Itty Bitty Double FLEX V2 Extruder (With mount for MakerFarm Printers)

by clough42, published

Itty Bitty Double FLEX V2 Extruder (With mount for MakerFarm Printers) by clough42 Dec 30, 2015
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This is the third evolution of the Itty Bitty Double Extruder.

NOTICE: Version 2.1 released. See notes below.

A hardware kit is available; links below.

New in this version

  • Better flexible filament control
  • Supports Hexagon AO
  • Designed for easier printability with less cleanup
  • Low-profile shelf brackets to support underslung X endstops
  • Support for more Z probe switch types

Key Features

  • Designed for Hexagon or E3Dv6 hot ends on 27mm centers
  • Short, straight filament path to accommodate flexible materials
  • Uses the same hardware kit as all Itty Bitty Double Extruders
  • NEMA 14 motors
  • Silent GT2 belt drives with printed pulleys
  • Integrated servo Z probe
  • Cam-lock idler bearing pins
  • Uses our custom hobbed bolts (or equivalent)
  • Lighter than a stock single Accessible Extruder
  • Integrated hot end cooling
  • Mounting hardware for Prusa i3v printers

Printable Files

All of the files are included for the entire extruder system for 1.75mm and 3mm filament, Hexagon and E3Dv6 hot ends. To assemble the entire system you will need to print:

One extruder block
  • For 3mm hot ends: Double Flex Block-300Universal.STL
  • For 1.75mm hot ends without a liner: Double Flex Block-175Universal.STL
  • For 1.75mm E3D hot ends with a PTFE liner and fitting: Double Flex Block-175E3dLiner.STL
Hot end-specific parts
  • Hexagon hot ends: All of the parts with "hexagon" in the file name. An alternate fan shroud is provided for the Hexagon AO.
  • E3D hot ends: All of the parts with "e3dv6" in the file name.
Common parts

You will need two copies each of the idler blocks, idler pins, pulleys and round spacers and one copy of everything else.

Optional parts
  • I3VXCarriagePlate.STL - replacement for standard i3v X carriage plate
  • Adjustable I3VXCarriagePlate.STL - X carriage plate with a larger hole to use an extra V-slot eccentric in one of the upper holes for leveling

Print Settings


MakerFarm Prusa i3v










I recommend ABS. Some people have reported great success with PETG.


Required Hardware

In addition to the printed parts, you will need the following vitamins:

  • Hardware kit
    • Available here
    • GT2 20-tooth Pulleys with set screws (2)
    • GT2 200mm Belts (2)
    • 688ZZ 8x16x5mm Bearings (6)
    • Extension springs (2)
    • Fiberglass/Polyimide insulator
    • M2.5×10 socket head cap screws (2)
    • M4x.7 hex nuts (2)
    • M4x20 button head cap screws (2)
    • M3 flat washers (6)
    • M3x.5 hex nuts (11)
    • M3x25 socket head cap screws (3)
    • M3x16 button head socket cap screws (10)
    • M3x12 flat head socket cap screws (10)
    • M3x8 socket head cap screws (6)
    • M3x6 button head socket cap screws (2)
  • Light springs for flexible filament (optional)
  • Hobbed bolts with jam nuts (2)
  • Hot Ends (matched pair)
    • Hexagon
    • E3Dv6
  • NEMA 14 stepper motors (2)
  • HXT-900 Servo
  • Z probe switch
    • You can use virtually any snap switch, including the one that came with your MakerFarm printer.
  • 25x25x10mm fan (Hexagon hot ends only)
  • 40x40x10mm fan (for print cooling)
    • A 40mm fan is now included with most Hexagon hot ends

Assembly Instructions

Detailed assembly instructions can be found here:

Firmware setup:


Release Notes for Version 2.1

Version 2.1 includes the following changes:

  • Added longer versions of the Z probe arms for switches without levers
  • Fixed thickness of Hexagon double groove mount for a better fit

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this extruder looks extremely heavy if i'm honest, how's it holding up and any print quality issues?

wouldn't it be smarter to have one bowden and one direct driver on the same carriage if a two colour print is necessary where one material needs DD?

