1. Introduction
Zinc die casting is a widely adopted manufacturing process that plays a critical role in the production of high-precision, high-volume metal components.
Leveraging the excellent castability, dimensional stability, and strength of zinc alloys, this process supports a wide range of industries—from automotive and electronics to medical and consumer goods.
Zinc’s low melting point (typically around 420–450 °C) allows for rapid cycle times, minimal energy consumption, and extended tool life, making it particularly cost-effective for complex, thin-walled designs.
Unlike other die-casting materials such as aluminum or magnesium, zinc offers superior surface finish quality and exceptional plating compatibility, which are essential for both functional and aesthetic applications.
2. What Is Zinc Die Casting?
Zinc die casting is a manufacturing process in which molten zinc or zinc alloys are forced under high pressure into reusable molds, known as dies, to create precise metal components.
The basic principle involves injecting the molten metal into the die cavity, allowing it to solidify, and then ejecting the finished part.
This process can produce parts with tight tolerances, smooth surface finishes, and complex geometries in a relatively short time.
3. Common Zinc Alloys for Die Casting
Zinc alloys used in die casting are formulated to maximize mechanical performance, surface finish, dimensional accuracy, and ease of processing.
Among the most widely used are the Zamak series (Zamak 2, 3, 5, 7) and ZA alloys (ZA-8, ZA-12, etc.).
Zinc Die Casting Alloys Table
| Alloy | Composition (wt%) | Key Features | Common Uses |
| Zamak 3 | Zn: ~96%, Al: 3.9%, Cu: 0.03%, Mg: 0.02% | Most widely used alloy; excellent dimensional stability, good strength, economical; best for general-purpose casting | Electrical housings, enclosures, consumer goods |
| Zamak 5 | Zn: ~95%, Al: 3.9%, Cu: 1.0%, Mg: 0.02% | Higher strength than Zamak 3 due to added copper; slightly reduced ductility; better creep resistance | Automotive parts, appliance hardware, structural components |
| Zamak 2 | Zn: ~95%, Al: 3.9%, Cu: 2.7%, Mg: 0.02% | Strongest of the Zamak family; lowest ductility; best wear resistance; aging hardenable | Precision gears, wear-resistant mechanical parts |
Zamak 7 |
Zn: ~99%, Al: 0.5–1.0%, Cu: <0.001%, Mg: 0.003% | Highest ductility in Zamak group; ultra-low impurities; excellent castability and surface finish | Thin-wall castings, miniature components, cosmetic parts |
| ZA-8 (Zinc–Aluminum) | Zn: 91%, Al: 8.4%, Cu: 0.8% | Stronger than Zamak 5; usable in hot-chamber machines; better for thin-walled structural parts | High-performance mechanical assemblies, housings, levers |
| ZA-12 | Zn: 88%, Al: 11%, Cu: 1.0% | Excellent strength and wear resistance; cold-chamber casting required; moderate castability | Heavy-duty gears, bushings, pulleys, brackets |
4. Die Casting Equipment and Tooling
Zinc die casting typically employs hot-chamber die casting machines, which immerse the injection mechanism directly into the molten metal.
This design enables high-speed operation with minimal energy loss.
Tooling Components:
- Gooseneck system: Transfers molten zinc from the holding pot into the shot sleeve.
- Shot sleeve & plunger: Injects metal into the mold under pressures of 10,000–15,000 psi.
- Die materials: Usually made of H13 tool steel or P20, with surface treatments like nitriding or PVD coating to resist thermal fatigue and erosion.
Because zinc is less erosive than aluminum, dies can last over 1 million cycles, significantly lowering long-term tooling costs.
5. Zinc Die Casting Process Steps
The zinc die casting process is a precise and efficient method for producing high-volume, high-accuracy metal components.
Thanks to zinc’s exceptional castability, low melting point, and dimensional stability, the process can achieve tight tolerances, smooth surface finishes, and thin-wall geometries.
Melt Preparation and Temperature Control
- Zinc alloys are typically melted at 420–450 °C (788–842 °F) depending on alloy type and process variation.
- Melting occurs in a furnace integrated with a hot-chamber machine or a separate crucible for cold-chamber machines.
- Precise temperature control is essential to avoid overheating (which causes oxidation and porosity) or underheating (which reduces flowability).
- Degassing and fluxing may be used to remove entrapped gases and oxides for improved casting quality.
Shot Charging and Injection
- Hot-Chamber Die Casting (most common for zinc):
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- The gooseneck system draws molten zinc directly into the die under hydraulic pressure (7–35 MPa).
