#emc-devel | Logs for 2006-03-18

[01:43:06] <cradek> hi jmk!
[01:43:36] <cradek> jepler says freqgen does work right - he must have been smoking someting odd before
[01:45:56] <jmkasunich> heh
[01:46:04] <jmkasunich> is he gonna undo his changes?
[01:46:45] <cradek> yes I'm sure he will
[01:46:49] <jmkasunich> ok
[01:46:53] <cradek> we've almost got motion here
[01:47:01] <cradek> very exciting (we've never done servos)
[01:47:13] <jmkasunich> we? you guys are working together on the etch-a-sketch?
[01:47:41] <cradek> yes
[01:47:45] <jmkasunich> cool
[01:48:02] <cradek> his driver board seems sound, and we have feedback
[01:48:21] <jmkasunich> whats he using for drivers? something like a L298?
[01:48:29] <cradek> yes
[01:49:06] <jmkasunich> I have my joystick sitting here from when I was testing the driver... I just had an image of a joystick controlled etch-a-sketch
[01:49:17] <jmkasunich> no emc or g-code, just draw with the stick ;-)
[01:49:26] <cradek> holy crap, it's working
[01:49:31] <jmkasunich> yay!!!
[01:49:45] <cradek> and it sings a little tune for us
[01:49:52] <jmkasunich> yeah ;-)
[01:50:04] <jmkasunich> that is the nature of the pseudo-PWM
[01:50:51] <jmkasunich> its actually PFM (pulse frequency modulation)
[01:50:53] <cradek> now if we had any idea how to tune, we'd be in business
[01:51:08] <jmkasunich> yeah, that the kicker isn't it
[01:51:12] <jmkasunich> I use halscope
[01:51:47] <jmkasunich> apply either a step or triangle command
[01:52:20] <jmkasunich> I try to set the scales first, so everything is in reasonable units
[01:52:32] <jmkasunich> encoder scale so that the encoder position is in inches
[01:52:44] <jmkasunich> commanded position will of course be in inches too
[01:53:04] <jmkasunich> freqgen scale so that the output is in volts at the motor
[01:53:15] <cradek> it's probably grossly untuned, but it seems to work
[01:53:46] <jmkasunich> (for example, if you have period=50uS (20KHz max freq = 100% duty cycle) and a 12V supply. set the scaling so a command of 12 will result in a frequency of 20KHz
[01:54:13] <jmkasunich> command 3 and you get 5KHz = 5KHz = 25% duty cycle = 3 volts at the motor
[01:54:33] <jmkasunich> oops, echo echo
[01:55:02] <cradek> ok I see what you mean
[01:55:22] <jmkasunich> then the gains become meaninfull
[01:55:22] <cradek> we're a little shaky on our scales because we don't know the etch-a-sketch internals
[01:55:29] <cradek> we'll have to measure and guess
[01:55:34] <jmkasunich> close enough
[01:55:48] <jmkasunich> for tuning being within 50% is good
[01:55:50] <cradek> modifying axis to show actual position...
[01:56:58] <jmkasunich> re: meaningfull gains: if scales are right, a Pgain of 200 means that with an error of 0.01 inches you'll be commanding a correction of 0.01*200 = 2 volts
[01:57:39] <jmkasunich> Igain of 100 means that an error of 0.01" for 1 second will result in 0.01 * 1.0 sec * 100 = 1 volt
[01:58:32] <jmkasunich> Dgain of 0.3 means that an error changing at 2 inch/sec will result in 2.0 in/sec * 0.3 = 0.6 volts
[01:58:34] <jmkasunich> and so on...
[01:58:40] <cradek> I see
[01:58:48] <cradek> that sounds useful because if you change power supply, you know what to do
[01:58:53] <jmkasunich> yep
[01:59:05] <cradek> well we don't know why, but it seems to follow the path as-is
[01:59:14] <jmkasunich> you guessed well on the gains
[01:59:19] <cradek> maybe it's not at all critical for our application
[01:59:20] <jmkasunich> (what are you using?)
[01:59:38] <cradek> 150 100 0.1
[01:59:45] <jmkasunich> sounds reasonable
[01:59:50] <cradek> 0 1
[01:59:52] <jmkasunich> I don't recall what I used for my little motors
[01:59:56] <cradek> * cradek shrugs
[02:00:03] <cradek> he copied them from somewhere :-)
[02:00:34] <jmkasunich> I did a bit of tweaking with halscope, I had the motor go from a standstill, turn 1/2 turn, and stop again in 40mS
[02:01:03] <jmkasunich> you're not asking it to do anything like that I suspect, so you can get away with minimal tuning
[02:01:05] <cradek> how much does it change when you change the load on the motor?
[02:01:18] <cradek> we just want it to have fast but not violent action
[02:01:19] <jmkasunich> "some" ;-)
[02:01:25] <cradek> I figured
[02:01:35] <cradek> we should hook it up the the eas before we tune anything
[02:01:57] <jmkasunich> I aimed for very good (fast) response on the position loop and then used accel and velocity limits for smoothness
[02:02:15] <jmkasunich> the the eas?
[02:02:29] <cradek> etch-a-sketch
[02:02:32] <jmkasunich> ;-)
[02:02:37] <cradek> oh TO the
[02:03:37] <jmkasunich> the eas load is almost entirely friction, right? (very little inertia)
[02:03:45] <cradek> probably
[02:03:52] <cradek> and it's surely not even friction
[02:03:57] <cradek> so it'll be a bit sloppy at best
[02:05:27] <cradek> wow, it flies
[02:05:31] <cradek> cds at 1000%
[02:05:41] <jmkasunich> nice
[02:05:56] <jmkasunich> you gotta bring that to the fest
[02:06:07] <cradek> oh we will!
[02:06:15] <cradek> it's jepler's only machine, he'll bring it
[02:08:58] <cradek> that's interesting - with deadband of .01, it lets you have -.01 to +.01
[02:09:04] <cradek> seems off by a factor of two
[02:10:10] <jmkasunich> guess it depends on how you define deadband
[02:10:36] <jmkasunich> its documented that if (fabs(error) < deadband ) error = 0
[02:11:02] <jmkasunich> dunno if that is the usual convention for deadband or not
[02:12:17] <jmkasunich> my way of looking at it is: "If you are within +/-<deadband> of the desired position, do nothing"
[02:15:21] <cradek> ok I assumed the other thing: there's a band |<---->| this wide, within which is "good enough"
[02:15:45] <jmkasunich> yeah, I've seen both conventions used - I like mine better ;-)
[02:15:56] <jmkasunich> more like a tolerance spec
[02:16:35] <cradek> hmm, it ferrors pretty easily when hooked to the actual eas...
[02:17:05] <jmkasunich> probably the friction slows it down
[02:17:24] <jmkasunich> you could either:
[02:17:39] <jmkasunich> 1) turn down vel or acc limits until it doesn't ferror
[02:17:47] <jmkasunich> 2) fire up the scope, see if the output is saturating
[02:18:07] <jmkasunich> if it's saturating (putting out 100% duty cycle) then you have to lower the vel and/or acc
[02:18:14] <jmkasunich> if not, you can probably raise gains
[02:18:49] <cradek> ok, that makes sense
[02:19:41] <cradek> working on set screws now
[02:19:57] <jmkasunich> I think if you raise P and I by the same amount (multiply both by 1.5, or 0.3, or 10, or...) then you'll maintain the same time constant
[02:20:03] <jmkasunich> changing only one changes the time constant
[02:20:14] <cradek> so meanwhile about threading: what does the encoder information look like? does the index pulse reset the count or something?
[02:20:23] <jmkasunich> depends on the driver
[02:20:38] <jmkasunich> but I'm aiming for some conventions for all HAL encoder drivers
[02:20:48] <jmkasunich> there will be a HAL pin that enables the index reset
[02:21:06] <jmkasunich> if that pins is true, every index resets the counter, and the position is a sawtooth
[02:21:32] <cradek> I'm not sure how else you would get absolute positioning
[02:21:35] <jmkasunich> when you are ready for the pass to start, set the index-reset-enable pin false, and the position becomes a ramp
[02:43:29] <jmkasunich> are you or jepler gonna post anything about the servo etch-a-sketch to a website?
[02:46:12] <cradek> I'm sure he will
[02:46:25] <cradek> ok we were saturating on Y, so we turned it down to 3ips
[02:46:33] <cradek> seems to run pretty well other than that
[02:46:37] <cradek> x at 4ips
[02:46:45] <jmkasunich> 3 ips isn't exactly slow
[02:46:58] <jmkasunich> the screen is what, 6" wide? so 2 secs end to end
[02:47:07] <cradek> es
[02:47:08] <cradek> yes
[02:47:11] <cradek> it runs pretty well actually
[02:47:22] <jmkasunich> how does it compare to the stepper version?
[02:47:24] <cradek> the action is much smoother than the 7 degree steppers
[02:47:27] <cradek> much better
[02:47:40] <jmkasunich> 7 degree?
[02:47:52] <jmkasunich> yeah, I guess it would be better ;-)
[02:48:54] <cradek> yes there was a lot of stairstep that showed on diagonals
[02:50:21] <jmkasunich> how many counts are the servo encoders?
[02:52:37] <cradek> 100/rev
[02:52:52] <jmkasunich> so not a whole lot higher resolution than the stepper
[02:52:54] <cradek> with a 6-1 gearhead (emc counts 2400 counts/shaft rev)
[02:53:00] <jmkasunich> that was 48 steps/rev
[02:53:11] <jmkasunich> oh - gearbox makes a big difference
[02:53:35] <jmkasunich> so its just a little bit finer resolution ;-)
[02:53:37] <cradek> err they were 7.5 degree halfstepped
[02:53:47] <cradek> so 96 halfsteps per revolution
[02:53:57] <cradek> and now we have 2400, cool
[02:53:58] <jmkasunich> still, 2400 >> 96
[02:54:00] <cradek> no wonder it's smoother
[02:54:27] <jmkasunich> where'd he get the motors?
[02:55:11] <jepler> http://emergent.unpy.net/index.cgi/projects/01142347802
[02:55:18] <jepler> link to servos on that page
[02:56:17] <jmkasunich> interesting - you are using separate direction and PWM bits?
