Switching from pla to abs and back

[Schnupp]

Does anyone do anything special when they switch between filaments?
I usually heat the extruder up about half way and pull out the filament by hand. This seems to bring out most or all of the filament I'm using. However I've been having consistent jamming with my three pla filaments. I suspect there is some abs in the hot end but I've extruded pla at abs temps in hopes of removing any unwanted abs still lurking. Any ideas?

[voodoo28]

Why would you only heat it up half way?

Does anyone do anything special when they switch between filaments?
I usually heat the extruder up about half way and pull out the filament by hand. This seems to bring out most or all of the filament I'm using. However I've been having consistent jamming with my three pla filaments. I suspect there is some abs in the hot end but I've extruded pla at abs temps in hopes of removing any unwanted abs still lurking. Any ideas?

[Schnupp]

When I pull it out fully heated it leaves a lot of filament in the extruder near the heated nozzle end. Having it a bit lower than its melting temp allows for it all to stick together and be removed as one solid piece

[PyramidDave]

I always heat mine up to the temp that I print with that plastic & retract 50mm, then pull it out by hand. After putting the new plastic in, I extrude 5mm at a time until it looks like the new color. It usually only takes 10mm. 50mm is probably more than I need to retract, but it has been working well.

[voodoo28]

its called purging....you must run the new filament to clear the old one

When I pull it out fully heated it leaves a lot of filament in the extruder near the heated nozzle end. Having it a bit lower than its melting temp allows for it all to stick together and be removed as one solid piece

[Schnupp]

Yeah I know what purging is... I was just curious if anyone did anything special when swapping filaments

[voodoo28]

Nope..just load the new filament, while at full temp and keep turning the gear until the filament is extruding in a straight drip...if it curls while extruding its still not clear in the nozzle.

[Schnupp]

Figured out my jamming problem. My part cooling fan was blowing air over a part of the heated extruder tip and this caused the jamming. Looks like I'll have to model up a better fan shroud now. Hopefully someone out there can learn from my mistake

[voodoo28]

have a look on thingiverse MakerFarm Group..lots of mods.

http://www.thingiverse.com/groups/makerfarm-i3v/things