CNC Material: How To Choose Right Material for CNC Machining

One of the great advantages of using CNC machining is its versatility. This is because precision CNC milling and turning can successfully use a wide variety of raw materials to produce finished parts. This gives design engineers multiple options when creating prototypes and commercial products.

Most CNC turned and milled parts are made of metal. This is because the metal is strong and hard and can withstand the rapid material removal caused by modern tools. We’ll look at the most common metal and plastic materials used for CNC machining, and how to choose the right CNC material.

As a professional CNC machining manufacturer, we have many years of CNC machining experience and are very familiar with the performance of various CNC material. If you have any questions, contact us and we will give you the most effective advice.

Common Metal Materials for CNC Machining

For various CNC material, we explore various common metal materials essential for CNC machining. The following CNC metal material are frequently utilized.

Aluminum 6061

Aluminum 6061 is the go-to CNC material for general-purpose CNC machining. Its primary alloying elements include magnesium, silicon, and iron. This aluminum alloy boasts a favorable strength-to-weight ratio and natural resistance to atmospheric corrosion. Additionally, it offers excellent workability, CNC machinability, weldability, and anodizability. Moreover, its widespread availability makes it a cost-effective option.

When heat-treated to a T6 temper, 6061 exhibits significantly higher yield strength than annealed 6061, albeit at a slightly higher cost. Nonetheless, one drawback is its limited corrosion resistance when exposed to saltwater or chemicals. It is not as robust as other aluminum alloys for more demanding applications. Typical uses for 6061 include auto parts, bicycle frames, sporting goods, some aircraft components, and RC vehicle frames.

Aluminum 7075

Aluminum 7075 represents a higher-grade aluminum alloy primarily alloyed with zinc. It ranks among the strongest aluminum alloys used in machining, showcasing exceptional strength-to-weight characteristics.

Due to its strength, 7075 has average workability, tending to spring back to its original shape when cold-formed. While it is machinable and anodizable, it is not suitable for welding in most cases. It is a CNC material commonly employed in manufacturing plastic injection mold tools, high-strength recreational equipment for mountain climbing, automotive and aerospace frames, and other structurally demanding parts.

Brass

Brass is an alloy of copper and zinc, known for its softness and often machinable nature without requiring lubrication. As a CNC material, it finds applications where high strength is not a prerequisite. Brass comes in various types, with corrosion resistance decreasing as the zinc content increases.

Brass can achieve a high polish resembling gold, making it popular in cosmetic applications. It possesses electrical conductivity without magnetism and can be easily recycled. Welding is possible but typically joined through low-temperature processes such as brazing or soldering. Interestingly, brass exhibits natural antibacterial and antimicrobial properties, an area of ongoing study. Common uses include plumbing fittings, decorative hardware, zippers, naval hardware, and musical instruments.

Magnesium AZ31

Magnesium AZ31 is an alloy featuring aluminum and zinc. It offers up to 35% lighter weight than aluminum with equivalent strength, albeit at a slightly higher cost. Magnesium is easy to machine but highly flammable in powder form, necessitating machining with a liquid lubricant. Anodization can enhance its corrosion resistance. Its stability as a structural material makes it an excellent choice for pressure die casting.

Magnesium AZ31 is frequently used in aircraft components demanding lightweight and high strength, as well as in power tool housings, laptop cases, and camera bodies.

Stainless Steel 303

Stainless Steel 303 is one of several stainless steel varieties, known for its chromium addition, which deters oxidation (rust). In the case of 303, sulfur is also added, making it the most readily machined stainless steel. However, this sulfur presence reduces its corrosion protection to some extent.

303 is unsuitable for cold forming or heat treatment and is not an ideal choice for welding. It offers excellent machining properties, though attention is required regarding cutting tools and machining speeds. Common applications include stainless nuts and bolts, fittings, shafts, and gears, but it should not be used for marine-grade fittings.

Stainless Steel 304

Stainless Steel 304 is the most common stainless steel variety found in various consumer and industrial products. Often referred to as 18/8, it contains 18% chromium and 8% nickel, imparting toughness and non-magnetism.

