#emc | Logs for 2006-02-03

[00:00:07] <bill2or3> I'm planning to make a small mill from scratch
[00:00:12] <bill2or3> about mini-mill sized
[00:00:30] <k4ts> night
[00:00:48] <bill2or3> night k4ts
[00:00:50] <sed_> http://www.jrkerr.com/boards.html
[00:02:01] <sed_> Amplifier capable of driving 6 amps continuously at up to 48vdc. Built-in thermal,
[00:02:03] <sed_> overcurrent and undervoltage protection.
[00:02:18] <bill2or3> ahh, I'm using steppers.
[00:02:20] <bill2or3> not servos
[00:02:53] <bill2or3> oh,
[00:02:56] <bill2or3> * bill2or3 scrolls down
[00:03:22] <sed_> you reading the pdf or the page?
[00:03:57] <SWPadnos> at those prices, you're better off with Geckos
[00:04:08] <SWPadnos> and you can throw in a G-Rex with the extra cash
[00:04:15] <sed_> oh? where are Geckos?
[00:04:22] <SWPadnos> http://www.geckodrive.com
[00:04:56] <SWPadnos> G320 for servos, G201 or G202 for steppers
[00:05:28] <sed_> whats the differance between servo and sttepper?
[00:05:30] <SWPadnos> the G-Rex does extremely fast pulse rates, so you don't need the step multipliers in the G340 or G212/G210)
[00:05:43] <SWPadnos> servo = DC motor that just runs when voltage is applied
[00:06:05] <SWPadnos> stepper = dual-coil motor that needs external controls to change the currents through the two phases
[00:06:18] <SWPadnos> (ie, internally vs externally commutated motors)
[00:06:39] <sed_> which one is gooder?
[00:06:47] <SWPadnos> depends on the application
[00:06:55] <SWPadnos> for the most part, servos are better
[00:07:18] <SWPadnos> they're more expensive for small motors though, so for smaller apps, steppers can be a better choice
[00:08:01] <SWPadnos> Mariss (the owner/engineer at Geckodrive) uses the rule of thimb that steppers are generally better for <200W, servos for >300W, and it depends between 200 and 300
[00:08:06] <SWPadnos> thumb
[00:08:19] <bill2or3> sed, I asked a ton of (probablly annoying) questions here and my decision was "use steppers"
[00:08:24] <bill2or3> heh
[00:08:35] <SWPadnos> but you're valuing cost over everything
[00:08:46] <SWPadnos> and you havea very small mill / project
[00:09:09] <sed_> I want to drive the knee on my mill for the z axis
[00:09:21] <SWPadnos> a Bridgeport (or a near-BP-sized Jet), is at the end of the stepper viability range
[00:09:30] <SWPadnos> you eed a servo, or a huge stepper for that
[00:09:32] <SWPadnos> need
[00:10:00] <SWPadnos> when you get into larger machines, and higher speeds, servos become more cost effective, because they work the opposite of steppers
[00:10:45] <bill2or3> that's true, my design objectives are pretty low-end.
[00:10:50] <SWPadnos> a servo can be overdriven for short periods of time, to get through a hard spot, so you can rate a servo for the amount of torque you expect to need
[00:11:07] <SWPadnos> and you'll have headroom for short bursts of extra power
[00:11:39] <SWPadnos> a stepper is a constant power device above its corner frequency (usuallly in the couple hundred to 1k RPM range, I think)
[00:11:52] <SWPadnos> that means that as you go faster, you have less torque available
[00:12:15] <SWPadnos> there's nothing you can do to increase the torque at high speeds
[00:12:41] <cradek> sure there is - you increase the voltage
[00:13:22] <bill2or3> time to go home, bye.
[00:13:28] <SWPadnos> yes - that gives you a higher constant power, but for a given supply voltage, you'll still have a constant power device, so torque will decrease linearly with speed
[00:13:40] <cradek> sure
[00:14:10] <SWPadnos> and, you'll be dissipating lots more power in the motor, so heat becomes a big issue
[00:14:14] <cradek> all you have to do is not go too fast... they sure are nice and cheap.
