Filament not extruding.
I've had my printer now for a year, and have been perfectly happy with it. However today something occurred which I have no clue how to resolve short of completely dismantling the hotend and extruder assembly.
This morning I switched the filament on. Swapped the colour successfully (as always) and started a print. I've printed this object many times in the past without incident. Half way through the print there is a colour change. The head goes back to the corner, it beeps at me to extract the current colour. I click the button and remove it. It says insert filament, and I do. It grabs it and starts feeding it down, then it starts clicking and completely fails to extrude anything. After a few rounds of filament not extruded, I have to abandon the print.
Any now there is nothing that I can do. I can eject and re-load as many times as I want, but nothing comes out. I've tried using the needle to jab up the inside of the hotend and that goes all the way in quite happily. Brings out some of the previous colour but it does come out quite happily. Whilst measuring the amount of filament that goes in from the top, and the distance the needle goes in from the bottom it would seem that there is an overlap of about 3-4mm. So I'm not understanding why the thing won't extrude. It doesn't appear to be blocked.
So just some extra details; MK3S. 0.4mm nozzle. I only ever print PLA. Have never tried any other filament. It's been perfectly OK up until now. Hotend gets fully hot.
I've tried a cold pull (releasing the gear tension and pulling the filament out whilst cold), and that seems perfectly OK. Though the end doesn't appear melted, so I don't think it reaches the melt zone.
Short of completely stripping the extruder assembly, is there anything else I could try?
Is this an issue with the PTFE tube? Could it have got blocked in someway? Is there some other way to test it? Hoping the more learned members can help me out on this.
Tighten your filament tension screw.
Sounds like your filament tension screw is not properly tightened. That's what is the main cause of "it's clicking"
Not the screw
Hi Dan, thanks for the reply. No, it's not the tension screw. I think there is something down in the melt zone thats blocking it. Which is why I asked about the PTFE tube.
Looks like I'll have to remove and replace the tube, which means breaking down the extruder assembly completely. I was hoping for a quick fix to this, but I guess thats not on the cards.
One more thing to check
Open the extruder access door, and look at the bondtech gears - the little bits that grab the filament. Are they clean and shiny? Or are they clogged with bits of filament. That's another issue often overlooked.
If you have to break down the hot end, don't fret. It's about a 15 minute job if you are confident and know the minimum screws to take out. 30 minutes round trip.
Solved!
OK, I'm going to update this thread as I have now resolved this issue on the advice of one of the forum members. They sent me a direct message as to something that I should look into and they were spot on. Not sure why they didn't want to be known as being the helpful person they were, but I will respect their privacy and just give the details on their resolution.
Before you take your hot end apart, try this simple "cure".
1) remove your nozzle
2) let hot end cool to eliminate chance of burning yourself (experience)
3) from the bottom insert the long end of a 1.5mm hex key, or 1.5 mm brass rod and push up. there should be a sudden release and the key will go all the way in.
4) take a length of filament that will reach he top of the ptfe tube and insert it up from the bottom as far as it will go and you should see a small blob of filament come out of the ptfe tube.
In my case the a small molten blob came off the tip while unloading and got stuck in the cold zone. That is why a newly loaded filament doesn't show signs of melting. It never gets to the hot zone.I had unloaded this roll of filament dozens of times, but this once...
re-install nozzle, verify your Z height is correct and happy printing
This was indeed the necessary fix to get things going again. It seems that the ejection of the filament during the change had caused a melted blob to move back up the tube into the cold zone and solidify, thereby blocking the PTFE tube enough that it wouldn't allow the full width of the filament to go down.
Removing the nozzle was easy enough (once I managed to get hold of a 7mm socket) but clearing the jam was a bit fraught. I thought that the advice was wrong as it just didn't want to move, but they it suddenly released and the feed tube was clear enough to put filament through from both ends. I re-attached the nozzle, ran through the calibration again and it's printing away even as I type.
So, take aways from this? It is possible to eject the filament and pull it out too fast so that a melted portion can be dragged back up the tube. Keep an eye on how forcefully you pull out the filament on a change.
So a big thank you to my adviser.