[02:56:26] <cradek> yes
[02:56:59] <jmkasunich> wow, those look like nice motors
[02:57:06] <jmkasunich> torquey?
[02:57:38] <cradek> with the loop closed, the shafts are hard to turn
[02:57:56] <jmkasunich> and it whines at you when you try?
[02:58:01] <cradek> definitely
[02:59:53] <cradek> (we're using 12v)
[02:59:55] <jepler> http://emergent.unpy.net/index.cgi-files/projects/01142347802/03_093_e.pdf
[02:59:57] <jepler> http://emergent.unpy.net/index.cgi-files/projects/01142347802/03_200_e.pdf
[03:00:00] <jepler> http://emergent.unpy.net/index.cgi-files/projects/01142347802/03_215_e.pdf
[03:00:04] <jepler> datasheets for the motor, gearhead, and encoder
[03:00:32] <jmkasunich> nice - I'm not used to having data for my surplus junk
[03:01:36] <jmkasunich> * jmkasunich scratches his head and pulls out the calculator
[03:01:46] <jmkasunich> milli-newton-meters? geez
[03:02:03] <cradek> dude, use units
[03:03:31] <cradek> units "nM n" "oz in force"
[03:03:35] <cradek> * 0.14161193
[03:03:51] <cradek> err mN
[03:04:21] <jmkasunich> so 31.9 mNm = ~4.5oz-in
[03:04:33] <cradek> * 6 for the gearhead
[03:04:36] <jmkasunich> * 6 in the gearbox = ~ 27 oz-in
[03:04:43] <cradek> so 27
[03:04:47] <cradek> yeah
[03:04:51] <cradek> not real strong?
[03:05:01] <jmkasunich> not really
[03:05:04] <cradek> perfect for this application
[03:05:50] <jmkasunich> wow, very low current
[03:06:20] <jmkasunich> max continuous about 1/4A, locked rotor current 1/2A
[03:13:09] <cradek> we're going to try 24v...
[03:13:21] <jmkasunich> was just looking at the schematic
[03:13:40] <jmkasunich> what caps do you have on the +12 (+24) supply?
[03:16:38] <cradek> very small
[03:16:49] <cradek> it's a switching PC supply
[03:17:16] <jmkasunich> I mean the ones right on the board with the L298
[03:17:26] <jmkasunich> 0.1uF, or electrolytics, or one of each?
[03:17:55] <cradek> looks like both
[03:18:01] <jmkasunich> good ;-)
[03:18:08] <cradek> small electrolytics and some ceramic discs
[03:18:16] <cradek> I think the schematic is on that web page
[03:18:23] <jmkasunich> I dunno what the voltage rating of the L298 is, but switching an inductive load makes spikes
[03:18:28] <jmkasunich> it is, I looked at it
[03:18:38] <jmkasunich> it shows two caps, but no values
[03:18:58] <cradek> there are those "fast" snubber diodes
[03:19:21] <cradek> the 5v regulato doesn't like 24v on its input side
[03:19:24] <cradek> so we're back to 12
[03:19:43] <jmkasunich> which do a fine job of dumping the transients into the supply rail - you're fine as long as the supply rail has enough C to absorb them
[03:19:49] <jmkasunich> got a bit warm did it?
[03:19:57] <cradek> yeah we didn't run it long...
[03:21:16] <cradek> well this is surprisingly successful
[03:21:35] <jmkasunich> I'm not surprised
[03:21:39] <cradek> once he got hal right, it was smooth sailing
[03:23:59] <jmkasunich> I wish I lived close enough to other emc folks to just drive over and spend an evening messing with stuff like that
[03:24:23] <cradek> I wish I lived close to cleveland so something would be interesting around me
[03:25:04] <jmkasunich> what is there in Lincoln?
[03:25:29] <cradek> as far as techie stuff, not too much - we have the surplus center
[03:25:35] <cradek> which is kind of cool I guess
[03:25:51] <jmkasunich> we have different kind of surplus
[03:25:58] <jmkasunich> much heavier
[03:26:07] <cradek> yeah a lot of that in your area (I explored there recently)
[03:26:09] <jmkasunich> www.hgrindustrialsurplus.com
[03:26:18] <cradek> yep, I sure went there
[03:26:21] <jmkasunich> you were in cleveland?
[03:26:30] <cradek> yes, last april I think it was
[03:26:42] <jmkasunich> dang, should have said hi while you were here
[03:26:55] <cradek> I don't think I knew you then...
[03:26:59] <jmkasunich> ah
[03:27:41] <cradek> otherwise I sure would have
[03:28:24] <cradek> have you been to the early television museum?
[03:28:28] <jmkasunich> no
[03:28:29] <cradek> I'm sure I've asked you that before
[03:28:44] <jmkasunich> I recall you talking about it a few weeks ago
[03:28:51] <jmkasunich> its near here?
[03:28:54] <cradek> yeah I try to tell everyone it's cool
[03:28:58] <cradek> columbus maybe?
[03:29:23] <jmkasunich> columbus is probalby 3 hours
[03:29:31] <cradek> ah
[03:29:37] <jmkasunich> dammit I can't spell probably
[03:29:43] <cradek> 3 hours is a short drive for me
[03:29:50] <jmkasunich> probalby can't spell?
[03:29:51] <cradek> takes 8 to get anywhere from here
[03:30:02] <jmkasunich> ouch
[03:30:22] <cradek> actually it will only be 6 to fest - I'm thrilled about that
[03:31:06] <jmkasunich> about 10 for me
[03:31:13] <cradek> ouch
[03:31:25] <cradek> that's getting too long for driving all at once...
[03:31:33] <jmkasunich> or is it 8?
[03:31:41] <jmkasunich> I'm getting mixed up with other trips
[03:32:07] <jmkasunich> my wife's parents live on the eastern shore of maryland, thats about 9-10 depending on traffic
[03:32:16] <jmkasunich> I think the CNC fest is 530 miles
[03:32:26] <jmkasunich> 8-9 depending on traffix
[03:33:01] <jmkasunich> traffic that is (and how heavy my foot is)
[03:33:23] <cradek> most of my drive is through IA which has a 65 speed limit - makes it even longer
[03:33:56] <jmkasunich> part of mine is through the south side of chicago - one massive road construction project
[03:34:02] <cradek> but I'm not complaining - it's rare to have any gathering of technical folks that I can drive to
[03:34:12] <cradek> oh yeah, I80 around chicago is hell
[03:34:14] <jmkasunich> both times I went thru there I got off course, one time by about10 miles
[03:34:22] <cradek> I try to go through in the middle of the night
[03:34:48] <jmkasunich> I don't like to drive long trips at night
[03:35:08] <jmkasunich> afraid I'll fall asleep (or just start bleeming)
[03:35:22] <cradek> I guess I never bleem - don't know what it is
[03:35:42] <jmkasunich> when you kinda get a blank look on your face
[03:35:46] <cradek> ah
[03:35:56] <cradek> I get goofy and start singing and crap
[03:35:57] <jmkasunich> sleeping with your eyes open, or very bored
[03:36:18] <cradek> it's pretty cool, the etch FEs and stops when it hits the edge
[03:36:21] <cradek> not used to that
[03:36:27] <jmkasunich> nice
[03:41:52] <jmkasunich> now I know why jepler added the "count" pin
[03:42:32] <jmkasunich> that approach uses 3 parport pins per motor though, using the up and down would only use 2
[03:43:50] <cradek> wish we could get 3 axes on a port
[03:44:11] <jmkasunich> you can if you drive the H-bridge differently
[03:44:54] <cradek> but feedback
[03:44:59] <jmkasunich> oops
[03:45:03] <jmkasunich> forgot about that
[03:45:10] <jmkasunich> lets see
[03:45:17] <jmkasunich> the 8 bit port can be in or out
[03:45:33] <jmkasunich> there are 5 dedicated ins and 4 dedicated outs
[03:45:45] <jmkasunich> yeah, either way it doesn't fit
[03:47:15] <jmkasunich> well its only 10:45, but I'm tired....
[03:47:48] <cradek> will you be around this weekend?
[03:48:00] <jmkasunich> somewhat
[03:48:11] <jmkasunich> I have a machining job to do by Friday
[03:48:11] <cradek> ok, see you then
[03:50:07] <cradek> I want us to work on threading sometime... I need your help with the hal part
[03:50:36] <jmkasunich> we can do that - not sure exactly when tho
[03:51:07] <cradek> ok, sometime
[03:51:16] <cradek> there's no hurry but I'd like to have something before fest
[03:52:00] <cradek> I'm kind of afraid I won't be able to work on it without some hardware, but maybe I can fake something up in hal (with your help)
[03:52:33] <jmkasunich> we can definitely fake something up
[03:52:42] <cradek> I wish someone could loan me the cnc parts for my sherline lathe, but I'm sure nobody has that sitting around
[03:52:56] <jmkasunich> jepler's little motors don't have an index pulse do they?
[03:52:58] <cradek> their controller is really expensive iirc
[03:53:03] <cradek> no, just quadrature
[03:53:24] <jmkasunich> you already have a sherline lathe?
[03:53:31] <cradek> yes
[03:53:32] <jmkasunich> so all you need is steppers and drivers?
[03:53:47] <cradek> yes and some kind of encoder for the spindle I guess
[03:54:00] <cradek> well the motor mounting stuff too
[03:54:05] <jmkasunich> I have an assorment of surplus encoders, I could probably come up with something
[03:54:21] <jmkasunich> the motors and mounts are the tough part
[03:54:29] <cradek> yeah
[03:54:41] <jmkasunich> Xylotex has a three axis stepper driver that works nice for NEMA23 motors, about $130 IIRC
[03:54:50] <jmkasunich> (I bought mine 2+ years ago)
[03:55:07] <cradek> I could even make the drivers for the cost of parts
[03:55:21] <cradek> man sherline's website is bad
[03:56:52] <jmkasunich> you have a CNC mill already right>?
[03:56:57] <cradek> (trying to find a price for the motors and mountings)
[03:57:01] <cradek> yes a small one
[03:57:09] <jmkasunich> how slow can the spindle turn?
