#emc-devel | Logs for 2006-07-07

[04:01:35] <zwisk> From $.50 -> $2.00 each
[04:01:35] <zwisk> ------------------------------
[04:11:03] <zwisk> hmm... seems my cat can cut and paste. Crafty little critter.
[04:15:10] <jmkasunich> so thats what that was...
[04:15:28] <jmkasunich> talented aren't they
[04:50:52] <zwisk> amazingly so.
[04:56:54] <zwisk> pesky at times as well.
[04:57:08] <jmkasunich> yep
[04:57:20] <jmkasunich> dancing on keyboards, or newspapers, or whatever
[04:57:24] <zwisk> just broke an endmill. Dang.
[04:57:55] <zwisk> yeah, they have no respect.
[04:58:02] <zwisk> And they hate the 4th of July. Whoa.
[04:58:10] <jmkasunich> heh
[12:09:49] <cradek> alex_joni: hi
[12:09:58] <cradek> alex_joni: did you see my X axis conversion picture?
[12:10:19] <alex_joni> not yet
[12:10:23] <alex_joni> just got back home ;)
[12:10:29] <alex_joni> cradek: hi ;)
[12:10:38] <cradek> hi
[12:10:44] <cradek> are you home for a while now?
[12:10:50] <cradek> http://timeguy.com/cradek-files/emc/DSCN6290.JPG
[12:10:56] <alex_joni> well.. depends on your definition for a while :D
[12:11:47] <cradek> have to get ready for work, bbl
[12:11:52] <alex_joni> I'll be around till next thursday, then I'll be in the mountain house for 3 days
[12:11:58] <alex_joni> and then I'm in sicily for 2 weeks
[12:12:54] <alex_joni> cradek: looks GREAT
[12:22:11] <jepler> what name should the library which contains hal_lib.c and XXX_ulapi.c have? someone's already taken libhal. libemchal?
[12:22:41] <alex_joni> what does it do?
[12:24:05] <jepler> it's the library of stuff necessary to make a userspace component
[12:24:12] <jepler> so that someone with emc2-dev installed can do so
[12:24:34] <alex_joni> ahh.. nice
[12:24:48] <alex_joni> libuserhal ?
[12:26:20] <jepler> hm .. maybe, since I'll be doing the same for realtime soon
[12:34:47] <jepler> no, I don't think I need to do anything for kernel, because there's hal_lib.ko
[12:39:53] <alex_joni> libemchal.so is fine too
[12:39:59] <alex_joni> care for some pictures?
[12:40:30] <jepler> I like pictures
[12:40:35] <alex_joni> http://dsplabs.utt.ro/~juve/blog/index.cgi/photography/01152273021
[12:40:39] <alex_joni> same here :D
[12:42:20] <jepler> ooh, time for free bagels for breakfast .. photos take second place to that, I'm afraid.
[12:42:36] <alex_joni> I can surely understand :D
[12:51:29] <Skunkworks> wow those are pretty
[12:51:58] <alex_joni> Skunkworks: thanks :)
[12:55:37] <alex_joni> hi ra
[12:55:39] <alex_joni> ray
[12:58:34] <rayh> Hi Alex]
[12:58:49] <rayh> darn cant type
[12:58:56] <rayh> How you doing?
[13:03:08] <alex_joni> very fine .. thx ;)
[13:05:53] <alex_joni> been kinda away recently
[13:07:23] <rayh> What's happening?
[13:07:28] <alex_joni> work mainly
[13:08:04] <alex_joni> and I'm going on vacation at the end of the next week
[13:08:11] <rayh> I have not kept up since fest.
[13:08:19] <rayh> To the mountains?
[13:10:25] <alex_joni> for a few days, then to sicily
[13:10:29] <alex_joni> for 2 weeks
[13:13:09] <rayh> Nice. Lucky Dog!
[13:14:37] <Skunkworks> ray: was the trip uneventful?
[13:14:57] <rayh> Hi Skunkworks.
[13:15:03] <rayh> For the most part it was.
[13:15:29] <rayh> I was awed by the interest in CNC.
