CNC Machining vs Sheet Metal Fabrication

Choosing between CNC machining and sheet metal fabrication depends on geometry, volume, precision, and function. Here’s a practical comparison to help you pick the right process for your part.

1. What Are They?

• CNC Machining: Subtractive process — parts are milled or turned from solid blocks (metal or plastic) using high-speed cutters.
• Sheet Metal Fabrication: Forming process — parts are cut, bent, punched, and joined from thin sheets (usually 0.5–6 mm thick).

2. Ideal Part Types

3. Geometry Limitations

• CNC: Can make solid parts, deep pockets, internal features, undercuts, threads.
• Sheet Metal: Limited to thin-walled forms; requires bends and flat patterns.

Tip: If your part looks like a box, lid, bracket, or housing, sheet metal is likely more cost-effective.

4. Volume & Cost

• Low volume (1–100 pcs): CNC may be better — no tooling required.
• Mid-high volume (100+ pcs): Sheet metal is faster and cheaper due to bending presses and laser cutting.

Sheet metal parts are faster to iterate, but require flat layout drawings.

5. Tolerances & Finish

Need precision fits, tight holes, threads, or sealing faces? CNC is the way to go.

6. Design Constraints

• CNC Design Tips:
  • Avoid deep, narrow cavities
  • Add fillets to internal corners
  • Keep tolerances realistic
• Sheet Metal Design Tips:
  • Maintain consistent bend radii
  • Allow space for fasteners or tabs
  • Use common material gauges (e.g. 1.5 mm, 2 mm)

7. Hybrid Option: CNC + Sheet Metal

For some assemblies, the best solution combines both:

• Sheet metal for housing + CNC machined inserts, bosses, or mating parts
• Saves cost while preserving functional accuracy

Summary: Which One to Choose?

Choose the process that aligns with your design intent, tolerance needs, and quantity.