PLA
PLA (polylactic acid) is a stiff, low-cost thermoplastic made from fermented plant starch, and the most widely used material in FDM 3D printing. It prints accurately and holds fine detail, but it is brittle and softens at about 55 to 60 °C (131 to 140 °F).
Updated 28 Sep 2026 · 4 min read · By Wyntek
What PLA is
PLA is a polyester built from lactic acid, which is made by fermenting starch from crops such as corn, cassava, or sugarcane. It melts at a low temperature, warps very little as it cools, and bonds well between layers. Those traits have made it the most widely used filament in FDM 3D printing.
The trade-off is heat. PLA's glass transition sits around 60 °C (140 °F), and above it the plastic softens quickly. Ultimaker rates its PLA as unsuitable for parts exposed to more than 59 °C, and Prusa notes that PLA deforms above 60 °C. A PLA part left in a closed car on a summer day can sag.
Typical properties
| Property | Typical value | What it means for a part |
|---|---|---|
| Tensile strength, in-plane | 53 to 59 MPa at yield | Strong enough for brackets and fixtures that stay cool |
| Tensile strength, across layers | About 33 MPa at break | The highest across-layer strength of the common filaments |
| Stiffness (tensile modulus) | About 3.1 to 3.3 GPa | The stiffest common filament, so thin sections flex very little |
| Elongation at break | 2 to 8% | Snaps rather than bends when overloaded |
| Notched impact (Charpy) | About 4 kJ/m² | Cracks under sharp knocks that ABS or nylon would absorb |
| Heat deflection at 0.455 MPa | About 59 °C (138 °F) | Softens in hot cars, sunny windows, and near warm machinery |
| Density | 1.24 g/cm³ | Close to PETG, so parts weigh about the same |
These figures come from Ultimaker's printed test bars at 100% infill. Real parts with walls and partial infill are weaker, and data measured on moulded bars reads higher than printed parts achieve. Printed PLA keeps about 60% of its in-plane strength across layers, a better ratio than PETG, ABS, or nylon.
Where PLA works well
- Form and fit checks. PLA warps very little, so printed prototypes stay close to the CAD model.
- Detailed models and display pieces. It reproduces fine features and crisp edges cleanly.
- Jigs, fixtures, and gauges used indoors, where its stiffness keeps them accurate under light loads.
- Large, flat parts that would lift and warp in ABS.
- Early design loops. PLA is inexpensive and quick to print, so it suits many cheap iterations.
Limits to design around
- Heat. PLA softens from about 55 to 60 °C (131 to 140 °F), so keep it away from car interiors, hot water, and warm machinery.
- Brittleness. It breaks with little warning, which makes it a poor choice for snap fits, living hinges, and parts that get dropped.
- Sunlight. UV light degrades PLA, and both Ultimaker and Prusa advise against long-term outdoor use.
- Food contact. Printed PLA is not a food-safe part. Layer lines trap bacteria, and Prusa does not recommend any printed filament for direct food contact.
- Composting claims. PLA is often called biodegradable, but that applies to hot industrial composting, not to a landfill, a garden compost heap, or a part in everyday use.
PLA compared with PETG, ABS, and nylon
| Material | Stiffness | Strength in-plane | Strength across layers | Notched impact | Heat deflection |
|---|---|---|---|---|---|
| PLA | 3.1 to 3.3 GPa | 53 to 59 MPa | 33 MPa | 3.9 kJ/m² | 59 °C |
| PETG | 1.7 to 1.9 GPa | 46 to 50 MPa | 19 MPa | 7.9 kJ/m² | 76 °C |
| ABS | 1.7 to 2.0 GPa | 38 MPa | 19 MPa | 14.2 kJ/m² | 87 °C |
| Nylon (PA6/66) | About 2.3 GPa | 63 to 65 MPa | 23 MPa | 13.7 kJ/m² | 89 °C |
PLA is the stiffest of the four and the strongest across layers, but it has the lowest impact strength and heat resistance. PETG, ABS, and nylon give up some stiffness in exchange for toughness and a higher working temperature.
Designing parts for PLA
- Keep working temperatures below about 50 °C (122 °F) to leave a margin under PLA's softening point.
- Use PLA where stiffness matters and impact does not. For clips, hinges, or parts that get dropped, choose PETG or nylon.
- Add fillets to internal corners. PLA is notch-sensitive, and sharp corners start cracks.
- Give load-bearing walls at least 1.2 mm, which is three perimeters on a standard 0.4 mm nozzle.
- Use its low warping for long, flat parts and fine surface detail.
At Wyntek
PLA is on every Wyntek plan, including the free tier. Upload your file, choose FDM and PLA, and you see the price in US dollars before you submit. Every part is scanned and inspected before it ships, with tracked shipping worldwide.
Get a price for a PLA part