Alex Extruder 1.75mm

by AlexBorro, published

Alex Extruder 1.75mm by AlexBorro Jan 6, 2014
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Alex Extruder 1.75mm by AlexBorro is licensed under the GNU - GPL license.

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ATTENTION: I do not update the files in thingiverse anymore. Download the latest version from my Google Drive:


After looking for a while for a 1.75mm, I decided to design my own.
First I tried some Direct Drive extruders available in the web..
The need for a motor fan for low Tg materials like PLA bored me.
The low resolution (low steps / mm) is not something pleasant to me..
And huge gap between the pinion and the filament output duct makes it difficult to push flexible filaments like Nylon..
So I came up with a geared 4:1 extruder, that has been working fine with many 1.75mm filaments, like ABS, PLA, Nylon and PET.
It is simple to assembly and low hardware parts count. Just download the correct extruder for your hotend, gears and Idler. Check Assembly Instructions for further information.
If you need the extruder for another hotend and/or hobbed bolt/pinion diameter, let me know on comments bellow.
Hotends provided:

  • Bowden
  • E3D V4/V5
  • Magma
  • JHead Generic
  • Sethi3D
  • 3DMachine
  • Movtech


ATTENTION: I do not update the files in thingiverse anymore. Download the latest version from my Google Drive:


You will need four printed parts:
1) The right Extruder for your hotend;
The files are named as follow:
Alex-Extruder[Effective Hobbed Diameter][Hotend]
For example:
is meant for E3D hotends and 8mm hobbed bolt (effective diameter of 7.6mm)
2) Idler
3) Hobbed Bolt Gear for your bolt
4) Motor gear;
All the files can be found in the ZIP package, just download the right one for your hobbed bolt/pulley.
The Washer.stl is optional and can be used tight the 8mm hobbed bolt with a nut.
For the extruder, you have some options. I have made, besides the generic JHead groove mount with 2 bolts, a "snap fit" mount for some specific hotends like E3D. You just need to insert the hotend in the right place and are ready to go.. no need for bolts, although I have provided a hole for a holding bolt if you fell more comfortable.
The same applies for the hobbed bolt. I have provided 2 versions, one for the regular 8mm hobbed bolt (with 7.6mm hobbed diameter) and other for MK8 pulley with M5 bolt.
If your hotend or hobbed bolt is not listed here (and probably will not), just ask me in the comments and I can provide you the right extruder... that's a way to make many versions available here.
To put the extruder together you will need:

  • 1 625 bearing
  • 1 M5 x 25mm bolt to mount the bearing
  • 1 M3 x 25mm bolt to mount it in the Extruder
  • 1 M3 x 40mm bolt for spring
  • 1 clothspin spring (see pictures)
  • Your favorite Hobbed Bolt or Pinion + Bolt;
  • 2 washer for your hobbed bolt.
  • 2x 688 bearings for 8mm Hobbed Bolt or 625 bearings for 5mm bolt;
  • 1 M3 nut for the spring bolt;
  • 3x M3 x 10mm bolts for mounting the step motor.
  • Optional washer and nut for the hobbed bolt. Since the gears are herringbone, they stay aligned...
  • Optional M3 x 16mm bolt for holding the snap fit hotend;
  • Optional 2x M3 x 25mm bolt for Generic JHead groove mount hotend.
  • M3 nut;
  • M3 set screw
    Since the pinion is made for a flat shaft - it has a D hole - the above nut and set screw are optional but recommended for long term use.
    Then.... just put all together.. Recommendations:
  • Let the motor for the fina step.
  • Put the gears in contact and fix the bolts.. there is no need for pressing the gears... just touch them and fix the motor bolts.
  • Put 2 washers between the hobbed bolt gear and the extruder.
  • If you choose to use a nut in the hobbed bolt, DO NOT over tight it.. again, DO NOT over tight it.. just tight enough to TOUCH the washer in the bearing.. I mean, TOUCH, no pressure at all. A nyloc nut will avoid the nut from loosening.
  • If your "snap fitted" hotend is a little bit loose, use the M3x16mm to hold it in place. Again, DO NOT tight this bolt as well.. otherwise you will break the plastic piece.. just tight it to touch the hotend.
  • Do not over tight any bolt.. there is no need and you are dealing with plastic not metal.. just tight them to touch its counterpart.
    Printing recommendations:
  • Layer height = 0.2mm
  • 3 or 4 perimeters
  • 20% infill is enough
  • Use a layer width 0.4mm or less.
    For gears, I recommend printing external perimeter first.
    Your printer will need some bridging skills for printing the extruder, but it is not a big deal.

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Dear Alex, this Thing is compatible for Movtech Cubica 3D Printer??

Alex....tem versão pro E3d V6?

Do you have any E3D V6?

Is this SolidWorks? Can I have the source files so I can remix it to fit my needs (mk7 with M5)? I really appreciate your design and would be awsome to use it in my printer. Thanks!

GDrive says that the folder is empty. :(

Sorry, I have just updated the link.. Click on it again.



