PLA. vs ABS - Whats the difference?

Note: I'm updating this post whenever I learn something new about the filaments!

During my conquest for finding the right 3D printer for me, I found myself frequently confronted at a crossroad of choosing which printer should I go for. There is a lot of factors like reliability, quality, speed, cost, service and availability to think about. One factor which usually is not so much mentioned is what kind of material filament it supports.

Most printers supports the two most popular materials: ABS (Acrylonitrile butadienestyrene) and PLA (Polylactic acid), but some printers only supports only of them, and they both recommend it as the preferred material for delivering the best quality prints. So what's the difference, and which one should I choose?

Prior to buying a printer I decided to look up the differences and asked around what the differences were and why it could be a factor when deciding a printer. Here is what I managed to gather.

PLA

• Bio-degradable, made of renewable resources. Less harm to the environment.
• Softens at 50C, melts at 160C, and bonds well at 180-190C.
• Insoluble in water, but it takes time can be speed up at higher temperatures, around 90c or so.
• Less prone to bending, and more likely to break instead when put under stress.
• Smells like cotton candy when heated for printing.
• Mild bottom warping which can be reduced with a heated printing bed.
• Sometimes harder to stick on the bed during the first few layers of print.
• Require a bit more manual work to clean and maintain a printer nozzle after some use.
• Sensitive to humidity, must be stored in a dry location.

ABS

• Made of the same plastic material as you will find in LEGO.
• Softens at 90C, melts at 180C and bonds strongly to itself at around 230C.
• Insoluble in acetone, can speed up with boiling.
• Bends rather than breaks, a lot sturdier than PLA when under stress.
• Releases unpleasant non-toxic fume during print.
• Very subject to bottom warping, curling and splits unless you have a heated bed and chamber.
• Easier to clean a nozzle and printer bed with acetone.

I remind you again that these are only gathered from forums, second hand words from others with 3D printers out there. I have no way of confirming until I have my own printer and cramming out the details. But I think it brings out some valid things one should know about when working with a 3D printer.

Why I should choose or not choose PLA?

When it comes down to practical use and easiness to work with, I believe PLA is a clear favorite. There is a less chance for prints to fail due to bottom warping and splits. And it of course smells nice. My bedroom is next door to where I will put my printer (bad idea, I know) and I won't be bothered by the fume ABS would produce. The downside with PLA is it's sensitivity to humidity. If stored somewhere with a humidity is a problem (like the laundry room next door), it would render your whole exposed spool of PLA useless for printing after a while. But that should be in theory an easy fix: Don't store it where it is exposed. A second downside to PLA, which is the strongest counter argument in my case is the ability to do post processing on my prints. Mainly speaking sanding and painting. I've no idea how oil or water based or any other stronger chemicals would affect PLA. I'm a bit concerned it could melt my prints. And the same goes for sanding, due to the lower melting point of PLA (50c). Heat could be generated by the friction of sanding, and maybe make the plastic melt to a sticky substance and thus ruining the print.

Why I should choose or not choose ABS?

Bottom warping in the lower right corner

ABS plastic can withstand sanding and higher temperatures. It might be harder to paint on, but a simple primer should fix that. This makes ABS a very tempting choice. The smelly fume could always be fixed with a proper ventilation, but here is where the problem comes in. Despite ABS having a higher melting point, it is also more affected by temperature side effects. Mainly speaking expanding and contracting as the temperature rise or cools down. This is one of the main reasons why many ABS prints lose their adhesion to the printer platform and starts curving, also called bottom warping. And should you be lucky to not be affected by it, there is also a chance of splitting in taller prints. Some say it could be fixed in the software settings by adjusting the correct temperature, printing speed, layer thickness etc. And some say its unavoidable unless you have closed heated chamber to contain the heat until your whole print is done. 

Conclusion 

These are issues I hope I'm lucky enough to avoid. If I don't I will work it out and see what can be done to fix them. I hope I can stick with PLA if it proves to be sanding and painting worthy, or ABS if it doesn't warp too much. We will see when I have my printer.

More reading about differences between PLA and ABS:

• http://www.protoparadigm.com/blog/2013/01/the-difference-between-abs-and-pla-for-3d-printing/ 

-WJ