ROFI bipedal robot

by jdow, published

ROFI bipedal robot by jdow Oct 22, 2012

Featured Thing!


ROFI is the fifth prototype from Project Biped. It is a self-contained, bipedal robot that uses accelerometer feedback to balance. It has 12 DOF (degrees of freedom) and can walk around while avoiding obstacles using an ultrasonic range sensor. A small on board Android tablet provides the brains and an Arduino mega board provides the hardware interface. All of the designs, source code, and parts lists are free and open source. Detailed step-by-step animated assembly instructions are provided to allow anyone with a low cost 3D printer and an interest in learning about robotics to build ROFI.

A full overview (with source Blender files) can be found at the Project Biped ROFI website:


walking info:

video of the robot:

Recent Comments

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Has anyone tried to making a ROFI with Cube 2 Printer?

When I build in software, these files doesnt compile.


Whats going wrong?

Has anyone tried to making a ROFI with android 4.1 or upper?

I'm thinking to make an ROFI using an updated android phone with the same weight of Archos 28 (68g) and size (100 x 54 x 9 mm).
or I'm thinking try to making and parametric ROFI that accept some Androids phones like mine (113.2 x 61.6 x 11.6mm 120.6g).

Has anyone tried something like that?

You're on. I have a spool of 3mm blue ABS sitting around now that I've moved to 1.75mm. Unused, but out of the original package. Want it? Let me know off list ([email protected]) where to ship it to.

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Step by step animated assembly instructions:

printed part diagrams:

non-printed parts list (vender and cost):
docs.google.com/spreadsheet/ccc?key=0Ai_h1KTMNaWNdHktUVZlT3RZaGdzZm1tSXFrSm QzTmc#gid=0

UPDATE 11-05-2012

Thanks to the CSULB EE class (building the first ROFI clone) for pointing out that some of the parts designed to work with the new MG966R horn style were too thick. Affected parts are:

- Center Bracket
- Foot
- Body Riser
- Servo Bracket Left
- Servo Bracket Right

The new parts have been fixed and the zip and STL files have been updated.

UPDATE 11-28-2012

A few parts weren't slicable with Slic3r because they had problems with their meshes. Interestingly they all sliced fine with ReplicatorG, so I didn't catch the problems with the parts when I printed them. Thanks to 3daybreaker and Architect for pointing this out! Affected parts are :

- body strut.stl
- center bracket NH v2.stl
- heel left.stl
- heel right.stl
- servo bracket left NH v4.stl
- servo bracket right NH v4.stl
- servo wrap lower left.stl
- servo wrap lower right.stl
- side knee bracket.stl

The new parts have been posted along with a new zip file for the entire set of ROFI parts.

UPDATE 11-30-2012

Thanks to wildseyed for pointing out that the foot was missing part of the bracing on the rear riser! This was causing the feet to be much weaker than they should be. The bracing has been added back in and the file "foot NH v3" has been posted. Also the zip file has been updated.

File Name




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damenon on Jun 26, 2014 said:

Has anyone tried to making a ROFI with Cube 2 Printer?

When I build in software, these files doesnt compile.


Whats going wrong?

guilherbot on May 5, 2014 said:

Has anyone tried to making a ROFI with android 4.1 or upper?

I'm thinking to make an ROFI using an updated android phone with the same weight of Archos 28 (68g) and size (100 x 54 x 9 mm).
or I'm thinking try to making and parametric ROFI that accept some Androids phones like mine (113.2 x 61.6 x 11.6mm 120.6g).

Has anyone tried something like that?

wildseyed on Jan 24, 2014 said:

That very tablet, unless you are willing to cut holes for something a little bigger, or can find one with the same dimensions. It is surprisingly small. If you need one, I still have one here that I'm not using.

SkyRider on Jan 24, 2014 said:

I just ordered one from Amazon, but I can get my hands on any of a variety of these things. But I seem to have read that the software is specifically geared for this particular tablet. Have you tried any other? I can easily modify the head to carry a different tablet, that's not an issue, but I'd hate to be tied to something that's largely dead technologically that can't be replaced. What do you want for the one you are not using?

