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Should my enclosure or bracket be sheet metal or machined?
Use sheet metal fabrication for enclosures, brackets, panels and chassis with uniform walls of 0.020–0.250 in (0.5–6.4 mm): it is usually far cheaper than machining, because blanks nest on sheet instead of being cut from solid. Machine the part when it needs thick sections, pockets, bosses, varying walls, or tolerances tighter than the ±0.010 in (±0.25 mm) typical across bends.
Which is cheaper at your quantity?
The same bracket, each process in a suitable material (5052-H32 and 6061-T6).
| Quantity | Sheet metal | CNC machining |
|---|---|---|
| 10 | $15.70 | $112 |
| 50 | $6.08 | $69.20 |
| 100 | $4.88 | $61.50 |
| 500 | $3.92 | $46.60 |
| 1,000 | $3.80 | $41.90 |
| 5,000 | $3.70 | $39.00 |
| 10,000 | $3.69 | $39.00 |
| 50,000 | $3.68 | $38.90 |
| 100,000 | $3.68 | $38.90 |
Where each pays off
Sheet metal fabrication
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- First article
- 1–2 weeks
- Production
- 2–4 weeks per release, including finishing
±0.004–0.005 in (±0.10–0.13 mm) laser or punch
Production machining, turning, and sawing
1101001k10k100k1M+
- First article
- 1–3 weeks
- Production
- 2–6 weeks per release
±0.005 in (±0.13 mm), or ISO 2768-m
Which should you pick?
Pick Sheet metal when
- The part is a uniform-wall enclosure, chassis or bracket
- Panels run up to full sheet size
- It is a welded frame with inserted hardware
- Assemblies are powder coated at low to medium volume
Pick CNC machining when
- Features need ±0.001–0.005 in (±0.025–0.13 mm) relative to each other
- The part has thick sections, pockets or bosses
- It needs sealing faces, heat sink fins or bearing bores
- It must be one piece with no welds or fasteners
Key differences
| Sheet metal | CNC machining | |
|---|---|---|
| Tolerance | Cut features ±0.005 in (±0.13 mm); per bend ±0.010–0.015 in (±0.25–0.38 mm), ±1°; stacks with each bend | ±0.005 in (±0.13 mm) standard; ±0.001 in (±0.025 mm) critical |
| Material use | Blanks nested on sheet | Everything outside the part becomes chips |
| Geometry | Uniform thickness; flanges at least 4× thickness; bend reliefs | Varying walls, pockets and bosses; radiused inside corners |
| Joining | Welds, tab-and-slot joints and self-clinching hardware | One piece; no joints |
| Cost driver | Cut length, bend count and welding labor | Machine time and setups |
| Lead time | 1–2 weeks simple; 2–4 weeks finished assemblies | 1–3 weeks to first article |
Questions
Is sheet metal or machining cheaper for an enclosure?
Sheet metal, in almost every case. A bent enclosure uses little more material than its own weight, while a machined enclosure turns most of a block into chips. Machine enclosures only for thick walls, sealing faces or dense features.
Can sheet metal hold tight tolerances?
Cut features hold about ±0.005 in (±0.13 mm), but dimensions across bends usually hold ±0.010–0.015 in (±0.25–0.38 mm) and stack with each bend. Put tight features on one flat face, or machine them after forming.
When is a machined bracket better than a bent one?
When it needs varying thickness, precise bores, or stiffness from a solid section in a small envelope. For light brackets with uniform walls, bent sheet usually costs a fraction as much.
Try both on your part.
The builder prices the same geometry in every suitable process and material, with DFM for each.