Por acaso teria a versão para o hotend da GTMax 3D. O ajuste do motor fica no limite mesmo?

Alex, teria como modificar pra usar mk7 com m5? Tem um remix que usa essa combinação, mas ele mudou bastante coisa pra ficar para 3mm..seria muito difícil? Obrigado!

Oi Alex, desculpa escrever em português por aqui mas é que eu não tenho muita pratica com o inglês e provavelmente eu não conseguiria me expressar corretamente.
Enfim... Eu tenho um hotend da 3D Machine e imprimi o seu extruder correspondente mas depois de um tempo que o hotend chega na temperatura de trabalho ele acaba ficando folgado no encaixe. Eu pensei em fazer um adaptator como esse:
mas eu precisaria de uma versão do seu extruder que não tivesse encaixe pra nenhum hotend, que saísse o furo do filamento direto.
Você poderia alterar e incluir esse extruder modificado? ou você tem alguma outra sugestão para eu fazer?

Parametrized version of J-Head mount by Acarius10
by imrahil

Cara, seu problema é outro.. a cabeça do hotend está esquentando MUITO mais do q deveria.. isso vai te causar outros problemas mais graves, como entupimentos..
Tente colocar um cooler no hotend ou descobrir a causa disso.

Eu imprimi o extrusor em PLA, pode ser por isso também?
Porque a temperatura eu medi com dois termômetros diferentes pra garantir e a temperatura bateu entre eles e o NTC do hotend.
Agora eu quero imprimir de novo o seu extrusor mas dessa vez em ABS.
Eu só achei que faltou algum tipo de trava no hotend, porque de resto eu achei ele o melhor do thingiverse.
A minha impressora imprime bem só que o meu extrusor atual é um direct drive e meu motor não é tão forte pra imprimir na velocidade que eu quero, por isso eu quero migrar de extrusor.

Cara, nunca se faz um extrusor em PLA... esse material resiste muito pouco as temperaturas mais elevadas. Sugiro q compre (ou imprima, caso tenha outra impressora) um extrusor em ABS. E sim, ele tem uma trava, um furo para se colocar um parafuso.

Oi Alex, eu uso o hotend da 3D Machine, eu nesse modelo eu não achei o furo pra por o parafuso de trava.

Só para os desavisados que passarem por aqui, no hotend não vai ter furo mesmo. O furo é na estrutura plástica da extrusora que somente apoia (firma) o hotend no encaixe da extrusora. O hotend (parte de metal) não tem furos mesmo. Eu uso este extrusor do Alex e funciona beleza.

Can I use MK7 pulley with M5 bolt?

Check my remix.

Will it work on a makerfarm - I believe you had one correct? Or what would need to be modified?

It should work.. Just replace the original one.

Done ! the problem was the different variable for X and Y .... One more question for you , do you have any recommendation regarding the step for extrusion ?

thanks a lot

It depends on your hobbed bolt. If you have a 8mm one and 1/16th microsteps, starts with 500 steps/mm and perform a fine tuning.

Let me ask you something , always that I try to print bolt gear i get a oval piece and not round , it is right?

No, it is not.. probably you have some issue in your printer.. usually some play in the belts have such behavior.

Printed with 0.55 layer width and still working fine! Gota be careful to use proper cooling and/or low speed when printing the small gear though.

I have to say this is a great design, I was messing with this for use in as bowden extruder it was powerful enough to push the 1.75mm pla filament I had through a meter of 2mm id tubing and the hot end. but that said I also tried some flex pla with the same setup and it got to the hot end then just chewed up the flex pla at the hobbed bolt.. not really a design flaw because its alot to ask for any extruder and as suspected it didnt start finding new paths as other extruders would have.. Only thing I wish was it had a ubis hotend mount

I made this last night and it came out great. However, I would love to see it for the 608 bearings, which are more common for the larger hobbed bolts. The larger gear is what I am using and my bolt fits that perfectly, but the bearings I have don't (I have a TON of the 608zz bearings for various Wade type extruders). Any chance of one that works for that bearing set? Leave the idle as is, as the shaft for that is not critical and I can source it, but the bearings for the hobbed bolt I can't source readily.

i second the request for a 608 bearing.

The 608 is really larger than 688zz.. It is quite impossible to make a small extruder with 608..
Realize the cutout for 688 is on boundaries of the extruder "tower".. There is no space left.
In order to fit a 608, I should rebuild all the extruder because the idler will hit the bearing before touching the filament.
So it is not a small change..
If you live in USA, it is really easy to source a 688zz.. Even in Brazil - where I live - I can source them for less than $1.



Thanks Alex. I certainly can get a 688zz, but my issue, to be honest, is that I have a lot of 608's lying around. i will go dig and see what I have scavanged and hope that 688zz's are in my box of goodies. If not, I'm sure I can get them easily.


ok!, and can we use a 625 with a 8mm hobbed bar?, if you upload the source file i will try to make it work

The 625 has a 5mm ID.. how do you plan to fit a 8mm bolt??? For a 8mm you need the 688.