#linuxcnc Logs

Oct 10 2023

12:12 AM Deejay: moin
01:33 AM solarwind: I'm thinking what's the best way to extend a NEMA 17 motor's shaft (on the back) in order to add an encoder as well as handle full torque for driving a load at the back
01:34 AM solarwind: The shaft diameter of these things is 5mm
01:35 AM solarwind: It's not a lot to work with. But my only idea so far is to drill and tap a 20mm long hole for an M3 screw thread
01:36 AM solarwind: then machine an appropriate mating shaft and permanently seal it with loctite red
01:40 AM solarwind: Should be fine for the kind of drive torques I'm dealing with ( < 1 N·m)
03:38 AM rigid: does probing more than x,y and z axis work?
03:40 AM rigid: afais no GUI currently supports that so I guess a use case never came up.
03:51 AM rigid: solarwind: aren't there NEMA 17s with extended shafts for cheap?
03:52 AM rigid: i guess you think differently with a shop full of machines :)
03:57 AM rmu: solarwind: i would grind/machine a flat onto the shaft and use a set-screw, loctite that in
04:01 AM rmu: solarwind: it's probably a hybrid stepper. you can't disassemble the stepper motor without damaging it, so it is probably very tricky to center-drill the shaft, even more so because you want to drill to depth of D*20
04:09 AM jpa-: and then to get it spin true.. doesn't sound very promising
04:09 AM jpa-: on some stepper motors you can remove the rear side bearing without taking the rotor out (which can damage magnetism), that could give slightly more options
04:12 AM Tom_L: rubber tube connection :) somewhat self centering, very little torque from the encoder
04:12 AM Tom_L: unless you're doing alot of abrupt start/stop/reverse etc
04:18 AM NoSpark: Doesn linuxcnc run well on an RPI3?
04:23 AM Tom_L: graphics are sluggish
04:24 AM Tom_L: rpi4 is better
04:24 AM Tom_L: with 8g ram
04:28 AM NoSpark: How does the extra ram help?
04:37 AM rmu: NoSpark: graphics is kinda sluggish, and SPI frequency depends on core frequency and sometimes changes abruptly. 1kHz thread with external step generator like remora or mesa 7c80 is possible if you can live with a somewhat laggy interface and don't try to backplot large gcode files with lots of adaptive machining
04:42 AM NoSpark: just trying to get a rought idea of the horsepower required to drive linuxcnc, I have a rpi4 board hear on the 7c80 (the big rpi mesa board) and it has been brilliant
04:42 AM NoSpark: *hear = here
04:43 AM NoSpark: but that board has 8gb too, and a closed source graphics driver
04:44 AM NoSpark: succinctly, would it be fair to sat that a rpi3 is not quite enough, and anything more powerful than a RPI4 should be okay
04:44 AM NoSpark: ?
05:50 AM -!- #linuxcnc mode set to +v by ChanServ
05:50 AM JT-Mobile: morning
06:30 AM -!- #linuxcnc mode set to +v by ChanServ
06:30 AM JT-Mobile: heading out this morning
06:35 AM rmu: NoSpark: it depends on what you want to do
06:36 AM rmu: for simple things or if you don't need graphical backplot / preview, the rpi3 is mostly OK
06:37 AM rmu: it probably won't work with ethernet mesa cards or ethercat
07:51 AM Nalesque: Hello all
09:31 AM solarwind: rigid these are special/custom motors with ultra low inductance (0.6mH) designed for high speed
09:31 AM solarwind: rmu it is indeed a hybrid stepper
09:32 AM solarwind: jpa- and yes I can take the bearings out without pulling out the shaft
09:32 AM solarwind: on both sides
09:32 AM solarwind: the magnet is insanely strong
09:34 AM solarwind: rigid if I didn't need the special low inductance, I'd just buy one of these for $10 lol https://www.omc-stepperonline.com/nema-17-stepper-motor?mfp=71-single-shaft-dual-shaft[Dual%20Shaft]
09:35 AM solarwind: But there's a _huge_ difference between even "low inductance" 3mH steppers and 0.6mH
09:37 AM rigid: oh, that makes sense then
09:54 AM solarwind: rigid https://www.3dlabtech.ca/product/ldo-nema17-motor-ldo-42sth48-2804ac/ that's a 2.8 Amp NEMA17 with 0.7ohm phase resistance and 0.6mH phase inductance and a torque curve that goes UP with increased speed
09:55 AM solarwind: I can ask the manufacturer to customize it with a dual shaft but there's a minimum order quantity :(
09:55 AM solarwind: probably 100 units or so
10:08 AM Loetmichel: NIICE! We just had a sales rep wit a new industrial 3d-scanner here. can scan parts up to 670mm diameter and 400mm height in one go with 0.01mm accuracy AND put out a .step, not only an .STL... or you can dismount tha head from the base and do parts up do a few meters in diameter at reduced accuracy in multiple manual scans. only bad thing is that they want close to 100kEur for the machine
10:08 AM Loetmichel: and soft. :(
10:10 AM rigid: Loetmichel: what kind of markers do they use?
