Unable to unload  

RE: Unable to unload

Posted by: @mikebuto

Help!

After pulling the nozzle and trying to insert it properly, now I can't unload filament. When you press the button, it just rattles. I haven't moved the hotend much, and I think it's sitting right, but something is obviously wrong.

Mike

Pulling the nozzle (pulling on the thread)? Move the hotend?

Would you explain in more detail what you have done and upload some pictures?

RE: Unable to unload

@karl-herbert

Pulling nozzle - removed the nozzle to change it to a smaller diameter. Changed my mind and put nozzle back. However, I was getting some excess dark blobs on my print. Looks like filament was leaking after the nozzle was replaced. So trying to move the hotend (as per Prusa nozzle change video) and adjust nozzle is what I've done. However this is what I get now when I try and unload filament.

hot-end-prob

RE: Unable to unload

@mikebuto

Here is a schematic representation of the E3D hotend. There should be about 0.5mm gap between the hexagon of the nozzle and the heating block and the nozzle collar must seal 100% at the heatbreak.

RE: Unable to unload

Useful and cool.

Questions:

1) Since a gap tool isn't normally referenced, I just look at my caliper to see what 0.5mm looks like and go from there. The printer has been running fine until I started monkeying with the nozzle.

2) How is the nozzle collar seal managed? The Prusa nozzle change video cautions about over-tightening.

3) What have I likely done to produce the noise in the video? How to fix this?

4) Is there anything specific about rotating the hot end back and forth while dealing with the nozzle?

RE: Unable to unload

https://e3d-online.dozuki.com/Guide/Changing+Nozzles/45

https://wiki.e3d-online.com/E3D-v6_Assembly

The nozzle is in intimate contact with the heat break, and that contact forms the seal.  The aluminum heater block is just a carrier for the two threaded parts that mate and seal. If the nozzle is bottomed out in the heater block (hex in contact with the aluminum) you've set the heat break too high.

RE: Unable to unload

RE: Unable to unload

Still do not understand how I went from a working printer to one producing the noise in the video and not allowing me to unload filament. In other words, what is it about an improperly installed nozzle that would cause my current problem?

RE: Unable to unload

Melted plastic gets in places it isn't supposed to get into. 

In really bad cases, melt gets into the PTFE/heat sink / heat break gap (3).  Requires a full disassembly to correct. Or, if the nozzle/heat break seal is left too wide, then the heater can't melt all of the plastic in that zone - again, disassembly, or raise the temp and hope it melts enough. to allow a manual removal from above.

RE: Unable to unload

I'm guessing that. So how to fix? Dis-assembly? If so, how to clear out plastic that needs to be hot when you've taken things apart?

RE: Unable to unload

ps: Karl's image is of a 3 mm Bowden version of the V6, it isn't what the 1.75 mm direct version looks like. My image is correct for the Prusa Mk3/s.

RE: Unable to unload

Once the hot end is out of the extruder, it can still be connected and heated up. Also, heat guns can be useful for parts you've taken off.  In many cases, removing the nozzle and heating allows you to clear of of the jams (push down from the top with a 14 or 16 awg copper wire - same diameter as the filament). Also, removing the PTFE collet and PTFE tube sometimes is enough to free up jams that happen above the nozzle and in the heat break.

RE: Unable to unload

I'm puzzled by the references to E3D documentation. Would I just not reverse the Prusa E-axis assembly document that I used to assemble my printer?

RE: Unable to unload

This looks to be what I need

https://help.prusa3d.com/en/guide/how-to-replace-a-ptfe-tube-mk3s-mk2-5s-mmu2s_21664/

RE: Unable to unload

The hot end is manufactured by E3D ... they are the experts on it.