It does look that way, but it turns out it actually weighs less than the stock extruder that came with the printer--mostly because of the NEMA14 motors.

I have one that's about two years old now on a 12" MakerFarm i3v. I print everything on that printer, unless it's busy. I've run about 12Kg of filament through it, and the print quality is still excellent. The zero-backlash belt drive and the milled bolts I use make a big difference.

This is a photo of something I printed this week. Those are .2mm layers in PETG.

Can this be adapted for thr CR -10,

I'm not familiar with the CR-10, but I just looked at some photos. It looks like a very lightweight frame with a single aluminum bar for the X axis. This appears to be enough structure to support the default bowden extruder, but I wonder how it would handle the weight of a double extruder with the motors on the X carriage.

In theory, you could design parts to make this fit. I would just worry if the frame and X motor are strong enough.

can make a mount for the dyze hotend ?

This is actually the first I've heard of the Dyze hot end. In theory, it looks like it could fit, since it's only 25mm wide. The mount at the top looks similar to the groove mounts used by the Hexagon and E3D hot ends, but having the wide heat sink at the top means that it would interfere with the shelf and would require larger cutouts.

If you want to try to make it fit, I would start by printing out the shelf and the groove mount for the E3dV6 and see what it will take to make it fit. You'll need to cut away parts of the shelf for clearance, and it isn't clear to me if there will still be enough material left for the M4 mounting screws that hold the mount and extruder to the shelf.

If you try it and there's room, let me know and I'd be happy to draw up alternate versions of those parts.

That what exactly what I did I didn't use fan shroud and after modifying groove for them to fit.

I'd love to see what you did. You can upload your designs as a derivative and they'll get linked here for other users. Or if you modified the parts by hand, you can upload a "make" and share photos.

I'm working on putting together a parts list so I can build this and put it on my FT-5 and I was wondering if you think there would be any advantage to using .9deg steppers?

I don't think there's much point, and depending on the details it could cause problems. If you're using normal 1.8deg (200 steps) motors, with a 1/16 microstepping driver, the 4:1 belt drive and an 8mm bolt, you're already around 640 steps/mm. For 1.75mm filament, it doesn't seem like more resolution than this will be very helpful unless you're printing slowly with a very small nozzle. Switching to .9deg motors will double your volume resolution, but will also double the number of steps you have to make, and this will likely cause problems getting a fast retract. Ideally, you should be retracting at 30mm/s or more to get a crisp stop, and most stepper motors are limited to around this speed by their inductance when running on 12V. If you are running the steppers on 24V or have very low inductance motors (1.5uH or lower) then maybe you could make .9deg motors work and still maintain your retract speed.

Thanks for the sanity check. I figured the same with the 4:1 ratio. I'm getting ready to order the hardware and I'm trying to decide if I want to go with the AO or the regular hexagon. I've got the regular on my delta and I love it. Not sure what difference I would see between the two but I know the AO is used on the Taz so they must think there is a noticeable difference.

My understanding is that the AO has more mass in the heat block, so it's easier to maintain the temperature precisely, at the expense of having less cooling area on the heat sink.

Compliments splendid job. I have two questions:

1: what is the total width?

2: where did you get the belts?

I have a few in stock, if you're in the US: http://clough42.com/product/200mm-gt2-belt/

But it looks like you're in Italy? I would check out eBay or AliExpress. Another useful search term is "2GT-200"

Just measured it, at 148.5mm width.

I bought mine on Aliexpress, just search for GT2 200mm belt

I found it on Aliexpress, very kind, thank you!

Jesus, now that is a beast! 0_o


I've been having some trouble with the ao hexagon jamming when using pla during dual extrusion -- even if I set the hotend to drop to 170C or lower when idle, eventually the filament will jam. At first I thought it was just due to the (rather excellent!) hobbed bolt grinding the filament down, but it does not affect abs and I was able to feed 20mm, retract 15, and repeat for dozens of cycles when using just one. I also have the recommended sunon maglev fan and have yet to find a more powerful 25mm fan.

