CNC machining is known for being fast, efficient, precise, and versatile, making it a top choice for all kinds of engineering materials like metals, plastics, and more. It’s a powerful process for everything from one-off prototypes to full-scale production runs.
However, the success of any CNC project heavily depends on one critical factor: choosing the right material. This decision impacts the part’s functionality, durability, and cost, so it’s essential to get it right.
At Getzshape, we’re specialists in custom CNC machining. We have the experience and advanced equipment to deliver high-quality, custom parts for projects of any size. From small prototype batches to large production orders, our team ensures precision and quality every step of the way.
To help you with your next project, here’s a guide to the key factors you should consider when selecting a material.
Framework for Material Selection
Choosing a material can feel complex, but you can break it down into three simple steps:
- Define your requirements: Start by making a list of everything the part needs to do. Consider its function, required strength, hardness, and any specific electrical properties. Also, think about the environment it will be used in.
- Identify potential materials: Based on your list of requirements and design specs, create a shortlist of materials that could potentially work.
- Make the final choice: From your shortlist, pick the material that best balances all your needs. You’ll often have to make trade-offs, like choosing a material with better performance over a slightly cheaper one to guarantee quality.
8 Key Factors to Consider When Choosing a Material
1. Part Application
First and foremost, what will the part be used for? Different applications have vastly different needs. For example, aerospace parts require materials that are lightweight but strong, which is why aluminum like 7075 is popular for its excellent strength-to-weight ratio. The part’s application determines which physical properties matter most, whether it’s tensile strength or resistance to stress. Heavier materials like steel can handle more stress, but for weight-sensitive applications, a lighter aluminum alloy like 6061 is a better choice.
2. Operating Environment
Where will the part live? The environment plays a huge role in material selection. You need to consider temperature, exposure to chemicals, UV radiation, moisture, and fire resistance. A material’s melting point must be well above its operating temperature to avoid structural failure. For instance, 316L stainless steel has high heat resistance, withstanding temperatures up to 861°C (1582°F). Indoor parts have predictable conditions, but outdoor applications demand materials like stainless steel that can resist humidity and rust to maintain their appearance and integrity.
3. Dimensional Stability & Tolerance
In high-precision industries like aerospace, parts must maintain their exact shape and size under extreme conditions. This requires a material with high dimensional stability (meaning it doesn’t warp or deform easily). Materials also react differently to the forces of machining, so your choice must be able to meet the project’s tolerance requirements. Aluminum is generally easy to machine, but achieving extremely tight tolerances will always increase machining time and cost. If your part doesn’t need razor-thin precision, relaxing the tolerances can save you money.
4. Electrical Conductivity
Materials vary widely in their ability to conduct electricity. Metals like copper and silver are excellent conductors, while polymers like PTFE (Teflon) are excellent insulators. For any part used in an electrical application, the choice is simple: select a material based on whether you need electricity to flow through it or be blocked by it.
5. Machinability
How easily can a material be cut and shaped? For high-volume production runs, choosing a material with good machinability, like aluminum or brass, can significantly reduce production time and lower costs. If you’re only making a few parts and have a flexible timeline, you can consider a less machinable material. However, remember that these harder-to-work-with materials require more time and resources. Machinability should be a secondary consideration—never sacrifice the core functional requirements of your part just to make it easier to machine.
6. Appearance
While aesthetics aren’t always the top priority, they are crucial for many products, especially consumer goods. A specific color or a smooth surface finish can make all the difference in how a product is received. Metals typically offer a great surface finish with minimal polishing. Plastics come in a wide variety of built-in colors, whereas metals often require a secondary process like anodizing or painting to add color.
7. Material Cost
Sometimes, the “perfect” material for a job is too expensive for the budget. In these cases, you’ll need to find a more affordable alternative. When considering a substitute, carefully check that it still meets all the critical requirements for functionality, strength, chemical resistance, and performance. For example, 316Ti stainless steel has great wear resistance and machinability, but it costs twice as much as 1.7131 steel, which also offers excellent wear resistance. If wear resistance is your main concern, the 1.7131 steel is the more economical choice.
8. Availability
Finally, don’t overlook the practical issue of availability. If a material is difficult to source, it can cause major delays. For large production runs, it’s crucial to select a material that not only meets your functional needs but is also readily available from suppliers. This ensures your CNC project can be completed efficiently and on schedule.
Also Read: What is a CNC Machine? A Beginner’s Guide to Computerized Machining
