[NorwegianDude]

Noctua wants their fans to last for many years, spinning at 2K rpm, with heat.

Being able to produce something with lower tolerance is one thing. Making it work long term at ~10 m/s and ~200G is another thing. Have you ever been in a car that brakes really hard? You'll move. Now, multiply that force by 100 and you'll get around what the fans must sustain over time.

[buran77]

But that's literally not what the article says. You are talking about the design - Noctua puts 0.5mm because any more and airflow is affected and performance drops. They also use a super duper polymer that mitigates everything you mentioned. The article talks about manufacturing tolerances.

> Their influence on the dimensional precision and stability of the fan blade may be minute, but if the tolerance is only a few tenths of a millimetre, being off by a tenth or two suddenly becomes a problem.

> Achieving such small tip clearances is essentially at the absolute limit of what injection moulding can consistently reproduce.

I'm not questioning their engineering but the wording of whoever wrote this article. For anything with a clearance in the tenths of a millimeter, injection moulding doesn't even sweat, let alone be at the limit. Anything better than bog standard injection moulds get you better precision than "a tenth or two" millimeters.

Let me put it another way, if achieving a 0.7mm gap is "at the absolute limit of what injection moulding can consistently reproduce", what would you say consistently achieving 2-10um (microns) gap is? Magic? Fairy tale? Because LEGO as I said earlier is said to have 2um tolerances [1] over their decades of producing the bricks. Even a more conventional 10-20um (order of magnitude higher) still works.

[1] https://news.ycombinator.com/item?id=47335237

[overfeed]

> The article talks about manufacturing tolerances.

As shown by your quotes, the article clearly mentions tip clearance, and not manufacturing tolerances, which you are infering. The article doesn't characterize the thermal expansion the "super polymer" is expected to undergo under normal operating conditions[1]: something Lego doesn't contend with.

All this to say: Lego's manufacturing tolerances alone can't falsify Noctua's claims because they ultimately are different metrics.

1. I imagine the expansion rate of the fan blade radius doesn't correlate linearly with that of the shroud, so the tip clearance changes with temperature. With this constraint, not even Lego could make its manufacturing tolerances equal the fan clearance, which has to be larger if you want the fan to predictably work without jamming over a 40-degree temperature range.