material includes a glass filler. 
     
     
         14 . The apparatus of  claim 11 , wherein the molded part produced by the mold has a first region and a second region. 
     
     
         15 . The apparatus of  claim 14 , wherein the first region has at least one physical property different from the second region. 
     
     
         16 . An apparatus for injection molding a part with non-uniform material properties, the apparatus comprising:
 means for holding a first material;   means for holding a second material;   means for melting the first and second materials;   means for simultaneously injecting the first and second melted materials; and   means for receiving the injected first and second materials;   
     
     
         17 . The apparatus of  claim 16  wherein the simultaneously injecting the first and second melted materials comprises:
 means for controlling the injection of the first material through a first gate; and 
 means for controlling the injection of the second material through a second gate. 
 
     
     
         18 . The apparatus of  claim 16 , further comprising:
 means for controlling a flow front of the first melted material; and   means for controlling a flow front of the second melted material.