#emc-devel | Logs for 2009-05-20

[02:38:38] <cradek> any last requests for stuff I could bring to fest?
[02:39:07] <cradek> anyone need a 12" tilting rotary table to make a 5 axis machine?
[02:42:23] <skunkworks> umm - Hording isn't in your nature?
[02:43:48] <cradek> so you're saying you need it??
[02:44:09] <skunkworks> heh - no
[02:44:27] <cradek> It seems like I'm just not understanding you - surely you need one.
[02:44:42] <jmkasunich> cradek: is it motorized?
[02:44:49] <KimK> Is it motorized or hand cranked?
[02:44:57] <skunkworks> I think we have a shelf full of rotory tables.
[02:44:58] <KimK> ha
[02:45:06] <cradek> it's manual
[02:45:13] <cradek> skunkworks: but tilting!
[02:45:34] <cradek> it would make a 3 axis machine into a fun 5 axis project
[02:45:41] <cradek> sadly it's too big for my mill
[02:46:37] <skunkworks> tilting is sloted?
[02:46:40] <cradek> "A" pivots around the center of rotation of "C" so it doesn't use up a huge amount of extra Z travel like some that pivot at one side
[02:47:05] <cradek> skunkworks: dual worms, not just tilt slots
[02:47:11] <KimK> Tilting at 12" it must be, what, 300-400 lbs?
[02:47:19] <jmkasunich> photo?
[02:47:25] <cradek> maybe 500
[02:47:25] <skunkworks> cradek: oooh...
[02:47:29] <skunkworks> heh
[02:47:35] <cradek> jmkasunich: if I was smart I would have taken photos before I reboxed it
[02:47:41] <jmkasunich> how did you wind up with it in the first place?
[02:47:53] <cradek> if someone is interested, I'll go do it, but I have to un-nail the box
[02:48:00] <cradek> jmkasunich: you know how some stories are long?
[02:48:13] <jmkasunich> just curious, not interested enough to be worth un-nailing the box
[02:48:54] <KimK> Are you in Lincoln, or is that Jeff?
[02:49:29] <cradek> we're both in lincoln
[02:49:35] <skunkworks> yes - don't unnail it on my account.
[02:49:40] <cradek> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250350873153
[02:49:53] <cradek> I think this is it
[02:50:08] <cradek> very crappy picture though - doesn't even show the other crank
[02:50:33] <jmkasunich> new import? or used?
[02:50:50] <cradek> new, surely an import
[02:51:18] <KimK> How much is it? I can check with someone and get back to you later. And maybe pick it up in Lincoln if he's interested.
[02:51:34] <steves_logging> steves_logging is now known as steve_stallings
[02:53:24] <steve_stallings> thank goodness I didn't plan on driving, 500 lbs, yikes
[02:53:56] <jmkasunich> heh
[02:54:17] <cradek> another ebay auction says a similar device is only 350
[02:54:21] <cradek> lb
[02:54:23] <cradek> not $ :-)
[02:54:24] <steve_stallings> cradek: do you have a power supply suitable for skunkworks servo driver, say 24 to 48 volts at 2 amps?
[02:54:51] <cradek> I have one that might work - let me check the rating
[02:55:04] <steve_stallings> my "kit" shipped yesterday, so anything I bring has to come as luggage
[02:56:07] <cradek> it has 24v 7a, 5v 30a, a few more
[02:56:20] <cradek> I'm 80% sure it works
[02:56:51] <steve_stallings> I have a nice servo about the size of a soda can we can use for testing
[02:57:20] <cradek> I'll bring it
[02:57:39] <steve_stallings> thanks
[02:58:25] <steve_stallings> so, JMK, will the tilting rotary table fit on the table of the gantry you are building? 8-)
[02:59:45] <skunkworks> I can bring the transformer/rectifier I have been using - it is a 220/440 to 120 - so on 120 it would give you around 45v
[02:59:51] <skunkworks> unregulated
[03:00:00] <skunkworks> about 500w I think
[03:01:10] <steve_stallings> I am not sure, but the servo is relatively low voltage 24 maybe, not more than 48 and while duty cycle limiting is workable I would not want to go too high with supply voltage
[03:02:11] <steve_stallings> on the other hand if JMK wants to stick a scope in there you should push it nearer its limits
[03:02:36] <skunkworks> :)
[03:02:58] <skunkworks> * skunkworks needs to make sure he brings some extra parts...
[03:04:44] <steve_stallings> and some spare clean drawers 8-)
[03:05:17] <skunkworks> I have pushed it to about 180v 22A. no bangs...
[03:05:21] <skunkworks> yes
[03:05:23] <skunkworks> yet
[03:07:05] <skunkworks> that is really pushing the limit of some of the parts. (boot strap diode is only rated for 200v and the current sense resistor has a max current of 22a)
[03:07:40] <skunkworks> (and my isolation might be a little small) ;)
[03:10:28] <jmkasunich> steve_stallings: that rotary is a bit heavy
[03:10:36] <jmkasunich> I think my entire table will be about 40-50 lbs
[03:11:24] <jmkasunich> 26 x 11-3/4 table, 16 x 10-1/2 travels
[03:11:45] <jmkasunich> Z travel is undecided - I was just gonna do about 2" for boards, etc, but I've been thinking more would be nice
[03:11:57] <steve_stallings> perfect size, just beef it up a bit 8-)
[03:12:20] <steve_stallings> oops, Z will need to be MUCH more to clear the rotary
[03:12:28] <jmkasunich> heh
[03:12:48] <jmkasunich> my spindle is only 1/2 HP, and only takes 1/8" tool shanks
[03:13:01] <jmkasunich> ~25,000 or 30,000 RPM, haven't finalized the pulley ratio
[03:13:13] <steve_stallings> did you manage to convert the ones from HGR?
