Why Does It Matter?
The density of 3D printing materials seems to be largely unknown. When looking into a filament, the first things we want to find out are the diameter and weight. When setting up slicers, the specifications required are the diameter and the printing temperature. Density is set later, but it’s sometimes even ignored.
Setting up the correct density of materials can be helpful for your material usage computations. Before printing, you can check for the correct material density of the filament, referring to the manufacturer’s data. Of course, predicting the exact amount of filament usage is impossible, but using density would make this calculation more accurate.
So let’s break down the density of PLA, the most common consumer FDM material.
What Is PLA’s Density?
PLA, or polylactic acid, is one of the most common 3D printing materials due to its ease of use. From most manufacturers, the density of PLA is 1.24 g/cm³. However, when PLA is blended with materials, such as metal or wood, the density varies.
Blended PLA is the same thermoplastic, it’s just mixed with particles or fibers of some other material. The blend achieves a look and feel similar to real material. However, they don’t necessarily replicate the mechanical properties of the blended material.
Below are some of the composite filaments and their typical densities.
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The main selling point of these metal blends is the lustrous surface that results from polishing. That’s because they’re PLA mixed with a certain percentage of fine metallic powder.
Among the PLA blends, metal-filled PLA is the densest. Because of the added weight per volume, these filaments tend to have limitations with extreme overhangs and bridges.
These metal filaments are commonly available in copper, brass, bronze, stainless steel, or a blend of these metals. Depending on the manufacturer, the percentage of metal filling included in these filaments can vary. Thus, metal-filled PLA is heavier, at around 2-4 g/cm³.
Wood-filled PLA is composed of a PLA base and powdered wood. The typical mixture involves 30% wood and 70% PLA, but this varies depending on the brand.
Since fine wood dust doesn’t weigh as much as metal, the density of wood-filled PLA doesn’t differ much from standard PLA. Popular wood filament brands give a value between 1.15 and 1.25 g/cm³.
Carbon Fiber-filled PLA
Carbon fiber filament boasts increased strength and stiffness. Moreover, carbon-fiber-infused filaments are light, yet display good mechanical strength. The common density of carbon fiber PLA falls at around 1.3 g/cm³.
Carbon fiber can also be infused with other materials, namely ABS, PETG, nylon, and polycarbonate.
What About Other Materials?
Aside from PLA, materials such as ABS and PETG are also commonly-used filaments. In comparison to advanced materials such as nylon, polycarbonate, flexible filament, and others, these two are the easiest and cheapest ones to print.
ABS, or acrylonitrile butadiene styrene, is a tougher material than PLA. It’s less brittle, permitting a bit of flexibility in order to absorb impact. When it comes to density, ABS is a lighter material. The density of ABS is about 1.04 g/cm³.
PETG, on the other hand, is considered to be the “middle ground” between PLA and ABS: Easier to print than ABS but tougher and more heat resistant than PLA. PETG has almost the same density as PLA at 1.23-1.27 g/cm³.
If you’re keen on exploring exotic 3D printing materials, you’ll like our dedicated article on the topic.
Density is the measure of mass per unit volume. It’s the result of dividing the weight of a material by its volume. With this definition, density relates to two of the most-used parameters around 3D printing material. And this solves the dilemma of measuring our filaments: Do we measure by weight or length?
Slicers provide two ways to compute filament usage, but you can only verify the weight of the printed part. If you may want to have a basis of usage on length, make sure you set all variables right.
Weight or Length?
In most slicers, the filament usage is projected both by length and weight. The values shown may not be correct, let alone close to the actual value. This is inevitable, but the estimate can be improved by setting the density of your filament.
In order to know how it’s computed, let’s say we have a roll of filament. To know how much we have in terms of weight and length, we can use the formula of density.
Among the three parameters in the formula (density = weight/volume), we have values for the weight and density, as provided in our filament package or a technical datasheet.
As for the volume, it’s equal to the product of the cross-sectional area of the filament and the length. In this way, you can consider filament to be a very long cylinder: volume = cross-sectional area x length
The cross-sectional area of the filament is the formula of an area of a circle, equal to the product of the square of the filament diameter and one-fourth of pi: cross-sectional area = filament diameter^2 x pi/4. In this formula, the only unknown variable is the length. The diameter is given in the specs or measured precisely using a caliper.
We can begin by computing the volume first in the density formula, then solving for the cross-sectional area, and finally placing the values into the volume formula, obtaining the full filament length.
Using the formulas provided above will let you know how much filament you have. Take note that manufacturers already provide the filament by a standard weight. The diameter is also a set standard for filaments. This means that the length will be the value changing for each kind of filament, depending on the material density
Therefore, an ABS spool will have a longer length than a roll of PLA filament when both are 1 kg in weight and 1.75 mm in diameter. Heavier materials are shorter in length given both are of the same weight and same diameter.
Moreover, a 3DBenchy boat printed in ABS will be lighter than a PLA version. More material is used for denser materials even printing the same object.
And having accurate measurements for material usage can help in 3D printing, especially when considering costs and efficiency. Density will no doubt be useful in this respect.
Published on all3dp.com