A Guide to Selecting the Best Materials for CNC Machining Parts

Published by worthyhardware at May 6, 2023

Factors That Affect The Choice of CNC Machining Materials

Choosing a suitable material is critical for the success of a CNC machining project, as it can directly impact the quality, cost, and performance of the final product. Factors such as mechanical and chemical properties, environmental requirements, budget, and processing difficulty must all be carefully considered when selecting a material.

By considering these factors, manufacturers can optimize the manufacturing process and ensure the production of high-quality and reliable products.

Application

The application of the product is the ultimate consideration goal for us in machining each part. For example, customers usually choose metal materials such as stainless steel and titanium alloy for applications requiring high strength and wear resistance.

Customers typically choose special plastics or metal materials for medical devices that require biocompatibility and low toxicity.

In addition, for applications that require insulation or thermal conductivity, customers may choose ceramics or unique metal materials.

Budget

Budget is one of the critical factors that affect the choice of materials by customers. Customers must choose inexpensive materials that meet performance requirements based on their budget. The main factors of the budget include material cost, processing cost, and design cost.

Material cost usually accounts for a portion of the total cost, and customers need to consider the impact of material cost on the total cost.

For low-budget projects, customers may need to choose cheaper materials, such as some plastic materials or alloy steel materials. In contrast, customers can select high-performance materials for high-budget projects, such as high-strength steel, titanium alloys, or nickel-based alloys.

In addition, processing costs and design costs also need to be considered.

Performance requirements

During the CNC machining process, customers need to consider the performance requirements of their products thoroughly and choose the most suitable materials based on the mechanical properties, corrosion resistance, insulation properties, and other characteristics of the materials to ensure that the products have excellent performance and quality. Additionally, processing costs and design costs also need to be considered.

Machining Difficulty

In CNC machining, the difficulty of processing is an essential factor that affects the choice of materials by customers. The problem of processing depends on factors such as the shape, size, quantity, material, and quality requirements of the processed surface.

For parts with complex shapes and high precision requirements, customers usually must choose materials with excellent processing performance, such as aluminum alloys, steel, or titanium alloys. These materials have good processing performance, which can reduce processing difficulties and improve processing efficiency and product yield.

In contrast, difficult-to-machine materials, such as high hardness, high strength, high temperature, and high wear-resistant materials, will increase processing difficulties and costs. Customers must now consider using different processing methods or choosing relatively easy-to-process materials, such as aluminum alloys or plastics.

Surface Treatment

During the CNC machining process, many products require surface treatments to achieve effects such as corrosion resistance, aesthetics, and improved mechanical properties.

For example, steel products require galvanizing or spray coating of anti-corrosion agents to prevent rust, car bodies require spray paint to beautify their appearance, and mechanical parts require spray coating or anodizing to enhance hardness and wear resistance.

However, surface treatments may cause changes in the dimensions and shape of the product, which is unacceptable for products that require high accuracy. Therefore, suitable surface treatment materials must be carefully selected to achieve the desired results.

Tolerance

Tolerance is an essential factor to consider in CNC machining. The general tolerance in the CNC machining field is ISO2768-M standard, but customers usually design stricter tolerances for the practical functionality of their products. In this case, we need to consider whether the chosen materials can achieve these tolerances and try to minimize the difficulty of machining and reduce scrap.

Mechanical performance

Mechanical performance usually includes strength, hardness, wear resistance, and toughness, which are essential in different application scenarios. Therefore, when selecting materials, it is necessary to consider the product’s usage environment and requirements comprehensively and choose the most suitable materials.

Chemical properties

Chemical properties usually refer to the performance of materials in a chemical environment. This includes corrosion resistance, chemical stability, chemical reactivity, and other material aspects. For parts or equipment that need to be used in a chemical environment, chemical properties are one of the crucial factors to consider. For example, if a material is prone to corrosion in an acidic environment, a more corrosion-resistant material should be selected when designing the component or equipment.

Common CNC Machining Materials

CNC machining materials can include a variety of metals, plastics, wood, ceramics, glass, foam, and composites. Below we will write details of each material.

Metals Materials for CNC Machining

Metals are widely used in CNC machining due to their high strength, durability, and versatility, which are suitable for various applications, from aerospace components to automotive parts to medical devices. Each metal has its own unique properties, allowing for a variety of design options and specifications.

