Die Casting

High pressure die casting injects molten metal into hardened steel molds for thin-wall, complex parts with good accuracy and surface finish at high volumes.

Overview

Die casting, or high pressure die casting (HPDC), forces molten non‑ferrous metal into precision steel dies under high pressure. It produces thin-walled, complex shapes with tight repeatability and excellent as-cast surface finish, often eliminating or minimizing machining. Cycle times are short, so unit cost drops sharply at volume once the tooling is amortized.

Die casting fits small to medium-sized parts that need good dimensional control, integral features (ribs, bosses, threads), and production volumes from tens of thousands into the millions. It excels for aluminum, zinc, and magnesium alloys where weight and stiffness matter. Tradeoffs: very high upfront tooling cost, design constraints around draft and uniform wall thickness, and limited section thickness range. Very large parts, very low annual volumes, or alloys with high melting temperatures (like most steels) are usually poor candidates for HPDC.

Common Materials

  • Aluminum 380
  • Aluminum 413
  • Zinc Zamak 3
  • Zinc Zamak 5
  • Magnesium AZ91

Tolerances

±0.002" to ±0.005"

Applications

  • Automotive transmission and engine housings
  • Pump and compressor housings
  • Power tool and handheld device bodies
  • LED lighting housings and heat sinks
  • Small brackets, covers, and mounting flanges
  • Consumer electronics structural frames

When to Choose Die Casting

Choose die casting for small to medium non‑ferrous parts with thin walls, complex geometry, and annual volumes high enough to justify steel tooling. It’s a strong fit when you want good as-cast surfaces, integrated features, and minimal secondary machining. Target stable, repeat production runs rather than one-off or prototype work.

vs Sand Casting

Pick die casting when you need higher volumes, tighter repeatability, and better surface finish than sand can provide. It also suits thinner walls and more intricate features, as long as the part fits typical die casting size limits and you can justify the tooling cost.

vs Investment Casting

Choose die casting instead of investment casting when you want lower part cost at high volumes and can accept slightly looser tolerances with some design constraints. Die casting offers faster cycle times and cheaper large runs, especially for aluminum, zinc, and magnesium, but is less suitable for very high-temperature alloys.

vs Permanent Mold Casting

Go with die casting when you need thinner walls, more complex geometry, and higher production rates than permanent mold casting usually supports. Die casting tooling is more complex and expensive, but delivers shorter cycle times and better suitability for high-volume, intricate housings and small components.

vs Centrifugal Casting

Select die casting for prismatic or irregular shapes, housings, and brackets instead of the rotationally symmetric parts centrifugal casting favors. Die casting is better when you care about fine details, integrated bosses and ribs, and high-volume production rather than thick-walled tubular forms.

Design Considerations

  • Keep wall thickness uniform where possible and target thin but manufacturable walls (often 0.06–0.12" for aluminum) to avoid porosity and shrink issues
  • Apply adequate draft on all die-pulled surfaces (commonly 1–3°) to improve ejection, extend tool life, and reduce flash and drag marks
  • Avoid heavy, solid sections; use ribs and gussets to build stiffness while controlling cooling rates and minimizing internal porosity
  • Locate and design the parting line early, keeping critical cosmetic or sealing surfaces away from it and from ejector pin marks
  • Design cores, undercuts, and slides only where they add clear value, since each moving element increases tooling cost and maintenance
  • Add machining stock only where required and call out critical datum structure and tolerances clearly so the shop can plan secondary operations and fixturing