In today’s market, when quality, speed, and cost can make or break a project’s success, selecting the right production method makes a huge difference. Two of the largest technology choices are CNC machining and additive manufacturing. They both offer advantages, limitations, and ideal use cases. Understanding their differences is vital to making the right choice for your requirements.
In this blog post, we’ll discuss how each process works, sub-categories in each, materials, tolerances, finishes, and which process is better for specific applications.
CNC Machining: Subtractive Precision
As a subtractive manufacturing process, CNC machining begins with a solid block of material and removes material with cutting tools to reveal the final product. It is a highly automated method, driven by CAD/CAM software and G-code instructions that are fed into the machine.
Types of CNC Machines
| Machine Type | Description | Typical Operations |
|---|---|---|
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Rotating tools cut stationary workpieces. |
Milling, drilling, and boring. |
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The workpiece rotates and a stationary tool shapes it. |
Turning and threading. |
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Often used for softer materials and larger workpieces. |
Cutting and engraving. |
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Electrical discharges erode and cut hard metals. |
Die sinking and wire cutting. |
CNC Machining Materials
- Metals: Aluminum, steel, stainless steel, titanium, brass, copper, bronze, and superalloys.
- Plastics: ABS, polycarbonate, polypropylene, PEEK, Delrin, acrylic, and Ultem.
- Composites: Macor and Garolite.
- Note: These are only a few of the materials we offer. If your project requires something specific, let us know!
Tolerances and Surface Finishes
- Tolerances:
- General: We adhere to ISO 2768 standards or ± 0.005 inches (± 0.127 mm) for metal parts and ± 0.010 inches ( ± 0.254 mm) for plastic and composite parts.
- Precision: We can achieve tolerances of sub-±0.001 inches for precision parts, as specified by your drawings and GD&T callouts.
- Surface Finishes
- Our standard finish is As Machined (Ra 126 µin).
- Anodizing, electroplating, electroless plating, black oxide, chem film, galvanizing, polishing, and many more finishes.
Workflow
CNC machining is exceptional for high-precision, strength, and repeatable parts in demanding industries.
- CAD Design (Provided by You)
- CAM Programming
- Job Planning
- Setup
- Machining
- Inspecition
- Finishing and Post-Processing
Additive Manufacturing: 3D Printing
Additive manufacturing, or 3D Printing, is the opposite of subtractive manufacturing. Rather than removing material, it adds material layer by layer, building components by depositing, curing, or fusing. Additive manufacturing allows for complex geometries with internal features, previously impossible with traditional manufacturing methods.
Additive manufacturing Technologies
| Technology | Process Description | Materials |
|---|---|---|
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Laer sinters nylon powders. |
Nylon and TPU |
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DMLS |
Laser fuses metal powders. |
Stainless Steel and Titanium |
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Fuses nylon powder with agents. |
Nylon |
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Laser-cures liquid resin. |
Photopolymer Resins |
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Extrudes thermoplastic filament. |
ABS, PLA, Nylon, and TPU |
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Jets and cures photopolymers. |
Rigid and Flexible Resins |
For more additive manufacturing technologies, check out 3D printing services and solutions.
Additive Manufacturing Materials
At Prototek, we offer a lot of additive manufacturing materials. If you would like to compare them, visit our AM Material Pro.
- Plastics: ABS, PLA, PC, Nylon, TPU, and PETG.
- Resins: Standard, tough, flexible, dental, and castable.
- Metals: Stainless steel, aluminum, titanium, and Inconel.
- Composites: Glass-filled, ceramic-filled, and carbon-filled.
- Note: These are only a few of the materials we offer. If your project requires something specific, let us know!
Tolerances and Finishes
| Technology | Tolerance | Layer Thickness | Max Build Size | Finishing Levels |
|---|---|---|---|---|
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SLS |
First Inch: ±0.005 in Additional Inches: ±0.002 in/in |
EOS: 0.005 in 3D Systems: 0.004 in |
26 x 13.5 x 21.8 in |
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MJF |
First Inch: ±0.010 in Additional Inches: ±0.003 in/in |
Standard: 0.003 in |
14.96 x 11.18 x 14.96 in |
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SLA |
First Inch: ± 0.005 in Additional Inches: ± 0.0015 in/in |
Normal Resolution: 0.004 in High-Resolution: 0.002 in |
31 x 31 x 23 in |
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FFF |
0.005 Layers Tolerance:
First Inch: ± 0.005 in
Additional Inches: ± 0.002 in/in 0.010 Layers Tolerance: Fist Inch: ± 0.010 in Additional Inches ± 0.002 in/in 0.013 Layers Tolerance: First Inch: ± 0.013 in Additional Inches: ± 0.002 in/in |
Standard: 0.010 inch Also Available: 0.005 and 0.013 |
36 x 24 x 36 in |
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Material Jetting |
First Inch: ± 0.004 in Additional Inches ± 0.0015 in/in |
High-Quality: 0.0006 in High-Speed: 0.0012 in |
19.3 x 15.4 x 7.9 in |
Workflow
Additive manufacturing is an excellent choice for rapid prototyping, design freedom, and cost-effective production of complex or highly customizable parts.