Has anyone else experienced the same problem or have any fixes? I think that the heatsink on the hexagon is simply too short to cool two of them with a single 25mm fan adequately enough to prevent pla from swelling. I was contemplating trying to design a shroud to fit onto the hexagons (pushing with 2x40mm fans and reversing the 25mm to blow upward), or removing the heatsink shroud and just using a pair of external shrouds, but was hoping someone else had already experienced/solved this problem.

Sorry, unknown_lamer, I didn't see your question (back in January!)

It's possible that the long retract might be making the problem worse. The end of the filament that's near the melt chamber swells, both from the heat and also from the pressure of the extruder driving it into the nozzle. As long as this swelled, soft, sticky filament stays down near or in the melt chamber, you'll be fine. But if you retract significantly, like the 15mm you mention, you're pulling this soft filament plug up into the cooler bore of the hot end, where it can freeze and stick to the walls. Better cooling of the hot end might actually make this worse.

Unfortunately, you're fighting a battle with ooze, too, so having a much shorter retract might not give you good results. The best balance will probably be the lowest practical extrusion temperature, with the shortest possible retract. A slicer with an ooze shield (like Simplify3D) can help a lot, so you don't have to completely solve the oozing problem. Lubricating the bore as @DragonFire370 mentions is also worth trying.

If you're only printing PLA, you might actually be better off with an extruder with a PTFE liner or an E3dV6, which has a better polish in the bore and a sharper thermal gradient in the melt chamber.


It ended up mostly being that I had the fan backward (we chatted about it in my make a few months ago actually!). There is still a bit of a heat creep problem though, around 2-3h in with pla it starts gumming up, but it only affects pla and most of my long prints are in petg.

I'm going to give a bit more powerful fan that recently appeared on digikey a shot (https://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=242319281&uq=636453502922706648) -- the airflow vs pressure curves look way better than the sunon fan (on the downside, 31dBa, youch). I'll report back results with long pla prints probably some time in the next few weeks.

Failing that, I'm probably going to sacrifice the cooling duct for a pair of 30mm clip on mounts (such is life).

For idle hotend retractions, I was just using the settings from the lulzbot cura profiles as a starting point. Did you have any recommendations for distance? I saw your slic3r profiles were using 10mm, I'll start there (not sure that would resolve pulling molten filament into the cold end though).

After all this, I just noticed the letters "AO" in your first message. I haven't used the Hexagon AO, but I can see how it would have trouble cooling itself. There's not a lot ofheat sink there.

yeah, I think it might need more air that a 25mm fan can provide given the back pressure and tiny heatsinks, but we'll see how this 5v fan works next week.

If not I think I can live with a pair of 30/40mm fans and extra 30g of mass (seems like ABS would be the main material benefiting from the ducted design keeping the heatsink air away from the build volume, but since I mainly use PLA/PETG/Nylon... ).

Which Nylon are you using, and how is it working for you?

Just Alloy 910 since Taulman said it was the easiest, hasn't been any more of a pain than ABS to use (using PVA + water mixture for adhesion @ 86C just using the recommendations from lulzbot, doesn't like to stick to even PEI). I do have a printdry oven and dry it while printing though (glorified food dehydrator, but it cost less than getting one and modding it so works for me, and has paid for itself reviving a few reels of petg and tpu I left out way too long in the summer), it really does adsorb water insanely fast.

Be warned though, I have yet to go through a full 0.5kg reel yet (about to use the rest of it printing an air hockey mallet though, biggest thing yet so I'll find out soon if it really is worse than abs for warping I guess), probably shouldn't have listed it as one of my main filaments (unless you only count the last two months...).

I am kind of thinking about re-printing the extruder body out of it because of the lower surface friction than abs, it doesn't get more than around 45-50C at the top of heatsinks on the hotend, thinking it might make it possible to print tpu a bit faster and make feeding some stiffer pla easier (assuming the motor holders don't warp and split away badly).

