#linuxcnc Logs

Mar 08 2022

#linuxcnc Calendar

01:18 AM Deejay: moin
04:22 AM JT-Cave: morning
04:50 AM Tom_L: morning
12:15 PM Tom_L: lunchtime
12:15 PM mrec_: did anyone do threading on a lathe with linuxcnc? Does anyone know the concept behind it?
12:15 PM Tom_L: i'm sure many have
12:15 PM mrec_: I wonder if I can slave linuxcnc somehow move Z ... wait until Z has been reached
12:16 PM Tom_L: single point?
12:16 PM mrec_: my spindle does not have a constant speed
12:16 PM mrec_: and I only have a parallel port available here
12:16 PM mrec_: well single point multiple passes
12:16 PM Tom_L: does the spindle have an encoder on it?
12:16 PM mrec_: I'm adding that now but I can't get the signal into linuxcnc within a reasonable time
12:17 PM Tom_L: http://linuxcnc.org/docs/2.8/html/gcode/g-code.html#gcode:g76
12:17 PM mrec_: I have an as5048 encoder available here, I can get the signal into a microcontroller
12:17 PM Tom_L: i _think_ that was intended for lathe
12:20 PM mrec_: I could report Z reached from the microcontroller to linuxcnc
12:21 PM Tom_L: the axis needs to be in sync with the spindle
12:21 PM mrec_: the microcontroller can do that
12:21 PM mrec_: synchronizing the Z speed to the spindle
12:21 PM mrec_: the spindle speed is not reliable
12:22 PM Tom_L: doesn't need to be but it does need to be in sync
12:22 PM mrec_: those mini lathe controllers are a joke
12:22 PM mrec_: 750W motor and practically delivers less power than a 300w motor due to missing encoder on the motor
12:25 PM mrec_: Tom_L: how can Z be synchronized with the spindle speed?
12:26 PM mrec_: that should be very difficult...
12:26 PM Tom_L: read about G33
12:26 PM mrec_: I'd expect the other way around
12:26 PM Tom_L: you need an encoder on the spindle with 3 channels
12:26 PM Tom_L: A B & Z
12:27 PM Tom_L: Z being the index pulse
12:28 PM Tom_L: iirc it's like 1 line of code in the hal file
12:29 PM Tom_L: been a while...
12:29 PM mrec_: ok that should not work with my AS5048 encoder.
12:29 PM mrec_: I have no index pulses
12:29 PM mrec_: so that still pushes me back that I have to re-implement it in the microcontroller
12:31 PM Tom_L: https://www.youtube.com/watch?v=g99lUtjLfMU
12:31 PM Tom_L: same idea using G33
12:31 PM Tom_L: see how the spindle kinda stalls out? but it stays in sync and makes a good thread
12:31 PM Tom_L: on a crappy little sherline
12:32 PM mrec_: I only have speed control on the spindle but not position control
12:33 PM Tom_L: get a better encoder
12:33 PM mrec_: so linuxcnc would require to offload the step generation of Z in my case to the microcontroller
12:36 PM unterhausen: linuxcnc doesn't ever require that, maybe your hardware doesn't fit into the linuxcnc way of doing things
12:37 PM mrec_: well it's opensource a bridge can be made
12:37 PM unterhausen: true, you can do whatever you want
12:37 PM mrec_: I have integrated the microcontroller in linuxcnc here to control the spindle speed
12:38 PM mrec_: linuxcnc is sending the raw rpm value to the controller and will generate the 0-5v reference voltage from that
12:39 PM mrec_: the vfd of that spindle is not really good there's a certain step available from 100-~1200 rpm
12:39 PM mrec_: some steps are not available at all
12:41 PM mrec_: https://snipboard.io/XrQUuM.jpg
12:41 PM mrec_: pwm vs rpm
12:41 PM mrec_: and the pwm is generating the ref voltage via a filter
12:42 PM mrec_: it's just interfacing the potentiometer
12:43 PM mrec_: which on the other side feeds into the VFD analog input pin of the cheap chinese VFD
04:15 PM JT-Shop: aye I thread on my CHNC
04:31 PM -!- #linuxcnc mode set to +v by ChanServ
05:06 PM JT-Shop: one of the rubber grips on my Robert Sorby reversing jaws split... I can find replacements in UK only :(
05:06 PM JT-Shop: https://www.ockenden-timber.co.uk/woodturning-chucks-accessories-patriot-woodturning-chuck-c-107_108_109_973/robert-sorby-bowl-reversing-jaws-spare-rubber-grips-p-531
05:06 PM JT-Shop: anyone want to buy them and post them over?
05:06 PM * JT-Shop looks at McMaster-Carr
05:06 PM XXCoder: wonder if you can go to say lowes and buy a rubber cork
05:07 PM XXCoder: then you mill it into nesscaru shape
05:09 PM roycroft: seems like you could make those pretty easily
05:09 PM roycroft: i'd make them out of frozen hockey pucks
05:09 PM JT-Shop: machining soft rubber sounds like too much of a challenge and too little reward
05:09 PM roycroft: they machine pretty decently when they are really cold
05:10 PM roycroft: and you can get hockey pucks really cheap