[03:58:01] <jmkasunich> you have a pic or your mill somewhere on your website don't you?
[03:58:01] <cradek> pretty darn slow, it's a closed loop control
[03:58:07] <cradek> yes
[03:58:32] <cradek> http://timeguy.com/cradek-files/cnc/spindle-mount.jpg
[03:59:03] <jmkasunich> think you could mount an encoder on the spindle?
[03:59:24] <jmkasunich> thats the head of the drawbar on top isn't it?
[03:59:27] <cradek> http://timeguy.com/cradek-files/cnc/milling-setup.jpg
[03:59:30] <cradek> yes
[03:59:48] <cradek> see the threads where the nut used to hold the tool in?
[03:59:55] <jmkasunich> a mill is just a lathe standing on its ear
[03:59:58] <cradek> at the bottom above the new style of toolholder
[04:00:10] <cradek> that's sure true
[04:00:26] <cradek> the sherline 3-jaw actually threads onto those threads
[04:00:33] <jmkasunich> nice
[04:00:47] <cradek> you have a good idea here
[04:01:41] <jmkasunich> my dad was a machinist for 40 years, but he never had a lathe at home (something he regrets now) - but he has turned small parts in a drill press several times
[04:01:47] <cradek> I am not familiar with encoders - how much height do they take?
[04:01:58] <jmkasunich> how big is a box?
[04:02:20] <cradek> well assuming you know your junkbox
[04:02:23] <jmkasunich> depends on the encoder, some are 4" dia x 2" long, some are 1" dia x 1/2" long
[04:02:52] <cradek> so they aren't like a pancake
[04:03:29] <cradek> I could spare that height down at the bottom, but then I couldn't thread on that chuck
[04:03:43] <cradek> would be ok for experimenting, but not too useful after it works
[04:04:24] <jmkasunich> since you need to keep the drawbar clear, the best bet would be a toothed belt
[04:04:56] <jmkasunich> I'm looking at the pic of the motor and mount
[04:05:09] <jmkasunich> that belt isn't toothed is it?
[04:05:14] <cradek> no
[04:05:17] <cradek> just a V
[04:05:36] <jmkasunich> looks like a couple steps for different ratios?
[04:05:44] <cradek> I have a different (huge) back pulley now for high speed
[04:05:58] <cradek> the slow setting is about 1:1
[04:06:16] <jmkasunich> threading would probably be done at a few hundred RPM
[04:06:21] <cradek> fast is about 3:1
[04:06:36] <cradek> I'm not sure it has any power at that speed, but it might be enough
[04:06:59] <jmkasunich> the idea is that you reduce speed with the belt, not with the drive
[04:07:12] <jmkasunich> can you change the ratio from 3:1 to 1:3?
[04:07:26] <cradek> not without entirely new pulleys
[04:07:34] <jmkasunich> ok
[04:07:52] <cradek> the 1:1 might be ok
[04:07:55] <jmkasunich> duh, I was thinking swap spindle and motor pulleys, but they mount differently
[04:08:05] <jmkasunich> for testing, you'd be cutting air first
[04:08:06] <cradek> yeah different sizes
[04:08:11] <jmkasunich> then probably something soft
[04:08:26] <jmkasunich> wax, plastic, something like that
[04:08:52] <jmkasunich> that drawbar looks like an ordinary bolt head...
[04:09:05] <cradek> it is, with the back machined flat and concentric
[04:09:22] <cradek> actually the whole bolt is cleaned up so it's concentric
[04:09:23] <jmkasunich> what size bolt?
[04:09:32] <cradek> not sure
[04:09:40] <jmkasunich> bigger than 1/4" ?
[04:10:03] <jmkasunich> * jmkasunich has no concept of scale from the pic
[04:10:30] <cradek> the bolts holding the motor on are 3/8 I think I think
[04:10:34] <cradek> I think
[04:10:36] <jmkasunich> waitaminnit - if you're using the lathe chuck, you don't even need the drawbar do you?
[04:10:36] <cradek> I think
[04:11:13] <cradek> nope, I could take it out
[04:11:57] <jmkasunich> I found a couple encoders here that are about 1.5" dia, 1.5" long, with a 1/4" stub shaft about 3/8 long, and ball bearings
[04:12:00] <cradek> I think that front pulley is 2" dia
[04:12:43] <jmkasunich> if you could make a dummy drawbar that locks in somehow (threads into an empty toolholder?) and has a 1/4" hole at the top end
[04:12:56] <jmkasunich> you could mount the encoder by its shaft (its very light)
[04:13:08] <jmkasunich> use a little arm to keep it from spinning
[04:13:20] <cradek> there is not clearance above the spindle
[04:13:32] <jmkasunich> ?
[04:13:35] <cradek> the motor is actually somewhat over the drawbar - have to remove the motor to get the drawbar out
[04:13:56] <jmkasunich> oh, the picture is deceptive, it looks like the bar could come straight out
[04:13:57] <jmkasunich> damn
[04:14:17] <cradek> yeah.
[04:14:40] <cradek> it could mount to the side with another belt, but the "no teeth" problem is still there.
[04:14:55] <jmkasunich> how is the pulley attached to the spindle?
[04:15:46] <cradek> a setscrew
[04:16:29] <cradek> it's a tight friction fit plus one big setscrew
[04:16:50] <jmkasunich> looks like the spindle OD below the pulley is about an inch or so
[04:17:26] <cradek> yes something like that
[04:18:13] <cradek> I'm about to be kicked out of jeff's house
[04:18:39] <jmkasunich> $12 for an aluminum 60 tooth timing belt pulley, 1.73 OD, .531 overall thickness
[04:18:56] <jmkasunich> it has a 1/4 bore, but that could be opened way up
[04:19:06] <jmkasunich> and maybe mounted on the bottom of the existing pulley
[04:19:29] <jmkasunich> that distance from the bottom of the existing pulley to the casting looks like 1/4" or so
[04:19:44] <cradek> yes
[04:19:58] <jmkasunich> the actual pulley part is .276 thick
[04:20:00] <cradek> the spindle gets a bit wider there, but you're right I could mount to the other pulley
[04:20:23] <jmkasunich> and you could probably machine off the flanges to make it thinner (the matching belt is only 1/8 wide)
[04:20:24] <cradek> it could go on the bottom
[04:20:45] <jmkasunich> I'm looking at mcmaster-carr P/N 1375K53, if you want to look at it when you get home
[04:20:47] <cradek> if I could put those big threads in it, it would just thread on
[04:20:51] <cradek> ok
[04:22:05] <jmkasunich> these encoders (I have two) have five leads - I assume red and black are power, I'm hoping the other three are A, B, and index
[04:22:16] <jmkasunich> I'll try to make time to test them, if they work I'll send you one
[04:22:53] <cradek> if we can rig this up, I'll bring it to fest for us to work on
[04:23:16] <cradek> I better go
[04:23:20] <jmkasunich> we can also investigate rigid tapping...
[04:23:23] <cradek> I'll be around tomorrow
[04:23:25] <jmkasunich> ok, time for sleep here too
[04:23:27] <jmkasunich> goodnight
[04:23:29] <cradek> true
[04:23:34] <cradek> if we're tapping wax or something :-)
[04:23:44] <cradek> well there's no reverse on mine
[04:23:53] <cradek> ok, goodnight
[04:23:53] <jmkasunich> the sherline drive can't reverse?
[04:23:55] <cradek> thanks for all your help
[04:23:59] <cradek> no
[04:24:04] <jmkasunich> you're welcome
[04:24:07] <cradek> well not as-is
[04:24:09] <jmkasunich> darn
[04:24:14] <cradek> simple matter of hacking I guess
[04:24:22] <jmkasunich> nefs
[04:24:27] <cradek> ?
[04:24:38] <jmkasunich> nuttin's ever fsckin' simple
[04:24:42] <cradek> heh
[04:24:44] <cradek> yep
[04:24:54] <cradek> ok goodnight for real now, we'll work on it tomorrow
[04:25:00] <jmkasunich> night
[05:15:20] <SWP_Away> SWP_Away is now known as SWPadnos
[05:49:48] <SWPadnos> SWPadnos is now known as SWP_Away
[17:19:51] <SWP_Away> SWP_Away is now known as SWPadnos
[18:32:28] <alex_joni> hello
[18:33:54] <cradek> hi alex
[18:33:59] <cradek> are you home now?
[18:34:05] <alex_joni> yeah, finally
[18:34:11] <alex_joni> trying to get back in shape
[18:34:38] <alex_joni> darn, anon CVS still not working.. I wanted to make a new testing package :(
[18:34:41] <SWPadnos> well, drink lots of coffee, eat donuts, and read email. that should help ;)
[18:34:48] <alex_joni> guess I'll make one with devel checkout
[18:35:35] <SWPadnos> I was just looking into making a cvs repository copy on dreamhost, but there's no anonymous access (as jepler had pointed out)
[19:05:28] <alex_joni> jepler: you there?
[19:15:21] <alex_joni> jepler: n/m, I'll bbl and we'll talk then ;)
[19:15:29] <alex_joni> alex_joni is now known as alex_joni_away
[19:38:39] <jmkasunich> * jmkasunich thaws his fingers
[19:39:19] <rayh> Cold there?
[19:39:28] <jmkasunich> 28F
[19:39:39] <jmkasunich> cold when you're running a mill tho
[19:39:48] <jmkasunich> cast iron doesn't heat up very fast
[19:39:54] <rayh> Wow. Colder than the ~40 here.
[19:40:05] <rayh> Right.
[19:40:07] <jmkasunich> that's gotta be rare!
[19:40:29] <rayh> You guys are normally warmer that we are.
[19:40:37] <jmkasunich> right, sometimes by a lot
[19:40:53] <jmkasunich> I was expecting you to come back and say "28 is balmy, it's -15 here" ;-)
[19:41:09] <rayh> I've got a hal file sorter looking for AXIS_
[19:41:26] <jmkasunich> cool
[19:41:38] <jmkasunich> couldn't it just look for '['?
