FAQ

1. What is an “Investment Casting”?

The term “investment” may conjure images of money, but in investment casting, it refers to the ceramic materials used to create the mold into which molten metal is poured. The name originates from the traditional solid mold process, where a plaster-like material is “invested” (or poured) into a container holding a cluster of patterns. Once hardened, these patterns are removed—leaving a hollow mold ready for casting.

The Investment Casting Process

In the modern lost wax investment casting method, here's how the process works:

1. Wax Pattern Creation

Wax is injected into a precision-machined aluminium die to form a pattern that is an exact replica of the final part. A new wax pattern must be made for each casting.

2. Pattern Assembly

Multiple wax patterns are assembled onto a central sprue to form a "tree." This allows multiple parts to be cast in one mold.

3. Ceramic Shell Building

The wax assembly is repeatedly dipped into an agitated vat of ceramic slurry, then coated with refractory sand and dried. This process is repeated to build a ceramic shell ~3/8″ thick.

4. Dewaxing

The shell is heated in a flash furnace (~1400°F) or autoclave to remove the wax. This leaves a hollow ceramic mold.

5. Shell Preheating & Metal Pouring

The empty shell is then preheated to 1800–2000°F, depending on the alloy, and molten metal is poured directly into the hot mold.

6. Shell Removal & Finishing

Once cooled, the ceramic shell is vibrated and blasted off, and the castings are separated from the sprue. Further processes like cut-off, grinding, heat treatment, straightening, and blasting are performed—similar to other casting methods.

This highly controlled process allows for the production of complex, high-precision metal parts with excellent surface finishes and dimensional accuracy—making investment casting ideal for aerospace, medical, defence, automotive, and industrial applications.

2. What Alloys Can Be Poured as an Investment Casting?

One of the greatest advantages of the investment casting process is its versatility in accommodating a wide range of ferrous and non-ferrous alloys. This flexibility allows us to produce high-performance components tailored to specific mechanical, thermal, and chemical requirements.

Ferrous Alloys

We commonly pour a broad range of ferrous materials, including:

• Carbon Steels – Ideal for general-purpose structural applications
• Alloy Steels – For improved strength, hardness, and wear resistance
• Stainless Steels
• 300 Series (e.g., 304, 316) – Corrosion-resistant and non-magnetic
• 400 Series – Heat-treatable with moderate corrosion resistance
• Precipitation Hardening (PH) Grades – 15-5PH, 17-4PH for high strength and corrosion resistance
• Duplex Stainless Steels – Excellent strength and resistance to stress corrosion cracking
• Nickel-Based Super Alloys – High strength and oxidation resistance at elevated temperatures
• Cobalt-Based Alloys – Superior wear and corrosion resistance in extreme environments

Non-Ferrous Alloys

We also pour a variety of non-ferrous metals, including:

• Copper-Based Alloys – Including bronze and brass, offering excellent thermal and electrical conductivity

3. What Are the "As-Cast" Dimensional Tolerances I Can Expect?

Investment casting offers excellent dimensional accuracy compared to other casting methods. While tolerances can vary depending on part size, geometry, and alloy, the general as-cast tolerance guideline is:

• ±0.010 inch for the first inch of a linear dimension
• ±0.005 inch for each additional inch

This rule of thumb provides a strong baseline for most parts and materials.

Tight Tolerances with Secondary Operations

If tighter tolerances are required beyond as-cast capabilities, secondary machining or finishing operations (e.g., CNC, VMC, HMC machining, grinding) can be applied to critical features.

4. What Type of Surface Finish Can I Expect from an Investment Casting?

Investment casting provides an excellent as-cast surface finish due to the use of smooth wax patterns and fine ceramic shell materials.

Typical Surface Finish:

• Standard as-cast finish: ~125 microinches (Ra)
• Finer finishes (63–32 Ra microinches) are achievable, particularly on high-spec components like aerospace or turbine parts

Because the wax patterns are created in polished aluminium dies, the resulting metal surfaces are smoother than those produced by sand or shell moulding processes—often eliminating the need for extensive post-processing.

5. Aren’t Investment Castings Expensive? And If So, How Can They Save Me Money?

While investment castings are generally more expensive than forged parts or those produced by other casting methods, they often offer significant overall cost savings. This is primarily due to the near-net shape accuracy of the process, which allows for tight as-cast tolerances and greatly reduces the need for extensive machining.

In many cases, parts that would otherwise require milling, turning, drilling, or grinding can be investment cast with only 0.010" to 0.020" of finish stock—minimizing material waste, machining time, and labour. Additionally, features such as holes, fillets, and even complex geometries can be cast directly into the part, further eliminating secondary operations and reducing total production costs.

When evaluated from a total cost perspective—including material efficiency, reduced machining, fewer assembly steps, and improved part consistency—investment casting is often the most cost-effective manufacturing method, especially for complex or high-precision components.

6. What Are the Lead Times I Can Expect When Ordering an Investment Casting?

Standard Delivery Schedule

Simple Parts

For components with straightforward geometry and standard material grades, we offer a delivery timeline of 8 weeks from:

• Final drawing and technical specification approval
• Purchase order confirmation
• Completion of pattern/tooling development (if applicable)

Complex Parts

For parts with intricate designs, tight tolerances, special alloys, or additional machining/heat treatment requirements, the delivery timeline is typically 12 weeks from:

• Final approval of detailed specifications and 3D models
• Order confirmation and tooling readiness

Expedited Options

• For urgent requirements, expedited delivery options may be available depending on tooling complexity and production capacity. Please contact our team to discuss feasibility.