Saintflint Extruder

by mmemetea, published

Saintflint Extruder by mmemetea Aug 22, 2015
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Not your mother's extruder! Kidding... This simple yet very effective extruder is the brainchild of some members of the QR's community (in no particular order: Shauki B. / Mauro Manco (Exilaus) / Dale Dunn / Darkberg Aryavis (Flint Eastwood) and myself). I just tried to put it in a pleasant form. The name comes from the ring that looks like an aureola and it uses the flint wheel of a lighter. It was done initially for a NEMA17 and 1.75mm filament.

The nice detail about this design is that it's almost self-locking on the filament and the forces applied on the stepper motor are cancelled by each others.


This is an original design of an extruder that has the following features:

  • Symmetrical load on stepper axis;
  • Adjustable filament pressure without spring;
  • Simple & open design (easy to see what's happening inside);
  • No need for a geared reducer, direct drive;
  • Support flexible filament (anti-buckling support on both extrusion and retraction);
  • Best bang for your buck;

Bill of Material:

  • 1 flint from either mini bic or clipper lighter;
  • PTFE liner 40 cm for the loop + your regular bowden line;
  • 2 608 bearings;
  • 2 screws M3 20 mm length;
  • 3 M4 nuts to secure the PTFE line;
  • 1 stepper motor NEMA 1.7A (or even lower);
  • 4 shims / inner diameter >5 mm (I used rolls from a used bicycle chain;
  • 1 screw M3 5 mm length

See it in action:

Files for modification are publicly available and with a free Onshape account here:

Successfully printed in PLA, ABS or PETG (2 shells and 20% infill is enough... But your milage may vary).

For details about fitting the coil on the stepper motor, you can find them by looking for #bicgear, #saintflint or #flintfeeder on Google Plus.

For fixing of the coil, the trickiest part of this build, having it only glued on the stepper shaft is not enough, it must be compressed axially, otherwise, it will "uncoil" and break on pushing or retracting the filament (depending on the direction of the filament vs the direction of the coil) and this will happen:

Some alternatives were available (Clipper lighter with solid flint wheel and internal 5 mm diameter), but more recent models have smaller holes and drilling this stuff is REALLY hard (You need to get a drill made for ceramic or glass as shown in one of the picture. Better to be good quality if you intend to make several, otherwise you can cheap but it probably won't last 1 or 2). To secure it, the best is to tap the axle with an M3 thread and use wasted bicycle chain rolls as spacers (ask them to your local bike shop, they should give them for free) and stack them.

Steps to tap the shaft of the stepper motor:

Imobilize the axle with the tool used to secure the thread maker (which means you may need another one);
Drill a hole 2.5 mm diameter 10 mm deep into the shaft;
Form the thread with a 3 steps M3 forming tool, since the hole is blind (not going through) this is required;
You can also put some strong Loctite or Super Glue to help secure the coil (watch out not to cover the curled part);
You should be good to go... Hope it helps. Like I said, not your mother's extruder! But it worth every cent...

2015-09-03 Due to popular demand, I've just uploaded an MK8 edition.

2015-09-08 Adding the following postscript GCODE in your slicer will ease the change of material (will retract enough filament making it easy to empty the Bowden by hand). In my case 16 mm seems a good length for the E3DV6:

G92 E0; zero the extruded length
G1 F250 E-16; Retract filament from barrel
G92 E0; zero the extruded length again

Note: Add the reverse action at the beginning of a print to pull the correct length before starting. If you interrupt a print, remember that you won't have an empty extruder...

2015-09-13 Added Casino Chip
Print (x4) and insert in the bearing place BEFORE putting the bearings and the axles in place. Center and glue to the external race of the bearing on each side. Help if the color has a good contrast with the body of the extruder.

2015-09-29 Corrected diameter of drilling for tapping the step motor
The corrected diameter before forming the thread is 2.5 mm. 2 mm is possible (I did it), but it's way easier to go with 2.5 mm. Thanks Shauki B. for the note.

2015-10-20 Added 3 mm version.

