Pressurized Gating System
The total cross sectional area decreases towards the mold cavity
Back pressure is maintained by the restrictions in the metal flow
Flow of liquid (volume) is almost equal from all gates
Back pressure helps in reducing the aspiration as the sprue always runs full
Because of the restrictions the metal flows at high velocity leading to more turbulence and chances of mold erosion
Un-Pressurized Gating System
The total cross sectional area increases towards the mold cavity
Restriction only at the bottom of sprue
Flow of liquid (volume) is different from all gates
aspiration in the gating system as the system never runs full
Less turbulence