#garfield Logs
Mar 12 2019
#garfield Calendar
05:49 AM Tom_L: zhanx at least you've moved up from crayola :)
09:17 PM rue_shop1: 42g 197mm 2.6A
09:21 PM rue_shop1: 12V 2500RPM
10:30 PM rue_mohr: after all the numbers are boiled
10:30 PM rue_mohr: it comes out to 5mm/rev of the motor
10:32 PM rue_mohr: 1/4" is 20tip
10:32 PM rue_mohr: whats 5/16
10:32 PM rue_mohr: 18?
10:32 PM rue_mohr: thats a long way from 5
10:34 PM Tom_itx: ?
10:34 PM rue_mohr: well
10:34 PM Tom_itx: working on your table/
10:34 PM Tom_itx: ?
10:34 PM rue_mohr: yea
10:35 PM rue_mohr: if I were to entertain the notion of threaded rod
10:35 PM rue_mohr: I'd have to throw in a pulley system
10:35 PM Tom_itx: it would be a bad idea
10:35 PM Tom_itx: unless you turn the coupler not the rod
10:35 PM rue_mohr: pullies are like 2:1, so I'd have to be down to either 10 or 20 tpi
10:35 PM Tom_itx: 20 is fairly common
10:36 PM rue_mohr: 4:1 with pullies is a lot of extra mechanics
10:36 PM Tom_itx: my z is 3:1
10:36 PM rue_mohr: tho it means the main drive rod would only ahve to be 2 feet long
10:36 PM rue_mohr: throwing out that idea
10:36 PM rue_mohr: I'm looking at 5mm travel per motor rev
10:37 PM Tom_itx: http://tom-itx.no-ip.biz:81/~webpage/cnc/Mill_Steel/Belt_Guard/New_Belt_installed.jpg
10:37 PM rue_mohr: yup
10:37 PM rue_mohr: but the bed is 8' long
10:38 PM rue_mohr: I'm leaning towards rack/pinion
10:39 PM rue_mohr: most of the big ones are
10:39 PM rue_mohr: I'v seen one done with cables
10:40 PM rue_mohr: at 100ppr on the motor, I only peak out at 20Khz
10:40 PM rue_mohr: that might be doable
10:41 PM rue_mohr: that gives me 10 error counts for 0.5mm resolution
10:45 PM Tom_itx: got any design pics or start of design yet?
10:45 PM rue_mohr: this will just be a gantry router
10:45 PM rue_mohr: like furrys
10:45 PM Tom_itx: 2 motors on Y?
10:45 PM rue_mohr: hahah no
10:46 PM Tom_itx: why not?
10:46 PM rue_mohr: :) the engine timing belt I have is 54"
10:47 PM rue_mohr: no threaded rod (ok, maybe for z), 48*96 WORKABLE, 1m/s peak
10:47 PM rue_mohr: dc servomotor
10:47 PM rue_mohr: inclined table
10:47 PM rue_mohr: so footprint ~ 3'x11' worst?
10:48 PM rue_mohr: goal 2'x10'
10:48 PM Tom_itx: oh!
10:48 PM Tom_itx: garage door screw
10:48 PM rue_mohr: screw?
10:48 PM rue_mohr: screws get awefull heavy
10:49 PM rue_mohr: I'm thinking X:(8') rack/pinion and y:(4') gearbelt or another rack/pinion
10:49 PM Tom_itx: https://www.linearmotiontips.com/what-are-the-benefits-of-a-rotating-ball-nut-aka-driven-nut/
10:49 PM rue_mohr: yea, too much reduction, too slow, too expensive
10:50 PM rue_mohr: $20 budget dude
10:50 PM Tom_itx: concept not parts
10:50 PM rue_mohr: ah I 3d printed one
10:50 PM rue_mohr: its how I was going to build my machien like 20 years ago
10:50 PM rue_mohr: 20?
10:51 PM rue_mohr: 23...
10:51 PM rue_mohr: burn
10:55 PM rue_mohr: I'm trying to think up a way to mix course and fine encoders
10:55 PM Tom_itx: what for?
