Knowledge Hub
10/01/2024
What is Investment Tooling and How Does it Work?
How Do You Define Investment Tooling?
Investment tooling is known by several different names, including investment casting and lost-wax casting.
It is essentially a method of tooling which involves the manufacture of a tool which acts as a mould for wax or plastic.
Wax has properties which make it ideal for use in the investment tooling process. For instance, it has a low melting temperature, excellent flow properties, and a smooth surface.
The shaping and dimensions of the tool mirror the shaping and dimensions of the required final component. Hot wax or plastic is poured into the tool pattern. Once hardened, the wax is removed and then coated with ceramic and stucco material. Heat is then applied until the wax or plastic pattern melts away, leaving only the mould.
Molten metal is then poured into the mould to create a final metal part that is identical to the original wax pattern.
The process is ideal for producing parts where tight tolerances are required.
Why Aluminium?
Aluminium is often used for investment tooling.
Its thermal properties allow heat to be reduced quickly, which helps to reduce cycle times.
Its versatility means that it can also be easily melted, cast, and machined, allowing complex designs to be created with relative ease.
Aluminium also gives a particularly smooth finish to parts created from investment casting.
It’s less dense than some other metals, such as steel. This lower density means that it is easier for production operatives to handle and transport during the manufacturing process.
Aluminium is highly recyclable, making it a more environmentally friendly option than some other metal-based materials.
Castings made from aluminium alloys are also highly resistant to corrosion. This protects the integrity of the final component, ensuring that a higher quality of part can be produced.
Step-by-Step Process
Investment tooling can be divided into 3 main phases: design, manufacture, and post-manufacture testing.
Each stage of the process is crucial in ensuring that the final components are produced to meet the precise specifications outlined, and to achieve the optimum level of part quality.
We will now look at each of these stages in more detail.
Design
The first step in the process is to create an aluminium tool. To do this, a design for the tool needs to be created. This is achieved by creating a 3D model of the tool using computer-aided design (CAD) software.
It is crucial to get the 3D model correct, as this will form the basis for the specifications and dimensions of the tool. The tool will need to be robust and precise, given that it will need to hold up to substantial production runs where repeat components may be needed over time.
Manufacturing the Tool
As soon as the design has been completed, the tool is ready to be manufactured. The first step in the manufacturing process will be the fabrication of the tool. There are a variety of fabrication techniques which can be used, many of which depend upon the complexity of the tool design.
A common manufacturing technique is CNC machining, while laser cutting can also be employed. Toolmakers produce the wax dies using CNC lathes, mills, and electrical discharge machining (EDM), or spark erosion, as it is otherwise commonly known. If required, tools can then be given specialist finishes, such as texturing, engraving, or polishing.
The metal mould or die is designed specifically to hold the wax or plastic inside the tool. Liquid wax or plastic is then injected into the mould at high temperatures. The wax then undergoes a significant cooling process, at the end of which the final metal part is formed.
Post-manufacture Testing & Analysis
The tool is then put through a rigorous testing process to ensure the integrity of its manufacture. It needs to be absolutely accurate and precise. Any slight anomalies in its design or manufacture could affect the quality of the final components. This is particularly important in investment tooling if the tight tolerances already discussed are to be achieved.
Any outstanding issues with the tooling will need to be identified at this stage and resolved.
As soon as this process has been concluded, the production cycle can begin.
Advantages of Investment Tooling
Precision and Accuracy – Investment casting tooling can achieve very tight tolerances and high levels of detail.
Cost effective – Investment casting tooling is a less expensive option than some other forms of tooling due to lower production costs.
Multiple Alloys – Manufacturers can use a variety of potential alloys according to the desired objective. This allows for significant cost savings which can be transferred to the customer.
Flexibility of design – Because a variety of alloys are used, there is the flexibility to achieve pretty much any design feature that is required.
High Consistency of Final Product – Using the same tool continuously to produce the same wax patterns ensures consistent delivery of final components to the same tolerances.
Waste Reduction – There is less material wastage with this method due to the lower levels of machining that is required. It is, therefore, a more environmentally friendly option.
Quicker route to market – The overall process time is reduced, meaning that final components can be turned around in shorter cycle times ahead of full-scale market rollout.