[13:15:38] <Skunkworks> * Skunkworks hasn't been around much
[13:16:09] <rayh> Nearly every little machine tool factory had prototypes or production machines.
[13:16:57] <rayh> Most had demo machines at the show in Beijing.
[13:20:15] <rayh> What you been doing Skunkworks?
[13:20:47] <Skunkworks> mainly working on the house and my car
[13:21:50] <rayh> I need to get up to speed on where EMC2 is now.
[13:22:27] <rayh> I kinda just fell apart after fest.
[13:24:14] <cradek> hi ray
[13:24:48] <alex_joni> cradek: that mounting looks great
[13:24:56] <cradek> thank you
[13:25:06] <cradek> I'm very pleased with it
[13:25:13] <alex_joni> how much space is there between the motor wheel and the drive wheel?
[13:25:19] <alex_joni> the foto is not very conclusive
[13:25:25] <cradek> it has a ball bearing and thrust bearings on both sides
[13:25:40] <alex_joni> I meant motor housing
[13:26:00] <rayh> Hi Chris
[13:26:04] <cradek> 10mm, the angle is deceptive
[13:26:18] <alex_joni> ok, thought it's closer
[13:26:19] <cradek> err maybe 6mm
[13:26:25] <cradek> "plenty"
[13:26:26] <alex_joni> heh.. I just noticed the keyboard in the back
[13:26:34] <alex_joni> if it's more than 1mm it's plenty
[13:26:47] <cradek> jepler commented on the cat hair stuck to the wrist rest
[13:27:04] <alex_joni> I 'overlooked' that
[13:27:09] <cradek> haha
[13:27:22] <alex_joni> seen the flowers I shot?
[13:27:35] <cradek> rayh: this is kind of a big image but it's the X axis of my sherline servo conversion: http://timeguy.com/cradek-files/emc/DSCN6290.JPG
[13:27:46] <cradek> nope
[13:27:51] <alex_joni> http://dsplabs.utt.ro/~juve/blog/index.cgi/photography/01152273021
[13:28:11] <alex_joni> * alex_joni heads home early today..
[13:28:14] <alex_joni> catch you later guys
[13:28:32] <cradek> bye alex
[13:29:35] <cradek> rayh: were you around for the talk about the lathe tool shape compensation?
[13:32:58] <cradek> I did all of that after fest, maybe when you were traveling
[13:44:49] <Skunkworks> cradek: I had asked yesterday - did you machine the mounts (outside and holes/slots) totally on you max?
[13:44:59] <Skunkworks> your
[13:45:07] <cradek> yes
[13:45:30] <cradek> both pieces were done on max
[13:45:33] <Skunkworks> have you machined "bigger" stuff like that before?
[13:45:42] <cradek> sure, I've even cut steel on it
[13:45:46] <cradek> it just takes patience and care
[13:45:54] <Skunkworks> very nice
[13:46:35] <cradek> I wrote gcode subroutines to cut holes and slots in multiple passes
[13:47:01] <cradek> a hole cut is just some helixes, and the slot cut is like that but arc/line/arc/line
[13:47:32] <SWPadnos> does the slot routine do angled slots, or only axis aligned?
[13:47:41] <cradek> arbitrary slots
[13:47:45] <SWPadnos> cool
[13:47:46] <cradek> you specify the endpoints and width
[13:47:51] <cradek> http://cvs.linuxcnc.org/cvs/emc2/nc_files/useful-subroutines.ngc?rev=1.3
[13:48:07] <SWPadnos> saw the code, but didn't really study it ;)
[13:48:17] <cradek> just load this file in axis to see the samples
[13:49:19] <SWPadnos> one day, when I get back my emc development computer, I'll do that
[13:49:25] <cradek> heh ok
[13:49:36] <cradek> I'll make a screen shot in a minute
[13:49:46] <SWPadnos> I saw the motor mount though
[13:50:00] <Skunkworks> wait - your not supposed to use o-words for "usefull" programs
[13:50:07] <Skunkworks> whats the fun in that
[13:50:13] <SWPadnos> now if only we had a #include in g-code
[13:50:19] <Skunkworks> :)
[13:50:36] <Skunkworks> I was supprised to find mod
[13:51:39] <cradek> http://timeguy.com/cradek-files/emc/useful.png
[13:51:53] <SWPadnos> ye - way cool
[13:51:56] <SWPadnos> yep
[13:52:24] <cradek> and they use radius compensation which is nice
[13:52:30] <Skunkworks> show off. ;)
[13:52:36] <Skunkworks> that is cool
[13:53:56] <cradek> a secret to cutting metal on a small machine is to never just plunge
[13:54:13] <SWPadnos> that helps with non-centercutting endmills as well ;)
[13:54:13] <cradek> these all spiral down from the safety height
[13:54:45] <Skunkworks> where you using an 1/8 inch mill?
