Print with rubber on your Lulzbot!

Per the other belt drive thread, but in order to keep all the development files in the same thread, here is a theoretical belt drive flexystruder (normal, not quickfit for now). I will make a quickfit variant of it next since I’ll need one for my machine if nothing else. It’s 2 parts at the moment, an optional belt tensioner designed to have a threaded insert in the hole in the side. the base belt drive flexystruder can be used without the tensioner plate, but the nema mount might be too thin without it. the tensioner is designed to sandwich between the base and the motor, turn an M3 screw in the threaded insert to put tension on the belt with the motor losely in place, then tighten all 4 motor mount bolts when you have the desired belt tension in place. also should prevent belt tension loss over time.

feel free to use the design in any way you see fit.

Parts required for the belt mod (aside from already required flexystruder parts)

  1. gt2 belt, 2mm pitch, 200T, 400mm length, 6mm-with, fiberglass-reinforced, closed-loop
  2. gt2 65T plastic pulley w/8mm bore, flanges, set-screw
  3. gt2 17T aluminum pulley w/5mm bore, flanges, set-screw
    the gear set can be purchased here with the belt for $25. select "belt and gears only from the drop down instead of the full kit for the other style extruder:
  4. an additional heat set insert
  5. an additional bolt that fits the heat set insert.

edit: to use this extruder in place of a wade’s geared herringbone version, you may need to adjust the extruder steps per mm line of your controller configuration. The measurements to do so accuratly are as follows:

Extruder Calibration (borrowed from the reprapwiki)

The procedure to calibrate the belt flexystruder is as follows:
Measure the Outer Diameter of the knurled (hobbed) area of yiur hobbed bolt, preferably with digital calipers. The exact Outer Diameter will depend on things like manufacturer and batch. this should be the narrowest point of your bolt.
Calculate the gear ratio between small and larger pulley (example below is valid for the specified pulleys).
Find the step angle for the motor - most common NEMA17 motors are 200 steps per revolution.
Find the microstepping value supported by your stepper drivers. This usually depends on brand of driver and type of control electronics.
Use the following formula:
steps_per_mm = (gear_ratio / (hobbed_bolt_OD * Pi)) * ((360 / motor_step_size) * (1 / driver_microstepping))

For example:
A hobbed bolt where the knurled bolt measures 7.52mm in outer-diameter (O.D.)
The gear ratio for a 17-to-65-tooth gear system is ~3.8235. In other words, ~3.8235 revolutions of the smaller gear equal one revolution of the larger gear.
NEMA17 motors are common with 1.8 step angle and RAMPS 1.4 with pololu drivers supports 1/16 microstepping.

steps_per_mm = (3.8235 / (7.52 * 3.1416)) * ((360 / 1.8) * (1 / 1/16)) = 517.8957 ~= 517.9

I “think” that you would replace the “800” in this line: DEFAULT_AXIS_STEPS_PER_UNIT {44.7,44.7,1512,800) with that value. I haven’t tried it yet though.
flexystruder_03_mod_belt_1a_tensioner.stl (63.9 KB)
flexystruder_03_mod_belt_1a_base.stl (267 KB)
flexystruder_03_mod_belt_1a.stp (3.49 MB)
flexystruder_03_mod_belt_1a.dwg (954 KB)

I really like this. Super excited to see one running.

Glad you like it! Belt and pulley should be here tuesday-ish? The order got stuck in processing for a few days, but it has shipped.

We’ve now printed some NinjaFlex filament with the Flexystruder (dual, no less) in addition to the FilaFlex. The NinjaFlex is easier to print, but not as flexible. It is a far more consistent diameter too.


Did you print a ninja with it? It’s important to have flexibility in your ninjas just in case!

Belt and pulley assembly has not arrived yet, so I haven’t had a chance to play with the belt extruder yet.

Is this material available from a US distributor yet?

been using the flexPLA for a while with good results (dual extrude with HIPS too), but urethane is very interesting too

Urethane is way more flexible than the soft/flexible PLA. We’re working on getting both into our store. Also, the urethane stuff is VERY strong.

Apperently the belt parts still haven’t even shipped yet from the other vendor. No idea what the delay is. I guess I’ll keep playing with the Z-rail project until they do for now.

The Flexystruder V0.5 is here!

I’m really happy with the way that the newest version of the flexystruder is printing, And I think it’s time to get some feedback from our users.
So far we’ve tested it with flexible PLA, filaflex (black and pink) and Ninjaflex (Sapphire, white and red) without issues. The flexystruder “will” print with ABS, PLA or other hard polymers, but since this wears out the PTFE lining we suggest only printing small amounts when you need to hotswap between flexible and rigid materials.

Up on we’ve posted an updated bill of materials, as well as assembly instructions. Look under TAZ/accessories/flexystruder

Let me know if you’ve got any questions/comments/cool things to share


Nice job! I like the improved threaded fitting on the side. Good job! One possible addition to the bill of materials: a press fit thumb screw cap fitting for the M5 bolt?

I’ll update the belt design sometime in here. assuming I ever see my belt parts haha.

Thanks! The M5 makes it a much more solid unit, definitely a worthwhile change. I’ll give that a shot tomorrow, I’ve been toying with the idea of a printed lever style cap that would prevent overtightening, but this would certainly improve it in the mean time.

According to tracking, I should finally see the belts and pulleys for mine today or tomorrow. I just realized that for V5 i’ll also need to find some PTFE tubing. Where does one typically find PTFE tubing? any ideas ona local source, or is that a Mcmaster carr type item?

a V5 belt quickfit is in progress, will toss the STL up when its done.

We get PTFE tubing from McMaster frequently.

We have printed maybe 10-20 “rubber” parts so far. This material is very strong. The parts are turning out very well. This is going to be a hugely useful material for people to use.

Belts and pulley set arrived! I’ve also ordered the rest of the parts which should get here soon. For the PTFE tube, I ordered the white colored “Shapes Made with Teflon® PTFE” stuff off this page:

is that the right PTFE tube, or did I really want the Delrin filled or glass reinforced stuff?

Awesome! We use the regular teflon for this, though either should work. I’m excited to see what you can do with it. Do you have any materials in mind to try out?

I have a roll of Nylon to try out with it, and i’m thinking of ordering some of that ninjaflex stuff if I can find it under $120 anywhere. I definitly want to try some of the printble urathane though too, That would be very useful for making integrated vibration isolation mounts / pads. I also might see if I can make a 3d printed linear rail cover. that would be kind of an iffy prospect at best, but given the cost and availability of them, if it worked and held up it would be something that would be very useful and save me some money on other projects.

If the belt works out the way I think it will, I’ll probably also make a more traditional wades style belt mount for ABS, as the two existing ones lack a belt tensioner. That will be the next project after I get done with the top deck plate and linear Z rail projects I think. Those are getting to the point where finishing won’t take long. I just haven’t had downtime to tear the machine apart again and start installing the new bits due to holliday printing

Seeing all the speaker prints lately, this is inspiring some ideas.

I went ahead and made a quick fit standard idler belted extruder at the same time so I can compare the two directly. It uses the same tensioner as the flexystruder belt variant.

Here’s the standard wades belted unit printed. I changed the tensioner around a bit. the belted flexystruder will be the same general motor layout. But now I’m waiting on filament since I ran out. Oops.

Lookin good!