Lightweight PLA (PLA Aero): Deliberate Under-Extrusion

Lightweight PLA (often called PLA Aero) does something no other material in our knowledge base does on purpose: it foams slightly at the nozzle and prints with dramatically reduced flow, trading a small amount of surface detail for parts that are noticeably lighter than the same geometry in regular PLA. If it's printing exactly like normal PLA, the settings are wrong.

Baseline: Bambu's stock PLA Aero profile

Why a 0.6 flow ratio is correct, not broken

Every other flow-ratio discussion in this guide series treats a value far from 1.0 as a calibration problem (see the flow ratio guide). Lightweight PLA is the deliberate exception: Bambu's own profile sets flow ratio to 0.6, well outside the normal 0.95–1.05 working range, because the material is designed to foam slightly as it extrudes — expanding after leaving the nozzle so a deliberately under-fed line still fills the expected wall width. If a lightweight PLA print is coming out with normal PLA's weight and density, flow ratio was probably reset to a standard value; put it back near 0.6 rather than treating the low number as a mistake.

Trade-offs versus regular PLA

• Weight: the whole point — noticeably lighter finished parts at the same wall/infill settings, useful for anything where mass matters (RC and drone parts, props, large display models that need to hang or balance).
• Strength: impact strength of 3.1 kJ/m² is a fraction of regular PLA's 13.8 — this is not a structural material. Reserve it for parts where weight matters more than mechanical load.
• Speed: the low 3 mm³/s max volumetric speed means slower printing than regular PLA at the same layer height — the foaming process itself is the bottleneck, not a setting to push past.

Common problems

• Print came out heavy and dense: flow ratio got reset toward 1.0 — restore it near the stock value above.
• Under-extrusion-looking gaps at normal PLA speeds: the low volumetric ceiling was exceeded; slow down rather than treating it as a clog. See the under-extrusion guide for the general volumetric-speed logic, keeping in mind Aero's ceiling is well below plain PLA's.
• Parts too weak for their job: that's expected behavior, not a bug — switch to regular PLA (or a stronger material) for anything load-bearing. See the PLA guide for the standard alternative.