Unresolved Tips for swapping between ABS and PLA? Extruder nozzle clogging.

I'd used the whole roll of blue PLA that came with the printer with pretty good success, then started using some other PLA that I bought from Fry's with no trouble. Since I was having some pretty good results, I started using some black ABS to make some prints.

The prints came out great with the ABS, too, but I wanted to make something that wasn't black, so I swapped back to the PLA. I was able to print several small objects without any trouble, then I started having failures halfway through some larger prints last night.

The printer would stop extruding for a couple of layers, then start up again. I raised the extruder and extruded some filament, and it was coming out very thin and curly. I tried to dislodge any debris with a thin guitar string from the bottom, but it wasn't doing the job. It would come out fine for a few millimeters, then go skinny and curly again. I tried some ABS just to see what happened, and after a bit of skinny extrusion, it started to come out more or less the right way, with just the slightest bend when exiting the nozzle - much better than the PLA.

I happened to buy a new hex head (from someone's eBay link in another thread) last week, and as luck would have it, the new hot end arrived this morning. I was going to completely replace the whole thing, but decided to take the nozzle off and see what it looked like.

When I removed it, there appeared to be a ring of black ABS around the interior of the nozzle, with a much thinner center of PLA. I'm pretty convinced that the ABS wasn't completely extruded and hardened around the inside of the nozzle, and was only allowing a thin stream of PLA to make it through. I assume that it is probably my fault, and this can be prevented if I know what I'm doing wrong and start doing it the right way.

Instead of cleaning the nozzle right away, I just replaced it with the new one, then ran some canola on the new filament to season the extruder. When I fired it up again, the PLA was being extruded properly again.

I used a torch to burn out the ABS from the original nozzle, then cleaned it with the guitar string until the hole looked round when held up to a light.

When changing from ABS to PLA, I left the extruder temp at 230, which is what I was using to print the ABS. I swapped the filament, then ran it until it looked like there wasn't anymore ABS coming out. Is there something else I should be doing to make sure that all of the ABS is extruded?

 

Ok, I'll give that a shot next time.

I ended up needing to swap the entire hot end, after all. When I changed the nozzle, I didn't know about needing to heat it up before tightening it all the way, and I also inadvertent loosened the threads between the heater block and the heat sink.

I had tons of PLA leaking out, but I was halfway through a big print before I noticed and decided to let it try to finish, goops and all. About ten layers left to finish, and the heating element crapped out. The heating element and thermistor wires were covered in burnt PLA, so I think it must have carbonized and allowed the current to follow another path.

It works fine with the new hex hot end (with the original, cleaned out extruder) and I made sure that everything was tightened up before printing. I ran it for a couple of hours and don't see any leaks, so I guess it's good now. I cleaned up the dirty heater block and nozzle, but I think the heating element and thermistor are toast - at least enough that I don't want to bother wasting any time on them. I didn't have any filament jam, so I think the metal parts are probably okay.

I can really see why a lot of folks get frustrated with these printers, because they seem to want a great deal of TLC, and I haven't found a good place where all of the common problems are compiled together. Lots of research to even figure out what the symptoms even are...

On the bright side, my latest prints have been the best yet. I printed out the Robo3D calibration box, and it came out absolutely perfect. Every side was smooth, every corner sharp. I'm keeping it as both a trophy and as a reminder that even when the printer starts acting up, if I take my time and work with it, I can make it right.

 

Hey.. I'm the one you bought the hotend from... glad to hear it arrived okay and fixed the problem. The reason I have them is because I had the same issue you ran into! Accidentally stripped the heater block when trying to reassemble... it's easy to do.

so... make sure you keep it tightened (while hot) from now on! That's what I am doing, and it has been working great. Also, if you get a jam, you can remove the silicone boot and wired components, and can bake the whole think in the oven (at whatever temp needed to melt your material -- I did 420 for PLA) and that might help you clear another jam if it happens in the future...

 

Also... make sure that heat sink fan is positioned well and always running! If it falls off or dies, you could get a jam.. (I think that's one of the things that happened to me)

 

https://docs.google.com/document/d/1fryBbKG8rpOCfsWk3UbcJzHEItqHU0iFY7uVRF3sFx0/edit?usp=sharing

 

I tried looking for Robo 3D R1 FAQ on Wiki and could not find it, do you have a link to it
Thanks

 

For switching between filaments I suggest using a cleaning filament like nylon. Preferably a few cold pulls to pull any gunk out.