Hotend blocked  

RE: Hotend blocked

I have the same problem regularly. I described it here: https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-hardware-firmware-and-software-help/piece-of-filament-stuck-in-the-ptfe-tube/#post-567814

I now know it is not the PTFE tube, because I replaced it. I also know it is not the nozzle, because I replaced the nozzle (with a NozzleX). None of this changed the symptoms.

Sometimes (not always), removing filament will fail. Pulling it out by force might succeed, but there will be a blockage, which I can sometimes push through by loading another filament, sometimes using the needle from the other side, sometimes having to remove the PTFE tube if there is a piece stuck inside.

This is getting frustrating — I've spent some time with online chat support with no conclusions. I don't want to stress about whether I will be able to remove filament or not.

This is what the end of the filament looks like, when I was able to pull it out. I don't think it should look like that.

RE: Hotend blocked

In neither thread do you tell us which PLA you use.  Based on what you tell us, it sounds like either you're not using a high enough hot end temperature, or your PLA is brittle, maybe it's old, and it breaks due to that brittleness.

Cheers

-Bob

RE: Hotend blocked

Bob: these blockages happen with Prusament PLA, newly unpacked from the sealed bags. The hot end temperatures are from the PrusaSlicer "Prusament PLA" preset.

RE: Hotend blocked

Have you confirmed that your hot end is actually getting to the correct temperature?  Maybe your thermistor is reporting incorrectly?

Regards

-Bob

RE: Hotend blocked

In the meantime the thermistor managed to fail (well, the cable to be specific) and I replaced the thermistor as well. So unless two thermistors were reporting similarly incorrect temperatures, that is not the problem either.

And just to be clear, the prints that come off the printer are perfect.

RE: Hotend blocked

“New” from the bag does not mean that it is new or dry.

Posted by: @jwr

Bob: these blockages happen with Prusament PLA, newly unpacked from the sealed bags. The hot end temperatures are from the PrusaSlicer "Prusament PLA" preset.

RE: Hotend blocked

An easy basic check is to make sure that the Bondtech gears line up well with the filament path.  To do this, unload the filament, then open the idler door by unscrewing the tension bolt until the door can be flipped open.  Place a small allen wrench or other straight rod of about the same diameter as filament in the filament feed.... the groove in the motor gear should line up exactly with the filament path.  While it is open, check the idler gear for free movement.

If the groove does not line up, loosen the setscrews and slide the motor gear until it does. The idler side will move on its own as necessary to match. Make sure the setscrews are tight when finished, even if you don't have to move the gear.

If the Bodntech gears are not well aligned, the filament has to follow a curved path when it should be straight. This can cause all sorts of jamming and even overheat the extruder motor.

Good luck!

RE: Hotend blocked

I guess I have nothing to offer.  Good luck figuring this out.

Regards

-Bob

RE: Hotend blocked

New thread (prusa 1ste time and 2 arianeplast) Hot end temperature from prusaslicer and just checked the bondtech gears and they line up. Printer is 5 months old. I get the feeling that there might be a construction fault with de gears. I can't remove the thread it's completely stuck, but the hotend is clear (high temperature don't work to get the thread out), thermistor is ok! Last time I had to remove the PTFE tube, the thread was stuck halfway through and I replaced it with a new one (7 weeks ago). So any ideas why this is happening, I really don’t like to open up the extruder every 7 weeks. Thanks Heleen

RE: Hotend blocked

You might have heat creep so you might need to lower the print temperature a little.  I would replace the PTFE tubing and try 5-10 degrees lower to see if it reoccurs.  

Can you start another print with the same filament or is it stuck going both ways?

Cheerio,

RE: Hotend blocked

It's stuck both ways

RE: Hotend blocked

I already lowered the temp to 210, need I go lower. And the PTFE Tube is new.

RE: Hotend blocked

Are you printing in an enclosure?

RE: Hotend blocked

No

RE: Hotend blocked

Can I ask, when you unload the filament, is this immediately/not long after printing or is this much later when every thing has cooled down and you are reheating the printer to change filament ?

RE: Hotend blocked

Can I ask, when you unload the filament, is this immediately/not long after printing or is this much later when every thing has cooled down and you are reheating the printer to change filament

I am not the OP, but in my case, I tried unloading both immediately, and after a while. No difference. It just sometimes gets stuck.

RE: Hotend blocked

The first time was de next morning, this time just ather printing a piece

Two thoughts:

To remove stuck filament try raising the temperature20 or 30 degrees above printing temperature and then unload, load the new immediately and flush extra through as you drop to printing temperature.

Are you either: switching off the printer as soon as the print finishes so stopping the fan cooling prematurely.

OR leaving the nozzle on preheat for longish periods so baking filament inside the hotend ... ?