10:55 PM rue_mohr: so that the fine one losing signal at high rpm isn't an issue for fine positioning at low speeds
10:56 PM Tom_itx: once you establish direction read the index pulse
10:56 PM rue_mohr: hmm
10:56 PM Tom_itx: then it turns into 1 per rev
10:56 PM rue_mohr: yup
10:56 PM Tom_itx: instead of 1024 etc
10:56 PM rue_mohr: esp if the index pulse is 50% duty
10:57 PM Tom_itx: above a certain count switch and know each pulse is 1024 or whatever
10:58 PM Tom_itx: read the quadrature docs for the 68332 microcode. i think that's how they did it
10:59 PM Tom_itx: or something like that
10:59 PM rue_mohr: sounds good
11:00 PM rue_mohr: another issue is what to do for rails over 8'
11:00 PM rue_mohr: for the resolution, electrical conduit may be ok
11:00 PM Tom_itx: http://www.seattlerobotics.org/encoder/200006/tpurm.pdf
11:01 PM Tom_itx: QDEC
11:02 PM rue_mohr: I have one of those HP HCTL(?) chips, that does sensor managment from the olde days
11:04 PM Tom_itx: i probably still have that set of books
11:04 PM Tom_itx: ok. diamond ceramic tile cutter to cut carbide endmills
11:04 PM Tom_itx: go or nogo?
11:04 PM rue_mohr: this is a subsystem on the 68332 eh?
11:04 PM Tom_itx: yes
11:05 PM Tom_itx: it comes with mask G
11:05 PM rue_mohr: with water I'd think you would beok
11:05 PM Tom_itx: which is designed for motor control
11:05 PM rue_mohr: k
11:05 PM Tom_itx: i gotta shorten one of the cutters
11:05 PM Tom_itx: the shank
11:05 PM Tom_itx: don't have em yet though
11:05 PM rue_mohr: notch and snap?
11:05 PM Tom_itx: no
11:05 PM Tom_itx: i want a clean cut
11:06 PM rue_mohr: isn't that pretty crisp?
11:06 PM rue_mohr: carbide dosn't bend
11:06 PM rue_mohr: tho
11:06 PM rue_mohr: the shank may not be fully hardened
11:06 PM Tom_itx: it's still carbide
11:06 PM Tom_itx: the cutting part is coated
11:06 PM rue_mohr: your cutting back the shank tho
11:06 PM rue_mohr: ?
11:07 PM Tom_itx: yeah, i'm afraid it will be too long otherwise
11:07 PM Tom_itx: i'll make the call once i see it
11:08 PM rue_mohr: hmm
11:08 PM rue_mohr: what might have a metal rack in it suitable for this cnc
11:08 PM rue_mohr: or ateast a 2 or 3 foot segment
11:08 PM Tom_itx: for what part?
11:09 PM rue_mohr: the 8' and 4'
11:09 PM rue_mohr: xy
11:09 PM rue_mohr: too bad I couldn't trust a hyd cyl and + displacement pump
11:12 PM Tom_itx: sleep once again...
11:12 PM rue_mohr: tho, a rotary piston pump would prolly be low slip
11:12 PM rue_mohr: arg, its out of my budget
11:12 PM rue_mohr: unless I land who offset hydraulic motors
11:12 PM rue_mohr: and a 4' cylinder
11:12 PM rue_mohr: er, 8...
11:13 PM rue_mohr: hmm
11:13 PM rue_mohr: prolly doable with a 4 and levers
11:13 PM rue_mohr: without taking up 16' of space
11:14 PM Tom_itx: vertical not horizontal :)
11:14 PM rue_mohr: hmm :)
11:15 PM Tom_itx: later..
11:15 PM rue_mohr: gngiht
11:15 PM Tom_itx: i get toys tomorrow
11:16 PM rue_mohr: :)
11:16 PM Tom_itx: too bad i'm too busy to use em right now
11:51 PM rue_mohr: I suppose if I could make a 200steps/rev DC servo I'd be doing pretty good
11:51 PM rue_mohr: x4
11:51 PM rue_mohr: 50 line encoder
11:51 PM rue_mohr: well arg, 10 counts of error
11:52 PM rue_mohr: 2000 counts/rev
11:52 PM rue_mohr: thats more than 10 bit too
11:52 PM rue_mohr: ah, but
11:52 PM rue_mohr: 2048 is 2 cycles/rev
11:52 PM rue_mohr: 16 bit adc?
11:52 PM rue_mohr: well 10 bit, 2 cycle, but
11:58 PM rue_mohr: oo, loop speed
11:58 PM rue_mohr: hmm