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Everything You Want To Know About Precision Casting

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Precision casting is a casting method relative to the traditional casting process. It can obtain relatively accurate shapes and high casting accuracy. The more common practice is to first make an electrode of the desired blank (which can be left with very little or no margin), and then erode the mold with the electrode to form a cavity.

Then the wax is cast by casting to obtain the original wax mold. The wax mold is then brushed with a high-temperature resistant liquid abrasive in one layer. After obtaining sufficient thickness, it is dried and then heated up to dissolve the internal wax mold to obtain a cavity consistent with the desired blank. Iron is then cast in the cavity and the shell is stripped off after curing to obtain a precision-manufactured product.

Modern investment casting methods

History and Development of Investment Casting

Lost wax casting, now called investment casting, is a kind of casting process with less cutting or no cutting and is an excellent process technology in the foundry industry, which is very widely used. It is not only applicable to various types and alloys of casting, but also produces castings with higher dimensional accuracy and surface quality than other casting methods, and even complex, high temperature resistant, not easy-to-process castings.

Investment casting is developed on the basis of ancient wax casting. As an ancient civilization, China is one of the countries using this technology earlier, as far as several hundred years BC, China’s ancient working people created this lost wax casting technology, used to cast with a variety of fine patterns and words of the bell.

Modern investment casting method in industrial production was practically applied in the 1940s. At that time, the development of aviation jet engines, required the manufacture of complex shapes like blades, impellers, nozzles, etc., the size of precise and smooth surface heat-resistant alloy parts.

Due to the heat-resistant alloy material being difficult to mechanical process, and the complex shape of the parts. They needed to find a new precision molding process, so drawing on the ancient handed-down lost wax casting, after the improvement of materials and processes, modern investment casting methods in the ancient process based on the important development.

Pressed melt

Investment Casting Process

  1. Creating the Model: First, a model is made using fusible materials like wax or plastic. This is known as the fusible model or mold.
  2. Applying the Coating: This model is then coated with several layers of special refractory material.
  3. Forming the Shell: Once the coating dries and hardens, it forms a solid shell around the model.
  4. Removing the Model: Steam or hot water is used to melt and remove the fusible material from inside the shell, leaving behind a hollow cavity in the shape of the model.
  5. Preparing for Casting: The empty shell is placed in a sandbox and surrounded with dry sand for support.
  6. High-Temperature Roasting: The shell, now in the sandbox, is heated to high temperatures in a roaster. If the shell is strong enough, it can be roasted without needing the sandbox.
  7. Casting the Metal: Finally, molten metal is poured into the heated shell. Once the metal cools and solidifies, it forms the final casting, replicating the original model’s shape.
Investment casting process

Accuracy of investment casting

The dimensional accuracy of investment casting is high, generally up to CT4-6 (CT10-13 for sand casting, CT5-7 for die casting).

Casting process method Alloy Type Tolerance class (CT)
Sand hand shaping Cast steel 11-13
Sand hand shaping Grey cast iron 11-13
Sand hand shaping Ductile Iron 11-13
Sand hand shaping Malleable Iron 11-13
Sand hand shaping Copper Alloy 10-12
Sand hand shaping Light metal alloys 9-11
Sand machine molding and shell shape Cast steel 8-10
Sand machine molding and shell shape Grey cast iron 8-10
Sand machine molding and shell shape Ductile Iron 8-10
Sand machine molding and shell shape Malleable Iron 8-10

Factors affecting the dimensional accuracy of the casting

-The shrinkage of the mold material.
-The deformation of the molten mold.
-The change in the linear volume of the shell in the heating and cooling process.
-The shrinkage of the alloy and the deformation of the casting in the solidification process.

Advantages of Investment Casting

-High Precision and Accuracy
-Superior Surface Finish
-Complex Design Capability
-Reduced Material Waste
-Versatility in Material Choice
-Minimal Machining Requirements
-Ability to Produce High-Temperature Resistant Parts

Conclusion

Precision casting is a manufacturing process that produces highly accurate and detailed components, often with a fine surface finish, using a mold created from a wax or plastic model.

Get Quality Investment Casting Services  in China

Easiahome Foundry stands out as the premier custom investment casting manufacturer based in China. Our expertise lies in delivering a diverse array of investment casting parts crafted from steel, iron, aluminum, and more.

Should you require an investment casting solution, please do not hesitate to reach out to us!

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