CNC material selection is an integral part of the project planning process. The material chosen will affect the final component’s price, longevity, and suitability for your application.
Deciding which metal to use in your next project depends on a variety of considerations, including the material’s machinability, environmental conditions of the application, and the part’s intended use. See a full guide of all relevant considerations below.
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First, you’ll need to have a broad understanding of which metals are machinable in order to have a relevant range to select from. Below is a list of commonly machined materials and their general properties.
Aluminum and brass are known for being economical material choices for machining projects. Both materials are highly corrosion resistant, making them long-lasting against several environmental factors. Aluminum is often the fastest material to machine and is lightweight but strong. Brass has a low friction coefficient, making it ideal for a slew of engineering applications.
Copper alloys are most often used in electrical applications due to their conductive properties. Like aluminum and brass, copper is also highly resistant to corrosion, so it lasts longer before rusting. Although pure copper can be difficult to machine due to its toughness, copper can be alloyed with other common metals like zinc, tin, aluminum, or nickel for improved machinability.
One of the most commonly used materials in manufacturing, steel is known for its strength, durability, and versatility. Depending on the exact type of steel or alloy used, it may be direct hardened, case hardened, or heat treatable. Steel is also cost-effective and easy to machine or weld.
Stainless steel is equally strong and exceptionally resistant to corrosion. The addition of corrosion-resistant qualities on top of the aforementioned benefits of using steel makes stainless steel popular for applications where cleanliness is of the utmost importance, such as medical tools or food and dairy processors.
The defining features of titanium are its high strength for its weight, recyclability, and resistance to rust and chemicals. Less machinable than other materials above, it requires a rigid setup, heavy use of coolant, lower speeds, and continuous motion to avoid creating a built-up edge, work hardening, or excessive stress on the tool.
Like titanium, nickel is also a strong metal that has the potential to harden rapidly and generate high heat during cutting. Although it’s popular for use in the aerospace and automotive industries, overcoming difficulties in machining nickel requires a stringent approach.
Engineers must prioritize qualities needed for the component’s end use in order to choose the most suitable material for its application. For instance, a combination of lightness and strength will be a top quality to consider for aerospace or automotive applications, making titanium or nickel often ideal despite their higher difficulty in the machining process.
However, if working in the food industry, FDA guideline compliance will be the most important factor in material selection. Since many industries and applications have stringent guidelines for the resulting product of any machining project, engineers and project managers must avoid choosing materials that are suitable for machining but will not be long-lasting in the final components’ application.
Discussing the environment that a final component or piece of equipment will be operating in is an essential part of the material decision-making process. The level of corrosion resistance for a given material will come into play here, especially for outdoor applications or components that must come into contact with harsh chemicals.
Temperature is also a deciding environmental factor, as materials may need to withstand either high heat or extreme cold in their application. Since some materials respond more drastically than others to temperature changes, engineers must also consider fluctuations and their frequency in the operating environment’s temperature during material selection.
Dimensional tolerance, or the permissible limit of variation from the design’s dimensions of any part, is important to set at the outset of any project and will contribute to the conversation of CNC material selection. The movement of a part — i.e., whether it will remain static, rotate, oscillate, etc. — and the conditions it will be subject to — i.e., whether it is a load bearing component or will be subjected to friction — should all be considered when determining tolerances and selecting materials.
The weight and stress capacity needed for the final part should also be discussed during CNC material selection. The strength profile of every material and alloy includes a unique combination of load bearing weight, tensile strength (resistance to breaking under tension), wear resistance (ability to withstand friction and recurring loads over time), endurance strength (how much cyclic stress can be applied to the material at regular intervals over time without failure), and material hardness (ability to withstand pinpoint surface loads).
While heavier materials are often equated with strength, they are not the right fit for every application. Specific applications, like aerospace or automotive parts, require both lightness and strength to function, while other applications prioritize flexibility, corrosion resistance, or another quality above the ability to absorb stress or bear heavy loads.
Naturally, the logistical elements of your project are also essential to material choice, including budget and timeline. The uniquely high strength but low weight materials mentioned above like nickel or titanium are often only used in applications where this combination is critical to success, as they are often more difficult to source and more expensive. Conversely, more common materials such as aluminum, brass, or steel are easier and less expensive to source but may or may not be the right choice for your project depending on the highest priority qualities needed in the final product.
Ultimately, it is essential to choose the correct machining partner that can help you choose the most cost-effective, suitable materials for your specific project, in order to balance top quality with on-time delivery. Working with an experienced team of engineers will ensure long-lasting success in the final part or equipment within its specific application.
With a focus on precision and empowered, forward-thinking employees, Aztalan helps companies across industries with expert engineering and CNC machining services. Our engineers will help you select the most cost-effective and precise material for any application.