SkyRider on Jan 23, 2014 said:

Did anyone try something other than the Archos tablet or must it be that very tablet?

kojote on Nov 5, 2013 said:

To a certain degree i hate you - some parts really have some issues printing, especially the feet (tried 5 different layer infills/stuff, every single one broke) but since it's a PrintJob i just can't say no :) Especially the Top Part with the pieces printed in the air is not a nice thing to do.

SkyRider on Jan 23, 2014 said:

I had similar problems as you when I printed my parts, particularly with the heels. I am using a Solidoodle. To get around this, I imported the parts into TinkerCAD and then exported them back out, creating a plate for parts to do a bunch at once and that worked. I'm guessing TinkerCAD cleans up some of the points in the process.

Ddiao on Jun 15, 2013 said:

Hi, do you sell the package of printed parts?

burkeam on May 23, 2013 said:

ROFi's photo is in the news. Looking good..


3daybreaker on Mar 15, 2013 said:


I could not locate the prescrybed SKY lipo's, but after some intense googling I found these for replacement at Honny King (NL Warehouse)

T1300.2S.20/35821 Turnigy 1300mAh 2S 20C Lipo Pack

You can see the ftting on my blog www.3daybreaker.blogspot.com

or here: http://2.bp.blogspot.com/-6Cwz...


3daybreaker on Mar 15, 2013 said:

To all ROFI builders:

The horns that Architect has developed fit perfect into the ROFI parts, but mine will not slide over the servo. I have reworked them with a hot 5mm hex-wrench after which I pressed them onto the servo to have it cool down together. After that the fitting is good: Heat the hex, push the horn onto it, rotate it 2x 360 degrees and push it onto the servo.

Pictures on my blog www.3daybreaker.blogspot.com

or: http://4.bp.blogspot.com/-qi5G...

and: http://1.bp.blogspot.com/-nScD...

and: http://3.bp.blogspot.com/-2a0c...


peterhorst on Jan 9, 2013 said:

ROFI IS great.
ROFI is tough to build until he (or Her?) really "static" walks. Really tough..
You get so addicted, that you are willing to spend lots of money (Euros in my cas) and time.
The hardes things are printing the parts with a (wooden !!!) Replicator and cabling all those parts and wires.
I use ABS on my (wooden..) dual replicator, lots of capton tape and many days of trial and error. Then I reworked all Parts with acethone to get as much strength out of it. I filled the bores which act as nuts with dissolved ABS to get screws to hold.
To "train" ROFI, build some Stand as you can see in my 1st picture to give full freedom of movement.
Headaches (some more) are caused by too much play in construction and especially gear-play inside the servos. Watch out: even a well (poser-) trained ROFI will do funny things when falling over his legs...
Thanks Jonathan for that mountain of (fun!-) work

jdow on Jan 10, 2013 said:


Thanks for all of your great feedback, and also let me apologize for your time and money ;-) Be warned that building robots is contagious ... once you make the first one it is hard to stop. In the future I'll be careful to record all of my printer settings because it sounds like you've been working too hard to get your plastic parts strong enough (my ROFI has face planted so many times during development that if he wasn't rock solid he'd be in pieces by now). I'll be releasing an update to the Robot Poser application soon with your suggestions incorporated. I'm also trying to get Google to undepricate gifs in their new version of presentations so I can finish the calibration presentation.

Architect on Jan 3, 2013 said:

HA! just received mine. they say "TowardPro" on the same looking sticker as the towerpro. Haven't tested yet. :-/ i'm sure I can use them somewhere if they don't workout.

burkeam on Jan 3, 2013 said:

TowardPro is normal. Both the good and fake has TowardPro. TowerPro website even shows it

burkeam on Dec 28, 2012 said:

Hello Jdow,

Sorry no photos yet. I had my to take my ROFI apart to replace the counterfeit Towerpro servos which also explains why the horn/arms were a different sizes. New/real ones might not make it this year. Value Hobby is stocking the MG996R state side for $11.99. Watch out for Ebay. Hard to believe the Chinese are now coping/counterfeiting their own cheap products.

