INVESTMENT CASTING

WHAT IS INVESTMENT CASTING?

Investment casting, also known as lost wax casting, is a traditional manufacturing process that originated thousands of years ago. This process is utilised to create metal parts and components with complex shapes and intricate details. It is a cost-effective method to produce complex parts.

The process commences with the crafting of a wax or plastic pattern, an exact replica of the desired part. Our experienced engineers excel in designing tooling for creating these patterns. Once the tools are devised, we utilise 3D printing for initial rapid prototyping, which undergoes testing before the production phase. Subsequently, the pattern is coated with a ceramic slurry to form a shell around it. After the shell has hardened, the wax or plastic is melted out, leaving behind a cavity in the shape of the desired part. Molten metal is then poured into the cavity, filling the space vacated by the melted pattern. Following solidification, the ceramic shell is removed, revealing the finished metal part. Investment casting is esteemed for its capability to produce parts with tight tolerances, excellent surface finish, and intricate geometries.

Here at A & M Manufacturing Company Ltd, we possess the capability to manufacture metal parts and components with extremely tight tolerances and complex and intricate shapes and designs, both internally and externally. We can cast metal parts and components with a wide range of materials using the investment casting technique, including stainless steel, carbon steel, cast iron, aluminium, and many more.

INVESTMENT CASTING PROCESS

1. Pattern Creation
The process begins with the creation of a master pattern, typically made from wax, but sometimes plastic or frozen mercury are used. This pattern is an exact replica of the part to be cast, including allowances for material shrinkage during the cooling process.

2. Assembly
Multiple wax patterns are attached to a central wax sprue, creating a tree-like assembly. This assembly allows multiple parts to be cast in a single process, improving efficiency.

3. Shell Creation
The wax tree is dipped into a ceramic slurry, coated with fine sand, and then left to dry. This process is repeated several times to build up a thick ceramic shell around the wax patterns. Each layer must dry thoroughly before the next is applied, ensuring the shell’s strength and thickness.

4. Wax Removal
Once the ceramic shell is dry and hard, the wax is melted out, leaving a hollow cavity in the shape of the patterns. This step is typically done in an autoclave or by using steam to ensure complete wax removal.

5. Ceramic Shell Firing
After wax removal, the ceramic shell is fired at high temperatures to burn out any remaining wax residue and to strengthen the mould. This firing process hardens the shell and prepares it for the metal casting phase.

6. Pouring
The molten metal, which can be steel, aluminium, bronze, or any other alloy, is poured into the preheated ceramic shell. The metal fills the cavity left by the wax patterns, taking on the precise shape of the original designs.

7. Shell Removal
Once the metal has cooled and solidified, the ceramic shell is broken away to reveal the metal casting. This is often done using vibration or by blasting with water or media.

8. Cut-off and Finishing
The individual castings are cut away from the central sprue using a high-speed cutting tool. The parts are then finished, which may involve grinding to remove any marks from the sprue attachment points and further machining for dimensional accuracy.

9. Inspection and Quality Control
The final step in the investment casting process is inspection and quality control. Castings are inspected for dimensional accuracy, surface finish, and structural integrity. Techniques such as X-ray, ultrasonic testing, and dye penetrant inspection may be used to identify any internal or surface defects.

INVESTMENT CASTING ADVANTAGES

Unlike other manufacturing processes, investment casting offers several clear advantages, particularly for smaller products with intricate and complex designs. The advantages are as follows:

High Precision: Investment casting technique allows for intricate and complex shapes to be produced with tight tolerances, resulting in high precision and accuracy in the final product.
Smooth Surface Finish: The process produces parts with smooth surface finishes, reducing the need for additional machining or surface finishing operations such as polishing.
Wide Range of Materials: Investment casting can be used with a wide variety of metals and alloys, such as stainless steel, carbon steel, high strength steel, nickle based steel, manganese based steel, cast iron, aluminium, bronze, titanium, and many other alloys, offering flexibility in material selection for different applications.
Cost-Effective for Large Quantities: While the initial tooling costs can be high, investment casting is cost-effective for producing parts in large quantities compare to machining.
Design Flexibility: Investment casting allows for design flexibility, enabling the production of complex shapes, thin walls, and intricate details that may be difficult or impossible to achieve with other manufacturing methods.
Versatility: Investment casting is suitable for producing a wide range of parts across various industries, including aerospace, automotive, defence, marine, oil and gas, as well as railway system, among others.
Dimensional Stability: Parts produced through investment casting process exhibit good dimensional stability and repeatability, ensuring consistency and reliability in the final product.

