V4 Hot End and Flexible Filament

[Dave K]

I've used both NinjaFlex and PolyFlex in the V4 hot end, and with both filaments I've had problems with the flament getting wrapped around the extruder gear (see photo). It happens mostly when I'm feeding the filament into the hot end, but with NinjaFlex it has happened while printing as well, even after a good 20 minutes or so of printing. As long as I feed the filament slowly when loading it initially, it will snake through to the hot end OK. I didn't record my print speed with the NinjaFlex, but slowing it down might prevent it from kinking and getting wrapped around the gear. The PolyFlex hasn't done that once I've got it to feed into the hot end OK.

I'm just wondering if anyone else has had this happen to them (with v4 or other hot end), and if there's a solution I might have missed. My solution is, basically, just to slow down the speed at which I push it through the hot end when feeding and when printing.

FWIW, I do find PolyFlex easier to work with than NinjaFlex, so far, but I'm doing my first print with it tonight, so that's preliminary and I don't have settings dialed in yet.

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[jimc]

i have to ask...is the hole in the filament drive where the drive gear goes supposed to be so big and egged like that? thats nothing like the old one. the drive gear just fit into the hole on the old style. i am assuming the v4 is different? flexible filaments seem to print at about 20mm/sec so thats pretty darn slow. are your running your print speed around that?

[Dave K]

Yeah, that's an odd shape, but it's the same with with both extruder assemblies. The PolyFlex just finished. I printed at 40mm/sec (recommended 30-60mm/sec). When I printed the NinjaFlex, it was at about 33mm/sec, so maybe that was pushing it too fast. If I go down to 20mm/sec, I bet that would work without buckling and getting caught up in the gear.

I noticed the PolyFlex seems quite a bit stiffer than the Ninja, but that was at 50%. It feels very strong. Less rubbery than Ninja. I'll try another test part at 30% and see how much more flexible it is. I'll have to try hairspray or blue tape, maybe even glue stick. I did it on bare glass...a mistake...and it lifted up to the point where it almost detached from the glass entirely (40C bed).

[dryeti]

The same has happened to me when feeding PolyFlex into the V4 filament drive. My guess is also that it is a matter of speed. I wonder how it could happen to you during printing though? Did the filament break first or was it a sling of filament which was sucked into the gear?

[Dave K]

I'm doing the initial feed slowly now, and that has worked well. Before, I was hitting the +10 jog repeatedly (using S3D) and I think that was a bad idea. As far as the Ninja filament goes, I was probably trying to extrude too quickly and I bet that's what caused it to buckle and get wrapped around the gear during the print. I'm going to try a print with Ninjaflex this week, with slower print speed, and see how it goes. The PolyFlex turns out to be very easy to print. It is far less flexible than the NinjaFlex I have, which is downright rubbery, but I printed my test part at 25% infill this time, and its flexibility is just right for what I need. I used glue stick and raised the bed temp to 60C (might be overkill) and the filament stayed down this time, no lifting whatsoever.