Everyday products — from the sleek body of your smartphone to the metal gears in your car — often start off as solid raw material. Subtractive manufacturing is a time-tested process in which excess material is gradually removed using tools like lathes, mills or grinders to produce parts with precise dimensions and tight tolerances. It’s a bit like chipping away at a marble statue or shaping a slab of clay, precisely sculpting until the final form is revealed.
Subtractive Manufacturing Definition
Subtractive manufacturing is a process that shapes a final part by removing material, or “subtracting” it, from a solid block. It uses computer-controlled tools to cut, drill, mill or melt the material with micron-level accuracy based on a digital design.
This centuries-old machining technique creates tough, structurally-sound parts made to exact specifications for high level performance. It’s especially vital in industries like aerospace, automotive and medical devices, where reliability isn’t just important — it’s essential.
What Is Subtractive Manufacturing?
Subtractive manufacturing is a process where material is removed from a solid block — also known as a “workpiece” — to create a final part or product. Unlike additive manufacturing, which builds objects layer by layer, subtractive methods start with a large chunk of raw material, then systematically cut, drill, mill, grind or even vaporize away excess to achieve the desired shape.
This high-precision machining process relies on computer-aided design (CAD) models to define the exact dimensions and features of an object, which are then translated into machine-literate instructions using computer-aided manufacturing (CAM) software.
Objects made from subtractive methods, like computer numerical control (CNC) milling — the most frequently used technique — are known for their sturdy, durable one-piece builds that are machined with a tight tolerance, smooth finishes and can stand up to demanding conditions. They’re made out of a wide array of metals like aluminum, steel, brass and titanium, and are also compatible with engineering plastics, woods and composites like carbon fiber and fiberglass. A major benefit of subtractive manufacturing is its ability to machine tough, abrasive and heat-resistant materials that are often too harsh for additive methods.
Subtractive Manufacturing vs. Additive Manufacturing
It’s all in the names. Subtractive manufacturing works by cutting away from something that’s already there — like carving from a block of metal or plastic to reveal the final shape. Additive manufacturing, on the other hand, builds up from nothing, adding material layer by layer until the part takes form. One takes away to create, the other constructs from scratch.
In terms of use cases, subtractive manufacturing is ideal for producing rugged, high-precision parts from metals, plastics, wood and composites. Carved from solid blocks, these parts are strong and seamless, with no weak points caused by layering or bonding. Meanwhile, additive manufacturing is typically reserved for more complex, flexible designs — like intricate geometries, lightweighting parts or one-off prototypes — and works with materials such as thermoplastics, resins and metal powders.
While subtractive methods typically deliver superior surface finishes and structural integrity (especially for load-bearing components), additive manufacturing offers greater design freedom and faster turnaround for custom or low-volume production.
How Does Subtractive Manufacturing Work?
Subtractive manufacturing works by removing material from a solid block (called a “workpiece”) of material to create a desired shape. The process starts by securing the workpiece to a machine bed or specialized fixture to keep it stable during the machining process. After that, a digital model of the desired part is uploaded to the machine, containing instructions generated prior using CAD and CAM software. These instructions, or “toolpaths” dictate exactly how the cutting tools will move, exactly what material is removed and in what sequence.
With the setup complete, cutting tools such as end mills, drills or lathe tools are installed, and essential settings like spindle speed, feed rate and tool paths are configured to suit the material and the shape of the part being made.
The first passes are fast, heavy cuts that quickly shape the part — a process known as “roughing.” Then come slower, more precise finishing passes that refine details, lock in the final dimensions of the object and finalize its surface quality.
Once the machining is complete, the part is inspected and may go through post-processing steps like deburring or polishing.
Common Subtractive Manufacturing Techniques
There are many subtractive manufacturing techniques out there. Some of the more common ones include:
- Milling: Uses rotating cutting tools to remove material from a solid block; CNC milling automates this with computer-guided precision for complex shapes, and is the most commonly used subtractive manufacturing technique.
- Turning: Involves spinning the workpiece on a lathe while a stationary cutting tool shapes it. Typically, this is used to create cylindrical parts like shafts, pins or bushings.
- Drilling: Creates round holes in a material using a rotating drill bit.
- Grinding: Uses an abrasive wheel to smooth, shape or finish a surface.
- Electrical Discharge Machining (EDM): A non-contact process that uses electrical sparks to melt away or vaporize material. This method is ideal when working with hard metals or creating more intricate shapes.
- Broaching: Pushes or pulls a toothed tool, called a broach, through a material to cut detailed internal or external features. The shape of the finished part is directly determined by the cross-section of the broaching tool itself.
- Sawing: Slices materials into smaller pieces using bandsaws, circular saws or wire saws.
- Waterjet Cutting: Uses a high-pressure water stream, often mixed with abrasive particles, to cut through metal, stone or composites in a process that mimics erosion — only faster and precisely controlled.
- Laser Cutting: Uses a focused laser beam to cut or engrave materials like metal, wood or plastic.
