Filament blob below Bondtech gear (request for comments)
I would like to hear from others about their experience with filament problems, specifically just below the Bondtech drive gears and above the PTFE (Teflon) tube that extends out of the hotend.
I have had two threeblobs of filament accumulate there. The first lead to my having to disassemble my hotend and replace the PTFE tube as it was incurably blocked. I have had my printer back together for a week and just had another filament blob this weekend. Both happened with the Prusa PLA filament supplied with my printer kit, so I have taken that out of use and am only using PLA filament from other suppliers. Not saying their filament is the problem, I only know that both happened with that filament. Edited tonight as I have another blob with Matterhackers PLA
To help if this happens to you, here is my procedure on removing the blobs:
1) Open the idler pulley cover by releasing the two screws from the opposite side (screws are on the hotend cooling fan side of extruder assembly). Be careful of the small square insert nuts as they like to fall out.
2) Examine the filament below the Bondtech drive gear that is on the shaft of the extruder motor. Here's a photo of my recent blob.
3) Remove the idler pulley cover by releasing the screw on the backside (opposite the cooling fan). BE CAREFUL to catch the small white washers that are used as spacers on this screw and the cover. Set this aside.
4) Optional: Remove the cover above the filament sensor that guides the filament past the sensor. I needed to remove it as the end of the filament had spread and would not pass back through the small PTFE tubing in the cover.
5) If you haven't already broken the filament or cut it, do so with a small pair of cutters. My filament broke when I attempted to unload the filament.
6) Preheat the extruder to the appropriate temp for your filament.
7) Using a small pair of pliers, such as a needle nose set, grasp the filament blob firmly and pull it out of the PTFE tubing.
8) Reassemble your extruder and reload new filament.
9) Continue on and print.
Re: Filament blob below Bondtech gear (request for comments)
Seems like one of three things must be happening:
1. The heat break isn't working, or
2. The extrusion stepper motor is gecoming so hot that it's melting the filament as it runs through the extruder gears, or
3. Your fan is facing the wrong direction.
Re: Filament blob below Bondtech gear (request for comments)
I had this blob thing under the bond tech gears the other day. After 1500 hrs of printing it's only happened once.
Re: Filament blob below Bondtech gear (request for comments)
Seems like one of three things must be happening:
1. The heat break isn't working, or
2. The extrusion stepper motor is gecoming so hot that it's melting the filament as it runs through the extruder gears, or I agree with this theory
3. Your fan is facing the wrong direction. double checked the fan both times I have assembled it
Re: Filament blob below Bondtech gear (request for comments)
A couple of other less likely causes to think about:
Do you have ridiculous retraction settings going on? Are you printing a gcode file that was generated for a different kind of printer with a bowden tube? Too much retraction could bring melted plastic up to the gear area.
What's the tension on the extruder idler? The screw heads are supposed to be more or less flush with the body of the extruder. Too tight or too loose could be shredding the filament. I see from your photos that there's a very pronounced gear imprint on the filament you're retrieving from the hotend. Is your tension too tight? Too much idler tension could also make the extruder motor have to work harder, increasing heat.
Re: Filament blob below Bondtech gear (request for comments)
The same occurred to me with the silver PLA the mk3 shipped with. Has only occurred once, but had I taken a photo it would have looked identical. If it occurs again I'll gather more details. I was not on the latest firmware at the time.