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The CNC Machining Material Selection Process
To successfully choose the perfect material for your CNC machining, you have to adhere to these basic steps:
Step 1: Determine and Prioritize Your Products Requirements
Product requirements are the primary aspects of CNC machining, serving as the generic model for the perfect material for your products. These requirements include the part’s industrial applications and operating environments. For example, you need to consider where the parts will be used and the presumed product characteristics like wear resistance, tensile strength, project budget, etc.
Step 2: Identify Potential Materials
Once you determine the ideal requirements for your products, you can easily streamline suitable materials. You will notice that many CNC materials may fulfill some parts requirements, but very few will satisfy all. You can list these materials according to their features and compare them with your design.
Step 3: Pick the Most Suitable Material
Choose the right material for your parts after checking their compatibility status. Your choice will depend on various factors, which we will discuss in the coming sections. However, there are situations when you might have to make compromises sometimes. For instance, you can place your budget above mechanical performance if it is not crucial.
Common Metal Materials for CNC Machining
The following are the common metal materials you can consider for your custom machining projects.
Aluminum Alloys
Aluminum alloys are the most regularly used metal material in CNC machining. This is because they possess high machinability, good strength-to-weight ratio, and excellent workability. Some of the options available include:
- Al6061
Aluminum 6061 is the most popular material used for CNC machining. It is more economical and with better workability and corrosion resistance. In addition, the Al6061 exhibits great yield strength when heat treated to a T6 temper designation.
Al6061 is a multi-purpose aluminum alloy primarily suitable for producing automobile parts, bicycle frames, sporting components, consumer goods, etc. It is also compatible with various surface treatments like anodizing to improve its quality.
- Al7075
Aluminum 7075 is a high-grade metal with excellent properties like toughness, flexibility, high strength, and fatigue resistance. It is best suited for all your CNC machined parts that need sustained durability, like aerospace frames. You can use the Al7075 T6 for producing injection molding tools. In addition, it is the best material for high-strength recreational gear and other stressed parts.
Nevertheless, it is not suitable for welding purposes. Its superior strength also makes it difficult to manufacture parts with highly complex designs. It returns to its original form when being cold-formed due to its strength.
Stainless Steel
Stainless steels are metal alloys with excellent strength, high flexibility, and outstanding wear and corrosion resistance properties. You can easily weld, polish, and machine them.
Here are some of the stainless steel materials used in CNC machining:
- SS304
Stainless steel 304 has many applications due to its excellent mechanical properties and superb machinability. In addition, it has suitable resistance against environmental conditions and corrosive media. As a result, you will find SS304 in several consumer and industrial products.
SS304 alloy consists of 18% chromium and 8% nickel, making it nonmagnetic. Unlike the 303 variant, it can be welded and has good corrosion resistance. Therefore, it is an excellent material for kitchen cutlery and accessories, pipes, automotive components, etc.
- SS303
Stainless steel 303 possesses good toughness, although its corrosion resistance is lower than that of 304. It is suitable for high-volume applications, like nuts and bolts in the aeronautics and aerospace industries, because of its excellent machinability.
SS303 is not ideal for cold forming or heat treatment. Likewise, the presence of sulfur renders it unsuitable for welding purposes. Nevertheless, this material is suitable for bolts, nuts, shafts, gears, and fittings.
- SS316
It is a standard stainless steel alloy that shares identical mechanical properties with SS304. This metal is the perfect material for harsh environments because of its high corrosion and chemical resistance to compounds.
You can enhance the corrosion resistance of the SS316 by adding molybdenum. It is a typical marine-grade stainless steel, very tough, and can be readily welded.
Brass
Brass is a versatile and dominant material used in plumbing systems. It is perfect for home décor, cosmetic applications, and musical instruments. Its excellent workability and surface finish makes it suitable for components required to be aesthetically appealing. In addition, it naturally resists saltwater corrosion and is without flammable properties.
Brass is an excellent material for producing your electronic hardware, aerospace parts, and pipe fittings. Being a copper-zinc alloy, it possesses excellent thermal conductivity and does not become inflexible at low temperatures.
Carbon Steel 1045
Carbon Steel (EN 1045) is a workable material most suited for welding. It is a more economical choice than stainless steel, and it boasts higher strength. As a result, it is perfect for producing nuts, gears, and other mechanically solid parts. It is an excellent steel material for applications requiring greater hardness like studs, axles, shafts, and bolts.
Common Plastic Materials for CNC Machining
While metals are excellent CNC machining materials for various applications, many industries require plastic CNC machining for their parts. Here are the most common plastics to consider for your projects:
ABS
ABS is one of the traditional thermoplastic materials with remarkable mechanical properties, high heat resistance, excellent impact strength, and good machinability. It is suitable for lightweight applications because of its low density. You can make CNC prototypes with ABS before embarking on high-volume production. It is impact-resistant, chemical-resistant, and resistant to electrical current.
ABS is easy to paint, producing excelling surface finish results. In addition, ABS costs less than other machining plastics like Ultem or PEEK. However, it cannot withstand high temperatures for a more extended period.
POM (Acetal/Delrin)
POM (Polyoxymethylene) is a thermoplastic material highly suitable for making precision parts with high hardness requirements. This material is ideal for making your mechanical gears, bobbins, telephones, screws, and many more.