[13:54:49] <cradek> yes
[13:55:04] <Skunkworks> that must have worked great
[13:55:10] <cradek> the slots are .190 (#6 screws)
[13:55:45] <cradek> the 2-flute mill I use for Al is about .121, I got it somewhere used and resharpened
[13:56:07] <cradek> I should get some more before I break it
[13:56:45] <Skunkworks> hss or carbide?
[13:57:00] <cradek> probably just hss, not sure
[13:57:23] <Skunkworks> should be able to tell by weight - carbide just feels heavy
[13:57:24] <Skunkworks> :)
[13:57:37] <cradek> hm, I never noticed that
[13:57:57] <Skunkworks> comparable to weight to your pcb mills/drills
[13:58:56] <Skunkworks> hmmm - does carbide stick to a magenet?
[13:59:07] <cradek> I think so
[13:59:34] <Skunkworks> well that wouldn't be a test. Guess it doesn't matter
[14:01:07] <Skunkworks> (we had grabbed a cutter we thought was carbide - tried to take a cut assuming it was. the cutter turned red and got shorter and shorter 1 inch diam.
[14:01:34] <Skunkworks> quite the show :) sort of did some friction welding :)
[14:01:41] <SWPadnos> PCB mills and drills should all be carbide
[14:01:49] <cradek> SWPadnos: yes they are
[14:02:39] <cradek> Skunkworks: cutting what?
[14:03:10] <Skunkworks> it was a large steel backer plate for a sheer.
[14:03:32] <Skunkworks> the type of sheer you would see in a junk yard.
[14:03:36] <Skunkworks> for cutting up scrap
[14:03:48] <cradek> ah
[14:03:56] <Skunkworks> (this was on our big mill)
[14:04:47] <cradek> RIP
[14:13:59] <A-L-P-H-A> oops. hi.
[14:14:22] <cradek> ?
[14:14:37] <SWPadnos> heh
[14:26:03] <Skunkworks> cradek: can you reverse the direction of the cut?
[14:26:12] <Skunkworks> tecknically you are climb milling
[14:26:43] <cradek> yeah I noticed that but didn't change it
[14:27:27] <cradek> I should look at the cutouts and see which side has the better finish
[14:27:40] <cradek> just the largest hole left a piece
[14:30:08] <Skunkworks> the main problem with climb milling is that the cutter could catch and pull the slide (if there is any play in the mill) which could break the cutter.
[14:30:45] <cradek> I understand
[14:31:55] <cradek> I'll try to reverse them... do you think you'll use them?
[14:32:04] <SWPadnos> won't they ne climb on all sides??
[14:32:09] <SWPadnos> s/ne/be/
[14:32:21] <cradek> SWPadnos: not on the cutout piece from the center
[14:33:01] <SWPadnos> so the spiral sub goes one direction, and the slot the other?
[14:33:25] <cradek> no I think they both go ccw
[14:33:34] <Skunkworks> I think I would use the program.. I think it would come in handy.
