**CNC Machining vs. 3D Printing: A Structured Comparison**

1. **Process Type**:
   - **CNC Machining**: Subtractive manufacturing. Material is removed from a solid block using tools like mills, lathes, or grinders.
   - **3D Printing**: Additive manufacturing. Objects are built layer by layer from materials such as filaments, resins, or powders.

2. **Material Usage & Waste**:
   - **CNC**: Generates more waste (chips, shavings), though some materials can be recycled. Efficient for high material utilization in optimized designs.
   - **3D Printing**: Minimal waste (support structures may add to waste). Material-efficient but depends on design and process.

3. **Materials**:
   - **CNC**: Broad range, including metals (aluminum, steel), plastics, wood, and composites. Ideal for high-strength, durable parts.
   - **3D Printing**: Expanding options (plastics, resins, metals via SLS/DMLS), but some materials (e.g., high-performance alloys) are less accessible or costlier.

4. **Precision & Surface Finish**:
   - **CNC**: High precision (tight tolerances ±0.025 mm) and smooth finishes. Minimal post-processing needed for functional parts.
   - **3D Printing**: Layer lines may require post-processing (sanding, curing). Resolution varies by technology (e.g., SLA offers smooth surfaces).

5. **Design Complexity**:
   - **CNC**: Limited by tool access; complex geometries (undercuts, internal channels) may require multiple setups.
   - **3D Printing**: Excels at complex, organic shapes (lattices, hollow structures) without additional cost.

6. **Production Volume & Speed**:
   - **CNC**: Higher upfront setup time/cost but faster per-unit production at scale. Ideal for medium-large batches.
   - **3D Printing**: Faster for prototypes/small batches. Slower for large volumes but allows concurrent part printing.

7. **Cost Considerations**:
   - **CNC**: Higher initial setup (tooling, programming) but lower per-unit cost at scale. Machine costs vary widely.
   - **3D Printing**: Lower setup costs (digital files) but higher material costs. Economical for low-volume, complex parts.

8. **Applications**:
   - **CNC**: Automotive, aerospace, machinery (high-strength, precision parts).
   - **3D Printing**: Prototyping, medical implants, custom parts, and complex geometries.

9. **Environmental Impact**:
   - **CNC**: Material waste and energy use (coolants, power). Recycling possible for metals.
   - **3D Printing**: Less waste but energy-intensive processes. Some materials (e.g., thermoplastics) are recyclable.

10. **Post-Processing**:
    - **CNC**: Deburring, polishing, or additional machining.
    - **3D Printing**: Support removal, sanding, curing (resins), or surface treatments.

11. **Size Limitations**:
    - **CNC**: Handles large parts (depends on machine bed size).
    - **3D Printing**: Limited by build volume, though large-format printers are emerging.

12. **Skill Requirements**:
    - **CNC**: Expertise in machining, toolpaths, and G-code.
    - **3D Printing**: Knowledge of 3D modeling, slicer settings, and material behavior.

13. **Hybrid Approaches**:
    - Combine both: 3D print near-net shapes and CNC machine critical features for precision and efficiency.

**Pros and Cons Summary**:
- **CNC Pros**: High precision, material versatility, strength, and scalability for production.
- **CNC Cons**: Design limitations, waste, higher setup costs.
- **3D Printing Pros**: Design freedom, rapid prototyping, low waste, and cost-effective for small batches.
- **3D Printing Cons**: Lower strength (some materials), surface finish limitations, slower for large volumes.

**Conclusion**: Choose CNC for high-strength, precision parts in large batches; opt for 3D printing for complex, custom, or low-volume components. Hybrid methods leverage both strengths.