POM has high chemical resistance, low moisture sensitivity, electrical resistivity, and high hardness. However, it is not the best material for products that will be exposed to chemicals.
Nylon
Nylon offers the same attributes as ABS. It exhibits high tensile strength, which makes it the most suitable material for several components. You can use nylon and ABS resins with some glass fibers to improve their qualities.
Nylon is a better replacement for many mechanical parts because of its impressive surface lubrication. It is ideal for producing sliding components and moving gears. The major setback of nylon is its inability to absorb moisture over a long time. Therefore, it is not suitable for marine applications.
PTFE
PTFE (Polytetrafluoroethylene) is an engineering thermoplastic polymer with outstanding thermal and chemical resistance. It is a special plastic that withstands very high temperatures. In addition, it is an excellent electrical insulator with the lowest coefficient of friction of any solid material.
PEEK
This is an authentic, high-strength, and stable engineering plastic for CNC machining. You can use it as an alternative to metals in several applications. PEEK’s ability to withstand prolonged temperature makes it suitable for making electronics, aircraft components, and medical devices.
PEEK machining is ideal for lightweight fixtures because it does not deform over time like other resins. However, PEEK costs more than other plastics, so you might consider using it only when other plastics are unsuitable. In most cases, you must anneal it while machining to avoid stress fractures.
Key Considerations for Choosing CNC Machining Materials
Machining optimal components for your products begins with material choice. Narrowing down the various CNC materials is the first step to choosing the right material for your project. However, there are many factors to consider before making a choice. They include the following:
Part Application
A fundamental factor to consider when choosing a material is the application of the end product. For instance, stainless steel is better than carbon steel in making structural parts for marines. Although both materials have excellent machinability properties, stainless steel offers better corrosion-resistant properties. On the other hand, carbon steel will be best for a dry environment because it is much stronger and more durable.
Operating Environment
Typical operating environments may include harsh chemicals, temperature, constant contact with water, subjection to flame, or exposure to ultraviolet radiation. Any material you use must have a melting temperature that is safely higher than that of the operating environment. If not, the part will likely experience structural variations if not adequately protected.
Also, structural wrapping can occur in some materials due to extreme outdoor weather variations. Therefore, be more mindful of the material you choose after considering all operating environment factors.
Dimensional Stability and Tolerance
These properties are of primary importance to industries like aerospace and aeronautics. They often demand parts with highly accurate dimensions and excellent stability. Such applications require materials with excellent dimensional stability to meet tight tolerance requirements.
For instance, aluminum can achieve tighter tolerance due to its high machinability. However, you should understand that tighter tolerances cost more to produce. Therefore, you should opt for less tight tolerances in situations where tolerance is not compulsory. This will help optimize the time and cost of production.
Electrical Conductivity
The durability of electrical components will depend on the materials used for their fabrication. Therefore, you must carefully consider the electrical conductivity of any material you choose. Generally, metals are excellent conductors of electricity, while plastics are great insulators. CNC materials such as copper have excellent conductivity, while PTFE is an excellent insulator.
Machinability
A material’s machinability shows its compatibility with CNC machining processes. Suitable materials are often very machinable, resulting in increased production efficiency and decreased downtime. If you require parts in large quantities, it is best to choose highly machinable materials.
Typically, materials like aluminum and brass are more machinable than steel. You should only choose low-machinable materials only when you need small quantities or when lead times are flexible. Such materials may take more time, effort, and resources.
Surface Finish
The physical appearance of materials is not the foremost factor in choosing the right material. Nevertheless, it is a vital factor to consider. The surface finish of a component creates a protective layer on it and determines its general acceptability.
Your customers may require physical properties like a smooth surface finish or color. Although metals usually have a smooth surface after machining, they may require further finishing to improve their appearance.
Material Costs
This is a crucial CNC material consideration due to the subtractive nature of CNC machining. The cost of the material will affect the total CNC machining cost. Hence, you must consider the cost of your material before going ahead with production. Ensure that you pick a material with the perfect properties for your parts and within the budget range.
Contact AT Machining’s CNC Machining Services for Suitable Material
AT Machining provides a long list of materials for all your CNC machining needs. We work with you to analyze your design and find the most suitable material for your projects. Our expert technicians have in-depth knowledge of material properties and applications. Be rest assured that your machined parts will have the best qualities.
Contact us at AT Machining to discuss your project’s material requirements. Request a quote today, and let’s get your products to market faster and cost-effectively.
FAQs
What Is the Most Cost-Efficient Material for CNC Machining?
The most common and cost-efficient CNC machining material is the Aluminum 6061. Despite its low cost, it offers several benefits for a wide range of applications. Its high strength, corrosion and wear resistance, and other properties make it an ideal choice.
What’s the Best Plastic for CNC Machining?
POM (Delrin) is considered the best plastic for most CNC projects. It is very economical and has excellent machinability than others.
What Are the Advantages of CNC Machining with Metals?
Metal alloys are most suitable for machining applications requiring hardness, high strength, and or resistance to higher temperature degrees. Most metals are easily machined and offer better physical and mechanical properties for industrial applications. They are also durable materials, ensuring your parts last longer.
What Are the Advantages of CNC Machining with Plastics?
Plastics are the common materials for making lightweight CNC machined parts. Likewise, plastics are cost-effective options for producing prototypes before full-scale productions. Most metals are compatible with surface treatments, improving their aesthetic properties.
