Mold assembly and method for manufacturing metal castings

Abstract

A mold assembly for manufacturing a metal alloy casting includes a cope and drag mold, a plurality of sand cores and a pressure core. The cope mold includes an upper portion of a mold cavity. The drag mold includes a gating system, a lower portion of the mold cavity, and an upper portion of a plurality of riser cavities. The gating system is in communication with the riser cavities to provide pressurized liquid metal alloy to the riser cavities. The pressure core has a plurality of protrusions that are disposed in each of the upper portion of the plurality of riser cavities.

The following is claimed: 
     
         1 . A mold assembly for manufacturing a metal alloy casting, the mold assembly comprising;
 a cope mold including an upper portion of a mold cavity;   a drag mold including a lower portion of the mold cavity and an upper portion of at least a first riser cavity, and wherein the cope mold is disposed on top of the drag mold to combine the upper portion and lower portion of the mold cavity;   a plurality of sand cores disposed on the interior of the mold cavity of the cope and drag molds, and   a pressure core having at least a first protrusion, and wherein the first protrusion is disposed adjacent to the first riser cavity and includes a top surface that forms a bottom portion of the first riser cavity.   
     
     
         2 . The mold assembly of  claim 1  wherein the pressure core is disposed in one of a first position and a second position, and wherein the first riser cavity has a first volume when the pressure core is in the first position, and the first riser cavity has a second volume when the pressure core is in the second position, and the second volume is less than the first volume. 
     
     
         3 . The mold assembly of  claim 1  further including a gating system and a piston core, and wherein the gating system has a runner in communication with the first riser cavity and the piston core is disposed in one of a first and a second position. 
     
     
         4 . The mold assembly of  claim 3  wherein the first position of the piston core allows for communication between the first riser cavity and the runner and the second position of the piston core inhibits communication between the first riser cavity and the runner. 
     
     
         5 . The mold assembly of  claim 1  wherein the drag mold further includes a gating system that communicates liquid metal alloy from a pressurized source of liquid metal alloy to the riser cavities. 
     
     
         6 . The mold assembly of  claim 5  wherein the pressurized source of liquid metal alloy includes one of an electromagnetic pump, a mechanical pump, and a low-pressure furnace. 
     
     
         7 . The mold assembly of  claim 5  wherein the pressurized source of liquid metal alloy includes a pouring basin and sprue. 
     
     
         8 . The mold assembly of  claim 1  wherein the cope mold and drag mold are permanent metal molds. 
     
     
         9 . The mold assembly of  claim 8  wherein the pressure core is a movable portion of the drag mold. 
     
     
         10 . A mold assembly for manufacturing a metal alloy casting, the mold assembly comprising;
 a sand core assembly having a riser core and a first piston core, and wherein the riser core includes a gating system and at least a first riser cavity and the first piston core is disposed adjacent the first riser cavity;   a cope mold including an upper portion of a mold cavity;   a drag mold including a lower portion of the mold cavity and a first piston core actuator, and wherein the sand core assembly is disposed in the lower portion of the mold cavity, the cope mold is disposed on the drag mold, and the first piston core actuator is fixed for common movement with the piston core;   wherein the first piston core is disposed in one of a first position and a second position, and wherein the first riser cavity has a first volume when the first piston core is in the first position, and the first riser cavity has a second volume when the first piston core is in the second position, and the second volume of the first riser cavity is less than the first volume of the first riser cavity.   
     
     
         11 . The mold assembly of  claim 10  wherein the first piston core has a top surface that forms a portion of the first riser cavity. 
     
     
         12 . The mold assembly of  claim 11  wherein the first piston core includes a cross section having a width that is smaller than a cross section of the first riser cavity. 
     
     
         13 . The mold assembly of  claim 10  wherein the pressurized source of liquid metal alloy includes one of an electromagnetic pump, a mechanical pump, and a low-pressure furnace. 
     
     
         14 . The mold assembly of  claim 10  wherein the pressurized source of liquid metal alloy includes a pouring basin and sprue. 
     
     
         15 . The mold assembly of  claim 10  further including a second piston core, and wherein the gating system has a runner in communication with the first riser cavity, the second piston core is disposed proximate the runner in one of a first and a second position, the first position of the second piston core allows for communication between the first riser cavity and the runner and the second position of the second piston core inhibits communication between the first riser cavity and the runner. 
     
     
         16 . A method for manufacturing a lightweight metal alloy casting, the method comprising:
 providing a mold assembly including an cope mold, a drag mold, and a core assembly forming a mold cavity, and wherein the drag mold includes at least a first riser cavity and a gating system, and wherein the first riser cavity is at least partially formed by a movable first piston actuator, and the runner is at least partially formed by a movable second piston actuator;   initializing filling the gating system with a pressurized liquid metal alloy;   completing filling the gating system, the first riser cavity, and mold cavity with the pressurized liquid metal alloy;   discontinuing filling the mold assembly with the pressurized liquid metal alloy and activating the second piston actuator to close the runner;   applying a force to a bottom surface of the movable piston actuator mold in the direction of the drag mold and increasing the hydraulic pressure of the liquid metal alloy in the first riser cavity.   
     
     
         17 . The method of  claim 16  further comprises extracting a solidified casting from the mold cavity and placing the casting in an oven for heat treatment. 
     
     
         18 . The method of  claim 17  further comprises ejecting a solidified casting from the casting cavity. 
     
     
         19 . The method of  claim 18  further comprises placing the casting in an oven for heat treatment. 
     
     
         20 . The method of  claim 16  applying a force to a bottom surface of the movable piston actuator mold in the direction of the drag mold to increase the hydraulic pressure of the liquid metal alloy in the first riser cavity further comprises applying a force to a bottom surface of the movable piston actuator mold in the direction of the drag mold, decreasing the volume of the first riser cavity and increasing the hydraulic pressure of the liquid metal alloy in the first riser cavity.