Die Casting Basics Die is closed. Metal is drawn in to tool (plunger). Tool injects metal into cavity. Cavity continues to fill. (fractions of a second) Metal solidifies under pressure. Die is opened. Casting removed. Machine recovers to initial orientation (cycle starts over)

Properties: Pb-Sb vs. Zn-Al L35 Pb-Sb Alloy Zamak 3 Zn-Al Alloy Density ( g/cm^3) at 21ºC Solidification shrinkage ( % ) Freezing range ( ºC ) Specific heat capacity ( J/kg/ºC ) at ºC Thermal expansion ( um/m per ºC at ºC) Thermal conductivity ( cal/cm 2 /cm/ ºC/sec at ºC ) Viscosity (poise)

Stage III : Temperature Monitoring Overview  Nozzle temperature Nozzle freezing  Die temperature Thermal expansions  Holding pot temperature Temperature gradients Excess superheat

Results: Injection Pressure  Monitor weight as a function of pressure  Decreasing Pressure: Reduces flashing Decreases machine errors  Weight variation for each setting < 1% * Tolerance (41.24 – 43.80g) Pressure Dependency Analysis

Molten metal leaking through the gap is called ‘flashing’.

Upper Mold Lower Mold Pressurized Molten Metal Atmospheric Pressure Mold gap

Upper Mold Lower Mold Pressurized Molten Metal Atmospheric Pressure Mold gap L(t 1 )L(t 2 )L(t 3 )L(t 4 )

The approximation that the liquid:air interface velocity is equal to the average velocity of the steady stae profile was introduced by E. W. Washburn, Physical Review, vol. 17, pp , 1921.

AirFluid Further discussion of the planar interface approximation. Flow profile is disturbed at the fluid air interface Average velocity must be equal for incompressible fluid

Represent the surface tensions of a multi-phase junction as vectors drawn parallel to the respective surfaces The surface energies for the for the solid/liquid, the solid/vapor and the liquid/vapor interfaces are γ sl, γ sv, γ lv γ sl γ sv γ lv θ The contact angle θ is a measure of the magnitude of the solid liquid interface energy compared to the solid vapor and liquid vapor energies. Complications regarding the shape of the moving solid vapor interface. Meniscus Formation

Youngs’ Equation Represent the surface tensions of a multi-phase junction as vectors drawn parallel to the respective surfaces The surface energies for the for the solid/liquid, the solid/vapor and the liquid/vapor interfaces are γ sl, γ sv, γ lv. The vectors representing these surface energies must balance at the three phase triple junction. This equation representing this balance is known as ‘Youngs’ equation” γ sl γ sv γ lv θ

γ sl γ sv γ lv θ γ sl γ sv γ lv θ Large γ sl, non-wetting θ Large Large γ sv, wetting θ small

LiquidVapor Liquid Vapor Interface shapes for ‘wetting’ and non-wetting contact angles