When your component needs a clean as‑cast surface and stable dimensions at moderate volumes, gravity die casting (permanent mold casting) is often the sweet spot. In Poznan, we apply simulation‑led gating and robust thermal control to achieve consistent quality while preserving the cost and lead‑time advantages of permanent tooling.
What is Gravity Die Casting (GDC)?
In GDC, molten metal (typically aluminum alloys) is poured into a reusable steel or iron permanent mold under gravity, not high pressure. The solidification against the metal mold produces a refined microstructure and improved surface finish compared with sand casting, with lower gas entrapment than high‑pressure die casting (HPDC). Cycle times are slower than HPDC, and ultra‑thin walls are harder to achieve; however, dimensional stability and porosity performance are excellent for many geometries.
Where GDC fits vs HPDC, LPDC, Sand & Investment
HPDC (die casting / aluminum die casting): best for very high volumes, thin walls, intricate features; risk of gas entrapment addressed via vacuum and shot‑curve tuning.
LPDC (low‑pressure die casting): laminar fill, good for structural wheels/housings; tooling and cells are capital intensive but deliver excellent internal integrity.
Sand casting: flexible for large parts/low volumes; rougher surface finish and wider tolerance class.
Investment casting (lost‑wax casting): superb detail for complex shapes at low volumes; different cost/surface/tolerance economics.
GDC sits between these: better finish and accuracy than sand, less porosity risk than HPDC, and lower cost/complexity than LPDC for many medium‑volume parts.
Surface finish & tolerance strategy
Expect fine as‑cast surfaces suitable for cosmetic shot‑blast or minimal finishing.
Use ISO 8062 casting tolerances as baseline; assign GD&T to functional datums, bores and sealing faces.
Plan machining allowances only where function demands it—e.g., gasket lands, bearing bores, threads.
Design rules for permanent molds
Uniform wall thickness; use ribs/gussets to maintain stiffness without creating hot spots.
Draft on all vertical walls; additional draft on textured or polished cosmetic faces.
Generous fillets and radii to prevent stress risers and improve metal flow.
Gating/overflow placed to foster laminar fill; venting strategy verified via casting simulation.
Chills or localized cooling to manage heavy sections and avoid shrinkage.
Ejector layout that protects cosmetics and datum integrity.
Defect prevention in GDC
Gas porosity: minimized by controlled pouring temperature, well‑designed vents and steady fill.
Shrinkage porosity: addressed through thermal balance, chills, uniform sections and riser design where applicable.
Cold shuts/misruns: mitigated via gating geometry and mold pre‑heat; simulation helps validate fill time and flow paths.
Alloys & properties
Aluminum alloys from the Al‑Si family dominate GDC for their fluidity and castability; Al‑Mg grades are selected for higher strength and corrosion resistance.
For very small or extremely detailed parts, consider zinc die casting (Zamak/ZnAl) instead; for very thin walls at large volumes, HPDC (die casting) is usually superior.
Process control & metrology
Mold pre‑heat and thermal management stabilize cycle‑to‑cycle variation.
SPC on melt temperature, mold temperature and pour time; periodic CT scanning on critical parts.
FAI/PPAP with CMM inspection aligned to ISO 8062 + GD&T.
Where seal integrity matters, define leak‑test values and allow for impregnation as a backstop.
Typical applications
Pump/compressor bodies, hydraulic/pneumatic manifolds.
Housings and brackets for machinery where surface finish and dimensional stability are valued.
Medium‑volume structural components that don’t require ultra‑thin HPDC walls.
Quick selection guide
Choose GDC when: moderate volumes, robust dimensions, good surface finish, and low internal defect risk are priorities.
Choose HPDC when: high volume, thin walls, and complex features dominate.
Choose LPDC when: structural integrity and laminar fill are paramount (e.g., wheels).
Choose sand casting for: large size/low volume flexibility.
Choose investment casting for: intricate shapes at low volume with fine detail.
Takeaway: Gravity die casting (permanent mold) offers a practical balance of surface finish, dimensional accuracy and cost. With Poznan’s integrated toolmaking, casting simulation, disciplined thermal control and targeted CNC, you get consistent, production‑ready parts—and a process that scales cleanly with demand.