pybot Robotic Arm

January 2018

We are currently working (while we finish the control APPs of the blimpduino) in the SCARA robotic arm. The point of posting this on the web is to ask you for comments/ideas and any feedback. As we are still at this developing stage, we have time to re-think some aspects/features of this robot. A powerful, fast and reliable arm is the basic of modern robotics so… we wanted to “create” one but using regular “MAKER´s World” elements like NEMA17 motors, affordable electronics and common ancillary elements (GT2 timing belt, steel rod, aluminium tubes). The idea: create a very fast but precise robotic arm you can bring into existence using your own 3D printer.

This robotic arm is based on the awesome MPSCARA (by Williaty. Thanks Tyler for the ipt files!). We have modified almost everything but the main frame.

WhatsApp Image 2017 12 30 at 17.14.18 2
The current state of the robotic arm. Above: mounting the electromagnet and the medium size forearm

The advantages of this robotic arm:

  1. Affordable
  2. Easy to modify 
  3. You can create your own add-ons /actuators/ arms: adapters and 3D layouts have been create.
  4. Scalable
  5. Customizable 
  6. WIFI controllable

Mayor changes:

  • Motors placement
  • New center of gravity
  • The Z axis has been shifted looking for less torque forces during accelerations
  • Reduced friction
  • Aluminium structure were possible
  • Less expensive timing belts (shorter), but enlarging the working area
  • Different gear ratios for improved precision
  • Cables hidden inside the arms/structure

New ARM addon: Vacuum suction cup. Testing

New ARM addon: Electromagnet (12V, 500 mA): Currently working.

New ARM Addon: Vertical and horizontal Gripper (based on the Mantis gripper by 4ndreas). Horizontal version working. Designing Vertical version

  • 5 Degrees of freedom
  • Controllable from any smartphone via jjrobots free APP (currently can be controlled using basic commands using the app available at Google play)
  • Controllable via “queue of commands” from the computer/tablet/smartphone
  • Google blockly controllable
  • The kinetics behind a SCARA arm is way simpler than any other robotic arm/ alternative. This brings the possibility to easily understand how this robot works and create simple code to control it. A Cartesian XY+Z coordinate system is the natural approach to move its “hand”. We will create (beside the control APP/software) the “programming bricks” for everyone to control this robot in a simple way
The arm has been placed on top of the “control” platform which is carrying two stepper motors. The Z axis rod has been moved closer to the motors, modifying the center of gravity (now the motors weight is balancing the arm). Sudden UP+DOWN movements do not generate torque + vibrations.

gears DETAIL
Gears with guides for the timing belt keeping the pulling forces in the axis.
Gripper front view
The Mantis gripper´s clamp closes around a point 4.1 cms away from the end of the forearm, making the positional calculations easier.
gripper Working
Metal gears servos used for the gripper. Precise and fast but strong enough to lift or move the load. The electromagnet actuator is capable of lifting up to 400 grams (some tests still have to be carried out here)

Testing speed and accelerations: How much a 3D printer arm can handle? You will be surprised! 🙂

Two degrees of freedom for the gripper (we are currently working in a vertical gripper version). Metal gears servos for added precision and sturdiness

The Z axis movement has to be FAST.  A slow arm is not as… useful (nor cool) as a fast (but accurate) one.

The structure has to be sturdy but keeping a large working area.

UPDATE April 2018

The frame is almost finished. We have been testing the HORIZONTAL and VERTICAL clamp. It is easy to switch from one to another. You just only have to rotate the support part 90 degrees. The control APP will have an option (a check-box) to let the code knows the current robotic arm configuration. Why two versions of the clamp? The idea is to give this robot as much versatility as we can, not limiting its capabilities grabbing stuff. Once the vision system is working it should be able to pick almost any object not depending on its shape.

Armbot Vertical and horizontal CLAMPs

UPDATE November 2018

Mechanical design finished.

After testing the tear and wear, find out the perfect gears-ratio for common NEMA17 motors, balance,change several time its center of mass, improve the speed/acceleration comprise and check the “3D print-ability” in many 3D printers we can happily say that the frame is ready. You can take a look at it here


UPDATE June 2019

After being playing with the Robotic arm for 4 months we have decided to redesign some elements. The reason: Each 3D printer has its own way to print the part of the frame. Translation: the accuracy of the 3D printer will make difficult to insert some element into others, so we have redesigned some in order to increase the assembly “tolerance”. 

In the meantime, we have been working in the control CODE:  And Python was the language.

The computer control APP has been designed to be easy to understand and even easier to modify. It has a visual interface and APIs.

We have added some cool features like LEAP motion control and OPENCV compatibility

The assembly guide are almost finished and everything, as usual, has been documented. 

scheme V1
Electronic scheme. All you need to control the SCARA ROBOTIC ARM

Two SCARAs collaborating picking up and piling up 3D printed cubes. We are using a LEAP motion sensor to control both arms at the same time.
The SCARA moving a 3D printed cube during the reliability tests. It was doing that for DAYS!

UPDATE September 2019

All done! We have been testing everything the whole summer. Electronics, 3D printed parts (We ended with the 17th iteration for some parts :-P) and debugging the control APPs. We finally added Google blockly as we think it adds a lot to the Robot: It is a very simple way to control it and Blockly has been used by many MAKERs in other robots since it was released. Watch the video below and see it working

The reliability of the SCARA has been one of our design goals. With the reliability, a very good accuracy or, as technically called: “repeatability”, was the second thing to achieve. Those two goals made us re-think many elements of this robot. Below, the result of many iterations, brain-stormings and many starts from almost scratch: a 0.2 mm repeatability value!

The video shows the arm coming back to the same point after moving randomly several times.
The GCODE interpreter (working in progress) doing its job. This is a “of course you need something like this” add-on. Translate from G-code to Robotic Arm movement is a powerful tool. We have been playing with a laser engraver a little bit. More info soon 🙂

This is the final aspect of the SCARA: (electronics + cables not displayed)

SCARA Robotic ARM how to connect everything ELECTRONICS 1
We are currently working in the Assembly guide / Control APP user guide and “HOWTOs”. Laborious job but worth the effort.

UPDATE : We have released the DEVELOPERS VERSION. A fully working robot for everyone who wants to play with it now. For those, we are releasing and updating the control APP and Arduino CODE almost everyday.

Ausgust 2020: We have another 50 pyBot KITs back in STOCK (LIDAR sensor and 3D printed parts included) Thanks for the excellent reviews! 😉