Die Casting vs. Other Metal Processes: A Buyer's Guide to Zinc and Aluminium Parts

Die casting is one of the most efficient ways to produce complex metal components at volume. A single shot of molten metal into a hardened steel die can produce a part with thin walls, tight tolerances, and a smooth surface finish — all in a cycle time measured in seconds. But it is not the right process for every application, and choosing the wrong alloy or process can cost you significantly in tooling, lead time, or part performance.

This guide covers the fundamentals of die casting, the zinc vs. aluminium decision, how die casting compares to competing processes, and the design rules that keep tooling costs under control.

---

How Die Casting Works

In high-pressure die casting (HPDC), molten metal is injected into a hardened steel die at pressures of 10–175 MPa. The metal solidifies in milliseconds, the die opens, and the part is ejected. The entire cycle — from injection to ejection — takes 15–60 seconds depending on part size and wall thickness.

The die itself is a precision-machined tool steel assembly, typically H13, with water-cooling channels to control solidification rate. A well-maintained die can produce 100,000–1,000,000 shots before requiring refurbishment, making the per-part tooling amortisation very low at volume.

Two variants are common:

Hot-chamber die casting is used for zinc, magnesium, and lead alloys. The injection mechanism is submerged in the molten metal, enabling fast cycle times (under 20 seconds). Not suitable for aluminium, which attacks the steel injection system.

Cold-chamber die casting is used for aluminium and copper alloys. Molten metal is ladled into a separate shot sleeve for each cycle. Cycle times are longer (30–60 seconds), but the process handles the higher melting temperatures of aluminium.

---

Zinc vs. Aluminium: Choosing the Right Alloy

The zinc vs. aluminium decision is one of the most consequential choices in die casting. They are not interchangeable — each has a distinct set of strengths.

Zinc Alloys (Zamak)

The Zamak family (Zamak 2, 3, 5, 7) is the standard for zinc die casting. Zamak 3 is the most widely used — it offers a good balance of strength, ductility, and castability.

Advantages of zinc:

• Lowest tooling cost. Zinc's lower melting point (~385°C vs. ~660°C for aluminium) is gentler on tooling. Die life is 5–10× longer than aluminium, which directly reduces amortised tooling cost per part.
• Thinner walls. Zinc can be cast to walls as thin as 0.4 mm, enabling miniature and intricate geometries that aluminium cannot achieve.
• Better surface finish. Zinc produces a smoother as-cast surface, making it the preferred choice for decorative parts that will be plated or painted.
• Higher impact strength. Zamak alloys are tougher than most aluminium die casting alloys, making them suitable for parts that must absorb shock loads.
• Near-net-shape. Zinc's excellent fluidity allows complex features — undercuts, fine threads, thin ribs — to be cast directly, reducing secondary machining.

Limitations of zinc:

• Higher density. Zinc is approximately 2.7× denser than aluminium. For weight-sensitive applications, this is a significant disadvantage.
• Lower operating temperature. Zinc alloys begin to lose strength above 100°C. Not suitable for engine bay or high-temperature applications.
• Creep under sustained load. Zinc is susceptible to creep at elevated temperatures and under long-term static loads.

Best applications for zinc: door hardware, lock bodies, automotive trim, electrical connectors, small housings, decorative components, precision miniature parts.

Aluminium Alloys

A380 is the workhorse aluminium die casting alloy — good fluidity, excellent corrosion resistance, and moderate strength. A383 offers better castability for complex thin-wall parts. A360 provides superior corrosion resistance and ductility.

Advantages of aluminium:

• Low density. At 2.7 g/cm³, aluminium is roughly one-third the weight of steel and significantly lighter than zinc. Critical for automotive, aerospace, and portable electronics.
• High operating temperature. Aluminium retains useful strength up to 150–200°C, making it suitable for engine components, heat sinks, and industrial equipment.
• Excellent thermal and electrical conductivity. Aluminium die castings are widely used for heat sinks, motor housings, and electrical enclosures.
• Good strength-to-weight ratio. A380 has a tensile strength of ~320 MPa at a density of 2.74 g/cm³.
• Corrosion resistance. The natural aluminium oxide layer provides good protection in most environments without secondary coating.

Limitations of aluminium:

• Higher tooling cost. Aluminium's higher casting temperature reduces die life to 80,000–150,000 shots, increasing amortised tooling cost.
• Thicker minimum wall. Practical minimum wall thickness is 1.0–1.5 mm, compared to 0.4 mm for zinc.
• Porosity risk. Aluminium is more prone to gas porosity, which can affect pressure-tight applications and machined surfaces. Vacuum-assisted die casting mitigates this.