Aluminum

Characteristics: Aluminum is a lightweight, non-magnetic, ductile, and malleable metal that is easy to machine and has good conductivity and corrosion resistance.
Properties: Aluminum has good strength-to-weight ratio, good thermal and electrical conductivity, low density, and is non-toxic. It can be easily formed and welded and is resistant to corrosion.
Advantages: Aluminum is a popular material for CNC machining due to its versatility, lightweight, and cost-effectiveness. It is used in various applications, including aerospace, automotive, electronics, and construction industries.
Disadvantage: Aluminum has a higher coefficient of thermal expansion than other metals, which can lead to dimensional changes in parts due to temperature changes. Also, it is soft t susceptible to scratches, dents, and further damage.
Surface finish: Can be anodized, powder coating, blasting.
Common brands: Alu6061, Alu7075,Alu6063, Alu5083,Alu6082, Alu2024

Stainless Steel

Characteristics: a corrosion-resistant alloy of iron, chromium, and other elements, with a minimum of 10.5% chromium content
Properties: excellent corrosion resistance, high strength, toughness, and good ductility and formability.
Advantages: Stainless steel is highly durable and has a long lifespan, reducing the need for frequent replacement and maintenance;It is resistant to staining, rusting, and corrosion, making it suitable for use in harsh environments and outdoor applications.
Disadvantages: compared with carbon steel, stainless steel is more expensive;also, it is very tough and not easy to be cnc milled or cnc turned.
Surface finish: as machined, passivate
Common brands: SS303,SS304,SS316,17-4PH

Brass

Characteristics: yellow gold color with a shiny finish; Brass is a metal alloy made of copper and zinc.It is a malleable and ductile material that can be easily formed into various shapes.
Properties: good conductor of heat and electricity, relatively low melting point compared to other metals, making it easier to cast and machine.
Advantages:Brass is attractive and commonly used in decorative items; it has good machinability and can be easily formed into complex shapes.
Disadvantages: without the proper surface finish,the surface will be changed to black; brass is very expensive compared with steel and aluminum.
Surface finish: Electroplated Nickel, Electroless Nickel, Gold
Common brands: C36000.

Steel

Steel is a widely used material in CNC machining due to its durability and versatility. It is an alloy composed primarily of iron and carbon, with other elements such as manganese, silicon, and sometimes chromium added to improve its properties.

Advantages: Steel is strong and durable, has high tensile strength, and is less expensive,then it is widely used in many applications.
Disadvantages:It can corrode and rust over time if not adequately treated or coated;Steel is heavy, making it difficult to transport and handle.
Surface finish: Plating,black oxide.
Common brands: Steel 1008, 12L14, Steel 1045,4130.

Titanium

Titanium is a metallic element that is known for its high strength-to-weight ratio and excellent corrosion resistance.

It is biocompatible and non-toxic, making it suitable for medical implants. Also, titanium can withstand high temperatures.
However, titanium has a low modulus of elasticity, which can cause it to deform under heavy loads; plus, it is an expensive material that will limit its application.
Surface finish: oxidized.
Common brands: TA4

Copper

Copper is a highly conductive and malleable metal widely used in electrical and plumbing applications. I

Characteristics:Copper is a soft, malleable, reddish-orange color and ductile metal with excellent thermal and electrical conductivity.
Properties:Copper has a high melting point of 1,085°C and a density of 8.96 g/cm³.
Advantages:Copper is a highly versatile and durable material that is widely available and easy to recycle. It is also biostatic, meaning it inhibits the growth of bacteria, making it ideal for use in medical equipment and facilities.
Disadvantages:Copper is a relatively soft metal, which means it can be prone to bending and warping under pressure. Additionally, it is more expensive than other materials, making it less cost-effective for certain applications.
Surface finish:Gold plating
Common brands: C11000

Lead

Lead is a soft and malleable metal, making it relatively easy for CNC machines.

However, lead is also a toxic metal and poses health risks, particularly during machining operations that create dust or fumes.
Therefore, proper safety measures and ventilation systems are necessary when machining lead. Additionally, lead has poor mechanical properties compared to other metals, and its use is often restricted in specific applications.

Magnesium

A lightweight metal with a high strength-to-weight ratio, strong thermal conductivity, and great machinability is magnesium.

