CNC machining is everywhere — from car engines to smartphone parts, even medical implants. If you’re wondering what is CNC machining and what is a CNC machine used for, you’re in the right place. This guide breaks it all down in simple terms, without skipping the technical details that matter.
Whether you’re new to the concept or looking to deepen your understanding, this guide will cover the essentials and beyond — including machine types, materials, benefits, and real-world applications.
What is CNC Machining?
CNC stands for Computer Numerical Control. It refers to a subtractive manufacturing process where pre-programmed software dictates the movements of factory tools and machinery.
Unlike traditional manual methods, CNC machining automates the control of machine tools using a computer. This makes it possible to produce complex and highly accurate parts with remarkable efficiency. At its core, CNC machining involves:
- Converting CAD designs into G-code (machine language)
- Feeding the G-code into the CNC system
- Machining the raw material into a finished part via tools like mills, lathes, drills, or routers
What is a CNC Machine Used For?
A CNC machine is used for the automated shaping, cutting, and forming of materials. These machines are common across industries like aerospace, automotive, medical, and electronics due to their ability to produce:
- Engine components
- Prosthetics and implants
- Electronics casings
- Aerospace parts
- Custom fixtures and prototypes
CNC machines are valued for their repeatability, precision, and speed. Whether you’re machining metal, plastic, wood, or foam, these systems bring digital designs to life with unparalleled accuracy.
How Does CNC Machining Work?
Step 1: Design with CAD
The process begins with a CAD (Computer-Aided Design) file that defines the geometry of the part.
Step 2: Convert to G-code
The CAD model is translated into G-code, which acts as the language that CNC machines understand. This code instructs the machine how fast to move, where to cut, and what sequence to follow.
Step 3: Setup and Machining
The chosen material (e.g., aluminium, stainless steel, ABS plastic) is fixed onto the machine bed. The CNC machine then autonomously executes the programmed operations — cutting, drilling, or turning — to create the final component.
Types of CNC Machines
CNC Milling Machines
CNC milling uses rotary tools to remove material from a stationary workpiece. It’s ideal for flat surfaces, slots, holes and even complex geometries. Most milling machines operate on 3 to 5 axes, allowing for intricate detailing.
CNC Lathes
Lathes rotate the workpiece against a cutting tool. These machines are best for parts with rotational symmetry, such as screws, bolts, and cylindrical shafts.
CNC Routers
Primarily used for softer materials like wood, plastic, and foam, CNC routers are ideal for signage, cabinetry, and prototype development.
CNC Plasma Cutters and Water Jets
For cutting thicker sheets of metal or materials sensitive to heat, plasma and water jet cutters are used. Water jets, in particular, cut using a high-pressure stream mixed with abrasives and are used when thermal distortion must be avoided.
CNC EDM (Electric Discharge Machining)
EDM uses electrical sparks to shape metal. It’s often used in die-making and high-precision moulds.
What Materials Can Be CNC Machined?
Metals
- Aluminium – Lightweight, corrosion-resistant, cost-effective
- Stainless Steel – Durable and corrosion-resistant
- Mild Steel – Affordable and easy to machine
- Titanium – High strength-to-weight ratio, ideal for aerospace and medical use
- Brass – Decorative and corrosion-resistant
- Copper – Great electrical conductivity
Plastics
- ABS – Common in prototyping, strong and chemical resistant
- POM (Acetal/Delrin) – High wear resistance and machinability
- PEEK – High-performance thermoplastic, used in aerospace and medical sectors
- PC (Polycarbonate) – Impact-resistant and transparent
Common CNC Machining Processes
Drilling
Used to create round holes in a workpiece. CNC drilling ensures consistent depth and spacing.
Milling
Removes material using a rotating tool. Milling is used for slots, pockets, and contours.
Turning
The material rotates against a cutting tool. Often used to make cylindrical parts.
Tapping and Thread Milling
Creates internal or external threads. Thread milling is more precise for harder materials.
Surface Finishes in CNC Machining
As-Machined
The raw surface left after machining — smooth, with visible tool paths.
Bead Blasting
A matte finish achieved by blasting the surface with fine glass beads.
Anodising
A corrosion-resistant coating often applied to aluminium, available in different colours.
Powder Coating
A durable, decorative finish used for protection and aesthetics.
Mirror Polishing and Electropolishing
Used for aesthetic and functional benefits, especially in stainless steel parts.
Advantages of CNC Machining
- Precision & Accuracy – Repeatable tolerances within microns
- Automation – Minimal human intervention reduces errors
- Material Versatility – Metals, plastics, composites, and more
- Scalability – From one-off prototypes to mid-scale production
- Fast Turnaround – Rapid prototyping possible within hours
Limitations of CNC Machining
- Initial Setup Costs – Skilled setup and programming required
- Design Constraints – Complex internal geometries may be difficult
- Material Waste – Subtractive nature can lead to high scrap rates
- Tool Access Limitations – Internal sharp corners and deep cavities can be challenging
Design Guidelines for CNC Parts
- Use Fillets – Rounded internal corners reduce tool wear
- Avoid Thin Walls – Helps prevent vibrations and breakage
- Limit Deep Cavities – Depth should not exceed 4x the cavity width
- Use Standard Hole Sizes – Reduces tooling time and costs
Minimise Tolerances – Only apply where absolutely necessary
CNC Machining Applications by Industry
Aerospace
Precision parts like turbine blades, brackets, and housings are commonly machined from lightweight, high-strength materials like titanium.
Automotive
Used to manufacture engine blocks, gearboxes, and transmission components with tight tolerances.
Medical
CNC machining enables the production of surgical instruments, implants, and diagnostic equipment.
Electronics
Enclosures and heatsinks for devices are often made using CNC machining.
Industrial Equipment
Custom machinery components, jigs, and tools are regularly produced using CNC processes.
CNC Machining vs Other Manufacturing Methods
| Feature | CNC Machining | 3D Printing | Injection Moulding |
| Volume | Low to Mid | Low | High |
| Material Strength | High | Moderate | High |
| Tolerance | Very Tight | Moderate | Tight |
| Surface Finish | Excellent | Variable | Excellent |
| Setup Cost | Medium | Low | High |
Cost Reduction Tips for CNC Projects
- Combine Features – Reduce the number of setups
- Use Common Materials – More affordable and readily available
- Limit Part Complexity – Simplifies tooling and reduces time
- Batch Production – Spread setup cost over more units
- Request As-Machined Finishes – Avoid unnecessary surface treatments
Final Thoughts
Now that you know exactly what CNC machining is and what CNC machines are used for, it’s clear why this technology has transformed modern manufacturing. It offers unbeatable precision, fast production, and a wide range of applications.
Whether you’re building a prototype or scaling up for production, CNC machining provides the tools to make it happen — accurately, quickly, and cost-effectively. Looking for a trusted partner in precision engineering? Aeron Automation delivers expertly crafted CNC solutions backed by 40+ years of experience, state-of-the-art equipment, and a commitment to quality.
Get in touch today to discover how we can support your next project.