I am a huge fan of this design but found that some of the instructions either had mistakes or were lacking some information. I will do my best to fill in some of those gaps and hopefully make the build process easier! Note that I used the nicer looking remixed base from the same author. I was also missing some parts but managed to make due with random bits and bobs I have in my office.
If you are building this from scratch, you will probably save money by purchasing an existing robotic arm due to economy of scale. That being said, I prefer to build my own projects as I find it is more fulfilling and I learn more.
The comments I am going to make follow the assembly instructions found on Instructables. You can follow along the assembly instructions and reference my notes for some of the steps here. Be sure to read through everything before buying the parts as there are some mistakes in the BOM found on Instructables.
The servos I used are the FEETECH High-Torque Servo FS5115M-FB with Position Feedback.
Step B I found it easiest to insert the nuts using a pair of tweezers. Be sure to remove any support material ahead of time, in fact, print with as few supports as possible! I probably spent a good hour removing supports in different small areas designed to hold the nuts.
Step C The three M3 screws being used are M3x12mm.
Step D My servos did not come with self tapping screws, so I omitted them. I don't think I will see any problems since there is no tensile force acting on the single bolt holding the gear on the servo. I found that the M3x6mm which came with the servo was too short. Instead, I used an m3x10mm to attach the gear to the servo. The 25 tooth gear seemed to work just fine for me.
Step E I used 32 6mm bearings instead of the suggested 25.
Step F The suggested M3x20mm bolts were too short and M3x30mm bolts were too long. I ended up cutting two M3x30mm bolts down to 25mm which fit perfectly.
Step G I didn't have a washer that fit the M6 bolt so I omitted it. Just like in Step D, I feel like this shouldn't be too much of an issue since the tensile force on the bolt should be minimal. Make sure you don't tighten it too much! The locknut should keep it in place. The base should be able to swivel with minimal effort.
Step I The BOM mentions a 4x32mm threaded rod but the actual step properly states a 33mm rod. I see no reason to use a threaded rod here since it is not threaded into anything. Instead, I used a 1/8" diameter brass rod found in my office that I cut to 33mm long.
Step J I needed to add a cardboard insert so that the servo horn wouldn't have any play inside the 3D printed part. I did not use any other fasteners or adhesives to hold the servo in place inside the 3D printed part but I did use a bolt to hold the servo horn on the servo. In my corresponding photos, note that both servos are set to their center position. This means that the servo horns were purposely not placed at a zeroed position. I believe this approach will allow the arm a wider range of motion before hitting the end points of the servos.
Step K This step required M4x20 bolt. The 3D printed straight lever used in this step is the shorter of the two straight levers.
Step L Used an M4x20 bolt.
Step M I did not have the proper metric bolt so I took a #6x32x3 inch bolt instead and cut off the extra length.
Step N Noting the colors in my photos, I used an M4x20 bolt to connect the blue to blue and used an M4x30 to connect the blue to black.
Step O Again, noting colors in my photos, I used an M4x20 bolt for the long blue piece to the blue piece, M4x30 for the gripper holder to the black arm, and a #6x32x1 1/2" bolt to connect the link to the gripper holder (triangular blue piece).
Step Q The longer bolt I used is an M3x16 and the shorter bolt was an M3x12.
- Step R Used an M3x10 bolt.
While this description isn't comprehensive, I hope that it can help others have a more streamlined time while building their robotic arms! Near the end, I started to get a little bit lazy with my explanations so please do not hesitate to ask questions. Happy building!
Polymaker PolyTerra PLA
Charcoal black and Arctic Teal