304 is readily machineable and weldable, exhibiting better corrosion resistance in typical environments. Machinists should use sharp cutting tools and avoid contamination with other metals. It is an excellent choice for kitchen accessories, cutlery, industrial tanks, pipes, architecture, and automotive trim.

Stainless Steel 316

Stainless Steel 316, containing molybdenum, offers even higher corrosion resistance, making it suitable for marine applications. It is also tough and easily weldable.

316 is employed in architectural and marine fittings, industrial pipes and tanks, automotive trim, and kitchen cutlery.

Carbon Steel 1045

Carbon Steel 1045 is a common mild steel grade, distinct from stainless steel. It is typically more affordable than stainless steel but offers superior strength and toughness. It is easy to machine, weld, work harden, and heat treat for various hardness levels.

1045 steel finds use in numerous industrial applications, including nuts and bolts, gears, shafts, connecting rods, and other mechanical parts requiring high toughness and strength. It is also utilized in architecture, often surface-treated to prevent rust when exposed to the environment.

Titanium

Titanium is renowned for its high strength, light weight, toughness, and corrosion resistance. It can be welded, passivated, and anodized for added protection and improved appearance. However, it is challenging to machine, necessitating the use of specialized cutters.

Titanium is generally biocompatible and boasts a high melting point. While it is more expensive in commercial form, it is abundant in the Earth’s crust, though challenging to refine. It finds applications in demanding fields such as aerospace, military, biomedical, and industry, excelling in heat and corrosive acid environments. Additionally, it is suitable for powder bed 3D metal printing.

Common Plastic Materials for CNC Machining

In the realm of CNC milling and turning, plastic resins must possess the necessary rigidity to maintain their form when clamped in a vise or fixture. This consideration narrows the selection of available materials. The following plastic resin types have consistently demonstrated their suitability over the years due to their stability, strength, ease of machining, and ability to yield excellent finished parts and prototypes.

ABS (Acrylonitrile Butadiene Styrene)

ABS stands out as an exceptional CNC material for CNC machining. It’s a robust and impact-resistant plastic that also exhibits resistance to chemicals and electrical current. ABS readily accepts coloring, yielding aesthetically pleasing results. Thanks to its versatility and strength, ABS is the go-to plastic for rapid prototyping. Its applications span across automotive components, power tools, toys, sporting goods, and various other fields. While ABS is cost-effective, it’s important to note that it doesn’t withstand high temperatures for extended durations.

Nylon

Nylon shares many desirable attributes with ABS. Notably, it boasts higher tensile strength, making it the preferred choice for fabric and rope production. Often, nylon and ABS resins are combined, along with glass fibers, to enhance their favorable properties. Nylon serves as a suitable replacement for numerous mechanical parts, particularly those involving moving gears and sliding components. However, it does have a tendency to absorb moisture over time, rendering it unsuitable for marine applications. Additionally, nylon can be demanding on cutting tools during the machining process.

PMMA (Polymethyl Methacrylate) / Acrylic

PMMA, commonly known as acrylic, is a rigid and transparent resin employed as an alternative to glass or in the fabrication of other clear optical components. It exhibits resistance to scratching but has lower impact resistance compared to polycarbonate. An advantage of PMMA is its absence of Bisphenol-A, making it safe for food storage applications. Following machining, acrylic displays a hazy, matte surface, which can be rectified through vapor polishing, a process undertaken at Star Rapid, to achieve optical clarity. It’s worth noting that acrylic is susceptible to heat-induced deformation, necessitating stress relief before machining. PMMA finds use in display screens, light pipes, lenses, clear enclosures, food storage, and as a glass substitute when strength is not a primary concern.

PEEK (Polyether Ether Ketone)

PEEK stands as a true high-strength and stable engineering plastic. It serves as a viable substitute for metal in numerous applications and can endure prolonged exposure to high temperatures. PEEK is favored for advanced medical, aerospace, and electronic components. It also proves excellent for lightweight fixtures as it exhibits minimal creep or deformation over time compared to other resins. However, PEEK is considerably more expensive than many other plastics and is typically reserved for situations where no other material suffices. In many instances, annealing is necessary during the machining process to prevent the formation of stress fractures.

