Why Stainless Steel and Aluminium are Good for CNC Machining?
Finding the perfect material for our CNC machining projects may appear daunting, with numerous elements to consider, including machinability, mechanical properties, pricing, durability, weight, corrosion resistance and surface finish.
Aluminium and stainless steel are by far the most preferred metals for custom components manufacturing and prototyping out of the myriad of metals that can be handled with CNC machining. Both stainless steel and aluminium have similar aesthetics, are adaptable and frequently used in products we encounter daily.
Here is a comprehensive guide that covers every aspect of why CNC businesses prefer stainless steel and aluminium over other materials for manufacturing operations. Let’s discuss both of them one by one.
Stainless Steel
As the name suggests, stainless steel is an alloy of steel that doesn’t corrode. It consists of iron as the base element with a minimum 10.5% chromium incorporated to produce an alloy with corrosion-resistance properties.
While stainless steel is commonly assumed to be corrosion-resistant, numerous grades of stainless steel are produced, with alloying elements added to influence its properties, for example, mechanical strength and corrosion resistance.
Martensitic grades contain a proportion of carbon to boost their hardness and strength.
Adding nickel to the iron helps stabilise its crystalline structure by creating an austenitic structure. The addition of nickel increases the ductility, toughness and weldability of the stainless steel and can help to increase its resistance to reducing acids and improve high temperature oxidation resistance.
Talking about the benefits, one of the most significant advantages of employing stainless steel in CNC machining is its ability to instantaneously regenerate the protective chromium oxide layer after completion of the machining process. It is accomplished through a process known as passivation, in which chromium builds an extremely thin film 2-5nm thick to resist corrosion. . In the presence of oxygen, if the surface gets scraped, the layer immediately re-establishes itself.
It is why top-quality stainless steel doesn’t corrode even if it gets damaged during the machining operation. Also, stainless steel exhibits an excellent machinability-to-lower raw material cost ratio.
Now let’s discuss some other prominent properties displayed by stainless steel to make it suitable for CNC machining operations.
- Melting point
Stainless steel’s melting point ranges roughly between 1325-1530 °C, which is considerably good compared to other materials. It makes stainless steel the preferred choice if melting temperature is a critical aspect of the CNC machining operation.
- Hardness and durability
Stainless steel has a high Brinell hardness and is challenging to form; its typical Brinell hardness ranges from 80 to 600, which is preferred for CNC projects with hardness and durability considerations.
Some stainless steels can be heat treated following machining to improve their characteristics.
- Yield, tensile, and shear strength
Different families and grades of stainless steel have different properties that can make them an ideal choice of material for numerous applications. Some have yield strengths comparable to mild and carbon steels, and some precipitation hardened and duplex grades give very high yield, tensile and shear strength characteristics
Industrial applications of stainless steel
Most commonly used stainless steel grades include 303, 304, 316, 430, 434, and 420. The above-discussed properties make this material suitable for CNC machining projects in a plethora of industries, including-
Aluminium
Aluminium is a ductile, durable, lightweight and versatile metal, which makes it perfect for CNC machining operations. It carries a greyish colour texture that varies with the surface roughness.
Simply said, aluminium’s ease of machining is one of the primary factors engineers consider when selecting this material for their machined components. Although it might first seem that only CNC machinists manufacturing the products benefit from aluminium, there are also major advantages for the company procuring the parts and products and the final customer who will utilise them.
The degree to which different aluminium grades can withstand corrosion and chemical deterioration varies greatly. But generally, aluminium exhibits great temperature and corrosion resistance, has a high strength-to-weight ratio and is among the most cost-efficient metals employed for CNC machining operations. Interestingly, many of the most preferred CNC machining grades are also some of the most durable and resistant.
Let’s talk about the advantageous properties of aluminium for CNC machining.
- Formability and processability
Aluminium is considerably simpler to form and shape, softer, lighter, less rigid and has a lower melting point. It is ideal for extrusion or die casting and doesn’t demand additional processing.
- Electrical conductivity
If conductivity is the most important factor for any CNC machining project, aluminium is the best material owing to its excellent electrical conductivity compared to other materials.
- Corrosion resistance
Aluminium has superior corrosion resistance because the insulating oxide layer covers its surfaces and shields it from rust and other types of corrosion.
Industrial applications of aluminium
Applications of CNC-machined aluminium can be found in several core industries, including:
- marine engineering
- heat dissipation systems
- consumer goods
- healthcare
- automotive
- aerospace
The most common grades of aluminium that show great compatibility with CNC machining include 2024, 5052, 6061, 6063, and 7075. Also, CNC router equipment can easily work on Aluminium Composite (ACM) to meet the project demands.
Conclusion
We require a versatile, cost-effective and excellent strength CNC metal irrespective of whether we are working on projects related to custom household items or heavy-duty industrial components for the automotive or power industries. We have covered two of the most preferred choices in the article, but there are numerous other CNC machining metals to pick from. Hence, it is critical to study, compare and analyse all material options before making a decision.
About the Author: Peter Jacobs
Peter Jacobs is the Senior Director of Marketing at CNC Masters. He is actively involved in manufacturing processes and regularly contributes his insights to various blogs on CNC machining, 3D printing, rapid tooling, injection molding, metal casting, and manufacturing in general. 
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