- Short cycle times (typically <1 second fill time) make the process ideal for high-volume production.
- Cold-Chamber Die Casting (used for ZA-12, ZA-27):
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- Molten zinc is ladled into a shot sleeve, then a piston forces it into the die.
- Required for alloys with higher aluminum content that corrode gooseneck systems.
Cavity Filling and Solidification
- The molten zinc fills the steel die cavity at high speed (up to 1–3 m/s), ensuring it reaches all intricate shapes and thin walls.
- Rapid heat extraction occurs through the die walls, enabling:
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- Quick solidification (within milliseconds to a few seconds)
- High-dimensional accuracy
- Fine-grain structure with improved mechanical properties
- Die venting and vacuum assist may be used to prevent air entrapment and reduce porosity.
Ejection and Die Cycling
- Once the part solidifies, ejector pins push it out of the mold.
- Die surfaces are cooled or lubricated with die release agents to ensure smooth part release and prolong die life.
- Typical cycle time for zinc die casting: 20–60 seconds per shot, depending on part complexity and alloy type.
- Dies are then closed and prepared for the next injection—zinc’s fast cooling enables rapid die cycling.
Trimming and Flash Removal
- After ejection, excess material (flash, sprues, runners) is trimmed using:
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- Hydraulic or mechanical trimming presses
- CNC deburring systems
- Manual deburring tools for complex geometries
- Proper gating and overflow design minimizes waste and ensures clean part separation.
Inspection and Dimensional Verification
- Initial inspection may include:
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- Visual inspection for flash, surface defects, or cold shuts
- Dimensional gauging against CAD or technical drawing specs
- Optional X-ray or pressure testing for internal defects
6. Finishing and Post‑Processing of Zinc Die Casting
While zinc alloy die casting is renowned for producing components with excellent surface finish and tight tolerances right out of the mold,
most industrial and consumer applications still require post-processing to meet final specifications.
Deburring, Trimming, and Flash Removal
After ejection from the die, parts often have excess material at parting lines and gate areas.
This must be removed to meet design specifications and to ensure safety in handling and assembly.
Common Methods:
- Mechanical trimming presses: Fast and precise, ideal for high-volume production.
- Hand deburring: Used for small batches or parts with intricate geometries.
- Vibratory finishing: Tumbling parts with abrasive media for smoothing edges and surface preparation.
Goal: Achieve clean contours, remove sharp edges, and prepare parts for coatings.
Surface Cleaning and Pre-Treatment
Surface cleanliness is critical beefore plating, painting, or coating. Zinc’s natural oxide layer and die lubricants must be removed to ensure proper adhesion.
Techniques Include:
- Alkaline cleaning: Removes oils, greases, and die lubricants.
- Acid pickling: Removes oxides and flash rust.
- Shot blasting or bead blasting: Uniforms the surface and prepares for coatings.
Outcome: Improves bonding of paints and platings while enhancing cosmetic appearance.
Surface Finishing Techniques
Zinc alloys are highly compatible with decorative and functional coatings, making them ideal for parts requiring appearance or corrosion protection.
Plating
- Nickel Plating: Offers a bright, corrosion-resistant finish, often used in automotive and plumbing.
- Chrome Plating: A mirror-like finish for decorative or wear-resistant surfaces.
- Zinc or Zinc-Nickel Plating: Applied for additional corrosion protection in harsh environments.
Powder Coating
- Electrostatic application of a powdered polymer, followed by curing at ~180–200 °C.
- Offers durability, color flexibility, and good resistance to impact and chemicals.
Lacquering or Clear Coating
- Transparent coatings protect plated or polished surfaces without altering appearance.
Heat Treatment (Optional for Some Alloys)
Zinc alloys are not typically heat-treated for hardening, but stress relief treatments may be applied:
- Temperature Range: 80–120 °C for several hours.
- Purpose: Reduce internal stresses from casting or machining, enhance dimensional stability.
Some ZA (Zinc-Aluminum) alloys may undergo age hardening to improve strength over time.
Machining and Secondary Operations
Even though die casting delivers near-net shapes, secondary machining may be required for:
- Threading, drilling, or tapping
- Mating surfaces for assemblies
- Tight-tolerance features not achievable via casting alone
Note: Zinc’s excellent machinability makes it ideal for secondary operations, with low tool wear and smooth chip formation.
7. Material Properties of Zinc Die Castings
Zinc die castings are valued not only for their excellent castability but also for their robust mechanical and physical properties.
These properties make zinc alloys suitable for precision components requiring high strength, dimensional accuracy, and good surface finish.
