Monday, August 31, 2009


Polylactic Acid

It sounds nasty, but polylactic acid (PLA) is some pretty cool stuff. Up to this point I've been printing objects with ABS, but I've had recurring issues with warping, especially on larger objects (100mm or so). I've also started running my Reprap in my apartment again, until I can find a a new workshop out West; the smell of melting ABS hasn't been so popular with the other apartment dwellers. :)

I experimented with turkey bags and CPU fans to try and create a heated, sealed build envelope for ABS, but in the end it seemed more trouble than it was worth. Seeing Nophead, Vik and Adrian's results with PLA, I thought I'd give that a shot.

I'm glad I did! PLA is slightly more brittle than ABS once it's extruded, but that is more than made up for by it's almost complete lack of warping, the ease of part removal, and the lack of any bad smells. It gives off a faint odor of cotton candy when it's printing, which makes me think of Fraggles and Doozers, but so far I haven't started eating any of it.

Here's a shot of Adrian's pinch wheel extruder, printed out in tasty PLA. Even better, this stuff is more or less biodegradable, so if I don't end up building a pinch wheel extruder or recycling it, I can at least mulch it (slowly) in the garden. :)

Excellent print quality!
Thanks! It's hard to see in that photo, but the PLA objects turn out really nice. That one was plug and play - no post-processing with an exacto knife required!
that looks great! are you still in toronto, or out in british columbia these days? i'd like to try out PLA, and i'm wondering if you found a local source?

we're having pretty big problems with warping on large ABS objects, too. i tried using a hot-air rework station to blow fairly hot air on the work piece while it was being constructed, and while this helped a bit it was a lot of work, and there was still a great deal of warping.
I got that sample from Zach at Makerbot, and I had some sent from Vik in NZ as well, but I haven't tested it out yet. The shipping from NZ to Vancouver cost more than the filament, but it shouldn't be too bad from NYC to Toronto.

It may be worthwhile to order a large batch up to Canada eventually!

I'm cranking out parts again (4 Darwin corner brackets since last night!) , and this PLA is quite nice to use. I used to nearly break my Reprap getting the ABS parts off the bed with a chisel and a hammer, even though half of the part was often lifted due to warping. With PLA, a quick light tap on the corner with a chisel pops the part off immediately and cleanly. No rafts required either, which saves time and feedstock. Plus the lower temperatures are easier on the PTFE thermal break.
oh wow. what are you using for a build base, again?

we've been using double-sided tape on some dense cardboard and it works out pretty well, especially to make sure the raft adheres. unfortunately for some larger builds (we tried a ~80mm box), the object was peeling off the raft after only two or three layers...

that's great progress! you'll have another darwin printed out in no time :)
I've been using 1/4" acrylic; I was trying to go the brute force way of reducing ABS warping (stronger base with stronger adhesion), but it wasn't working out. I've even got 12 bolts holding down the acrylic, as otherwise it too would warp from the stress from the cooling ABS.
PLA really is the best build material, I think. I use nothing else.

For a build base for it Vik, the Bath RepRap Lab, and I use Scotch Blue Painter's Tape for multi surfaces #2090. It's cheap, easily changed, widely available, lasts for multiple builds, and adheres well to the PLA without making it too hard to remove.

We got our PLA in bulk from these guys:

in New Zealand. They do a first-rate extrusion job on it. The shipping makes it pretty expensive, but the more reprappers who order it and press for others to stock it, the cheaper it should become.
PS We're doing all the prints of Mendel on our Darwin using PLA, as is Vik. Keep watching the blogs...

That looks perfect.

Hopefully I'll have some PLA to play within a week or so.
I looked a around for suppliers of PLA in Auckland and New Zealand and couldn't find one.
I forgot to ask Vik when he spoke at RoboNZ if Imagin Plastics now have a continuous supply of it, as its not mentioned on their webpage.

Looking at the bits Vik had printed for me (Tamiya extruder), which were done with PLA, i'm not sure if Vik had the settings right when he printed it as some lengths of PLA hadn't stuck down to the previous layer.
On the whole the parts are good, some warpage, will compare them with ABS when my RepStrap is completed, whenever that will be
This is a ridiculous situation! We make all kinds of PLA in the States and we have adequate filament production capacity. The only obstacle to being able to get local PLA filament is that it is a nonstandard plastic for extrusion shops and they are unwilling in this economy to speculate on a new product line.

Anyhow, I've got a call in to Ashland in Dublin, Ohio who supply Natureworks PLA and have talked to Jim Waring at New Image in Canal Fulton, also in Ohio. If I have to buy him some bags to get an American supply going, so be it.
I should have been clearer in my earlier post but I did not want to get hopes up.

I have 50lbs PLA resins ordered and being shipped from Jamplast to be extruded into filament. I have been working on this for about a month. A lot of that time was back and forth with Ashland because they are so big (Had to set up account to get any answers, blah blah blah).

I chose to get 4032 because there was a ?shortage? of the 4042 for about a month according to the Ashland rep I talked to, and 4032 has identical extrusion specs but higher thermal tolerance.
So who's extruding it for you?

Per your suggestion on irc New Image is going to extrude it. I have talked to them several times and I think they are prepared for the run. They offered to do about 5 lbs, but there is a lot of setup time on their equipment, so in the best interest of everyone I went for 50lbs so they can recover their investment if extrusion goes well. Thanks for all your help. I think Wade is wanting some, but if you want a little to test also just email me. johnny +domain
I can definitely use 10-20 lbs or whatever you have available.
Johnny, newbie here....close to completion on assembly...would be interested in purchasing some PLA...let me know how we can put that together...I'm in Tampa, FL
I'm near Orlando, and would also be interested in 5lb-20lb.

Was looking for sources of PLA and came across this list of world-wide suppliers:

Haven't tried contacting any of those companies as I don't yet have a repstrap/rap machine, but it is a starting point for those looking for local sources of PLA.
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