Thermally directed die casting suitable for making hermetically sealed disc drives

Abstract

A hermetically sealed disc drive comprising at least one aluminum alloy housing component manufactured with a thermally directed die casting press subassembly is disclosed. In one embodiment, the thermally directed die casting press subassembly comprises a thermally directed funnel gate that is skewed to sample molten material from an off-center portion of the shot sleeve. Disc drive housing components can be manufactured by injecting an aluminum alloy slurry from the shot sleeve through the thermally directed funnel gate and the injection nozzle into the die cavity. The aluminum alloy slurry may be a thixotropic slurry comprising a uniform primary aluminum particle size in the range of approximately 50 to 80 microns. The primary aluminum particles of cast products produced according to the methodology of the present disclosure, with the aforementioned particle size distribution, are free of encapsulated eutectic at the micron scale.

What is claimed is: 
     
         1 . A thermally directed die casting press subassembly comprising a shot sleeve, a gate plate, a lower mold plate, and an upper mold plate, wherein:
 the upper mold plate and the lower mold plate define a die cavity there between;   the lower mold plate comprises a gate port, a die port, and an injection nozzle extending from the gate port to the die port across a thickness dimension of the lower mold plate;   a major portion of the injection nozzle comprises a contracting nozzle taper along a laminar injection path extending towards the die port;   the gate plate comprises a thermally directed funnel gate extending from the shot sleeve to the gate port of the lower mold plate across a thickness dimension of the gate plate;   the thermally directed funnel gate comprises a contracting funnel taper along a turbulence-inducing injection path extending towards the gate port of the lower mold plate;   the shot sleeve defines a temperature gradient profile rising from relatively low T portions at a periphery of the shot sleeve to relatively high T portions at a central region of the shot sleeve; and   the contracting funnel taper of the thermally directed funnel gate is skewed to sample molten material from an off-center portion of the shot sleeve temperature gradient profile.   
     
     
         2 . The thermally directed die casting press subassembly of  claim 1 , wherein:
 the shot sleeve defines a substantially circular shot sleeve footprint; and   the contracting funnel taper of the thermally directed funnel gate defines a substantially radial sampling footprint that overlies the circular shot sleeve footprint.   
     
     
         3 . The thermally directed die casting press subassembly of  claim 2 , wherein the radial sampling footprint covers a center of the central region of the shot sleeve. 
     
     
         4 . The thermally directed die casting press subassembly of  claim 2 , wherein the radial sampling footprint is displaced from a center of the central region of the shot sleeve. 
     
     
         5 . The thermally directed die casting press subassembly of  claim 1 , wherein:
 the shot sleeve defines a substantially circular shot sleeve footprint; and   the contracting funnel taper of the thermally directed funnel gate defines a substantially diametrical sampling footprint that overlies the circular shot sleeve footprint and is asymmetric with respect to a center of the circular shot sleeve footprint.   
     
     
         6 . The thermally directed die casting press subassembly of  claim 1 , wherein the contracting funnel taper of the thermally directed funnel gate defines a non-radial sampling footprint that is displaced from a center of the central region of the shot sleeve and extends along a projection that spans the relatively low T and relatively high T portions of the shot sleeve temperature gradient profile. 
     
     
         7 . The thermally directed die casting press subassembly of  claim 1 , wherein the contracting funnel taper of the thermally directed funnel gate defines a sampling footprint that extends over the shot sleeve along a linear projection that spans the relatively low T and relatively high T portions of the shot sleeve temperature gradient profile. 
     
     
         8 . The thermally directed die casting press subassembly of  claim 6 , wherein the sampling footprint of the thermally directed funnel gate extends to an outer boundary of a prime slurry portion of the shot sleeve. 
     
     
         9 . The thermally directed die casting press subassembly of  claim 6 , wherein the sampling footprint of the thermally directed funnel gate is excluded from extending beyond a prime slurry portion of the shot sleeve. 
     
     
         10 . The thermally directed die casting press subassembly of  claim 1 , wherein the thermally directed funnel gate is skewed such that molten material sampled from relatively high T portions of the shot sleeve temperature gradient profile moves towards the gate port of the lower mold plate at a higher velocity than molten material sampled from relatively low T portions of the shot sleeve temperature gradient profile moves towards the gate port of the lower mold plate. 
     
     
         11 . The thermally directed die casting press subassembly of  claim 1 , wherein the thermally directed funnel gate is skewed such that molten material sampled from relatively low T portions of the shot sleeve temperature gradient profile moves towards the gate port of the lower mold plate at a higher velocity than molten material sampled from relatively high T portions of the shot sleeve temperature gradient profile moves towards the gate port of the lower mold plate. 
     
     
         12 . The thermally directed die casting press subassembly of  claim 1 , wherein the thermally directed funnel gate is shaped such that a high temperature shot-to-port path length for molten material sampled from relatively high T portions of the shot sleeve temperature gradient profile is longer than a low temperature shot-to-port path length for molten material sampled from relatively low T portions of the shot sleeve temperature gradient profile. 
     
