#robotics Logs

Feb 05 2022

08:14 AM rue_mohr: ok I needed to design a _______
08:22 AM rue_mohr: or was it code
08:22 AM rue_mohr: oh my bigtrak software right ok
08:22 AM rue_mohr: I need a serial version
08:24 AM rue_mohr: I just switch it from IR to serial and.... I'm done
08:24 AM rue_mohr: well, new input event translator definitions...
08:24 AM rue_mohr: easy...
08:37 AM rue_mohr: now how do I deal with this 3.3V thing
10:23 AM Miyu is now known as hackkitten
04:13 PM mrdata: gear cutting with a slitting saw https://www.youtube.com/watch?v=eC-OctJoWv4
04:15 PM Tom_L: few extra steps over a hob
04:16 PM mrdata: yeah
04:17 PM Tom_L: and one wrong move...
04:17 PM mrdata: and not as smooth
04:17 PM mrdata: but it does sort of set the value of a hob
04:17 PM Tom_L: hobs are expensive
04:18 PM Tom_L: and they come in sets of 8 iirc
04:18 PM Tom_L: for different numbers of teeth
04:18 PM Tom_L: different angles
04:19 PM Tom_L: i've kinda wanted to try gear cutting but really have no need for it
04:20 PM Tom_L: alot of times shops will just buy the one they need
04:21 PM mrdata: are there gear hobbing services for hire?
04:21 PM Tom_L: i'm sure of it
04:22 PM Tom_L: https://www.amazon.com/DJDK-Involute-Cutter-Pieces-Cutting/dp/B08ZCD34FN/ref=sr_1_6?_encoding=UTF8&c=ts&keywords=Involute+Gear+Cutters&qid=1644098693&s=industrial&sr=1-6&ts_id=256308011
04:22 PM mrdata: i have a use for some strange custom gears
04:22 PM enleth: uh, but you can buy a proper gear cutting tool that mounts and works just like a slitting saw, neither hobbing nor weird hoop-jumping like this video is needed
04:22 PM Tom_L: and you've got 20 or 14.5 degree
04:22 PM enleth: they're called "module cutters"
04:22 PM Tom_L: a hob will have multiple 'teeth'
04:23 PM enleth: Tom_L: ah, you beat me to it
04:23 PM enleth: didn't see the link when typing
04:23 PM Tom_L: ^^ those are cheaper
04:23 PM mrdata: i have a weird application for planetary gears
04:24 PM Tom_L: sdp-si
04:24 PM mrdata: so i want to cut inside gears as well
04:24 PM Tom_L: will make them for you for $$
04:25 PM mrdata: i'll want to make a few prototypes
04:25 PM mrdata: so am wondering about the expense
04:25 PM mrdata: also the material
04:25 PM Tom_L: you have a mill?
04:25 PM mrdata: i may want delrin
04:25 PM mrdata: there is a mill at one of the local maker spaces
04:26 PM mrdata: i am not sure of the tooth size and count i want
04:26 PM mrdata: this will get settled over several prototypes
04:27 PM mrdata: the expense is a concern; if the project is a few hundred $ then feasible; if thousands, definitely no
04:28 PM mrdata: so gear tooth size and thickness are parameters; so are tolerances
04:28 PM mrdata: but a large part of the project isnt well described
04:28 PM mrdata: i need to unerstand torque and speed better
04:29 PM mrdata: and have brakes of some kind; this will get up to pretty high speeds and so speed control is an open question
04:31 PM enleth: mrdata: unless this is clearly and obviously not going to work even as the very first stage of testing, don't dismiss "dumb" ideas such as prototyping involute gears out of lasercut plywood - if all you need to know is whether stuff fits and moves freely before you speed it up, it might just be enough
04:31 PM enleth: and might save some money making delrin or steel gears that turn out to be scrap
04:32 PM mrdata: enleth, i did some early messing around with laser cut acrylic
04:33 PM enleth: also, regular straight tooth involute gears can be lasercut out of steel - not with the makerspace-grade CO2 laser, but still cheaper to have it made than milling
04:33 PM Tom_L: i would do calculations for gear size & strength to avoid the $$$ of having a bunch of them made
04:34 PM Tom_L: inch or metric?
04:35 PM mrdata: ok, so imagine this is for a motor for an aerial drone; so torque, speed, mass, and stength are all factors
04:35 PM Tom_L: https://www.sdp-si.com/products/Gears/Index.php
04:35 PM mrdata: yeah i have been down that rabbit hole part way
04:35 PM Tom_L: :)
04:36 PM mrdata: things got too complex for me so the project was set aside; but i still want to do it
04:38 PM mrdata: plus there are test jigs needed; i have to measure lift and do speed control
04:38 PM mrdata: i wonder if some 3D modelling tool with physics would help
04:41 PM mrdata: and budget is poverty scale
04:43 PM mrdata: i cant afford the monthly membership cost at the maker space
04:44 PM mrdata: imperial vs metric isnt important to me; here in Canada we end up having to use both, a lot
04:50 PM enleth: mrdata: yeah, so definitely look for a local business with a 2kW-ish fiber laser, that cuts aluminum as well and prices should be very affordable for small parts - 5 sets of those clutch teeth in 5mm carbon steel cost me an equivalent of $15: https://a360.co/31qsmrE
04:50 PM enleth: that's 10 separate parts
04:51 PM enleth: size and total cut length are probably similar to what you're dealing with for a drone
04:52 PM enleth: thing is, the guys I order from have a very efficient order handling system, so they take those tiny orders and batch them together
04:53 PM enleth: all I need to do is upload a DXF on their website, which immediately calculates the price based on the drawing, pay online and wait a few days
04:53 PM enleth: there could be someone in your area who got it right too
05:16 PM mrdata: hmm.. yes
05:16 PM mrdata: maybe