Machined Aluminum vs. Cast Aluminum, What is Difference?
Casting is an olden manufacturing process that dates back about 6000 years. With advances in technology, casting continues to grow in popularity. One of its most notable products is cast aluminum.
But for anyone who is used to CNC machining process to produce machined aluminum and other products may have a different opinion. That begs the question, what is the comparison between cast aluminum and machined aluminum? Is one actually better than the other one?
This article will outline the features and elements of the two types of manufacturing process. It is an analysis that can help you make a crucial decision for your next project involving aluminum alloys.
What is Machined Aluminum?
Machined aluminum refers to an aluminum part or product that has undergone machining process.
You can get machined aluminum alloys through different machining technologies. The most popular ones include vertical and horizontal milling, and computer numerical control (CNC) machining.
CNC machining processes incorporate CNC equipment and computer software. These control the operation of the cutting tool on the aluminum workpiece.
Various industries use machined parts of aluminum alloy for different applications. You will find machined aluminum parts in medical, automotive, aerospace, and telecommunications, among many other industries.
What is Cast Aluminum?
This another method of producing aluminum parts or products. Cast aluminum production involves spilling molten metal into a form or mold. This manufacturing method is popular for the production of complex and detailed aluminum components.
Permanent Mold Casting
The mold may be permanent/reusable or expendable. Under permanent mold casting, there are options such as die casting, vacuum die casting, investment casting, and lost foam casting.
In die-casting, pressure forces the molten metal into a mold. It is a fast process that produces accurate parts. Manufacturers looking for mass production of parts may use this permanent mold casting version. Die casting could be either cold or hot.
As the name suggests, vacuum die casting involves the formation of a vacuum. The vacuum forces the molten aluminum to flow into the mold cavity. Through vacuum control, the machinist can easily determine the quality of the finished part.
Expendable Mold Casting
When the mold is temporary, we call that and expendable mold. Sand casting and lost wax casting are both types of expendable mold casting.
The mold in this case is expendable or temporary because you need to break it down once the aluminum alloy is cast. The mold material are usually inexpensive, so this casting method is cost-effective.
Unfortunately, expendable mold casting does not have the dimensional accuracy of permanent mold casting. Its capability for scalability is also limited. Due to the significant amount of waste, this casting method can also have a negative impact on the environment.
The Difference Between Machined Aluminum Parts & Cast Aluminum Parts
Here are details of the areas where the differences between cast aluminum and machined parts are most notable:
#1 Machined Aluminum vs. Cast Aluminum: Types and grades of materials
The first difference is in the types and grades of aluminum that each of these processes uses. Cast aluminum parts typically come from aluminum grades A356, A390, and A380. On the other hand, machined aluminum parts usually comprise aluminum 2024, aluminum 6061, and aluminum 7075.
Each of these materials has its unique properties, hence its applicability. Aluminum A356 presents excellent capability for casting and welding, and is strong. Its popular applications include aerospace and automotive parts.
When it comes to A390, the biggest property is incredible wear resistance. This is due to the high silicon content. It could be a bit difficult to cast, but it offers significant hardness.
In aluminum A380, you are looking at superior mechanical properties. The aluminum type is also ideal for casting and is relatively affordable.
For the machined aluminum alloys, you also get unique properties. For instance, both aluminum 6061 and aluminum 7075 offer good strength.
#2 Machined Aluminum vs. Cast Aluminum: Production Speed
The lead time will make sense if a customer requires the product in bulk or quickly. In this case, you will note that the production speed for machined aluminum and cast aluminum differ. The reason for this is the difference in production steps for the manufacturing processes.
Aluminum casting entails mold design, melting the metal, pouring the molten metal into the mold, cooling and removing. Finally, the cast part undergoes the finishing stage, where sanding and related activities take place.
CNC machining processes follow a different set of steps compared to metal casting. The process starts with the programming stage. The machinist prepares a program aligned to the CAD model.
From programming, the operator needs to set up the CNC machine. Part of this is the selection of the right cutting tool and workpiece material. After machining processes, the machined aluminum part undergoes polishing, anodizing, or any other post-processing step.
Casting is typically faster than CNC machining, particularly for large volume production. However, Considering the time and cost of making molds, we recommend using CNC Machining for orders of less than 500pcs.
#3 Machined Aluminum vs. Cast Aluminum: Surface Finish
For a wide range of high-quality surface finishes, CNC machining for aluminum alloys is the better choice. CNC machined parts can have any type of surface finish, from super shiny to rough. Designers use this level of versatility in surface finish to attain different requirements of a part’s surface – grip, appearance, etc.
On the contrary, the customization capability level for aluminum casting is not as high. Of course, we can improve the surface finish of the parts for you through polishing, electroplating and other surface treatments
#4 Machined Aluminum vs. Cast Aluminum: Precision & Accuracy
When the focus for manufacturing aluminum alloys is precision and accuracy, CNC machined parts are the best bet. The fact that the process relies on a computer program means that it is possible to produce the most intricate parts to the smallest detail. This manufacturing method can reach tolerances of thousands.
While aluminum alloy casting is also of good quality, the possible tolerances may not be as tight. Variations come from aspects of casting such as thermal expansion and gradual mold wear.
#5 Machined Aluminum vs. Cast Aluminum: Application
Machined aluminum is often used in aerospace, automotive, and high-end electronics where precision and strength are paramount.
Cast aluminum is commonly used in automotive components, architectural structures, and furniture where the cost is a significant factor and the parts do not require the same level of precision as those made through machining.
Conclusion
The choice between machined and cast aluminum depends on the specific requirements of the application, including factors like cost, complexity of design, required precision, and the strength of the final part.
Author
Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.