I am currently building a test bench for gathering data to build a model which will be able to identify remaining useful lifespan of additively manufactured gears and mechanical parts based on vibration data and potentially dynamics as well with in-situ sensin.
I have been simultaneously working on the physical side of the project while also working on the electronics & firmware. I borrowed an ESP32 from the place where I work (very nice) and bought the motor controller, current sensor, hall sensor (for RPM), aluminum shell resistors to apply braking torque, the load & measuring motor, and the accelerometers. I have finished printing all of the parts I need, however I encountered a slight issue with alignment and spent some time fixing that. I made a drawing of my full assembly to place all of the holes properly on the aluminum plate I plan to use. I may add a little bit of extra space between the gearbox and the motor just so that the sun gear has no chance of rubbing up against the carrier; the printed-out drawing will definitely help me though (I can just tape it to the plate and make markings through the paper or just drill straight through).
Designed a few parts. The holder with 4 flanges is for the ADXL345 accelerometer to measure vibrations. The cylindrical part width the mounting face in the middle is for coupling the steel output shaft with the planetary carrier (I may end up getting it machined as I’m not sure what the strength capabilities of PLA are). The model with the two vertical plates is in progress but it is for the shaft (I did not extrude out the spaces where the bearings would go yet). I am also working on outlining a schematic of the electronics and thinking about starting firmware to gather data. I have a non-assembled devboard lying around that I got a few days ago (from a different project) that I may as well use as the central microcontroller for this project; it should have enough IO pins (if not, no big deal; I have a few IO expanders lying around).
After printing and checking the meshing of the gears, I decided to swap to helical gears as they are more reliable and produce less friction than a herringbone setup despite being slightly weaker and also prone to having the gears slide out of the planetary assembly. I redesigned the shaft clamp design to fit in a smaller size so that I can fit it onto the small shaft of the RS550 DC motor and also changed the gear ratio of the planetary gearbox to be 6. I finished the designs of all of the major motor mounting parts, and printed/verified their functionality with the motor (which just arrived). I have printed the ring gear, the planetary carrier, the 3 planet gears, and the sun gear; however the bearings are yet to arrive so I will not be able to test yet. I also realized that I will need a way to reduce contact surface area of the plastic so as to stop heat from building up, so I will have to reprint the planet gears to have a small notch in the middle that I can glue a small rubber spacer or a nut into.
I conducted some research and eventually decided to implement a planetary gear system to reduce the input RPM for gear testing, as it provides greater strength. I also designed a gear clamp system which allows me to clamp the gears onto the drive shaft reliably with a hex keyway. Below are a few screenshots of the hex keyway system and of the planetary gear system. I am going to conduct a preliminary test print to make sure the gears mesh well, they should mesh fine as my assembly indicates but the tolerances may not work out, or the gears may be too weak, etc.
Built a feature script to auto generate gears which will also be massively helpful in the future during experimentation. Also added some fillets to the front motor mount and two extra front-side mounting holes in case I need extra stability.
I found a motor to use (RS-550, most likely will use th e 18V variant) and designed a mount for the motor which I will most likely 3D print. I also quickly modeled a shaft coupler which I am planning to use
