Classifications of CNC Machining Material
The versatility of CNC machining technology allows its compatibility with a broad spectrum of materials. Typical CNC machining materials include conventional plastic, metals, wood, composites, and ceramics. However, plastic and metal machining materials have more diverse applications across industries than other materials. We’ll explore the common types of metals and plastics for CNC machining in this section:
Types of Metal Material for CNC Machining and Examples
Metal materials are the most commonly used CNC machining material for different CNC machined components. These CNC metals offer good mechanical properties, including high strength, thermal resistance, electrical conductivity, and hardness. Below are common CNC machining metals:
Aluminum
Aluminum is a highly machinable metal with diverse applications. Besides, it is one of the most common CNC materials and a better alternative to metals like titanium and steel. Aluminum and its alloys are amongst the most commonly used materials. Aluminum alloys exhibit excellent strength-to-weight ratio, corrosion resistance, low weight, and eye-catching silvery appearance.
Although aluminum has different grades, not all are suitable for making CNC-machined parts and components. However, 6061 and 7075 aluminum grades are the strongest aluminum alloys. They exhibit high machinability, making them ideal CNC machining materials for fabricating low-weight machined parts, such as aerospace frames, aircraft components, and automotive engine components.
7075 can be hardened to T6. 7075 T6 aluminum is suitable for fabricating plastic injection mold tools, automotive and aerospace frames, and high-strength recreational equipment for mountain climbing. Furthermore, most machinable aluminum materials are used in healthcare, consumer electronics, construction, and architecture.
Carbon Steel and Its Alloys
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Carbon steel and its alloys are ideal for diverse applications because of their higher machinability and superior strength. Carbon steel alloys are primarily compatible with different heat treatment procedures. Hence, they exhibit improved mechanical properties. Unlike most CNC metals, carbon steel material is not too expensive. Medium carbon steel is strong and suitable for heavy-duty applications like shafts, bolts, and studs.
Notably, the unattractive appearance of carbon steel makes the material incompatible with aesthetic applications. Similarly, carbon steel, mild steel, and its alloys are not intrinsically corrosion-resistant CNC materials. Although alloy steels are more corrosion-resistant and ductile than carbon, carbon steel is stronger. Nevertheless, these materials remain ideal for several industrial and manufacturing applications regardless of their limitations. They offer improved durability, machinability, and accessibility. Steel and its alloys are widely used in CNC machining structural components such as beams and mechanical fasteners.
Copper and Its Alloys
Copper is a popular CNC machining material with unique properties, including outstanding electrical and thermal conductivity. Since it exhibits excellent conductivity, product engineers consider copper and its alloy an ideal choice for electrical and electronic components. Similarly, copper alloys are perfect CNC materials for jewelry making due to their exceptional aesthetic appeal. Electrical wire, jewelry production, and magnetic devices are typical applications of copper.
Brass, bronze, and copper are indispensable CNC machining materials. Brass and bronze are common copper alloys with unique characteristics. Brass comprises of copper and zinc. It is a very soft metal and can be machined without lubrication. It exhibits excellent electrical conductivity, corrosion resistance, and machinability. Manufacturers often use brass for applications that don’t require great strength, such as fabricating low-strength fasteners, electrical equipment, consumer goods, and plumbing equipment.
On the other hand, bronze comprises copper, tin, and other compounding elements. It is strong, durable, and highly resistant to corrosion. Bronze exhibits excellent machinability, making it ideal for machining precise components like bearings and gears. Moreover, adding aluminum and phosphorous can increase the impact resistance, toughness, and strength of bronze.
Stainless Steel
Stainless steel is another widely used CNC metal with a glossy appearance. It has excellent strength, toughness, corrosion, and wear resistance. Alloy steel is reasonably priced and available in different grades. However, it exhibits high hardness, making it one of the most complex CNC materials to machine. Stainless steels contain chromium, which allows them to deter oxidation.
316 SS is one of the standard stainless steel grades with outstanding heat and corrosion resistance. Hence, it is often applicable in fabricating medical equipment, outdoor enclosures, and components used in the marine. 303, 304, and 316 stainless steel are other common CNC machined stainless steel grades used in fabricating fasteners like bushings, screws, bolts, etc.
However, manufacturers often add sulfur to 303 SS to make it more machinable. 303 stainless steel is suitable for machining nuts, bolts, shafts, gear, and fittings. Meanwhile, 304 stainless steel is readily machinable and can be welded. It is ideal for machining kitchen accessories, cutlery, architecture, and automotive components.
Magnesium
Magnesium is a versatile CNC machining metal with great strength and low-weight properties. Due to its excellent thermal properties, magnesium is an ideal metal for high-temperature components like engines. Furthermore, its light weight allows the manufacturing of lightweight and fuel-efficient vehicles. Magnesium is compatible with pressure die casting. Manufacturers use magnesium AZ31 for lightweight and high-strength applications such as camera frames, power tools housing, and laptop cases.
However, it is important to note that magnesium exhibits lower corrosion resistance than metals like aluminum. Also, magnesium machining is highly flammable and can be costly to process. Manufacturers often anodize magnesium machined parts to enhance their corrosion resistance.
