Flexible filament problem with feeder


Hello to all. I recently purchased some semiflex from fennerdrives due to the temperature specs it has. However, despite being succesful inserting the filament initially to the feeder, it seems that somehow afterwards instead of going into the printhead, the filament stacks up inside feeding motor area (or chamber?) of the printer. I can tell this since the filament roll keeps on spinning as if it were feeding the extruder but there’s nothing that is actually coming out in the toolhead. Consequently, this is not allowing the material to flow AT ALL onto the extruder. I read that this material was succesfully used in this printer, so i’d like to now if i’m missing something in the process, or if it’s a more technical issue, @Hunter ?

Thanks for the help.


This extruder was not designed for flexible filament, although several users have been lucky enough to get theirs to print. Slight differences in filament flexibility between brands could make all the difference. Also, with printers other than FLUX, it is extremely difficult to print flexible filament with a Bowden extruder, which is what we have here. The long tube presents too much resistance to filament movement, so it jams before getting to the hot end. If I were you I would stick with PLA and possibly look to get a printer with a direct drive extruder if you want to print flexible material regularly. Just my opinion…


What is your print speed (perimeters, infill, etc) and print temperature? My understanding is print speed should be below 30mm/s and temp above 220C if the filament is similar to Formfutura Flexifil. Check with @drmaettu, he uses Flexifil successfully. Unfortunately that material is not found easily in Canada and shipping from USA is expensive.


I thought the same, but seeing as some people have actually managed to print that way, i thought there was a chance of it being possible… @mc_ott the print speed i was trying was at about 20mm/s on every level, and the temperature at the max (230ºC). The problem is foreseeable when I try to change the filament, so it’s not a “while printing” issue… I checked the FormFutura filament and the shipping was expensive AF… maybe i could get some of it through ebay or something, gotta check.

Thanks for your time!


It seems i got the same issue using Prima eFlex™ Filament - 1.75mm.

Seems to me that this filament is to flexible to not curl up in the space between the feeder wheels and the bowden tube hex nut thingy. If this space was smaller this might less a problem.

This hex nut also often causing me headaches when loading normal PLA. Even though the filament line is cut pointy as per instruction it can be quite a hassle to hit the opening.


I was having similar issues when trying flexible filament… one thing I just thought which might help to is disabling retraction or at least lowering the retraction distance / speed.


A small update… it seems I can’t get the polyflex to work on the flux… maximim I managed was 1/3 of a marvin before the filement gets stuck in some way around the feeding gear…even with vey low retraction and retraction speed and a print speed of 30 mm/s :disappointed:

I think there is too much friction in the filament tube and at some point it messes up while trying to push it through.

Having a direct drive feeder probably would work but I don’t think that will ever be an option with the flux.


What seems to be working for me is to lower the feed rate. The problem with the bowden seems to be that the motors feed too much material and the extruder cant keep up, so presure builds inside the tube and eventualy it gets stuck.
So by lowering the feed rate you give enough time for extruder to work and by so, reducing the tension inside the tube. To at least 75% or what works for you.