Try a sponge with olive oil, for lubrication. Just sit a slot in some open cell foam, put a few drops of oil in it, then zip tie it around the filament where it enters the extruder. Only tighten it enough to make the sponge touch the filament, so it doesn't cause friction, and make sure it doesn't get caught in any moving parts.

Thanks for your reply. I totally missed the original question. Do you find that the oil affects the surface finish or layer adhesion of the PLA?

I personally haven't had any problems with layer adhesion, and I'm not sure about the surface finish. All of my prints so far have had to be done with oil because the Bowden tube on my printer is so long, and it causes so much friction. Also I only have black PLA.

May I make a suggestion: Add some kind of slot to the extruder block for holding the PTFE tubing. With long retracts on flexible filament, the filament sometimes tilts and prevents to be fed further into the nozzle....Just an idea

Are you using 1.75mm filament? If so, there's a version of the extruder block for the 1.75mm E3Dv6 with large bores to hold the PTFE liner. That's the version I use on my printers.

you happen to have this in a single flex extruder would you??? i have a wanhao i3 and it doesnt have the capabilities of dual extruders without having to swap the entire motherboard

You have a couple of options. You could use the double extruder, but only connect one motor, belt and hot end, or you could go with the Itty Bitty Belted Extruder (http://www.thingiverse.com/thing:389105) which is the single extruder I used as a test bed when designing the double extruder mechanics. I still use it every day on one of my printers, and I use it regularly with 3mm NinjaFlex.

Itty Bitty Belted Extruder

thank you for the quick reply but in your opinion which option would be best?

They both print well. If you already have an Accessible extruder, you can transfer your bearings and hardware over to the Itty Bitty Belted Extruder. If you go with the half-double, you'll have to get new bearings and hardware. It's up to you.

How do you make sure the heights of the extruder tips are aligned? Im thinking about printing this ;)

There are two ways I have done it. If you are using auto bed leveling, you can actually tilt the entire X axis to level the heads. The other way is to print out a new back plate for the X axis with a large hole for an extra eccentric cam on one of the top wheels. This allows you to adjust the level by turning the cam.

Thank you for that great design!
Sadly I'm not able to get that thing working. I made my own hobbed bolts, but all of them dont work. The filament just get's eaten by the bolt.
I've ordered now your bolts on ebay, I hope that will do the trick.

There are lots of factors that can affect bolt stripping. The geometry of the teeth on the bolt can make a big difference. It's also possible to run into trouble with spring tension. I've seen problems with too little tension (slipping and grinding) and with too much tension (deformation and jamming). You can also try changing speed and temperature. If nothing works, you might have some debris floating around in your melt chamber. This is especially an issue if you switch filaments a lot. Swapping hot ends or nozzles can help determine if this is what's happening.

Hello, I received your bolts. They are very nice, but I still had stripping filament. So the only thing which did the trick was lowering the extrusion feedrate from 22 to 2! I don't know if this is ok, but at least I can do some basic calibration.

Interesting. Is that in mm/sec or mm/min? 2mm/sec for the filament is a reasonable feed rate. 2mm/min is very slow.

It says mm/sec in marlin. I was just worried, because in your fw you have 22 which is way faster :-D.

Ahh...yes. That's the absolute maximum feedrate. You would only normally run that fast for retractions. Normal hot ends can't generally melt the filament that fast.

Ok I see, but how is it possible to just reduce the extrusion feedrate, without touching the retraction feedrate? I've now a lot of oozing problems(using 1mm retraction distance) and I think a quick retraction might help too. At the moment I'm limited to the same 2 mm/s which I've hard coded in marlin. I've did some research and found the command M203, but I'm not sure if that will only affect the extrusion speed and leaves the retraction speed alone(that would be perfect).

