In the realm of modern manufacturing, Computer Numerical Control (CNC) machining has revolutionized the way metal parts are designed, prototyped, and produced. This advanced technology CAD software with precision cutting tools, guided by programmed instructions, to achieve unparalleled levels of accuracy, repeatability, and versatility in metalworking.
This comprehensive guide delves into the intricacies of metal CNC machining, its principles, processes, advantages, and applications across various industries.
What is Metal CNC Machining?
Metal CNC machining is a subtractive manufacturing process that involves removing material from a solid block of metal (known as the workpiece or blank) to create a desired shape or component. This process is controlled by a computer program that dictates the movement of cutting tools along predetermined paths, enabling highly complex geometries to be achieved with remarkable precision.
Types of Metals Used in CNC Machining
CNC machining can work with a wide range of metals, each offering unique properties suited for different applications. Common metals include:
1. Aluminum
Aluminum is one of the most commonly used metals in CNC machining due to its excellent machinability, lightweight nature, and versatility. It is widely used across various industries, including aerospace, automotive, electronics, and consumer products
Key Properties:
- Density: 2.7 g/cm³ (2700 kg/m³)
- Melting Point: 660.3°C (1220.5°F)
- Boiling Point: 2519°C (4566°F)
- Thermal Conductivity: 235 W/m·K
- Electrical Conductivity: 37.7 x 10^6 S/m
- Specific Heat Capacity: 0.897 J/g·K
- Thermal Expansion Coefficient: 22.2 x 10^-6 /K
- Reflectivity: 80-85% of visible light
- Tensile Strength: 70-700 MPa
- Yield Strength: 40-550 MPa
- Elongation: 8-20% (varies with alloy)
- Modulus of Elasticity: 69 GPa (10,000 ksi)
Common Grades:
| Aluminum Grade | Key Properties | CNC Machining Techniques |
|---|---|---|
| 5052 | High corrosion resistance, good weldability, moderate to high strength | Machinable but tends to be more difficult; use lubricants to avoid galling |
| 6061 | Excellent mechanical properties, good weldability, good corrosion resistance | Highly machinable; use high-speed tools and consider chip removal strategies |
| 6063 | Good corrosion resistance, excellent weldability, medium strength | Machinable with high feed rates and smooth finishes; use sharp tools |
| 7075 | Very high strength, average corrosion resistance, difficult to weld | Requires precise machining with sharp tools and controlled feed rates due to its hardness |
| 5083 | Exceptional performance in extreme environments, high strength, excellent corrosion resistance | More challenging to machine; use slow speeds and plenty of lubrication to avoid tool wear |
Applications: Widely used in aerospace, automotive, electronics, and consumer goods industries. Common aluminum alloys like 6061 and 7075 are often chosen for structural components, housings, and enclosures.
2. Stainless Steel
Stainless steel is prized for its strength, durability, and resistance to corrosion, making it ideal for a wide range of applications, from medical instruments to automotive parts.
Key Properties:
- Density: 7.8 g/cm³ (7800 kg/m³)
- Melting Point: 1375-1530°C (2500-2800°F)
- Boiling Point: Approximately 2750°C (5000°F)
- Thermal Conductivity: 16-25 W/m·K
- Electrical Conductivity: 1.45 x 10^6 S/m
- Specific Heat Capacity: 0.50 J/g·K
- Thermal Expansion Coefficient: 16-20 x 10^-6 /K
- Tensile Strength: 480-1300 MPa
- Yield Strength: 210-1000 MPa
- Elongation: 40-60% (varies with grade)
- Hardness: Typically 150-200 HB
- Modulus of Elasticity: 200 GPa (29,000 ksi)
Common Grades:
| Stainless Steel Grade | Key Properties | CNC Machining Techniques |
|---|---|---|
| 303 | Excellent machinability, good corrosion resistance, non-magnetic | Easily machinable; ideal for high-speed CNC machining with minimal tool wear |
| 304 | Good corrosion resistance, excellent formability, non-magnetic | Moderate machinability; use sharp tools and lower speeds to prevent work hardening |
| 316 | Superior corrosion resistance, especially in marine environments, non-magnetic | More challenging to machine; use slow speeds, high lubrication, and sharp tools |
| 416 | Excellent machinability, good corrosion resistance, magnetic | Best machinability among stainless steels; suitable for high-speed machining with low tool wear |
| 440C | Very high hardness, excellent wear resistance, magnetic | Difficult to machine due to hardness; use very slow speeds and strong tooling |
| 17-4 PH | High strength, good corrosion resistance, excellent mechanical properties, magnetic | Requires careful machining with reduced speeds and high-quality tools to handle the hardness and strength |
Applications: Used in the medical, food processing, marine, and chemical industries. Stainless steel is ideal for parts that require a combination of strength and corrosion resistance, such as surgical instruments, fasteners, and marine components.
