Basics of CNC Machining Materials: How to Choose the Right One?

CNC machining has gained significant traction in the industrial sector because it produces high-precision parts and is used in countless applications in the aerospace, medical, automotive and other industries. In addition to its popularity due to its precision and application possibilities, another reason is its acceptance in processing a wide range of materials.

However, to obtain the desired parts that meet production requirements, there are some important things to consider when selecting materials for CNC machining. So which common materials are ideal for CNC machining? And is there any factor in choosing materials for CNC machining? Keep reading.

Different categories of materials in CNC machining

CNC machining is a versatile process that allows the use of different types of materials. These CNC machining materials range from traditional plastic and metal to wood, ceramics, and composites.

In this article, we will focus more on plastic and metal processing materials as they have more versatile uses in various industries.

Types of Metal Materials for CNC Machining and Examples

The most commonly used material for CNC machined parts is metal. These CNC materials offer numerous advantages, including heat resistance, hardness, high strength and electrical conductivity. Common metal materials for CNC machines include:

1. Aluminum

Aluminum is one of the most used materials in CNC machining. It is easier to machine than metals such as steel and titanium. It also has a remarkable strength-to-weight ratio, is lightweight, corrosion-resistant and has an attractive silver finish.

There are several types of aluminum materials, but not all are ideal for use in CNC machined parts and products. Regardless, aluminum grades such as 6061 and 7075 aluminum are highly machinable and are often used in production parts where weight is a concern, such as in automobile engine parts and aerospace structures. These grades of aluminum also find application in the consumer electronics, construction and medical industries.

2. Stainless steel

Stainless steel is very resistant to wear, corrosion, strong and resistant. Like aluminum, this material has a shiny appearance. It is available in different qualities and is often not very expensive. However, its hardness makes it one of the most difficult CNC materials to machine.

SS 316 is one of the most common types and is used in outdoor enclosures, medical devices, and marine applications due to its resistance to corrosion and heat. Other common types of stainless steel for CNC are 303, 304, and 316. They are used in manufacturing fasteners like bolts, screws, bushings, etc.

3. Carbon steel and its alloys

Due to their superior strength and machinability, carbon steel and related alloys are perfect for a variety of applications. They work well with various heat treatment techniques, which further improves their mechanical properties. Carbon steel is also cheap compared to other metals used in CNC machining.

However, it is important to note that carbon steel, mild steel and their alloys are not inherently resistant to corrosion. Furthermore, its unattractive appearance may not be suitable for aesthetic applications. Despite their drawbacks, these materials continue to be preferred for numerous industrial and manufacturing applications due to their durability, affordability, and machinability. Steel and its alloys are used to make mechanical fasteners and structural components such as beams.

4. Copper and its alloys

Copper is known for its high thermal and electrical conductivity. Its excellent conductivity properties make it an excellent choice for electrical and electronic applications, and its malleability and aesthetic appearance make it a popular choice in the jewelry industry. Copper is used in many different industries, including electrical wires, magnetic equipment, and jewelry making.

Brass is an alloy of copper and zinc known for its corrosion resistance, excellent electrical conductivity and machinability. It is commonly found in consumer products, low-strength fasteners, plumbing fixtures and household appliances.

Bronze is an alloy of copper, tin and other elements. It is durable, corrosion resistant and strong. Bronze is also easy to machine, allowing it to be used in the manufacture of gears, bearings and precision components. Furthermore, the addition of phosphorus and aluminum increases its strength and improves toughness and strength.

Overall, brass, bronze, and copper are important metals for CNC machining.

5. Titanium

Titanium has a high strength-to-weight ratio. In other words, it is not only extremely strong, but also lightweight. Not only does it have high thermal conductivity, but it is also resistant to corrosion. As titanium is also biocompatible, it is used in the biomedical industry.

Additionally, titanium is used to produce high-performance machine parts for a variety of industries, including military, aerospace, and medical. Titanium is also used as a material for CNC machine tools.

6. Magnesium

Magnesium metal combines strength and low weight. Due to its excellent thermal properties, it is the best material for high-temperature parts such as engines. Its low weight allows the production of lighter vehicles with low fuel consumption.

Magnesium is considered highly flammable and can be more expensive to process. It also has lower corrosion resistance than some other metals (including aluminum).

