Micro Robot arm (9g Micro Servo) see video

by bentommye Nov 18, 2012
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This is super confusing. Which files are needed? Why are there multiple types of the same file.

It would be better if its sorted into folders with explanations of what you need.

I am confused. In the instructions, you say to scale it by 10X. I'm using MakerBot software. If I take the file as is, the Armv4-_mm file comes out at 68.mm. If I try to scale it by 10X, it is too large for the build plate. I'm planning on using these servos https://www.adafruit.com/product/1450. Am I correct in assuming that the 4mm files have been resized and no longer need scaling?

Needed a fair amount of cleanup after printing but was overall very happy with it. The only issue I encountered was with the gripper gears which did not fit correctly. The 4mm variant was correctly sized for the v5 gripper but wouldn't fit the SG90 servo shaft. Created a new version of this gear to fix my servo properly and also engage with the gripper: https://www.thingiverse.com/thing:2861285

Micro Robot Arm Gripper Gear Remix
by tithead

I printed this and found myself having to force the servos into the holes which just broke the parts. They don't fit at all... The walls are very thin and break easily. Awful robot arm. Far too fragile. Wasted 5 hours and 13m of filament. Don't make the same mistake. Print something better! Print something that at least fits the motors! o.O

I printed Fot_for_mm.stl and Svingv2-_mm.stl last night and I have to say, they are a fantastic fit to the servos! The fit is so good, I had to remove the stickers from the servos in order to fit them.
Printed with linear supports, 25% hexagonal infill, 3 shells, 3 top and 3 bottom solid layers at 100 micros on the Flashforge Finder and sliced in Flashprint.
Thank you Bentommye.

Hello, is beautiful one, i want to resice for 2,5g servo, can u help me please? Thanks

Thanks for sharing, but do you have the OpenScad files? (Or whatever source you used.)
1) STLs are not good for multiple reasons, such as...
2) Scale is way off.
3) Orientation is wrong for 3D printers.

not sure why this is coming in so oversized......

Sving v2 will not slice correctly with repetier host

Way too small for use on Cura 15.04.2. Can anyone post the real-world size?

In Cura 15.04.2 when you have loaded the model, click on it to select it. Then there are three icons that appear bottom left of the screen.The middle one is scale. Click that and in the Scale X box, change the number from a 1 to a 10.2 ( I used 10.2x as it makes it easier to fit , if your printer is better, then just use 10) and you will have it at the right size for printing. Cura adjusts the Y and Z automatically providing the Uniform scale has a padlock closed symbol


Everything seemed to print just right, but its unclear how a stable connection is created between the foot and the base? The hole in the base is too large to fit snugly onto the servo output shaft. Also, the gripper doesn't seem to fit onto the "arm front," is there a second file or version for the gripper?

I was also wondering about how to make the connection between the foot and the base. Looking through the pictures, it seems that you need to screw a cross horn to the underside of the sving part, like so:

Hi , thanks for your job but i have probleme with Arm_v4 .. the circle does not print have an idea ?

How much did this cost to make? Im a Boy Scouts leader and looking into what kind of cheap robot they can make for their robotics merit badge.

You can get 5 9g servos of ebay for around 8 bucks and the rest is around 7 bucks again of ebay.

when i open the Arm_v4 file(or any file in the project) by XYZware software the message
(selected object is small .. Do you want to scale it up?!
Original size of the object 6.81 x 3.72 x 1.60 mm3
Auto scale up to 50.00 x 27.31 x 11.57 mm3
Import in inches 172,97 94.49 40.64 mm3 )
please ..what can I do :(

Can you give me dimensions of parts I need them.

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?

1000 worked for me

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)

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.