[19:41:45] <rayh> With a stepper setup I'm seeing stepgen max accel
[19:42:05] <rayh> but not the parallel max accel
[19:42:19] <rayh> course they go to different places.
[19:42:20] <jmkasunich> that one isn't used by hal, only by emc
[19:42:48] <rayh> Right it just seems that not being able to see the emc one means a shot in the dark for the one we do have control over.
[19:43:04] <jmkasunich> you can change hal params on the fly, but can you change emc params on the fly?
[19:43:28] <rayh> Back in the day when we had acces to globals we could.
[19:43:33] <rayh> at least some of em.
[19:43:56] <jmkasunich> what was the method? sending nml msgs?
[19:44:04] <rayh> There are still global PID they just don't do anything.
[19:44:24] <jmkasunich> right - the PIDs should go away as part of a cleanup one of these days
[19:44:38] <rayh> No hurry.
[19:44:44] <jmkasunich> but things like [TRAJ]MAX_ACCEL and [AXIS]MAX_ACCEL?
[19:45:08] <rayh> I'm not sure that we could ever change accel or max vel on the fly.
[19:46:16] <jmkasunich> it would be interesting to have a table of all the ini file items, with info about: where used, change on the fly vs change at startup only, and probably a few other bits of info
[19:46:18] <rayh> Quick fix is to call this widget EMC-HAL axis Calibration
[19:46:32] <rayh> or just hal axis calibration
[19:46:57] <jmkasunich> it would sure be nice if it could tweak all the modifiable items, not just the ones that go thru hal
[19:47:36] <rayh> Yes it would but I don't know any more how to handle the emc ones.
[19:48:02] <jmkasunich> for the most part they didn't change from emc1 I think
[19:48:09] <jmkasunich> some of course no longer work, like PID
[19:48:10] <rayh> I do have the old tweak code but didn't think much of it worked.
[19:48:34] <jmkasunich> but the rest of iniaxis.cc and friends still work the same as they always did
[19:49:37] <rayh> all of the ones I used went through emcsh. I'll look there for a bit and see what I find.
[19:49:48] <jmkasunich> well, fingers are getting warm, time to go outside again
[19:55:27] <rayh> see you
[19:57:11] <cradek> hi all
[19:57:30] <rayh> Hi Chris
[19:57:45] <rayh> jmk just went back out to the shop to make swarf
[19:58:51] <cradek> yeah he said he had some kind of task to finish
[19:59:16] <cradek> last might we were talking about fitting a spindle encoder to my mill for work on threading (aka rigid tapping)
[19:59:27] <rayh> Okay.
[20:00:06] <cradek> seems like the mechanical problems are always the hardest part
[20:00:18] <rayh> What kind of mill is this?
[20:00:20] <cradek> (like no good place to mount it)
[20:00:32] <cradek> a mishmash tabletop thing
[20:00:45] <cradek> http://timeguy.com/cradek/cnc
[20:01:21] <rayh> looking
[20:01:23] <cradek> the pictures are a bit out of date
[20:02:32] <staggerlytom> http://www.maxnc.com/
[20:02:51] <cradek> staggerlytom: yes, but it has little in common with their setup anymore
[20:03:22] <staggerlytom> dunno, tiny pictures
[20:03:37] <rayh> You have to keep the top section of the spindle drive to unload tools?
[20:03:54] <cradek> yes, it has a drawbar
[20:04:16] <cradek> seems like it will have to be off to the side somehow
[20:04:52] <rayh> Okay. You could try the joe martin sherline approach and paint stripes on the wheel below the pulley.
[20:05:20] <rayh> vertical stripes and read them with two photo transistors.
[20:05:26] <cradek> I'd rather it be able to work with the lights on...
[20:05:42] <cradek> also don't I need better resolution than that for threading?
[20:05:50] <rayh> How did you get that driven pulley in the stack
[20:06:22] <cradek> the front pulley is made in one piece
[20:06:30] <rayh> joe had 4 quadrant pie shaped and got a pretty good indication of speed.
[20:06:39] <rayh> You made it?
[20:06:58] <cradek> yes, I made the pulleys (new ones since these photos)
[20:07:16] <cradek> I made a large one for the motor to get the speed up for milling pcbs
[20:07:21] <rayh> couldn't you make two of them there and drive an encoder off the side.
[20:07:59] <cradek> the dead space on the bottom of the pulley is for a big set screw, but yes there could be another groove there
[20:08:13] <cradek> jmk thought they should be toothed pulleys though
[20:08:31] <rayh> Well between the spindle and encoder yes.
[20:08:45] <rayh> ah and you just used a v pulley.
[20:08:50] <cradek> yes
[20:09:08] <jmkasunich> I wonder exactly how many pulses per rev are needed for threading
[20:09:13] <cradek> otherwise I couldn't make the pulley
[20:09:15] <jmkasunich> the stripes idea is interesting
[20:09:31] <rayh> A few guys are using the one pulse per rev
[20:09:51] <jmkasunich> and I recall you being adamant that you can't make good threads that way ;-)
[20:09:51] <rayh> That seems like horsesxxt to me
[20:10:01] <rayh> Yes I was.
[20:10:01] <cradek> yeah sounds useless
[20:10:24] <rayh> I liked the 360 ppr we used at mazak
[20:10:28] <cradek> I would think at least 100? ppr
[20:10:29] <jmkasunich> if the spindle speed is absolutely constant (even as load changes) it could work
[20:10:42] <cradek> jmkasunich: it never is, at low speed
[20:10:54] <rayh> Right. It would have to be a large mass spindle.
[20:11:11] <SWPadnos> a single index per rev would be fine for single-pass threads (which are rare, AFAIK)
[20:11:11] <rayh> huge flywheel.
[20:11:27] <jmkasunich> 10HP induction motor at 1800 RPM, geared down (with back gears) to 100 RPM would do it
[20:12:02] <rayh> Yes it would but would we want to advertize that ability with emc?
[20:12:04] <cradek> my worry is this: this project will be hard enough - I don't want to fight with inadequate hardware
[20:12:19] <jmkasunich> SWP: I disagree - the problem isn't multi-pass indexing (single pulse per rev takes care of that) its drunken threads
[20:12:35] <jmkasunich> cradek: right, the single ppr thing is a distraction
[20:12:44] <rayh> Right. I remember arguing that the spindle drive needed to be a full servo.
[20:13:12] <cradek> wish I had real data about the sherline closed-loop speed control
[20:13:15] <jmkasunich> cradek: you don't have a dividing head or rotary table do you?
[20:13:19] <SWPadnos> the spindle drive shouldn't need to be servo
[20:13:20] <cradek> it may have something suitable built-in
[20:13:31] <cradek> jmkasunich: yes, I have a cnc rotary axis, but no driver for it currently
[20:13:32] <jmkasunich> but its vee-belted to the spindle
[20:13:43] <cradek> yes, would need to change that, but that's easy
[20:14:03] <jmkasunich> if you have rotary, you could machine teeth into the OD of your existing pulley
[20:14:13] <jmkasunich> either for a belt, or to be sensed directly
[20:14:16] <rayh> SWPadnos, That is exactly what a lot of folk said. They got pretty quiet after the guy from Giddings and Lewis said yes it would have to be.
[20:14:24] <cradek> directly how?
[20:14:31] <SWPadnos> heh - I may have to be quiet, then ;)
[20:14:36] <jmkasunich> ray, swp: let's please not go there now ;-)
[20:15:04] <rayh> Nah. It really depends upon how tightly we can electronically couple the axis to the spindle.
[20:15:22] <SWPadnos> jmkasunich, it's necessary to discuss whether emc threading will require a servo'ed spindle
[20:15:23] <cradek> that's the whole point of this, afaic
[20:15:41] <SWPadnos> if it will, then it's a lot different in software
[20:15:49] <cradek> if it does, that rules out the entire hobby class of machine
[20:15:50] <jmkasunich> SWP: threading as I envision it does not (but does require a decent ppr encoder)
[20:15:55] <rayh> I'm in favor of starting with a wild or nearly so spindle,
[20:15:58] <SWPadnos> I agree
[20:16:00] <cradek> in that case, I'm not interested in working on it
[20:16:09] <rayh> and see that we can get the cutting axis to match it.
[20:16:20] <jmkasunich> I have an induction motor on my spindle, so I'm in the same boat
[20:16:36] <cradek> I still don't think this is going to be too difficult, aside from hardware issues.
[20:16:39] <SWPadnos> I'd think that the encoder has to be able to provide a reasonably accurate spindle speed indication every servo cycle
[20:16:44] <jmkasunich> start with at decent resolution sensor, get that working, then see if lower resolution sensors can be made to work
[20:17:00] <rayh> Yep. I'm probably the only one with real servo spindles laying around.
[20:17:04] <jmkasunich> SWP: not speed, position
[20:17:19] <SWPadnos> actually, not at the servo rate, but at the expected spindle response rate (to applied / removed loads)
[20:17:27] <jmkasunich> yes
[20:17:30] <cradek> jmkasunich: I could machine those teeth on my manual mill if they're not an odd profile
[20:17:49] <rayh> cradek, There are belts with half round teeth.
[20:17:51] <jmkasunich> your pulley isn't steel is it?
[20:17:56] <cradek> no, Al
[20:17:59] <jmkasunich> bummer
[20:18:08] <jmkasunich> steel can be sensed with magnetic sensors
[20:18:11] <cradek> hall effect?
[20:18:12] <cradek> yeah
[20:18:15] <jmkasunich> (steel teeth)
[20:18:16] <cradek> no such luck
[20:18:30] <jmkasunich> and the tooth geometry isn't finicky
[20:18:34] <cradek> could go buy a $100 crankshaft position sensor
[20:18:41] <jmkasunich> belt tooth geometry is simpler
[20:18:42] <cradek> ... if I had $100
[20:18:44] <SWPadnos> or a $29 encoder ;)
[20:19:07] <jmkasunich> I might even have some magnetic sensors here too
[20:19:13] <jmkasunich> (in a box somewhere)
[20:19:27] <cradek> seems like that won't help though
[20:19:31] <staggerlytom> insert ferrous dots into alum pulley and sense speed and rpms( not accurate for posn tho)
[20:19:37] <cradek> so say I can rig up an encoder - what counts it?
