I thought I was finally winning with my battle against Ninjaflex. Setting the hot end to 230ºC and slowing the printing speed down to 10 mm/s did at least run for several good layers until, once again, the filament kinked out sideways and the printing ended. Any more suggestions?
I drilled out an extruder, and ran a ptfe tube from top to bottom. Notch out a slot for the pinchwheel only. There’s a pick further back in my post stream.
Flexible filaments tends to flex in between extruder hobbed gear and the cold nozzle end, adding something to keep it ‘in track’ the in between should suffice
Yes. I suggest you stop being cheap and shell out for that higher in quality injection molded parts made in guangzhou.
Flex filament is like pushing string. Like several others said above, install a guide to channel the material from the drive to the hot end. The smaller the gaps, the better. PTFE tube is the best I’ve seen yet. If you’re still having trouble, you might need to reduce retraction or check for clogs.
10mm/s is slow even for Ninjaflex. You definitely need to support the filament right from the drive down.
Has the BigBox been proven to work with flexible filament?
You might have a better experience with your Mendel90. @nop_head made some wise decisions in his extruder/hotend combination.
On the Hephestos 2 printer I can print Ninjaflex without any problems like normal filament. Just the speed needs to be below 30mm/s.
What is different on that printer is the extruder: there are double pulleys for the filament, so that it is grabbed and pushed from both sides (like Bondtech) and the pulleys are completely contained in an enclosure where there is no space for the filament above or below the pulleys.
So I think you need to make sure that there is no space below the pulleys so that the filament can not be pushed out.
I have had success with a fully supported PTFE tube, don’t even bother with an idler wheel, just make the drive pinch the filament with as small cut-out in the tube as possible - you should get 35mm/sec into a V6lite with the PTFE tube going all the way from tip to after the drive. And you can even feed in short sections of Filaflex/Ninjaflex doing it this way.
The Hephestos 2 extruder (1.75mm) is very happy to drive FilaFlex at upto 55mm/sec I run it at 40mm/sec without any issues at all on the Hep 2 / Semiflex can run 60mm/sec.
Without having a proper GUIDE you will never print out flexible filament! No matter the speed or temperature or extruder.
Start the process with zero retract and work up from there. 230 may be ten degrees too cold as well. I have had success on Creator Pros using Simplify 3D. The critical setting is the retract, print hotter than you think. You can keep the speed down and increase it as you have some success. For the FF creator pro, I made a new back plate for the extruder out of PET. In the design, I eliminated all the space around the gear and brought up the feed to the hotend as close to the drive wheel as practical. The gap between the output of the drive and where it feeds into the tube to the hotend is where the whole thing will go wrong even if your slicing values are in range. Looking closely at your pic, you should also have some soer of shroud around the gear do that just the part where it drives the filament is exposed. Flexible filament is a pain but it is possible 
The distance between the drive and the nozzle in your setup is huge for flexibles, almost a mini-bowden setup. That’s a lot of compression in your filament. when the filament compresses, it expands, thus increasing the side wall friction and the pressure increases etc etc.
You may find my blog on Flexible filament printing helpful : http://www.gyrobot.co.uk/blog/how-to-3d-print-with-flexible-filaments
Thanks Steve, Rich and everyone else who contributed useful comments.
This is the new BigBox 3D printer from the guys at E3D. It comes with an E3D v6 hot end complete with PTFE liner and shaped apex under the hobbed bolt. I believe the team did release videos of successfully printed flexible parts, so it ought to be possible.
The PTFE liner does not extend right up to the hobbed bolt and there is a narrow gap where the filament squeezed out sideways. I suspect that I may have had the extrusion multiplier a bit too high leading to pressure build up. It’s a fine balancing act finding the right settings!
@Richard_Horne thank you for the info about the Hephestos 2. I was thinking, that I can not print faster than what producer recommended.
@ilya_svatutsa BigBox is very new, you’re saying there are cloned injection molded BigBox parts already?
Injection molding != better than 3d printed parts. Injection molding has it’s own weaknesses and flaws, like weld seams and thin walls.
I’ve seen enough failed IM printer components that I believe a well designed 3d printed part will outlast it any day.
Main benefit of IM is the economy of scale aspect and thin wall design.
its easy!, insert a small tube between the MK8 and the hole
I agree with the recommendation of turning off retraction entirely. Mini-bowden setup on a 3ft tall printer here, turned off retraction, and turned all of the features of my slicer to basically make it so I remained at 30mm/s at all times (never speeding up, never slowing down), and I printed with NinjaFlex fantastically.
With flex filaments it’s all about guidance through the extruder. Look at the great extruders from Bondtech or at the one bq built for their Hephestos 2 - those are really great when it comes to close and tight filament guidance through the whole extruder. There are some videos from @Richard_Horne and @Thomas_Sanladerer showing the Hephestos 2 and i think at least Richards is takling closer about the extruder quality and guidance https://www.youtube.com/results?search_query=hephestos+2