Prusament PLA Lightweight Foams RC Parts Down 65%

Prusament PLA Lightweight is a new actively foaming spool for prints where grams are the spec. On September 17, 2026, Prusa Research said heat in the nozzle expands additives so parts can come out up to 65% lighter than regular PLA, with two to three times more models from the same kilogram. If you fly RC or print cosplay, this is a process change — temperature, multiplier, and a dryer — not a drop-in PLA profile.

What's Happening

Prusa’s September 17 product post is the source for the launch claims and the print recipe. Jakub Kočí describes an actively foaming PLA: additives expand in the hot end the way construction foam expands in a gap, leaving a matte, closed-cell structure. Prusa says that structure can cut printed mass by up to 65% versus regular PLA and stretch one kilogram into two to three times as many models. The 65% figure, the 2–3× yield, and the “perfect for aircraft” framing are Prusa’s. This article does not treat them as an independent coupon test of the new SKU.

Intended jobs, as Prusa lists them, are RC aircraft and drones, costume parts, floaters that sit on water “almost as well as polystyrene,” and thermal inserts such as bottle sleeves. The printed surface is matte and slightly textured, which Prusa compares to wood-filled filament or an SLS look; layer lines hide, and colors pale as foaming increases. Galaxy Black on the spool prints a concrete grey. Five launch colors: Army Green, Chocolate Brown, Galaxy Black, Natural, and Coral Orange. A kilogram is $56.99, or €59.90 including VAT. PrusaSlicer profiles in the post cover CORE One+, CORE One+ (gen 2), CORE One L+, and MK4S. Do not read that list as a claim that every FFF machine on the market ships a tuned profile.

The process window is narrow on purpose. Foaming is barely visible at 215 °C and strongest at 235 °C on Prusa’s standard profile. Going hotter does not buy meaningful extra lightness, Prusa says, and above 250 °C the material “may emit potentially dangerous fumes.” Default recipe: 230 °C nozzle, 60 °C bed, extrusion multiplier 0.45, retractions off, smooth PEI or satin sheet, 0.4 or 0.6 mm brass nozzle. Because expansion changes with temperature, Prusa tells users to print a single-wall hollow cube and chase wall thickness toward 0.45–0.5 mm before trusting the multiplier. The filament is hygroscopic: dry five hours at 55 °C and store it dry. Active foaming also oozes; stringing is expected. Prusa’s mitigation is “Avoid crossing perimeters” with a 40 mm max detour, one model at a time, and sequential printing for small parts.

Why Prusament PLA Lightweight Matters for Home Printers

A garage printer already makes the wing, the mask, and the thermos sleeve. What it has not done cheaply is make those parts light without switching to a foam board, a hollow vase mode, or a gyroid infill that still weighs more than you wanted. Active foaming moves the air into the bead. That is useful when the job is lift, wear-on-the-head comfort, or a cooler that should not conduct. It is the wrong tool when the job is a clamp that must not creep. Prusa itself says this is not an everyday PLA: it needs drying, a calibration cube, and some knife work on strings.

The brand-level lesson is a materials split, not a loyalty test. Foam PLA is a density knob. Continuous carbon fiber is a stiffness knob. Mixing them in your head — “lightweight so it must be strong” — is how an RC mount shears at the firewall. Use the foaming spool for the volume that has to fly or float. Use a fiber-capable machine for the hard points. Prusa’s supported-printer list is its own hardware. If you run something else, you are in Alduais-and-Özerinç territory: nozzle temperature and feed rate still control foam, but you own the calibration (Alduais & Özerinç, 2023).

How to Dial In Prusament PLA Lightweight on the Bench

Setting	Prusa default / note	What it changes
Nozzle temperature	230 °C default; foam from ~215 °C, peak 235 °C; do not exceed 250 °C	More heat, more expansion, paler color, more ooze. Past 250 °C Prusa warns of fumes.
Extrusion multiplier	0.45 at 230 °C; raise if cooler, lower if hotter	Wrong multiplier at a new temperature is under- or over-extrusion, not “more foam.”
Retraction	Off in the default profile	Foaming already pushes melt. Retraction can make the ooze worse, not better.
Drying	5 hours at 55 °C; keep the spool dry	Hygroscopic PLA plus a foaming agent is a wet-spool failure waiting to happen.
Travel / layout	Avoid crossing perimeters (40 mm detour); one model at a time	Prusa’s published way to cut visible stringing without pretending it vanishes.

