Is it OK to switch from ABS to PLA?

So I have always used ABS and my machine has a Budaschnozzle. Today with an order of ABS from Ultimachine they game me a few sample pieces of PLA.

Is it a bad thing to switch over? Will I just clog up the hotend?

If I can switch back and forth, are there any precautions to take (besides lowering the temp)?

Or is it just a bad idea to run both in the same nozzle?


Thanks!

there are different thoughts on this.
below is what i do, and what i would recommend. others may have different solutions. some people are lucky and just start switching and hope for the best, usually those are people who still do rafts.

it takes bout 1 meter of each material to clear the nozzle and hot end of each material. normally with 0.5mm nozzle minimal clogging. pla clogs at high temp. abs just becomes more runny. pla is a liquid that crystallizes at high temps (bad for clogging). abs really never becomes a liquid, it is in a glass transition state constantly.

before starting either procedure and after nozzle heats up, place a small wire, or drill bit inside the nozzle to clear it and make sure built up is removed. be careful here because if it is clogs the back pressure will release, and you will get some on your fingers. be prepared, use gloves.

so ideally if switching from abs to pla. use a meter of pla. at a low extrusion speed, place PLA into hot end, with a temp no lower than 215, and no higher than 220 , extrude a meter of PLA as it flows lower temp gradually to 190. make sure 1 meter has gone thru then lower temp to wherever you run your pla at.


if switching to abs, raise temp to 220, start running abs thru at half speed of pla as it swells. after about 1/2 meter raise temp to 230, then finish extruding the meter of abs. then set temp for whatever temp you use your abs at.

the issue with clogging happens when pla is mixed with abs, and crystallizes at the high temp abs runs at and pla clogs it
or with pla when it is at a temp that is too low for abs to flow, and abs clogs it

IMHO, this is what i do when switching between each. but with constant running of pla and abs, i just use separate printers and try not to switch.

Thanks for the info. Because I have a budaschnozzle I can actually remove the tip so it's fully open at 3mm diameter. This should make it easier to clear out the old material since it does not have to go through the nozzle.

With a Jhead I can heat ABS to 150C or PLA to 80C and pull the filament out in one piece leaving no residue to be flushed.

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[www.hydraraptor.blogspot.com]

I have followed nopheads' recommendation with great success - so much so that when I pull the filament out the 0.5mm plug comes out as well.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

If you can get it to work that way, it is a great way to get a visual on the internal structure of the hotend. Like if there was a bulge where the insulator meets the heatblock.

@nophead

Is this possible with a makergear hotend?

-Nick

I don't have a Makergear hot end so I don't know.

It doesn't work on a hot end I made myself. My guess would be because it has a longer brass section after the end of the PTFE. In that respect it is like a Makergear. I.e. the brass barrel screws into the PTFE which is inside the PEEK.

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[www.hydraraptor.blogspot.com]

Wow. I just did that... It worked great.
Im using a 1.75mm makergear with .25mm nozzle.
A bit was left behind, but WAY more effective that pushing it through.

thanks

-Nick

Lol, that's funny. I have used that method to pull crud out if all-metal hotends

These polymers can be and have even been mixed at different ratios. there is NO reason you can't use them interchangably, without problems, and i do it all the time. Just extrude 100 mm of filament to be sure you are printing the new material, as using white pla chased with black ABS would suggest is needed for clearing, though it isnt essential. It does make sense to purge ABS as fast as possible since PLA runs at lower temps.