#robotics Logs

Mar 11 2019

05:19 PM veverak: so
05:23 PM veverak: what's up doc?
05:27 PM morkDaBest: hi
08:39 PM SpeedEvil is now known as Guest81458
09:03 PM rue_mohr: not much chatting
09:08 PM Tom_L: got some thread mills coming
09:32 PM rue_mohr: cool!
09:32 PM rue_mohr: for what sizes?
09:32 PM rue_mohr: like #6-32 or 1/4-20?
09:49 PM Tom_L: 10-24 - 3/4 16
09:50 PM Tom_L: should cover all the bases i'll ever cross
09:50 PM Tom_L: smaller than 10-24 i think the spindle is strong enough to rigid tap
09:51 PM rue_mohr: DRAM, 128 updates required every 2ms
09:51 PM Tom_L: found something i didn't know they had...
09:52 PM Tom_itx: https://www.sherline.com/product/3082-end-mill-holder-style-fixture/
09:52 PM Tom_L: mill blanks
09:53 PM Tom_L: just a threaded blank you and diy
09:53 PM rue_mohr: oh
09:53 PM rue_mohr: hu
09:53 PM Tom_L: they have one 4" long too
09:57 PM Tom_L: i hope to be able to make my own collets with the 3/4 16 thread mill
09:57 PM rue_mohr: aaah
09:58 PM rue_mohr: I didn't know if you actaully had a direction for all that
09:58 PM Tom_L: i got some just over 1" alum barstock to practice on today
09:58 PM Tom_L: some could be aluminum and be fine
09:58 PM Tom_L: ie a particular drill size i can use in the tool changer
09:58 PM Tom_L: otherwise my drill chuck is usually too long
09:59 PM Tom_L: so just add a threaded base to the drill and bingo
09:59 PM Tom_L: i can make a bunch of em from the aluminum bar and they should work great
10:00 PM Tom_L: i'll probably make a softjaw fixture to hold the 1" round and maybe prepare them in the lathe then cut the threads on the mill
10:02 PM Tom_L: i'll have to shorten the 3/4 thread mill though
10:02 PM Tom_L: it's 4" long with a 5/8 shank. the tube on the sherline is smaller than that
10:03 PM Tom_L: the 'cut length' on it is 1.625 so the rest is all 5/8" carbide
10:04 PM Tom_L: ~2.3"
10:04 PM Tom_L: i'll probably cut at least half that off
10:05 PM Tom_L: rue_mohr, somebody the other day was looking at some kind of ram with DRAM inside with internal refresh
10:05 PM Tom_L: looked like SRAM on the outside
10:10 PM rue_mohr: heh
10:10 PM rue_mohr: a long time ago I read about using dram as a ccd
10:10 PM rue_mohr: and I decalled a bunch of chips, but the control seq was too complex for me at the time
10:10 PM orlock: heh
10:10 PM rue_mohr: but now I have microcontrolelrs
10:10 PM rue_mohr: so, I'm gonna try it
10:11 PM rue_mohr: if it works, I'll see if I can make laser-guided-rail-drift-compensation for the new cnc
10:11 PM rue_mohr: (I broke down and started working on the 48"*96" machine
10:11 PM rue_mohr: )
10:11 PM rue_mohr: ;
10:12 PM orlock: or, there's mouse sensors
10:12 PM rue_mohr: no, if I have a crookid guide rail on the cnc
10:12 PM rue_mohr: but I run a laser down it
10:12 PM rue_mohr: and have the servos automatically compensate for the drift in the rail
10:13 PM orlock: another one of our temperature sensors failed - it's a networked Z80 clone inside the box :)
10:13 PM rue_mohr: the sensor itself or the whole unit?
10:13 PM orlock: yeah - you could use any sensor? the laser fot might be a bit big though
10:13 PM orlock: just the sensor
10:13 PM orlock: oh
10:13 PM orlock: sorry, got confused
10:14 PM rue_mohr: I want to use the dram as a ccd to watch the laser line
10:14 PM orlock: the sensor is some thermocouple, the sensor server is a networked Z80 with a few screw terminals
10:14 PM rue_mohr: ah
10:14 PM rue_mohr: so, thermocouple fail
10:14 PM orlock: sensor server is a blackbox with one of these in it: https://en.wikipedia.org/wiki/Rabbit_2000
10:14 PM Tom_L: linuxcnc has mapping so you can map the whole table
10:14 PM orlock: sensor server does not power on at all
10:14 PM rue_mohr: rabbit is a z80 type?
10:15 PM Tom_L: i got some of those
10:15 PM orlock: The instruction set is based on the original Z80 microprocessor, but with some additions of new instructions as well as deletions of some instructions
10:15 PM rue_mohr: Tom_L, yea, I dont ahve money for linuxcnc
10:15 PM Tom_L: in gps trackers for commercial
10:15 PM Tom_L: it's free
10:15 PM Tom_L: use a parport
10:15 PM rue_mohr: yea, but not the hardware to make it run descent
10:15 PM rue_mohr: parport is way too slow
10:15 PM Tom_L: i might have spares
10:15 PM rue_mohr: that said
10:16 PM rue_mohr: I wonder step rate vs resolution for grbl
10:16 PM rue_mohr: hmmmm
10:16 PM rue_mohr: this isn't scaling well
10:16 PM Tom_L: if you had a decent pc i've got 2 ethernet cards that would control one
10:16 PM Tom_L: not sure what else
10:16 PM rue_mohr: their great, but if something blows up I cant make up the ground
10:17 PM Tom_L: i'm not using ethernet
10:17 PM Tom_L: just on the test pc
10:17 PM rue_mohr: :)
10:17 PM rue_mohr: I dont ahve any steppers large enough for a 4'x8' cnc
10:18 PM Tom_L: i've got the same config on one as i do on the parallel interface one on the mill
10:18 PM rue_mohr: so, DC servos and ...????