Magnesium also has good corrosion resistance and is recyclable.
However, its properties also include a high oxygen reactivity, making it susceptible to corrosion and flammability.
Magnesium alloys are known to be highly flammable and can ignite at relatively low temperatures; then it is hazardous if there is no protection in CNC machining.

Plastic Materials for CNC Machining

Plastic materials are commonly used in CNC machining due to their versatility, ease of processing, and cost-effectiveness. A wide variety of plastic materials can be used for CNC machining, each with unique characteristics and properties.

Acetal (POM/Delrin)

Acetal, or POM (polyoxymethylene), is a highly crystalline thermoplastic material.

Characteristics: high strength, stiffness, and resistance to abrasion
Properties: low friction, good dimensional stability, good electrical insulation properties, and can withstand high temperatures.
Advantages: withstand repetitive stress and its high strength-to-weight ratio.
Disadvantages:low resistance to UV radiation and also prone to stress cracking when exposed to certain chemicals.

Acrylic (PMMA)

Acrylic, also known as PMMA or poly(methyl methacrylate), is lightweight, transparent, and has excellent weather resistance, making it popular for outdoor applications such as signage and displays.

Acrylic also has good machinability, allowing for intricate designs and fine details to be easily produced.
However, it is relatively brittle and prone to cracking, which can limit its use in certain applications.
Additionally, it has a low melting point, which can result in melting or deformation during high-speed machining operations.

Nylon (PA)

Nylon, also known as polyamide (PA), is a synthetic thermoplastic material that is commonly used in CNC machining. It has a high strength-to-weight ratio, good chemical resistance, and excellent wear resistance, making it ideal for applications such as gears, bearings, and other mechanical parts.

When CNC machining nylon, it is essential to keep in mind its unique properties. Nylon has a high melting point, which means that it requires high cutting temperatures and speeds.
However, it also has a tendency to absorb moisture from the air, which can affect its dimensional stability and may cause warping or distortion during machining.

Polycarbonate (PC)

Polycarbonate (PC) is a thermoplastic material that is highly versatile and known for its excellent impact resistance, clarity, and heat resistance.

One of the key advantages of a PC is its ability to be machined to tight tolerances without losing its properties. It is also relatively easy to machine, with low tool wear and good chip control, making it a cost-effective choice for CNC machining.
Another advantage of a PC is its high dimensional stability, which means that it is less likely to warp or deform during CNC machining. This makes it ideal for producing complex parts with tight tolerances and intricate features.
However, it’s important to note that PC also has some disadvantages. For example, it can be brittle and may require annealing or stress-relieving to improve its toughness. It can also be prone to stress cracking when exposed to certain chemicals, so care must be taken to select the appropriate PC formulation for the specific application.

Polypropylene (PP)

Polypropylene (PP) is a popular thermoplastic polymer that is widely used in CNC machining due to its desirable properties and characteristics.

Characteristics:a lightweight, durable and tough material;has good chemical resistance;has a low moisture absorption rate
Advantages: it has good electrical insulation properties and is a cost-effective material that is easy to process.
Disadvantages:poor resistance to UV radiation and can deteriorate when exposed to sunlight for a long time;has a low melting point, limiting its use in high-temperature applications.

ABS

ABS is a popularpopular thermoplastic polymer that is suitable for CNC machining.

Characteristics:Good impact resistance and toughness;Resistant to chemicals and high temperatures;It can be easily molded and machined;Lightweight and durable
Advantages:It can be easily machined into various shapes and sizes;Suitable for producing small to medium-sized parts;It offers good dimensional stability and a surface finish
Disadvantages:It may require post-processing to achieve desired surface finish;Sensitive to UV light and can become brittle over time if exposed to sunlight

PVC (polyvinyl chloride)

PVC (polyvinyl chloride) is a common plastic material that is widely used in various applications. It is made of a thermoplastic polymer that is simple to form into various sizes and shapes.

Characteristics:PVC is a lightweight material with a density of 1.38 g/cm³;It has good chemical resistance and is resistant to most acids, bases, and salts;PVC is an excellent electrical insulator and has a high dielectric strength.

Advantages:PVC is a cost-effective material that is widely available;PVC has good chemical and weather resistance, making it suitable for outdoor applications.
Disadvantages:It is not suitable for high-temperature applications as it can deform and lose its dimensional stability;PVC can emit toxic fumes when heated, making it necessary to take proper safety precautions during machining.

