Polylactic acid (PLA) is the most widely utilized material in fused deposition modeling (FDM) 3D printing, especially among hobbyists and in educational settings. Understanding a material’s physical properties is fundamental for successful manufacturing. For PLA, density heavily influences both the printing process and the final product’s characteristics. Density determines how much mass is contained within a specific volume, which has direct implications for material cost, slicer software calculations, and the structural integrity of the printed part.
Defining Polylactic Acid (PLA)
PLA is a thermoplastic polymer popular in additive manufacturing due to its user-friendly nature. It is derived from renewable sources, such as fermented plant starch from corn, cassava, or sugarcane, classifying it as a bioplastic. PLA’s low melting temperature makes it easy to print without a heated print bed or an enclosed chamber. It is known for producing prints with minimal warping and a pleasant surface finish. While not truly biodegradable in a home compost bin, PLA is compostable in commercial facilities.
The Standard Density Range of PLA
Density is defined as a material’s mass per unit volume, typically expressed in grams per cubic centimeter (g/cm³) for 3D printing filament. This value is a fundamental characteristic of the polymer in its solid state. For pure, unmodified PLA filament, the standard density range is narrow, generally falling between 1.24 and 1.26 g/cm³. This range translates to 1240 to 1260 kilograms per cubic meter (kg/m³). This density is characteristic of PLA in its semi-crystalline state. Filaments with densities below this range may suggest internal air pockets, which can compromise the material’s integrity.
Factors Influencing PLA Density
The density of commercial PLA filaments can vary when manufacturers introduce specialized additives or modify the polymer structure. Density is commonly altered through fillers that create composite filaments for specific aesthetic or mechanical properties.
Composite Filaments
Metal-filled PLA, incorporating heavy powders like copper or bronze, results in a significantly higher density, often ranging from 2 to 4 g/cm³. Conversely, wood fiber is lighter than the base polymer, keeping wood-filled PLA density close to standard PLA, typically between 1.15 and 1.25 g/cm³. Carbon fiber-infused PLA, prized for increased stiffness, is slightly denser than the base material, usually around 1.3 g/cm³.
Lightweight PLA (LW-PLA)
A more dramatic modification uses specialty lightweight PLA (LW-PLA), which intentionally decreases density during printing via active foaming technology. These filaments contain chemical foaming agents that activate when heated in the nozzle, causing the material to expand and create microscopic air bubbles. This expansion can dramatically reduce the density of the printed part to levels as low as 0.40 to 0.54 g/cm³. This reduction allows users to achieve substantial weight savings where low mass is a primary design goal.
Practical Implications of PLA Density in 3D Printing
Density is important for slicer software, which translates a 3D model into printer instructions. Slicers use material density to accurately calculate the required weight of filament for a specific volume. Entering an incorrect density value results in inaccurate material usage and cost estimates, especially when switching between standard and composite filaments.
Density also dictates the final weight of the printed part, which is a consideration for functional applications. For example, lightweight PLA is used in remote-controlled (RC) planes and drones, where weight reduction improves flight performance. Conversely, dense, metal-filled PLA might be chosen for decorative pieces where a heavier feel is desired for stability or perceived quality.