PLA

PLA (polylactic acid, also called polylactide) is a thermoplastic aliphatic polyester made from lactic acid, obtained by fermenting plant sugars and starches, most often from corn or sugarcane. It is the most widely used material for FDM 3D printing. In industry it goes mainly into packaging, films, disposable tableware and fibers.

PLA has a glass transition temperature of roughly 55 to 65 °C and a melting point of about 150 to 175 °C. Standard, largely amorphous PLA therefore starts to soften under load at just 50 to 60 °C (HDT at 0.45 MPa is typically around 55 °C). Tensile modulus is 3 to 3.5 GPa, higher than that of ABS and PETG, and molded parts typically reach a tensile strength of 50 to 70 MPa. Elongation at break, however, is only a few percent and notched impact strength is low, so overloaded PLA tends to snap rather than bend.

Heat resistance can be raised by crystallization. Special annealable grades, or grades molded with nucleating agents into a heated mold, withstand roughly 80 to 100 °C. Annealing prints made from standard filament, however, causes shrinkage and warping, so test it first. There are also toughened grades (sold as PLA+ or Tough PLA, with no common definition) and grades filled with wood flour, minerals or carbon fiber.

In FDM printing, PLA usually runs at 190 to 220 °C at the nozzle and 50 to 60 °C on the bed, with no enclosure needed. It shrinks and warps little, prints fast with good dimensional accuracy and sharp detail, and has almost no odor. Injection molding PLA is possible but rare for engineering parts because of the low heat resistance. Machining PLA is impractical, as friction softens it.

PLA is the default choice for form and visual prototypes, concept models, checking fit in the assembly and ergonomics, architectural and exhibition models, templates, gauges and light-duty jigs working at room temperature. Low cost and reliable printing make it ideal for fast shape iterations.

For parts that must take impacts, repeated flexing (snap-fits, spring clips), sustained loads or temperatures above about 50 °C, choose PETG, ABS, ASA or nylon. PLA is also unsuitable for long-term outdoor use, because heat, moisture and UV radiation gradually degrade its properties.

The most common mistake is underestimating how little heat PLA tolerates. A PLA part can deform in a car in the sun, near a motor, power supply or heater, in a dishwasher or in a warehouse in summer. Under sustained load PLA also creeps, faster as the temperature nears its glass transition, so a bracket or fixture can gradually loosen or sag. Before functional testing, check the real operating temperature and load duration.

PLA is compostable only in industrial facilities with controlled temperature and humidity; in soil, water or a home compost pile it breaks down very slowly. A food-safe label on filament refers to the material, not to the finished print: the gaps between layers are hard to clean, so do not use FDM-printed PLA parts for repeated food contact without further verification. Store filament dry: moist filament snaps and gives weaker prints with a poorer surface.