Ninjaflex slab printing help

I am trying to print some 12cm x 12cm x 0.2cm slabs of Ninjaflex on a new Taz5 with Flexystruder. These are 100% fill, 0.2mm layer height, 1mm shell thickness, 30mm/s print speed, 230C printing temperature, 30C bed temperature, gluestick on the print bed, on a raft.

The filament jams in the extruder just after the raft starts to print.

I’ve tried raising the print temperature to 240, disabling retraction, and setting the travel speed to 30mm/s with no success.

I have printed many objects of various sizes with this unit and the Ninjaflex, but these slabs are giving me grief. Any suggestions?

I’m a noob and probably don’t know what I’m talking about, but why would the filament jam on a slab but not on other objects? Sounds like something changed that would also prevent you from printing other objects now as well. How does the hobbed bolt look? Clean or clogged? Maybe adjust the tension of the idler screws?

Could this be heat-creep related? If so:

Looking forward to other responses…

Can not say I have ever tried to print a raft with Ninjaflex and its sticking properties. I just tend to turn off the bed and print on a bare glass plate.

Another thought.

After you make sure the hobbed bolt is not gummed up, do some practice extruding with pronterface and experiment with different extrusion speeds to get it just right. Then calculate and correctly set the corresponding print speeds (for rafts also) and it would have to work – no more filament jams.

I’m not an expert in Ninjaflex by any means, so consider these more guesses than anything.

Ninjaflex jamming is either going to be caused by the actual physical path of the fillament allowing it too much range of motion and it kinking in the bore, or its going to be caused by a stoppage at the nozzle end, either due to overextrusion and backpressure caused by the layer being closer to the nozzle than it thinks it is after a bit of a run, heat issues (which I have no idea what the ideal temperature range should actually be), possibly lifting if it isn’t adhering to the glass correctly, or an actual material blockage.

I’d suspect that this is overextrusion. Printing at 100% infil is hard to do even with normal filaments if you aren’t 100% dialed in. If you have the fillament width diameter set wrong and are actually extruding an effective 105%, the excess material has no where to go. If you are printing at 90%, that extra 5% would just result in you printing basically 95% infil instead. At 100% the excess has to go up and out, and ends up in the path of the oncoming next layer of filimint. I’d adjust the fillament width setting, then try printing at 90% infil and see how that goes at first, then bump it up until you have issues with it.

Piercet - awesome explanation.
Crash - just curious, what infill were you using on your successful prints?

Thanks for all your replies! I’m going to try your suggestions. All of my previous prints have been at 100% infill. It’s just the slabs giving me problems.

Just a very late follow up on this issue.
The solution to this problem was to dial in my Estep value as suggested in the replies:
adjust my z print height, and level the bed more accurately.
The last thing I had to do was keep my filament out of the humidity when not in use. Except during the winter months, the air is very humid here and made the filament extra soft so it would get chewed up easily. Even at slow print speeds this would happen.

I am having the same issue, but the solution you use does not work for me.

Specifically, I am using a FlexiDually V2. I had trouble with it from day one. The ninjaflex jams on the second or third layer. I got it to work by turning up the temperature to 230 C and slowing way down to 10mm/s extrusion. I was able to print a large part (16 hours) with the slow settings. I tried to inch up on the speed (12 mm/s) but it did not work. Now I can no longer extrude NinjaFlex at the slower temperature either.

I was hopeful that your suggestion about recalibrating the extrusion parameter (Estep) may be the answer, so I tried to follow the instructions in the link you provided: … libration/

However, when the free-fall extrusion started, it jammed about 40% through. I thought the recommended extrusion speed was too fast, so I cut in half (from 100mm/s, to 50mm/s) with similar results. I slowed it down to 12 mm/s and it jammed about 60% through. Then I tried to manually turn the gear and noted that it jams at about 40%. There is no back pressure since it is extruding into the air, well above the bed.

I took apart the drive mechanism (not the hot end) and found no build up. So I’m perplexed.

Any suggestions?

this has been happening to me as well I honestly have had more luck printing with the v1 flexystruder

Make sure you follow the flexistruder guide and not the standard extruder calibration guide. The flexi needs to be feed MUCH slower or you will feed the heat block faster than the filament can melt! ~20 MM/sec or so is the fastest you really want to try printing at with the flexible filaments.

Also make very SURE the filament path is near perfectly straight. I have seen a few flexistruder that had bolt alignment issues that caused feeding troubles.

Also remember if you use your flexi to print other filament types you may and probably will have feeding issues, As that changes the diameter of the PTFE tube right where the bolt is.

yes, I noticed an issue with my flexys tub not being aligned properly but I have fixed that and I am printing as slow as 10mm/s which I think is crazy, do you suggest I go even slower? I have changed the infill to 85% and the filament diameter is 3mm in cura.

I tend to not need to go slower than 10MM, but I have printed as slow as 6-8MM before, while working on a Ninja-flex grinding issue. Any kind of hang-up or cause of friction will make it harder to push out and more likely to grind.

I found a solution that works for me. In my case, the hobbed bolt was fraying the filament so that the frayed pieces jammed in the feed tube down-stream of the bolt. Notice in the attached picture how the filament is frayed.

Assuming this fraying was caused by the sharp edges in the hobbed bolt, I made a new bolt, but instead of sharp edges, the curve in the bolt is just rough. The attached picture shows the replacement bolt below the original bolt.

The replacement bolt was purchased at Lowes (2 for $0.97) as S/S M8 x 60mm. I mounted the threaded end of the bolt into the chuck of a bench-top drill press and ground a groove into the bolt using a round file. When I had the groove deep enough, I took the bolt out of the drill press and made small scratchs in the groove by twisting the file in a direction perpendicular to the groove. Then I cut 10 mm off of the threads and installed the new bolt in place of the old. It worked like a champ. No more gear jumps and I was able to successfully print a key chain with no jamming. :smiley: Oh happy day!

The new Hobbed bolt prevented filament fraying, but it did not provide reproducible feed rates. I went through four iterations before making a bolt that works. I used a Dremel to first cut an indentation where the filament feeds, then I cut an x-pattern using a Dremel metal cutting wheel. I intentionally wore down the wheel to make it a small diameter (about 8-10mm diameter). The x-pattern cuts provide enough of a sharp edge to bite into the filament without fraying it. Even so, if it is fed too fast, or if the temperature too low, the filament swells and will not feed. I am now using 235 deg C nozzle temperature and 10mm/s print speed.

Second Update.
I continued to have trouble printing Ninjaflex, even using a new hobbed bolt. Although the extruder has not jammed, the filament would not extrude smoothly and fully. I was getting very thin lines of hot filament. I had to slow down to 8 mm/s with 235 deg nozzle and even then the extruded filament was too thin. I was able to get better prints by reducing the filament diameter setting in Cura to 2.5 mm. This causes Cura to extrude more filament for the same distance covered. But printing larger objects at 8 mm/s is frustratingly slow. So I wrote a small C program to independently change the speed for T0 and T1 in the G-code. I can now print ABS at 20 mm/s while the Ninjaflex extrudes at 8 mm/s. I can share the executable for windows, or the uncompiled program, if you’re interested. Inputs for the program are the gcode file name and desired speed for each extruder (or 0 to leave the speed unchanged for that extruder).