Materials for CNC Machining: How to select them?

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Selecting the right materials for CNC machining is essential to any manufacturing process or cnc machining project. Since this process is compatible with a wide variety of materials, it is uneasy about choosing a material that’s sufficient for the project but not the best suited. 

How to select the right materials for CNC machining?

There’s no one-size-fits-all answer to this question, as the best material for CNC machining will vary depending on the specific application. 

However, You can start by considering the questions below to help choose the suitable material for your project.

1. Where will the material be applied?

Different applications require different materials. The application area will also determine the material’s physical properties, such as tensile strength, strength-to-weight ratio, crack resistance, rigidity, or flexibility. 

For example, a part produced for aerospace applications needs to be lightweight. As such, aluminum 7050 is commonly used in wing skins and fuselage and more so in military crafts. Its high resistance to fractures compared to other alloys is one of the reasons it’s highly regarded in the aerospace industry.

2. What’s the operating environment for the parts?

The environment in which the part will be used is another critical factor in deciding the material. Operating conditions include temperature, harsh chemicals, exposure to UV radiation, continuous contact with water, and even subjection to flames.

(1) temperature

 Any material selected must have its melting temperature safely above the operating temperature. If not, the part might undergo structural variations when exposed to the high operating temperature. Steel 1.4404 has excellent heat resistance, up to 861°C. 

(2) Moisture

Does the product need to withstand freshwater? Some metals and plastics are naturally resistant to corrosion, while other materials may need additional surface treatments such as painting, plating, or anodizing. And notably, even many types of plastic, such as Nylon, can absorb water over time which will lead to premature part failure. 

(3) Corrosion Resistance

Corrosion involves much more than just exposure to water. Any adverse chemical reaction with another foreign substance could potentially cause part failure. These substances include oils, reagents, acids, salts, and alcohol.

(4) Notices 

In outdoor applications, it is best to select materials such as stainless steel that can withstand large moisture concentrations and rusting while maintaining their physical appearance and structure. In addition, extreme weather variations are more likely to occur outdoors, which could cause structural warping in certain materials.

3. What’s your budget?

Material costs almost always influence material selection. 

In order to successfully replace a material with an alternative, it is necessary to consider the functionality, strength, hardness, chemical tolerance, electrical properties, and other properties of the alternative. For example, steel 1.4571 has excellent wear and corrosion resistance, as well as good Machinability. However, it is twice as expensive as steel 1.7131, which also has excellent wear resistance.

And if you require us to choose the material, we are committed to selecting a material that maximizes desired material properties and performance while minimizing expenditure.

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4. Are materials readily available?

Availability is an important consideration when selecting materials for CNC machining.

Sometimes, the most suitable material may not be available in large quantities to sustain production. Thus, it is wise to select materials that fit the functional requirements and are readily available for use, especially if the part will be produced in large numbers. 

5. How about the electrical conductivity of the material?

It is vital to consider the electrical conductivity of the chosen material. Certain materials, such as copper and silver, are excellent conductors, while plastics, such as PTFE is a good insulators. For parts for electrical applications, the choice of material will depend on the electrical properties.

6. How about the Machinability of materials?

A CNC machined component may be exposed to high or fluctuating operational stress and strain. In such cases, choosing materials with easy Machinability is more suitable for producing large quantities and reducing time and expenses. Metal alloys with good bend and stress resistance can be a suitable choice. Materials like aluminum and brass are much more machinable than tool steel. 

7. For certain products, physical appearance also matters!

For certain products, the physical appearance will determine the consumers’ general acceptability of such products. Consumer products are an example of that. As is known, many consumer products require specific physical features such as color or a smooth surface finish.

Metals typically have a good surface finish after machining, thus requiring less work during polishing. Plastics are usually available in different colors, while metals require post-processing to color them.

8. Dimensional Stability and Tolerance

Often industries like aerospace demand precise dimensioning and stability in components. In such cases, the part selected must be able to attain the tight tolerances required. 

Note that tighter tolerances are more expensive to produce. So whenever dimensional tolerance is not a vital requirement, it is advisable to use less tight tolerances to reduce the time and expenses involved in machining the part. 

CNC-machining

9. Common materials for CNC machining

(1) Metal 

① aluminum:

Aluminum alloys are easy to machine in large volumes, have a good strength-to-weight ratio, and have high thermal and electrical conductivity. They are also naturally resistant to corrosion. Aluminum 6061 is an all-purpose aluminum alloy often used for CNC machining. It is typically found in automotive parts, bike parts, sporting goods, and other recreational items. 