What the Research Says

Alduais and Özerinç printed a commercial foaming PLA — ColorFabb LW-PLA, 2.85 mm, not Prusament — on an Ultimaker 2+ and mapped nozzle temperature, feed rate, and infill against density and strength. Higher nozzle temperature and lower feed rate increased foaming. Density spanned 0.24 to 1.17 g/cm³. Elastic modulus ran from 0.24 to 3.7 GPa and tensile strength from 4.2 to 34.5 MPa, tracking Gibson–Ashby foam scaling. That is the peer-reviewed reason “turn up the heat, get more air” is a real process window, and also why a 65% mass cut cannot be copied from a press post onto every infill and every machine. Their filament was a different SKU on a different printer (Alduais & Özerinç, 2023).

Kalia, Francoeur, Amirkhizi, and Ameli compounded PLA with thermally expandable microspheres (0–5 wt%) plus a plasticizer, then foamed in situ during material extrusion. Density fell as TEM content rose, by as much as 50% at 5 wt%. Local expansion closed interbead gaps that normally show up as FFF air channels. Specific tensile strength and modulus dropped; ductility and toughness rose several-fold. Glass transition, melting, and decomposition temperatures only shifted slightly. Their feedstock is a lab compound, not a Prusa retail spool, but it is the published picture of what in-nozzle foaming does to mesostructure: you buy lower density and you pay in specific stiffness (Kalia et al., 2022). That trade is the whole product category.

Frequently Asked Questions

What is Prusament PLA Lightweight used for?

Prusa launched an actively foaming PLA it says can print up to 65% lighter than regular PLA. The company points it at RC aircraft, drones, cosplay, floaters, and thermal inserts. One kilogram can make two to three times more printed volume. Those figures are Prusa’s, not a third-party test of this SKU.

How do I set up foaming PLA 3D printing temperatures?

Prusa’s default profile is 230 °C nozzle, 60 °C bed, extrusion multiplier 0.45, and retractions off. Foaming starts near 215 °C and peaks at 235 °C. Prusa says do not go past 250 °C because of potentially dangerous fumes. Dry the hygroscopic spool five hours at 55 °C. Recalibrate the multiplier if you change temperature.

Is foamed PLA a substitute for continuous carbon fiber?

No. Foaming PLA trades solid polymer for air so the part weighs less and can float or insulate. Continuous carbon fiber co-extrusion lays a tow for stiffness and tensile load. Use foam for airframes, masks, and sleeves where grams matter. Use continuous fiber for brackets that must stay stiff. They are complementary, not interchangeable.

Fibricate's Place in This Story

A foaming PLA wing still needs a stiff motor mount, a servo horn that does not flex, and a fixture while the epoxy kicks. Companies like Fibricate, whose FibreSeeker 3 continuous carbon fiber 3D printer can lay tow from feedstock such as the continuous carbon fiber spool, sit on that hard-point side of the same project. Prusa’s new SKU is a density material with a PrusaSlicer profile on Prusa machines. Keep the lanes straight: foam for the volume that has to be light; continuous fiber for the joints that have to stay put.

What to Watch Next

Watch whether other filament brands answer with their own actively foaming PLAs in the same mass and price band, and whether Prusa adds profiles beyond the CORE One and MK4S list. Watch independent density and tensile numbers on this SKU — Alduais and Kalia measured other foams, not this spool. For the next 12–24 months the garage signal is a two-material bench: one hygroscopic foam for flying and wearing, one fiber path for brackets. If you only buy one new roll this month, decide whether your next print fails from weight or from bending. That choice is the product, not the color name on the cardboard.

References & Further Reading

1. Alduais, A., & Özerinç, S. (2023). Tunable mechanical properties of thermoplastic foams produced by additive manufacturing. Express Polymer Letters.
2. Kalia, K., Francoeur, B., Amirkhizi, A. V., & Ameli, A. (2022). In Situ Foam 3D Printing of Microcellular Structures Using Material Extrusion Additive Manufacturing. ACS Applied Materials & Interfaces.
3. Prusament PLA Lightweight: 65% lighter than regular PLA. Perfect choice for aircraft, cosplay, and more. Prusa Research. Retrieved September 18, 2026.