Best applications for aluminium: automotive structural components, engine brackets, gearbox housings, heat sinks, power tool bodies, industrial equipment housings, consumer electronics enclosures.

---

Die Casting vs. Competing Processes

Die Casting vs. Sand Casting

Sand casting uses expendable sand moulds and is suitable for very large parts, low volumes, and alloys that cannot be die cast (iron, bronze, large aluminium). It produces rougher surfaces (Ra 6–25 µm vs. Ra 1–2 µm for die casting), looser tolerances, and requires more machining. For volumes above 1,000 parts, die casting is almost always more economical for aluminium and zinc components.

Die Casting vs. CNC Machining

CNC machining from billet produces superior mechanical properties (wrought vs. cast microstructure) and tighter tolerances, but generates significant material waste and has much higher per-part cost at volume. Die casting is the right choice when volumes exceed roughly 500–1,000 parts and the part geometry is too complex to machine economically. Many designs use both: die cast the near-net shape, then machine critical bearing surfaces and threaded holes. Read our CNC machining guide for a detailed breakdown of tolerances and when to choose each process.

Die Casting vs. Investment Casting

Investment casting (lost-wax) can produce more complex geometries with thinner walls and tighter tolerances than die casting, and works with a wider range of alloys including stainless steel and titanium. However, cycle times are much longer (hours vs. seconds), and per-part costs are higher. Investment casting is preferred for small, complex, high-value parts in materials unsuitable for die casting.

Die Casting vs. Plastic Injection Molding

For applications where metal properties (strength, conductivity, heat resistance) are not required, plastic injection molding is significantly cheaper — both in tooling and per-part cost. The decision is usually driven by functional requirements: if the part must conduct heat, carry structural loads, or provide EMI shielding, metal die casting wins. If it is a housing, cover, or bracket with modest loads, plastic is often the better choice. See our complete injection molding guide for a full material and process comparison.

---

Design Rules for Die Casting

Getting the design right before tooling is cut saves significant cost and lead time.

Draft angles. All surfaces parallel to the die-opening direction need draft to allow ejection. Minimum draft is 1° for external surfaces and 2° for internal surfaces (cores). Textured surfaces need additional draft — typically 1° per 0.025 mm of texture depth.

Wall thickness. Uniform wall thickness promotes even solidification and minimises porosity. For aluminium, target 2–4 mm. For zinc, 1–2.5 mm. Abrupt thickness changes create stress concentrations and shrinkage defects.

Ribs. Ribs add stiffness without adding wall thickness. Rib thickness should be 60–70% of the adjacent wall. Rib height should not exceed 5× the rib thickness. Add fillets at the rib base (minimum R0.5 mm) to reduce stress concentration.

Undercuts. Features that prevent straight ejection require side-actions (slides) in the die, which significantly increase tooling cost and complexity. Minimise undercuts where possible, or discuss with your toolmaker whether a side-action is justified.

Parting line. The parting line is where the two die halves meet. Flash (a thin fin of metal) forms at the parting line and must be trimmed. Place the parting line at a natural break in the geometry, away from critical sealing or mating surfaces.

Bosses and inserts. Bosses for threaded inserts should have a wall thickness of at least 2× the insert diameter. Threaded inserts pressed or ultrasonically inserted after casting provide stronger threads than cast-in threads.

---

Quality and Inspection

At Keiteq Direct, every die casting batch undergoes:

• Visual inspection for surface defects, cold shuts, and flash
• Dimensional inspection using CMM against the approved drawing
• X-ray or CT scanning for critical pressure-tight components (porosity detection)
• Tensile and hardness testing on first-article and periodic production samples
• Leak testing for hydraulic and pneumatic housings

Our IATF 16949 certification means our quality management system meets the requirements of the global automotive supply chain — the most demanding standard in high-volume manufacturing.

---

Working with Keiteq Direct

We offer zinc and aluminium die casting from our facility in Senai, Johor, with tooling fabricated in-house on our CNC machining centres. This means shorter tooling lead times (4–6 weeks for a typical tool) and faster engineering change cycles compared to sourcing tooling and casting separately.

Malaysia's Johor manufacturing corridor is one of Southeast Asia's most capable locations for precision metal components. Discover why global OEMs choose Malaysia for quality-critical production.

For new projects, we recommend a DFM review before tooling is committed. Send us your 3D model and we will identify any features that will increase tooling cost or risk, and suggest modifications that preserve your design intent while reducing manufacturing complexity. Learn more about our 45-year manufacturing heritage →

Request a Die Casting Quote →