I’m wondering if the small gap between the filament drive gear and the top of the head mount is too much open space for NinjaFlex?
It could be. I’ve tried a couple times to print ninjaflex, but without success so far. The first time, it buckled between the drive gear and the inlet to the extruder body. Slowing down and heating up more seemed to help. I actually drilled the extruder body out to 4mm and inserted a piece of PTFE tubing (2mm ID, 4mm OD) that I extended as close to the drive gear as I could to see if that would help. It did help with the buckling, but I still got very poor extrusion (not enough material) and I haven’t gotten back to it yet.
I just tried with some Sainsmart flexible filament last night and managed to get the thinwall test to print just fine, but on longer prints i’m getting the buckling problem between the extruder body and the drive gear - I’ve got some PTFE on the way and will try again after i get that installed… I believe the sainsmart flexible is a little bit more rigid than ninja flex
fwiw - the thinwall test and the layers on my other prints that are put down before the buckling look great
Here’s what I ended up doing to get the flexible filament to print out with out any buckling between the drive gear and the extruder body - pretty sure I could have done this with just one piece of teflon tubing, but i ended up using two; it’s the one on top of the extruder that really made all the difference - I drilled out the top of the extruder to 4mm, and then split the end of the teflon tube in half so that it would hold the filament against the drive gear using pressure from the bering to keep it in place…
I did a couple of prints at 30mm/s and had zero issues - a bit stringy but I guess thats kind how it goes with the tpu… At this point I’m happy to be getting prints out with no buckling issues during extrusion
Thanks for the update. Nice print. I have my tubing now, and will (hopefully) work on it this weekend.
That make no sense to me, not what you did but why it helps. Unless it’s effectively increasing the drive gear pressure on the filament? Or maybe that slight extension below the bearing from the upper tube is preventing some of the buckling? I’ve seen other setups, like the Titan Extruder, where the lower tubing is cut into a shape that hugs the drive gear and bearing with (mostly) no gap.
First! …print with Sain Smart TPU that is. Came out perfectly. Had a few aborts when it lifted from the bed until I raised the bed temperature enough. Bed was 60 first layer, 55 after. Extruder started at 230, ended at 210, 5 degree drop per layer. .2mm layer, .2mm retraction, 25mm/s speed.
Single PTFE tube from just below hobbed gear to bottom of heat break (normal location).
How flexible is the final print? Just curious to what the uses of flexible print material would be, seems sort of interesting
Very flexible, and virtually impossible to ‘break’ by hand, it elongates, gets thinner, and starts cutting into your fingers. I’ve given a strand and the first couple of layers of one octopus print to multiple people, and no one has been able to break it.
The 10% infill gave the octopus some interesting properties. It’s not as squishy in the Z axis, but is very squishy in the X axis.
How did you manage to “shove” the PTFE tubing in there? Isn’t it 4mm OD?
Nope, it’s 5/32" Which I happened to have a drill bit that size. I removed the hot-head, loosened the stepper to move the hobbed gear out, and drilled from top to bottom. I then re-mounted the heat break only, shoved in the tubing until it was level with the bottom. I did that because the first time around it didn’t make it to the bottom (because of plastic back-flow outside of tube) until I tried to print with it, then the tubing sunk down 1/4". I loosened the heat break clamp and screwed into the heater block with the nozzle already in place. It’ll be a little more difficult to remove now as the PTFE tubing has to be removed to get the heat break out. I then sliced a triangle tip into the tubing to site tight against the gear and bearing.
So you had to drill the whole pathway before the hobbed gear?
I was looking into not removing the hot-end, but I guess it would be safer and better.
Anyway, the print looks really good!
Yes, drill baby drill! If you didn’t remove the hot-end, you’d have to use two tubes, drilling carefully with a flat bottom bit, wouldn’t you? Or how would you remove the existing tube? At least for me, it’s a 1 min operation to remove the head, two screws. I have enough slack in the cabling to remove it without cutting zip-ties.
Thanks, I was pleased with the quality of the print. Did a iPhone case for my son, was tough to put on, but once there, worked well.
You know when you have everything nicely calibrated and it just work well… that’s what I didn’t want to change. Anyway, removing the hotend shouldn’t change my bed or X axis alignment.
I’ll order some “el cheapo” TPU filament from China and see what I can achieve out of it. Low expectation about the quality, should be good enough for my functional parts.