I then decided to go for what I called the "Shark Tooth" method. The teeth would just bind regardless of how much backlash I had. However after a couple f tests it didn't work at all. To start off I originally tried to make the ring gear using a spur gear to cut the profile out of a circle. Just to reiterate what I needed, a small profile with a nice gear reduction. So I basically took his idea and modified it to fit the specs/bearings/motors that I was using. this gear reduction is a little too intense for what I'm looking for, plus, its not made for the motors I plan on using. He's using them to make a larger robotic arm using NEMA 23's. In fact, it completely changed the way ow looked at strain wave gears. However, another amazing YouTube came out with a video on how he made his 3D printed strain wave gear that didn't use a giant flex spline and housing. by the way, definitely check out his video/channel while you're at it. Very similar to the way How To Mechatronics made his which is shown above. Now, I originally thought you had to design it in an extremely convoluted way, mainly with a giant flex spline, and this huge housing. this is because the flex spline rotates in the opposite direction as the wave generator leaving you with a "negative direction" reduction. This if you noticed will leave you with a negative number. The reduction works as follows you take the number of teeth in the flex spine and subtract it by the teeth in the outer gear, then you divide that number by the teeth on the flex spline. I've included a GIF from Wikipedia below to show how it works. thin as in with a giant hole in it, and a wave generator which flexes the flex spline and magically causes it to rotate in the opposite direction. You have an outer ring gear, similar to the planetary gear reduction. I have no clue how they physically work, but the concept is simple. The first thing i need to say about SW gear reductions (AKA Harmonic Drives) is that they're basically magical. it was the right size, it just didn't have the reduction needed, and therefore not giving me the torque necessary to make a functioning robotic arm The problem is that I mentioned before that I needed 30-1, unfortunately after spending a couple of weeks working on this I had to scratch the planetary gearbox. I just made a cover to keep everything contained and that was it! a simple 4-1 planetary gear box. lastly I added the sun gear, which is what ends up being attached to the motor. I then made a housing to hold everything with screws. I then made 3 smaller gears using the same tooth profile, just less teeth as the planet gears. which can be found by clicking Shift+S and then scrolling down to find the Spur Gear plug-in.Īfter playing around with the backlash, and the number of teeth I used that gear as a cutter, to cut away from a circle leaving me an outer gear. To skip over the bring math bits, I first used the Fusion360 plug in for Spur Gears. Īnd I highly recommend you check his channel out. There's an amazing series on gears by Antalz. Since i had no idea how to design anything gear related in fusion360 I took to YouTube to offer me some guidance. Unfortunately the cycloidal gear reduction would've been too expensive bearing wise so I had to forget about using those. Most of the parts need to be 3d printable, and I wanted the cost to be below 30 dollars per gear reduction, of which, 2/3 of it will be going to bearings anyway.īecause of these "limitations" I only had 2 options, planetary, or strain wave. I cant spend hundreds of dollars on bearings and spacers and screws. The last characteristic is that it needs to be CHEAP. Since I wanted this to be a desktop robotic arm, everything had to be in a small package. I also needed it to be in a small package (bye bye spur reduction). I was hoping for a 30-1 reduction, meaning that when the motor spins 30 times, the output will only spin once. I needed it to be a REALLY good gear reduction. In my case I needed 3 specific characteristics. Now, I'm not going to get into an argument as to which gear reduction is best, obviously each scenario requires different mechanical systems.
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