#garfield Logs

Aug 02 2017

01:37 AM rue_bed: https://www.thingiverse.com/thing:1137112
01:39 AM rue_bed: https://www.thingiverse.com/thing:1009659
01:39 AM rue_bed: https://www.thingiverse.com/thing:2204279
01:39 AM rue_bed: that last one might be close
01:39 AM rue_bed: na, have to design something
10:48 PM ^kat^: rue, if i glue 12 irf540 to a heatsink, cani parallel them all to toggle 15vdc on-off for 250 microsec 240 times per sec?
10:48 PM ^kat^: carrying 100 amps?
10:48 PM ^kat^: yeas, right?
10:49 PM ^kat^: the SOA of the irf540 says at 1ms it's good for 20amp with 15v across it
10:50 PM ^kat^: since they can be had on ebay for 20 cents each, why has this not been done before?
10:51 PM ^kat^: 12 of them is .006 ohms
10:51 PM ^kat^: that would be .6v drop at 100 amps
10:52 PM ^kat^: 64 watts into the heatsink
10:52 PM ^kat^: any heatsink big enough to mount 12 irf540 (and assicaited diodes and gate driver) can easily handle 64 watts
10:53 PM ^kat^: so..........
10:54 PM ^kat^: why ot use the irfz44 or irf1404? caue the 540 is 100v
10:55 PM Tom_L: he went to a party is why he's not answering
10:55 PM ^kat^: o
10:56 PM Tom_L: bday
10:56 PM ^kat^: i have a mill query too, if you like
10:56 PM Tom_L: so do i
10:56 PM ^kat^: wanna swap queations?
10:56 PM Tom_L: you can
10:56 PM Tom_L: you can't answer mine
10:57 PM ^kat^: for an ER16 or an ER20 mill, should i be thinking 1000-2000 rpm, or 10,000-12,000 rpm?
10:57 PM Tom_L: <- how do i set up linuxcnc to orient the spindle on stop
10:57 PM Tom_L: iirc you asked me that
10:57 PM Tom_L: i'm not so familiar with those size collets
10:57 PM ^kat^: i did not see the answer
10:58 PM ^kat^: er16 max is 3/8 shank, er20 max is 5/8 inch
10:58 PM Tom_L: i would say it would depend on the spindle etc and how well the collets are balanced
10:58 PM ^kat^: "supposed to be" .001 , but no telling onthe bearing runout
10:58 PM Tom_L: $ or $$$ would also affect that
10:59 PM Tom_L: i would guess
10:59 PM ^kat^: but i need a ballpark for the belt pulley ratios
11:01 PM ^kat^: i have a 0-4500 rpm 90vdc 1/3 hp for the ER16, and 3:1 belt drive, which is gonna max the spindle at 1500 rpm, which smells too low
11:01 PM ^kat^: your opinion, please?
11:03 PM ^kat^: i dunno linuxcnc, but if i am to assume you mean to automagically change bits, then a positive stop on the spindle should put it exactly where you want it int eh most accurate of ways
11:03 PM ^kat^: you will wanna lock it anyhow, i think, and that wold be 1/2 of the lock mechanism
11:06 PM ^kat^: <cough>
11:07 PM ^kat^: :-/
11:08 PM ^kat^: se,, i have no clue what i did to cause you to stop talking to me
11:09 PM Tom_L: my spindle goes to 5k
11:09 PM Tom_L: i had to go do something
11:10 PM ^kat^: but do you use it over 1500?
11:10 PM Tom_L: it's got something like a 1.2:1 ratio
11:10 PM Tom_L: all the time
11:10 PM Tom_L: generally around 3k
11:10 PM Tom_L: it's on a PID loop now so it's fairly accurate
11:11 PM ^kat^: i can get 2:1 , giving me 2.2k, or 1:1, which i fear may not give me enough torque
11:12 PM Tom_L: mine will barely pull a 10:32 tap out of aluminum
11:12 PM ^kat^: regarding your index at stop: i'd drill a set of matching holes each side of the spindle, on a larger pulley, for a shaft you have, and fill one hole full of something hard and lightweight
11:13 PM Tom_L: https://www.youtube.com/watch?v=g99lUtjLfMU&feature=youtu.be
11:13 PM ^kat^: when the pin falls intot he other hole, the spindle is indexed and held in postion
11:14 PM Tom_L: it's got a quadrature encoder on it with index
11:14 PM * ^kat^ dl's the video
11:14 PM Tom_L: https://www.youtube.com/watch?v=Jsjde_pKUkk
11:15 PM ^kat^: indexing it in software i canot do for you, i dunno nix or your interface or your cam stuff,, and trying to hold the spindle witht he motor while you wrench the collet off it, won;t work
11:15 PM Tom_L: it can be oriented electrically, i just haven't figured out how yet
11:15 PM Tom_L: that's how the big ones do it
11:15 PM ^kat^: i bet they have a brake somewhere
11:15 PM Tom_L: it's just an exercise for me
11:16 PM Tom_L: i'm not gonna use it
11:16 PM Tom_L: they do have a brake
11:16 PM ^kat^: you need a unique signature in the quadrature decode disk (i presume it;s optical), and i bet you do not have that
11:16 PM Tom_L: they use collets with retention knobs so they just change the whole collet when they do a tool change
11:16 PM ^kat^: so you will be adding something somehow
11:17 PM Tom_L: it has an index channel
11:17 PM Tom_L: http://linuxcnc.org/docs/2.7/html/man/man9/orient.9.html
11:17 PM ^kat^: oh, then slow to 1rpm, then stop and servo position in the index, then apply brake
11:17 PM Tom_L: http://linuxcnc.org/docs/2.7/html/man/man9/motion.9.html
11:18 PM Tom_L: the magic happens in those 2 functions
11:18 PM ^kat^: i dunno lix
11:18 PM ^kat^: nix
11:19 PM Tom_L: the motion.spindle-orient stuff
11:19 PM ^kat^: i would do it with a positive mechanical stop, it's guaranteed repeatable and you don;t need to add a brake,,,,,,, on the other paw, why wold you need to index the spindle to change a tool?
