So what's so special about ABS ?
Hi,
I originally started printing with the Prusa PLA that came with the printer and loved it. When I ran out I tried other PLA from a local store and although not as good as the Prusa PLA it still prints pretty good. I have found my PLA prints to be strong and somewhat flexible, enough to withstand a lot of torque on longer pieces before splitting. I tried some Form Futura Crystal Flex thinking it would be better than PLA for this and turned out to be crap.
Now I bought some Prusa ABS and re-printed some parts for which I wanted a better finish and more strength than PLA but I have found ABS to be brittle and cracks with much less torque than the same piece even with cheap PLA. And when I use Prusa PLA is much, much stronger.
I am aware this the opposite of what most ABS vs. PLA out there say.. ABS is supposed to be more flexible and resistant than PLA yet I'm experiencing the exact opposite!
So what is so special about ABS ? Why does everyone seem to love it so much ? Is it only for the acetone vapour finish ? Or there many other advantages of using ABS versus some good PLA? I must be missing something...
I used the standard Prusa ABS settings but noticed that it doesn't stick too well to the support material, which in some parts of this print are 2cm high at least (I only have single filament so it's all ABS) Maybe I need to raise the temp a little bit? The Z is fine since the support material prints very nice, but the first few layers above the support material are very messy. Even though the print surface is maintaining the 100C perhaps the room is too cold (15-18C)? what is the minimum ambient temperature for ABS printing? is this critical?? (I didn't notice any warping but it may explain the non-sticking of the first few layers after the support material).
TIA,
Alex
Re: So what's so special about ABS ?
ABS has slightly lower (10-15%) tensile strength than PLA, at least in bulk. If printed correctly, you can achieve stronger adhesion between layers than you can with PLA, so generally speaking, PLA will be a bit stronger than ABS if the forces are parallel to the print bed plane when the object was printed (at a right angle to the actual layers/Z-axis).
ABS will take more force to break in the direction of the Z-axis/at a right angle to the layers, compared to PLA.
ABS also has *much* better impact resistance. This means that ABS will withstand impacts that would crack or shatter PLA.
But, to answer your question as to what is so special about ABS... there is actually a very specific answer :).
ABS can withstand high temperatures. In fact, it's ability to withstand heat exceeds pretty much every common filament type out there. Only a few more exotic engineering plastics like polycarbonate or PEEK can beat ABS. ABS is good to about 110°C. This is why most of the i3 (any version)'s parts are printed in ABS: it won't melt when motors or the hotend get hot.
PLA, on the other hand, will melt if you leave it in t he car. I've had it melt because curtains were drawn and a beam of sunlight stayed on some PLA printed thing too long. Granted, I live in a fairly hot desert area, but still. PLA begins to melt at around 55°C-60°C.
In my experience, ABS is generally slightly more robust than PLA, but it's really kind of a usage case thing. It might be that PLA is a superior choice for whatever you're doing.
That said, support materials aren't universal, they only work with certain filaments. If you're using HIPS, ABS will pretty much just refuse to stick to it. HIPS is mostly just for PLA.
However, give this a try: use PLA as the support material for your ABS. Then dunk the print in almost boiling water. The PLA will come off from the ABS easily while the ABS will still be quite hard.
Re: So what's so special about ABS ?
Thanks for such a detailed reply and really answers my original question.
PLA seems so much easier to print and like you said if temperature and other factors are not important in a particular application then I guess PLA should be the better choice as it's cheap and even environmentally friendly, as I understand it most PLA should be biodegradable.
In my case, I think I am going to continue using PLA and only use ABS for very specific parts. For example, I have a friction plate that I would like to smoothen out with a acetone vapour, and that particular part will have a lot of wear so I think I'll use ABS just for that for now.