3D Printing & Imaging
Side by side: Standard in black, FlexyStruder in green.
Side by side: Standard in black, FlexyStruder in green.

LulzBot / LulzBot.com

Price: $294.95

Review unit supplied by LulzBot.

Why a special extruder?

Flexible filaments can be printed on many extruders. However, if you look at the most common designs for extruders, they rely on the rigidity of the filament to go from your drive gear to the hot end. In the example of LulzBot’s standard extruder there is a gap of roughly 10mm. While ABS and PLA are rigid enough not to bend in 10mm, NinjaFlex can quite easily.

If you read about flexible material printing on 3D printing forums, you’ll see that this causes an issue for many people. LulzBot has designed a system specifically for flexible filaments that has no gap between the drive gear and the hot end. Below, you can see both models, the standard in black and the FlexyStruder in green.

The test rig and printing

I’m testing the FlexyStruder on a LulzBot TAZ 4. The entire unit was supplied for the review. I have a LulzBot A0-100 on my workbench, but they wanted to make sure I was working with the latest and greatest for best results. I’m glad they did too as the quick swap tool head that they use was very convenient. It is one single screw and 3 wire plugs to switch heads. I did not calibrate my FlexyStruder as you’re supposed to, I was curious to see how it would print without me fiddling with it. After the first print, I decided that I didn’t want to calibrate it as the print quality was fantastic.

NinjaFlex prints a little bit differently than ABS or PLA, it oozes and strings. Aside from that, I had no real issues whatsoever. I did find that when beginning a new print I would have best results if I would “prime” the nozzle by extruding a bit to build up pressure, otherwise it would not begin to come out of the extruder immediately. I experienced no clogs or print failures.

The hard way

After printing a bunch of designs with zero issues, I thought it would be nice to compare the normal head to the FlexyStruder head. I swapped them out and began to print.

The very first time I tried to extrude, the NinjaFlex kinked right at the drive gear.


DSC01453 (Small)
See the little orange bit at the center of the image? That is the bulge of NinjaFlex

I re-seated it and tried again and it began pushing the ABS out of the way (I had been printing with ABS on the standard extruder). Once it began extruding plastic I had no more kinks. I have had zero issue printing NinjaFlex on this standard extruder since the first feed. There have been no kinks or clogs.

Out of curiosity, I tried the flexible filament in my A0-100 and found that I had clogs or kinks about half the time causing the print to fail. I suspect the newer extruder works better due to a better thermal design at the hot end.

Older LulzBot extruder
Older LulzBot extruder

The biggest problem I had with printing NinjaFlex with the standard extruder was the fact that there were remnants of ABS in there. The different consistency of the NinjaFlex means that it didn’t clear out the extruder as quickly as might happen if I was just pushing more ABS through. ABS would randomly plop through for several prints, causing major issues in print quality.

Once the ABS was purged from the system however, the quality of the print between LulzBot’s latest standard extruder and the FlexyStruder was minimal. It appears as though the FlexyStruder might supply a more consistent pressure resulting in a slightly higher quality print.


However, the difference between my older model was considerable due to mis-feeds and clogs.

While it may be possible to simply use the FlexyStruder for all materials, it appears as though it may be more difficult to access the drive gear should you need to clean it, like I frequently have to on my older printer.

Pro tips

  • “Prime” your extruder by extruding until filament actually comes out the tip before you print. The flexible nature of the filament reduces the pressure as it sits.
  • Run a lot of filament through your extruder if you’re switching from rigid to flexible materials. The prints that had ABS debris were ruined.

It is also worth noting that the FlexyStruder, like everything at Lulzbot is open source. This means you can download the files to print your own if you would like.



Senior Editor for Make: I get ridiculously excited seeing people make things. I just want to revel in the creativity of the masses! My favorite thing in the world is sharing the hard work of a maker.

I'd always love to hear about what you're making, so send me an email any time at caleb@make.co

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