11:19 PM Tom_L: because of the tool change
11:20 PM ^kat^: the nut holding the collet is guranteed to NOT be in a repeatable plase related to the spindle index
11:20 PM Tom_L: the big ones have tabs on them to fit the spindle so they don't slip
11:20 PM ^kat^: ah
11:21 PM ^kat^: i cannot see the optical index being as accurate as a mechanical stop for less than $$$
11:22 PM Tom_L: https://www.mscdirect.com/browse/tnpla/80265234?cid=ppc-google-New+-+Tool+Holding+-+PLA_sN07I2qng___164110813620_c_S&mkwid=sN07I2qng|dc&pcrid=164110813620&rd=k&product_id=80265234&gclid=EAIaIQobChMIzqae05S61QIVj1p-Ch01DwS2EAQYAyABEgI9PvD_BwE
11:22 PM Tom_L: you can see the locating tabs
11:22 PM ^kat^: i thinkit may be constantly hunting the correct position, even if it's only a couple of degrees of rotation
11:22 PM Tom_L: no, it sets a pin and stops
11:23 PM Tom_L: gonna go sleep now
11:23 PM ^kat^: that's a BIG tool, that spindle is so far outa my price range
11:23 PM Tom_L: i just wanted to play with it to see it work
11:24 PM Tom_L: that's a cat 40 collet
11:24 PM * ^kat^ nods
11:24 PM Tom_L: we ran those and cat 50
11:24 PM Tom_L: which are bigger yet
11:24 PM ^kat^: and the spindle they fit into, too big
11:24 PM ^kat^: prolly make really pretty work tho
11:25 PM Tom_L: most are cooled
11:25 PM Tom_L: some are water cooled
11:25 PM ^kat^: i'd go with a 90% mechanical stop-index, it's only $, and accurate enough, doit right to keep stuff ballanced at rpm
11:26 PM Tom_L: this is more an exercise to see their software in action
11:26 PM * ^kat^ nods
11:27 PM ^kat^: admirable quality i may have lost somewhere
11:27 PM * ^kat^ typoed, i have ER16 and ER32
11:27 PM Tom_L: https://www.dzsalesllc.com/v/vspfiles/assets/images/32-70-BTC.jpg
11:27 PM Tom_L: to give an idea of size
11:28 PM ^kat^: one shop in town has one
11:28 PM ^kat^: i dunno why he has it
11:28 PM Tom_L: one what?
11:28 PM ^kat^: mill that has an auto changer m using those bug cat 40's
11:29 PM Tom_L: oh
11:29 PM ^kat^: pours so much water nt he work, cannot see anything it is doing
11:29 PM Tom_L: my bud had one with a 99 tool changer
11:29 PM Tom_L: chain drive on the back side of the machine held them until called up
11:29 PM * ^kat^ nods
11:29 PM Tom_L: then a prefetch command would locate the next tool in position for the tool change
11:30 PM ^kat^: must have been huge
11:30 PM Tom_L: one had a 2 toumbstone pallet changer on it
11:31 PM ^kat^: one in town is simple table, they manually put work and manually bolt it down
11:32 PM ^kat^: i pretty much decided to lay down a plate of steel, and swiss cheese it with threaded holes
11:32 PM Tom_L: i have one like that
11:33 PM ^kat^: what's best size hole? same size as the max collet holding capacity?
11:33 PM Tom_L: mine are small because i have a small mill
11:34 PM ^kat^: yeas
11:34 PM Tom_L: iirc his were 1/2 or 5/8"
11:34 PM Tom_L: on a 2" grid pattern iirc
11:34 PM ^kat^: yeas, i donl;t see a 1/2 is needed if biggest bit is 3/8
11:35 PM ^kat^: lotta common stuff for t-bolts in 1/2 tho
11:36 PM Tom_L: i'm gonna go sleep now.
11:36 PM Tom_L: gnite
11:36 PM ^kat^: happy sleeps
11:50 PM rue_more: I'm back
11:52 PM ^kat^: i'm kat
11:54 PM * ^kat^ logged Tom's threading movie in 2015
11:55 PM ^kat^: ok, well, i guess i am outa here