Micro Robot arm (9g Micro Servo) see video

by bentommye, published

Micro Robot arm (9g Micro Servo) see video by bentommye Nov 18, 2012

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A very small and inexpensive robot. 4 axes plus gripper. Build on 9g micro servo.
The robot can be controlled by remote control, Arduino, etc
I see that there are different diameter on the shaft from the servo. If the gear does not fit I'll fix a new one. Just send me the diameters of the shaft.
See it in action:



If you want servo that lift arm is replaced with a stronger MG955 servo see:
Latest uppdate

  • Arm w spring.stl and Sving v2.stl
    Are to adding a rubber band and spring for increasing handle wight. Not tested yet.
  • Grippper v5 with new "spring" for bether grip on the gear.
  • Gear v5 is smaller for stronger gripp and fit gripper v5
  • ArmFront_v3 (design for the gripper)
  • Gripper (x2)
  • GripperGear - mounting on the gripperservo
    You will need:
  • 5 micro servo 9g and it's accessories
  • 4 very small screws (for the 4 armed servo horn)
  • 3D printer (made for uPrint but it should work on other)
  • Some things to controll det robot - i use an Arduino and a servoshield.
    3D print:
    Enlarge 10 times before printing. And put the two measurement metric not inches.
    1 - Fot
    1 - Sving
    2 - Arm
    1 - ArmFront
    2 - Gripper
    1 - GripperGear
    Servo inserted in custom holes.
    Fit the two arms together.
    Adjust the servo so that it is in the middle.
    Install the servo horn with one arm.
    Servo on the fot platform should have the servo horn with 4 arms for stability.
    I welcome suggestions for improvements.
    Robot program for Arduino:

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Really nice design, but I have hard time to print parts...They so easily break while inserting servo or removing support...!!
Will it be possible to have a more "strength" version ? :)

The arm and armfront seem to print out messed up. I've tried multiple slicers, but it still does the same thing. The end with the circles aren't completely filled in, so they fall off really easily. Any idea why?

Could you post the dimensions of the screws/nuts you are using for the build?



The gear is way too big for me. Anyone know of a fix?

Same thing here..

This no longer seems to print out right ...... Slic3r doesn't seem to up scale it correctly and frankly I can't understand why I should have to scale this up in the 1st place other than a lazy author who couldn't be bothered to do it correctly and make it actual size ... That's just asking for compatibility problems down the road

Walls one line thick just aren't going to work but that's how it scales up so it has the structural integrity of candy glass .....

agree totally with rocket...
interesting that the "lazy author" didn't forsee your particular problems.. just cause you are to busy to solve them yourself!!!
Great job bentommye!! Also mightly big of you not to have b*tchslapped some sense into dumbjohn's inneptitude.. or deleted his idiotic comment.

I don't mean to point out the obvious... but did you really just complain about a file that somebody made for their own personal use and shared free-of-charge to the entire community? Grab a caliper and a calculator, learn how to use some CAD software, and scale it yourself.

Great job, bentommye! This thing is awesome! I've got boxes of old servos lying around that will be perfect for this!

Sorry but this is constructed in an old Lighwave and it is not as easy to get things out in the right size. It is often 1 000 times smaller or larger. How much should they be scaled? 1000?

Apr 9, 2015 - Modified Apr 9, 2015
freshprints - in reply to bentommye

It looks to me that it was intended to be scaled 10 times (in Repetier). I had trouble fitting the servo cables. So a 10.2 or something should do the trick.

(I printed at 0.1 mm / layer PLA)

Jan 10, 2015 - Modified Jan 13, 2015

very cool project. I am printing now, but i have problems with slicing (slic3r) "Arm w spring.stl and Sving v2.stl". Can you tell your slicer settings? Slic3r cuts off the rod you made.

What nozzle size do u use.

And can u please publish the LCD and Mega shield holder?!

