phenoptix meArm

I recently found a nice robot arm called meArm at It is open source, so the design files are openly available as well as the code. At the time of this writing, the current version of the arm is 0.4

I ordered the arm including the servos and fittings from pheonptix and the price is remarkably low (25 GBP) and the shipping took a few days. As the company is located within the EU, I had no duty or tax to pay.

The robot is a nice and easy to build robot arm and comparable arms cost almost a factor of 10 more. To support this development, I here show the build process I went through to build the arm. It took about 2 hours to complete the job with a break at halftime. I did some errors in the process but decided not to correct them in the documentaiton but to show the real flow.

The only deviation to the original kit is that I replace the base servo with a metal gear servo. I strongly suggest to anyone building this robot to do so as well.

Building the meArm

Sort the Parts

The kit comes with 33 laser cut parts. The first tep is to remove the plastic coating from both sides of the parts. In addition to the body parts, there are 4 servos and a set of M3 screws and nuts:

# Size Length
4 M3 20
6 M3 12
2 M3 10
13 M3 8
11 M3 6
10 M3 nuts

Base Plate

Parts: 1, 2 and 3 - 4 M3x20 - 4 M3 nuts

Insert the M3 screws into the holes and losely attach the nuts.

The sqared plate (part 2) will serve as nut for the screws, so carefully drive the screws into the plate until the screw shows up at the other end. Then tighten the nuts to the base plate (1). There is not much force needed!

Insert the servo into the holding (3) using the small opening to handle the cables.

Attach the servo using the M3x8 screws. Do not use too much force or the holding may break. Again, the sqared plate (2) serves as nut for the screws. The result should look like this:

Arm Body

Parts: 4,5,6,7,8,9 - 4 screws M3x12 - 4 M3 nuts

The parts of the arm body have joints that prohibit the assembly of the parts in a wrong way. However, it still leaves two mirror options. I therefore show how I assembled the parts in line with the instructions on

The follwoing picture shows the body parts aligned before assembly. Please not that the hole at the top of the standing part (5) is opposite to the top hole of the side part (6)

All parts assembled:

Now insert the nuts and connect the parts with the M3x12 screws. The best way to insert the nuts (without giong nuts) is to put the body on the side and to lay the nut into the hole. Then drop the M3 screw from the top and tighten:

At that point in time I foudn that I forgot to attach the servo horn. You can attach it to the body or quickly disassemble the body, attach the horn and reassemble.

Main Arm

Parts: 10, 11, 12 - 1 M3x6 - 2 M3x12. 2 M3 nuts

The picture shows the servo horn that gets attached to the big hole in part 10. Before assembling the arm, one side (11) needs to be connected to the middle part of the body (5). Otherwise, the fitting screw will be hard to reach afterwards.

Note that the arm is located in the smaller compartment.Assemble the arm as shown above.

The Lift

Parts:13, 14, 15, 18 (This is one of the errors: the picture below shows part 16 instead of 13) and 28 - 1 M3x6 - 2 M3x8

Assemble the parts as shown here:

The picture above shows the correct part inserted (see circle)

The Extender

Parts:16, 17, 19 - 2 M3x6 - servo horn and screw

The smaller part holding a servo horn (20) is used for the gripper - do not mix.

The final assembly:

The Gripper

Parts: 21, 22, 23, 24, 25, 26 - 2 M3x6 - 4 M3x8 - 2 M3x10 - 1 servo

Attach the gripper claws, the one with the hole to the left

There are two small parts (23,24) that need to be placed to the side of the servo, the horn (24) pointing forward on the right side:

Use the M3x8 screws to tighten teh servo:

The Gripper Driver

Parts: 20, 27, 29

When assemblingf the driving handle, I found the construction not optimal so I added washers and a longer M3 screw:

Before connecting the servo horn, postion the servo to 90° using an arduino or similar (I use an arduino plus LCD shield with encoder as servo tester) and connect the gripper in a fully open position.

Adding the Servos

Finally add the lifting and extending servos:

Please take care to position the servos to a known position (i.e. 90°) before attaching the horns.

Attaching the Gripper

As the last step, the gripper needs to be attached to the arm. It is quite easy if you attach the upper arm to the horn on the right side of the gripper:

Once it hangs (and moves) freely, you can attach the gripper servo to the remaing two arms:

I highlighted the hole you have to hit with the screw.


I found one washer and one servo holding to be unused.


Building thsi robot arm is easy. I have two more of them and one fo them is bult by my son (13 years). I consider this an excellent kit to be used in schools. The price is amazing and the result is great.