Micro injection molding machine

Abstract

A molding machine for molding microparts containing between 0.001 to 3.5 cubic centimeters of plastic shot volume includes a plasticizing portion operatively connected to an injection portion and a mold portion. A valve member is provided to open and close the connection between the plasticizing portion and the injection portion. A linear motor member is associated with the injection portion to permit molding times of 0.01 seconds at pressures up to about 100,000 psi during injection of the molten plastic into the mold portion.

We claims:  
     
         1 . An injection molding machine for molding microparts containing a plastic shot volume of between about 0.001 to 3.5 cubic centimeters, including in combination: 
 a mold portion axially movable relative to the molding machine between an open and closed position, said mold portion including a cavity plate member, a core plate member and ejector means to remove the molded micropart from said mold portion;    a plasticizing portion adapted to receive and melt plastic material, said plastic portion including a heated cylinder block having a chamber and a cooperating plunger operatively moveable into and out of said chamber;    an injection portion adapted to receive a predetermined shot volume of plastic from said plasticizing portion, said injection portion including an axially aligned injection pin, a resin flow channel, a nozzle and an injection cylinder, with said injection pin being axially moveable within said injection cylinder between an at-rest position and an extended position wherein said predetermined shot volume of plastic is injected through said resin flow channel, said nozzle and into the mold portion to mold the micropart;    a conduit positioned between said plasticizing portion and said injection portion to permit the flow of melted plastic material from said plasticizing portion to said injection portion;    valve means associated with said conduit and operable between an open position wherein a predetermined shot volume of melted plastic flows into said injection portion to position said injection pin at said at rest position and a closed position wherein said melted plastic in said plasticizing portion is isolated from said injection portion during movement of said injection pin from said at-rest position to said extended position; and    electric motor means engageable with said injection pin to axially move the same from said at-rest position to said extended position to inject the molten plastic into said mold portion.    
     
     
         2 . The injection molding machine in accordance with  claim 1 , wherein said electric motor means is a linear motor which moves said injection pin at a speed of 500 cm/seconds or less.  
     
     
         3 . The injection molding machine in accordance with  claim 1 , wherein said heated cylinder block of said plasticizing portion is maintained at a temperature between about 350° to 650° F.  
     
     
         4 . The injection molding machine in accordance with  claim 1 , wherein said valve means is a valve member structurally positioned perpendicularly with respect to said conduit and operable between said open position and said close position.  
     
     
         5 . The injection molding machine in accordance with  claim 1 , wherein said valve means is valve member concentrically positioned with respect to said cooperating plunger.  
     
     
         6 . The injection molding machine in accordance with  claim 1 , wherein said conduit means extends between said chamber in said plasticizing portion to said resin flow channel in said injection portion.  
     
     
         7 . The injection molding machine in accordance with  claim 1 , wherein said axial centerline control of said mold portion with respect to said injection portion to about 0.1 mm or less.  
     
     
         8 . The injection molding machine in accordance with  claim 1 , wherein the predetermined shot volume received by said injection portion is between about 0.01 to 2.0 cubic centimeters.  
     
     
         9 . The injection molding machine in accordance with  claim 1 , wherein said tolerance between said injection pin and said injection cylinder is within the range of about 0.012 mm or less.  
     
     
         10 . The injection molding machine in accordance with  claim 1 , wherein said resin flow channel has a diameter of about 0.5 to 6.0 mm.  
     
     
         11 . The injection molding machine in accordance with  claim 1 , when the wall thickness of the molded micropart is between about 0.025 to 0.3 mm and said injection time for the movement of the injection between said at-rest and said extended position is between about 0.01 to 0.5 seconds.  
     
     
         12 . The injection molding machine in accordance with  claim 1 , wherein the plastic pressure engageable with said injection pin is between about 5,000 to 100,000 psi.  
     
     
         13 . A method of molding microparts utilizing a molding machine having a plasticizing portion, an injection portion and a mold portion, including the steps of: 
 plasticizing resin material in the plasticizing portion;    filling the injection portion with a predetermined plastic shot volume of between about 0.001 to 3.5 cubic centimeters of and the plasticized resin material from the plasticizing portion; and    injecting said predetermined plastic shot volume into the mold portion to complete the molding of the micropart.    
     
     
         14 . The method in accordance with  claim 13  further including the step of depositing a predetermined amount of resin material in the plasticizing portion prior to plasticizing of the resin material.  
     
     
         15 . The method in accordance with  claim 14  wherein said resin material is in the form of pellets.  
     
     
         16 . The method in accordance with  claim 15  where said resin pellets range is size from about 1 to 3 mm.  
     
     
         17 . The method in accordance with  claim 13  wherein the step of injecting is completed between the time of about 0.01 to 0.5 seconds.  
     
     
         18 . The method in accordance with  claim 13  wherein the step of injecting occurs at a plastic pressure of between about 50,000 to 100,000 psi.  
     
     
         19 . In an injection molding machine for molding microparts containing a plastic shot volume of between about 0.001 to 3.5 cubic centimeters, the injection molding machine including a mold portion and an injection portion adapted to receive a predetermined shot volume of plastic, with the injection portion including an axially aligned injection pin, a resin flow channel and a nozzle, with the injection pin being axially moveable between an at-rest position and an extended position wherein the predetermined shot volume of plastic is injected through the resin flow channel, the nozzle and into the mold portion to mold the micropart, the improvement comprising: 
 a linear motor means engageable with the injection portion to inject the molten plastic into the mold portion.