Zinc Alloy
Zinc Die-Casting Alloy (Zamak) · Metal Alloy
Key Properties
High precision, thin walls, excellent castability.
Applications
Housings, brackets, hardware, E/E components.
Pros
Tight tolerances; long tool life.
Cons
Heavier than plastics; higher energy to cast.
What Is Zinc Alloy Die Casting?
Zinc alloy die casting — most commonly with the Zamak family (Zamak 3, 5 and 7) — is a high-volume metal manufacturing process in which molten zinc alloy is injected into precision steel dies under high pressure. Zinc alloys have the lowest melting point of the common die-casting metals, roughly 380 – 420 °C, which makes them fast to cast, gentle on tooling, and capable of wall thicknesses and dimensional tolerances that aluminum and magnesium cannot match. The result is a metal part with excellent precision, a smooth as-cast surface and very high production rates.
For many products, zinc die casting is the premium alternative to plastic injection molding: where a plastic part feels light or flexes, a zinc part feels substantial, shields electromagnetic interference and survives higher temperatures. Zinc parts can be plated, painted, polished or powder coated, so the surface-finish options are broad. The trade-offs are weight — zinc at roughly 6.6 – 7.2 g/cm³ is far denser than any plastic — and the energy and tooling involved in casting.
Hot-chamber zinc casting is one of the fastest metal-forming processes in production: shot-to-shot cycles of a few seconds are routine, dies last for hundreds of thousands of shots at the low casting temperature, and near-net-shape parts often need no machining at all.
Key Properties of Zinc Die-Casting Alloys
| Property | Typical Value | Why It Matters |
|---|---|---|
| Density | ≈ 6.6 – 7.2 g/cm³ (Zamak 3 ≈ 6.6) | Heavy, solid feel; adds mass where it is wanted. |
| Melting range | ≈ 380 – 420 °C | Lowest melting point of the common casting alloys — fast cycles, long die life. |
| Tensile strength (as cast) | ≈ 283 MPa (Zamak 3); ≈ 328 MPa (Zamak 5) | Stronger than most molded plastics by a wide margin. |
| Elongation at break | ≈ 10% (Zamak 3) | Absorbs impact better than aluminum die castings. |
| Hardness | ≈ 82 HB (Zamak 3) | Resists denting and wear in service. |
| Electrical conductivity | Good — metallic | Natural EMI shielding and grounding for electronics housings. |
| Wall thickness capability | As thin as ≈ 0.5 – 1.0 mm | Intricate, light-for-metal geometries without losing castability. |
Die-Casting Parameters We Control
Zinc die casting is typically run on hot-chamber machines, where the injection mechanism is immersed in the molten alloy. The parameters below are the standard industry ranges that our casting partners control to hit dimensional and surface targets; every value is a published typical range, not a machine-specific specification.
| Parameter | Typical Range |
|---|---|
| Metal (holding) temperature | 400 – 430 °C |
| Die temperature | 180 – 220 °C |
| Casting (injection) pressure | High — typically 10 – 35 MPa at the plunger |
| Wall thickness | 0.5 – 4 mm typical design range |
| Mold shrinkage (Zamak) | ≈ 0.7 – 1.2% |
| Achievable tolerance | ± 0.05 mm on critical dimensions |
Zamak 3 is the workhorse alloy for general components; Zamak 5 adds roughly 10 – 15% strength for demanding mechanical parts; Zamak 7 offers the best ductility and surface finish. All three cast at similar temperatures and share the same design rules, so alloy selection is usually a strength-versus-cost decision made during the DFM.
Common Applications
- Electronics housings and frames: EMI shielding, heat dissipation and a premium metal feel.
- Hardware and locks: handles, latches, escutcheons and lock bodies that need strength and long-term durability.
- Automotive components: brackets, bezels, fuel-system fittings and trim parts.
- E/E components: connectors, switch bodies and terminal blocks that carry current and ground signals.
- Furniture and architectural hardware: hinges, knobs and fittings available with decorative plating.
Design Guidelines for Zinc Die-Cast Parts
- Uniform walls: design for 0.75 – 3 mm walls; uniformity prevents porosity and distortion.
- Ribs and bosses: use ribs at 0.5 – 1 × wall thickness and bosses with generous fillets to stiffen without creating thick sections.
- Draft: provide 0.5 – 1° of draft on external walls and 1 – 2° on internal cores.
- Radii: fillet all corners — sharp corners concentrate stress and impede metal flow.
- Avoid large flat areas: break them up with ribs or texture to prevent surface defects.
- Shrinkage allowance: design for roughly 1% shrinkage across the Zamak family and confirm with sampling.
Common Defects and Prevention
- Porosity: gas trapped during fill; design gates for smooth flow, use overflow wells, and specify vacuum assist for pressure-tight parts.
- Cold shuts: weld-like surface lines from metal that cools before flow fronts merge; raise die temperature and metal temperature.
- Flash: metal escaping the die cavity; maintain die fit and control clamping force.
- Soldering: alloy sticking to the die; improve die release and use proper die surface treatment.
- Surface pitting: often caused by die-temperature fluctuation; stabilize the thermal cycle.
Zinc Die Casting vs. Aluminum and Plastics
Against aluminum die casting, zinc offers a much lower melting temperature (380 – 420 °C versus roughly 660 °C), which means dramatically longer die life, thinner achievable walls, tighter tolerances and a smoother as-cast surface. Aluminum wins where light weight and high service temperatures matter; zinc wins where precision, thin walls, plating quality and EMI shielding are the priorities, and where die amortization must be kept low.
Against plastic injection molding, zinc parts are heavier but much stronger and stiffer, inherently conductive, EMI-shielding and heat-tolerant, and they carry a premium tactile quality. Many products start as zinc castings and migrate to engineering plastics for cost and weight — or start as plastics and upgrade to zinc for durability and feel. MOLDITQUICK helps customers make exactly this metal-versus-plastic decision with real cost and performance data on both routes. Learn more on our die casting service page.
MOLDITQUICK Capabilities
MOLDITQUICK coordinates zinc die casting through qualified casting partners while keeping post-casting work in-house: CNC machining for critical dimensions, surface finishing and plating coordination, and assembly when the casting is part of a larger product. Because we also operate an injection molding plant and tool room, we can evaluate a part both as a zinc casting and as an injection-molded plastic, and recommend the route that meets performance targets at the lowest total cost.
If you are evaluating a zinc casting, a metal-to-plastic conversion, or a plastic part that should become metal, send us the drawings. We will return a DFM review covering wall thickness, draft, tolerance feasibility and comparative piece pricing. Request a quotation through our quote form, or explore our CNC machining and surface finishing services.