Polishing

I worked on adding motor screws so I could mount all the motors to the 3d printed parts. For most of the motors this was pretty simple, but for some, mainly segment 4, I had to split the segment into two pieces so the screws would be accessible. This took a bunch of time, but worked out. Segment 5 was also time consuming because it didn’t have enough clearance for mounting the screws on the front, so I spent a while trying to think of solutions before discovering that there were mounting holes on the back of the motor as well. I used those for segment 5, but I have a feeling that the order of assembly is going to be very important for this to work. I also had to update the CAD of the motor to be more accurate instead of a box because I needed the geometry to be accurate in my tight spaces. Then I updated the end effectors to allow clearance for a washer which I needed for the driven gear. At this point I was feeling good about the CAD and felt it was finished, so I probably won’t work on it anymore until I actually build and test it. I also made a wiring diagram and finished up my BOM but forgot to record it. Anyway, now I am ready to publish everything into a Github Repository and submit for funding.

Fixing Technical Issues

I checked the CAD for completeness and making sure it was possible to assemble. I realized that there were no holes for accessing set screws for joint 3, so I added those. I also added a notch under the servo 3d printed shaft for a screw which goes under it. Additionally, I added a huge countersink in the bottom of the lid so that the screws I bought would actually fit. Then, I figured out where all the wires on the arm need to go and added slots to some segments so that I can zip tie the wire bundle to the arm. I still need to:

• Finalize the BOM
• Create a Github repo
• Make a full wiring schematic

Stabilizing Joints

I realized that the motors powering joints 3 and 4 were very badly supported and also cantilevered, which would result in the motor’s internal bearing taking all the load and possibly breaking. I had to redo it, and the first change I made was adding a plum coupler to take the load off of the servo’s internal bearing. I then added 2 more bearings to actually support the load, but once I was done with the first version (see the second picture) I realized it was too big, which would increase the reach but significantly decrease the lifting capacity. So, I redesigned it to be offset from its pivot, which would allow the motor to be mounted on the other end of the pivot (see third picture) and also shorten the arm. I also had the same cantilever problem on joint 4 so I changed it to support the shaft from both sides (see fourth picture). I then assembled everything in CAD and it ended up weighing around 930 grams, which isn’t terrible. Anyway, next time I need to:

• Make sure everything can be physically assembled
• Make a wiring diagram
• Update the BOM with all the components for wiring and links

Thanks for reading!

Today I worked on the base. When making the belt ratio, I accidentally flipped the pulley belts to make it a speed 2:1 instead of a torque 1:2, so I had to redo it which took a while. Once I was done with the base, I attached it to the rest of the arm and it looks good. However, I did realize that a cantilevered motor holding up the weight of the arm (the wrist rotate) is bound to break, so I have to find out how to add a bearing so it is at least supported better. Also it is currently using a plastic printed adapter so gotta fix that as well, I should find a metal adapter of some kind. Things left to do:

• Replace all the weak plastic adapters with a stronger material, probably metal
• Find a way to support the wrist rotate joint better with a bearing
• Make the claw a bit smaller so it is more compact
• Find out how and where to attach the camera
• Add some speakers for the audio triangulation feature I want to add (basically, it detects the difference in between the time audio signals are received and triangulates where the source of the sound is. Idrk if this is a thing but it would be cool if the robot could look at me when I start talking.)

Yesterday I worked on making the whole arm assembly by connecting the parts I had already made to the fasteners I am planning to buy. I had to fix a few compatibility issues but got the arm to look complete. After that, I compiled a full parts list so that I knew what I needed to order for the arm. Once that was done, I realized that the base was way too small and would tip over. It also did not have ay method of power, and because I want the arm to be easily portable, I want to put all the electronics and power in the base. So, I CADed the layout and made a simple electrical diagram in Canva, and using that I was able to figure out where everything should go. The first iteration of the base was WAY too big (400 x 200 mm) so I made it more compact by rotating the power supply and moving everything closer together. Also experimented with most compact arm orientation (see screenshot). I still need to:

• Figure out what camera I should use and where/how to mount it
• Make the lid
• Add cooling vents for the power supply/computer fans
• Figure out how I am going to gear/put a timing belt the base for more accuracy while still not losing much torque (like deciding ratio)

Today I worked on the end effector attachments for the arm. This included the simple drill end effector as well as the claw end effector. I already had prototype CADs of these, and I previously had redesigned the arm to make it lighter and improve the range of motion with better motor placement. So today, I adapted the end effectors to work with the new arm design.

Things that still need to be worked on:

• Make the claw lighter and shorter
• Update the CAD with all the fasteners and other hardware
• Make the parts list for the arm