[14:33:38] <jepler> jmkasunich: by the way, it almost works to create multiple user components from one process, but it segfaults when one of them calls hal_exit(id)
[14:34:20] <jepler> jmkasunich: maybe with something as simple as a reference count of "components in this process" it could be made to work
[14:34:32] <SWPadnos> cradek, why would the finish be different then? (if the round and slotted holes are all cut in the same direction)
[14:34:53] <cradek> ok back up a second
[14:34:58] <SWPadnos> heh
[14:35:04] <cradek> if you cut a hole ccw, there's a piece left in the center
[14:35:16] <SWPadnos> ah - thanks
[14:35:38] <SWPadnos> if you cut a (big) hole in either direction, there's a piece in the center :)
[14:35:40] <cradek> I just meant I should compare that piece to the other, and see which finish looks better
[14:35:47] <Skunkworks> I always understood climb milling had a better surface
[14:36:02] <SWPadnos> right - got it now - it's another piece (duh)
[14:36:03] <Skunkworks> finish - but never really noticed
[14:36:26] <cradek> Skunkworks: these parts are a bit gouged up, I'm curious to see if the center piece looks the same
[14:36:31] <Skunkworks> and with our big mill - there is not backlash - we ran both directions
[14:36:47] <SWPadnos> "conventional" milling can also tend to bind the tool, I understand - maybe because the tool is trying to sink itself further into the work
[14:37:31] <Skunkworks> conventional milling you are preloading the cutter into the lead screw
[14:38:13] <SWPadnos> I'm thinking of the forces perpendicular to the direction of travel (though I haven't had a lot of coffee, so I may be thinking poorly)
[14:38:29] <SWPadnos> I may be thinking poorly for other reasons as well ;)
[14:38:58] <cradek> I think it's traditional to take a very light climb pass at the end of the work
[14:39:13] <cradek> I think heavy climb milling is usually a bad idea like Skunkworks said - it pulls on the work
[14:42:29] <Skunkworks> I have only seen a mill break once because of in on an old sloppy mill
[14:42:47] <Skunkworks> (taking a heavy edge cut)
[17:22:19] <alex_joni> hello
[17:23:42] <Lerneaen_Hydra> hi
[17:24:09] <alex_joni> hi LH
[18:17:07] <zwisk> wow... well, the ulp for creating gcode from eagle files is sweet. Alas, I think I'm using the wrong tools with it :)
[18:17:27] <alex_joni> hi zwisk
[18:17:32] <zwisk> howdy alex_joni...
[18:17:44] <alex_joni> how goes it?
[18:18:15] <zwisk> Alright I suppose. Shot an endmill into the wall yesterday. That was fun :)
[18:18:26] <zwisk> (woops)
[18:18:45] <zwisk> How goes with you?
[18:19:31] <alex_joni> pretty good.. kinda busy unfortunately
[18:20:20] <zwisk> I guess that's better than the alternative; bored or dead...
[18:21:35] <alex_joni> or both
[20:20:28] <alex_joni> jepler: around?
[20:32:56] <jepler> alex_joni: for a minute
[20:33:15] <alex_joni> wanted to ask you about hal create pin
[20:33:27] <alex_joni> I think I remember seeing some work from you regarding that?
[20:33:57] <jepler> umm .. I made a function that combines the snprintf() to create the pin name with the actual pin creation
[20:35:28] <alex_joni> jepler: is that in hal.h ?
[20:35:48] <jepler> extern int hal_pin_bit_newf(hal_dir_t dir,
[20:35:48] <jepler> hal_bit_t ** data_ptr_addr, int comp_id, char *fmt, ...);
[20:35:48] <jepler> yes
[20:36:25] <alex_joni> ok, another thing :D
[20:36:42] <alex_joni> would it be hard to add a show world/joint to the Axis menu?
[20:36:57] <alex_joni> for the backplot & readouts?
[20:37:13] <alex_joni> * alex_joni imagines it's just the emcstatus variable that changes
[20:37:41] <jepler> how would you backplot the joint position?
[20:37:57] <alex_joni> only for diagnostics reasons :D
[20:38:06] <alex_joni> as if it were XYZ...
