Faze4 Robotic arm

Faze4 is 3d printable 6 axis robotic arm . It uses stepper motors and 3d printed cycloidal reducers.

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If you are interested in PCB used in this robotic arm send me a msg! I have been building robot arms for around 7 years now. Every one better the next one , and this is my latest arm. It came to be when i made a working 3d printable cycloidal gearbox and saw some potential in it. After that i designed whole arm around it .It uses 6 stepper motors , 3 nema 23 , 2 nema 17 and 1 nema 14 . Joints 1-5 use cycloidal gearboxes and belts while joint 6 uses planetary gearbox. Joints 1 and 6 are homed on inductive sensors. All other joints are homed on limit switches. The arms software is running on teensy 3.5. The total cost of the arm is around 1000 dollars

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So the whole project started with cycloidal drives. Why cycloidal drives?

  • They are really easy to 3d print
  • can have large reduction ratio
  • cheap
  • low backlash even when 3d printed

When 3d printing them there are few things to keep in mind , but i might make video about that later.

They were all designed using this great tool , and them in solidworks. There are 3 versions of cycloidal drives in this arm 11:1 version , 15:1 version and 27:1 version.

Design of the arm.

Esthetic design was inspired by FANUC’s LR Mate 200iD. 

Goal was also to hide all wires in the arm like most industrial arms do. Only visible wires ( or pipes ) would be ones for gripper. 

Weight of the arm is around 14-15 kg , but it can be reduced by printing with less infill.

Motor position

Firstly i wanted to move all motors to the base of the arm to reduce weight each motor should carry. First idea was to just copy the design of this kuka arm. I decided against that design and just went with probably most basic design where every motor is directly on the joint of actuation ( Except for joint 5 that i moved a little bit away).

Joints 1,4 and 5 use belts in addition to cycloidal reducers. Belts are mostly used to offset the place where joint will be rotating so that we can route wires thru the body of robot. They also give some additional reduction ratio. For example Joint 1 has 15:1 cyclo but with belt our reduction ratio jumps to 25:1.

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  • 1
    assembly instructions of arm

    Whole instruction is in PDF file

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Luis Valle wrote 05/03/2021 at 18:20 point

Can I still buy the controller board? I'm not able to buy it from the link provided. Please let me know specifically how I can obtain it. Thanks,

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Petar Crnjak wrote 05/27/2021 at 18:45 point

Hey, send me an email on

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chris.hexx wrote 02/17/2021 at 21:03 point

Is the original manipulable CAD file available? I'm working on a build of this, and half of the J2 fork is undersized in the STL, like a horizontal slice is missing from its bottom.

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Petar Crnjak wrote 03/14/2021 at 13:51 point

Sorry I didn't see this comment. I made CADS for this robot and a new CM6 robotic arm available on Patreon.

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Zoé wrote 10/02/2020 at 21:09 point

I wonder if you could add a (torsion) spring to Joint2 in order to balance the arm's own weight, and reduce torque requirement on the gearbox.

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Petar Crnjak wrote 10/03/2020 at 10:44 point

It is really hard to add anything in  this faze of development without destroying overall look of the arm and need to change bunch of parts. But if someone wanted i belive it could be done.

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bozkurt13 wrote 08/27/2020 at 15:07 point

koparma kartının markası ne ve kaç eksenli?

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Petar Crnjak wrote 08/28/2020 at 10:35 point

I am not sure i understand correctly but that black pcb board that everything is connected to is made by me and if you are interested i will be selling them soon. For axis question robot arm has 6 axis.

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thorning wrote 08/27/2020 at 12:58 point

Looking forward to study your upcoming video.

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thorning wrote 08/26/2020 at 22:35 point

So I succeeded, sort of.  I reduced the diameter of the both cyclo discs by means of files to a diameter, so I could put them in place and take them out by fingers only (before tools were needed). Both discs are facing the bearings upwards, like shown in your manual.  Then I turned the upper disc to a position where I could insert the output shaft with ø3x8x4 bearings. The stepper wobbles a bit when running, but the gear is working.

Kind regards Niels

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Petar Crnjak wrote 08/26/2020 at 22:43 point

Hey, thx for info. This weekend i will make a video about tolerances and how to fit those gears since i dont like how i explained it in PDF tutorial. Also i will release disk step files so they are easier to edit. 

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thorning wrote 08/24/2020 at 14:30 point

I have for years been building and experimenting with robotarms. Like you I have the problem with suitable and cheap reduction gears for the axis. When I discovered your robotarm, I fell in love with the design right away. Before I start building it, I wanted to make a test of one of the the cycloidal gearboxes, so I printed the gear for the forearm and assembled it. I have carefully read the comments in your fine manual several times, but I still have the problem that there is no way I can get 5 pins with each 2 pcs  3x8x4 bearings down in the 5 holes in each of the 2   11:1 cyclo discs at the same time. I can not make a full rotation with a single ø8.0 mm rod inserted in 2 aligned holes in the cyclo discs. I can make it work with 5 pins ø3.0 mm in the Joint 5 Output shaft.

Now I am writing you to find out whether is is me not being able to read the manual properly or is there some information I have overlooked somewhere.

Hope you will find time to answer my question.

Thanks in advance

Kind regards Niels 

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Petar Crnjak wrote 08/24/2020 at 23:08 point

Hey , It is late now here but only thing i can think of is that i messed up that part where you need to align 2 holes on cyclo discs. You maybe need to make them face opposite sides. If that does not work try other combinations by attaching one cyclo disc and rotating the other one until you see holes where you could fit these pins with 3x8x4 bearings. Please keep me informed on what you did since it is probably mistake on my part. Thanks.

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Scott wrote 09/18/2019 at 13:42 point

This is great! I'm an industrial robot programmer by trade, and I'm literally sitting a meter away from an LR Mate 200iD/7L at this very moment. This is one of the more promising DIY six axis designs I've seen. I've been looking for one to build, and this may be it. I look forward to your updates!

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Petar Crnjak wrote 09/22/2019 at 19:35 point

Wow thx . I am making some improvements to make it more stable at high speeds so maybe I wil drop a new video of movement soon.

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dekutree64 wrote 08/23/2019 at 15:36 point


Looking through the assembly guide, are you sure all those bearings on the cycloidal ring pins are necessary? I thought the disc shape was calculated to have rolling contact on cylindrical pins, so the bearings should theoretically never turn anyway. I've seen several other people use bearings on the pins too, but no explanation of why. Is it a different tooth profile than hypocycloidal, or just a way to compensate for inaccuracy in fabrication, or something else?

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Petar Crnjak wrote 08/24/2019 at 11:35 point

They are necessary , i made few designes with 3d printed roller pins and they work but can get jammed and have more backlash. I only used bearing because they were cheap , better choice would be screw and metal sleeve ( like this : but i could not find suitable components.

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