Real-World Applications of Subtractive Manufacturing
Aerospace and Automotive Parts
Critical components like turbine blades, structural brackets, engine housings and gearbox parts demand extremely tight tolerances and high strength-to-weight ratios. Simply put: There’s no room for error. In aerospace, CNC machining is used to meet the strict quality and safety requirements set by the FAA as well as international standards like AS9100. Subtractive manufacturing is also used in the automotive sector to produce mission-critical parts like engine blocks, brake components and transmission housings to help manufacturers comply with IATF 16949 and SAE industry standards.
Medical Devices
Subtractive manufacturing is used to create medical devices such as implants, surgical instruments and orthopedic parts from tough materials — like titanium, stainless steel and PEEK (polyether ether ketone) — that can handle wear and tear. CNC machining also delivers the precision and sleek finishes essential for custom-made devices that interact directly with the human body. For instance, hip and knee implants must comply with strict ISO 13485 standards for biocompatibility and accuracy, while small surgical screws are manufactured to micron-level tolerances to ensure safety and effectiveness.
Prototypes and One-Off Components
Engineers often choose CNC machining for early-stage functional prototypes that have to pass stress testing or simulate final-use conditions. In fact, a 2023 study found that companies using CNC machining for rapid prototyping reduced their product cycle time by 32 percent — largely because the parts are made from production-grade materials and often usable straight off the machine, with minimal finishing required.
Consumer Electronics
High-end consumer electronics often rely on subtractive manufacturing techniques to achieve both structural integrity and refined aesthetics. For example, Apple famously uses CNC milling to carve MacBook “unibodies” from solid blocks of aluminum, creating its signature look featuring strong, seamless enclosures with consistent finishes. Similarly, companies like DJI use CNC-machined aluminum parts to lightweight its drones and ensure tight tolerances. Other products, like smartwatch cases, camera lens housings and headphone frames are also typically milled or turned for durability and an accurate internal fit.
Industrial Equipment and Tooling
Subtractive manufacturing is the backbone of tooling production, including jigs, dies, molds and fixtures used across manufacturing lines. These tools require exact tolerances to ensure repeatability and accuracy in high-volume production. For example, injection molds — often machined from hardened steel — can cost tens of thousands of dollars, but are capable of producing millions of plastic parts with minimal wear over time.
Benefits of Subtractive Manufacturing
There are several reasons why, in certain scenarios, subtractive manufacturing is a preferred machining method.
High Precision and Accuracy
Subtractive manufacturing delivers extremely tight tolerances and precise dimensions, making it ideal for parts that require an exact fit. The standard CNC machine can achieve a tolerance of ±0.05 mm (±0.002 inch) — that’s finer than a strand of hair. More advanced setups can get as close as ±0.01 mm (±0.0004 inch) or tighter.
Compatibility with Tough Materials
Subtractive manufacturing stands out for its ability to cut through high-strength materials that are difficult to work with in other processes. It’s widely used to machine hardened alloys, carbon fiber composites and high-performance thermoplastics like PEEK — all of which are essential materials in industries where part durability and thermal resistance are non-negotiable.
Well-Established and Widely Understood
Subtractive manufacturing is based on tried-and-true technology and processes that date back to Ancient Egypt, offering consistently reliable and predictable results. This is made possible by a large pool of skilled CNC operators and engineers, supported by credentialed training programs around the world — like those from the National Institute for Metalworking Skills and the Society of Manufacturing Engineers — which keep the workforce well-prepared as machining equipment evolves.
Minimal Post-Production
Parts made through subtractive methods often retain the full mechanical properties of the original material and typically require less post-processing, thanks to their smoother surface finishes. This is in contrast to some additive techniques, where layering can introduce weak points and affect an object’s overall strength.
Limitations of Subtractive Manufacturing
Still, there are several reasons why subtractive manufacturing is being overshadowed by emerging 3D printing tech and other additive methods.
Material Waste
The very nature of subtractive manufacturing — removing excess from the original block — implies material waste. This leftover scrap can add up, especially with costly materials, making the process less efficient than additive methods, depending on the project.
Struggles to Deliver Complex Shapes
Subtractive manufacturing has a hard time with detailed internal shapes or complex geometries because the cutting tools simply can’t reach everywhere. Deep cavities, undercuts and intricate internal channels are often inaccessible due to tool length limitations and clearance issues.
Low Volume
Each step in subtractive manufacturing requires careful setup, which can slow turnaround times — especially for more detailed designs or short-lived runs. While ideal for precise, low-volume parts, long prep times ultimately make it less efficient for rapid prototyping or one-offs compared to additive methods.
Frequently Asked Questions
How is subtractive manufacturing different from 3D printing?
Subtractive manufacturing removes material from a solid block to create a part, while 3D printing builds a part layer by layer by adding material.
What is an example of subtractive manufacturing?
The most common type of subtractive manufacturing is CNC milling, where rotating cutting tools cut into material from a solid block — often aluminum, steel or engineered plastics — to create highly precise, complex parts based on a computer-aided design.
What types of machines are used in subtractive manufacturing?
Subtractive manufacturing relies on machines like CNC mills, lathes and routers, which feature spinning cutting heads to remove material from a solid block. Other specialized equipment include EDM machines for intricate metal cutting projects, grinders for ultra-smooth finishes and waterjet or laser cutters for slicing through tough or heat-sensitive materials.
