Injection Molding Process for Molding Mechanical Interlocks Between Molded Components

Abstract

A two-shot or multi-shot multi-material injection molding process is provided. The process allows dissimilar materials to be injection molded to form a single, injection molded part by creating a structural interlock between the materials to prevent the materials from separating. The structural interlock is formed by forming at least one interlock cavity adjacent to a interfacial surface of a first portion of a molded part molded from a first material, and injecting a second, different material into the mold so that the second material flows into the interlock cavity and fills it. Solidification of the second material in the interlock cavity formed by the first material creates the structural interlock between the two materials.

1 . A method of molding a molded part formed from at least two materials comprising the steps of:
 (a) injecting a first molten material into a mold so that the first material forms a first portion of the molded part, the first portion of the molded part having an interfacial surface and at least one interlock cavity formed adjacent to the interfacial surface;   (b) injecting a second molten material into the mold such that the second material contacts the interfacial surface and flows into the interlock cavity adjacent to the interfacial surface, and   (c) allowing the second material to cool and solidify, whereby solidification of the second material in the interlock cavity forms a mechanical interlock between the first material and the second material that prevents the first and second materials from being separated.   
     
     
         2 . The method of  claim 1 , wherein the interlock cavity has an opening at the interfacial surface that is less than the diameter of the interlock cavity. 
     
     
         3 . The method of  claim 2 , wherein the interlock cavity has an opening at the interfacial surface that is less than one-half the diameter of the interlock cavity. 
     
     
         4 . The method of  claim 1 , wherein the interlock cavity is closed by a wall formed from the first material, the wall having a thickness in the range of about 0.005 to about 0.010 inches, and wherein fill pressure from the injection of the second material into the mold breaches the wall to permit the second material to flow into the interlock cavity. 
     
     
         5 . The method of  claim 1 , wherein the first portion of the molded part has a plurality of interlock cavities formed adjacent to the interfacial surface. 
     
     
         6 . The method of  claim 1 , wherein at least one of the first or second materials comprises a thermoplastic polymer. 
     
     
         7 . The method of  claim 1 , wherein the first and second materials are dissimilar. 
     
     
         8 . The method of  claim 1 , wherein the first and second materials are similar. 
     
     
         9 . The method of  claim 1 , wherein the first material comprises a polycarbonate resin and the second material comprises a desiccant entrained polymer. 
     
     
         10 . The method of  claim 1 , wherein at least one of the first or the second materials comprises a desiccant entrained polymer. 
     
     
         11 . The method of  claim 10 , wherein the desiccant entrained polymer comprises at least one polymer and a desiccant. 
     
     
         12 . The method of  claim 11 , wherein the desiccant entrained polymer comprises at least two immiscible polymers and a desiccant. 
     
     
         13 . The method of  claim 1 , wherein the at least one interlock cavity is formed by a pin inserted into the mold. 
     
     
         14 . The method of  claim 1 , wherein the first and second materials are injection molded in a two-shot injection mold. 
     
     
         15 . The method of  claim 1 , wherein the first and second materials are injection molded in an overmolding process. 
     
     
         16 . An injection molded part formed from at least two materials comprising:
 (a) a first material that forms a first portion of the molded part having an interfacial surface and at least one interlock cavity formed adjacent to the interfacial surface;   (b) a second material that forms a second portion of the molded part such that the second material contacts the interfacial surface and fills the interlock cavity adjacent to the interfacial surface, thereby forming a mechanical interlock between the first material and the second material that prevents the first and second materials from being separated.   
     
     
         17 . The injection molded part of  claim 16 , wherein the mechanical interlock has a neck that is narrower than the diameter of the interlock cavity. 
     
     
         18 . The injection molded part of  claim 16 , wherein the first portion of the molded part has a plurality of cavities formed adjacent to the interfacial surface. 
     
     
         19 . The injection molded part of  claim 16 , wherein at least one of the first or second materials comprises a thermoplastic polymer. 
     
     
         20 . The injection molded part of  claim 16 , wherein the first and second materials are dissimilar. 
     
     
         21 . The injection molded part of  claim 16 , wherein the first and second materials are similar. 
     
     
         22 . The injection molded part of  claim 16 , wherein the first material comprises a polycarbonate resin and the second material comprises a desiccant entrained polymer. 
     
     
         23 . The injection molded part of  claim 16 , wherein at least one of the first or the second materials comprises a desiccant entrained polymer. 
     
     
         24 . The injection molded part of  claim 23 , wherein the desiccant entrained polymer comprises at least one polymer and a desiccant. 
     
     
         25 . The injection molded part of  claim 24 , wherein the desiccant entrained polymer comprises at least two immiscible polymers and a desiccant.