3. Steel
Steel, particularly carbon steel, is a staple in CNC machining due to its strength, affordability, and wide availability. It’s often used for parts requiring durability and structural integrity.
Key Properties:
- Density: 7.75-8.05 g/cm³ (7750-8050 kg/m³)
- Melting Point: 1425-1540°C (2597-2804°F)
- Boiling Point: Approximately 3000°C (5432°F)
- Thermal Conductivity: 43-60 W/m·K
- Electrical Conductivity: 10-20% IACS
- Specific Heat Capacity: 0.486 J/g·K
- Thermal Expansion Coefficient: 11-16 x 10^-6 /K
- Magnetic Properties: Magnetic
- Tensile Strength: 370-2000 MPa
- Yield Strength: 250-1500 MPa
- Elongation: 10-50%
- Hardness: 120-600 HB
- Modulus of Elasticity: 200-210 GPa (29,000-30,500 ksi)
Common Grades:
| Steel Grade | Key Properties | CNC Machining Techniques |
|---|---|---|
| 4140 (Alloy Steel) | High strength, good toughness, excellent fatigue resistance | More challenging to machine; use slower speeds and strong, heat-resistant tools |
| A36 (Structural Steel) | Good weldability, moderate strength, widely used | Easily machinable; can be processed at high speeds with standard tooling |
| O1 (Tool Steel) | High hardness, excellent wear resistance, good toughness | Difficult to machine; use low speeds, high lubrication, and strong carbide tools |
| D2 (Tool Steel) | Very high hardness, excellent wear resistance, high compressive strength | Very difficult to machine; requires very slow speeds and robust tooling to handle the hardness |
| A2 (Air-Hardening Tool Steel) | High hardness, good wear resistance, excellent dimensional stability | Difficult to machine; use low speeds, plenty of lubrication, and high-quality tools |
Applications: Commonly used in the automotive industry for gears, shafts, and other mechanical components. It’s also used in construction for making tools, bolts, and structural elements.
4. Titanium
Titanium is known for its exceptional strength, low density, and corrosion resistance, making it an ideal choice for high-performance applications, especially in the aerospace, medical, and marine industries.
Key Properties:
- Density: 4.5 g/cm³ (4500 kg/m³)
- Melting Point: 1885°C (3415°F)
- Boiling Point: 3287°C (5949°F)
- Thermal Conductivity: 21.9 W/m·K
- Electrical Conductivity: 2.38 x 10^6 S/m
- Specific Heat Capacity: 0.523 J/g·K
- Thermal Expansion Coefficient: 8.6 x 10^-6 /K
- Tensile Strength: 240-1400 MPa
- Yield Strength: 140-1300 MPa
- Elongation: 10-30%
- Modulus of Elasticity: 116 GPa (16,800 ksi)
Common Grades:
| Titanium Grade | Key Properties | CNC Machining Techniques |
|---|---|---|
| Grade 1 | Pure titanium, excellent corrosion resistance, high ductility | Easy to machine with standard tools; use higher speeds and sharp tools to avoid work hardening |
| Grade 2 | Pure titanium, good balance of strength and ductility, excellent corrosion resistance | Similar to Grade 1; requires sharp tools and moderate speeds to manage heat buildup |
| Grade 3 | Higher strength than Grade 2, good corrosion resistance, moderate ductility | Requires controlled cutting speeds and sharp tools to prevent excessive tool wear |
| Grade 4 | High strength, good corrosion resistance, lower ductility | More challenging to machine; use slow speeds, high lubrication, and robust tooling |
| Grade 5 (Ti-6Al-4V) | Alloyed with aluminum and vanadium, high strength, good fatigue resistance | Difficult to machine; use low speeds, high-quality tooling, and high lubrication to manage heat and tool wear |
Applications: Extensively used in the aerospace, medical, and military industries. Titanium is ideal for critical components like aircraft parts, implants, and high-performance sports equipment.