10:10 AM rigid: or is it laser?
10:11 AM Loetmichel: ... but it looks like my engineering boss will push it into the budget for first quarter/24! :)
10:11 AM Loetmichel: rigid: none. apart from a dulling spray for shiny objects
10:12 AM solarwind: Loetmichel just ask CaptHindsight to build it for you
10:12 AM rigid: is it optical? then there must be some kind of marker for calibration i assume
10:15 AM Loetmichel: it is a combination of camera(s) and a line/grid video projector
10:15 AM Loetmichel: and an automated turntable
10:16 AM Loetmichel: they have a calibration template but its only needed to use after moving the scanner
10:18 AM rigid: i wonder what the template looks like to get that level of accuracy. or maybe they have awesome lenses/lense calibration
10:19 AM Loetmichel: the template is actually two part. one rather large (~400mm diameter) "qr-code" and a 300mm bar with half a dozen different sized balls
10:22 AM rigid: ahm
10:22 AM rigid: if you want to build something yourself, there's a lot of guides/projects for the https://alicevision.org/ opensource framework
10:23 AM Loetmichel: basically: you use the "QR-code" to calibrate and then check with the ball bar
10:23 AM Loetmichel: rigid: why shoudl i if the Engineering boss will puss the CEO to spew out the 100k?
10:23 AM Loetmichel: s/puss/push
10:24 AM rigid: dunno, because it's fun? or maybe charge the boss a cheaper version and pocket the 80k? :-P
10:25 AM Loetmichel: rigid: if you will write mie the "step-converter" software for free: sure ;)
10:26 AM Loetmichel: -i
10:29 AM rigid: it outputs wavefront objects. there are converters.
10:30 AM rigid: i remember doing it with freecad even
10:30 AM rigid: not sure how robust that is in production
10:31 AM Loetmichel: Yeah, the intruiging part about that packet is the "Flächenrückführung" part of the .step converter. That it makes solid objects out of parts scanned
10:31 AM Loetmichel: autmatically, without any user input
10:33 AM Loetmichel: its even inteligent enough to give you indicators for WHY a divergence happened. like "Thats probably casting shinkage" or "bend sheet metal?" (the latter we had on the laptop hinge after scanning because one of the hinge flanges was 0,2mm "out of flat"
10:35 AM rigid: yeah, meshroom can produce solids. I didn't care for the exact specs tho.
10:35 AM rigid: ah nice... not sure if there's an alicevision library for that
11:13 AM CaptHindsight: https://www.thefabricator.com/thefabricator/article/bending/k-factors-y-factors-and-press-brake-bending-precision
11:13 AM CaptHindsight: is this like rocket science to a sheet metal fabricator? ^^
11:16 AM Unterhausen: I'm sure some people that bend metal are pretty good at using those factors and most of them have never heard of it
11:21 AM roycroft: most sheet metal fabricators i've known bend by eye
11:21 AM roycroft: they just know from experience what to do
11:21 AM roycroft: but they do not use teh maths
11:22 AM roycroft: and they can always fix things with a little weld and/or a hammer
11:30 AM Unterhausen: I almost used sendcutsend's bending service to see how good they are. They have a nice tutorial about solidwork's sheet metal tools
11:31 AM Unterhausen: I have trust issues though
12:46 PM Scopeuk: Don't know if it makes things better or worse but it's run by one of the battle bots teams
12:48 PM -!- #linuxcnc mode set to +v by ChanServ
01:13 PM Unterhausen: I'm pretty happy with sendcutsend, just don't know about their bending
02:19 PM CaptHindsight: Powermill has a additive plugin now, this should be interesting
04:00 PM -!- #linuxcnc mode set to +v by ChanServ
04:03 PM JT-Mobile: yo
04:03 PM Tom_L: one more mobile day?
04:03 PM JT-Mobile: yep we are in Tuscaloosa tonight
04:04 PM JT-Mobile: trying to decide if I want to watch Leo's latest video or wait until tomorrow
04:04 PM Tom_L: about to head out the door..
04:07 PM JT-Mobile: later
05:40 PM Unterhaus_ is now known as Unterhausen
08:06 PM acer is now known as _unreal_
08:29 PM flyback: https://realterm.sourceforge.io/