which parts to print in which materials

I've been discovering items over time that are better when printed in PLA and which are better for ABS.

of course this is very anecdotal, not meant to spark religious debate.

better in ABS:
The filament drive block. Both the extruder motor and thermal break can get very hot, ABS is perfect here.
X carriage can benefit from the heat tolerance, although there are other things to mitigate this.

better in PLA:

printed bushings. More of a requirement than a preference.

extruder gears. you dont want gears to have much flex. my PLA gears have outlasted my ABS gears repeatedly.

Z motor couplings for prusa mendel. I had 2 sets of 2 different designs for the motor couplings they failed. PLA ones stayed good, and were easier to adjust with a hair dryer.

I mention this because most people have parts that are all one plastic or another, so it's good to trade a few parts with others for optimal use.

If by chance this message catches anyone with a virgin extruder... you can safely print some PLA parts in your extruder before switch to ABS, it's a pain to go the other way around.

Thanks for the tips.
I am just getting ready to start printing and was wondering whether to try PLA or ABS first

If you want to print ABS in the future, then you should print your Mendel in ABS. If you want to print big parts in ABS, then you need to put your Mendel in a box at around 50C in addition to using a heated bed. In that case, PLA bushings are out of the question. If all you want to print is PLA, then you can print your Mendel in PLA.

I've found that the quality of the parts that I get with my Mendel is better when I print ABS than PLA. But I may not have spent enough time optimizing PLA. PLA does limit application since it softens at around 60C while ABS is good to at least 100C.

I like PLA just for the simplicity.
Sure in the future i may need higher temp stuff but sheesh.
For starters PLA sticks to my kapton covered plexiglass print be with no issues.
No warping or need for a heated bed.
The smell of the heated plastics is not overwhelming, in fact its almost sweet.
And PLA is "green"
Biogeradable, made from renewable resources.
Pretty cool when i had someone a prototype and tell em they are holding a green product.
Just my 2cents
-E

PS i have not used ABS personally.
I plan to order some but have only been printing for less then a week.
That also means im no expert lol.
Happy printing

PLA is also generally cheaper. I started out printing in ABS but recently made the move to PLA and I couldn't be happier. ABS is so fiddly! Preventing it from curling or warping is an endless exercise in frustration. I also like PLA's more rigid feel as well, although there are sometimes when a part with some flex to it is called for. Finally, crazy bridges are possible when you print with PLA and direct a fan at the nozzle. The ridiculous 30mm bridge on [www.thingiverse.com] was no problem at all when I printed it yesterday. ABS would be practically impossible for that.

Odd, I have no problem with that bridge in ABS. PLA, on the other hand, has always drooped badly for me at 15mm. I haven't tried printing with a fan though.

tbfleming Wrote:
-------------------------------------------------------
> Odd, I have no problem with that bridge in ABS.
> PLA, on the other hand, has always drooped badly
> for me at 15mm. I haven't tried printing with a
> fan though.

PLA needs to be "stretched" as it is printed, i.e. the filament cross section should be smaller than your nozzle area. I have no problems printing bridges that big in PLA. Might try lowering the temperature slightly, and a fan will help.

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