If you know anything about 3D printing then you have probably heard some of the myths involving PLA. “It's weak” “It's hard to sand” “It will degrade” ect. ect.
This has led quite a lot of people to believe that PLA is not a good material. Some makers even advertise that they use PETG, claiming that it is superior, and they usually charge more for it. But this is a sham!!
We have been using PLA in production since 2016. Since then we have tried just about every material available. After all, if there is a better material we want to use it! Yet in the end we always go back to PLA.
What makes PLA so good?
- It is readily available in dozens of colors.
- It is priced reasonably.
- It is easy to print with.
- It is easy to sand.
- It shrinks very little.
- It does not emit harmful vapors.
- It does not require a heated bed or chamber.
- It can be printed much faster than other materials.
- It requires less power.
- It is very strong, stronger than PETG in many cases.
- You can get very high quality prints with PLA.
- Items made with PLA are very easy to work with.
- It absorbs very little moisture, and print quality is affected less by it.
All of this means we can produce high quality items, very quickly, and at low cost.
Where does PLA fall short?
The only real drawback of PLA is its temperature resistance. Items made from cheaper PLA may warp if left in a hot car. Even quality PLA might warp in a hot car in some regions.
Fortunately there are solutions. The first is an easy fix, and it is a technique you should be using to finish 3D printed items anyway. Resin coating!
What is Resin Coating?
The primary purpose of resin coating 3D printed items is to provide a smooth surface. A fortunate side effect is that it significantly increases the temp resistance of the item, thus preventing PLA items from warping. It is an all inclusive solution that solves 2 problems with one action. Resin coating has many benefits, increased strength, less sanding, but those are out of the scope of this article so you can read more here. https://3dcauldron.com/pages/smoothing-3d-printed-items
The second technique for increasing the temp resistance of PLA is annealing. This is an advanced technique and should only be used when you cannot resin coat, or if you need extreme temperature resistance.
Annealing PLA is similar to heat treating metal. The process bonds the layers, and changes the molecular structure such that the PLA can resist much higher temperatures. Most PLA starts to get soft around 55c, annealing can increase that up to 85c. In addition annealing increases the impact resistance such that the part is stronger than ABS!
You can learn more about annealing here: https://all3dp.com/2/annealing-pla-prints-for-strength-easy-ways/
Why not just use ABS or PETG?
While both ABS and PETG naturally have a higher temp resistance than PLA they fall drastically short in other areas.
ABS is the strongest and has the highest temp resistance of the 3 most used materials, it is tough to print with. It shrinks much more than the other materials leading to adhesion issues, warpage and poor dimensional accuracy. ABS must be printed slower than PLA, it requires much more energy, and typically requires a heated chamber. In addition ABS fades due to uv exposure. It turns white when put under stress, and it emits toxic vapors while printing. ABS also absorbs moisture quite easily. ABS was used in the early days of FDM 3D printing due to its availablity, and the lack of other options. ASA is a derivative which is less susceptible to UV damage, is more chemical resistant, and less susceptible to moisture absorption. Despite these positives, ASA still shares the other shortcoming of ABS. Frankly ABS/ASA is obsolete and should only be used for very specific needs.
You may have heard grand claims about PETG. It was intended to be something of a middle ground between PLA and ABS, taking all the pros, and solving the negatives of each material. These claims have led people to believe it is a wonder material, but after extensive testing we have found it simply falls short of these claims.
PETG has a slightly higher temp resistance than PLA, which is enough to keep the part from warping in a hot car. Adhesion is more difficult with PETG, and it requires a heated bed. Print quality is decent if done slowly, but at higher speeds PETG produces the worst prints of the big 3. PETG absorbs moisture fairly easily and print quality is affected more than ABS or PLA. PETG is very stringy, again printing slowly helps this. PETG can be strong in some situations, but it is incorrect to say that it is stronger than PLA. Firstly to get the strength advertised with PETG it must be printed very slowly. ⅓ to ¼ the speed of PLA!. Since PETG needs to be printed so slowly it is not a good material for production.
PETG is decent at taking an impact, but has very little bending strength. PETG is less rigid than PLA. This means that while a PETG part may not snap off, it can be deformed much more easily than PLA. When bending PETG it stretches the material. It’s much easier to repair a clean break than it is to repair a stretched part!
PETG can be purchased at around 2/3 the price of PLA+ so sellers claiming PETG items are superior, are really just saving a few bucks.
Here is a video comparing the big 3: https://www.youtube.com/watch?v=ycGDR752fT0
Here is a video showing how moisture affects filaments. https://www.youtube.com/watch?v=5CFxT1q6dX8&t
We have already debunked the myth that PLA is not strong. But what about the others?
“PLA is hard to sand.”
This one is somewhat subjective, but frankly we don't get it. We have sanded PLA for years and with no issues. The trick is to use the proper sandpaper. Coarse imperfections will require a lower grit. Mechanical sanding can be tricky as it can produce enough heat to melt the plastic. Hand sanding is easy and effective. Resin coating will eliminate 90% of the sanding needed anyway!
“PLA items will degrade”
This myth has taken root due to the claims that PLA is biodegradable. While technically PLA is biodegradable, it will not decompose, nor degrade under normal conditions. PLA must be broken down in a commercial facility. It requires a steady temperature of around 55c, and a chemical bath with specific microbes, where the levels are constantly maintained. Even then it takes several months to break it down.
This video shows PLA being tested for degradation over several years. https://www.youtube.com/watch?v=jCsnVp6mEbk&t