05:10 PM JT-Shop: not too much hockey going on in swamp east missouri
05:11 PM Tom_L: i used to have a whole box full of em
05:11 PM roycroft: there's that website owned by the guy with the penis rocket
05:11 PM roycroft: it will have more hockey pucks than you can shake a stick at
05:11 PM XXCoder: JT theres tons of hockeu pucks on amazon
05:11 PM roycroft: you could rough them out with a hole saw
05:12 PM XXCoder: just make sure to find proper ones, some is fakes plastic
05:12 PM JT-Shop: what's the durometer rating of a hockey puck?
05:12 PM Tom_L: dunno
05:13 PM Tom_L: 90
05:13 PM Tom_L: shore A
05:13 PM roycroft: you might contact sorby directly - i'm sure they disptach to the us
05:13 PM XXCoder: https://www.youtube.com/watch?v=UzgpqBIV7pw
05:13 PM roycroft: it would certainly be easier to just pull out a credit card and then wait
05:13 PM JT-Shop: and do other more productive things
05:14 PM XXCoder: 63 or so apparentlky
05:14 PM Tom_L: The hard rubber in hockey pucks has a durometer of 90 (Shore A).
05:15 PM XXCoder: tom saw some say that, I guess one in that video is cheap fake one
05:16 PM JT-Shop: just sent a message to robert sorby...
05:17 PM JT-Shop: Friday night low forecast is 17°F
05:18 PM Tom_L: yeah it's on a downward slop here too
05:18 PM roycroft: hartville hardware are a good source for sorby turning tools, but i don't see those parts on their website
05:18 PM Tom_L: slope
05:18 PM JT-Shop: that's where I got the patriot chuck and the jaws
05:18 PM roycroft: that's where i got mine too
05:19 PM roycroft: there's a canadian distributor, but i forget who they are
05:23 PM JT-Shop: sent a message to hartville tool as well
05:26 PM roycroft: you might contact lee valley as well
05:26 PM roycroft: the almost certainly won't stock the parts, but they have been willing to special order for me in the past
05:26 PM roycroft: it might take a few months, though
05:27 PM JT-Shop: in any case lesson learned today don't misplace the decimal point for 3-phase overloads
05:27 PM JT-Shop: the result is predicable
05:28 PM roycroft: it blowed up?
05:29 PM JT-Shop: just let the magic smoke out and got pretty hot in the process
05:29 PM JT-Shop: big difference between .35 and 3.5 amps
05:30 PM JT-Shop: $40 difference exactly
05:34 PM JT-Shop: to purchase the replacement
05:37 PM unterhausen: ups man working late tonight
05:38 PM JT-Shop: shop cat is keeping my lap warm
05:45 PM roycroft: have you considered making the clamping knobs out of pine dowel stock?
05:46 PM roycroft: that should be softer than most of the wood you'll use for turning bowls, but hard enough to hold well
05:46 PM JT-Shop: no, that thought has not crossed my mind
05:46 PM roycroft: it might work
05:47 PM roycroft: you could even turn some v grooves into them to grip the lip of the bowl better
05:47 PM roycroft: or just make them tapered
05:48 PM JT-Shop: https://treasuredstocks.com/product/handcrafted-purpleheart-curly-maple-segmented-wooden-bowl-2/
05:48 PM JT-Shop: somewhat interesting
05:52 PM JT-Shop: https://thepatriotwoodworker.com/forums/topic/36204-segmented-bowls-for-the-beginning-turner-by-don-jovag/
05:53 PM roycroft: i should probably turn a bowl some day
05:54 PM Tom_L: you get yours engraved?
05:54 PM roycroft: that's one thing i've never done before
05:54 PM roycroft: i've made bowls out of clay, but never wood
06:10 PM JT-Shop: yes
06:15 PM JT-Shop: working on this table top from junk red oak https://gnipsel.com/images/wood-working/table/table-top-01.jpg
06:18 PM JT-Shop: Tom_L, https://gnipsel.com/images/wood-working/bowls/bowls-11.jpg
06:23 PM Tom_L: engraving looks nice
06:36 PM JT-Cave: used f-engrave
06:37 PM Tom_L: what bit?
07:17 PM roycroft: i installed a half-height equipment rack at the country fair office a few weeks ago
07:18 PM roycroft: it occured to me that folks might pile stuff on top of the machines, so i just made a cover for it with some oak plywood and beech edge strips
07:18 PM roycroft: probably a lot nicer than an equipment rack warrants, but why not do it well?
07:19 PM CloudEvil: :)
07:19 PM roycroft: the plywood was damaged on one side, so i got it for a song
07:19 PM roycroft: and i had the beech wood in stock
07:58 PM XXCoder: JT-Cave: nice job
08:28 PM mrec_: hmm the threading stuff gives me some idea just interface the AS5048A with the microcontroller and generate the pulses for the parallel port on the microcontroller;
08:29 PM mrec_: I'll try that next after re-wiring the system with a belt (before I used some gears but they weren't the same size which just makes it unnecessary complicated)