[00:14:27] <SWPadnos> right - for slow / low power apps, they're fine
[00:14:37] <sed_> http://puga.mauibuilt.com/shop/DSCF0091.JPG
[00:14:40] <sed_> thats my mill
[00:14:48] <SWPadnos> a BP-sized machine doesn't necessarily qualify
[00:15:23] <SWPadnos> what's the total weight on that machine?
[00:15:41] <sed_> thousand pounds??? if that
[00:16:11] <SWPadnos> ok - what's the table size
[00:16:37] <sed_> um 8x30?? small
[00:16:57] <sed_> has like 24" of travel on X
[00:17:36] <sed_> the knee is not that hard to crank
[00:17:48] <SWPadnos> they usually aren't - the 10TPI screw helps ;)
[00:17:58] <SWPadnos> at least on a bridgeport
[00:17:58] <sed_> think its 8
[00:18:13] <sed_> 1.25 per rev
[00:18:27] <SWPadnos> 1.25 mm?
[00:18:42] <SWPadnos> or 0.125?
[00:18:48] <sed_> sorry 0.125
[00:19:10] <sed_> so that would make it 8
[00:19:26] <SWPadnos> well - a bridgeport knee+saddle+table is around 900 pounds, and has a 10TPI screw
[00:19:34] <SWPadnos> that's before you add a vise or a workpiece
[00:19:53] <sed_> thats as heavy as my mill in total with the stand Im sure
[00:19:59] <SWPadnos> heh - probably
[00:20:29] <SWPadnos> to run a BP knee, you should have at least a 40 in-lb servo, and 50-60 is preferable
[00:20:42] <SWPadnos> (a 40 gets hot in normal use)
[00:21:15] <sed_> http://puga.mauibuilt.com/shop/DSCF0085.JPG
[00:21:20] <sed_> thats my lathe
[00:21:34] <sed_> I probably shold have cleand up before I took the pictures
[00:21:51] <SWPadnos> a stepper would need to be 1.5-2x the torque, so figure 75 in-Lb, or 1200 oz-in
[00:22:21] <SWPadnos> your mill has probably 1/3 the weight to move, but 8/10 the drive ratio
[00:22:41] <SWPadnos> so you probably need a 600 oz-in stepper or more for the knee
[00:24:02] <sed_> how much do they cost about??
[00:24:27] <SWPadnos> damfino
[00:24:32] <SWPadnos> I'm a servo guy ;)
[00:25:02] <sed_> so how much would a 40 in-lb servo cost??
[00:25:07] <sed_> :)
[00:25:39] <SWPadnos> loads, if you get it new, like $1200
[00:25:46] <sed_> dam
[00:25:52] <sed_> the mill cost less
[00:26:11] <SWPadnos> you only need half that though, so something in the $600 -700 range (new)
[00:26:23] <SWPadnos> ebay has servos in that range pretty frequently
[00:26:42] <sed_> I would like one I could attach the hand crank to..
[00:27:11] <SWPadnos> you'd generally use a belt drive to couple the servo to the crank, so you could probably have a handle after the gear
[00:27:33] <sed_> 1" bellt do it?