The BOM could reflect 12 bearings instead of 10. I'm also using some 20 mm long bolts on the knee frame which is giving me 3-4 mm of threads engagement.

Thanks for the updated instructions

Notes to others about the real Towerpro servos. My fake servo were glossy not matte/flat black, did not have the "do not throw in trash" symbol on the bottom, The CE symbol was at the cord end, bottoms screw were black. The real Towerpro servo are very responsive and smooth when turning by hand. Huge difference in performance.

jdow on Dec 29, 2012 said:

Bummer ... I've added a warning in the BOM about the fake servos (I'll update it if you give me any additional info about the seller). I also modified the number of bearings in the BOM, thanks for posting!

Architect on Dec 28, 2012 said:

Hmm, that's a bummer. I am expecting my servos from china this week. can you explain a little more what the problem was with yours?

3daybreaker on Dec 3, 2012 said:

Me too, I now have finished printing all parts.
Peliminary fitting parts on my old servo"s is going well.

(progress and parts on www.3daybreaker.blogspot.com)

As referenced, I also added some support on the foot inside the front riser.

I see your point around slippingbhorns and printer resolution. This might be an issue,mhowever, if that does notnwork I might be forced to design a converter between my horns and your spaces for them.

One more issue: if I include your .stl in Openscad and add some stuff to it, new heels will generate new .stl. Old heels did not. Current feed do not either. Do you have some parameters that orevent openscad to regenerate on your parts?


jdow on Dec 4, 2012 said:

 Nice blog posts!  With my R2 printer I've started printing in PLA and I've suspected that my white PLA is stronger than my clear and orange PLA although I've never quantified that. One trick that some people have done with FOBO when they had the wrong horns is they just super glued the horns into place. It isn't the ideal solution, but it gets the job done and you can still change out the servo if one burns out.  I'm not sure I understand your last question about Openscad.

burkeam on Dec 3, 2012 said:

Love it Jdow,
Everything is on order today. Had to juggle a few things around due to some items out of stock. Thanks you for the detailed BOM (saved me hours) and instructions. Will post photos from the Christmas build with the kidsDo you mind adding what your replicator settings were at. My TOM been dormant for a few months and needs tweaked  Not sure upgrading to rev40 was a good idea. Never the less your input could save me a few more hours trying to get a clean print again.Many thanks

jdow on Dec 4, 2012 said:

The TOM settings that I used to print ROFI :
  Layer height 270 microns
  exterior walls 3
  (think this was with Skienforge 37)

Favorite R2 settings so far :
  use the finest quality setting from makerware 1.02
  Layer height 200 microns
  infill 25%
  exterior walls 5

I tried 1.03 because it is supposed to fix some issues, but the prints came out a lot worse for me.

3daybreaker on Dec 1, 2012 said:

It seems the foot also lacks support at front side for strength. I broke one foot already at that point. Inadded somemsupport myself, just as you did at the backside.

One thing puzzles me though: my servo control horns are way smaller than the spaces in the brackets. Did you specify bigger horns? I have Hitec HS 300 servos from flying.

Maybe have a printable horn that fits?

jdow on Dec 3, 2012 said:

A printable horn is a good idea!  My only concern is that if the horn started slipping it could cause some strange issues. Perhaps with a high resolution printer you could make the teeth mesh well enough to avoid any slippage.

wildseyed on Nov 29, 2012 said:

O.K. I'm taking the plunge.  If anyone is bored, they can watch the printing at http://wildseyed.com:9090/

@jdow: The feet need some work, to make them stronger 

jdow on Nov 30, 2012 said:

 The feet turned out plenty strong on my TOM ... but maybe your ROFI is going to do some serious stomping?  Definitely send me/ post your mods!  If you're going to make the feet bigger/stronger I'd avoid going too far inward so that the feed won't rub when it walks.  This might mean that you'll have to make too separate models (mirrored) for the feet.  I'll check out the video feed later if it is still up!

