Aluminium Foil Thickness Tolerance: What Two Microns Cost You
Thickness tolerance is usually the last line on a specification sheet and the first thing that decides your yield. Here is why it matters more than the nominal gauge.
Most foil enquiries specify a nominal thickness and treat tolerance as a detail. In practice the tolerance band is what determines whether your line runs profitably, because it decides how much material you actually receive and how consistently the process behaves.
Why nominal thickness is not enough
If you order 0.009 mm and the mill ships anywhere from 0.0082 to 0.0098 mm, you are buying a variable. Two consequences follow:
- Yield. Material at the bottom of the band gives you more square metres per tonne, so a wide band means your cost per finished unit moves shipment to shipment.
- Process stability. Converters running thin foil at high speed have a narrow window. A roll that drifts below the lower limit will tear or wrinkle; one that runs heavy wastes metal.
What a workable specification looks like
| Nominal | Typical commercial tolerance | Tight tolerance on request |
|---|---|---|
| 0.006 - 0.009 mm | ± 8% | ± 5% |
| 0.010 - 0.030 mm | ± 6% | ± 4% |
| 0.031 - 0.200 mm | ± 5% | ± 3% |
The right choice depends on your process, not on buying the tightest band available. Tight tolerance costs more to produce and is wasted if your line cannot hold that precision anyway.
How tolerance is controlled and proven
Thickness is held by roll gap and tension control during rolling, then confirmed by continuous gauging and by destructive testing on samples from each coil. Good practice is a thickness profile across the strip width, not a single point reading, because edge-to-edge variation is what causes wrinkles in wide webs.
What to ask your supplier
- Is the quoted tolerance a full-band figure or a one-sided one?
- Is a thickness profile across the width available for each coil?
- How is variation controlled along the length, coil to coil?
We supply aluminium foil roll and foil for packaging to commercial or tight tolerances depending on your process, with test certificates per batch. If you tell us your line speed and web width, we can recommend the band that suits it.