[20:20:00] <cradek> can I hook it right up to the parport?
[20:20:03] <jmkasunich> if the count freq is less than about 20KHz, the HAL encoder counter block could do it
[20:20:14] <jmkasunich> higher than that and you'd need a board with an encoder input
[20:20:17] <cradek> I think I have several parport bits left
[20:20:44] <jmkasunich> thats one thing that concerns me about the encoders I have here
[20:20:48] <jmkasunich> I think they are 1000 ppr
[20:20:56] <SWPadnos> I think I can make a fairly inexpensive encoder counter that operates serially or something
[20:21:05] <jmkasunich> I dunno if that is 1000 counts, or 1000 cycles (which is 4000 counts)
[20:21:14] <cradek> so that means I have to be under 20 rps
[20:21:19] <cradek> way under?
[20:21:23] <jmkasunich> either way, software encoder counting tops out pretty quick
[20:21:32] <cradek> sounds like
[20:21:44] <jmkasunich> but something like 360 counts per rev would be nicer
[20:22:21] <jmkasunich> if I have magnetic sensors, could you machine a steel ring that presses onto the pulley, then machine teeth in it?
[20:22:55] <jmkasunich> say 1/4" wide, 1/4" thick, machine teeth 1/16" deep and wide
[20:22:57] <cradek> what radius variation is necessary to make it work?
[20:23:17] <cradek> don't we need an index pulse still?
[20:23:29] <jmkasunich> if the OD is 3", circumfirence is about 9" and you have 9x8 = 72 slots
[20:23:32] <SWPadnos> it's probably best to have an index
[20:23:49] <jmkasunich> yes, that can be as simple as a screw head that a third sensor sees once per rev
[20:24:02] <jmkasunich> 72 slots = 288 counts per rev
[20:24:16] <cradek> fyi the driven pulley is 1.5 OD
[20:24:48] <jmkasunich> so the OD of the ring wouldn't be more than about 2"
[20:25:39] <jmkasunich> until I find the sensors and see how big of a tooth they need its moot I guess
[20:25:51] <jmkasunich> if they need a tooth that is 1/4" wide and deep, forget it
[20:25:58] <cradek> yeah
[20:26:18] <cradek> about how much would it be for me to just buy an appropriate encoder?
[20:26:27] <SWPadnos> www.usdigital.com
[20:26:27] <jmkasunich> the problem is still mounting it
[20:26:38] <cradek> right
[20:26:47] <SWPadnos> there are a number of encoders on ebay as well
[20:26:49] <cradek> the thing is so small there's not much extra room anywhere
[20:26:51] <jmkasunich> most of the usdigital's expect a 1/4" stub shaft (or at least, some small diameter shaft)
[20:27:03] <SWPadnos> or they have a shaft
[20:27:07] <jmkasunich> right
[20:27:23] <jmkasunich> I have some of those here - 1/4" shaft and ball-bearings
[20:27:30] <SWPadnos> what's the hub diameter on the spindle pulley(s)?
[20:27:40] <jmkasunich> but you're right back to how to mount and drive it
[20:28:00] <jmkasunich> the spindle pulley fits over the entire spindle, probably 3/4" or more
[20:28:06] <SWPadnos> use the spindle like a lathe, and bore a hole into the hub or axle, then put a pin in it
[20:28:12] <jmkasunich> and the drawbar sticks out the back of the spindle
[20:28:24] <SWPadnos> hmmm - drawbar - damn
[20:28:29] <cradek> right
[20:28:38] <cradek> ID of spindle pulley is .625
[20:28:45] <SWPadnos> the other option is to mount the encoder on the motor, and hope for the best
[20:28:47] <jmkasunich> I actually thought about replacing the drawbar with a stubshaft
[20:28:56] <jmkasunich> but there is also a clearance issue above the spindle
[20:29:10] <jmkasunich> encoder on motor will never work
[20:29:18] <jmkasunich> unless you change the main drive to a toothbelt
[20:29:28] <SWPadnos> that would be best
[20:29:42] <SWPadnos> but under light loads, it may be good enough
[20:29:59] <jmkasunich> even under light loads, you don't get exactly 1:1 with regular belts
[20:30:04] <jmkasunich> there's always creep
[20:30:05] <SWPadnos> of course, you'd need different configs depending on which ratio you're on
[20:30:08] <SWPadnos> yep
[20:30:09] <jmkasunich> it might be 1.001 to 1
[20:30:36] <jmkasunich> hmm
[20:30:49] <jmkasunich> this gets a little esoteric, but...
[20:31:05] <jmkasunich> speed sensor on motor, index sensor (1ppr) on spindle
[20:31:10] <SWPadnos> was ray suggesting a separate encoder shaft, belt driven from the spindle?
[20:31:15] <jmkasunich> yes
[20:31:16] <SWPadnos> interesting
[20:31:21] <jmkasunich> thats what we did for the mazak
[20:31:24] <jmkasunich> 1:1 toothbelts
[20:31:34] <jmkasunich> the belt can be tiny cause there's no load to speak of
[20:31:39] <SWPadnos> right
[20:31:52] <jmkasunich> I think the mazak used 1/4" wide belt, but 1/8" would be plenty
[20:31:59] <cradek> that still seems like the best general idea
[20:32:16] <cradek> ... if I can manage to mill the existing front pulley
[20:32:52] <jmkasunich> or take a commercial toothbelt pully, bore most of it out leaving only a ring with teeth, and press it onto the main pully
[20:32:55] <SWPadnos> the front pulley looks like a flat cylinder to me (with an inside-out toothed belt on it)
[20:33:01] <jmkasunich> (or fasten it some other way)
[20:33:01] <cradek> there would be a tooth over the setscrew, but that wouldn't matter
[20:33:28] <cradek> SWPadnos: it is a cylinder, but the belt is meant to be that way
[20:33:37] <cradek> SWPadnos: the belt is a V on the back
[20:33:42] <SWPadnos> right
[20:33:54] <SWPadnos> I noticed the V-groove pulley on the motor
[20:33:55] <jmkasunich> I actually made a toothbelt pulley once, but it was for a bigger belt (0.200" pitch IIRC)
[20:34:15] <jmkasunich> I still have the cutter with the tooth profile
[20:34:26] <SWPadnos> the trouble with belt-driving an encoder is the side load
[20:34:30] <jmkasunich> but I think you want something smaller
[20:34:54] <jmkasunich> SWP: the ones I have have ball bearings, and toothbelts don't need much tension at all
[20:34:57] <staggerlytom> bearing above and below belt pulley on encoder... no side load
[20:35:16] <staggerlytom> (to encoder)
[20:35:17] <SWPadnos> I was thinking of what vibration would do to a not-very-tight belt
[20:35:35] <cradek> SWPadnos: remember this will be very low speed
[20:35:37] <jmkasunich> this isn't a very demanding belt application
[20:35:45] <jmkasunich> large diameter and short span
[20:35:52] <cradek> SWPadnos: I often run 20krpm but would disconnect the encoder (right?)
[20:35:58] <cradek> that's why a belt is going to be best
[20:36:11] <jmkasunich> it must be 1:1, so both pulleys will be about 1.5" OD, center distance might only be 2"
[20:36:15] <rayh> Those automationdirect encoders will handle some side load.
[20:36:24] <rayh> at least some of them.
[20:36:45] <rayh> or a 2 pulley spindle with a hollow shaft encoder.
[20:36:49] <cradek> jmkasunich: why 1:1?
[20:36:50] <SWPadnos> it doesn't need to be 1:1 (except for index)
[20:36:54] <jmkasunich> indexing
[20:36:56] <cradek> oh duh
[20:37:05] <SWPadnos> even that can be done with a trivial HAL module
[20:37:10] <SWPadnos> (swallow counter)
[20:37:20] <staggerlytom> do these encoders have the index pulse?
[20:37:31] <rayh> notice how easily you guys say trivial when thinking of hal
[20:37:32] <SWPadnos> most are available with index
[20:37:33] <jmkasunich> mine? I think so, but haven't tested them
[20:37:40] <jmkasunich> automation direct, I dunno
[20:37:43] <SWPadnos> but you can't add it later ;)
[20:38:07] <SWPadnos> rayh, the module I'm thinking of would be a very simple module. using it or explaining its use may not be ;)
[20:38:10] <jmkasunich> swp: how exactlly would you deal with indexing?
[20:38:47] <SWPadnos> have a component that has a "ratio" parameter, and only set the index output true every "ratio" index pulses
[20:38:57] <cradek> my parport pins in use are 2-9,1,14 which I think means I have >= 3 inputs free
[20:39:01] <jmkasunich> ray: one of the fundamental concepts of HAL is to divide the problem until the inidividual tasks are trivial, then write trivial code to do the individual tasks that make up a non-trivial whole
[20:39:12] <cradek> having another output for eventual spindle reverse would be good
[20:39:13] <SWPadnos> then put it together with complex config files ;)
[20:39:18] <rayh> and then check to see if the derrived index pulse matches the real every ratio times around.
[20:39:48] <staggerlytom> SWP: software gearing ( electronic earing ) yes
[20:39:52] <SWPadnos> the derived pulse would be output as a divided input pulse, so they would always match up
[20:39:54] <jmkasunich> SWP: I think I see - so you'd still require an N:1 ratio?
[20:39:55] <SWPadnos> yes
[20:40:04] <SWPadnos> not if the param is a float
[20:40:11] <SWPadnos> hmmm - yes ;)
[20:40:21] <staggerlytom> yes N:1 so get a fine encoder to get 'more float like'
[20:40:24] <rayh> No I'm thinking of really knowing where in the rotation of the real spindle we are.
