Finished Claw Design + Started BOM-Sheet

Got a claw design done today :D. and with that I have everything but a PCB desgin, design review and a clean and organized BOM and ReadMe. The claw design I used was mainly borrowed from this youtube video I found: https://youtube.com/shorts/wmAnCUXIYNk?si=n38H_gmRiVCv12PW I love the simplicity of it and just the way it works. I made some more minor changes to the rest of the arm and labeled every part that will be 3D-printed. I also assigned materials to all parts other than the servo and M3 heat insert, at the current moment the arm costs $126.92 but since I have access to some of the materials on the BOM it should cost just a bit less. The weight in the cad is a bit off at 8.89lbs It should be less becuase OnShape is calculating if the print was 100% solid. I might change the arm design later if I find a reason to but im currently happy with how it works, being driven by a custom M11 screwon a servo. Ill probably start PCB design tommorow or at least learn the basics of PCB design since I havent done that before. Im also thinking about raising the gear ratio from 13:1 to 20:1 on the cycloidal gear boxes.

BOM: https://docs.google.com/spreadsheets/d/1Lh4vcFsB7JDnlQWwo5IQARkVCZ8p0WDa4wIufgZOBxc/edit?gid=1715060129#gid=1715060129

New Base + 1st & 2nd Wrist axis done

SO, I did stuff, now I'm gonna talk about it. Firstly, the wrist now has a second axis :D I was able to add this second axis with the servo I chose for this project, being the SpringRC SM-S4303R, it's a continuous servo, meaning it can spin infinitely in both directions, unlike most other common types of servos. I then made a servo horn to attach a gear to the servo to allow for the actual movement of this second axis. The gears I decided to use are herringbone gears set to a 20-degree slant with a gear ratio of around 0.86 for more speed. The next addition since the last journal has been the base of the arm. For the base, I didn't want to move away from the casing I had cadded earlier in the project, and luckily I didn't have to, although you can't really see it. Other than the Nema-17 case, the base itself is made of 3 3D-printed parts at a height of 185mm or around 7.3in. Other than that, I started coloring the 3D printed parts in an orange-white-black color scheme (it looks pretty cool imo). It looks like I'm going to have the arm end with 5 motors and 2 servos. After this journal, I will try to get the claw finished before the next one and start on PCB design, which I have never done before, which is kinda exciting. Also, I've gotten quite a few more views since I last checked, so I'll re-add the OnShape link here: https://cad.onshape.com/documents/ecbd6cc453a8401336b7f5f6/w/f74fdc9fda9bb867202e9585/e/a6897884a06ac11cb13f5e31?renderMode=0&uiState=68f57788594fd9c4d4a5c7c8

More Redesign

I think I'm going to stick to a 2-3 day journal update from this point forward, it's becoming much less stressful that way, sorta. Anyways, these past 3 days I reflected over the progress I made and what I liked and didn't like, and decided to make quite a few design changes. Firstly, I was able to find a structure/ housing for the NEMA-17 that I'm using that allows the rest of the arm to become more modular with the help of cycloidal gearboxes. In my experience with this project, I've had a better time packaging cycloidal gear boxes compared to planetary gear boxes, and for that reason think I'm going to try and stick to the cycloidal gear boxes. Speaking of, I believe I got a great idea of how the wrist joint is going to come together. Another change I made was upping the gear ratio from 12:1 to 13:1; this still might change in the future. I'm going to try and make my design much more tubular from what it is currently to help support its own weight. That's it for today's journal. This weekend, I really want to get a final? draft the design and start working on the other electronic components.

Update+Slight Redesign

YO, hi, it's been a few days, I got a little burnt out on Friday, so I took Saturday as a break day, and since then I've forgotten to update my journal :/ Anyway, I didn't like how the joint between the forearm and the first joint was just pure motor, so I designed a cycloidal gearbox over the past few days to allow the arm to have more torque. Tomorrow,






I plan on using more cycloidal gearboxes and try to get everything, including a wrist, done in CAD so that I can start researching how I'm actually going to control the arm.

Planetary Gear Box CAD

So today I mainly focused on how to get the second arm portion of the robot arm to spin, and after thinking through my options, I decided to go through one motor driving a planetary gearbox. To those who don't know what that is, the system is usually comprised of the outer gear, some "planet" gears, and a main "sun" gear in the center, and depending on which gear you make stationary/drive the system, there are 6 different possible gear ratios that can come out of it(I think). The great thing about this gearbox in particular is that it gives me a great amount of torque for a relatively compact design. After designing my gearbox system, I started to work on actually attaching it to the rest of the arm, and that's when I realized that I'm going to have to remove the 7x7x15in the starting config requirement I set at the start of this project, unfortunately. However, I'm proud of today's progress, and if I keep this pace up, I should have the majority of this arm in CAD by Sunday.

Shoulder CAD

Today, I spent a little too much time overthinking how I would implement the first pivot/axis of movement on the arm. Eventually, I decided on a simple pulley and belt system. The rest of the CAD should be easier, up until the wrist and claw, or gripper, or hand. I haven't really decided on what will be at the end of the arm yet; maybe something modular would be nice. But this will be the end of day 3 of working on the arm, and I'm quite happy with how it's turning out.

CAD base of arm

Today I spent around an hour and a half researching motors, and eventually I decided to use E Series NEMA 17s. These stepper motors, I feel, will be easier for me to program down the line when / if I get to assemble this project, and are very cost-effective, being around 4-8 dollars depending on which vendor you buy from. Anyways, I made my base plate into an octagon and added two motors to the bottom, allowing the plate above the base to rotate, meaning that I now have 1 axis on my robot :D. Tomorrow I will try to get two more axis done on the arm and start looking into what electronic specifications I'll actually need to control the stepper motors, but at the current moment, I'm feeling pretty good about this project. (feel free to check out the public CAD on OnShape btw) [one more thing, I think I spent at least 30 minutes trying to find the size specifications of the motor I decided to use before realizing there was a .step file from the vendor.]

Created Onshape DOC and made a readme

Today I'm just trying to figure out the parameters of my project, so I made some limits in Onshape and started looking at some references online. The image attached is just a VERY rough sketch (It's getting pretty late for me). The plan for tomorrow is to research what motors I'll be using and basing the rest of the project on, and get more geometry done in Onshape (I think it'll be really cool if I can reuse some random motor off another mechanism, like a 3D printer or something, but we'll see).