Titanium
This CNC metal is incredibly strong and lightweight and offers a great strength-to-weight ratio. Its corrosion resistance property, heat conductivity, and biocompatibility make titanium compatible with CNC machining in the biomedical industry. Titanium is compatible with welding, passivation, and anodizing processes for enhanced appearance and increased protection. Although titanium possesses poor electricity conductivity, it exhibits good heat conductivity and a high melting point.
Furthermore, titanium is ideal for fabricating high-performance machined parts for the medical, military, aerospace, and automotive industries. More notably, titanium is suitable for making cutting tools for CNC machines.
Types of Plastic Material for CNC Machining
Different plastic resins are compatible with CNC machining process, and each is suitable for machining finished parts and prototypes. These plastic materials are usually lightweight materials and suitable alternatives for metals in certain applications. Here are common plastic materials for CNC machining:
Acrylic
Acrylic or PMMA (Polymethyl methacrylate) offers various desirable material properties, including rigidity and optical clarity. PMMA is a reliable alternative for glass due to its high rigidity and transparency. It is a perfect CNC plastic material for different applications because it allows the production of precise machined parts with superior quality.
Although PMMA exhibits a high propensity for cracking and thermal softening, its adaptability and simplicity make it a suitable material for CNC machining tasks. Similarly, PMMA acrylic is less impact-resistant than Polycarbonate, even though it resists scratching. Typical applications of PMMA include display screens, lenses, food storage components, light pipes, and clear enclosures.
ABS
ABS is the most economical plastic with a unique combination of material properties, including excellent machinability, tensile strength, and chemical and impact resistance. Product developers often choose ABS as the perfect CNC material for most plastic machined parts due to its versatility and cost-effectiveness. ABS plastic can withstand high temperatures for extended periods and is cheaper than most engineering plastics like PEEK.
Similarly, ABS material is best suited for applications where aesthetics is critical because it is easy to color. ABS is compatible with CNC applications, including rapid prototyping, protective enclosures, and fabrication of automotive parts. In addition to CNC machining, ABS material is also suitable for other manufacturing processes, such as 3D printing and injection molding.
Acetal
Acetal, Delrin, or POM, is a highly versatile CNC machining plastic with remarkable toughness, impact, and moisture resistance. Due to Delrin’s excellent fatigue resistance and stiffness, manufacturers often use POM to machine high-precision components such as valves, gears, and bearings.
Acetal maintains exceptional dimensional precision in machining parts of different dimensions and structures for various aerospace, automotive, and consumer goods applications. Acetal machined parts maintain superior mechanical properties and excellent resistance to environmental conditions.
Polycarbonate (PC)
Polycarbonate is another commonly used CNC machining plastic with several beneficial characteristics, including optical clarity. Aside from being heat- and shatter-resistant, Polycarbonate exhibits strong heat resistance, which makes it suitable for high-temperature applications. More so, polycarbonate is a commonly used CNC plastic for machining applications like medical devices, electronic components, and automotive parts.
Polyether ketone (PEEK)
PEEK is a high-strength CNC machining plastic with unique properties such as excellent chemical resistance, high mechanical strength, and dimensional stability. This engineering plastic is well suited for use in extreme environments because it maintains stiffness at extreme temperatures.
Product manufacturers across different industries often use PEEK in food and beverage processing, aerospace, and oil and gas industries. In addition, it is widely embraced in fabricating bushings, pump and valve components, seals, semiconductor components, and bearings. This high-performance plastic resin is best suited for machining lightweight fixtures since it doesn’t deform or creep over time.
Polypropylene (PP)
Polypropylene is an adaptable CNC machining plastic with excellent fatigue strength and high chemical resistance. Besides, PP is a medical-grade CNC machining material. CNC-machined polypropylene parts offer a smooth surface finish. However, PP softens easily upon exposure to high temperatures, resulting in machining complications.
Polyvinyl Chloride (PVC)
PVC is an affordable CNC plastic with an excellent machinability rating. Its high strength makes it stiff and resistant to high impact. Similarly, PVC material is suitable for fabricating welded chemical tanks, cabinet and working surfaces, valve and pump housings, fittings, and manifolds. Plastic machined parts manufacturers widely use PVC for applications that require high corrosion and chemical resistance.
Nylon
This plastic resin is amongst the strongest and most durable plastic CNC machining materials. Its excellent impact resistance makes it compatible with several applications. It exhibits great lubricating properties and is available in different composite forms, including glass-fiber-reinforced nylon. Nylon material is particularly suitable for applications that require protection from frictional forces. Sliding surfaces, bearings, gears, and sprockets are typical nylon machined parts. Moisture absorption is one of the major drawbacks of nylon. Hence, it is not an ideal option for marine applications.
UHMW-PE
Ultra-high molecular Weight Polyethylene (UHMWPE) is a standard CNC machining plastic with unique mechanical properties. It exhibits excellent endurance, wear, abrasion resistance, high toughness, and a naturally slippery surface. Although UHMW-PE has low machinability, its slippery surface is well-suited for making sliding surfaces in different components like rollers, gears, and bearings. UHMWPE is also applicable to marine environments, gear trains, conveyor belts, food, and chemical processing.