2015-11-09 After some experiment, I wouldn't recommend the 3 mm version for the following reasons:

  • Due to the layout and the compact size of the extruder, in order to fit, the path has to be curved (otherwise the M6 nuts won't fit). This is adding substantial friction.
  • The ratio of surface contact vs radius of the gear doesn't play in favor of the 3 mm version. Grinding is much likely to happen;
  • The 3 mm filament is much less flexible and more prone to break in the curves than the 1.75 mm;

For all the above reason, I think it's better to stick with Wade's or other derivatives that privilege a straight path... Sorry guy, I tried!
(Note: I still enthusiastically recommend it for 1.75 mm. It never let me down...)

01-10-2016 Added MK7 version.

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i built the first one and used a mk8 gear . It worked great but needed a torquey nema17 to make it work.. recently i needed a extruder and got hands on a bic lighter.. i made the extruder using a small 34mm nema17 ... this thing has got loads of torque and no stripping of the filament.. i think this is one of the most brilliant extruders i have used. Only thing is loaded filament is a PITA. great work! .. thanks.

Hello mmemetea, I really like this design. I am excited to try it out but I ran into a small problem. I printed the MK7 version from here on thingiverse only to discover that my mk7 gear heads are not standard. They must be some cheap fakes. In any case I need to change the diameter of the gear head to 12mm with a gap of something small like .5 mm or .25 mm. Not sure on the Gap exactly. Is that a measure of how deep the groove is on the gear head? Because my gearhead has an OD of 12mm and the groove ID is 11.5. So the groove is only .25 mm deep Or does the gap variable refer to the gap between the extruder and the drive gear.

So I found your link here in the comments about the onshape doc with the variables and I changed the variables. Before I printed that file i noticed that the holes where the filament go through have been changed to groves or channels. I don't think that will work for soft filaments.

So I found your main file on OnShape that has the holes but it doesn't have variables.

I am not asking you to do the work for me but I would like your advise. How should I proceed? Should I make a copy of the main file with the holes and make my modifications from there or should I trust/change the other file with the variables?

The file with the variables was supposed to accommodate small variations around standard values. I think the main file doesn't have the variables and only the version called HbP has them. I've just modified it with the values you mentioned. It's just a question of getting a print and adjusted from there (always depends significantly on the printer itself). Let me know how good (or bad) it went... ;)
The file should be here:

Works great thanks to the double transport. The only issue that i ran into is if the hotend leaves a thicker spot on the filament when unloading its often catched at the bow and ripps as i try to pull it out. Id then have to fully dissaseble it.. Maybe ive to widen or wear it out a little more. I had to print an in xy direction scaled up retention ring as the original one was too hard pushing the halves together. Iam using the original mini bic lighter wheel and it performs! As iam coming from a geared extruder its quite a change to are not able to turn the drive by hand to load it or pushing some fila out by hand. Maybe ive to print a kind of knob to turn the shaft by hand as i used 6 sided long nuts as the spacers for the bic wheel. Anyway a genius design, thx (:

I also had this problem sometimes in the past. Not sure it's related specifically with the Saintflint technical solution, but you can probably get rid of it by including a small retraction at the end of your print. Something like this should the trick:

"G1 Z10 E-3 F3000 ; move extruder up 10 mm and retract filament 3 mm"

Glad you're enjoying the solution... ;)

why have you not used the push fir connectors ? wont it be simpler ?

The main reason as +Shauki B is mentioning in Google+ is the fact that the nut were allowing a compact design. The trick to get the nuts held in place is:

  • Get a sufficiently rigid PTFE tube. You don't want it too flexible/ductile;
  • Pre-thread the external part of the tube with thread forming tool;
  • Form a cone at the internal diameter of the tube AFTER the nut is in place;
  • Insure no debris is present that would catch the filament;
    ... You should be good to go;
    I have thousand of hours logged with this. I get probably more problem with the quick fitting (heatsink side) than with nuts.
    Good luck and give it a go...

Saw this design and was very excited! Double the pushing force and symmetric load on the motor!

But it doesn't work for me...
The fillement is rather slippering with lower tension of the nut or motor is stuck with stronger tension...

What am i doing wrong here...?

Check the alignment of the groove with the holes.
What hobbed gear are you using?
Did you clean properly the guiding holes (no friction should be felt when passing a filament by hand without hobbed gear/nuts).
Which stepper are you using?
A photo would help to diagnose the problem...

Hi, I think that PORBLEM IS SOLVED!