[20:40:16] <jepler> for the backplot, the coordinates are taken from motion.traj.position at around line 1391 of emcmodule.cc
[20:40:24] <cradek> seems to me like the backplot is not useful for joint mode
[20:40:34] <cradek> maybe it should just be disabled
[20:40:50] <alex_joni> cradek: hello, indeed it's hard to picture that
[20:40:55] <cradek> hi
[20:40:59] <alex_joni> * alex_joni has an idea though :D
[20:41:02] <jepler> what are the 'stat' buffer fields called for the joint positions? they may not be available to pyhton yet.
[20:41:05] <alex_joni> for AXIS 2.5...
[20:42:48] <alex_joni> cradek: ideally you'd have bargraphs for each joint (minpos .. current pos .. maxpos)
[20:42:56] <alex_joni> for joint mode I mean
[20:43:23] <cradek> interesting idea
[20:43:53] <alex_joni> jepler: I think it's this: emcStatus->motion.axis[axis].input
[20:44:25] <alex_joni> cradek: at least for the present ..
[20:44:49] <alex_joni> the future might involve knowledge about kinematics, and display a nice robot in 3D :D
[20:45:52] <alex_joni> ok, enough of me nagging.. go home, enjoy the weekend :D
[20:46:08] <zwisk> G43/G49 in axis would be cool too...
[20:46:29] <cradek> yeah we're going to add that soon, since I'll need it for my lathe
[20:46:31] <zwisk> The position shown isn't the commanded position, but... I dunno... the top of the tool with G43 on I guess.
[20:46:54] <cradek> it just ignores tool offsets (as if they're all zero)
[20:46:59] <zwisk> ahh...
[20:47:17] <zwisk> I made modification to the ULP to use G43 tool height compensation, since I can't align my tools all the same like you do :)
[20:47:34] <zwisk> The G0 in the prologue got me though ! :)
[20:48:34] <cradek> I don't understand
[20:48:43] <cradek> G0 honors G43 right?
[20:49:15] <jepler> alex_joni: is .input like actual and .output like commanded position?
[20:49:16] <zwisk> Yup, if it's on. :) The prologue torns it off with G49, then seeks to the 'safety height'. The safety heigh without compensating for the tool, though, was under my bed :)
[20:49:31] <cradek> ouch
[20:49:38] <alex_joni> jepler: may I admit I have no idea? :D
[20:49:40] <cradek> that'll teach you to run my gcode wihtout checking it
[20:49:42] <alex_joni> I'm looking
[20:49:47] <jepler> alex_joni: it looks like those fields are already available, but not in a convenient list representation
[20:49:50] <cradek> (hope it didn't hurt anything)
[20:49:54] <zwisk> yeah... mistakes happen :)
[20:50:37] <zwisk> Nah.. at that point it was my code, not yours :) I modified it to do G43. You were happily not using bit offsets. I broke my bit and put a nice gouge in my clad, but that was all. And bits and clad are cheap compared to other things :)
[20:51:00] <cradek> yuck
[20:51:16] <zwisk> I'm getting pretty rough cutting though. I dunno if my bit is just poor, or if I'm going too fast, but it basically is tearing the copper traces off the board at this point.
[20:51:43] <cradek> are these the thinktink tools?
[20:52:36] <zwisk> Nope, not yet. The thinktinks are on their way... This is a HSS dremel bit. I can only get it spinning about 5K rpm, so I've dumped my speeds down to about 1/5 of what you were doing....
[20:53:24] <cradek> you may need to rig a different kind of spindle
[20:53:30] <alex_joni> jepler: it seems it's busted for usage:
[20:53:31] <alex_joni> stat[axis].output = 0.0;
[20:53:31] <alex_joni> stat[axis].input = joint->pos_fb;
[20:53:46] <cradek> the chips (dust actually) fly out of the cutter now on mine and I get a nice clean cut
[20:53:50] <alex_joni> so only joint feedback is available, output shouldn't do anything
[20:54:00] <cradek> even when I was at 8-10krpm it was not like that
[20:54:12] <zwisk> I tried a constant stream of air thinking chip removeable might be a problem, though it didn't seem to help.
[20:54:36] <cradek> I bet the right tools will be better.