UHMW-PE exhibits exceptional material properties, making it a perfect CNC machining plastic for applications requiring remarkable wear resistance and endurance. This CNC plastic can provide outstanding efficiency and longevity when machined appropriately.
Factors to Consider When Selecting a Material for CNC Machining
CNC machining materials are of different types and properties. Hence, it is essential to carefully consider certain factors when choosing right CNC materials for your machining project. Here are some of these factors:
Weight of the Part
CNC machining materials have varying weight properties. Hence, this factor will influence your CNC material choice since it will influence the machining process and the machined part’s overall performance. Generally, heavier parts often need stronger materials to ensure their load-bearing capacity. Meanwhile, low-weight machined parts may require lower-density materials like aluminum or titanium to optimize performance and reduce weight.
The Part’s Application
Ensure that the intended CNC material meets the requirements of the intended application and its working environment. For instance, let’s compare the difference between carbon steel and stainless steel if they were chosen as materials intended for marine application.
Both stainless steel and carbon steel exhibit excellent machining properties. However, marine-grade stainless steel is more suitable for marine applications because it exhibits greater corrosion resistance. However, carbon steel will be the perfect CNC material choice in a regular, dry environment due to its remarkable strength and durability.
Surface Finish Options
The preferred surface finish you want your finished product to have is a major determinant of the ideal material for your CNC machining task. There are several surface finishing options available for CNC plastic and metal materials. These include anodizing, polishing, painting, passivation, powder coating, brushing, and electroplating. These surface treatments help enhance both the performance and aesthetics of machined parts.
Accuracy and Tolerance of the Part
Some CNC machining materials are challenging to machine to preferred tolerances. For instance, certain CNC plastics such as PVC, prone to warping, may require higher machining allowances to get the desired tolerance range. Meanwhile, CNC metals like titanium or steel are often used for industrial applications requiring high accuracy and tight tolerances.
Part’s Properties
The intended application and working environment in which a CNC part will be used determines its required material properties. Variables, including toughness, strength, and resistance to wear, are important material properties expected in CNC parts that will be exposed to greater stress or wear.
Moreover, certain CNC metals like steel and titanium and plastics like nylon and acetal exhibit remarkable strength and durability, making them ideal CNC materials for high-stress or wear applications. However, materials with excellent thermal stability, including certain metals and ceramics, may be the preferable CNC materials for CNC parts that will be exposed to high temperatures.
Machinability of the Material
The machinability of a CNC material is how relatively easy it is to cut. Softer materials like CNC plastic and metals like aluminum are relatively easy to machine. Meanwhile, machining may become more challenging with tougher CNC materials such as titanium and carbon fiber. These materials are rigid and often damage the edges of cutting tools. Hence, machining parts with CNC materials that have high machinability ratings helps save cost and time.
Cost
The cost of a material for a CNC machining job is a critical consideration. However, we strongly recommend that all product developers and engineers choose a lower grade of material to save on costs. It is advisable to purchase a high-quality cost-efficient material that provides all the required properties. By doing so, you ensure the durability of the finished parts.
Expert Tips for Effective CNC Machining Materials Selection
There are several factors critical to the success of your machining operation. Here are helpful tips to follow as a guide to your CNC material machining:
Choose Common Machining Materials
You can quickly choose from the list of common materials expert engineers identified and considered suitable for machining and widely accepted for the intended applications instead of worrying about picking from the broad spectrum of materials available for CNC machining.
Brass, aluminum, copper, and stainless steel are typical CNC metals commonly used for different applications, while PEEK, Polycarbonate (PC), ABS, Acetal, and Nylon are commonly used CNC plastic materials.
Use Quality Tooling
Use high-quality cutting tools irrespective of the CNC material you want to shape to the desired dimensions. You can spare yourself from headaches and further expenses by avoiding inexpensive cutting tools that readily break and soon wear out. These high-quality CNC tooling are designed to handle the rigors of high-speed machining. Hence, these machining tools not only optimize the consistency of output but also improve quality.
Install Reliable Work-Holding Devices on Your CNC Machine
A workpiece must maintain a stable position during CNC machining. However, this is easier said than done. Maintaining a part in place is more challenging when handling delicate materials and intricate designs. As such, installing a reliable work holding capable of keeping your workpiece in place during machining is better, ensuring better precision and accuracy.
Conclusion
CNC machining relies principally on thoughtful material selection as material science evolves. Even though CNC machines are highly flexible and adaptable with diverse materials, it is important to choose a material that matches the requirements of your project. This guide has discussed everything you need to know about common CNC materials to make informed decisions about your machining project for optimal performance and durability of machined components.
AT-Machining is the perfect CNC shop in China to consult whenever you need help choosing the right material for your machining projects. We are a leading CNC machining services expert with good years of experience machining top quality products from different raw materials, including plastics, metals, ceramics, composites, etc. Trust us to deliver quality prototypes and CNC machine components precisely to your technical drawing with faster lead time. We are excited to render professional assistance when you upload your CAD files for an instant quote!
