The Sixi 3 robot arm is the result of many years of study and research. I’m trying to build my dream machine that avoids every problem discovered in my previous robot arms. My short list of desirable things include:
Easy manufacturing = use less unique parts = use repeating components.
Easy maintenance = daisy chain components.
Safer = no loose wires, always know where the arm is, responsive behaviour. (safety third!)
To that end I’m on my second attempt to design and program the board of my needs. Here’s where I’m at today, December 31, 2022. Read on for all the details.
Monday, I made a new tool to talk to my robots. Arduino Serial monitor is all well and good but I needed more features and some color coding.
Sixi 3
Tuesday I tackled a problem with the base of the robot. When I designed the first version it seemed fine! Then I tried to drive it while in a Zoom meeting for the Vancouver Robotics Club and discovered that at the right spot the base and the J1 actuator collide.
…which didn’t work! The screws to attach the base to the board could not be accessed after the base was on the J0 gearbox. No tool clearance is bad! Taking the whole robot off the board just to fix J0 is bad! So that went in the recycling and I tried again.
The screws that go on an angle through the top and bottom halves of the base need a nut. The nut can’t turn. I could make a really tight slot that the nut barely fits into… but then how do i get the nut out later? My solution is these nut holding tools. They fit snugly, prevent the nut from turning, and give me a convenient handle to grab with pliers when I need to pull them out. A gift to my future self!
Makelangelo 5
As you know from the previous post, there’s a new firmware coming that is faster, smoother, and much more friendly to all they DIY people out there. Much of this week has been talking with people on Discord, showing them how to set up their custom versions. In short,
Install the apps mentioned in https://mcr.dozuki.com/Guide/How+to+upload+Makelangelo-firmware+from+Windows+(2021+)/33?lang=en
Get the firmware currently at https://github.com/i-make-robots/Marlin-polargraph
read Marlin/Configuration.h and change where needed for your board, your drivers, your LCD.
For size changes and more advanced stuff, come talk with us!
I’ve also filmed raw footage about how to use 3M hooks to put a Makelangelo on a flat wall. Some people don’t like the suction cups or they don’t have a big window. No problem! Subscribe to my Youtube channel and watch for the announcement.
Sixi robot now has a URDF description and can be found on the ROS wiki.
ROS (Robot Operating System) was first developed by Willow Garage, a Boston robotics company. Though Willow Garage no longer exists, the ROS has been so successful that it has outlived its creator.
Since ROS is such a popular tool, I hired sachinkumar1235 on Fiverr who built the URDF package. It includes decimated STL files created by Andre.
An eccentric cam shaft is at the heart of our cycloid gearbox. Any force acting on the gearbox is focused at this point. So it makes sense that a good gearbox has a super strong cam shaft. This design is made to connect on a motor with a 1/4in diameter shaft, which happens to be the same as the NEMA23 motor in the elbow of the Sixi Robot.
Want to practice your CAD skills? Try making a 3D model of this part, yourself. Tag us on social media if you do!
A good designer and leader knows when to say “no”. In today’s example… I have tried several times with the help of Instagram friends and my own employees to build a gripper that we can use with the Sixi robot. I decided, finally, to say No. We’re in the robot arm business, not the gripper business. If that’s true then how will Sixi hold grippers made by other people?
“ISO 9409-1:2004 defines the main dimensions, designation and marking for a circular plate as mechanical interface. It is intended to ensure the exchangeability and to keep the orientation of hand-mounted end effectors.”
Are you looking for a challenge? How about making a gripper that works with our STL model of the hand? Then it should work with all commercial robot arms that match the standard, too.
