This guide is intended for the purpose of discussing the varying density of PLA filament and why it is a major factor to consider in the process of 3D printing.
Why Density of PLA Filament Matter?
The density of PLA filament material is often taken for granted or considered secondary to other parameters that have to do with the actual printing. In the case of filaments, people tend to look for information on diameter and weight, while most slicer settings focus on diameter and temperature for printing. Thus, density is considered some way down the line and sometimes omitted altogether.
If you set the material density correctly, you give yourself an opportunity for more accurate material usage calculations. The density of any filament can be looked up from the manufacturer’s data sheets and applied before any print job. Although predicting the exact amount of filament being infused in an operation is difficult, this can however improve the reliability of your estimates.
Now, let’s step in and view density of PLA filament more closely, with a special emphasis on consumer-grade FDM 3D printing, and one of its most widely used materials.
What Is PLA and How Does Its Density Change?
In general, polylactic acid or PLA is classified as one of the most useful materials in 3D-printing due to its simple usage. The general density of pure PLA is approximately 1.24 g/cm³, but the density can easily stray from this value when other materials are mixed into the PLA: for example, metals and woods.
PLA-composites blend retain the thermoplastic PLA’s basic properties; however, the addition of particles or fibers from other materials modifies the texture and appearances of the blends to imitate various real-world materials. The consequence of this is a blend whose mechanical properties may not perfectly match those added materials.
Here are the common densities of a few popular composite PLA filaments:
Metal-filled PLA
Metal-filled PLA is a mixture of PLA and metal powder to a semi-shiny finish. Among the mixing types of PLA, it has the heaviest density due to the heavy metal powder mixed, which is generally in the range of 2-4 g/cm3. Even though the blend gives a good appearance, the added weight will bring problems in printing properties such as overhangs and bridges. The filaments are usually sold mixed with copper, brass, bronze, and stainless steel, with the percentage of metal filling set differently by different manufacturers.
Wood-filled PLA
Wood-filled PLA consists of PLA mixed with wood powder, usually about 30 percent wood and 70 percent PLA, although this can vary by brand. Since wood is much lighter than metal, there is still comparable density to standard PLA, usually between 1.15 and 1.25 g/cm³.
Carbon Fiber-Filled PLA
Carbon-fiber-infused PLA filament is lightweight while exhibiting great strength and rigidity. The density of carbon fiber PLA is typically at 1.3 g/cm³. This filament can also be obtained as a blend with different materials like ABS, PETG, nylon, and polycarbonate; hence, their densities may differ slightly.
Other Common 3D Printing Materials
PLA may dominate 3D printing, but others like ABS and PETG are also popular with artists and artisans alike. Their ease of use and affordability make them good options, especially in comparison with advanced nylon, polycarbonate, and flexible materials.
ABS
Acrylonitrile-Butadiene-Styrene, ABS, is stronger and tougher than PLA. PLA is very brittle, while ABS, to some extent, displays flexibility allowing it to withstand impacts. It is lighter than other plastics at a density of around 1.04 g/cm³, making it less dense than that of PLA.
PETG
Polyethylene Terephthalate Glycol, PETG, is a compromise between PLA and ABS said to be easier than ABS to print and more heat resistant and durable than PLA. PETG is somewhat close to PLA in density, between 1.23-1.27 g/cm³.
If you’re interested in exotic materials for 3D printing, you should head on over to our excellent article on the subject!
Understanding Density of PLA Filament and Calculations
Density is defined as the mass of the substance as it fits into a defined volume and is found by dividing the weight of the material by the volume. This concept becomes a major parameter for working with 3D-printing filaments and their essential properties: weight and length. In this respect, it helps solve the question of measuring filament consumption: by weight or length?
Slicers will calculate filament consumption on weight and length bases; that said, sometimes these calculations are off. Proper filament density can help improve these calculations.
So, in estimating filament consumption, we start with a filament roll. With the density formula, we can derive the weight and lengths of the filament as follows:
Density = Weight / Volume
We know weight and densities are given in the technical data sheet or package of the filament. The volume is given by multiplying the filament cross-sectional area by length. Now, here, we could consider filament as a long cylinder:
Volume = Cross-sectional Area × Length
Cross-sectional area for a filament will be defined by the area of a circle:
Cross-sectional Area = (Filament Diameter² × π) / 4
Once you get the cross-sectional area, substitute it into the volume equation to find the length of filament.
Key Insights of Density of PLA Filament
The amount of filament is determined with the help of the above formulas. Note that filament manufacturers allocate materials via weight, whereas filament diameters are mostly standard. Thus the length of filaments will vary due to different material densities.
For example, an ABS spool will produce a longer filament relative to a 1 kg, 1.75 mm diameter roll of PLA. The reason being that, given the same weight and diameter, denser materials would have a shorter length.
Both the ABS and PLA 3DBenchy will weigh the same assuming identical models; however, the ABS version will use less filament in the process of fabrication. Denser materials require more filament to close the given dimensions of an object.
Generally accurate accounting of materials consumed in 3D printing is important; especially in matters of costs and overcoming the problems of optimization in printing. Density assumes importance during the calculations in this respect.