[00:27:37] <SWPadnos> note that a knee drive without feedback is probably a bad idea, unles syou really overspec the stepper motor
[00:28:02] <SWPadnos> overkill, the best elts are Gates GT2, and 15mm width would be plenty for you
[00:28:05] <SWPadnos> belts
[00:28:30] <SWPadnos> har dto find the pulleys online though (or at least, hard to find both belts and pulleys at teh same place)
[00:28:46] <sed_> I think I have a source localy
[00:28:51] <SWPadnos> cool
[00:28:57] <sed_> just bought some cogged belts for a polisher
[00:29:09] <SWPadnos> GT2 seem to be harder to find for some reason
[00:29:13] <SWPadnos> could be the patents and stuff
[00:29:47] <sed_> If I lived in the real world I would just wait for some old ebay CNC I could retro fit
[00:29:53] <SWPadnos> heh
[00:29:58] <SWPadnos> plenty to choose from right now
[00:30:31] <sed_> My Friend got a working Maho 400 for like $2500
[00:31:38] <sed_> no 1500
[00:31:41] <sed_> I belive
[00:32:02] <SWPadnos> there are a lot of good deals (now that I already bought a mill)
[00:37:56] <sed_> well time to go home, thanks for your help
[00:38:03] <SWPadnos> sure - see you later
[00:41:26] <giacus> G night
[00:41:39] <giacus> giacus is now known as giacus_afk
[00:42:54] <rayh_away> rayh_away is now known as rayh
[06:17:03] <lerman_> lerman_ is now known as lerman
[07:34:37] <lilo> [Global Notice] Hi all. We just experienced a brief connectivity loss on a main rotation server. Looking at the problem now. Apologies for the inconvenience!
[07:35:32] <SWPadnos> SWPadnos is now known as SWP_Away
[11:53:28] <giacus> morning
[13:32:46] <rayh> Hi fenn. You becoming a day person now or just not sleeping at all?
[13:33:21] <fenn> i have a 25.5 hour schedule
[13:33:54] <rayh> each day?
[13:34:18] <fenn> i try to skip the "wake up at 10 pm" part of the cycle as fast as i can
[13:34:40] <rayh> Okay.
[13:36:22] <fenn> i have some responsibilities now so i guess i'll have to try to stay on regular hours
[13:36:53] <rayh> Really. You able to elaborate?
[13:37:06] <fenn_> oops
[14:31:20] <les_w> morning!
[14:31:46] <cradek> hi les
[14:31:49] <giacus> morning les_w
[14:31:54] <jepler> hi jacky
[14:31:54] <giacus> hi cradek
[14:32:04] <les_w> great fun last night!
[14:32:11] <giacus> yeah :)
[14:32:14] <les_w> so my sound was ok?
[14:32:16] <giacus> nice music
[14:32:27] <giacus> les_w: great !
[14:32:44] <giacus> no distortion ;P
[14:33:16] <les_w> I managed to route digital direct to paltalk
[14:33:24] <jepler> * jepler looks at the screenshot of "weave"
[14:33:41] <giacus> les_w: nice
[14:34:16] <les_w> the weave stuff reminds me a little of the dovetail gcode I am making
[14:35:05] <les_w> I may write it up as a little expert system c program to generate the code
[14:35:31] <les_w> enter dimensions, type of dovetail, etc
[14:36:29] <les_w> I have a swivel so I can lock the spindle at 30,45,60,90 degrees
[14:36:30] <cradek> I don't understand why he doesn't just generate g-code for that path
[14:36:41] <les_w> the weave?
[14:36:45] <cradek> yeah
[14:37:02] <les_w> i lost the link
[14:37:12] <cradek> it's email
[14:37:18] <les_w> oh let me look
[14:37:44] <jepler> there's a jpeg attachment to the last mail from Colin Wildsmith
[14:38:00] <fenn> http://fenn.freeshell.org/weavesnapshot1.jpg
[14:38:20] <cradek> holy cow look at his rapids
[14:38:34] <fenn> nice blend huh
[14:38:40] <cradek> ugh
[14:38:54] <fenn> * fenn cackles
[14:39:06] <les_w> yeah, well little c programs to generate special g codes are pretty easy
[14:39:14] <les_w> Eveb I can write them!
[14:39:23] <les_w> even
[14:39:25] <les_w> haha
[14:40:31] <jepler> I also find it easy to write programs to generate g code
[14:42:19] <les_w> well, I had better get to wiring
[14:42:27] <les_w> converting to optocouplers
[16:49:59] <bill2or3> g'morining people.
[16:50:04] <bill2or3> morning, too.
[19:05:25] <Jymmm> Howdy!
[19:07:26] <A-L-P-H-A> runaway. run away! r u n!!!!!
