What to do after a print

I just built a prusa I3. I couldn't get the original head to feed correctly so I installed a V6 with bowden and it works fine EXCEPT...

After a successful print the machine cools down and when I try another print it won't extrude. I started pulling the filament out to see why it would not feed and when I take the filament out and check the nozzle it is always jammed up and there is usually a piece of filament broken off in the nozzle. I have been careful to not pull out the filament unless the head was above 180 so I don't understand how there could be an unmelted piece of PLA in the nozzle but everytime there it is.

What do you guys do after a print to keep the nozzle clear and to be ready for the next print? Should I pull the filament out at the end of each print? Pull when the nozzle is still 180+ or wait until it's cooler?

I think I am pretty close to being able to print at will but this has me really confused.

Thanks in advance for any help.

Jeff

This is normal for most 3D printers - the filament will solidify in the nozzle, slightly fatter than the approach duct, and won't be able to back out once the extruder cools down. The extruder is then effectively "pre-primed" ready to go when you start the next job.

If you want to be able to change filament after every print job, you should fully retract the filament while the printer is still hot (50 mm retraction, say), which you can do manually as soon as printing has finished. Alternatively, you can insert the appropriate G-Code into your Slicer settings for the end of each print job - but you will need to load new filament and "prime' the extruder before starting the next print job.

---

Follow my Mendel Prusa build here: [julianh72.blogspot.com]

Hi guys,

I agree with wost that you say julianh72.
I'm not sure Jeff wants to change filament often.

I believe you're printing out of PLA Jeff, am I right ?
Some cheap filaments gets brittle after to have been heated once.
The eSun PLA is known for that.
Until you buy quality filament, you can let the hotend cool until 90°C then plull gently the filament out of the hotend.
This way, it won't make thin wires that will cause issues later.
And you can break-out the brittle part.
Anytime you want to change filament, you want to proceed @ 90°C.

Sometimes full metal hotends knows that jamming issue.
It's because of a machining issue of the heatbreak part : the hole is not smooth enough.
You can find videos on youtube about how to polish it with a drill and some metal polish.

You can buy a heatbreak with a PTFE tubing inside too. It will solves all your actual problems.
But if you want to print materials that needs an extrusion temperature over 245°C,
you must go back to your original full metal heatbreak.

++JM

You guys are great. julianh72 answered my next question first and J-Max answered the original questions. Guess what? I am using eSun PLA so pretty darn accurate on that suggestion.

OK so for now I will order some better grade PLA but I will keep running what I have. At the end of every job I will pull out the filament before it cools down, cut off the more brittle end and reprime when I start the next job. If I want to change colors then it's easy because the filament is already out.

What is your favorite brand of PLA?

I'm 51 and about as excited about this as anything in a long time. You guys just made it easier and better.

Thanks!
Jeff

Hi guys,

My favorite : Dutch (Real) PLA from reprapworld.com.
Their ABS is a bit soft but don't warp easily. Good brand.
Their red PLA is so gorgious !

++JM