10:18 PM rue_mohr: working on that
10:18 PM orlock: cordless drill motors
10:18 PM orlock: print your own quad encoders
10:18 PM orlock: :)
10:18 PM rue_mohr: well
10:18 PM Tom_L: he's got encoders he could make
10:18 PM rue_mohr: quad encoders have two edges
10:18 PM rue_mohr: low resolution, or freq limit
10:19 PM rue_mohr: I'd like a resoluton of atleast 0.5mm
10:19 PM rue_mohr: but I need a descent traversal speed over 96"
10:19 PM rue_mohr: theaded rod is out of the question
10:20 PM Tom_L: timing belt would probably work best
10:20 PM rue_mohr: rack/pinion or chain
10:20 PM rue_mohr: Tom_L, 96" :(
10:20 PM Tom_L: any shaft will whip unless you turn the nut instead of the screw
10:20 PM rue_mohr: threaded rod is too slow
10:20 PM Tom_L: double lead
10:21 PM Tom_L: or quad
10:21 PM rue_mohr: chain / rack
10:21 PM Tom_L: stretch
10:21 PM Tom_L: too many links to wear
10:21 PM rue_mohr: not with rack/pinion
10:21 PM rue_mohr: yea, I'm weighing
10:22 PM orlock: so i realised yesterday
10:22 PM rue_mohr: I'm considering shop vac motors
10:22 PM orlock: that in my compound mitre saw
10:22 PM Tom_L: everything is a trade off
10:22 PM rue_mohr: yea
10:22 PM orlock: i can mode the "saw" bit backwards and forwards, this is what makes it a compound saw apparently
10:23 PM orlock: i've bene flopping all my bits of wood as it would not cut through in the location it shipped in :-\
10:23 PM rue_mohr: hmm
10:24 PM rue_mohr: you usually avoid cutting into the direction of the saw cause if it snags, bad things happen
10:24 PM rue_mohr: but yea
10:24 PM Tom_L: i think i'll test the 3/4" cutter on a wood dowell before i commit
10:24 PM orlock: rue_mohr: yeah, i mean, i just needed to move the saw 1" which i'd never done before
10:25 PM orlock: now it cuts all the way through on one slice
10:25 PM orlock: before it only got half, and i had to flip the wood to get the other half
10:25 PM rue_mohr: oh, you mean you always had it set all the way back?
10:25 PM rue_mohr: hah
10:25 PM Tom_L: why does everybody wait til bedtime to wake up?
10:25 PM orlock: forwards, but same thing
10:26 PM rue_mohr: Tom_L, I been asking that for 4 years now
10:27 PM zhanx: time zones
10:27 PM rue_mohr: no
10:28 PM rue_mohr: no I seen too many channel with too many people in time zones that are tooo far apart to beleive that
10:28 PM zhanx: waiting on my printer
10:28 PM zhanx: 98 pages to go
10:29 PM rue_mohr: isnt' that what their for?
10:29 PM rue_mohr: haha oh 2d
10:29 PM zhanx: yep
10:30 PM zhanx: rue_mohr, once all this business stuff is done, wife ok'd me doing the arm with the boys, which she said no on first
10:30 PM zhanx: but after the oldest got that A for stuff i teach when he asked questions i am golden for a month
10:33 PM rue_mohr: ARM or arm?
10:33 PM zhanx: arm, 6 dog
10:33 PM zhanx: dof
10:35 PM Tom_L: anything i want usually cost me 2x
10:36 PM rue_mohr: hobby serovs?
10:37 PM zhanx: only for the gripper
10:37 PM Tom_L: so i just doubled up this time
10:37 PM rue_mohr: did you hear about using 4 2512 SMT resistors in a wheatstone as a force sensor?
10:37 PM zhanx: who
10:37 PM rue_mohr: my 100pcs of 2512 smt resistors came in today
10:38 PM rue_mohr: gonna try it
10:38 PM rue_mohr: https://hackaday.com/2019/01/27/quartet-of-smd-resistors-used-to-sense-z-axis-height/
10:42 PM Tom_L: does the resistor flex change it's value?
10:42 PM Tom_L: you might want 1% or less for that ehh?
10:42 PM rue_mohr: I got 1%
10:42 PM rue_mohr: I presume its the stretch/compression
10:42 PM rue_mohr: I'll play
10:43 PM rue_mohr: spooky, cause its on a ceramic substrate
10:43 PM Tom_L: could also rip up the trace on a fail
10:43 PM rue_mohr: held down by lead
10:43 PM rue_mohr: your not supposed to bend them much
10:43 PM Tom_L: it's interesting what we can measure today we couldn't 10 yrs ago
10:50 PM Tom_L: rue_mohr did you see the strain gage link in the article?
11:11 PM rue_mohr: yea, too expensive
11:11 PM rue_mohr: I just paid $4.20 for 100 resistors
11:11 PM rue_mohr: so 4c ea
11:12 PM rue_mohr: tchnically I need 4 per sensor