[20:54:56] <zwisk> Probably so. Should be in early next week...
[20:55:29] <zwisk> I may try another go or two at slower speeds and see if that helps. Maybe I'm trying to take too much off too quickly for the bit.
[20:56:03] <cradek> at 5krpm you should be going no faster than 5ipm
[20:56:18] <zwisk> Yeah, I'm doing around 3-4 ...
[20:56:25] <cradek> seems like that should be ok
[20:56:34] <jepler> alex_joni: so in effect I can only get the actual joint position, not the commanded joint position.
[20:56:39] <alex_joni> right
[20:57:09] <zwisk> seemed reasonable to me :)
[20:57:35] <jepler> alex_joni: I'll commit something now to give python easy access to the joint positions
[20:57:46] <jepler> alex_joni: but it's only one step on the way
[20:58:11] <alex_joni> jepler: no need to rush it for me..
[20:58:21] <alex_joni> but thanks anyways
[20:58:33] <alex_joni> I'm trying to figure out what goetler is doing..
[20:58:37] <jepler> alex_joni: goetler?
[20:58:50] <alex_joni> goettler
[20:58:53] <jepler> goettler?
[20:59:11] <alex_joni> talked to him a bit, he's the guy doing the 45 degrees tilted workspace
[20:59:16] <jepler> oh
[20:59:20] <fenn> he's demonstrating how badly kinematics really is :)
[20:59:23] <fenn> that's what he's doing
[20:59:25] <alex_joni> volker goettler
[20:59:30] <jepler> that reminds me, I should get back to working on ckins
[20:59:36] <alex_joni> fenn: I think his math is borked
[20:59:49] <alex_joni> fenn: my kins worked great with emc2
[21:00:28] <alex_joni> well, he didn't really tilt the axes, but rotated them
[21:00:40] <jepler> if I had one of those tripod machines I'm sure I'd get around to proper nontrivial kinematics support in axis
[21:00:52] <alex_joni> want me to mail it to you? :)
[21:00:57] <fenn> jepler: what are you working on?
[21:01:12] <jepler> fenn: axis can't jog in joint space
[21:01:20] <jepler> and it won't display joint positions in the DRO
[21:01:25] <jepler> I think those are the main two problems
[21:01:29] <jepler> alex may know better
[21:01:38] <alex_joni> jepler: I don't have any stepper drivers and interest to keep working on it
[21:01:48] <fenn> ah so like if the tool strays off course you'll see that on the backplot?
[21:02:34] <alex_joni> jepler: bet you can build one easily
[21:02:54] <cradek> how do you jog joints at the nml level?
[21:03:22] <alex_joni> normal jog commands
[21:03:35] <cradek> so you just switch modes somehow?
[21:03:38] <alex_joni> and in teleop you set carthesian vectors
[21:03:39] <alex_joni> yeah
[21:04:46] <jepler> alex_joni: how hard would it be to ship? I can come up with the drivers, unless they're unreasonably big motors
[21:05:13] <alex_joni> cradek: EMC_TRAJ_SET_TELEOP_ENABLE emc_set_teleop_enable_msg;
[21:05:21] <alex_joni> jepler: this really is a TOY
[21:05:27] <alex_joni> 3 HDD steppers
[21:05:40] <alex_joni> I ran them at 5V
[21:06:01] <jepler> alex_joni: that sounds nearly ideal .. any fool with 12 transistors and perfboard could put together a driver
[21:06:04] <alex_joni> the only problem is that it's a bit big
[21:06:19] <zwisk> Hmm... maybe my 'step up' from the bridgeport for CNC should be a tripod....
[21:06:20] <jepler> bulky is bad when you need to ship overseas
[21:06:22] <alex_joni> to ship via airmail
[21:06:33] <fenn> yah that 1 square meter steel plate seems kinda bulky :)
[21:06:43] <alex_joni> jepler: my cousin is coming over this summer, maybe I'll convince him to take it with him
[21:06:50] <alex_joni> it's hardly 1 square meter
[21:06:54] <alex_joni> rat
[21:06:59] <fenn> * fenn squeaks
[21:07:02] <alex_joni> more like 40cm x 40 cm
[21:07:23] <alex_joni> jepler: but I bet you can build one in 2-3 hours
[21:07:25] <alex_joni> http://dsplabs.cs.upt.ro/~juve/emc/mytoy/Resize%20of%20HPIM4955.JPG
[21:07:30] <alex_joni> you can see all details here
[21:08:11] <zwisk> hmm... does it take a tool?