UHMWPE (Ultra High Molecular Weight Polyethylene)

UHMWPE, with its long name signifying “ultra high molecular weight polyethylene,” encompasses several variations of polyethylene, each possessing distinct mechanical and chemical properties. UHMWPE, in particular, exhibits exceptional hardness and strength, exceptional resistance to chemicals, and a naturally slippery surface. These attributes render UHMWPE the material of choice for joint replacements, as well as for applications in marine environments, food and chemical processing, and gear trains and conveyor belts.

How to Make Informed Choices for CNC Machining Materials: A Step-by-Step Guide

The information provided above serves as a valuable guide to assist you in making informed decisions regarding the selection of CNC materials for your CNC machining needs. It’s important to keep in mind that, in many instances, multiple CNC material options can prove suitable for your application.

At our facility, we consistently advise our partner clients to take into consideration the environment in which the part will be utilized and the types of forces it will endure during its operational lifespan. While there are numerous variables to consider, our experience has shown that certain key areas significantly influence the suitability of raw materials.

Moisture

Begin by assessing whether the product needs to withstand exposure to saltwater or freshwater. Some metals and plastics exhibit inherent resistance to corrosion, while others may require additional surface treatments such as painting, plating, or anodizing. Remarkably, certain plastics, like nylon, can gradually absorb water over time, leading to premature part failure.

Strength

Understanding the concept of strength within material science can be complex and multifaceted. In general, product engineers typically focus on the following aspects of strength:

• • Tensile Strength
    How effectively does the material resist a pulling force?
  • Compression or Load-Bearing Strength
    How well does the material endure a sustained load?
  • Toughness
    How resilient is the material to tearing?
  • Elasticity
    How effectively does the material return to its original shape after the removal of a load?

Each material possesses distinct strengths in these areas, making it crucial to identify your tolerable limits and select a material with a safety margin well above those thresholds. Fortunately, numerous online material data resources provide comprehensive technical information on available commercial metals and plastics, serving as valuable references.

Heat

All materials undergo thermal expansion and contraction in response to temperature changes. If your part will be subjected to frequent heating and cooling cycles, it’s essential to consider the impact of heat. As materials heat up, they tend to become softer and more pliable before reaching their melting point. Additionally, heat can induce outgassing and thermal degradation in some plastic resins, causing chemical bond breakdown. To prevent critical part failure, always opt for a material that maintains thermal stability at temperatures significantly higher than your anticipated working conditions.

Corrosion Resistance

Corrosion extends beyond exposure to water; it encompasses any adverse chemical reactions with foreign substances that could potentially lead to part failure. These substances may include oils, reagents, acids, salts, alcohols, cleaners, and more. Consult relevant material data sheets to confirm whether your chosen metal or plastic can withstand expected chemical exposures.

Machinability

While relatively soft plastics present fewer challenges, machinability becomes a significant consideration for specific metals and carbon fiber. Exceptionally tough materials, including carbon fiber, can rapidly wear out expensive cutting tools. Others may demand precise control of cutting speed and feed rates. Furthermore, some materials lend themselves to faster processing than others. For extended production runs, opting for a metal that machines efficiently can result in substantial time and cost savings over the long term.

Cost

Cost considerations naturally play a role in material selection. However, we strongly advocate that product developers prioritize choosing the best material within their budget constraints, one that provides all necessary functionality. This approach ensures the finished part’s durability, guaranteeing long-term success rather than focusing solely on initial cost savings, which may prove detrimental.

Sungplastic Helps with CNC Material Selection and CNC Machining Services

Sungplastic specializes in manufacturing CNC machined parts made from kinds of CNC material. Other rapid manufacturing solutions include:

CNC rapid prototyping
Plastic injection molding
Low to high volume production
Mini parts manufacturing
Large parts manufacturing
3D printing
Surface finishes services
Custom manufacturing services
…….

If your projects are suitable for one of them, please directly contact us for more information.

Related Resources:

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