Types of Plastic Materials for CNC Machining and Examples

Most plastics have a low melting point, which affects their workability. However, there are some plastic materials available for CNC machining, including:

1. Acrylic

This material, also known as PMMA (polymethyl methacrylate), has several desirable properties, such as optical clarity and rigidity. Its high optical clarity and durability make it suitable as a glass replacement.

Despite its disadvantages, including tendency to crack and thermal softening, acrylic is still a preferred material for CNC machining due to its adaptability and simplicity. Acrylic is a fantastic material choice for many applications because it can be used to create high-quality, precise components.

2. Polypropylene (PP)

High chemical resistance and fatigue resistance are the two advantages of adaptable polypropylene. Furthermore, it is a medical grade material and CNC machining results in a smooth surface. However, one of its disadvantages is that it softens at high temperatures, making it a little difficult to work with.

3. Acetal

This material, also known as POM (polyoxymethylene) or Delrin, is extremely versatile. It is robust and moisture and shockproof. Furthermore, this material has excellent fatigue resistance.

One of the main characteristics of acetal is its rigidity, which allows easy processing with excellent dimensional accuracy. For this reason, it is often used in precision components such as bearings, gears and valves.

Furthermore, POM is a reliable material for many industries, including automotive, aerospace and consumer goods, due to its excellent mechanical properties and high resistance to environmental influences.

4.Nylon

Nylon is a strong, durable and impact-resistant material used in a variety of applications. It has excellent surface lubricating properties and can be used in various forms of composites, such as fiberglass reinforced nylon.

Nylon is particularly suitable for applications requiring protection against frictional forces. This includes parts such as sprockets, bearings, sliding surfaces and gears.

5.ABS

Due to its excellent machinability, tensile strength, impact resistance and chemical resistance, ABS material is a very affordable plastic suitable for CNC machining. Additionally, it is easy to color, making it perfect for applications where aesthetics are critical.

ABS can be used in various CNC processes such as protective housing manufacturing, rapid prototyping, and automotive parts manufacturing. In addition to CNC machining, ABS manufacturers also produce ABS through injection molding and 3D printing.

6. UHMW-PE

UHMWPE is a widely used material for CNC machining due to its excellent properties, which include high toughness, abrasion and wear resistance, and durability.

Although UHMWPE is difficult to machine, it is ideal for producing sliding surfaces on bearings, gears and rollers. Its exceptional properties make it perfect for applications where high wear resistance and durability are required. Compared to other materials, UHMWPE offers excellent efficiency and durability when processed properly.

7. Polycarbonate (PC)

A commonly used plastic for CNC machining is polycarbonate (PC), which has a number of beneficial properties such as optical clarity. This material is resistant to breakage and heat. Additionally, its high heat resistance means it can be used in high temperature applications. Additionally, polycarbonate is used in the manufacture of electronic components, medical devices and automotive parts.

8. Polyetheretherketone (PEEK)

PEEK is a high-performance plastic with excellent chemical resistance. This material also has high dimensional stability and mechanical resistance. One of its main advantages is its ability to maintain rigidity at high temperatures, making it ideal for use in extreme environments.

PEEK is used in a variety of industries, including aerospace, food and beverage processing, and oil and gas. It is widely used in the production of semiconductor components, bushings, seals, bearings, pump and valve components, etc.

9. Polyvinyl chloride (PVC)

This is a low-cost and highly machinable plastic material. It is resistant to impacts, corrosion and chemicals. It has high resistance which makes it rigid. PVC plastic is ideal for manufacturing welded chemical tanks, valve and pump housings, cabinets and work surfaces, manifolds and connections.

Quick view: CNC machining materials table

Key Factors for Selecting Materials for CNC Machining

While there are generally several factors to consider when choosing the right materials, here are a few important ones.

Consider Part Manufacturing Requirements

The basic requirements of the parts to be machined are a crucial part of CNC machining and also provide a guideline for the type of material to be used. General part requirements include:

Subapplications

Make sure the CNC material you plan to use is suitable for the intended application and environment. For example, consider the comparison between stainless steel and carbon steel when used to manufacture components in the maritime sector.

Both materials can be machined well, but stainless steel is more suitable because it has greater corrosion resistance. However, in a normal, dry environment, carbon steel is a better choice because it is more durable and strong.

Partial weight

Part weight influences CNC material selection because it can affect the machining process and the overall performance of the part. Heavier parts typically require stronger, denser materials to ensure they can support the load. For lighter parts, lower density materials such as aluminum or titanium can be used to reduce weight and improve performance.

