Guide to printing PLA on a Solidoodle (Page 1 of 3)

Some notes from my experiences:

- 180ish depending on your hot end is good, but may vary from filament to filament. Experimentation is the key here.
- I have gotten PLA to stick to blue tape without heating or glass at ~120 degrees (yes higher than ABS temps). Either way I needed to turn the first layer speed down low to help it stick. Once I had a good stick the rest of the print was good.
- I changed no other slic3r settings besides this.
- I ran a fan over the print the whole time which seemed to work out well. Consensus is that PLA is runnier and needs the fan to stop it distorting, although it will suffer less from warping and shrinkage overall compared to ABS.

That will print fine in PLA, even without a fan.
Fan is needed for overhangs, bridging and fine detail work - PLA oozes so keeps 'moving' a little bit. This can be good on low surface detail prints though, as it hides the layers much better than ABS. plain models will print fine without it though...

I personally use 60oC bed with ceramic tile + hairspray the most often. Depending on the PLA, it could be 165°C through to 185°C.
Blue Painters works fine on a COLD bed.
Glass all by itself works, at 110°C (but you'll need an upgraded bed to get there reliably - and Borosillicate to stop it exploding)
Kapton + Acetone on the Alu Bed @ 65-70°C OR on a Sheet of Glass 65-70°C worked fine...

And just to cause issues - I'm experimenting with Sugar Water next day or so which over on RepRappers is supposed to work a treat as well...

If you find its a bit oozy, drop the temp 5°C.... I also have to have a BIG retraction value to reduce stringing and layer-change bulges...

Okay, so I made my first try, and it didn't work that well.

Extruder: I found I had to change this in Slic3r settings in like three places as well as Manual Control.  But what's the right temperature?  I understand that there's some room for it to vary from around 180, but how do I know when the temperature is right?  At 180 it looked too goopy so I tried 175, and it still seemed a little goopy, but when I got down to 170 I started getting the "cold extrusion prevented" and I couldn't find any way to change that limit, so I settled on 175.  But given my later results, maybe it needed to be goopier than it was?  I don't know what the right runniness level is.

Bed: I don't have blue painter's tape or ceramic, so I went with glass and hairspray.  It wasn't clear to me that people are saying you want a low temperature with tape/ceramic and a high one with glass, so I started at 65 as DesigerFred suggested, but it wouldn't even come close to sticking, so I cranked it up to 90.  That's what you'll see in the picture below.  Plenty of hairspray.  Basically ended up back at what I already use for ABS.

Slic3r: I set the first layer speed to 50% (it had been at 75%) but otherwise no changes apart from the temperature having to be changed in fifty thousand places.

Transition: I ran the extruder at 190 while I pushed through the remaining ABS and worked in the PLA, gradually cranking it down to 180.  That part worked fine.

Results: While the head ran across the glass it seemed like it would spit out a little bit and then trail a tiny thin line of filament, then spit out a bit more, and so on.  By the time it finished doing that 'warm-up lap' it does, it was laying down a modestly but not entirely consistent amount of filament.  Sometimes when it took a corner, the filament would follow it, dragging across the arc, so the lines weren't being formed right, since it wasn't sticking.  It also seemed that it wasn't consistently extruding a reasonable amount of filament, and this continued throughout the entire print -- if anything it got worse later.  I left it running anyway since it was a fairly short job, and this is what I ended up with:

All those lines are strands of filament left behind during some of the extruder movements.  One thing this picture doesn't reveal is that there's almost no third dimension here; this is all pretty nearly flat.  The original design is not particularly thick, admittedly, but it's supposed to have a raised edge, and there's no sign of it.  A lot of the time, while the head was zigzagging across the bed, I couldn't even tell if anything was coming out.

Conclusion: Either I need to run the bed way hotter than I normally run it for ABS (and I don't think I can get it to more than 97 with the stock heater and my plexiglas enclosure), or I need to try the painter's tape solution, once I can get some painter's tape.  Do I put the painter's tape on top of the glass, or in place of the kapton, or what?  (No matter what the answer is, I imagine I'll have to recalibrate Z to account for the glass's and tape's thickness.)

I'm still not sure how to know what the right extruder temperature is, other than to do a jillion failed prints at each number until one seems right, and even that only if by coincidence all other settings happen to be right.  It's the same problem I keep having as I learn this stuff.  I can look at a print like this and tell it didn't work, but I can't tell that the extruder temperature contributed, and if it did, whether that means it needs to be hotter or colder.  And there's a hundred other adjustments that could be made, and no idea which ones would do what to the outcome.  Without somewhere to start on what each thing does and what I'm trying to get to, this is like trying to crack a combination iteratively, only where each attempt takes 20 minutes and wastes filament.

I'm also wondering if there's a way to set that cold extrusion temperature limit.  What little I could find Googling that suggested that I can't.  Which seems really silly.

you can lower it permanently via Firmware (configuration.h) - but if you tend to alternate filaments, best to leave it using the gcode.

I'm printing PLA at 170 (M302 in GCode) and have been printing on glass (no hairspray) with the bed at 60.

As long as the glass is clean, it sticks without issue.

All glass is not equal, and thickness makes a big difference.

Have a read of http://hydraraptor.blogspot.com.au/2010 … glass.html

I'm just using some glass I got from an old picture frame. It's about 3mm thick.

heat the extruder, and pull it out with tweezers, after undoing the tension arm (the thing with the bearing).

I hate to say it - but I have dozens of PLA printed parts. I didn't find nearly half the hassle you've been reporting. And touch wood - despite doing regular swaps between ABS and PLA, haven't managed to clog myself.

So don't go hating on the PLA...

Yeah, I'm pretty sure I am pushing on the filament and it's not budging.

The process documented for removing and replacing the hot end is full of warnings not to do it casually as it's tricky, but when I watch the video here:
http://vimeo.com/55528973
It doesn't seem that hard to me, or over my head.  (Where most of the time when I see videos like this, they seem way harder than everyone describes them.)  Am I really underestimating how tricky that is?

I've pushed a sewing needle up there with a thimble, and it won't go in more than a tiny bit, but this has also caused a bit more PLA to ooze out.  Just a few drops.

Sounds like I have a hot end clog, not a cold clog, despite visible filament above the PEEK.

Guess I can't even try to solve this until I can get to someplace that sells guitar strings, then.  Strangely, none of my toolkits come standard with those.

I was using a sewing needle (since I have those) and got a bit of goop to ooze out for a few minutes, the nothing.  John advised me to keep working at it, even though the needle only went in 1mm or so, so I did, but nothing more came.  After a while, I think maybe the tip of the needle broke off inside, because now I can't even get it that far in.

I guess the idea is if even if a broken needle tip and the clog make it impossible to get a needle in at all, a guitar string somehow will get in and, slowly, break up the clog?  Not sure how that's going to work, but it seems I can't get any other ideas until I've exhausted that one, successfully or not, so I will just have to try to find a local source for guitar strings later in the week.

It's unclear to me whether removing the hot-end would actually help.  Would I be able to push on the clog from the top any better?  If not, probably wouldn't.  John has mostly been discouraging of that approach, anyway.