Architect on Nov 29, 2012 said:

Sweet! Just in time for me getting in some more servo's .
Every Time I review this project, I just can't get out of my head the days of playing Mech Warrior 4...  I soooo want a minuature Mech to do battle with!! lol, baby steps here, baby steps.

jdow on Nov 30, 2012 said:

 I'm sure there is enough extra carrying capacity for a gatling gun (or at least a nurf rocket launcher ;-).

3daybreaker on Nov 29, 2012 said:

Great, thanks for the rework.
I wiil give the new parts a go this weekend.

Congrats for being featured too :-)



3daybreaker on Nov 25, 2012 said:

Can't reply below anymore.

Slic3r v97 does slice the bracket indeed.
I am gonna try and print them today.

However, the heels still are not manifold.

rgrds Thomas 

3daybreaker on Nov 20, 2012 said:

I printed 2 feet,

I was surprised by the bridging demand, which turned out not to be very nice in my Orca. (Never bridget that much before),

o for conveiniace, I added 3 support shields to the 2nd foot, which turned out to be better after that.

(Images on my latest blog: http://3daybreaker.blogspot.nl... )

jdow on Nov 20, 2012 said:

Nice idea with the support!  I was actually very surprised that my TOM handled the cavity in the feet so well ... didn't have any sagging issues except for the first layer of the roof ( which I just cleaned up with a razor).  Maybe printing at a lower temperature would also help?

3daybreaker on Nov 18, 2012 said:

The Servo Bracket files give 'not manifold' warnings before and 'no layer detected' warnings after slicing (Slic3r)

Any Clue ?


indieflow on Nov 18, 2012 said:

Run the stl's through netfabb cloud first!

3daybreaker on Nov 18, 2012 said:

Hi Jonathan,

great thing you have established over time.

I am starting this ROFI project, however I only print PLA.
Would that be a problem ?  weight-wise for balance I mean ?



jdow on Nov 19, 2012 said:

  I would think that PLA should be fine. Have you had any particular issues with PLA in the past?  I recently got an R2, so I'm going to be using a lot more PLA in the future ;-) If there are any issues, the walking cycles can always be reworked using the Robot Poser application (to be released within a couple of weeks). 

PieterBos on Nov 10, 2012 said:

very very cool, made me smile

Architect on Nov 9, 2012 said:

for weight reason, what infill are they printed at?

jdow on Nov 9, 2012 said:

The parts were all printed in ABS with 10% infill and a single shell.

jdow on Nov 6, 2012 said:

Apologies to anyone who already finished printing ROFI, I just updated a few of the parts that are designed for the newer MG966R horn style (see UPDATE 11-05-2012).  The original ROFI has the old horn style, so I didn't notice the issue until the CSLUB EE class building the robot pointed it out.  Thanks guys!

UechiMike on Oct 23, 2012 said:

I love the way it walks - looks like Jackie Chan in Drunken Master :D

jdow on Oct 23, 2012 said:

 Haha ... I'd have to agree! Sadly I just replaced the static walking cycle (a.k.a. drunken master style) with a dynamic walking cycle that looks much more natural. Check out the new video and let me know what you think.  I still have a link to the old video at the bottom of the video ( I renamed it "drunken master" in your honor).

JuliaDee on Oct 23, 2012 said:

That is some damn fine work there, congratulations!

AUGuru on Oct 22, 2012 said:

Very cool. Is it possible to use any other Android devices? It would be nice to recycle an older Android phone. 

jdow on Oct 23, 2012 said:

 Other Android devices should interface properly with the robot.  Some redesign would be necessary for the body enclosure and the walking cycle would need to be reworked to accommodate a heavier phone.  The main motivations for using the Archos28 (the Android tablet in the design) are that it is really light, small, and inexpensive.

mkfloria on Oct 22, 2012 said:

Really sensational project !!!
Grande congratulations!!!

schmarty on Oct 22, 2012 said:

This project has come a long way!  So exciting!