The Ins and Outs of PLA Filament Density for Optimal 3D Printing

Polylactic acid (PLA) is one of the most common filament materials used in 3D printing today. Understanding the density of PLA filament is key to optimizing your 3D prints. This guide will provide an in-depth look at PLA density, including how it affects print quality, material usage, and mechanical properties.

What is PLA Filament Density?

Density measures the mass of a material per unit volume. It is commonly expressed in grams per cubic centimeter (g/cm3).

The density of PLA filament typically ranges from 1.21-1.25 g/cm3. This makes it denser than ABS (1.04-1.19 g/cm3) but less dense than materials like PETG (1.27 g/cm3).

Density can vary slightly between different PLA filament manufacturers and grades. Higher quality PLA tends to have more consistent density while cheaper PLA may have more variation.

Why PLA Density Matters for 3D Printing

The density of your PLA filament impacts several aspects of the 3D printing process:

• Print quality: Consistent density leads to uniform extrusion and better surface finish. Variable density can cause imperfections.
• Material usage: Knowing the exact density helps to accurately calculate how much material is required to print a given part.
• Mechanical properties: Density affects the stiffness, strength and performance characteristics of printed parts.
• Weight: Higher density leads to heavier printed parts, which may matter for some applications.
• Cost: More dense material results in higher filament usage and cost for printing large or solid parts.

Thus, understanding and controlling PLA density is essential for optimizing the 3D printing workflow.

Measuring the Density of PLA Filament

Since PLA density can vary, it is useful to measure the specific density of your filament spools. This allows you to dial in the perfect material settings.

Here are two common methods of measuring PLA filament density:

1. Calculate from Filament Diameter and Weight

This simple method only requires measuring the weight of a known length of filament.

For example, weigh a 10cm length of filament. If it weighs 1.236g, then the density is found by:

Density = Mass / Volume

Where Volume = πr2h

r is the radius of the filament and h is the measured length.

Plugging in the numbers gives a density of 1.24 g/cm3 for the example filament.

While easy, this method can have inaccuracies if the diameter and length are not precisely measured.

2. Use a Density Measurement Kit

For the most accurate density measurements, use a filament density tester. These devices measure the oscillation frequency of the filament suspended in a fluid of known density.

By inputting the measured frequency into the provided formula, the density of the filament can be calculated. Density testers provide repeatable lab-grade precision.

Dialing in Correct PLA Densities

Once you know the true density of your PLA filament, you can better optimize your print settings.

In your slicer software, enter the measured density into the filament settings. This will improve the accuracy of:

• The calculated volume and weight of the printed part.
• The amount of material to be extruded.
• Print time estimates.

You may also wish to adjust temperature, speed, extrusion widths, and retraction settings to account for any density inconsistencies in cheaper filament.

Typical PLA Filament Density Values

While measurement is ideal, reported densities from filament manufacturers can also serve as a starting point. Here are some typical PLA densities:

• Polymaker Polylite PLA: 1.24 g/cm3
• eSUN PLA+: 1.24 g/cm3
• Hatchbox PLA: 1.24 g/cm3
• MatterHackers Pro PLA: 1.24 g/cm3
• ColorFabb PLA/PHA: 1.25 g/cm3
• Prusament PLA: 1.24 g/cm3
• Ultimaker PLA: 1.24 g/cm3
• Geeetech PLA: 1.21-1.24 g/cm3
• OVERTURE PLA Filament: 1.24 g/cm3
• TTYT3D PLA Filament: 1.23 g/cm3
• MG Chemicals PLA: 1.21-1.24 g/cm3
• Devil Design PLA Filament: 1.24 g/cm3

As shown above, most quality PLAs share a similar density range. Cheaper or lower tolerance PLA may deviate further from the norm.

Effects of PLA Density on Print Quality

The consistency of the PLA density directly correlates to print quality. Higher variance in density leads to issues like:

• Weak layers and splitting: Drastic changes in density during printing can cause extruded material not to fuse properly. This produces weak, split layers and a poor surface finish.
• Blobs and zits: Light sections followed by dense sections can result in excess material oozing out on the print.
• Dimensional accuracy errors: Inconsistent material flow due to density fluctuations leads to inaccuracies in the printed part dimensions.
• Voids and holes: If the material density drops enough during printing, gaps may form in the part.

By using high consistency PLA filament measured with a density tester, you can avoid these defects.

PLA Density and Mechanical Properties

The density of PLA affects key mechanical properties, including:

• Tensile strength: Denser PLA plastic forms stronger molecular bonds, increasing tensile strength. Parts with low porosity due to consistent density excel in tensile applications.
• Stiffness: Higher density leads to greater stiffness, allowing PLA to hold shape and resist deformation under load.
• Hardness and toughness: Dense, solid PLA with low voids demonstrates enhanced hardness and abrasion resistance compared to porous low-density PLA.
• Fatigue strength: Porosity from density variations produces internal stress concentrations in parts. This results in lower fatigue life compared to more consistent dense PLA.

Testing samples printed from known density PLA lets you empirically determine the optimal PLA density for your application.

Optimizing PLA Usage by Measuring Density

Knowing the exact density of your PLA lets you minimize material use and cost.

With precise density, you can input the filament weight into your slicer, allowing it to accurately determine the length of filament required. Without the correct density, you may over or under-extrude.

For printing very large or multiple copies of objects, small density errors can multiply into wasted material and expense. Even a few cents difference per part adds up over thousands of prints.

Dialing in the perfect flow rate based on density testing saves you money while also giving great quality.

In Conclusion: The Density of PLA Matters

Understanding the density of your PLA filament is a key factor in getting the highest performance from your 3D printer. Measure the density, optimize your settings, and get the best possible prints. Consistent density promotes quality, optimizes material use, and improves part properties. Consider density as one of the vital “need-to-know” specifications of your PLA filament.