I drilled with 2 mm drill the PTFE tube where the M4 nuts are holding. there was pretty high friction because the PTFE tube was squeezed under the nut.
Now it's working very nice and seems to be OK. also added a small chamfer to the tube inside, so it's also much less trouble replacing fillement!

I would advice to add this tip to the instructions...


If use the item from airtripper, the extruder get stronger. http://www.thingiverse.com/make:299935
screws that hold the halves, bend under load.

Saintflint Extruder

The link to Onshape version doesn't work anymore. It says Not Found.

Thanks for the quick reply. ^^
Can't wati to try this out!

Be sure to modify the dimensions to fit your hobbed gear if you're using the Onshape document (they are the 2 variables that are at the beginning of the history on the left). Happy extruding!

I'm looking at your onshape doc and the MK7 version and it looks like two features are not re-generating properly: sketch and extrude straighten bridge. When I copied the original doc and adjusted the first two variables as suggested, those features failed as well. Are these clitical to the print? Thank you!

You can live without them, it's just cleaner with.
If you want, share the document with me with YOUR values and I can try to rebuild the bridge.

It happens on your mk7 version too. I think I used 12.5 and .4.

I've actually found this extruder to be quite reliable. I've put in a brass mk7 gear of small diameter and everything else fits perfect! It takes a bit of bowden tubing to get right, but when it does, it's like perfect torque all the time. Not as torquey as a gear system, but close! Motor easily skips when the filament isn't aligned instead of blowing out a bowden connection.

Is mk7 version step/iges available?
My M4 nuts larger than general, so might need to tune it ^^

Just uploaded what you've requested... Hope it'll do it.

Actually I found it on onshape,
And found the original design might for my M4 nuts? but it's not deep enough to be center.
I drilled it deeper to let my nuts much near the center.

Excellent work! Seems awesome to get the maximum power from our stepper motors.
Could you re-upload the cassino chips? The one supplyed seems to be broken (to thin and small).
Also could you upload all the pieces separately? I'm building the MK8 version and need the bearings and PTFE supports and canonly find them at the combined files.

Thank you!!

Casino chip files is OK. What is your slicer?

That is weird, because even the thingiverse preview shows it flattened.
I'm using Cura slicer.

It is supposed to be flat, take a look at the pictures, it is a disc that lays flat on the side of the bearing to give the user a notion if there is motion (no slipping, everything ok) or not (some clogging happening, not ok). They have to be very flat otherwise they're not possible to slide in... Hope it clears your doubts.

Oh wait, I'm so sorry. I misinterpreted the usage and I thought the cassino chip where supposed to be the lock wheel.

Hi, mballoni... Thank you! Appreciated. You can separate the parts that in a single STL file using Cura, Meshmixer (both free) or Simplify3D.
The Casino must be printed at 0.1 mm for layer thickness otherwise, it's too thick to be able to assemble, but the model is not broken. I'll check anyway and will reload a verified version.

You are right, I used freecad to separate the parts. I'm still a newbie.
Thank you for your patience.

Thanks for the mk7 version. In that file, it appears the locking ring and the two main clamp halves are combined together as a single print. Also the locking ring is set to be printed on edge instead of flat. I tried to open the .stl to see if I could fix this myself and print it, but it won't open in sketchup.

Thanks for the design and thanks for your help,

Thank you for the notice. I'm just uploading a corrected version right now. Sorry about that.

I have printed this to test with my CoreXY machine I am building, how did you mount the motor to the machine? From the pictures it looks like some kind of bottom mount.

You're right... Actually is a custom made and mounts on the Z-bracing rod that I've added to my Prusa for increased rigidity. But there's a lot of NEMA17 support that would serve the same purpose for your case. The only caveat being that longer screws are likely to be required to accommodate the extra thickness of the support.

in the description you don't say if it's for 1.75mm or 3mm... also you don't specify which motor it would fit? nema 17? could you clarify, please? great job btw, thank you

You're right, it's not mentioned. Will correct right away, but it was initially done for 1.75 mm and NEMA 17 (42 mm).
I've done a lot variant for other people (3 mm, NEMA 14, 625 bearing, other type of hobbed gear, etc...). My point being that it's easy to modify with the free online application that was used: Onshape.

