What Is Precision Casting?
The demands of modern-day manufacturing are becoming more complex by the day. This calls for more sophisticated casting techniques that guarantee high precision parts. This can only be achieved through precision casting.
The precision casting process results in more resilient parts, making it one of the most used industrial casting processes.
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The precision casing is also known as investment casting or lost wax casting. The process uses wax and ceramic mod to cast metal parts into various shapes. Being one of the oldest casting techniques, precision casting has advanced and become more prevalent in industrial applications.
Applications of precision casting range from the firearms industry, gas, oil, food industry to the medical sector. Many manufacturers have proven that precision casting can produce more durable and stronger metal components. This has seen an increase in its use in aerospace, defense, and medical applications.
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What Is Precision Casting? The Method and Its History
Precision casting is an industrial process as known as the lost wax casting technique. The process is one of the oldest casting techniques ever used to produce metal components. Precision casting has been used in various industries for at least 5,000 years. Back in the day, blacksmiths used beeswax to create patterns required for the casting process.
Currently, more developed wax technology, refractory materials, and alloys are used to make these patterns. Precision casting is mainly preferred due to its ability to create metal parts with high precision, integrity, and versatility. Additionally, the process can be repeated to produce more accurate components.
The wax pattern used in precision casting should withstand all the force associated with making molds. Most of the wax used in precision casting can be reused. Alternatively, you may not want to go through all the steps of the precision casting process. In this case, you can use the lost foam casting method to eliminate various phases of the process.
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The process is also called investment casting because of the patterns invested using refractory materials. Many materials can be used for precision casting, including alloys of stainless steel, brass, aluminum, carbon steel, and glass.
The refractory material used is poured into the mold, a cavity created to produce the desired size and shape. The refractory material is usually hard, meaning precision casting produces metal components with excellent surface finish and quality. This reduces the need for other machining processes.
The common methods of precision casting include water glass casting and silica sol casting. The most notable difference between the two is the surface quality and the overall cost that goes into the process. For instance, during water glass casting, the waxes are removed in water with extremely high temperatures. Accordingly, the ceramic mold is often created using water glass quartz sand.
On the other hand, during silica sol casting, the wax is removed in the flash fire. Accordingly, the ceramic mold is made using silica sol zircon sand. This method is costlier but also guarantees products with an excellent surface finish.
Precision casting can be used for manufacturing smaller components and larger components of about hundreds of pounds. It is essential to note that precision casting is often more expensive than sand casting and die casting. However, the cost for every unit of production reduces with an increase in production volume.
Precision casting is typically used to manufacture metal parts with high precision and more complex features that cannot b achieved using other casting processes. Additionally, it is used to produce an excellent surface finish and low tolerances with minimal or no machining.
The Precision Casting Process
The following is an outline of the precision casting process. The steps may vary, depending on a manufacturer’s preference or the part being cast.
1. Making The Mold
The process starts with designing the mold according to the required product shape and size.
2. Wax Injection
Using a machine, the wax is injected by injection molding. This process is used to create wax patterns.
3. Assembly Tree
The wax patterns created in the previous step is attached to a sprue to make an assembly tree.
4. Making The Shell
The assembly tree is immersed in a ceramic slurry then sand to create a shell. A maximum of six layers can be used before the shell is left to dry.
5. Dewaxing
After the shell has dried, the wax is removed through heating. The wax melts and flows out of the shell.
6. Casting
The molten metal is poured into the shell and allowed to cool and solidify.
7. The Knockout Phase
After the molten metal in the shell has solidified, the shell is broken using a knockout machine. The parts are then cut off from the sprue.
8. Post Treatments
After the product is cast, it is inspected for flaws according to the required quality. If flaws are detected, it is subjected to post-treatment, including grinding and other machining processes. This phase ensures the item is of high surface finish and quality.
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Precision Casting Advantages
Most manufacturers prefer the precision casting technique because it comes with lots of benefits, such as:
- Excellent surface finish
- Produces parts that are relatively closer to the finished design
- Tighter tolerance
- Relatively cost-effective when producing high volumes
- Does not require machining and other post processes
However, precision casting can also be expensive when the production volume is low. Additionally, the process tends to be more sophisticated and requires many tools that increase the overall cost. Lastly, precision casting requires specialized skills and knowledge. These are some of the disadvantages of precision casting.
Final Thoughts
Like any other production technique, precision casting has its sets of pros and cons. However, it is safe to say that the advantages far outweigh the disadvantages. This means that precision casting remains one of the best casting methods you can use for the industrial manufacture of metal parts.
You can be sure to produce parts with exceptional surface finish and highly delicate features through precision casting. Additionally, your products will come with highly accurate dimensions and details. As much as the cost can be an issue, this should not be a worry if you intend to embark on large-scale production.