5. Brass
Brass, an alloy of copper and zinc, is favored for its excellent machinability, corrosion resistance, and attractive appearance. It’s commonly used in decorative, electrical, and plumbing applications.
Key Properties:
- Density: 8.4-8.7 g/cm³ (8400-8700 kg/m³)
- Melting Point: 900-940°C (1652-1724°F)
- Boiling Point: Approximately 2700°C (4892°F)
- Thermal Conductivity: 109-130 W/m·K
- Electrical Conductivity: 15-50% IACS
- Specific Heat Capacity: 0.380 J/g·K
- Thermal Expansion Coefficient: 18.7 x 10^-6 /K
- Tensile Strength: 200-600 MPa
- Yield Strength: 100-450 MPa
- Elongation: 15-60%
- Hardness: Typically 55-100 HB
- Modulus of Elasticity: 90-110 GPa (13,000-16,000 ksi)
Common Grades:
| Brass Grade | Key Properties | CNC Machining Techniques |
|---|---|---|
| C36000 (Free-Cutting Brass) | Excellent machinability, good corrosion resistance, high machinability | Best machinability among brass grades; use high-speed machining with minimal tool wear |
| C26000 (Yellow Brass) | Good corrosion resistance, moderate strength, good formability | Easily machinable with standard tools; use moderate cutting speeds to avoid work hardening |
| C28000 (Brass) | Good corrosion resistance, moderate machinability, good strength | Machinable with standard tooling; use moderate speeds and lubrication to manage heat buildup |
| C33000 (Low Leaded Brass) | Good machinability, high wear resistance, reduced lead content for safety | Similar to C36000; use high-speed machining with minimal tool wear and proper cooling |
Applications: Used in plumbing, electrical components, and decorative items. Brass is often chosen for parts that require precision and a smooth finish, such as fittings, valves, and connectors.
6. Copper
Copper is valued for its high electrical and thermal conductivity, making it ideal for electrical components, heat exchangers, and plumbing systems.
Key Properties:
- Density: 8.96 g/cm³ (8960 kg/m³)
- Melting Point: 1084.62°C (1984.32°F)
- Boiling Point: 2562°C (4644°F)
- Thermal Conductivity: 401 W/m·K
- Electrical Conductivity: 58.6 x 10^6 S/m (100% IACS)
- Specific Heat Capacity: 0.385 J/g·K
- Thermal Expansion Coefficient: 16.5 x 10^-6 /K
- Tensile Strength: 210-370 MPa
- Yield Strength: 33-350 MPa
- Elongation: 15-50% (varies with processing)
- Hardness: Typically 40-110 HB
- Modulus of Elasticity: 110-128 GPa (16,000-18,500 ksi)
Common Grades:
| Copper Grade | Key Properties | CNC Machining Techniques |
|---|---|---|
| C11000 (Electrolytic Copper) | High electrical and thermal conductivity, excellent corrosion resistance | Easily machinable; use high speeds and sharp tools for optimal results |
| C10100 (Oxygen-Free Copper) | High purity, excellent electrical conductivity, good corrosion resistance | Similar to C11000; suitable for high-speed machining with minimal tool wear |
| C36000 (Free-Cutting Copper) | Excellent machinability, good electrical conductivity, high corrosion resistance | Best machinability; use high-speed machining with minimal tool wear |
| C19400 (Copper-Phosphorus Alloy) | High strength, good thermal and electrical conductivity, good fatigue resistance | Requires careful machining with controlled speeds and high-quality tools |
Applications: Common in the electronics, automotive, and HVAC industries. Copper is used for electrical connectors, heat exchangers, and components requiring high conductivity.