Usually, you have the feed rate in Marlin set to the maximum the motors will support, but you configure the actual feed rates in your slicer. Generally, the Slicer calculates the forward feed rate based on the printing speed, the diameter of the filament, the diameter of the nozzle and the layer height. The retraction feed rate is usually a configurable item (in the slicer).

i made a remix of this, so it fits two Nema 17 motors, and it fits on the original Prusa i3. i've also made a fanshroud for e3dv6 that fits two 30mm fan. And last but not least there is a inductive sensor mount. Clough42 feel free to add the files to the files section of yours. http://www.thingiverse.com/thing:1649430

Prusa i3, Nema 17, Itty Bitty Double Flex V2 Extruder

Thanks for sharing. I have had lots of requests for NEMA17 motors. What length/torque motors are you using and what's the total mass? Does the extra weight affect the print? I would expect to see more ringing on the left and right sides of printed parts if so.

I'm using NEMA 17 motors, with a length off 33mm and a rotor torque off 35g.cm^2. About the extra wheight, i don't know, because i only made three print so far with it, but i saw a little bit of ringing on one of the prints. i don't know the total mass of the whole extruder with the NEMA 17, but one of my NEMA 17 motors weigh about 220 grams

looks like a v8 engine

clough42, can I get a merged complete assembly to put into my solidworks to get be able to create a mount for my corexy.

Sure thing. I'll PM you the details. Please be sure to share whatever you create!

And now, I can print the engine block, err, uhh extruder block in PET-G with the letters 'C42' and 'IE' in black PLA...

http://www.thingiverse.com/thing:1575952 (imbed a monogram in the stl...)

Customizable Monogram Pendant with multiple loops_Dual
by gddeen

UPDATED: Version 2.1!

I just released version 2.1 of the Itty Bitty Double FLEX extruder. The update includes longer Z probe arms and a minor tweak to the thickness of the Hexagon double groove mount so it should fit better.

I had to modify the servo arm included with the e3d stuff (from your website) to be longer as it was too short compared to my e3d. I extended it 10mm.

Oh, that doesn't sound good. Which file did you print? What switch are you using? Are you using the E3Dv6, or the Volcano? Is it an official v6, or one of the Chinese clones?

It's an official E3Dv6 I bought from Makerfarm. I printed the arm that was in the e3dv6 directory although it's possible I screwed something up.

No, you didn't screw up. I just checked, and it was my bad. I have longer versions of the Z probe arms for both the Hexagon and E3Dv6 that are designed for use with switches that don't have levers. These are included in printed parts kits purchased through clough42.com, but I never got the updated files here on Thingiverse, or on the web site.

I just uploaded the extra long files here and updated the downloadable parts bundle on my web site. Sorry for the inconvenience.

Geeze... Now you tell me... I redesigned THAT one awhile back. My Zprobe 1573283 fits a E3DV5.

Also, there is no DUAL MINI FAN MOUNT part to mount the 2 25mm fans to fit E3Dv6 heatsinks. So...

I used 30 guage magnet wire and weaved the fans together and to the heatsinks. It is
much lighter than the fan mounts. It is also weaved to keep the nozzles the same dist apart.
But metal will stretch soon...

Hey, no problem at all.. Thanks for a great design. I actually decided to throw out the server and am expecting a Proximity sensor int the mail any day. Can't wait to get this new printer going.

Hi, your extruder rocks! I made it fit to my MendelMax V3. Although not yet tested, I think this will be the foundation for some speed improvement (coming from a Bowden extruder).

Since I am so happy with it, I want to share the following additions with you, feel free to add them to your Thingy Files:

By the way: I love your calibration object along with your simple but nonetheless very useful tool to calculate the right settings!!

There is room for (slight) improvement: since maintenance is part of the business, it would be nice to have a short section about how to quickly disassemble the Extruder in order to clean nozzles etc.

So, final word: two thumbs up for your product and services. I like the result and I truly loved your exceptional documentation. There is only one thing that was even better: reaction time (questions, shipping, etc). Less than 12 hours. Wow.

Thanks for sharing and wish you have lots of people buying your kit!

