MK3 PTFE Tube Pulling Out
Hello,
To give a little information I have 8 MK3 units each with over 150 days of printing. I really do love Prusa and the printers. For some reason I keep having this issue over and over again and was wondering if anyone had some insight on how I could refrain from having it in the future.
Over time it seems the PTFE tubing is lifting out from the hotend and not allowing my bondtech gears to properly grip the filament. The fix is I will take apart the extruder and replace the tubing with new. I have replaced each machines PTFE tubing at least twice at this point and am about to do it on two more units. The reason I replace it is because as the PTFE tubing gets pulled up it deforms the tubing and makes it unusable. A perfectly printing machine will now stop mid-print almost everytime because of this issue. Should I be replacing the black plastic piece on top also?
Any help would be appreciated...
Re: MK3 PTFE Tube Pulling Out
Sounds like you could use some of these...
https://www.thingiverse.com/thing:1276626
They lock the collet up preventing this from happening.
Re: MK3 PTFE Tube Pulling Out
yup, the clip is a must.
I have a Prusa,therefore I research.
Re: MK3 PTFE Tube Pulling Out
Is this something the two of you use?
I have never seen this before but it looks like the answer to my problem. I appreciate you sharing that. Printing 2 right now once I swap these out I wont have any real information on if it solves my issue since it seems to happen over the course of 60 days of printing. Definitely worth a shot though, anything to avoid having to take apart the extruder any more than necessary.
Re: MK3 PTFE Tube Pulling Out
I've used the official E3D collet clips on all of my printers since I built them. I have never had a PTFE tube shift. IMO this part should be fitted as standard on all v6 hotends, and I'm puzzled as to why Prusa do not fit them. They solve an issue and they cost pennies.
Re: MK3 PTFE Tube Pulling Out
Is this something the two of you use?
I have never seen this before but it looks like the answer to my problem. I appreciate you sharing that. Printing 2 right now once I swap these out I wont have any real information on if it solves my issue since it seems to happen over the course of 60 days of printing. Definitely worth a shot though, anything to avoid having to take apart the extruder any more than necessary.
Yes, I definitely use one. I too had the ptfe wander up slightly and start rubbing on my gears.
Make sure you also follow prusa's instructions to firmly push the PTFE tube down, and pull up on the collet while still pushing the tube down. THEN install the clip and you should be golden.
Re: MK3 PTFE Tube Pulling Out
I went ahead and did this last night on 4 of my machines. I was extremely impressed with the strength of the bondtech gears after doing this. It was so powerful that during the load filament feature it caused my extruder to hop a couple times during the start where it feeds quickly. Looks like not blocking the teeth of the gears with the PTFE tube was my problem on those units. Also I replaced the PTFE tubing put some mineral oil on the contact area of the gears and re-installed the filament sensor cap etc. to improve flow of the filament. Unfortunately on one machine I damaged the heater cables.
Another unit I have is still struggling to feed the filament. I am not sure what the issue is at this point its like the gears are not gripping the filament. If I pinch the filament with my fingers the motor and gears continue to spin without issue and the filament stops easily. I have done the following.
1. Measure filament diameter (incase it was too small)
2. Installed new PTFE liner and clip
3. Replaced the nozzle with a new one
4. Overtightened the idler temporarily to see if it resolved issue
Some thoughts I had were if I got mineral oil on the teeth of the gears maybe thats why its still slipping. Perhaps the PTFE tube liner is not all the way down or my heatbreak is too high up which is causing it to still interfere. I do love my MK3 but never had these issues with the old extruder design on the MK2. If I could have the frame and electronics of the MK3 but the extruder of the MK2 I would be a pretty happy camper.
https://manual.prusa3d.com/Guide/How+to+change+a+PTFE+tube+-+Original+Prusa+i3+MK3-MK2.5/761
Does anyone know if there is information on how much PTFE tube should be sticking out the top?
Going to try cleaning the gears first (cause its easiest) then I will pull apart the extruder and make sure the heatbreak is installed correctly and the liner but if you guys have any more insight of something I could do let me know.
Re: MK3 PTFE Tube Pulling Out
Easier than expected. The issue was completely un-related to all of the above on this particular printer. I had printed an extruder idler out of PLA in a pinch and forgotten about it. Looks like it needs to be PET-G or ABS as it warped and caused the gears to have a larger gap between them. Took the idler from the machine with the damaged heater cable and am printing a replacement now. Thankfully back to printing as this machine is one I have in an enclosure to print exotic filaments reliably and had some nylon parts I need to finish this weekend.
Re: MK3 PTFE Tube Pulling Out
Yup, PLA will warp under constant load.
Re: MK3 PTFE Tube Pulling Out
Here is a photo showing my worst tube and a new one.
