Introduction: Aluminum Robotic Arm

About: I'm an engineer in mechatronics

So, I finally decided to do my first instructable.

This is a 4 axis robotic arm made of aluminum and controlled with arduino mega. This robotic arm was a project from the college where I used to study.

As you may noticed the English is not my main language,I'm form Mexico, so I'll try to do my best, be nice with me :).

In this instructable I'll show you the whole process to make an arm like this, may you need some previous skills like listed bellow.

  • 3D modeling.
  • Design skills.
  • Lathe.
  • Vertical Milling.
  • Knowledge in Arduino interface.
  • Some electronics skills.
  • CNC

The mechanical structure was made of aluminum 6061 because is the most common material friendly machining, it's very cheap,it's light and easy to find.

I think that this robotic arm is a beta release and in the near future I will need to do some modifications in the structure and change some components in order to reduce the weight.

If you have any comment or any idea to improve this tutorial I will appreciate that.

**The slow speed is for safety. (can be 10 times more fast)

Step 1: Materials

To be honest I don't have a picture with all parts before the assembly, because the most of the parts were purchased as I needed.

For mechanism:

  1. Aluminum 6061 – ½ x 2 ½ x 42” (for all parts)
  2. Aluminum 6061 – Plate ½ x 4 x 6” (base)
  3. Aluminum 6061 – Rod DIA. 1 ¼ x 12” (rotation shaft)
  4. Steel Rod – DIA. 3/8 x 6” (separators)
  5. Pulley 5M-15W-40T:
  6. Pulley 5M-15W-18T:
  7. Belt HTD 5M-300 (15mm):
  8. Linear shaft rods kit (SRB16-650):
  9. Nema 23 (8mm bore )– 3PCS
  10. Nema 17 (5mm bore)
  11. GT2 pulley (8mm bore):
  12. GT2 15mm belt (+60 inch)
  13. Necessary screws (10-24, 10-32 , ½-13, ¼ -20 etc see drawings)
  14. 21 x 31” for base plate ( I used an old sheet metal door)
  15. Ball bearing -

For the electronics:

  1. L298N Motor Driver ( 4pcs) -
  2. Arduino Mega
  3. Cool fan 12v (3PCS) 4inch
  4. Control wire ( 4 colors minimum – see pics)
  5. Switch button
  6. Wire carrier chain (like this )
  7. Tie wraps -
  8. Heat shrink tubing
  9. ATX PC Power supply (680W +)
  10. DB25 25-Pin Male Solder Cup Connector -
  11. DB25 25-Pin Female Solder Cup Connector -
  12. 4 pin connector waterproof -
  13. Some housing for all electronics.


Maybe I forgot some component, but I hope to improve this instructable.

Step 2: Design

I have always believed that you can not start a project without a paper hand sketch.This allows you to have an idea and how to start to design and if you need modified some issues if there any.

So first I started this project with a piece of paper and
some ideas, as it would be, possible materials to use, necessary motors and the configuration of each axis and them rotation.

With the idea more clear my next task was 3D modeling that ideas. For this kind of project the more convenient is to use a CAD software that do more easy this task, I’ve used Autodesk Inventor and Solidworks too in order to create the models and the same time designing the mechanism of the robotic arm to determinate the size of the parts to be machined as well as the necessary materials for the whole assembly.

Now we know the sizes of the materials to use and the other different parts that we will need.Use a CAD software as Inventor is very useful because we be able to generate .IGS files which can be used in any CAM software like Mastercam.

On the top you can see some screens of the 3D design and
some the drawings of fabrication for this project, also I’ve attached the 3D part in Inventor and one .STEP file of the whole assembly that work in Solidworks too. If you need the Solidworks files please just say me.


The robotic arm was designed and machined whit ½ thickness aluminum but in order to reduce some weight might be better a 3/8 thickness aluminum but like I say before this is my beta release. :)

Step 3: Machining

Once you have the idea, then you have the hand sketch and then you have the 3D models, the real fun part can be start. :)
By saving as .IGS the 3D model part that you want to machining , you can use a CAM software like Mastercam, Solidcam or Espirit to simulate the CNC milling process and generate the G code to be used. And then put this file on your CNC machine and just run the program that you create before.

But I know that many of normal people just like me doesn't have a CNC machine in their houses, so it's not a really big deal, with a single milling machine and a basic lathe machine you can create a very good stuff like I will show below.

Milling machine:

Lathe machine:

CNC machine:

There are many information to share here, but it's too much, if you have any question about this part of the process just let me know I'm glad to share information.

Tools and machines that I've used:

  1. Milling machine
  2. Lathe
  3. Vertical CNC
  4. Horizontal grinder
  5. Drill
  6. Bench saw

Step 4: Assembly

The assembly process means to put all parts together.
First put the rail shaft into main base , in my case was a old sheet metal door like I say before. Then insert the linear bearings whit the robot arm base. Next match the pre asembled arm into its base.

You need to connect the stepper motor cables, soldering the DB25 male and female pin connector using the cotrol wire.

I don't have at this moment the number of each pins for each motor I've soldered the cable of the motor to the male pin connector and then check them with my multi-meter to see the continuity. Whit this I'm able to know waht pins is for each coil of the steppers.

Holding the L298N motor drivers to the housing of electronics and then conected each cable and wire to the arduino and from the motor to it, see the diagram that I attached to the top part of this step.

By checking the 3D model is to easy to understand the assembly process.

The 4 pin connector was soldered to the ATX Power supply.

The db25 male came from the motors of the arm, please check the photos.

The 3 12v cooling fans are connected to the power supply.

There is a green LED that indicates the status of the voltage.

The GT2 band goes to the arm base whit a little piece of aluminum with 2 flat screws on it.

Translation axis test:

Angular axis test:


If you check the 3D model the mechanical assembly will be easy.

The electronics is easy to, it is only 4 L298N connected to the arduino pins like the diagram shows , each motor has a 4 color wires, those wires goes to the L298N and that's it. There is a status controller button this button goes to the pin 6 of arduino mega that indicates if the arm is in manual mode or automatic mode.

Step 5: Programing

Arduino is one of the best option when you need to do a prototype of any semi automatic project, this is not the exception. This robotic arms uses an Arduino Mega to control the 4 stepper motors ,can be one by one or simultaneously using loop in the code for each step.

I've attached the whole code below if you have any question, again just contact to me.

Thanks to my friend Erick Aceves he is an amazing programmer if you use his code just give the credits to him.


This code uses the stepper.h library.

Step 6: Lest Do It!

That's all for now.

If there are many of you interested on this project I will constantly adding information and constantly improve the redaction and other things.

I just hope that this project likes you and see how you can do it too.

Any question, suggestion, idea, improvement, change or anything just tell me I'm all ears.

Thanks to:

Luis Baltazar

Omar Gil

Erick Aceves


I've noticed that I need to use 3/8 thickness aluminum instead of 1/2 thickness in order to reduce weight and increases the speed in the angular axis

Guys, I told you my English is very very bad, be nice with that (si hablas español: pronto espero poder hacer uno en español mas detallado)

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