Part accuracy and tolerance

Some materials are more difficult to achieve tight tolerances than others. For example, materials prone to warping, such as certain types of plastic (PVC), may require greater machining tolerances to achieve the desired tolerances.

On the other hand, materials such as steel or titanium are often preferred for applications that require high precision and tight tolerances.

Part Properties

The required characteristics of the part depend on its intended use and the environment in which it is used. Factors such as strength, toughness and wear resistance are critical for parts subject to high stress or wear.

Materials such as steel, titanium and certain plastics such as nylon or acetal are known for their strength and durability and are therefore suitable for these types of applications. For parts exposed to high temperatures, materials with good thermal stability, such as ceramics or certain metals, may be preferred.

Product aesthetics

When choosing the material to be processed, the aesthetics of the product must be taken into account. Especially in the case of consumer goods, the acceptance of the product in the market depends largely on its appearance.

CNC-machinable materials such as plastics are available in a wide range of colors and opacities, allowing you to choose from a wide variety of material appearances. With metals, however, improving aesthetics would require subsequent surface treatment.

Surface Finish Options

The surface finish you want your product to have has a big impact on the type of material you use for CNC machining. Various surface finishing options are available for metals and plastics such as polishing, anodizing, passivation, painting, brushing, powder coating, etc. These surface finish options not only improve surface appearance but also functionality.

It is important to note that these surface treatments interact with materials in different ways. Before choosing a material, it is best to make sure that the surface treatment is ideal.

Machinability

This depends on how easy the material is to work with. Softer materials like plastic and metals like aluminum are fairly easy to work with. However, harder materials such as carbon fiber and titanium are a little more difficult to machine because these materials often destroy cutting tools. Producing parts from materials with a high degree of machinability saves time and money in the long run.

Cost

Of course, every material for CNC machining has a cost. However, we strongly advise all product designers to keep in mind that choosing an inferior material to save money is never a wise decision in the long run.

Choose the highest quality material you can buy that offers all the features you need. This is the only way to increase the durability of finished pieces.

Tips for using CNC processes to machine various materials

What you want to do ultimately determines which CNC machining materials you use to produce your parts. However, the following tips can serve as a quick guide for CNC materials.

Use quality tools

No matter what material you want to work with, it's important to use high-quality tools. By avoiding cheap cutters that break easily and wear out quickly, you can save money and hassle. High-quality tools are designed to withstand the rigors of high-speed machining, improving the quality and consistency of your results.

Install reliable workpiece clamping on your machine

While it's important to keep a piece in place while editing, sometimes that's easier said than done. This is even more difficult when working with delicate materials and complex shapes. Therefore, it is better to install a reliable workpiece fixture on your CNC machine to improve machining precision and accuracy.

Choose common processing materials

Instead of worrying about choosing from a variety of available materials, you can select common machining materials that have been identified by top engineers and concluded that they are suitable for machining and that such applications are generally accepted.

Common metals include brass, copper, stainless steel and aluminum. Common plastics include PEEK, acetal, nylon, ABS, and polycarbonate.

Get the right CNC machining material for your projects

Furthermore, with our complete CNC machining services that meet your expectations, you can safely receive prototypes and parts with high quality and precision. If you have specific questions about materials processing, please do not hesitate to contact us.

Concluding

A CNC machine's ability to work with diverse materials is one of the reasons it remains one of the best manufacturing processes. Facilitates the production of parts made of metal, plastic, wood and composite materials. Before choosing a material for your part, it's best to learn about the material's strengths, weaknesses, and other properties so you can make the right decisions.

Common questions

What factors should you consider when choosing a CNC material?

It is best to consider several factors, including environment, usage, machinability, tolerances and material costs.

Which aluminum alloy is best for CNC machining?

6061-T6 aluminum is a commonly used aluminum alloy and is considered a standard grade for CNC machining. Its characteristics such as lightness, corrosion resistance, versatility and machinability make it applicable in the automobile and aviation industries.

Which plastics are easiest to process?

Acetal, PEEK and PVC plastic materials offer good dimensional stability, excellent machining properties and resistance to melting and chipping. Due to its low price and excellent machinability, Delrin is also considered the most economical plastic.

Which metal is the hardest to mill?

Titanium is known for being one of the most difficult metals to work with, and there are many stories of destroyed parts and broken tools. However, titanium has excellent properties that make it a commonly used material in the aerospace and medical industries.