[20:40:32] <cradek> a "rational" ratio
[20:40:44] <SWPadnos> yes, the drive ratio between spindle and encoder
[20:40:45] <jmkasunich> any gear ratio is rational
[20:40:56] <SWPadnos> all it does is change the "scale" - counts per rev
[20:41:21] <jmkasunich> as long as you don't power down or reset between passes you'd be OK
[20:41:21] <cradek> jmkasunich: nah, if my pulleys are 1" and pi", the ratio isn't rational
[20:41:32] <cradek> uh "ratio"
[20:41:38] <jmkasunich> if they got teeth they are rational
[20:41:38] <cradek> * cradek waves his hands
[20:41:43] <cradek> right, teeth
[20:41:43] <jmkasunich> can't machine pi teeth
[20:41:57] <cradek> sorry I forgot we were talking about teeth
[20:42:05] <jmkasunich> teeth are for eating pi
[20:42:10] <SWPadnos> the index ratio does need to be an integer, or you aren't basing the output on the input any more
[20:42:14] <staggerlytom> not float, big int ( think Forth), the encoder has pulses, is digital, not analog ( else you got leftover fractions )
[20:42:15] <SWPadnos> mmmmm - pie
[20:42:16] <cradek> now I want some pie
[20:42:37] <SWPadnos> I could go for some warm chocolate pecan pie
[20:42:44] <jmkasunich> hush
[20:42:48] <SWPadnos> sorry
[20:42:59] <staggerlytom> pie are snot square, pie are round, cornbread are square
[20:43:00] <rayh> with a scoop of 'niller ice cream
[20:43:06] <SWPadnos> that would do it
[20:43:16] <jmkasunich> dammit
[20:43:22] <jmkasunich> now I'm hungry
[20:43:39] <SWPadnos> heh. maybe I'll just eaqt that eclair, and see of my wife notices it's gone
[20:43:43] <SWPadnos> eat
[20:43:51] <jmkasunich> and I gotta go back out in the garage, and I forgot what I came down here to fetch
[20:44:07] <cradek> you'll remember when you get back out there
[20:44:18] <jmkasunich> I remembered - part drawingh
[20:44:43] <jmkasunich> * jmkasunich takes his box of t-nuts, studs, washers, nuts, clamps, and misc crap outside
[20:44:58] <cradek> bye
[20:45:10] <SWPadnos> heh - gotta know where to cut ;)
[20:47:00] <cradek> well crap, I still don't know what to do
[20:48:24] <rayh> Got room on the spindle top to add a plastic pulley?
[20:49:04] <cradek> looks like there is .125 of height available
[20:49:37] <rayh> I've not seen timing belts smaller than .25
[20:49:40] <cradek> and maybe 1.7 dia before something hits something else
[20:50:12] <rayh> The diameter isn't critical at all. Just have to match to the encoder pulley.
[20:50:43] <SWPadnos> I think sdp-si has 1/8 width belts
[20:50:50] <cradek> I don't think I can add .25 of height anywhere
[20:51:00] <SWPadnos> yep - they do
[20:52:11] <rayh> there you go.
[20:52:19] <cradek> looking...
[20:52:24] <rayh> mcmaster only has 1/4 and up.
[20:52:26] <staggerlytom> is the picture on http://timeguy.com/cradek/cnc at all valid?
[20:52:43] <cradek> staggerlytom: pretty close, front pulley is still the same, back pulley is much bigger now
[20:53:09] <staggerlytom> it looks like you can crak the motor plate up, openin all the vert room you want
[20:53:22] <staggerlytom> on those wing nut stand offs
[20:53:24] <cradek> yes but I can't raise the front pulley
[20:53:37] <cradek> the spindle is only so long and the drawbar tightens against it
[20:54:12] <rayh> How about the alum below the belt?
[20:54:22] <staggerlytom> yes, is the belt to pulley still very small?
[20:54:42] <cradek> rayh: I don't understand what you're asking
[20:55:17] <SWPadnos> there's another V-groove down below, right?
[20:55:22] <SWPadnos> on the motor pulley
[20:55:32] <cradek> both pulleys have two grooves
[20:55:41] <cradek> the bottom gives a 1:1 ratio, the top set about 3:1
[20:55:51] <SWPadnos> I don't see a groove on the spindle pulley
[20:56:09] <SWPadnos> well, one, but it's above the belt in the photo
[20:56:10] <cradek> there are two grooves, in that pic the belt is in the bottom one
[20:56:18] <cradek> the top one is small
[20:56:45] <cradek> in that space under the bottom groove, I could possibly mill teeth
[20:56:47] <SWPadnos> ok. maybe it's just behind the belt, and not deep enough for the sides to show with the belt in the groove
[20:57:06] <cradek> right, the belt fills the groove
[21:22:20] <staggerlytom> cradek: tried gimp to edit your foto.. ng
[21:22:47] <staggerlytom> it looks like theres room below where the belt is now, to ad another belt for encoder
[21:24:07] <jmkasunich> cradek: an alternative to milling teeth down there is to machine away some alum so you have a step
[21:24:23] <jmkasunich> then bore a stock pully until its a slip or press fit over the step
[21:24:31] <cradek> the problem with cutting that away is the set screw that you don't see in the photo
[21:24:35] <jmkasunich> oops
[21:24:39] <jmkasunich> never mind ;-)
[21:25:12] <cradek> I was thinking if I could mill the teeth, they would go right over that hole
[21:25:19] <jmkasunich> yep
[21:25:34] <jmkasunich> trick is the tooth profile
[21:25:39] <cradek> I bet
[21:26:34] <jmkasunich> I have a cutter I modified to cut tooth-belt teeth
[21:26:48] <jmkasunich> but I think its for either 0.2 or 0.25" pitch belts
[21:26:54] <jmkasunich> and I doubt it would fit your mill
[21:27:04] <jmkasunich> its a horizontal mill cutter
[21:27:24] <cradek> I can only do .25 dia tools
[21:27:31] <jmkasunich> 1" bore, 3" OD, gotta run it at about 150RPM or so
[21:27:40] <cradek> ha
[21:27:46] <jmkasunich> about 24 teeth
[21:28:04] <cradek> wow
[21:28:10] <jmkasunich> you'd be coming at it 90 degrees from that
[21:28:31] <jmkasunich> (cutter axis pointing at the centerline of the pulley)
[21:28:48] <cradek> yeah
[21:29:12] <cradek> I know sherline sells cnc lathes - do they have spindle encoders at all?
[21:29:26] <jmkasunich> don't think so
[21:30:03] <jmkasunich> darn
[21:30:17] <jmkasunich> the belts with curved teeth have a minimum width of 12mm
[21:30:32] <jmkasunich> curved teeth could be cut with a ball end mill I think
[21:30:54] <cradek> I could do that but .5" is way too thick
[21:31:14] <jmkasunich> the trapezoidal teeth come as narrow as 1/8"
[21:31:27] <jmkasunich> pitch is 0.080
[21:31:35] <jmkasunich> tiny little thangs
[21:31:38] <cradek> another problem - depending on the belt's DP my pulley's diameter may be incompatible
[21:31:53] <jmkasunich> that can be fixed, you have a lathe don't you?
[21:32:10] <jmkasunich> maximum diameter change is belt pitch / pi I think
[21:32:15] <cradek> I suppose
[21:32:47] <jmkasunich> .080 pitch means teeth are 0.040 wide
[21:32:49] <cradek> can't cut the whole cylinder, because of the groove, but I could make a step if there isn't a lot of change required
[21:33:00] <jmkasunich> right
[21:33:19] <jmkasunich> the step would even act as a flange on one side
[21:33:54] <jmkasunich> if the teeth are only 0.040 wide, that takes a mighty tiny endmill
[21:34:12] <jmkasunich> I'd be very temted to try to do it with a 0.040 thick slitting saw
[21:34:22] <cradek> yeah I have some 03125 but I'd hate to try to cut Al with them
[21:34:32] <jmkasunich> why?
[21:34:42] <cradek> uh, I'd just break them
[21:34:48] <jmkasunich> oh, you mean 0.03125 end mills
[21:34:50] <jmkasunich> yes
[21:34:52] <cradek> right
[21:35:00] <jmkasunich> I thought you meant 0.03125 slitting saws
[21:35:45] <cradek> are you done making your parts already?
[21:35:53] <jmkasunich> no, thawing fingers again
[21:35:59] <jmkasunich> ends are milled, sides are milled
[21:36:14] <jmkasunich> need to make a cleanup cut on the faces, then I'm done outside
[21:36:23] <jmkasunich> but still several more hours of inside work
[21:36:38] <jmkasunich> boring, and marking a scale on the (dang, wish I had CNC for that!!!)
[21:36:39] <cradek> sounds like you need some heat out there
[21:36:52] <jmkasunich> and then making plungers to fit in the bores
[21:36:55] <cradek> you don't have cnc?
[21:36:58] <jmkasunich> nope
[21:37:10] <jmkasunich> whats that they say about the shoemakers kids?
[21:37:21] <cradek> well come on over, I have cnc and 60 degree pointy tools
[21:37:40] <cradek> bring your encoders :-)
[21:37:42] <jmkasunich> if you were less than an hour away I'd take you up on that
[21:38:00] <jmkasunich> as it is, I can do it manually in an hour or two
[21:38:17] <jmkasunich> (I don't mill them, I scribe the lines and stamp the numbers)
[21:38:35] <cradek> I'd mill the numbers made with truetype-tracer - it would be fun
[21:38:44] <jmkasunich> I know it would be fun
[21:38:54] <jmkasunich> maybe I should mail them to you, and you could mail them back ;-)
[21:39:06] <jmkasunich> except I have to ship by thursday evening
[21:39:21] <cradek> yeah probably no good then...