② Stainless steel:

Stainless steel alloys are strong and resistant to distortion, wear, and corrosion. For example, 304 is well-suited for a wide range of consumer and industrial applications, kitchen accessories, tanks and pipes, architecture, and more. 316 stainless steel is even more corrosion-resistant than 304 or 303, thanks to the addition of molybdenum. It’s strong, weldable, and one of the few marine-grade stainless plate steel.

(2) Plastics 

① POM:

Easily machinable POM is a popular choice for CNC machining. There are many popular POM applications, including mechanical gears, sliding and guiding elements, connector elements, cogwheels, and some medical equipment.

② Nylon:

Nylon is an all-purpose, low-friction thermoplastic that is often used as an alternative to metal in CNC-manufactured parts. This material is stiff, strong, impact-resistant, and chemical-resistant, but surprisingly elastic. Nylon responds well to additives and fillers, so engineers can feel free to manipulate this material to achieve their desired properties.

③ PMMA Acrylic

PMMA is a rigid, transparent resin used as a substitute for glass or when making other clear optical parts. One advantage of PMMA is that it doesn’t contain Bisphenol-A so it can be used for food storage. After machining, acrylic shows a hazy, matte surface. PMMA is used for display screens, light pipes, lenses, clear enclosures, food storage, and to replace glass if strength is not an issue.

How to Choose the Right Material for Your CNC Machined Parts?

How to Choose the Right Material

When it comes to choosing the right material for your CNC machined parts, there are a few factors you should consider.

  • First, consider the end-use of the part. Different materials have different properties that may be better suited for specific applications. For example, if your part will experience a lot of wear and tear then aluminum or stainless steel may be the best option.
  • Next, consider the cost; some materials can be more expensive than others. It would help if you also considered any additional manufacturing processes that may be necessary to create your parts such as heat treating or plating.
  • Lastly, make sure that the material is compatible with your CNC machine and any other machines you plan to use in its fabrication process. By carefully considering these factors when selecting a material for your CNC machined parts, you can ensure that you get the best possible results from them.

At EJ CNC, we can provide you with various kinds of materials CNC machined parts. Contact us today!

FAQ:

What is the most common material used for CNC milling?

CNC milling is a process that is used to create complex shapes from materials such as metal, plastic, and wood. The most commonly used material for CNC milling is aluminum. Aluminum is a lightweight yet strong metal that can be easily machined into intricate shapes and designs. It also has excellent thermal properties which make it ideal for use in high-speed applications such as aerospace components and automotive parts. In addition, its relatively low cost makes it an affordable option for many manufacturing processes. Other materials that are often used in CNC milling operations include steel, titanium, brass, and copper. Depending on the project requirements, any of these materials may be chosen to achieve the desired outcome.

What are the advantages of CNC machining with metals?

CNC machining with metals offers a number of advantages over traditional methods of metalworking. Firstly, it is much more precise and accurate than manual machining. This means that intricate parts can be produced to a high level of precision which would not be possible with manual machining. CNC also offers greater repeatability, as the same parts can be made quickly and easily with minimal variation from the original design. Additionally, CNC machines are able to run for longer without having to stop for maintenance or repairs, which makes them ideal for high-volume production. Finally, CNC machining with metals is less labor intensive than traditional methods, allowing for cost savings due to fewer workers required on the production line.

What are the advantages of CNC machining with plastics?

CNC machining with plastics is a reliable and cost-effective way to produce parts with exceptional accuracy and repeatability. It can be used for both prototyping and production runs, allowing for the production of high-quality parts quickly and efficiently. CNC machining also offers excellent surface finish, tight tolerances, minimal material waste, and low set-up costs. The material selection of plastic available for CNC machining is vast; from ultra-high performance materials like Ultem® to budget-friendly, commodity materials like HDPE or ABS. There are options for a variety of finishes including metallic, textured, matte and glossy. Additionally, CNC machining allows for multi-axis capabilities which can create complex geometries with ease. Finally, the automated process eliminates human error and provides for consistent quality across all parts produced.

Conclusion:

Material selection influences almost every stage of the product life cycle, from prototyping to production, even to the part’s performance in its end application. Therefore, material selection is a vital part that needs to be diligently considered before beginning CNC machining operations. 

This above consideration may provide some insight and guidance to your decision-making process, hope you will find it useful. If you have any further questions, you can contact us to learn more!