I'm digging this thing, can't wait to print it

I've tried at least 4 different extruders and all have been unreliable. This very clever design solves many of the slipping and skipping problems that have plagued the other extruders. I made slight modifications to allow 3mm filament and it works great! I did not use the lighter flint wheel, but instead used a mk8 gear that I already owned. I will post a remix when I get a chance. Thanks for posting this great design!

I was convinced that I had posted a 3 mm version here as well, you just proved me wrong :)
I'm glad you appreciate the principle and design of this community driven effort. Please do post your remix, I'll be curious to find how you managed to the arrange the layout. And a last question: which CAD tool did you use?

Hi, I've seen you do the same thing with a nema 14 motor.
What about nema 11 ? I have it, i can test ...
Mk8 or Mk7 i own both.

I can try. I would recommend an MK7, the space will be cramped. Also like to switch to 625 bearings. Let me check and I'll be back to you here.

Ok but i need to buy the 625 bearings as actually i have 608... so a little more time needed.

Thanks in advance !

Not doable on 608 for sure. Looks very tiny but more or less ok with NEMA 11. What are you extruding with that, noodles? :)
Have a look here (WIP):

It's ok with 625, i'll arrange the buy.
And well, near my home there is a farm that print "spaghetti" and other type of "pasta" with 3D printer :)
So noodles aren't a bad idea :)

Thanks for the MK8 version!

Let me know how it turned out (clearance, gap, etc...). Since I don't have a physical MK8, feedback is most welcome.

Seems to fit ok, although not tested yet. Needed to mount the MK8 Gear Drive upside down to fit well.
I have uploadeed some photos and guidelines under 'made'.

I can confirm the MK8 version works perfectly, no need to find the correct lighter.
After some testing with PLA, I am very impressed by the performance.
This simplistic design is easy to print, build and without the need to source a lot or difficult parts.

The only thing to take note of, is the 200mm PTFE suggested in the description which is far from sufficient. I have used 300mm length, which I believe is the minimum length needed for a smooth loopback.
Check the photo's I included in the 'make' I posted.

You're completely right. I've corrected this and put 40 cm for good measure. Thanks again for the feedback.

You are welcome and thanks again for this design and ideaby you, Mauro Manco and Shauki B (maybe I forgot someone)!

With a longer PTFE loopback it will be easier to assemble the extruder and change filament.
I will need to test this with flexible filament in the near future.

Add Dale Dunn for good measure and let's call it a day.

Very interesting design indeed.
I wonder if the force required on the first step, to push the filament in the PTFE tube and make the curve, is adding too much stress to the motor?

How did you secured the BIC coil? Could you post a photo with it disassembled?
It is a brilliant idea!


Another important detail: to load it, you have to open it! Maybe I put a video showing the operation, it simple, but without opening it, it's rather hard and could put your coil at risk (they are brittle and could be damaged by "high speed" manual loading).

At first, it takes a little additional effort when PTFE line and nuts are not in place (that is, not properly aligned). Once done, this doesn't take more effort than to push the filament through regular bowden tube. The "curve enforcer" can help if the extra PTFE line is a little short, but with 20 cm, it shouldn't be needed. Adding some silicon oil (other mention canola oil) in the PTFE does help to smooth out, but in general, the added benefit of the double traction overcomes largely the little added friction. Printing semi-flexible filament is perfectly possible and with great results:

For fixing of the coil, the trickiest part of this build, having it only glued on the stepper shaft is not enough, it must be compressed axially, otherwise, it will "uncoil" and break on pushing or retracting the filament (depending on the direction of the filament vs the direction of the coil) and this will happen:

Some alternatives were available (Clipper lighter with solid flint wheel and internal 5 mm diameter), but more recent models have smaller holes and drilling this stuff is REALLY hard (even with diamond drill, the diamonds get loose!). The best is to tap the axle with an M3 thread and use wasted bicycle chain rolls as spacers (ask them to your local bike shop, they should give them for free).

Steps to tap the shaft of the stepper motor:

  1. Immobilize the axle with the tool used to secure the thread maker (which means you may need another one);
  2. Drill a hole 2 mm diameter 10 mm deep into the shaft;
  3. Form the thread with a 3 steps M3 forming tool, since the hole is blind (not going through) this is required;
  4. You can also put some strong Loctite or Super-glue to help secure the coil (watch out not to cover the curled part);

You should be good to go... Hope it helps. Like I said, not your mother's extruder! But it worth every cents...

Thanks... Corrected.