PLA — the complete guide
PLA (polylactic acid) is the default 3D printing filament for a reason: it prints easily on any FDM machine without an enclosure, smells like cooking pancakes instead of burning plastic, and handles fine details better than any other common material. It also softens at 60 °C, so it's the wrong choice for anything sitting in a hot car or near a heat source. Here's when to use it, what settings work, and which PLA variant wins for your part.
Nozzle 200–220 °C, bed 55–65 °C, fan 100%, no enclosure. Use PLA for cosmetic prints, prototypes, fixtures, miniatures, and indoor parts. Don't use it for parts that will see >55 °C (car dashboards, anything outdoors in the sun), high-stress mechanical loads, or sustained outdoor UV.
What PLA actually is
Polylactic acid is a polyester made from fermented corn starch or sugarcane. Unlike ABS or PETG (petroleum-derived), PLA is biobased and theoretically biodegradable — but only in industrial composting facilities with sustained 60 °C+ temperatures. Don't bury your prints expecting them to vanish.
Its glass transition temperature (Tg) of ~60 °C is PLA's defining limit. Above it, the plastic softens and parts deform under their own weight. This is why PLA isn't suitable for parts that will live in a hot environment.
Recommended print settings
| Setting | Range | Notes |
|---|---|---|
| Nozzle temperature | 200–220 °C | Lower (~200) reduces stringing; higher (~215) improves layer bonding. |
| First-layer temperature | +5 °C above print temp | Bond to bed. |
| Bed temperature | 55–65 °C | Above 70 causes elephant's foot. |
| Print speed | 50–100 mm/s (standard); 200–500 mm/s (HS PLA) | Volumetric flow ~10 mm³/s on standard PLA; ~24 mm³/s on HS PLA. |
| Part cooling fan | 100% | PLA loves cool. Don't enclose; vent if you can. |
| Retraction (direct drive) | 0.4–1.0 mm at 30 mm/s | Less is more — over-retraction causes heat creep. |
| Retraction (Bowden) | 4–6 mm at 30 mm/s | The defaults for most stock profiles. |
| Layer height | 0.08–0.32 mm (0.4 nozzle) | 0.20 is sweet spot; thicker layers tip into under-extrusion. |
| Bed surface | Smooth PEI, textured PEI, glass | No glue needed on clean PEI. |
PLA variants — which to pick
| Variant | Best for | Trade-off |
|---|---|---|
| Basic PLA | Default for everything else | None — the baseline |
| PLA+ / PLA Pro / Tough PLA | Functional parts that need some impact strength | Slightly higher temp (210–225); marginally trickier first layer |
| Silk PLA | Cosmetic prints, decorative | Brittle; weaker; stringy |
| Matte PLA | Cosmetic prints without sheen | Slightly weaker; absorbs moisture faster |
| HS PLA / High Speed PLA | Fast prints on capable machines (Bambu, Prusa MK4) | Needs higher volumetric flow hotend; only worth it above 200 mm/s |
| PLA-CF (carbon-fibre) | Functional parts needing stiffness | Abrasive — needs hardened nozzle; weaker in tensile |
| PLA Aero / LW-PLA | Lightweight RC planes, foam-like parts | Foams at 230–245 °C; not for normal use |
| Wood-filled PLA | Decorative wood-aesthetic prints | Abrasive (hardened nozzle); larger nozzle recommended (0.6+) |
| Glow-in-the-dark PLA | Cosmetic glow effect | Highly abrasive; ruins brass nozzles in 10–30 hours |
Strengths
- Easy: prints on any machine, any bed, any climate.
- Detailed: PLA holds the finest features of any common filament.
- Stiff: high modulus, ideal for jigs and fixtures.
- Visually clean: minimal warping, low stringing when tuned, accurate dimensions.
- Low odor: safe to print in living spaces with normal ventilation.
- Cheap: $15–$25/kg for standard brands.
- Wide colour selection: hundreds of options.
Weaknesses
- Heat: deforms above 55 °C. Useless in cars in summer.
- Brittle: snaps rather than bends under stress. PLA+ helps.
- UV degradation: outdoor parts go brittle/discolor within months.
- Hydrolysis when wet: permanent strength loss if you print wet repeatedly.
- Hard to glue: most cyanoacrylates work; epoxies are stronger but slower.
- Not food-safe (officially): porous layers harbor bacteria; food-grade additives may not be.
Mechanical properties (typical)
| Property | Standard PLA | PLA+ |
|---|---|---|
| Tensile strength | 50–65 MPa | 55–70 MPa |
| Flexural strength | 80–110 MPa | 90–120 MPa |
| Impact (Izod, notched) | 3–5 kJ/m² | 5–9 kJ/m² |
| HDT (heat deflection) | ~55 °C | ~55 °C |
| Density | 1.24 g/cm³ | 1.24 g/cm³ |
Annealing PLA (oven at 80–100 °C for 1–2 hours) can raise HDT to 90 °C+ but shrinks the part ~3% — only useful for non-precision pieces.
When to choose PLA
- Prototypes and proof-of-concept models.
- Cosmetic and decorative pieces.
- Jigs and fixtures for shop use (not heat-exposed).
- Miniatures, figurines, character models.
- Indoor brackets, mounts, hooks.
- Costume props and educational projects.
- Anything you want printed easily, cheaply, and accurately.
Avoid for: car interiors, outdoor parts in sun, mechanical parts under sustained load, anything you'll boil or autoclave, gears with high friction loads.
Related articles
Sources & further reading
- Prusa Knowledge Base — PLA material guide
- Bambu Lab Wiki — Bambu PLA documentation
- Polymaker — PolyMax PLA / PolyTerra PLA datasheets