What Is Subtractive Manufacturing in CNC Milling?

Subtractive manufacturing remains the preferred choice for producing high-precision components across industries because it delivers excellent dimensional accuracy, superior surface finishes, and compatibility with a wide range of materials.

Whether you’re comparing subtractive vs additive manufacturing, exploring CNC milling as a subtractive manufacturing example, or deciding between CNC machining and 3D printing, understanding how subtractive manufacturing works will help you choose the right production method for your project.

What is Subtractive Manufacturing?  

This is the process of creating parts by removing unwanted material from a larger workpiece until the desired shape is achieved.   Unlike additive manufacturing, which builds objects by adding material layer by layer, subtractive manufacturing begins with a solid block of material and removes excess material using cutting tools.   Common subtractive manufacturing processes include:  
  • CNC milling   
  • CNC turning   
  • Grinding   
  • Drilling   
  • Boring   
  • Sawing  
Among these, CNC milling is one of the most versatile methods because it can produce complex shapes while maintaining exceptional accuracy. 

How Does CNC Milling Work?  

CNC (Computer Numerical Control) milling uses computer-programmed instructions to guide rotating cutting tools that remove material from a workpiece.  

Step 1: CAD Design  

The part is designed using CAD (Computer-Aided Design) software.  

Step 2: CAM Programming  

The CAD model is converted into machine instructions (G-code).  

Step 3: Material Setup  

The selected material is securely clamped to the milling machine.  

Step 4: Machining  

The cutting tools gradually remove material according to the programmed toolpaths.  

Step 5: Inspection  

Finished components are measured to verify dimensions and quality. Because the entire process is digitally controlled, CNC milling consistently produces repeatable, high-quality parts. 

How Material is Removed in CNC Milling  

Material removal occurs through high-speed rotating cutting tools that shave away small amounts of material during each pass.   Several cutting operations include:  
  • Face Milling: Removes material from the top surface.  
  • Slot Milling: Cuts grooves or channels.  
  • End Milling: Produces profiles, pockets, and intricate shapes.  
  • Pocket Milling: Removes material from enclosed areas.  
  • Drilling: Creates accurate holes.  
Each cutting pass removes only a small amount of material, allowing extremely precise control over the finished component. 

CNC Milling as a Subtractive Manufacturing Example  

The process starts with a solid aluminium billet. The CNC machine removes excess material until only the finished housing remains.   During machining, the machine creates:  
  • Mounting holes   
  • Precision pockets   
  • Flat surfaces   
  • Internal cavities   
  • Complex contours  
Rather than building the part layer by layer, material is removed until the desired geometry is achieved. 

Subtractive Manufacturing Materials List  

One major advantage of subtractive manufacturing is its compatibility with numerous engineering materials.   Common subtractive manufacturing materials include:  

Metals  

  • Aluminium   
  • Stainless steel   
  • Mild steel   
  • Brass   
  • Copper   
  • Titanium   
  • Tool steel  

Plastics  

  • ABS   
  • Nylon   
  • Delrin (Acetal)   
  • PEEK   
  • Polycarbonate   
  • PTFE  

Composites  

  • Carbon fibre composites   
  • Fibreglass   
  • Engineering laminates  

Wood  

  • MDF   
  • Hardwood   
  • Plywood  
Material selection depends on:  
  • Strength requirements   
  • Weight   
  • Corrosion resistance   
  • Temperature resistance   
  • Cost   
  • Surface finish  

Subtractive vs Additive Manufacturing Comparison  

Feature  Subtractive Manufacturing  Additive Manufacturing 
Process  Removes material  Adds material 
Strength  Excellent  Depends on process 
Surface Finish  Very smooth  Often requires finishing 
Accuracy  Extremely high  Moderate to high 
Production Speed  Fast for production  Better for prototypes 
Material Options  Very wide  More limited 
Waste  More material waste  Minimal waste 
   Subtractive manufacturing remains the preferred choice when precision, durability, and repeatability are critical.  

Subtractive vs 3D Printing for Parts  

CNC Milling is Better For:  
  • Production components   
  • Tight tolerances   
  • Metal parts   
  • High-strength applications   
  • Long-lasting components  
3D Printing Is Better For:  
  • Concept models   
  • Rapid prototypes   
  • Complex internal structures   
  • Low-volume custom designs  
In many engineering projects, both technologies are used together, 3D printing for prototyping and CNC milling for final production. 