[21:40:07] <jmkasunich> mcmaster has 0.032 wide slitting saws, 1" OD, 3/8" hole, for $4.60
[21:40:54] <cradek> seems like you could make a trapezoid with three very careful passes
[21:41:03] <jmkasunich> 1/16" thick 1-1/4dia 1/2 hole is $7.77
[21:41:21] <jmkasunich> it would probably deflect on the later passes
[21:41:40] <cradek> you'd want to cut the "middle" last
[21:41:58] <cradek> maybe the two outside passes would be enough
[21:42:16] <cradek> don't know how critical the shape is
[21:42:29] <jmkasunich> depending on how bad I wanted to do this, I'd get the 1/16" one, set up my dremel on the lathe, put the cutter in the chuck, and with the cutter spinnind I'd modify the 0.062 wide cutter to cut a 0.040 wide trapezoid
[21:42:32] <cradek> starting with a pre-made $10 pulley seems more tempting
[21:42:38] <jmkasunich> yes it does
[21:43:33] <jmkasunich> (the dremel trick is how I made the cutter when I did it before - started with a 3" diameter cutter about 3/16 or 1/4 wide
[21:43:46] <jmkasunich> took a long time to grind to shape
[21:44:22] <cradek> sounds like not much fun
[21:44:36] <jmkasunich> but I was motivated - I needed a 6" plus pulley for my mill's power feed, and a purchased one was either $100+ or unobtainium, I don't remember which
[21:45:07] <jmkasunich> the original pulley was for silent chain, but worn beyond usability - so I turned off the teeth and recut it for toothbelt
[21:45:26] <jmkasunich> bought the motor end pulley, that was only about 1.5" dia and $10-15
[21:45:35] <cradek> heh, cool
[21:45:45] <cradek> it's fun to fix stuff like that
[21:45:59] <jmkasunich> yep
[21:46:25] <cradek> I can't help but think we're missing some obvious easy way on my mill problem
[21:46:50] <cradek> wish I had an appropriate junkbox to dig through - usually that's what I do, but I'm woefully inequipped
[21:47:10] <jmkasunich> how about taking a stock pully and using the drawbar to hold it to the top of the spindle?
[21:47:14] <jmkasunich> remove when not threading
[21:47:50] <cradek> there's virtually no height available above the spindle
[21:48:04] <jmkasunich> where's that pic again?
[21:48:24] <cradek> I can't raise the motor any
[21:48:37] <cradek> I need to take a new one
[21:48:40] <cradek> just a minute
[21:49:16] <jmkasunich> another way to make a tooth profile cutter:
[21:49:32] <jmkasunich> turn the tooth profile on a piece of 1/4" drill rod
[21:49:55] <jmkasunich> so it would be about 0.15 on either side of the tooth, 0.250 center of tooth
[21:50:04] <SWPadnos> what's inside the housing?
[21:50:08] <jmkasunich> the cut flutes and harden
[21:50:20] <SWPadnos> presumably nothing that spins ;)
[21:50:21] <jmkasunich> then cut flutes and harden
[21:51:38] <jmkasunich> like this: http://www.metalworking.com/DropBox/_2001_retired_files/Worm06.jpg
[21:52:09] <jmkasunich> the cutter on the left has made 6-8 40 tooth wormgears from bronze and is still sharp
[21:52:28] <SWPadnos> damn
[21:52:32] <SWPadnos> that's cool
[21:52:55] <jmkasunich> that's 5/8 OD, much bigger and heavier than needed here
[21:53:12] <jmkasunich> check out the rest of the pics in that series - I'm kinda proud of that project
[21:54:14] <jmkasunich> pic 5 is another pic of the tooling
[21:54:22] <jmkasunich> you'd only need the middle one
[21:55:02] <jmkasunich> pic 8 is it in action
[21:55:15] <cradek> that's slick
[21:55:22] <cradek> http://timeguy.com/cradek-files/emc/spindle.jpg
[21:55:24] <SWPadnos> I'm just looking at #8
[21:55:50] <SWPadnos> I can't see if the gear is tilted (relative to the cutter plane)
[21:55:52] <cradek> this is what it looks like today
[21:56:01] <jmkasunich> SWP, it is
[21:56:16] <jmkasunich> pic 7 shows the tilt better
[21:56:39] <jmkasunich> cradek: and the motor plate comes out how far?
[21:56:45] <SWPadnos> Ah, OK. you let the gear spin with the worm cutter during a later pass
[21:56:45] <jmkasunich> to the spindle centerline? beyond?
[21:56:54] <jmkasunich> yes
[21:57:07] <jmkasunich> first pass is gashing, second pass is hobbing
[21:57:07] <cradek> slightly over the bolt head at this pulley setting
[21:57:33] <jmkasunich> whats that under the bolt head? a washer?
[21:57:50] <cradek> the top of the spindle
[21:57:58] <jmkasunich> duh
[21:58:13] <cradek> the fillet you see is the spindle
[21:58:27] <jmkasunich> for threading you'd be using the lower drive belt groove...
[21:58:38] <cradek> yes
[21:58:43] <cradek> that's ~ 1:1 with the motor
[21:58:48] <SWPadnos> so the "easiest" thing to do would be to mill a toothed pulley profile in the bottom
[21:58:49] <jmkasunich> so, bore a stock pulley to slip over the top step of the pully and rest on the top of the bottom pulley
[21:59:10] <SWPadnos> that would interfere with the belt in the top position, wouldn't it?
[21:59:16] <jmkasunich> put a washer under the head of the bolt to hold the pulley down
[21:59:20] <cradek> you can't see it but the two pulleys overlap somewhat
[21:59:26] <jmkasunich> if you're doing high speed work, take it off
[21:59:36] <jmkasunich> oops, so much for that idea
[21:59:38] <cradek> so the stock pulley would have to be < 1.5 dia
[21:59:47] <SWPadnos> can you remove the spindle pulley easily?
[21:59:48] <cradek> no, it could be fine if it was small enough
[21:59:59] <cradek> SWPadnos: not very, it's a tight fit
[22:00:06] <SWPadnos> (not on a regular basis, for machining)
[22:00:13] <jmkasunich> ah, in this pic I can see the setscrew
[22:00:14] <cradek> oh yes, sure I could take it off
[22:00:38] <SWPadnos> is the lower part of the spindle pulley needed for anything else?
[22:00:50] <SWPadnos> or could you turn that down a lot?
[22:00:54] <jmkasunich> how much space between the bottom of the pulley and the casting?
[22:00:56] <cradek> it's just there for the setscrew.
[22:01:20] <cradek> jmkasunich: .150
[22:01:30] <jmkasunich> thin
[22:01:50] <cradek> from the pulley to the top of that clip that is part of the spindle
[22:01:55] <jmkasunich> I think the most attractive idea is machining teeth down there using a homemade cutter
[22:01:57] <SWPadnos> can you just put a spur gear on the outside of the toothed belt that's already there?
[22:02:08] <SWPadnos> I suppose that could slip though
[22:02:20] <jmkasunich> the belt could slip wrt the pulley
[22:02:42] <jmkasunich> oh, that reminds me of an off the wall idea I had last night as I was falling assleed
[22:02:45] <cradek> you can see the pulley could be mounted a tad higher
[22:02:50] <jmkasunich> asleep even
[22:03:04] <SWPadnos> assleed - good one ;)
[22:03:14] <jmkasunich> get a verys small but wide tooth belt
[22:03:30] <SWPadnos> make a gear out of it
[22:03:32] <jmkasunich> turn it inside out, make the pulley a tight slip fit
[22:03:38] <jmkasunich> make a pulley out of it actually
[22:03:44] <SWPadnos> yeah - pulley
[22:04:00] <jmkasunich> but it would still obstruct the setscrew hole
[22:04:15] <jmkasunich> also, I think turning the belt inside out would fsck up the pitch
[22:04:23] <SWPadnos> the setscrew isn't accessed often, is it?
[22:04:55] <SWPadnos> the profile would have to be trapezoidal, and symmetric
[22:05:06] <SWPadnos> more of a gear profile than a tooth belt
[22:05:20] <cradek> no, the setscrew is not used often
[22:05:30] <cradek> but I think turning a belt inside-out would badly screw up the DP
[22:05:32] <jmkasunich> the standard toothbelt profile is a trap, and is symmetric (or pretty near)
[22:05:43] <jmkasunich> yeah
[22:05:54] <SWPadnos> DP?
[22:06:02] <jmkasunich> diametrical pitch
[22:06:08] <SWPadnos> ok
[22:06:22] <SWPadnos> I think I was going to say that, but in many more words :)
[22:06:33] <jmkasunich> although belts more commenly use regular pitch, not DP
[22:06:36] <jmkasunich> same issue tho
[22:07:06] <SWPadnos> trying to find the correct one would be a bear, since none of the specs would be what you're looking for
[22:07:17] <jmkasunich> number of teeth tells all
[22:07:30] <jmkasunich> well that and pitch
[22:07:38] <SWPadnos> thickness of tension member or backing would also be needed
[22:07:57] <jmkasunich> sort of
[22:07:59] <cradek> http://timeguy.com/cradek-files/emc/spindle-side.jpg
[22:08:13] <jmkasunich> I'd order a belt that is close then machine the pulley bit by bit to fit
[22:08:28] <SWPadnos> yep
[22:08:38] <jmkasunich> ok, heres another idea
[22:08:48] <jmkasunich> the side pic shows some clearance above the bolt
[22:09:22] <jmkasunich> bore a 1/8" or 3/16" hole in the bolthead, drill one flat of the head for a setscrew
[22:09:40] <jmkasunich> run a 1/8" shaft up to the top of the motor, and mount the encoder up there
[22:10:03] <jmkasunich> shaft is flexible enough to tolerate minor misalignment
[22:10:06] <cradek> a flexy shaft
[22:10:10] <cradek> right
[22:10:13] <cradek> interesting idea
[22:10:14] <jmkasunich> remove it before you do 20,000 rpm milling
[22:10:19] <cradek> haha
[22:10:19] <jmkasunich> ;-)
[22:10:36] <cradek> if I'm using the 3-jaw, the drawbar would have to be removed though
[22:10:40] <jmkasunich> is the top of the motor amenable to mounting anything
[22:10:54] <cradek> with zip ties, sure
[22:11:04] <cradek> (so not really)
[22:11:09] <jmkasunich> could you put an empty toolholder in the spindle to give the drawbar something to thread into?