Could you post a non micro version? LIke one that is sized for futaba 3003's? Also were you able to print this without supports? It looks a bit tricky

Were can I get the file to make one

Click download Download This Thing! on this page and you are ready to 3D print it.

Anyone have the code for arduino?

I am new to arduino. do u know why my lcd 1602 won't start. but the led light behind the lcd is on

Would you please post your version of LiquidCrystal_I2C.h? Because I keep getting error

Do you have the code?

I re-wrote your design in OpenScad: http://www.thingiverse.com/thing:65081http://www.thingiverse.com/thi... (and made some changes to make it easier to print).

OpenScad Micro Servo Robot Arm
by holgero


thanks for lending a hand :)

Two suggestions:


by hyla

Suggestions for a turnable wrist.

Remove the gripper. Mount a 4 cross horn on the gripper servo. Print an extra foot.stl if nessesary. Then mount the foot on the horn.

The old gripperservo is now the writst servo.

Add a new servo to the new foot and use that for the gripper.

Maybe it's an ide to use an extra strong servo for the lifting arm. Because of the extra weight. See: http://www.thingiverse.com/thing:38875http://www.thingiverse.com/thi...

Micro and MG995 servo robot

I like the foot. A turntable is maybe too heavy? But I can trye.

When I load the files into Repetier or Pront3rface, they appear very very tiny… what units did you use? I just got my servos, and I can't wait to start!

I have to scale it 10 times before I print it. 

I do not know why but various programs make different sizes of STL files. From some programs do I enlarge 1000 times and from any I must magnify 10 times.

try scaling by 10x. at least in replicatorG it seems like 10x is the correct ratio. the base piece appears to fit with the 9g servo with 10x scaling. for a 7g servo its around 9.4x

I had the same problem. I imported the files in Google Sketchup with Jim Foltz stl importer (which makes stl files super huge by the way) and scaled them down to fit the servos (a factor of 0.4 in my case) and then exported them back to stl. That worked for me with Slic3r.

What Shield are you using on the Arduino?

"Arduino MEGA Sensor Shield V1.0 Sensor Expansion Board" and "Arduino Sensor Shield V5.0 Sensor Expansion Board" depending on the Arduino I use.

I'm considering trying a servo card with your own driver for higher accuracy of servos. Arduino provides about 175 steps (180 degrees at 8 bit) and it gets chopped for movement.

i've started making this on a MakerBot Replicator for a dynam 7g servo. the 7g servo is slightly smaller than the 9g one, but has very similar dimensions. it seems like scaling it by 10x and then .94 seem to give a pretty good fit. will update as i proceed :)

Cool. Do you have picture or videoto share?

Let me know hivs you need any help. 

finished the second piece (sving). i had to break it into two pieces - the round disc and the servo holder. i couldn't get the vertical overhangs to print properly with PLA (it may be better with ABS?)

now onto the arm... having a hard time getting the piece to work in one pass. i'm thinking about breaking into into smaller pieces again, similar to the sving piece.

are you able to make those prints in one go using the uPrint? do you use any raft/support structures?

this is what it looks like so far... :)

uPrint using a support plastic which later dissolved in a base solution. The parts are designed to reduce weight not to be easy too print.

Perhaps one should divide up the parts and glue them together afterwards. 

yup. thats what i've been doing - dividing the parts and gluing them together. will let you know when i make more progress!

More work for my Printer :) Thanks!

Which printer do you use?

The Mechanics is a Mendel90 and I use LinuxCNC to control it.

I only printed one of the arm pieces but it seems to fit. I post an update when I get the time to build the rest of the parts.

Awesome project! I really like how your design for using the servo horns to attach to the parts. I just ordered up 5 servos :)

 agreed.  I will be copying that method for my 3-servo class arm that I'm working on, it's far more efficient than what I was doing.

Hope you post it so that we can see.

For Arduino conroller - I recommend that power is connected to the servoshield rather to the Arduino.