OUR PROMINENT INVESTMENT CASTING CAPABILITIES

A & M Manufacturing Company Ltd has one of the world’s most advanced silica sol investment casting techniques. The complete implementation of silica sol binders in investment casting has revolutionised the process in several key ways:

Replacing environmentally harmful curing agents with silica sol improves the working environment and enhances the quality of castings.
Drying time for the silica sol shells has been drastically reduced from 8 hours to just one hour per layer, significantly boosting production efficiency and shell strength.
This innovation has expanded the application of silica sol technology to encompass a wider range of materials, including carbon steel and various alloy steels, while also enabling the production of larger investment casting parts weighing up to 50 kg. This expansion not only diversified our offerings but greatly reduced production costs, especially for carbon and alloy steels that were historically costly to produce using silica sol binders.
The introduction of a fully automated shell-making process, incorporating mechanical handling and automatic drying. This system has the capacity to create up to 8 layers of shells, with each layer managed by a separate automated unit, ensuring precise control and eliminating human-operated variability.
we have created shells with markedly greater strength compared to conventional silica sol binders. At the same time, we have succeeded in reducing shell thickness by nearly half. This decrease in thickness improves shell permeability and is instrumental in achieving the high-quality surface finish of our castings.

We offer silica sol investment casting services from our Chinese affiliated foundries and workshops, while we provide tooling design and manufacturing guidance and support. Our capabilities include:

We create small and large castings, ranging from as light as 1g up to 50kg, using the silica sol investment casting technique. Without compromising dimensional accuracy and mechanical properties, we consistently deliver top-quality castings that meet customers’ requirements.
We are capable of supplying all types of castings, from class 1 aerospace castings to commercial grade castings, regardless of their design complexities and intricacies. Our experienced engineers excel at solving challenges, including tooling design, and they possess the expertise to overcome obstacles that may arise during the manufacturing process, such as gas porosity, shrinkage defects, mould defects, irregularities during the pouring stage, as well as metallurgical defects.
All order volumes are welcome at A & M Manufacturing, we are capable of supplying over 5000 tons of investment casting parts per year.
We utilise various types of materials and alloys in our investment casting technique, including carbon steel, stainless steel, high-strength steel, cast iron, aluminium, titanium, bronze, and various types of heat-resistant and wear-resistant alloys. Castings created from these alloys are often used in aerospace, defence, automotive, railway systems, medical, oil & gas, construction machinery, mining, marine, and many other industries and applications.

WHY A & M MANUFACTURING COMPANY LTD?

We take pride in our ability to manufacture investment casting parts of the highest quality and meet your requirements. Over the past 30 years, we have consistently delivered top-quality products and solutions for safety-critical sectors such as aerospace and railway systems.

With 30 years of manufacturing experience, we have worked with a wide array of industries and applications, placing us in a leading position as a provider of manufacturing solutions, services, and product supply.

In addition to our expertise in providing valuable guidance and support, we are equipped to work with the most advanced facilities and equipment in the industry, ranging from wax pattern production equipment such as automated wax injection machines to inspection equipment including X-Ray machine.

Our large manufacturing network in China and Taiwan has made us extremely cost effective.

Beyond our manufacturing expertise, we provide versatile supply options, such as UK-based stockholding facilities, to meet diverse customer requirements and preferences. This approach ensures streamlined logistics and prompt delivery.

WHY SHOULD YOU CHOOSE INVESTMENT CASTING

There are numerous manufacturing processes available to consider, so why opt for investment casting? Several factors should be taken into account.

The investment casting process yields parts with unparalleled precision, making it ideal for products with intricate designs both internally and externally.

For medium to large order quantities, where the combined cost of tooling and casting is lower than that of machining, investment casting is a favourable option.

If a visually appealing surface finish is required for cosmetic purposes, the investment casting technique should be considered.

However, if your products exceed 50kg in weight, sand casting, which is typically more suitable for heavier items, may be a preferable choice.