[19:07:48] <Jymmm> OH SHIT A-L-P-H-A HERE! RUN RUN FOR YOUR LIVES!!!!!!!!!!!!!!!1
[19:07:58] <A-L-P-H-A> good.
[19:08:02] <A-L-P-H-A> you better fear me!
[19:08:19] <Jymmm> it be much easier to just /kick you
[19:08:36] <A-L-P-H-A> abuse of power...
[19:08:39] <A-L-P-H-A> sad sad sad.
[19:08:42] <giacus> :D
[19:08:50] <Jymmm> A-L-P-H-A and your point is?
[19:08:58] <A-L-P-H-A> just take your abuse like a good beeeyatch.
[19:09:53] <Jymmm> and I have an alias for it.... dont tempt me
[19:09:59] <A-L-P-H-A> Jymmm, what ever happened to that machine you had?
[19:10:14] <Jymmm> what do you mean?
[19:10:17] <A-L-P-H-A> the one with sooo many initial problems...
[19:10:21] <A-L-P-H-A> did you get them all resolved?
[19:10:42] <A-L-P-H-A> that gantry thing.
[19:10:47] <Jymmm> AS best to be expected, yeah. Better if I had geckos of course.
[19:11:05] <A-L-P-H-A> what cha been making with it?
[19:11:13] <A-L-P-H-A> my mill hasn't been turned on in like 6 months.
[19:11:22] <A-L-P-H-A> it's sitting there... doing nothing.
[19:11:23] <Jymmm> Signs, have pics, but haven't posted them yet.
[19:11:25] <A-L-P-H-A> nor my lathe.
[19:11:30] <A-L-P-H-A> post post.
[19:11:32] <A-L-P-H-A> let me see.
[19:12:01] <Jymmm> let me see what I have available, gimme a few. you sw the parrot, right?
[19:12:19] <A-L-P-H-A> nope
[19:12:28] <A-L-P-H-A> I haven't seen anything... I haven't been in here much.
[19:12:44] <A-L-P-H-A> Jymmm, just put them up on flickr or something
[19:14:05] <A-L-P-H-A> I'll check them later... as my blood sugar level I think just dropped... as I'm suddenly feeling really tired
[19:14:21] <A-L-P-H-A> then again, I've been up for like 4 hrs, without eating anything yet
[19:14:38] <Jymmm> A-L-P-H-A chk your msgs
[19:15:30] <Jymmm> http://static.flickr.com/33/61765799_f610fa36cb_m.jpg
[19:16:14] <A-L-P-H-A> checking
[19:16:41] <A-L-P-H-A> what are you using to draw things?
[19:17:07] <Jymmm> art or cad wise?
[19:17:11] <A-L-P-H-A> both
[19:17:44] <Jymmm> various tools, depending on the situation... Corel mostly of editing vector graphics
[19:28:27] <A-L-P-H-A> cool.
[19:30:20] <jepler> Jymmm: Thanks for suggesting that onsrud(?) tool for cutting plexiglass. I finally got back to that project last night, and the results were very good.
[19:31:01] <Jymmm> jepler Yeah? let me see
[19:31:24] <Jymmm> jepler and which one did you order?
[19:34:01] <jepler> Jymmm: I don't remember which one. "O" cut, 3/16, something..
[19:34:17] <Jymmm> jepler you have pics?
[19:35:36] <Jymmm> jepler: They have about 8 different 3/16" 'O' Cut bits. I'd liek to compare the bit with a pic of the results.
[19:36:08] <jepler> Jymmm: I don't have a picture of it, but maybe I can put one online this weekend
[19:39:25] <k4ts> hello
[19:40:44] <Jymmm> jepler: Ok, cool. Maybe you can get the PN at the same time.
[19:42:02] <Jymmm> jepler: See, I had done the research, even talked to the Sales Engineer, but was still reloctant to buy =) So you were the beta bitch in this case - But all they make are tools for (mostly) plastics.
[19:43:09] <Jymmm> jepler also what spindle RPM
[19:43:11] <Jymmm> ?
