I am currently planning to build a prusa mendel, and I wanted to know your opinions on which material is better to use.

I don't really have any specific criteria as far as strength, flexibility, etc goes. I simply want to know which material is the easiest to get good quality prints with. Also, how does the quality of the plastic affect print quality/difficulty? What are the best places to buy plastic from (I'm based in the US)

Thanks,

Justin.

In my opinion PLA is by far easier to get you working. With PLA you can do without a heated bed too (though you will get some warping). And with PLA you do not need to have a ventilation system in place.

Based on my limited experience here's a few things I've noticed.

ABS needs higher temperatures to get a good print quality. Those higher temps are going to wear down your printer faster.

PLA smells better, whether or not it's less toxic than ABS I don't know.

With PLA the filament is more brittle, breakable, prone to temperature issues. Here's an example. Every other print I would make with PLA would jam the extruder. It turns out that after the first print, the residual heat would deform the filament already in the extruder. Then when I started the second print this deformed filament would always catch in the extruder assembly. So now after every print I take out the filament and cut off the last 4 inches.

Maybe this is just my printer or my settings but the actual extrusion of ABS seems a little more well behaved. Extruding ABS is a little like squeezing toothpaste which hardens in about 3 seconds. PLA by contrast seems a bit gooier. It has to extrude constantly or else it might ooze a little. But this is probably a setting I have wrong.

ABS is supposedly tougher and more heat resistant.

I'd say focus on PLA just because the extra heat for ABS causes more problems.

Hope that helps.

I am not having any problems with PLA in my extruder/hotend: [reprap-fab.org]

I only have a few days of experience with ABS but I am glad I started with PLA, as I can see ABS is more difficult to work with.

I reckon PLA is harmless while ABS fumes are not: [forums.reprap.org]

I use PLA exclusively, mainly due to my printer being in the house and not wanting to have the ABS fumes in here. I have printed at least 20 sets of Prusa parts now in PLA with no problems at all apart from me breaking the last extruder by accident

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__________________________________________________________________________
Experimenting in 3D in New Zealand

I switched from PLA to ABS mainly because I had too many PLA-printed pieces go soft on me in various uses. I found ABS almost as easy to print with. And quality ABS (PP3DP's for example) is practically odorless when printing.

i've had nothing but issues with PLA. the idea that it doesn't require a heated bed is rubbish. it'll warp like crazy and sometimes not even stick well enough to complete a print (using blue painters tape as a surface). that said, each material has it's advantages and drawbacks.

i've never gotten a single ABS print to complete without *some* warping on the corners/bottom layer. i've gone all the way to 130c on the bed, using PET and Kapton.

with PLA, the problem is reversed. with the heat set to 90c on blue painters tape, the first layer will stick like crazy, no warping. in fact, it's quite hard to remove the print if you let the bed cool before removal. the downside is that i can't seem to get overhangs (slight ones, nothing crazy... like pink panther woman's butt cheeks) to print without curling up. i think well-aimed fan will solve that problem, but as far as "ease of use" is concerned, PLA has definitely given me the most headaches. it seems very "fiddly" and temperature seems to have a far greater effect than it does with ABS.

ABS prints overhangs perfectly, and overall print quality is much more consistent, but then you always have the warping issue.

i guess it depends on the application and how much warping/fiddling you are willing to deal with.

EDIT: as far as suppliers, you only need to talk to Ultimachine. top quality material and the customer service is second to none. you even get free color samples with every order! just recently they had mistakenly sent me PLA when i ordered ABS. two days later i had the ABS i ordered AND a free thermistor for the trouble. oh yeah, he didn't bother making me send back the PLA either, so i got two pounds for the price of one. I can't recommend shopping anywhere else when they offer products that good and service to match.

Edited 1 time(s). Last edit at 04/09/2012 05:50PM by PastaRocket848.

I started with ABS and found it extremely easy to get going, my first print was pretty decent and the quality quickly improved after that. I have found that there is barely any smell with the current batch of ABS I've been using. I switched over to PLA just today and found it extremely finicky as for as print quality. Any kind of temperature change completely changes the print quality.

PastaRocket848 Wrote:
-------------------------------------------------------
> i've never gotten a single ABS print to complete
> without *some* warping on the corners/bottom
> layer. i've gone all the way to 130c on the bed,
> using PET and Kapton.