[21:08:20] <jepler> it's just a toy
[21:08:28] <alex_joni> zwisk: I used a pencil
[21:08:29] <fenn> you could probably jam a pencil in it
[21:08:34] <alex_joni> a very small one
[21:08:34] <zwisk> ahh. You could put a pen in the .. right..
[21:08:45] <alex_joni> that's a washer :D
[21:08:58] <alex_joni> zwisk:
[21:09:08] <alex_joni> zwisk: http://dsplabs.cs.upt.ro/~juve/emc/mytoy/
[21:09:18] <alex_joni> sorry.. I'm clumsy around my keyboard today :(
[21:09:54] <alex_joni> jepler: http://dsplabs.cs.upt.ro/~juve/emc/mytoy/Resize%20of%20HPIM4959.JPG
[21:10:04] <zwisk> ooh... I like the work on the guides from which the string comes out...
[21:10:28] <alex_joni> those are MIG current tips
[21:10:31] <alex_joni> for welding
[21:10:47] <fenn> but.. why mess around with a tripod when it's practically just as easy to make a hexpod?
[21:11:06] <alex_joni> fenn: always easier to build 3 axes than 6
[21:11:21] <fenn> but you've already got it all set up
[21:11:21] <alex_joni> and you need to get it perfect so it'll work
[21:11:27] <fenn> no you dont
[21:11:30] <alex_joni> I doubt I can do that for 6 axes
[21:11:38] <zwisk> Ooh... ST h-bridge chip.... :)
[21:12:02] <fenn> alex_joni: there's no redundant constraints in a hexapod.. any way you slap it together it will work
[21:12:29] <alex_joni> hmmm.. I see
[21:13:25] <alex_joni> fenn: maybe one day I'll build a second tripod :D
[21:13:28] <alex_joni> and mate them
[21:17:07] <alex_joni> jepler: if I put the parts in a box?
[21:17:13] <alex_joni> without the metal sheet?
[21:17:49] <cradek> alex_joni: is it fishing line?
[21:17:51] <zwisk> I wonder how useful a hexpod using 'string', like alex_joni's toy, would be...
[21:18:25] <alex_joni> cradek: yes
[21:18:27] <jepler> alex_joni: maybe .. I would have to find 3 matching stepper motors otherwise
[21:18:42] <jepler> *shrug*
[21:18:43] <jepler> I dunno
[21:18:48] <alex_joni> jepler: I can do that ;)
[21:19:00] <alex_joni> but you'll have to mount them on a table
[21:19:05] <cradek> did you add a cylinder to the motor shaft or is that the bare shaft?
[21:19:08] <alex_joni> and measure the distances :)
[21:19:11] <alex_joni> bare shaft
[21:19:25] <alex_joni> those were steppers that moved the HDD head
[21:19:38] <alex_joni> you can see there's a small pointy thing coming out of the shaft
[21:19:38] <cradek> what are the guides that the fishing line goes through?
[21:19:41] <jepler> do you really mean HDD?
[21:19:47] <alex_joni> yes, the older ones
[21:19:51] <alex_joni> 5.25 HDD
[21:19:57] <cradek> floppy
[21:19:59] <cradek> right?
[21:20:04] <alex_joni> no, hard drive :D
[21:20:11] <cradek> ok
[21:20:26] <cradek> jeff should go to surplus center instead I bet
[21:20:29] <alex_joni> * alex_joni hmmms
[21:20:30] <fenn> zwisk: http://www.isd.mel.nist.gov/projects/robocrane/
[21:20:52] <cradek> what are the guides that the fishing line goes through?