     
         13 . The thermally directed die casting press subassembly of  claim 1 , wherein the thermally directed funnel gate is shaped such that a low temperature shot-to-port path length for molten material sampled from relatively low T portions of the shot sleeve temperature gradient profile is longer than a high temperature shot-to-port path length for molten material sampled from relatively high T portions of the shot sleeve temperature gradient profile. 
     
     
         14 . The thermally directed die casting press subassembly of  claim 1 , wherein the contracting funnel taper of the thermally directed funnel gate defines a sampling footprint having a cross-sectional area selected such that the volume of the funnel gate is at least approximately 40% of the volume of the die cavity. 
     
     
         15 . The thermally directed die casting press subassembly of  claim 1 , wherein the gate port to which the thermally directed funnel gate extends is offset relative to the central region of the shot sleeve. 
     
     
         16 . The thermally directed die casting press subassembly of  claim 1 , wherein:
 the injection nozzle comprises the contracting nozzle taper along the laminar injection path extending towards the die port;   a minor portion of the injection nozzle comprises an expanding nozzle taper along the laminar injection path extending towards the die port;   the contracting nozzle taper is positioned between the gate port and the expanding nozzle taper; and   the expanding nozzle taper is positioned between the contracting nozzle taper and the die port.   
     
     
         17 . The thermally directed die casting press subassembly of  claim 1 , wherein:
 the thermally directed funnel gate is configured to create turbulent flow in molten material sampled from the shot sleeve; and   the injection nozzle promotes laminar flow of the sampled molten material into the die cavity.   
     
     
         18 . A method of operating the thermally directed die casting press subassembly of  claim 1 , wherein a housing component is manufactured by injecting an aluminum alloy slurry from the shot sleeve through the thermally directed funnel gate and the injection nozzle into the die cavity. 
     
     
         19 . The method of  claim 18 , wherein the aluminum alloy slurry is a thixotropic slurry comprising a uniform primary aluminum particle size in the range of approximately 50 to 80 microns. 
     
     
         20 . A thermally directed die casting press subassembly comprising a shot sleeve, a gate plate, a lower mold plate, and an upper mold plate, wherein:
 the upper mold plate and the lower mold plate define a die cavity there between;   the lower mold plate comprises a gate port, a die port, and an injection nozzle extending from the gate port to the die port across a thickness dimension of the lower mold plate;   a major portion of the injection nozzle comprises a contracting nozzle taper along a laminar injection path extending towards the die port;   the gate plate comprises a thermally directed funnel gate extending from the shot sleeve to the gate port of the lower mold plate across a thickness dimension of the gate plate;   the thermally directed funnel gate comprises a contracting funnel taper along a turbulence-inducing injection path extending towards the gate port of the lower mold plate;   the shot sleeve defines a temperature gradient profile rising from relatively low T portions at a periphery of the shot sleeve to relatively high T portions at a central region of the shot sleeve; and   the thermally directed funnel gate is shaped such that a high temperature shot-to-port path length for molten material sampled from relatively high T portions of the shot sleeve temperature gradient profile is different than a low temperature shot-to-port path length for molten material sampled from relatively low T portions of the shot sleeve temperature gradient profile.   
     
     
         21 . A vertical die casting press comprising a shot piston, a shot piston rod, a thermally directed press subassembly, and an upper mold ejection subassembly, wherein:
 the thermally directed press subassembly comprises a shot sleeve, a gate plate, a lower mold plate, and an upper mold plate;   the upper mold ejection subassembly engages the thermally directed press subassembly along the upper mold plate of the thermally directed press subassembly;   the shot piston is positioned within the shot sleeve;   the shot piston rod is configured to advance the shot piston mechanically through the shot sleeve;   the upper mold plate and the lower mold plate define a die cavity there between;   the lower mold plate comprises a gate port, a die port, and an injection nozzle extending from the gate port to the die port across a thickness dimension of the lower mold plate;   a major portion of the injection nozzle comprises a contracting nozzle taper along a laminar injection path extending towards the die port;   the gate plate comprises a thermally directed funnel gate extending from the shot sleeve to the gate port of the lower mold plate across a thickness dimension of the gate plate;   the thermally directed funnel gate comprises a contracting funnel taper along a turbulence-inducing injection path extending towards the gate port of the lower mold plate;   the shot sleeve defines a temperature gradient profile rising from relatively low T portions at a periphery of the shot sleeve to relatively high T portions at a central region of the shot sleeve; and   the contracting funnel taper of the thermally directed funnel gate is skewed to sample molten material from an off-center portion of the shot sleeve temperature gradient profile.   
     
     
         22 . The vertical die casting press of claim  23 , wherein the thermally directed funnel gate is shaped such that a high temperature shot-to-port path length for molten material sampled from relatively high T portions of the shot sleeve temperature gradient profile is different than a low temperature shot-to-port path length for molten material sampled from relatively low T portions of the shot sleeve temperature gradient profile.