Not a single one? That's odd, I have printed things like this: Y carriage with no curling up. 110C Kapton bed, 69 grams of plastic in the 120x190 mm object.

Well... even though that's a big object, something with a solid square base and sharp corners seems to want to lift a lot more. One 100x100mm object I printed, which accidentally had too many solid layers at the bottom, ripped the tape clean off the bed at the corners.

I rarely print PLA. In my experience if ABS smells strongly when you're printing you're either printing too hot, or you have poor quality ABS. I have a roll of blue 3mm from Makerbot that has no smell at all.

ttsalo Wrote:
-------------------------------------------------------
> PastaRocket848 Wrote:
> --------------------------------------------------
> -----
> > i've never gotten a single ABS print to
> complete
> > without *some* warping on the corners/bottom
> > layer. i've gone all the way to 130c on the
> bed,
> > using PET and Kapton.
>
> Not a single one? That's odd, I have printed
> things like this: Y carriage with no curling up.
> 110C Kapton bed, 69 grams of plastic in the
> 120x190 mm object.
>
> Well... even though that's a big object, something
> with a solid square base and sharp corners seems
> to want to lift a lot more. One 100x100mm object I
> printed, which accidentally had too many solid
> layers at the bottom, ripped the tape clean off
> the bed at the corners.

not a single one. and i've tried hundreds of times lol. very small parts don't lift at the corners, they just break off the bed full-stock and end up getting dragged around by the nozzle. does reducing the number of solid layers help with the curling?

so far i've tried:

- extrusion temps between 210-240c
- bed temps from 90-130c (maybe 140 i can't remember)
- first layer speeds down to a crawl (10mm/s minimum)
- first layer height from smashed down dragging the nozzle through the extrusion all the way up to where it was basically just laying down a round bead.
- PET
- Kapton
- ABS juice on glass

the only thing i havent changed is the filament supplier, though they're "known good" with others reporting great results, so who knows.
my next attempt is to re-level the bed and see if that has any effect, though it hasn't made much difference in the past so long as it isn't wildly off.

PastaRocket848 Wrote:
-------------------------------------------------------
> not a single one. and i've tried hundreds of
> times lol. very small parts don't lift at the
> corners, they just break off the bed full-stock
> and end up getting dragged around by the nozzle.
> does reducing the number of solid layers help with
> the curling?

The one time I printed a 100x100 mm square object with 8 solid layers (after that it continued with empty box shape), I got enormous pull at the corners. A lot more than with 3-4 solid layers and continuing with sparse infill. The speed matters too (and not just the first layer), I have had some hard to print slender pieces and they printed fine below a certain threshold, but going over it caused them to very soon curl up.

But it really sounds like you have some adhesion problems rather than curling problems. I'd try fresh tape with some ABS smeared onto it with acetone. My tape (both PET and Kapton) has couple of times just decided to lose the adhesion to the print no matter how I clean it (sometimes even on just some of the tape strips, so I suspect contamination with grease or something like that) but fresh tape and some scraps of ABS dissolved onto it with acetone has always helped. If that doesn't keep the prints in place, I don't know what will.

> so far i've tried:
>
> - extrusion temps between 210-240c
> ...

Maybe try going even hotter?

I print at 260C (I have found that the layers won't fuse really well at temperatures below it) and the first layer at about 30-40 mm/s. The Z height isn't even all that critical, the first effect of that being wrong is too sparse or too wide first layer, not the print detaching... too sparse doesn't stick as well but for most prints it isn't even an issue.

nigel_mck Wrote:
-------------------------------------------------------
> I started with ABS and found it extremely easy to
> get going, my first print was pretty decent and
> the quality quickly improved after that. I have
> found that there is barely any smell with the
> current batch of ABS I've been using. I switched
> over to PLA just today and found it extremely
> finicky as for as print quality. Any kind of
> temperature change completely changes the print
> quality.

I had pretty much the same experience, ABS was quite easy to use apart from warping issue, which I have now pretty much solved with heated bed. I have never needed a ventilation system.
PLA otoh also warps some without a heated bed, and had lot of extruder jams, plus stringy prints (which may be matter of tuning).
Cost wise there is nothing in it, so really I think it is 50/50. No harm in trying both and see which performs better with your setup.