Polyethylene (PE)

Polyethylene (PE) is a thermoplastic polymer widely used in various applications due to its excellent balance of properties, including toughness, flexibility, chemical resistance, and low friction coefficient.

PE is a popular material for CNC machining due to its ease of machining and ability to hold tight tolerances.

Teflon (PTFE)

Teflon, also known as PTFE (polytetrafluoroethylene), is a synthetic fluoropolymer with unique characteristics, making it suitable for various applications.

Characteristics: no-stick; High-temperature resistance;Electrical insulator
Advantages:Its non-stick qualities make it the best choice for usage in packaging and food processing;High-temperature resistance allows it to be used in high-temperature applications, such as gaskets and seals.
Disadvantages:A low coefficient of friction can make it difficult to machine, as it tends to stick to cutting tools;Teflon is a soft material, which means that it can be easily scratched or damaged.

Wood Materials for CNC machining

Wood materials don’t like metals or plastic during CNC machining; it does not control the tolerances. However, wood materials are very popular and used in many applications due to their natural beauty and versatility.

One advantage of wood for CNC machining is its availability and affordability. Many different types of wood are available, each with unique characteristics and properties that can be leveraged for different applications. Softwoods, such as cedar and pine, are easy to carve and work with, while hardwoods like oak and cherry are more durable and have a tighter grain pattern.
Another advantage of wood is its ability to be stained, painted, or finished in a variety of ways. This allows for customization and personalization of wood projects, making them unique and tailored to the individual’s preferences.
But keep in mind that wood requires careful dust management to avoid creating a potentially hazardous working environment.

Other materials for CNC machining

Foam materials

Foam materials are adaptable, lightweight, and frequently used in many different applications, including packing, insulation, and cushioning.
Foam materials are suitable for CNC machining because they are relatively soft and easy to cut, carve, and shape with precision.
They are also generally affordable and widely available, making them a popular choice for prototyping, modeling, and custom fabrication.

Glass materials

As a non-crystalline solid material, glass is widely used from the construction of consumer products.

Glass is not commonly used for CNC machining because it is a brittle material that is prone to cracking and chipping during the machining process.
However, we could use waterjet cutting or abrasive waterjet machining to cut the glasses in various shapes.

Ceramic

Ceramic materials are a diverse group of materials that have a wide range of properties, including high hardness, high strength, and high-temperature resistance.

CNC machining of ceramic materials can be challenging due to their hardness and brittleness. However, with the development of advanced machining techniques and tools, it is now possible to machine ceramics to very high precision and tolerances.
One of the most common ceramic materials used in CNC machining is alumina (Al2O3). Alumina is a high-purity ceramic that is extremely hard and wear-resistant, making it ideal for applications such as cutting tools and bearings.

Composites

Composites are substances created by mixing two or more different substances to produce a substance with better characteristics than the sum of its parts. Common composites used for CNC machining are carbon fiber,fiberglass, and kevlar.

when it reaches to CNC machining,there are some factors that need to be cared for.Some composites can be challenging to machine, particularly those that contain abrasive materials like carbon fibers. Machining can lead to excessive tool wear and can generate a significant amount of dust.
Composites can have varying material properties based on the manufacturing process, which can lead to difficulties in machining and inconsistencies in the final product.

Conclusion

Thank you for reading this blog on materials for CNC machining. We hope you found it informative and helpful in selecting the right material for your project.Remember, selecting the right material is crucial for the success of your project. By understanding the properties and characteristics of different materials, you can ensure that your parts will be durable, functional, and cost-effective.

So, whether you need to machine plastic, metal, or composite materials, choose a reliable and experienced CNC machining service provider to help you achieve your goals. Contact us today to learn more about our services and capabilities.

Frequently Asked Questions

What factors should be considered when choosing a material for CNC machining?

A: Factors to consider include the material’s mechanical properties (strength, hardness, stiffness, etc.), chemical resistance, thermal stability, dimensional stability, cost, availability, and the specific requirements of the application.

What is the most common material for CNC machining?

A: Aluminum is one of the most common materials for CNC machining due to its strength, lightweight, and excellent machinability.

What is the most difficult material to machine?

A: Some of the most difficult materials for the machine include superalloys, titanium, and hardened steel.