[03:13:31] <jmkasunich> the HGR spindles are bigger
[03:13:52] <jmkasunich> when I get back to them, I'll be fitting 3/4" collets for Tormach tooling
[03:15:27] <steve_stallings> the CDCO guy was at NAMES and I tried to talk him into chasing down the outfit in China that is cloning the Tormach style stuff
[03:15:40] <steve_stallings> there is a guy from HongKong selling it on eBay
[03:17:05] <steve_stallings> I wish there was something similar for smaller mills
[03:19:42] <cradek> steve_stallings: like 1/4 shank for all the desktop machines?
[03:20:13] <jmkasunich> or 3/8" - lots of HSS tooling has 3/8" shanks
[03:20:32] <cradek> yeah but taig/sherline/maxnc size machines don't have the spindle clearance for that
[03:20:41] <cradek> (not sure how much smaller he means)
[03:20:48] <steve_stallings> maybe 3/8", but the real problem is small machines typically use Morse taper spindles and the shallow taper does not work with this technique
[03:21:01] <jmkasunich> steve_stallings: says who?
[03:21:16] <jmkasunich> I'm using TTS tooling in the shoptask - MT3 spindle
[03:21:17] <cradek> I bet it would work ok actually
[03:21:30] <steve_stallings> well me, I guess, it would seem that the collet would have to move too far
[03:22:03] <cradek> it just has to move enough to go from "touching" to "tight"
[03:22:11] <steve_stallings> JMK: does it release easily, or do you have to tap on the drawbar?
[03:22:20] <jmkasunich> I have to tap it
[03:22:35] <jmkasunich> I typically unscrew it about a turn to a turn and a half, then whack it
[03:23:24] <cradek> yeah sherline spindle is MT1
[03:23:33] <jmkasunich> if I was clever, I'd rig something to keep the drawbar from moving up, so when I unscrew the drawbar it would force the collet out
[03:23:44] <steve_stallings> maybe I should try to find some cheap collet holder to see if I can turn it down
[03:23:46] <cradek> 3/8 looks awful big
[03:24:42] <steve_stallings> EMCO used to have a cap on top of their spindle to push down on the drawbar after you loosened it
[03:25:30] <steve_stallings> safer than a whack, but more trouble since you needed a wrench
[03:26:33] <steve_stallings> Seig micromills are Morse 2 which can go up to 1/2"
[03:27:02] <steve_stallings> an ER-16 collet holder on 1/2" shank should be workable
[03:28:36] <jmkasunich> the reason I liked 3/8 is that I'd try shrinking steel rings right onto the shanks of tools - no collet holder needed
[03:28:49] <jmkasunich> still need holders for anything else - drills, tools with smaller shanks, etc
[03:29:56] <cradek> your tools must last a long time, to consider doing that
[03:29:58] <steve_stallings> 1/2" straight shank drill chuck arbors are available
[03:30:28] <jmkasunich> cradek: depends
[03:31:00] <jmkasunich> if you make a big batch of rings at one time, it wouldn't be that big a deal to throw one away when the tool gets dull
[03:31:08] <jmkasunich> but yes, it would be better with carbide tooling
[03:31:44] <jmkasunich> unfortunately carbide tooling usually has a wider range of shank sizes - they don't put 3/8" on 1/4" carbide cutters
[03:31:49] <cradek> sounds like a fun thing to try. you could have a 1/4 collet (and 1/4 tools) for smaller jobs too
[03:32:00] <cradek> yeah, too much wasted carbide surely
[03:32:08] <jmkasunich> then you gotta change the collet, which defeats the purpose
[03:32:21] <jmkasunich> I'm taking that approach (sort of) with the pcbmill
[03:32:32] <jmkasunich> 1/8" shanks, and using the depth rings
[03:32:41] <jmkasunich> it won't be as consistant in Z
[03:33:07] <cradek> well depends what you think the purpose is - if it's to have repeatable depths for all the tools in a job, picking the right collet does not screw it up
[03:33:44] <cradek> how tight are those depth rings?
[03:33:52] <jmkasunich> probably not tight enough
[03:35:14] <steve_stallings> I think the changers on PCB drilling machines handle the ring and the bit goes along for the ride, so no slippage
[03:36:08] <jmkasunich> the ring probably hits the front of the collet, not the spindle nose - so when the collet draws in, Z changes
[03:36:18] <jmkasunich> but there is no force trying to pull the tool out of the ring
[03:36:38] <jmkasunich> if the ring hit the spindle nose, Z would be more consistent, unless the tool gets pulled up in the ring
[03:36:58] <jmkasunich> crap, 11:30
[03:37:06] <jmkasunich> gonna be a late one tonight
[03:38:04] <steve_stallings> Z depth is also less critical on a drill or edge router, just make sure you go all the way through
[03:50:09] <steve_stallings> nite all....
[03:50:20] <steve_stallings> steve_stallings is now known as steves_logging
[12:50:43] <steves_logging> steves_logging is now known as steve_stallings
[19:09:26] <steve_stallings> steve_stallings is now known as steves_logging
[22:58:33] <jmkasunich> I wonder what I'm forgetting to pack
[23:21:50] <jepler> I should pack
[23:21:56] <jepler> cradek started driving a few hours ago
[23:24:51] <jepler> darn, wholefoods.com doesn't know about the wholefoods locations in wichita that google says there are
[23:24:56] <jepler> I bet wholefoods.com is right.
[23:24:56] <jepler> :(