- CAD Design (Provided by You)
- File Preparation
- Slicing
- Printing
- Finishing and Post-Processing
- Inspection
Head-to-Head Comparison: CNC Machining vs Additive Manufacturing
| Parameter | 3D Printing | CNC Machining |
|---|---|---|
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Setup Cost |
Low |
High |
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Per-Part Cost (1-10 units) |
Lower |
Higher |
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Per-Part Cost (100+ units) |
Rises with volume. |
Drops with volume. |
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Prototyping Speed |
Hours to Days |
Days to Weeks |
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Production Speed |
Slower for large batches. |
Fast after the setup. |
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Material Options |
Plastics, metals, resins, and composites. |
Metals, plastics and composites. |
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Part Complexity |
Exceptional, no tooling limits. |
Limited to tool access. |
Choosing CNC Machining vs Additive manufacturing
When should you choose CNC Machining?
- If your project requires high-strength, tight-tolerance metal parts, for example, aerospace turbine blades and engine components.
- If your project requires large production runs, for example, automotive parts and electronics housings.
- If your project requires functional end-use components, where the mechanical properties and surface finishes are crucial for the parts’ success.
When should you choose additive manufacturing?
- If your project is in early-stage product development and requires rapid prototyping or design iterations.
- If your project requires complex, lightweight structures, for example, aerospace brackets, or medical implants with lattice interiors.
- If your project requires low-volume or highly customizable parts such as implants, prosthetics, or custom jigs.
- If your project requires internal features, for example, manifolds or conformal cooling channels.
Specific Decision-Making Questions
- What is the required precision and surface finish? For tight tolerances and smooth finishes, choose CNC machining.
- How complex is the part geometry? For complex, internal features, choose additive manufacturing.
- What is the production volume? For low-volume or prototyping, choose additive manufacturing. For medium- to high-volume production, choose CNC machining.
- What materials are required? For exotic plastics or flexible materials, choose additive manufacturing. For full-strength metals or composites, choose CNC machining.
- Is customization or rapid iteration important? If the answer is yes, choose additive manufacturing.
- Can a hybrid approach optimize the cost or performance? If the answer is yes, both might be options. Consult our engineering team for the best options.
CNC Machining vs Additive Manufacturing: Industry-Specific Applications
| Industry | 3D Printing Use Cases | CNC Machining Use Cases |
|---|---|---|
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Lightweight brackets and complex ducting. |
Turbine blades and structural frames. |
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Custom implants, prosthetics, and surgical guides. |
Surgical tools and orthopedic implants. |
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Prototyping, custom jigs, and lightweight structures. |
Engine blocks, transmission parts, and custom tooling. |
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Custom enclosures, wearables, and design prototypes. |
Electronics housings and durable enclosures. |
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Conformal cooling channels and rapid tooling inserts. |
Injection molds, dies, jigs, and fixtures. |
FAQs
When to choose CNC machining vs additive manufacturing?
CNC machining is ideal for high-precision, high-volume parts with tight tolerances, while additive manufacturing is best for complex geometries, rapid prototyping, and low-volume production.
What are the main differences between CNC machining and additive manufacturing?
CNC machining is a subtractive manufacturing process that removes material from a solid block to create a part, while additive manufacturing builds parts layer by layer from the ground up. CNC machining is typically faster and more precise for certain geometries, while additive manufacturing allows for greater design freedom and the ability to create complex, lightweight structures.
What are the core differences between cnc machining materials and additive manufacturing materials?
CNC machining materials are typically solid, rigid materials such as metals, plastics, and composites that are cut and shaped into the desired part geometry. Additive manufacturing materials, on the other hand, are often powders or filaments that are built up layer by layer to create the final part. This fundamental difference in the manufacturing process leads to variations in material properties, part complexity, and production efficiency between the two methods.