[22:11:51] <cradek> umm I would have to cut up a toolholder, but yes I could
[22:11:52] <SWPadnos> just make a threaded shaft for the encoder - a second drawbar, as it were
[22:12:09] <SWPadnos> hmmm
[22:12:28] <jmkasunich> if the drawbar isn't gonna be there anyway
[22:12:44] <SWPadnos> you still need the tool "blank" to thread into
[22:12:59] <jmkasunich> take a stock gear, bore the lower side of it to fit over the top of the spindle
[22:13:06] <jmkasunich> countersink the top
[22:13:19] <jmkasunich> and use a long flathead screw instead of the drawbar
[22:13:52] <jmkasunich> the gear thickness could be the bolthead thickness + the spinde "nub" height plus a little, and still clear the motor mount plate
[22:14:59] <jmkasunich> make a dummy toolholder, the "drawbar" thread doesn't have to match the original drawbar, and the "toolholder" doesn't have to be steel or even particularly accurate
[22:16:05] <jmkasunich> depends on what you can mount on top of the motor
[22:16:49] <jmkasunich> I take it theres a setscrew in the bottom part of the motor pulley too?
[22:16:52] <cradek> not much unless I just use foam tape or something
[22:17:00] <cradek> yes same thing
[22:17:50] <jmkasunich> depending on how deep in the hole the setscrew is, I'd be tempted to make another groove in the bottom of the spindle pulley, and turn a smaller step (as small as the setscrew allows) in the motor pulley
[22:17:57] <jmkasunich> gives you a slower speed (more torque)
[22:18:30] <SWPadnos> how long is the setscrew (and are shorter ones available)?
[22:18:34] <cradek> can't do that without making a bigger one on the spindle
[22:18:39] <cradek> or getting a different belt
[22:18:42] <jmkasunich> not true
[22:18:53] <SWPadnos> tensioner
[22:18:59] <jmkasunich> ah
[22:19:02] <cradek> the motor can't move forward or back more than a tiny bit
[22:19:07] <jmkasunich> you'd have to move the motor back
[22:19:12] <jmkasunich> right, I wasn't thinking
[22:19:31] <jmkasunich> either move the motor (not practical) or get a shorter belt
[22:19:32] <cradek> it can't go back more than about .2 before it hits the stepper
[22:19:44] <jmkasunich> side issue anyway
[22:19:54] <SWPadnos> bridgeports are so much ... roomier on top ;)
[22:20:32] <jmkasunich> the top of the motor looks pretty flat
[22:20:44] <cradek> it is quite flat except for in the center
[22:21:05] <jmkasunich> piece of 1/8" alum sheet, drill a hole to clear the bump in the middle
[22:21:14] <cradek> right
[22:21:24] <cradek> and some foam tape
[22:21:28] <cradek> a hole for the encoder
[22:21:28] <jmkasunich> let it hang over on the sides, run 6/32 threaded rods down to the motor mount plate with nuts to hold it on
[22:21:32] <jmkasunich> right
[22:22:09] <cradek> what hookup is required on your encoders?
[22:22:19] <jmkasunich> mechanical you mean?
[22:22:21] <cradek> yes
[22:22:31] <jmkasunich> 1/4 shaft, about 1/2" long
[22:22:58] <cradek> I'm imagining something that is like a screen-door spring (?) with 1/4" ID
[22:23:07] <cradek> it would just press over the encoder shaft
[22:23:19] <jmkasunich> for the shaft itself?
[22:23:28] <jmkasunich> thats too flexible
[22:24:20] <cradek> yeah maybe
[22:24:28] <cradek> could put a solid core in it maybe
[22:24:31] <jmkasunich> 1/8 drill rod I tell you!
[22:24:47] <cradek> yeah, good idea
[22:24:55] <cradek> setscrew in the drawbar head
[22:25:05] <cradek> simple lathe-made coupler on the encoder
[22:25:08] <cradek> with two setscrews
[22:25:09] <jmkasunich> only annoyance is you have to make a coupler to connect to the encode
[22:25:14] <jmkasunich> ryeah
[22:25:16] <cradek> trivial
[22:25:23] <jmkasunich> hmm
[22:25:44] <jmkasunich> do the us digital encoders (the ones without bearings) come in 1/8" shaft size?
[22:26:23] <jmkasunich> mount a single 1/8" ID ball bearing on that alum plate at the top, mount the encoder electronics module to the plate, add the codewheel to the shaft, done
[22:27:11] <cradek> would the whole shaft pull out the top then to remove it?
[22:27:17] <cradek> the whole works has to come off easily
[22:27:55] <jmkasunich> http://www.usdigital.com/products/e2/
[22:28:37] <jmkasunich> http://www.usdigital.com/products/e2/e2assem.shtml
[22:28:48] <jmkasunich> 10 mins maybe?
[22:29:24] <jmkasunich> remove cover, electronics module, then either remove disk, or pull shaft and disk together up and out
[22:29:35] <cradek> I'd be worried about handling that disk all the time
[22:29:49] <cradek> maybe I could come up with a shaft that would come out more easily
[22:30:29] <jmkasunich> disk is mylar
[22:30:36] <cradek> I could just remove the whole assembly from the top of the spindle motor
[22:30:44] <jmkasunich> yeah
[22:30:44] <cradek> use a wingnut somehow
[22:30:54] <jmkasunich> maybe use two plates
[22:31:01] <jmkasunich> one attached permanently to the motor
[22:31:16] <jmkasunich> the other, smaller, sits on top and is held on with a couple screws
[22:32:18] <cradek> this sounds promising
[22:32:28] <cradek> I can make all the parts here
[22:32:45] <jmkasunich> drill two holes, tap one in the drawbar
[22:32:53] <jmkasunich> two pieces of flat alum sheet
[22:32:57] <jmkasunich> some all-thread
[22:33:16] <jmkasunich> and some small drillrod
[22:33:58] <jmkasunich> oh, I see a cheaper encoder
[22:34:00] <cradek> do I still need a bearing?
[22:34:16] <jmkasunich> you need a bearing at the top
[22:34:26] <jmkasunich> you could buy an encoder with a bearing in it
[22:34:38] <jmkasunich> then just make a shaft coupler to extend the shaft
[22:34:56] <cradek> I would be more comfortable with that
[22:35:06] <cradek> then to store it, I could unhook the shaft without taking the encoder apart
[22:35:07] <jmkasunich> http://www.usdigital.com/products/s1s2/
[22:35:26] <jmkasunich> the ball bearing version is good to 10,000 rpm
[22:35:30] <cradek> cool, ttl outputs
[22:35:59] <cradek> argh $50
[22:37:13] <jmkasunich> if you want the cheapest choice, either use my encoders (assuming they work) and make a 1/4" to 1/8" coupler
[22:37:22] <jmkasunich> or use this encoder and use a bearing:
[22:37:28] <jmkasunich> http://www.usdigital.com/products/e4p/e4passem.shtml
[22:37:31] <jmkasunich> encoder is $19
[22:37:47] <jmkasunich> I probably have a 1/8" ID bearing around here you can have
[22:38:10] <jmkasunich> this one is very interesting, it looks like the electronics only go on the one side of the disk
[22:38:25] <jmkasunich> so you could remove the disk and shaft together
[22:38:37] <jmkasunich> just loosen the setscrew in the drawbar head and lift the whole thing off
[22:39:38] <cradek> hmm this S1/S2 is 1/4" shaft too
[22:39:56] <jmkasunich> looks like the $19 encoder has no index pulse
[22:40:55] <jmkasunich> wow, $10 each in high volumn
[22:40:58] <jmkasunich> thats amazing
[22:41:42] <jmkasunich> I should get back to work
[22:41:51] <cradek> thanks for your help
[22:41:54] <cradek> I think we have this nailed
[22:42:46] <jmkasunich> make a 1/4 to 1/8 spacer, if my encoder works you're home free, otherwise buy the shafted encoder
[22:43:07] <jmkasunich> these are 1.5" OD, with a 3/4" section that has the bearings in it
[22:43:15] <jmkasunich> there are four threaded holes on the face
[22:43:16] <cradek> I could even make those parts right away
[22:43:33] <jmkasunich> so a 3/4" hole in the alum plate and two or four clearance holes for screws is all you need to mount it
[22:43:44] <cradek> that sounds great as long as the resolution isn't too high for software counting
[22:43:51] <jmkasunich> true
[22:44:24] <jmkasunich> they have a $40 shafted encoder
[22:44:57] <cradek> I shouldn't worry about $10-20 difference, I should get the surest bet
[22:45:18] <jmkasunich> you'll have to look closer at pricing anyway, the ball bearings might be an adder
[22:45:25] <cradek> when you have your work done, let's put together an order
[22:45:35] <jmkasunich> the sleeve bearing versions are only good to 100RPM
[22:45:35] <cradek> tomorrow even
[22:45:41] <jmkasunich> ok
[22:45:50] <cradek> yeah I need the ball bearing then
[22:46:08] <jmkasunich> found the pricing
[22:46:16] <jmkasunich> ball bearings are a $6 option
[22:46:23] <cradek> ok no problem
[22:46:26] <jmkasunich> S4 series is the cheapest shafted ones
[22:46:43] <jmkasunich> $46.95 for 1 with ball bearings
[22:46:50] <cradek> too bad there's no 1/8 shaft
[22:46:56] <jmkasunich> looks like there ius
[22:46:57] <jmkasunich> is
[22:47:28] <jmkasunich> S4-ppr-B8 is probably the PN you want
[22:47:33] <jmkasunich> B = ball bearings
[22:47:37] <jmkasunich> 8 = 1/8 shaft
[22:47:56] <cradek> ok
[22:48:07] <cradek> I'll try to figure out how to order after dinner
[22:48:13] <cradek> need the cable too, <$10
[22:48:41] <cradek> 100-300 ppr?
[22:48:50] <jmkasunich> fsck
[22:48:58] <jmkasunich> the S4 series doesn't have an index pulse
[22:49:05] <cradek> ah crap
[22:50:32] <jmkasunich> well, you can read the website while I make chips
[22:50:59] <jmkasunich> if price is a major driver the kit encoders win by a lot
[22:51:05] <cradek> I'll be back in an hour or so
[22:51:11] <jmkasunich> if convenience matters, then the shafted ones win
[22:51:15] <cradek> ok, I'll figure it out
[22:51:22] <cradek> cheap - fast - good, pick two
[22:51:26] <jmkasunich> yep
[22:51:40] <cradek> ok bbl
[22:51:42] <cradek> thanks again
[23:07:04] <LawrenceG> dfgdfgdfgdfgdfg internet is up/down like crazy today