[21:21:07] <zwisk> fenn: nifty...
[21:21:10] <alex_joni> cradek: welding current tips
[21:21:19] <alex_joni> about 1-2$ / piece
[21:21:23] <cradek> I don't know what that is
[21:21:53] <fenn> zwisk: i dont think you can really get a sense of how rigid it is without actually poking at it
[21:22:00] <zwisk> fenn: Seems to take a litlte bit higher garage than your typical gantry though.
[21:22:28] <alex_joni> cradek: on MIG welding you have a welding wire
[21:22:35] <alex_joni> which passes through the welding gun
[21:22:54] <cradek> maybe when I send fred's lathe back someone else can try to talk him out of his portable hexapod
[21:23:09] <alex_joni> in order to get current on it, so it melts (from the arc produced), there is a small piece called the current tip which does the energy transfer
[21:24:10] <cradek> ok I see
[21:24:29] <alex_joni> cradek: http://en.wikipedia.org/wiki/Metal_inert_gas_welding
[21:24:44] <alex_joni> http://en.wikipedia.org/wiki/Image:MIG_cut-away.jpg
[21:24:45] <alex_joni> #4
[21:26:00] <jepler> surplus center does have some 12V stepper motors for $4
[21:27:03] <jepler> alex_joni: so I measure Bx, Cx, and Cy and edit tripodkins.c ?
[21:27:07] <alex_joni> right
[21:27:20] <alex_joni> eventually (when we'll care enough) those should come from the ini
[21:27:39] <fenn> eventually those should be determined by a ball-bar test
[21:28:22] <jepler> the comments indicate the controlled position is in XYZ .. does it "move" in Z by creating slack on the wires?
[21:28:24] <alex_joni> jepler: I used a metal rod placed between the tips, to have the same distance between the three tips
[21:28:29] <alex_joni> yes
[21:28:39] <alex_joni> but you need some weight for that to work properly
[21:29:00] <alex_joni> as I've seen it there is about 1-2mm tolerance on Z where nothing seems to be happening ;)
[21:29:03] <cradek> that's cool
[21:29:07] <jepler> so the shape the wires take on is less like a catenary and more like a line?
[21:29:20] <jepler> (is that the word I mean?)
[21:29:21] <alex_joni> what's a catenary?
[21:29:37] <cradek> so the shape is less like the fishing line falling off the motor shafts
[21:29:39] <jepler> http://mathworld.wolfram.com/Catenary.html
[21:29:40] <fenn> a catenary is the shape a slack wire takes :)
[21:30:12] <alex_joni> well.. actually it looks like crap when you slack it
[21:30:27] <alex_joni> because the fishing rod has been tightly run around the motor shafts
[21:30:33] <alex_joni> which causes it to bend
[21:30:42] <jepler> I'm imagining hanging this thing off the ceiling of a dark room, with an LED and a weight at the controlled point
[21:30:55] <alex_joni> and when you slack it (at least without significant weight) it twists & curls
[21:30:58] <jepler> a ghostly light moving around in 3 dimensions
[21:31:05] <alex_joni> jepler: that might be cool :D
[21:31:07] <fenn> and time-lapse photoing it?
[21:31:16] <alex_joni> you can make 3D pictures :D
[21:31:25] <alex_joni> by varying the LED light
[21:31:49] <alex_joni> 30 minutes exposure in a pitch black room :D
[21:32:13] <alex_joni> jepler: sounds like a great idea
[21:32:39] <alex_joni> the only problem will be homing :D
[21:35:08] <jepler> yeah
[21:35:18] <jepler> well I'm trying to talk cradek into building one of these when he's done with his lathe
[21:36:09] <alex_joni> jepler: this one is soo easy you can build it yourself
[21:37:12] <fenn> i call it.. the tilliepod
[21:37:52] <jepler> goodnight
[21:37:58] <jepler> weell, good afternoon
[21:38:05] <fenn> ciao babe
[21:38:07] <alex_joni> laters ;)
[21:46:41] <alex_joni> * alex_joni heads to bed
[21:46:43] <alex_joni> night all