#robotics Logs

Mar 02 2020

03:13 AM DnzAtWrk: yo lo
03:19 AM DnzAtWrk: trying to figure out the best way to stabilize a arm relative to a stepper motor
03:19 AM DnzAtWrk: my first thought was to squeeze the arm between two thrust bearings connected to the motor, but then I read that thrust bearings shouldn't have any radial load at all, so now I'm wonder if 2 tapered roller bearings is the way to go
03:19 AM DnzAtWrk: I'm wondering*
03:19 AM DnzAtWrk: https://www.dropbox.com/s/3nvbpo73fjeyp1v/arm.png?raw=1
03:19 AM DnzAtWrk: ms paint illustration
09:24 AM rue_mohr: hi
09:24 AM rue_mohr: DnzAtWrk,
09:25 AM rue_mohr: its best if you seperate the bearing for the arm structure and the drive system
09:25 AM rue_mohr: what angle range do you need?
09:26 AM DnzAtWrk: yeah, I've read as much, that you need a flexible coupler of some kind to detach the drive from the arm itself
09:27 AM DnzAtWrk: preferably as much range as possible, but at least > 180 degrees
09:27 AM rue_mohr: in verry few pro system is anything directly driven
09:27 AM rue_mohr: s
09:27 AM DnzAtWrk: yeah. But is there really not a flexible flange?
09:27 AM DnzAtWrk: I don't want to have to go stepper shaft coupler shaft flange
09:28 AM rue_mohr: drive belt, parallel shaft
09:28 AM rue_mohr: give it some reduction, about 2:1 or 3:1
09:30 AM rue_mohr: you have a 3d printer to make pats?
09:30 AM rue_mohr: parts?
09:30 AM DnzAtWrk: yepp. I was hoping to avoid a secondary shaft since that adds a lot of additional components
09:31 AM DnzAtWrk: ie, 2 pieces to hold the secondary axis in place
09:31 AM DnzAtWrk: hmm
09:31 AM rue_mohr: I mean, I dont know anything about the project, but like I say, its best to not use the motor as the structure
09:31 AM DnzAtWrk: also, not sure if I should use deep groove ball bearings, or angular tapered roller bearings
09:32 AM rue_mohr: how big is it?
09:32 AM DnzAtWrk: tiny, I'm planning on using NEMA 8 steppers
09:32 AM rue_mohr: then you should need tapered
09:33 AM DnzAtWrk: ah, so basically. Two tapered bearings pointing inwards keeping the arm in place
09:33 AM rue_mohr: I could help more, but I"m off to work
09:33 AM DnzAtWrk: inside the housing that the stepper screws on to
09:33 AM rue_mohr: I'd just say use ball bearings
09:33 AM DnzAtWrk: some flexible coupler between the arm and stepper
09:33 AM rue_mohr: no coupler
09:33 AM rue_mohr: no direct drive
09:33 AM rue_mohr: belt and pullies, with some reduction
09:33 AM DnzAtWrk: ah, ok
09:34 AM rue_mohr: you have a 3d printer to make pats?
09:34 AM DnzAtWrk: yes
09:34 AM rue_mohr: awesome
09:34 AM rue_mohr: you familiar with cogbelt?
09:35 AM DnzAtWrk: I know what it is, but do you really need a belt if the shafts are right next to each other?
09:35 AM rue_mohr: do you have access to used parts or are you using all new stuff?
09:35 AM rue_mohr: reduction is good
09:35 AM DnzAtWrk: I'm going to be ordering parts, but I'm aiming to use really common cheap parts
09:36 AM rue_mohr: ok, use 3d printer parts then!
09:36 AM rue_mohr: their everywhere
09:36 AM rue_mohr: !
09:36 AM rue_mohr: doyou need to make a lot of them?
09:37 AM DnzAtWrk: Was gonna try to make a modular design so they can be extended with as many limbs as required
09:37 AM DnzAtWrk: out of curosity, why is it better to use belts over just using gears of different sizes?
09:37 AM rue_mohr: back in about 8 hours!
09:37 AM DnzAtWrk: curiosity*
09:37 AM rue_mohr: gears work
10:08 AM DnzAtWrk: https://www.dropbox.com/s/oa5inu0v3qm2r11/arm1.png?raw=1
10:08 AM DnzAtWrk: this is what I came up with, got a lot of bigger
10:09 AM DnzAtWrk: I don't know if the bearings is enough to keep the second shaft in place
10:17 AM DnzAtWrk: https://www.dropbox.com/s/6znrr7ounf8yljx/arm_000.png?raw=1
10:17 AM DnzAtWrk: this was the first version, in which I planned to use directly drive the arm with no bearings
07:05 PM rue_mohr: I hope he understands where that gear ration needs to be