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FDM 3D Printing Materials Part 1: PLA

By Mitch

September 21st, 2023


A reel of yellow 3D printing filament
Reel to reel. PLA filament is a common FDM printing material (Image: Unsplash)

PLA (Polylactic Acid) is the most commonly used type of filament material in the world of FDM 3D printing. In this, the first of a series of articles about different materials, we explore the makeup of PLA, its good and bad points and the best use scenarios for the material.


So, let's start by looking at what makes PLA such a popular and useful 3D printing material.


PLA - The Basics


We've established that PLA is commonly used in 3D printing and has a variety of uses. But why is this? In simple terms, PLA is easy to use and work with, it's easy to produce and has good dimensional accuracy. PLA is the go-to material for most new users and old hands alike for these exact same reasons and the range of colors and different types within the PLA genre is extensive.


As we looked at in previous posts, standard PLA is the most common but you can also find PLA+, silk, matt, rainbow, glow-in -the-dark and even colour changing PLA to name but a few. There are also variants of PLA where a particular additive has been included which changes the consistency and performance of standard PLA.


We've talked about the how PLA is easy to work with and this is partly due to its low melting point. To become workable for 3D printing, you need a nozzle temperature of between 190-220ºC and a hot bed temperature of around 50-60ºC. This is pretty much the standard for entry level FDM printers which is why PLA is used so much in that realm.


The other aspect of PLA which is sometimes overlooked is that it is entirely made from natural, renewable sources such as corn starch or sugar cane. This makes PLA fully biodegradable under the right conditions which, in today's issues with waste and climate change, can only be a good thing.


PLA though does have both good points and things that could cause issues so let's now look then at these Pros and Cons as we commonly know them.


Pros

  • Easy to work with: Low printing temperatures and easy to cut and sand in post processing

  • Rigid and relatively strong: Can withstand a certain degree of impact

  • *Good dimensional accuracy: Good quality PLA will be +/- 0.02mm or better

  • Long shelf life: If stored correctly: PLA will last as long as you need it

(*Dimensional accuracy refers to the possible variation in diameter throughout a spool of PLA. The most commonly used diameter is 1.75mm so a dimensional accuracy of +/- 0.02mm means that some parts of the filament may be between 1.73 and 1.77mm)


Cons

  • Low heat resistance: The low working temperature has a disadvantage when it comes to heat exposure when printed

  • Blockages occur regularly: The low melting point again plays a part at slow printing speeds

  • Requires cooling fans: Somewhere between a pro and con for this as most printers have fans anyway

  • Filament can get brittle and break: If not stored correctly, the filament will harden and break. Vacuum storage is suggested and/or the use of a filament dryer

  • Not suitable for outdoor use: PLA is vulnerable to water and UV light so won’t react well to being outdoors

That then is a basic overview of PLA as a 3D printing material but let's now look at some of the ways PLA can be used in 3D printing.


PLA - Printing Examples


A 3D printed model of a turbine in progress
Building a good fan base. PLA is the perfect choice for large scale models (Image: Politech)

PLA has many uses in FDM printing but particularly lends itself to the world of prototyping and also scale models of larger engineering items.


Jet Turbine


Take for instance this project by Politech which is a model of a jet turbine engine. You can see in the image above the detail that can be achieved with PLA as well as the larger scale pieces that can be printed. The base layers are relatively easy to manipulate to get the best foundation for a successful model. The lightweight structure of PLA married with its strength and durability make it an ideal choice for such models. You can see the finished model in the image below.



A 3D printed model of a jet turbine
Jet power. The completed model shows PLA's versatility (Image: Politech)

Waving Baby Groot

A 3D printed model of a tree like character strapped into a car seat.
"I am Groot". A creature of few words (Image: Politech)

If you're a fan of the Marvel universe then you'll surely be aware of Groot, the monosyllabic tree like character from the Guardians of the Galaxy series. Even if you're not a fan, it's hard to resist this model of the Baby Groot incarnation of the character created by Politech.


The model is beautifully printed and painted but the secret to the detail and shape of the figure is down to the fact that its printed in several pieces. This allows for attention to be given to the overall model without the risk of losing the whole print due to one failed area. You'll remember that one of the "cons" of PLA is that it can cause nozzle clogs while printing and the risk of this is increase when printing a larger model. Printing it in small parts and then assembling as a whole reduces the risk of failed prints.


You can see from the image below that the model of the head is a much easier printing prospect when printed separately like this and in PLA. The overall model has a total of 17 parts that can be either printed individually or in groups if your printer allows.


A blue 3D printed model  head
Head Start. Printing PLA parts for larger models reduces the risk of print failure (Image: Politech)

In Conclusion


PLA is a versatile and easy to use 3D printing filament which lends itself perfectly to creating models and prototypes. There are some issues that can occur while printing which can make quality and consistency a problem but overall, PLA is the perfect choice for display or demonstration items as long as they're used indoors and don't need to be subjected to any force or stress.







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