FlexyDually questions


I’m about to buy a Taz 5 and was wondering if buying a FlexyDually Tool Head was a good idea or not. I will definitely print flexible objects, and will eventually need a dual extruder. But I have some questions:

  1. Is it that hard to install on the machine ? The LulzBot TAZ FlexyDually Tool Head page says that it’s for experts only, what is the challenge ?

  2. Can we print with say two PLA filaments with the FlexyDually, or is the second extruder reserved only for flexible materials ?

  3. With normal extruders (i.e: the one that comes with the taz for instance), can we use other flexible filaments from other websites (that are not the one mentioned on Lulz website, like Rubber Flex for instance) ? If not, then why, since other printers seem to have no issue with that ?

  4. What’s the difference between ninjaFlex and other flexible 3rd party filament that we find everywhere ?

  5. What happens if I put ninjaFlex into the extruder that comes with the Taz ?

Hope some will find time to answer my questions :slight_smile:

Hi, welcome to the forums :slight_smile:

Rather than answering your questions directly I’m going to try to explain the differences between the extruders so you can appreciate why one is used over the other.

The way the standard extruder works is it “grabs” the filament by squeezing it between a hobbed bolt and a ball bearing and pushes it down towards the hot end. Most filament is rigid and can easily be pushed along. Pushing on flexible material is like pushing on a rope - it doesn’t want to go straight. If you look carefully at the extruder you will see a gap on either side of the bolt/bearing mechanism. This gap is the problem. With flexible material, it can bend at these gaps causing it to jam.

With the Flexystruder, the design is very similar. It still uses a hobbed bolt to grab and push the flexible material along. The biggest difference is that to get around the gaps the entire path of the filament is encased in a white PTFE tube. There is a notch drilled out to give just enough room for the hobbed bolt to touch the filament, but not enough room for anything else. This ensures that the flexible material doesn’t have anywhere else to go. In order to push the filament into the hobbed bolt to give it grip, a thumb screw is positioned on the outside of the PTFE tube to push the tube towards the bolt.

I’m sure this would make more sense if you looked at pictures. Unfortunately I’m going to be a little lazy and not hunt them down right now. Maybe you can find some or someone else will post a link.

Anyway, now that I’ve explained the differences between the two extruders and why flexible material doesn’t work in the standard extruder lets talk about why you shouldn’t use rigid filament in a flexystruder. By the way, it definitely does work. The problem is that the rigid filament is harder than the PTFE tube and acts like sandpaper where it rubs tightly (around the hobbed bolt). I haven’t tried it myself but I’ve heard that it doesn’t take long for the tube to degrade and need to be replaced. Replacing the tube involves using a drill press. It isn’t that hard, but I wouldn’t want to do it often.

So that’s standard extruders and flexystruders. The dual extruder just holds two standard extruders close to each other and the dually flexy has one of each. What makes them complicated is it is tricky to get them calibrated to each other. Also, in order to slice a model to print with multiple filaments requires a bit of work.

Regarding types of filament, as long as the TAZ can handle the temperature requirements it should work. Flexible material in the flexystruder and rigid filament in the standard extruder. If you want to use a flexy dually to combine flexible and rigid filament into a print you want to check out that the two filaments will bond to each other. For instance NinjaFlex works well with ABS but I don’t think it works well with PLA. I believe the extrusion temperature differences between the two is part of the reason.

Oh yeah, it is very easy to physically swap extruders. The only other thing you will likely need to do is to change the firmware on the printer. The Marlin firmware needs to be set up differently when the type of heater changes or the number of extruders changes.

I hope this all makes sense and I appologize if I dumbed it down too much. :slight_smile:

Good luck.

First be aware that all the dual extruders currently use the Buda extruder, and I assume your TAZ5 uses the new V2 extruder with the hex hotend. These extruders are different and use different firmware. Also the dual extruders are pretty heavy and the extra weight can make the extruder nozzles closer to the print bed in the middle. I think the dual extruders are harder to align and adjust (my opinion). Unless you specifically want to print with 2 extruders simultaneously I’d recommend you just get or build a new extruder for flexible filament and change extruders depending on what you want to print. I’m not sure anyone has developed a flexystruder with the new hex hot end or not but I wouldn’t be surprised if Lulzbot comes out with one soon or that someone else has developed one. Using a second flexystuder with a hex hot end would alleviate the need to change firmware as it would be compatible with your existing firmware. Otherwise you’ll have to change firmware when you change extruders.


Thank you both very much for your answers, they’re very explicit.

So if I understand well, with a TAZ 5 I’d better wait for a V2 of the flexystruder and stick to a single extruder for now (since I’m just beginning with 3D printers). Although changing firmware is usually quite straightforward, so I assume it’s not that much different with a TAZ…

Do you know if Lulzbot has plan for a Flexystruder V2 ? And if not, would it be hard to print with a V1 apart from changing firmware each time I change the extruder ?

@john_c_kennedy : You say that dual extruders are heavier and that the extra-weight can make the nozzle come closer to the print bed. What are the parameters that I would have to change to compensate for the extra-weight ?

There is a lot of info on this forum regarding the Lulzbot dual extruder including the flexydually, do a little searching around and read everything you can find (sorry I don’t have time to point out the links).

The extra weight of the dual extruder causes the X axis rods to flex which is why the extruder is closer to the middle of the print bed than the edges. This also happens with the single extruder but to a lesser extent. My (very limited) experience with Ninjaflex filament indicates that a perfectly flat and level bed is very important with this filament for proper adhesion between layers YMMV. Also Ninjaflex sticks very agressively to PEI so that may be an issue with the TAZ5.

Many people have replaced the X and Y axis rods and linear bearings with hardened rods and all metal linear bearings, as these cause other print issues, again search the forums about this. Others have made “lighter” versions of dual extruders, but this sounds like its not trivial. It also sounds like Lulzbot is working on a dual extruder and a flex extruder using the new V2 hex hot end. Hopefully these will be improved designs over the existing designs which use the Buda hot ends? You might want to wait to see what Lulzbot comes up with, unless you really like the challenge of blazing a new path.

Finally I don’t mean to imply that you can’t make the flexydually work, I have, others have, and you can too, just be aware of all the issues before you dive in.