Sheet for envelope.
CNC for precision.
Combined wisely.
Many products use both CNC machined and sheet metal parts. Understanding when to use each and how to design hybrid assemblies reduces cost while meeting requirements.
CNC vs sheet metal decision.
Tight tolerance, complex
±0.025 mm tolerance, complex 3D geometry, internal features, threaded holes — CNC territory.
Large area, low cost
Large flat surfaces, enclosures, brackets, low-cost high-volume — sheet metal wins.
Best of both
Sheet metal main structure + CNC inserts/features. Common for enclosures with precision mounting points.
100mm² area threshold
Below ~100mm² total: CNC competitive. Above: sheet metal usually cheaper for similar geometry.
Combining processes effectively.
Threaded inserts
Sheet metal panel with PEM inserts pressed in. Provides threaded mounting in thin sheet.
Machined precision feature
CNC bracket welded or fastened to sheet metal panel. Provides precision feature on cheap structure.
Mixed parts
CNC parts welded into sheet metal frame. Common for industrial equipment.
Adhesive-mounted
CNC features bonded to sheet metal with structural adhesive. No welding heat distortion.
Multiple panels
Sheet metal panels with CNC connecting brackets. Common for cabinets and enclosures.
Structure + cover
CNC frame structure with sheet metal cover panels. Common for vehicle bodies, equipment housings.
Make assembly easier.
Tolerance allocation: assign tight tolerance to CNC features, looser to sheet metal. Sheet metal ±0.5 mm, CNC ±0.05 mm typical.
Mating features: CNC creates precise mating surface, sheet metal provides bulk. Pin holes, threaded inserts, locating features all CNC.
Heat affected zone: welding sheet metal to CNC creates HAZ. Specify CNC features 5-10 mm from weld edge.
Handling: hybrid assemblies need handling fixtures — design protective features (chamfered edges, no sharp protrusions).
Hybrid cost benefits.
Hybrid saves cost
- • Large parts: sheet metal envelope cheaper than full CNC
- • Internal precision: CNC inserts provide tolerance
- • Material efficiency: sheet metal yields 80-90% vs CNC 30-50%
- • Production scaling: high volume exploits sheet metal
Common hybrid products
- • Industrial enclosures (sheet metal box, CNC mounting brackets)
- • Equipment frames (sheet metal frame, CNC pivot points)
- • Electronic enclosures (sheet metal case, CNC connectors)
- • Automotive components (sheet metal body, CNC mounts)
- • Medical equipment (sheet metal frame, CNC sterile features)
FAQ
When to design hybrid vs single-process?
Hybrid wins when part has both bulk geometry and precision features. Pure CNC for small precision parts (<100mm). Pure sheet metal for low-precision panels. Hybrid for medium-to-large parts with precision mounting needs.
Welding CNC to sheet metal?
Yes — common technique. Use TIG for precision. Account for heat affected zone (5-10 mm). Plan precise CNC features away from welds. Sheet metal can warp from welding heat — fixture during welding.
PEM hardware in sheet metal?
Standard solution. PEM inserts (self-clinching) provide threaded mounting in thin sheet. Various sizes (M3-M10), various sheet thicknesses. We install PEM hardware as standard.
Adhesive bonding alternative to welding?
Structural adhesives (3M, Loctite, Lord) bond CNC to sheet metal without heat distortion. Suitable for: lower stress, environmentally protected, dissimilar metals.
Cost split for hybrid?
Typical: sheet metal portion 30-40% of cost, CNC portion 50-60%, assembly 10-20%. Optimize by minimizing CNC mass while keeping CNC for precision features.
Tolerance achievable?
CNC features ±0.025 mm. Sheet metal positions ±0.5 mm typical, ±0.2 mm with care. Hybrid: CNC tolerance preserved, sheet metal locations to ±0.3 mm.
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