What is investment casting？
Investment casting, also known as lost wax casting or precision casting, is the method of producing precise products. The term investment comes from investing which means surrounding. So, this method involves a manufacturing process in which a ceramic mold surrounds a wax pattern.
The wax pattern has a coating of refractory material and it obtains the shape which needs to be cast for the final product. The shell becomes hard which is then melted and converted into a mold. Mold breaks and you will get the final product successfully.
Compared with other casting processes, the investment casting process not only produces products with high surface finish and precise dimensions but also produces parts with more complex designs. In addition, the cost of investment casting is lower, and there are no restrictions on the size of the product. This makes the investment casting process more favored by consumers.
Why is the investment casting process better than others?
Various other cast manufacturing processes such as sand casting can also make the mold or final product. However, lost wax casting or investment casting methods are most commonly used. The reason lies in its unique features which are as follows:
- Unlike other methods, it produces highly accurate and precise components hence also known as precision casting.
- The casting of extremely complex and intricate products are achieved easily with this method.
- Its short length and highly in-depth features can cast objects of even 0.40mm thickness.
- With a high tolerance of 0.075mm, it provides excellent dimensional precision of the objects.
Investment casting process & lost wax casting process
The investment casting process consists of several steps: design of the master module, mold making, pouring and solidification, pattern assembly, wax dipping, dewaxing, mold shell roasting, solidification, and knockout
1. Design of the master module
The first step in investment casting is to design and manufacture the mold with the customer. Our engineers will prepare a master pattern for the customer to start the project.
Master patterns can be created in wax, clay, steel, or other materials. The pattern is then shaped according to the final product shape required by the customer. This can be done manually or with the help of machine molds. After eliminating errors and mistakes, the final shape of the product is formed.
2. Mold making
To make a copy of the wax mold, you need to create a mold, also called a master mold. You can easily produce such molds using machining tools.
However, if your wax mold is of steel, then you should prepare the mold directly from the steel master. The number of molds depends on the number of cast products you need.
Then, divide the prepared mold into two halves so that you can produce the exact part without separating the lines.
3. Poring and solidification
The produced mold pattern is then poured into the ceramic shell. After pouring the molten wax into the master pattern, cover it with sand stucco and allowed it to dry.
The coating process repeats until you get the required thickness ranging about 3mm. The dimensions and configuration of the final product are then adjusted following this thickness.
4. Pattern assembly
The shell is then heated, the wax pattern melts away and the hard shell turns into a hollow ceramic shell.
Onto a wax sprue, these wax patterns are then assembled. With the help of heating tools, all the wax patterns are then attached with a central sprue. This makes a tree-like arrangement or an assembly of wax patterns.
5. Wax dipping
The main purpose of dipping the wax pattern is to produce a prime coat. For this, dip the pattern into a refractory material so a uniform coating surface forms.
This involves the production of a very thin and smooth layer so a delicate and accurate final product forms, and this is the key to precision casting.
At this stage of investment casting, you’ll get the layers, then dry the first or initial layer so the strength will enhance further.
This will increase the hardness and strength of the final product and then the leftovers will dry completely.
After the wax material has dried completely, it puts into a de-waxing autoclave or simply in an oven to initiate the melting process.
Just after you put the wax material into the autoclave, it starts melting and the residues begin to vaporize quickly. This is the de-waxing of the prepared wax material.
The most important thing to note down is, this is the most crucial stage of the investment casting process. This is because any error in it will affect your yield production.
6. Mold shell roasting
Once the dewaxing process is complete, heat the mold shell at about 1100℃ to 1200℃. So it heats effectively. Steel temperature at 1500℃-1600℃. This preheating process may take up to 1-2 hours.
Then an elevated temperature is maintained and the residual wax is burnt off. Pre-heating of the mold is done to increase the accuracy of the casting product and smooth the production method.
7. Solidification and knockout
With the help of hammering, and different techniques, solidify the metal, break it down and cut down the excess material.
Sprue the sprue and the final product obtains successfully with accurate shape, and size.
Dimensions & Tolerances
Precision casting requires precise dimensions. To ensure that we can accurately help our customers with the final product and save money during the fabrication process, we follow precise tolerances to determine the best dimensions.
Investment casting tooling
For better production casting, it is essential to use the right tools for investment casting. Our tools include manual, semi-automatic, and fully automatic, and each type of model has its own determination, click to learn more and see more information
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