Guide to Selecting CNC Machining Materials

Table of Contents

CNC (Computer Numerical Control) machining is a highly flexible manufacturing technology suitable for various applications from prototype development to mass production. Choosing the right material not only affects a part’s performance but also directly influences machining efficiency and cost control. This article systematically introduces common metallic, plastic, and other materials used in CNC machining, analyzing their performance characteristics, applicable scenarios, machining challenges, and cost considerations to help readers make informed material selection decisions.

Metallic Materials

Aluminum Alloys

Aluminum is one of the most widely used metals in CNC machining, favored for its lightweight nature, easy machinability, and moderate cost. Common grades include 6061, 7075, and 2024.
  • 6061 aluminum alloy offers moderate strength and good corrosion resistance, serving as a general-purpose material for mechanical parts, structural components, and automotive parts.
  • 7075 aluminum alloy has higher strength, suitable for aerospace, military, and racing applications with strict mechanical property requirements.
  • 2024 aluminum features excellent fatigue strength and high tensile strength but slightly poorer corrosion resistance, often used in aerospace structural parts.
    Aluminum alloys have good thermal conductivity and allow high-speed cutting. However, their softness makes them prone to burrs, requiring attention to tool selection and cooling methods.

Stainless Steel

Stainless steel is valued for its high strength, corrosion resistance, and aesthetic appearance, making it a common choice for industries with strict environmental and hygiene requirements, such as medical, food, and architectural hardware. Common grades include 304, 316, 303, and 17-4PH.
  • 304 is the most widely used stainless steel, suitable for most applications due to its balanced performance.
  • 316 contains molybdenum, offering enhanced corrosion resistance for marine and chemical equipment.
  • 303 adds sulfur to improve machinability.
  • 17-4PH is a precipitation-hardened stainless steel with extremely high strength and good mechanical properties, used in aerospace and high-stress components.
    Stainless steel is more difficult to machine than aluminum, prone to heat generation and rapid tool wear, necessitating appropriate tool materials and machining parameters.

Carbon and Alloy Steels

Carbon steels are widely used in mechanical manufacturing for their high strength and low cost. Common grades include 1018, 1045, and 4140.
  • 1018 is easy to machine and cost-effective, suitable for bolts and shafts.
  • 1045 medium carbon steel offers moderate strength for structural parts.
  • 4140 alloy steel features high strength and wear resistance, ideal for high-stress parts like molds and gears.
    Most of these steels can be heat-treated to enhance hardness and wear resistance. During machining, higher cutting forces and effective cooling are required to reduce tool wear.

Copper and Brass

Copper is prized for its excellent electrical and thermal conductivity, making it a key material for electronic components, heat sinks, and connectors. Brass, valued for its good machinability and corrosion resistance, is widely used in valves, pipe fittings, and decorative parts. Common grades include C110 (pure copper) and C360 (free-cutting brass).
Copper materials are prone to tool adhesion during machining, requiring control of cutting speed and the use of appropriate coolants.

Titanium Alloys

Titanium alloys offer high strength, corrosion resistance, low density, and biocompatibility, widely used in aerospace, medical implants, racing, and chemical equipment. The common grade is Ti-6Al-4V (Grade 5).
Despite their excellent performance, titanium alloys are difficult to machine. Poor thermal conductivity can cause tool overheating, and high cutting forces lead to high machining costs, limiting their use to high-value critical components.

Magnesium Alloys

Magnesium is the lightest structural metal, suitable for fields with strict weight control, such as aerospace and 3C products. It machines well but is flammable, requiring strict safety precautions during processing.

Plastic Materials

ABS (Acrylonitrile-Butadiene-Styrene)

ABS is a general-purpose plastic with moderate strength and low cost. Easy to machine and offering good surface finish, it is commonly used for housings, prototypes, toys, and automotive interiors. Its low heat deflection temperature makes it unsuitable for high-temperature environments.

POM (Polyoxymethylene / Acetal / Delrin)

POM features excellent wear resistance, low friction coefficient, and dimensional stability, making it an ideal material for mechanical structural parts like gears, pulleys, and bearing seats. It machines easily, produces neat chips, and ensures good surface quality.

PC (Polycarbonate)

PC offers good impact resistance and transparency, suitable for transparent covers, protective shields, and electronic components. Although strong, it is prone to cracking during machining, requiring attention to feed rate and tool sharpness.

PTFE (Polytetrafluoroethylene / Teflon)

PTFE is highly chemically stable, has a low friction coefficient, and withstands high temperatures, making it suitable for seals, chemical pipes, and bearings. Due to its extreme softness, sharp tools must be used to avoid plastic deformation during machining.

PE (Polyethylene), PP (Polypropylene), PVC (Polyvinyl Chloride)

These plastics are low-cost and corrosion-resistant, widely used in containers, gaskets, medical components, and water treatment equipment. Their machining properties vary, but they are generally unsuitable for precision structural parts.

Nylon

Nylon is strong, wear-resistant, and impact-resistant, suitable for gears, pulleys, and insulating parts. Its high hygroscopicity may affect dimensional stability, so storage and usage environments should be controlled after machining.

Other Special Materials

Ultem (PEI)

Ultem is a high-performance engineering plastic with good dimensional stability, thermal stability, and flame retardancy. Widely used in aerospace, electrical connectors, and medical devices, it requires high machining precision.

PEEK (Polyether Ether Ketone)

PEEK represents high-end engineering plastics, featuring high strength, high temperature resistance, and chemical corrosion resistance. It is commonly used in high-demand environments such as semiconductors, aerospace, and medical fields. Due to its high cost and processing expenses, it is typically reserved for critical components.

Graphite

Graphite is suitable for special machining scenarios like molds and electrodes. However, it generates dust during processing, imposing strict requirements on equipment and the environment.

Graphite

Graphite is suitable for special machining scenarios like molds and electrodes. However, it generates dust during processing, imposing strict requirements on equipment and the environment.

How to Select the Right Material

When selecting materials for CNC machining, consider the following aspects comprehensively:
  1. Performance Requirements: Need for high strength, corrosion resistance, insulation, conductivity, lightweight properties, etc.
  2. Machinability: Ease of cutting, tendency to adhere to tools, and acceptability of machining time.
  3. Cost Control: Material cost, machining time, and tool wear all impact overall costs.
  4. Post-Processing Needs: Requirements for electroplating, anodizing, heat treatment, polishing, etc.
  5. Batch Size and Purpose: Whether for prototype validation, functional parts, small-batch production, or mass manufacturing.

Materials perform differently in CNC machining. Metals like aluminum, stainless steel, copper, and titanium have distinct advantages for varying strength and environmental requirements, while plastics such as ABS, POM, PTFE, and PEEK suit low-load, lightweight, or corrosion-resistant environments. When selecting materials, evaluating both performance and machining difficulty/cost is essential to balance quality, efficiency, and economy optimally.

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut elit tellus, luctus nec ullamcorper mattis, pulvinar dapibus leo.

Facebook
Twitter
LinkedIn
en_USEnglish
en_USEnglish
Scroll to Top