I decided to build a 6 DOF robot in January. Since mechanical engineering is not my cup of tea, I decided to use an open source project. After some research, I found Chris Annin’s AR3 robot. You get all the 3D files, the component list of things to buy and also some basic software to run the robot. I had built robots at work but there was a whole team to do those. The hardware team would take care of schematics, component lists etc. The mechanical team would make the designs. The 3D printing of prototypes was outsourced. I was a system architect who knew the whole thing but lacked the details of everything.
The AR3 robot manual described every step of the process with photos. I made a rough estimate of the costs and it added up to €2000. I found out how much the world depends on China when I could not buy certain parts anywhere else but in aliexpress. Most items were available in amazon, digikey or reichelt but there is no way avoiding China for some critical parts such as pneumatic tubes for the robot’s gripper. I found out that Europe also lacks the kind of choice available in the US when it comes to building things. A website like mcmaster is just not available here. Naturally, I overshot my budget by about 15% as I had to pay a lot of customs and shipping. However, this budget also included the anycubic 3D printer.
I 3D printed the parts with PLA and started building the robot as per the manual. There were several issues that had to be dealt with. For example,
- A lower setting of infill for 3D printing does not work for structural parts.
- Since the original design was for aluminium parts, some screws that worked for aluminium would not be long enough for PLA. I even broke a part after building the whole thing.
- Fitting a metal bearing ring into a PLA bearing ring holder is not the easiest of tasks. Normally, I use a hot air blower to soften the plastic just so much that it allows the metal ring to slide in. I lost at least one plastic piece because I heated it too much that it deformed completely.
- Set screws can give a lot of trouble if they lose their thread.
- and so on.
There were a lot of mistakes made but it is those mistakes that help you learn the most about building a robot. Finally, I have the robot. It calibrates when in open loop but has some issues with the encoder. The gripper still needs to be attached. I have to make it work with ROS. Probably there are some more mistakes to fix and some more things to learn.