How to select iron casting process in China?

In industrial manufacturing, selecting the optimal casting process is a critical decision that balances performance, cost, and volume. Among all methods, sand casting remains the most widely adopted, accounting for approximately 60–70% of global casting production. Specialized processes such as metal mold casting, investment casting, and plaster casting offer alternatives for specific technical requirements.

This guide outlines key principles for selecting the most suitable casting method, emphasizing practicality, efficiency, and economic viability.

1. Prioritize Sand Casting for Versatility and Cost-Effectiveness

Sand casting dominates foundry production due to its low initial tooling cost, adaptable production cycle, and suitability for a wide range of part sizes—from a few kilograms to several tons. Within sand casting, green sand molding is the most common, representing about 70% of sand-cast components. It is extensively used for automotive parts like engine blocks, cylinder heads, and crankshafts.

When higher dimensional stability or surface finish is required, self-hardening resin sand is preferred for medium-to-large iron castings, while sodium silicate (water glass) sand is often chosen for steel castings. Although these bonded sand systems improve accuracy and surface quality, they come at a higher cost.

Limitation note: Sand casting typically provides moderate levels of dimensional precision, surface finish, and metallurgical density. When superior mechanical properties or tighter tolerances are necessary, advanced processes such as investment casting, die casting, or low-pressure casting should be evaluated.

2. Match the Process to Annual Production Volume

Production quantity directly influences process selection:

• High-volume runs (mass production): Automated sand molding lines or high-pressure molding systems deliver consistency and efficiency. Traditional jolt-squeeze machines are less viable due to lower productivity and labor intensity.

• Medium to large batches: High-pressure molding or resin sand processes offer a balance of quality and output.

• Low-volume or heavy castings: Manual molding with resin sand remains a flexible and cost-effective solution, accommodating complex geometries without significant tooling investment.

• Specialized high-volume methods: Die casting, low-pressure casting, and centrifugal casting require substantial upfront investment in equipment and dies, making them economical only at large scales.

3. Evaluate Cost Against Dimensional and Performance Requirements

Each casting method involves trade-offs among precision, surface quality, tooling cost, and per-part price. A comprehensive cost-benefit analysis should consider:

• Initial investment: Sand casting requires minimal tooling; permanent mold and die casting involve higher capital expenditure.

• Dimensional accuracy: Investment casting and die casting achieve tighter tolerances and smoother surfaces than sand casting.

• Production rate: Automated lines and die casting support high throughput, whereas manual and resin sand processes are slower.

• Material properties: Some processes enhance metallurgical integrity (e.g., vacuum casting, squeeze casting) for demanding applications.

The optimal choice aligns technical specifications with economic feasibility, ensuring the selected method meets both performance targets and budget constraints.

Professional Insight: When to Consult a Foundry Expert

While these guidelines provide a foundation, real-world selection often requires technical consultation. Factors such as part geometry, alloy type, heat treatment needs, and post-machining requirements can significantly influence the ideal process.

Engaging with an experienced foundry partner early in the design phase can help:

• Optimize component design for castability

• Reduce total cost through process optimization

• Minimize defects and improve yield

• Shorten development timelines

Conclusion

Selecting the right iron casting process is a multidimensional decision based on volume, cost, quality, and component function. Sand casting offers unmatched flexibility for most applications, while specialized methods address needs for precision, surface finish, or high-volume efficiency. A strategic approach—combining technical knowledge with economic analysis—ensures reliable, cost-effective manufacturing outcomes.