Having trouble unloading filament
I'm having trouble unloading filament after a print. I run through the normal unloading process and the filament makes it all the way past the bondtech gears, so it is almost fully removed. But then I have trouble pulling it out. When I do get it out, sometimes by pulling hard and once by partially disassembling the extruder (steps 2-5 on this page), it looks like the end of the filament has been flattened. I've attached a picture. Sorry for the bad focus, but I think it gets the idea across.
I think the problem is that when the end is flattened, the filament won't go through the last hole on the top of the extruder.
The printer is working beautifully otherwise and this is a new problem cropping up after about 140 total hours of printing.
Any thoughts on what would cause the filament to get flattened like this?
RE: Having trouble unloading filament
Not sure what’s causing the filament end to flatten but this should be fairly easy to fix.
When the filament gets jammed you should be able to open the idler pulley door, pull the filament out using a pair of needle nose pliers, and clip off the flattened end with a pair of flush cutters. This is much easier than removing the hotend.
For a more permanent solution, remove the single Allen head screw that holds the FS cover in place and remove it from the printer. Using a piece of the flattened filament end as a guide, match up a slightly oversized drill bit and drill out the filament feed hole in the cover. Test that the flattened filament end fits through the oversized hole and reinstall the cover.
See Steps 35 through 38 in this link for reference:
https://help.prusa3d.com/guide/5-e-axis-assembly_169235
That should do it.
Cheers
The flat head may be a distraction. The blob at the end may be distorted by the repeated tugging.
Big end-blobs are often caused by incorrectly inserted PTFE tubes in the hotend, usually this shows up soon after assembly but perhaps your collet has slipped.
You can also damage the PTFE if the filament path is not quite straight.
Cheerio,
RE: Having trouble unloading filament
I decided to change the PTFE tube. The one I removed was slightly swollen at the top and the hole was a bit larger than in the new one. It otherwise looked like the new one. I swapped them out and then ran a first layer calibration and everything looked good. The filament came out just fine, which is a good sign, although I suppose I'll have to make multiple prints before I'm sure the problem has been solved.
RE:
As I noted above, I changed the PTFE tube. But I had the same problem again today. I didn't pull hard to get the filament out and I got better pictures (attached). To remove the filament, I pushed the filament back down a bit and clipped it with a wire cutter. Then it came out just fine. It is that flattened end that prevents it from coming all the way out.
Here's one theory - Maybe the idler screw is holding the door too tight and the the filament is still soft when it hits the bontech pulleys such that they flatten the filament. I notice sometimes when I remove the filament that the bondtech gears have left some teeth marks on the filament.
Does that make sense? Any other thoughts?
RE: Having trouble unloading filament
I would definitely run the idler screw a bit looser. You’ve got some pretty deep teeth marks in the unloaded filament. It’s possible that the still soft end is getting squeezed by the gears as it runs through, as you have suggested.
Cheers