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Switching from ABS to PLA
Posted: Fri Mar 15, 2013 1:32 pm
by jesse
I tried switching to PLA filament from ABS.
How can I clear the ABS out of the hot end without taking it apart?
Re: Switching from ABS to PLA
Posted: Fri Mar 15, 2013 1:48 pm
by mhackney
I remove the Bowden from the hot end. Clip the filament about 2" above where it enters. Then, heat up the hot end to 220°C. Then, start to push the filament through. When 5cm or so extends at the nozzle, give it a few seconds to cool. Then, grab it and the filament above the hot end and pull each in opposite directions quickly. I find this clears the orifice if you do it quick enough. You want the temp on the cool side, too hot and you have too large a melt zone.
Re: Switching from ABS to PLA
Posted: Fri Mar 15, 2013 3:38 pm
by geneb
I just feed it like normal until I see the new color and then drop the temp down and feed a few hundred mm through it as it cools.
g.
Re: Switching from ABS to PLA
Posted: Fri Mar 15, 2013 4:43 pm
by cassetti
geneb wrote:I just feed it like normal until I see the new color and then drop the temp down and feed a few hundred mm through it as it cools.
g.
Agreed - on my Makerbot Replicator I just keep feeding for a bit to clear out as much ABS as possible. I've never had an issue. Same story for my Ecksbot - preheat and extrude.
Re: Switching from ABS to PLA
Posted: Fri Mar 15, 2013 4:57 pm
by mhackney
Gentlemen, how does what you suggest work with a Bowden tube? You can't "push" one filament with another through a Bowden reliably.
Re: Switching from ABS to PLA
Posted: Fri Mar 15, 2013 5:30 pm
by Polygonhell
mhackney wrote:Gentlemen, how does what you suggest work with a Bowden tube? You can't "push" one filament with another through a Bowden reliably.
I do that all the time FWIW.
But the way I usually do this is heat up the hotend a bit below my usual ABS temperature (say 210-220), retract the existing plastic all the way out.
Feed in the PLA, run 200-300mm of plastic through then drop the temperature.
I'd be wary of continually connecting and disconnecting the quick disconnects on the bowden, I've had one fail.
Re: Switching from ABS to PLA
Posted: Fri Mar 15, 2013 6:33 pm
by cambo3d
hmm maybe i should get another add a struder kit set up just for pla, so could just swap hotends..?
Re: Switching from ABS to PLA
Posted: Sat Mar 16, 2013 1:51 pm
by jesse
Printing in PLA has been frustrating.
It melts too soon and stays hot too long.
Re: Switching from ABS to PLA
Posted: Sat Mar 16, 2013 9:31 pm
by Polygonhell
jesse wrote:Printing in PLA has been frustrating.
It melts too soon and stays hot too long.
Yes if you have a heated bed in general ABS is a lot less hassle IMO, the advantage of PLA is you can print lower layer heights because of the reduced viscosity and it warps considerably less.
You really need active cooling to print PLA effectively, get the print temperature as low as you can then blow a lot of air at it.