7. Magnesium
Magnesium is the lightest structural metal, offering a combination of low density, good strength, and excellent machinability. It’s used in applications where weight reduction is critical, such as in the automotive and aerospace industries.
Key Properties:
- Density: 1.74 g/cm³ (1740 kg/m³)
- Melting Point: 650°C (1202°F)
- Boiling Point: 1091°C (1994°F)
- Thermal Conductivity: 156 W/m·K
- Electrical Conductivity: 2.3 x 10^6 S/m
- Specific Heat Capacity: 1.023 J/g·K
- Thermal Expansion Coefficient: 24-26 x 10^-6 /K
- Tensile Strength: 150-300 MPa
- Yield Strength: 65-160 MPa
- Elongation: 2-20%
- Hardness: Typically 30-100 HB
- Modulus of Elasticity: 45 GPa (6,500 ksi)
Common Grades:
| Magnesium Grade | Key Properties | CNC Machining Techniques |
|---|---|---|
| AZ31B | Good balance of strength, ductility, and corrosion resistance | Easily machinable with standard tools; use moderate speeds and ample cooling to manage heat |
| AZ61A | Higher strength than AZ31B, good corrosion resistance | Machinable with moderate speeds; use proper lubrication to avoid galling and tool wear |
| AZ80A | High strength, moderate ductility, good corrosion resistance | Requires careful machining; use slow speeds and high-quality tools to manage heat and tool wear |
| AM60B | High strength, good impact resistance, good corrosion resistance | More challenging to machine; use slow speeds, high lubrication, and robust tooling |
| WE43 | High strength, excellent corrosion resistance, good fatigue resistance | Difficult to machine; use very slow speeds, high-quality tools, and thorough cooling to manage heat |
Applications: Commonly used in the automotive, aerospace, and electronics industries. Magnesium is often chosen for lightweight components like housings, brackets, and frames.
8. Inconel
Inconel is a family of nickel-chromium superalloys known for their ability to withstand extreme temperatures, corrosion, and oxidation. It’s commonly used in aerospace, chemical processing, and power generation.
Key Properties:
- Density: 8.2-8.5 g/cm³ (8200-8500 kg/m³)
- Melting Point: 1350-1400°C (2462-2552°F)
- Boiling Point: Approximately 2500°C (4532°F)
- Thermal Conductivity: 11-15 W/m·K
- Electrical Conductivity: 1.3 x 10^6 S/m
- Specific Heat Capacity: 0.435 J/g·K
- Thermal Expansion Coefficient: 12.8-13.3 x 10^-6 /K
- Tensile Strength: 550-1100 MPa
- Yield Strength: 240-850 MPa
- Elongation: 30-50%
- Hardness: Typically 180-350 HB
- Modulus of Elasticity: 205 GPa (29,700 ksi)
Common Grades:
| Inconel Grade | Key Properties | CNC Machining Techniques |
|---|---|---|
| Inconel 600 | Excellent oxidation and corrosion resistance, good mechanical properties at high temperatures | Requires slow speeds and strong, high-quality tools to manage heat and tool wear |
| Inconel 625 | High strength, excellent fatigue and thermal-fatigue strength, superior oxidation and corrosion resistance | Difficult to machine; use very slow speeds, high-quality tooling, and thorough cooling to handle hardness and heat |
| Inconel 718 | High strength, excellent oxidation and corrosion resistance, good weldability | Challenging to machine; use slow speeds, strong tooling, and proper lubrication to manage the material’s toughness |
| Inconel 730 | High strength and resistance to oxidation and corrosion at elevated temperatures | Requires controlled speeds, high-quality tooling, and ample cooling to manage machining difficulties |
| Inconel 800 | Good oxidation and corrosion resistance, excellent high-temperature stability | Machinable with slower speeds and high-quality tools to handle the material’s toughness and manage heat |
Applications: Predominantly used in the aerospace and energy sectors. Inconel is ideal for turbine blades, exhaust systems, and other high-temperature applications.