When we create models and tag them in Thingiverse, what is a good tag for dual extrusions? dual_extrusions 2_colors
anything else?

Thanks. Feel free to post your parts as derivatives, and they'll show up in my Thingiverse listing so others can find them.

Hi, do you think these would work for the light springs? I'm trying to source parts in my country but I can't seem to find the exact same spring as you have in your store.
Here's a picture: goo.gl/tHCg9h
Total Length: 36.5 mm, Spring portion Length: 25 mm, Ring diameter: 5 mm, Material: carbon steel

Springs are very hard to specify, since the thickness and material of the wire varies so much. I actually cut and bend my springs to length from longer stock, but there must be something available near where you live that is similar.

You're looking for a spring that will provide between 0.5 and 1.0Kg force per spring when stretched to 50mm.

But that isn't a magic formula. The ones I have work well for the filaments I've tried, but you can likely use a lot of different materials. You could even try stacking up rubber bands across the screws. They won't last as long as springs, but they will work.

Ok, will keep that in mind. Thanks!

Could we get a side bracket to hold an inductive/capacitive sensor as an alternative to the servo/switch?

That should be straightforward. I don't actually have one to use for the model. Is there an existing model that works with the standard extruder you can point me to as a starting point?

did an 18mm inductive sensor bracket ever get made?

I haven't gotten back to it. I don't know if anyone else has.


I forgot that I had modified it for the i3v. Sending you a link in a PM in the forum.

Makerfarm Non-Contact Z-Probe Bracket
Comments deleted.

The download does not have all the files in it.

These are what is there -

flex blocks
idler blocks
idler pin
servo shelf brackets
servo spacer

You're totally right. I'm not sure what's going on there. I don't provide that zip file. It's generated by Thingiverse. I'll try to contact them.

Is this a replacement for the itty bitty double, or just for those using flexible filament?

It's a replacement. If you already have one and are not having trouble, there is no particular need to upgrade.

where do i find the belt or do you have a file for printing it? i know of people printing them with lots of success.... kinda wanted to try....

I have never attempted to print the belt. I would think a printed belt would be very stretchy, but I've never tried.

200mm GT2 belts are available from lots of sources, including my web site: http://clough42.com/shop/

  • Could a printed clip be used to make a belt from a long piece of belt? I was thinking 1 side would have 3 teeth which runs smoothly over the small pulley. The other side clamps the ends. Then I could test before actually buying a fixed belt size.
  • I found http://www.thingiverse.com/thing:84339 for dummy stepper motors and bearings. (I added the missing 688zz)
  • I found http://www.thingiverse.com/thing:193647 for temp "hobbed" bolts.
  • I'm using all Metal J-H E3D 25mm center to center. (a previous Itty bitty didn't fit two extruders. Luckily I 3d printed and fit everything together to see it didn't work prior to printing everything and seeing it didn't work. Hmmm. Heh heh heh.)
  • I'm still going to go to the other 2 things (ver 0, 1, and this one) and read all the comments. I don't want to miss cool stuff.
  • I have a HICTOP i3dp08 and no clue at all what a makerfarm is. It probably just means that steel Angle bracket attached to X rods has to be replaced...
  • I'm concerned because my extruder has a 4.86mm female fitting at the top which connects to a male 4.86mm compression fitting with a long PTFE tube and another male fitting. That is what I started with, a tube to put the heavy motor parts elsewhere. (I only have extruder and host, no remote motor and filament push/pull traction gear. Sorry for making up all my terms. It's probably some jeff bowden richard wade whatachacallit.)
    I'm hoping the shelf bracket securely fastens the extruder somehow and I can eliminate the cable feed here.

Great work! Unbelievably awesome jpegs. Like something outta autocad fusion 360. (I need to ask the autocad people to give me a shiny, dimpled, z wobbled, extremely monochromatic filter so I can publish what MY parts look like with shading!)

OpenSCAD stepper and bearings script
NUT JOB | Nut, Bolt, Washer and Threaded Rod Factory