[19:43:34] <jepler> Jymmm: 2400rpm, feedrate 13ipm
[19:44:01] <Jymmm> jepler: eeeeeew, I can only go down to 8000RPM
[19:44:09] <Jymmm> But they did say it SHOULD work.
[19:44:25] <Jymmm> jepler no melt over at all?
[19:44:43] <fenn> say jymmm how much does a spindle with 1/4" collet cost?
[19:45:02] <cradek> I'm pretty sure it was 7200RPM?
[19:45:04] <fenn> i mean so you wouldnt have to whine about your minimum speed anymore
[19:45:34] <jepler> cradek: I wrote down 2400RPM. Whatever it was, it was the innermost ring on that little disc
[19:45:45] <Jymmm> fenn : I'm using a router, and I haven't seen one that goes THAT slow.
[19:45:57] <cradek> ok maybe you're right - that's the .005" per tooth
[19:47:07] <jepler> Jymmm: no, I didn't see any melted plastic. Just tiny chips -- maybe 1/4 inch? -- everywhere
[19:47:52] <Jymmm> jepler Very cool! No issues in curves or when it had to slow done in the corners?
[19:47:59] <Jymmm> s/done/down/
[19:49:24] <jepler> Jymmm: it was just a rectangle last night, but the corners were fine
[19:49:28] <jepler> Jymmm: there's plenty of accel on cradek's mill
[19:50:12] <Jymmm> jepler: Ah, ok. whe I had it goin at 120IPM it was icky =)
[19:51:34] <fenn> aw now this is just sad http://cgi.ebay.com/A111-G-CODE-DXF-cnc-mill-router-plasma-engraver-STAR_W0QQitemZ7586583367QQcategoryZ57122QQrdZ1QQcmdZViewItem
[19:51:37] <jepler> Jymmm: I bet the tool was 63-766
[19:51:52] <jepler> Jymmm: 13ipm << 120ipm
[19:52:29] <Jymmm> jepler: Well you're doin 2400RPM too, probably the right chipload
[19:52:31] <jepler> Jymmm: the material was .092"-thick plexiglass (clear w/blue film) so I don't know if it's anything like what you are doing
[19:53:01] <Jymmm> jepler if it had a blue film that's Extruded Acrylic. Paper film is Cast Acrylic
[19:53:49] <Jymmm> jepler Cast usually has a bit better results. Especially when laser engraded (just fyi)
[19:54:00] <Jymmm> engraved
[19:54:07] <jepler> Jymmm: this is what I'm doing with it: http://emergent.unpy.net/stippler
[19:54:59] <jepler> Jymmm: the onsrud tool is just to cut out the plexiglass to the right size, nothing complicated.
[19:55:26] <jepler> Jymmm: but an edge that transmits a lot of light is important
[19:55:54] <Jymmm> jepler: Ah, I want to carve/engrave in acrylic, thus my research.
[19:56:02] <Jymmm> jepler did you flame polish the edge?
[19:56:57] <jepler> Jymmm: I don't remember what I did for the one on the website, the one I made last night, the edges were buffed with "jeweler's rouge"
[19:57:57] <Jymmm> jepler If you have a clean, smooth, but fristed edge on acrylic, you can flame polish it so it's perfectly clear using a propane blortorch.
[19:58:02] <Jymmm> frosted
[19:59:30] <jepler> Jymmm: I'll have to try that sometime
[19:59:32] <Jymmm> jepler : http://www.sdplastics.com/plex.html
[19:59:57] <Jymmm> jepler: It's how you get a perfect finished edge, especial for light transfer
[20:00:03] <Jymmm> especially
[20:00:27] <jepler> thank goodness for "Adblock Background Image "
[20:00:39] <jepler> oops .. that makes the page unreadable
[20:00:40] <jepler> doh
[20:00:50] <Jymmm> jepler: Practice on some scraps, and iirc read up on tempering acrylic too, or you'll end up with micro fractures.
