At COMPUTEX 2023, Noctua gave insights into the challenges of the development process and manufacturing of their next generation 140 mm fan.
Inception
While the project was started as early as 2015, it took until 2020 and several iterative feedback cycles with new approaches in construction until the performance benchmark of providing a meaningful improvement over NF-A14 and NF-A12x25 with NA-FMA1 adaptors was finally reached.
By October 2021, the design was finalized for manufacturing and the tooling phase was initiated. After designing, manufacturing and validating the injection molding tool, the final validation phase started in June 2022. Unfortunately, the Manufacturing Validation Test (MVT) revealed a minute deviation at the fan hub at after several years of usage at elevated temperatures as simulated by this accelerated lifetime test.
Further Validations
Since the MVT has to run for 4 months and takes several weeks to prepare and analyze, this prompted Noctua to delay the release of the fan by one year in late 2022 in order to give sufficient time for root cause analysis, corrective action and repetition of the test. After temperature fluctuations in the cooling fluid were identified as the root cause and corrected, the second MVT test passed, yet the Long-term Thermal Creep Validation (LTCV) showed tolerance issues due to mounting pressure from heatsink fan clips and radiator mounting screws. To avoid this issue, Noctua now plans to use Sterrox® LCP not only for the impeller, but also for the frame of the fan to make it more resistant against external stress.
If the ongoing validation tests show no further issues, Noctua targets to start mass production in late 2023 and bring the fan to the market in Q1 2024.
Challenges
What makes the next-gen 140mm fan so challenging to manufacture is its ultra-tight tip clearance of only 0.7mm, which is more difficult to implement than the 0.5mm of NF-A12x25 due to the longer blade radius, higher centrifugal forces and higher rotating mass. This results in extremely tight tolerances where minute deviations in the range of a tenth of a millimeter can cause concerns regarding the targeted lifetime of more than 10 years.
While increasing the clearance would be an easy solution, it would involve severe performance penalties due to increased wingtip vortices and backflow in high resistance applications. Therefore, Noctua is fully committed to overcoming the challenges in mass production in order to reap the fan’s full potential of providing improvements of up to 3°C in a noise normalized comparison to NF-A14 on a typical 140mm radiator at a 200W heat load.