Industries That Use Subtractive Manufacturing  

Many industries rely heavily on subtractive manufacturing because of its precision and repeatability.   Aerospace   Manufactures:  
  • Aircraft brackets   
  • Structural components   
  • Engine parts  

Automotive  

Produces:  
  • Engine blocks   
  • Transmission housings   
  • Suspension components  

Medical  

Machines:  
  • Surgical instruments   
  • Orthopaedic implants   
  • Medical equipment  

Mining  

Creates:  
  • Heavy-duty machine components   
  • Wear-resistant parts  

Defence  

Produces highly accurate precision components.  

Electronics  

Manufactures:  
  • Heat sinks   
  • Enclosures   
  • Precision housings  

Industrial Equipment  

Produces custom machine components and replacement parts.   According to the Australian Bureau of Statistics (ABS), advanced manufacturing continues to play an important role in Australia’s industrial economy, with precision engineering and high-value manufacturing supporting sectors such as aerospace, defence, medical technology and mining.  

Subtractive Manufacturing Advantages and Disadvantages  

Advantages  

Exceptional Precision  

CNC machines can consistently produce highly accurate components.  

Excellent Surface Finish  

Many parts require minimal secondary finishing.  

Wide Material Compatibility  

Almost any engineering material can be machined.  

High Structural Strength  

Since parts are machined from solid stock, material properties remain intact.  

Fast Production  

Modern CNC machines produce components quickly with minimal manual intervention.  

Disadvantages  

Material Waste  

Removed material becomes chips that require recycling or disposal.  

Higher Material Usage  

Large billets may generate considerable waste for complex parts.  

Tool Wear  

Cutting tools require maintenance and replacement over time.  

Geometry Limitations  

Some intricate internal geometries are easier to achieve using additive manufacturing.  

Subtractive Manufacturing Cost vs Additive Manufacturing  

Cost depends on:  
  • Part complexity   
  • Material   
  • Batch size   
  • Machine time   
  • Surface finish   
  • Tolerance requirements  
CNC Milling Is More Cost-Effective For:  
  • Medium-to-high production volumes   
  • Precision engineering   
  • Metal parts   
  • Functional components  
3D Printing Is More Cost-Effective For:  
  • One-off prototypes   
  • Product development   
  • Concept validation   
  • Low-volume custom parts  
According to Wohlers Associates’ annual industry reports, additive manufacturing continues to grow globally, but conventional machining remains the dominant production method for precision metal components across many industries.

Why CNC Milling Remains an Industry Standard  

Despite rapid advancements in additive manufacturing, CNC milling remains the preferred manufacturing method for countless applications.    Reasons include: 
  • Outstanding dimensional accuracy   
  • Excellent repeatability   
  • High-quality surface finishes   
  • Broad material compatibility   
  • Proven reliability   
  • Efficient production for small and large batches  
Manufacturers continue to choose CNC milling because it consistently produces durable, high-performance parts that meet demanding engineering specifications.  

Partner with Just Routing for Professional CNC Milling & More  

At Just Routing, we specialise in delivering high-quality CNC machining and routing solutions tailored to your exact requirements. Whether you need prototypes, custom components, or production runs, our experienced team combines advanced CNC technology with precision craftsmanship to achieve outstanding results.   We proudly support businesses across Brisbane, the Gold Coast, and the Sunshine Coast, providing reliable machining solutions that meet the highest standards of quality and performance. Contact us now for more details.  

FAQs

Is subtractive manufacturing good for prototyping or only for mass production?

Subtractive manufacturing is ideal for both prototyping and mass production. CNC milling produces accurate prototypes for testing and delivers consistent, repeatable parts for low, medium, or high-volume manufacturing with excellent dimensional precision. 

Yes. Modern CNC milling and routing machines can produce complex geometries, curved surfaces, pockets, and intricate profiles. The level of complexity depends on the machine’s axes, tooling, and the part’s design requirements. 

CNC milling typically machines metals and engineering plastics using rigid cutting tools, while CNC routing is commonly used for timber, MDF, plastics, aluminium composite panels, and sheet materials at higher cutting speeds. 

Material waste varies depending on the part design and starting stock size. While subtractive manufacturing removes excess material, many metal and plastic offcuts can be recycled, helping reduce environmental impact and material costs. 

Most CNC milling projects begin with CAD files in STEP, IGES, DWG, DXF, or STL format. These are converted into machine toolpaths using CAM software before machining starts. 

Yes, thread milling is highly suitable for blind holes. It offers improved chip control and reduces the risk of tool breakage, making it a reliable option for both blind and through holes. 

Yes. Subtractive manufacturing is suitable for metals such as aluminium and steel, as well as timber, plywood, MDF, acrylic, engineering plastics, and composite panels, making it highly versatile across industries. 

You can access professional subtractive manufacturing and CNC milling services through specialised machining companies like Just Routing, offering precision machining, CNC routing, custom components, and production solutions for businesses across Australia.