[20:01:44] <Jymmm> jepler fuck it, just VIEW SOURCE
[20:01:53] <Jymmm> gawd that's annoying
[20:03:33] <fenn> is tempering basically just baking the water out of it?
[20:03:58] <Jymmm> fenn: No, it's more heating it to 120 deg F for 5 to 10 minutes.
[20:04:13] <Jymmm> iirc
[20:04:27] <Jymmm> the temp and times are varied depending on the material
[20:04:45] <fenn> i'm not finding anything on google
[20:11:25] <Jymmm> me neither, I have some stuff here in dead tree format
[20:14:06] <fenn> well then could you explain it a little for the sake of posterity?
[20:14:52] <Jymmm> You... want me... to explain properties of polymers?
[20:15:40] <Jymmm> That's like asking Darwin about Gawd
[20:16:48] <fenn> * fenn wonders whats burning..
[20:17:04] <Jymmm> the bush
[20:18:27] <Jymmm> when you thermoform or fabricate plastics (in this case acrylic) to prevent micro fractures in the material, it needs to be tempered to release the stress in the material itself.
[20:19:01] <Jymmm> Unlike metals, tempering plastics doesn't take much effort or heat at all.
[20:20:13] <Jymmm> If you want to play around... grab some acrylic scrap, and hit it with a upside down can of air.
[20:28:04] <Jymmm> then let the piece sit in sun for a bit and warm up
[20:41:33] <dmessier> les around??
[20:46:51] <anonimasu> hey dmessier how's stuff going?
[23:04:28] <k4ts> night
[23:15:09] <anonimasu> ssh io23.net
[23:15:12] <anonimasu> whoops
[23:16:39] <Jymmm> * Jymmm pushes anonimasu to the OTHER window
[23:19:32] <anonimasu> whats up?
[23:19:55] <fenn> * fenn is reading about microcontrollers
[23:23:15] <anonimasu> nice
[23:23:42] <fenn> i'm drooling over the at91 series
[23:23:58] <Jymmm> fenn get the butterfly, it's $20
[23:24:09] <fenn> waiting forever for my avr's to arrive
[23:24:26] <anonimasu> hm, the butterflys is just a demoboard..
[23:24:30] <anonimasu> ;)
[23:24:34] <anonimasu> well, gtg
[23:24:38] <Jymmm> anonimasu and your point is?
[23:24:38] <fenn> yeah avr can do plenty just on a breadboard
[23:25:57] <fenn> http://www.robot119.com/market/bookpic/2004425162058663.gif
[23:26:13] <fenn> is that weird or what
[23:26:36] <Jymmm> fenn goatse
[23:27:29] <A-L-P-H-A> nasty
[23:38:58] <bill2or3> can anyone tell what this is? http://tinyurl.com/e4hkg
[23:40:23] <fenn> how come you always post quicksrv forwarded links?
[23:40:31] <Jymmm> * Jymmm dont do tiny urls
[23:40:47] <Jymmm> too many XSS
[23:41:09] <fenn> tinyurl doesnt bother me but i have quicksrv blocked out (cause they're spammers)
[23:41:31] <Jymmm> I like to see where I'm goin befor eI get there
[23:41:59] <bill2or3> just because the real url was like 150 characters
[23:42:11] <bill2or3> http://cgi.ebay.com/3-Xilinx-Stepper-Cutter-403650-031P-2844-Parallel-Ports_W0QQitemZ8759300798QQcategoryZ56084QQrdZ1QQcmdZViewItem#ebayphotohosting
[23:42:24] <bill2or3> some sort of embedded controller, I think.
[23:42:27] <fenn> i wonder if all tinyurls go throughh quicksrv now..
[23:42:58] <fenn> ah damn thats really annoying
[23:45:30] <fenn> probably a rack mount parallel port for server rooms
[23:46:07] <fenn> like for putting printers on a network maybe?
[23:46:17] <fenn> * fenn shrugs
[23:47:52] <bill2or3> google finds nothing, I found it in a search for 'stepper'