Types of Metal CNC Machining Operations
Within metal CNC machining, several specific processes are employed based on the desired outcome and material properties:
| Machining Process | Description | Common Uses | Key Processes |
|---|---|---|---|
| Turning | Rotating workpiece while a cutting tool removes material | Cylindrical parts (shafts, bushings, rings) | Facing, turning, drilling, boring |
| Milling | Rotary cutters remove material from a stationary workpiece | Complex shapes, slots, holes, surface finishes | Face milling, end milling, slot milling, contour milling |
| Drilling | Creating holes using a rotating drill bit | Precise holes for fasteners, alignment | Drill, ream, tap |
| Grinding | Abrasive wheel removes material for fine surface finish | Precise dimensions, smooth surfaces | Surface grinding, cylindrical grinding, internal grinding |
| Electrical Discharge Machining (EDM) | Removing material using electrical discharges | Hard metals, complex shapes, precision parts | Sinker EDM, wire EDM |
| Laser Cutting | Cutting metal with a high-powered laser beam | Complex shapes, intricate designs | Sheet metal cutting, engraving |
| Waterjet Cutting | Cutting with high-pressure water, sometimes mixed with abrasives | Thick materials, complex shapes, heat-sensitive materials | Abrasive waterjet cutting, pure waterjet cutting |
| Electrochemical Machining (ECM) | Removing material through electrochemical reactions | Precision machining of hard materials | Electrochemical grinding, electrochemical drilling |
| Swiss Machining | High-precision turning for small-diameter parts | Medical devices, aerospace components, small mechanical parts | Longitudinal turning, cross drilling, thread cutting |
Advantages of Metal CNC Machining
Here’s a list of the advantages of metal CNC machining:
- Delivers exact measurements and tight tolerances for high-quality parts.
- Capable of machining intricate and detailed designs that are difficult to achieve manually.
- Ensures uniformity and consistency across multiple production runs.
- Faster machining processes reduce lead times and boost productivity.
- Minimizes manual intervention, cutting down on labor expenses and human error.
- Works with a wide range of metals, including aluminum, steel, titanium, and more.
- Achieves high-quality surface finishes with minimal additional processing required.
- Efficient cutting techniques reduce waste and lower material costs.
- Utilizes multi-axis and advanced techniques for complex operations and improved accuracy.
- Easily programmable to adapt to different designs and production requirements.
- Maintains consistent quality and dimensions for large quantities of parts.
- Interfaces with design software for precise and efficient production planning.
- Meets stringent specifications for high-precision industries like aerospace and medical.
- Reduces manual handling of sharp tools and dangerous operations, improving safety standards.
Future of Metal CNC Machining
Advancements in CNC technology, such as 5-axis machining, hybrid machining (combining additive and subtractive processes), and the integration of AI for predictive maintenance, are pushing the boundaries of what can be achieved with metal CNC machining. As industries continue to demand higher precision, faster production times, and more complex designs, metal CNC machining will remain at the forefront of modern manufacturing.
Contact BOYI for Metal CNC Machining Services
Ready to experience precision and efficiency with your metal components? At BOYI, we offer top-notch CNC machining services for a wide range of metals, ensuring high-quality, accurate, and consistent results. Contact us today to discuss your project needs and discover how BOYI’s metal CNC machining can elevate your manufacturing process. Let’s bring your vision to life—get in touch with us now!
Let’s Start A New Project Today
Our engineers will contact you within 2 hours.
FAQ
CNC machining works with metals like aluminum, steel, stainless steel, titanium, brass, copper, magnesium, Inconel, bronze, and zinc. Each metal offers different properties like strength, corrosion resistance, or machinability.
Metal CNC machining can be expensive due to factors like the cost of machinery, tooling, and materials, as well as labor and overhead. However, the cost can vary depending on the complexity of the parts, the type of metal used, and the volume of production.
The time required for metal CNC machining varies based on factors such as the complexity of the part, material type, and production volume. Simple parts might be machined in a few hours, while more complex or large parts can take days. Generally, CNC machining is efficient, but exact times depend on specific project requirements.
Typically, CNC machines can handle metal thicknesses ranging from a few millimeters to several centimeters. For example, standard CNC mills may cut metal up to about 10-20 cm (4-8 inches) thick, while larger, more robust machines or specialized equipment can handle thicker materials.
This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