Physical Properties of Zinc Alloys
| Property | Typical Value (Zamak 3) | Significance |
| Density | 6.6–6.8 g/cm³ | Provides strength and rigidity; heavier than aluminum |
| Melting Point Range | 380–390 °C (716–734 °F) | Enables low-energy melting and short cycle times |
| Thermal Conductivity | ~113 W/m·K | Excellent heat dissipation, useful in electronic housings |
| Electrical Conductivity | ~27% IACS | Suitable for some electrical grounding applications |
| Coefficient of Thermal Expansion | 27 × 10⁻⁶ /K | Dimensional changes predictable under thermal cycling |
Mechanical Properties of Zinc Alloys
| Property | Zamak 3 | Zamak 5 | ZA-8 |
| Tensile Strength | ~280 MPa | ~310 MPa | ~350 MPa |
| Yield Strength | ~210 MPa | ~250 MPa | ~275 MPa |
| Elongation at Break | ~7–10% | ~6–8% | ~3–6% |
| Hardness (Brinell) | 82–90 | 85–95 | 90–100 |
| Modulus of Elasticity | ~96 GPa | ~96 GPa | ~100 GPa |
| Impact Strength | Moderate | Slightly lower | Higher than Zamak 3 |
Dimensional Stability & Creep Resistance
- Dimensional Stability: Zinc die castings can maintain precise tolerances over long periods, especially in moderate temperature environments.
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- Typical tolerances: ±0.05 mm or better
- Creep Resistance: Limited above 100 °C. Zinc alloys are not ideal for high-temperature structural loads, but perform well at room to moderately elevated temperatures.
8. Quality Control and Defect Mitigation
Maintaining high product quality in zinc die casting requires robust monitoring and inspection systems.
Typical Defects and Remedies:
| Defect | Cause | Mitigation |
| Porosity | Air entrapment | Vacuum die casting, gating design |
| Cold shuts | Incomplete flow or fill | Raise temperature, improve fluidity |
| Flash | High injection pressure | Tighten die fit, modify clamping |
| Die soldering | Metal fusing to die wall | Apply die lubricant, use coatings |
Non-destructive testing methods such as X-ray inspection, ultrasound, and dye penetrant testing are often used to detect internal or surface defects.
9. Advantages & Limitations of Zinc Die Castings
Advantages
Superior Fluidity:
Zinc alloys exhibit excellent fluidity, enabling the production of intricate components with thin walls, as thin as 0.8 mm.
This property allows molten zinc to fill complex mold cavities precisely, facilitating the manufacturing of highly detailed parts.
High-Precision Dimensional Accuracy:
Zinc die casting can achieve extremely tight dimensional tolerances, typically within ±0.05-0.1 mm for small-to-medium-sized parts.
This precision often eliminates the need for extensive post-machining, saving both time and cost.
Rapid Production Rates:
Die-casting machines for zinc can operate with short cycle times, usually ranging from 10-60 seconds per cycle, depending on part complexity.
This high-speed production capability makes it ideal for mass manufacturing, reducing overall production costs.
Good Surface Finish:
Parts produced through zinc die casting generally have a smooth and glossy surface right out of the mold.
This eliminates the need for many surface-finishing operations and provides an excellent base for further treatments like plating or painting.
Cost-Effectiveness:
Zinc is relatively inexpensive compared to many other die-casting metals.
Additionally, the process generates minimal material waste as excess metal can be easily recycled, further reducing costs.
The lower cost of tooling and equipment also contributes to its economic viability.
Wide Range of Alloy Options:
There are various zinc alloys available, each tailored to specific performance requirements.
For example, Zamak alloys offer a balance of strength, corrosion resistance, and casting properties,
while ZA alloys are known for their high wear resistance, providing flexibility in material selection.
Limitations
Limited High-Temperature Performance:
Zinc alloys have low melting points and poor heat resistance.
Their mechanical properties degrade significantly at elevated temperatures (usually above 120°C),
making them unsuitable for applications involving continuous exposure to high heat, such as engine internals in high-performance vehicles.
Size Constraints:
The size of zinc die-cast parts is limited by the capacity of die-casting machines and molds.
Producing large-scale components is challenging and costly, as it requires more powerful machines and larger, more expensive molds.
Thermal Sensitivity:
Zinc alloys are sensitive to rapid temperature changes during the die-casting process.
This thermal sensitivity can lead to issues like thermal stresses, warping, and cracking in the cast parts if the process parameters, such as cooling rates, are not carefully controlled.
Susceptibility to Certain Corrosive Environments:
Although zinc has some inherent corrosion resistance, in highly corrosive environments, especially those with strong acids or alkalis, the material may corrode over time.
