Both gravity and low-pressure casting pour liquid aluminum into a metal mold, but the way the metal fills the cavity is fundamentally different. In gravity casting the melt flows under its own weight; in low-pressure casting it is pushed up from a pressurized furnace below the mold.

That single difference explains most of the trade-offs buyers care about: gas porosity, achievable wall thickness, mechanical strength and the price of the machine itself.

Key Points

  • Gravity casting: excellent for medium-to-large parts 0.1–30 kg, lowest per-unit tooling cost, ideal when annual volume is below roughly 80,000 pcs.
  • Low-pressure casting: pressurized fill reduces gas porosity and allows thinner walls, giving stronger, heat-treatable parts preferred for motor housings, wheels and structural brackets.
  • Choose gravity when cost per part dominates and the design is tolerant of CT7–CT9; choose low-pressure when pressure tightness, strength or wall thickness below ~4 mm matter.
  • When in doubt, send the drawing for DFM review — our engineers simulate the fill and recommend one process with both cost and risk explained.