Choosing the right casting method isn’t always straightforward. Each process comes with trade-offs in cost, tolerances, surface finish, and material options.

If you’re developing custom metal parts and not sure which method fits best, this quick guide is for you. We’ll walk through the most common casting processes. Detail their tolerance levels and best-use cases.

Quick Comparison: Custom Metal Casting Methods

Method	Best For	Volume	Tolerance	Surface Finish	Materials
Sand Casting	Large, simple parts	Low-High	±0.5–1 mm	Fair	Steel, Iron, Aluminum
Investment Casting	Thin-walled, detailed parts	Med-High	±0.1–0.2 mm	Excellent	Stainless, Alloys, Titanium
Die Casting	High-volume precision components	High	±0.05 mm	Excellent	Aluminum, Zinc, Magnesium
Full Mold Casting	Complex foam shapes	Low-Medium	±0.5 mm	Good	Gray Iron, Aluminum
Plaster Mold Casting	Lightweight prototypes	Low	±0.25 mm	Very Good	Aluminum, Zinc

 

What Is Metal Casting?

Metal casting is the process of pouring molten metal into a mold, where it cools and solidifies into a final part. It’s one of the oldest and most flexible manufacturing production techniques.

The typical casting workflow includes:

1. Pattern Development: Creating a 3D pattern of the part.
2. Mold Preparation: Using sand, plaster, or permanent molds.
3. Melting & Pouring: Heating and filling the mold with metal.
4. Cooling & Removal: Extracting the solidified part.
5. Post-Processing: Trimming, heat treatment, or machining.

Casting is categorised by mold type: expendable molds (used once) and non-expendable molds (reused for multiple cycles).

Expendable castings are discarded once finished with. Non-expendable casting uses permanent molds intended for long-term usage. Aside from the molds. Casting is divided into further categories depending on the material used to make the molds.

Let’s take a look at the different types in more detail.

What Are the Main Expendable Mold Castings?

1. Sand Casting

Sand casting uses molds created from sand mixed with polymers/chemical binders. Compared to other expendable molds, it’s more durable. Therefore, it allows for longer production runs using the same mold.

This is one of the oldest casting methods. Today it’s used for sand casting parts such as pump housings, engine brackets, and industrial machinery. Compared to other methods, sand casting suppliers can often offer large mold sizes with minimal tooling cost. Especially for prototypes or low-volume jobs.

Why use it?

• Mold sizes up to several meters.
• Tolerances of ±0.5-1.0 mm (standard).
• 3D printed sand molds possible for low-volume runs.
• Excellent option when comparing sand casting vs die casting for large or simple shapes.

 

2. Plaster Mold Casting

Plaster mold casting uses molds made from gypsum plaster. It offers faster setup than sand casting but with lower durability. It’s suited for non-ferrous metals and is used for short-run or prototype parts.

Why use it?

• Quick mold preparation.
• Good dimensional accuracy.
• Surface finish averages ~2.5 µm Ra.
• Ideal for casting thin-walled parts during early-stage prototyping.

3. Investment Casting (Lost-Wax Casting)

Investment casting, known as lost-wax casting, uses advanced wax materials more stable than traditional composites. It’s ideal for parts with complex geometries or made from high-performance alloys. Especially when tight tolerances or intricate detailing are required.

Tooling for investment casting can be expensive, making it more suitable for higher-volume production. However, 3D printing the wax patterns can reduce tooling costs and make it viable for small-batch runs as well.

Why use it?

• Tolerances as tight as ±0.1 mm.
• Surface finishes as fine as 1.6 µm Ra.
• Ideal for complex alloys and net-shape parts.
• A preferred choice in investment casting vs sand casting when tolerances and intricacy matter.

What Are the Main Non-Expendable (Permanent) Mold Casting?

1.    Die Casting

The die casting process involves injecting molten metal into a reusable steel mold, using high pressure. It is often used for aluminum, zinc, and magnesium parts.

Why use it?

• Tight tolerances (±0.05 mm).
• Minimal post-processing.
• Ideal for aluminum, zinc, magnesium.
• Often compared in sand casting vs die casting evaluations when scale & precision are priorities.

2. Permanent Mold Casting

Permanent mold casting uses gravity to fill reusable molds made from steel or cast iron. It offers better dimensional stability than sand casting. Ideal for medium-volume production.

Why use it?

• Reusable molds reduce per-part cost over time.
• Suitable for non-ferrous metals like aluminum and magnesium.
• Good dimensional consistency.

3. Centrifugal Casting

Centrifugal casting involves spinning the mold at high speeds while molten metal is poured in. The centrifugal force distributes the metal evenly, helping eliminate impurities and improving overall density.

Why use it?

• Produces high-strength, defect-free parts.
• Ideal for symmetrical shapes such as pipes, rings, and cylinders.
• Excellent material purity and grain structure.
  
  

When to Use Each Casting Method

Process	Best For	Volume	Tolerance	Surface Finish
Sand Casting	Large, simple geometries; low-cost prototyping	Low–High	±0.5–1.0 mm	Fair (Ra 6.3–25 µm)
Plaster Mold Casting	Thin-walled prototypes with good detail	Low	±0.25–0.5 mm	Very Good (Ra ~2.5 µm)
Investment Casting	Intricate, tight-tolerance parts; complex alloys	Medium–High	±0.1–0.2 mm	Excellent (Ra 1.6 µm)
Full Mold Casting	Complex foam patterns; parts with no parting lines	Low–Medium	±0.5–0.75 mm	Good (Ra 3.2–6.3 µm)
Die Casting	High-volume precision parts in non-ferrous metals	High	±0.05–0.1 mm	Excellent (Ra 1.6–3.2 µm)

Conclusion: Custom Metal Casting: Methods, Materials & When to Use Each

Every casting method has trade-offs. Some offer lower costs. Others deliver superior tolerances/smoother finishes. But the key is matching the right process to your part geometry, performance needs, and production volume.

Once the appropriate casting method is defined, selecting from the best metal casting platforms online becomes the next step in securing qualified foundries and competitive quotations.

At Haizol, we simplify the sourcing process for custom metal casting companies. Our platform connects you with trusted sand casting suppliers, investment casting experts, and other verified foundries across Asia. Submit your request for custom metal casting services today and get multiple quotations within 24 hours.