While surface treatments can enhance corrosion resistance, it adds to the overall cost.
Regional Alloy Availability:
The production and availability of specific zinc alloys may be limited in some regions.
This can lead to supply chain challenges, longer lead times, and increased costs for sourcing specialized alloys.
10. Applications of Zinc Die Castings
Automotive Industry
- Application Areas: Vehicle structural components, interior/exterior trim, and functional parts
- Components: Engine mounts, brackets, door handles, knobs, wheel hubs, grilles, and decorative trims
Electronics Industry
- Application Areas: Electronic enclosures, connectors, and heat management
- Components: Plug connectors, device housings, heat sinks for semiconductors, and circuit board fixtures
Consumer Goods Sector
- Application Areas: Home appliances, toys, and decorative products
- Components: Handles/knobs for kitchen appliances, toy models, decorative figurines, and hardware for furniture
Hardware & Plumbing Industry
- Application Areas: Construction fixtures and plumbing systems
- Components: Faucets, valves, door locks, hinges, and architectural hardware
Medical Devices Field
- Application Areas: Surgical equipment and biomedical components
- Components: Biocompatible instrument housings, implantable device casings (with surface treatment), and diagnostic tool parts
Renewable Energy Sector
- Application Areas: Wind and solar energy infrastructure
- Components: Wind turbine brackets, solar panel mounting systems, and energy storage system enclosures
11. Comparison Table: Zinc vs Aluminum vs Magnesium Die Casting
| Property / Feature | Zinc Die Casting | Aluminum Die Casting | Magnesium Die Casting |
| Density (g/cm³) | 6.6–6.8 | 2.6–2.8 | 1.74–1.84 |
| Melting Point (°C) | 380–390 | 615–660 | 595–650 |
| Tensile Strength (MPa) | 250–400 | 170–310 | 180–280 |
| Yield Strength (MPa) | 210–350 | 120–280 | 150–230 |
| Elongation (%) | 7–15 | 2–8 | 3–10 |
| Hardness (Brinell) | 82–120 | 50–110 | 60–90 |
| Castability | Excellent (thin walls, tight tolerances) | Good (less fluid than zinc) | Moderate (requires controlled conditions) |
| Tool Life | Very High (up to 1 million shots) | Moderate (100k–150k shots typical) | Moderate to High |
| Corrosion Resistance | Good (can be improved via plating) | Moderate (needs coating in harsh environments) | Good (especially AZ91D alloy) |
Machinability |
Excellent | Good | Good |
| Surface Finish | Superior (ready for plating or painting) | Fair (post-processing often needed) | Fair to Good |
| Thermal Conductivity (W/m·K) | ~109 | ~150–170 | ~60–90 |
| Unit Cost (material + process) | Low (low melting point = energy savings) | Moderate | High (material & tooling costs) |
| Recyclability | Excellent | Excellent | Excellent |
| Weight-Saving Potential | Low (high density) | Medium | High (lightest of the three) |
| Typical Applications | Small gears, connectors, enclosures, trims | Engine blocks, housings, structural brackets | Laptop frames, automotive steering wheels, casings |
| Environmental Impact | Moderate (energy-efficient but heavy) | Moderate to high (energy-intensive) | Lower (lightweight, less material needed) |
Key Takeaways:
- Zinc is ideal for high-precision, small, complex parts with superior surface quality and low tooling cost, especially in high-volume production.
- Aluminum is preferred for lightweight structural components with moderate strength and higher thermal resistance.
- Magnesium offers the best strength-to-weight ratio, making it suitable for aerospace and portable electronics, but requires more specialized processing and safety controls.
12. Conclusion
Zinc die casting is a mature, precise, and cost-efficient manufacturing process ideally suited for producing complex metal components in high volumes.
Its mechanical robustness, superior castability, and excellent surface quality continue to make it the preferred choice for industries ranging from automotive to medical devices.
While it has some thermal limitations, its design flexibility, low production cost, and recyclability firmly secure zinc die casting as a leading metal forming technology for the future.
Custom Die Casting Services by DEZE
DEZE offers high-quality custom die casting services tailored to meet your exact specifications.
With years of experience and advanced equipment, we specialize in producing precision metal components using aluminum, zinc, and magnesium alloys.
What We Offer:
- OEM & ODM Die Casting Solutions
- Support for small to high-volume production
- Custom mold design and engineering support
- Tight dimensional tolerances and excellent surface finishes
- Secondary operations, including CNC machining, surface treatment, and assembly
